[analyzer] Stop implementing some shared types in public API.

The following adjustements are made to the analyzer class hierarchy:

- `SharedNamedFunctionParameterStructure` is moved from the
  `implements` clause of `ParameterElement` to the implements clause
  of `ParameterElementMixin`, a mixin that is used by all concrete
  subtypes of `ParameterElement`, but which is not part of the
  analyzer's public API.

- `SharedNamedTypeStructure` is moved from the `implements` clause of
  `RecordTypeNamedField` to the implements clause of
  `RecordTypeNamedFieldImpl`, the sole concrete subtype of
  `RecordTypeNamedField`, which is not part of the analyzer's public
  API.

To account for these changes, the analyzer's use of the shared types
`FunctionTypeImpl`, `TypeConstraintGenerator`, and
`TypeConstraintGeneratorMixin` needed to be adjusted so
`ParameterElementMixin` is supplied as a type parameter instead of
`ParameterElement`. This required adding a cast to the
`FunctionTypeImpl` constructor, which I intend to remove in a future
CL.

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: I889b9f87d7d077d10935c4506c454507a480afcd
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/402380
Reviewed-by: Konstantin Shcheglov <[email protected]>
Commit-Queue: Paul Berry <[email protected]>

Author: stereotype441

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

@@ -2142,10 +2142,7 @@ sealed class NamespaceCombinator {}
 ///
 /// Clients may not extend, implement or mix-in this class.
 abstract class ParameterElement
-    implements
-        PromotableElement,
-        ConstantEvaluationTarget,
-        SharedNamedFunctionParameterStructure<DartType> {
+    implements PromotableElement, ConstantEvaluationTarget {
   @override
   ParameterElement get declaration;
 
@@ -2202,7 +2199,6 @@ abstract class ParameterElement
   /// change the meaning of this getter. The parameter `{@required int x}`
   /// will return `false` and the parameter `{@required required int x}`
   /// will return `true`.
-  @override
   bool get isRequired;
 
   /// Whether the parameter is both a required and named parameter.

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

@@ -604,10 +604,8 @@ abstract class RecordTypeField {
 /// A named field in a [RecordType].
 ///
 /// Clients may not extend, implement or mix-in this class.
-abstract class RecordTypeNamedField
-    implements RecordTypeField, SharedNamedTypeStructure<DartType> {
+abstract class RecordTypeNamedField implements RecordTypeField {
   /// The name of the field.
-  @override
   String get name;
 }
 

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

@@ -10,6 +10,7 @@ import 'package:_fe_analyzer_shared/src/type_inference/type_analyzer.dart'
     as shared;
 import 'package:_fe_analyzer_shared/src/type_inference/type_analyzer_operations.dart'
     as shared;
+import 'package:_fe_analyzer_shared/src/types/shared_type.dart';
 import 'package:analyzer/dart/analysis/features.dart';
 import 'package:analyzer/dart/analysis/session.dart';
 import 'package:analyzer/dart/ast/token.dart';
@@ -9188,7 +9189,10 @@ 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,
+        SharedNamedFunctionParameterStructure<DartType> {
   @override
   bool get isNamed => parameterKind.isNamed;
 

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

@@ -90,7 +90,7 @@ class FunctionTypeImpl extends TypeImpl
     implements
         FunctionType,
         SharedFunctionTypeStructure<DartType, TypeParameterElement,
-            ParameterElement> {
+            ParameterElementMixin> {
   @override
   late int hashCode = _computeHashCode();
 
@@ -113,7 +113,7 @@ class FunctionTypeImpl extends TypeImpl
   final int requiredPositionalParameterCount;
 
   @override
-  final List<ParameterElement> sortedNamedParameters;
+  final List<ParameterElementMixin> sortedNamedParameters;
 
   factory FunctionTypeImpl({
     required List<TypeParameterElement> typeFormals,
@@ -166,7 +166,9 @@ class FunctionTypeImpl extends TypeImpl
         nullabilitySuffix: nullabilitySuffix,
         positionalParameterTypes: positionalParameterTypes,
         requiredPositionalParameterCount: requiredPositionalParameterCount,
-        sortedNamedParameters: sortedNamedParameters,
+        // TODO(paulberry): avoid the cast by changing the type of
+        // `sortedNamedParameters`.
+        sortedNamedParameters: sortedNamedParameters.cast(),
         alias: alias);
   }
 
@@ -1453,7 +1455,7 @@ class RecordTypeImpl extends TypeImpl implements RecordType {
 }
 
 class RecordTypeNamedFieldImpl extends RecordTypeFieldImpl
-    implements RecordTypeNamedField {
+    implements RecordTypeNamedField, SharedNamedTypeStructure<DartType> {
   @override
   final String name;
 

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

@@ -95,7 +95,7 @@ typedef UnknownTypeConstraintOrigin = shared.UnknownTypeConstraintOrigin<
 /// attempt to make one type schema a subtype of another.
 class TypeConstraintGatherer extends shared.TypeConstraintGenerator<
         DartType,
-        ParameterElement,
+        ParameterElementMixin,
         PromotableElementImpl2,
         TypeParameterElement,
         InterfaceType,
@@ -104,7 +104,7 @@ class TypeConstraintGatherer extends shared.TypeConstraintGenerator<
     with
         shared.TypeConstraintGeneratorMixin<
             DartType,
-            ParameterElement,
+            ParameterElementMixin,
             PromotableElementImpl2,
             TypeParameterElement,
             InterfaceType,