[dart2js] Allow SpecialMemberDefinition to copy Deferrable from ClosureMemberDefiniton

Codegen deserialization was inadvertantly loading the nodes for many ClosureMemberDefinitions, specifically ones for generators. The node doesn't actually end up being used after this point though so the Deferrable is unnecessarily triggered.

To get around this we have the SpecialMemberDefinition constructor copy the Deferrable out of the ClosureMemberDefinition.

To avoid exposing the deferrable I've moved the ClosureMemberDefinition into the same library as SpecialMemberDefinition.

This brings the number of Kernel AST function bodies being deserialized down to 2 in cm_shell (down from many thousand).

Change-Id: I0781ab490dc1972118cf2ac2359f467916031633
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/247283
Reviewed-by: Stephen Adams <[email protected]>
Commit-Queue: Nate Biggs <[email protected]>
Reviewed-by: Joshua Litt <[email protected]>

Author: natebiggs

pkg/compiler/lib/src/js_model/closure.dart

@@ -1361,51 +1361,6 @@ class ClosureFieldData extends ClosureMemberData implements JFieldData {
       ClassTypeVariableAccess.none;
 }
 
-class ClosureMemberDefinition implements MemberDefinition {
-  /// Tag used for identifying serialized [ClosureMemberDefinition] objects in a
-  /// debugging data stream.
-  static const String tag = 'closure-member-definition';
-
-  @override
-  final SourceSpan location;
-  @override
-  final MemberKind kind;
-  @override
-  ir.TreeNode get node => _node.loaded();
-  final Deferrable<ir.TreeNode> _node;
-
-  ClosureMemberDefinition(this.location, this.kind, ir.TreeNode node)
-      : _node = Deferrable.eager(node),
-        assert(
-            kind == MemberKind.closureCall || kind == MemberKind.closureField);
-
-  ClosureMemberDefinition._deserialized(this.location, this.kind, this._node)
-      : assert(
-            kind == MemberKind.closureCall || kind == MemberKind.closureField);
-
-  factory ClosureMemberDefinition.readFromDataSource(
-      DataSourceReader source, MemberKind kind) {
-    source.begin(tag);
-    SourceSpan location = source.readSourceSpan();
-    Deferrable<ir.TreeNode> node =
-        source.readDeferrable(() => source.readTreeNode());
-    source.end(tag);
-    return ClosureMemberDefinition._deserialized(location, kind, node);
-  }
-
-  @override
-  void writeToDataSink(DataSinkWriter sink) {
-    sink.writeEnum(kind);
-    sink.begin(tag);
-    sink.writeSourceSpan(location);
-    sink.writeDeferrable(() => sink.writeTreeNode(node));
-    sink.end(tag);
-  }
-
-  @override
-  String toString() => 'ClosureMemberDefinition(kind:$kind,location:$location)';
-}
-
 class RecordContainerDefinition implements ClassDefinition {
   /// Tag used for identifying serialized [RecordContainerDefinition] objects in
   /// a debugging data stream.

pkg/compiler/lib/src/js_model/element_map.dart

@@ -422,6 +422,11 @@ class SpecialMemberDefinition implements MemberDefinition {
   SpecialMemberDefinition(ir.TreeNode node, this.kind)
       : _node = Deferrable.eager(node);
 
+  SpecialMemberDefinition.from(MemberDefinition baseMember, this.kind)
+      : _node = baseMember is ClosureMemberDefinition
+            ? baseMember._node
+            : Deferrable.eager(baseMember.node);
+
   SpecialMemberDefinition._deserialized(this._node, this.kind);
 
   factory SpecialMemberDefinition.readFromDataSource(
@@ -449,6 +454,51 @@ class SpecialMemberDefinition implements MemberDefinition {
       'node:$node,location:$location)';
 }
 
+class ClosureMemberDefinition implements MemberDefinition {
+  /// Tag used for identifying serialized [ClosureMemberDefinition] objects in a
+  /// debugging data stream.
+  static const String tag = 'closure-member-definition';
+
+  @override
+  final SourceSpan location;
+  @override
+  final MemberKind kind;
+  @override
+  ir.TreeNode get node => _node.loaded();
+  final Deferrable<ir.TreeNode> _node;
+
+  ClosureMemberDefinition(this.location, this.kind, ir.TreeNode node)
+      : _node = Deferrable.eager(node),
+        assert(
+            kind == MemberKind.closureCall || kind == MemberKind.closureField);
+
+  ClosureMemberDefinition._deserialized(this.location, this.kind, this._node)
+      : assert(
+            kind == MemberKind.closureCall || kind == MemberKind.closureField);
+
+  factory ClosureMemberDefinition.readFromDataSource(
+      DataSourceReader source, MemberKind kind) {
+    source.begin(tag);
+    SourceSpan location = source.readSourceSpan();
+    Deferrable<ir.TreeNode> node =
+        source.readDeferrable(() => source.readTreeNode());
+    source.end(tag);
+    return ClosureMemberDefinition._deserialized(location, kind, node);
+  }
+
+  @override
+  void writeToDataSink(DataSinkWriter sink) {
+    sink.writeEnum(kind);
+    sink.begin(tag);
+    sink.writeSourceSpan(location);
+    sink.writeDeferrable(() => sink.writeTreeNode(node));
+    sink.end(tag);
+  }
+
+  @override
+  String toString() => 'ClosureMemberDefinition(kind:$kind,location:$location)';
+}
+
 /// Definition information for a [ClassEntity].
 abstract class ClassDefinition {
   /// The kind of the defined class. This determines the semantics of [node].

pkg/compiler/lib/src/js_model/element_map_impl.dart

@@ -1380,7 +1380,7 @@ class JsKernelToElementMap implements JsToElementMap, IrToElementMap {
     return lookup;
   }
 
-  String /*?*/ _getStringArgument(ir.StaticInvocation node, int index) {
+  String _getStringArgument(ir.StaticInvocation node, int index) {
     return node.arguments.positional[index].accept(Stringifier());
   }
 
@@ -2161,14 +2161,15 @@ class JsKernelToElementMap implements JsToElementMap, IrToElementMap {
     JGeneratorBody generatorBody = _generatorBodies[function];
     if (generatorBody == null) {
       FunctionData functionData = members.getData(function);
-      ir.TreeNode node = functionData.definition.node;
       DartType elementType =
           elementEnvironment.getFunctionAsyncOrSyncStarElementType(function);
       generatorBody = createGeneratorBody(function, elementType);
       members.register<IndexedFunction, FunctionData>(
           generatorBody,
-          GeneratorBodyFunctionData(functionData,
-              SpecialMemberDefinition(node, MemberKind.generatorBody)));
+          GeneratorBodyFunctionData(
+              functionData,
+              SpecialMemberDefinition.from(
+                  functionData.definition, MemberKind.generatorBody)));
 
       if (function.enclosingClass != null) {
         // TODO(sra): Integrate this with ClassEnvImpl.addConstructorBody ?

pkg/compiler/lib/src/serialization/deferrable.dart

@@ -55,7 +55,6 @@ import 'package:compiler/src/serialization/serialization_interfaces.dart';
 /// }
 abstract class Deferrable<E> {
   E loaded();
-  static int count = 0;
 
   factory Deferrable.deferred(DataSourceReader reader, E f(), int offset,
           {bool cacheData = true}) =>