[analyzer] Change InheritanceManager3 to use Impl types.

The following methods of `InheritanceManager3` are changed so that
their return types refer to Impl classes rather than analyzer public
API classes:

- `combineSignatures`
- `getInherited2`
- `getInheritedMap2`
- `getMember`
- `getMember2`

To reduce the number of type casts this introduces, some of the
parameters and return types of various private methods of
`InheritanceManager3` are also changed to use Impl types, and some
similar changes are made to the inheritance manager's internal data
structures (`Interface` and `_ExtensionTypeCandidates`).

Also, the following new classes are introduced, to act as common base
classes for analyzer-internal classes in situations where no common
base class previously existed:

- `ExecutableElementOrMember` (the common base class for all internal
  classes that implement `ExecutableElement`)

- `PropertyAccessorElementOrMember` (the common base class for all
  internal classes that implement `PropertyAccessorElement`)

- `PropertyInducingElementOrMember` (the common base class for all
  internal classes that implement `PropertyInducingElement`)

- `VariableElement2OrMember` (the common base class for all internal
  classes that implement `VariableElement2`)

- `VariableElementOrMember` (the common base class for all internal
  classes that implement `VariableElement`)

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: Ib7f20480c1f57af22a0214075e8f0e13c3429340
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/405565
Commit-Queue: Paul Berry <[email protected]>
Reviewed-by: Konstantin Shcheglov <[email protected]>

Author: stereotype441

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

@@ -1746,7 +1746,8 @@ class ConstructorElementImpl2 extends ExecutableElementImpl2
 }
 
 /// Common implementation for methods defined in [ConstructorElement].
-mixin ConstructorElementMixin implements ConstructorElement {
+mixin ConstructorElementMixin
+    implements ConstructorElement, ExecutableElementOrMember {
   @override
   bool get isDefaultConstructor {
     // unnamed
@@ -3723,7 +3724,7 @@ class EnumElementImpl2 extends InterfaceElementImpl2
 /// A base class for concrete implementations of an [ExecutableElement].
 abstract class ExecutableElementImpl extends _ExistingElementImpl
     with TypeParameterizedElementMixin, MacroTargetElement
-    implements ExecutableElement, ExecutableFragment {
+    implements ExecutableElementOrMember, ExecutableFragment {
   /// A list containing all of the parameters defined by this executable
   /// element.
   List<ParameterElementImpl> _parameters = const [];
@@ -3950,6 +3951,16 @@ abstract class ExecutableElementImpl2 extends FunctionTypedElementImpl2
   }
 }
 
+/// Common base class for all analyzer-internal classes that implement
+/// `ExecutableElement`.
+abstract class ExecutableElementOrMember implements ExecutableElement {
+  @override
+  TypeImpl get returnType;
+
+  @override
+  FunctionTypeImpl get type;
+}
+
 /// A concrete implementation of an [ExtensionElement].
 class ExtensionElementImpl extends InstanceElementImpl
     with AugmentableElement<ExtensionElementImpl>
@@ -4046,7 +4057,7 @@ class ExtensionElementImpl extends InstanceElementImpl
   }
 
   @override
-  PropertyAccessorElement? getGetter(String getterName) {
+  PropertyAccessorElementOrMember? getGetter(String getterName) {
     for (var accessor in augmented.accessors) {
       if (accessor.isGetter && accessor.name == getterName) {
         return accessor;
@@ -4056,7 +4067,7 @@ class ExtensionElementImpl extends InstanceElementImpl
   }
 
   @override
-  MethodElement? getMethod(String methodName) {
+  MethodElementOrMember? getMethod(String methodName) {
     for (var method in augmented.methods) {
       if (method.name == methodName) {
         return method;
@@ -4426,7 +4437,7 @@ class FieldElementImpl2 extends PropertyInducingElementImpl2
   SetterElement? get setter2 => firstFragment.setter?.element as SetterElement?;
 
   @override
-  DartType get type => firstFragment.type;
+  TypeImpl get type => firstFragment.type;
 
   @override
   T? accept2<T>(ElementVisitor2<T> visitor) {
@@ -4662,7 +4673,10 @@ class FormalParameterElementImpl extends PromotableElementImpl2
 /// A mixin that provides a common implementation for methods defined in
 /// [FormalParameterElement].
 mixin FormalParameterElementMixin
-    implements FormalParameterElement, SharedNamedFunctionParameter {
+    implements
+        FormalParameterElement,
+        SharedNamedFunctionParameter,
+        VariableElement2OrMember {
   @override
   TypeImpl get type;
 
@@ -5157,7 +5171,8 @@ class FunctionElementImpl extends ExecutableElementImpl
         FunctionElement,
         FunctionTypedElementImpl,
         LocalFunctionFragment,
-        TopLevelFunctionFragment {
+        TopLevelFunctionFragment,
+        ExecutableElementOrMember {
   @override
   String? name2;
 
@@ -5698,10 +5713,10 @@ abstract class InstanceElementImpl2 extends ElementImpl2
   List<FieldElement> fields = [];
 
   @override
-  List<PropertyAccessorElement> accessors = [];
+  List<PropertyAccessorElementOrMember> accessors = [];
 
   @override
-  List<MethodElement> methods = [];
+  List<MethodElementOrMember> methods = [];
 
   final List<MethodElementImpl2> internal_methods2 = [];
 
@@ -7734,7 +7749,10 @@ class LocalFunctionElementImpl extends ExecutableElementImpl2
 
 /// A concrete implementation of a [LocalVariableElement].
 class LocalVariableElementImpl extends NonParameterVariableElementImpl
-    implements LocalVariableElement, LocalVariableFragment {
+    implements
+        LocalVariableElement,
+        LocalVariableFragment,
+        VariableElementOrMember {
   late LocalVariableElementImpl2 _element2 = switch (this) {
     BindPatternVariableElementImpl() => BindPatternVariableElementImpl2(this),
     JoinPatternVariableElementImpl() => JoinPatternVariableElementImpl2(this),
@@ -8268,6 +8286,8 @@ final class MetadataImpl implements Metadata {
   }
 }
 
+/// Common base class for all analyzer-internal classes that implement
+/// `MethodElement2`.
 abstract class MethodElement2OrMember implements MethodElement2 {
   @override
   FunctionTypeImpl get type;
@@ -8433,7 +8453,13 @@ class MethodElementImpl2 extends ExecutableElementImpl2
   }
 }
 
-abstract class MethodElementOrMember implements MethodElement {
+/// Common base class for all analyzer-internal classes that implement
+/// `MethodElement`.
+abstract class MethodElementOrMember
+    implements MethodElement, ExecutableElementOrMember {
+  @override
+  TypeImpl get returnType;
+
   @override
   FunctionTypeImpl get type;
 }
@@ -9522,7 +9548,8 @@ class ParameterElementImpl_ofImplicitSetter extends ParameterElementImpl {
 
 /// A mixin that provides a common implementation for methods defined in
 /// [ParameterElement].
-mixin ParameterElementMixin implements ParameterElement {
+mixin ParameterElementMixin
+    implements ParameterElement, VariableElementOrMember {
   @override
   bool get isNamed => parameterKind.isNamed;
 
@@ -9893,7 +9920,7 @@ abstract class PromotableElementImpl2 extends VariableElementImpl2
 class PropertyAccessorElementImpl extends ExecutableElementImpl
     with AugmentableElement<PropertyAccessorElementImpl>
     implements
-        PropertyAccessorElement,
+        PropertyAccessorElementOrMember,
         PropertyAccessorFragment,
         GetterFragment,
         SetterFragment {
@@ -10244,11 +10271,22 @@ class PropertyAccessorElementImpl_ImplicitSetter
   PropertyInducingElementImpl get variable2 => super.variable2!;
 }
 
+/// Common base class for all analyzer-internal classes that implement
+/// `PropertyAccessorElement`.
+abstract class PropertyAccessorElementOrMember
+    implements PropertyAccessorElement, ExecutableElementOrMember {
+  @override
+  TypeImpl get returnType;
+
+  @override
+  PropertyInducingElementOrMember? get variable2;
+}
+
 /// A concrete implementation of a [PropertyInducingElement].
 abstract class PropertyInducingElementImpl
     extends NonParameterVariableElementImpl
     with MacroTargetElement
-    implements PropertyInducingElement, PropertyInducingFragment {
+    implements PropertyInducingElementOrMember, PropertyInducingFragment {
   @override
   String? name2;
 
@@ -10449,6 +10487,14 @@ abstract class PropertyInducingElementImpl2 extends VariableElementImpl2
   List<PropertyInducingElementImpl> get _fragments;
 }
 
+/// Common base class for all analyzer-internal classes that implement
+/// `PropertyInducingElement`.
+abstract class PropertyInducingElementOrMember
+    implements PropertyInducingElement, VariableElementOrMember {
+  @override
+  TypeImpl get type;
+}
+
 /// Instances of this class are set for fields and top-level variables
 /// to perform top-level type inference during linking.
 abstract class PropertyInducingElementTypeInference {
@@ -10844,7 +10890,7 @@ class TopLevelVariableElementImpl2 extends PropertyInducingElementImpl2
       firstFragment.setter2?.element as SetterElement?;
 
   @override
-  DartType get type => firstFragment.type;
+  TypeImpl get type => firstFragment.type;
 
   @override
   T? accept2<T>(ElementVisitor2<T> visitor) {
@@ -11553,9 +11599,16 @@ abstract class UriReferencedElementImpl extends _ExistingElementImpl
   }
 }
 
+/// Common base class for all analyzer-internal classes that implement
+/// `VariableElement2`.
+abstract class VariableElement2OrMember implements VariableElement2 {
+  @override
+  TypeImpl get type;
+}
+
 /// A concrete implementation of a [VariableElement].
 abstract class VariableElementImpl extends ElementImpl
-    implements VariableElement {
+    implements VariableElementOrMember {
   /// The type of this variable.
   TypeImpl? _type;
 
@@ -11665,7 +11718,7 @@ abstract class VariableElementImpl extends ElementImpl
 }
 
 abstract class VariableElementImpl2 extends ElementImpl2
-    implements VariableElement2 {
+    implements VariableElement2OrMember {
   @override
   void visitChildren2<T>(ElementVisitor2<T> visitor) {
     for (var child in children2) {
@@ -11674,6 +11727,13 @@ abstract class VariableElementImpl2 extends ElementImpl2
   }
 }
 
+/// Common base class for all analyzer-internal classes that implement
+/// `VariableElement`.
+abstract class VariableElementOrMember implements VariableElement {
+  @override
+  TypeImpl get type;
+}
+
 mixin WrappedElementMixin implements ElementImpl2 {
   @override
   bool get isSynthetic => _wrappedElement.isSynthetic;