// Copyright (c) 2016, 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.

library fasta.class_builder;

import 'package:kernel/ast.dart'
    show
        Arguments,
        AsExpression,
        Class,
        Constructor,
        DartType,
        DynamicType,
        Expression,
        Field,
        FunctionNode,
        FunctionType,
        InterfaceType,
        InvalidType,
        Member,
        MethodInvocation,
        Name,
        Nullability,
        Procedure,
        ProcedureKind,
        ReturnStatement,
        Supertype,
        ThisExpression,
        TypeParameter,
        TypeParameterType,
        VariableDeclaration,
        VoidType,
        getAsTypeArguments;

import 'package:kernel/class_hierarchy.dart' show ClassHierarchy;

import 'package:kernel/core_types.dart' show CoreTypes;

import 'package:kernel/src/legacy_erasure.dart';

import 'package:kernel/text/text_serialization_verifier.dart';

import 'package:kernel/type_algebra.dart' show Substitution, substitute;

import 'package:kernel/type_environment.dart'
    show SubtypeCheckMode, TypeEnvironment;

import 'package:kernel/src/types.dart' show Types;

import '../dill/dill_member_builder.dart' show DillMemberBuilder;

import '../fasta_codes.dart';

import '../kernel/redirecting_factory_body.dart' show getRedirectingFactoryBody;

import '../kernel/kernel_target.dart' show KernelTarget;

import '../loader.dart';

import '../modifier.dart';

import '../names.dart' show noSuchMethodName;

import '../problems.dart' show internalProblem, unhandled, unimplemented;

import '../scope.dart';

import '../source/source_library_builder.dart' show SourceLibraryBuilder;

import '../source/source_loader.dart';

import '../type_inference/type_schema.dart' show UnknownType;

import 'builder.dart';
import 'constructor_builder.dart';
import 'constructor_reference_builder.dart';
import 'declaration_builder.dart';
import 'field_builder.dart';
import 'function_builder.dart';
import 'library_builder.dart';
import 'member_builder.dart';
import 'metadata_builder.dart';
import 'named_type_builder.dart';
import 'never_type_builder.dart';
import 'nullability_builder.dart';
import 'procedure_builder.dart';
import 'type_alias_builder.dart';
import 'type_builder.dart';
import 'type_declaration_builder.dart';
import 'type_variable_builder.dart';
import 'void_type_builder.dart';

abstract class ClassBuilder implements DeclarationBuilder {
  /// The type variables declared on a class, extension or mixin declaration.
  List<TypeVariableBuilder> typeVariables;

  /// The type in the `extends` clause of a class declaration.
  ///
  /// Currently this also holds the synthesized super class for a mixin
  /// declaration.
  TypeBuilder supertypeBuilder;

  /// The type in the `implements` clause of a class or mixin declaration.
  List<TypeBuilder> interfaceBuilders;

  /// The types in the `on` clause of an extension or mixin declaration.
  List<TypeBuilder> onTypes;

  ConstructorScope get constructors;

  ConstructorScopeBuilder get constructorScopeBuilder;

  Map<String, ConstructorRedirection> redirectingConstructors;

  ClassBuilder actualOrigin;

  ClassBuilder get patchForTesting;

  bool get isAbstract;

  bool get declaresConstConstructor;

  bool get isMixin;

  bool get isMixinApplication;

  bool get isAnonymousMixinApplication;

  TypeBuilder get mixedInTypeBuilder;

  void set mixedInTypeBuilder(TypeBuilder mixin);

  List<ConstructorReferenceBuilder> get constructorReferences;

  void buildOutlineExpressions(LibraryBuilder library, CoreTypes coreTypes);

  /// Registers a constructor redirection for this class and returns true if
  /// this redirection gives rise to a cycle that has not been reported before.
  bool checkConstructorCyclic(String source, String target);

  MemberBuilder findConstructorOrFactory(
      String name, int charOffset, Uri uri, LibraryBuilder accessingLibrary);

  void forEach(void f(String name, Builder builder));

  void forEachDeclaredField(
      void Function(String name, FieldBuilder fieldBuilder) f);

  void forEachDeclaredConstructor(
      void Function(String name, ConstructorBuilder constructorBuilder)
          callback);

  /// Find the first member of this class with [name]. This method isn't
  /// suitable for scope lookups as it will throw an error if the name isn't
  /// declared. The [scope] should be used for that. This method is used to
  /// find a member that is known to exist and it will pick the first
  /// declaration if the name is ambiguous.
  ///
  /// For example, this method is convenient for use when building synthetic
  /// members, such as those of an enum.
  MemberBuilder firstMemberNamed(String name);

  /// The [Class] built by this builder.
  ///
  /// For a patch class the origin class is returned.
  Class get cls;

  @override
  ClassBuilder get origin;

  Class get actualCls;

  bool isNullClass;

  InterfaceType get legacyRawType;

  InterfaceType get nullableRawType;

  InterfaceType get nonNullableRawType;

  InterfaceType rawType(Nullability nullability);

  List<DartType> buildTypeArguments(
      LibraryBuilder library, List<TypeBuilder> arguments,
      [bool notInstanceContext]);

  Supertype buildSupertype(LibraryBuilder library, List<TypeBuilder> arguments);

  Supertype buildMixedInType(
      LibraryBuilder library, List<TypeBuilder> arguments);

  void checkSupertypes(CoreTypes coreTypes);

  void handleSeenCovariant(
      Types types,
      Member declaredMember,
      Member interfaceMember,
      bool isSetter,
      callback(Member declaredMember, Member interfaceMember, bool isSetter));

  void checkOverride(
      Types types,
      Member declaredMember,
      Member interfaceMember,
      bool isSetter,
      callback(Member declaredMember, Member interfaceMember, bool isSetter),
      {bool isInterfaceCheck = false});

  bool hasUserDefinedNoSuchMethod(
      Class klass, ClassHierarchy hierarchy, Class objectClass);

  /// Returns whether a covariant parameter was seen and more methods thus have
  /// to be checked.
  bool checkMethodOverride(Types types, Procedure declaredMember,
      Procedure interfaceMember, bool isInterfaceCheck);

  void checkGetterOverride(Types types, Member declaredMember,
      Member interfaceMember, bool isInterfaceCheck);

  /// Returns whether a covariant parameter was seen and more methods thus have
  /// to be checked.
  bool checkSetterOverride(Types types, Member declaredMember,
      Member interfaceMember, bool isInterfaceCheck);

  // When the overriding member is inherited, report the class containing
  // the conflict as the main error.
  void reportInvalidOverride(bool isInterfaceCheck, Member declaredMember,
      Message message, int fileOffset, int length,
      {List<LocatedMessage> context});

  void checkMixinApplication(ClassHierarchy hierarchy, CoreTypes coreTypes);

  // Computes the function type of a given redirection target. Returns [null] if
  // the type of the target could not be computed.
  FunctionType computeRedirecteeType(
      RedirectingFactoryBuilder factory, TypeEnvironment typeEnvironment);

  String computeRedirecteeName(ConstructorReferenceBuilder redirectionTarget);

  void checkRedirectingFactory(
      RedirectingFactoryBuilder factory, TypeEnvironment typeEnvironment);

  void checkRedirectingFactories(TypeEnvironment typeEnvironment);

  /// Returns a map which maps the type variables of [superclass] to their
  /// respective values as defined by the superclass clause of this class (and
  /// its superclasses).
  ///
  /// It's assumed that [superclass] is a superclass of this class.
  ///
  /// For example, given:
  ///
  ///     class Box<T> {}
  ///     class BeatBox extends Box<Beat> {}
  ///     class Beat {}
  ///
  /// We have:
  ///
  ///     [[BeatBox]].getSubstitutionMap([[Box]]) -> {[[Box::T]]: Beat]]}.
  ///
  /// It's an error if [superclass] isn't a superclass.
  Map<TypeParameter, DartType> getSubstitutionMap(Class superclass);

  /// Looks up the member by [name] on the class built by this class builder.
  ///
  /// If [isSetter] is `false`, only fields, methods, and getters with that name
  /// will be found.  If [isSetter] is `true`, only non-final fields and setters
  /// will be found.
  ///
  /// If [isSuper] is `false`, the member is found among the interface members
  /// the class built by this class builder. If [isSuper] is `true`, the member
  /// is found among the class members of the superclass.
  ///
  /// If this class builder is a patch, interface members declared in this
  /// patch are searched before searching the interface members in the origin
  /// class.
  Member lookupInstanceMember(ClassHierarchy hierarchy, Name name,
      {bool isSetter: false, bool isSuper: false});

  /// Looks up the constructor by [name] on the the class built by this class
  /// builder.
  ///
  /// If [isSuper] is `true`, constructors in the superclass are searched.
  Constructor lookupConstructor(Name name, {bool isSuper: false});
}

abstract class ClassBuilderImpl extends DeclarationBuilderImpl
    implements ClassBuilder {
  @override
  List<TypeVariableBuilder> typeVariables;

  @override
  TypeBuilder supertypeBuilder;

  @override
  List<TypeBuilder> interfaceBuilders;

  @override
  List<TypeBuilder> onTypes;

  @override
  final ConstructorScope constructors;

  @override
  final ConstructorScopeBuilder constructorScopeBuilder;

  @override
  Map<String, ConstructorRedirection> redirectingConstructors;

  @override
  ClassBuilder actualOrigin;

  @override
  ClassBuilder get patchForTesting => _patchBuilder;

  @override
  bool isNullClass = false;

  InterfaceType _legacyRawType;
  InterfaceType _nullableRawType;
  InterfaceType _nonNullableRawType;
  InterfaceType _thisType;
  ClassBuilder _patchBuilder;

  ClassBuilderImpl(
      List<MetadataBuilder> metadata,
      int modifiers,
      String name,
      this.typeVariables,
      this.supertypeBuilder,
      this.interfaceBuilders,
      this.onTypes,
      Scope scope,
      this.constructors,
      LibraryBuilder parent,
      int charOffset)
      : constructorScopeBuilder = new ConstructorScopeBuilder(constructors),
        super(metadata, modifiers, name, parent, charOffset, scope);

  @override
  String get debugName => "ClassBuilder";

  @override
  bool get isAbstract => (modifiers & abstractMask) != 0;

  bool get isMixin => (modifiers & mixinDeclarationMask) != 0;

  @override
  bool get isMixinApplication => mixedInTypeBuilder != null;

  @override
  bool get isNamedMixinApplication {
    return isMixinApplication && (modifiers & namedMixinApplicationMask) != 0;
  }

  @override
  bool get isAnonymousMixinApplication {
    return isMixinApplication && !isNamedMixinApplication;
  }

  bool get declaresConstConstructor =>
      (modifiers & declaresConstConstructorMask) != 0;

  @override
  List<ConstructorReferenceBuilder> get constructorReferences => null;

  @override
  void buildOutlineExpressions(LibraryBuilder library, CoreTypes coreTypes) {
    void build(String ignore, Builder declaration) {
      MemberBuilder member = declaration;
      member.buildOutlineExpressions(library, coreTypes);
    }

    MetadataBuilder.buildAnnotations(
        isPatch ? origin.cls : cls, metadata, library, this, null);
    constructors.forEach(build);
    scope.forEach(build);
  }

  /// Registers a constructor redirection for this class and returns true if
  /// this redirection gives rise to a cycle that has not been reported before.
  bool checkConstructorCyclic(String source, String target) {
    ConstructorRedirection redirect = new ConstructorRedirection(target);
    redirectingConstructors ??= <String, ConstructorRedirection>{};
    redirectingConstructors[source] = redirect;
    while (redirect != null) {
      if (redirect.cycleReported) return false;
      if (redirect.target == source) {
        redirect.cycleReported = true;
        return true;
      }
      redirect = redirectingConstructors[redirect.target];
    }
    return false;
  }

  @override
  Builder findStaticBuilder(
      String name, int charOffset, Uri fileUri, LibraryBuilder accessingLibrary,
      {bool isSetter: false}) {
    if (accessingLibrary.origin != library.origin && name.startsWith("_")) {
      return null;
    }
    Builder declaration = isSetter
        ? scope.lookupSetter(name, charOffset, fileUri, isInstanceScope: false)
        : scope.lookup(name, charOffset, fileUri, isInstanceScope: false);
    if (declaration == null && isPatch) {
      return origin.findStaticBuilder(
          name, charOffset, fileUri, accessingLibrary,
          isSetter: isSetter);
    }
    return declaration;
  }

  @override
  MemberBuilder findConstructorOrFactory(
      String name, int charOffset, Uri uri, LibraryBuilder accessingLibrary) {
    if (accessingLibrary.origin != library.origin && name.startsWith("_")) {
      return null;
    }
    MemberBuilder declaration = constructors.lookup(name, charOffset, uri);
    if (declaration == null && isPatch) {
      return origin.findConstructorOrFactory(
          name, charOffset, uri, accessingLibrary);
    }
    return declaration;
  }

  @override
  void forEach(void f(String name, Builder builder)) {
    scope.forEach(f);
  }

  void forEachDeclaredField(
      void Function(String name, FieldBuilder fieldBuilder) callback) {
    void callbackFilteringFieldBuilders(String name, Builder builder) {
      if (builder is FieldBuilder) {
        callback(name, builder);
      }
    }

    // Currently, fields can't be patched, but can be injected.  When the fields
    // will be made available for patching, the following code should iterate
    // first over the fields from the patch and then -- over the fields in the
    // original declaration, filtering out the patched fields.  For now, the
    // assert checks that the names of the fields from the original declaration
    // and from the patch don't intersect.
    assert(
        _patchBuilder == null ||
            _patchBuilder.scope.localMembers
                .where((b) => b is FieldBuilder)
                .map((b) => (b as FieldBuilder).name)
                .toSet()
                .intersection(scope.localMembers
                    .where((b) => b is FieldBuilder)
                    .map((b) => (b as FieldBuilder).name)
                    .toSet())
                .isEmpty,
        "Detected an attempt to patch a field.");
    _patchBuilder?.scope?.forEach(callbackFilteringFieldBuilders);
    scope.forEach(callbackFilteringFieldBuilders);
  }

  @override
  void forEachDeclaredConstructor(
      void Function(String name, ConstructorBuilder constructorBuilder)
          callback) {
    Set<String> visitedConstructorNames = {};
    void callbackFilteringFieldBuilders(String name, Builder builder) {
      if (builder is ConstructorBuilder &&
          visitedConstructorNames.add(builder.name)) {
        callback(name, builder);
      }
    }

    // Constructors can be patched, so iterate first over constructors in the
    // patch, and then over constructors in the original declaration skipping
    // those with the names that are in the patch.
    _patchBuilder?.constructors?.forEach(callbackFilteringFieldBuilders);
    constructors.forEach(callbackFilteringFieldBuilders);
  }

  @override
  Builder lookupLocalMember(String name,
      {bool setter: false, bool required: false}) {
    Builder builder = scope.lookupLocalMember(name, setter: setter);
    if (builder == null && isPatch) {
      builder = origin.scope.lookupLocalMember(name, setter: setter);
    }
    if (required && builder == null) {
      internalProblem(
          templateInternalProblemNotFoundIn.withArguments(
              name, fullNameForErrors),
          -1,
          null);
    }
    return builder;
  }

  @override
  MemberBuilder firstMemberNamed(String name) {
    Builder declaration = lookupLocalMember(name, required: true);
    while (declaration.next != null) {
      declaration = declaration.next;
    }
    return declaration;
  }

  @override
  ClassBuilder get origin => actualOrigin ?? this;

  @override
  InterfaceType get thisType {
    return _thisType ??= new InterfaceType(cls, library.nonNullable,
        getAsTypeArguments(cls.typeParameters, library.library));
  }

  @override
  InterfaceType get legacyRawType {
    return _legacyRawType ??= new InterfaceType(cls, Nullability.legacy,
        new List<DartType>.filled(typeVariablesCount, const DynamicType()));
  }

  @override
  InterfaceType get nullableRawType {
    return _nullableRawType ??= new InterfaceType(cls, Nullability.nullable,
        new List<DartType>.filled(typeVariablesCount, const DynamicType()));
  }

  @override
  InterfaceType get nonNullableRawType {
    return _nonNullableRawType ??= new InterfaceType(
        cls,
        Nullability.nonNullable,
        new List<DartType>.filled(typeVariablesCount, const DynamicType()));
  }

  @override
  InterfaceType rawType(Nullability nullability) {
    switch (nullability) {
      case Nullability.legacy:
        return legacyRawType;
      case Nullability.nullable:
        return nullableRawType;
      case Nullability.nonNullable:
        return nonNullableRawType;
      case Nullability.undetermined:
      default:
        return unhandled("$nullability", "rawType", noOffset, noUri);
    }
  }

  @override
  InterfaceType buildTypesWithBuiltArguments(LibraryBuilder library,
      Nullability nullability, List<DartType> arguments) {
    assert(arguments == null || cls.typeParameters.length == arguments.length);
    if (isNullClass) {
      nullability = Nullability.nullable;
    }
    return arguments == null
        ? rawType(nullability)
        : new InterfaceType(cls, nullability, arguments);
  }

  @override
  int get typeVariablesCount => typeVariables?.length ?? 0;

  @override
  List<DartType> buildTypeArguments(
      LibraryBuilder library, List<TypeBuilder> arguments,
      [bool notInstanceContext]) {
    if (arguments == null && typeVariables == null) {
      return <DartType>[];
    }

    if (arguments == null && typeVariables != null) {
      List<DartType> result =
          new List<DartType>.filled(typeVariables.length, null, growable: true);
      for (int i = 0; i < result.length; ++i) {
        result[i] = typeVariables[i].defaultType.build(library);
      }
      if (library is SourceLibraryBuilder) {
        library.inferredTypes.addAll(result);
      }
      return result;
    }

    if (arguments != null && arguments.length != typeVariablesCount) {
      // That should be caught and reported as a compile-time error earlier.
      return unhandled(
          templateTypeArgumentMismatch
              .withArguments(typeVariablesCount)
              .message,
          "buildTypeArguments",
          -1,
          null);
    }

    // arguments.length == typeVariables.length
    List<DartType> result =
        new List<DartType>.filled(arguments.length, null, growable: true);
    for (int i = 0; i < result.length; ++i) {
      result[i] = arguments[i].build(library);
    }
    return result;
  }

  @override
  InterfaceType buildType(LibraryBuilder library,
      NullabilityBuilder nullabilityBuilder, List<TypeBuilder> arguments,
      [bool notInstanceContext]) {
    return buildTypesWithBuiltArguments(
        library,
        nullabilityBuilder.build(library),
        buildTypeArguments(library, arguments, notInstanceContext));
  }

  @override
  Supertype buildSupertype(
      LibraryBuilder library, List<TypeBuilder> arguments) {
    Class cls = isPatch ? origin.cls : this.cls;
    return new Supertype(cls, buildTypeArguments(library, arguments));
  }

  @override
  Supertype buildMixedInType(
      LibraryBuilder library, List<TypeBuilder> arguments) {
    Class cls = isPatch ? origin.cls : this.cls;
    if (arguments != null) {
      return new Supertype(cls, buildTypeArguments(library, arguments));
    } else {
      return new Supertype(
          cls,
          new List<DartType>.filled(
              cls.typeParameters.length, const UnknownType(),
              growable: true));
    }
  }

  @override
  void checkSupertypes(CoreTypes coreTypes) {
    // This method determines whether the class (that's being built) its super
    // class appears both in 'extends' and 'implements' clauses and whether any
    // interface appears multiple times in the 'implements' clause.
    // Moreover, it checks that `FutureOr` and `void` are not among the
    // supertypes.

    void fail(NamedTypeBuilder target, Message message,
        TypeAliasBuilder aliasBuilder) {
      int nameOffset = target.nameOffset;
      int nameLength = target.nameLength;
      // TODO(eernst): nameOffset not fully implemented; use backup.
      if (nameOffset == -1) {
        nameOffset = this.charOffset;
        nameLength = noLength;
      }
      if (aliasBuilder != null) {
        addProblem(message, nameOffset, nameLength, context: [
          messageTypedefCause.withLocation(
              aliasBuilder.fileUri, aliasBuilder.charOffset, noLength),
        ]);
      } else {
        addProblem(message, nameOffset, nameLength);
      }
    }

    // Extract and check superclass (if it exists).
    ClassBuilder superClass;
    TypeBuilder superClassType = supertypeBuilder;
    if (superClassType is NamedTypeBuilder) {
      TypeDeclarationBuilder decl = superClassType.declaration;
      TypeAliasBuilder aliasBuilder; // Non-null if a type alias is use.
      if (decl is TypeAliasBuilder) {
        aliasBuilder = decl;
        decl = aliasBuilder.unaliasDeclaration(superClassType.arguments);
      }
      // TODO(eernst): Should gather 'restricted supertype' checks in one place,
      // e.g., dynamic/int/String/Null and more are checked elsewhere.
      if (decl is VoidTypeBuilder) {
        fail(superClassType, messageExtendsVoid, aliasBuilder);
      } else if (decl is NeverTypeBuilder) {
        fail(superClassType, messageExtendsNever, aliasBuilder);
      } else if (decl is ClassBuilder) {
        if (decl.cls == coreTypes.futureOrClass) {
          fail(superClassType, messageExtendsFutureOr, aliasBuilder);
        }
        superClass = decl;
      }
    }
    if (interfaceBuilders == null) return;

    // Validate interfaces.
    Map<ClassBuilder, int> problems;
    Map<ClassBuilder, int> problemsOffsets;
    Set<ClassBuilder> implemented = new Set<ClassBuilder>();
    for (TypeBuilder type in interfaceBuilders) {
      if (type is NamedTypeBuilder) {
        int charOffset = -1; // TODO(ahe): Get offset from type.
        TypeDeclarationBuilder typeDeclaration = type.declaration;
        TypeDeclarationBuilder decl;
        TypeAliasBuilder aliasBuilder; // Non-null if a type alias is used.
        if (typeDeclaration is TypeAliasBuilder) {
          aliasBuilder = typeDeclaration;
          decl = aliasBuilder.unaliasDeclaration(type.arguments);
        } else {
          decl = typeDeclaration;
        }
        if (decl is ClassBuilder) {
          ClassBuilder interface = decl;
          if (superClass == interface) {
            addProblem(
                templateImplementsSuperClass.withArguments(interface.name),
                this.charOffset,
                noLength);
          } else if (implemented.contains(interface)) {
            // Aggregate repetitions.
            problems ??= new Map<ClassBuilder, int>();
            problems[interface] ??= 0;
            problems[interface] += 1;
            problemsOffsets ??= new Map<ClassBuilder, int>();
            problemsOffsets[interface] ??= charOffset;
          } else if (interface.cls == coreTypes.futureOrClass) {
            fail(type, messageImplementsFutureOr, aliasBuilder);
          } else {
            implemented.add(interface);
          }
        }
        if (decl != superClass) {
          // TODO(eernst): Have all 'restricted supertype' checks in one place.
          if (decl is VoidTypeBuilder) {
            fail(type, messageImplementsVoid, aliasBuilder);
          } else if (decl is NeverTypeBuilder) {
            fail(type, messageImplementsNever, aliasBuilder);
          }
        }
      }
    }
    if (problems != null) {
      problems.forEach((ClassBuilder interface, int repetitions) {
        addProblem(
            templateImplementsRepeated.withArguments(
                interface.name, repetitions),
            problemsOffsets[interface],
            noLength);
      });
    }
  }

  @override
  void handleSeenCovariant(
      Types types,
      Member declaredMember,
      Member interfaceMember,
      bool isSetter,
      callback(Member declaredMember, Member interfaceMember, bool isSetter)) {
    // When a parameter is covariant we have to check that we also
    // override the same member in all parents.
    for (Supertype supertype in interfaceMember.enclosingClass.supers) {
      Member m = types.hierarchy.getInterfaceMember(
          supertype.classNode, interfaceMember.name,
          setter: isSetter);
      if (m != null) {
        callback(declaredMember, m, isSetter);
      }
    }
  }

  @override
  void checkOverride(
      Types types,
      Member declaredMember,
      Member interfaceMember,
      bool isSetter,
      callback(Member declaredMember, Member interfaceMember, bool isSetter),
      {bool isInterfaceCheck = false}) {
    if (declaredMember == interfaceMember) {
      return;
    }
    if (declaredMember is Constructor || interfaceMember is Constructor) {
      unimplemented(
          "Constructor in override check.", declaredMember.fileOffset, fileUri);
    }
    if (declaredMember is Procedure && interfaceMember is Procedure) {
      if (declaredMember.kind == ProcedureKind.Method &&
          interfaceMember.kind == ProcedureKind.Method) {
        bool seenCovariant = checkMethodOverride(
            types, declaredMember, interfaceMember, isInterfaceCheck);
        if (seenCovariant) {
          handleSeenCovariant(
              types, declaredMember, interfaceMember, isSetter, callback);
        }
      }
      if (declaredMember.kind == ProcedureKind.Getter &&
          interfaceMember.kind == ProcedureKind.Getter) {
        checkGetterOverride(
            types, declaredMember, interfaceMember, isInterfaceCheck);
      }
      if (declaredMember.kind == ProcedureKind.Setter &&
          interfaceMember.kind == ProcedureKind.Setter) {
        bool seenCovariant = checkSetterOverride(
            types, declaredMember, interfaceMember, isInterfaceCheck);
        if (seenCovariant) {
          handleSeenCovariant(
              types, declaredMember, interfaceMember, isSetter, callback);
        }
      }
    } else {
      bool declaredMemberHasGetter = declaredMember is Field ||
          declaredMember is Procedure && declaredMember.isGetter;
      bool interfaceMemberHasGetter = interfaceMember is Field ||
          interfaceMember is Procedure && interfaceMember.isGetter;
      bool declaredMemberHasSetter = (declaredMember is Field &&
              !declaredMember.isFinal &&
              !declaredMember.isConst) ||
          declaredMember is Procedure && declaredMember.isSetter;
      bool interfaceMemberHasSetter = (interfaceMember is Field &&
              !interfaceMember.isFinal &&
              !interfaceMember.isConst) ||
          interfaceMember is Procedure && interfaceMember.isSetter;
      if (declaredMemberHasGetter && interfaceMemberHasGetter) {
        checkGetterOverride(
            types, declaredMember, interfaceMember, isInterfaceCheck);
      }
      if (declaredMemberHasSetter && interfaceMemberHasSetter) {
        bool seenCovariant = checkSetterOverride(
            types, declaredMember, interfaceMember, isInterfaceCheck);
        if (seenCovariant) {
          handleSeenCovariant(
              types, declaredMember, interfaceMember, isSetter, callback);
        }
      }
    }
    // TODO(ahe): Handle other cases: accessors, operators, and fields.
  }

  @override
  bool hasUserDefinedNoSuchMethod(
      Class klass, ClassHierarchy hierarchy, Class objectClass) {
    Member noSuchMethod = hierarchy.getDispatchTarget(klass, noSuchMethodName);
    return noSuchMethod != null && noSuchMethod.enclosingClass != objectClass;
  }

  void transformProcedureToNoSuchMethodForwarder(
      Member noSuchMethodInterface, KernelTarget target, Procedure procedure) {
    String prefix =
        procedure.isGetter ? 'get:' : procedure.isSetter ? 'set:' : '';
    Expression invocation = target.backendTarget.instantiateInvocation(
        target.loader.coreTypes,
        new ThisExpression(),
        prefix + procedure.name.name,
        new Arguments.forwarded(procedure.function, library.library),
        procedure.fileOffset,
        /*isSuper=*/ false);
    Expression result = new MethodInvocation(new ThisExpression(),
        noSuchMethodName, new Arguments([invocation]), noSuchMethodInterface)
      ..fileOffset = procedure.fileOffset;
    if (procedure.function.returnType is! VoidType) {
      result = new AsExpression(result, procedure.function.returnType)
        ..isTypeError = true
        ..isForDynamic = true
        ..isForNonNullableByDefault = library.isNonNullableByDefault
        ..fileOffset = procedure.fileOffset;
    }
    procedure.function.body = new ReturnStatement(result)
      ..fileOffset = procedure.fileOffset;
    procedure.function.body.parent = procedure.function;

    procedure.isAbstract = false;
    procedure.isNoSuchMethodForwarder = true;
    procedure.isForwardingStub = false;
    procedure.isForwardingSemiStub = false;
  }

  Uri _getMemberUri(Member member) {
    if (member is Field) return member.fileUri;
    if (member is Procedure) return member.fileUri;
    // Other member types won't be seen because constructors don't participate
    // in override relationships
    return unhandled('${member.runtimeType}', '_getMemberUri', -1, null);
  }

  Substitution _computeInterfaceSubstitution(
      Types types,
      Member declaredMember,
      Member interfaceMember,
      FunctionNode declaredFunction,
      FunctionNode interfaceFunction,
      bool isInterfaceCheck) {
    Substitution interfaceSubstitution = Substitution.empty;
    if (interfaceMember.enclosingClass.typeParameters.isNotEmpty) {
      Class enclosingClass = interfaceMember.enclosingClass;
      interfaceSubstitution = Substitution.fromPairs(
          enclosingClass.typeParameters,
          types.hierarchy
              .getTypeArgumentsAsInstanceOf(thisType, enclosingClass));
    }

    if (declaredFunction?.typeParameters?.length !=
        interfaceFunction?.typeParameters?.length) {
      reportInvalidOverride(
          isInterfaceCheck,
          declaredMember,
          templateOverrideTypeVariablesMismatch.withArguments(
              "${declaredMember.enclosingClass.name}."
                  "${declaredMember.name.name}",
              "${interfaceMember.enclosingClass.name}."
                  "${interfaceMember.name.name}"),
          declaredMember.fileOffset,
          noLength,
          context: [
            templateOverriddenMethodCause
                .withArguments(interfaceMember.name.name)
                .withLocation(_getMemberUri(interfaceMember),
                    interfaceMember.fileOffset, noLength)
          ]);
    } else if (declaredFunction?.typeParameters != null) {
      Map<TypeParameter, DartType> substitutionMap =
          <TypeParameter, DartType>{};
      for (int i = 0; i < declaredFunction.typeParameters.length; ++i) {
        substitutionMap[interfaceFunction.typeParameters[i]] =
            new TypeParameterType.forAlphaRenaming(
                interfaceFunction.typeParameters[i],
                declaredFunction.typeParameters[i]);
      }
      Substitution substitution = Substitution.fromMap(substitutionMap);
      for (int i = 0; i < declaredFunction.typeParameters.length; ++i) {
        TypeParameter declaredParameter = declaredFunction.typeParameters[i];
        TypeParameter interfaceParameter = interfaceFunction.typeParameters[i];
        if (!interfaceParameter.isGenericCovariantImpl) {
          DartType declaredBound = declaredParameter.bound;
          DartType interfaceBound = interfaceParameter.bound;
          if (interfaceSubstitution != null) {
            declaredBound = interfaceSubstitution.substituteType(declaredBound);
            interfaceBound =
                interfaceSubstitution.substituteType(interfaceBound);
          }
          DartType computedBound = substitution.substituteType(interfaceBound);
          if (!library.isNonNullableByDefault) {
            computedBound =
                legacyErasure(types.hierarchy.coreTypes, computedBound);
          }
          if (!types
              .performNullabilityAwareMutualSubtypesCheck(
                  declaredBound, computedBound)
              .isSubtypeWhenUsingNullabilities()) {
            reportInvalidOverride(
                isInterfaceCheck,
                declaredMember,
                templateOverrideTypeVariablesBoundMismatch.withArguments(
                    declaredBound,
                    declaredParameter.name,
                    "${declaredMember.enclosingClass.name}."
                        "${declaredMember.name.name}",
                    computedBound,
                    "${interfaceMember.enclosingClass.name}."
                        "${interfaceMember.name.name}",
                    library.isNonNullableByDefault),
                declaredMember.fileOffset,
                noLength,
                context: [
                  templateOverriddenMethodCause
                      .withArguments(interfaceMember.name.name)
                      .withLocation(_getMemberUri(interfaceMember),
                          interfaceMember.fileOffset, noLength)
                ]);
          }
        }
      }
      interfaceSubstitution =
          Substitution.combine(interfaceSubstitution, substitution);
    }
    return interfaceSubstitution;
  }

  Substitution _computeDeclaredSubstitution(
      Types types, Member declaredMember) {
    Substitution declaredSubstitution = Substitution.empty;
    if (declaredMember.enclosingClass.typeParameters.isNotEmpty) {
      Class enclosingClass = declaredMember.enclosingClass;
      declaredSubstitution = Substitution.fromPairs(
          enclosingClass.typeParameters,
          types.hierarchy
              .getTypeArgumentsAsInstanceOf(thisType, enclosingClass));
    }
    return declaredSubstitution;
  }

  void _checkTypes(
      Types types,
      Substitution interfaceSubstitution,
      Substitution declaredSubstitution,
      Member declaredMember,
      Member interfaceMember,
      DartType declaredType,
      DartType interfaceType,
      bool isCovariant,
      VariableDeclaration declaredParameter,
      bool isInterfaceCheck,
      {bool asIfDeclaredParameter = false}) {
    if (interfaceSubstitution != null) {
      interfaceType = interfaceSubstitution.substituteType(interfaceType);
    }
    if (declaredSubstitution != null) {
      declaredType = declaredSubstitution.substituteType(declaredType);
    }

    if (!declaredMember.isNonNullableByDefault &&
        interfaceMember.isNonNullableByDefault) {
      interfaceType = legacyErasure(types.hierarchy.coreTypes, interfaceType);
    }

    bool inParameter = declaredParameter != null || asIfDeclaredParameter;
    DartType subtype = inParameter ? interfaceType : declaredType;
    DartType supertype = inParameter ? declaredType : interfaceType;

    if (types.isSubtypeOf(
        subtype, supertype, SubtypeCheckMode.withNullabilities)) {
      // No problem--the proper subtyping relation is satisfied.
    } else if (isCovariant &&
        types.isSubtypeOf(
            supertype, subtype, SubtypeCheckMode.withNullabilities)) {
      // No problem--the overriding parameter is marked "covariant" and has
      // a type which is a subtype of the parameter it overrides.
    } else if (subtype is InvalidType || supertype is InvalidType) {
      // Don't report a problem as something else is wrong that has already
      // been reported.
    } else {
      // Report an error.
      bool isErrorInNnbdOptedOutMode = !types.isSubtypeOf(
              subtype, supertype, SubtypeCheckMode.ignoringNullabilities) &&
          (!isCovariant ||
              !types.isSubtypeOf(
                  supertype, subtype, SubtypeCheckMode.ignoringNullabilities));
      if (isErrorInNnbdOptedOutMode || library.isNonNullableByDefault) {
        String declaredMemberName = '${declaredMember.enclosingClass.name}'
            '.${declaredMember.name.name}';
        String interfaceMemberName = '${interfaceMember.enclosingClass.name}'
            '.${interfaceMember.name.name}';
        Message message;
        int fileOffset;
        if (declaredParameter == null) {
          if (asIfDeclaredParameter) {
            // Setter overridden by field
            message = templateOverrideTypeMismatchSetter.withArguments(
                declaredMemberName,
                declaredType,
                interfaceType,
                interfaceMemberName,
                library.isNonNullableByDefault);
          } else {
            message = templateOverrideTypeMismatchReturnType.withArguments(
                declaredMemberName,
                declaredType,
                interfaceType,
                interfaceMemberName,
                library.isNonNullableByDefault);
          }
          fileOffset = declaredMember.fileOffset;
        } else {
          message = templateOverrideTypeMismatchParameter.withArguments(
              declaredParameter.name,
              declaredMemberName,
              declaredType,
              interfaceType,
              interfaceMemberName,
              library.isNonNullableByDefault);
          fileOffset = declaredParameter.fileOffset;
        }
        reportInvalidOverride(
            isInterfaceCheck, declaredMember, message, fileOffset, noLength,
            context: [
              templateOverriddenMethodCause
                  .withArguments(interfaceMember.name.name)
                  .withLocation(_getMemberUri(interfaceMember),
                      interfaceMember.fileOffset, noLength)
            ]);
      }
    }
  }

  @override
  bool checkMethodOverride(Types types, Procedure declaredMember,
      Procedure interfaceMember, bool isInterfaceCheck) {
    assert(declaredMember.kind == ProcedureKind.Method);
    assert(interfaceMember.kind == ProcedureKind.Method);
    bool seenCovariant = false;
    FunctionNode declaredFunction = declaredMember.function;
    FunctionNode interfaceFunction = interfaceMember.function;

    Substitution interfaceSubstitution = _computeInterfaceSubstitution(
        types,
        declaredMember,
        interfaceMember,
        declaredFunction,
        interfaceFunction,
        isInterfaceCheck);

    Substitution declaredSubstitution =
        _computeDeclaredSubstitution(types, declaredMember);

    _checkTypes(
        types,
        interfaceSubstitution,
        declaredSubstitution,
        declaredMember,
        interfaceMember,
        declaredFunction.returnType,
        interfaceFunction.returnType,
        false,
        null,
        isInterfaceCheck);
    if (declaredFunction.positionalParameters.length <
        interfaceFunction.positionalParameters.length) {
      reportInvalidOverride(
          isInterfaceCheck,
          declaredMember,
          templateOverrideFewerPositionalArguments.withArguments(
              "${declaredMember.enclosingClass.name}."
                  "${declaredMember.name.name}",
              "${interfaceMember.enclosingClass.name}."
                  "${interfaceMember.name.name}"),
          declaredMember.fileOffset,
          noLength,
          context: [
            templateOverriddenMethodCause
                .withArguments(interfaceMember.name.name)
                .withLocation(interfaceMember.fileUri,
                    interfaceMember.fileOffset, noLength)
          ]);
    }
    if (interfaceFunction.requiredParameterCount <
        declaredFunction.requiredParameterCount) {
      reportInvalidOverride(
          isInterfaceCheck,
          declaredMember,
          templateOverrideMoreRequiredArguments.withArguments(
              "${declaredMember.enclosingClass.name}."
                  "${declaredMember.name.name}",
              "${interfaceMember.enclosingClass.name}."
                  "${interfaceMember.name.name}"),
          declaredMember.fileOffset,
          noLength,
          context: [
            templateOverriddenMethodCause
                .withArguments(interfaceMember.name.name)
                .withLocation(interfaceMember.fileUri,
                    interfaceMember.fileOffset, noLength)
          ]);
    }
    for (int i = 0;
        i < declaredFunction.positionalParameters.length &&
            i < interfaceFunction.positionalParameters.length;
        i++) {
      VariableDeclaration declaredParameter =
          declaredFunction.positionalParameters[i];
      VariableDeclaration interfaceParameter =
          interfaceFunction.positionalParameters[i];
      _checkTypes(
          types,
          interfaceSubstitution,
          declaredSubstitution,
          declaredMember,
          interfaceMember,
          declaredParameter.type,
          interfaceFunction.positionalParameters[i].type,
          declaredParameter.isCovariant || interfaceParameter.isCovariant,
          declaredParameter,
          isInterfaceCheck);
      if (declaredParameter.isCovariant) seenCovariant = true;
    }
    if (declaredFunction.namedParameters.isEmpty &&
        interfaceFunction.namedParameters.isEmpty) {
      return seenCovariant;
    }
    if (declaredFunction.namedParameters.length <
        interfaceFunction.namedParameters.length) {
      reportInvalidOverride(
          isInterfaceCheck,
          declaredMember,
          templateOverrideFewerNamedArguments.withArguments(
              "${declaredMember.enclosingClass.name}."
                  "${declaredMember.name.name}",
              "${interfaceMember.enclosingClass.name}."
                  "${interfaceMember.name.name}"),
          declaredMember.fileOffset,
          noLength,
          context: [
            templateOverriddenMethodCause
                .withArguments(interfaceMember.name.name)
                .withLocation(interfaceMember.fileUri,
                    interfaceMember.fileOffset, noLength)
          ]);
    }
    int compareNamedParameters(VariableDeclaration p0, VariableDeclaration p1) {
      return p0.name.compareTo(p1.name);
    }

    List<VariableDeclaration> sortedFromDeclared =
        new List.from(declaredFunction.namedParameters)
          ..sort(compareNamedParameters);
    List<VariableDeclaration> sortedFromInterface =
        new List.from(interfaceFunction.namedParameters)
          ..sort(compareNamedParameters);
    Iterator<VariableDeclaration> declaredNamedParameters =
        sortedFromDeclared.iterator;
    Iterator<VariableDeclaration> interfaceNamedParameters =
        sortedFromInterface.iterator;
    outer:
    while (declaredNamedParameters.moveNext() &&
        interfaceNamedParameters.moveNext()) {
      while (declaredNamedParameters.current.name !=
          interfaceNamedParameters.current.name) {
        if (!declaredNamedParameters.moveNext()) {
          reportInvalidOverride(
              isInterfaceCheck,
              declaredMember,
              templateOverrideMismatchNamedParameter.withArguments(
                  "${declaredMember.enclosingClass.name}."
                      "${declaredMember.name.name}",
                  interfaceNamedParameters.current.name,
                  "${interfaceMember.enclosingClass.name}."
                      "${interfaceMember.name.name}"),
              declaredMember.fileOffset,
              noLength,
              context: [
                templateOverriddenMethodCause
                    .withArguments(interfaceMember.name.name)
                    .withLocation(interfaceMember.fileUri,
                        interfaceMember.fileOffset, noLength)
              ]);
          break outer;
        }
      }
      VariableDeclaration declaredParameter = declaredNamedParameters.current;
      _checkTypes(
          types,
          interfaceSubstitution,
          declaredSubstitution,
          declaredMember,
          interfaceMember,
          declaredParameter.type,
          interfaceNamedParameters.current.type,
          declaredParameter.isCovariant,
          declaredParameter,
          isInterfaceCheck);
      if (declaredParameter.isRequired &&
          !interfaceNamedParameters.current.isRequired) {
        reportInvalidOverride(
            isInterfaceCheck,
            declaredMember,
            templateOverrideMismatchRequiredNamedParameter.withArguments(
                declaredParameter.name,
                "${declaredMember.enclosingClass.name}."
                    "${declaredMember.name.name}",
                "${interfaceMember.enclosingClass.name}."
                    "${interfaceMember.name.name}"),
            declaredParameter.fileOffset,
            noLength,
            context: [
              templateOverriddenMethodCause
                  .withArguments(interfaceMember.name.name)
                  .withLocation(_getMemberUri(interfaceMember),
                      interfaceMember.fileOffset, noLength)
            ]);
      }
      if (declaredParameter.isCovariant) seenCovariant = true;
    }
    return seenCovariant;
  }

  void checkGetterOverride(Types types, Member declaredMember,
      Member interfaceMember, bool isInterfaceCheck) {
    Substitution interfaceSubstitution = _computeInterfaceSubstitution(
        types, declaredMember, interfaceMember, null, null, isInterfaceCheck);
    Substitution declaredSubstitution =
        _computeDeclaredSubstitution(types, declaredMember);
    DartType declaredType = declaredMember.getterType;
    DartType interfaceType = interfaceMember.getterType;
    _checkTypes(
        types,
        interfaceSubstitution,
        declaredSubstitution,
        declaredMember,
        interfaceMember,
        declaredType,
        interfaceType,
        false,
        null,
        isInterfaceCheck);
  }

  @override
  bool checkSetterOverride(Types types, Member declaredMember,
      Member interfaceMember, bool isInterfaceCheck) {
    Substitution interfaceSubstitution = _computeInterfaceSubstitution(
        types, declaredMember, interfaceMember, null, null, isInterfaceCheck);
    Substitution declaredSubstitution =
        _computeDeclaredSubstitution(types, declaredMember);
    DartType declaredType = declaredMember.setterType;
    DartType interfaceType = interfaceMember.setterType;
    VariableDeclaration declaredParameter =
        declaredMember.function?.positionalParameters?.elementAt(0);
    bool isCovariant = declaredParameter?.isCovariant ?? false;
    if (!isCovariant && declaredMember is Field) {
      isCovariant = declaredMember.isCovariant;
    }
    if (!isCovariant && interfaceMember is Field) {
      isCovariant = interfaceMember.isCovariant;
    }
    _checkTypes(
        types,
        interfaceSubstitution,
        declaredSubstitution,
        declaredMember,
        interfaceMember,
        declaredType,
        interfaceType,
        isCovariant,
        declaredParameter,
        isInterfaceCheck,
        asIfDeclaredParameter: true);
    return isCovariant;
  }

  @override
  void reportInvalidOverride(bool isInterfaceCheck, Member declaredMember,
      Message message, int fileOffset, int length,
      {List<LocatedMessage> context}) {
    if (declaredMember.enclosingClass == cls) {
      // Ordinary override
      library.addProblem(message, fileOffset, length, declaredMember.fileUri,
          context: context);
    } else {
      context = [
        message.withLocation(declaredMember.fileUri, fileOffset, length),
        ...?context
      ];
      if (isInterfaceCheck) {
        // Interface check
        library.addProblem(
            templateInterfaceCheck.withArguments(
                declaredMember.name.name, cls.name),
            cls.fileOffset,
            cls.name.length,
            cls.fileUri,
            context: context);
      } else {
        if (cls.isAnonymousMixin) {
          // Implicit mixin application class
          String baseName = cls.superclass.demangledName;
          String mixinName = cls.mixedInClass.name;
          int classNameLength = cls.nameAsMixinApplicationSubclass.length;
          library.addProblem(
              templateImplicitMixinOverride.withArguments(
                  mixinName, baseName, declaredMember.name.name),
              cls.fileOffset,
              classNameLength,
              cls.fileUri,
              context: context);
        } else {
          // Named mixin application class
          library.addProblem(
              templateNamedMixinOverride.withArguments(
                  cls.name, declaredMember.name.name),
              cls.fileOffset,
              cls.name.length,
              cls.fileUri,
              context: context);
        }
      }
    }
  }

  @override
  String get fullNameForErrors {
    return isMixinApplication && !isNamedMixinApplication
        ? "${supertypeBuilder.fullNameForErrors} with "
            "${mixedInTypeBuilder.fullNameForErrors}"
        : name;
  }

  @override
  void checkMixinApplication(ClassHierarchy hierarchy, CoreTypes coreTypes) {
    // A mixin declaration can only be applied to a class that implements all
    // the declaration's superclass constraints.
    InterfaceType supertype = cls.supertype.asInterfaceType;
    Substitution substitution = Substitution.fromSupertype(cls.mixedInType);
    for (Supertype constraint in cls.mixedInClass.superclassConstraints()) {
      InterfaceType interface =
          substitution.substituteSupertype(constraint).asInterfaceType;
      if (hierarchy.getTypeAsInstanceOf(
              supertype, interface.classNode, library.library, coreTypes) !=
          interface) {
        library.addProblem(
            templateMixinApplicationIncompatibleSupertype.withArguments(
                supertype,
                interface,
                cls.mixedInType.asInterfaceType,
                library.isNonNullableByDefault),
            cls.fileOffset,
            noLength,
            cls.fileUri);
      }
    }
  }

  @override
  void applyPatch(Builder patch) {
    if (patch is ClassBuilder) {
      patch.actualOrigin = this;
      _patchBuilder = patch;
      // TODO(ahe): Complain if `patch.supertype` isn't null.
      scope.forEachLocalMember((String name, Builder member) {
        Builder memberPatch =
            patch.scope.lookupLocalMember(name, setter: false);
        if (memberPatch != null) {
          member.applyPatch(memberPatch);
        }
      });
      scope.forEachLocalSetter((String name, Builder member) {
        Builder memberPatch = patch.scope.lookupLocalMember(name, setter: true);
        if (memberPatch != null) {
          member.applyPatch(memberPatch);
        }
      });
      constructors.local.forEach((String name, Builder member) {
        Builder memberPatch = patch.constructors.local[name];
        if (memberPatch != null) {
          member.applyPatch(memberPatch);
        }
      });

      int originLength = typeVariables?.length ?? 0;
      int patchLength = patch.typeVariables?.length ?? 0;
      if (originLength != patchLength) {
        patch.addProblem(messagePatchClassTypeVariablesMismatch,
            patch.charOffset, noLength, context: [
          messagePatchClassOrigin.withLocation(fileUri, charOffset, noLength)
        ]);
      } else if (typeVariables != null) {
        int count = 0;
        for (TypeVariableBuilder t in patch.typeVariables) {
          typeVariables[count++].applyPatch(t);
        }
      }
    } else {
      library.addProblem(messagePatchDeclarationMismatch, patch.charOffset,
          noLength, patch.fileUri, context: [
        messagePatchDeclarationOrigin.withLocation(
            fileUri, charOffset, noLength)
      ]);
    }
  }

  @override
  FunctionType computeRedirecteeType(
      RedirectingFactoryBuilder factory, TypeEnvironment typeEnvironment) {
    ConstructorReferenceBuilder redirectionTarget = factory.redirectionTarget;
    FunctionNode target;
    if (redirectionTarget.target == null) return null;
    if (redirectionTarget.target is FunctionBuilder) {
      FunctionBuilder targetBuilder = redirectionTarget.target;
      target = targetBuilder.function;
    } else if (redirectionTarget.target is DillMemberBuilder &&
        (redirectionTarget.target.isConstructor ||
            redirectionTarget.target.isFactory)) {
      DillMemberBuilder targetBuilder = redirectionTarget.target;
      // It seems that the [redirectionTarget.target] is an instance of
      // [DillMemberBuilder] whenever the redirectee is an implicit constructor,
      // e.g.
      //
      //   class A {
      //     factory A() = B;
      //   }
      //   class B implements A {}
      //
      target = targetBuilder.member.function;
    } else if (redirectionTarget.target is AmbiguousBuilder) {
      // Multiple definitions with the same name: An error has already been
      // issued.
      // TODO(http://dartbug.com/35294): Unfortunate error; see also
      // https://dart-review.googlesource.com/c/sdk/+/85390/.
      return null;
    } else {
      unhandled("${redirectionTarget.target}", "computeRedirecteeType",
          charOffset, fileUri);
    }

    List<DartType> typeArguments =
        getRedirectingFactoryBody(factory.procedure).typeArguments;
    FunctionType targetFunctionType =
        target.computeFunctionType(library.nonNullable);
    if (typeArguments != null &&
        targetFunctionType.typeParameters.length != typeArguments.length) {
      addProblem(
          templateTypeArgumentMismatch
              .withArguments(targetFunctionType.typeParameters.length),
          redirectionTarget.charOffset,
          noLength);
      return null;
    }

    // Compute the substitution of the target class type parameters if
    // [redirectionTarget] has any type arguments.
    Substitution substitution;
    bool hasProblem = false;
    if (typeArguments != null && typeArguments.length > 0) {
      substitution = Substitution.fromPairs(
          targetFunctionType.typeParameters, typeArguments);
      for (int i = 0; i < targetFunctionType.typeParameters.length; i++) {
        TypeParameter typeParameter = targetFunctionType.typeParameters[i];
        DartType typeParameterBound =
            substitution.substituteType(typeParameter.bound);
        DartType typeArgument = typeArguments[i];
        // Check whether the [typeArgument] respects the bounds of
        // [typeParameter].
        Loader loader = library.loader;
        if (!typeEnvironment.isSubtypeOf(typeArgument, typeParameterBound,
            SubtypeCheckMode.ignoringNullabilities)) {
          addProblem(
              templateRedirectingFactoryIncompatibleTypeArgument.withArguments(
                  typeArgument,
                  typeParameterBound,
                  library.isNonNullableByDefault),
              redirectionTarget.charOffset,
              noLength);
          hasProblem = true;
        } else if (library.isNonNullableByDefault && loader is SourceLoader) {
          if (!typeEnvironment.isSubtypeOf(typeArgument, typeParameterBound,
              SubtypeCheckMode.withNullabilities)) {
            addProblem(
                templateRedirectingFactoryIncompatibleTypeArgument
                    .withArguments(typeArgument, typeParameterBound,
                        library.isNonNullableByDefault),
                redirectionTarget.charOffset,
                noLength);
            hasProblem = true;
          }
        }
      }
    } else if (typeArguments == null &&
        targetFunctionType.typeParameters.length > 0) {
      // TODO(hillerstrom): In this case, we need to perform type inference on
      // the redirectee to obtain actual type arguments which would allow the
      // following program to type check:
      //
      //    class A<T> {
      //       factory A() = B;
      //    }
      //    class B<T> implements A<T> {
      //       B();
      //    }
      //
      return null;
    }

    // Substitute if necessary.
    targetFunctionType = substitution == null
        ? targetFunctionType
        : (substitution.substituteType(targetFunctionType.withoutTypeParameters)
            as FunctionType);

    return hasProblem ? null : targetFunctionType;
  }

  @override
  String computeRedirecteeName(ConstructorReferenceBuilder redirectionTarget) {
    String targetName = redirectionTarget.fullNameForErrors;
    if (targetName == "") {
      return redirectionTarget.target.parent.fullNameForErrors;
    } else {
      return targetName;
    }
  }

  @override
  void checkRedirectingFactory(
      RedirectingFactoryBuilder factory, TypeEnvironment typeEnvironment) {
    // The factory type cannot contain any type parameters other than those of
    // its enclosing class, because constructors cannot specify type parameters
    // of their own.
    FunctionType factoryType = factory.procedure.function
        .computeThisFunctionType(library.nonNullable)
        .withoutTypeParameters;
    FunctionType redirecteeType =
        computeRedirecteeType(factory, typeEnvironment);

    // TODO(hillerstrom): It would be preferable to know whether a failure
    // happened during [_computeRedirecteeType].
    if (redirecteeType == null) return;

    // Check whether [redirecteeType] <: [factoryType].
    Loader loader = library.loader;
    if (!typeEnvironment.isSubtypeOf(
        redirecteeType, factoryType, SubtypeCheckMode.ignoringNullabilities)) {
      addProblem(
          templateIncompatibleRedirecteeFunctionType.withArguments(
              redirecteeType, factoryType, library.isNonNullableByDefault),
          factory.redirectionTarget.charOffset,
          noLength);
    } else if (library.isNonNullableByDefault && loader is SourceLoader) {
      if (!typeEnvironment.isSubtypeOf(
          redirecteeType, factoryType, SubtypeCheckMode.withNullabilities)) {
        addProblem(
            templateIncompatibleRedirecteeFunctionType.withArguments(
                redirecteeType, factoryType, library.isNonNullableByDefault),
            factory.redirectionTarget.charOffset,
            noLength);
      }
    }
  }

  @override
  void checkRedirectingFactories(TypeEnvironment typeEnvironment) {
    Map<String, MemberBuilder> constructors = this.constructors.local;
    Iterable<String> names = constructors.keys;
    for (String name in names) {
      Builder constructor = constructors[name];
      do {
        if (constructor is RedirectingFactoryBuilder) {
          checkRedirectingFactory(constructor, typeEnvironment);
        }
        constructor = constructor.next;
      } while (constructor != null);
    }
  }

  @override
  Map<TypeParameter, DartType> getSubstitutionMap(Class superclass) {
    Supertype supertype = cls.supertype;
    Map<TypeParameter, DartType> substitutionMap = <TypeParameter, DartType>{};
    List<DartType> arguments;
    List<TypeParameter> variables;
    Class classNode;

    while (classNode != superclass) {
      classNode = supertype.classNode;
      arguments = supertype.typeArguments;
      variables = classNode.typeParameters;
      supertype = classNode.supertype;
      if (variables.isNotEmpty) {
        Map<TypeParameter, DartType> directSubstitutionMap =
            <TypeParameter, DartType>{};
        for (int i = 0; i < variables.length; i++) {
          DartType argument =
              i < arguments.length ? arguments[i] : const DynamicType();
          if (substitutionMap != null) {
            // TODO(ahe): Investigate if requiring the caller to use
            // `substituteDeep` from `package:kernel/type_algebra.dart` instead
            // of `substitute` is faster. If so, we can simply this code.
            argument = substitute(argument, substitutionMap);
          }
          directSubstitutionMap[variables[i]] = argument;
        }
        substitutionMap = directSubstitutionMap;
      }
    }

    return substitutionMap;
  }

  @override
  Member lookupInstanceMember(ClassHierarchy hierarchy, Name name,
      {bool isSetter: false, bool isSuper: false}) {
    Class instanceClass = cls;
    if (isPatch) {
      assert(identical(instanceClass, origin.cls),
          "Found ${origin.cls} expected $instanceClass");
      if (isSuper) {
        // The super class is only correctly found through the origin class.
        instanceClass = origin.cls;
      } else {
        Member member =
            hierarchy.getInterfaceMember(instanceClass, name, setter: isSetter);
        if (member?.parent == instanceClass) {
          // Only if the member is found in the patch can we use it.
          return member;
        } else {
          // Otherwise, we need to keep searching in the origin class.
          instanceClass = origin.cls;
        }
      }
    }

    if (isSuper) {
      instanceClass = instanceClass.superclass;
      if (instanceClass == null) return null;
    }
    Member target = isSuper
        ? hierarchy.getDispatchTarget(instanceClass, name, setter: isSetter)
        : hierarchy.getInterfaceMember(instanceClass, name, setter: isSetter);
    if (isSuper && target == null) {
      if (cls.isMixinDeclaration ||
          (library.loader.target.backendTarget.enableSuperMixins &&
              this.isAbstract)) {
        target =
            hierarchy.getInterfaceMember(instanceClass, name, setter: isSetter);
      }
    }
    return target;
  }

  @override
  Constructor lookupConstructor(Name name, {bool isSuper: false}) {
    Class instanceClass = cls;
    if (isSuper) {
      instanceClass = instanceClass.superclass;
    }
    if (instanceClass != null) {
      for (Constructor constructor in instanceClass.constructors) {
        if (constructor.name == name) return constructor;
      }
    }

    /// Performs a similar lookup to [lookupConstructor], but using a slower
    /// implementation.
    Constructor lookupConstructorWithPatches(Name name, bool isSuper) {
      ClassBuilder builder = this.origin;

      ClassBuilder getSuperclass(ClassBuilder builder) {
        // This way of computing the superclass is slower than using the kernel
        // objects directly.
        Object supertype = builder.supertypeBuilder;
        if (supertype is NamedTypeBuilder) {
          Object builder = supertype.declaration;
          if (builder is ClassBuilder) return builder;
          if (builder is TypeAliasBuilder) {
            TypeDeclarationBuilder declarationBuilder =
                builder.unaliasDeclaration(supertype.arguments);
            if (declarationBuilder is ClassBuilder) return declarationBuilder;
          }
        }
        return null;
      }

      if (isSuper) {
        builder = getSuperclass(builder)?.origin;
      }
      if (builder != null) {
        Class cls = builder.cls;
        for (Constructor constructor in cls.constructors) {
          if (constructor.name == name) return constructor;
        }
      }
      return null;
    }

    return lookupConstructorWithPatches(name, isSuper);
  }
}

class ConstructorRedirection {
  String target;
  bool cycleReported;

  ConstructorRedirection(this.target) : cycleReported = false;
}