pkg/compiler/lib/src/js_model/element_map_impl.dart

// Copyright (c) 2017, 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:js_shared/variance.dart';
import 'package:kernel/ast.dart' as ir;
import 'package:kernel/class_hierarchy.dart' as ir;
import 'package:kernel/core_types.dart' as ir;
// ignore: implementation_imports
import 'package:kernel/src/bounds_checks.dart' as ir;
import 'package:kernel/text/debug_printer.dart';
import 'package:kernel/type_environment.dart' as ir;

import '../closure.dart' show BoxLocal;
import '../common.dart';
import '../common/elements.dart';
import '../common/names.dart';
import '../constants/values.dart';
import '../deferred_load/output_unit.dart' show LateOutputUnitDataBuilder;
import '../elements/entities.dart';
import '../elements/entity_map.dart';
import '../elements/entity_utils.dart' as utils;
import '../elements/names.dart';
import '../elements/types.dart';
import '../ir/closure.dart';
import '../ir/element_map.dart';
import '../ir/types.dart';
import '../ir/util.dart';
import '../ir/visitors.dart';
import '../js_backend/annotations.dart';
import '../js_backend/native_data.dart';
import '../kernel/dart2js_target.dart' show allowedNativeTest;
import '../kernel/element_map.dart';
import '../kernel/env.dart';
import '../native/behavior.dart';
import '../options.dart';
import '../ordered_typeset.dart';
import '../serialization/serialization.dart';
import '../universe/call_structure.dart';
import '../universe/member_usage.dart';
import '../universe/record_shape.dart';
import '../universe/selector.dart';
import 'class_type_variable_access.dart';
import 'closure.dart';
import 'element_map.dart';
import 'elements.dart';
import 'env.dart';
import 'locals.dart';
import 'records.dart'
    show JRecordClass, RecordClassData, JRecordGetter, RecordGetterData;

class JsKernelToElementMap implements JsToElementMap, IrToElementMap {
  /// Tag used for identifying serialized [JsKernelToElementMap] objects in a
  /// debugging data stream.
  static const String tag = 'js-kernel-to-element-map';

  /// Tags used for identifying serialized subsections of a
  /// [JsKernelToElementMap] object in a debugging data stream.
  static const String libraryTag = 'libraries';
  static const String classTag = 'classes';
  static const String memberTag = 'members';
  static const String typeVariableTag = 'type-variables';
  static const String nestedClosuresTag = 'nested-closures';

  final CompilerOptions options;
  @override
  final DiagnosticReporter reporter;
  late final JCommonElements _commonElements;
  late final JsElementEnvironment _elementEnvironment;
  late final DartTypeConverter _typeConverter;
  late final KernelDartTypes _types;
  late final ConstantValuefier _constantValuefier;

  /// Library environment. Used for fast lookup.
  late final JProgramEnv programEnv;

  final EntityDataEnvMap<JLibrary, JLibraryData, JLibraryEnv> libraries =
      EntityDataEnvMap<JLibrary, JLibraryData, JLibraryEnv>();
  final EntityDataEnvMap<JClass, JClassData, JClassEnv> classes =
      EntityDataEnvMap<JClass, JClassData, JClassEnv>();
  final EntityDataMap<JMember, JMemberData> members =
      EntityDataMap<JMember, JMemberData>();
  final EntityDataMap<JTypeVariable, JTypeVariableData> typeVariables =
      EntityDataMap<JTypeVariable, JTypeVariableData>();

  final Map<ir.Library, JLibrary> libraryMap = {};
  final Map<ir.Class, JClass> classMap = {};

  /// Map from [ir.TypeParameter] nodes to the corresponding
  /// [TypeVariableEntity].
  ///
  /// Normally the type variables are [JTypeVariable]s, but for type
  /// parameters on local function (in the frontend) these are _not_ since
  /// their type declaration is neither a class nor a member. In the backend,
  /// these type parameters belong to the call-method and are therefore indexed.
  final Map<ir.TypeParameter, TypeVariableEntity> typeVariableMap = {};
  final Map<ir.Member, JConstructor> constructorMap = {};
  final Map<ir.Procedure, JFunction> methodMap = {};
  final Map<ir.Field, JField> fieldMap = {};
  final Map<ir.TreeNode, Local> localFunctionMap = {};

  /// Map from members to the call methods created for their nested closures.
  final Map<JMember, List<JFunction>> _nestedClosureMap = {};

  /// NativeData is need for computation of the default super class and
  /// parameter ordering.
  late final NativeData nativeData;

  final Map<JFunction, JGeneratorBody> _generatorBodies = {};

  final Map<JClass, List<JMember>> _injectedClassMembers = {};

  late final LateOutputUnitDataBuilder lateOutputUnitDataBuilder;

  final Map<JMember, JMember> kToJMembers = {};

  JsKernelToElementMap(
    this.reporter,
    KernelToElementMap _elementMap,
    Map<MemberEntity, MemberUsage> liveMemberUsage,
    Iterable<MemberEntity> liveAbstractMembers,
    AnnotationsData annotations,
  ) : options = _elementMap.options {
    _elementEnvironment = JsElementEnvironment(this);
    _typeConverter = DartTypeConverter(this);
    _types = KernelDartTypes(this);
    _commonElements = JCommonElements(_types, _elementEnvironment);
    _constantValuefier = ConstantValuefier(this);

    programEnv = _elementMap.env.convert();

    _elementMap.libraries.forEach((
      JLibrary library,
      KLibraryData data,
      KLibraryEnv oldEnv,
    ) {
      JLibraryEnv newEnv = oldEnv.convert(_elementMap, liveMemberUsage);
      libraryMap[oldEnv.library] = libraries
          .register<JLibrary, JLibraryData, JLibraryEnv>(
            library,
            data.convert(),
            newEnv,
          );
      programEnv.registerLibrary(newEnv);
    });

    // TODO(johnniwinther): Filter unused classes.
    _elementMap.classes.forEach((JClass cls, KClassData data, KClassEnv env) {
      final library = cls.library;
      JClassEnv newEnv = env.convert(
        _elementMap,
        liveMemberUsage,
        liveAbstractMembers,
        (ir.Library library) => libraryMap[library]!,
      );
      classMap[env.cls] = classes.register(cls, data.convert(), newEnv);
      libraries.getEnv(library).registerClass(cls.name, newEnv);
    });

    _elementMap.members.forEach((JMember oldMember, KMemberData data) {
      MemberUsage? memberUsage = liveMemberUsage[oldMember];
      if (memberUsage == null && !liveAbstractMembers.contains(oldMember)) {
        // Ensure indices are consistent across both K- and J- entity maps since
        // some K- maps are queried after registration in J- world maps.
        members.skipIndex();
        return;
      }
      final library = oldMember.library;
      final cls = oldMember.enclosingClass;
      JMember? newMember;
      Name memberName = oldMember.memberName;

      // Only create a new entity if some parameters are unused and can be
      // elided.
      if (!annotations.hasNoElision(oldMember) &&
          memberUsage != null &&
          oldMember is JFunction &&
          !identical(
            oldMember.parameterStructure,
            memberUsage.invokedParameters,
          )) {
        if (oldMember is ConstructorEntity) {
          final newParameters = memberUsage.invokedParameters!;
          final constructor = oldMember as ConstructorEntity;
          if (constructor.isFactoryConstructor) {
            // TODO(redemption): This should be a JFunction.
            newMember = JFactoryConstructor(
              cls!,
              memberName,
              newParameters,
              isExternal: constructor.isExternal,
              isConst: constructor.isConst,
              isFromEnvironmentConstructor:
                  constructor.isFromEnvironmentConstructor,
            );
          } else {
            newMember = JGenerativeConstructor(
              cls!,
              memberName,
              newParameters,
              isExternal: constructor.isExternal,
              isConst: constructor.isConst,
            );
          }
        } else if (oldMember.isFunction && !oldMember.isAbstract) {
          final newParameters = memberUsage.invokedParameters!;
          newMember = JMethod(
            library,
            cls,
            memberName,
            newParameters,
            oldMember.asyncMarker,
            isStatic: oldMember.isStatic,
            isExternal: oldMember.isExternal,
            isAbstract: oldMember.isAbstract,
          );
        }
      }
      members.register(newMember ?? oldMember, data.convert());
      newMember ??= oldMember;
      kToJMembers[oldMember] = newMember;
      if (newMember is JField) {
        fieldMap[data.node as ir.Field] = newMember;
      } else if (newMember is ConstructorEntity) {
        constructorMap[data.node] = newMember as JConstructor;
      } else {
        methodMap[data.node as ir.Procedure] = newMember as JFunction;
      }
    });

    _elementMap.typeVariables.forEach((
      JTypeVariable oldTypeVariable,
      KTypeVariableData oldTypeVariableData,
    ) {
      // [JLocalTypeVariable] can have [Local] as a `typeDeclaration` but those
      // should never be inserted into the TypeVariable entity map.
      assert(
        oldTypeVariable.typeDeclaration is ClassEntity ||
            oldTypeVariable.typeDeclaration is MemberEntity,
      );

      MemberEntity? newTypeDeclaration;
      // TODO(johnniwinther): Skip type variables of unused classes.
      if (oldTypeVariable.typeDeclaration is MemberEntity) {
        final member = oldTypeVariable.typeDeclaration as JMember;
        newTypeDeclaration = kToJMembers[member];
        if (newTypeDeclaration == null) {
          // Ensure indices are consistent across both K- and J- entity maps
          // since some K- maps are queried after registration in J- world maps.
          typeVariables.skipIndex();
          return;
        }
      }
      JTypeVariable? newTypeVariable;
      if (newTypeDeclaration != null) {
        newTypeVariable = createTypeVariable(
          newTypeDeclaration,
          oldTypeVariable.name,
          oldTypeVariable.index,
        );
      }
      typeVariableMap[oldTypeVariableData.node] = typeVariables
          .register<JTypeVariable, JTypeVariableData>(
            newTypeVariable ?? oldTypeVariable,
            oldTypeVariableData.copy(),
          );
    });
    // TODO(johnniwinther): We should close the environment in the beginning of
    // this constructor but currently we need the [MemberEntity] to query if the
    // member is live, thus potentially creating the [MemberEntity] in the
    // process. Avoid this.
    _elementMap.envIsClosed = true;
  }

  JsKernelToElementMap.readFromDataSource(
    this.options,
    this.reporter,
    ir.Component component,
    DataSourceReader source,
  ) {
    _elementEnvironment = JsElementEnvironment(this);
    _typeConverter = DartTypeConverter(this);
    _types = KernelDartTypes(this);
    _commonElements = JCommonElements(_types, _elementEnvironment);
    _constantValuefier = ConstantValuefier(this);

    source.registerComponentLookup(ComponentLookup(component));

    programEnv = JProgramEnv([component]);

    source.begin(tag);
    source.begin(libraryTag);
    int libraryCount = source.readInt();
    for (int i = 0; i < libraryCount; i++) {
      JLibrary library = source.readLibrary() as JLibrary;
      JLibraryData data = JLibraryData.readFromDataSource(source);
      JLibraryEnv env = JLibraryEnv.readFromDataSource(source);
      libraryMap[env.library] = libraries.register(library, data, env);
      programEnv.registerLibrary(env);
    }
    source.end(libraryTag);

    source.begin(classTag);
    int classCount = source.readInt();
    for (int i = 0; i < classCount; i++) {
      JClass cls = source.readClass() as JClass;
      JClassData data = JClassData.readFromDataSource(source);
      JClassEnv env = JClassEnv.readFromDataSource(source);
      classes.register<JClass, JClassData, JClassEnv>(cls, data, env);
      if (env.cls != null) {
        classMap[env.cls!] = cls;
      }
      if (cls is! JContext && cls is! JClosureClass && cls is! JRecordClass) {
        // Synthesized classes are not part of the library environment.
        libraries.getEnv(cls.library).registerClass(cls.name, env);
      }
    }
    source.end(classTag);

    source.begin(memberTag);
    int memberCount = source.readInt();
    for (int i = 0; i < memberCount; i++) {
      JMember member = source.readMember() as JMember;
      JMemberData data = JMemberData.readFromDataSource(source);
      members.register(member, data);
      switch (data.definition.kind) {
        case MemberKind.regular:
        case MemberKind.constructor:
          final node = data.definition.node as ir.Member;
          if (member is JField) {
            fieldMap[node as ir.Field] = member;
          } else if (member is ConstructorEntity) {
            constructorMap[node] = member as JConstructor;
          } else {
            methodMap[node as ir.Procedure] = member as JFunction;
          }
          break;
        case MemberKind.closureCall:
        case MemberKind.closureField:
        case MemberKind.constructorBody:
        case MemberKind.generatorBody:
        case MemberKind.recordGetter:
        case MemberKind.signature:
        case MemberKind.parameterStub:
          break;
      }
    }
    source.end(memberTag);

    source.begin(typeVariableTag);
    int typeVariableCount = source.readInt();
    for (int i = 0; i < typeVariableCount; i++) {
      JTypeVariable typeVariable = source.readTypeVariable() as JTypeVariable;
      // TODO(natebiggs): Defer reading these type variables as they trigger
      //   loading of some method bodies in the Kernel AST.
      JTypeVariableData data = JTypeVariableData.readFromDataSource(source);
      typeVariableMap[data.node] = typeVariables.register(typeVariable, data);
    }
    source.end(typeVariableTag);

    source.begin(nestedClosuresTag);
    _nestedClosureMap.addAll(
      source.readMemberMap(
        (MemberEntity member) => source.readMembers<JFunction>(),
      ),
    );
    source.end(nestedClosuresTag);

    _symbolLibraries.addAll(source.readConstantMap(() => source.readUri()));

    source.end(tag);
  }

  /// Prepares the entity maps for codegen serialization by creating all lazy
  /// member bodies and returning a list of them for serialization on the side.
  List<MemberEntity> prepareForCodegenSerialization() {
    final lazyMemberBodies = <MemberEntity>[];
    members.forEach((JMember member, JMemberData data) {
      if (member is JGenerativeConstructor) {
        lazyMemberBodies.add(
          getConstructorBody(data.definition.node as ir.Constructor),
        );
      }
      if (member is JFunction && member.asyncMarker != AsyncMarker.sync) {
        lazyMemberBodies.add(getGeneratorBody(member));
      }
    });
    return lazyMemberBodies;
  }

  void registerLazyMemberBodies(List<MemberEntity> lazyMemberBodies) {
    for (var member in lazyMemberBodies) {
      if (member is JConstructorBody) {
        final constructor = member.constructor;
        final data = members.getData(constructor) as JConstructorData;
        final constructorBody = data.constructorBody;
        if (constructorBody == null) {
          _registerConstructorBody(constructor, data, member);
        } else {
          // The same member can be created by different codegen shards but each
          // should point to the same member data.
          members.markAsCopy(original: constructorBody, copy: member);
        }
      } else if (member is JGeneratorBody) {
        final function = member.function;
        final generatorBody = _generatorBodies[function];
        if (generatorBody == null) {
          final data = members.getData(function) as FunctionData;
          _registerGeneratorBody(function, data, member);
        } else {
          // The same member can be created by different codegen shards but each
          // should point to the same member data.
          members.markAsCopy(original: generatorBody, copy: member);
        }
      }
    }
  }

  /// Serializes this [JsToElementMap] to [sink].
  void writeToDataSink(DataSinkWriter sink) {
    sink.begin(tag);

    // Serialize the entities before serializing the data.
    sink.begin(libraryTag);
    sink.writeInt(libraries.length);
    libraries.forEach((JLibrary library, JLibraryData data, JLibraryEnv env) {
      sink.writeLibrary(library);
      data.writeToDataSink(sink);
      env.writeToDataSink(sink);
    });
    sink.end(libraryTag);

    sink.begin(classTag);
    sink.writeInt(classes.length);
    classes.forEach((JClass cls, JClassData data, JClassEnv env) {
      sink.writeClass(cls);
      data.writeToDataSink(sink);
      env.writeToDataSink(sink);
    });
    sink.end(classTag);

    sink.begin(memberTag);
    sink.writeInt(members.length);
    members.forEach((JMember member, JMemberData data) {
      sink.writeMember(member);
      data.writeToDataSink(sink);
    });
    sink.end(memberTag);

    sink.begin(typeVariableTag);
    sink.writeInt(typeVariables.length);
    typeVariables.forEach((JTypeVariable typeVariable, JTypeVariableData data) {
      sink.writeTypeVariable(typeVariable);
      data.writeToDataSink(sink);
    });
    sink.end(typeVariableTag);

    sink.begin(nestedClosuresTag);
    sink.writeMemberMap(_nestedClosureMap, (member, value) {
      sink.writeMembers(value);
    });
    sink.end(nestedClosuresTag);

    sink.writeConstantMap(_symbolLibraries, (Uri uri) => sink.writeUri(uri));

    sink.end(tag);
  }

  @override
  DartTypes get types => _types;

  @override
  JsElementEnvironment get elementEnvironment => _elementEnvironment;

  @override
  JCommonElements get commonElements => _commonElements;

  FunctionEntity? get _mainFunction {
    return programEnv.mainMethod != null
        ? getMethodInternal(programEnv.mainMethod as ir.Procedure)
        : null;
  }

  LibraryEntity? get _mainLibrary {
    return programEnv.mainMethod != null
        ? getLibraryInternal(programEnv.mainMethod!.enclosingLibrary)
        : null;
  }

  SourceSpan getSourceSpan(Spannable? spannable, Entity? currentElement) {
    SourceSpan fromSpannable(Spannable? spannable) {
      if (spannable is JLibrary) {
        JLibraryEnv env = libraries.getEnv(spannable);
        return computeSourceSpanFromTreeNode(env.library);
      } else if (spannable is JClass) {
        JClassData data = classes.getData(spannable);
        return data.definition.location;
      } else if (spannable is JMember) {
        JMemberData data = members.getData(spannable);
        return data.definition.location;
      } else if (spannable is JLocal) {
        return getSourceSpan(spannable.memberContext, currentElement);
      }
      return SourceSpan.unknown();
    }

    SourceSpan sourceSpan = fromSpannable(spannable);
    if (sourceSpan.isKnown) return sourceSpan;
    return fromSpannable(currentElement);
  }

  LibraryEntity? lookupLibrary(Uri uri) {
    JLibraryEnv? libraryEnv = programEnv.lookupLibrary(uri);
    if (libraryEnv == null) return null;
    return getLibraryInternal(libraryEnv.library, libraryEnv);
  }

  String _getLibraryName(JLibrary library) {
    assert(checkFamily(library));
    JLibraryEnv libraryEnv = libraries.getEnv(library);
    return libraryEnv.library.name ?? '';
  }

  MemberEntity? lookupLibraryMember(
    JLibrary library,
    String name, {
    bool setter = false,
  }) {
    assert(checkFamily(library));
    JLibraryEnv libraryEnv = libraries.getEnv(library);
    ir.Member? member = libraryEnv.lookupMember(name, setter: setter);
    return member != null ? getMember(member) : null;
  }

  void _forEachLibraryMember(
    JLibrary library,
    void Function(MemberEntity member) f,
  ) {
    assert(checkFamily(library));
    JLibraryEnv libraryEnv = libraries.getEnv(library);
    libraryEnv.forEachMember((ir.Member node) {
      f(getMember(node));
    });
  }

  ClassEntity? lookupClass(JLibrary library, String name) {
    assert(checkFamily(library));
    JLibraryEnv libraryEnv = libraries.getEnv(library);
    JClassEnv? classEnv = libraryEnv.lookupClass(name);
    if (classEnv != null) {
      return getClassInternal(classEnv.cls!, classEnv);
    }
    return null;
  }

  void _forEachClass(JLibrary library, void Function(ClassEntity cls) f) {
    assert(checkFamily(library));
    JLibraryEnv libraryEnv = libraries.getEnv(library);
    libraryEnv.forEachClass((JClassEnv classEnv) {
      if (!classEnv.isUnnamedMixinApplication) {
        f(getClassInternal(classEnv.cls!, classEnv));
      }
    });
  }

  MemberEntity? lookupClassMember(JClass cls, Name name) {
    assert(checkFamily(cls));
    JClassEnv classEnv = classes.getEnv(cls);
    return classEnv.lookupMember(this, name);
  }

  ConstructorEntity? lookupConstructor(JClass cls, String name) {
    assert(checkFamily(cls));
    JClassEnv classEnv = classes.getEnv(cls);
    return classEnv.lookupConstructor(this, name);
  }

  @override
  InterfaceType createInterfaceType(
    ir.Class cls,
    List<ir.DartType> typeArguments,
  ) {
    return types.interfaceType(getClass(cls), getDartTypes(typeArguments));
  }

  @override
  LibraryEntity getLibrary(ir.Library node) => getLibraryInternal(node);

  @override
  ClassEntity getClass(ir.Class node) => getClassInternal(node);

  @override
  InterfaceType? getSuperType(JClass cls) {
    assert(checkFamily(cls));
    JClassData data = classes.getData(cls);
    _ensureSupertypes(cls, data);
    return data.supertype;
  }

  void _ensureCallType(ClassEntity cls, JClassData data) {
    assert(checkFamily(cls));
    if (data is JClassDataImpl && !data.isCallTypeComputed) {
      MemberEntity? callMember = _elementEnvironment.lookupClassMember(
        cls,
        Names.call,
      );
      if (callMember is FunctionEntity &&
          callMember.isFunction &&
          !callMember.isAbstract) {
        data.callType = _elementEnvironment.getFunctionType(callMember);
      }
      data.isCallTypeComputed = true;
    }
  }

  void _ensureThisAndRawType(ClassEntity cls, JClassData data) {
    assert(checkFamily(cls));
    if (data is JClassDataImpl && data.thisType == null) {
      ir.Class node = data.cls;
      if (node.typeParameters.isEmpty) {
        data.thisType = data.rawType = types.interfaceType(
          cls,
          const <DartType>[],
        );
      } else {
        data.thisType = types.interfaceType(
          cls,
          List<DartType>.generate(node.typeParameters.length, (int index) {
            return types.typeVariableType(
              getTypeVariableInternal(node.typeParameters[index]),
            );
          }),
        );
        data.rawType = types.interfaceType(
          cls,
          List<DartType>.filled(
            node.typeParameters.length,
            types.dynamicType(),
          ),
        );
      }
    }
  }

  void _ensureJsInteropType(ClassEntity cls, JClassData data) {
    assert(checkFamily(cls));
    if (data is JClassDataImpl && data.jsInteropType == null) {
      ir.Class node = data.cls;
      if (node.typeParameters.isEmpty) {
        _ensureThisAndRawType(cls, data);
        data.jsInteropType = data.thisType;
      } else {
        data.jsInteropType = types.interfaceType(
          cls,
          List<DartType>.filled(node.typeParameters.length, types.anyType()),
        );
      }
    }
  }

  void _ensureClassInstantiationToBounds(ClassEntity cls, JClassData data) {
    assert(checkFamily(cls));
    if (data is JClassDataImpl && data.instantiationToBounds == null) {
      ir.Class node = data.cls;
      if (node.typeParameters.isEmpty) {
        _ensureThisAndRawType(cls, data);
        data.instantiationToBounds = data.thisType;
      } else {
        data.instantiationToBounds = getInterfaceType(
          ir.instantiateToBounds(
            coreTypes.nonNullableRawType(node),
            coreTypes.objectClass,
          ) as ir.InterfaceType,
        );
      }
    }
  }

  @override
  TypeVariableEntity getTypeVariable(ir.TypeParameter node) =>
      getTypeVariableInternal(node);

  void _ensureSupertypes(ClassEntity cls, JClassData data) {
    assert(checkFamily(cls));
    if (data is JClassDataImpl && data.orderedTypeSet == null) {
      _ensureThisAndRawType(cls, data);

      ir.Class node = data.cls;

      if (node.supertype == null) {
        data.orderedTypeSet = OrderedTypeSet.singleton(data.thisType!);
        data.isMixinApplication = false;
        data.interfaces = const <InterfaceType>[];
      } else {
        // Set of canonical supertypes.
        //
        // This is necessary to support when a class implements the same
        // supertype in multiple non-conflicting ways, like implementing A<int*>
        // and A<int?> or B<Object?> and B<dynamic>.
        Set<InterfaceType> canonicalSupertypes = {};

        InterfaceType processSupertype(ir.Supertype supertypeNode) {
          supertypeNode = classHierarchy.getClassAsInstanceOf(
            node,
            supertypeNode.classNode,
          )!;
          InterfaceType supertype = _typeConverter.visitSupertype(
            supertypeNode,
          );
          canonicalSupertypes.add(supertype);
          final superclass = supertype.element as JClass;
          JClassData superdata = classes.getData(superclass);
          _ensureSupertypes(superclass, superdata);
          for (InterfaceType supertype
              in superdata.orderedTypeSet!.supertypes!) {
            ClassDefinition definition = getClassDefinition(supertype.element);
            if (definition.kind == ClassKind.regular) {
              ir.Supertype? canonicalSupertype = classHierarchy
                  .getClassAsInstanceOf(node, definition.node as ir.Class);
              if (canonicalSupertype != null) {
                supertype = _typeConverter.visitSupertype(canonicalSupertype);
              } else {
                assert(
                  supertype.typeArguments.isEmpty,
                  "Generic synthetic supertypes are not supported",
                );
              }
            }
            canonicalSupertypes.add(supertype);
          }
          return supertype;
        }

        InterfaceType supertype;
        List<InterfaceType> interfaces = <InterfaceType>[];
        if (node.isMixinDeclaration) {
          // A mixin declaration
          //
          //   mixin M on A, B, C {}
          //
          // is encoded by CFE as
          //
          //   abstract class M extends A implements B, C {}
          //   abstract class M extends A&B&C {}
          //
          // but we encode it as
          //
          //   abstract class M extends Object implements A, B, C {}
          //
          // so we need get the superclasses from the on-clause, A, B, and C,
          // through [superclassConstraints].
          for (ir.Supertype constraint in node.onClause) {
            interfaces.add(processSupertype(constraint));
          }
          // Set superclass to `Object`.
          supertype = _commonElements.objectType;
        } else {
          supertype = processSupertype(node.supertype!);
        }
        if (supertype == _commonElements.objectType) {
          ClassEntity defaultSuperclass = _commonElements.getDefaultSuperclass(
            cls,
            nativeData,
          );
          InterfaceType defaultSupertype = data.supertype = _elementEnvironment
              .getRawType(defaultSuperclass);
          assert(
            defaultSupertype.typeArguments.isEmpty,
            "Generic default supertypes are not supported",
          );
          canonicalSupertypes.add(defaultSupertype);
        } else {
          data.supertype = supertype;
        }
        if (node.mixedInType != null) {
          data.isMixinApplication = true;
          interfaces.add(
            data.mixedInType = processSupertype(node.mixedInType!),
          );
        } else {
          data.isMixinApplication = false;
        }
        for (var supertype in node.implementedTypes) {
          interfaces.add(processSupertype(supertype));
        }
        OrderedTypeSetBuilder setBuilder = KernelOrderedTypeSetBuilder(
          this,
          cls,
        );
        data.orderedTypeSet = setBuilder.createOrderedTypeSet(
          canonicalSupertypes,
        );
        data.interfaces = interfaces;
      }
    }
  }

  @override
  MemberEntity getMember(ir.Member node) {
    if (node is ir.Field) {
      return getFieldInternal(node);
    } else if (node is ir.Constructor) {
      return getConstructorInternal(node);
    } else if (node is ir.Procedure) {
      if (node.kind == ir.ProcedureKind.Factory) {
        return getConstructorInternal(node);
      } else {
        return getMethodInternal(node);
      }
    }
    throw UnsupportedError("Unexpected member: $node");
  }

  @override
  ConstructorEntity getConstructor(ir.Member node) =>
      getConstructorInternal(node);

  ConstructorEntity getSuperConstructor(
    ir.Constructor sourceNode,
    ir.Member targetNode,
  ) {
    ConstructorEntity source = getConstructor(sourceNode);
    final sourceClass = source.enclosingClass as JClass;
    ConstructorEntity target = getConstructor(targetNode);
    ClassEntity targetClass = target.enclosingClass;
    JClass superClass = getSuperType(sourceClass)!.element as JClass;
    if (superClass == targetClass) return target;
    JClassEnv env = classes.getEnv(superClass);
    return env.lookupConstructor(this, target.name!)!;
  }

  @override
  FunctionEntity getMethod(ir.Procedure node) => getMethodInternal(node);

  @override
  bool containsMethod(ir.Procedure node) => methodMap.containsKey(node);

  @override
  FieldEntity getField(ir.Field node) => getFieldInternal(node);

  @override
  DartType getDartType(ir.DartType type) => _typeConverter.visitType(type);

  @override
  TypeVariableType getTypeVariableType(ir.TypeParameterType type) =>
      getDartType(type).withoutNullability as TypeVariableType;

  @override
  List<DartType> getDartTypes(List<ir.DartType> types) {
    List<DartType> list = <DartType>[];
    for (var type in types) {
      list.add(getDartType(type));
    }
    return list;
  }

  @override
  InterfaceType getInterfaceType(ir.InterfaceType type) =>
      _typeConverter.visitType(type).withoutNullability as InterfaceType;

  @override
  FunctionType getFunctionType(ir.FunctionNode node) {
    DartType returnType;
    if (node.parent is ir.Constructor) {
      // The return type on generative constructors is `void`, but we need
      // `dynamic` type to match the element model.
      returnType = types.dynamicType();
    } else {
      returnType = getDartType(node.returnType);
    }
    List<DartType> parameterTypes = <DartType>[];
    List<DartType> optionalParameterTypes = <DartType>[];

    DartType getParameterType(ir.Variable variable) {
      // isCovariant implies this FunctionNode is a class Procedure.
      var isCovariant =
          variable.isCovariantByDeclaration || variable.isCovariantByClass;
      return types.getTearOffParameterType(
        getDartType(variable.type),
        isCovariant,
      );
    }

    for (ir.PositionalParameter parameter in node.positionalParameters) {
      if (parameterTypes.length == node.requiredParameterCount) {
        optionalParameterTypes.add(getParameterType(parameter));
      } else {
        parameterTypes.add(getParameterType(parameter));
      }
    }
    var namedParameters = <String>[];
    var requiredNamedParameters = <String>{};
    List<DartType> namedParameterTypes = [];
    List<ir.NamedParameter> sortedNamedParameters =
        node.namedParameters.toList()
          ..sort((a, b) => a.parameterName.compareTo(b.parameterName));
    for (ir.NamedParameter parameter in sortedNamedParameters) {
      namedParameters.add(parameter.parameterName);
      namedParameterTypes.add(getParameterType(parameter));
      if (parameter.isRequired) {
        requiredNamedParameters.add(parameter.parameterName);
      }
    }
    List<FunctionTypeVariable> typeVariables;
    if (node.typeParameters.isNotEmpty) {
      List<DartType> typeParameters = <DartType>[];
      for (ir.TypeParameter typeParameter in node.typeParameters) {
        typeParameters.add(
          getDartType(
            ir.TypeParameterType(typeParameter, ir.Nullability.nonNullable),
          ),
        );
      }
      typeVariables = List<FunctionTypeVariable>.generate(
        node.typeParameters.length,
        (int index) => types.functionTypeVariable(index),
      );

      DartType subst(DartType type) {
        return types.subst(typeVariables, typeParameters, type);
      }

      returnType = subst(returnType);
      parameterTypes = parameterTypes.map(subst).toList();
      optionalParameterTypes = optionalParameterTypes.map(subst).toList();
      namedParameterTypes = namedParameterTypes.map(subst).toList();
      for (int index = 0; index < typeVariables.length; index++) {
        typeVariables[index].bound = subst(
          getDartType(node.typeParameters[index].bound),
        );
      }
    } else {
      typeVariables = const <FunctionTypeVariable>[];
    }

    return types.functionType(
      returnType,
      parameterTypes,
      optionalParameterTypes,
      namedParameters,
      requiredNamedParameters,
      namedParameterTypes,
      typeVariables,
    );
  }

  @override
  DartType substByContext(DartType type, InterfaceType context) {
    return types.subst(
      context.typeArguments,
      getThisType(context.element as JClass).typeArguments,
      type,
    );
  }

  /// Returns the type of the `call` method on 'type'.
  ///
  /// If [type] doesn't have a `call` member or has a non-method `call` member,
  /// `null` is returned.
  @override
  FunctionType? getCallType(InterfaceType type) {
    final cls = type.element as JClass;
    assert(checkFamily(cls));
    JClassData data = classes.getData(cls);
    _ensureCallType(cls, data);
    if (data.callType != null) {
      return substByContext(data.callType!, type) as FunctionType;
    }
    return null;
  }

  @override
  InterfaceType getThisType(JClass cls) {
    assert(checkFamily(cls));
    JClassData data = classes.getData(cls);
    _ensureThisAndRawType(cls, data);
    return data.thisType!;
  }

  InterfaceType _getJsInteropType(JClass cls) {
    assert(checkFamily(cls));
    JClassData data = classes.getData(cls);
    _ensureJsInteropType(cls, data);
    return data.jsInteropType!;
  }

  InterfaceType _getRawType(JClass cls) {
    assert(checkFamily(cls));
    JClassData data = classes.getData(cls);
    _ensureThisAndRawType(cls, data);
    return data.rawType!;
  }

  InterfaceType _getClassInstantiationToBounds(JClass cls) {
    assert(checkFamily(cls));
    JClassData data = classes.getData(cls);
    _ensureClassInstantiationToBounds(cls, data);
    return data.instantiationToBounds!;
  }

  FunctionType _getFunctionType(JFunction function) {
    assert(checkFamily(function));
    final data = members.getData(function) as FunctionData;
    return data.getFunctionType(this);
  }

  List<TypeVariableType> _getFunctionTypeVariables(JFunction function) {
    assert(checkFamily(function));
    final data = members.getData(function) as FunctionData;
    return data.getFunctionTypeVariables(this);
  }

  DartType _getFieldType(JField field) {
    assert(checkFamily(field));
    final data = members.getData(field) as JFieldData;
    return data.getFieldType(this);
  }

  bool _isFieldCovariantByDeclaration(JField field) {
    assert(checkFamily(field));
    final data = members.getData(field) as JFieldData;
    return data.isCovariantByDeclaration;
  }

  @override
  DartType getTypeVariableBound(JTypeVariable typeVariable) {
    assert(checkFamily(typeVariable));
    JTypeVariableData data = typeVariables.getData(typeVariable);
    return data.getBound(this);
  }

  @override
  List<Variance> getTypeVariableVariances(JClass cls) {
    assert(checkFamily(cls));
    JClassData data = classes.getData(cls);
    return data.getVariances();
  }

  final Map<ConstantValue, Uri> _symbolLibraries = {};

  @override
  void registerSymbolLibrary(ConstantValue value, Uri libraryUri) {
    _symbolLibraries[value] = libraryUri;
  }

  @override
  Uri? getSymbolLibraryUri(ConstantValue value) {
    return _symbolLibraries[value];
  }

  DartType _getTypeVariableDefaultType(JTypeVariable typeVariable) {
    assert(checkFamily(typeVariable));
    JTypeVariableData data = typeVariables.getData(typeVariable);
    return data.getDefaultType(this);
  }

  ClassEntity? getAppliedMixin(JClass cls) {
    assert(checkFamily(cls));
    JClassData data = classes.getData(cls);
    _ensureSupertypes(cls, data);
    return data.mixedInType?.element;
  }

  bool _isMixinApplication(JClass cls) {
    assert(checkFamily(cls));
    JClassData data = classes.getData(cls);
    _ensureSupertypes(cls, data);
    return data.isMixinApplication!;
  }

  bool _isUnnamedMixinApplication(JClass cls) {
    assert(checkFamily(cls));
    JClassEnv env = classes.getEnv(cls);
    return env.isUnnamedMixinApplication;
  }

  bool _isMixinApplicationWithMembers(JClass cls) {
    assert(checkFamily(cls));
    JClassEnv env = classes.getEnv(cls);
    return env.isMixinApplicationWithMembers;
  }

  void _forEachSupertype(JClass cls, void Function(InterfaceType supertype) f) {
    assert(checkFamily(cls));
    JClassData data = classes.getData(cls);
    _ensureSupertypes(cls, data);
    data.orderedTypeSet!.supertypes!.forEach(f);
  }

  void _forEachConstructor(
    JClass cls,
    void Function(ConstructorEntity member) f,
  ) {
    assert(checkFamily(cls));
    JClassEnv env = classes.getEnv(cls);
    env.forEachConstructor(this, f);
  }

  void _forEachLocalClassMember(
    JClass cls,
    void Function(MemberEntity member) f,
  ) {
    assert(checkFamily(cls));
    JClassEnv env = classes.getEnv(cls);
    env.forEachMember(this, (MemberEntity member) {
      f(member);
    });
  }

  void _forEachClassMember(
    JClass cls,
    void Function(ClassEntity cls, MemberEntity member) f,
  ) {
    assert(checkFamily(cls));
    JClassEnv env = classes.getEnv(cls);
    env.forEachMember(this, (MemberEntity member) {
      f(cls, member);
    });
    JClassData data = classes.getData(cls);
    _ensureSupertypes(cls, data);
    if (data.supertype != null) {
      _forEachClassMember(data.supertype!.element as JClass, f);
    }
  }

  @override
  InterfaceType? asInstanceOf(InterfaceType type, ClassEntity cls) {
    assert(checkFamily(cls));
    OrderedTypeSet orderedTypeSet = getOrderedTypeSet(type.element as JClass);
    InterfaceType? supertype = orderedTypeSet.asInstanceOf(
      cls,
      getHierarchyDepth(cls as JClass),
    );
    if (supertype != null) {
      supertype = substByContext(supertype, type) as InterfaceType;
    }
    return supertype;
  }

  @override
  OrderedTypeSet getOrderedTypeSet(JClass cls) {
    assert(checkFamily(cls));
    JClassData data = classes.getData(cls);
    _ensureSupertypes(cls, data);
    return data.orderedTypeSet!;
  }

  @override
  int getHierarchyDepth(JClass cls) {
    assert(checkFamily(cls));
    JClassData data = classes.getData(cls);
    _ensureSupertypes(cls, data);
    return data.orderedTypeSet!.maxDepth;
  }

  @override
  Iterable<InterfaceType> getInterfaces(JClass cls) {
    assert(checkFamily(cls));
    JClassData data = classes.getData(cls);
    _ensureSupertypes(cls, data);
    return data.interfaces;
  }

  MemberDefinition getMemberDefinitionInternal(JMember member) {
    assert(checkFamily(member));
    return members.getData(member).definition;
  }

  ClassDefinition getClassDefinitionInternal(JClass cls) {
    assert(checkFamily(cls));
    return classes.getData(cls).definition;
  }

  @override
  ImportEntity getImport(ir.LibraryDependency node) {
    ir.Library library = node.enclosingLibrary;
    JLibraryData data = libraries.getData(
      getLibraryInternal(library) as JLibrary,
    );
    return data.imports[node]!;
  }

  @override
  late final ir.CoreTypes coreTypes = ir.CoreTypes(programEnv.mainComponent);

  late final ir.TypeEnvironment typeEnvironment = ir.TypeEnvironment(
    coreTypes,
    classHierarchy,
  );

  late final ir.ClassHierarchy classHierarchy = ir.ClassHierarchy(
    programEnv.mainComponent,
    coreTypes,
  );

  @override
  Name getName(ir.Name name, {bool setter = false}) {
    return Name(
      name.text,
      name.isPrivate ? name.library!.importUri : null,
      isSetter: setter,
    );
  }

  @override
  CallStructure getCallStructure(ir.Arguments arguments) {
    int argumentCount = arguments.positional.length + arguments.named.length;
    List<String> namedArguments = arguments.named.map((e) => e.name).toList();
    return CallStructure(argumentCount, namedArguments, arguments.types.length);
  }

  @override
  Selector getSelector(ir.Expression node) {
    // TODO(efortuna): This is screaming for a common interface between
    // PropertyGet and SuperPropertyGet (and same for *Get). Talk to kernel
    // folks.
    if (node is ir.InstanceGet) {
      return getGetterSelector(node.name);
    }
    if (node is ir.InstanceTearOff) {
      return getGetterSelector(node.name);
    }
    if (node is ir.DynamicGet) {
      return getGetterSelector(node.name);
    }
    if (node is ir.FunctionTearOff) {
      return getGetterSelector(ir.Name.callName);
    }
    if (node is ir.SuperPropertyGet) {
      return getGetterSelector(node.name);
    }
    if (node is ir.InstanceSet) {
      return getSetterSelector(node.name);
    }
    if (node is ir.DynamicSet) {
      return getSetterSelector(node.name);
    }
    if (node is ir.SuperPropertySet) {
      return getSetterSelector(node.name);
    }
    if (node is ir.InvocationExpression) {
      return getInvocationSelector(node);
    }
    throw failedAt(
      currentElementSpannable,
      "Can only get the selector for a property get or an invocation: "
      "$node",
    );
  }

  Selector getInvocationSelector(ir.InvocationExpression invocation) {
    Name name = getName(invocation.name);
    SelectorKind kind;
    if (Selector.isOperatorName(name.text)) {
      if (name == Names.indexName || name == Names.indexSetName) {
        kind = SelectorKind.index_;
      } else {
        kind = SelectorKind.operator;
      }
    } else {
      kind = SelectorKind.call;
    }

    CallStructure callStructure = getCallStructure(invocation.arguments);
    return Selector(kind, name, callStructure);
  }

  Selector getGetterSelector(ir.Name irName) {
    Name name = Name(
      irName.text,
      irName.isPrivate ? irName.library!.importUri : null,
    );
    return Selector.getter(name);
  }

  Selector getSetterSelector(ir.Name irName) {
    Name name = Name(
      irName.text,
      irName.isPrivate ? irName.library!.importUri : null,
    );
    return Selector.setter(name);
  }

  /// Looks up [typeName] for use in the spec-string of a `JS` call.
  // TODO(johnniwinther): Use this in [native.NativeBehavior] instead of calling
  // the `ForeignResolver`.
  TypeLookup typeLookup({bool resolveAsRaw = true}) {
    return resolveAsRaw
        ? (_cachedTypeLookupRaw ??= _typeLookup(resolveAsRaw: true))
        : (_cachedTypeLookupFull ??= _typeLookup(resolveAsRaw: false));
  }

  TypeLookup? _cachedTypeLookupRaw;
  TypeLookup? _cachedTypeLookupFull;

  TypeLookup _typeLookup({required bool resolveAsRaw}) {
    bool? cachedMayLookupInMain;

    DartType? lookup(String typeName, {bool required = false}) {
      DartType? findInLibrary(LibraryEntity? library) {
        if (library != null) {
          ClassEntity? cls = elementEnvironment.lookupClass(library, typeName);
          if (cls != null) {
            // TODO(johnniwinther): Align semantics.
            return resolveAsRaw
                ? elementEnvironment.getRawType(cls)
                : elementEnvironment.getThisType(cls);
          }
        }
        return null;
      }

      DartType? findIn(Uri uri) {
        return findInLibrary(elementEnvironment.lookupLibrary(uri));
      }

      // TODO(johnniwinther): Narrow the set of lookups based on the depending
      // library.
      // TODO(johnniwinther): Cache more results to avoid redundant lookups?
      cachedMayLookupInMain ??=
          // Tests permit lookup outside of dart: libraries.
          allowedNativeTest(elementEnvironment.mainLibrary!.canonicalUri);
      DartType? type;
      if (cachedMayLookupInMain!) {
        type ??= findInLibrary(elementEnvironment.mainLibrary);
      }
      type ??= findIn(Uris.dartCore);
      type ??= findIn(Uris.dartJSHelper);
      type ??= findIn(Uris.dartLateHelper);
      type ??= findIn(Uris.dartInterceptors);
      type ??= findIn(Uris.dartNativeTypedData);
      type ??= findIn(Uris.dartCollection);
      type ??= findIn(Uris.dartMath);
      type ??= findIn(Uris.dartHtml);
      type ??= findIn(Uris.dartHtmlCommon);
      type ??= findIn(Uris.dartSvg);
      type ??= findIn(Uris.dartWebAudio);
      type ??= findIn(Uris.dartWebGL);
      type ??= findIn(Uris.dartIndexedDB);
      type ??= findIn(Uris.dartTypedData);
      type ??= findIn(Uris.dartRti);
      type ??= findIn(Uris.dartMirrors);
      if (type == null && required) {
        reporter.reportErrorMessage(
          currentElementSpannable,
          MessageKind.generic,
          {'text': "Type '$typeName' not found."},
        );
      }
      return type;
    }

    return lookup;
  }

  String? _getStringArgument(ir.StaticInvocation node, int index) {
    return node.arguments.positional[index].accept(Stringifier());
  }

  // TODO(johnniwinther): Cache this for later use.
  @override
  NativeBehavior getNativeBehaviorForJsCall(ir.StaticInvocation node) {
    if (node.arguments.positional.length < 2 ||
        node.arguments.named.isNotEmpty) {
      reporter.reportErrorMessage(
        currentElementSpannable,
        MessageKind.wrongArgumentForJS,
      );
      return NativeBehavior();
    }
    String? specString = _getStringArgument(node, 0);
    if (specString == null) {
      reporter.reportErrorMessage(
        currentElementSpannable,
        MessageKind.wrongArgumentForJSFirst,
      );
      return NativeBehavior();
    }

    String? codeString = _getStringArgument(node, 1);
    if (codeString == null) {
      reporter.reportErrorMessage(
        currentElementSpannable,
        MessageKind.wrongArgumentForJSSecond,
      );
      return NativeBehavior();
    }

    return NativeBehavior.ofJsCall(
      specString,
      codeString,
      typeLookup(resolveAsRaw: true),
      currentElementSpannable,
      reporter,
      commonElements,
    );
  }

  // TODO(johnniwinther): Cache this for later use.
  @override
  NativeBehavior getNativeBehaviorForJsBuiltinCall(ir.StaticInvocation node) {
    if (node.arguments.positional.isEmpty) {
      reporter.internalError(
        currentElementSpannable,
        "JS builtin expression has no type.",
      );
    }
    if (node.arguments.positional.length < 2) {
      reporter.internalError(
        currentElementSpannable,
        "JS builtin is missing name.",
      );
    }
    String? specString = _getStringArgument(node, 0);
    if (specString == null) {
      reporter.internalError(
        currentElementSpannable,
        "Unexpected first argument.",
      );
    }
    return NativeBehavior.ofJsBuiltinCall(
      specString,
      typeLookup(resolveAsRaw: true),
      currentElementSpannable,
      reporter,
      commonElements,
    );
  }

  // TODO(johnniwinther): Cache this for later use.
  @override
  NativeBehavior getNativeBehaviorForJsEmbeddedGlobalCall(
    ir.StaticInvocation node,
  ) {
    if (node.arguments.positional.isEmpty) {
      reporter.internalError(
        currentElementSpannable,
        "JS embedded global expression has no type.",
      );
    }
    if (node.arguments.positional.length < 2) {
      reporter.internalError(
        currentElementSpannable,
        "JS embedded global is missing name.",
      );
    }
    if (node.arguments.positional.length > 2 ||
        node.arguments.named.isNotEmpty) {
      reporter.internalError(
        currentElementSpannable,
        "JS embedded global has more than 2 arguments.",
      );
    }
    String? specString = _getStringArgument(node, 0);
    if (specString == null) {
      reporter.internalError(
        currentElementSpannable,
        "Unexpected first argument.",
      );
    }
    return NativeBehavior.ofJsEmbeddedGlobalCall(
      specString,
      typeLookup(resolveAsRaw: true),
      currentElementSpannable,
      reporter,
      commonElements,
    );
  }

  @override
  ConstantValue? getConstantValue(
    ir.Expression? node, {
    bool requireConstant = true,
    bool implicitNull = false,
  }) {
    if (node == null) {
      if (!implicitNull) {
        throw failedAt(currentElementSpannable, 'No expression for constant.');
      }
      return NullConstantValue();
    } else if (node is ir.ConstantExpression) {
      return _constantValuefier.visitConstant(node.constant);
    } else if (requireConstant) {
      throw UnsupportedError(
        'No constant for ${DebugPrinter.prettyPrint(node)}',
      );
    } else {
      return null;
    }
  }

  @override
  ConstantValue getRequiredSentinelConstantValue() {
    return ConstructedConstantValue(_commonElements.requiredSentinelType, {});
  }

  JTypeVariable createTypeVariable(
    Entity typeDeclaration,
    String name,
    int index,
  ) {
    return JTypeVariable(typeDeclaration, name, index);
  }

  JConstructorBody createConstructorBody(
    ConstructorEntity constructor,
    ParameterStructure parameterStructure,
  ) {
    return JConstructorBody(constructor as JConstructor, parameterStructure);
  }

  JGeneratorBody createGeneratorBody(
    FunctionEntity function,
    DartType elementType,
  ) {
    return JGeneratorBody(function as JFunction, elementType);
  }

  void forEachNestedClosure(
    MemberEntity member,
    void Function(FunctionEntity closure) f,
  ) {
    assert(checkFamily(member));
    _nestedClosureMap[member]?.forEach(f);
  }

  @override
  InterfaceType? getMemberThisType(MemberEntity member) {
    return members.getData(member as JMember).getMemberThisType(this);
  }

  @override
  ClassTypeVariableAccess getClassTypeVariableAccessForMember(
    MemberEntity member,
  ) {
    return members.getData(member as JMember).classTypeVariableAccess;
  }

  bool checkFamily(Entity entity) {
    assert(
      '$entity'.startsWith(jsElementPrefix),
      failedAt(
        entity,
        "Unexpected entity $entity, expected family $jsElementPrefix.",
      ),
    );
    return true;
  }

  @override
  Spannable getSpannable(MemberEntity member, ir.Node node) =>
      node is ir.TreeNode
      ? computeSourceSpanFromTreeNode(node)
      : getSourceSpan(member, null);

  Iterable<LibraryEntity> get libraryListInternal {
    return libraryMap.values;
  }

  LibraryEntity getLibraryInternal(ir.Library node, [JLibraryEnv? env]) =>
      libraryMap[node]!;

  ClassEntity getClassInternal(ir.Class node, [JClassEnv? env]) =>
      classMap[node]!;

  FieldEntity getFieldInternal(ir.Field node) => fieldMap[node]!;

  FunctionEntity getMethodInternal(ir.Procedure node) => methodMap[node]!;

  ConstructorEntity getConstructorInternal(ir.Member node) =>
      constructorMap[node]!;

  TypeVariableEntity getTypeVariableInternal(ir.TypeParameter node) {
    TypeVariableEntity? typeVariable = typeVariableMap[node];
    if (typeVariable == null) {
      final declaration = node.declaration;
      if (declaration is ir.Procedure) {
        int index = declaration.typeParameters.indexOf(node);
        if (declaration.kind == ir.ProcedureKind.Factory) {
          ir.Class cls = declaration.enclosingClass!;
          typeVariableMap[node] = typeVariable = getTypeVariableInternal(
            cls.typeParameters[index],
          );
        }
      }
    }
    if (typeVariable == null) {
      throw failedAt(
        currentElementSpannable,
        "No type variable entity for $node on "
        "${node.declaration}",
      );
    }
    return typeVariable;
  }

  @override
  FunctionEntity getConstructorBody(ir.Constructor node) {
    ConstructorEntity constructor = getConstructor(node);
    return _getConstructorBody(constructor as JConstructor);
  }

  JConstructorBody _getConstructorBody(JConstructor constructor) {
    JConstructorData data = members.getData(constructor) as JConstructorData;
    JConstructorBody? constructorBody = data.constructorBody;
    if (constructorBody == null) {
      /// The constructor calls the constructor body with all parameters.
      // TODO(johnniwinther): Remove parameters that are not used in the
      //  constructor body.
      ParameterStructure parameterStructure =
          _getParameterStructureFromFunctionNode(data.node.function!);

      constructorBody = createConstructorBody(constructor, parameterStructure);
      _registerConstructorBody(constructor, data, constructorBody);
    }
    return constructorBody;
  }

  void _registerConstructorBody(
    JConstructor constructor,
    JConstructorData data,
    JConstructorBody constructorBody,
  ) {
    members.register<JFunction, FunctionData>(
      constructorBody,
      ConstructorBodyDataImpl(
        data.node,
        data.node.function!,
        SpecialMemberDefinition(data.node, MemberKind.constructorBody),
      ),
    );
    final cls = constructor.enclosingClass;
    final classEnv = classes.getEnv(cls) as JClassEnvImpl;
    // TODO(johnniwinther): Avoid this by only including live members in the
    // js-model.
    classEnv.addConstructorBody(constructorBody);
    lateOutputUnitDataBuilder.registerColocatedMembers(
      constructor,
      constructorBody,
    );
    data.constructorBody = constructorBody;
  }

  @override
  MemberDefinition getMemberDefinition(MemberEntity member) {
    return getMemberDefinitionInternal(member as JMember);
  }

  @override
  ir.Member? getMemberContextNode(MemberEntity member) {
    ir.Member? getParentMember(ir.TreeNode? node) {
      while (node != null) {
        if (node is ir.Member) {
          return node;
        }
        node = node.parent;
      }
      return null;
    }

    MemberDefinition definition = getMemberDefinition(member);
    switch (definition.kind) {
      case MemberKind.regular:
      case MemberKind.constructor:
      case MemberKind.constructorBody:
        return definition.node as ir.Member;
      case MemberKind.closureCall:
      case MemberKind.closureField:
      case MemberKind.signature:
      case MemberKind.generatorBody:
        return getParentMember(definition.node as ir.TreeNode?);
      case MemberKind.parameterStub:
      case MemberKind.recordGetter:
        return null;
    }
  }

  @override
  ClassDefinition getClassDefinition(ClassEntity cls) {
    return getClassDefinitionInternal(cls as JClass);
  }

  /// Calls [f] for each parameter of [function] providing the type and name of
  /// the parameter and the [defaultValue] if the parameter is optional.
  void forEachParameter(
    JFunction function,
    void Function(DartType type, String? name, ConstantValue? defaultValue) f, {
    bool isNative = false,
  }) {
    final data = members.getData(function) as FunctionData;
    data.forEachParameter(
      this,
      function.parameterStructure,
      f,
      isNative: isNative,
    );
  }

  void forEachConstructorBody(
    JClass cls,
    void Function(ConstructorBodyEntity member) f,
  ) {
    JClassEnv env = classes.getEnv(cls);
    env.forEachConstructorBody(f);
  }

  void forEachInjectedClassMember(
    JClass cls,
    void Function(MemberEntity member) f,
  ) {
    _injectedClassMembers[cls]?.forEach(f);
  }

  JContextField _constructContextFieldEntry(
    InterfaceType? memberThisType,
    ir.Variable variable,
    BoxLocal boxLocal,
    Map<Name, MemberEntity> memberMap,
  ) {
    JContextField boxedField = JContextField(
      variable.cosmeticName!,
      boxLocal,
      isConst: variable.isConst,
    );
    members.register(
      boxedField,
      ClosureFieldData(
        ClosureMemberDefinition(
          computeSourceSpanFromTreeNode(variable),
          MemberKind.closureField,
          variable,
        ),
        memberThisType,
      ),
    );
    memberMap[boxedField.memberName] = boxedField;

    return boxedField;
  }

  /// Make a container controlling access to contexts, that is, variables that
  /// are accessed in different scopes. This function creates the container
  /// and returns a map of locals to the corresponding records created.
  @override
  Map<ir.Variable, JContextField> makeContextContainer(
    KernelScopeInfo info,
    MemberEntity member,
  ) {
    Map<ir.Variable, JContextField> boxedFields = {};
    if (info.boxedVariables.isNotEmpty) {
      NodeBox box = info.capturedVariablesAccessor!;

      Map<Name, JMember> memberMap = {};
      JContext container = JContext(member.library, box.name);
      BoxLocal boxLocal = BoxLocal(container);
      InterfaceType thisType = types.interfaceType(
        container,
        const <DartType>[],
      );
      InterfaceType supertype = commonElements.objectType;
      JClassData containerData = ContextClassData(
        ContextContainerDefinition(getMemberDefinition(member).location),
        thisType,
        supertype,
        getOrderedTypeSet(supertype.element as JClass)
            .extendClass(types, thisType),
      );
      classes.register(container, containerData, ContextEnv(memberMap));

      InterfaceType? memberThisType = member.enclosingClass != null
          ? elementEnvironment.getThisType(member.enclosingClass!)
          : null;
      for (ir.Variable variable in info.boxedVariables) {
        boxedFields[variable] = _constructContextFieldEntry(
          memberThisType,
          variable,
          boxLocal,
          memberMap,
        );
      }
    }
    return boxedFields;
  }

  ParameterStructure _getParameterStructureFromFunctionNode(
    ir.FunctionNode node,
  ) {
    int requiredPositionalParameters = node.requiredParameterCount;
    int positionalParameters = node.positionalParameters.length;
    int typeParameters = node.typeParameters.length;
    var namedParameters = <String>[];
    var requiredNamedParameters = <String>{};
    for (var p
        in node.namedParameters.toList()
          ..sort((a, b) => a.parameterName.compareTo(b.parameterName))) {
      namedParameters.add(p.parameterName);
      if (p.isRequired) {
        requiredNamedParameters.add(p.parameterName);
      }
    }
    return ParameterStructure(
      requiredPositionalParameters,
      positionalParameters,
      namedParameters,
      requiredNamedParameters,
      typeParameters,
    );
  }

  JsClosureClassInfo constructClosureClass(
    MemberEntity member,
    ir.FunctionNode node,
    JLibrary enclosingLibrary,
    Map<ir.Variable, JContextField> contextFieldsVisibleInScope,
    KernelScopeInfo info,
    InterfaceType supertype, {
    required bool createSignatureMethod,
  }) {
    InterfaceType? memberThisType = member.enclosingClass != null
        ? elementEnvironment.getThisType(member.enclosingClass!)
        : null;
    ClassTypeVariableAccess typeVariableAccess = members
        .getData(member as JMember)
        .classTypeVariableAccess;
    if (typeVariableAccess == ClassTypeVariableAccess.instanceField) {
      // A closure in a field initializer will only be executed in the
      // constructor and type variables are therefore accessed through
      // parameters.
      typeVariableAccess = ClassTypeVariableAccess.parameter;
    }
    String name = _computeClosureName(node);
    SourceSpan location = computeSourceSpanFromTreeNode(node);
    Map<Name, JMember> memberMap = {};

    JClass classEntity = JClosureClass(enclosingLibrary, name);
    // Create a classData and set up the interfaces and subclass
    // relationships that _ensureSupertypes and _ensureThisAndRawType are doing
    InterfaceType thisType = types.interfaceType(
      classEntity,
      const <DartType>[],
    );
    ClosureClassData closureData = ClosureClassData(
      ClosureClassDefinition(location),
      thisType,
      supertype,
      getOrderedTypeSet(supertype.element as JClass)
          .extendClass(types, thisType),
    );
    classes.register(classEntity, closureData, ClosureClassEnv(memberMap));

    Local? closureEntity;
    ir.Variable? closureEntityNode;
    if (node.parent is ir.FunctionDeclaration) {
      final parent = node.parent as ir.FunctionDeclaration;
      closureEntityNode = parent.variable;
    } else if (node.parent is ir.FunctionExpression) {
      closureEntity = AnonymousClosureLocal(classEntity as JClosureClass);
    }

    JFunction callMethod = JClosureCallMethod(
      classEntity,
      _getParameterStructureFromFunctionNode(node),
      getAsyncMarker(node),
    );
    _nestedClosureMap.putIfAbsent(member, () => <JFunction>[]).add(callMethod);
    // We need create the type variable here - before we try to make local
    // variables from them (in `JsScopeInfo.from` called through
    // `KernelClosureClassInfo.fromScopeInfo` below).
    int index = 0;
    for (ir.TypeParameter typeParameter in node.typeParameters) {
      typeVariableMap[typeParameter] = typeVariables.register(
        createTypeVariable(callMethod, typeParameter.name!, index),
        JTypeVariableData(typeParameter),
      );
      index++;
    }

    JsClosureClassInfo closureClassInfo = JsClosureClassInfo.fromScopeInfo(
      classEntity,
      node,
      <ir.Variable, JContextField>{},
      info,
      member.enclosingClass,
      closureEntity,
      closureEntityNode,
    );
    _buildClosureClassFields(
      closureClassInfo,
      member,
      memberThisType,
      info,
      contextFieldsVisibleInScope,
      memberMap,
    );

    if (createSignatureMethod) {
      _constructSignatureMethod(
        closureClassInfo,
        memberMap,
        node,
        memberThisType,
        location,
        typeVariableAccess,
      );
    }

    closureData.callType = getFunctionType(node);

    members.register<JFunction, FunctionData>(
      callMethod,
      ClosureFunctionData(
        ClosureMemberDefinition(location, MemberKind.closureCall, node.parent!),
        memberThisType,
        closureData.callType!,
        node,
        typeVariableAccess,
      ),
    );
    memberMap[callMethod.memberName] = closureClassInfo.callMethod = callMethod;
    return closureClassInfo;
  }

  void _buildClosureClassFields(
    JsClosureClassInfo closureClassInfo,
    MemberEntity member,
    InterfaceType? memberThisType,
    KernelScopeInfo info,
    Map<ir.Variable, JContextField> contextFieldsVisibleInScope,
    Map<Name, MemberEntity> memberMap,
  ) {
    // TODO(efortuna): Limit field number usage to when we need to distinguish
    // between two variables with the same name from different scopes.
    int fieldNumber = 0;

    // For the captured variables that are boxed, ensure this closure has a
    // field to reference the box. This puts the boxes first in the closure like
    // the AST front-end, but otherwise there is no reason to separate this loop
    // from the one below.
    // TODO(redemption): Merge this loop and the following.

    for (ir.Node variable in info.freeVariables) {
      if (variable is ir.Variable) {
        if (contextFieldsVisibleInScope.containsKey(variable)) {
          bool constructedField = _constructClosureFieldForRecord(
            variable,
            closureClassInfo,
            memberThisType,
            memberMap,
            variable,
            contextFieldsVisibleInScope,
            fieldNumber,
          );
          if (constructedField) fieldNumber++;
        }
      }
    }

    // Add a field for the captured 'this'.
    if (info.thisUsedAsFreeVariable) {
      closureClassInfo.registerFieldForLocal(
        closureClassInfo.thisLocal!,
        _constructClosureField(
          closureClassInfo.thisLocal!.name!,
          closureClassInfo,
          memberThisType,
          memberMap,
          getClassDefinition(member.enclosingClass!).node as ir.TreeNode,
          true,
          false,
          fieldNumber,
        ),
      );
      fieldNumber++;
    }

    for (ir.Node variable in info.freeVariables) {
      // Make a corresponding field entity in this closure class for the
      // free variables in the KernelScopeInfo.freeVariable.
      if (variable is ir.Variable) {
        if (!contextFieldsVisibleInScope.containsKey(variable)) {
          closureClassInfo.registerFieldForVariable(
            variable,
            _constructClosureField(
              variable.cosmeticName!,
              closureClassInfo,
              memberThisType,
              memberMap,
              variable,
              variable.isConst,
              false, // Closure field is never assigned (only box fields).
              fieldNumber,
            ),
          );
          fieldNumber++;
        }
      } else if (variable is TypeVariableTypeWithContext) {
        TypeVariableEntity typeVariable = getTypeVariable(
          variable.type.parameter,
        );
        // We can have distinct TypeVariableTypeWithContexts that have the same
        // local variable but with different nullabilities. We only want to
        // construct a closure field once for each local variable.
        if (closureClassInfo.hasFieldForTypeVariable(
          typeVariable as JTypeVariable,
        )) {
          continue;
        }
        closureClassInfo.registerFieldForTypeVariable(
          typeVariable,
          _constructClosureField(
            variable.type.parameter.name!,
            closureClassInfo,
            memberThisType,
            memberMap,
            variable.type.parameter,
            true,
            false,
            fieldNumber,
          ),
        );
        fieldNumber++;
      } else {
        throw UnsupportedError("Unexpected field node type: $variable");
      }
    }
  }

  /// Contexts point to one or more local variables declared in another scope
  /// that are captured in a scope. Access to those variables goes entirely
  /// through the context container, so we only create a field for the *context*
  /// holding [capturedLocal] and not the individual local variables accessed
  /// through the context. Contexts, by definition, are not mutable (though the
  /// locals they contain may be). Returns `true` if we constructed a new field
  /// in the closure class.
  bool _constructClosureFieldForRecord(
    ir.Variable capturedLocal,
    JsClosureClassInfo closureClassInfo,
    InterfaceType? memberThisType,
    Map<Name, MemberEntity> memberMap,
    ir.TreeNode sourceNode,
    Map<ir.Variable, JContextField> contextFieldsVisibleInScope,
    int fieldNumber,
  ) {
    JContextField contextField = contextFieldsVisibleInScope[capturedLocal]!;

    // Don't construct a new field if the box that holds this local already has
    // a field in the closure class.
    if (closureClassInfo.hasFieldForLocal(contextField.box)) {
      closureClassInfo.registerFieldForBoxedVariable(
        capturedLocal,
        contextField,
      );
      return false;
    }

    final closureField = JClosureField(
      '_box_$fieldNumber',
      closureClassInfo,
      contextField.box.name,
      isConst: true,
      isAssignable: false,
    );

    members.register<JField, JFieldData>(
      closureField,
      ClosureFieldData(
        ClosureMemberDefinition(
          computeSourceSpanFromTreeNode(sourceNode),
          MemberKind.closureField,
          sourceNode,
        ),
        memberThisType,
      ),
    );
    memberMap[closureField.memberName] = closureField;
    closureClassInfo.registerFieldForLocal(contextField.box, closureField);
    closureClassInfo.registerFieldForBoxedVariable(capturedLocal, contextField);
    return true;
  }

  void _constructSignatureMethod(
    JsClosureClassInfo closureClassInfo,
    Map<Name, MemberEntity> memberMap,
    ir.FunctionNode closureSourceNode,
    InterfaceType? memberThisType,
    SourceSpan location,
    ClassTypeVariableAccess typeVariableAccess,
  ) {
    final signatureMethod = JSignatureMethod(
      closureClassInfo.closureClassEntity,
    );
    members.register<JFunction, FunctionData>(
      signatureMethod,
      SignatureFunctionData(
        SpecialMemberDefinition(
          closureSourceNode.parent!,
          MemberKind.signature,
        ),
        memberThisType,
        closureSourceNode.typeParameters,
        typeVariableAccess,
      ),
    );
    memberMap[signatureMethod.memberName] = closureClassInfo.signatureMethod =
        signatureMethod;
  }

  JField _constructClosureField(
    String name,
    JsClosureClassInfo closureClassInfo,
    InterfaceType? memberThisType,
    Map<Name, MemberEntity> memberMap,
    ir.TreeNode sourceNode,
    bool isConst,
    bool isAssignable,
    int fieldNumber,
  ) {
    JField closureField = JClosureField(
      _getClosureVariableName(name, fieldNumber),
      closureClassInfo,
      name,
      isConst: isConst,
      isAssignable: isAssignable,
    );

    members.register<JField, JFieldData>(
      closureField,
      ClosureFieldData(
        ClosureMemberDefinition(
          computeSourceSpanFromTreeNode(sourceNode),
          MemberKind.closureField,
          sourceNode,
        ),
        memberThisType,
      ),
    );
    memberMap[closureField.memberName] = closureField;
    return closureField;
  }

  // Returns a non-unique name for the given closure element.
  String _computeClosureName(ir.TreeNode treeNode) {
    var parts = <String>[];
    // First anonymous is called 'closure', outer ones called '' to give a
    // compound name where increasing nesting level corresponds to extra
    // underscores.
    var anonymous = 'closure';
    ir.TreeNode? current = treeNode;
    // TODO(johnniwinther): Simplify computed names.
    while (current != null) {
      var node = current;
      if (node is ir.FunctionExpression) {
        parts.add(anonymous);
        anonymous = '';
      } else if (node is ir.FunctionDeclaration) {
        String name = node.variable.name;
        if (name != "") {
          parts.add(utils.operatorNameToIdentifier(name)!);
        } else {
          parts.add(anonymous);
          anonymous = '';
        }
      } else if (node is ir.Class) {
        // TODO(sra): Do something with abstracted mixin type names like '^#U0'.
        parts.add(node.name);
        break;
      } else if (node is ir.Procedure) {
        if (node.kind == ir.ProcedureKind.Factory) {
          parts.add(
            utils.reconstructConstructorName(getMember(node) as FunctionEntity),
          );
        } else {
          parts.add(utils.operatorNameToIdentifier(node.name.text)!);
        }
      } else if (node is ir.Constructor) {
        parts.add(
          utils.reconstructConstructorName(getMember(node) as FunctionEntity),
        );
        break;
      } else if (node is ir.Field) {
        // Add the field name for closures in field initializers.
        parts.add(node.name.text);
      }
      current = current.parent;
    }
    return parts.reversed.join('_');
  }

  /// Generate a unique name for the [id]th closure field, with proposed name
  /// [name].
  ///
  /// The result is used as the name of [ClosureFieldElement]s, and must
  /// therefore be unique to avoid breaking an invariant in the element model
  /// (classes cannot declare multiple fields with the same name).
  ///
  /// Also, the names should be distinct from real field names to prevent
  /// clashes with selectors for those fields.
  ///
  /// These names are not used in generated code, just as element name.
  String _getClosureVariableName(String name, int id) {
    return "_captured_${name}_$id";
  }

  JParameterStub? createParameterStub(
    JFunction function,
    Selector selector, {
    required Selector? callSelector,
    required bool needsSuper,
  }) {
    CallStructure callStructure = selector.callStructure;
    ParameterStructure parameterStructure = function.parameterStructure;
    int positionalArgumentCount = callStructure.positionalArgumentCount;
    assert(
      callStructure.typeArgumentCount == 0 ||
          callStructure.typeArgumentCount == parameterStructure.typeParameters,
    );
    assert(
      callStructure.typeArgumentCount != parameterStructure.typeParameters ||
          positionalArgumentCount != parameterStructure.totalParameters ||
          (parameterStructure.namedParameters.isNotEmpty &&
              callStructure.namedArgumentCount ==
                  parameterStructure.namedParameters.length),
    );

    final newParameterStructure = ParameterStructure(
      callStructure.positionalArgumentCount,
      callStructure.positionalArgumentCount,
      callStructure.namedArguments,
      callStructure.namedArguments.toSet(),
      callStructure.typeArgumentCount,
    );

    final stub = JParameterStub(
      function,
      newParameterStructure,
      callSelector: callSelector,
      needsSuper: needsSuper,
    );
    final data = members.getData(function) as FunctionData;
    final definition = data.definition;
    switch (definition.kind) {
      case MemberKind.regular:
      case MemberKind.closureCall:
        final node = definition.node;
        final stubDefinition = SpecialMemberDefinition(
          node as ir.TreeNode,
          MemberKind.parameterStub,
        );
        members.register(stub, ParameterStubFunctionData(data, stubDefinition));
        lateOutputUnitDataBuilder.registerColocatedMembers(function, stub);
        // We intentionally avoid registering the stub on a class here. We don't
        // want the emitter to emit code for the stub as if it were a normal
        // member. Code will be emitted alongside the target member.
        break;
      case MemberKind.signature:
      case MemberKind.recordGetter:
      case MemberKind.closureField:
      case MemberKind.constructor:
      case MemberKind.constructorBody:
      case MemberKind.generatorBody:
      case MemberKind.parameterStub:
        throw UnsupportedError(
          'Cannot generate stub for $function with kind ${definition.kind}',
        );
    }

    return stub;
  }

  @override
  JGeneratorBody getGeneratorBody(covariant JFunction function) {
    JGeneratorBody? generatorBody = _generatorBodies[function];
    if (generatorBody == null) {
      final functionData = members.getData(function) as FunctionData;
      DartType elementType = elementEnvironment
          .getFunctionAsyncOrSyncStarElementType(function);
      generatorBody = createGeneratorBody(function, elementType);
      _registerGeneratorBody(function, functionData, generatorBody);
    }
    return generatorBody;
  }

  void _registerGeneratorBody(
    JFunction function,
    FunctionData functionData,
    JGeneratorBody generatorBody,
  ) {
    members.register<JFunction, FunctionData>(
      generatorBody,
      GeneratorBodyFunctionData(
        functionData,
        SpecialMemberDefinition.from(
          functionData.definition,
          MemberKind.generatorBody,
        ),
      ),
    );

    if (function.enclosingClass != null) {
      // TODO(sra): Integrate this with ClassEnvImpl.addConstructorBody ?
      (_injectedClassMembers[function.enclosingClass as JClass] ??= <JMember>[])
          .add(generatorBody);
    }
    lateOutputUnitDataBuilder.registerColocatedMembers(
      generatorBody.function,
      generatorBody,
    );
    _generatorBodies[function] = generatorBody;
  }

  String _nameForShape(RecordShape shape) {
    final sb = StringBuffer();
    sb.write('_Record_');
    sb.write(shape.fieldCount);
    for (String name in shape.fieldNames) {
      sb.write('_');
      // 'hex' escape to remove `$` and `_`.
      // `send_$_bux` --> `sendx5Fx24x5Fbux78`.
      sb.write(
        name
            .replaceAll(r'x', r'x78')
            .replaceAll(r'$', r'x24')
            .replaceAll(r'_', r'x5F'),
      );
    }
    return sb.toString();
  }

  /// [getters] is an out parameter that gathers all the getters created for
  /// this shape.
  JClass generateRecordShapeClass(
    RecordShape shape,
    InterfaceType supertype,
    List<MemberEntity> getters,
  ) {
    JLibrary library = supertype.element.library as JLibrary;

    String name = _nameForShape(shape);
    SourceSpan location = SourceSpan.unknown(); // TODO(50081): What to use?

    Map<Name, JMember> memberMap = {};
    final classEntity = JRecordClass(library, name, isAbstract: false);

    // Create a classData and set up the interfaces and subclass relationships
    // that for regular classes would be done by _ensureSupertypes and
    // _ensureThisAndRawType.
    InterfaceType thisType = types.interfaceType(classEntity, const []);
    RecordClassData recordData = RecordClassData(
      RecordClassDefinition(location),
      thisType,
      supertype,
      getOrderedTypeSet(supertype.element as JClass)
          .extendClass(types, thisType),
    );
    classes.register(classEntity, recordData, RecordClassEnv(memberMap));

    // Add field getters, which are called only from dynamic getter invocations.

    for (int i = 0; i < shape.fieldCount; i++) {
      String name = shape.getterNameOfIndex(i);
      Name memberName = Name(name, null);
      final getter = JRecordGetter(classEntity, memberName);
      getters.add(getter);

      // The function type of a dynamic getter is a function of no arguments
      // that returns `dynamic` (any other top would be ok too).
      FunctionType functionType = commonElements.dartTypes.functionType(
        commonElements.dartTypes.dynamicType(),
        const [],
        const [],
        const [],
        const {},
        const [],
        const [],
      );
      final data = RecordGetterData(
        RecordGetterDefinition(location, i),
        thisType,
        functionType,
      );

      members.register<JFunction, FunctionData>(getter, data);
      memberMap[memberName] = getter;
    }

    // TODO(49718): Implement `==` specialized to the shape.

    return classEntity;
  }
}

class JsElementEnvironment extends ElementEnvironment
    implements JElementEnvironment {
  @override
  final JsKernelToElementMap elementMap;

  JsElementEnvironment(this.elementMap);

  @override
  DartType get dynamicType => elementMap.types.dynamicType();

  @override
  LibraryEntity? get mainLibrary => elementMap._mainLibrary;

  @override
  FunctionEntity? get mainFunction => elementMap._mainFunction;

  @override
  Iterable<LibraryEntity> get libraries => elementMap.libraryListInternal;

  @override
  String getLibraryName(LibraryEntity library) {
    return elementMap._getLibraryName(library as JLibrary);
  }

  @override
  InterfaceType getThisType(ClassEntity cls) {
    return elementMap.getThisType(cls as JClass);
  }

  @override
  InterfaceType getJsInteropType(ClassEntity cls) {
    return elementMap._getJsInteropType(cls as JClass);
  }

  @override
  InterfaceType getRawType(ClassEntity cls) {
    return elementMap._getRawType(cls as JClass);
  }

  @override
  InterfaceType getClassInstantiationToBounds(ClassEntity cls) =>
      elementMap._getClassInstantiationToBounds(cls as JClass);

  @override
  bool isGenericClass(ClassEntity cls) {
    return getThisType(cls).typeArguments.isNotEmpty;
  }

  @override
  bool isMixinApplication(ClassEntity cls) {
    return elementMap._isMixinApplication(cls as JClass);
  }

  @override
  bool isUnnamedMixinApplication(ClassEntity cls) {
    return elementMap._isUnnamedMixinApplication(cls as JClass);
  }

  @override
  bool isMixinApplicationWithMembers(ClassEntity cls) {
    return elementMap._isMixinApplicationWithMembers(cls as JClass);
  }

  @override
  ClassEntity? getEffectiveMixinClass(ClassEntity cls) {
    if (!isMixinApplication(cls)) return null;
    do {
      cls = elementMap.getAppliedMixin(cls as JClass)!;
    } while (isMixinApplication(cls));
    return cls;
  }

  @override
  DartType getTypeVariableBound(TypeVariableEntity typeVariable) {
    return elementMap.getTypeVariableBound(typeVariable as JTypeVariable);
  }

  @override
  List<Variance> getTypeVariableVariances(ClassEntity cls) {
    return elementMap.getTypeVariableVariances(cls as JClass);
  }

  @override
  DartType getTypeVariableDefaultType(TypeVariableEntity typeVariable) {
    return elementMap._getTypeVariableDefaultType(
      typeVariable as JTypeVariable,
    );
  }

  @override
  InterfaceType createInterfaceType(
    ClassEntity cls,
    List<DartType> typeArguments,
  ) {
    return elementMap.types.interfaceType(cls, typeArguments);
  }

  @override
  FunctionType getFunctionType(FunctionEntity function) {
    return elementMap._getFunctionType(function as JFunction);
  }

  @override
  List<TypeVariableType> getFunctionTypeVariables(FunctionEntity function) {
    return elementMap._getFunctionTypeVariables(function as JFunction);
  }

  @override
  DartType getFunctionAsyncOrSyncStarElementType(FunctionEntity function) {
    DartType returnType = getFunctionType(function).returnType;
    return getAsyncOrSyncStarElementType(function, returnType);
  }

  @override
  DartType getAsyncOrSyncStarElementType(
    FunctionEntity function,
    DartType returnType,
  ) {
    final asyncMarker = function.asyncMarker;
    switch (asyncMarker) {
      case AsyncMarker.sync:
        return returnType;
      case AsyncMarker.syncStar:
      case AsyncMarker.async:
      case AsyncMarker.asyncStar:
        return elementMap.getDartType(
          getFunctionNode(elementMap, function)!.emittedValueType!,
        );
    }
  }

  @override
  DartType getFieldType(FieldEntity field) {
    return elementMap._getFieldType(field as JField);
  }

  @override
  bool isFieldCovariantByDeclaration(FieldEntity field) {
    return elementMap._isFieldCovariantByDeclaration(field as JField);
  }

  @override
  FunctionType getLocalFunctionType(covariant JLocalFunction function) {
    return function.functionType;
  }

  @override
  ConstructorEntity? lookupConstructor(
    ClassEntity cls,
    String name, {
    bool required = false,
  }) {
    ConstructorEntity? constructor = elementMap.lookupConstructor(
      cls as JClass,
      name,
    );
    if (constructor == null && required) {
      throw failedAt(
        currentElementSpannable,
        "The constructor '$name' was not found in class '${cls.name}' "
        "in library ${cls.library.canonicalUri}.",
      );
    }
    return constructor;
  }

  @override
  MemberEntity? lookupLocalClassMember(
    ClassEntity cls,
    Name name, {
    bool required = false,
  }) {
    MemberEntity? member = elementMap.lookupClassMember(cls as JClass, name);
    if (member == null && required) {
      throw failedAt(
        currentElementSpannable,
        "The member '$name' was not found in ${cls.name}.",
      );
    }
    return member;
  }

  @override
  ClassEntity? getSuperClass(
    ClassEntity cls, {
    bool skipUnnamedMixinApplications = false,
  }) {
    assert(elementMap.checkFamily(cls));
    JClass? superclass =
        elementMap.getSuperType(cls as JClass)?.element as JClass?;
    if (skipUnnamedMixinApplications) {
      while (superclass != null &&
          elementMap._isUnnamedMixinApplication(superclass)) {
        superclass = elementMap.getSuperType(superclass)?.element as JClass?;
      }
    }
    return superclass;
  }

  @override
  void forEachSupertype(
    ClassEntity cls,
    void Function(InterfaceType supertype) f,
  ) {
    elementMap._forEachSupertype(cls as JClass, f);
  }

  @override
  void forEachLocalClassMember(
    ClassEntity cls,
    void Function(MemberEntity member) f,
  ) {
    elementMap._forEachLocalClassMember(cls as JClass, f);
  }

  @override
  void forEachInjectedClassMember(
    ClassEntity cls,
    void Function(MemberEntity member) f,
  ) {
    elementMap.forEachInjectedClassMember(cls as JClass, f);
  }

  @override
  void forEachClassMember(
    ClassEntity cls,
    void Function(ClassEntity declarer, MemberEntity member) f,
  ) {
    elementMap._forEachClassMember(cls as JClass, f);
  }

  @override
  void forEachConstructor(
    ClassEntity cls,
    void Function(ConstructorEntity constructor) f,
  ) {
    elementMap._forEachConstructor(cls as JClass, f);
  }

  @override
  void forEachConstructorBody(
    ClassEntity cls,
    void Function(ConstructorBodyEntity constructor) f,
  ) {
    elementMap.forEachConstructorBody(cls as JClass, f);
  }

  @override
  void forEachNestedClosure(
    MemberEntity member,
    void Function(FunctionEntity closure) f,
  ) {
    elementMap.forEachNestedClosure(member, f);
  }

  @override
  void forEachLibraryMember(
    LibraryEntity library,
    void Function(MemberEntity member) f,
  ) {
    elementMap._forEachLibraryMember(library as JLibrary, f);
  }

  @override
  MemberEntity? lookupLibraryMember(
    LibraryEntity library,
    String name, {
    bool setter = false,
    bool required = false,
  }) {
    MemberEntity? member = elementMap.lookupLibraryMember(
      library as JLibrary,
      name,
      setter: setter,
    );
    if (member == null && required) {
      failedAt(
        currentElementSpannable,
        "The member '$name' was not found in library '${library.name}'.",
      );
    }
    return member;
  }

  @override
  ClassEntity? lookupClass(
    LibraryEntity library,
    String name, {
    bool required = false,
  }) {
    ClassEntity? cls = elementMap.lookupClass(library as JLibrary, name);
    if (cls == null && required) {
      failedAt(
        currentElementSpannable,
        "The class '$name'  was not found in library '${library.name}'.",
      );
    }
    return cls;
  }

  @override
  void forEachClass(LibraryEntity library, void Function(ClassEntity cls) f) {
    elementMap._forEachClass(library as JLibrary, f);
  }

  @override
  LibraryEntity? lookupLibrary(Uri uri, {bool required = false}) {
    LibraryEntity? library = elementMap.lookupLibrary(uri);
    if (library == null && required) {
      failedAt(currentElementSpannable, "The library '$uri' was not found.");
    }
    return library;
  }

  @override
  bool isEnumClass(ClassEntity cls) {
    assert(elementMap.checkFamily(cls));
    JClassData classData = elementMap.classes.getData(cls as JClass);
    return classData.isEnumClass;
  }

  @override
  void forEachParameter(
    FunctionEntity function,
    void Function(DartType type, String? name, ConstantValue? defaultValue) f,
  ) {
    elementMap.forEachParameter(
      function as JFunction,
      f,
      isNative: elementMap.nativeData.isNativeMember(function),
    );
  }

  @override
  void forEachParameterAsLocal(
    GlobalLocalsMap globalLocalsMap,
    FunctionEntity function,
    void Function(Local parameter) f,
  ) {
    forEachOrderedParameterAsLocal(globalLocalsMap, elementMap, function, (
      Local parameter, {
      required bool isElided,
    }) {
      if (!isElided) {
        f(parameter);
      }
    });
  }

  @override
  void forEachInstanceField(
    ClassEntity cls,
    void Function(ClassEntity declarer, FieldEntity field) f,
  ) {
    forEachClassMember(cls, (ClassEntity declarer, MemberEntity member) {
      if (member is FieldEntity && member.isInstanceMember) {
        f(declarer, member);
      }
    });
  }

  @override
  void forEachDirectInstanceField(
    ClassEntity cls,
    void Function(FieldEntity field) f,
  ) {
    // TODO(sra): Add ElementEnvironment.forEachDirectInstanceField or
    // parameterize [forEachInstanceField] to filter members to avoid a
    // potentially O(n^2) scan of the superclasses.
    forEachClassMember(cls, (ClassEntity declarer, MemberEntity member) {
      if (declarer != cls) return;
      if (member is! FieldEntity) return;
      if (!member.isInstanceMember) return;
      f(member);
    });
  }
}