[analyzer] Refine some internal getter types.

The types of the following getters are changed:

- From `DartType` to `TypeImpl`:
  - `ExecutableElementImpl.returnType`
  - `FormalParameterElementImpl.type`
  - `FunctionTypeImpl.returnType`
  - `GenericFunctionTypeElementImpl.returnType`
  - `ParameterElementImpl_ofImplicitSetter.type`
  - `PropertyAccessorElementImpl_ImplicitGetter.returnType`
  - `PropertyAccessorElementImpl_ImplicitSetter.returnType`
  - `PropertyInducingElementImpl.type`
  - `RecordTypeFieldImpl.type`
  - `VariableElementImpl.type`
  - `VariableMember.type`
- From `InterfaceType` to `InterfaceTypeImpl`:
  - `ConstructorElementImpl.returnType`
  - `ConstructorElementMixin.returnType`
  - `ConstructorMember.returnType`
  - `InterfaceElementImpl.thisType`
  - `InterfaceElementImpl2.thisType`
- From `AugmentedInterfaceElement` to `InterfaceElementImpl2`:
  - `InterfaceElementImpl.augmented`

There is no change to the analyzer public API.

To make this possible, a few type casts had to be added, and the
return type of some type inference methods had to be changed from
`DartType` to `TypeImpl`. Some other type casts were able to be
eliminated. I hope to eliminate the added type casts in future CLs.

To ensure that type promotion continues to occur, a few `is` and `as`
tests had to be changed so that they test against Impl types rather
than public API types.

This is part of a larger arc of work to change the analyzer's use of
the shared code so that the type parameters it supplies are not part
of the analyzer public API. See
#59763.

Change-Id: Ibf58396c46381aa49e465dcebc14877c6952aa01
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/403943
Reviewed-by: Konstantin Shcheglov <[email protected]>
Commit-Queue: Paul Berry <[email protected]>

Author: stereotype441

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

@@ -76,7 +76,7 @@ class ClassHierarchy {
     }
 
     append(element.supertype);
-    if (augmented is AugmentedMixinElement) {
+    if (augmented is MixinElementImpl2) {
       for (var type in augmented.superclassConstraints) {
         append(type);
       }

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

@@ -1561,15 +1561,15 @@ class ConstructorElementImpl extends ExecutableElementImpl
   }
 
   @override
-  InterfaceType get returnType {
+  InterfaceTypeImpl get returnType {
     var result = _returnType;
     if (result != null) {
-      return result as InterfaceType;
+      return result as InterfaceTypeImpl;
     }
 
     var augmentedDeclaration = enclosingElement3.augmented.firstFragment;
     result = augmentedDeclaration.thisType;
-    return _returnType = result as InterfaceType;
+    return _returnType = result as InterfaceTypeImpl;
   }
 
   @override
@@ -1763,6 +1763,9 @@ mixin ConstructorElementMixin implements ConstructorElement {
   bool get isGenerative {
     return !isFactory;
   }
+
+  @override
+  InterfaceTypeImpl get returnType;
 }
 
 /// A [TopLevelVariableElement] for a top-level 'const' variable that has an
@@ -3722,7 +3725,7 @@ abstract class ExecutableElementImpl extends _ExistingElementImpl
   List<ParameterElementImpl> _parameters = const [];
 
   /// The inferred return type of this executable element.
-  DartType? _returnType;
+  TypeImpl? _returnType;
 
   /// The type of function defined by this executable element.
   FunctionType? _type;
@@ -3860,13 +3863,15 @@ abstract class ExecutableElementImpl extends _ExistingElementImpl
   }
 
   @override
-  DartType get returnType {
+  TypeImpl get returnType {
     linkedData?.read(this);
     return _returnType!;
   }
 
   set returnType(DartType returnType) {
-    _returnType = returnType;
+    // TODO(paulberry): eliminate this cast by changing the setter parameter
+    // type to `TypeImpl`.
+    _returnType = returnType as TypeImpl;
     // We do this because of return type inference. At the moment when we
     // create a local function element we don't know yet its return type,
     // because we have not done static type analysis yet.
@@ -4619,7 +4624,7 @@ class FormalParameterElementImpl extends PromotableElementImpl2
 
   @override
   // TODO(augmentations): Implement the merge of formal parameters.
-  DartType get type => wrappedElement.type;
+  TypeImpl get type => wrappedElement.type;
 
   @override
   // TODO(augmentations): Implement the merge of formal parameters.
@@ -5264,7 +5269,7 @@ class GenericFunctionTypeElementImpl extends _ExistingElementImpl
         FunctionTypedElementImpl,
         GenericFunctionTypeFragment {
   /// The declared return type of the function.
-  DartType? _returnType;
+  TypeImpl? _returnType;
 
   /// The elements representing the parameters of the function.
   List<ParameterElement> _parameters = const [];
@@ -5343,15 +5348,17 @@ class GenericFunctionTypeElementImpl extends _ExistingElementImpl
   GenericFunctionTypeElementImpl? get previousFragment => null;
 
   @override
-  DartType get returnType {
+  TypeImpl get returnType {
     return _returnType!;
   }
 
   /// Set the return type defined by this function type element to the given
   /// [returnType].
   @override
   set returnType(DartType returnType) {
-    _returnType = returnType;
+    // TODO(paulberry): eliminate this cast by changing the setter parameter
+    // type to `TypeImpl`.
+    _returnType = returnType as TypeImpl;
   }
 
   @override
@@ -6111,7 +6118,7 @@ abstract class InterfaceElementImpl extends InstanceElementImpl
   InterfaceElementImpl? get augmentationTarget;
 
   @override
-  AugmentedInterfaceElement get augmented;
+  InterfaceElementImpl2 get augmented;
 
   @override
   List<Element> get children => [
@@ -6215,7 +6222,7 @@ abstract class InterfaceElementImpl extends InstanceElementImpl
   }
 
   @override
-  InterfaceType get thisType {
+  InterfaceTypeImpl get thisType {
     return augmented.thisType;
   }
 
@@ -6536,7 +6543,7 @@ abstract class InterfaceElementImpl2 extends InstanceElementImpl2
   @override
   List<ConstructorElement> constructors = [];
 
-  InterfaceType? _thisType;
+  InterfaceTypeImpl? _thisType;
 
   @override
   List<InterfaceType> get allSupertypes => firstFragment.allSupertypes;
@@ -6586,7 +6593,7 @@ abstract class InterfaceElementImpl2 extends InstanceElementImpl2
   InterfaceType? get supertype => firstFragment.supertype;
 
   @override
-  InterfaceType get thisType {
+  InterfaceTypeImpl get thisType {
     if (_thisType == null) {
       List<DartType> typeArguments;
       var typeParameters = firstFragment.typeParameters;
@@ -9441,7 +9448,7 @@ class ParameterElementImpl_ofImplicitSetter extends ParameterElementImpl {
   }
 
   @override
-  DartType get type => setter.variable2.type;
+  TypeImpl get type => setter.variable2.type;
 
   @override
   set type(DartType type) {
@@ -10075,7 +10082,7 @@ class PropertyAccessorElementImpl_ImplicitGetter
   }
 
   @override
-  DartType get returnType => variable2.type;
+  TypeImpl get returnType => variable2.type;
 
   @override
   set returnType(DartType returnType) {
@@ -10141,7 +10148,7 @@ class PropertyAccessorElementImpl_ImplicitSetter
   }
 
   @override
-  DartType get returnType => VoidTypeImpl.instance;
+  TypeImpl get returnType => VoidTypeImpl.instance;
 
   @override
   set returnType(DartType returnType) {
@@ -10280,15 +10287,15 @@ abstract class PropertyInducingElementImpl
   }
 
   @override
-  DartType get type {
+  TypeImpl get type {
     linkedData?.read(this);
     if (_type != null) return _type!;
 
     if (isSynthetic) {
       if (getter != null) {
         return _type = getter!.returnType;
       } else if (setter != null) {
-        List<ParameterElement> parameters = setter!.parameters;
+        var parameters = setter!.parameters;
         return _type = parameters.isNotEmpty
             ? parameters[0].type
             : DynamicTypeImpl.instance;
@@ -10378,7 +10385,7 @@ abstract class PropertyInducingElementImpl2 extends VariableElementImpl2
 /// Instances of this class are set for fields and top-level variables
 /// to perform top-level type inference during linking.
 abstract class PropertyInducingElementTypeInference {
-  DartType perform();
+  TypeImpl perform();
 }
 
 class SetterElementImpl extends PropertyAccessorElementImpl2
@@ -11477,7 +11484,7 @@ abstract class UriReferencedElementImpl extends _ExistingElementImpl
 abstract class VariableElementImpl extends ElementImpl
     implements VariableElement {
   /// The type of this variable.
-  DartType? _type;
+  TypeImpl? _type;
 
   /// Initialize a newly created variable element to have the given [name] and
   /// [offset].
@@ -11569,10 +11576,12 @@ abstract class VariableElementImpl extends ElementImpl
   String get name => super.name!;
 
   @override
-  DartType get type => _type!;
+  TypeImpl get type => _type!;
 
   set type(DartType type) {
-    _type = type;
+    // TODO(paulberry): eliminate this cast by changing the setter parameter
+    // type to `TypeImpl`.
+    _type = type as TypeImpl;
   }
 
   @override

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

@@ -13,6 +13,7 @@ import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/source/source.dart';
 import 'package:analyzer/src/dart/element/display_string_builder.dart';
 import 'package:analyzer/src/dart/element/element.dart';
+import 'package:analyzer/src/dart/element/type.dart';
 import 'package:analyzer/src/dart/element/type_algebra.dart';
 import 'package:analyzer/src/generated/engine.dart' show AnalysisContext;
 import 'package:analyzer/src/generated/utilities_dart.dart';
@@ -111,7 +112,10 @@ class ConstructorMember extends ExecutableMember
   }
 
   @override
-  InterfaceType get returnType => type.returnType as InterfaceType;
+  InterfaceTypeImpl get returnType =>
+      // TODO(paulberry): eliminate this cast by changing the type of `type` to
+      // `FunctionTypeImpl`.
+      type.returnType as InterfaceTypeImpl;
 
   @override
   Source get source => _declaration.source!;
@@ -1244,7 +1248,7 @@ class ParameterMember extends VariableMember
   @override
   List<ParameterElement> get parameters {
     var type = this.type;
-    if (type is FunctionType) {
+    if (type is FunctionTypeImpl) {
       return type.parameters;
     }
     return const <ParameterElement>[];
@@ -1643,7 +1647,7 @@ class TopLevelVariableMember extends VariableMember
 /// A variable element defined in a parameterized type where the values of the
 /// type parameters are known.
 abstract class VariableMember extends Member implements VariableElement {
-  DartType? _type;
+  TypeImpl? _type;
 
   /// Initialize a newly created element to represent a variable, based on the
   /// [declaration], with applied [substitution].
@@ -1675,13 +1679,15 @@ abstract class VariableMember extends Member implements VariableElement {
   bool get isStatic => declaration.isStatic;
 
   @override
-  DartType get type {
+  TypeImpl get type {
     if (_type != null) return _type!;
 
     var result = declaration.type;
     result = augmentationSubstitution.substituteType(result);
     result = _substitution.substituteType(result);
-    return _type = result;
+    // TODO(paulberry): remove this cast by changing the type of `declaration`
+    // and the return type of `substituteType`
+    return _type = result as TypeImpl;
   }
 
   @override

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

@@ -96,7 +96,7 @@ class FunctionTypeImpl extends TypeImpl
   late int hashCode = _computeHashCode();
 
   @override
-  final DartType returnType;
+  final TypeImpl returnType;
 
   @override
   final List<TypeParameterElement> typeFormals;
@@ -163,7 +163,9 @@ class FunctionTypeImpl extends TypeImpl
     return FunctionTypeImpl._(
         typeFormals: typeFormals,
         parameters: parameters,
-        returnType: returnType,
+        // TODO(paulberry): eliminate this cast by changing the type of
+        // `returnType`.
+        returnType: returnType as TypeImpl,
         nullabilitySuffix: nullabilitySuffix,
         positionalParameterTypes: positionalParameterTypes,
         requiredPositionalParameterCount: requiredPositionalParameterCount,
@@ -348,7 +350,7 @@ class FunctionTypeImpl extends TypeImpl
       return true;
     }
 
-    return (returnType as TypeImpl).referencesAny(parameters);
+    return returnType.referencesAny(parameters);
   }
 
   @override
@@ -375,7 +377,7 @@ class FunctionTypeImpl extends TypeImpl
       return true;
     }
 
-    return (returnType as TypeImpl).referencesAny2(parameters);
+    return returnType.referencesAny2(parameters);
   }
 
   @override
@@ -881,7 +883,7 @@ class InterfaceTypeImpl extends TypeImpl implements InterfaceType {
   List<InterfaceType> get superclassConstraints {
     var element = this.element;
     var augmented = element.augmented;
-    if (augmented is AugmentedMixinElement) {
+    if (augmented is MixinElementImpl2) {
       var constraints = augmented.superclassConstraints;
       return _instantiateSuperTypes(constraints);
     } else {
@@ -1350,11 +1352,14 @@ class NullTypeImpl extends InterfaceTypeImpl
 
 abstract class RecordTypeFieldImpl implements RecordTypeField {
   @override
-  final DartType type;
+  final TypeImpl type;
 
   RecordTypeFieldImpl({
-    required this.type,
-  });
+    required DartType type,
+  }) :
+        // TODO(paulberry): eliminate this cast by changing the type of the
+        // constructor parameter to `TypeImpl`.
+        type = type as TypeImpl;
 }
 
 class RecordTypeImpl extends TypeImpl

pkg/analyzer/lib/src/generated/error_verifier.dart

@@ -3288,7 +3288,7 @@ class ErrorVerifier extends RecursiveAstVisitor<void>
     EnumElementImpl element,
   ) {
     var valuesFieldType = element.valuesField?.type;
-    if (valuesFieldType is InterfaceType) {
+    if (valuesFieldType is InterfaceTypeImpl) {
       var isWellBounded = typeSystem.isWellBounded(
         valuesFieldType.typeArguments.single,
         allowSuperBounded: true,

pkg/analyzer/lib/src/summary2/constructor_initializer_resolver.dart

@@ -30,8 +30,7 @@ class ConstructorInitializerResolver {
         for (var constructorElement in interfaceElement.constructors) {
           _constructor(
             unitElement,
-            // TODO(scheglov): Avoid cast.
-            interfaceElement.augmented.firstFragment as InterfaceElementImpl,
+            interfaceElement.augmented.firstFragment,
             constructorElement,
           );
         }

pkg/analyzer/lib/src/summary2/top_level_inference.dart

@@ -6,7 +6,6 @@
 
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/scope.dart';
-import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/dart/ast/ast.dart';
 import 'package:analyzer/src/dart/ast/extensions.dart';
 import 'package:analyzer/src/dart/element/element.dart';
@@ -214,7 +213,7 @@ class _PropertyInducingElementTypeInference
       this._libraryBuilder);
 
   @override
-  DartType perform() {
+  TypeImpl perform() {
     if (_node.initializer == null) {
       _status = _InferenceStatus.inferred;
       return DynamicTypeImpl.instance;
@@ -277,10 +276,12 @@ class _PropertyInducingElementTypeInference
     }
 
     var initializerType = _node.initializer!.typeOrThrow;
-    return _refineType(initializerType);
+    // TODO(paulberry): eliminate this cast by changing the return type of
+    // `typeOrThrow` to `TypeImpl`.
+    return _refineType(initializerType as TypeImpl);
   }
 
-  DartType _refineType(DartType type) {
+  TypeImpl _refineType(TypeImpl type) {
     if (type.isDartCoreNull) {
       return DynamicTypeImpl.instance;
     }