Specify that 'get element' for FunctionType, RecordType and VoidType always return 'Null'.

Change-Id: I4bbf7aaef2afc3d9ad5d2f7da35a4c8bd9e39caa
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/256421
Reviewed-by: Brian Wilkerson <[email protected]>
Commit-Queue: Konstantin Shcheglov <[email protected]>

Author: scheglov

pkg/analyzer/lib/dart/element/type.dart

@@ -210,6 +210,13 @@ abstract class DynamicType implements DartType {}
 ///
 /// Clients may not extend, implement or mix-in this class.
 abstract class FunctionType implements DartType {
+  @Deprecated('Use element2 instead')
+  @override
+  Null get element;
+
+  @override
+  Null get element2;
+
   /// Return a map from the names of named parameters to the types of the named
   /// parameters of this type of function. The entries in the map will be
   /// iterated in the same order as the order in which the named parameters were
@@ -436,10 +443,10 @@ abstract class ParameterizedType implements DartType {
 abstract class RecordType implements DartType {
   @Deprecated('Use element2 instead')
   @override
-  Element? get element;
+  Null get element;
 
   @override
-  Element? get element2;
+  Null get element2;
 
   /// The named fields (might be empty).
   List<RecordTypeNamedField> get namedFields;
@@ -497,4 +504,11 @@ abstract class TypeParameterType implements DartType {
 
 /// The special type `void` is used to indicate that the value of an
 /// expression is meaningless, and intended to be discarded.
-abstract class VoidType implements DartType {}
+abstract class VoidType implements DartType {
+  @Deprecated('Use element2 instead')
+  @override
+  Null get element;
+
+  @override
+  Null get element2;
+}

pkg/analyzer/lib/src/dart/element/type.dart

@@ -102,8 +102,12 @@ class FunctionTypeImpl extends TypeImpl implements FunctionType {
   })  : parameters = _sortNamedParameters(parameters),
         super(null, alias: alias);
 
+  @Deprecated('Use element2 instead')
+  @override
+  Null get element => null;
+
   @override
-  Element? get element2 => null;
+  Null get element2 => null;
 
   @override
   int get hashCode {
@@ -1010,8 +1014,12 @@ class RecordTypeImpl extends TypeImpl implements RecordType {
   })  : namedFields = _sortNamedFields(namedFields),
         super(null, alias: alias);
 
+  @Deprecated('Use element2 instead')
   @override
-  Element? get element2 => null;
+  Null get element => null;
+
+  @override
+  Null get element2 => null;
 
   @override
   int get hashCode {
@@ -1448,8 +1456,12 @@ class VoidTypeImpl extends TypeImpl implements VoidType {
   /// Prevent the creation of instances of this class.
   VoidTypeImpl._() : super(null);
 
+  @Deprecated('Use element2 instead')
+  @override
+  Null get element => null;
+
   @override
-  Element? get element2 => null;
+  Null get element2 => null;
 
   @override
   int get hashCode => 2;