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

// Copyright (c) 2014, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'package:analyzer/dart/analysis/session.dart';
import 'package:analyzer/dart/constant/value.dart';
import 'package:analyzer/dart/element/element.dart';
import 'package:analyzer/dart/element/nullability_suffix.dart';
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';
import 'package:analyzer/src/utilities/extensions/element.dart';
import 'package:pub_semver/pub_semver.dart';

/// A constructor element defined in a parameterized type where the values of
/// the type parameters are known.
class ConstructorMember extends ExecutableMember
    with ConstructorElementMixin, ConstructorElementMixin2
    implements ConstructorElement {
  /// Initialize a newly created element to represent a constructor, based on
  /// the [declaration], and applied [substitution].
  ConstructorMember({
    required ConstructorFragmentImpl super.declaration,
    required super.substitution,
  }) : super(typeParameters: const <TypeParameterFragmentImpl>[]);

  @override
  ConstructorElementImpl2 get baseElement => _element2;

  @override
  ConstructorFragmentImpl get declaration =>
      _declaration as ConstructorFragmentImpl;

  @override
  String get displayName => declaration.displayName;

  @override
  InterfaceElementImpl2 get enclosingElement => _element2.enclosingElement;

  @Deprecated('Use enclosingElement instead')
  @override
  InterfaceElementImpl2 get enclosingElement2 => enclosingElement;

  @override
  ConstructorFragment get firstFragment => _element2.firstFragment;

  @override
  List<ConstructorFragment> get fragments {
    return [
      for (
        ConstructorFragment? fragment = firstFragment;
        fragment != null;
        fragment = fragment.nextFragment
      )
        fragment,
    ];
  }

  @override
  bool get isConst => declaration.isConst;

  @override
  bool get isConstantEvaluated => declaration.isConstantEvaluated;

  @override
  bool get isFactory => declaration.isFactory;

  @override
  LibraryElementImpl get library2 {
    return _declaration.library!;
  }

  @override
  String? get lookupName => _element2.lookupName;

  @override
  String get name => declaration.name;

  @override
  String? get name3 => _element2.name3;

  @override
  ConstructorElementMixin? get redirectedConstructor {
    var element = declaration.redirectedConstructor;
    return _redirect(element);
  }

  @override
  ConstructorElementMixin2? get redirectedConstructor2 {
    return redirectedConstructor?.asElement2;
  }

  @override
  InterfaceTypeImpl get returnType {
    var returnType = declaration.returnType;
    return substitution.mapInterfaceType(returnType);
  }

  @override
  Source get source => _declaration.source!;

  ConstructorElementMixin? get superConstructor {
    var element = declaration.superConstructor;
    return _redirect(element);
  }

  @override
  ConstructorElementMixin2? get superConstructor2 {
    return superConstructor?.asElement2;
  }

  @override
  ConstructorElementImpl2 get _element2 => declaration.asElement2;

  @override
  T? accept2<T>(ElementVisitor2<T> visitor) {
    return visitor.visitConstructorElement(this);
  }

  @override
  void appendTo(ElementDisplayStringBuilder builder) {
    builder.writeConstructorElement(this);
  }

  ConstructorElementMixin? _redirect(ConstructorElementMixin? element) {
    switch (element) {
      case null:
        return null;
      case ConstructorFragmentImpl():
        return element;
      case ConstructorMember():
        var memberMap = element.substitution.map;
        var map = <TypeParameterElement, DartType>{
          for (var MapEntry(:key, :value) in memberMap.entries)
            key: substitution.substituteType(value),
        };
        return ConstructorMember(
          declaration: element.declaration,
          substitution: Substitution.fromMap2(map),
        );
      default:
        throw UnimplementedError('(${element.runtimeType}) $element');
    }
  }

  /// If the given [element]'s type is different when any type parameters
  /// from the defining type's declaration are replaced with the actual type
  /// arguments from the [definingType], create a constructor member
  /// representing the given constructor. Return the member that was created, or
  /// the original constructor if no member was created.
  static ConstructorElementMixin from(
    ConstructorFragmentImpl element,
    InterfaceType definingType,
  ) {
    if (definingType.typeArguments.isEmpty) {
      return element;
    }

    return ConstructorMember(
      declaration: element,
      substitution: Substitution.fromInterfaceType(definingType),
    );
  }

  /// If the given [element]'s type is different when any type parameters
  /// from the defining type's declaration are replaced with the actual type
  /// arguments from the [definingType], create a constructor member
  /// representing the given constructor. Return the member that was created, or
  /// the original constructor if no member was created.
  static ConstructorElementMixin2 from2(
    ConstructorElementImpl2 element,
    InterfaceType definingType,
  ) {
    if (definingType.typeArguments.isEmpty) {
      return element;
    }

    return ConstructorMember(
      declaration: element.asElement,
      substitution: Substitution.fromInterfaceType(definingType),
    );
  }
}

/// An executable element defined in a parameterized type where the values of
/// the type parameters are known.
abstract class ExecutableMember extends Member
    implements ExecutableElementOrMember, ExecutableElement2OrMember {
  @override
  final List<TypeParameterFragmentImpl> typeParameters;

  FunctionTypeImpl? _type;

  /// Initialize a newly created element to represent a callable element (like a
  /// method or function or property), based on the [declaration], and applied
  /// [substitution].
  ///
  /// The [typeParameters] are fresh, and [substitution] is already applied to
  /// their bounds.  The [substitution] includes replacing [declaration] type
  /// parameters with the provided fresh [typeParameters].
  ExecutableMember({
    required ExecutableFragmentImpl super.declaration,
    required super.substitution,
    required this.typeParameters,
  });

  @override
  List<Element> get children2 {
    return [...typeParameters2, ...formalParameters];
  }

  @override
  ExecutableFragmentImpl get declaration =>
      _declaration as ExecutableFragmentImpl;

  @override
  String get displayName => declaration.displayName;

  @override
  Element? get enclosingElement => _element2.enclosingElement;

  @Deprecated('Use enclosingElement instead')
  @override
  Element? get enclosingElement2 => enclosingElement;

  @override
  List<FormalParameterElementMixin> get formalParameters =>
      parameters.map((fragment) => fragment.asElement2).toList();

  @override
  List<ExecutableFragment> get fragments {
    return [
      for (
        ExecutableFragment? fragment = firstFragment;
        fragment != null;
        fragment = fragment.nextFragment
      )
        fragment,
    ];
  }

  @override
  bool get hasImplicitReturnType => declaration.hasImplicitReturnType;

  @override
  bool get isAbstract => declaration.isAbstract;

  @override
  bool get isAsynchronous => declaration.isAsynchronous;

  @override
  bool get isAugmentation => declaration.isAugmentation;

  @override
  bool get isExtensionTypeMember => declaration.isExtensionTypeMember;

  @override
  bool get isExternal => declaration.isExternal;

  @override
  bool get isGenerator => declaration.isGenerator;

  @override
  bool get isOperator => declaration.isOperator;

  @override
  bool get isSimplyBounded => declaration.isSimplyBounded;

  @override
  bool get isStatic => declaration.isStatic;

  @override
  bool get isSynchronous => declaration.isSynchronous;

  @override
  LibraryElement get library2 => _element2.library2;

  @override
  Source get librarySource => _declaration.librarySource!;

  @override
  MetadataImpl get metadata => baseElement.metadata;

  @Deprecated('Use metadata instead')
  @override
  MetadataImpl get metadata2 => metadata;

  @override
  int get nameOffset => declaration.nameOffset;

  @override
  Element get nonSynthetic2 => _element2;

  @override
  List<ParameterElementMixin> get parameters {
    return declaration.parameters.map<ParameterElementMixin>((element) {
      switch (element) {
        case FieldFormalParameterFragmentImpl():
          return FieldFormalParameterMember(
            declaration: element,
            substitution: substitution,
          );
        case SuperFormalParameterFragmentImpl():
          return SuperFormalParameterMember(
            declaration: element,
            substitution: substitution,
          );
        default:
          return ParameterMember(
            declaration: element,
            substitution: substitution,
          );
      }
    }).toList();
  }

  @override
  TypeImpl get returnType {
    var result = declaration.returnType;
    result = substitution.substituteType(result);
    return result;
  }

  @override
  FunctionTypeImpl get type {
    return _type ??= substitution.mapFunctionType(declaration.type);
  }

  @override
  List<TypeParameterElementImpl2> get typeParameters2 =>
      typeParameters.map((fragment) => fragment.asElement2).toList();

  @override
  ExecutableElement get _element2 => declaration.asElement2;

  @override
  void appendTo(ElementDisplayStringBuilder builder) {
    builder.writeExecutableElement(this, displayName);
  }

  @override
  String displayString2({
    bool multiline = false,
    bool preferTypeAlias = false,
  }) {
    var builder = ElementDisplayStringBuilder(
      multiline: multiline,
      preferTypeAlias: preferTypeAlias,
    );
    appendTo(builder);
    return builder.toString();
  }

  @override
  bool isAccessibleIn2(LibraryElement library) =>
      _element2.isAccessibleIn2(library);

  @override
  Element? thisOrAncestorMatching2(bool Function(Element p1) predicate) =>
      _element2.thisOrAncestorMatching2(predicate);

  @override
  E? thisOrAncestorOfType2<E extends Element>() =>
      _element2.thisOrAncestorOfType2();

  @override
  void visitChildren2<T>(ElementVisitor2<T> visitor) {
    for (var child in children2) {
      child.accept2(visitor);
    }
  }

  static ExecutableElement2OrMember from(
    ExecutableElement element,
    MapSubstitution substitution,
  ) {
    return from2(element.asElement, substitution).asElement2;
  }

  static ExecutableElementOrMember from2(
    ExecutableElementOrMember element,
    MapSubstitution substitution,
  ) {
    if (identical(substitution, Substitution.empty)) {
      return element;
    }

    ExecutableFragmentImpl declaration;
    var combined = substitution;
    if (element is ExecutableMember) {
      declaration = element.declaration;

      var map = <TypeParameterElement, DartType>{
        for (var MapEntry(:key, :value) in element.substitution.map.entries)
          key: substitution.substituteType(value),
      };
      combined = Substitution.fromMap2(map);
    } else {
      declaration = element as ExecutableFragmentImpl;
      if (!declaration.hasEnclosingTypeParameterReference) {
        return declaration;
      }
    }

    switch (declaration) {
      case ConstructorFragmentImpl():
        return ConstructorMember(
          declaration: declaration,
          substitution: combined,
        );
      case MethodFragmentImpl():
        return MethodMember(declaration: declaration, substitution: combined);
      case PropertyAccessorFragmentImpl():
        return PropertyAccessorMember(
          declaration: declaration,
          substitution: combined,
        );
      default:
        throw UnimplementedError('(${declaration.runtimeType}) $element');
    }
  }
}

/// A parameter element defined in a parameterized type where the values of the
/// type parameters are known.
class FieldFormalParameterMember extends ParameterMember
    implements FieldFormalParameterElementOrMember {
  factory FieldFormalParameterMember({
    required FieldFormalParameterFragmentImpl declaration,
    required MapSubstitution substitution,
  }) {
    var freshTypeParameters = _SubstitutedTypeParameters(
      declaration.typeParameters,
      substitution,
    );
    return FieldFormalParameterMember._(
      declaration: declaration,
      substitution: freshTypeParameters.substitution,
      typeParameters: freshTypeParameters.elements,
    );
  }

  FieldFormalParameterMember._({
    required FieldFormalParameterFragmentImpl super.declaration,
    required super.substitution,
    required super.typeParameters,
  }) : super._();

  @override
  FieldFormalParameterFragmentImpl get declaration {
    return _declaration as FieldFormalParameterFragmentImpl;
  }

  @override
  FieldElementOrMember? get field {
    var field = declaration.field;
    if (field == null) {
      return null;
    }

    return FieldMember(declaration: field, substitution: substitution);
  }

  @override
  bool get hasDefaultValue => declaration.hasDefaultValue;

  @override
  bool get isCovariant => declaration.isCovariant;
}

/// A field element defined in a parameterized type where the values of the type
/// parameters are known.
class FieldMember extends VariableMember
    implements FieldElementOrMember, FieldElement2OrMember {
  /// Initialize a newly created element to represent a field, based on the
  /// [declaration], with applied [substitution].
  FieldMember({
    required FieldFragmentImpl super.declaration,
    required super.substitution,
  });

  @override
  FieldElementImpl2 get baseElement => _element2;

  @override
  List<Element> get children2 => const [];

  @override
  ConstantInitializer? get constantInitializer2 {
    return baseElement.constantInitializer2;
  }

  @override
  FieldFragmentImpl get declaration => _declaration as FieldFragmentImpl;

  @override
  String get displayName => declaration.displayName;

  @override
  InstanceElement get enclosingElement => _element2.enclosingElement;

  @Deprecated('Use enclosingElement instead')
  @override
  InstanceElement get enclosingElement2 => enclosingElement;

  @override
  FieldFragment get firstFragment => _element2.firstFragment;

  @override
  List<FieldFragment> get fragments {
    return [
      for (
        FieldFragment? fragment = firstFragment;
        fragment != null;
        fragment = fragment.nextFragment
      )
        fragment,
    ];
  }

  @override
  GetterElement2OrMember? get getter2 {
    var baseGetter = declaration.getter;
    if (baseGetter == null) {
      return null;
    }
    return GetterMember._(
      declaration: baseGetter,
      substitution: substitution,
      typeParameters: baseGetter.typeParameters,
    );
  }

  @override
  bool get hasInitializer => declaration.hasInitializer;

  @override
  bool get isAbstract => declaration.isAbstract;

  @override
  bool get isCovariant => declaration.isCovariant;

  @override
  bool get isEnumConstant => declaration.isEnumConstant;

  @override
  bool get isExternal => declaration.isExternal;

  @override
  bool get isPromotable => declaration.isPromotable;

  @override
  LibraryElement get library2 => _element2.library2;

  @override
  String? get lookupName => _element2.lookupName;

  @override
  MetadataImpl get metadata => baseElement.metadata;

  @Deprecated('Use metadata instead')
  @override
  MetadataImpl get metadata2 => metadata;

  @override
  String get name => declaration.name;

  @override
  String? get name3 => _element2.name3;

  @override
  Element get nonSynthetic2 => _element2.nonSynthetic2;

  @override
  SetterElement2OrMember? get setter2 {
    var baseSetter = declaration.setter;
    if (baseSetter == null) {
      return null;
    }
    return SetterMember._(
      declaration: baseSetter,
      substitution: substitution,
      typeParameters: baseSetter.typeParameters,
    );
  }

  @override
  Source? get source => _declaration.source;

  @override
  FieldElementImpl2 get _element2 => declaration.asElement2;

  @override
  T? accept2<T>(ElementVisitor2<T> visitor) {
    return visitor.visitFieldElement(this);
  }

  @override
  String displayString2({
    bool multiline = false,
    bool preferTypeAlias = false,
  }) {
    return _element2.displayString2(
      multiline: multiline,
      preferTypeAlias: preferTypeAlias,
    );
  }

  @override
  bool isAccessibleIn2(LibraryElement library) {
    return _element2.isAccessibleIn2(library);
  }

  @override
  Element? thisOrAncestorMatching2(bool Function(Element e) predicate) {
    return _element2.thisOrAncestorMatching2(predicate);
  }

  @override
  E? thisOrAncestorOfType2<E extends Element>() {
    return _element2.thisOrAncestorOfType2<E>();
  }

  @override
  void visitChildren2<T>(ElementVisitor2<T> visitor) {}

  static FieldElement2OrMember from(
    FieldElementImpl2 element,
    MapSubstitution substitution,
  ) {
    if (substitution.map.isEmpty) {
      return element;
    }
    return FieldMember(
      declaration: element.firstFragment,
      substitution: substitution,
    );
  }

  static FieldElementOrMember from2(
    FieldFragmentImpl element,
    MapSubstitution substitution,
  ) {
    if (substitution.map.isEmpty) {
      return element;
    }
    return FieldMember(declaration: element, substitution: substitution);
  }
}

/// A getter element defined in a parameterized type where the values of the
/// type parameters are known.
class GetterMember extends PropertyAccessorMember
    implements GetterElement2OrMember {
  GetterMember._({
    required super.declaration,
    required super.substitution,
    required super.typeParameters,
  }) : super._();

  @override
  GetterElementImpl get baseElement => _element2;

  @override
  SetterElement2OrMember? get correspondingSetter2 {
    var setter = correspondingSetter;
    if (setter is SetterMember) {
      return setter;
    }
    return setter?.asElement2 as SetterElementImpl?;
  }

  @override
  GetterFragment get firstFragment => _element2.firstFragment;

  @override
  List<GetterFragment> get fragments {
    return [
      for (
        GetterFragment? fragment = firstFragment;
        fragment != null;
        fragment = fragment.nextFragment
      )
        fragment,
    ];
  }

  @override
  String? get lookupName => _element2.lookupName;

  @override
  Element get nonSynthetic2 {
    if (!isSynthetic) {
      return this;
    } else if (variable3 case var variable?) {
      return variable.nonSynthetic2;
    }
    throw StateError('Synthetic getter has no variable');
  }

  @override
  PropertyInducingElement2OrMember? get variable3 => variable2?.asElement2;

  @override
  GetterElementImpl get _element2 {
    return declaration.asElement2 as GetterElementImpl;
  }

  @override
  T? accept2<T>(ElementVisitor2<T> visitor) {
    return visitor.visitGetterElement(this);
  }

  static GetterElement2OrMember from(
    GetterElementImpl element,
    InterfaceType definingType,
  ) {
    if (definingType.typeArguments.isEmpty) {
      return element;
    }

    return GetterMember._(
      declaration: element.asElement,
      substitution: Substitution.fromInterfaceType(definingType),
      typeParameters: const [],
    );
  }
}

/// An element defined in a parameterized type where the values of the type
/// parameters are known.
abstract class Member implements FragmentOrMember {
  /// The element on which the parameterized element was created.
  final FragmentImpl _declaration;

  /// The substitution for type parameters referenced in the base element.
  final MapSubstitution substitution;

  /// Initialize a newly created element to represent a member, based on the
  /// [declaration], and applied [substitution].
  Member({required FragmentImpl declaration, required this.substitution})
    : _declaration = declaration {
    if (_declaration is Member) {
      throw StateError(
        'Members must be created from a declaration, but is '
        '(${_declaration.runtimeType}) "$_declaration".',
      );
    }
  }

  Element get baseElement;

  @override
  // TODO(scheglov): stop implementing [Fragment] and remove
  List<Fragment> get children3 => throw UnimplementedError();

  @override
  AnalysisContext get context => _declaration.context;

  @override
  FragmentImpl get declaration => _declaration;

  @override
  String get displayName => _declaration.displayName;

  @override
  String? get documentationComment => _declaration.documentationComment;

  @override
  // TODO(scheglov): stop implementing [Fragment] and remove
  Element get element => throw UnimplementedError();

  @override
  // TODO(scheglov): stop implementing [Fragment] and remove
  Fragment? get enclosingFragment => throw UnimplementedError();

  @override
  int get id => _declaration.id;

  @override
  bool get isPrivate => _declaration.isPrivate;

  @override
  bool get isPublic => _declaration.isPublic;

  @override
  bool get isSynthetic => _declaration.isSynthetic;

  @override
  ElementKind get kind => _declaration.kind;

  @override
  // TODO(scheglov): stop implementing [Fragment] and remove
  LibraryFragment? get libraryFragment => throw UnimplementedError();

  @override
  Source? get librarySource => _declaration.librarySource;

  @override
  List<ElementAnnotation> get metadata3 => _declaration.metadata3;

  @override
  String? get name => _declaration.name;

  @override
  // TODO(scheglov): stop implementing [Fragment] and remove
  String? get name2 => throw UnimplementedError();

  @override
  int get nameLength => _declaration.nameLength;

  @override
  int get nameOffset => _declaration.nameOffset;

  @override
  // TODO(scheglov): stop implementing [Fragment] and remove
  int? get nameOffset2 => throw UnimplementedError();

  @override
  // TODO(scheglov): stop implementing [Fragment] and remove
  Fragment? get nextFragment => throw UnimplementedError();

  @override
  // TODO(scheglov): stop implementing [Fragment] and remove
  int get offset => throw UnimplementedError();

  @override
  // TODO(scheglov): stop implementing [Fragment] and remove
  Fragment? get previousFragment => throw UnimplementedError();

  @override
  AnalysisSession? get session => _declaration.session;

  @override
  Version? get sinceSdkVersion => _declaration.sinceSdkVersion;

  Element get _element2;

  /// Append a textual representation of this element to the given [builder].
  void appendTo(ElementDisplayStringBuilder builder);

  @override
  String getDisplayString({
    @Deprecated('Only non-nullable by default mode is supported')
    bool withNullability = true,
    bool multiline = false,
    bool preferTypeAlias = false,
  }) {
    var builder = ElementDisplayStringBuilder(
      multiline: multiline,
      preferTypeAlias: preferTypeAlias,
    );
    appendTo(builder);
    return builder.toString();
  }

  String getExtendedDisplayName2({String? shortName}) {
    return _element2.getExtendedDisplayName2(shortName: shortName);
  }

  @override
  String toString() {
    return getDisplayString();
  }
}

/// A method element defined in a parameterized type where the values of the
/// type parameters are known.
class MethodMember extends ExecutableMember
    implements MethodElementOrMember, MethodElement2OrMember {
  factory MethodMember({
    required MethodFragmentImpl declaration,
    required MapSubstitution substitution,
  }) {
    var freshTypeParameters = _SubstitutedTypeParameters(
      declaration.typeParameters,
      substitution,
    );
    return MethodMember._(
      declaration: declaration,
      substitution: freshTypeParameters.substitution,
      typeParameters: freshTypeParameters.elements,
    );
  }

  MethodMember._({
    required MethodFragmentImpl super.declaration,
    required super.substitution,
    required super.typeParameters,
  });

  @override
  MethodElementImpl2 get baseElement => _element2;

  @override
  MethodFragmentImpl get declaration => _declaration as MethodFragmentImpl;

  @override
  MethodFragment get firstFragment => _element2.firstFragment;

  @override
  List<MethodFragment> get fragments {
    return [
      for (
        MethodFragment? fragment = firstFragment;
        fragment != null;
        fragment = fragment.nextFragment
      )
        fragment,
    ];
  }

  @override
  LibraryElement get library2 => _element2.library2;

  @override
  String? get lookupName => name3;

  @override
  String get name => declaration.name;

  @override
  String? get name3 => _element2.name3;

  @override
  Source get source => _declaration.source!;

  @override
  MethodElementImpl2 get _element2 => declaration.asElement2;

  @override
  T? accept2<T>(ElementVisitor2<T> visitor) {
    return visitor.visitMethodElement(this);
  }

  /// If [definingType] has type parameters, returns [MethodMember] with
  /// type substitutions. Otherwise returns [element] as is.
  static MethodElement2OrMember from2(
    MethodElementImpl2 element,
    InterfaceType definingType,
  ) {
    if (definingType.typeArguments.isEmpty) {
      return element;
    }

    return MethodMember(
      declaration: element.asElement,
      substitution: Substitution.fromInterfaceType(definingType),
    );
  }
}

/// A parameter element defined in a parameterized type where the values of the
/// type parameters are known.
class ParameterMember extends VariableMember
    with ParameterElementMixin, FormalParameterElementMixin {
  @override
  final List<TypeParameterFragmentImpl> typeParameters;

  factory ParameterMember({
    required FormalParameterFragmentImpl declaration,
    required MapSubstitution substitution,
  }) {
    var freshTypeParameters = _SubstitutedTypeParameters(
      declaration.typeParameters,
      substitution,
    );
    return ParameterMember._(
      declaration: declaration,
      substitution: freshTypeParameters.substitution,
      typeParameters: freshTypeParameters.elements,
    );
  }

  /// Initialize a newly created element to represent a parameter, based on the
  /// [declaration], with applied [substitution].
  ParameterMember._({
    required FormalParameterFragmentImpl super.declaration,
    required super.substitution,
    required this.typeParameters,
  });

  @override
  FormalParameterElementImpl get baseElement => _element2;

  @override
  List<Element> get children2 {
    return [...typeParameters2, ...formalParameters];
  }

  @override
  ConstantInitializer? get constantInitializer2 {
    return baseElement.constantInitializer2;
  }

  @override
  FormalParameterFragmentImpl get declaration =>
      _declaration as FormalParameterFragmentImpl;

  @override
  String? get defaultValueCode => declaration.defaultValueCode;

  @override
  FormalParameterElementImpl get element => declaration.element;

  @override
  Element? get enclosingElement => _element2.enclosingElement;

  @Deprecated('Use enclosingElement instead')
  @override
  Element? get enclosingElement2 => enclosingElement;

  @override
  FormalParameterFragment get firstFragment => _element2.firstFragment;

  @override
  List<FormalParameterElementImpl> get formalParameters =>
      _element2.formalParameters;

  @override
  List<FormalParameterFragment> get fragments {
    return [
      for (
        FormalParameterFragment? fragment = firstFragment;
        fragment != null;
        fragment = fragment.nextFragment
      )
        fragment,
    ];
  }

  @override
  bool get hasDefaultValue => declaration.hasDefaultValue;

  @override
  bool get isCovariant => declaration.isCovariant;

  @override
  bool get isInitializingFormal => declaration.isInitializingFormal;

  @override
  bool get isSuperFormal => declaration.isSuperFormal;

  @override
  LibraryElement? get library2 => _element2.library2;

  @override
  String? get lookupName => _element2.lookupName;

  @override
  MetadataImpl get metadata => baseElement.metadata;

  @Deprecated('Use metadata instead')
  @override
  MetadataImpl get metadata2 => metadata;

  @override
  String get name => declaration.name;

  @override
  String? get name3 => _element2.name3;

  @override
  String get nameShared => name;

  @override
  Element get nonSynthetic2 => _element2;

  @deprecated
  @override
  ParameterKind get parameterKind {
    return declaration.parameterKind;
  }

  @override
  List<ParameterElementMixin> get parameters {
    var type = this.type;
    if (type is FunctionTypeImpl) {
      return type.parameters.map((element) => element.asElement).toList();
    }
    return const <ParameterElementMixin>[];
  }

  @override
  Source? get source => _declaration.source;

  @override
  List<TypeParameterElement> get typeParameters2 => _element2.typeParameters2;

  @override
  TypeImpl get typeShared => type;

  @override
  FormalParameterElementImpl get _element2 => declaration.asElement2;

  @override
  T? accept2<T>(ElementVisitor2<T> visitor) {
    return visitor.visitFormalParameterElement(this);
  }

  @override
  void appendTo(ElementDisplayStringBuilder builder) {
    builder.writeFormalParameter(this);
  }

  @override
  String displayString2({
    bool multiline = false,
    bool preferTypeAlias = false,
  }) {
    return _element2.displayString2(
      multiline: multiline,
      preferTypeAlias: preferTypeAlias,
    );
  }

  @override
  bool isAccessibleIn2(LibraryElement library) =>
      _element2.isAccessibleIn2(library);

  @override
  Element? thisOrAncestorMatching2(bool Function(Element p1) predicate) {
    return _element2.thisOrAncestorMatching2(predicate);
  }

  @override
  E? thisOrAncestorOfType2<E extends Element>() {
    return _element2.thisOrAncestorOfType2();
  }

  @override
  void visitChildren2<T>(ElementVisitor2<T> visitor) {
    _element2.visitChildren2(visitor);
  }

  static ParameterElementMixin from(
    ParameterElementMixin element,
    MapSubstitution substitution,
  ) {
    FormalParameterFragmentImpl declaration;
    var combined = substitution;
    if (element is ParameterMember) {
      var member = element;
      declaration = member.declaration;

      var map = <TypeParameterElement, DartType>{
        for (var MapEntry(:key, :value) in member.substitution.map.entries)
          key: substitution.substituteType(value),
      };
      combined = Substitution.fromMap2(map);
    } else {
      declaration = element as FormalParameterFragmentImpl;
    }

    if (combined.map.isEmpty) {
      return element;
    }

    return ParameterMember(declaration: declaration, substitution: combined);
  }

  static FormalParameterElementMixin from2(
    FormalParameterElementMixin element,
    MapSubstitution substitution,
  ) {
    FormalParameterElementImpl baseElement;
    var combined = substitution;
    if (element is ParameterMember) {
      var member = element;
      baseElement = member.baseElement;

      var map = <TypeParameterElement, DartType>{
        for (var MapEntry(:key, :value) in member.substitution.map.entries)
          key: substitution.substituteType(value),
      };
      combined = Substitution.fromMap2(map);
    } else {
      baseElement = element as FormalParameterElementImpl;
    }

    if (combined.map.isEmpty) {
      return element;
    }

    return ParameterMember(
      declaration: baseElement.asElement,
      substitution: combined,
    );
  }
}

/// A property accessor element defined in a parameterized type where the values
/// of the type parameters are known.
abstract class PropertyAccessorMember extends ExecutableMember
    implements
        PropertyAccessorElementOrMember,
        PropertyAccessorElement2OrMember {
  factory PropertyAccessorMember({
    required PropertyAccessorFragmentImpl declaration,
    required MapSubstitution substitution,
  }) {
    var freshTypeParameters = _SubstitutedTypeParameters(
      declaration.typeParameters,
      substitution,
    );
    if (declaration.isGetter) {
      return GetterMember._(
        declaration: declaration,
        substitution: freshTypeParameters.substitution,
        typeParameters: freshTypeParameters.elements,
      );
    } else {
      return SetterMember._(
        declaration: declaration,
        substitution: freshTypeParameters.substitution,
        typeParameters: freshTypeParameters.elements,
      );
    }
  }

  PropertyAccessorMember._({
    required PropertyAccessorFragmentImpl super.declaration,
    required super.substitution,
    required super.typeParameters,
  });

  @override
  PropertyAccessorElementOrMember? get correspondingGetter {
    var baseGetter = declaration.correspondingGetter;
    if (baseGetter == null) {
      return null;
    }
    return PropertyAccessorMember(
      declaration: baseGetter,
      substitution: substitution,
    );
  }

  @override
  PropertyAccessorElementOrMember? get correspondingSetter {
    var baseSetter = declaration.correspondingSetter;
    if (baseSetter == null) {
      return null;
    }
    return PropertyAccessorMember(
      declaration: baseSetter,
      substitution: substitution,
    );
  }

  @override
  PropertyAccessorFragmentImpl get declaration =>
      _declaration as PropertyAccessorFragmentImpl;

  @override
  Element get enclosingElement {
    return super.enclosingElement!;
  }

  @Deprecated('Use enclosingElement instead')
  @override
  Element get enclosingElement2 => enclosingElement;

  @override
  bool get isGetter => declaration.isGetter;

  @override
  bool get isSetter => declaration.isSetter;

  @override
  String get name => declaration.name;

  @override
  String? get name3 => _element2.name3;

  @override
  Source get source => _declaration.source!;

  @override
  PropertyInducingElementOrMember? get variable2 {
    var variable = declaration.variable2;
    switch (variable) {
      case FieldFragmentImpl():
        return FieldMember(declaration: variable, substitution: substitution);
      default:
        return variable;
    }
  }

  @override
  void appendTo(ElementDisplayStringBuilder builder) {
    builder.writeExecutableElement(
      this,
      (isGetter ? 'get ' : 'set ') + displayName,
    );
  }

  /// If the given [element]'s type is different when any type parameters from
  /// the defining type's declaration are replaced with the actual type
  /// arguments from the [definingType], create an accessor member representing
  /// the given accessor. Return the member that was created, or the base
  /// accessor if no member was created.
  static PropertyAccessorElementOrMember? from(
    PropertyAccessorFragmentImpl? element,
    InterfaceType definingType,
  ) {
    if (element == null || definingType.typeArguments.isEmpty) {
      return element;
    }

    return PropertyAccessorMember(
      declaration: element,
      substitution: Substitution.fromInterfaceType(definingType),
    );
  }
}

/// A setter element defined in a parameterized type where the values of the
/// type parameters are known.
class SetterMember extends PropertyAccessorMember
    implements SetterElement2OrMember {
  SetterMember._({
    required super.declaration,
    required super.substitution,
    required super.typeParameters,
  }) : super._();

  @override
  SetterElementImpl get baseElement => _element2;

  @override
  GetterElement2OrMember? get correspondingGetter2 {
    var getter = correspondingGetter;
    if (getter is GetterMember) {
      return getter;
    }
    return getter?.asElement2 as GetterElementImpl?;
  }

  @override
  SetterFragment get firstFragment => _element2.firstFragment;

  @override
  List<SetterFragment> get fragments {
    return [
      for (
        SetterFragment? fragment = firstFragment;
        fragment != null;
        fragment = fragment.nextFragment
      )
        fragment,
    ];
  }

  @override
  String? get lookupName => _element2.lookupName;

  @override
  Element get nonSynthetic2 {
    if (!isSynthetic) {
      return this;
    } else if (variable3 case var variable?) {
      return variable.nonSynthetic2;
    }
    throw StateError('Synthetic setter has no variable');
  }

  @override
  PropertyInducingElement2OrMember? get variable3 => variable2?.asElement2;

  @override
  SetterElementImpl get _element2 {
    return declaration.asElement2 as SetterElementImpl;
  }

  @override
  T? accept2<T>(ElementVisitor2<T> visitor) {
    return visitor.visitSetterElement(this);
  }

  static SetterElement2OrMember from(
    SetterElementImpl element,
    InterfaceType definingType,
  ) {
    if (definingType.typeArguments.isEmpty) {
      return element;
    }

    return SetterMember._(
      declaration: element.asElement,
      substitution: Substitution.fromInterfaceType(definingType),
      typeParameters: const [],
    );
  }
}

class SuperFormalParameterMember extends ParameterMember
    implements SuperFormalParameterElementOrMember {
  factory SuperFormalParameterMember({
    required SuperFormalParameterFragmentImpl declaration,
    required MapSubstitution substitution,
  }) {
    var freshTypeParameters = _SubstitutedTypeParameters(
      declaration.typeParameters,
      substitution,
    );
    return SuperFormalParameterMember._(
      declaration: declaration,
      substitution: freshTypeParameters.substitution,
      typeParameters: freshTypeParameters.elements,
    );
  }

  SuperFormalParameterMember._({
    required SuperFormalParameterFragmentImpl super.declaration,
    required super.substitution,
    required super.typeParameters,
  }) : super._();

  @override
  SuperFormalParameterFragmentImpl get declaration {
    return _declaration as SuperFormalParameterFragmentImpl;
  }

  @override
  bool get hasDefaultValue => declaration.hasDefaultValue;

  @override
  bool get isCovariant => declaration.isCovariant;

  @override
  ParameterElementMixin? get superConstructorParameter {
    var superConstructorParameter = declaration.superConstructorParameter;
    if (superConstructorParameter == null) {
      return null;
    }

    return ParameterMember.from(superConstructorParameter, substitution);
  }

  FormalParameterElement? get superConstructorParameter2 =>
      superConstructorParameter?.asElement2;
}

/// A variable element defined in a parameterized type where the values of the
/// type parameters are known.
abstract class VariableMember extends Member
    implements VariableElementOrMember {
  TypeImpl? _type;

  /// Initialize a newly created element to represent a variable, based on the
  /// [declaration], with applied [substitution].
  VariableMember({
    required VariableFragmentImpl super.declaration,
    required super.substitution,
  });

  @override
  VariableFragmentImpl get declaration => _declaration as VariableFragmentImpl;

  @override
  bool get hasImplicitType => declaration.hasImplicitType;

  @override
  bool get isConst => declaration.isConst;

  @override
  bool get isConstantEvaluated => declaration.isConstantEvaluated;

  @override
  bool get isFinal => declaration.isFinal;

  @override
  bool get isLate => declaration.isLate;

  @override
  bool get isStatic => declaration.isStatic;

  @override
  TypeImpl get type {
    if (_type != null) return _type!;

    var result = declaration.type;
    result = substitution.substituteType(result);
    return _type = result;
  }

  @override
  void appendTo(ElementDisplayStringBuilder builder) {
    builder.writeVariableElement(this);
  }

  @override
  DartObject? computeConstantValue() => declaration.computeConstantValue();
}

class _SubstitutedTypeParameters {
  final List<TypeParameterFragmentImpl> elements;
  final MapSubstitution substitution;

  factory _SubstitutedTypeParameters(
    List<TypeParameterFragmentImpl> elements,
    MapSubstitution substitution,
  ) {
    if (elements.isEmpty) {
      return _SubstitutedTypeParameters._(const [], substitution);
    }

    // Create type formals with specialized bounds.
    // For example `<U extends T>` where T comes from an outer scope.
    var newElements = <TypeParameterFragmentImpl>[];
    var newTypes = <TypeParameterType>[];
    for (int i = 0; i < elements.length; i++) {
      var element = elements[i];
      var newElement = TypeParameterFragmentImpl.synthetic(name: element.name);
      newElements.add(newElement);
      newTypes.add(
        newElement.instantiate(nullabilitySuffix: NullabilitySuffix.none),
      );
    }

    // Update bounds to reference new TypeParameterElement(s).
    var substitution2 = Substitution.fromPairs(elements, newTypes);
    for (int i = 0; i < newElements.length; i++) {
      var element = elements[i];
      var newElement = newElements[i];
      var bound = element.bound;
      if (bound != null) {
        var newBound = substitution2.substituteType(bound);
        newBound = substitution.substituteType(newBound);
        newElement.bound = newBound;
      }
    }

    if (substitution.map.isEmpty) {
      return _SubstitutedTypeParameters._(newElements, substitution2);
    }

    return _SubstitutedTypeParameters._(
      newElements,
      Substitution.fromMap2({...substitution.map, ...substitution2.map}),
    );
  }

  _SubstitutedTypeParameters._(this.elements, this.substitution);
}