Add InterfaceElementImpl, move many methods into it.

Change-Id: I7f77e318586b2c05874b3a0d25d2d940869b6a0d
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/312240
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Samuel Rawlins <srawlins@google.com>

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

@@ -789,7 +789,7 @@ class InterfaceTypeImpl extends TypeImpl implements InterfaceType {
     }
 
     if (recoveryStatic) {
-      final element = this.element as AbstractClassElementImpl;
+      final element = this.element as InterfaceElementImpl;
       return element.lookupStaticGetter(name, library);
     }
 
@@ -828,7 +828,7 @@ class InterfaceTypeImpl extends TypeImpl implements InterfaceType {
     }
 
     if (recoveryStatic) {
-      final element = this.element as AbstractClassElementImpl;
+      final element = this.element as InterfaceElementImpl;
       return element.lookupStaticMethod(name, library);
     }
 
@@ -867,7 +867,7 @@ class InterfaceTypeImpl extends TypeImpl implements InterfaceType {
     }
 
     if (recoveryStatic) {
-      final element = this.element as AbstractClassElementImpl;
+      final element = this.element as InterfaceElementImpl;
       return element.lookupStaticSetter(name, library);
     }
 

pkg/analyzer/lib/src/dart/resolver/type_property_resolver.dart

@@ -258,7 +258,7 @@ class TypePropertyResolver {
     _needsGetterError = _getterRequested == null;
 
     if (_getterRequested == null && recoverWithStatic) {
-      var classElement = type.element as AbstractClassElementImpl;
+      var classElement = type.element as InterfaceElementImpl;
       _getterRecovery ??=
           classElement.lookupStaticGetter(_name, _definingLibrary) ??
               classElement.lookupStaticMethod(_name, _definingLibrary);
@@ -271,7 +271,7 @@ class TypePropertyResolver {
     _needsSetterError = _setterRequested == null;
 
     if (_setterRequested == null && recoverWithStatic) {
-      var classElement = type.element as AbstractClassElementImpl;
+      var classElement = type.element as InterfaceElementImpl;
       _setterRecovery ??=
           classElement.lookupStaticSetter(_name, _definingLibrary);
       _needsSetterError = _setterRecovery == null;

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

@@ -32,7 +32,7 @@ class ElementTypeProvider {
   void freshTypeParameterCreated(TypeParameterElement newTypeParameter,
       TypeParameterElement oldTypeParameter) {}
 
-  List<InterfaceType> getClassInterfaces(AbstractClassElementImpl element) =>
+  List<InterfaceType> getClassInterfaces(InterfaceElementImpl element) =>
       element.interfacesInternal;
 
   /// Queries the parameters of an executable element's signature.

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

@@ -101,8 +101,8 @@ class ClassElementLinkedData extends ElementLinkedData<ClassElementImpl> {
   /// as well access them through their [Reference]s. For a class declaration
   /// this means reading them, for a named mixin application this means
   /// computing constructors.
-  void readMembers(ClassOrMixinElementImpl element) {
-    if (element is ClassElementImpl && element.isMixinApplication) {
+  void readMembers(ClassElementImpl element) {
+    if (element.isMixinApplication) {
       element.constructors;
     } else {
       _readMembers?.call();
@@ -668,7 +668,7 @@ class LibraryReader {
 
   List<ConstructorElementImpl> _readConstructors(
     CompilationUnitElementImpl unitElement,
-    AbstractClassElementImpl classElement,
+    InterfaceElementImpl classElement,
     Reference classReference,
   ) {
     var containerRef = classReference.getChild('@constructor');

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

@@ -17,7 +17,7 @@ class ConstructorInitializerResolver {
 
   void resolve() {
     for (var unitElement in _libraryElement.units) {
-      var interfaceElements = [
+      var interfaceElements = <InterfaceElementImpl>[
         ...unitElement.classes,
         ...unitElement.enums,
         ...unitElement.mixins,
@@ -36,7 +36,7 @@ class ConstructorInitializerResolver {
 
   void _constructor(
     CompilationUnitElementImpl unitElement,
-    AbstractClassElementImpl classElement,
+    InterfaceElementImpl classElement,
     ConstructorElementImpl element,
   ) {
     if (element.isSynthetic) return;

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

@@ -1241,7 +1241,7 @@ class ElementBuilder extends ThrowingAstVisitor<void> {
     node?.accept(this);
   }
 
-  void _resolveConstructorFieldFormals(AbstractClassElementImpl element) {
+  void _resolveConstructorFieldFormals(InterfaceElementImpl element) {
     for (var constructor in element.constructors) {
       for (var parameter in constructor.parameters) {
         if (parameter is FieldFormalParameterElementImpl) {

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

@@ -362,14 +362,14 @@ class TypesBuilder {
     );
   }
 
-  static InterfaceType _objectType(AbstractClassElementImpl element) {
+  static InterfaceType _objectType(InterfaceElementImpl element) {
     return element.library.typeProvider.objectType;
   }
 }
 
 /// Performs mixins inference in a [ClassDeclaration].
 class _MixinInference {
-  final AbstractClassElementImpl element;
+  final InterfaceElementImpl element;
   final TypeSystemImpl typeSystem;
   final FeatureSet featureSet;
   final InterfaceType classType;
@@ -534,15 +534,14 @@ class _MixinsInference {
   /// we are inferring the [element] now, i.e. there is a loop.
   ///
   /// This is an error. So, we return the empty list, and break the loop.
-  List<InterfaceType> _callbackWhenLoop(AbstractClassElementImpl element) {
+  List<InterfaceType> _callbackWhenLoop(InterfaceElementImpl element) {
     element.mixinInferenceCallback = null;
     return <InterfaceType>[];
   }
 
   /// This method is invoked when mixins are asked from the [element], and
   /// we are not inferring the [element] now, i.e. there is no loop.
-  List<InterfaceType>? _callbackWhenRecursion(
-      AbstractClassElementImpl element) {
+  List<InterfaceType>? _callbackWhenRecursion(InterfaceElementImpl element) {
     var node = _linker.getLinkingNode(element);
     if (node != null) {
       _inferDeclaration(node);
@@ -551,7 +550,7 @@ class _MixinsInference {
     return null;
   }
 
-  void _infer(AbstractClassElementImpl element, WithClause? withClause) {
+  void _infer(InterfaceElementImpl element, WithClause? withClause) {
     if (withClause != null) {
       element.mixinInferenceCallback = _callbackWhenLoop;
       try {

pkg/analyzer/lib/src/task/strong_mode.dart

@@ -303,7 +303,7 @@ class InstanceMemberInferrer {
   /// [classElement].
   void _inferClass(InterfaceElement classElement) {
     _setInducedModifier(classElement);
-    if (classElement is AbstractClassElementImpl) {
+    if (classElement is InterfaceElementImpl) {
       if (classElement.hasBeenInferred) {
         return;
       }
@@ -338,7 +338,7 @@ class InstanceMemberInferrer {
           );
         }
         for (var method in classElement.methods) {
-          _inferExecutable(method as MethodElementImpl);
+          _inferExecutable(method);
         }
         //
         // Infer initializing formal parameter types. This must happen after

pkg/nnbd_migration/lib/src/fix_builder.dart

@@ -374,7 +374,7 @@ class MigrationResolutionHooksImpl
   }
 
   @override
-  List<InterfaceType> getClassInterfaces(AbstractClassElementImpl element) {
+  List<InterfaceType> getClassInterfaces(InterfaceElementImpl element) {
     return _wrapExceptions(
         _fixBuilder.unit,
         () => element.interfacesInternal,