diff --git a/packages/pigeon/CHANGELOG.md b/packages/pigeon/CHANGELOG.md
index 6e05728aa341..d403f0802a1c 100644
--- a/packages/pigeon/CHANGELOG.md
+++ b/packages/pigeon/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 16.0.1
+
+* Adds support for `ProxyApi` generation only for Dart.
+
 ## 16.0.0
 
 * [java] Adds `VoidResult` type for `Void` returns.
diff --git a/packages/pigeon/example/app/lib/src/messages.g.dart b/packages/pigeon/example/app/lib/src/messages.g.dart
index 59213e4ef2bb..961e9c5856b5 100644
--- a/packages/pigeon/example/app/lib/src/messages.g.dart
+++ b/packages/pigeon/example/app/lib/src/messages.g.dart
@@ -3,7 +3,7 @@
 // found in the LICENSE file.
 // Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
-// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers
+// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers, camel_case_types
 
 import 'dart:async';
 import 'dart:typed_data' show Float64List, Int32List, Int64List, Uint8List;
diff --git a/packages/pigeon/lib/ast.dart b/packages/pigeon/lib/ast.dart
index 9d79a781afbd..7b0e32511fae 100644
--- a/packages/pigeon/lib/ast.dart
+++ b/packages/pigeon/lib/ast.dart
@@ -29,7 +29,10 @@ class Method extends Node {
     required this.name,
     required this.returnType,
     required this.parameters,
+    required this.location,
+    this.required = false,
     this.isAsynchronous = false,
+    this.isStatic = false,
     this.offset,
     this.objcSelector = '',
     this.swiftFunction = '',
@@ -68,6 +71,18 @@ class Method extends Node {
   /// For example: [" List of documentation comments, separated by line.", ...]
   List<String> documentationComments;
 
+  /// Where the implementation of this method is located, host or Flutter.
+  ApiLocation location;
+
+  /// Whether this method is required to be implemented.
+  ///
+  /// This flag is typically used to determine whether a callback method for
+  /// a `ProxyApi` is nullable or not.
+  bool required;
+
+  /// Whether this is a static method of a ProxyApi.
+  bool isStatic;
+
   @override
   String toString() {
     final String objcSelectorStr =
@@ -78,29 +93,185 @@ class Method extends Node {
   }
 }
 
-/// Represents a collection of [Method]s that are hosted on a given [location].
-class Api extends Node {
+/// Represents a collection of [Method]s that are implemented on the platform
+/// side.
+class AstHostApi extends Api {
+  /// Parametric constructor for [AstHostApi].
+  AstHostApi({
+    required super.name,
+    required super.methods,
+    super.documentationComments = const <String>[],
+    this.dartHostTestHandler,
+  });
+
+  /// The name of the Dart test interface to generate to help with testing.
+  String? dartHostTestHandler;
+
+  @override
+  String toString() {
+    return '(HostApi name:$name methods:$methods documentationComments:$documentationComments dartHostTestHandler:$dartHostTestHandler)';
+  }
+}
+
+/// Represents a collection of [Method]s that are hosted on the Flutter side.
+class AstFlutterApi extends Api {
+  /// Parametric constructor for [AstFlutterApi].
+  AstFlutterApi({
+    required super.name,
+    required super.methods,
+    super.documentationComments = const <String>[],
+  });
+
+  @override
+  String toString() {
+    return '(FlutterApi name:$name methods:$methods documentationComments:$documentationComments)';
+  }
+}
+
+/// Represents an API that wraps a native class.
+class AstProxyApi extends Api {
+  /// Parametric constructor for [AstProxyApi].
+  AstProxyApi({
+    required super.name,
+    required super.methods,
+    super.documentationComments = const <String>[],
+    required this.constructors,
+    required this.fields,
+    this.superClassName,
+    this.interfacesNames = const <String>{},
+  });
+
+  /// List of constructors inside the API.
+  final List<Constructor> constructors;
+
+  /// List of fields inside the API.
+  List<Field> fields;
+
+  /// Name of the class this class considers the super class.
+  final String? superClassName;
+
+  /// Name of the classes this class considers to be implemented.
+  final Set<String> interfacesNames;
+
+  /// Methods implemented in the host platform language.
+  Iterable<Method> get hostMethods => methods.where(
+        (Method method) => method.location == ApiLocation.host,
+      );
+
+  /// Methods implemented in Flutter.
+  Iterable<Method> get flutterMethods => methods.where(
+        (Method method) => method.location == ApiLocation.flutter,
+      );
+
+  /// All fields that are attached.
+  ///
+  /// See [attached].
+  Iterable<Field> get attachedFields => fields.where(
+        (Field field) => field.isAttached,
+      );
+
+  /// All fields that are not attached.
+  ///
+  /// See [attached].
+  Iterable<Field> get unattachedFields => fields.where(
+        (Field field) => !field.isAttached,
+      );
+
+  @override
+  String toString() {
+    return '(ProxyApi name:$name methods:$methods documentationComments:$documentationComments superClassName:$superClassName interfacesNames:$interfacesNames)';
+  }
+}
+
+/// Represents a constructor for an API.
+class Constructor extends Node {
+  /// Parametric constructor for [Constructor].
+  Constructor({
+    required this.name,
+    required this.parameters,
+    this.offset,
+    this.swiftFunction = '',
+    this.documentationComments = const <String>[],
+  });
+
+  /// The name of the method.
+  String name;
+
+  /// The parameters passed into the [Constructor].
+  List<Parameter> parameters;
+
+  /// The offset in the source file where the field appears.
+  int? offset;
+
+  /// An override for the generated swift function signature (ex. "divideNumber(_:by:)").
+  String swiftFunction;
+
+  /// List of documentation comments, separated by line.
+  ///
+  /// Lines should not include the comment marker itself, but should include any
+  /// leading whitespace, so that any indentation in the original comment is preserved.
+  /// For example: [" List of documentation comments, separated by line.", ...]
+  List<String> documentationComments;
+
+  @override
+  String toString() {
+    final String swiftFunctionStr =
+        swiftFunction.isEmpty ? '' : ' swiftFunction:$swiftFunction';
+    return '(Constructor name:$name parameters:$parameters $swiftFunctionStr documentationComments:$documentationComments)';
+  }
+}
+
+/// Represents a field of an API.
+class Field extends NamedType {
+  /// Constructor for [Field].
+  Field({
+    required super.name,
+    required super.type,
+    super.offset,
+    super.documentationComments,
+    this.isAttached = false,
+    this.isStatic = false,
+  }) : assert(!isStatic || isAttached);
+
+  /// Whether this is an attached field for a [AstProxyApi].
+  ///
+  /// See [attached].
+  final bool isAttached;
+
+  /// Whether this is a static field of a [AstProxyApi].
+  ///
+  /// A static field must also be attached. See [attached].
+  final bool isStatic;
+
+  /// Returns a copy of [Parameter] instance with new attached [TypeDeclaration].
+  @override
+  Field copyWithType(TypeDeclaration type) {
+    return Field(
+      name: name,
+      type: type,
+      offset: offset,
+      documentationComments: documentationComments,
+      isAttached: isAttached,
+      isStatic: isStatic,
+    );
+  }
+}
+
+/// Represents a collection of [Method]s.
+sealed class Api extends Node {
   /// Parametric constructor for [Api].
   Api({
     required this.name,
-    required this.location,
     required this.methods,
-    this.dartHostTestHandler,
     this.documentationComments = const <String>[],
   });
 
   /// The name of the API.
   String name;
 
-  /// Where the API's implementation is located, host or Flutter.
-  ApiLocation location;
-
   /// List of methods inside the API.
   List<Method> methods;
 
-  /// The name of the Dart test interface to generate to help with testing.
-  String? dartHostTestHandler;
-
   /// List of documentation comments, separated by line.
   ///
   /// Lines should not include the comment marker itself, but should include any
@@ -110,7 +281,7 @@ class Api extends Node {
 
   @override
   String toString() {
-    return '(Api name:$name location:$location methods:$methods documentationComments:$documentationComments)';
+    return '(Api name:$name methods:$methods documentationComments:$documentationComments)';
   }
 }
 
@@ -123,6 +294,7 @@ class TypeDeclaration {
     required this.isNullable,
     this.associatedEnum,
     this.associatedClass,
+    this.associatedProxyApi,
     this.typeArguments = const <TypeDeclaration>[],
   });
 
@@ -132,6 +304,7 @@ class TypeDeclaration {
         isNullable = false,
         associatedEnum = null,
         associatedClass = null,
+        associatedProxyApi = null,
         typeArguments = const <TypeDeclaration>[];
 
   /// The base name of the [TypeDeclaration] (ex 'Foo' to 'Foo<Bar>?').
@@ -158,6 +331,12 @@ class TypeDeclaration {
   /// Associated [Class], if any.
   final Class? associatedClass;
 
+  /// Associated [AstProxyApi], if any.
+  final AstProxyApi? associatedProxyApi;
+
+  /// Whether the [TypeDeclaration] has an [associatedProxyApi].
+  bool get isProxyApi => associatedProxyApi != null;
+
   @override
   int get hashCode {
     // This has to be implemented because TypeDeclaration is used as a Key to a
@@ -207,11 +386,21 @@ class TypeDeclaration {
     );
   }
 
+  /// Returns duplicated `TypeDeclaration` with attached `associatedProxyApi` value.
+  TypeDeclaration copyWithProxyApi(AstProxyApi proxyApiDefinition) {
+    return TypeDeclaration(
+      baseName: baseName,
+      isNullable: isNullable,
+      associatedProxyApi: proxyApiDefinition,
+      typeArguments: typeArguments,
+    );
+  }
+
   @override
   String toString() {
     final String typeArgumentsStr =
         typeArguments.isEmpty ? '' : 'typeArguments:$typeArguments';
-    return '(TypeDeclaration baseName:$baseName isNullable:$isNullable$typeArgumentsStr isEnum:$isEnum isClass:$isClass)';
+    return '(TypeDeclaration baseName:$baseName isNullable:$isNullable$typeArgumentsStr isEnum:$isEnum isClass:$isClass isProxyApi:$isProxyApi)';
   }
 }
 
diff --git a/packages/pigeon/lib/cpp_generator.dart b/packages/pigeon/lib/cpp_generator.dart
index 5247f424052e..b9cb140f39d5 100644
--- a/packages/pigeon/lib/cpp_generator.dart
+++ b/packages/pigeon/lib/cpp_generator.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'package:collection/collection.dart';
+
 import 'ast.dart';
 import 'functional.dart';
 import 'generator.dart';
@@ -175,7 +177,7 @@ class CppHeaderGenerator extends StructuredGenerator<CppOptions> {
         indent, anEnum.documentationComments, _docCommentSpec);
     indent.write('enum class ${anEnum.name} ');
     indent.addScoped('{', '};', () {
-      enumerate(anEnum.members, (int index, final EnumMember member) {
+      anEnum.members.forEachIndexed((int index, EnumMember member) {
         addDocumentationComments(
             indent, member.documentationComments, _docCommentSpec);
         indent.writeln(
@@ -191,14 +193,21 @@ class CppHeaderGenerator extends StructuredGenerator<CppOptions> {
     Indent indent, {
     required String dartPackageName,
   }) {
-    final bool hasHostApi = root.apis.any((Api api) =>
-        api.methods.isNotEmpty && api.location == ApiLocation.host);
-    final bool hasFlutterApi = root.apis.any((Api api) =>
-        api.methods.isNotEmpty && api.location == ApiLocation.flutter);
+    final bool hasHostApi = root.apis
+        .whereType<AstHostApi>()
+        .any((Api api) => api.methods.isNotEmpty);
+    final bool hasFlutterApi = root.apis
+        .whereType<AstFlutterApi>()
+        .any((Api api) => api.methods.isNotEmpty);
 
     _writeFlutterError(indent);
     if (hasHostApi) {
-      _writeErrorOr(indent, friends: root.apis.map((Api api) => api.name));
+      _writeErrorOr(
+        indent,
+        friends: root.apis
+            .where((Api api) => api is AstFlutterApi || api is AstHostApi)
+            .map((Api api) => api.name),
+      );
     }
     if (hasFlutterApi) {
       // Nothing yet.
@@ -291,7 +300,8 @@ class CppHeaderGenerator extends StructuredGenerator<CppOptions> {
             indent.writeln('friend class ${friend.name};');
           }
         }
-        for (final Api api in root.apis) {
+        for (final Api api in root.apis
+            .where((Api api) => api is AstFlutterApi || api is AstHostApi)) {
           // TODO(gaaclarke): Find a way to be more precise with our
           // friendships.
           indent.writeln('friend class ${api.name};');
@@ -317,10 +327,9 @@ class CppHeaderGenerator extends StructuredGenerator<CppOptions> {
     CppOptions generatorOptions,
     Root root,
     Indent indent,
-    Api api, {
+    AstFlutterApi api, {
     required String dartPackageName,
   }) {
-    assert(api.location == ApiLocation.flutter);
     if (getCodecClasses(api, root).isNotEmpty) {
       _writeCodec(generatorOptions, root, indent, api);
     }
@@ -349,7 +358,7 @@ class CppHeaderGenerator extends StructuredGenerator<CppOptions> {
             return _flutterApiArgumentType(hostType);
           });
           final Iterable<String> argNames =
-              indexMap(func.parameters, _getArgumentName);
+              func.parameters.mapIndexed(_getArgumentName);
           final List<String> parameters = <String>[
             ...map2(argTypes, argNames, (String x, String y) => '$x $y'),
             ..._flutterApiCallbackParameters(returnType),
@@ -370,10 +379,9 @@ class CppHeaderGenerator extends StructuredGenerator<CppOptions> {
     CppOptions generatorOptions,
     Root root,
     Indent indent,
-    Api api, {
+    AstHostApi api, {
     required String dartPackageName,
   }) {
-    assert(api.location == ApiLocation.host);
     if (getCodecClasses(api, root).isNotEmpty) {
       _writeCodec(generatorOptions, root, indent, api);
     }
@@ -775,9 +783,10 @@ class CppSourceGenerator extends StructuredGenerator<CppOptions> {
         returnType: classDefinition.name,
         parameters: <String>['const EncodableList& list'], body: () {
       const String instanceVariable = 'decoded';
-      final Iterable<_IndexedField> indexedFields = indexMap(
-          getFieldsInSerializationOrder(classDefinition),
-          (int index, NamedType field) => _IndexedField(index, field));
+      final Iterable<_IndexedField> indexedFields =
+          getFieldsInSerializationOrder(classDefinition).mapIndexed(
+              (int index, NamedType field) => _IndexedField(index, field));
+
       final Iterable<_IndexedField> nullableFields = indexedFields
           .where((_IndexedField field) => field.field.type.isNullable);
       final Iterable<_IndexedField> nonNullableFields = indexedFields
@@ -823,10 +832,9 @@ class CppSourceGenerator extends StructuredGenerator<CppOptions> {
     CppOptions generatorOptions,
     Root root,
     Indent indent,
-    Api api, {
+    AstFlutterApi api, {
     required String dartPackageName,
   }) {
-    assert(api.location == ApiLocation.flutter);
     if (getCodecClasses(api, root).isNotEmpty) {
       _writeCodec(generatorOptions, root, indent, api);
     }
@@ -852,7 +860,7 @@ class CppSourceGenerator extends StructuredGenerator<CppOptions> {
       // Determine the input parameter list, saved in a structured form for later
       // use as platform channel call arguments.
       final Iterable<_HostNamedType> hostParameters =
-          indexMap(func.parameters, (int i, NamedType arg) {
+          func.parameters.mapIndexed((int i, NamedType arg) {
         final HostDatatype hostType =
             getFieldHostDatatype(arg, _shortBaseCppTypeForBuiltinDartType);
         return _HostNamedType(_getSafeArgumentName(i, arg), hostType, arg.type);
@@ -937,10 +945,9 @@ class CppSourceGenerator extends StructuredGenerator<CppOptions> {
     CppOptions generatorOptions,
     Root root,
     Indent indent,
-    Api api, {
+    AstHostApi api, {
     required String dartPackageName,
   }) {
-    assert(api.location == ApiLocation.host);
     if (getCodecClasses(api, root).isNotEmpty) {
       _writeCodec(generatorOptions, root, indent, api);
     }
@@ -981,7 +988,7 @@ class CppSourceGenerator extends StructuredGenerator<CppOptions> {
                   indent.writeln(
                       'const auto& args = std::get<EncodableList>(message);');
 
-                  enumerate(method.parameters, (int index, NamedType arg) {
+                  method.parameters.forEachIndexed((int index, NamedType arg) {
                     final HostDatatype hostType = getHostDatatype(
                         arg.type,
                         (TypeDeclaration x) =>
@@ -1678,7 +1685,7 @@ void _writeFunction(
     indent.add('(${parameters.first})');
   } else {
     indent.addScoped('(', null, () {
-      enumerate(parameters, (int index, final String param) {
+      parameters.forEachIndexed((int index, final String param) {
         if (index == parameters.length - 1) {
           indent.write('$param)');
         } else {
diff --git a/packages/pigeon/lib/dart_generator.dart b/packages/pigeon/lib/dart_generator.dart
index 52e2d0e68d95..9b9ea5afbe12 100644
--- a/packages/pigeon/lib/dart_generator.dart
+++ b/packages/pigeon/lib/dart_generator.dart
@@ -2,6 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'package:code_builder/code_builder.dart' as cb;
+import 'package:collection/collection.dart';
+import 'package:dart_style/dart_style.dart';
 import 'package:path/path.dart' as path;
 
 import 'ast.dart';
@@ -94,7 +97,7 @@ class DartGenerator extends StructuredGenerator<DartOptions> {
     indent.writeln('// ${getGeneratedCodeWarning()}');
     indent.writeln('// $seeAlsoWarning');
     indent.writeln(
-      '// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers',
+      '// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers, camel_case_types',
     );
     indent.newln();
   }
@@ -111,9 +114,19 @@ class DartGenerator extends StructuredGenerator<DartOptions> {
       "import 'dart:typed_data' show Float64List, Int32List, Int64List, Uint8List;",
     );
     indent.newln();
-    indent.writeln(
-        "import 'package:flutter/foundation.dart' show ReadBuffer, WriteBuffer;");
+    if (root.apis.any((Api api) => api is AstProxyApi)) {
+      indent.writeln(
+          "import 'package:flutter/foundation.dart' show ReadBuffer, WriteBuffer, immutable, protected;");
+    } else {
+      indent.writeln(
+          "import 'package:flutter/foundation.dart' show ReadBuffer, WriteBuffer;");
+    }
     indent.writeln("import 'package:flutter/services.dart';");
+    if (root.apis.any((Api api) => api is AstProxyApi)) {
+      indent.writeln(
+        "import 'package:flutter/widgets.dart' show WidgetsFlutterBinding;",
+      );
+    }
   }
 
   @override
@@ -288,8 +301,8 @@ $resultAt != null
       indent.writeln('result as List<Object?>;');
       indent.write('return ${classDefinition.name}');
       indent.addScoped('(', ');', () {
-        enumerate(getFieldsInSerializationOrder(classDefinition),
-            (int index, final NamedType field) {
+        getFieldsInSerializationOrder(classDefinition)
+            .forEachIndexed((int index, final NamedType field) {
           indent.write('${field.name}: ');
           writeValueDecode(field, index);
           indent.addln(',');
@@ -312,12 +325,11 @@ $resultAt != null
     DartOptions generatorOptions,
     Root root,
     Indent indent,
-    Api api, {
+    AstFlutterApi api, {
     String Function(Method)? channelNameFunc,
     bool isMockHandler = false,
     required String dartPackageName,
   }) {
-    assert(api.location == ApiLocation.flutter);
     String codecName = _standardMessageCodec;
     if (getCodecClasses(api, root).isNotEmpty) {
       codecName = _getCodecName(api);
@@ -344,7 +356,9 @@ $resultAt != null
         final String returnType = isAsync
             ? 'Future<${_addGenericTypesNullable(func.returnType)}>'
             : _addGenericTypesNullable(func.returnType);
-        final String argSignature = _getMethodParameterSignature(func);
+        final String argSignature = _getMethodParameterSignature(
+          func.parameters,
+        );
         indent.writeln('$returnType ${func.name}($argSignature);');
         indent.newln();
       }
@@ -352,115 +366,17 @@ $resultAt != null
           'static void setup(${api.name}? api, {BinaryMessenger? binaryMessenger}) ');
       indent.addScoped('{', '}', () {
         for (final Method func in api.methods) {
-          indent.write('');
-          indent.addScoped('{', '}', () {
-            indent.writeln(
-              'final BasicMessageChannel<Object?> ${_varNamePrefix}channel = BasicMessageChannel<Object?>(',
-            );
-            final String channelName = channelNameFunc == null
+          _writeFlutterMethodMessageHandler(
+            indent,
+            name: func.name,
+            parameters: func.parameters,
+            returnType: func.returnType,
+            channelName: channelNameFunc == null
                 ? makeChannelName(api, func, dartPackageName)
-                : channelNameFunc(func);
-            indent.nest(2, () {
-              indent.writeln("'$channelName', $_pigeonChannelCodec,");
-              indent.writeln(
-                'binaryMessenger: binaryMessenger);',
-              );
-            });
-            final String messageHandlerSetterWithOpeningParentheses = isMockHandler
-                ? '_testBinaryMessengerBinding!.defaultBinaryMessenger.setMockDecodedMessageHandler<Object?>(${_varNamePrefix}channel, '
-                : '${_varNamePrefix}channel.setMessageHandler(';
-            indent.write('if (api == null) ');
-            indent.addScoped('{', '}', () {
-              indent.writeln(
-                  '${messageHandlerSetterWithOpeningParentheses}null);');
-            }, addTrailingNewline: false);
-            indent.add(' else ');
-            indent.addScoped('{', '}', () {
-              indent.write(
-                '$messageHandlerSetterWithOpeningParentheses(Object? message) async ',
-              );
-              indent.addScoped('{', '});', () {
-                final String returnType =
-                    _addGenericTypesNullable(func.returnType);
-                final bool isAsync = func.isAsynchronous;
-                const String emptyReturnStatement =
-                    'return wrapResponse(empty: true);';
-                String call;
-                if (func.parameters.isEmpty) {
-                  call = 'api.${func.name}()';
-                } else {
-                  indent.writeln('assert(message != null,');
-                  indent.writeln("'Argument for $channelName was null.');");
-                  const String argsArray = 'args';
-                  indent.writeln(
-                      'final List<Object?> $argsArray = (message as List<Object?>?)!;');
-                  String argNameFunc(int index, NamedType type) =>
-                      _getSafeArgumentName(index, type);
-                  enumerate(func.parameters, (int count, NamedType arg) {
-                    final String argType = _addGenericTypes(arg.type);
-                    final String argName = argNameFunc(count, arg);
-                    final String genericArgType =
-                        _makeGenericTypeArguments(arg.type);
-                    final String castCall = _makeGenericCastCall(arg.type);
-
-                    final String leftHandSide = 'final $argType? $argName';
-                    if (arg.type.isEnum) {
-                      indent.writeln(
-                          '$leftHandSide = $argsArray[$count] == null ? null : $argType.values[$argsArray[$count]! as int];');
-                    } else {
-                      indent.writeln(
-                          '$leftHandSide = ($argsArray[$count] as $genericArgType?)${castCall.isEmpty ? '' : '?$castCall'};');
-                    }
-                    if (!arg.type.isNullable) {
-                      indent.writeln('assert($argName != null,');
-                      indent.writeln(
-                          "    'Argument for $channelName was null, expected non-null $argType.');");
-                    }
-                  });
-                  final Iterable<String> argNames =
-                      indexMap(func.parameters, (int index, Parameter field) {
-                    final String name = _getSafeArgumentName(index, field);
-                    return '${field.isNamed ? '${field.name}: ' : ''}$name${field.type.isNullable ? '' : '!'}';
-                  });
-                  call = 'api.${func.name}(${argNames.join(', ')})';
-                }
-                indent.writeScoped('try {', '} ', () {
-                  if (func.returnType.isVoid) {
-                    if (isAsync) {
-                      indent.writeln('await $call;');
-                    } else {
-                      indent.writeln('$call;');
-                    }
-                    indent.writeln(emptyReturnStatement);
-                  } else {
-                    if (isAsync) {
-                      indent.writeln('final $returnType output = await $call;');
-                    } else {
-                      indent.writeln('final $returnType output = $call;');
-                    }
-
-                    const String returnExpression = 'output';
-                    final String nullability =
-                        func.returnType.isNullable ? '?' : '';
-                    final String valueExtraction =
-                        func.returnType.isEnum ? '$nullability.index' : '';
-                    final String returnStatement = isMockHandler
-                        ? 'return <Object?>[$returnExpression$valueExtraction];'
-                        : 'return wrapResponse(result: $returnExpression$valueExtraction);';
-                    indent.writeln(returnStatement);
-                  }
-                }, addTrailingNewline: false);
-                indent.addScoped('on PlatformException catch (e) {', '}', () {
-                  indent.writeln('return wrapResponse(error: e);');
-                }, addTrailingNewline: false);
-
-                indent.writeScoped('catch (e) {', '}', () {
-                  indent.writeln(
-                      "return wrapResponse(error: PlatformException(code: 'error', message: e.toString()));");
-                });
-              });
-            });
-          });
+                : channelNameFunc(func),
+            isMockHandler: isMockHandler,
+            isAsynchronous: func.isAsynchronous,
+          );
         }
       });
     });
@@ -488,10 +404,9 @@ $resultAt != null
     DartOptions generatorOptions,
     Root root,
     Indent indent,
-    Api api, {
+    AstHostApi api, {
     required String dartPackageName,
   }) {
-    assert(api.location == ApiLocation.host);
     String codecName = _standardMessageCodec;
     if (getCodecClasses(api, root).isNotEmpty) {
       codecName = _getCodecName(api);
@@ -521,92 +436,1264 @@ final BinaryMessenger? ${_varNamePrefix}binaryMessenger;
         } else {
           first = false;
         }
-        addDocumentationComments(
-            indent, func.documentationComments, _docCommentSpec);
-        String argSignature = '';
-        String sendArgument = 'null';
-        if (func.parameters.isNotEmpty) {
-          final Iterable<String> argExpressions =
-              indexMap(func.parameters, (int index, NamedType type) {
-            final String name = _getParameterName(index, type);
-            if (type.type.isEnum) {
-              return '$name${type.type.isNullable ? '?' : ''}.index';
-            } else {
-              return name;
-            }
-          });
-          sendArgument = '<Object?>[${argExpressions.join(', ')}]';
-          argSignature = _getMethodParameterSignature(func);
-        }
-        indent.write(
-          'Future<${_addGenericTypesNullable(func.returnType)}> ${func.name}($argSignature) async ',
+        _writeHostMethod(
+          indent,
+          name: func.name,
+          parameters: func.parameters,
+          returnType: func.returnType,
+          documentationComments: func.documentationComments,
+          channelName: makeChannelName(api, func, dartPackageName),
         );
-        indent.addScoped('{', '}', () {
-          indent.writeln(
-              "const String ${_varNamePrefix}channelName = '${makeChannelName(api, func, dartPackageName)}';");
-          indent.writeScoped(
-              'final BasicMessageChannel<Object?> ${_varNamePrefix}channel = BasicMessageChannel<Object?>(',
-              ');', () {
-            indent.writeln('${_varNamePrefix}channelName,');
-            indent.writeln('$_pigeonChannelCodec,');
-            indent
-                .writeln('binaryMessenger: ${_varNamePrefix}binaryMessenger,');
-          });
-          final String returnType = _makeGenericTypeArguments(func.returnType);
-          final String genericCastCall = _makeGenericCastCall(func.returnType);
-          const String accessor = '${_varNamePrefix}replyList[0]';
-          // Avoid warnings from pointlessly casting to `Object?`.
-          final String nullablyTypedAccessor =
-              returnType == 'Object' ? accessor : '($accessor as $returnType?)';
-          final String nullHandler = func.returnType.isNullable
-              ? (genericCastCall.isEmpty ? '' : '?')
-              : '!';
-          String returnStatement = 'return';
-          if (func.returnType.isEnum) {
-            if (func.returnType.isNullable) {
-              returnStatement =
-                  '$returnStatement ($accessor as int?) == null ? null : $returnType.values[$accessor! as int]';
-            } else {
-              returnStatement =
-                  '$returnStatement $returnType.values[$accessor! as int]';
-            }
-          } else if (!func.returnType.isVoid) {
-            returnStatement =
-                '$returnStatement $nullablyTypedAccessor$nullHandler$genericCastCall';
-          }
-          returnStatement = '$returnStatement;';
+      }
+    });
+  }
 
-          indent.format('''
-final List<Object?>? ${_varNamePrefix}replyList =
-\t\tawait ${_varNamePrefix}channel.send($sendArgument) as List<Object?>?;
-if (${_varNamePrefix}replyList == null) {
-\tthrow _createConnectionError(${_varNamePrefix}channelName);
-} else if (${_varNamePrefix}replyList.length > 1) {
-\tthrow PlatformException(
-\t\tcode: ${_varNamePrefix}replyList[0]! as String,
-\t\tmessage: ${_varNamePrefix}replyList[1] as String?,
-\t\tdetails: ${_varNamePrefix}replyList[2],
-\t);''');
-          // On iOS we can return nil from functions to accommodate error
-          // handling.  Returning a nil value and not returning an error is an
-          // exception.
-          if (!func.returnType.isNullable && !func.returnType.isVoid) {
-            indent.format('''
-} else if (${_varNamePrefix}replyList[0] == null) {
-\tthrow PlatformException(
-\t\tcode: 'null-error',
-\t\tmessage: 'Host platform returned null value for non-null return value.',
-\t);''');
-          }
-          indent.format('''
-} else {
-\t$returnStatement
-}''');
-        });
+  @override
+  void writeInstanceManager(
+    DartOptions generatorOptions,
+    Root root,
+    Indent indent, {
+    required String dartPackageName,
+  }) {
+    _writeProxyApiBaseClass(indent);
+
+    const String proxyApiBaseClassName = '${classNamePrefix}ProxyApiBaseClass';
+    final Iterable<String> apiHandlerSetups =
+        root.apis.whereType<AstProxyApi>().map(
+      (AstProxyApi api) {
+        return '${api.name}.${classMemberNamePrefix}setUpMessageHandlers(${classMemberNamePrefix}instanceManager: instanceManager);';
+      },
+    );
+    indent.format('''
+/// Maintains instances used to communicate with the native objects they
+/// represent.
+///
+/// Added instances are stored as weak references and their copies are stored
+/// as strong references to maintain access to their variables and callback
+/// methods. Both are stored with the same identifier.
+///
+/// When a weak referenced instance becomes inaccessible,
+/// [onWeakReferenceRemoved] is called with its associated identifier.
+///
+/// If an instance is retrieved and has the possibility to be used,
+/// (e.g. calling [getInstanceWithWeakReference]) a copy of the strong reference
+/// is added as a weak reference with the same identifier. This prevents a
+/// scenario where the weak referenced instance was released and then later
+/// returned by the host platform.
+class $instanceManagerClassName {
+  /// Constructs a [$instanceManagerClassName].
+  $instanceManagerClassName({required void Function(int) onWeakReferenceRemoved}) {
+    this.onWeakReferenceRemoved = (int identifier) {
+      _weakInstances.remove(identifier);
+      onWeakReferenceRemoved(identifier);
+    };
+    _finalizer = Finalizer<int>(this.onWeakReferenceRemoved);
+  }
+
+  // Identifiers are locked to a specific range to avoid collisions with objects
+  // created simultaneously by the host platform.
+  // Host uses identifiers >= 2^16 and Dart is expected to use values n where,
+  // 0 <= n < 2^16.
+  static const int _maxDartCreatedIdentifier = 65536;
+
+  /// The default [$instanceManagerClassName] used by ProxyApis.
+  ///
+  /// On creation, this manager makes a call to clear the native
+  /// InstanceManager. This is to prevent identifier conflicts after a host
+  /// restart.
+  static final $instanceManagerClassName instance = _initInstance();
+
+  // Expando is used because it doesn't prevent its keys from becoming
+  // inaccessible. This allows the manager to efficiently retrieve an identifier
+  // of an instance without holding a strong reference to that instance.
+  //
+  // It also doesn't use `==` to search for identifiers, which would lead to an
+  // infinite loop when comparing an object to its copy. (i.e. which was caused
+  // by calling instanceManager.getIdentifier() inside of `==` while this was a
+  // HashMap).
+  final Expando<int> _identifiers = Expando<int>();
+  final Map<int, WeakReference<$proxyApiBaseClassName>> _weakInstances =
+      <int, WeakReference<$proxyApiBaseClassName>>{};
+  final Map<int, $proxyApiBaseClassName> _strongInstances = <int, $proxyApiBaseClassName>{};
+  late final Finalizer<int> _finalizer;
+  int _nextIdentifier = 0;
+
+  /// Called when a weak referenced instance is removed by [removeWeakReference]
+  /// or becomes inaccessible.
+  late final void Function(int) onWeakReferenceRemoved;
+
+  static $instanceManagerClassName _initInstance() {
+    WidgetsFlutterBinding.ensureInitialized();
+    final _${instanceManagerClassName}Api api = _${instanceManagerClassName}Api();
+    // Clears the native `$instanceManagerClassName` on the initial use of the Dart one.
+    api.clear();
+    final $instanceManagerClassName instanceManager = $instanceManagerClassName(
+      onWeakReferenceRemoved: (int identifier) {
+        api.removeStrongReference(identifier);
+      },
+    );
+    _${instanceManagerClassName}Api.setUpMessageHandlers(instanceManager: instanceManager);
+    ${apiHandlerSetups.join('\n\t\t')}
+    return instanceManager;
+  }
+
+  /// Adds a new instance that was instantiated by Dart.
+  ///
+  /// In other words, Dart wants to add a new instance that will represent
+  /// an object that will be instantiated on the host platform.
+  ///
+  /// Throws assertion error if the instance has already been added.
+  ///
+  /// Returns the randomly generated id of the [instance] added.
+  int addDartCreatedInstance($proxyApiBaseClassName instance) {
+    final int identifier = _nextUniqueIdentifier();
+    _addInstanceWithIdentifier(instance, identifier);
+    return identifier;
+  }
+
+  /// Removes the instance, if present, and call [onWeakReferenceRemoved] with
+  /// its identifier.
+  ///
+  /// Returns the identifier associated with the removed instance. Otherwise,
+  /// `null` if the instance was not found in this manager.
+  ///
+  /// This does not remove the strong referenced instance associated with
+  /// [instance]. This can be done with [remove].
+  int? removeWeakReference($proxyApiBaseClassName instance) {
+    final int? identifier = getIdentifier(instance);
+    if (identifier == null) {
+      return null;
+    }
+
+    _identifiers[instance] = null;
+    _finalizer.detach(instance);
+    onWeakReferenceRemoved(identifier);
+
+    return identifier;
+  }
+
+  /// Removes [identifier] and its associated strongly referenced instance, if
+  /// present, from the manager.
+  ///
+  /// Returns the strong referenced instance associated with [identifier] before
+  /// it was removed. Returns `null` if [identifier] was not associated with
+  /// any strong reference.
+  ///
+  /// This does not remove the weak referenced instance associated with
+  /// [identifier]. This can be done with [removeWeakReference].
+  T? remove<T extends $proxyApiBaseClassName>(int identifier) {
+    return _strongInstances.remove(identifier) as T?;
+  }
+
+  /// Retrieves the instance associated with identifier.
+  ///
+  /// The value returned is chosen from the following order:
+  ///
+  /// 1. A weakly referenced instance associated with identifier.
+  /// 2. If the only instance associated with identifier is a strongly
+  /// referenced instance, a copy of the instance is added as a weak reference
+  /// with the same identifier. Returning the newly created copy.
+  /// 3. If no instance is associated with identifier, returns null.
+  ///
+  /// This method also expects the host `InstanceManager` to have a strong
+  /// reference to the instance the identifier is associated with.
+  T? getInstanceWithWeakReference<T extends $proxyApiBaseClassName>(int identifier) {
+    final $proxyApiBaseClassName? weakInstance = _weakInstances[identifier]?.target;
+
+    if (weakInstance == null) {
+      final $proxyApiBaseClassName? strongInstance = _strongInstances[identifier];
+      if (strongInstance != null) {
+        final $proxyApiBaseClassName copy = strongInstance.${classMemberNamePrefix}copy();
+        _identifiers[copy] = identifier;
+        _weakInstances[identifier] = WeakReference<$proxyApiBaseClassName>(copy);
+        _finalizer.attach(copy, identifier, detach: copy);
+        return copy as T;
       }
+      return strongInstance as T?;
+    }
+
+    return weakInstance as T;
+  }
+
+  /// Retrieves the identifier associated with instance.
+  int? getIdentifier($proxyApiBaseClassName instance) {
+    return _identifiers[instance];
+  }
+
+  /// Adds a new instance that was instantiated by the host platform.
+  ///
+  /// In other words, the host platform wants to add a new instance that
+  /// represents an object on the host platform. Stored with [identifier].
+  ///
+  /// Throws assertion error if the instance or its identifier has already been
+  /// added.
+  ///
+  /// Returns unique identifier of the [instance] added.
+  void addHostCreatedInstance($proxyApiBaseClassName instance, int identifier) {
+    _addInstanceWithIdentifier(instance, identifier);
+  }
+
+  void _addInstanceWithIdentifier($proxyApiBaseClassName instance, int identifier) {
+    assert(!containsIdentifier(identifier));
+    assert(getIdentifier(instance) == null);
+    assert(identifier >= 0);
+
+    _identifiers[instance] = identifier;
+    _weakInstances[identifier] = WeakReference<$proxyApiBaseClassName>(instance);
+    _finalizer.attach(instance, identifier, detach: instance);
+
+    final $proxyApiBaseClassName copy = instance.${classMemberNamePrefix}copy();
+    _identifiers[copy] = identifier;
+    _strongInstances[identifier] = copy;
+  }
+
+  /// Whether this manager contains the given [identifier].
+  bool containsIdentifier(int identifier) {
+    return _weakInstances.containsKey(identifier) ||
+        _strongInstances.containsKey(identifier);
+  }
+
+  int _nextUniqueIdentifier() {
+    late int identifier;
+    do {
+      identifier = _nextIdentifier;
+      _nextIdentifier = (_nextIdentifier + 1) % _maxDartCreatedIdentifier;
+    } while (containsIdentifier(identifier));
+    return identifier;
+  }
+}
+''');
+  }
+
+  @override
+  void writeInstanceManagerApi(
+    DartOptions generatorOptions,
+    Root root,
+    Indent indent, {
+    required String dartPackageName,
+  }) {
+    const String apiName = '${instanceManagerClassName}Api';
+    final String removeStrongReferenceName = makeChannelNameWithStrings(
+      apiName: apiName,
+      methodName: 'removeStrongReference',
+      dartPackageName: dartPackageName,
+    );
+    final String clearName = makeChannelNameWithStrings(
+      apiName: apiName,
+      methodName: 'clear',
+      dartPackageName: dartPackageName,
+    );
+
+    indent.writeln('''
+/// Generated API for managing the Dart and native `$instanceManagerClassName`s.
+class _$apiName {
+  /// Constructor for [_$apiName ].
+  _$apiName({BinaryMessenger? binaryMessenger})
+      : _binaryMessenger = binaryMessenger;
+
+  final BinaryMessenger? _binaryMessenger;
+  
+  static const MessageCodec<Object?> $_pigeonChannelCodec =
+     StandardMessageCodec();
+
+  static void setUpMessageHandlers({
+    BinaryMessenger? binaryMessenger,
+    $instanceManagerClassName? instanceManager,
+  }) {
+    const String channelName =
+        r'$removeStrongReferenceName';
+    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      channelName,
+      $_pigeonChannelCodec,
+      binaryMessenger: binaryMessenger,
+    );
+    channel.setMessageHandler((Object? message) async {
+      assert(
+        message != null,
+        'Argument for \$channelName was null.',
+      );
+      final int? identifier = message as int?;
+      assert(
+        identifier != null,
+        r'Argument for \$channelName, expected non-null int.',
+      );
+      (instanceManager ?? $instanceManagerClassName.instance).remove(identifier!);
+      return;
     });
   }
 
+  Future<void> removeStrongReference(int identifier) async {
+    const String channelName =
+        r'$removeStrongReferenceName';
+    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      channelName,
+      $_pigeonChannelCodec,
+      binaryMessenger: _binaryMessenger,
+    );
+    final List<Object?>? replyList =
+        await channel.send(identifier) as List<Object?>?;
+    if (replyList == null) {
+      throw _createConnectionError(channelName);
+    } else if (replyList.length > 1) {
+      throw PlatformException(
+        code: replyList[0]! as String,
+        message: replyList[1] as String?,
+        details: replyList[2],
+      );
+    } else {
+      return;
+    }
+  }
+
+  /// Clear the native `$instanceManagerClassName`.
+  ///
+  /// This is typically called after a hot restart.
+  Future<void> clear() async {
+    const String channelName =
+        r'$clearName';
+    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      channelName,
+      $_pigeonChannelCodec,
+      binaryMessenger: _binaryMessenger,
+    );
+    final List<Object?>? replyList = await channel.send(null) as List<Object?>?;
+    if (replyList == null) {
+      throw _createConnectionError(channelName);
+    } else if (replyList.length > 1) {
+      throw PlatformException(
+        code: replyList[0]! as String,
+        message: replyList[1] as String?,
+        details: replyList[2],
+      );
+    } else {
+      return;
+    }
+  }
+}''');
+  }
+
+  @override
+  void writeProxyApiBaseCodec(
+    DartOptions generatorOptions,
+    Root root,
+    Indent indent,
+  ) {
+    const String codecName = '_${classNamePrefix}ProxyApiBaseCodec';
+
+    indent.writeln('''
+class $codecName extends StandardMessageCodec {
+ const $codecName(this.instanceManager);
+
+ final $instanceManagerClassName instanceManager;
+
+ @override
+ void writeValue(WriteBuffer buffer, Object? value) {
+   if (value is ${classNamePrefix}ProxyApiBaseClass) {
+     buffer.putUint8(128);
+     writeValue(buffer, instanceManager.getIdentifier(value));
+   } else {
+     super.writeValue(buffer, value);
+   }
+ }
+
+ @override
+ Object? readValueOfType(int type, ReadBuffer buffer) {
+   switch (type) {
+     case 128:
+       return instanceManager
+           .getInstanceWithWeakReference(readValue(buffer)! as int);
+     default:
+       return super.readValueOfType(type, buffer);
+   }
+ }
+}
+''');
+  }
+
+  @override
+  void writeProxyApi(
+    DartOptions generatorOptions,
+    Root root,
+    Indent indent,
+    AstProxyApi api, {
+    required String dartPackageName,
+  }) {
+    const String codecName = '_${classNamePrefix}ProxyApiBaseCodec';
+
+    // Each api has an private codec instance used by every host method.
+    // constructor, or non-static field.
+    final String codecInstanceName = '${_varNamePrefix}codec${api.name}';
+
+    final Iterable<AstProxyApi> allProxyApis =
+        root.apis.whereType<AstProxyApi>();
+
+    // A list of ProxyApis where each `extends` the API that follows it.
+    final List<AstProxyApi> superClassApisChain =
+        recursiveGetSuperClassApisChain(
+      api,
+      allProxyApis,
+    );
+
+    // The proxy api this api `extends` if it exists.
+    final AstProxyApi? superClassApi =
+        superClassApisChain.isNotEmpty ? superClassApisChain.first : null;
+
+    // All ProxyApis this API `implements` and all the interfaces those APIs
+    // `implements`.
+    final Set<AstProxyApi> interfacesApis = recursiveFindAllInterfacesApis(
+      api,
+      allProxyApis,
+    );
+
+    // All methods inherited from interfaces and the interfaces of interfaces.
+    final List<Method> interfacesMethods = <Method>[];
+    for (final AstProxyApi proxyApi in interfacesApis) {
+      interfacesMethods.addAll(proxyApi.methods);
+    }
+
+    // A list of Flutter methods inherited from the ProxyApi that this ProxyApi
+    // `extends`. This also recursively checks the ProxyApi that the super class
+    // `extends` and so on.
+    //
+    // This also includes methods that super classes inherited from interfaces
+    // with `implements`.
+    final List<Method> superClassFlutterMethods = <Method>[];
+    if (superClassApi != null) {
+      for (final AstProxyApi proxyApi in superClassApisChain) {
+        superClassFlutterMethods.addAll(proxyApi.flutterMethods);
+      }
+
+      final Set<AstProxyApi> superClassInterfacesApis =
+          recursiveFindAllInterfacesApis(
+        superClassApi,
+        allProxyApis,
+      );
+      for (final AstProxyApi proxyApi in superClassInterfacesApis) {
+        superClassFlutterMethods.addAll(proxyApi.methods);
+      }
+    }
+
+    // Ast class used by code_builder.
+    final cb.Class proxyApi = cb.Class(
+      (cb.ClassBuilder builder) => builder
+        ..name = api.name
+        ..extend = superClassApi != null
+            ? cb.refer(superClassApi.name)
+            : cb.refer('${classNamePrefix}ProxyApiBaseClass')
+        ..implements.addAll(<cb.Reference>[
+          if (api.interfacesNames.isNotEmpty)
+            ...api.interfacesNames.map((String name) => cb.refer(name))
+        ])
+        ..docs.addAll(asDocumentationComments(
+          api.documentationComments,
+          _docCommentSpec,
+        ))
+        ..constructors.addAll(_proxyApiConstructors(
+          api.constructors,
+          apiName: api.name,
+          dartPackageName: dartPackageName,
+          codecName: codecName,
+          codecInstanceName: codecInstanceName,
+          superClassApi: superClassApi,
+          unattachedFields: api.unattachedFields,
+          superClassFlutterMethods: superClassFlutterMethods,
+          interfacesMethods: interfacesMethods,
+          flutterMethods: api.flutterMethods,
+        ))
+        ..fields.addAll(_proxyApiFields(
+          unattachedFields: api.unattachedFields,
+          attachedFields: api.attachedFields,
+          apiName: api.name,
+          dartPackageName: dartPackageName,
+          codecInstanceName: codecInstanceName,
+          codecName: codecName,
+          interfacesApis: interfacesApis,
+          flutterMethods: api.flutterMethods,
+          referencesCodecInstance: api.hostMethods.isNotEmpty ||
+              api.constructors.isNotEmpty ||
+              api.attachedFields.any((Field field) => !field.isStatic),
+        ))
+        ..methods.addAll(_proxyApiMethods(
+          hostMethods: api.hostMethods,
+          flutterMethods: api.flutterMethods,
+          superClassFlutterMethods: superClassFlutterMethods,
+          apiName: api.name,
+          dartPackageName: dartPackageName,
+          codecInstanceName: codecInstanceName,
+          codecName: codecName,
+          unattachedFields: api.unattachedFields,
+          attachedFields: api.attachedFields,
+          interfacesApis: interfacesApis,
+          hasCallbackConstructor: api.methods
+              .followedBy(superClassFlutterMethods)
+              .followedBy(interfacesMethods)
+              .every(
+            (Method method) {
+              return method.location != ApiLocation.flutter || !method.required;
+            },
+          ),
+        )),
+    );
+
+    final cb.DartEmitter emitter = cb.DartEmitter(useNullSafetySyntax: true);
+    indent.write(DartFormatter().format('${proxyApi.accept(emitter)}'));
+  }
+
+  Iterable<cb.Constructor> _proxyApiConstructors(
+    Iterable<Constructor> constructors, {
+    required String apiName,
+    required String dartPackageName,
+    required String codecName,
+    required String codecInstanceName,
+    required AstProxyApi? superClassApi,
+    required Iterable<Field> unattachedFields,
+    required Iterable<Method> superClassFlutterMethods,
+    required Iterable<Method> interfacesMethods,
+    required Iterable<Method> flutterMethods,
+  }) {
+    final cb.Parameter binaryMessengerParameter = cb.Parameter(
+      (cb.ParameterBuilder builder) => builder
+        ..name = '${classMemberNamePrefix}binaryMessenger'
+        ..named = true
+        ..toSuper = true,
+    );
+    final cb.Parameter instanceManagerParameter = cb.Parameter(
+      (cb.ParameterBuilder builder) => builder
+        ..name = '${classMemberNamePrefix}instanceManager'
+        ..named = true
+        ..toSuper = true,
+    );
+    return <cb.Constructor>[
+      // All constructors for this api defined in the pigeon file.
+      ...constructors.map(
+        (Constructor constructor) => cb.Constructor(
+          (cb.ConstructorBuilder builder) {
+            final String channelName = makeChannelNameWithStrings(
+              apiName: apiName,
+              methodName: constructor.name.isNotEmpty
+                  ? constructor.name
+                  : '${classMemberNamePrefix}defaultConstructor',
+              dartPackageName: dartPackageName,
+            );
+            builder
+              ..name = constructor.name.isNotEmpty ? constructor.name : null
+              ..docs.addAll(asDocumentationComments(
+                constructor.documentationComments,
+                _docCommentSpec,
+              ))
+              ..optionalParameters.addAll(
+                <cb.Parameter>[
+                  binaryMessengerParameter,
+                  instanceManagerParameter,
+                  for (final Field field in unattachedFields)
+                    cb.Parameter(
+                      (cb.ParameterBuilder builder) => builder
+                        ..name = field.name
+                        ..named = true
+                        ..toThis = true
+                        ..required = !field.type.isNullable,
+                    ),
+                  for (final Method method in superClassFlutterMethods)
+                    cb.Parameter(
+                      (cb.ParameterBuilder builder) => builder
+                        ..name = method.name
+                        ..named = true
+                        ..toSuper = true
+                        ..required = method.required,
+                    ),
+                  for (final Method method in interfacesMethods)
+                    cb.Parameter(
+                      (cb.ParameterBuilder builder) => builder
+                        ..name = method.name
+                        ..named = true
+                        ..toThis = true
+                        ..required = method.required,
+                    ),
+                  for (final Method method in flutterMethods)
+                    cb.Parameter(
+                      (cb.ParameterBuilder builder) => builder
+                        ..name = method.name
+                        ..named = true
+                        ..toThis = true
+                        ..required = method.required,
+                    ),
+                  ...constructor.parameters.mapIndexed(
+                    (int index, NamedType parameter) => cb.Parameter(
+                      (cb.ParameterBuilder builder) => builder
+                        ..name = _getParameterName(index, parameter)
+                        ..type = cb.refer(
+                          _addGenericTypesNullable(parameter.type),
+                        )
+                        ..named = true
+                        ..required = !parameter.type.isNullable,
+                    ),
+                  )
+                ],
+              )
+              ..initializers.addAll(
+                <cb.Code>[
+                  if (superClassApi != null)
+                    const cb.Code('super.${classMemberNamePrefix}detached()')
+                ],
+              )
+              ..body = cb.Block(
+                (cb.BlockBuilder builder) {
+                  final StringBuffer messageCallSink = StringBuffer();
+                  _writeHostMethodMessageCall(
+                    Indent(messageCallSink),
+                    channelName: channelName,
+                    parameters: <Parameter>[
+                      Parameter(
+                        name: '${_varNamePrefix}instanceIdentifier',
+                        type: const TypeDeclaration(
+                            baseName: 'int', isNullable: false),
+                      ),
+                      ...unattachedFields.map(
+                        (Field field) => Parameter(
+                          name: field.name,
+                          type: field.type,
+                        ),
+                      ),
+                      ...constructor.parameters,
+                    ],
+                    returnType: const TypeDeclaration.voidDeclaration(),
+                  );
+                  builder.statements.addAll(<cb.Code>[
+                    const cb.Code(
+                      'final int ${_varNamePrefix}instanceIdentifier = ${classMemberNamePrefix}instanceManager.addDartCreatedInstance(this);',
+                    ),
+                    cb.Code('final $codecName $_pigeonChannelCodec =\n'
+                        '    $codecInstanceName;'),
+                    cb.Code(
+                      'final BinaryMessenger? ${_varNamePrefix}binaryMessenger = ${binaryMessengerParameter.name};',
+                    ),
+                    const cb.Code('() async {'),
+                    cb.Code(messageCallSink.toString()),
+                    const cb.Code('}();'),
+                  ]);
+                },
+              );
+          },
+        ),
+      ),
+      // The detached constructor present for every ProxyApi. This constructor
+      // doesn't include a host method call to create a new native class
+      // instance. It is mainly used when the native side once to create a Dart
+      // instance and when the `InstanceManager` wants to create a copy for
+      // garbage collection.
+      cb.Constructor(
+        (cb.ConstructorBuilder builder) => builder
+          ..name = '${classMemberNamePrefix}detached'
+          ..docs.addAll(<String>[
+            '/// Constructs $apiName without creating the associated native object.',
+            '///',
+            '/// This should only be used by subclasses created by this library or to',
+            '/// create copies.',
+          ])
+          ..optionalParameters.addAll(<cb.Parameter>[
+            binaryMessengerParameter,
+            instanceManagerParameter,
+            for (final Field field in unattachedFields)
+              cb.Parameter(
+                (cb.ParameterBuilder builder) => builder
+                  ..name = field.name
+                  ..named = true
+                  ..toThis = true
+                  ..required = !field.type.isNullable,
+              ),
+            for (final Method method in superClassFlutterMethods)
+              cb.Parameter(
+                (cb.ParameterBuilder builder) => builder
+                  ..name = method.name
+                  ..named = true
+                  ..toSuper = true
+                  ..required = method.required,
+              ),
+            for (final Method method in interfacesMethods)
+              cb.Parameter(
+                (cb.ParameterBuilder builder) => builder
+                  ..name = method.name
+                  ..named = true
+                  ..toThis = true
+                  ..required = method.required,
+              ),
+            for (final Method method in flutterMethods)
+              cb.Parameter(
+                (cb.ParameterBuilder builder) => builder
+                  ..name = method.name
+                  ..named = true
+                  ..toThis = true
+                  ..required = method.required,
+              ),
+          ])
+          ..initializers.addAll(<cb.Code>[
+            if (superClassApi != null)
+              const cb.Code('super.${classMemberNamePrefix}detached()'),
+          ]),
+      ),
+    ];
+  }
+
+  Iterable<cb.Field> _proxyApiFields({
+    required Iterable<Field> unattachedFields,
+    required Iterable<Field> attachedFields,
+    required String apiName,
+    required String dartPackageName,
+    required String codecInstanceName,
+    required String codecName,
+    required Iterable<AstProxyApi> interfacesApis,
+    required Iterable<Method> flutterMethods,
+    required bool referencesCodecInstance,
+  }) {
+    return <cb.Field>[
+      if (referencesCodecInstance)
+        cb.Field(
+          (cb.FieldBuilder builder) => builder
+            ..name = codecInstanceName
+            ..type = cb.refer(codecName)
+            ..late = true
+            ..modifier = cb.FieldModifier.final$
+            ..assignment =
+                cb.Code('$codecName(${classMemberNamePrefix}instanceManager)'),
+        ),
+      for (final Field field in unattachedFields)
+        cb.Field(
+          (cb.FieldBuilder builder) => builder
+            ..name = field.name
+            ..type = cb.refer(_addGenericTypesNullable(field.type))
+            ..modifier = cb.FieldModifier.final$
+            ..docs.addAll(asDocumentationComments(
+              field.documentationComments,
+              _docCommentSpec,
+            )),
+        ),
+      for (final Method method in flutterMethods)
+        cb.Field(
+          (cb.FieldBuilder builder) => builder
+            ..name = method.name
+            ..modifier = cb.FieldModifier.final$
+            ..docs.addAll(asDocumentationComments(
+              <String>[
+                ...method.documentationComments,
+                ...<String>[
+                  if (method.documentationComments.isNotEmpty) '',
+                  'Dart:',
+                  'For the associated Native object to be automatically garbage collected,',
+                  "it is required that the implementation of this `Function` doesn't have a",
+                  'strong reference to the encapsulating class instance. When this `Function`',
+                  'references a non-local variable, it is strongly recommended to access it',
+                  'from a `WeakReference`:',
+                  '',
+                  '```dart',
+                  'final WeakReference weakMyVariable = WeakReference(myVariable);',
+                  'final $apiName instance = $apiName(',
+                  '  ${method.name}: ($apiName ${classMemberNamePrefix}instance, ...) {',
+                  '    print(weakMyVariable?.target);',
+                  '  },',
+                  ');',
+                  '```',
+                  '',
+                  'Alternatively, `$instanceManagerClassName.removeWeakReference` can be used to',
+                  'release the associated Native object manually.',
+                ],
+              ],
+              _docCommentSpec,
+            ))
+            ..type = cb.FunctionType(
+              (cb.FunctionTypeBuilder builder) => builder
+                ..returnType = _refer(
+                  _addGenericTypesNullable(method.returnType),
+                  isFuture: method.isAsynchronous,
+                )
+                ..isNullable = !method.required
+                ..requiredParameters.addAll(<cb.Reference>[
+                  cb.refer('$apiName ${classMemberNamePrefix}instance'),
+                  ...method.parameters.mapIndexed(
+                    (int index, NamedType parameter) {
+                      return cb.refer(
+                        '${_addGenericTypesNullable(parameter.type)} ${_getParameterName(index, parameter)}',
+                      );
+                    },
+                  ),
+                ]),
+            ),
+        ),
+      for (final AstProxyApi proxyApi in interfacesApis)
+        for (final Method method in proxyApi.methods)
+          cb.Field(
+            (cb.FieldBuilder builder) => builder
+              ..name = method.name
+              ..modifier = cb.FieldModifier.final$
+              ..annotations.add(cb.refer('override'))
+              ..docs.addAll(asDocumentationComments(
+                  method.documentationComments, _docCommentSpec))
+              ..type = cb.FunctionType(
+                (cb.FunctionTypeBuilder builder) => builder
+                  ..returnType = _refer(
+                    _addGenericTypesNullable(method.returnType),
+                    isFuture: method.isAsynchronous,
+                  )
+                  ..isNullable = !method.required
+                  ..requiredParameters.addAll(<cb.Reference>[
+                    cb.refer('${proxyApi.name} instance'),
+                    ...method.parameters
+                        .mapIndexed((int index, NamedType parameter) {
+                      return cb.refer(
+                        '${_addGenericTypesNullable(parameter.type)} ${_getParameterName(index, parameter)}',
+                      );
+                    }),
+                  ]),
+              ),
+          ),
+      for (final Field field in attachedFields)
+        cb.Field(
+          (cb.FieldBuilder builder) => builder
+            ..name = field.name
+            ..type = cb.refer(_addGenericTypesNullable(field.type))
+            ..modifier = cb.FieldModifier.final$
+            ..static = field.isStatic
+            ..late = !field.isStatic
+            ..docs.addAll(asDocumentationComments(
+              field.documentationComments,
+              _docCommentSpec,
+            ))
+            ..assignment = cb.Code('$_varNamePrefix${field.name}()'),
+        ),
+    ];
+  }
+
+  Iterable<cb.Method> _proxyApiMethods({
+    required Iterable<Method> hostMethods,
+    required Iterable<Method> flutterMethods,
+    required Iterable<Method> superClassFlutterMethods,
+    required String apiName,
+    required String dartPackageName,
+    required String codecInstanceName,
+    required String codecName,
+    required Iterable<Field> unattachedFields,
+    required Iterable<Field> attachedFields,
+    required Iterable<AstProxyApi> interfacesApis,
+    required bool hasCallbackConstructor,
+  }) {
+    return <cb.Method>[
+      // Flutter methods message handler `*setUpMessageHandlers()`
+      cb.Method.returnsVoid(
+        (cb.MethodBuilder builder) => builder
+          ..name = '${classMemberNamePrefix}setUpMessageHandlers'
+          ..returns = cb.refer('void')
+          ..static = true
+          ..optionalParameters.addAll(<cb.Parameter>[
+            cb.Parameter(
+              (cb.ParameterBuilder builder) => builder
+                ..name = '${classMemberNamePrefix}clearHandlers'
+                ..type = cb.refer('bool')
+                ..named = true
+                ..defaultTo = const cb.Code('false'),
+            ),
+            cb.Parameter(
+              (cb.ParameterBuilder builder) => builder
+                ..name = '${classMemberNamePrefix}binaryMessenger'
+                ..named = true
+                ..type = cb.refer('BinaryMessenger?'),
+            ),
+            cb.Parameter(
+              (cb.ParameterBuilder builder) => builder
+                ..name = '${classMemberNamePrefix}instanceManager'
+                ..named = true
+                ..type = cb.refer('$instanceManagerClassName?'),
+            ),
+            if (hasCallbackConstructor)
+              cb.Parameter(
+                (cb.ParameterBuilder builder) => builder
+                  ..name = '${classMemberNamePrefix}newInstance'
+                  ..named = true
+                  ..type = cb.FunctionType(
+                    (cb.FunctionTypeBuilder builder) => builder
+                      ..returnType = cb.refer(apiName)
+                      ..isNullable = true
+                      ..requiredParameters.addAll(
+                        unattachedFields.mapIndexed(
+                          (int index, Field field) {
+                            return cb.refer(
+                              '${_addGenericTypesNullable(field.type)} ${_getParameterName(index, field)}',
+                            );
+                          },
+                        ),
+                      ),
+                  ),
+              ),
+            for (final Method method in flutterMethods)
+              cb.Parameter(
+                (cb.ParameterBuilder builder) => builder
+                  ..name = method.name
+                  ..type = cb.FunctionType(
+                    (cb.FunctionTypeBuilder builder) => builder
+                      ..returnType = _refer(
+                        _addGenericTypesNullable(method.returnType),
+                        isFuture: method.isAsynchronous,
+                      )
+                      ..isNullable = true
+                      ..requiredParameters.addAll(<cb.Reference>[
+                        cb.refer('$apiName ${classMemberNamePrefix}instance'),
+                        ...method.parameters.mapIndexed(
+                          (int index, NamedType parameter) {
+                            return cb.refer(
+                              '${_addGenericTypesNullable(parameter.type)} ${_getParameterName(index, parameter)}',
+                            );
+                          },
+                        ),
+                      ]),
+                  ),
+              ),
+          ])
+          ..body = cb.Block.of(<cb.Code>[
+            cb.Code(
+              'final $codecName $_pigeonChannelCodec = $codecName(${classMemberNamePrefix}instanceManager ?? $instanceManagerClassName.instance);',
+            ),
+            const cb.Code(
+              'final BinaryMessenger? binaryMessenger = ${classMemberNamePrefix}binaryMessenger;',
+            ),
+            if (hasCallbackConstructor)
+              ...cb.Block((cb.BlockBuilder builder) {
+                final StringBuffer messageHandlerSink = StringBuffer();
+                const String methodName = '${classMemberNamePrefix}newInstance';
+                _writeFlutterMethodMessageHandler(
+                  Indent(messageHandlerSink),
+                  name: methodName,
+                  parameters: <Parameter>[
+                    Parameter(
+                      name: '${classMemberNamePrefix}instanceIdentifier',
+                      type: const TypeDeclaration(
+                        baseName: 'int',
+                        isNullable: false,
+                      ),
+                    ),
+                    ...unattachedFields.map(
+                      (Field field) => Parameter(
+                        name: field.name,
+                        type: field.type,
+                      ),
+                    ),
+                  ],
+                  returnType: const TypeDeclaration.voidDeclaration(),
+                  channelName: makeChannelNameWithStrings(
+                    apiName: apiName,
+                    methodName: methodName,
+                    dartPackageName: dartPackageName,
+                  ),
+                  isMockHandler: false,
+                  isAsynchronous: false,
+                  nullHandlerExpression:
+                      '${classMemberNamePrefix}clearHandlers',
+                  onCreateApiCall: (
+                    String methodName,
+                    Iterable<Parameter> parameters,
+                    Iterable<String> safeArgumentNames,
+                  ) {
+                    final String argsAsNamedParams = map2(
+                      parameters,
+                      safeArgumentNames,
+                      (Parameter parameter, String safeArgName) {
+                        return '${parameter.name}: $safeArgName,\n';
+                      },
+                    ).skip(1).join();
+                    return '(${classMemberNamePrefix}instanceManager ?? $instanceManagerClassName.instance)\n'
+                        '    .addHostCreatedInstance(\n'
+                        '  $methodName?.call(${safeArgumentNames.skip(1).join(',')}) ??\n'
+                        '      $apiName.${classMemberNamePrefix}detached('
+                        '        ${classMemberNamePrefix}binaryMessenger: ${classMemberNamePrefix}binaryMessenger,\n'
+                        '        ${classMemberNamePrefix}instanceManager: ${classMemberNamePrefix}instanceManager,\n'
+                        '        $argsAsNamedParams\n'
+                        '      ),\n'
+                        '  ${safeArgumentNames.first},\n'
+                        ')';
+                  },
+                );
+                builder.statements.add(cb.Code(messageHandlerSink.toString()));
+              }).statements,
+            ...flutterMethods.fold<List<cb.Code>>(
+              <cb.Code>[],
+              (List<cb.Code> list, Method method) {
+                final StringBuffer messageHandlerSink = StringBuffer();
+                _writeFlutterMethodMessageHandler(
+                  Indent(messageHandlerSink),
+                  name: method.name,
+                  parameters: <Parameter>[
+                    Parameter(
+                      name: '${classMemberNamePrefix}instance',
+                      type: TypeDeclaration(
+                        baseName: apiName,
+                        isNullable: false,
+                      ),
+                    ),
+                    ...method.parameters,
+                  ],
+                  returnType: TypeDeclaration(
+                    baseName: method.returnType.baseName,
+                    isNullable:
+                        !method.required || method.returnType.isNullable,
+                    typeArguments: method.returnType.typeArguments,
+                    associatedEnum: method.returnType.associatedEnum,
+                    associatedClass: method.returnType.associatedClass,
+                    associatedProxyApi: method.returnType.associatedProxyApi,
+                  ),
+                  channelName: makeChannelNameWithStrings(
+                    apiName: apiName,
+                    methodName: method.name,
+                    dartPackageName: dartPackageName,
+                  ),
+                  isMockHandler: false,
+                  isAsynchronous: method.isAsynchronous,
+                  nullHandlerExpression:
+                      '${classMemberNamePrefix}clearHandlers',
+                  onCreateApiCall: (
+                    String methodName,
+                    Iterable<Parameter> parameters,
+                    Iterable<String> safeArgumentNames,
+                  ) {
+                    final String nullability = method.required ? '' : '?';
+                    return '($methodName ?? ${safeArgumentNames.first}.$methodName)$nullability.call(${safeArgumentNames.join(',')})';
+                  },
+                );
+                return list..add(cb.Code(messageHandlerSink.toString()));
+              },
+            ),
+          ]),
+      ),
+      for (final Field field in attachedFields)
+        cb.Method(
+          (cb.MethodBuilder builder) {
+            final String type = _addGenericTypesNullable(field.type);
+            const String instanceName = '${_varNamePrefix}instance';
+            const String identifierInstanceName =
+                '${_varNamePrefix}instanceIdentifier';
+            builder
+              ..name = '$_varNamePrefix${field.name}'
+              ..static = field.isStatic
+              ..returns = cb.refer(type)
+              ..body = cb.Block(
+                (cb.BlockBuilder builder) {
+                  final StringBuffer messageCallSink = StringBuffer();
+                  _writeHostMethodMessageCall(
+                    Indent(messageCallSink),
+                    channelName: makeChannelNameWithStrings(
+                      apiName: apiName,
+                      methodName: field.name,
+                      dartPackageName: dartPackageName,
+                    ),
+                    parameters: <Parameter>[
+                      if (!field.isStatic)
+                        Parameter(
+                          name: 'this',
+                          type: TypeDeclaration(
+                            baseName: apiName,
+                            isNullable: false,
+                          ),
+                        ),
+                      Parameter(
+                        name: identifierInstanceName,
+                        type: const TypeDeclaration(
+                          baseName: 'int',
+                          isNullable: false,
+                        ),
+                      ),
+                    ],
+                    returnType: const TypeDeclaration.voidDeclaration(),
+                  );
+                  builder.statements.addAll(<cb.Code>[
+                    if (!field.isStatic) ...<cb.Code>[
+                      cb.Code(
+                        'final $type $instanceName = $type.${classMemberNamePrefix}detached(\n'
+                        '  pigeon_binaryMessenger: pigeon_binaryMessenger,\n'
+                        '  pigeon_instanceManager: pigeon_instanceManager,\n'
+                        ');',
+                      ),
+                      cb.Code('final $codecName $_pigeonChannelCodec =\n'
+                          '    $codecInstanceName;'),
+                      const cb.Code(
+                        'final BinaryMessenger? ${_varNamePrefix}binaryMessenger = ${classMemberNamePrefix}binaryMessenger;',
+                      ),
+                      const cb.Code(
+                        'final int $identifierInstanceName = ${classMemberNamePrefix}instanceManager.addDartCreatedInstance($instanceName);',
+                      ),
+                    ] else ...<cb.Code>[
+                      cb.Code(
+                        'final $type $instanceName = $type.${classMemberNamePrefix}detached();',
+                      ),
+                      cb.Code(
+                        'final $codecName $_pigeonChannelCodec = $codecName($instanceManagerClassName.instance);',
+                      ),
+                      const cb.Code(
+                        'final BinaryMessenger ${_varNamePrefix}binaryMessenger = ServicesBinding.instance.defaultBinaryMessenger;',
+                      ),
+                      const cb.Code(
+                        'final int $identifierInstanceName = $instanceManagerClassName.instance.addDartCreatedInstance($instanceName);',
+                      ),
+                    ],
+                    const cb.Code('() async {'),
+                    cb.Code(messageCallSink.toString()),
+                    const cb.Code('}();'),
+                    const cb.Code('return $instanceName;'),
+                  ]);
+                },
+              );
+          },
+        ),
+      for (final Method method in hostMethods)
+        cb.Method(
+          (cb.MethodBuilder builder) => builder
+            ..name = method.name
+            ..static = method.isStatic
+            ..modifier = cb.MethodModifier.async
+            ..docs.addAll(asDocumentationComments(
+              method.documentationComments,
+              _docCommentSpec,
+            ))
+            ..returns = _refer(
+              _addGenericTypesNullable(method.returnType),
+              isFuture: true,
+            )
+            ..requiredParameters.addAll(
+              method.parameters.mapIndexed(
+                (int index, NamedType parameter) => cb.Parameter(
+                  (cb.ParameterBuilder builder) => builder
+                    ..name = _getParameterName(index, parameter)
+                    ..type = cb.refer(
+                      _addGenericTypesNullable(parameter.type),
+                    ),
+                ),
+              ),
+            )
+            ..optionalParameters.addAll(<cb.Parameter>[
+              if (method.isStatic) ...<cb.Parameter>[
+                cb.Parameter(
+                  (cb.ParameterBuilder builder) => builder
+                    ..name = '${classMemberNamePrefix}binaryMessenger'
+                    ..type = cb.refer('BinaryMessenger?')
+                    ..named = true,
+                ),
+                cb.Parameter(
+                  (cb.ParameterBuilder builder) => builder
+                    ..name = '${classMemberNamePrefix}instanceManager'
+                    ..type = cb.refer('$instanceManagerClassName?'),
+                ),
+              ],
+            ])
+            ..body = cb.Block(
+              (cb.BlockBuilder builder) {
+                final StringBuffer messageCallSink = StringBuffer();
+                _writeHostMethodMessageCall(
+                  Indent(messageCallSink),
+                  channelName: makeChannelNameWithStrings(
+                    apiName: apiName,
+                    methodName: method.name,
+                    dartPackageName: dartPackageName,
+                  ),
+                  parameters: <Parameter>[
+                    if (!method.isStatic)
+                      Parameter(
+                        name: 'this',
+                        type: TypeDeclaration(
+                          baseName: apiName,
+                          isNullable: false,
+                        ),
+                      ),
+                    ...method.parameters,
+                  ],
+                  returnType: method.returnType,
+                );
+                builder.statements.addAll(<cb.Code>[
+                  if (!method.isStatic)
+                    cb.Code('final $codecName $_pigeonChannelCodec =\n'
+                        '    $codecInstanceName;')
+                  else
+                    cb.Code(
+                      'final $codecName $_pigeonChannelCodec = $codecName(${classMemberNamePrefix}instanceManager ?? $instanceManagerClassName.instance);',
+                    ),
+                  const cb.Code(
+                    'final BinaryMessenger? ${_varNamePrefix}binaryMessenger = ${classMemberNamePrefix}binaryMessenger;',
+                  ),
+                  cb.Code(messageCallSink.toString()),
+                ]);
+              },
+            ),
+        ),
+      cb.Method(
+        (cb.MethodBuilder builder) => builder
+          ..name = '${classMemberNamePrefix}copy'
+          ..returns = cb.refer(apiName)
+          ..annotations.add(cb.refer('override'))
+          ..body = cb.Block.of(<cb.Code>[
+            cb
+                .refer('$apiName.${classMemberNamePrefix}detached')
+                .call(
+                  <cb.Expression>[],
+                  <String, cb.Expression>{
+                    '${classMemberNamePrefix}binaryMessenger':
+                        cb.refer('${classMemberNamePrefix}binaryMessenger'),
+                    '${classMemberNamePrefix}instanceManager':
+                        cb.refer('${classMemberNamePrefix}instanceManager'),
+                    for (final Field field in unattachedFields)
+                      field.name: cb.refer(field.name),
+                    for (final Method method in superClassFlutterMethods)
+                      method.name: cb.refer(method.name),
+                    for (final AstProxyApi proxyApi in interfacesApis)
+                      for (final Method method in proxyApi.methods)
+                        method.name: cb.refer(method.name),
+                    for (final Method method in flutterMethods)
+                      method.name: cb.refer(method.name),
+                  },
+                )
+                .returned
+                .statement,
+          ]),
+      ),
+    ];
+  }
+
+  // The base class of all generated ProxyApis.
+  void _writeProxyApiBaseClass(Indent indent) {
+    const String className = '${classNamePrefix}ProxyApiBaseClass';
+    const String messengerVarName = '${classMemberNamePrefix}binaryMessenger';
+    const String instanceManagerVarName =
+        '${classMemberNamePrefix}instanceManager';
+    indent.writeln('''
+/// An immutable object that serves as the base class for all ProxyApis and
+/// can provide functional copies of itself.
+///
+/// All implementers are expected to be [immutable] as defined by the annotation
+/// and override [${classMemberNamePrefix}copy] returning an instance of itself.
+@immutable
+abstract class $className {
+  /// Construct a [$className].
+  $className({
+    this.$messengerVarName,
+    $instanceManagerClassName? $instanceManagerVarName,
+  }) : $instanceManagerVarName =
+            $instanceManagerVarName ?? $instanceManagerClassName.instance;
+
+  /// Sends and receives binary data across the Flutter platform barrier.
+  ///
+  /// If it is null, the default BinaryMessenger will be used, which routes to
+  /// the host platform.
+  final BinaryMessenger? $messengerVarName;
+
+  /// Maintains instances stored to communicate with native language objects.
+  final $instanceManagerClassName $instanceManagerVarName;
+
+  /// Instantiates and returns a functionally identical object to oneself.
+  ///
+  /// Outside of tests, this method should only ever be called by
+  /// [$instanceManagerClassName].
+  ///
+  /// Subclasses should always override their parent's implementation of this
+  /// method.
+  @protected
+  $className ${classMemberNamePrefix}copy();
+}
+''');
+  }
+
   /// Generates Dart source code for test support libraries based on the given AST
   /// represented by [root], outputting the code to [sink]. [sourceOutPath] is the
   /// path of the generated dart code to be tested. [testOutPath] is where the
@@ -641,12 +1728,10 @@ if (${_varNamePrefix}replyList == null) {
       indent.writeln("import 'package:$dartOutputPackageName/$path';");
     }
     for (final Api api in root.apis) {
-      if (api.location == ApiLocation.host && api.dartHostTestHandler != null) {
-        final Api mockApi = Api(
+      if (api is AstHostApi && api.dartHostTestHandler != null) {
+        final AstFlutterApi mockApi = AstFlutterApi(
           name: api.dartHostTestHandler!,
           methods: api.methods,
-          location: ApiLocation.flutter,
-          dartHostTestHandler: api.dartHostTestHandler,
           documentationComments: api.documentationComments,
         );
         writeFlutterApi(
@@ -696,15 +1781,18 @@ if (${_varNamePrefix}replyList == null) {
     Indent indent, {
     required String dartPackageName,
   }) {
-    final bool hasHostApi = root.apis.any((Api api) =>
-        api.methods.isNotEmpty && api.location == ApiLocation.host);
-    final bool hasFlutterApi = root.apis.any((Api api) =>
-        api.methods.isNotEmpty && api.location == ApiLocation.flutter);
+    final bool hasHostApi = root.apis
+        .whereType<AstHostApi>()
+        .any((Api api) => api.methods.isNotEmpty);
+    final bool hasFlutterApi = root.apis
+        .whereType<AstFlutterApi>()
+        .any((Api api) => api.methods.isNotEmpty);
+    final bool hasProxyApi = root.apis.any((Api api) => api is AstProxyApi);
 
-    if (hasHostApi) {
+    if (hasHostApi || hasProxyApi) {
       _writeCreateConnectionError(indent);
     }
-    if (hasFlutterApi) {
+    if (hasFlutterApi || hasProxyApi) {
       _writeWrapResponse(generatorOptions, root, indent);
     }
   }
@@ -736,6 +1824,249 @@ PlatformException _createConnectionError(String channelName) {
 \t);
 }''');
   }
+
+  void _writeHostMethod(
+    Indent indent, {
+    required String name,
+    required Iterable<Parameter> parameters,
+    required TypeDeclaration returnType,
+    required List<String> documentationComments,
+    required String channelName,
+  }) {
+    addDocumentationComments(indent, documentationComments, _docCommentSpec);
+    String argSignature = '';
+    if (parameters.isNotEmpty) {
+      argSignature = _getMethodParameterSignature(parameters);
+    }
+    indent.write(
+      'Future<${_addGenericTypesNullable(returnType)}> $name($argSignature) async ',
+    );
+    indent.addScoped('{', '}', () {
+      _writeHostMethodMessageCall(
+        indent,
+        channelName: channelName,
+        parameters: parameters,
+        returnType: returnType,
+      );
+    });
+  }
+
+  void _writeHostMethodMessageCall(
+    Indent indent, {
+    required String channelName,
+    required Iterable<Parameter> parameters,
+    required TypeDeclaration returnType,
+  }) {
+    String sendArgument = 'null';
+    if (parameters.isNotEmpty) {
+      final Iterable<String> argExpressions =
+          parameters.mapIndexed((int index, NamedType type) {
+        final String name = _getParameterName(index, type);
+        if (type.type.isEnum) {
+          return '$name${type.type.isNullable ? '?' : ''}.index';
+        } else {
+          return name;
+        }
+      });
+      sendArgument = '<Object?>[${argExpressions.join(', ')}]';
+    }
+
+    indent
+        .writeln("const String ${_varNamePrefix}channelName = '$channelName';");
+    indent.writeScoped(
+        'final BasicMessageChannel<Object?> ${_varNamePrefix}channel = BasicMessageChannel<Object?>(',
+        ');', () {
+      indent.writeln('${_varNamePrefix}channelName,');
+      indent.writeln('$_pigeonChannelCodec,');
+      indent.writeln('binaryMessenger: ${_varNamePrefix}binaryMessenger,');
+    });
+    final String returnTypeName = _makeGenericTypeArguments(returnType);
+    final String genericCastCall = _makeGenericCastCall(returnType);
+    const String accessor = '${_varNamePrefix}replyList[0]';
+    // Avoid warnings from pointlessly casting to `Object?`.
+    final String nullablyTypedAccessor = returnTypeName == 'Object'
+        ? accessor
+        : '($accessor as $returnTypeName?)';
+    final String nullHandler =
+        returnType.isNullable ? (genericCastCall.isEmpty ? '' : '?') : '!';
+    String returnStatement = 'return';
+    if (returnType.isEnum) {
+      if (returnType.isNullable) {
+        returnStatement =
+            '$returnStatement ($accessor as int?) == null ? null : $returnTypeName.values[$accessor! as int]';
+      } else {
+        returnStatement =
+            '$returnStatement $returnTypeName.values[$accessor! as int]';
+      }
+    } else if (!returnType.isVoid) {
+      returnStatement =
+          '$returnStatement $nullablyTypedAccessor$nullHandler$genericCastCall';
+    }
+    returnStatement = '$returnStatement;';
+
+    indent.format('''
+final List<Object?>? ${_varNamePrefix}replyList =
+\t\tawait ${_varNamePrefix}channel.send($sendArgument) as List<Object?>?;
+if (${_varNamePrefix}replyList == null) {
+\tthrow _createConnectionError(${_varNamePrefix}channelName);
+} else if (${_varNamePrefix}replyList.length > 1) {
+\tthrow PlatformException(
+\t\tcode: ${_varNamePrefix}replyList[0]! as String,
+\t\tmessage: ${_varNamePrefix}replyList[1] as String?,
+\t\tdetails: ${_varNamePrefix}replyList[2],
+\t);''');
+    // On iOS we can return nil from functions to accommodate error
+    // handling.  Returning a nil value and not returning an error is an
+    // exception.
+    if (!returnType.isNullable && !returnType.isVoid) {
+      indent.format('''
+} else if (${_varNamePrefix}replyList[0] == null) {
+\tthrow PlatformException(
+\t\tcode: 'null-error',
+\t\tmessage: 'Host platform returned null value for non-null return value.',
+\t);''');
+    }
+    indent.format('''
+} else {
+\t$returnStatement
+}''');
+  }
+
+  void _writeFlutterMethodMessageHandler(
+    Indent indent, {
+    required String name,
+    required Iterable<Parameter> parameters,
+    required TypeDeclaration returnType,
+    required String channelName,
+    required bool isMockHandler,
+    required bool isAsynchronous,
+    String nullHandlerExpression = 'api == null',
+    String Function(String methodName, Iterable<Parameter> parameters,
+            Iterable<String> safeArgumentNames)
+        onCreateApiCall = _createFlutterApiMethodCall,
+  }) {
+    indent.write('');
+    indent.addScoped('{', '}', () {
+      indent.writeln(
+        'final BasicMessageChannel<Object?> ${_varNamePrefix}channel = BasicMessageChannel<Object?>(',
+      );
+      indent.nest(2, () {
+        indent.writeln("'$channelName', $_pigeonChannelCodec,");
+        indent.writeln(
+          'binaryMessenger: binaryMessenger);',
+        );
+      });
+      final String messageHandlerSetterWithOpeningParentheses = isMockHandler
+          ? '_testBinaryMessengerBinding!.defaultBinaryMessenger.setMockDecodedMessageHandler<Object?>(${_varNamePrefix}channel, '
+          : '${_varNamePrefix}channel.setMessageHandler(';
+      indent.write('if ($nullHandlerExpression) ');
+      indent.addScoped('{', '}', () {
+        indent.writeln('${messageHandlerSetterWithOpeningParentheses}null);');
+      }, addTrailingNewline: false);
+      indent.add(' else ');
+      indent.addScoped('{', '}', () {
+        indent.write(
+          '$messageHandlerSetterWithOpeningParentheses(Object? message) async ',
+        );
+        indent.addScoped('{', '});', () {
+          final String returnTypeString = _addGenericTypesNullable(returnType);
+          final bool isAsync = isAsynchronous;
+          const String emptyReturnStatement =
+              'return wrapResponse(empty: true);';
+          String call;
+          if (parameters.isEmpty) {
+            call = 'api.$name()';
+          } else {
+            indent.writeln('assert(message != null,');
+            indent.writeln("'Argument for $channelName was null.');");
+            const String argsArray = 'args';
+            indent.writeln(
+                'final List<Object?> $argsArray = (message as List<Object?>?)!;');
+            String argNameFunc(int index, NamedType type) =>
+                _getSafeArgumentName(index, type);
+            parameters.forEachIndexed((int count, NamedType arg) {
+              final String argType = _addGenericTypes(arg.type);
+              final String argName = argNameFunc(count, arg);
+              final String genericArgType = _makeGenericTypeArguments(arg.type);
+              final String castCall = _makeGenericCastCall(arg.type);
+
+              final String leftHandSide = 'final $argType? $argName';
+              if (arg.type.isEnum) {
+                indent.writeln(
+                    '$leftHandSide = $argsArray[$count] == null ? null : $argType.values[$argsArray[$count]! as int];');
+              } else {
+                indent.writeln(
+                    '$leftHandSide = ($argsArray[$count] as $genericArgType?)${castCall.isEmpty ? '' : '?$castCall'};');
+              }
+              if (!arg.type.isNullable) {
+                indent.writeln('assert($argName != null,');
+                indent.writeln(
+                    "    'Argument for $channelName was null, expected non-null $argType.');");
+              }
+            });
+            final Iterable<String> argNames =
+                parameters.mapIndexed((int index, Parameter field) {
+              final String name = _getSafeArgumentName(index, field);
+              return '${field.isNamed ? '${field.name}: ' : ''}$name${field.type.isNullable ? '' : '!'}';
+            });
+            call = onCreateApiCall(name, parameters, argNames);
+          }
+          indent.writeScoped('try {', '} ', () {
+            if (returnType.isVoid) {
+              if (isAsync) {
+                indent.writeln('await $call;');
+              } else {
+                indent.writeln('$call;');
+              }
+              indent.writeln(emptyReturnStatement);
+            } else {
+              if (isAsync) {
+                indent.writeln('final $returnTypeString output = await $call;');
+              } else {
+                indent.writeln('final $returnTypeString output = $call;');
+              }
+
+              const String returnExpression = 'output';
+              final String nullability = returnType.isNullable ? '?' : '';
+              final String valueExtraction =
+                  returnType.isEnum ? '$nullability.index' : '';
+              final String returnStatement = isMockHandler
+                  ? 'return <Object?>[$returnExpression$valueExtraction];'
+                  : 'return wrapResponse(result: $returnExpression$valueExtraction);';
+              indent.writeln(returnStatement);
+            }
+          }, addTrailingNewline: false);
+          indent.addScoped('on PlatformException catch (e) {', '}', () {
+            indent.writeln('return wrapResponse(error: e);');
+          }, addTrailingNewline: false);
+
+          indent.writeScoped('catch (e) {', '}', () {
+            indent.writeln(
+                "return wrapResponse(error: PlatformException(code: 'error', message: e.toString()));");
+          });
+        });
+      });
+    });
+  }
+
+  static String _createFlutterApiMethodCall(
+    String methodName,
+    Iterable<Parameter> parameters,
+    Iterable<String> safeArgumentNames,
+  ) {
+    return 'api.$methodName(${safeArgumentNames.join(', ')})';
+  }
+}
+
+cb.Reference _refer(
+  String symbol, {
+  bool isFuture = false,
+  bool isNullable = false,
+}) {
+  final String nullability = isNullable ? '?' : '';
+  return cb.refer(
+    isFuture ? 'Future<$symbol$nullability>' : '$symbol$nullability',
+  );
 }
 
 String _escapeForDartSingleQuotedString(String raw) {
@@ -762,7 +2093,8 @@ void _writeCodec(Indent indent, String codecName, Api api, Root root) {
     indent.writeln('@override');
     indent.write('void writeValue(WriteBuffer buffer, Object? value) ');
     indent.addScoped('{', '}', () {
-      enumerate(codecClasses, (int index, final EnumeratedClass customClass) {
+      codecClasses
+          .forEachIndexed((int index, final EnumeratedClass customClass) {
         final String ifValue = 'if (value is ${customClass.name}) ';
         if (index == 0) {
           indent.write('');
@@ -824,20 +2156,20 @@ String _getParameterName(int count, NamedType field) =>
 
 /// Generates the parameters code for [func]
 /// Example: (func, _getParameterName) -> 'String? foo, int bar'
-String _getMethodParameterSignature(Method func) {
+String _getMethodParameterSignature(Iterable<Parameter> parameters) {
   String signature = '';
-  if (func.parameters.isEmpty) {
+  if (parameters.isEmpty) {
     return signature;
   }
 
-  final List<Parameter> requiredPositionalParams = func.parameters
+  final List<Parameter> requiredPositionalParams = parameters
       .where((Parameter p) => p.isPositional && !p.isOptional)
       .toList();
-  final List<Parameter> optionalPositionalParams = func.parameters
+  final List<Parameter> optionalPositionalParams = parameters
       .where((Parameter p) => p.isPositional && p.isOptional)
       .toList();
   final List<Parameter> namedParams =
-      func.parameters.where((Parameter p) => !p.isPositional).toList();
+      parameters.where((Parameter p) => !p.isPositional).toList();
 
   String getParameterString(Parameter p) {
     final String required = p.isRequired && !p.isPositional ? 'required ' : '';
diff --git a/packages/pigeon/lib/functional.dart b/packages/pigeon/lib/functional.dart
index 8e23950e9e70..59e477783c3a 100644
--- a/packages/pigeon/lib/functional.dart
+++ b/packages/pigeon/lib/functional.dart
@@ -2,26 +2,6 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-/// A [map] function that calls the function with an enumeration as well as the
-/// value.
-Iterable<U> indexMap<T, U>(
-    Iterable<T> iterable, U Function(int index, T value) func) sync* {
-  int index = 0;
-  for (final T value in iterable) {
-    yield func(index, value);
-    ++index;
-  }
-}
-
-/// Performs like [forEach] but invokes [func] with an enumeration.
-void enumerate<T>(Iterable<T> iterable, void Function(int, T) func) {
-  int count = 0;
-  for (final T value in iterable) {
-    func(count, value);
-    ++count;
-  }
-}
-
 /// A [map] function that takes in 2 iterables.  The [Iterable]s must be of
 /// equal length.
 Iterable<V> map2<T, U, V>(
diff --git a/packages/pigeon/lib/generator.dart b/packages/pigeon/lib/generator.dart
index 1bd083078745..3711fd28dbe3 100644
--- a/packages/pigeon/lib/generator.dart
+++ b/packages/pigeon/lib/generator.dart
@@ -63,6 +63,24 @@ abstract class StructuredGenerator<T> extends Generator<T> {
       dartPackageName: dartPackageName,
     );
 
+    if (root.apis.any((Api api) => api is AstProxyApi)) {
+      writeInstanceManager(
+        generatorOptions,
+        root,
+        indent,
+        dartPackageName: dartPackageName,
+      );
+
+      writeInstanceManagerApi(
+        generatorOptions,
+        root,
+        indent,
+        dartPackageName: dartPackageName,
+      );
+
+      writeProxyApiBaseCodec(generatorOptions, root, indent);
+    }
+
     writeEnums(
       generatorOptions,
       root,
@@ -224,22 +242,31 @@ abstract class StructuredGenerator<T> extends Generator<T> {
     required String dartPackageName,
   }) {
     for (final Api api in root.apis) {
-      if (api.location == ApiLocation.host) {
-        writeHostApi(
-          generatorOptions,
-          root,
-          indent,
-          api,
-          dartPackageName: dartPackageName,
-        );
-      } else if (api.location == ApiLocation.flutter) {
-        writeFlutterApi(
-          generatorOptions,
-          root,
-          indent,
-          api,
-          dartPackageName: dartPackageName,
-        );
+      switch (api) {
+        case AstHostApi():
+          writeHostApi(
+            generatorOptions,
+            root,
+            indent,
+            api,
+            dartPackageName: dartPackageName,
+          );
+        case AstFlutterApi():
+          writeFlutterApi(
+            generatorOptions,
+            root,
+            indent,
+            api,
+            dartPackageName: dartPackageName,
+          );
+        case AstProxyApi():
+          writeProxyApi(
+            generatorOptions,
+            root,
+            indent,
+            api,
+            dartPackageName: dartPackageName,
+          );
       }
     }
   }
@@ -249,7 +276,7 @@ abstract class StructuredGenerator<T> extends Generator<T> {
     T generatorOptions,
     Root root,
     Indent indent,
-    Api api, {
+    AstFlutterApi api, {
     required String dartPackageName,
   });
 
@@ -258,7 +285,49 @@ abstract class StructuredGenerator<T> extends Generator<T> {
     T generatorOptions,
     Root root,
     Indent indent,
-    Api api, {
+    AstHostApi api, {
     required String dartPackageName,
   });
+
+  /// Writes the implementation of an `InstanceManager` to [indent].
+  void writeInstanceManager(
+    T generatorOptions,
+    Root root,
+    Indent indent, {
+    required String dartPackageName,
+  }) {}
+
+  /// Writes the implementation of the API for the `InstanceManager` to
+  /// [indent].
+  void writeInstanceManagerApi(
+    T generatorOptions,
+    Root root,
+    Indent indent, {
+    required String dartPackageName,
+  }) {}
+
+  /// Writes the base codec to be used by all ProxyApis.
+  ///
+  /// This codec should use `128` as the identifier for objects that exist in
+  /// an `InstanceManager`. The write implementation should convert an instance
+  /// to an identifier. The read implementation should covert the identifier
+  /// to an instance.
+  ///
+  /// This will serve as the default codec for all ProxyApis. If a ProxyApi
+  /// needs to create its own codec (it has methods/fields/constructor that use
+  /// a data class) it should extend this codec and not `StandardMessageCodec`.
+  void writeProxyApiBaseCodec(
+    T generatorOptions,
+    Root root,
+    Indent indent,
+  ) {}
+
+  /// Writes a single Proxy Api to [indent].
+  void writeProxyApi(
+    T generatorOptions,
+    Root root,
+    Indent indent,
+    AstProxyApi api, {
+    required String dartPackageName,
+  }) {}
 }
diff --git a/packages/pigeon/lib/generator_tools.dart b/packages/pigeon/lib/generator_tools.dart
index ba32f720a2a0..f3fe858fe525 100644
--- a/packages/pigeon/lib/generator_tools.dart
+++ b/packages/pigeon/lib/generator_tools.dart
@@ -13,7 +13,7 @@ import 'ast.dart';
 /// The current version of pigeon.
 ///
 /// This must match the version in pubspec.yaml.
-const String pigeonVersion = '16.0.0';
+const String pigeonVersion = '16.0.1';
 
 /// Read all the content from [stdin] to a String.
 String readStdin() {
@@ -164,9 +164,22 @@ class Indent {
   }
 }
 
-/// Create the generated channel name for a [func] on a [api].
-String makeChannelName(Api api, Method func, String dartPackageName) {
-  return 'dev.flutter.pigeon.$dartPackageName.${api.name}.${func.name}';
+/// Create the generated channel name for a [method] on an [api].
+String makeChannelName(Api api, Method method, String dartPackageName) {
+  return makeChannelNameWithStrings(
+    apiName: api.name,
+    methodName: method.name,
+    dartPackageName: dartPackageName,
+  );
+}
+
+/// Create the generated channel name for a method on an api.
+String makeChannelNameWithStrings({
+  required String apiName,
+  required String methodName,
+  required String dartPackageName,
+}) {
+  return 'dev.flutter.pigeon.$dartPackageName.$apiName.$methodName';
 }
 
 // TODO(tarrinneal): Determine whether HostDataType is needed.
@@ -282,6 +295,24 @@ String getGeneratedCodeWarning() {
 /// String to be printed after `getGeneratedCodeWarning()'s warning`.
 const String seeAlsoWarning = 'See also: https://pub.dev/packages/pigeon';
 
+/// Prefix for utility classes generated for ProxyApis.
+///
+/// This lowers the chances of variable name collisions with user defined
+/// parameters.
+const String classNamePrefix = 'Pigeon_';
+
+/// Name for the generated InstanceManager for ProxyApis.
+///
+/// This lowers the chances of variable name collisions with user defined
+/// parameters.
+const String instanceManagerClassName = '${classNamePrefix}InstanceManager';
+
+/// Prefix for class member names not defined by the user.
+///
+/// This lowers the chances of variable name collisions with user defined
+/// parameters.
+const String classMemberNamePrefix = 'pigeon_';
+
 /// Collection of keys used in dictionaries across generators.
 class Keys {
   /// The key in the result hash for the 'result' value.
@@ -313,37 +344,6 @@ void addLines(Indent indent, Iterable<String> lines, {String? linePrefix}) {
   }
 }
 
-/// Recursively merges [modification] into [base].
-///
-/// In other words, whenever there is a conflict over the value of a key path,
-/// [modification]'s value for that key path is selected.
-Map<String, Object> mergeMaps(
-  Map<String, Object> base,
-  Map<String, Object> modification,
-) {
-  final Map<String, Object> result = <String, Object>{};
-  for (final MapEntry<String, Object> entry in modification.entries) {
-    if (base.containsKey(entry.key)) {
-      final Object entryValue = entry.value;
-      if (entryValue is Map<String, Object>) {
-        assert(base[entry.key] is Map<String, Object>);
-        result[entry.key] =
-            mergeMaps((base[entry.key] as Map<String, Object>?)!, entryValue);
-      } else {
-        result[entry.key] = entry.value;
-      }
-    } else {
-      result[entry.key] = entry.value;
-    }
-  }
-  for (final MapEntry<String, Object> entry in base.entries) {
-    if (!result.containsKey(entry.key)) {
-      result[entry.key] = entry.value;
-    }
-  }
-  return result;
-}
-
 /// A class name that is enumerated.
 class EnumeratedClass {
   /// Constructor.
@@ -510,6 +510,23 @@ void addDocumentationComments(
   DocumentCommentSpecification commentSpec, {
   List<String> generatorComments = const <String>[],
 }) {
+  asDocumentationComments(
+    comments,
+    commentSpec,
+    generatorComments: generatorComments,
+  ).forEach(indent.writeln);
+}
+
+/// Formats documentation comments and adds them to current Indent.
+///
+/// The [comments] list is meant for comments written in the input dart file.
+/// The [generatorComments] list is meant for comments added by the generators.
+/// Include white space for all tokens when called, no assumptions are made.
+Iterable<String> asDocumentationComments(
+  Iterable<String> comments,
+  DocumentCommentSpecification commentSpec, {
+  List<String> generatorComments = const <String>[],
+}) sync* {
   final List<String> allComments = <String>[
     ...comments,
     if (comments.isNotEmpty && generatorComments.isNotEmpty) '',
@@ -518,24 +535,20 @@ void addDocumentationComments(
   String currentLineOpenToken = commentSpec.openCommentToken;
   if (allComments.length > 1) {
     if (commentSpec.closeCommentToken != '') {
-      indent.writeln(commentSpec.openCommentToken);
+      yield commentSpec.openCommentToken;
       currentLineOpenToken = commentSpec.blockContinuationToken;
     }
     for (String line in allComments) {
       if (line.isNotEmpty && line[0] != ' ') {
         line = ' $line';
       }
-      indent.writeln(
-        '$currentLineOpenToken$line',
-      );
+      yield '$currentLineOpenToken$line';
     }
     if (commentSpec.closeCommentToken != '') {
-      indent.writeln(commentSpec.closeCommentToken);
+      yield commentSpec.closeCommentToken;
     }
   } else if (allComments.length == 1) {
-    indent.writeln(
-      '$currentLineOpenToken${allComments.first}${commentSpec.closeCommentToken}',
-    );
+    yield '$currentLineOpenToken${allComments.first}${commentSpec.closeCommentToken}';
   }
 }
 
@@ -609,6 +622,88 @@ enum FileType {
   na,
 }
 
+/// Recursively search for all the interfaces apis from a list of names of
+/// interfaces.
+///
+/// This method assumes that all interfaces names can be found in
+/// [allProxyApis]. Otherwise, throws an [ArgumentError].
+Set<AstProxyApi> recursiveFindAllInterfacesApis(
+  AstProxyApi api,
+  Iterable<AstProxyApi> allProxyApis,
+) {
+  final Set<AstProxyApi> interfacesApis = <AstProxyApi>{};
+
+  for (final AstProxyApi proxyApi in allProxyApis) {
+    if (api.interfacesNames.contains(proxyApi.name)) {
+      interfacesApis.add(proxyApi);
+    }
+  }
+
+  if (interfacesApis.length != api.interfacesNames.length) {
+    throw ArgumentError(
+      'Could not find a ProxyApi for every interface name: '
+      '${api.interfacesNames}, ${allProxyApis.map((Api api) => api.name)}',
+    );
+  }
+
+  for (final AstProxyApi proxyApi in Set<AstProxyApi>.from(interfacesApis)) {
+    interfacesApis.addAll(
+      recursiveFindAllInterfacesApis(proxyApi, allProxyApis),
+    );
+  }
+
+  return interfacesApis;
+}
+
+/// Creates a list of ProxyApis where each `extends` the ProxyApi that follows
+/// it.
+///
+/// Returns an empty list if [proxyApi] does not extend a ProxyApi.
+///
+/// This method assumes the super classes of each ProxyApi doesn't create a
+/// loop. Throws a [ArgumentError] if a loop is found.
+///
+/// This method also assumes that all super class names can be found in
+/// [allProxyApis]. Otherwise, throws an [ArgumentError].
+List<AstProxyApi> recursiveGetSuperClassApisChain(
+  AstProxyApi proxyApi,
+  Iterable<AstProxyApi> allProxyApis,
+) {
+  final List<AstProxyApi> proxyApis = <AstProxyApi>[];
+
+  String? currentProxyApiName = proxyApi.superClassName;
+  while (currentProxyApiName != null) {
+    if (proxyApis.length > allProxyApis.length) {
+      final Iterable<String> apiNames = proxyApis.map(
+        (AstProxyApi api) => api.name,
+      );
+      throw ArgumentError(
+        'Loop found when processing super classes for a ProxyApi: '
+        '${proxyApi.name},${apiNames.join(',')}',
+      );
+    }
+
+    AstProxyApi? nextProxyApi;
+    for (final AstProxyApi node in allProxyApis) {
+      if (currentProxyApiName == node.name) {
+        nextProxyApi = node;
+        proxyApis.add(node);
+      }
+    }
+
+    if (nextProxyApi == null) {
+      throw ArgumentError(
+        'Could not find a ProxyApi for every super class name: '
+        '$currentProxyApiName, ${allProxyApis.map((Api api) => api.name)}',
+      );
+    }
+
+    currentProxyApiName = nextProxyApi.superClassName;
+  }
+
+  return proxyApis;
+}
+
 /// Options for [Generator]s that have multiple output file types.
 ///
 /// Specifies which file to write as well as wraps all language options.
diff --git a/packages/pigeon/lib/java_generator.dart b/packages/pigeon/lib/java_generator.dart
index 43b42c40e909..7a8a0fc65552 100644
--- a/packages/pigeon/lib/java_generator.dart
+++ b/packages/pigeon/lib/java_generator.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'package:collection/collection.dart';
+
 import 'ast.dart';
 import 'functional.dart';
 import 'generator.dart';
@@ -183,7 +185,7 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
 
     indent.write('public enum ${anEnum.name} ');
     indent.addScoped('{', '}', () {
-      enumerate(anEnum.members, (int index, final EnumMember member) {
+      anEnum.members.forEachIndexed((int index, final EnumMember member) {
         addDocumentationComments(
             indent, member.documentationComments, _docCommentSpec);
         indent.writeln(
@@ -369,8 +371,8 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
       const String result = 'pigeonResult';
       indent.writeln(
           '${classDefinition.name} $result = new ${classDefinition.name}();');
-      enumerate(getFieldsInSerializationOrder(classDefinition),
-          (int index, final NamedType field) {
+      getFieldsInSerializationOrder(classDefinition)
+          .forEachIndexed((int index, final NamedType field) {
         final String fieldVariable = field.name;
         final String setter = _makeSetter(field);
         indent.writeln('Object $fieldVariable = list.get($index);');
@@ -400,7 +402,7 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
     JavaOptions generatorOptions,
     Root root,
     Indent indent,
-    Api api, {
+    AstFlutterApi api, {
     required String dartPackageName,
   }) {
     /// Returns an argument name that can be used in a context where it is possible to collide
@@ -414,7 +416,6 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
       return '${_getArgumentName(count, argument)}Arg';
     }
 
-    assert(api.location == ApiLocation.flutter);
     if (getCodecClasses(api, root).isNotEmpty) {
       _writeCodec(indent, api, root);
     }
@@ -463,9 +464,9 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
           final Iterable<String> argTypes = func.parameters
               .map((NamedType e) => _nullsafeJavaTypeForDartType(e.type));
           final Iterable<String> argNames =
-              indexMap(func.parameters, _getSafeArgumentName);
+              func.parameters.mapIndexed(_getSafeArgumentName);
           final Iterable<String> enumSafeArgNames =
-              indexMap(func.parameters, getEnumSafeArgumentExpression);
+              func.parameters.mapIndexed(getEnumSafeArgumentExpression);
           if (func.parameters.length == 1) {
             sendArgument =
                 'new ArrayList<Object>(Collections.singletonList(${enumSafeArgNames.first}))';
@@ -556,9 +557,9 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
     required String dartPackageName,
   }) {
     if (root.apis.any((Api api) =>
-        api.location == ApiLocation.host &&
+        api is AstHostApi &&
             api.methods.any((Method it) => it.isAsynchronous) ||
-        api.location == ApiLocation.flutter)) {
+        api is AstFlutterApi)) {
       indent.newln();
       _writeResultInterfaces(indent);
     }
@@ -577,10 +578,9 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
     JavaOptions generatorOptions,
     Root root,
     Indent indent,
-    Api api, {
+    AstHostApi api, {
     required String dartPackageName,
   }) {
-    assert(api.location == ApiLocation.host);
     if (getCodecClasses(api, root).isNotEmpty) {
       _writeCodec(indent, api, root);
     }
@@ -713,7 +713,7 @@ class JavaGenerator extends StructuredGenerator<JavaOptions> {
             if (method.parameters.isNotEmpty) {
               indent.writeln(
                   'ArrayList<Object> args = (ArrayList<Object>) message;');
-              enumerate(method.parameters, (int index, NamedType arg) {
+              method.parameters.forEachIndexed((int index, NamedType arg) {
                 // The StandardMessageCodec can give us [Integer, Long] for
                 // a Dart 'int'.  To keep things simple we just use 64bit
                 // longs in Pigeon with Java.
@@ -979,10 +979,12 @@ protected static ArrayList<Object> wrapError(@NonNull Throwable exception) {
     Indent indent, {
     required String dartPackageName,
   }) {
-    final bool hasHostApi = root.apis.any((Api api) =>
-        api.methods.isNotEmpty && api.location == ApiLocation.host);
-    final bool hasFlutterApi = root.apis.any((Api api) =>
-        api.methods.isNotEmpty && api.location == ApiLocation.flutter);
+    final bool hasHostApi = root.apis
+        .whereType<AstHostApi>()
+        .any((Api api) => api.methods.isNotEmpty);
+    final bool hasFlutterApi = root.apis
+        .whereType<AstFlutterApi>()
+        .any((Api api) => api.methods.isNotEmpty);
 
     indent.newln();
     _writeErrorClass(indent);
diff --git a/packages/pigeon/lib/kotlin_generator.dart b/packages/pigeon/lib/kotlin_generator.dart
index 88ffb487406e..d0a0ccb06cec 100644
--- a/packages/pigeon/lib/kotlin_generator.dart
+++ b/packages/pigeon/lib/kotlin_generator.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'package:collection/collection.dart';
+
 import 'ast.dart';
 import 'functional.dart';
 import 'generator.dart';
@@ -124,7 +126,7 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
         indent, anEnum.documentationComments, _docCommentSpec);
     indent.write('enum class ${anEnum.name}(val raw: Int) ');
     indent.addScoped('{', '}', () {
-      enumerate(anEnum.members, (int index, final EnumMember member) {
+      anEnum.members.forEachIndexed((int index, final EnumMember member) {
         addDocumentationComments(
             indent, member.documentationComments, _docCommentSpec);
         indent.write('${member.name.toUpperCase()}($index)');
@@ -240,8 +242,8 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
       indent.write('fun fromList(list: List<Any?>): $className ');
 
       indent.addScoped('{', '}', () {
-        enumerate(getFieldsInSerializationOrder(classDefinition),
-            (int index, final NamedType field) {
+        getFieldsInSerializationOrder(classDefinition)
+            .forEachIndexed((int index, final NamedType field) {
           final String listValue = 'list[$index]';
           final String fieldType = _kotlinTypeForDartType(field.type);
 
@@ -307,7 +309,7 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
     required String dartPackageName,
   }) {
     if (root.apis.any((Api api) =>
-        api.location == ApiLocation.host &&
+        api is AstHostApi &&
         api.methods.any((Method it) => it.isAsynchronous))) {
       indent.newln();
     }
@@ -325,10 +327,9 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
     KotlinOptions generatorOptions,
     Root root,
     Indent indent,
-    Api api, {
+    AstFlutterApi api, {
     required String dartPackageName,
   }) {
-    assert(api.location == ApiLocation.flutter);
     final bool isCustomCodec = getCodecClasses(api, root).isNotEmpty;
     if (isCustomCodec) {
       _writeCodec(indent, api, root);
@@ -376,9 +377,8 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
           final Iterable<String> argTypes = func.parameters
               .map((NamedType e) => _nullsafeKotlinTypeForDartType(e.type));
           final Iterable<String> argNames =
-              indexMap(func.parameters, _getSafeArgumentName);
-          final Iterable<String> enumSafeArgNames = indexMap(
-              func.parameters,
+              func.parameters.mapIndexed(_getSafeArgumentName);
+          final Iterable<String> enumSafeArgNames = func.parameters.mapIndexed(
               (int count, NamedType type) =>
                   _getEnumSafeArgumentExpression(count, type));
           sendArgument = 'listOf(${enumSafeArgNames.join(', ')})';
@@ -448,11 +448,9 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
     KotlinOptions generatorOptions,
     Root root,
     Indent indent,
-    Api api, {
+    AstHostApi api, {
     required String dartPackageName,
   }) {
-    assert(api.location == ApiLocation.host);
-
     final String apiName = api.name;
 
     final bool isCustomCodec = getCodecClasses(api, root).isNotEmpty;
@@ -551,7 +549,8 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
                   final List<String> methodArguments = <String>[];
                   if (method.parameters.isNotEmpty) {
                     indent.writeln('val args = message as List<Any?>');
-                    enumerate(method.parameters, (int index, NamedType arg) {
+                    method.parameters
+                        .forEachIndexed((int index, NamedType arg) {
                       final String argName = _getSafeArgumentName(index, arg);
                       final String argIndex = 'args[$index]';
                       indent.writeln(
@@ -742,10 +741,12 @@ class KotlinGenerator extends StructuredGenerator<KotlinOptions> {
     Indent indent, {
     required String dartPackageName,
   }) {
-    final bool hasHostApi = root.apis.any((Api api) =>
-        api.methods.isNotEmpty && api.location == ApiLocation.host);
-    final bool hasFlutterApi = root.apis.any((Api api) =>
-        api.methods.isNotEmpty && api.location == ApiLocation.flutter);
+    final bool hasHostApi = root.apis
+        .whereType<AstHostApi>()
+        .any((Api api) => api.methods.isNotEmpty);
+    final bool hasFlutterApi = root.apis
+        .whereType<AstFlutterApi>()
+        .any((Api api) => api.methods.isNotEmpty);
 
     if (hasHostApi) {
       _writeWrapResult(indent);
diff --git a/packages/pigeon/lib/objc_generator.dart b/packages/pigeon/lib/objc_generator.dart
index 903957d083c2..378393b46dc0 100644
--- a/packages/pigeon/lib/objc_generator.dart
+++ b/packages/pigeon/lib/objc_generator.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'package:collection/collection.dart';
+
 import 'ast.dart';
 import 'functional.dart';
 import 'generator.dart';
@@ -149,7 +151,7 @@ class ObjcHeaderGenerator extends StructuredGenerator<ObjcOptions> {
 
     indent.write('typedef NS_ENUM(NSUInteger, $enumName) ');
     indent.addScoped('{', '};', () {
-      enumerate(anEnum.members, (int index, final EnumMember member) {
+      anEnum.members.forEachIndexed((int index, final EnumMember member) {
         addDocumentationComments(
             indent, member.documentationComments, _docCommentSpec);
         // Capitalized first letter to ensure Swift compatibility
@@ -572,8 +574,8 @@ class ObjcSourceGenerator extends StructuredGenerator<ObjcOptions> {
     indent.addScoped('{', '}', () {
       const String resultName = 'pigeonResult';
       indent.writeln('$className *$resultName = [[$className alloc] init];');
-      enumerate(getFieldsInSerializationOrder(classDefinition),
-          (int index, final NamedType field) {
+      getFieldsInSerializationOrder(classDefinition)
+          .forEachIndexed((int index, final NamedType field) {
         final bool isEnumType = field.type.isEnum;
         final String valueGetter =
             _listGetter('list', field, index, generatorOptions.prefix);
@@ -617,10 +619,9 @@ class ObjcSourceGenerator extends StructuredGenerator<ObjcOptions> {
     ObjcOptions generatorOptions,
     Root root,
     Indent indent,
-    Api api, {
+    AstFlutterApi api, {
     required String dartPackageName,
   }) {
-    assert(api.location == ApiLocation.flutter);
     final String apiName = _className(generatorOptions.prefix, api.name);
 
     _writeCodecAndGetter(generatorOptions, root, indent, api);
@@ -649,10 +650,9 @@ class ObjcSourceGenerator extends StructuredGenerator<ObjcOptions> {
     ObjcOptions generatorOptions,
     Root root,
     Indent indent,
-    Api api, {
+    AstHostApi api, {
     required String dartPackageName,
   }) {
-    assert(api.location == ApiLocation.host);
     final String apiName = _className(generatorOptions.prefix, api.name);
 
     _writeCodecAndGetter(generatorOptions, root, indent, api);
@@ -702,10 +702,12 @@ class ObjcSourceGenerator extends StructuredGenerator<ObjcOptions> {
     Indent indent, {
     required String dartPackageName,
   }) {
-    final bool hasHostApi = root.apis.any((Api api) =>
-        api.methods.isNotEmpty && api.location == ApiLocation.host);
-    final bool hasFlutterApi = root.apis.any((Api api) =>
-        api.methods.isNotEmpty && api.location == ApiLocation.flutter);
+    final bool hasHostApi = root.apis
+        .whereType<AstHostApi>()
+        .any((Api api) => api.methods.isNotEmpty);
+    final bool hasFlutterApi = root.apis
+        .whereType<AstFlutterApi>()
+        .any((Api api) => api.methods.isNotEmpty);
 
     if (hasHostApi) {
       _writeWrapError(indent);
@@ -858,7 +860,7 @@ static FlutterError *createConnectionError(NSString *channelName) {
       final Iterable<String> selectorComponents =
           _getSelectorComponents(func, lastSelectorComponent);
       final Iterable<String> argNames =
-          indexMap(func.parameters, _getSafeArgName);
+          func.parameters.mapIndexed(_getSafeArgName);
       final String callSignature =
           map2(selectorComponents.take(argNames.length), argNames,
               (String selectorComponent, String argName) {
@@ -1453,7 +1455,7 @@ String _makeObjcSignature({
       (int _, NamedType e) =>
           e.type.isNullable && e.type.isEnum ? '${e.name}Boxed' : e.name;
   final Iterable<String> argNames =
-      followedByOne(indexMap(func.parameters, argNameFunc), lastArgName);
+      followedByOne(func.parameters.mapIndexed(argNameFunc), lastArgName);
   final Iterable<String> selectorComponents =
       _getSelectorComponents(func, lastArgName);
   final Iterable<String> argTypes = followedByOne(
diff --git a/packages/pigeon/lib/pigeon_lib.dart b/packages/pigeon/lib/pigeon_lib.dart
index e114af93caa4..56dc43ed5b21 100644
--- a/packages/pigeon/lib/pigeon_lib.dart
+++ b/packages/pigeon/lib/pigeon_lib.dart
@@ -22,6 +22,7 @@ import 'package:analyzer/dart/ast/visitor.dart' as dart_ast_visitor;
 import 'package:analyzer/error/error.dart' show AnalysisError;
 import 'package:args/args.dart';
 import 'package:collection/collection.dart' as collection;
+import 'package:collection/collection.dart';
 import 'package:path/path.dart' as path;
 
 import 'ast.dart';
@@ -39,9 +40,44 @@ class _Asynchronous {
   const _Asynchronous();
 }
 
+class _Attached {
+  const _Attached();
+}
+
+class _Static {
+  const _Static();
+}
+
 /// Metadata to annotate a Api method as asynchronous
 const Object async = _Asynchronous();
 
+/// Metadata to annotate the field of a ProxyApi as an Attached Field.
+///
+/// Attached fields provide a synchronous [AstProxyApi] instance as a field
+/// for another [AstProxyApi].
+///
+/// Attached fields:
+/// * Must be nonnull.
+/// * Must be a ProxyApi type.
+/// * Must be a ProxyApi that contains any fields.
+/// * Must be a ProxyApi that does not have a required Flutter method.
+///
+/// Example generated code:
+///
+/// ```dart
+/// class MyProxyApi {
+///   final MyOtherProxyApi myField = __pigeon_myField().
+/// }
+/// ```
+///
+/// The field provides access to the value synchronously, but the native
+/// instance is stored in the native `InstanceManager` asynchronously. Similar
+/// to how constructors are implemented.
+const Object attached = _Attached();
+
+/// Metadata to annotate an method or an Attached Field of a ProxyApi as static.
+const Object static = _Static();
+
 /// Metadata annotation used to configure how Pigeon will generate code.
 class ConfigurePigeon {
   /// Constructor for ConfigurePigeon.
@@ -88,6 +124,30 @@ class FlutterApi {
   const FlutterApi();
 }
 
+/// Metadata to annotate a Pigeon API that wraps a native class.
+///
+/// The abstract class with this annotation groups a collection of Dart↔host
+/// constructors, fields, methods and host↔Dart methods used to wrap a native
+/// class.
+///
+/// The generated Dart class acts as a proxy to a native type and
+/// maintains instances automatically with an `InstanceManager`. The generated
+/// host language class implements methods to interact with class instances
+/// or static methods.
+class ProxyApi {
+  /// Parametric constructor for [ProxyApi].
+  const ProxyApi({this.superClass});
+
+  /// The proxy api that is a super class to this one.
+  ///
+  /// This provides an alternative to calling `extends` on a class since this
+  /// requires calling the super class constructor.
+  ///
+  /// Note that using this instead of `extends` can cause unexpected conflicts
+  /// with inherited method names.
+  final Type? superClass;
+}
+
 /// Metadata to annotation methods to control the selector used for objc output.
 /// The number of components in the provided selector must match the number of
 /// arguments in the annotated method.
@@ -787,7 +847,16 @@ List<Error> _validateAst(Root root, String source) {
       }
     }
   }
+
   for (final Api api in root.apis) {
+    if (api is AstProxyApi) {
+      result.addAll(_validateProxyApi(
+        api,
+        source,
+        customClasses: customClasses.toSet(),
+        proxyApis: root.apis.whereType<AstProxyApi>().toSet(),
+      ));
+    }
     for (final Method method in api.methods) {
       for (final Parameter param in method.parameters) {
         if (param.type.baseName.isEmpty) {
@@ -809,7 +878,7 @@ List<Error> _validateAst(Root root, String source) {
             lineNumber: _calculateLineNumberNullable(source, param.offset),
           ));
         }
-        if (api.location == ApiLocation.flutter) {
+        if (api is AstFlutterApi) {
           if (!param.isPositional) {
             result.add(Error(
               message:
@@ -847,7 +916,7 @@ List<Error> _validateAst(Root root, String source) {
         }
       }
       if (method.taskQueueType != TaskQueueType.serial &&
-          api.location != ApiLocation.host) {
+          method.location == ApiLocation.flutter) {
         result.add(Error(
           message: 'Unsupported TaskQueue specification on ${method.name}',
           lineNumber: _calculateLineNumberNullable(source, method.offset),
@@ -859,6 +928,275 @@ List<Error> _validateAst(Root root, String source) {
   return result;
 }
 
+List<Error> _validateProxyApi(
+  AstProxyApi api,
+  String source, {
+  required Set<String> customClasses,
+  required Set<AstProxyApi> proxyApis,
+}) {
+  final List<Error> result = <Error>[];
+
+  bool isDataClass(NamedType type) =>
+      customClasses.contains(type.type.baseName);
+  bool isProxyApi(NamedType type) => proxyApis.any(
+        (AstProxyApi api) => api.name == type.type.baseName,
+      );
+  Error unsupportedDataClassError(NamedType type) {
+    return Error(
+      message: 'ProxyApis do not support data classes: ${type.type.baseName}.',
+      lineNumber: _calculateLineNumberNullable(source, type.offset),
+    );
+  }
+
+  // Validate super class is another ProxyApi
+  final String? superClassName = api.superClassName;
+  if (api.superClassName != null &&
+      !proxyApis.any((AstProxyApi api) => api.name == superClassName)) {
+    result.add(Error(
+      message:
+          'Super class of ${api.name} is not marked as a @ProxyApi: $superClassName',
+    ));
+  }
+
+  // Validate all interfaces are other ProxyApis
+  for (final String interfaceName in api.interfacesNames) {
+    if (!proxyApis.any((AstProxyApi api) => api.name == interfaceName)) {
+      result.add(Error(
+        message:
+            'Interface of ${api.name} is not marked as a @ProxyApi: $interfaceName',
+      ));
+    }
+  }
+
+  List<AstProxyApi>? superClassChain;
+  try {
+    superClassChain = recursiveGetSuperClassApisChain(api, proxyApis);
+  } catch (error) {
+    result.add(Error(message: error.toString()));
+  }
+
+  // Validate that the api does not inherit a non attached field from its super class.
+  if (superClassChain != null &&
+      superClassChain.isNotEmpty &&
+      superClassChain.first.unattachedFields.isNotEmpty) {
+    result.add(Error(
+      message:
+          'Non attached fields can not be inherited. Non attached field found for parent class ${api.unattachedFields.first.name}',
+      lineNumber: _calculateLineNumberNullable(
+        source,
+        api.unattachedFields.first.offset,
+      ),
+    ));
+  }
+
+  for (final AstProxyApi proxyApi in proxyApis) {
+    // Validate this api is not used as an attached field while either:
+    // 1. Having an unattached field.
+    // 2. Having a required Flutter method.
+    final bool hasUnattachedField = api.unattachedFields.isNotEmpty;
+    final bool hasRequiredFlutterMethod =
+        api.flutterMethods.any((Method method) => method.required);
+    if (hasUnattachedField || hasRequiredFlutterMethod) {
+      for (final Field field in proxyApi.attachedFields) {
+        if (field.type.baseName == api.name) {
+          if (hasUnattachedField) {
+            result.add(Error(
+              message:
+                  'ProxyApis with fields can not be used as attached fields: ${field.name}',
+              lineNumber: _calculateLineNumberNullable(
+                source,
+                field.offset,
+              ),
+            ));
+          }
+          if (hasRequiredFlutterMethod) {
+            result.add(Error(
+              message:
+                  'ProxyApis with required callback methods can not be used as attached fields: ${field.name}',
+              lineNumber: _calculateLineNumberNullable(
+                source,
+                field.offset,
+              ),
+            ));
+          }
+        }
+      }
+    }
+
+    // Validate this api isn't used as an interface and contains anything except
+    // Flutter methods.
+    final bool isValidInterfaceProxyApi = api.hostMethods.isEmpty &&
+        api.constructors.isEmpty &&
+        api.fields.isEmpty;
+    if (!isValidInterfaceProxyApi) {
+      for (final String interfaceName in proxyApi.interfacesNames) {
+        if (interfaceName == api.name) {
+          result.add(Error(
+            message:
+                'ProxyApis used as interfaces can only have callback methods: ${proxyApi.name}',
+          ));
+        }
+      }
+    }
+  }
+
+  // Validate constructor parameters
+  for (final Constructor constructor in api.constructors) {
+    for (final Parameter parameter in constructor.parameters) {
+      if (isDataClass(parameter)) {
+        result.add(unsupportedDataClassError(parameter));
+      }
+
+      if (api.fields.any((Field field) => field.name == parameter.name) ||
+          api.flutterMethods
+              .any((Method method) => method.name == parameter.name)) {
+        result.add(Error(
+          message:
+              'Parameter names must not share a name with a field or callback method in constructor "${constructor.name}" in API: "${api.name}"',
+          lineNumber: _calculateLineNumberNullable(source, parameter.offset),
+        ));
+      }
+
+      if (parameter.type.baseName.isEmpty) {
+        result.add(Error(
+          message:
+              'Parameters must specify their type in constructor "${constructor.name}" in API: "${api.name}"',
+          lineNumber: _calculateLineNumberNullable(source, parameter.offset),
+        ));
+      } else if (parameter.name.startsWith('__pigeon_')) {
+        result.add(Error(
+          message:
+              'Parameter name must not begin with "__pigeon_" in constructor "${constructor.name}" in API: "${api.name}"',
+          lineNumber: _calculateLineNumberNullable(source, parameter.offset),
+        ));
+      } else if (parameter.name == 'pigeonChannelCodec') {
+        result.add(Error(
+          message:
+              'Parameter name must not be "pigeonChannelCodec" in constructor "${constructor.name}" in API: "${api.name}"',
+          lineNumber: _calculateLineNumberNullable(source, parameter.offset),
+        ));
+      } else if (parameter.name.startsWith(classNamePrefix)) {
+        result.add(Error(
+          message:
+              'Parameter name must not begin with "$classNamePrefix" in constructor "${constructor.name}" in API: "${api.name}"',
+          lineNumber: _calculateLineNumberNullable(source, parameter.offset),
+        ));
+      } else if (parameter.name.startsWith(classMemberNamePrefix)) {
+        result.add(Error(
+          message:
+              'Parameter name must not begin with "$classMemberNamePrefix" in constructor "${constructor.name}" in API: "${api.name}"',
+          lineNumber: _calculateLineNumberNullable(source, parameter.offset),
+        ));
+      }
+    }
+    if (constructor.swiftFunction.isNotEmpty) {
+      final RegExp signatureRegex =
+          RegExp('\\w+ *\\((\\w+:){${constructor.parameters.length}}\\)');
+      if (!signatureRegex.hasMatch(constructor.swiftFunction)) {
+        result.add(Error(
+          message:
+              'Invalid constructor signature, expected ${constructor.parameters.length} parameters.',
+          lineNumber: _calculateLineNumberNullable(source, constructor.offset),
+        ));
+      }
+    }
+  }
+
+  // Validate method parameters
+  for (final Method method in api.methods) {
+    for (final Parameter parameter in method.parameters) {
+      if (isDataClass(parameter)) {
+        result.add(unsupportedDataClassError(parameter));
+      }
+
+      if (parameter.name.startsWith(classNamePrefix)) {
+        result.add(Error(
+          message:
+              'Parameter name must not begin with "$classNamePrefix" in method "${method.name}" in API: "${api.name}"',
+          lineNumber: _calculateLineNumberNullable(source, parameter.offset),
+        ));
+      } else if (parameter.name.startsWith(classMemberNamePrefix)) {
+        result.add(Error(
+          message:
+              'Parameter name must not begin with "$classMemberNamePrefix" in method "${method.name}" in API: "${api.name}"',
+          lineNumber: _calculateLineNumberNullable(source, parameter.offset),
+        ));
+      }
+    }
+
+    if (method.location == ApiLocation.flutter && method.isStatic) {
+      result.add(Error(
+        message: 'Static callback methods are not supported: ${method.name}.',
+        lineNumber: _calculateLineNumberNullable(source, method.offset),
+      ));
+    }
+  }
+
+  // Validate fields
+  for (final Field field in api.fields) {
+    if (isDataClass(field)) {
+      result.add(unsupportedDataClassError(field));
+    } else if (field.isStatic) {
+      if (!isProxyApi(field)) {
+        result.add(Error(
+          message:
+              'Static fields are considered attached fields and must be a ProxyApi: ${field.type.baseName}.',
+          lineNumber: _calculateLineNumberNullable(source, field.offset),
+        ));
+      } else if (field.type.isNullable) {
+        result.add(Error(
+          message:
+              'Static fields are considered attached fields and must not be nullable: ${field.type.baseName}.',
+          lineNumber: _calculateLineNumberNullable(source, field.offset),
+        ));
+      }
+    } else if (field.isAttached) {
+      if (!isProxyApi(field)) {
+        result.add(Error(
+          message:
+              'Attached fields must be a ProxyApi: ${field.type.baseName}.',
+          lineNumber: _calculateLineNumberNullable(source, field.offset),
+        ));
+      }
+      if (field.type.isNullable) {
+        result.add(Error(
+          message:
+              'Attached fields must not be nullable: ${field.type.baseName}.',
+          lineNumber: _calculateLineNumberNullable(source, field.offset),
+        ));
+      }
+    }
+
+    if (field.name.startsWith('__pigeon_')) {
+      result.add(Error(
+        message:
+            'Field name must not begin with "__pigeon_" in API: "${api.name}"',
+        lineNumber: _calculateLineNumberNullable(source, field.offset),
+      ));
+    } else if (field.name == 'pigeonChannelCodec') {
+      result.add(Error(
+        message:
+            'Field name must not be "pigeonChannelCodec" in API: "${api.name}"',
+        lineNumber: _calculateLineNumberNullable(source, field.offset),
+      ));
+    } else if (field.name.startsWith(classNamePrefix)) {
+      result.add(Error(
+        message:
+            'Field name must not begin with "$classNamePrefix" in API: "${api.name}"',
+        lineNumber: _calculateLineNumberNullable(source, field.offset),
+      ));
+    } else if (field.name.startsWith(classMemberNamePrefix)) {
+      result.add(Error(
+        message:
+            'Field name must not begin with "$classMemberNamePrefix" in API: "${api.name}"',
+        lineNumber: _calculateLineNumberNullable(source, field.offset),
+      ));
+    }
+  }
+
+  return result;
+}
+
 class _FindInitializer extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
   dart_ast.Expression? initializer;
   @override
@@ -927,6 +1265,10 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
           !referencedEnums
               .map((Enum e) => e.name)
               .contains(element.key.baseName) &&
+          !_apis
+              .whereType<AstProxyApi>()
+              .map((AstProxyApi e) => e.name)
+              .contains(element.key.baseName) &&
           !validTypes.contains(element.key.baseName) &&
           !element.key.isVoid &&
           element.key.baseName != 'dynamic' &&
@@ -943,7 +1285,9 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
     for (final Class classDefinition in referencedClasses) {
       final List<NamedType> fields = <NamedType>[];
       for (final NamedType field in classDefinition.fields) {
-        fields.add(field.copyWithType(_attachClassesAndEnums(field.type)));
+        fields.add(field.copyWithType(
+          _attachClassesEnumsAndProxyApis(field.type),
+        ));
       }
       classDefinition.fields = fields;
     }
@@ -952,10 +1296,31 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
       for (final Method func in api.methods) {
         final List<Parameter> paramList = <Parameter>[];
         for (final Parameter param in func.parameters) {
-          paramList.add(param.copyWithType(_attachClassesAndEnums(param.type)));
+          paramList.add(param.copyWithType(
+            _attachClassesEnumsAndProxyApis(param.type),
+          ));
         }
         func.parameters = paramList;
-        func.returnType = _attachClassesAndEnums(func.returnType);
+        func.returnType = _attachClassesEnumsAndProxyApis(func.returnType);
+      }
+      if (api is AstProxyApi) {
+        for (final Constructor constructor in api.constructors) {
+          final List<Parameter> paramList = <Parameter>[];
+          for (final Parameter param in constructor.parameters) {
+            paramList.add(
+              param.copyWithType(_attachClassesEnumsAndProxyApis(param.type)),
+            );
+          }
+          constructor.parameters = paramList;
+        }
+
+        final List<Field> fieldList = <Field>[];
+        for (final Field field in api.fields) {
+          fieldList.add(field.copyWithType(
+            _attachClassesEnumsAndProxyApis(field.type),
+          ));
+        }
+        api.fields = fieldList;
       }
     }
 
@@ -968,15 +1333,21 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
     );
   }
 
-  TypeDeclaration _attachClassesAndEnums(TypeDeclaration type) {
+  TypeDeclaration _attachClassesEnumsAndProxyApis(TypeDeclaration type) {
     final Enum? assocEnum = _enums.firstWhereOrNull(
         (Enum enumDefinition) => enumDefinition.name == type.baseName);
     final Class? assocClass = _classes.firstWhereOrNull(
         (Class classDefinition) => classDefinition.name == type.baseName);
+    final AstProxyApi? assocProxyApi =
+        _apis.whereType<AstProxyApi>().firstWhereOrNull(
+              (Api apiDefinition) => apiDefinition.name == type.baseName,
+            );
     if (assocClass != null) {
       return type.copyWithClass(assocClass);
     } else if (assocEnum != null) {
       return type.copyWithEnum(assocEnum);
+    } else if (assocProxyApi != null) {
+      return type.copyWithProxyApi(assocProxyApi);
     }
     return type;
   }
@@ -1003,6 +1374,8 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
       return expression.value!;
     } else if (expression is dart_ast.BooleanLiteral) {
       return expression.value;
+    } else if (expression is dart_ast.SimpleIdentifier) {
+      return expression.name;
     } else if (expression is dart_ast.ListLiteral) {
       final List<dynamic> list = <dynamic>[];
       for (final dart_ast.CollectionElement element in expression.elements) {
@@ -1016,6 +1389,19 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
         }
       }
       return list;
+    } else if (expression is dart_ast.SetOrMapLiteral) {
+      final Set<dynamic> set = <dynamic>{};
+      for (final dart_ast.CollectionElement element in expression.elements) {
+        if (element is dart_ast.Expression) {
+          set.add(_expressionToMap(element));
+        } else {
+          _errors.add(Error(
+            message: 'expected Expression but found $element',
+            lineNumber: _calculateLineNumber(source, element.offset),
+          ));
+        }
+      }
+      return set;
     } else {
       _errors.add(Error(
         message:
@@ -1081,19 +1467,57 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
             }
           }
         }
-        _currentApi = Api(
+
+        _currentApi = AstHostApi(
           name: node.name.lexeme,
-          location: ApiLocation.host,
           methods: <Method>[],
           dartHostTestHandler: dartHostTestHandler,
           documentationComments:
               _documentationCommentsParser(node.documentationComment?.tokens),
         );
       } else if (_hasMetadata(node.metadata, 'FlutterApi')) {
-        _currentApi = Api(
+        _currentApi = AstFlutterApi(
+          name: node.name.lexeme,
+          methods: <Method>[],
+          documentationComments:
+              _documentationCommentsParser(node.documentationComment?.tokens),
+        );
+      } else if (_hasMetadata(node.metadata, 'ProxyApi')) {
+        final dart_ast.Annotation proxyApiAnnotation = node.metadata.firstWhere(
+          (dart_ast.Annotation element) => element.name.name == 'ProxyApi',
+        );
+
+        final Map<String, Object?> annotationMap = <String, Object?>{};
+        for (final dart_ast.Expression expression
+            in proxyApiAnnotation.arguments!.arguments) {
+          if (expression is dart_ast.NamedExpression) {
+            annotationMap[expression.name.label.name] =
+                _expressionToMap(expression.expression);
+          }
+        }
+
+        final String? superClassName = annotationMap['superClass'] as String?;
+        if (superClassName != null && node.extendsClause != null) {
+          _errors.add(
+            Error(
+              message:
+                  'ProxyApis should either set the super class in the annotation OR use extends: ("${node.name.lexeme}").',
+              lineNumber: _calculateLineNumber(source, node.offset),
+            ),
+          );
+        }
+
+        _currentApi = AstProxyApi(
           name: node.name.lexeme,
-          location: ApiLocation.flutter,
           methods: <Method>[],
+          constructors: <Constructor>[],
+          fields: <Field>[],
+          superClassName:
+              superClassName ?? node.extendsClause?.superclass.name2.lexeme,
+          interfacesNames: node.implementsClause?.interfaces
+                  .map<String>((dart_ast.NamedType type) => type.name2.lexeme)
+                  .toSet() ??
+              <String>{},
           documentationComments:
               _documentationCommentsParser(node.documentationComment?.tokens),
         );
@@ -1204,6 +1628,7 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
     final List<Parameter> arguments =
         parameters.parameters.map(formalParameterToPigeonParameter).toList();
     final bool isAsynchronous = _hasMetadata(node.metadata, 'async');
+    final bool isStatic = _hasMetadata(node.metadata, 'static');
     final String objcSelector = _findMetadata(node.metadata, 'ObjCSelector')
             ?.arguments
             ?.arguments
@@ -1243,6 +1668,13 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
                   typeAnnotationsToTypeArguments(returnType.typeArguments),
               isNullable: returnType.question != null),
           parameters: arguments,
+          required: true,
+          isStatic: isStatic,
+          location: switch (_currentApi!) {
+            AstHostApi() => ApiLocation.host,
+            AstProxyApi() => ApiLocation.host,
+            AstFlutterApi() => ApiLocation.flutter,
+          },
           isAsynchronous: isAsynchronous,
           objcSelector: objcSelector,
           swiftFunction: swiftFunction,
@@ -1298,8 +1730,8 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
 
   @override
   Object? visitFieldDeclaration(dart_ast.FieldDeclaration node) {
+    final dart_ast.TypeAnnotation? type = node.fields.type;
     if (_currentClass != null) {
-      final dart_ast.TypeAnnotation? type = node.fields.type;
       if (node.isStatic) {
         _errors.add(Error(
             message:
@@ -1335,6 +1767,88 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
             message: 'Expected a named type but found "$node".',
             lineNumber: _calculateLineNumber(source, node.offset)));
       }
+    } else if (_currentApi is AstProxyApi) {
+      final bool isStatic = _hasMetadata(node.metadata, 'static');
+      if (type is dart_ast.GenericFunctionType) {
+        final List<Parameter> parameters = type.parameters.parameters
+            .map(formalParameterToPigeonParameter)
+            .toList();
+        final String swiftFunction =
+            _findMetadata(node.metadata, 'SwiftFunction')
+                    ?.arguments
+                    ?.arguments
+                    .first
+                    .asNullable<dart_ast.SimpleStringLiteral>()
+                    ?.value ??
+                '';
+        final dart_ast.ArgumentList? taskQueueArguments =
+            _findMetadata(node.metadata, 'TaskQueue')?.arguments;
+        final String? taskQueueTypeName = taskQueueArguments == null
+            ? null
+            : getFirstChildOfType<dart_ast.NamedExpression>(taskQueueArguments)
+                ?.expression
+                .asNullable<dart_ast.PrefixedIdentifier>()
+                ?.name;
+        final TaskQueueType taskQueueType =
+            _stringToEnum(TaskQueueType.values, taskQueueTypeName) ??
+                TaskQueueType.serial;
+
+        // Methods without named return types aren't supported.
+        final dart_ast.TypeAnnotation returnType = type.returnType!;
+        returnType as dart_ast.NamedType;
+
+        _currentApi!.methods.add(
+          Method(
+            name: node.fields.variables[0].name.lexeme,
+            returnType: TypeDeclaration(
+              baseName: _getNamedTypeQualifiedName(returnType),
+              typeArguments:
+                  typeAnnotationsToTypeArguments(returnType.typeArguments),
+              isNullable: returnType.question != null,
+            ),
+            location: ApiLocation.flutter,
+            required: type.question == null,
+            isStatic: isStatic,
+            parameters: parameters,
+            isAsynchronous: _hasMetadata(node.metadata, 'async'),
+            swiftFunction: swiftFunction,
+            offset: node.offset,
+            taskQueueType: taskQueueType,
+            documentationComments:
+                _documentationCommentsParser(node.documentationComment?.tokens),
+          ),
+        );
+      } else if (type is dart_ast.NamedType) {
+        final _FindInitializer findInitializerVisitor = _FindInitializer();
+        node.visitChildren(findInitializerVisitor);
+        if (findInitializerVisitor.initializer != null) {
+          _errors.add(Error(
+              message:
+                  'Initialization isn\'t supported for fields in ProxyApis ("$node"), just use nullable types with no initializer (example "int? x;").',
+              lineNumber: _calculateLineNumber(source, node.offset)));
+        } else {
+          final dart_ast.TypeArgumentList? typeArguments = type.typeArguments;
+          (_currentApi as AstProxyApi?)!.fields.add(
+                Field(
+                  type: TypeDeclaration(
+                    baseName: _getNamedTypeQualifiedName(type),
+                    isNullable: type.question != null,
+                    typeArguments: typeAnnotationsToTypeArguments(
+                      typeArguments,
+                    ),
+                  ),
+                  name: node.fields.variables[0].name.lexeme,
+                  isAttached:
+                      _hasMetadata(node.metadata, 'attached') || isStatic,
+                  isStatic: isStatic,
+                  offset: node.offset,
+                  documentationComments: _documentationCommentsParser(
+                    node.documentationComment?.tokens,
+                  ),
+                ),
+              );
+        }
+      }
     } else if (_currentApi != null) {
       _errors.add(Error(
           message: 'Fields aren\'t supported in Pigeon API classes ("$node").',
@@ -1346,7 +1860,30 @@ class _RootBuilder extends dart_ast_visitor.RecursiveAstVisitor<Object?> {
 
   @override
   Object? visitConstructorDeclaration(dart_ast.ConstructorDeclaration node) {
-    if (_currentApi != null) {
+    if (_currentApi is AstProxyApi) {
+      final dart_ast.FormalParameterList parameters = node.parameters;
+      final List<Parameter> arguments =
+          parameters.parameters.map(formalParameterToPigeonParameter).toList();
+      final String swiftFunction = _findMetadata(node.metadata, 'SwiftFunction')
+              ?.arguments
+              ?.arguments
+              .first
+              .asNullable<dart_ast.SimpleStringLiteral>()
+              ?.value ??
+          '';
+
+      (_currentApi as AstProxyApi?)!.constructors.add(
+            Constructor(
+              name: node.name?.lexeme ?? '',
+              parameters: arguments,
+              swiftFunction: swiftFunction,
+              offset: node.offset,
+              documentationComments: _documentationCommentsParser(
+                node.documentationComment?.tokens,
+              ),
+            ),
+          );
+    } else if (_currentApi != null) {
       _errors.add(Error(
           message: 'Constructors aren\'t supported in API classes ("$node").',
           lineNumber: _calculateLineNumber(source, node.offset)));
diff --git a/packages/pigeon/lib/swift_generator.dart b/packages/pigeon/lib/swift_generator.dart
index ae869426e620..36d0c0d8dbea 100644
--- a/packages/pigeon/lib/swift_generator.dart
+++ b/packages/pigeon/lib/swift_generator.dart
@@ -2,6 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'package:collection/collection.dart';
+
 import 'ast.dart';
 import 'functional.dart';
 import 'generator.dart';
@@ -100,7 +102,7 @@ import FlutterMacOS
 
     indent.write('enum ${anEnum.name}: Int ');
     indent.addScoped('{', '}', () {
-      enumerate(anEnum.members, (int index, final EnumMember member) {
+      anEnum.members.forEachIndexed((int index, final EnumMember member) {
         addDocumentationComments(
             indent, member.documentationComments, _docCommentSpec);
         indent.writeln('case ${_camelCase(member.name)} = $index');
@@ -191,8 +193,8 @@ import FlutterMacOS
     indent.write('static func fromList(_ list: [Any?]) -> $className? ');
 
     indent.addScoped('{', '}', () {
-      enumerate(getFieldsInSerializationOrder(classDefinition),
-          (int index, final NamedType field) {
+      getFieldsInSerializationOrder(classDefinition)
+          .forEachIndexed((int index, final NamedType field) {
         final String listValue = 'list[$index]';
 
         _writeDecodeCasting(
@@ -236,7 +238,7 @@ import FlutterMacOS
     required String dartPackageName,
   }) {
     if (root.apis.any((Api api) =>
-        api.location == ApiLocation.host &&
+        api is AstHostApi &&
         api.methods.any((Method it) => it.isAsynchronous))) {
       indent.newln();
     }
@@ -256,11 +258,9 @@ import FlutterMacOS
     SwiftOptions generatorOptions,
     Root root,
     Indent indent,
-    Api api, {
+    AstFlutterApi api, {
     required String dartPackageName,
   }) {
-    assert(api.location == ApiLocation.flutter);
-
     /// Returns an argument name that can be used in a context where it is possible to collide.
     String getEnumSafeArgumentExpression(
         Root root, int count, NamedType argument) {
@@ -380,11 +380,9 @@ import FlutterMacOS
     SwiftOptions generatorOptions,
     Root root,
     Indent indent,
-    Api api, {
+    AstHostApi api, {
     required String dartPackageName,
   }) {
-    assert(api.location == ApiLocation.host);
-
     final String apiName = api.name;
 
     final bool isCustomCodec = getCodecClasses(api, root).isNotEmpty;
@@ -473,8 +471,8 @@ import FlutterMacOS
               final List<String> methodArgument = <String>[];
               if (components.arguments.isNotEmpty) {
                 indent.writeln('let args = message as! [Any?]');
-                enumerate(components.arguments,
-                    (int index, _SwiftFunctionArgument arg) {
+                components.arguments
+                    .forEachIndexed((int index, _SwiftFunctionArgument arg) {
                   final String argName =
                       _getSafeArgumentName(index, arg.namedType);
                   final String argIndex = 'args[$index]';
@@ -802,10 +800,12 @@ private func nilOrValue<T>(_ value: Any?) -> T? {
     Indent indent, {
     required String dartPackageName,
   }) {
-    final bool hasHostApi = root.apis.any((Api api) =>
-        api.methods.isNotEmpty && api.location == ApiLocation.host);
-    final bool hasFlutterApi = root.apis.any((Api api) =>
-        api.methods.isNotEmpty && api.location == ApiLocation.flutter);
+    final bool hasHostApi = root.apis
+        .whereType<AstHostApi>()
+        .any((Api api) => api.methods.isNotEmpty);
+    final bool hasFlutterApi = root.apis
+        .whereType<AstFlutterApi>()
+        .any((Api api) => api.methods.isNotEmpty);
 
     if (hasHostApi) {
       _writeWrapResult(indent);
@@ -906,12 +906,12 @@ String _getMethodSignature(Method func) {
   } else {
     final Iterable<String> argTypes = func.parameters
         .map((NamedType e) => _nullsafeSwiftTypeForDartType(e.type));
-    final Iterable<String> argLabels = indexMap(components.arguments,
-        (int index, _SwiftFunctionArgument argument) {
+    final Iterable<String> argLabels = components.arguments
+        .mapIndexed((int index, _SwiftFunctionArgument argument) {
       return argument.label ?? _getArgumentName(index, argument.namedType);
     });
     final Iterable<String> argNames =
-        indexMap(func.parameters, _getSafeArgumentName);
+        func.parameters.mapIndexed(_getSafeArgumentName);
     final String argsSignature = map3(argTypes, argLabels, argNames,
             (String type, String label, String name) => '$label $name: $type')
         .join(', ');
diff --git a/packages/pigeon/pigeons/core_tests.dart b/packages/pigeon/pigeons/core_tests.dart
index a0c6a3ccf29f..0a98f5b95128 100644
--- a/packages/pigeon/pigeons/core_tests.dart
+++ b/packages/pigeon/pigeons/core_tests.dart
@@ -699,3 +699,460 @@ class TestMessage {
   // ignore: always_specify_types, strict_raw_type
   List? testList;
 }
+
+/// The core interface that each host language plugin must implement in
+/// platform_test integration tests.
+@ProxyApi()
+abstract class ProxyIntegrationCoreApi extends ProxyApiSuperClass
+    implements ProxyApiInterface {
+  ProxyIntegrationCoreApi(
+    // ignore: avoid_unused_constructor_parameters
+    bool boolParam,
+    // ignore: avoid_unused_constructor_parameters
+    int intParam,
+    // ignore: avoid_unused_constructor_parameters
+    double doubleParam,
+    // ignore: avoid_unused_constructor_parameters
+    String stringParam,
+    // ignore: avoid_unused_constructor_parameters
+    Uint8List aUint8ListParam,
+    // ignore: avoid_unused_constructor_parameters
+    List<Object?> listParam,
+    // ignore: avoid_unused_constructor_parameters
+    Map<String?, Object?> mapParam,
+    // ignore: avoid_unused_constructor_parameters
+    AnEnum enumParam,
+    // ignore: avoid_unused_constructor_parameters
+    ProxyApiSuperClass proxyApiParam,
+    // ignore: avoid_unused_constructor_parameters
+    bool? nullableBoolParam,
+    // ignore: avoid_unused_constructor_parameters
+    int? nullableIntParam,
+    // ignore: avoid_unused_constructor_parameters
+    double? nullableDoubleParam,
+    // ignore: avoid_unused_constructor_parameters
+    String? nullableStringParam,
+    // ignore: avoid_unused_constructor_parameters
+    Uint8List? nullableUint8ListParam,
+    // ignore: avoid_unused_constructor_parameters
+    List<Object?>? nullableListParam,
+    // ignore: avoid_unused_constructor_parameters
+    Map<String?, Object?>? nullableMapParam,
+    // ignore: avoid_unused_constructor_parameters
+    AnEnum? nullableEnumParam,
+    // ignore: avoid_unused_constructor_parameters
+    ProxyApiSuperClass? nullableProxyApiParam,
+  );
+
+  late bool aBool;
+  late int anInt;
+  late double aDouble;
+  late String aString;
+  late Uint8List aUint8List;
+  late List<Object?> aList;
+  late Map<String?, Object?> aMap;
+  late AnEnum anEnum;
+  late ProxyApiSuperClass aProxyApi;
+
+  late bool? aNullableBool;
+  late int? aNullableInt;
+  late double? aNullableDouble;
+  late String? aNullableString;
+  late Uint8List? aNullableUint8List;
+  late List<Object?>? aNullableList;
+  late Map<String?, Object?>? aNullableMap;
+  late AnEnum? aNullableEnum;
+  late ProxyApiSuperClass? aNullableProxyApi;
+
+  @attached
+  late ProxyApiSuperClass attachedField;
+
+  @static
+  late ProxyApiSuperClass staticAttachedField;
+
+  /// A no-op function taking no arguments and returning no value, to sanity
+  /// test basic calling.
+  late void Function()? flutterNoop;
+
+  /// Responds with an error from an async function returning a value.
+  late Object? Function()? flutterThrowError;
+
+  /// Responds with an error from an async void function.
+  late void Function()? flutterThrowErrorFromVoid;
+
+  // ========== Non-nullable argument/return type tests ==========
+
+  /// Returns the passed boolean, to test serialization and deserialization.
+  late bool Function(bool aBool)? flutterEchoBool;
+
+  /// Returns the passed int, to test serialization and deserialization.
+  late int Function(int anInt)? flutterEchoInt;
+
+  /// Returns the passed double, to test serialization and deserialization.
+  late double Function(double aDouble)? flutterEchoDouble;
+
+  /// Returns the passed string, to test serialization and deserialization.
+  late String Function(String aString)? flutterEchoString;
+
+  /// Returns the passed byte list, to test serialization and deserialization.
+  late Uint8List Function(Uint8List aList)? flutterEchoUint8List;
+
+  /// Returns the passed list, to test serialization and deserialization.
+  late List<Object?> Function(List<Object?> aList)? flutterEchoList;
+
+  /// Returns the passed list with ProxyApis, to test serialization and
+  /// deserialization.
+  late List<ProxyIntegrationCoreApi?> Function(
+      List<ProxyIntegrationCoreApi?> aList)? flutterEchoProxyApiList;
+
+  /// Returns the passed map, to test serialization and deserialization.
+  late Map<String?, Object?> Function(Map<String?, Object?> aMap)?
+      flutterEchoMap;
+
+  /// Returns the passed map with ProxyApis, to test serialization and
+  /// deserialization.
+  late Map<String?, ProxyIntegrationCoreApi?> Function(
+      Map<String?, ProxyIntegrationCoreApi?> aMap)? flutterEchoProxyApiMap;
+
+  /// Returns the passed enum to test serialization and deserialization.
+  late AnEnum Function(AnEnum anEnum)? flutterEchoEnum;
+
+  /// Returns the passed ProxyApi to test serialization and deserialization.
+  late ProxyApiSuperClass Function(ProxyApiSuperClass aProxyApi)?
+      flutterEchoProxyApi;
+
+  // ========== Nullable argument/return type tests ==========
+
+  /// Returns the passed boolean, to test serialization and deserialization.
+  late bool? Function(bool? aBool)? flutterEchoNullableBool;
+
+  /// Returns the passed int, to test serialization and deserialization.
+  late int? Function(int? anInt)? flutterEchoNullableInt;
+
+  /// Returns the passed double, to test serialization and deserialization.
+  late double? Function(double? aDouble)? flutterEchoNullableDouble;
+
+  /// Returns the passed string, to test serialization and deserialization.
+  late String? Function(String? aString)? flutterEchoNullableString;
+
+  /// Returns the passed byte list, to test serialization and deserialization.
+  late Uint8List? Function(Uint8List? aList)? flutterEchoNullableUint8List;
+
+  /// Returns the passed list, to test serialization and deserialization.
+  late List<Object?>? Function(List<Object?>? aList)? flutterEchoNullableList;
+
+  /// Returns the passed map, to test serialization and deserialization.
+  late Map<String?, Object?>? Function(Map<String?, Object?>? aMap)?
+      flutterEchoNullableMap;
+
+  /// Returns the passed enum to test serialization and deserialization.
+  late AnEnum? Function(AnEnum? anEnum)? flutterEchoNullableEnum;
+
+  /// Returns the passed ProxyApi to test serialization and deserialization.
+  late ProxyApiSuperClass? Function(ProxyApiSuperClass? aProxyApi)?
+      flutterEchoNullableProxyApi;
+
+  // ========== Async tests ==========
+  // These are minimal since async FlutterApi only changes Dart generation.
+  // Currently they aren't integration tested, but having them here ensures
+  // analysis coverage.
+
+  /// A no-op function taking no arguments and returning no value, to sanity
+  /// test basic asynchronous calling.
+  @async
+  late void Function()? flutterNoopAsync;
+
+  /// Returns the passed in generic Object asynchronously.
+  @async
+  late String Function(String aString)? flutterEchoAsyncString;
+
+  // ========== Synchronous host method tests ==========
+
+  /// A no-op function taking no arguments and returning no value, to sanity
+  /// test basic calling.
+  void noop();
+
+  /// Returns an error, to test error handling.
+  Object? throwError();
+
+  /// Returns an error from a void function, to test error handling.
+  void throwErrorFromVoid();
+
+  /// Returns a Flutter error, to test error handling.
+  Object? throwFlutterError();
+
+  /// Returns passed in int.
+  int echoInt(int anInt);
+
+  /// Returns passed in double.
+  double echoDouble(double aDouble);
+
+  /// Returns the passed in boolean.
+  bool echoBool(bool aBool);
+
+  /// Returns the passed in string.
+  String echoString(String aString);
+
+  /// Returns the passed in Uint8List.
+  Uint8List echoUint8List(Uint8List aUint8List);
+
+  /// Returns the passed in generic Object.
+  Object echoObject(Object anObject);
+
+  /// Returns the passed list, to test serialization and deserialization.
+  List<Object?> echoList(List<Object?> aList);
+
+  /// Returns the passed list with ProxyApis, to test serialization and
+  /// deserialization.
+  List<ProxyIntegrationCoreApi> echoProxyApiList(
+    List<ProxyIntegrationCoreApi> aList,
+  );
+
+  /// Returns the passed map, to test serialization and deserialization.
+  Map<String?, Object?> echoMap(Map<String?, Object?> aMap);
+
+  /// Returns the passed map with ProxyApis, to test serialization and
+  /// deserialization.
+  Map<String, ProxyIntegrationCoreApi> echoProxyApiMap(
+    Map<String, ProxyIntegrationCoreApi> aMap,
+  );
+
+  /// Returns the passed enum to test serialization and deserialization.
+  AnEnum echoEnum(AnEnum anEnum);
+
+  /// Returns the passed ProxyApi to test serialization and deserialization.
+  ProxyApiSuperClass echoProxyApi(ProxyApiSuperClass aProxyApi);
+
+  // ========== Synchronous host nullable method tests ==========
+
+  /// Returns passed in int.
+  int? echoNullableInt(int? aNullableInt);
+
+  /// Returns passed in double.
+  double? echoNullableDouble(double? aNullableDouble);
+
+  /// Returns the passed in boolean.
+  bool? echoNullableBool(bool? aNullableBool);
+
+  /// Returns the passed in string.
+  String? echoNullableString(String? aNullableString);
+
+  /// Returns the passed in Uint8List.
+  Uint8List? echoNullableUint8List(Uint8List? aNullableUint8List);
+
+  /// Returns the passed in generic Object.
+  Object? echoNullableObject(Object? aNullableObject);
+
+  /// Returns the passed list, to test serialization and deserialization.
+  List<Object?>? echoNullableList(List<Object?>? aNullableList);
+
+  /// Returns the passed map, to test serialization and deserialization.
+  Map<String?, Object?>? echoNullableMap(Map<String?, Object?>? aNullableMap);
+
+  AnEnum? echoNullableEnum(AnEnum? aNullableEnum);
+
+  /// Returns the passed ProxyApi to test serialization and deserialization.
+  ProxyApiSuperClass? echoNullableProxyApi(
+    ProxyApiSuperClass? aNullableProxyApi,
+  );
+
+  // ========== Asynchronous method tests ==========
+
+  /// A no-op function taking no arguments and returning no value, to sanity
+  /// test basic asynchronous calling.
+  @async
+  void noopAsync();
+
+  /// Returns passed in int asynchronously.
+  @async
+  int echoAsyncInt(int anInt);
+
+  /// Returns passed in double asynchronously.
+  @async
+  double echoAsyncDouble(double aDouble);
+
+  /// Returns the passed in boolean asynchronously.
+  @async
+  bool echoAsyncBool(bool aBool);
+
+  /// Returns the passed string asynchronously.
+  @async
+  String echoAsyncString(String aString);
+
+  /// Returns the passed in Uint8List asynchronously.
+  @async
+  Uint8List echoAsyncUint8List(Uint8List aUint8List);
+
+  /// Returns the passed in generic Object asynchronously.
+  @async
+  Object echoAsyncObject(Object anObject);
+
+  /// Returns the passed list, to test asynchronous serialization and deserialization.
+  @async
+  List<Object?> echoAsyncList(List<Object?> aList);
+
+  /// Returns the passed map, to test asynchronous serialization and deserialization.
+  @async
+  Map<String?, Object?> echoAsyncMap(Map<String?, Object?> aMap);
+
+  /// Returns the passed enum, to test asynchronous serialization and deserialization.
+  @async
+  AnEnum echoAsyncEnum(AnEnum anEnum);
+
+  /// Responds with an error from an async function returning a value.
+  @async
+  Object? throwAsyncError();
+
+  /// Responds with an error from an async void function.
+  @async
+  void throwAsyncErrorFromVoid();
+
+  /// Responds with a Flutter error from an async function returning a value.
+  @async
+  Object? throwAsyncFlutterError();
+
+  /// Returns passed in int asynchronously.
+  @async
+  int? echoAsyncNullableInt(int? anInt);
+
+  /// Returns passed in double asynchronously.
+  @async
+  double? echoAsyncNullableDouble(double? aDouble);
+
+  /// Returns the passed in boolean asynchronously.
+  @async
+  bool? echoAsyncNullableBool(bool? aBool);
+
+  /// Returns the passed string asynchronously.
+  @async
+  String? echoAsyncNullableString(String? aString);
+
+  /// Returns the passed in Uint8List asynchronously.
+  @async
+  Uint8List? echoAsyncNullableUint8List(Uint8List? aUint8List);
+
+  /// Returns the passed in generic Object asynchronously.
+  @async
+  Object? echoAsyncNullableObject(Object? anObject);
+
+  /// Returns the passed list, to test asynchronous serialization and deserialization.
+  @async
+  List<Object?>? echoAsyncNullableList(List<Object?>? aList);
+
+  /// Returns the passed map, to test asynchronous serialization and deserialization.
+  @async
+  Map<String?, Object?>? echoAsyncNullableMap(Map<String?, Object?>? aMap);
+
+  /// Returns the passed enum, to test asynchronous serialization and deserialization.
+  @async
+  AnEnum? echoAsyncNullableEnum(AnEnum? anEnum);
+
+  // ========== Static method test ==========
+
+  @static
+  void staticNoop();
+
+  @static
+  String echoStaticString(String aString);
+
+  @static
+  @async
+  void staticAsyncNoop();
+
+  // ========== Flutter methods test wrappers ==========
+
+  @async
+  void callFlutterNoop();
+
+  @async
+  Object? callFlutterThrowError();
+
+  @async
+  void callFlutterThrowErrorFromVoid();
+
+  @async
+  bool callFlutterEchoBool(bool aBool);
+
+  @async
+  int callFlutterEchoInt(int anInt);
+
+  @async
+  double callFlutterEchoDouble(double aDouble);
+
+  @async
+  String callFlutterEchoString(String aString);
+
+  @async
+  Uint8List callFlutterEchoUint8List(Uint8List aUint8List);
+
+  @async
+  List<Object?> callFlutterEchoList(List<Object?> aList);
+
+  @async
+  List<ProxyIntegrationCoreApi?> callFlutterEchoProxyApiList(
+      List<ProxyIntegrationCoreApi?> aList);
+
+  @async
+  Map<String?, Object?> callFlutterEchoMap(Map<String?, Object?> aMap);
+
+  @async
+  Map<String?, ProxyIntegrationCoreApi?> callFlutterEchoProxyApiMap(
+      Map<String?, ProxyIntegrationCoreApi?> aMap);
+
+  @async
+  AnEnum callFlutterEchoEnum(AnEnum anEnum);
+
+  @async
+  ProxyApiSuperClass callFlutterEchoProxyApi(ProxyApiSuperClass aProxyApi);
+
+  @async
+  bool? callFlutterEchoNullableBool(bool? aBool);
+
+  @async
+  int? callFlutterEchoNullableInt(int? anInt);
+
+  @async
+  double? callFlutterEchoNullableDouble(double? aDouble);
+
+  @async
+  String? callFlutterEchoNullableString(String? aString);
+
+  @async
+  Uint8List? callFlutterEchoNullableUint8List(Uint8List? aUint8List);
+
+  @async
+  List<Object?>? callFlutterEchoNullableList(List<Object?>? aList);
+
+  @async
+  Map<String?, Object?>? callFlutterEchoNullableMap(
+    Map<String?, Object?>? aMap,
+  );
+
+  @async
+  AnEnum? callFlutterEchoNullableEnum(AnEnum? anEnum);
+
+  @async
+  ProxyApiSuperClass? callFlutterEchoNullableProxyApi(
+    ProxyApiSuperClass? aProxyApi,
+  );
+
+  @async
+  void callFlutterNoopAsync();
+
+  @async
+  String callFlutterEchoAsyncString(String aString);
+}
+
+/// ProxyApi to serve as a super class to the core ProxyApi interface.
+@ProxyApi()
+abstract class ProxyApiSuperClass {
+  ProxyApiSuperClass();
+
+  void aSuperMethod();
+}
+
+/// ProxyApi to serve as an interface to the core ProxyApi interface.
+@ProxyApi()
+abstract class ProxyApiInterface {
+  late void Function()? anInterfaceMethod;
+}
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/background_platform_channels.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/background_platform_channels.gen.dart
index 7222e263b32b..91dee132ceba 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/background_platform_channels.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/background_platform_channels.gen.dart
@@ -4,7 +4,7 @@
 //
 // Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
-// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers
+// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers, camel_case_types
 
 import 'dart:async';
 import 'dart:typed_data' show Float64List, Int32List, Int64List, Uint8List;
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/core_tests.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/core_tests.gen.dart
index 6815f461c943..8d83750e71fc 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/core_tests.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/core_tests.gen.dart
@@ -4,13 +4,15 @@
 //
 // Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
-// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers
+// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers, camel_case_types
 
 import 'dart:async';
 import 'dart:typed_data' show Float64List, Int32List, Int64List, Uint8List;
 
-import 'package:flutter/foundation.dart' show ReadBuffer, WriteBuffer;
+import 'package:flutter/foundation.dart'
+    show ReadBuffer, WriteBuffer, immutable, protected;
 import 'package:flutter/services.dart';
+import 'package:flutter/widgets.dart' show WidgetsFlutterBinding;
 
 PlatformException _createConnectionError(String channelName) {
   return PlatformException(
@@ -30,6 +32,365 @@ List<Object?> wrapResponse(
   return <Object?>[error.code, error.message, error.details];
 }
 
+/// An immutable object that serves as the base class for all ProxyApis and
+/// can provide functional copies of itself.
+///
+/// All implementers are expected to be [immutable] as defined by the annotation
+/// and override [pigeon_copy] returning an instance of itself.
+@immutable
+abstract class Pigeon_ProxyApiBaseClass {
+  /// Construct a [Pigeon_ProxyApiBaseClass].
+  Pigeon_ProxyApiBaseClass({
+    this.pigeon_binaryMessenger,
+    Pigeon_InstanceManager? pigeon_instanceManager,
+  }) : pigeon_instanceManager =
+            pigeon_instanceManager ?? Pigeon_InstanceManager.instance;
+
+  /// Sends and receives binary data across the Flutter platform barrier.
+  ///
+  /// If it is null, the default BinaryMessenger will be used, which routes to
+  /// the host platform.
+  final BinaryMessenger? pigeon_binaryMessenger;
+
+  /// Maintains instances stored to communicate with native language objects.
+  final Pigeon_InstanceManager pigeon_instanceManager;
+
+  /// Instantiates and returns a functionally identical object to oneself.
+  ///
+  /// Outside of tests, this method should only ever be called by
+  /// [Pigeon_InstanceManager].
+  ///
+  /// Subclasses should always override their parent's implementation of this
+  /// method.
+  @protected
+  Pigeon_ProxyApiBaseClass pigeon_copy();
+}
+
+/// Maintains instances used to communicate with the native objects they
+/// represent.
+///
+/// Added instances are stored as weak references and their copies are stored
+/// as strong references to maintain access to their variables and callback
+/// methods. Both are stored with the same identifier.
+///
+/// When a weak referenced instance becomes inaccessible,
+/// [onWeakReferenceRemoved] is called with its associated identifier.
+///
+/// If an instance is retrieved and has the possibility to be used,
+/// (e.g. calling [getInstanceWithWeakReference]) a copy of the strong reference
+/// is added as a weak reference with the same identifier. This prevents a
+/// scenario where the weak referenced instance was released and then later
+/// returned by the host platform.
+class Pigeon_InstanceManager {
+  /// Constructs a [Pigeon_InstanceManager].
+  Pigeon_InstanceManager({required void Function(int) onWeakReferenceRemoved}) {
+    this.onWeakReferenceRemoved = (int identifier) {
+      _weakInstances.remove(identifier);
+      onWeakReferenceRemoved(identifier);
+    };
+    _finalizer = Finalizer<int>(this.onWeakReferenceRemoved);
+  }
+
+  // Identifiers are locked to a specific range to avoid collisions with objects
+  // created simultaneously by the host platform.
+  // Host uses identifiers >= 2^16 and Dart is expected to use values n where,
+  // 0 <= n < 2^16.
+  static const int _maxDartCreatedIdentifier = 65536;
+
+  /// The default [Pigeon_InstanceManager] used by ProxyApis.
+  ///
+  /// On creation, this manager makes a call to clear the native
+  /// InstanceManager. This is to prevent identifier conflicts after a host
+  /// restart.
+  static final Pigeon_InstanceManager instance = _initInstance();
+
+  // Expando is used because it doesn't prevent its keys from becoming
+  // inaccessible. This allows the manager to efficiently retrieve an identifier
+  // of an instance without holding a strong reference to that instance.
+  //
+  // It also doesn't use `==` to search for identifiers, which would lead to an
+  // infinite loop when comparing an object to its copy. (i.e. which was caused
+  // by calling instanceManager.getIdentifier() inside of `==` while this was a
+  // HashMap).
+  final Expando<int> _identifiers = Expando<int>();
+  final Map<int, WeakReference<Pigeon_ProxyApiBaseClass>> _weakInstances =
+      <int, WeakReference<Pigeon_ProxyApiBaseClass>>{};
+  final Map<int, Pigeon_ProxyApiBaseClass> _strongInstances =
+      <int, Pigeon_ProxyApiBaseClass>{};
+  late final Finalizer<int> _finalizer;
+  int _nextIdentifier = 0;
+
+  /// Called when a weak referenced instance is removed by [removeWeakReference]
+  /// or becomes inaccessible.
+  late final void Function(int) onWeakReferenceRemoved;
+
+  static Pigeon_InstanceManager _initInstance() {
+    WidgetsFlutterBinding.ensureInitialized();
+    final _Pigeon_InstanceManagerApi api = _Pigeon_InstanceManagerApi();
+    // Clears the native `Pigeon_InstanceManager` on the initial use of the Dart one.
+    api.clear();
+    final Pigeon_InstanceManager instanceManager = Pigeon_InstanceManager(
+      onWeakReferenceRemoved: (int identifier) {
+        api.removeStrongReference(identifier);
+      },
+    );
+    _Pigeon_InstanceManagerApi.setUpMessageHandlers(
+        instanceManager: instanceManager);
+    ProxyIntegrationCoreApi.pigeon_setUpMessageHandlers(
+        pigeon_instanceManager: instanceManager);
+    ProxyApiSuperClass.pigeon_setUpMessageHandlers(
+        pigeon_instanceManager: instanceManager);
+    ProxyApiInterface.pigeon_setUpMessageHandlers(
+        pigeon_instanceManager: instanceManager);
+    return instanceManager;
+  }
+
+  /// Adds a new instance that was instantiated by Dart.
+  ///
+  /// In other words, Dart wants to add a new instance that will represent
+  /// an object that will be instantiated on the host platform.
+  ///
+  /// Throws assertion error if the instance has already been added.
+  ///
+  /// Returns the randomly generated id of the [instance] added.
+  int addDartCreatedInstance(Pigeon_ProxyApiBaseClass instance) {
+    final int identifier = _nextUniqueIdentifier();
+    _addInstanceWithIdentifier(instance, identifier);
+    return identifier;
+  }
+
+  /// Removes the instance, if present, and call [onWeakReferenceRemoved] with
+  /// its identifier.
+  ///
+  /// Returns the identifier associated with the removed instance. Otherwise,
+  /// `null` if the instance was not found in this manager.
+  ///
+  /// This does not remove the strong referenced instance associated with
+  /// [instance]. This can be done with [remove].
+  int? removeWeakReference(Pigeon_ProxyApiBaseClass instance) {
+    final int? identifier = getIdentifier(instance);
+    if (identifier == null) {
+      return null;
+    }
+
+    _identifiers[instance] = null;
+    _finalizer.detach(instance);
+    onWeakReferenceRemoved(identifier);
+
+    return identifier;
+  }
+
+  /// Removes [identifier] and its associated strongly referenced instance, if
+  /// present, from the manager.
+  ///
+  /// Returns the strong referenced instance associated with [identifier] before
+  /// it was removed. Returns `null` if [identifier] was not associated with
+  /// any strong reference.
+  ///
+  /// This does not remove the weak referenced instance associated with
+  /// [identifier]. This can be done with [removeWeakReference].
+  T? remove<T extends Pigeon_ProxyApiBaseClass>(int identifier) {
+    return _strongInstances.remove(identifier) as T?;
+  }
+
+  /// Retrieves the instance associated with identifier.
+  ///
+  /// The value returned is chosen from the following order:
+  ///
+  /// 1. A weakly referenced instance associated with identifier.
+  /// 2. If the only instance associated with identifier is a strongly
+  /// referenced instance, a copy of the instance is added as a weak reference
+  /// with the same identifier. Returning the newly created copy.
+  /// 3. If no instance is associated with identifier, returns null.
+  ///
+  /// This method also expects the host `InstanceManager` to have a strong
+  /// reference to the instance the identifier is associated with.
+  T? getInstanceWithWeakReference<T extends Pigeon_ProxyApiBaseClass>(
+      int identifier) {
+    final Pigeon_ProxyApiBaseClass? weakInstance =
+        _weakInstances[identifier]?.target;
+
+    if (weakInstance == null) {
+      final Pigeon_ProxyApiBaseClass? strongInstance =
+          _strongInstances[identifier];
+      if (strongInstance != null) {
+        final Pigeon_ProxyApiBaseClass copy = strongInstance.pigeon_copy();
+        _identifiers[copy] = identifier;
+        _weakInstances[identifier] =
+            WeakReference<Pigeon_ProxyApiBaseClass>(copy);
+        _finalizer.attach(copy, identifier, detach: copy);
+        return copy as T;
+      }
+      return strongInstance as T?;
+    }
+
+    return weakInstance as T;
+  }
+
+  /// Retrieves the identifier associated with instance.
+  int? getIdentifier(Pigeon_ProxyApiBaseClass instance) {
+    return _identifiers[instance];
+  }
+
+  /// Adds a new instance that was instantiated by the host platform.
+  ///
+  /// In other words, the host platform wants to add a new instance that
+  /// represents an object on the host platform. Stored with [identifier].
+  ///
+  /// Throws assertion error if the instance or its identifier has already been
+  /// added.
+  ///
+  /// Returns unique identifier of the [instance] added.
+  void addHostCreatedInstance(
+      Pigeon_ProxyApiBaseClass instance, int identifier) {
+    _addInstanceWithIdentifier(instance, identifier);
+  }
+
+  void _addInstanceWithIdentifier(
+      Pigeon_ProxyApiBaseClass instance, int identifier) {
+    assert(!containsIdentifier(identifier));
+    assert(getIdentifier(instance) == null);
+    assert(identifier >= 0);
+
+    _identifiers[instance] = identifier;
+    _weakInstances[identifier] =
+        WeakReference<Pigeon_ProxyApiBaseClass>(instance);
+    _finalizer.attach(instance, identifier, detach: instance);
+
+    final Pigeon_ProxyApiBaseClass copy = instance.pigeon_copy();
+    _identifiers[copy] = identifier;
+    _strongInstances[identifier] = copy;
+  }
+
+  /// Whether this manager contains the given [identifier].
+  bool containsIdentifier(int identifier) {
+    return _weakInstances.containsKey(identifier) ||
+        _strongInstances.containsKey(identifier);
+  }
+
+  int _nextUniqueIdentifier() {
+    late int identifier;
+    do {
+      identifier = _nextIdentifier;
+      _nextIdentifier = (_nextIdentifier + 1) % _maxDartCreatedIdentifier;
+    } while (containsIdentifier(identifier));
+    return identifier;
+  }
+}
+
+/// Generated API for managing the Dart and native `Pigeon_InstanceManager`s.
+class _Pigeon_InstanceManagerApi {
+  /// Constructor for [_Pigeon_InstanceManagerApi ].
+  _Pigeon_InstanceManagerApi({BinaryMessenger? binaryMessenger})
+      : _binaryMessenger = binaryMessenger;
+
+  final BinaryMessenger? _binaryMessenger;
+
+  static const MessageCodec<Object?> pigeonChannelCodec =
+      StandardMessageCodec();
+
+  static void setUpMessageHandlers({
+    BinaryMessenger? binaryMessenger,
+    Pigeon_InstanceManager? instanceManager,
+  }) {
+    const String channelName =
+        r'dev.flutter.pigeon.pigeon_integration_tests.Pigeon_InstanceManagerApi.removeStrongReference';
+    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      channelName,
+      pigeonChannelCodec,
+      binaryMessenger: binaryMessenger,
+    );
+    channel.setMessageHandler((Object? message) async {
+      assert(
+        message != null,
+        'Argument for $channelName was null.',
+      );
+      final int? identifier = message as int?;
+      assert(
+        identifier != null,
+        r'Argument for $channelName, expected non-null int.',
+      );
+      (instanceManager ?? Pigeon_InstanceManager.instance).remove(identifier!);
+      return;
+    });
+  }
+
+  Future<void> removeStrongReference(int identifier) async {
+    const String channelName =
+        r'dev.flutter.pigeon.pigeon_integration_tests.Pigeon_InstanceManagerApi.removeStrongReference';
+    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      channelName,
+      pigeonChannelCodec,
+      binaryMessenger: _binaryMessenger,
+    );
+    final List<Object?>? replyList =
+        await channel.send(identifier) as List<Object?>?;
+    if (replyList == null) {
+      throw _createConnectionError(channelName);
+    } else if (replyList.length > 1) {
+      throw PlatformException(
+        code: replyList[0]! as String,
+        message: replyList[1] as String?,
+        details: replyList[2],
+      );
+    } else {
+      return;
+    }
+  }
+
+  /// Clear the native `Pigeon_InstanceManager`.
+  ///
+  /// This is typically called after a hot restart.
+  Future<void> clear() async {
+    const String channelName =
+        r'dev.flutter.pigeon.pigeon_integration_tests.Pigeon_InstanceManagerApi.clear';
+    final BasicMessageChannel<Object?> channel = BasicMessageChannel<Object?>(
+      channelName,
+      pigeonChannelCodec,
+      binaryMessenger: _binaryMessenger,
+    );
+    final List<Object?>? replyList = await channel.send(null) as List<Object?>?;
+    if (replyList == null) {
+      throw _createConnectionError(channelName);
+    } else if (replyList.length > 1) {
+      throw PlatformException(
+        code: replyList[0]! as String,
+        message: replyList[1] as String?,
+        details: replyList[2],
+      );
+    } else {
+      return;
+    }
+  }
+}
+
+class _Pigeon_ProxyApiBaseCodec extends StandardMessageCodec {
+  const _Pigeon_ProxyApiBaseCodec(this.instanceManager);
+
+  final Pigeon_InstanceManager instanceManager;
+
+  @override
+  void writeValue(WriteBuffer buffer, Object? value) {
+    if (value is Pigeon_ProxyApiBaseClass) {
+      buffer.putUint8(128);
+      writeValue(buffer, instanceManager.getIdentifier(value));
+    } else {
+      super.writeValue(buffer, value);
+    }
+  }
+
+  @override
+  Object? readValueOfType(int type, ReadBuffer buffer) {
+    switch (type) {
+      case 128:
+        return instanceManager
+            .getInstanceWithWeakReference(readValue(buffer)! as int);
+      default:
+        return super.readValueOfType(type, buffer);
+    }
+  }
+}
+
 enum AnEnum {
   one,
   two,
@@ -3446,3 +3807,4650 @@ abstract class FlutterSmallApi {
     }
   }
 }
+
+/// The core interface that each host language plugin must implement in
+/// platform_test integration tests.
+class ProxyIntegrationCoreApi extends ProxyApiSuperClass
+    implements ProxyApiInterface {
+  ProxyIntegrationCoreApi({
+    super.pigeon_binaryMessenger,
+    super.pigeon_instanceManager,
+    required this.aBool,
+    required this.anInt,
+    required this.aDouble,
+    required this.aString,
+    required this.aUint8List,
+    required this.aList,
+    required this.aMap,
+    required this.anEnum,
+    required this.aProxyApi,
+    this.aNullableBool,
+    this.aNullableInt,
+    this.aNullableDouble,
+    this.aNullableString,
+    this.aNullableUint8List,
+    this.aNullableList,
+    this.aNullableMap,
+    this.aNullableEnum,
+    this.aNullableProxyApi,
+    this.anInterfaceMethod,
+    this.flutterNoop,
+    this.flutterThrowError,
+    this.flutterThrowErrorFromVoid,
+    this.flutterEchoBool,
+    this.flutterEchoInt,
+    this.flutterEchoDouble,
+    this.flutterEchoString,
+    this.flutterEchoUint8List,
+    this.flutterEchoList,
+    this.flutterEchoProxyApiList,
+    this.flutterEchoMap,
+    this.flutterEchoProxyApiMap,
+    this.flutterEchoEnum,
+    this.flutterEchoProxyApi,
+    this.flutterEchoNullableBool,
+    this.flutterEchoNullableInt,
+    this.flutterEchoNullableDouble,
+    this.flutterEchoNullableString,
+    this.flutterEchoNullableUint8List,
+    this.flutterEchoNullableList,
+    this.flutterEchoNullableMap,
+    this.flutterEchoNullableEnum,
+    this.flutterEchoNullableProxyApi,
+    this.flutterNoopAsync,
+    this.flutterEchoAsyncString,
+    required bool boolParam,
+    required int intParam,
+    required double doubleParam,
+    required String stringParam,
+    required Uint8List aUint8ListParam,
+    required List<Object?> listParam,
+    required Map<String?, Object?> mapParam,
+    required AnEnum enumParam,
+    required ProxyApiSuperClass proxyApiParam,
+    bool? nullableBoolParam,
+    int? nullableIntParam,
+    double? nullableDoubleParam,
+    String? nullableStringParam,
+    Uint8List? nullableUint8ListParam,
+    List<Object?>? nullableListParam,
+    Map<String?, Object?>? nullableMapParam,
+    AnEnum? nullableEnumParam,
+    ProxyApiSuperClass? nullableProxyApiParam,
+  }) : super.pigeon_detached() {
+    final int __pigeon_instanceIdentifier =
+        pigeon_instanceManager.addDartCreatedInstance(this);
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    () async {
+      const String __pigeon_channelName =
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.pigeon_defaultConstructor';
+      final BasicMessageChannel<Object?> __pigeon_channel =
+          BasicMessageChannel<Object?>(
+        __pigeon_channelName,
+        pigeonChannelCodec,
+        binaryMessenger: __pigeon_binaryMessenger,
+      );
+      final List<Object?>? __pigeon_replyList =
+          await __pigeon_channel.send(<Object?>[
+        __pigeon_instanceIdentifier,
+        aBool,
+        anInt,
+        aDouble,
+        aString,
+        aUint8List,
+        aList,
+        aMap,
+        anEnum.index,
+        aProxyApi,
+        aNullableBool,
+        aNullableInt,
+        aNullableDouble,
+        aNullableString,
+        aNullableUint8List,
+        aNullableList,
+        aNullableMap,
+        aNullableEnum?.index,
+        aNullableProxyApi,
+        boolParam,
+        intParam,
+        doubleParam,
+        stringParam,
+        aUint8ListParam,
+        listParam,
+        mapParam,
+        enumParam.index,
+        proxyApiParam,
+        nullableBoolParam,
+        nullableIntParam,
+        nullableDoubleParam,
+        nullableStringParam,
+        nullableUint8ListParam,
+        nullableListParam,
+        nullableMapParam,
+        nullableEnumParam?.index,
+        nullableProxyApiParam
+      ]) as List<Object?>?;
+      if (__pigeon_replyList == null) {
+        throw _createConnectionError(__pigeon_channelName);
+      } else if (__pigeon_replyList.length > 1) {
+        throw PlatformException(
+          code: __pigeon_replyList[0]! as String,
+          message: __pigeon_replyList[1] as String?,
+          details: __pigeon_replyList[2],
+        );
+      } else {
+        return;
+      }
+    }();
+  }
+
+  /// Constructs ProxyIntegrationCoreApi without creating the associated native object.
+  ///
+  /// This should only be used by subclasses created by this library or to
+  /// create copies.
+  ProxyIntegrationCoreApi.pigeon_detached({
+    super.pigeon_binaryMessenger,
+    super.pigeon_instanceManager,
+    required this.aBool,
+    required this.anInt,
+    required this.aDouble,
+    required this.aString,
+    required this.aUint8List,
+    required this.aList,
+    required this.aMap,
+    required this.anEnum,
+    required this.aProxyApi,
+    this.aNullableBool,
+    this.aNullableInt,
+    this.aNullableDouble,
+    this.aNullableString,
+    this.aNullableUint8List,
+    this.aNullableList,
+    this.aNullableMap,
+    this.aNullableEnum,
+    this.aNullableProxyApi,
+    this.anInterfaceMethod,
+    this.flutterNoop,
+    this.flutterThrowError,
+    this.flutterThrowErrorFromVoid,
+    this.flutterEchoBool,
+    this.flutterEchoInt,
+    this.flutterEchoDouble,
+    this.flutterEchoString,
+    this.flutterEchoUint8List,
+    this.flutterEchoList,
+    this.flutterEchoProxyApiList,
+    this.flutterEchoMap,
+    this.flutterEchoProxyApiMap,
+    this.flutterEchoEnum,
+    this.flutterEchoProxyApi,
+    this.flutterEchoNullableBool,
+    this.flutterEchoNullableInt,
+    this.flutterEchoNullableDouble,
+    this.flutterEchoNullableString,
+    this.flutterEchoNullableUint8List,
+    this.flutterEchoNullableList,
+    this.flutterEchoNullableMap,
+    this.flutterEchoNullableEnum,
+    this.flutterEchoNullableProxyApi,
+    this.flutterNoopAsync,
+    this.flutterEchoAsyncString,
+  }) : super.pigeon_detached();
+
+  late final _Pigeon_ProxyApiBaseCodec __pigeon_codecProxyIntegrationCoreApi =
+      _Pigeon_ProxyApiBaseCodec(pigeon_instanceManager);
+
+  final bool aBool;
+
+  final int anInt;
+
+  final double aDouble;
+
+  final String aString;
+
+  final Uint8List aUint8List;
+
+  final List<Object?> aList;
+
+  final Map<String?, Object?> aMap;
+
+  final AnEnum anEnum;
+
+  final ProxyApiSuperClass aProxyApi;
+
+  final bool? aNullableBool;
+
+  final int? aNullableInt;
+
+  final double? aNullableDouble;
+
+  final String? aNullableString;
+
+  final Uint8List? aNullableUint8List;
+
+  final List<Object?>? aNullableList;
+
+  final Map<String?, Object?>? aNullableMap;
+
+  final AnEnum? aNullableEnum;
+
+  final ProxyApiSuperClass? aNullableProxyApi;
+
+  /// A no-op function taking no arguments and returning no value, to sanity
+  /// test basic calling.
+  ///
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyIntegrationCoreApi instance = ProxyIntegrationCoreApi(
+  ///  flutterNoop: (ProxyIntegrationCoreApi pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final void Function(ProxyIntegrationCoreApi pigeon_instance)? flutterNoop;
+
+  /// Responds with an error from an async function returning a value.
+  ///
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyIntegrationCoreApi instance = ProxyIntegrationCoreApi(
+  ///  flutterThrowError: (ProxyIntegrationCoreApi pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final Object? Function(ProxyIntegrationCoreApi pigeon_instance)?
+      flutterThrowError;
+
+  /// Responds with an error from an async void function.
+  ///
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyIntegrationCoreApi instance = ProxyIntegrationCoreApi(
+  ///  flutterThrowErrorFromVoid: (ProxyIntegrationCoreApi pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final void Function(ProxyIntegrationCoreApi pigeon_instance)?
+      flutterThrowErrorFromVoid;
+
+  /// Returns the passed boolean, to test serialization and deserialization.
+  ///
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyIntegrationCoreApi instance = ProxyIntegrationCoreApi(
+  ///  flutterEchoBool: (ProxyIntegrationCoreApi pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final bool Function(
+    ProxyIntegrationCoreApi pigeon_instance,
+    bool aBool,
+  )? flutterEchoBool;
+
+  /// Returns the passed int, to test serialization and deserialization.
+  ///
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyIntegrationCoreApi instance = ProxyIntegrationCoreApi(
+  ///  flutterEchoInt: (ProxyIntegrationCoreApi pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final int Function(
+    ProxyIntegrationCoreApi pigeon_instance,
+    int anInt,
+  )? flutterEchoInt;
+
+  /// Returns the passed double, to test serialization and deserialization.
+  ///
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyIntegrationCoreApi instance = ProxyIntegrationCoreApi(
+  ///  flutterEchoDouble: (ProxyIntegrationCoreApi pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final double Function(
+    ProxyIntegrationCoreApi pigeon_instance,
+    double aDouble,
+  )? flutterEchoDouble;
+
+  /// Returns the passed string, to test serialization and deserialization.
+  ///
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyIntegrationCoreApi instance = ProxyIntegrationCoreApi(
+  ///  flutterEchoString: (ProxyIntegrationCoreApi pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final String Function(
+    ProxyIntegrationCoreApi pigeon_instance,
+    String aString,
+  )? flutterEchoString;
+
+  /// Returns the passed byte list, to test serialization and deserialization.
+  ///
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyIntegrationCoreApi instance = ProxyIntegrationCoreApi(
+  ///  flutterEchoUint8List: (ProxyIntegrationCoreApi pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final Uint8List Function(
+    ProxyIntegrationCoreApi pigeon_instance,
+    Uint8List aList,
+  )? flutterEchoUint8List;
+
+  /// Returns the passed list, to test serialization and deserialization.
+  ///
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyIntegrationCoreApi instance = ProxyIntegrationCoreApi(
+  ///  flutterEchoList: (ProxyIntegrationCoreApi pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final List<Object?> Function(
+    ProxyIntegrationCoreApi pigeon_instance,
+    List<Object?> aList,
+  )? flutterEchoList;
+
+  /// Returns the passed list with ProxyApis, to test serialization and
+  /// deserialization.
+  ///
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyIntegrationCoreApi instance = ProxyIntegrationCoreApi(
+  ///  flutterEchoProxyApiList: (ProxyIntegrationCoreApi pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final List<ProxyIntegrationCoreApi?> Function(
+    ProxyIntegrationCoreApi pigeon_instance,
+    List<ProxyIntegrationCoreApi?> aList,
+  )? flutterEchoProxyApiList;
+
+  /// Returns the passed map, to test serialization and deserialization.
+  ///
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyIntegrationCoreApi instance = ProxyIntegrationCoreApi(
+  ///  flutterEchoMap: (ProxyIntegrationCoreApi pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final Map<String?, Object?> Function(
+    ProxyIntegrationCoreApi pigeon_instance,
+    Map<String?, Object?> aMap,
+  )? flutterEchoMap;
+
+  /// Returns the passed map with ProxyApis, to test serialization and
+  /// deserialization.
+  ///
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyIntegrationCoreApi instance = ProxyIntegrationCoreApi(
+  ///  flutterEchoProxyApiMap: (ProxyIntegrationCoreApi pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final Map<String?, ProxyIntegrationCoreApi?> Function(
+    ProxyIntegrationCoreApi pigeon_instance,
+    Map<String?, ProxyIntegrationCoreApi?> aMap,
+  )? flutterEchoProxyApiMap;
+
+  /// Returns the passed enum to test serialization and deserialization.
+  ///
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyIntegrationCoreApi instance = ProxyIntegrationCoreApi(
+  ///  flutterEchoEnum: (ProxyIntegrationCoreApi pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final AnEnum Function(
+    ProxyIntegrationCoreApi pigeon_instance,
+    AnEnum anEnum,
+  )? flutterEchoEnum;
+
+  /// Returns the passed ProxyApi to test serialization and deserialization.
+  ///
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyIntegrationCoreApi instance = ProxyIntegrationCoreApi(
+  ///  flutterEchoProxyApi: (ProxyIntegrationCoreApi pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final ProxyApiSuperClass Function(
+    ProxyIntegrationCoreApi pigeon_instance,
+    ProxyApiSuperClass aProxyApi,
+  )? flutterEchoProxyApi;
+
+  /// Returns the passed boolean, to test serialization and deserialization.
+  ///
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyIntegrationCoreApi instance = ProxyIntegrationCoreApi(
+  ///  flutterEchoNullableBool: (ProxyIntegrationCoreApi pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final bool? Function(
+    ProxyIntegrationCoreApi pigeon_instance,
+    bool? aBool,
+  )? flutterEchoNullableBool;
+
+  /// Returns the passed int, to test serialization and deserialization.
+  ///
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyIntegrationCoreApi instance = ProxyIntegrationCoreApi(
+  ///  flutterEchoNullableInt: (ProxyIntegrationCoreApi pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final int? Function(
+    ProxyIntegrationCoreApi pigeon_instance,
+    int? anInt,
+  )? flutterEchoNullableInt;
+
+  /// Returns the passed double, to test serialization and deserialization.
+  ///
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyIntegrationCoreApi instance = ProxyIntegrationCoreApi(
+  ///  flutterEchoNullableDouble: (ProxyIntegrationCoreApi pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final double? Function(
+    ProxyIntegrationCoreApi pigeon_instance,
+    double? aDouble,
+  )? flutterEchoNullableDouble;
+
+  /// Returns the passed string, to test serialization and deserialization.
+  ///
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyIntegrationCoreApi instance = ProxyIntegrationCoreApi(
+  ///  flutterEchoNullableString: (ProxyIntegrationCoreApi pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final String? Function(
+    ProxyIntegrationCoreApi pigeon_instance,
+    String? aString,
+  )? flutterEchoNullableString;
+
+  /// Returns the passed byte list, to test serialization and deserialization.
+  ///
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyIntegrationCoreApi instance = ProxyIntegrationCoreApi(
+  ///  flutterEchoNullableUint8List: (ProxyIntegrationCoreApi pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final Uint8List? Function(
+    ProxyIntegrationCoreApi pigeon_instance,
+    Uint8List? aList,
+  )? flutterEchoNullableUint8List;
+
+  /// Returns the passed list, to test serialization and deserialization.
+  ///
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyIntegrationCoreApi instance = ProxyIntegrationCoreApi(
+  ///  flutterEchoNullableList: (ProxyIntegrationCoreApi pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final List<Object?>? Function(
+    ProxyIntegrationCoreApi pigeon_instance,
+    List<Object?>? aList,
+  )? flutterEchoNullableList;
+
+  /// Returns the passed map, to test serialization and deserialization.
+  ///
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyIntegrationCoreApi instance = ProxyIntegrationCoreApi(
+  ///  flutterEchoNullableMap: (ProxyIntegrationCoreApi pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final Map<String?, Object?>? Function(
+    ProxyIntegrationCoreApi pigeon_instance,
+    Map<String?, Object?>? aMap,
+  )? flutterEchoNullableMap;
+
+  /// Returns the passed enum to test serialization and deserialization.
+  ///
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyIntegrationCoreApi instance = ProxyIntegrationCoreApi(
+  ///  flutterEchoNullableEnum: (ProxyIntegrationCoreApi pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final AnEnum? Function(
+    ProxyIntegrationCoreApi pigeon_instance,
+    AnEnum? anEnum,
+  )? flutterEchoNullableEnum;
+
+  /// Returns the passed ProxyApi to test serialization and deserialization.
+  ///
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyIntegrationCoreApi instance = ProxyIntegrationCoreApi(
+  ///  flutterEchoNullableProxyApi: (ProxyIntegrationCoreApi pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final ProxyApiSuperClass? Function(
+    ProxyIntegrationCoreApi pigeon_instance,
+    ProxyApiSuperClass? aProxyApi,
+  )? flutterEchoNullableProxyApi;
+
+  /// A no-op function taking no arguments and returning no value, to sanity
+  /// test basic asynchronous calling.
+  ///
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyIntegrationCoreApi instance = ProxyIntegrationCoreApi(
+  ///  flutterNoopAsync: (ProxyIntegrationCoreApi pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final Future<void> Function(ProxyIntegrationCoreApi pigeon_instance)?
+      flutterNoopAsync;
+
+  /// Returns the passed in generic Object asynchronously.
+  ///
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyIntegrationCoreApi instance = ProxyIntegrationCoreApi(
+  ///  flutterEchoAsyncString: (ProxyIntegrationCoreApi pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final Future<String> Function(
+    ProxyIntegrationCoreApi pigeon_instance,
+    String aString,
+  )? flutterEchoAsyncString;
+
+  @override
+  final void Function(ProxyApiInterface instance)? anInterfaceMethod;
+
+  late final ProxyApiSuperClass attachedField = __pigeon_attachedField();
+
+  static final ProxyApiSuperClass staticAttachedField =
+      __pigeon_staticAttachedField();
+
+  static void pigeon_setUpMessageHandlers({
+    bool pigeon_clearHandlers = false,
+    BinaryMessenger? pigeon_binaryMessenger,
+    Pigeon_InstanceManager? pigeon_instanceManager,
+    ProxyIntegrationCoreApi Function(
+      bool aBool,
+      int anInt,
+      double aDouble,
+      String aString,
+      Uint8List aUint8List,
+      List<Object?> aList,
+      Map<String?, Object?> aMap,
+      AnEnum anEnum,
+      ProxyApiSuperClass aProxyApi,
+      bool? aNullableBool,
+      int? aNullableInt,
+      double? aNullableDouble,
+      String? aNullableString,
+      Uint8List? aNullableUint8List,
+      List<Object?>? aNullableList,
+      Map<String?, Object?>? aNullableMap,
+      AnEnum? aNullableEnum,
+      ProxyApiSuperClass? aNullableProxyApi,
+    )? pigeon_newInstance,
+    void Function(ProxyIntegrationCoreApi pigeon_instance)? flutterNoop,
+    Object? Function(ProxyIntegrationCoreApi pigeon_instance)?
+        flutterThrowError,
+    void Function(ProxyIntegrationCoreApi pigeon_instance)?
+        flutterThrowErrorFromVoid,
+    bool Function(
+      ProxyIntegrationCoreApi pigeon_instance,
+      bool aBool,
+    )? flutterEchoBool,
+    int Function(
+      ProxyIntegrationCoreApi pigeon_instance,
+      int anInt,
+    )? flutterEchoInt,
+    double Function(
+      ProxyIntegrationCoreApi pigeon_instance,
+      double aDouble,
+    )? flutterEchoDouble,
+    String Function(
+      ProxyIntegrationCoreApi pigeon_instance,
+      String aString,
+    )? flutterEchoString,
+    Uint8List Function(
+      ProxyIntegrationCoreApi pigeon_instance,
+      Uint8List aList,
+    )? flutterEchoUint8List,
+    List<Object?> Function(
+      ProxyIntegrationCoreApi pigeon_instance,
+      List<Object?> aList,
+    )? flutterEchoList,
+    List<ProxyIntegrationCoreApi?> Function(
+      ProxyIntegrationCoreApi pigeon_instance,
+      List<ProxyIntegrationCoreApi?> aList,
+    )? flutterEchoProxyApiList,
+    Map<String?, Object?> Function(
+      ProxyIntegrationCoreApi pigeon_instance,
+      Map<String?, Object?> aMap,
+    )? flutterEchoMap,
+    Map<String?, ProxyIntegrationCoreApi?> Function(
+      ProxyIntegrationCoreApi pigeon_instance,
+      Map<String?, ProxyIntegrationCoreApi?> aMap,
+    )? flutterEchoProxyApiMap,
+    AnEnum Function(
+      ProxyIntegrationCoreApi pigeon_instance,
+      AnEnum anEnum,
+    )? flutterEchoEnum,
+    ProxyApiSuperClass Function(
+      ProxyIntegrationCoreApi pigeon_instance,
+      ProxyApiSuperClass aProxyApi,
+    )? flutterEchoProxyApi,
+    bool? Function(
+      ProxyIntegrationCoreApi pigeon_instance,
+      bool? aBool,
+    )? flutterEchoNullableBool,
+    int? Function(
+      ProxyIntegrationCoreApi pigeon_instance,
+      int? anInt,
+    )? flutterEchoNullableInt,
+    double? Function(
+      ProxyIntegrationCoreApi pigeon_instance,
+      double? aDouble,
+    )? flutterEchoNullableDouble,
+    String? Function(
+      ProxyIntegrationCoreApi pigeon_instance,
+      String? aString,
+    )? flutterEchoNullableString,
+    Uint8List? Function(
+      ProxyIntegrationCoreApi pigeon_instance,
+      Uint8List? aList,
+    )? flutterEchoNullableUint8List,
+    List<Object?>? Function(
+      ProxyIntegrationCoreApi pigeon_instance,
+      List<Object?>? aList,
+    )? flutterEchoNullableList,
+    Map<String?, Object?>? Function(
+      ProxyIntegrationCoreApi pigeon_instance,
+      Map<String?, Object?>? aMap,
+    )? flutterEchoNullableMap,
+    AnEnum? Function(
+      ProxyIntegrationCoreApi pigeon_instance,
+      AnEnum? anEnum,
+    )? flutterEchoNullableEnum,
+    ProxyApiSuperClass? Function(
+      ProxyIntegrationCoreApi pigeon_instance,
+      ProxyApiSuperClass? aProxyApi,
+    )? flutterEchoNullableProxyApi,
+    Future<void> Function(ProxyIntegrationCoreApi pigeon_instance)?
+        flutterNoopAsync,
+    Future<String> Function(
+      ProxyIntegrationCoreApi pigeon_instance,
+      String aString,
+    )? flutterEchoAsyncString,
+  }) {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        _Pigeon_ProxyApiBaseCodec(
+            pigeon_instanceManager ?? Pigeon_InstanceManager.instance);
+    final BinaryMessenger? binaryMessenger = pigeon_binaryMessenger;
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.pigeon_newInstance',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.pigeon_newInstance was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final int? arg_pigeon_instanceIdentifier = (args[0] as int?);
+          assert(arg_pigeon_instanceIdentifier != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.pigeon_newInstance was null, expected non-null int.');
+          final bool? arg_aBool = (args[1] as bool?);
+          assert(arg_aBool != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.pigeon_newInstance was null, expected non-null bool.');
+          final int? arg_anInt = (args[2] as int?);
+          assert(arg_anInt != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.pigeon_newInstance was null, expected non-null int.');
+          final double? arg_aDouble = (args[3] as double?);
+          assert(arg_aDouble != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.pigeon_newInstance was null, expected non-null double.');
+          final String? arg_aString = (args[4] as String?);
+          assert(arg_aString != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.pigeon_newInstance was null, expected non-null String.');
+          final Uint8List? arg_aUint8List = (args[5] as Uint8List?);
+          assert(arg_aUint8List != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.pigeon_newInstance was null, expected non-null Uint8List.');
+          final List<Object?>? arg_aList =
+              (args[6] as List<Object?>?)?.cast<Object?>();
+          assert(arg_aList != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.pigeon_newInstance was null, expected non-null List<Object?>.');
+          final Map<String?, Object?>? arg_aMap =
+              (args[7] as Map<Object?, Object?>?)?.cast<String?, Object?>();
+          assert(arg_aMap != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.pigeon_newInstance was null, expected non-null Map<String?, Object?>.');
+          final AnEnum? arg_anEnum =
+              args[8] == null ? null : AnEnum.values[args[8]! as int];
+          assert(arg_anEnum != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.pigeon_newInstance was null, expected non-null AnEnum.');
+          final ProxyApiSuperClass? arg_aProxyApi =
+              (args[9] as ProxyApiSuperClass?);
+          assert(arg_aProxyApi != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.pigeon_newInstance was null, expected non-null ProxyApiSuperClass.');
+          final bool? arg_aNullableBool = (args[10] as bool?);
+          final int? arg_aNullableInt = (args[11] as int?);
+          final double? arg_aNullableDouble = (args[12] as double?);
+          final String? arg_aNullableString = (args[13] as String?);
+          final Uint8List? arg_aNullableUint8List = (args[14] as Uint8List?);
+          final List<Object?>? arg_aNullableList =
+              (args[15] as List<Object?>?)?.cast<Object?>();
+          final Map<String?, Object?>? arg_aNullableMap =
+              (args[16] as Map<Object?, Object?>?)?.cast<String?, Object?>();
+          final AnEnum? arg_aNullableEnum =
+              args[17] == null ? null : AnEnum.values[args[17]! as int];
+          final ProxyApiSuperClass? arg_aNullableProxyApi =
+              (args[18] as ProxyApiSuperClass?);
+          try {
+            (pigeon_instanceManager ?? Pigeon_InstanceManager.instance)
+                .addHostCreatedInstance(
+              pigeon_newInstance?.call(
+                      arg_aBool!,
+                      arg_anInt!,
+                      arg_aDouble!,
+                      arg_aString!,
+                      arg_aUint8List!,
+                      arg_aList!,
+                      arg_aMap!,
+                      arg_anEnum!,
+                      arg_aProxyApi!,
+                      arg_aNullableBool,
+                      arg_aNullableInt,
+                      arg_aNullableDouble,
+                      arg_aNullableString,
+                      arg_aNullableUint8List,
+                      arg_aNullableList,
+                      arg_aNullableMap,
+                      arg_aNullableEnum,
+                      arg_aNullableProxyApi) ??
+                  ProxyIntegrationCoreApi.pigeon_detached(
+                    pigeon_binaryMessenger: pigeon_binaryMessenger,
+                    pigeon_instanceManager: pigeon_instanceManager,
+                    aBool: arg_aBool!,
+                    anInt: arg_anInt!,
+                    aDouble: arg_aDouble!,
+                    aString: arg_aString!,
+                    aUint8List: arg_aUint8List!,
+                    aList: arg_aList!,
+                    aMap: arg_aMap!,
+                    anEnum: arg_anEnum!,
+                    aProxyApi: arg_aProxyApi!,
+                    aNullableBool: arg_aNullableBool,
+                    aNullableInt: arg_aNullableInt,
+                    aNullableDouble: arg_aNullableDouble,
+                    aNullableString: arg_aNullableString,
+                    aNullableUint8List: arg_aNullableUint8List,
+                    aNullableList: arg_aNullableList,
+                    aNullableMap: arg_aNullableMap,
+                    aNullableEnum: arg_aNullableEnum,
+                    aNullableProxyApi: arg_aNullableProxyApi,
+                  ),
+              arg_pigeon_instanceIdentifier!,
+            );
+            return wrapResponse(empty: true);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterNoop',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterNoop was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyIntegrationCoreApi? arg_pigeon_instance =
+              (args[0] as ProxyIntegrationCoreApi?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterNoop was null, expected non-null ProxyIntegrationCoreApi.');
+          try {
+            (flutterNoop ?? arg_pigeon_instance!.flutterNoop)
+                ?.call(arg_pigeon_instance!);
+            return wrapResponse(empty: true);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterThrowError',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterThrowError was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyIntegrationCoreApi? arg_pigeon_instance =
+              (args[0] as ProxyIntegrationCoreApi?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterThrowError was null, expected non-null ProxyIntegrationCoreApi.');
+          try {
+            final Object? output =
+                (flutterThrowError ?? arg_pigeon_instance!.flutterThrowError)
+                    ?.call(arg_pigeon_instance!);
+            return wrapResponse(result: output);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterThrowErrorFromVoid',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterThrowErrorFromVoid was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyIntegrationCoreApi? arg_pigeon_instance =
+              (args[0] as ProxyIntegrationCoreApi?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterThrowErrorFromVoid was null, expected non-null ProxyIntegrationCoreApi.');
+          try {
+            (flutterThrowErrorFromVoid ??
+                    arg_pigeon_instance!.flutterThrowErrorFromVoid)
+                ?.call(arg_pigeon_instance!);
+            return wrapResponse(empty: true);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoBool',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoBool was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyIntegrationCoreApi? arg_pigeon_instance =
+              (args[0] as ProxyIntegrationCoreApi?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoBool was null, expected non-null ProxyIntegrationCoreApi.');
+          final bool? arg_aBool = (args[1] as bool?);
+          assert(arg_aBool != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoBool was null, expected non-null bool.');
+          try {
+            final bool? output =
+                (flutterEchoBool ?? arg_pigeon_instance!.flutterEchoBool)
+                    ?.call(arg_pigeon_instance!, arg_aBool!);
+            return wrapResponse(result: output);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoInt',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoInt was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyIntegrationCoreApi? arg_pigeon_instance =
+              (args[0] as ProxyIntegrationCoreApi?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoInt was null, expected non-null ProxyIntegrationCoreApi.');
+          final int? arg_anInt = (args[1] as int?);
+          assert(arg_anInt != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoInt was null, expected non-null int.');
+          try {
+            final int? output =
+                (flutterEchoInt ?? arg_pigeon_instance!.flutterEchoInt)
+                    ?.call(arg_pigeon_instance!, arg_anInt!);
+            return wrapResponse(result: output);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoDouble',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoDouble was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyIntegrationCoreApi? arg_pigeon_instance =
+              (args[0] as ProxyIntegrationCoreApi?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoDouble was null, expected non-null ProxyIntegrationCoreApi.');
+          final double? arg_aDouble = (args[1] as double?);
+          assert(arg_aDouble != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoDouble was null, expected non-null double.');
+          try {
+            final double? output =
+                (flutterEchoDouble ?? arg_pigeon_instance!.flutterEchoDouble)
+                    ?.call(arg_pigeon_instance!, arg_aDouble!);
+            return wrapResponse(result: output);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoString',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoString was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyIntegrationCoreApi? arg_pigeon_instance =
+              (args[0] as ProxyIntegrationCoreApi?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoString was null, expected non-null ProxyIntegrationCoreApi.');
+          final String? arg_aString = (args[1] as String?);
+          assert(arg_aString != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoString was null, expected non-null String.');
+          try {
+            final String? output =
+                (flutterEchoString ?? arg_pigeon_instance!.flutterEchoString)
+                    ?.call(arg_pigeon_instance!, arg_aString!);
+            return wrapResponse(result: output);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoUint8List',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoUint8List was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyIntegrationCoreApi? arg_pigeon_instance =
+              (args[0] as ProxyIntegrationCoreApi?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoUint8List was null, expected non-null ProxyIntegrationCoreApi.');
+          final Uint8List? arg_aList = (args[1] as Uint8List?);
+          assert(arg_aList != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoUint8List was null, expected non-null Uint8List.');
+          try {
+            final Uint8List? output = (flutterEchoUint8List ??
+                    arg_pigeon_instance!.flutterEchoUint8List)
+                ?.call(arg_pigeon_instance!, arg_aList!);
+            return wrapResponse(result: output);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoList',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoList was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyIntegrationCoreApi? arg_pigeon_instance =
+              (args[0] as ProxyIntegrationCoreApi?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoList was null, expected non-null ProxyIntegrationCoreApi.');
+          final List<Object?>? arg_aList =
+              (args[1] as List<Object?>?)?.cast<Object?>();
+          assert(arg_aList != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoList was null, expected non-null List<Object?>.');
+          try {
+            final List<Object?>? output =
+                (flutterEchoList ?? arg_pigeon_instance!.flutterEchoList)
+                    ?.call(arg_pigeon_instance!, arg_aList!);
+            return wrapResponse(result: output);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoProxyApiList',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoProxyApiList was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyIntegrationCoreApi? arg_pigeon_instance =
+              (args[0] as ProxyIntegrationCoreApi?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoProxyApiList was null, expected non-null ProxyIntegrationCoreApi.');
+          final List<ProxyIntegrationCoreApi?>? arg_aList =
+              (args[1] as List<Object?>?)?.cast<ProxyIntegrationCoreApi?>();
+          assert(arg_aList != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoProxyApiList was null, expected non-null List<ProxyIntegrationCoreApi?>.');
+          try {
+            final List<ProxyIntegrationCoreApi?>? output =
+                (flutterEchoProxyApiList ??
+                        arg_pigeon_instance!.flutterEchoProxyApiList)
+                    ?.call(arg_pigeon_instance!, arg_aList!);
+            return wrapResponse(result: output);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoMap',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoMap was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyIntegrationCoreApi? arg_pigeon_instance =
+              (args[0] as ProxyIntegrationCoreApi?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoMap was null, expected non-null ProxyIntegrationCoreApi.');
+          final Map<String?, Object?>? arg_aMap =
+              (args[1] as Map<Object?, Object?>?)?.cast<String?, Object?>();
+          assert(arg_aMap != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoMap was null, expected non-null Map<String?, Object?>.');
+          try {
+            final Map<String?, Object?>? output =
+                (flutterEchoMap ?? arg_pigeon_instance!.flutterEchoMap)
+                    ?.call(arg_pigeon_instance!, arg_aMap!);
+            return wrapResponse(result: output);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoProxyApiMap',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoProxyApiMap was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyIntegrationCoreApi? arg_pigeon_instance =
+              (args[0] as ProxyIntegrationCoreApi?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoProxyApiMap was null, expected non-null ProxyIntegrationCoreApi.');
+          final Map<String?, ProxyIntegrationCoreApi?>? arg_aMap =
+              (args[1] as Map<Object?, Object?>?)
+                  ?.cast<String?, ProxyIntegrationCoreApi?>();
+          assert(arg_aMap != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoProxyApiMap was null, expected non-null Map<String?, ProxyIntegrationCoreApi?>.');
+          try {
+            final Map<String?, ProxyIntegrationCoreApi?>? output =
+                (flutterEchoProxyApiMap ??
+                        arg_pigeon_instance!.flutterEchoProxyApiMap)
+                    ?.call(arg_pigeon_instance!, arg_aMap!);
+            return wrapResponse(result: output);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoEnum',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoEnum was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyIntegrationCoreApi? arg_pigeon_instance =
+              (args[0] as ProxyIntegrationCoreApi?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoEnum was null, expected non-null ProxyIntegrationCoreApi.');
+          final AnEnum? arg_anEnum =
+              args[1] == null ? null : AnEnum.values[args[1]! as int];
+          assert(arg_anEnum != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoEnum was null, expected non-null AnEnum.');
+          try {
+            final AnEnum? output =
+                (flutterEchoEnum ?? arg_pigeon_instance!.flutterEchoEnum)
+                    ?.call(arg_pigeon_instance!, arg_anEnum!);
+            return wrapResponse(result: output?.index);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoProxyApi',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoProxyApi was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyIntegrationCoreApi? arg_pigeon_instance =
+              (args[0] as ProxyIntegrationCoreApi?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoProxyApi was null, expected non-null ProxyIntegrationCoreApi.');
+          final ProxyApiSuperClass? arg_aProxyApi =
+              (args[1] as ProxyApiSuperClass?);
+          assert(arg_aProxyApi != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoProxyApi was null, expected non-null ProxyApiSuperClass.');
+          try {
+            final ProxyApiSuperClass? output = (flutterEchoProxyApi ??
+                    arg_pigeon_instance!.flutterEchoProxyApi)
+                ?.call(arg_pigeon_instance!, arg_aProxyApi!);
+            return wrapResponse(result: output);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableBool',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableBool was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyIntegrationCoreApi? arg_pigeon_instance =
+              (args[0] as ProxyIntegrationCoreApi?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableBool was null, expected non-null ProxyIntegrationCoreApi.');
+          final bool? arg_aBool = (args[1] as bool?);
+          try {
+            final bool? output = (flutterEchoNullableBool ??
+                    arg_pigeon_instance!.flutterEchoNullableBool)
+                ?.call(arg_pigeon_instance!, arg_aBool);
+            return wrapResponse(result: output);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableInt',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableInt was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyIntegrationCoreApi? arg_pigeon_instance =
+              (args[0] as ProxyIntegrationCoreApi?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableInt was null, expected non-null ProxyIntegrationCoreApi.');
+          final int? arg_anInt = (args[1] as int?);
+          try {
+            final int? output = (flutterEchoNullableInt ??
+                    arg_pigeon_instance!.flutterEchoNullableInt)
+                ?.call(arg_pigeon_instance!, arg_anInt);
+            return wrapResponse(result: output);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableDouble',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableDouble was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyIntegrationCoreApi? arg_pigeon_instance =
+              (args[0] as ProxyIntegrationCoreApi?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableDouble was null, expected non-null ProxyIntegrationCoreApi.');
+          final double? arg_aDouble = (args[1] as double?);
+          try {
+            final double? output = (flutterEchoNullableDouble ??
+                    arg_pigeon_instance!.flutterEchoNullableDouble)
+                ?.call(arg_pigeon_instance!, arg_aDouble);
+            return wrapResponse(result: output);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableString',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableString was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyIntegrationCoreApi? arg_pigeon_instance =
+              (args[0] as ProxyIntegrationCoreApi?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableString was null, expected non-null ProxyIntegrationCoreApi.');
+          final String? arg_aString = (args[1] as String?);
+          try {
+            final String? output = (flutterEchoNullableString ??
+                    arg_pigeon_instance!.flutterEchoNullableString)
+                ?.call(arg_pigeon_instance!, arg_aString);
+            return wrapResponse(result: output);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableUint8List',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableUint8List was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyIntegrationCoreApi? arg_pigeon_instance =
+              (args[0] as ProxyIntegrationCoreApi?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableUint8List was null, expected non-null ProxyIntegrationCoreApi.');
+          final Uint8List? arg_aList = (args[1] as Uint8List?);
+          try {
+            final Uint8List? output = (flutterEchoNullableUint8List ??
+                    arg_pigeon_instance!.flutterEchoNullableUint8List)
+                ?.call(arg_pigeon_instance!, arg_aList);
+            return wrapResponse(result: output);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableList',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableList was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyIntegrationCoreApi? arg_pigeon_instance =
+              (args[0] as ProxyIntegrationCoreApi?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableList was null, expected non-null ProxyIntegrationCoreApi.');
+          final List<Object?>? arg_aList =
+              (args[1] as List<Object?>?)?.cast<Object?>();
+          try {
+            final List<Object?>? output = (flutterEchoNullableList ??
+                    arg_pigeon_instance!.flutterEchoNullableList)
+                ?.call(arg_pigeon_instance!, arg_aList);
+            return wrapResponse(result: output);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableMap',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableMap was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyIntegrationCoreApi? arg_pigeon_instance =
+              (args[0] as ProxyIntegrationCoreApi?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableMap was null, expected non-null ProxyIntegrationCoreApi.');
+          final Map<String?, Object?>? arg_aMap =
+              (args[1] as Map<Object?, Object?>?)?.cast<String?, Object?>();
+          try {
+            final Map<String?, Object?>? output = (flutterEchoNullableMap ??
+                    arg_pigeon_instance!.flutterEchoNullableMap)
+                ?.call(arg_pigeon_instance!, arg_aMap);
+            return wrapResponse(result: output);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableEnum',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableEnum was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyIntegrationCoreApi? arg_pigeon_instance =
+              (args[0] as ProxyIntegrationCoreApi?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableEnum was null, expected non-null ProxyIntegrationCoreApi.');
+          final AnEnum? arg_anEnum =
+              args[1] == null ? null : AnEnum.values[args[1]! as int];
+          try {
+            final AnEnum? output = (flutterEchoNullableEnum ??
+                    arg_pigeon_instance!.flutterEchoNullableEnum)
+                ?.call(arg_pigeon_instance!, arg_anEnum);
+            return wrapResponse(result: output?.index);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableProxyApi',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableProxyApi was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyIntegrationCoreApi? arg_pigeon_instance =
+              (args[0] as ProxyIntegrationCoreApi?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoNullableProxyApi was null, expected non-null ProxyIntegrationCoreApi.');
+          final ProxyApiSuperClass? arg_aProxyApi =
+              (args[1] as ProxyApiSuperClass?);
+          try {
+            final ProxyApiSuperClass? output = (flutterEchoNullableProxyApi ??
+                    arg_pigeon_instance!.flutterEchoNullableProxyApi)
+                ?.call(arg_pigeon_instance!, arg_aProxyApi);
+            return wrapResponse(result: output);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterNoopAsync',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterNoopAsync was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyIntegrationCoreApi? arg_pigeon_instance =
+              (args[0] as ProxyIntegrationCoreApi?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterNoopAsync was null, expected non-null ProxyIntegrationCoreApi.');
+          try {
+            await (flutterNoopAsync ?? arg_pigeon_instance!.flutterNoopAsync)
+                ?.call(arg_pigeon_instance!);
+            return wrapResponse(empty: true);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoAsyncString',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoAsyncString was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyIntegrationCoreApi? arg_pigeon_instance =
+              (args[0] as ProxyIntegrationCoreApi?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoAsyncString was null, expected non-null ProxyIntegrationCoreApi.');
+          final String? arg_aString = (args[1] as String?);
+          assert(arg_aString != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.flutterEchoAsyncString was null, expected non-null String.');
+          try {
+            final String? output = await (flutterEchoAsyncString ??
+                    arg_pigeon_instance!.flutterEchoAsyncString)
+                ?.call(arg_pigeon_instance!, arg_aString!);
+            return wrapResponse(result: output);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+  }
+
+  ProxyApiSuperClass __pigeon_attachedField() {
+    final ProxyApiSuperClass __pigeon_instance =
+        ProxyApiSuperClass.pigeon_detached(
+      pigeon_binaryMessenger: pigeon_binaryMessenger,
+      pigeon_instanceManager: pigeon_instanceManager,
+    );
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    final int __pigeon_instanceIdentifier =
+        pigeon_instanceManager.addDartCreatedInstance(__pigeon_instance);
+    () async {
+      const String __pigeon_channelName =
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.attachedField';
+      final BasicMessageChannel<Object?> __pigeon_channel =
+          BasicMessageChannel<Object?>(
+        __pigeon_channelName,
+        pigeonChannelCodec,
+        binaryMessenger: __pigeon_binaryMessenger,
+      );
+      final List<Object?>? __pigeon_replyList = await __pigeon_channel
+          .send(<Object?>[this, __pigeon_instanceIdentifier]) as List<Object?>?;
+      if (__pigeon_replyList == null) {
+        throw _createConnectionError(__pigeon_channelName);
+      } else if (__pigeon_replyList.length > 1) {
+        throw PlatformException(
+          code: __pigeon_replyList[0]! as String,
+          message: __pigeon_replyList[1] as String?,
+          details: __pigeon_replyList[2],
+        );
+      } else {
+        return;
+      }
+    }();
+    return __pigeon_instance;
+  }
+
+  static ProxyApiSuperClass __pigeon_staticAttachedField() {
+    final ProxyApiSuperClass __pigeon_instance =
+        ProxyApiSuperClass.pigeon_detached();
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        _Pigeon_ProxyApiBaseCodec(Pigeon_InstanceManager.instance);
+    final BinaryMessenger __pigeon_binaryMessenger =
+        ServicesBinding.instance.defaultBinaryMessenger;
+    final int __pigeon_instanceIdentifier = Pigeon_InstanceManager.instance
+        .addDartCreatedInstance(__pigeon_instance);
+    () async {
+      const String __pigeon_channelName =
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.staticAttachedField';
+      final BasicMessageChannel<Object?> __pigeon_channel =
+          BasicMessageChannel<Object?>(
+        __pigeon_channelName,
+        pigeonChannelCodec,
+        binaryMessenger: __pigeon_binaryMessenger,
+      );
+      final List<Object?>? __pigeon_replyList = await __pigeon_channel
+          .send(<Object?>[__pigeon_instanceIdentifier]) as List<Object?>?;
+      if (__pigeon_replyList == null) {
+        throw _createConnectionError(__pigeon_channelName);
+      } else if (__pigeon_replyList.length > 1) {
+        throw PlatformException(
+          code: __pigeon_replyList[0]! as String,
+          message: __pigeon_replyList[1] as String?,
+          details: __pigeon_replyList[2],
+        );
+      } else {
+        return;
+      }
+    }();
+    return __pigeon_instance;
+  }
+
+  /// A no-op function taking no arguments and returning no value, to sanity
+  /// test basic calling.
+  Future<void> noop() async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.noop';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return;
+    }
+  }
+
+  /// Returns an error, to test error handling.
+  Future<Object?> throwError() async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.throwError';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return __pigeon_replyList[0];
+    }
+  }
+
+  /// Returns an error from a void function, to test error handling.
+  Future<void> throwErrorFromVoid() async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.throwErrorFromVoid';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return;
+    }
+  }
+
+  /// Returns a Flutter error, to test error handling.
+  Future<Object?> throwFlutterError() async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.throwFlutterError';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return __pigeon_replyList[0];
+    }
+  }
+
+  /// Returns passed in int.
+  Future<int> echoInt(int anInt) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoInt';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, anInt]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as int?)!;
+    }
+  }
+
+  /// Returns passed in double.
+  Future<double> echoDouble(double aDouble) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoDouble';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aDouble]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as double?)!;
+    }
+  }
+
+  /// Returns the passed in boolean.
+  Future<bool> echoBool(bool aBool) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoBool';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aBool]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as bool?)!;
+    }
+  }
+
+  /// Returns the passed in string.
+  Future<String> echoString(String aString) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoString';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aString]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as String?)!;
+    }
+  }
+
+  /// Returns the passed in Uint8List.
+  Future<Uint8List> echoUint8List(Uint8List aUint8List) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoUint8List';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, aUint8List]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as Uint8List?)!;
+    }
+  }
+
+  /// Returns the passed in generic Object.
+  Future<Object> echoObject(Object anObject) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoObject';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, anObject]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return __pigeon_replyList[0]!;
+    }
+  }
+
+  /// Returns the passed list, to test serialization and deserialization.
+  Future<List<Object?>> echoList(List<Object?> aList) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoList';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aList]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as List<Object?>?)!.cast<Object?>();
+    }
+  }
+
+  /// Returns the passed list with ProxyApis, to test serialization and
+  /// deserialization.
+  Future<List<ProxyIntegrationCoreApi?>> echoProxyApiList(
+      List<ProxyIntegrationCoreApi?> aList) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoProxyApiList';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aList]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as List<Object?>?)!
+          .cast<ProxyIntegrationCoreApi?>();
+    }
+  }
+
+  /// Returns the passed map, to test serialization and deserialization.
+  Future<Map<String?, Object?>> echoMap(Map<String?, Object?> aMap) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoMap';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aMap]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as Map<Object?, Object?>?)!
+          .cast<String?, Object?>();
+    }
+  }
+
+  /// Returns the passed map with ProxyApis, to test serialization and
+  /// deserialization.
+  Future<Map<String?, ProxyIntegrationCoreApi?>> echoProxyApiMap(
+      Map<String?, ProxyIntegrationCoreApi?> aMap) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoProxyApiMap';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aMap]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as Map<Object?, Object?>?)!
+          .cast<String?, ProxyIntegrationCoreApi?>();
+    }
+  }
+
+  /// Returns the passed enum to test serialization and deserialization.
+  Future<AnEnum> echoEnum(AnEnum anEnum) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoEnum';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, anEnum.index]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return AnEnum.values[__pigeon_replyList[0]! as int];
+    }
+  }
+
+  /// Returns the passed ProxyApi to test serialization and deserialization.
+  Future<ProxyApiSuperClass> echoProxyApi(ProxyApiSuperClass aProxyApi) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoProxyApi';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, aProxyApi]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as ProxyApiSuperClass?)!;
+    }
+  }
+
+  /// Returns passed in int.
+  Future<int?> echoNullableInt(int? aNullableInt) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoNullableInt';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, aNullableInt]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as int?);
+    }
+  }
+
+  /// Returns passed in double.
+  Future<double?> echoNullableDouble(double? aNullableDouble) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoNullableDouble';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, aNullableDouble]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as double?);
+    }
+  }
+
+  /// Returns the passed in boolean.
+  Future<bool?> echoNullableBool(bool? aNullableBool) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoNullableBool';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, aNullableBool]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as bool?);
+    }
+  }
+
+  /// Returns the passed in string.
+  Future<String?> echoNullableString(String? aNullableString) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoNullableString';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, aNullableString]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as String?);
+    }
+  }
+
+  /// Returns the passed in Uint8List.
+  Future<Uint8List?> echoNullableUint8List(
+      Uint8List? aNullableUint8List) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoNullableUint8List';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, aNullableUint8List]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as Uint8List?);
+    }
+  }
+
+  /// Returns the passed in generic Object.
+  Future<Object?> echoNullableObject(Object? aNullableObject) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoNullableObject';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, aNullableObject]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return __pigeon_replyList[0];
+    }
+  }
+
+  /// Returns the passed list, to test serialization and deserialization.
+  Future<List<Object?>?> echoNullableList(List<Object?>? aNullableList) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoNullableList';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, aNullableList]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as List<Object?>?)?.cast<Object?>();
+    }
+  }
+
+  /// Returns the passed map, to test serialization and deserialization.
+  Future<Map<String?, Object?>?> echoNullableMap(
+      Map<String?, Object?>? aNullableMap) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoNullableMap';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, aNullableMap]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as Map<Object?, Object?>?)
+          ?.cast<String?, Object?>();
+    }
+  }
+
+  Future<AnEnum?> echoNullableEnum(AnEnum? aNullableEnum) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoNullableEnum';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, aNullableEnum?.index]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as int?) == null
+          ? null
+          : AnEnum.values[__pigeon_replyList[0]! as int];
+    }
+  }
+
+  /// Returns the passed ProxyApi to test serialization and deserialization.
+  Future<ProxyApiSuperClass?> echoNullableProxyApi(
+      ProxyApiSuperClass? aNullableProxyApi) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoNullableProxyApi';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, aNullableProxyApi]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as ProxyApiSuperClass?);
+    }
+  }
+
+  /// A no-op function taking no arguments and returning no value, to sanity
+  /// test basic asynchronous calling.
+  Future<void> noopAsync() async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.noopAsync';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return;
+    }
+  }
+
+  /// Returns passed in int asynchronously.
+  Future<int> echoAsyncInt(int anInt) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoAsyncInt';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, anInt]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as int?)!;
+    }
+  }
+
+  /// Returns passed in double asynchronously.
+  Future<double> echoAsyncDouble(double aDouble) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoAsyncDouble';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aDouble]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as double?)!;
+    }
+  }
+
+  /// Returns the passed in boolean asynchronously.
+  Future<bool> echoAsyncBool(bool aBool) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoAsyncBool';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aBool]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as bool?)!;
+    }
+  }
+
+  /// Returns the passed string asynchronously.
+  Future<String> echoAsyncString(String aString) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoAsyncString';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aString]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as String?)!;
+    }
+  }
+
+  /// Returns the passed in Uint8List asynchronously.
+  Future<Uint8List> echoAsyncUint8List(Uint8List aUint8List) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoAsyncUint8List';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, aUint8List]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as Uint8List?)!;
+    }
+  }
+
+  /// Returns the passed in generic Object asynchronously.
+  Future<Object> echoAsyncObject(Object anObject) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoAsyncObject';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, anObject]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return __pigeon_replyList[0]!;
+    }
+  }
+
+  /// Returns the passed list, to test asynchronous serialization and deserialization.
+  Future<List<Object?>> echoAsyncList(List<Object?> aList) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoAsyncList';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aList]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as List<Object?>?)!.cast<Object?>();
+    }
+  }
+
+  /// Returns the passed map, to test asynchronous serialization and deserialization.
+  Future<Map<String?, Object?>> echoAsyncMap(Map<String?, Object?> aMap) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoAsyncMap';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aMap]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as Map<Object?, Object?>?)!
+          .cast<String?, Object?>();
+    }
+  }
+
+  /// Returns the passed enum, to test asynchronous serialization and deserialization.
+  Future<AnEnum> echoAsyncEnum(AnEnum anEnum) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoAsyncEnum';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, anEnum.index]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return AnEnum.values[__pigeon_replyList[0]! as int];
+    }
+  }
+
+  /// Responds with an error from an async function returning a value.
+  Future<Object?> throwAsyncError() async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.throwAsyncError';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return __pigeon_replyList[0];
+    }
+  }
+
+  /// Responds with an error from an async void function.
+  Future<void> throwAsyncErrorFromVoid() async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.throwAsyncErrorFromVoid';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return;
+    }
+  }
+
+  /// Responds with a Flutter error from an async function returning a value.
+  Future<Object?> throwAsyncFlutterError() async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.throwAsyncFlutterError';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return __pigeon_replyList[0];
+    }
+  }
+
+  /// Returns passed in int asynchronously.
+  Future<int?> echoAsyncNullableInt(int? anInt) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoAsyncNullableInt';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, anInt]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as int?);
+    }
+  }
+
+  /// Returns passed in double asynchronously.
+  Future<double?> echoAsyncNullableDouble(double? aDouble) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoAsyncNullableDouble';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aDouble]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as double?);
+    }
+  }
+
+  /// Returns the passed in boolean asynchronously.
+  Future<bool?> echoAsyncNullableBool(bool? aBool) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoAsyncNullableBool';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aBool]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as bool?);
+    }
+  }
+
+  /// Returns the passed string asynchronously.
+  Future<String?> echoAsyncNullableString(String? aString) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoAsyncNullableString';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aString]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as String?);
+    }
+  }
+
+  /// Returns the passed in Uint8List asynchronously.
+  Future<Uint8List?> echoAsyncNullableUint8List(Uint8List? aUint8List) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoAsyncNullableUint8List';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, aUint8List]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as Uint8List?);
+    }
+  }
+
+  /// Returns the passed in generic Object asynchronously.
+  Future<Object?> echoAsyncNullableObject(Object? anObject) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoAsyncNullableObject';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, anObject]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return __pigeon_replyList[0];
+    }
+  }
+
+  /// Returns the passed list, to test asynchronous serialization and deserialization.
+  Future<List<Object?>?> echoAsyncNullableList(List<Object?>? aList) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoAsyncNullableList';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aList]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as List<Object?>?)?.cast<Object?>();
+    }
+  }
+
+  /// Returns the passed map, to test asynchronous serialization and deserialization.
+  Future<Map<String?, Object?>?> echoAsyncNullableMap(
+      Map<String?, Object?>? aMap) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoAsyncNullableMap';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aMap]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as Map<Object?, Object?>?)
+          ?.cast<String?, Object?>();
+    }
+  }
+
+  /// Returns the passed enum, to test asynchronous serialization and deserialization.
+  Future<AnEnum?> echoAsyncNullableEnum(AnEnum? anEnum) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoAsyncNullableEnum';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, anEnum?.index]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as int?) == null
+          ? null
+          : AnEnum.values[__pigeon_replyList[0]! as int];
+    }
+  }
+
+  static Future<void> staticNoop({
+    BinaryMessenger? pigeon_binaryMessenger,
+    Pigeon_InstanceManager? pigeon_instanceManager,
+  }) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        _Pigeon_ProxyApiBaseCodec(
+            pigeon_instanceManager ?? Pigeon_InstanceManager.instance);
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.staticNoop';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(null) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return;
+    }
+  }
+
+  static Future<String> echoStaticString(
+    String aString, {
+    BinaryMessenger? pigeon_binaryMessenger,
+    Pigeon_InstanceManager? pigeon_instanceManager,
+  }) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        _Pigeon_ProxyApiBaseCodec(
+            pigeon_instanceManager ?? Pigeon_InstanceManager.instance);
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.echoStaticString';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[aString]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as String?)!;
+    }
+  }
+
+  static Future<void> staticAsyncNoop({
+    BinaryMessenger? pigeon_binaryMessenger,
+    Pigeon_InstanceManager? pigeon_instanceManager,
+  }) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        _Pigeon_ProxyApiBaseCodec(
+            pigeon_instanceManager ?? Pigeon_InstanceManager.instance);
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.staticAsyncNoop';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(null) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return;
+    }
+  }
+
+  Future<void> callFlutterNoop() async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.callFlutterNoop';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return;
+    }
+  }
+
+  Future<Object?> callFlutterThrowError() async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.callFlutterThrowError';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return __pigeon_replyList[0];
+    }
+  }
+
+  Future<void> callFlutterThrowErrorFromVoid() async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.callFlutterThrowErrorFromVoid';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return;
+    }
+  }
+
+  Future<bool> callFlutterEchoBool(bool aBool) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.callFlutterEchoBool';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aBool]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as bool?)!;
+    }
+  }
+
+  Future<int> callFlutterEchoInt(int anInt) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.callFlutterEchoInt';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, anInt]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as int?)!;
+    }
+  }
+
+  Future<double> callFlutterEchoDouble(double aDouble) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.callFlutterEchoDouble';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aDouble]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as double?)!;
+    }
+  }
+
+  Future<String> callFlutterEchoString(String aString) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.callFlutterEchoString';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aString]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as String?)!;
+    }
+  }
+
+  Future<Uint8List> callFlutterEchoUint8List(Uint8List aUint8List) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.callFlutterEchoUint8List';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, aUint8List]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as Uint8List?)!;
+    }
+  }
+
+  Future<List<Object?>> callFlutterEchoList(List<Object?> aList) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.callFlutterEchoList';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aList]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as List<Object?>?)!.cast<Object?>();
+    }
+  }
+
+  Future<List<ProxyIntegrationCoreApi?>> callFlutterEchoProxyApiList(
+      List<ProxyIntegrationCoreApi?> aList) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.callFlutterEchoProxyApiList';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aList]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as List<Object?>?)!
+          .cast<ProxyIntegrationCoreApi?>();
+    }
+  }
+
+  Future<Map<String?, Object?>> callFlutterEchoMap(
+      Map<String?, Object?> aMap) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.callFlutterEchoMap';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aMap]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as Map<Object?, Object?>?)!
+          .cast<String?, Object?>();
+    }
+  }
+
+  Future<Map<String?, ProxyIntegrationCoreApi?>> callFlutterEchoProxyApiMap(
+      Map<String?, ProxyIntegrationCoreApi?> aMap) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.callFlutterEchoProxyApiMap';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aMap]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as Map<Object?, Object?>?)!
+          .cast<String?, ProxyIntegrationCoreApi?>();
+    }
+  }
+
+  Future<AnEnum> callFlutterEchoEnum(AnEnum anEnum) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.callFlutterEchoEnum';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, anEnum.index]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return AnEnum.values[__pigeon_replyList[0]! as int];
+    }
+  }
+
+  Future<ProxyApiSuperClass> callFlutterEchoProxyApi(
+      ProxyApiSuperClass aProxyApi) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.callFlutterEchoProxyApi';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, aProxyApi]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as ProxyApiSuperClass?)!;
+    }
+  }
+
+  Future<bool?> callFlutterEchoNullableBool(bool? aBool) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.callFlutterEchoNullableBool';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aBool]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as bool?);
+    }
+  }
+
+  Future<int?> callFlutterEchoNullableInt(int? anInt) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.callFlutterEchoNullableInt';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, anInt]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as int?);
+    }
+  }
+
+  Future<double?> callFlutterEchoNullableDouble(double? aDouble) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.callFlutterEchoNullableDouble';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aDouble]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as double?);
+    }
+  }
+
+  Future<String?> callFlutterEchoNullableString(String? aString) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.callFlutterEchoNullableString';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aString]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as String?);
+    }
+  }
+
+  Future<Uint8List?> callFlutterEchoNullableUint8List(
+      Uint8List? aUint8List) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.callFlutterEchoNullableUint8List';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, aUint8List]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as Uint8List?);
+    }
+  }
+
+  Future<List<Object?>?> callFlutterEchoNullableList(
+      List<Object?>? aList) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.callFlutterEchoNullableList';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aList]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as List<Object?>?)?.cast<Object?>();
+    }
+  }
+
+  Future<Map<String?, Object?>?> callFlutterEchoNullableMap(
+      Map<String?, Object?>? aMap) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.callFlutterEchoNullableMap';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aMap]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as Map<Object?, Object?>?)
+          ?.cast<String?, Object?>();
+    }
+  }
+
+  Future<AnEnum?> callFlutterEchoNullableEnum(AnEnum? anEnum) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.callFlutterEchoNullableEnum';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, anEnum?.index]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as int?) == null
+          ? null
+          : AnEnum.values[__pigeon_replyList[0]! as int];
+    }
+  }
+
+  Future<ProxyApiSuperClass?> callFlutterEchoNullableProxyApi(
+      ProxyApiSuperClass? aProxyApi) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.callFlutterEchoNullableProxyApi';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList = await __pigeon_channel
+        .send(<Object?>[this, aProxyApi]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return (__pigeon_replyList[0] as ProxyApiSuperClass?);
+    }
+  }
+
+  Future<void> callFlutterNoopAsync() async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.callFlutterNoopAsync';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return;
+    }
+  }
+
+  Future<String> callFlutterEchoAsyncString(String aString) async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyIntegrationCoreApi;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyIntegrationCoreApi.callFlutterEchoAsyncString';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this, aString]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else if (__pigeon_replyList[0] == null) {
+      throw PlatformException(
+        code: 'null-error',
+        message: 'Host platform returned null value for non-null return value.',
+      );
+    } else {
+      return (__pigeon_replyList[0] as String?)!;
+    }
+  }
+
+  @override
+  ProxyIntegrationCoreApi pigeon_copy() {
+    return ProxyIntegrationCoreApi.pigeon_detached(
+      pigeon_binaryMessenger: pigeon_binaryMessenger,
+      pigeon_instanceManager: pigeon_instanceManager,
+      aBool: aBool,
+      anInt: anInt,
+      aDouble: aDouble,
+      aString: aString,
+      aUint8List: aUint8List,
+      aList: aList,
+      aMap: aMap,
+      anEnum: anEnum,
+      aProxyApi: aProxyApi,
+      aNullableBool: aNullableBool,
+      aNullableInt: aNullableInt,
+      aNullableDouble: aNullableDouble,
+      aNullableString: aNullableString,
+      aNullableUint8List: aNullableUint8List,
+      aNullableList: aNullableList,
+      aNullableMap: aNullableMap,
+      aNullableEnum: aNullableEnum,
+      aNullableProxyApi: aNullableProxyApi,
+      anInterfaceMethod: anInterfaceMethod,
+      flutterNoop: flutterNoop,
+      flutterThrowError: flutterThrowError,
+      flutterThrowErrorFromVoid: flutterThrowErrorFromVoid,
+      flutterEchoBool: flutterEchoBool,
+      flutterEchoInt: flutterEchoInt,
+      flutterEchoDouble: flutterEchoDouble,
+      flutterEchoString: flutterEchoString,
+      flutterEchoUint8List: flutterEchoUint8List,
+      flutterEchoList: flutterEchoList,
+      flutterEchoProxyApiList: flutterEchoProxyApiList,
+      flutterEchoMap: flutterEchoMap,
+      flutterEchoProxyApiMap: flutterEchoProxyApiMap,
+      flutterEchoEnum: flutterEchoEnum,
+      flutterEchoProxyApi: flutterEchoProxyApi,
+      flutterEchoNullableBool: flutterEchoNullableBool,
+      flutterEchoNullableInt: flutterEchoNullableInt,
+      flutterEchoNullableDouble: flutterEchoNullableDouble,
+      flutterEchoNullableString: flutterEchoNullableString,
+      flutterEchoNullableUint8List: flutterEchoNullableUint8List,
+      flutterEchoNullableList: flutterEchoNullableList,
+      flutterEchoNullableMap: flutterEchoNullableMap,
+      flutterEchoNullableEnum: flutterEchoNullableEnum,
+      flutterEchoNullableProxyApi: flutterEchoNullableProxyApi,
+      flutterNoopAsync: flutterNoopAsync,
+      flutterEchoAsyncString: flutterEchoAsyncString,
+    );
+  }
+}
+
+/// ProxyApi to serve as a super class to the core ProxyApi interface.
+class ProxyApiSuperClass extends Pigeon_ProxyApiBaseClass {
+  ProxyApiSuperClass({
+    super.pigeon_binaryMessenger,
+    super.pigeon_instanceManager,
+  }) {
+    final int __pigeon_instanceIdentifier =
+        pigeon_instanceManager.addDartCreatedInstance(this);
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyApiSuperClass;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    () async {
+      const String __pigeon_channelName =
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyApiSuperClass.pigeon_defaultConstructor';
+      final BasicMessageChannel<Object?> __pigeon_channel =
+          BasicMessageChannel<Object?>(
+        __pigeon_channelName,
+        pigeonChannelCodec,
+        binaryMessenger: __pigeon_binaryMessenger,
+      );
+      final List<Object?>? __pigeon_replyList = await __pigeon_channel
+          .send(<Object?>[__pigeon_instanceIdentifier]) as List<Object?>?;
+      if (__pigeon_replyList == null) {
+        throw _createConnectionError(__pigeon_channelName);
+      } else if (__pigeon_replyList.length > 1) {
+        throw PlatformException(
+          code: __pigeon_replyList[0]! as String,
+          message: __pigeon_replyList[1] as String?,
+          details: __pigeon_replyList[2],
+        );
+      } else {
+        return;
+      }
+    }();
+  }
+
+  /// Constructs ProxyApiSuperClass without creating the associated native object.
+  ///
+  /// This should only be used by subclasses created by this library or to
+  /// create copies.
+  ProxyApiSuperClass.pigeon_detached({
+    super.pigeon_binaryMessenger,
+    super.pigeon_instanceManager,
+  });
+
+  late final _Pigeon_ProxyApiBaseCodec __pigeon_codecProxyApiSuperClass =
+      _Pigeon_ProxyApiBaseCodec(pigeon_instanceManager);
+
+  static void pigeon_setUpMessageHandlers({
+    bool pigeon_clearHandlers = false,
+    BinaryMessenger? pigeon_binaryMessenger,
+    Pigeon_InstanceManager? pigeon_instanceManager,
+    ProxyApiSuperClass Function()? pigeon_newInstance,
+  }) {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        _Pigeon_ProxyApiBaseCodec(
+            pigeon_instanceManager ?? Pigeon_InstanceManager.instance);
+    final BinaryMessenger? binaryMessenger = pigeon_binaryMessenger;
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyApiSuperClass.pigeon_newInstance',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyApiSuperClass.pigeon_newInstance was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final int? arg_pigeon_instanceIdentifier = (args[0] as int?);
+          assert(arg_pigeon_instanceIdentifier != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyApiSuperClass.pigeon_newInstance was null, expected non-null int.');
+          try {
+            (pigeon_instanceManager ?? Pigeon_InstanceManager.instance)
+                .addHostCreatedInstance(
+              pigeon_newInstance?.call() ??
+                  ProxyApiSuperClass.pigeon_detached(
+                    pigeon_binaryMessenger: pigeon_binaryMessenger,
+                    pigeon_instanceManager: pigeon_instanceManager,
+                  ),
+              arg_pigeon_instanceIdentifier!,
+            );
+            return wrapResponse(empty: true);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+  }
+
+  Future<void> aSuperMethod() async {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        __pigeon_codecProxyApiSuperClass;
+    final BinaryMessenger? __pigeon_binaryMessenger = pigeon_binaryMessenger;
+    const String __pigeon_channelName =
+        'dev.flutter.pigeon.pigeon_integration_tests.ProxyApiSuperClass.aSuperMethod';
+    final BasicMessageChannel<Object?> __pigeon_channel =
+        BasicMessageChannel<Object?>(
+      __pigeon_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: __pigeon_binaryMessenger,
+    );
+    final List<Object?>? __pigeon_replyList =
+        await __pigeon_channel.send(<Object?>[this]) as List<Object?>?;
+    if (__pigeon_replyList == null) {
+      throw _createConnectionError(__pigeon_channelName);
+    } else if (__pigeon_replyList.length > 1) {
+      throw PlatformException(
+        code: __pigeon_replyList[0]! as String,
+        message: __pigeon_replyList[1] as String?,
+        details: __pigeon_replyList[2],
+      );
+    } else {
+      return;
+    }
+  }
+
+  @override
+  ProxyApiSuperClass pigeon_copy() {
+    return ProxyApiSuperClass.pigeon_detached(
+      pigeon_binaryMessenger: pigeon_binaryMessenger,
+      pigeon_instanceManager: pigeon_instanceManager,
+    );
+  }
+}
+
+/// ProxyApi to serve as an interface to the core ProxyApi interface.
+class ProxyApiInterface extends Pigeon_ProxyApiBaseClass {
+  /// Constructs ProxyApiInterface without creating the associated native object.
+  ///
+  /// This should only be used by subclasses created by this library or to
+  /// create copies.
+  ProxyApiInterface.pigeon_detached({
+    super.pigeon_binaryMessenger,
+    super.pigeon_instanceManager,
+    this.anInterfaceMethod,
+  });
+
+  /// Dart:
+  /// For the associated Native object to be automatically garbage collected,
+  /// it is required that the implementation of this `Function` doesn't have a
+  /// strong reference to the encapsulating class instance. When this `Function`
+  /// references a non-local variable, it is strongly recommended to access it
+  /// from a `WeakReference`:
+  ///
+  /// ```dart
+  /// final WeakReference weakMyVariable = WeakReference(myVariable);
+  /// final ProxyApiInterface instance = ProxyApiInterface(
+  ///  anInterfaceMethod: (ProxyApiInterface pigeon_instance, ...) {
+  ///    print(weakMyVariable?.target);
+  ///  },
+  /// );
+  /// ```
+  ///
+  /// Alternatively, `Pigeon_InstanceManager.removeWeakReference` can be used to
+  /// release the associated Native object manually.
+  final void Function(ProxyApiInterface pigeon_instance)? anInterfaceMethod;
+
+  static void pigeon_setUpMessageHandlers({
+    bool pigeon_clearHandlers = false,
+    BinaryMessenger? pigeon_binaryMessenger,
+    Pigeon_InstanceManager? pigeon_instanceManager,
+    ProxyApiInterface Function()? pigeon_newInstance,
+    void Function(ProxyApiInterface pigeon_instance)? anInterfaceMethod,
+  }) {
+    final _Pigeon_ProxyApiBaseCodec pigeonChannelCodec =
+        _Pigeon_ProxyApiBaseCodec(
+            pigeon_instanceManager ?? Pigeon_InstanceManager.instance);
+    final BinaryMessenger? binaryMessenger = pigeon_binaryMessenger;
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyApiInterface.pigeon_newInstance',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyApiInterface.pigeon_newInstance was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final int? arg_pigeon_instanceIdentifier = (args[0] as int?);
+          assert(arg_pigeon_instanceIdentifier != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyApiInterface.pigeon_newInstance was null, expected non-null int.');
+          try {
+            (pigeon_instanceManager ?? Pigeon_InstanceManager.instance)
+                .addHostCreatedInstance(
+              pigeon_newInstance?.call() ??
+                  ProxyApiInterface.pigeon_detached(
+                    pigeon_binaryMessenger: pigeon_binaryMessenger,
+                    pigeon_instanceManager: pigeon_instanceManager,
+                  ),
+              arg_pigeon_instanceIdentifier!,
+            );
+            return wrapResponse(empty: true);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+
+    {
+      final BasicMessageChannel<Object?> __pigeon_channel = BasicMessageChannel<
+              Object?>(
+          'dev.flutter.pigeon.pigeon_integration_tests.ProxyApiInterface.anInterfaceMethod',
+          pigeonChannelCodec,
+          binaryMessenger: binaryMessenger);
+      if (pigeon_clearHandlers) {
+        __pigeon_channel.setMessageHandler(null);
+      } else {
+        __pigeon_channel.setMessageHandler((Object? message) async {
+          assert(message != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyApiInterface.anInterfaceMethod was null.');
+          final List<Object?> args = (message as List<Object?>?)!;
+          final ProxyApiInterface? arg_pigeon_instance =
+              (args[0] as ProxyApiInterface?);
+          assert(arg_pigeon_instance != null,
+              'Argument for dev.flutter.pigeon.pigeon_integration_tests.ProxyApiInterface.anInterfaceMethod was null, expected non-null ProxyApiInterface.');
+          try {
+            (anInterfaceMethod ?? arg_pigeon_instance!.anInterfaceMethod)
+                ?.call(arg_pigeon_instance!);
+            return wrapResponse(empty: true);
+          } on PlatformException catch (e) {
+            return wrapResponse(error: e);
+          } catch (e) {
+            return wrapResponse(
+                error: PlatformException(code: 'error', message: e.toString()));
+          }
+        });
+      }
+    }
+  }
+
+  @override
+  ProxyApiInterface pigeon_copy() {
+    return ProxyApiInterface.pigeon_detached(
+      pigeon_binaryMessenger: pigeon_binaryMessenger,
+      pigeon_instanceManager: pigeon_instanceManager,
+      anInterfaceMethod: anInterfaceMethod,
+    );
+  }
+}
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/enum.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/enum.gen.dart
index 8354d159d33e..f465bf2b765c 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/enum.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/enum.gen.dart
@@ -4,7 +4,7 @@
 //
 // Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
-// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers
+// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers, camel_case_types
 
 import 'dart:async';
 import 'dart:typed_data' show Float64List, Int32List, Int64List, Uint8List;
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/flutter_unittests.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/flutter_unittests.gen.dart
index 73f100cf28b6..99cbf7fa3711 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/flutter_unittests.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/flutter_unittests.gen.dart
@@ -4,7 +4,7 @@
 //
 // Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
-// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers
+// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers, camel_case_types
 
 import 'dart:async';
 import 'dart:typed_data' show Float64List, Int32List, Int64List, Uint8List;
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/message.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/message.gen.dart
index cc7b8b53c360..04dbc6d43a2a 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/message.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/message.gen.dart
@@ -4,7 +4,7 @@
 //
 // Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
-// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers
+// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers, camel_case_types
 
 import 'dart:async';
 import 'dart:typed_data' show Float64List, Int32List, Int64List, Uint8List;
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/multiple_arity.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/multiple_arity.gen.dart
index bec054b4be49..19455117087d 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/multiple_arity.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/multiple_arity.gen.dart
@@ -4,7 +4,7 @@
 //
 // Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
-// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers
+// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers, camel_case_types
 
 import 'dart:async';
 import 'dart:typed_data' show Float64List, Int32List, Int64List, Uint8List;
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/non_null_fields.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/non_null_fields.gen.dart
index 7279e85c40ea..be9c48422aef 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/non_null_fields.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/non_null_fields.gen.dart
@@ -4,7 +4,7 @@
 //
 // Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
-// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers
+// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers, camel_case_types
 
 import 'dart:async';
 import 'dart:typed_data' show Float64List, Int32List, Int64List, Uint8List;
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/null_fields.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/null_fields.gen.dart
index ecf7c7f7e970..bc18ccd0ada0 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/null_fields.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/null_fields.gen.dart
@@ -4,7 +4,7 @@
 //
 // Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
-// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers
+// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers, camel_case_types
 
 import 'dart:async';
 import 'dart:typed_data' show Float64List, Int32List, Int64List, Uint8List;
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/nullable_returns.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/nullable_returns.gen.dart
index dd1665a463c1..d5c2bb3f63df 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/nullable_returns.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/nullable_returns.gen.dart
@@ -4,7 +4,7 @@
 //
 // Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
-// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers
+// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers, camel_case_types
 
 import 'dart:async';
 import 'dart:typed_data' show Float64List, Int32List, Int64List, Uint8List;
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/primitive.gen.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/primitive.gen.dart
index 72c115d65278..b1f618a72b6e 100644
--- a/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/primitive.gen.dart
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/lib/src/generated/primitive.gen.dart
@@ -4,7 +4,7 @@
 //
 // Autogenerated from Pigeon, do not edit directly.
 // See also: https://pub.dev/packages/pigeon
-// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers
+// ignore_for_file: public_member_api_docs, non_constant_identifier_names, avoid_as, unused_import, unnecessary_parenthesis, prefer_null_aware_operators, omit_local_variable_types, unused_shown_name, unnecessary_import, no_leading_underscores_for_local_identifiers, camel_case_types
 
 import 'dart:async';
 import 'dart:typed_data' show Float64List, Int32List, Int64List, Uint8List;
diff --git a/packages/pigeon/platform_tests/shared_test_plugin_code/test/instance_manager_test.dart b/packages/pigeon/platform_tests/shared_test_plugin_code/test/instance_manager_test.dart
new file mode 100644
index 000000000000..3d3de761a977
--- /dev/null
+++ b/packages/pigeon/platform_tests/shared_test_plugin_code/test/instance_manager_test.dart
@@ -0,0 +1,168 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// This file specifically tests the test Pigeon_InstanceManager generated by core_tests.
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:shared_test_plugin_code/src/generated/core_tests.gen.dart';
+
+void main() {
+  group('InstanceManager', () {
+    test('addHostCreatedInstance', () {
+      final Pigeon_InstanceManager instanceManager =
+          Pigeon_InstanceManager(onWeakReferenceRemoved: (_) {});
+
+      final CopyableObject object = CopyableObject(
+        pigeon_instanceManager: instanceManager,
+      );
+
+      instanceManager.addHostCreatedInstance(object, 0);
+
+      expect(instanceManager.getIdentifier(object), 0);
+      expect(
+        instanceManager.getInstanceWithWeakReference(0),
+        object,
+      );
+    });
+
+    test('addHostCreatedInstance prevents already used objects and ids', () {
+      final Pigeon_InstanceManager instanceManager =
+          Pigeon_InstanceManager(onWeakReferenceRemoved: (_) {});
+
+      final CopyableObject object = CopyableObject(
+        pigeon_instanceManager: instanceManager,
+      );
+
+      instanceManager.addHostCreatedInstance(object, 0);
+
+      expect(
+        () => instanceManager.addHostCreatedInstance(object, 0),
+        throwsAssertionError,
+      );
+
+      expect(
+        () => instanceManager.addHostCreatedInstance(
+          CopyableObject(pigeon_instanceManager: instanceManager),
+          0,
+        ),
+        throwsAssertionError,
+      );
+    });
+
+    test('addFlutterCreatedInstance', () {
+      final Pigeon_InstanceManager instanceManager =
+          Pigeon_InstanceManager(onWeakReferenceRemoved: (_) {});
+
+      final CopyableObject object = CopyableObject(
+        pigeon_instanceManager: instanceManager,
+      );
+
+      instanceManager.addDartCreatedInstance(object);
+
+      final int? instanceId = instanceManager.getIdentifier(object);
+      expect(instanceId, isNotNull);
+      expect(
+        instanceManager.getInstanceWithWeakReference(instanceId!),
+        object,
+      );
+    });
+
+    test('removeWeakReference', () {
+      int? weakInstanceId;
+      final Pigeon_InstanceManager instanceManager =
+          Pigeon_InstanceManager(onWeakReferenceRemoved: (int instanceId) {
+        weakInstanceId = instanceId;
+      });
+
+      final CopyableObject object = CopyableObject(
+        pigeon_instanceManager: instanceManager,
+      );
+
+      instanceManager.addHostCreatedInstance(object, 0);
+
+      expect(instanceManager.removeWeakReference(object), 0);
+      expect(
+        instanceManager.getInstanceWithWeakReference(0),
+        isA<CopyableObject>(),
+      );
+      expect(weakInstanceId, 0);
+    });
+
+    test('removeWeakReference removes only weak reference', () {
+      final Pigeon_InstanceManager instanceManager =
+          Pigeon_InstanceManager(onWeakReferenceRemoved: (_) {});
+
+      final CopyableObject object = CopyableObject(
+        pigeon_instanceManager: instanceManager,
+      );
+
+      instanceManager.addHostCreatedInstance(object, 0);
+
+      expect(instanceManager.removeWeakReference(object), 0);
+      final CopyableObject copy = instanceManager.getInstanceWithWeakReference(
+        0,
+      )!;
+      expect(identical(object, copy), isFalse);
+    });
+
+    test('removeStrongReference', () {
+      final Pigeon_InstanceManager instanceManager =
+          Pigeon_InstanceManager(onWeakReferenceRemoved: (_) {});
+
+      final CopyableObject object = CopyableObject(
+        pigeon_instanceManager: instanceManager,
+      );
+
+      instanceManager.addHostCreatedInstance(object, 0);
+      instanceManager.removeWeakReference(object);
+      expect(instanceManager.remove(0), isA<CopyableObject>());
+      expect(instanceManager.containsIdentifier(0), isFalse);
+    });
+
+    test('removeStrongReference removes only strong reference', () {
+      final Pigeon_InstanceManager instanceManager =
+          Pigeon_InstanceManager(onWeakReferenceRemoved: (_) {});
+
+      final CopyableObject object = CopyableObject(
+        pigeon_instanceManager: instanceManager,
+      );
+
+      instanceManager.addHostCreatedInstance(object, 0);
+      expect(instanceManager.remove(0), isA<CopyableObject>());
+      expect(
+        instanceManager.getInstanceWithWeakReference(0),
+        object,
+      );
+    });
+
+    test('getInstance can add a new weak reference', () {
+      final Pigeon_InstanceManager instanceManager =
+          Pigeon_InstanceManager(onWeakReferenceRemoved: (_) {});
+
+      final CopyableObject object = CopyableObject(
+        pigeon_instanceManager: instanceManager,
+      );
+
+      instanceManager.addHostCreatedInstance(object, 0);
+      instanceManager.removeWeakReference(object);
+
+      final CopyableObject newWeakCopy =
+          instanceManager.getInstanceWithWeakReference(
+        0,
+      )!;
+      expect(identical(object, newWeakCopy), isFalse);
+    });
+  });
+}
+
+class CopyableObject extends Pigeon_ProxyApiBaseClass {
+  // ignore: non_constant_identifier_names
+  CopyableObject({super.pigeon_instanceManager});
+
+  @override
+  // ignore: non_constant_identifier_names
+  CopyableObject pigeon_copy() {
+    return CopyableObject(pigeon_instanceManager: pigeon_instanceManager);
+  }
+}
diff --git a/packages/pigeon/pubspec.yaml b/packages/pigeon/pubspec.yaml
index c820df9256f8..904aaebdd965 100644
--- a/packages/pigeon/pubspec.yaml
+++ b/packages/pigeon/pubspec.yaml
@@ -2,7 +2,7 @@ name: pigeon
 description: Code generator tool to make communication between Flutter and the host platform type-safe and easier.
 repository: https://github.com/flutter/packages/tree/main/packages/pigeon
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+pigeon%22
-version: 16.0.0 # This must match the version in lib/generator_tools.dart
+version: 16.0.1 # This must match the version in lib/generator_tools.dart
 
 environment:
   sdk: ">=3.0.0 <4.0.0"
@@ -10,7 +10,9 @@ environment:
 dependencies:
   analyzer: ">=5.13.0 <7.0.0"
   args: ^2.1.0
+  code_builder: ^4.8.0
   collection: ^1.15.0
+  dart_style: ^2.3.4
   meta: ^1.7.0
   path: ^1.8.0
   yaml: ^3.1.1
diff --git a/packages/pigeon/test/cpp_generator_test.dart b/packages/pigeon/test/cpp_generator_test.dart
index cbd290b42fa3..af7865815d3a 100644
--- a/packages/pigeon/test/cpp_generator_test.dart
+++ b/packages/pigeon/test/cpp_generator_test.dart
@@ -25,7 +25,7 @@ final Enum emptyEnum = Enum(
 void main() {
   test('gen one api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
           parameters: <Parameter>[
@@ -37,6 +37,8 @@ void main() {
                 ),
                 name: 'input')
           ],
+          required: true,
+          location: ApiLocation.host,
           returnType: TypeDeclaration(
             baseName: 'Output',
             isNullable: false,
@@ -101,7 +103,7 @@ void main() {
 
   test('naming follows style', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
           parameters: <Parameter>[
@@ -113,6 +115,7 @@ void main() {
                 ),
                 name: 'someInput')
           ],
+          location: ApiLocation.host,
           returnType: TypeDeclaration(
             baseName: 'Output',
             isNullable: false,
@@ -179,9 +182,10 @@ void main() {
 
   test('FlutterError fields are private with public accessors', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 type: const TypeDeclaration(
@@ -230,9 +234,10 @@ void main() {
 
   test('Error field is private with public accessors', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 type: const TypeDeclaration(
@@ -273,9 +278,10 @@ void main() {
 
   test('Spaces before {', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -350,9 +356,10 @@ void main() {
 
   test('include blocks follow style', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 type: const TypeDeclaration(
@@ -423,9 +430,10 @@ void main() {
 
   test('namespaces follows style', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 type: const TypeDeclaration(
@@ -478,9 +486,10 @@ void main() {
 
   test('data classes handle nullable fields', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -661,9 +670,10 @@ void main() {
 
   test('data classes handle non-nullable fields', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -804,9 +814,10 @@ void main() {
 
   test('host nullable return types map correctly', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'returnNullableBool',
+          location: ApiLocation.host,
           parameters: <Parameter>[],
           returnType: const TypeDeclaration(
             baseName: 'bool',
@@ -815,6 +826,7 @@ void main() {
         ),
         Method(
           name: 'returnNullableInt',
+          location: ApiLocation.host,
           parameters: <Parameter>[],
           returnType: const TypeDeclaration(
             baseName: 'int',
@@ -823,6 +835,7 @@ void main() {
         ),
         Method(
           name: 'returnNullableString',
+          location: ApiLocation.host,
           parameters: <Parameter>[],
           returnType: const TypeDeclaration(
             baseName: 'String',
@@ -831,6 +844,7 @@ void main() {
         ),
         Method(
           name: 'returnNullableList',
+          location: ApiLocation.host,
           parameters: <Parameter>[],
           returnType: const TypeDeclaration(
             baseName: 'List',
@@ -845,6 +859,7 @@ void main() {
         ),
         Method(
           name: 'returnNullableMap',
+          location: ApiLocation.host,
           parameters: <Parameter>[],
           returnType: const TypeDeclaration(
             baseName: 'Map',
@@ -863,6 +878,7 @@ void main() {
         ),
         Method(
           name: 'returnNullableDataClass',
+          location: ApiLocation.host,
           parameters: <Parameter>[],
           returnType: TypeDeclaration(
             baseName: 'ReturnData',
@@ -921,9 +937,10 @@ void main() {
 
   test('host non-nullable return types map correctly', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'returnBool',
+          location: ApiLocation.host,
           parameters: <Parameter>[],
           returnType: const TypeDeclaration(
             baseName: 'bool',
@@ -932,6 +949,7 @@ void main() {
         ),
         Method(
           name: 'returnInt',
+          location: ApiLocation.host,
           parameters: <Parameter>[],
           returnType: const TypeDeclaration(
             baseName: 'int',
@@ -940,6 +958,7 @@ void main() {
         ),
         Method(
           name: 'returnString',
+          location: ApiLocation.host,
           parameters: <Parameter>[],
           returnType: const TypeDeclaration(
             baseName: 'String',
@@ -948,6 +967,7 @@ void main() {
         ),
         Method(
           name: 'returnList',
+          location: ApiLocation.host,
           parameters: <Parameter>[],
           returnType: const TypeDeclaration(
             baseName: 'List',
@@ -962,6 +982,7 @@ void main() {
         ),
         Method(
           name: 'returnMap',
+          location: ApiLocation.host,
           parameters: <Parameter>[],
           returnType: const TypeDeclaration(
             baseName: 'Map',
@@ -980,6 +1001,7 @@ void main() {
         ),
         Method(
           name: 'returnDataClass',
+          location: ApiLocation.host,
           parameters: <Parameter>[],
           returnType: TypeDeclaration(
             baseName: 'ReturnData',
@@ -1024,9 +1046,10 @@ void main() {
 
   test('host nullable arguments map correctly', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 name: 'aBool',
@@ -1179,9 +1202,10 @@ void main() {
 
   test('host non-nullable arguments map correctly', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 name: 'aBool',
@@ -1329,9 +1353,10 @@ void main() {
 
   test('flutter nullable arguments map correctly', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 name: 'aBool',
@@ -1488,9 +1513,10 @@ void main() {
 
   test('flutter non-nullable arguments map correctly', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 name: 'aBool',
@@ -1621,9 +1647,10 @@ void main() {
 
   test('host API argument extraction uses references', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 name: 'anArg',
@@ -1661,9 +1688,10 @@ void main() {
   test('enum argument', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Bar', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Bar', methods: <Method>[
           Method(
               name: 'bar',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1705,13 +1733,13 @@ void main() {
 
     final Root root = Root(
       apis: <Api>[
-        Api(
+        AstFlutterApi(
           name: 'Api',
-          location: ApiLocation.flutter,
           documentationComments: <String>[comments[count++]],
           methods: <Method>[
             Method(
               name: 'method',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               documentationComments: <String>[comments[count++]],
               parameters: <Parameter>[
@@ -1785,12 +1813,12 @@ void main() {
   test("doesn't create codecs if no custom datatypes", () {
     final Root root = Root(
       apis: <Api>[
-        Api(
+        AstFlutterApi(
           name: 'Api',
-          location: ApiLocation.flutter,
           methods: <Method>[
             Method(
               name: 'method',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1827,9 +1855,10 @@ void main() {
 
   test('creates custom codecs if custom datatypes present', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -1884,9 +1913,10 @@ void main() {
 
   test('Does not send unwrapped EncodableLists', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 name: 'aBool',
@@ -1966,15 +1996,17 @@ void main() {
 
   test('does not keep unowned references in async handlers', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'HostApi', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'HostApi', methods: <Method>[
         Method(
           name: 'noop',
+          location: ApiLocation.host,
           parameters: <Parameter>[],
           returnType: const TypeDeclaration.voidDeclaration(),
           isAsynchronous: true,
         ),
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 type: const TypeDeclaration(
@@ -1988,15 +2020,17 @@ void main() {
           isAsynchronous: true,
         ),
       ]),
-      Api(name: 'FlutterApi', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'FlutterApi', methods: <Method>[
         Method(
           name: 'noop',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[],
           returnType: const TypeDeclaration.voidDeclaration(),
           isAsynchronous: true,
         ),
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 type: const TypeDeclaration(
@@ -2038,12 +2072,12 @@ void main() {
   test('connection error contains channel name', () {
     final Root root = Root(
       apis: <Api>[
-        Api(
+        AstFlutterApi(
           name: 'Api',
-          location: ApiLocation.flutter,
           methods: <Method>[
             Method(
               name: 'method',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
diff --git a/packages/pigeon/test/dart_generator_test.dart b/packages/pigeon/test/dart_generator_test.dart
index 83a6556c7fab..24fb50f39026 100644
--- a/packages/pigeon/test/dart_generator_test.dart
+++ b/packages/pigeon/test/dart_generator_test.dart
@@ -85,9 +85,10 @@ void main() {
 
   test('gen one host api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -137,9 +138,10 @@ void main() {
 
   test('host multiple args', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'add',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 name: 'x',
@@ -170,9 +172,10 @@ void main() {
 
   test('flutter multiple args', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'add',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 name: 'x',
@@ -305,9 +308,10 @@ void main() {
 
   test('flutterApi', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -358,9 +362,10 @@ void main() {
 
   test('host void', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -398,9 +403,10 @@ void main() {
 
   test('flutter void return', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -441,9 +447,10 @@ void main() {
 
   test('flutter void argument', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[],
           returnType: TypeDeclaration(
             baseName: 'Output',
@@ -477,9 +484,10 @@ void main() {
 
   test('flutter enum argument with enum class', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -531,9 +539,10 @@ void main() {
 
   test('primitive enum host', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Bar', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Bar', methods: <Method>[
         Method(
             name: 'bar',
+            location: ApiLocation.host,
             returnType: const TypeDeclaration.voidDeclaration(),
             parameters: <Parameter>[
               Parameter(
@@ -567,9 +576,10 @@ void main() {
 
   test('flutter non-nullable enum argument with enum class', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -620,9 +630,10 @@ void main() {
 
   test('host void argument', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[],
           returnType: TypeDeclaration(
             baseName: 'Output',
@@ -655,42 +666,40 @@ void main() {
 
   test('mock dart handler', () {
     final Root root = Root(apis: <Api>[
-      Api(
-          name: 'Api',
+      AstHostApi(name: 'Api', dartHostTestHandler: 'ApiMock', methods: <Method>[
+        Method(
+          name: 'doSomething',
           location: ApiLocation.host,
-          dartHostTestHandler: 'ApiMock',
-          methods: <Method>[
-            Method(
-              name: 'doSomething',
-              parameters: <Parameter>[
-                Parameter(
-                    type: TypeDeclaration(
-                      baseName: 'Input',
-                      isNullable: false,
-                      associatedClass: emptyClass,
-                    ),
-                    name: '')
-              ],
-              returnType: TypeDeclaration(
-                baseName: 'Output',
-                isNullable: false,
-                associatedClass: emptyClass,
-              ),
-            ),
-            Method(
-              name: 'voidReturner',
-              parameters: <Parameter>[
-                Parameter(
-                    type: TypeDeclaration(
-                      baseName: 'Input',
-                      isNullable: false,
-                      associatedClass: emptyClass,
-                    ),
-                    name: '')
-              ],
-              returnType: const TypeDeclaration.voidDeclaration(),
-            )
-          ])
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
+                  baseName: 'Input',
+                  isNullable: false,
+                  associatedClass: emptyClass,
+                ),
+                name: '')
+          ],
+          returnType: TypeDeclaration(
+            baseName: 'Output',
+            isNullable: false,
+            associatedClass: emptyClass,
+          ),
+        ),
+        Method(
+          name: 'voidReturner',
+          location: ApiLocation.host,
+          parameters: <Parameter>[
+            Parameter(
+                type: TypeDeclaration(
+                  baseName: 'Input',
+                  isNullable: false,
+                  associatedClass: emptyClass,
+                ),
+                name: '')
+          ],
+          returnType: const TypeDeclaration.voidDeclaration(),
+        )
+      ])
     ], classes: <Class>[
       Class(name: 'Input', fields: <NamedType>[
         NamedType(
@@ -748,9 +757,10 @@ void main() {
 
   test('gen one async Flutter Api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -803,9 +813,10 @@ void main() {
 
   test('gen one async Flutter Api with void return', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -853,9 +864,10 @@ void main() {
 
   test('gen one async Host Api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -906,9 +918,10 @@ void main() {
 
   test('async host void argument', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[],
           returnType: TypeDeclaration(
             baseName: 'Output',
@@ -1027,9 +1040,10 @@ void main() {
   test('host generics argument', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1061,9 +1075,10 @@ void main() {
   test('flutter generics argument with void return', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+        AstFlutterApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1095,9 +1110,10 @@ void main() {
   test('host generics return', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration(
                   baseName: 'List',
                   isNullable: false,
@@ -1129,9 +1145,10 @@ void main() {
   test('flutter generics argument non void return', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+        AstFlutterApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration(
                   baseName: 'List',
                   isNullable: false,
@@ -1173,9 +1190,10 @@ void main() {
   test('return nullable host', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration(
                 baseName: 'int',
                 isNullable: true,
@@ -1202,9 +1220,10 @@ void main() {
   test('return nullable collection host', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration(
                   baseName: 'List',
                   isNullable: true,
@@ -1236,9 +1255,10 @@ void main() {
   test('return nullable async host', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration(
                 baseName: 'int',
                 isNullable: true,
@@ -1266,9 +1286,10 @@ void main() {
   test('return nullable flutter', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+        AstFlutterApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration(
                 baseName: 'int',
                 isNullable: true,
@@ -1295,9 +1316,10 @@ void main() {
   test('return nullable async flutter', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+        AstFlutterApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration(
                 baseName: 'int',
                 isNullable: true,
@@ -1325,9 +1347,10 @@ void main() {
   test('platform error for return nil on nonnull', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration(
                 baseName: 'int',
                 isNullable: false,
@@ -1356,9 +1379,10 @@ void main() {
   test('nullable argument host', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1388,9 +1412,10 @@ void main() {
   test('nullable argument flutter', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+        AstFlutterApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1420,9 +1445,10 @@ void main() {
   test('named argument flutter', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+        AstFlutterApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1502,13 +1528,13 @@ name: foobar
 
     final Root root = Root(
       apis: <Api>[
-        Api(
+        AstFlutterApi(
           name: 'Api',
-          location: ApiLocation.flutter,
           documentationComments: <String>[comments[count++]],
           methods: <Method>[
             Method(
               name: 'method',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               documentationComments: <String>[comments[count++]],
               parameters: <Parameter>[
@@ -1577,12 +1603,12 @@ name: foobar
   test("doesn't create codecs if no custom datatypes", () {
     final Root root = Root(
       apis: <Api>[
-        Api(
+        AstFlutterApi(
           name: 'Api',
-          location: ApiLocation.flutter,
           methods: <Method>[
             Method(
               name: 'method',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1615,9 +1641,10 @@ name: foobar
 
   test('creates custom codecs if custom datatypes present', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -1668,13 +1695,13 @@ name: foobar
   test('host test code handles enums', () {
     final Root root = Root(
       apis: <Api>[
-        Api(
+        AstHostApi(
             name: 'Api',
-            location: ApiLocation.host,
             dartHostTestHandler: 'ApiMock',
             methods: <Method>[
               Method(
                   name: 'doit',
+                  location: ApiLocation.host,
                   returnType: const TypeDeclaration.voidDeclaration(),
                   parameters: <Parameter>[
                     Parameter(
@@ -1721,9 +1748,10 @@ name: foobar
 
   test('connection error contains channel name', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'method',
+          location: ApiLocation.host,
           parameters: <Parameter>[],
           returnType:
               const TypeDeclaration(baseName: 'Output', isNullable: false),
@@ -1746,4 +1774,973 @@ name: foobar
         contains(
             '\'Unable to establish connection on channel: "\$channelName".\''));
   });
+
+  group('ProxyApi', () {
+    test('one api', () {
+      final Root root = Root(apis: <Api>[
+        AstProxyApi(name: 'Api', constructors: <Constructor>[
+          Constructor(name: 'name', parameters: <Parameter>[
+            Parameter(
+              type: const TypeDeclaration(
+                baseName: 'Input',
+                isNullable: false,
+              ),
+              name: 'input',
+            ),
+          ]),
+        ], fields: <Field>[
+          Field(
+            name: 'someField',
+            type: const TypeDeclaration(
+              baseName: 'int',
+              isNullable: false,
+            ),
+          )
+        ], methods: <Method>[
+          Method(
+            name: 'doSomething',
+            location: ApiLocation.host,
+            parameters: <Parameter>[
+              Parameter(
+                type: const TypeDeclaration(
+                  baseName: 'Input',
+                  isNullable: false,
+                ),
+                name: 'input',
+              )
+            ],
+            returnType: const TypeDeclaration(
+              baseName: 'String',
+              isNullable: false,
+            ),
+          ),
+          Method(
+            name: 'doSomethingElse',
+            location: ApiLocation.flutter,
+            parameters: <Parameter>[
+              Parameter(
+                type: const TypeDeclaration(
+                  baseName: 'Input',
+                  isNullable: false,
+                ),
+                name: 'input',
+              )
+            ],
+            returnType: const TypeDeclaration(
+              baseName: 'String',
+              isNullable: false,
+            ),
+          ),
+        ])
+      ], classes: <Class>[], enums: <Enum>[]);
+      final StringBuffer sink = StringBuffer();
+      const DartGenerator generator = DartGenerator();
+      generator.generate(
+        const DartOptions(),
+        root,
+        sink,
+        dartPackageName: DEFAULT_PACKAGE_NAME,
+      );
+      final String code = sink.toString();
+      final String collapsedCode = _collapseNewlineAndIndentation(code);
+
+      // Instance Manager
+      expect(code, contains(r'class Pigeon_InstanceManager'));
+      expect(code, contains(r'class _Pigeon_InstanceManagerApi'));
+
+      // Base Api class
+      expect(
+        code,
+        contains(r'abstract class Pigeon_ProxyApiBaseClass'),
+      );
+
+      // Codec and class
+      expect(code, contains('class _Pigeon_ProxyApiBaseCodec'));
+      expect(code, contains(r'class Api extends Pigeon_ProxyApiBaseClass'));
+
+      // Constructors
+      expect(
+        collapsedCode,
+        contains(
+          r'Api.name({ super.pigeon_binaryMessenger, super.pigeon_instanceManager, required this.someField, this.doSomethingElse, required Input input, })',
+        ),
+      );
+      expect(
+        code,
+        contains(
+          r'Api.pigeon_detached',
+        ),
+      );
+
+      // Field
+      expect(code, contains('final int someField;'));
+
+      // Dart -> Host method
+      expect(code, contains('Future<String> doSomething(Input input)'));
+
+      // Host -> Dart method
+      expect(code, contains(r'static void pigeon_setUpMessageHandlers({'));
+      expect(
+        collapsedCode,
+        contains(
+          'final String Function( Api pigeon_instance, Input input, )? doSomethingElse;',
+        ),
+      );
+
+      // Copy method
+      expect(code, contains(r'Api pigeon_copy('));
+    });
+
+    group('inheritance', () {
+      test('extends', () {
+        final Root root = Root(apis: <Api>[
+          AstProxyApi(
+            name: 'Api',
+            constructors: <Constructor>[],
+            fields: <Field>[],
+            methods: <Method>[],
+            superClassName: 'Api2',
+          ),
+          AstProxyApi(
+            name: 'Api2',
+            constructors: <Constructor>[],
+            fields: <Field>[],
+            methods: <Method>[],
+          )
+        ], classes: <Class>[], enums: <Enum>[]);
+        final StringBuffer sink = StringBuffer();
+        const DartGenerator generator = DartGenerator();
+        generator.generate(
+          const DartOptions(),
+          root,
+          sink,
+          dartPackageName: DEFAULT_PACKAGE_NAME,
+        );
+        final String code = sink.toString();
+        final String collapsedCode = _collapseNewlineAndIndentation(code);
+        expect(code, contains(r'class Api extends Api2'));
+        expect(
+          collapsedCode,
+          contains(
+            r'Api.pigeon_detached({ super.pigeon_binaryMessenger, super.pigeon_instanceManager, }) : super.pigeon_detached();',
+          ),
+        );
+      });
+
+      test('implements', () {
+        final Root root = Root(apis: <Api>[
+          AstProxyApi(
+            name: 'Api',
+            constructors: <Constructor>[],
+            fields: <Field>[],
+            methods: <Method>[],
+            interfacesNames: <String>{'Api2'},
+          ),
+          AstProxyApi(
+            name: 'Api2',
+            constructors: <Constructor>[],
+            fields: <Field>[],
+            methods: <Method>[],
+          )
+        ], classes: <Class>[], enums: <Enum>[]);
+        final StringBuffer sink = StringBuffer();
+        const DartGenerator generator = DartGenerator();
+        generator.generate(
+          const DartOptions(),
+          root,
+          sink,
+          dartPackageName: DEFAULT_PACKAGE_NAME,
+        );
+        final String code = sink.toString();
+        expect(
+          code,
+          contains(
+            r'class Api extends Pigeon_ProxyApiBaseClass implements Api2',
+          ),
+        );
+      });
+
+      test('implements 2 ProxyApis', () {
+        final Root root = Root(apis: <Api>[
+          AstProxyApi(
+            name: 'Api',
+            constructors: <Constructor>[],
+            fields: <Field>[],
+            methods: <Method>[],
+            interfacesNames: <String>{'Api2', 'Api3'},
+          ),
+          AstProxyApi(
+            name: 'Api2',
+            constructors: <Constructor>[],
+            fields: <Field>[],
+            methods: <Method>[],
+          ),
+          AstProxyApi(
+            name: 'Api3',
+            constructors: <Constructor>[],
+            fields: <Field>[],
+            methods: <Method>[],
+          ),
+        ], classes: <Class>[], enums: <Enum>[]);
+        final StringBuffer sink = StringBuffer();
+        const DartGenerator generator = DartGenerator();
+        generator.generate(
+          const DartOptions(),
+          root,
+          sink,
+          dartPackageName: DEFAULT_PACKAGE_NAME,
+        );
+        final String code = sink.toString();
+        expect(
+          code,
+          contains(
+            r'class Api extends Pigeon_ProxyApiBaseClass implements Api2, Api3',
+          ),
+        );
+      });
+
+      test('implements inherits flutter method', () {
+        final Root root = Root(apis: <Api>[
+          AstProxyApi(
+            name: 'Api',
+            constructors: <Constructor>[],
+            fields: <Field>[],
+            methods: <Method>[],
+            interfacesNames: <String>{'Api2'},
+          ),
+          AstProxyApi(
+            name: 'Api2',
+            constructors: <Constructor>[],
+            fields: <Field>[],
+            methods: <Method>[
+              Method(
+                name: 'aFlutterMethod',
+                returnType: const TypeDeclaration.voidDeclaration(),
+                parameters: <Parameter>[],
+                location: ApiLocation.flutter,
+              ),
+              Method(
+                name: 'aNullableFlutterMethod',
+                returnType: const TypeDeclaration.voidDeclaration(),
+                parameters: <Parameter>[],
+                location: ApiLocation.flutter,
+                required: true,
+              ),
+            ],
+          ),
+        ], classes: <Class>[], enums: <Enum>[]);
+        final StringBuffer sink = StringBuffer();
+        const DartGenerator generator = DartGenerator();
+        generator.generate(
+          const DartOptions(),
+          root,
+          sink,
+          dartPackageName: DEFAULT_PACKAGE_NAME,
+        );
+        final String code = sink.toString();
+        final String collapsedCode = _collapseNewlineAndIndentation(code);
+        expect(
+          code,
+          contains(
+            r'class Api extends Pigeon_ProxyApiBaseClass implements Api2',
+          ),
+        );
+        expect(
+          collapsedCode,
+          contains(
+            r'Api.pigeon_detached({ super.pigeon_binaryMessenger, '
+            r'super.pigeon_instanceManager, '
+            r'this.aFlutterMethod, '
+            r'required this.aNullableFlutterMethod, })',
+          ),
+        );
+      });
+    });
+
+    group('Constructors', () {
+      test('empty name and no params constructor', () {
+        final Root root = Root(
+          apis: <Api>[
+            AstProxyApi(name: 'Api', constructors: <Constructor>[
+              Constructor(
+                name: '',
+                parameters: <Parameter>[],
+              )
+            ], fields: <Field>[], methods: <Method>[]),
+          ],
+          classes: <Class>[],
+          enums: <Enum>[],
+        );
+        final StringBuffer sink = StringBuffer();
+        const DartGenerator generator = DartGenerator();
+        generator.generate(
+          const DartOptions(),
+          root,
+          sink,
+          dartPackageName: DEFAULT_PACKAGE_NAME,
+        );
+        final String code = sink.toString();
+        final String collapsedCode = _collapseNewlineAndIndentation(code);
+        expect(code, contains('class Api'));
+        expect(
+          collapsedCode,
+          contains(
+            r'Api({ super.pigeon_binaryMessenger, '
+            r'super.pigeon_instanceManager, })',
+          ),
+        );
+        expect(
+          collapsedCode,
+          contains(
+            r"const String __pigeon_channelName = 'dev.flutter.pigeon.test_package.Api.pigeon_defaultConstructor';",
+          ),
+        );
+        expect(
+          collapsedCode,
+          contains(
+            r'__pigeon_channel .send(<Object?>[__pigeon_instanceIdentifier])',
+          ),
+        );
+      });
+
+      test('multiple params constructor', () {
+        final Enum anEnum = Enum(
+          name: 'AnEnum',
+          members: <EnumMember>[EnumMember(name: 'one')],
+        );
+        final Root root = Root(
+          apis: <Api>[
+            AstProxyApi(name: 'Api', constructors: <Constructor>[
+              Constructor(
+                name: 'name',
+                parameters: <Parameter>[
+                  Parameter(
+                    type: const TypeDeclaration(
+                      isNullable: false,
+                      baseName: 'int',
+                    ),
+                    name: 'validType',
+                  ),
+                  Parameter(
+                    type: TypeDeclaration(
+                      isNullable: false,
+                      baseName: 'AnEnum',
+                      associatedEnum: anEnum,
+                    ),
+                    name: 'enumType',
+                  ),
+                  Parameter(
+                    type: const TypeDeclaration(
+                      isNullable: false,
+                      baseName: 'Api2',
+                    ),
+                    name: 'proxyApiType',
+                  ),
+                  Parameter(
+                    type: const TypeDeclaration(
+                      isNullable: true,
+                      baseName: 'int',
+                    ),
+                    name: 'nullableValidType',
+                  ),
+                  Parameter(
+                    type: TypeDeclaration(
+                      isNullable: true,
+                      baseName: 'AnEnum',
+                      associatedEnum: anEnum,
+                    ),
+                    name: 'nullableEnumType',
+                  ),
+                  Parameter(
+                    type: const TypeDeclaration(
+                      isNullable: true,
+                      baseName: 'Api2',
+                    ),
+                    name: 'nullableProxyApiType',
+                  ),
+                ],
+              )
+            ], fields: <Field>[], methods: <Method>[]),
+            AstProxyApi(
+              name: 'Api2',
+              constructors: <Constructor>[],
+              fields: <Field>[],
+              methods: <Method>[],
+            ),
+          ],
+          classes: <Class>[],
+          enums: <Enum>[anEnum],
+        );
+        final StringBuffer sink = StringBuffer();
+        const DartGenerator generator = DartGenerator();
+        generator.generate(
+          const DartOptions(),
+          root,
+          sink,
+          dartPackageName: DEFAULT_PACKAGE_NAME,
+        );
+        final String code = sink.toString();
+        final String collapsedCode = _collapseNewlineAndIndentation(code);
+        expect(code, contains('class Api'));
+        expect(
+          collapsedCode,
+          contains(
+            r'Api.name({ super.pigeon_binaryMessenger, '
+            r'super.pigeon_instanceManager, '
+            r'required int validType, '
+            r'required AnEnum enumType, '
+            r'required Api2 proxyApiType, '
+            r'int? nullableValidType, '
+            r'AnEnum? nullableEnumType, '
+            r'Api2? nullableProxyApiType, })',
+          ),
+        );
+        expect(
+          collapsedCode,
+          contains(
+            r'__pigeon_channel.send(<Object?>[ '
+            r'__pigeon_instanceIdentifier, '
+            r'validType, enumType.index, proxyApiType, '
+            r'nullableValidType, nullableEnumType?.index, nullableProxyApiType ])',
+          ),
+        );
+      });
+    });
+
+    group('Fields', () {
+      test('constructor with fields', () {
+        final Enum anEnum = Enum(
+          name: 'AnEnum',
+          members: <EnumMember>[EnumMember(name: 'one')],
+        );
+        final Root root = Root(
+          apis: <Api>[
+            AstProxyApi(
+              name: 'Api',
+              constructors: <Constructor>[
+                Constructor(
+                  name: 'name',
+                  parameters: <Parameter>[],
+                )
+              ],
+              fields: <Field>[
+                Field(
+                  type: const TypeDeclaration(
+                    isNullable: false,
+                    baseName: 'int',
+                  ),
+                  name: 'validType',
+                ),
+                Field(
+                  type: TypeDeclaration(
+                    isNullable: false,
+                    baseName: 'AnEnum',
+                    associatedEnum: anEnum,
+                  ),
+                  name: 'enumType',
+                ),
+                Field(
+                  type: const TypeDeclaration(
+                    isNullable: false,
+                    baseName: 'Api2',
+                  ),
+                  name: 'proxyApiType',
+                ),
+                Field(
+                  type: const TypeDeclaration(
+                    isNullable: true,
+                    baseName: 'int',
+                  ),
+                  name: 'nullableValidType',
+                ),
+                Field(
+                  type: TypeDeclaration(
+                    isNullable: true,
+                    baseName: 'AnEnum',
+                    associatedEnum: anEnum,
+                  ),
+                  name: 'nullableEnumType',
+                ),
+                Field(
+                  type: const TypeDeclaration(
+                    isNullable: true,
+                    baseName: 'Api2',
+                  ),
+                  name: 'nullableProxyApiType',
+                ),
+              ],
+              methods: <Method>[],
+            ),
+            AstProxyApi(
+              name: 'Api2',
+              constructors: <Constructor>[],
+              fields: <Field>[],
+              methods: <Method>[],
+            ),
+          ],
+          classes: <Class>[],
+          enums: <Enum>[anEnum],
+        );
+        final StringBuffer sink = StringBuffer();
+        const DartGenerator generator = DartGenerator();
+        generator.generate(
+          const DartOptions(),
+          root,
+          sink,
+          dartPackageName: DEFAULT_PACKAGE_NAME,
+        );
+        final String code = sink.toString();
+        final String collapsedCode = _collapseNewlineAndIndentation(code);
+        expect(code, contains('class Api'));
+        expect(
+          collapsedCode,
+          contains(
+            r'Api.name({ super.pigeon_binaryMessenger, '
+            r'super.pigeon_instanceManager, '
+            r'required this.validType, '
+            r'required this.enumType, '
+            r'required this.proxyApiType, '
+            r'this.nullableValidType, '
+            r'this.nullableEnumType, '
+            r'this.nullableProxyApiType, })',
+          ),
+        );
+        expect(
+          collapsedCode,
+          contains(
+            r'__pigeon_channel.send(<Object?>[ '
+            r'__pigeon_instanceIdentifier, '
+            r'validType, enumType.index, proxyApiType, '
+            r'nullableValidType, nullableEnumType?.index, nullableProxyApiType ])',
+          ),
+        );
+        expect(
+          code,
+          contains(r'final int validType;'),
+        );
+        expect(
+          code,
+          contains(r'final AnEnum enumType;'),
+        );
+        expect(
+          code,
+          contains(r'final Api2 proxyApiType;'),
+        );
+        expect(
+          code,
+          contains(r'final int? nullableValidType;'),
+        );
+        expect(
+          code,
+          contains(r'final AnEnum? nullableEnumType;'),
+        );
+        expect(
+          code,
+          contains(r'final Api2? nullableProxyApiType;'),
+        );
+      });
+
+      test('attached field', () {
+        final AstProxyApi api2 = AstProxyApi(
+          name: 'Api2',
+          constructors: <Constructor>[],
+          fields: <Field>[],
+          methods: <Method>[],
+        );
+        final Root root = Root(
+          apis: <Api>[
+            AstProxyApi(
+              name: 'Api',
+              constructors: <Constructor>[],
+              fields: <Field>[
+                Field(
+                  name: 'aField',
+                  isAttached: true,
+                  type: TypeDeclaration(
+                    baseName: 'Api2',
+                    isNullable: false,
+                    associatedProxyApi: api2,
+                  ),
+                ),
+              ],
+              methods: <Method>[],
+            ),
+            api2,
+          ],
+          classes: <Class>[],
+          enums: <Enum>[],
+        );
+        final StringBuffer sink = StringBuffer();
+        const DartGenerator generator = DartGenerator();
+        generator.generate(
+          const DartOptions(),
+          root,
+          sink,
+          dartPackageName: DEFAULT_PACKAGE_NAME,
+        );
+        final String code = sink.toString();
+        expect(code, contains('class Api'));
+        expect(code, contains(r'late final Api2 aField = __pigeon_aField();'));
+        expect(code, contains(r'Api2 __pigeon_aField()'));
+      });
+
+      test('static attached field', () {
+        final AstProxyApi api2 = AstProxyApi(
+          name: 'Api2',
+          constructors: <Constructor>[],
+          fields: <Field>[],
+          methods: <Method>[],
+        );
+        final Root root = Root(
+          apis: <Api>[
+            AstProxyApi(
+              name: 'Api',
+              constructors: <Constructor>[],
+              fields: <Field>[
+                Field(
+                  name: 'aField',
+                  isStatic: true,
+                  isAttached: true,
+                  type: TypeDeclaration(
+                    baseName: 'Api2',
+                    isNullable: false,
+                    associatedProxyApi: api2,
+                  ),
+                ),
+              ],
+              methods: <Method>[],
+            ),
+            api2,
+          ],
+          classes: <Class>[],
+          enums: <Enum>[],
+        );
+        final StringBuffer sink = StringBuffer();
+        const DartGenerator generator = DartGenerator();
+        generator.generate(
+          const DartOptions(),
+          root,
+          sink,
+          dartPackageName: DEFAULT_PACKAGE_NAME,
+        );
+        final String code = sink.toString();
+        expect(code, contains('class Api'));
+        expect(
+            code, contains(r'static final Api2 aField = __pigeon_aField();'));
+        expect(code, contains(r'static Api2 __pigeon_aField()'));
+      });
+    });
+
+    group('Host methods', () {
+      test('multiple params method', () {
+        final Enum anEnum = Enum(
+          name: 'AnEnum',
+          members: <EnumMember>[EnumMember(name: 'one')],
+        );
+        final Root root = Root(
+          apis: <Api>[
+            AstProxyApi(
+              name: 'Api',
+              constructors: <Constructor>[],
+              fields: <Field>[],
+              methods: <Method>[
+                Method(
+                  name: 'doSomething',
+                  location: ApiLocation.host,
+                  parameters: <Parameter>[
+                    Parameter(
+                      type: const TypeDeclaration(
+                        isNullable: false,
+                        baseName: 'int',
+                      ),
+                      name: 'validType',
+                    ),
+                    Parameter(
+                      type: TypeDeclaration(
+                        isNullable: false,
+                        baseName: 'AnEnum',
+                        associatedEnum: anEnum,
+                      ),
+                      name: 'enumType',
+                    ),
+                    Parameter(
+                      type: const TypeDeclaration(
+                        isNullable: false,
+                        baseName: 'Api2',
+                      ),
+                      name: 'proxyApiType',
+                    ),
+                    Parameter(
+                      type: const TypeDeclaration(
+                        isNullable: true,
+                        baseName: 'int',
+                      ),
+                      name: 'nullableValidType',
+                    ),
+                    Parameter(
+                      type: TypeDeclaration(
+                        isNullable: true,
+                        baseName: 'AnEnum',
+                        associatedEnum: anEnum,
+                      ),
+                      name: 'nullableEnumType',
+                    ),
+                    Parameter(
+                      type: const TypeDeclaration(
+                        isNullable: true,
+                        baseName: 'Api2',
+                      ),
+                      name: 'nullableProxyApiType',
+                    ),
+                  ],
+                  returnType: const TypeDeclaration.voidDeclaration(),
+                ),
+              ],
+            ),
+            AstProxyApi(
+              name: 'Api2',
+              constructors: <Constructor>[],
+              fields: <Field>[],
+              methods: <Method>[],
+            ),
+          ],
+          classes: <Class>[],
+          enums: <Enum>[anEnum],
+        );
+        final StringBuffer sink = StringBuffer();
+        const DartGenerator generator = DartGenerator();
+        generator.generate(
+          const DartOptions(),
+          root,
+          sink,
+          dartPackageName: DEFAULT_PACKAGE_NAME,
+        );
+        final String code = sink.toString();
+        final String collapsedCode = _collapseNewlineAndIndentation(code);
+        expect(code, contains('class Api'));
+        expect(
+          collapsedCode,
+          contains(
+            r'Future<void> doSomething( int validType, AnEnum enumType, '
+            r'Api2 proxyApiType, int? nullableValidType, '
+            r'AnEnum? nullableEnumType, Api2? nullableProxyApiType, )',
+          ),
+        );
+        expect(
+          collapsedCode,
+          contains(
+            r'await __pigeon_channel.send(<Object?>[ this, validType, '
+            r'enumType.index, proxyApiType, nullableValidType, '
+            r'nullableEnumType?.index, nullableProxyApiType ])',
+          ),
+        );
+      });
+
+      test('static method', () {
+        final Root root = Root(
+          apis: <Api>[
+            AstProxyApi(
+              name: 'Api',
+              constructors: <Constructor>[],
+              fields: <Field>[],
+              methods: <Method>[
+                Method(
+                  name: 'doSomething',
+                  location: ApiLocation.host,
+                  isStatic: true,
+                  parameters: <Parameter>[],
+                  returnType: const TypeDeclaration.voidDeclaration(),
+                ),
+              ],
+            ),
+          ],
+          classes: <Class>[],
+          enums: <Enum>[],
+        );
+        final StringBuffer sink = StringBuffer();
+        const DartGenerator generator = DartGenerator();
+        generator.generate(
+          const DartOptions(),
+          root,
+          sink,
+          dartPackageName: DEFAULT_PACKAGE_NAME,
+        );
+        final String code = sink.toString();
+        final String collapsedCode = _collapseNewlineAndIndentation(code);
+        expect(code, contains('class Api'));
+        expect(
+          collapsedCode,
+          contains(
+            r'static Future<void> doSomething({ BinaryMessenger? pigeon_binaryMessenger, '
+            r'Pigeon_InstanceManager? pigeon_instanceManager, })',
+          ),
+        );
+        expect(
+          collapsedCode,
+          contains(r'await __pigeon_channel.send(null)'),
+        );
+      });
+    });
+
+    group('Flutter methods', () {
+      test('multiple params flutter method', () {
+        final Enum anEnum = Enum(
+          name: 'AnEnum',
+          members: <EnumMember>[EnumMember(name: 'one')],
+        );
+        final Root root = Root(apis: <Api>[
+          AstProxyApi(
+              name: 'Api',
+              constructors: <Constructor>[],
+              fields: <Field>[],
+              methods: <Method>[
+                Method(
+                  name: 'doSomething',
+                  location: ApiLocation.flutter,
+                  parameters: <Parameter>[
+                    Parameter(
+                      type: const TypeDeclaration(
+                        isNullable: false,
+                        baseName: 'int',
+                      ),
+                      name: 'validType',
+                    ),
+                    Parameter(
+                      type: TypeDeclaration(
+                        isNullable: false,
+                        baseName: 'AnEnum',
+                        associatedEnum: anEnum,
+                      ),
+                      name: 'enumType',
+                    ),
+                    Parameter(
+                      type: const TypeDeclaration(
+                        isNullable: false,
+                        baseName: 'Api2',
+                      ),
+                      name: 'proxyApiType',
+                    ),
+                    Parameter(
+                      type: const TypeDeclaration(
+                        isNullable: true,
+                        baseName: 'int',
+                      ),
+                      name: 'nullableValidType',
+                    ),
+                    Parameter(
+                      type: TypeDeclaration(
+                        isNullable: true,
+                        baseName: 'AnEnum',
+                        associatedEnum: anEnum,
+                      ),
+                      name: 'nullableEnumType',
+                    ),
+                    Parameter(
+                      type: const TypeDeclaration(
+                        isNullable: true,
+                        baseName: 'Api2',
+                      ),
+                      name: 'nullableProxyApiType',
+                    ),
+                  ],
+                  returnType: const TypeDeclaration.voidDeclaration(),
+                )
+              ])
+        ], classes: <Class>[], enums: <Enum>[
+          anEnum
+        ]);
+        final StringBuffer sink = StringBuffer();
+        const DartGenerator generator = DartGenerator();
+        generator.generate(
+          const DartOptions(),
+          root,
+          sink,
+          dartPackageName: DEFAULT_PACKAGE_NAME,
+        );
+        final String code = sink.toString();
+        final String collapsedCode = _collapseNewlineAndIndentation(code);
+        expect(code, contains('class Api'));
+        expect(
+          collapsedCode,
+          contains(
+            r'final void Function( Api pigeon_instance, int validType, '
+            r'AnEnum enumType, Api2 proxyApiType, int? nullableValidType, '
+            r'AnEnum? nullableEnumType, Api2? nullableProxyApiType, )? '
+            r'doSomething;',
+          ),
+        );
+        expect(
+          collapsedCode,
+          contains(
+              r'void Function( Api pigeon_instance, int validType, AnEnum enumType, '
+              r'Api2 proxyApiType, int? nullableValidType, '
+              r'AnEnum? nullableEnumType, Api2? nullableProxyApiType, )? '
+              r'doSomething'),
+        );
+        expect(
+          code,
+          contains(r'final Api? arg_pigeon_instance = (args[0] as Api?);'),
+        );
+        expect(
+          code,
+          contains(r'final int? arg_validType = (args[1] as int?);'),
+        );
+        expect(
+          collapsedCode,
+          contains(
+            r'final AnEnum? arg_enumType = args[2] == null ? '
+            r'null : AnEnum.values[args[2]! as int];',
+          ),
+        );
+        expect(
+          code,
+          contains(r'final Api2? arg_proxyApiType = (args[3] as Api2?);'),
+        );
+        expect(
+          code,
+          contains(r'final int? arg_nullableValidType = (args[4] as int?);'),
+        );
+        expect(
+          collapsedCode,
+          contains(
+            r'final AnEnum? arg_nullableEnumType = args[5] == null ? '
+            r'null : AnEnum.values[args[5]! as int];',
+          ),
+        );
+        expect(
+          collapsedCode,
+          contains(
+            r'(doSomething ?? arg_pigeon_instance!.doSomething)?.call( arg_pigeon_instance!, '
+            r'arg_validType!, arg_enumType!, arg_proxyApiType!, '
+            r'arg_nullableValidType, arg_nullableEnumType, '
+            r'arg_nullableProxyApiType);',
+          ),
+        );
+      });
+    });
+  });
+}
+
+/// Replaces a new line and the indentation with a single white space
+///
+/// This
+///
+/// ```dart
+/// void method(
+///   int param1,
+///   int param2,
+/// )
+/// ```
+///
+/// converts to
+///
+/// ```dart
+/// void method( int param1, int param2, )
+/// ```
+String _collapseNewlineAndIndentation(String string) {
+  final StringBuffer result = StringBuffer();
+  for (final String line in string.split('\n')) {
+    result.write('${line.trimLeft()} ');
+  }
+  return result.toString().trim();
 }
diff --git a/packages/pigeon/test/functional_test.dart b/packages/pigeon/test/functional_test.dart
index 1c2079ccae4d..ade909799aca 100644
--- a/packages/pigeon/test/functional_test.dart
+++ b/packages/pigeon/test/functional_test.dart
@@ -6,34 +6,6 @@ import 'package:pigeon/functional.dart';
 import 'package:test/test.dart';
 
 void main() {
-  test('indexMap', () {
-    final List<String> items = <String>['a', 'b', 'c'];
-    final List<String> result =
-        indexMap(items, (int index, String value) => value + index.toString())
-            .toList();
-    expect(result[0], 'a0');
-    expect(result[1], 'b1');
-    expect(result[2], 'c2');
-  });
-
-  test('enumerate', () {
-    final List<String> items = <String>['a', 'b', 'c'];
-    int saw = 0;
-    enumerate(items, (int index, String value) {
-      if (index == 0) {
-        expect(value, 'a');
-        saw |= 0x1;
-      } else if (index == 1) {
-        expect(value, 'b');
-        saw |= 0x2;
-      } else if (index == 2) {
-        expect(value, 'c');
-        saw |= 0x4;
-      }
-    });
-    expect(saw, 0x7);
-  });
-
   test('map2', () {
     final List<int> result =
         map2(<int>[3, 5, 7], <int>[1, 2, 3], (int x, int y) => x * y).toList();
diff --git a/packages/pigeon/test/generator_tools_test.dart b/packages/pigeon/test/generator_tools_test.dart
index 4570ac633aaa..68a2cb0861fa 100644
--- a/packages/pigeon/test/generator_tools_test.dart
+++ b/packages/pigeon/test/generator_tools_test.dart
@@ -6,37 +6,6 @@ import 'package:pigeon/ast.dart';
 import 'package:pigeon/generator_tools.dart';
 import 'package:test/test.dart';
 
-bool _equalSet<T>(Set<T> x, Set<T> y) {
-  if (x.length != y.length) {
-    return false;
-  }
-  for (final T object in x) {
-    if (!y.contains(object)) {
-      return false;
-    }
-  }
-  return true;
-}
-
-bool _equalMaps(Map<String, Object> x, Map<String, Object> y) {
-  if (!_equalSet(x.keys.toSet(), y.keys.toSet())) {
-    return false;
-  }
-  for (final String key in x.keys) {
-    final Object xValue = x[key]!;
-    if (xValue is Map<String, Object>) {
-      if (!_equalMaps(xValue, (y[key] as Map<String, Object>?)!)) {
-        return false;
-      }
-    } else {
-      if (xValue != y[key]) {
-        return false;
-      }
-    }
-  }
-  return true;
-}
-
 final Class emptyClass = Class(name: 'className', fields: <NamedType>[
   NamedType(
     name: 'namedTypeName',
@@ -50,38 +19,11 @@ final Enum emptyEnum = Enum(
 );
 
 void main() {
-  test('test merge maps', () {
-    final Map<String, Object> source = <String, Object>{
-      '1': '1',
-      '2': <String, Object>{
-        '1': '1',
-        '3': '3',
-      },
-      '3': '3', // not modified
-    };
-    final Map<String, Object> modification = <String, Object>{
-      '1': '2', // modify
-      '2': <String, Object>{
-        '2': '2', // added
-      },
-    };
-    final Map<String, Object> expected = <String, Object>{
-      '1': '2',
-      '2': <String, Object>{
-        '1': '1',
-        '2': '2',
-        '3': '3',
-      },
-      '3': '3',
-    };
-    expect(_equalMaps(expected, mergeMaps(source, modification)), isTrue);
-  });
-
   test('get codec classes from argument type arguments', () {
-    final Api api =
-        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+    final Api api = AstFlutterApi(name: 'Api', methods: <Method>[
       Method(
         name: 'doSomething',
+        location: ApiLocation.flutter,
         parameters: <Parameter>[
           Parameter(
             type: TypeDeclaration(
@@ -123,10 +65,10 @@ void main() {
   });
 
   test('get codec classes from return value type arguments', () {
-    final Api api =
-        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+    final Api api = AstFlutterApi(name: 'Api', methods: <Method>[
       Method(
         name: 'doSomething',
+        location: ApiLocation.flutter,
         parameters: <Parameter>[
           Parameter(
             type: TypeDeclaration(
@@ -168,10 +110,10 @@ void main() {
   });
 
   test('get codec classes from all arguments', () {
-    final Api api =
-        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+    final Api api = AstFlutterApi(name: 'Api', methods: <Method>[
       Method(
         name: 'doSomething',
+        location: ApiLocation.flutter,
         parameters: <Parameter>[
           Parameter(
             type: TypeDeclaration(
@@ -216,9 +158,10 @@ void main() {
 
   test('getCodecClasses: nested type arguments', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'foo',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 name: 'x',
@@ -272,12 +215,12 @@ void main() {
 
   test('getCodecClasses: with Object', () {
     final Root root = Root(apis: <Api>[
-      Api(
+      AstFlutterApi(
         name: 'Api1',
-        location: ApiLocation.flutter,
         methods: <Method>[
           Method(
             name: 'foo',
+            location: ApiLocation.flutter,
             parameters: <Parameter>[
               Parameter(
                   name: 'x',
@@ -311,12 +254,12 @@ void main() {
 
   test('getCodecClasses: unique entries', () {
     final Root root = Root(apis: <Api>[
-      Api(
+      AstFlutterApi(
         name: 'Api1',
-        location: ApiLocation.flutter,
         methods: <Method>[
           Method(
             name: 'foo',
+            location: ApiLocation.flutter,
             parameters: <Parameter>[
               Parameter(
                   name: 'x',
@@ -330,12 +273,12 @@ void main() {
           )
         ],
       ),
-      Api(
+      AstFlutterApi(
         name: 'Api2',
-        location: ApiLocation.host,
         methods: <Method>[
           Method(
             name: 'foo',
+            location: ApiLocation.host,
             parameters: <Parameter>[
               Parameter(
                   name: 'x',
@@ -372,4 +315,97 @@ void main() {
 
     expect(dartPackageName, 'pigeon');
   });
+
+  test('recursiveGetSuperClassApisChain', () {
+    final AstProxyApi api = AstProxyApi(
+      name: 'Api',
+      methods: <Method>[],
+      constructors: <Constructor>[],
+      fields: <Field>[],
+      superClassName: 'Api2',
+    );
+    final AstProxyApi superClassApi = AstProxyApi(
+      name: 'Api2',
+      methods: <Method>[],
+      constructors: <Constructor>[],
+      fields: <Field>[],
+      superClassName: 'Api3',
+    );
+    final AstProxyApi superClassOfSuperClassApi = AstProxyApi(
+      name: 'Api3',
+      methods: <Method>[],
+      constructors: <Constructor>[],
+      fields: <Field>[],
+    );
+
+    final List<AstProxyApi> apiChain = recursiveGetSuperClassApisChain(
+      api,
+      <AstProxyApi>[superClassOfSuperClassApi, api, superClassApi],
+    );
+
+    expect(
+      apiChain,
+      containsAllInOrder(<AstProxyApi>[
+        superClassApi,
+        superClassOfSuperClassApi,
+      ]),
+    );
+  });
+
+  test('recursiveFindAllInterfacesApis', () {
+    final AstProxyApi api = AstProxyApi(
+      name: 'Api',
+      methods: <Method>[],
+      constructors: <Constructor>[],
+      fields: <Field>[],
+      interfacesNames: <String>{'Api2', 'Api3'},
+    );
+    final AstProxyApi interfaceApi = AstProxyApi(
+      name: 'Api2',
+      methods: <Method>[],
+      constructors: <Constructor>[],
+      fields: <Field>[],
+      interfacesNames: <String>{'Api4', 'Api5'},
+    );
+    final AstProxyApi interfaceApi2 = AstProxyApi(
+      name: 'Api3',
+      methods: <Method>[],
+      constructors: <Constructor>[],
+      fields: <Field>[],
+      interfacesNames: <String>{'Api5'},
+    );
+    final AstProxyApi interfaceOfInterfaceApi = AstProxyApi(
+      name: 'Api4',
+      methods: <Method>[],
+      constructors: <Constructor>[],
+      fields: <Field>[],
+    );
+    final AstProxyApi interfaceOfInterfaceApi2 = AstProxyApi(
+      name: 'Api5',
+      methods: <Method>[],
+      constructors: <Constructor>[],
+      fields: <Field>[],
+    );
+
+    final Set<AstProxyApi> allInterfaces = recursiveFindAllInterfacesApis(
+      api,
+      <AstProxyApi>[
+        api,
+        interfaceApi,
+        interfaceApi2,
+        interfaceOfInterfaceApi,
+        interfaceOfInterfaceApi2,
+      ],
+    );
+
+    expect(
+      allInterfaces,
+      containsAll(<AstProxyApi>[
+        interfaceApi,
+        interfaceApi2,
+        interfaceOfInterfaceApi,
+        interfaceOfInterfaceApi2,
+      ]),
+    );
+  });
 }
diff --git a/packages/pigeon/test/java_generator_test.dart b/packages/pigeon/test/java_generator_test.dart
index cba2d702255c..97cbfe8b4d09 100644
--- a/packages/pigeon/test/java_generator_test.dart
+++ b/packages/pigeon/test/java_generator_test.dart
@@ -123,9 +123,10 @@ void main() {
 
   test('gen one host api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -265,9 +266,10 @@ void main() {
 
   test('gen one flutter api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -318,9 +320,10 @@ void main() {
 
   test('gen host void api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -359,9 +362,10 @@ void main() {
 
   test('gen flutter void return api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -403,9 +407,10 @@ void main() {
 
   test('gen host void argument api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[],
           returnType: TypeDeclaration(
             baseName: 'Output',
@@ -440,9 +445,10 @@ void main() {
 
   test('gen flutter void argument api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[],
           returnType: TypeDeclaration(
             baseName: 'Output',
@@ -578,9 +584,10 @@ void main() {
 
   test('gen one async Host Api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -639,9 +646,10 @@ void main() {
 
   test('gen one async Flutter Api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -745,9 +753,10 @@ void main() {
 
   test('primitive enum host', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Bar', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Bar', methods: <Method>[
         Method(
             name: 'bar',
+            location: ApiLocation.host,
             returnType: const TypeDeclaration.voidDeclaration(),
             parameters: <Parameter>[
               Parameter(
@@ -875,9 +884,10 @@ void main() {
   test('host generics argument', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -910,9 +920,10 @@ void main() {
   test('flutter generics argument', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+        AstFlutterApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -945,9 +956,10 @@ void main() {
   test('host generics return', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration(
                   baseName: 'List',
                   isNullable: false,
@@ -977,9 +989,10 @@ void main() {
   test('flutter generics return', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+        AstFlutterApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration(
                   baseName: 'List',
                   isNullable: false,
@@ -1010,9 +1023,10 @@ void main() {
   test('flutter int return', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+        AstFlutterApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.flutter,
               returnType:
                   const TypeDeclaration(baseName: 'int', isNullable: false),
               parameters: <Parameter>[],
@@ -1041,9 +1055,10 @@ void main() {
 
   test('host multiple args', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'add',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 name: 'x',
@@ -1082,9 +1097,10 @@ void main() {
 
   test('if host argType is Object not cast', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'objectTest',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 name: 'x',
@@ -1110,9 +1126,10 @@ void main() {
 
   test('flutter multiple args', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'add',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 name: 'x',
@@ -1152,9 +1169,10 @@ void main() {
 
   test('flutter single args', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'send',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 name: 'x',
@@ -1184,9 +1202,10 @@ void main() {
   test('return nullable host', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration(
                 baseName: 'int',
                 isNullable: true,
@@ -1213,9 +1232,10 @@ void main() {
   test('return nullable host async', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration(
                 baseName: 'int',
                 isNullable: true,
@@ -1244,9 +1264,10 @@ void main() {
   test('nullable argument host', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1277,9 +1298,10 @@ void main() {
   test('nullable argument flutter', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+        AstFlutterApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1313,9 +1335,10 @@ void main() {
   test('background platform channel', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1415,13 +1438,13 @@ void main() {
 
     final Root root = Root(
       apis: <Api>[
-        Api(
+        AstFlutterApi(
           name: 'api',
-          location: ApiLocation.flutter,
           documentationComments: <String>[comments[count++]],
           methods: <Method>[
             Method(
               name: 'method',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               documentationComments: <String>[comments[count++]],
               parameters: <Parameter>[
@@ -1496,12 +1519,12 @@ void main() {
   test("doesn't create codecs if no custom datatypes", () {
     final Root root = Root(
       apis: <Api>[
-        Api(
+        AstFlutterApi(
           name: 'Api',
-          location: ApiLocation.flutter,
           methods: <Method>[
             Method(
               name: 'method',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1535,9 +1558,10 @@ void main() {
 
   test('creates custom codecs if custom datatypes present', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -1587,8 +1611,7 @@ void main() {
   });
 
   test('creates api error class for custom errors', () {
-    final Api api =
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[]);
+    final Api api = AstHostApi(name: 'Api', methods: <Method>[]);
     final Root root = Root(
       apis: <Api>[api],
       classes: <Class>[],
@@ -1610,12 +1633,12 @@ void main() {
   test('connection error contains channel name', () {
     final Root root = Root(
       apis: <Api>[
-        Api(
+        AstFlutterApi(
           name: 'Api',
-          location: ApiLocation.flutter,
           methods: <Method>[
             Method(
               name: 'method',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
diff --git a/packages/pigeon/test/kotlin_generator_test.dart b/packages/pigeon/test/kotlin_generator_test.dart
index f51c68b32bcc..e680e3ac66d2 100644
--- a/packages/pigeon/test/kotlin_generator_test.dart
+++ b/packages/pigeon/test/kotlin_generator_test.dart
@@ -140,9 +140,10 @@ void main() {
 
   test('primitive enum host', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Bar', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Bar', methods: <Method>[
         Method(
             name: 'bar',
+            location: ApiLocation.host,
             returnType: const TypeDeclaration.voidDeclaration(),
             parameters: <Parameter>[
               Parameter(
@@ -176,9 +177,10 @@ void main() {
 
   test('gen one host api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
               type: TypeDeclaration(
@@ -405,9 +407,10 @@ void main() {
 
   test('gen one flutter api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
               type: TypeDeclaration(
@@ -462,9 +465,10 @@ void main() {
 
   test('gen host void api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
               type: TypeDeclaration(
@@ -505,9 +509,10 @@ void main() {
 
   test('gen flutter void return api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
               type: TypeDeclaration(
@@ -550,9 +555,10 @@ void main() {
 
   test('gen host void argument api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[],
           returnType: TypeDeclaration(
             baseName: 'Output',
@@ -590,9 +596,10 @@ void main() {
 
   test('gen flutter void argument api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[],
           returnType: TypeDeclaration(
             baseName: 'Output',
@@ -732,9 +739,10 @@ void main() {
 
   test('gen one async Host Api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
               type: TypeDeclaration(
@@ -790,9 +798,10 @@ void main() {
 
   test('gen one async Flutter Api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
               type: TypeDeclaration(
@@ -979,9 +988,10 @@ void main() {
   test('host generics argument', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1015,9 +1025,10 @@ void main() {
   test('flutter generics argument', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+        AstFlutterApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1051,9 +1062,10 @@ void main() {
   test('host generics return', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration(
                   baseName: 'List',
                   isNullable: false,
@@ -1084,9 +1096,10 @@ void main() {
   test('flutter generics return', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+        AstFlutterApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration(
                   baseName: 'List',
                   isNullable: false,
@@ -1116,9 +1129,10 @@ void main() {
 
   test('host multiple args', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'add',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 name: 'x',
@@ -1159,9 +1173,10 @@ void main() {
 
   test('flutter multiple args', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'add',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 name: 'x',
@@ -1203,9 +1218,10 @@ void main() {
   test('return nullable host', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration(
                 baseName: 'int',
                 isNullable: true,
@@ -1232,9 +1248,10 @@ void main() {
   test('return nullable host async', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration(
                 baseName: 'int',
                 isNullable: true,
@@ -1262,9 +1279,10 @@ void main() {
   test('nullable argument host', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1298,9 +1316,10 @@ void main() {
   test('nullable argument flutter', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+        AstFlutterApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1333,9 +1352,10 @@ void main() {
 
   test('nonnull fields', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
               type: TypeDeclaration(
@@ -1389,13 +1409,13 @@ void main() {
 
     final Root root = Root(
       apis: <Api>[
-        Api(
+        AstFlutterApi(
           name: 'api',
-          location: ApiLocation.flutter,
           documentationComments: <String>[comments[count++]],
           methods: <Method>[
             Method(
               name: 'method',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               documentationComments: <String>[comments[count++]],
               parameters: <Parameter>[
@@ -1470,12 +1490,12 @@ void main() {
   test("doesn't create codecs if no custom datatypes", () {
     final Root root = Root(
       apis: <Api>[
-        Api(
+        AstFlutterApi(
           name: 'Api',
-          location: ApiLocation.flutter,
           methods: <Method>[
             Method(
               name: 'method',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1509,9 +1529,10 @@ void main() {
 
   test('creates custom codecs if custom datatypes present', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -1563,10 +1584,11 @@ void main() {
   test('creates api error class for custom errors', () {
     final Method method = Method(
         name: 'doSomething',
+        location: ApiLocation.host,
         returnType: const TypeDeclaration.voidDeclaration(),
         parameters: <Parameter>[]);
-    final Api api = Api(
-        name: 'SomeApi', location: ApiLocation.host, methods: <Method>[method]);
+    final AstHostApi api =
+        AstHostApi(name: 'SomeApi', methods: <Method>[method]);
     final Root root = Root(
       apis: <Api>[api],
       classes: <Class>[],
@@ -1593,12 +1615,12 @@ void main() {
   test('connection error contains channel name', () {
     final Root root = Root(
       apis: <Api>[
-        Api(
+        AstFlutterApi(
           name: 'Api',
-          location: ApiLocation.flutter,
           methods: <Method>[
             Method(
               name: 'method',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1639,12 +1661,12 @@ void main() {
   test('gen host uses default error class', () {
     final Root root = Root(
       apis: <Api>[
-        Api(
+        AstHostApi(
           name: 'Api',
-          location: ApiLocation.host,
           methods: <Method>[
             Method(
               name: 'method',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1678,12 +1700,12 @@ void main() {
   test('gen flutter uses default error class', () {
     final Root root = Root(
       apis: <Api>[
-        Api(
+        AstFlutterApi(
           name: 'Api',
-          location: ApiLocation.flutter,
           methods: <Method>[
             Method(
               name: 'method',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1717,12 +1739,12 @@ void main() {
   test('gen host uses error class', () {
     final Root root = Root(
       apis: <Api>[
-        Api(
+        AstHostApi(
           name: 'Api',
-          location: ApiLocation.host,
           methods: <Method>[
             Method(
               name: 'method',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1759,12 +1781,12 @@ void main() {
   test('gen flutter uses error class', () {
     final Root root = Root(
       apis: <Api>[
-        Api(
+        AstFlutterApi(
           name: 'Api',
-          location: ApiLocation.flutter,
           methods: <Method>[
             Method(
               name: 'method',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
diff --git a/packages/pigeon/test/objc_generator_test.dart b/packages/pigeon/test/objc_generator_test.dart
index f77f186ac8df..267747e1e913 100644
--- a/packages/pigeon/test/objc_generator_test.dart
+++ b/packages/pigeon/test/objc_generator_test.dart
@@ -188,9 +188,10 @@ void main() {
 
   test('primitive enum host', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Bar', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Bar', methods: <Method>[
         Method(
             name: 'bar',
+            location: ApiLocation.host,
             returnType: const TypeDeclaration.voidDeclaration(),
             parameters: <Parameter>[
               Parameter(
@@ -251,9 +252,10 @@ void main() {
 
   test('validate nullable primitive enum', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Bar', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Bar', methods: <Method>[
         Method(
             name: 'bar',
+            location: ApiLocation.host,
             returnType: const TypeDeclaration.voidDeclaration(),
             parameters: <Parameter>[
               Parameter(
@@ -328,9 +330,10 @@ void main() {
 
   test('gen one api header', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
             name: 'doSomething',
+            location: ApiLocation.host,
             parameters: <Parameter>[
               Parameter(
                   type: TypeDeclaration(
@@ -383,9 +386,10 @@ void main() {
 
   test('gen one api source', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
             name: 'doSomething',
+            location: ApiLocation.host,
             parameters: <Parameter>[
               Parameter(
                   type: TypeDeclaration(
@@ -656,9 +660,10 @@ void main() {
 
   test('prefix nested class header', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
             name: 'doSomething',
+            location: ApiLocation.host,
             parameters: <Parameter>[
               Parameter(
                   type: TypeDeclaration(
@@ -711,9 +716,10 @@ void main() {
 
   test('prefix nested class source', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
             name: 'doSomething',
+            location: ApiLocation.host,
             parameters: <Parameter>[
               Parameter(
                   type: TypeDeclaration(
@@ -766,9 +772,10 @@ void main() {
 
   test('gen flutter api header', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
             name: 'doSomething',
+            location: ApiLocation.flutter,
             parameters: <Parameter>[
               Parameter(
                   type: TypeDeclaration(
@@ -821,9 +828,10 @@ void main() {
 
   test('gen flutter api source', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
             name: 'doSomething',
+            location: ApiLocation.flutter,
             parameters: <Parameter>[
               Parameter(
                   type: TypeDeclaration(
@@ -872,9 +880,10 @@ void main() {
 
   test('gen host void header', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
             name: 'doSomething',
+            location: ApiLocation.host,
             parameters: <Parameter>[
               Parameter(
                   type: TypeDeclaration(
@@ -913,9 +922,10 @@ void main() {
 
   test('gen host void source', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
             name: 'doSomething',
+            location: ApiLocation.host,
             parameters: <Parameter>[
               Parameter(
                   type: TypeDeclaration(
@@ -956,9 +966,10 @@ void main() {
 
   test('gen flutter void return header', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
             name: 'doSomething',
+            location: ApiLocation.flutter,
             parameters: <Parameter>[
               Parameter(
                   type: TypeDeclaration(
@@ -997,9 +1008,10 @@ void main() {
 
   test('gen flutter void return source', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
             name: 'doSomething',
+            location: ApiLocation.flutter,
             parameters: <Parameter>[
               Parameter(
                   type: TypeDeclaration(
@@ -1039,9 +1051,10 @@ void main() {
 
   test('gen host void arg header', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
             name: 'doSomething',
+            location: ApiLocation.host,
             parameters: <Parameter>[],
             returnType: TypeDeclaration(
               baseName: 'Output',
@@ -1076,9 +1089,10 @@ void main() {
 
   test('gen host void arg source', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
             name: 'doSomething',
+            location: ApiLocation.host,
             parameters: <Parameter>[],
             returnType: TypeDeclaration(
               baseName: 'Output',
@@ -1113,9 +1127,10 @@ void main() {
 
   test('gen flutter void arg header', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
             name: 'doSomething',
+            location: ApiLocation.flutter,
             parameters: <Parameter>[],
             returnType: TypeDeclaration(
               baseName: 'Output',
@@ -1153,9 +1168,10 @@ void main() {
 
   test('gen flutter void arg source', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
             name: 'doSomething',
+            location: ApiLocation.flutter,
             parameters: <Parameter>[],
             returnType: TypeDeclaration(
               baseName: 'Output',
@@ -1281,9 +1297,10 @@ void main() {
 
   test('gen map argument with object', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
             name: 'doit',
+            location: ApiLocation.host,
             returnType: const TypeDeclaration.voidDeclaration(),
             parameters: <Parameter>[
               Parameter(
@@ -1317,9 +1334,10 @@ void main() {
 
   test('async void (input) HostApi header', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
             name: 'doSomething',
+            location: ApiLocation.host,
             parameters: <Parameter>[
               Parameter(
                   type: TypeDeclaration(
@@ -1367,9 +1385,10 @@ void main() {
 
   test('async output(input) HostApi header', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
             name: 'doSomething',
+            location: ApiLocation.host,
             parameters: <Parameter>[
               Parameter(
                   type: TypeDeclaration(
@@ -1421,9 +1440,10 @@ void main() {
 
   test('async output(void) HostApi header', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
             name: 'doSomething',
+            location: ApiLocation.host,
             parameters: <Parameter>[],
             returnType: TypeDeclaration(
               baseName: 'Output',
@@ -1462,9 +1482,10 @@ void main() {
 
   test('async void (void) HostApi header', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
             name: 'doSomething',
+            location: ApiLocation.host,
             parameters: <Parameter>[],
             returnType: const TypeDeclaration.voidDeclaration(),
             isAsynchronous: true)
@@ -1493,9 +1514,10 @@ void main() {
 
   test('async output(input) HostApi source', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
             name: 'doSomething',
+            location: ApiLocation.host,
             parameters: <Parameter>[
               Parameter(
                   type: TypeDeclaration(
@@ -1547,9 +1569,10 @@ void main() {
 
   test('async void (input) HostApi source', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
             name: 'doSomething',
+            location: ApiLocation.host,
             parameters: <Parameter>[
               Parameter(
                   type: TypeDeclaration(
@@ -1597,9 +1620,10 @@ void main() {
 
   test('async void (void) HostApi source', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
             name: 'doSomething',
+            location: ApiLocation.host,
             parameters: <Parameter>[],
             returnType: const TypeDeclaration.voidDeclaration(),
             isAsynchronous: true)
@@ -1628,9 +1652,10 @@ void main() {
 
   test('async output(void) HostApi source', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
             name: 'doSomething',
+            location: ApiLocation.host,
             parameters: <Parameter>[],
             returnType: TypeDeclaration(
               baseName: 'Output',
@@ -1755,9 +1780,10 @@ void main() {
   test('host generics argument', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1818,9 +1844,10 @@ void main() {
   test('flutter generics argument', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+        AstFlutterApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1878,9 +1905,10 @@ void main() {
   test('host nested generic argument', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1926,9 +1954,10 @@ void main() {
   test('host generics return', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration(
                   baseName: 'List',
                   isNullable: false,
@@ -1983,9 +2012,10 @@ void main() {
   test('flutter generics return', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+        AstFlutterApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration(
                   baseName: 'List',
                   isNullable: false,
@@ -2040,9 +2070,10 @@ void main() {
 
   test('host multiple args', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'add',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 name: 'x',
@@ -2110,9 +2141,10 @@ void main() {
 
   test('host multiple args async', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'add',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 name: 'x',
@@ -2180,9 +2212,10 @@ void main() {
 
   test('flutter multiple args', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'add',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 name: 'x',
@@ -2245,25 +2278,48 @@ void main() {
 
   Root getDivideRoot(ApiLocation location) => Root(
         apis: <Api>[
-          Api(name: 'Api', location: location, methods: <Method>[
-            Method(
-                name: 'divide',
-                objcSelector: 'divideValue:by:',
-                parameters: <Parameter>[
-                  Parameter(
-                    type: const TypeDeclaration(
-                        baseName: 'int', isNullable: false),
-                    name: 'x',
-                  ),
-                  Parameter(
-                    type: const TypeDeclaration(
-                        baseName: 'int', isNullable: false),
-                    name: 'y',
-                  ),
-                ],
-                returnType: const TypeDeclaration(
-                    baseName: 'double', isNullable: false))
-          ])
+          switch (location) {
+            ApiLocation.host => AstHostApi(name: 'Api', methods: <Method>[
+                Method(
+                    name: 'divide',
+                    location: location,
+                    objcSelector: 'divideValue:by:',
+                    parameters: <Parameter>[
+                      Parameter(
+                        type: const TypeDeclaration(
+                            baseName: 'int', isNullable: false),
+                        name: 'x',
+                      ),
+                      Parameter(
+                        type: const TypeDeclaration(
+                            baseName: 'int', isNullable: false),
+                        name: 'y',
+                      ),
+                    ],
+                    returnType: const TypeDeclaration(
+                        baseName: 'double', isNullable: false))
+              ]),
+            ApiLocation.flutter => AstFlutterApi(name: 'Api', methods: <Method>[
+                Method(
+                    name: 'divide',
+                    location: location,
+                    objcSelector: 'divideValue:by:',
+                    parameters: <Parameter>[
+                      Parameter(
+                        type: const TypeDeclaration(
+                            baseName: 'int', isNullable: false),
+                        name: 'x',
+                      ),
+                      Parameter(
+                        type: const TypeDeclaration(
+                            baseName: 'int', isNullable: false),
+                        name: 'y',
+                      ),
+                    ],
+                    returnType: const TypeDeclaration(
+                        baseName: 'double', isNullable: false))
+              ]),
+          }
         ],
         classes: <Class>[],
         enums: <Enum>[],
@@ -2378,9 +2434,10 @@ void main() {
   test('return nullable flutter header', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+        AstFlutterApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration(
                 baseName: 'int',
                 isNullable: true,
@@ -2414,9 +2471,10 @@ void main() {
   test('return nullable flutter source', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+        AstFlutterApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration(
                 baseName: 'int',
                 isNullable: true,
@@ -2447,9 +2505,10 @@ void main() {
   test('return nullable host header', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration(
                 baseName: 'int',
                 isNullable: true,
@@ -2480,9 +2539,10 @@ void main() {
   test('nullable argument host', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -2537,9 +2597,10 @@ void main() {
   test('nullable argument flutter', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+        AstFlutterApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -2593,9 +2654,10 @@ void main() {
   test('background platform channel', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration(
                 baseName: 'int',
                 isNullable: true,
@@ -2644,13 +2706,13 @@ void main() {
 
     final Root root = Root(
       apis: <Api>[
-        Api(
+        AstFlutterApi(
           name: 'api',
-          location: ApiLocation.flutter,
           documentationComments: <String>[comments[count++]],
           methods: <Method>[
             Method(
               name: 'method',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               documentationComments: <String>[comments[count++]],
               parameters: <Parameter>[
@@ -2725,12 +2787,12 @@ void main() {
   test("doesn't create codecs if no custom datatypes", () {
     final Root root = Root(
       apis: <Api>[
-        Api(
+        AstFlutterApi(
           name: 'Api',
-          location: ApiLocation.flutter,
           methods: <Method>[
             Method(
               name: 'method',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -2767,9 +2829,10 @@ void main() {
 
   test('creates custom codecs if custom datatypes present', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -2825,12 +2888,12 @@ void main() {
   test('connection error contains channel name', () {
     final Root root = Root(
       apis: <Api>[
-        Api(
+        AstFlutterApi(
           name: 'Api',
-          location: ApiLocation.flutter,
           methods: <Method>[
             Method(
               name: 'method',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
diff --git a/packages/pigeon/test/pigeon_lib_test.dart b/packages/pigeon/test/pigeon_lib_test.dart
index 5d60f92bf69d..7998733664ab 100644
--- a/packages/pigeon/test/pigeon_lib_test.dart
+++ b/packages/pigeon/test/pigeon_lib_test.dart
@@ -313,7 +313,7 @@ abstract class AFlutterApi {
     expect(results.errors.length, equals(0));
     expect(results.root.apis.length, equals(1));
     expect(results.root.apis[0].name, equals('AFlutterApi'));
-    expect(results.root.apis[0].location, equals(ApiLocation.flutter));
+    expect(results.root.apis[0], isA<AstFlutterApi>());
   });
 
   test('void host api', () {
@@ -370,8 +370,10 @@ abstract class ApiWithMockDartClass {
     final ParseResults results = parseSource(code);
     expect(results.errors.length, equals(0));
     expect(results.root.apis.length, equals(1));
-    expect(results.root.apis[0].dartHostTestHandler,
-        equals('ApiWithMockDartClassMock'));
+    expect(
+      (results.root.apis[0] as AstHostApi).dartHostTestHandler,
+      equals('ApiWithMockDartClassMock'),
+    );
   });
 
   test('only visible from nesting', () {
diff --git a/packages/pigeon/test/swift_generator_test.dart b/packages/pigeon/test/swift_generator_test.dart
index 4c07b784eb74..e43dc8efed62 100644
--- a/packages/pigeon/test/swift_generator_test.dart
+++ b/packages/pigeon/test/swift_generator_test.dart
@@ -84,9 +84,10 @@ void main() {
 
   test('primitive enum host', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Bar', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Bar', methods: <Method>[
         Method(
             name: 'bar',
+            location: ApiLocation.host,
             returnType: const TypeDeclaration.voidDeclaration(),
             parameters: <Parameter>[
               Parameter(
@@ -120,9 +121,10 @@ void main() {
 
   test('gen one host api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -248,9 +250,10 @@ void main() {
 
   test('gen one flutter api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -302,9 +305,10 @@ void main() {
 
   test('gen host void api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -343,9 +347,10 @@ void main() {
 
   test('gen flutter void return api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -385,9 +390,10 @@ void main() {
 
   test('gen host void argument api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[],
           returnType: TypeDeclaration(
             baseName: 'Output',
@@ -423,9 +429,10 @@ void main() {
 
   test('gen flutter void argument api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[],
           returnType: TypeDeclaration(
             baseName: 'Output',
@@ -560,9 +567,10 @@ void main() {
 
   test('gen one async Host Api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -615,9 +623,10 @@ void main() {
 
   test('gen one async Flutter Api', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -798,9 +807,10 @@ void main() {
   test('host generics argument', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -833,9 +843,10 @@ void main() {
   test('flutter generics argument', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+        AstFlutterApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -868,9 +879,10 @@ void main() {
   test('host generics return', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration(
                   baseName: 'List',
                   isNullable: false,
@@ -901,9 +913,10 @@ void main() {
   test('flutter generics return', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+        AstFlutterApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration(
                   baseName: 'List',
                   isNullable: false,
@@ -936,9 +949,10 @@ void main() {
 
   test('host multiple args', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'add',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 name: 'x',
@@ -979,9 +993,10 @@ void main() {
 
   test('flutter multiple args', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'add',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 name: 'x',
@@ -1023,9 +1038,10 @@ void main() {
   test('return nullable host', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration(
                 baseName: 'int',
                 isNullable: true,
@@ -1052,9 +1068,10 @@ void main() {
   test('return nullable host async', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration(
                 baseName: 'int',
                 isNullable: true,
@@ -1085,9 +1102,10 @@ void main() {
   test('nullable argument host', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.host,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1121,9 +1139,10 @@ void main() {
   test('nullable argument flutter', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+        AstFlutterApi(name: 'Api', methods: <Method>[
           Method(
               name: 'doit',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1156,9 +1175,10 @@ void main() {
 
   test('nonnull fields', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+      AstHostApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.host,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -1210,13 +1230,13 @@ void main() {
 
     final Root root = Root(
       apis: <Api>[
-        Api(
+        AstFlutterApi(
           name: 'api',
-          location: ApiLocation.flutter,
           documentationComments: <String>[comments[count++]],
           methods: <Method>[
             Method(
               name: 'method',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               documentationComments: <String>[comments[count++]],
               parameters: <Parameter>[
@@ -1287,12 +1307,12 @@ void main() {
   test("doesn't create codecs if no custom datatypes", () {
     final Root root = Root(
       apis: <Api>[
-        Api(
+        AstFlutterApi(
           name: 'Api',
-          location: ApiLocation.flutter,
           methods: <Method>[
             Method(
               name: 'method',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
@@ -1325,9 +1345,10 @@ void main() {
 
   test('creates custom codecs if custom datatypes present', () {
     final Root root = Root(apis: <Api>[
-      Api(name: 'Api', location: ApiLocation.flutter, methods: <Method>[
+      AstFlutterApi(name: 'Api', methods: <Method>[
         Method(
           name: 'doSomething',
+          location: ApiLocation.flutter,
           parameters: <Parameter>[
             Parameter(
                 type: TypeDeclaration(
@@ -1379,9 +1400,10 @@ void main() {
   test('swift function signature', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
             name: 'set',
+            location: ApiLocation.host,
             parameters: <Parameter>[
               Parameter(
                 type: const TypeDeclaration(
@@ -1422,9 +1444,10 @@ void main() {
   test('swift function signature with same name argument', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
             name: 'set',
+            location: ApiLocation.host,
             parameters: <Parameter>[
               Parameter(
                 type: const TypeDeclaration(
@@ -1458,9 +1481,10 @@ void main() {
   test('swift function signature with no arguments', () {
     final Root root = Root(
       apis: <Api>[
-        Api(name: 'Api', location: ApiLocation.host, methods: <Method>[
+        AstHostApi(name: 'Api', methods: <Method>[
           Method(
             name: 'clear',
+            location: ApiLocation.host,
             parameters: <Parameter>[],
             swiftFunction: 'removeAll()',
             returnType: const TypeDeclaration.voidDeclaration(),
@@ -1486,12 +1510,12 @@ void main() {
   test('connection error contains channel name', () {
     final Root root = Root(
       apis: <Api>[
-        Api(
+        AstFlutterApi(
           name: 'Api',
-          location: ApiLocation.flutter,
           methods: <Method>[
             Method(
               name: 'method',
+              location: ApiLocation.flutter,
               returnType: const TypeDeclaration.voidDeclaration(),
               parameters: <Parameter>[
                 Parameter(
diff --git a/script/configs/allowed_unpinned_deps.yaml b/script/configs/allowed_unpinned_deps.yaml
index fe4c138b0a63..84ff94a1101b 100644
--- a/script/configs/allowed_unpinned_deps.yaml
+++ b/script/configs/allowed_unpinned_deps.yaml
@@ -25,9 +25,11 @@
 - build_config
 - build_runner
 - build_test
+- code_builder
 - collection
 - convert
 - crypto
+- dart_style
 - fake_async
 - ffi
 - gcloud