pkg/front_end/lib/src/source/outline_builder.dart

// 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.

import 'package:_fe_analyzer_shared/src/parser/parser.dart'
    show
        Assert,
        ConstructorReferenceContext,
        DeclarationHeaderKind,
        DeclarationKind,
        FormalParameterKind,
        IdentifierContext,
        MemberKind,
        lengthOfSpan;
import 'package:_fe_analyzer_shared/src/parser/quote.dart' show unescapeString;
import 'package:_fe_analyzer_shared/src/parser/stack_listener.dart'
    show FixedNullableList, NullValues, ParserRecovery;
import 'package:_fe_analyzer_shared/src/scanner/token.dart'
    show Keyword, Token, TokenIsAExtension, TokenType;
import 'package:_fe_analyzer_shared/src/types/shared_type.dart' show Variance;
import 'package:_fe_analyzer_shared/src/util/link.dart';
import 'package:_fe_analyzer_shared/src/util/value_kind.dart';
import 'package:front_end/src/codes/diagnostic.dart' as diag;
import 'package:kernel/ast.dart'
    show InvalidType, Nullability, ProcedureKind, TreeNode;

import '../api_prototype/experimental_flags.dart';
import '../base/combinator.dart' show CombinatorBuilder;
import '../base/configuration.dart' show Configuration;
import '../base/identifiers.dart'
    show
        Identifier,
        OperatorIdentifier,
        SimpleIdentifier,
        flattenName,
        OmittedIdentifier;
import '../base/ignored_parser_errors.dart' show isIgnoredParserError;
import '../base/messages.dart';
import '../base/modifiers.dart' show Modifiers;
import '../base/operator.dart' show Operator;
import '../base/problems.dart' show unhandled;
import '../base/uris.dart';
import '../builder/compilation_unit.dart';
import '../builder/constructor_reference_builder.dart';
import '../builder/declaration_builders.dart';
import '../builder/fixed_type_builder.dart';
import '../builder/formal_parameter_builder.dart';
import '../builder/invalid_type_builder.dart';
import '../builder/metadata_builder.dart';
import '../builder/named_type_builder.dart';
import '../builder/nullability_builder.dart';
import '../builder/omitted_type_builder.dart';
import '../builder/record_type_builder.dart';
import '../builder/type_builder.dart';
import '../fragment/fragment.dart';
import '../kernel/utils.dart';
import '../util/helpers.dart';
import 'check_helper.dart';
import 'fragment_factory.dart';
import 'offset_map.dart';
import 'source_type_parameter_builder.dart';
import 'stack_listener_impl.dart';
import 'value_kinds.dart';

enum MethodBody { Abstract, Regular, RedirectingFactoryBody }

/// Enum for the context in which declarations occur.
///
/// This is used to determine whether instance type parameters access is
/// allowed.
enum DeclarationContext {
  /// In the context of the enclosing library.
  ///
  /// This is used for library, import, export, part, and part of declarations
  /// in libraries and parts, as well as annotations on top level declarations.
  Library,

  /// In a typedef declaration
  ///
  /// This excludes annotations on the typedef declaration itself, which are
  /// seen in the [Library] context.
  Typedef,

  /// In an enum declaration
  ///
  /// This excludes annotations on the enum declaration itself, which are seen
  /// in the [Library] context.
  Enum,

  /// In a top level method declaration.
  ///
  /// This includes return type of the declaration but excludes annotations on
  /// the method declaration itself, which are seen in the [Library] context.
  TopLevelMethod,

  /// In a top level field declaration.
  ///
  /// This includes  type of the declaration but excludes annotations on the
  /// field declaration itself, which are seen in the [Library] context.
  TopLevelField,

  /// In a `class Name<TypeParams>` or `mixin Name<TypeParams>` prefix of a
  /// class declaration `class Name<TypeParams> ... { ... }`, mixin declaration
  /// `mixin Name<TypeParams> ... { ... }` or named mixin application
  /// `class Name<TypeParams> = ...;`.
  ///
  /// This is replaced by [Class], [Mixin] or [NamedMixinApplication] after the
  /// type parameters have been parsed.
  ClassOrMixinOrNamedMixinApplication,

  /// In a named mixin application.
  ///
  /// This excludes type parameters declared on the named mixin application,
  /// which are seen in the [ClassOrMixinOrNamedMixinApplication] context,
  /// and annotations on the named mixin application itself, which are seen in
  /// the [Library] context.
  NamedMixinApplication,

  /// In a class declaration before the class body.
  ///
  /// This excludes type parameters declared on the class declaration, which are
  /// seen in the [ClassOrMixinOrNamedMixinApplication] context, and annotations
  /// on the class declaration itself, which are seen in the [Library] context.
  Class,

  /// In a class declaration body.
  ///
  /// This includes annotations on class member declarations.
  ClassBody,

  /// In a generative constructor declaration inside a class declaration.
  ///
  /// This  excludes annotations on the constructor declaration itself, which
  /// are seen in the [ClassBody] context.
  ClassConstructor,

  /// In a factory constructor declaration inside a class declaration.
  ///
  /// This excludes annotations on the constructor declaration itself, which
  /// are seen in the [ClassBody] context.
  ClassFactory,

  /// In an instance method declaration inside a class declaration.
  ///
  /// This includes return type of the declaration but excludes annotations on
  /// the method declaration itself, which are seen in the [ClassBody] context.
  ClassInstanceMethod,

  /// In an instance field declaration inside a class declaration.
  ///
  /// This includes type of the declaration but excludes annotations on the
  /// field declaration itself, which are seen in the [ClassBody] context.
  ClassInstanceField,

  /// In a static method declaration inside a class declaration.
  ///
  /// This includes return type of the declaration but excludes annotations on
  /// the method declaration itself, which are seen in the [ClassBody] context.
  ClassStaticMethod,

  /// In a static field declaration inside a class declaration.
  ///
  /// This includes type of the declaration but excludes annotations on the
  /// field declaration itself, which are seen in the [ClassBody] context.
  ClassStaticField,

  /// In a mixin declaration before the mixin body.
  ///
  /// This excludes type parameters declared on the mixin declaration, which are
  /// seen in the [ClassOrMixinOrNamedMixinApplication] context, and annotations
  /// on the mixin declaration itself, which are seen in the [Library] context.
  Mixin,

  /// In a mixin declaration body.
  ///
  /// This includes annotations on mixin member declarations.
  MixinBody,

  /// In a generative constructor declaration inside a mixin declaration. This
  /// is an error case.
  ///
  /// This excludes annotations on the constructor declaration itself, which
  /// are seen in the [MixinBody] context.
  MixinConstructor,

  /// In a factory constructor declaration inside a mixin declaration. This is
  /// an error case.
  ///
  /// This excludes annotations on the constructor declaration itself, which
  /// are seen in the [MixinBody] context.
  MixinFactory,

  /// In an instance method declaration inside a mixin declaration.
  ///
  /// This includes return type of the declaration but excludes annotations on
  /// the method declaration itself, which are seen in the [MixinBody] context.
  MixinInstanceMethod,

  /// In an instance field declaration inside a mixin declaration.
  ///
  /// This includes type of the declaration but excludes annotations on the
  /// field declaration itself, which are seen in the [MixinBody] context.
  MixinInstanceField,

  /// In a static method declaration inside a mixin declaration.
  ///
  /// This includes return type of the declaration but excludes annotations on
  /// the method declaration itself, which are seen in the [MixinBody] context.
  MixinStaticMethod,

  /// In a static field declaration inside a mixin declaration.
  ///
  /// This includes type of the declaration but excludes annotations on the
  /// field declaration itself, which are seen in the [MixinBody] context.
  MixinStaticField,

  /// In an extension declaration before the extension body.
  ///
  /// This includes type parameters declared on the extension declaration but
  /// excludes annotations on the extension declaration itself, which are seen
  /// in the [Library] context.
  ExtensionOrExtensionType,

  /// In an extension declaration before the extension body.
  ///
  /// This includes type parameters declared on the extension declaration but
  /// excludes annotations on the extension declaration itself, which are seen
  /// in the [Library] context.
  Extension,

  /// In a extension declaration body.
  ///
  /// This includes annotations on extension member declarations.
  ExtensionBody,

  /// In a generative constructor declaration inside an extension declaration.
  /// This is an error case.
  ///
  /// This excludes annotations on the constructor declaration itself, which
  /// are seen in the [ExtensionBody] context.
  ExtensionConstructor,

  /// In a factory constructor declaration inside an extension declaration. This
  /// is an error case.
  ///
  /// This excludes annotations on the constructor declaration itself, which
  /// are seen in the [ExtensionBody] context.
  ExtensionFactory,

  /// In an instance method declaration inside an extension declaration.
  ///
  /// This includes return type of the declaration but excludes annotations on
  /// the method declaration itself, which are seen in the [ExtensionBody]
  /// context.
  ExtensionInstanceMethod,

  /// In a non-external instance field declaration inside an extension
  /// declaration. This is an error case.
  ///
  /// This includes type of the declaration but excludes annotations on the
  /// field declaration itself, which are seen in the [ExtensionBody] context.
  ExtensionInstanceField,

  /// In an external instance field declaration inside an extension declaration.
  ///
  /// This includes type of the declaration but excludes annotations on the
  /// field declaration itself, which are seen in the [ExtensionBody] context.
  ExtensionExternalInstanceField,

  /// In a static method declaration inside an extension declaration.
  ///
  /// This includes return type of the declaration but excludes annotations on
  /// the method declaration itself, which are seen in the [ExtensionBody]
  /// context.
  ExtensionStaticMethod,

  /// In a static field declaration inside an extension declaration.
  ///
  /// This includes type of the declaration but excludes annotations on the
  /// field declaration itself, which are seen in the [ExtensionBody] context.
  ExtensionStaticField,

  /// In an extension type declaration before the extension type body.
  ///
  /// This includes type parameters declared on the extension type declaration
  /// but excludes annotations on the extension type declaration itself, which
  /// are seen in the [Library] context.
  ExtensionType,

  /// In a extension type declaration body.
  ///
  /// This includes annotations on extension type member declarations.
  ExtensionTypeBody,

  /// In a generative constructor declaration inside an extension type
  /// declaration.
  ///
  /// This excludes annotations on the constructor declaration itself, which
  /// are seen in the [ExtensionTypeBody] context.
  ExtensionTypeConstructor,

  /// In a factory constructor declaration inside an extension type declaration.
  ///
  /// This excludes annotations on the constructor declaration itself, which
  /// are seen in the [ExtensionTypeBody] context.
  ExtensionTypeFactory,

  /// In an instance method declaration inside an extension type declaration.
  ///
  /// This includes return type of the declaration but excludes annotations on
  /// the method declaration itself, which are seen in the [ExtensionTypeBody]
  /// context.
  ExtensionTypeInstanceMethod,

  /// In an instance field declaration inside an extension type declaration.
  /// This is an error case.
  ///
  /// This includes type of the declaration but excludes annotations on the
  /// field declaration itself, which are seen in the [ExtensionTypeBody]
  /// context.
  ExtensionTypeInstanceField,

  /// In a static method declaration inside an extension type declaration.
  ///
  /// This includes return type of the declaration but excludes annotations on
  /// the method declaration itself, which are seen in the [ExtensionTypeBody]
  /// context.
  ExtensionTypeStaticMethod,

  /// In a static field declaration inside an extension type declaration.
  ///
  /// This includes type of the declaration but excludes annotations on the
  /// field declaration itself, which are seen in the [ExtensionTypeBody]
  /// context.
  ExtensionTypeStaticField,

  /// In a generative constructor declaration inside an enum declaration.
  EnumConstructor,

  /// In a static method declaration inside an enum declaration.
  EnumStaticMethod,

  /// In a static field declaration inside an enum declaration.
  EnumStaticField,

  /// In an instance method declaration inside an enum declaration.
  EnumInstanceMethod,

  /// In an instance field declaration inside an enum declaration.
  EnumInstanceField,

  /// In a factory constructor declaration inside an enum declaration. This
  /// is an error case.
  ///
  /// This excludes annotations on the constructor declaration itself, which
  /// are seen in the [EnumBody] context.
  EnumFactory,

  /// In an enum declaration body.
  ///
  /// This includes annotations on extension member declarations.
  EnumBody,
}

extension on DeclarationContext {
  InstanceTypeParameterAccessState get instanceTypeParameterAccessState {
    switch (this) {
      case DeclarationContext.Library:
      case DeclarationContext.Typedef:
      case DeclarationContext.TopLevelMethod:
      case DeclarationContext.TopLevelField:
        return InstanceTypeParameterAccessState.Unexpected;
      case DeclarationContext.ClassOrMixinOrNamedMixinApplication:
      case DeclarationContext.NamedMixinApplication:
      case DeclarationContext.Class:
      case DeclarationContext.ClassConstructor:
      case DeclarationContext.ClassFactory:
      case DeclarationContext.ClassInstanceMethod:
      case DeclarationContext.ClassInstanceField:
      case DeclarationContext.Enum:
      case DeclarationContext.EnumConstructor:
      case DeclarationContext.EnumInstanceField:
      case DeclarationContext.EnumInstanceMethod:
      case DeclarationContext.Mixin:
      case DeclarationContext.MixinInstanceMethod:
      case DeclarationContext.MixinInstanceField:
      case DeclarationContext.ExtensionOrExtensionType:
      case DeclarationContext.Extension:
      case DeclarationContext.ExtensionInstanceMethod:
      case DeclarationContext.ExtensionExternalInstanceField:
      case DeclarationContext.ExtensionType:
      case DeclarationContext.ExtensionTypeConstructor:
      case DeclarationContext.ExtensionTypeFactory:
      case DeclarationContext.ExtensionTypeInstanceMethod:
      case DeclarationContext.ExtensionTypeInstanceField:
        return InstanceTypeParameterAccessState.Allowed;
      case DeclarationContext.ClassBody:
      case DeclarationContext.ClassStaticMethod:
      case DeclarationContext.ClassStaticField:
      case DeclarationContext.EnumStaticField:
      case DeclarationContext.EnumStaticMethod:
      case DeclarationContext.EnumBody:
      case DeclarationContext.MixinBody:
      case DeclarationContext.MixinStaticMethod:
      case DeclarationContext.MixinStaticField:
      case DeclarationContext.ExtensionBody:
      case DeclarationContext.ExtensionStaticMethod:
      case DeclarationContext.ExtensionStaticField:
      case DeclarationContext.ExtensionTypeBody:
      case DeclarationContext.ExtensionTypeStaticMethod:
      case DeclarationContext.ExtensionTypeStaticField:
        return InstanceTypeParameterAccessState.Disallowed;
      case DeclarationContext.MixinConstructor:
      case DeclarationContext.MixinFactory:
      case DeclarationContext.ExtensionConstructor:
      case DeclarationContext.ExtensionFactory:
      case DeclarationContext.ExtensionInstanceField:
      case DeclarationContext.EnumFactory:
        return InstanceTypeParameterAccessState.Invalid;
    }
  }

  /// Returns the kind of type parameter created in the current context.
  TypeParameterKind get typeParameterKind {
    switch (this) {
      case DeclarationContext.Class:
      case DeclarationContext.ClassOrMixinOrNamedMixinApplication:
      case DeclarationContext.Mixin:
      case DeclarationContext.NamedMixinApplication:
        return TypeParameterKind.classMixinOrEnum;
      case DeclarationContext.ExtensionOrExtensionType:
      case DeclarationContext.Extension:
      case DeclarationContext.ExtensionBody:
      case DeclarationContext.ExtensionType:
      case DeclarationContext.ExtensionTypeBody:
        return TypeParameterKind.extensionOrExtensionType;
      case DeclarationContext.ClassBody:
      case DeclarationContext.ClassConstructor:
      case DeclarationContext.ClassFactory:
      case DeclarationContext.ClassInstanceField:
      case DeclarationContext.ClassInstanceMethod:
      case DeclarationContext.ClassStaticField:
      case DeclarationContext.ClassStaticMethod:
      case DeclarationContext.Enum:
      case DeclarationContext.EnumBody:
      case DeclarationContext.EnumConstructor:
      case DeclarationContext.EnumFactory:
      case DeclarationContext.EnumInstanceField:
      case DeclarationContext.EnumInstanceMethod:
      case DeclarationContext.EnumStaticField:
      case DeclarationContext.EnumStaticMethod:
      case DeclarationContext.ExtensionConstructor:
      case DeclarationContext.ExtensionExternalInstanceField:
      case DeclarationContext.ExtensionFactory:
      case DeclarationContext.ExtensionInstanceField:
      case DeclarationContext.ExtensionInstanceMethod:
      case DeclarationContext.ExtensionStaticField:
      case DeclarationContext.ExtensionStaticMethod:
      case DeclarationContext.ExtensionTypeConstructor:
      case DeclarationContext.ExtensionTypeFactory:
      case DeclarationContext.ExtensionTypeInstanceField:
      case DeclarationContext.ExtensionTypeInstanceMethod:
      case DeclarationContext.ExtensionTypeStaticField:
      case DeclarationContext.ExtensionTypeStaticMethod:
      case DeclarationContext.Library:
      case DeclarationContext.MixinBody:
      case DeclarationContext.MixinConstructor:
      case DeclarationContext.MixinFactory:
      case DeclarationContext.MixinInstanceField:
      case DeclarationContext.MixinInstanceMethod:
      case DeclarationContext.MixinStaticField:
      case DeclarationContext.MixinStaticMethod:
      case DeclarationContext.TopLevelField:
      case DeclarationContext.TopLevelMethod:
      case DeclarationContext.Typedef:
        return TypeParameterKind.function;
    }
  }
}

class OutlineBuilder extends StackListenerImpl {
  final ProblemReporting _problemReporting;
  final SourceCompilationUnit _compilationUnit;
  final FragmentFactory _builderFactory;

  final bool enableNative;
  bool inAbstractOrSealedClass = false;

  String? nativeMethodName;

  Link<DeclarationContext> _declarationContext = const Link();

  /// Level of nesting of function-type type parameters
  ///
  /// For instance, `X` is at nesting level 1, and `Y` is at nesting level 2 in
  /// the following:
  ///
  ///    method() {
  ///      Function<X>(Function<Y extends X>(Y))? f;
  ///    }
  ///
  /// For simplicity, non-generic functions are considered generic functions
  /// with 0 type parameters.
  int _structuralParameterDepthLevel = 0;

  /// True if a type of a formal parameter is currently compiled
  ///
  /// This variable is needed to distinguish between the type of a formal
  /// parameter and its initializer because in those two regions of code the
  /// type parameters should be interpreted differently: as structural and
  /// nominal correspondingly.
  bool _insideOfFormalParameterType = false;

  bool get inFunctionType =>
      _structuralParameterDepthLevel > 0 || _insideOfFormalParameterType;

  OffsetMap _offsetMap;

  new(
    this._problemReporting,
    this._compilationUnit,
    this._builderFactory,
    this._offsetMap,
  ) : enableNative = _compilationUnit.loader.target.backendTarget.enableNative(
        _compilationUnit.importUri,
      );

  @override
  LibraryFeatures get libraryFeatures => _compilationUnit.libraryFeatures;

  @override
  bool get isDartLibrary => _compilationUnit.isDartLibrary;

  @override
  Message reportFeatureNotEnabled(
    LibraryFeature feature,
    int charOffset,
    int length,
  ) {
    return _compilationUnit.reportFeatureNotEnabled(
      feature,
      uri,
      charOffset,
      length,
    );
  }

  DeclarationContext get declarationContext => _declarationContext.head;

  void pushDeclarationContext(DeclarationContext value) {
    _declarationContext = _declarationContext.prepend(value);
  }

  void popDeclarationContext([DeclarationContext? expectedContext]) {
    assert(
      expectedContext == null || expectedContext == declarationContext,
      "Unexpected declaration context: "
      "Expected $expectedContext, actual $declarationContext.",
    );
    _declarationContext = _declarationContext.tail!;
  }

  @override
  Uri get uri => _compilationUnit.fileUri;

  int popCharOffset() => pop() as int;

  List<String>? popIdentifierList(int count) {
    assert(
      checkState(
        null,
        repeatedKind(ValueKinds.IdentifierOrParserRecovery, count),
      ),
    );
    if (count == 0) return null;
    List<String> list = new List<String>.filled(count, /* dummyValue = */ '');
    bool isParserRecovery = false;
    for (int i = count - 1; i >= 0; i--) {
      Object? identifier = pop();
      if (identifier is ParserRecovery) {
        isParserRecovery = true;
      } else {
        list[i] = (identifier as Identifier).name;
      }
    }
    return isParserRecovery ? null : list;
  }

  @override
  void beginCompilationUnit(Token token) {
    pushDeclarationContext(DeclarationContext.Library);
  }

  @override
  void endCompilationUnit(int count, Token token) {
    popDeclarationContext(DeclarationContext.Library);
    _builderFactory.checkStacks();
    super.endCompilationUnit(count, token);
  }

  @override
  void endMetadata(Token beginToken, Token? periodBeforeName, Token endToken) {
    debugEvent("endMetadata");
    assert(
      checkState(beginToken, [
        /* arguments */ ValueKinds.ArgumentsTokenOrNull,
        if (periodBeforeName != null) /* constructor name */
          ValueKinds.IdentifierOrParserRecovery,
        /* type arguments */ ValueKinds.TypeArgumentsOrNull,
        /* prefix or constructor */ ValueKinds.IdentifierOrParserRecovery,
      ]),
    );

    pop(NullValues.Arguments); // arguments
    if (periodBeforeName != null) {
      pop(); // constructor name
    }
    pop(NullValues.TypeArguments); // type arguments
    Object? sentinel = pop(); // prefix or constructor
    push(
      sentinel is ParserRecovery
          ? sentinel
          : new MetadataBuilder(beginToken, _compilationUnit.fileUri),
    );
  }

  @override
  void endMetadataStar(int count) {
    debugEvent("MetadataStar");
    push(
      const FixedNullableList<MetadataBuilder>().popNonNullable(
            stack,
            count,
            dummyMetadataBuilder,
          ) ??
          NullValues.Metadata,
    );
  }

  @override
  void handleInvalidTopLevelDeclaration(Token endToken) {
    debugEvent("InvalidTopLevelDeclaration");
    pop(); // metadata star
  }

  @override
  void endHide(Token hideKeyword) {
    debugEvent("endHide");
    assert(checkState(hideKeyword, [ValueKinds.NameListOrParserRecovery]));

    Object? names = pop();
    if (names is ParserRecovery) {
      // Coverage-ignore-block(suite): Not run.
      push(names);
    } else {
      push(new CombinatorBuilder.hide(names as Iterable<String>));
    }
  }

  @override
  void endShow(Token showKeyword) {
    debugEvent("Show");
    Object? names = pop();
    if (names is ParserRecovery) {
      // Coverage-ignore-block(suite): Not run.
      push(names);
    } else {
      push(new CombinatorBuilder.show(names as Iterable<String>));
    }
  }

  @override
  void endCombinators(int count) {
    debugEvent("Combinators");
    push(
      const FixedNullableList<CombinatorBuilder>().popNonNullable(
            stack,
            count,
            dummyCombinator,
          ) ??
          NullValues.Combinators,
    );
  }

  @override
  void endExport(Token exportKeyword, Token semicolon) {
    debugEvent("endExport");
    assert(
      checkState(exportKeyword, [
        /* show / hide combinators */ ValueKinds.CombinatorListOrNull,
        /* configurations */ ValueKinds.ConfigurationListOrNull,
        /* uri offset */ ValueKinds.Integer,
        /* uri */ ValueKinds.Name,
        /* metadata */ ValueKinds.MetadataListOrNull,
      ]),
    );

    List<CombinatorBuilder>? combinators =
        pop(NullValues.Combinators) as List<CombinatorBuilder>?;
    List<Configuration>? configurations =
        pop(NullValues.ConditionalUris) as List<Configuration>?;
    int uriOffset = popCharOffset();
    String uri = pop() as String;
    List<MetadataBuilder>? metadata = pop() as List<MetadataBuilder>?;
    _builderFactory.addExport(
      _offsetMap,
      exportKeyword,
      metadata,
      uri,
      configurations,
      combinators,
      exportKeyword.charOffset,
      uriOffset,
    );
    checkEmpty(exportKeyword.charOffset);
  }

  @override
  void handleImportPrefix(Token? deferredKeyword, Token? asKeyword) {
    debugEvent("handleImportPrefix");
    if (asKeyword == null) {
      // If asKeyword is null, then no prefix has been pushed on the stack.
      // Push a placeholder indicating that there is no prefix.
      push(NullValues.Prefix);
    }
    push(deferredKeyword != null);
  }

  @override
  void endImport(Token importKeyword, Token? semicolon) {
    debugEvent("endImport");
    assert(
      checkState(importKeyword, [
        /* show / hide combinators */ ValueKinds.CombinatorListOrNull,
        /* is deferred */ ValueKinds.Bool,
        /* prefix */ ValueKinds.PrefixOrParserRecoveryOrNull,
        /* configurations */ ValueKinds.ConfigurationListOrNull,
        /* uri offset */ ValueKinds.Integer,
        /* uri */ ValueKinds.Name,
        /* metadata */ ValueKinds.MetadataListOrNull,
      ]),
    );

    List<CombinatorBuilder>? combinators =
        pop(NullValues.Combinators) as List<CombinatorBuilder>?;
    bool isDeferred = pop() as bool;
    Object? prefix = pop(NullValues.Prefix);
    List<Configuration>? configurations =
        pop(NullValues.ConditionalUris) as List<Configuration>?;
    int uriOffset = popCharOffset();
    String uri =
        pop() as String; // For a conditional import, this is the default URI.
    List<MetadataBuilder>? metadata =
        pop(NullValues.Metadata) as List<MetadataBuilder>?;
    checkEmpty(importKeyword.charOffset);
    if (prefix is! Identifier?) {
      assert(
        prefix is ParserRecovery,
        "Unexpected prefix $prefix (${prefix.runtimeType}).",
      );
      return;
    }

    _builderFactory.addImport(
      offsetMap: _offsetMap,
      importKeyword: importKeyword,
      metadata: metadata,
      uri: uri,
      configurations: configurations,
      prefix: prefix?.name,
      combinators: combinators,
      deferred: isDeferred,
      charOffset: importKeyword.charOffset,
      prefixCharOffset: prefix?.nameOffset ?? TreeNode.noOffset,
      uriOffset: uriOffset,
    );
  }

  @override
  void endConditionalUris(int count) {
    debugEvent("endConditionalUris");
    push(
      const FixedNullableList<Configuration>().popNonNullable(
            stack,
            count,
            dummyConfiguration,
          ) ??
          NullValues.ConditionalUris,
    );
  }

  @override
  void endConditionalUri(Token ifKeyword, Token leftParen, Token? equalSign) {
    debugEvent("EndConditionalUri");
    int charOffset = popCharOffset();
    String uri = pop() as String;
    if (equalSign != null) {
      // Coverage-ignore-block(suite): Not run.
      popCharOffset();
    }
    String condition = popIfNotNull(equalSign) as String? ?? "true";
    Object? dottedName = pop();
    if (dottedName is ParserRecovery) {
      // Coverage-ignore-block(suite): Not run.
      push(dottedName);
    } else {
      push(new Configuration(charOffset, dottedName as String, condition, uri));
    }
  }

  @override
  void handleDottedName(int count, Token firstIdentifier) {
    debugEvent("DottedName");
    assert(
      checkState(
        firstIdentifier,
        repeatedKind(ValueKinds.IdentifierOrParserRecovery, count),
      ),
    );

    List<String>? names = popIdentifierList(count);
    if (names == null) {
      // Coverage-ignore-block(suite): Not run.
      push(new ParserRecovery(firstIdentifier.charOffset));
    } else {
      push(names.join('.'));
    }
  }

  @override
  void handleRecoverImport(Token? semicolon) {
    debugEvent("handleRecoverImport");
    assert(
      checkState(semicolon, [
        /* show / hide combinators */ ValueKinds.CombinatorListOrNull,
        /* is deferred */ ValueKinds.Bool,
        /* prefix */ ValueKinds.PrefixOrParserRecoveryOrNull,
        /* configurations */ ValueKinds.ConfigurationListOrNull,
      ]),
    );

    pop(NullValues.Combinators); // combinators
    pop(NullValues.Deferred); // deferredKeyword
    pop(NullValues.Prefix); // prefix
    pop(NullValues.ConditionalUris); // conditionalUris
  }

  @override
  void endPart(Token partKeyword, Token semicolon) {
    debugEvent("endPart");
    assert(
      checkState(partKeyword, [
        /* offset */ ValueKinds.Integer,
        /* uri string */ ValueKinds.String,
        /* metadata */ ValueKinds.MetadataListOrNull,
      ]),
    );

    int charOffset = popCharOffset();
    String uri = pop() as String;
    List<MetadataBuilder>? metadata = pop() as List<MetadataBuilder>?;
    _builderFactory.addPart(_offsetMap, partKeyword, metadata, uri, charOffset);
    checkEmpty(partKeyword.charOffset);
  }

  @override
  void handleOperatorName(Token operatorKeyword, Token token) {
    debugEvent("handleOperatorName");
    push(new OperatorIdentifier(token));
  }

  @override
  void handleInvalidOperatorName(Token operatorKeyword, Token token) {
    debugEvent("handleInvalidOperatorName");
    push(new SimpleIdentifier(token));
  }

  @override
  void handleIdentifier(Token token, IdentifierContext context) {
    debugEvent("handleIdentifier");
    if (context == IdentifierContext.enumValueDeclaration) {
      List<MetadataBuilder>? metadata = pop() as List<MetadataBuilder>?;
      if (token.isSynthetic) {
        push(new ParserRecovery(token.charOffset));
      } else {
        push(new EnumConstantInfo(metadata, token.lexeme, token.charOffset));
      }
    } else {
      if (!token.isSynthetic) {
        push(new SimpleIdentifier(token));
      } else {
        // This comes from a synthetic token which is inserted by the parser in
        // an attempt to recover.  This almost always means that the parser has
        // gotten very confused and we need to ignore the results.
        push(new ParserRecovery(token.charOffset));
      }
    }
  }

  @override
  void handleNoIdentifier(Token token, IdentifierContext context) {
    debugEvent("handleNoIdentifier");
    push(new OmittedIdentifier(token));
  }

  @override
  void handleStringPart(Token token) {
    debugEvent("StringPart");
    // Ignore string parts - report error later.
  }

  @override
  void endLiteralString(int interpolationCount, Token endToken) {
    debugEvent("endLiteralString");
    if (interpolationCount == 0) {
      Token token = pop() as Token;
      push(unescapeString(token.lexeme, token, this));
      push(token.charOffset);
    } else {
      Token beginToken = pop() as Token;
      int charOffset = beginToken.charOffset;
      push("${MALFORMED_URI_SCHEME}:bad${charOffset}");
      push(charOffset);
      // Point to dollar sign
      int interpolationOffset = charOffset + beginToken.lexeme.length;
      addProblem(diag.interpolationInUri, interpolationOffset, 1);
    }
  }

  @override
  void handleNativeClause(Token nativeToken, bool hasName) {
    debugEvent("NativeClause");
    if (hasName) {
      // Pop the native clause which in this case is a StringLiteral.
      pop(); // Char offset.
      Object? name = pop();
      if (name is ParserRecovery) {
        // Coverage-ignore-block(suite): Not run.
        nativeMethodName = '';
      } else {
        nativeMethodName = name as String; // String.
      }
    } else {
      nativeMethodName = '';
    }
  }

  @override
  // Coverage-ignore(suite): Not run.
  void handleAdjacentStringLiterals(Token startToken, int literalCount) {
    debugEvent("AdjacentStringLiterals");
    List<String> list = new List<String>.filled(
      literalCount,
      /* dummyValue = */ '',
    );
    int charOffset = -1;
    for (int i = literalCount - 1; i >= 0; i--) {
      charOffset = popCharOffset();
      list[i] = pop() as String;
    }
    push(list.join(""));
    push(charOffset);
  }

  @override
  void handleIdentifierList(int count) {
    debugEvent("endIdentifierList");
    assert(
      checkState(
        null,
        repeatedKind(ValueKinds.IdentifierOrParserRecovery, count),
      ),
    );
    push(
      popIdentifierList(count) ??
          // Coverage-ignore(suite): Not run.
          (count == 0 ? NullValues.IdentifierList : new ParserRecovery(-1)),
    );
  }

  @override
  void handleQualified(Token period) {
    assert(
      checkState(period, [
        /*suffix*/ ValueKinds.IdentifierOrParserRecovery,
        /*prefix*/ ValueKinds.IdentifierOrParserRecovery,
      ]),
    );
    debugEvent("handleQualified");
    Object? suffix = pop();
    Object prefix = pop()!;
    if (prefix is! Identifier) {
      // Coverage-ignore-block(suite): Not run.
      assert(
        prefix is ParserRecovery,
        "Unexpected prefix $prefix (${prefix.runtimeType})",
      );
      push(prefix);
    } else if (suffix is! SimpleIdentifier) {
      assert(
        suffix is ParserRecovery,
        "Unexpected suffix $suffix (${suffix.runtimeType})",
      );
      push(suffix);
    } else {
      push(suffix.withIdentifierQualifier(prefix));
    }
  }

  @override
  void endLibraryName(Token libraryKeyword, Token semicolon, bool hasName) {
    debugEvent("endLibraryName");
    assert(
      checkState(libraryKeyword, [
        if (hasName) ValueKinds.IdentifierOrParserRecovery,
        ValueKinds.MetadataListOrNull,
      ]),
    );
    Object? name = null;
    if (hasName) {
      name = pop();
    }
    String? libraryName;
    List<MetadataBuilder>? metadata = pop() as List<MetadataBuilder>?;
    if (name != null && name is! ParserRecovery) {
      libraryName = flattenName(
        name as Identifier,
        offsetForToken(libraryKeyword),
        uri,
      );
    } else {
      reportIfNotEnabled(
        libraryFeatures.unnamedLibraries,
        semicolon.charOffset,
        noLength,
      );
    }
    _builderFactory.addLibraryDirective(
      libraryName: libraryName,
      fileOffset: libraryKeyword.charOffset,
      metadata: metadata,
    );
  }

  @override
  // Coverage-ignore(suite): Not run.
  void endLibraryAugmentation(
    Token augmentKeyword,
    Token libraryKeyword,
    Token semicolon,
  ) {
    debugEvent("endLibraryAugmentation");
    assert(
      checkState(libraryKeyword, [
        /* uri offset */ ValueKinds.Integer,
        /* uri string */ ValueKinds.String,
        /* metadata */ ValueKinds.MetadataListOrNull,
      ]),
    );
    // TODO(johnniwinther): Pass uri to [libraryBuilder] and verify it.
    pop() as int;
    pop() as String;
    List<MetadataBuilder>? metadata = pop() as List<MetadataBuilder>?;
    _builderFactory.addLibraryDirective(
      libraryName: null,
      fileOffset: libraryKeyword.charOffset,
      metadata: metadata,
    );
  }

  @override
  void beginClassOrMixinOrNamedMixinApplicationPrelude(Token token) {
    debugEvent("beginClassOrNamedMixinApplicationPrelude");
    pushDeclarationContext(
      DeclarationContext.ClassOrMixinOrNamedMixinApplication,
    );
    _builderFactory.beginClassOrNamedMixinApplicationHeader();
  }

  @override
  void beginClassDeclaration(
    Token begin,
    Token? abstractToken,
    Token? sealedToken,
    Token? baseToken,
    Token? interfaceToken,
    Token? finalToken,
    Token? augmentToken,
    Token? mixinToken,
    Token name,
  ) {
    debugEvent("beginClassDeclaration");
    popDeclarationContext(
      DeclarationContext.ClassOrMixinOrNamedMixinApplication,
    );
    pushDeclarationContext(DeclarationContext.Class);
    NominalParameters? typeParameters =
        peek(NullValues.NominalParameters) as NominalParameters?;
    if (sealedToken != null) {
      if (reportIfNotEnabled(
        libraryFeatures.sealedClass,
        sealedToken.charOffset,
        sealedToken.length,
      )) {
        sealedToken = null;
      }
    }
    if (baseToken != null) {
      if (reportIfNotEnabled(
        libraryFeatures.classModifiers,
        baseToken.charOffset,
        baseToken.length,
      )) {
        baseToken = null;
      }
    }
    if (interfaceToken != null) {
      if (reportIfNotEnabled(
        libraryFeatures.classModifiers,
        interfaceToken.charOffset,
        interfaceToken.length,
      )) {
        interfaceToken = null;
      }
    }
    if (finalToken != null) {
      if (reportIfNotEnabled(
        libraryFeatures.classModifiers,
        finalToken.charOffset,
        finalToken.length,
      )) {
        finalToken = null;
      }
    }
    if (mixinToken != null) {
      if (reportIfNotEnabled(
        libraryFeatures.classModifiers,
        mixinToken.charOffset,
        mixinToken.length,
      )) {
        mixinToken = null;
      }
    }
    _builderFactory.beginClassDeclaration(
      name.lexeme,
      name.charOffset,
      typeParameters?.fragments,
    );
    Modifiers modifiers = Modifiers.from(
      abstractToken: abstractToken,
      sealedToken: sealedToken,
      baseToken: baseToken,
      interfaceToken: interfaceToken,
      finalToken: finalToken,
      augmentToken: augmentToken,
      mixinToken: mixinToken,
    );

    inAbstractOrSealedClass = modifiers.isAbstract || modifiers.isSealed;
    push(modifiers);
  }

  @override
  void beginMixinDeclaration(
    Token beginToken,
    Token? augmentToken,
    Token? baseToken,
    Token mixinKeyword,
    Token name,
  ) {
    debugEvent("beginMixinDeclaration");
    popDeclarationContext(
      DeclarationContext.ClassOrMixinOrNamedMixinApplication,
    );
    pushDeclarationContext(DeclarationContext.Mixin);
    NominalParameters? typeParameters =
        pop(NullValues.NominalParameters) as NominalParameters?;
    if (baseToken != null) {
      if (reportIfNotEnabled(
        libraryFeatures.classModifiers,
        baseToken.charOffset,
        baseToken.length,
      )) {
        baseToken = null;
      }
    }
    Modifiers modifiers = Modifiers.from(
      augmentToken: augmentToken,
      baseToken: baseToken,
    );
    push(modifiers);
    push(typeParameters ?? NullValues.NominalParameters);
    _builderFactory.beginMixinDeclaration(
      name.lexeme,
      name.charOffset,
      typeParameters?.fragments,
    );
  }

  @override
  void beginClassOrMixinOrExtensionBody(DeclarationKind kind, Token token) {
    DeclarationContext declarationContext;
    switch (kind) {
      case DeclarationKind.TopLevel:
        // Coverage-ignore(suite): Not run.
        throw new UnsupportedError('Unexpected top level body.');
      case DeclarationKind.Class:
        declarationContext = DeclarationContext.ClassBody;
        _builderFactory.beginClassBody();
        break;
      case DeclarationKind.Mixin:
        declarationContext = DeclarationContext.MixinBody;
        _builderFactory.beginMixinBody();
        break;
      case DeclarationKind.Extension:
        declarationContext = DeclarationContext.ExtensionBody;
        assert(
          checkState(token, [
            unionOfKinds([
              ValueKinds.ParserRecovery,
              ValueKinds.TypeBuilder,
              ValueKinds.Modifiers,
              ValueKinds.NominalTypeParametersOrNull,
            ]),
          ]),
        );
        _builderFactory.beginExtensionBody();
        break;
      case DeclarationKind.ExtensionType:
        declarationContext = DeclarationContext.ExtensionTypeBody;
        _builderFactory.beginExtensionTypeBody();
        break;
      // Coverage-ignore(suite): Not run.
      case DeclarationKind.Enum:
        declarationContext = DeclarationContext.Enum;
        // [BuilderFactory.beginEnumBody] is called in [handleEnumHeader].
        break;
    }
    pushDeclarationContext(declarationContext);
    debugEvent("beginClassOrMixinBody");
  }

  @override
  void beginNamedMixinApplication(
    Token begin,
    Token? abstractToken,
    Token? sealedToken,
    Token? baseToken,
    Token? interfaceToken,
    Token? finalToken,
    Token? augmentToken,
    Token? mixinToken,
    Token name,
  ) {
    debugEvent("beginNamedMixinApplication");
    popDeclarationContext(
      DeclarationContext.ClassOrMixinOrNamedMixinApplication,
    );
    pushDeclarationContext(DeclarationContext.NamedMixinApplication);
    NominalParameters? typeParameters =
        peek(NullValues.NominalParameters) as NominalParameters?;
    _builderFactory.beginNamedMixinApplication(
      name.lexeme,
      name.charOffset,
      typeParameters?.fragments,
    );
    if (sealedToken != null) {
      if (reportIfNotEnabled(
        libraryFeatures.sealedClass,
        sealedToken.charOffset,
        sealedToken.length,
      )) {
        sealedToken = null;
      }
    }
    if (baseToken != null) {
      if (reportIfNotEnabled(
        libraryFeatures.classModifiers,
        baseToken.charOffset,
        baseToken.length,
      )) {
        baseToken = null;
      }
    }
    if (interfaceToken != null) {
      if (reportIfNotEnabled(
        libraryFeatures.classModifiers,
        interfaceToken.charOffset,
        interfaceToken.length,
      )) {
        interfaceToken = null;
      }
    }
    if (finalToken != null) {
      if (reportIfNotEnabled(
        libraryFeatures.classModifiers,
        finalToken.charOffset,
        finalToken.length,
      )) {
        finalToken = null;
      }
    }
    if (mixinToken != null) {
      if (reportIfNotEnabled(
        libraryFeatures.classModifiers,
        mixinToken.charOffset,
        mixinToken.length,
      )) {
        mixinToken = null;
      }
    }
    push(
      Modifiers.from(
        abstractToken: abstractToken,
        sealedToken: sealedToken,
        baseToken: baseToken,
        interfaceToken: interfaceToken,
        finalToken: finalToken,
        augmentToken: augmentToken,
        mixinToken: mixinToken,
      ),
    );
  }

  @override
  void handleImplements(Token? implementsKeyword, int interfacesCount) {
    debugEvent("Implements");
    push(
      const FixedNullableList<TypeBuilder>().popNonNullable(
            stack,
            interfacesCount,
            dummyTypeBuilder,
          ) ??
          NullValues.TypeBuilderList,
    );

    if (implementsKeyword != null &&
        declarationContext == DeclarationContext.Enum) {
      reportIfNotEnabled(
        libraryFeatures.enhancedEnums,
        implementsKeyword.charOffset,
        implementsKeyword.length,
      );
    }
  }

  @override
  void handleRecoverDeclarationHeader(DeclarationHeaderKind kind) {
    debugEvent("handleRecoverClassHeader");
    assert(
      checkState(null, [
        /* interfaces */ ValueKinds.TypeBuilderListOrNull,
        /* mixins */ unionOfKinds([
          ValueKinds.TypeBuilderListOrNull,
          ValueKinds.ParserRecovery,
        ]),
        /* supertype offset */ ValueKinds.Integer,
        /* supertype */ unionOfKinds([
          ValueKinds.TypeBuilderOrNull,
          ValueKinds.ParserRecovery,
        ]),
      ]),
    );
    // TODO(jensj): Possibly use these instead... E.g. "class A extend B {}"
    // will get here (because it's 'extends' with an 's') and discard the B...
    // Also Analyzer actually merges the information meaning that the two could
    // give different errors (if, say, one later assigns
    // A to a variable of type B).
    pop(NullValues.TypeBuilderList); // Interfaces.
    pop(NullValues.TypeBuilderList); // Mixins.
    pop(); // Supertype offset.
    pop(NullValues.TypeBuilder); // Supertype.
  }

  @override
  void handleRecoverMixinHeader() {
    debugEvent("handleRecoverMixinHeader");
    // TODO(jensj): Possibly use these instead...
    // See also handleRecoverClassHeader
    pop(NullValues.TypeBuilderList); // Interfaces.
    pop(NullValues.TypeBuilderList); // Supertype constraints.
  }

  @override
  void handleClassExtends(Token? extendsKeyword, int typeCount) {
    debugEvent("handleClassExtends");
    while (typeCount > 1) {
      pop();
      typeCount--;
    }
    push(extendsKeyword?.charOffset ?? -1);
  }

  @override
  void handleMixinOn(Token? onKeyword, int typeCount) {
    debugEvent("handleMixinOn");
    push(
      const FixedNullableList<TypeBuilder>().popNonNullable(
            stack,
            typeCount,
            dummyTypeBuilder,
          ) ??
          new ParserRecovery(offsetForToken(onKeyword)),
    );
  }

  @override
  void endClassDeclaration(Token beginToken, Token endToken) {
    debugEvent("endClassDeclaration");
    assert(
      checkState(beginToken, [
        /* interfaces */ ValueKinds.TypeBuilderListOrNull,
        /* mixins */ unionOfKinds([
          ValueKinds.TypeBuilderListOrNull,
          ValueKinds.ParserRecovery,
        ]),
        /* supertype offset */ ValueKinds.Integer,
        /* supertype */ unionOfKinds([
          ValueKinds.TypeBuilderOrNull,
          ValueKinds.ParserRecovery,
        ]),
        /* modifiers */ ValueKinds.Modifiers,
        /* type parameters */ ValueKinds.NominalTypeParametersOrNull,
        /* name */ ValueKinds.IdentifierOrParserRecovery,
        /* metadata */ ValueKinds.MetadataListOrNull,
      ]),
    );

    List<TypeBuilder>? interfaces =
        pop(NullValues.TypeBuilderList) as List<TypeBuilder>?;
    List<TypeBuilder>? mixins = nullIfParserRecovery(
      pop(NullValues.TypeBuilderList),
    ) as List<TypeBuilder>?;
    int supertypeOffset = popCharOffset();
    TypeBuilder? supertype = nullIfParserRecovery(pop()) as TypeBuilder?;
    Modifiers modifiers = pop() as Modifiers;
    NominalParameters? typeParameters =
        pop(NullValues.NominalParameters) as NominalParameters?;
    Object? name = pop();
    List<MetadataBuilder>? metadata = pop() as List<MetadataBuilder>?;
    inAbstractOrSealedClass = false;
    checkEmpty(beginToken.charOffset);
    if (name is ParserRecovery) {
      // Coverage-ignore-block(suite): Not run.
      _builderFactory.endClassDeclarationForParserRecovery(
        typeParameters?.fragments,
      );
    } else {
      Identifier identifier = name as Identifier;
      final int startOffset = metadata?.first.atOffset ?? beginToken.charOffset;

      String classNameForErrors = identifier.name;
      if (supertype != null) {
        if (supertype.nullabilityBuilder.build() == Nullability.nullable) {
          _compilationUnit.addProblem(
            diag.nullableSuperclassError.withArguments(
              supertypeName: supertype.fullNameForErrors,
            ),
            identifier.nameOffset,
            classNameForErrors.length,
            uri,
          );
        }
      }
      if (mixins != null) {
        for (TypeBuilder mixin in mixins) {
          if (mixin.nullabilityBuilder.build() == Nullability.nullable) {
            _compilationUnit.addProblem(
              diag.nullableMixinError.withArguments(
                mixinName: mixin.fullNameForErrors,
              ),
              identifier.nameOffset,
              classNameForErrors.length,
              uri,
            );
          }
        }
      }
      if (interfaces != null) {
        for (TypeBuilder interface in interfaces) {
          if (interface.nullabilityBuilder.build() == Nullability.nullable) {
            _compilationUnit.addProblem(
              diag.nullableInterfaceError.withArguments(
                interfaceName: interface.fullNameForErrors,
              ),
              identifier.nameOffset,
              classNameForErrors.length,
              uri,
            );
          }
        }
      }

      if (modifiers.isSealed) {
        modifiers |= Modifiers.Abstract;
      }
      _builderFactory.addClass(
        offsetMap: _offsetMap,
        metadata: metadata,
        modifiers: modifiers,
        identifier: identifier,
        typeParameters: typeParameters?.fragments,
        supertype: supertype,
        mixins: mixins,
        interfaces: interfaces,
        startOffset: startOffset,
        nameOffset: identifier.nameOffset,
        endOffset: endToken.charOffset,
        supertypeOffset: supertypeOffset,
      );
    }
    popDeclarationContext(DeclarationContext.Class);
  }

  Object? nullIfParserRecovery(Object? node) {
    return node is ParserRecovery ? null : node;
  }

  @override
  void endMixinDeclaration(Token beginToken, Token endToken) {
    debugEvent("endMixinDeclaration");
    assert(
      checkState(beginToken, [
        /* interfaces */ ValueKinds.TypeBuilderListOrNull,
        /* supertypeConstraints */ unionOfKinds([
          ValueKinds.TypeBuilderListOrNull,
          ValueKinds.ParserRecovery,
        ]),
        /* type parameters */ ValueKinds.NominalTypeParametersOrNull,
        /* modifiers */ ValueKinds.Modifiers,
        /* name */ ValueKinds.IdentifierOrParserRecovery,
        /* metadata */ ValueKinds.MetadataListOrNull,
      ]),
    );

    List<TypeBuilder>? interfaces =
        pop(NullValues.TypeBuilderList) as List<TypeBuilder>?;
    List<TypeBuilder>? supertypeConstraints =
        nullIfParserRecovery(pop()) as List<TypeBuilder>?;
    NominalParameters? typeParameters =
        pop(NullValues.NominalParameters) as NominalParameters?;
    Modifiers modifiers = pop() as Modifiers;
    Object? name = pop();
    List<MetadataBuilder>? metadata =
        pop(NullValues.Metadata) as List<MetadataBuilder>?;
    checkEmpty(beginToken.charOffset);
    if (name is ParserRecovery) {
      // Coverage-ignore-block(suite): Not run.
      _builderFactory.endMixinDeclarationForParserRecovery(
        typeParameters?.fragments,
      );
    } else {
      Identifier identifier = name as Identifier;
      int startOffset =
          metadata
              // Coverage-ignore(suite): Not run.
              ?.first // Coverage-ignore(suite): Not run.
              .atOffset ??
          beginToken.charOffset;
      String classNameForErrors = identifier.name;
      if (supertypeConstraints != null) {
        for (TypeBuilder supertype in supertypeConstraints) {
          if (supertype.nullabilityBuilder.build() == Nullability.nullable) {
            _compilationUnit.addProblem(
              diag.nullableSuperclassError.withArguments(
                supertypeName: supertype.fullNameForErrors,
              ),
              identifier.nameOffset,
              classNameForErrors.length,
              uri,
            );
          }
        }
      }
      if (interfaces != null) {
        for (TypeBuilder interface in interfaces) {
          if (interface.nullabilityBuilder.build() == Nullability.nullable) {
            _compilationUnit.addProblem(
              diag.nullableInterfaceError.withArguments(
                interfaceName: interface.fullNameForErrors,
              ),
              identifier.nameOffset,
              classNameForErrors.length,
              uri,
            );
          }
        }
      }

      _builderFactory.addMixinDeclaration(
        offsetMap: _offsetMap,
        metadata: metadata,
        modifiers: modifiers,
        identifier: identifier,
        typeParameters: typeParameters?.fragments,
        supertypeConstraints: supertypeConstraints,
        interfaces: interfaces,
        startOffset: startOffset,
        nameOffset: identifier.nameOffset,
        endOffset: endToken.charOffset,
      );
    }
    popDeclarationContext(DeclarationContext.Mixin);
  }

  @override
  void beginExtensionDeclarationPrelude(Token extensionKeyword) {
    assert(checkState(extensionKeyword, [ValueKinds.MetadataListOrNull]));
    debugEvent("beginExtensionDeclaration");
    pushDeclarationContext(DeclarationContext.ExtensionOrExtensionType);
    _builderFactory.beginExtensionOrExtensionTypeHeader();
  }

  @override
  void beginExtensionDeclaration(
    Token? augmentToken,
    Token extensionKeyword,
    Token? nameToken,
  ) {
    assert(
      checkState(extensionKeyword, [
        ValueKinds.NominalTypeParametersOrNull,
        ValueKinds.MetadataListOrNull,
      ]),
    );
    debugEvent("beginExtensionDeclaration");
    popDeclarationContext(DeclarationContext.ExtensionOrExtensionType);
    pushDeclarationContext(DeclarationContext.Extension);
    NominalParameters? typeParameters =
        pop(NullValues.NominalParameters) as NominalParameters?;
    int offset = nameToken?.charOffset ?? extensionKeyword.charOffset;
    push(
      nameToken != null
          ? new SimpleIdentifier(nameToken)
          : NullValues.Identifier,
    );
    push(typeParameters ?? NullValues.NominalParameters);
    _builderFactory.beginExtensionDeclaration(
      nameToken?.lexeme,
      offset,
      typeParameters?.fragments,
    );
    Modifiers modifiers = Modifiers.from(augmentToken: augmentToken);
    push(modifiers);
  }

  @override
  void endExtensionDeclaration(
    Token beginToken,
    Token extensionKeyword,
    Token? onKeyword,
    Token endToken,
  ) {
    assert(
      checkState(extensionKeyword, [
        if (onKeyword != null)
          unionOfKinds([ValueKinds.ParserRecovery, ValueKinds.TypeBuilder]),
        ValueKinds.Modifiers,
        ValueKinds.NominalTypeParametersOrNull,
        ValueKinds.IdentifierOrNull,
        ValueKinds.MetadataListOrNull,
      ]),
    );
    debugEvent("endExtensionDeclaration");

    Object? onType;
    if (onKeyword == null) {
      onType = new FixedTypeBuilderImpl(
        const InvalidType(),
        uri,
        extensionKeyword.charOffset,
      );
    } else {
      onType = pop();
      if (onType is ParserRecovery) {
        ParserRecovery parserRecovery = onType;
        onType = new FixedTypeBuilderImpl(
          const InvalidType(),
          uri,
          parserRecovery.charOffset,
        );
      }
    }
    Modifiers modifiers = pop() as Modifiers;
    NominalParameters? typeParameters =
        pop(NullValues.NominalParameters) as NominalParameters?;
    Identifier? name = pop(NullValues.Identifier) as Identifier?;
    List<MetadataBuilder>? metadata =
        pop(NullValues.Metadata) as List<MetadataBuilder>?;
    checkEmpty(extensionKeyword.charOffset);
    int startOffset = metadata?.first.atOffset ?? extensionKeyword.charOffset;
    _builderFactory.addExtensionDeclaration(
      offsetMap: _offsetMap,
      beginToken: beginToken,
      metadata: metadata,
      modifiers: modifiers,
      identifier: name,
      typeParameters: typeParameters?.fragments,
      onType: onType as TypeBuilder,
      startOffset: startOffset,
      endOffset: endToken.charOffset,
    );
    popDeclarationContext(DeclarationContext.Extension);
  }

  @override
  void beginExtensionTypeDeclaration(
    Token? augmentToken,
    Token extensionKeyword,
    Token nameToken,
  ) {
    assert(
      checkState(extensionKeyword, [
        ValueKinds.NominalTypeParametersOrNull,
        ValueKinds.MetadataListOrNull,
      ]),
    );
    debugEvent("beginExtensionTypeDeclaration");
    popDeclarationContext(DeclarationContext.ExtensionOrExtensionType);
    pushDeclarationContext(DeclarationContext.ExtensionType);
    NominalParameters? typeParameters =
        pop(NullValues.NominalParameters) as NominalParameters?;
    String name = nameToken.lexeme;
    int nameOffset = nameToken.charOffset;
    push(new SimpleIdentifier(nameToken));
    push(typeParameters ?? NullValues.NominalParameters);

    _builderFactory.beginExtensionTypeDeclaration(
      name,
      nameOffset,
      typeParameters?.fragments,
    );

    Modifiers modifiers = Modifiers.from(augmentToken: augmentToken);
    push(modifiers);
  }

  @override
  void endExtensionTypeDeclaration(
    Token beginToken,
    Token? augmentToken,
    Token extensionKeyword,
    Token typeKeyword,
    Token endToken,
  ) {
    assert(
      checkState(extensionKeyword, [
        ValueKinds.TypeBuilderListOrNull,
        ValueKinds.Modifiers,
        ValueKinds.NominalTypeParametersOrNull,
        ValueKinds.Identifier,
        ValueKinds.MetadataListOrNull,
      ]),
    );
    reportIfNotEnabled(
      libraryFeatures.inlineClass,
      typeKeyword.charOffset,
      typeKeyword.length,
    );

    List<TypeBuilder>? interfaces =
        pop(NullValues.TypeBuilderList) as List<TypeBuilder>?;
    Modifiers modifiers = pop() as Modifiers;
    NominalParameters? typeParameters =
        pop(NullValues.NominalParameters) as NominalParameters?;
    Identifier identifier = pop() as Identifier;
    List<MetadataBuilder>? metadata =
        pop(NullValues.Metadata) as List<MetadataBuilder>?;
    checkEmpty(extensionKeyword.charOffset);

    reportIfNotEnabled(
      libraryFeatures.inlineClass,
      extensionKeyword.next!.charOffset,
      extensionKeyword.next!.length,
    );
    int startOffset = metadata?.first.atOffset ?? beginToken.charOffset;
    _builderFactory.addExtensionTypeDeclaration(
      offsetMap: _offsetMap,
      metadata: metadata,
      modifiers: modifiers,
      identifier: identifier,
      typeParameters: typeParameters?.fragments,
      interfaces: interfaces,
      startOffset: startOffset,
      endOffset: endToken.charOffset,
    );

    popDeclarationContext(DeclarationContext.ExtensionType);
  }

  @override
  void beginPrimaryConstructor(Token beginToken) {}

  @override
  void endPrimaryConstructor(
    DeclarationKind kind,
    Token beginToken,
    Token endToken,
    Token? constKeyword,
    bool hasConstructorName,
  ) {
    assert(
      checkState(beginToken, [
        ValueKinds.FormalListOrNull,
        /* formals offset */ ValueKinds.Integer,
        if (hasConstructorName) ValueKinds.IdentifierOrParserRecovery,
      ]),
    );
    List<FormalParameterBuilder>? formals =
        pop(NullValues.FormalParameters) as List<FormalParameterBuilder>?;
    int charOffset = pop() as int; // Pop formals char offset

    int? nameOffset;
    int formalsOffset = charOffset;

    String? name;
    if (hasConstructorName) {
      // TODO(johnniwinther): Handle [ParserRecovery].
      Identifier identifier = pop() as Identifier;
      nameOffset = charOffset = identifier.nameOffset;
      name = identifier.name;
    }

    int? startOffset = constKeyword?.charOffset ?? nameOffset ?? formalsOffset;

    switch (kind) {
      case DeclarationKind.TopLevel:
      case DeclarationKind.Mixin:
      case DeclarationKind.Extension:
        // Invalid. Error reported in the parser.
        break;
      case DeclarationKind.ExtensionType:
        // Always valid.
        break;
      case DeclarationKind.Class:
      case DeclarationKind.Enum:
        reportIfNotEnabled(
          libraryFeatures.primaryConstructors,
          beginToken.charOffset,
          noLength,
        );
    }

    if (formals != null) {
      int requiredPositionalCount = 0;
      int? firstNamedParameterOffset;
      int? firstOptionalPositionalParameterOffset;
      for (int i = 0; i < formals.length; i++) {
        FormalParameterBuilder formal = formals[i];
        List<MetadataBuilder>? metadata = formal.takeMetadata();
        Modifiers modifiers = formal.modifiers;
        if (kind == DeclarationKind.ExtensionType) {
          // Extension type representation fields are implicitly final.
          modifiers |= Modifiers.Final;
          modifiers |= Modifiers.DeclaringParameter;
          TypeBuilder type = formal.type;
          if (type is FunctionTypeBuilder &&
              type.hasFunctionFormalParameterSyntax) {
            _compilationUnit.addProblem(
              // ignore: lines_longer_than_80_chars
              diag.extensionTypePrimaryConstructorFunctionFormalParameterSyntax,
              formal.fileOffset,
              formal.name.length,
              formal.fileUri,
            );
          }
          if (libraryFeatures.primaryConstructors.isEnabled) {
            if (formal.modifiers.containsSyntacticModifiers(
              // Already reported in the parser.
              ignoreConst: true,
              ignoreCovariant: true,
              ignoreRequired: true,
              // Final is allowed.
              ignoreFinal: true,
            )) {
              _compilationUnit.addProblem(
                diag.representationFieldModifier,
                formal.fileOffset,
                formal.name.length,
                formal.fileUri,
              );
            }
          } else {
            if (type is ImplicitTypeBuilder) {
              _compilationUnit.addProblem(
                diag.expectedRepresentationType,
                formal.fileOffset,
                formal.name.length,
                formal.fileUri,
              );
              formal.type = new InvalidTypeBuilderImpl(
                formal.fileUri,
                formal.fileOffset,
              );
            }
            if (formal.modifiers.containsSyntacticModifiers(
              // Already reported in the parser.
              ignoreCovariant: true,
              ignoreRequired: true,
              // Reported above as missing a representation type.
              ignoreVar: true,
            )) {
              _compilationUnit.addProblem(
                diag.representationFieldModifier,
                formal.fileOffset,
                formal.name.length,
                formal.fileUri,
              );
            }
          }
          if (formal.isInitializingFormal) {
            _compilationUnit.addProblem(
              diag.extensionTypePrimaryConstructorWithInitializingFormal,
              formal.fileOffset,
              formal.name.length,
              formal.fileUri,
            );
          }
        }

        if (formal.isPositional) {
          if (formal.isOptionalPositional) {
            firstOptionalPositionalParameterOffset = formal.fileOffset;
          } else {
            requiredPositionalCount++;
          }
        }
        if (formal.isNamed) {
          firstNamedParameterOffset = formal.fileOffset;
        }
        if (modifiers.isDeclaringParameter) {
          _builderFactory.addPrimaryConstructorField(
            metadata: metadata,
            modifiers: modifiers,
            type: formal.type,
            name: formal.name,
            nameOffset: formal.fileOffset,
            // We copy the default value token to the primary constructor field
            // in order to support field type inference from the default value.
            defaultValueToken: libraryFeatures.primaryConstructors.isEnabled
                ? formal.copyDefaultValueToken()
                : null,
          );
        }
        formals[i] = formal.forPrimaryConstructor(
          _builderFactory,
          isDeclaring: modifiers.isDeclaringParameter,
        );
      }
      if (kind == DeclarationKind.ExtensionType) {
        if (libraryFeatures.primaryConstructors.isEnabled) {
          if (formals.isEmpty) {
            _compilationUnit.addProblem(
              diag.expectedRepresentationField,
              charOffset,
              1,
              uri,
            );
          } else if (formals.length > 1) {
            _compilationUnit.addProblem(
              diag.multipleRepresentationFields,
              charOffset,
              1,
              uri,
            );
          }
        } else {
          if (firstOptionalPositionalParameterOffset != null) {
            _compilationUnit.addProblem(
              diag.optionalParametersInExtensionTypeDeclaration,
              firstOptionalPositionalParameterOffset,
              1,
              uri,
            );
          } else if (firstNamedParameterOffset != null) {
            _compilationUnit.addProblem(
              diag.namedParametersInExtensionTypeDeclaration,
              firstNamedParameterOffset,
              1,
              uri,
            );
          } else if (requiredPositionalCount == 0) {
            _compilationUnit.addProblem(
              diag.expectedRepresentationField,
              charOffset,
              1,
              uri,
            );
          } else if (formals.length > 1) {
            _compilationUnit.addProblem(
              diag.multipleRepresentationFields,
              charOffset,
              1,
              uri,
            );
          }
        }
      }
    }

    bool forAbstractClassOrEnumOrMixin =
        inAbstractOrSealedClass ||
        kind == DeclarationKind.Mixin ||
        kind == DeclarationKind.Enum;

    _builderFactory.addPrimaryConstructor(
      offsetMap: _offsetMap,
      beginToken: beginToken,
      name: name,
      startOffset: startOffset,
      endOffset: endToken.charOffset,
      nameOffset: nameOffset,
      formalsOffset: formalsOffset,
      formals: formals,
      isConst: constKeyword != null,
      forAbstractClassOrEnumOrMixin: forAbstractClassOrEnumOrMixin,
    );
  }

  @override
  void endPrimaryConstructorBody(
    Token beginToken,
    Token thisToken,
    Token? beginInitializers,
    Token endToken,
  ) {
    debugEvent("endPrimaryConstructorBody");
    assert(
      checkState(beginToken, [
        /* method body token */ ValueKinds.Token,
        ValueKinds.MethodBody,
        ValueKinds.AsyncModifier,
        ValueKinds.MetadataListOrNull,
      ]),
    );

    Token methodBodyToken = pop() as Token;
    MethodBody methodBody = pop() as MethodBody;
    pop() as AsyncModifier;
    List<MetadataBuilder>? metadata = pop() as List<MetadataBuilder>?;
    _builderFactory.addPrimaryConstructorBody(
      offsetMap: _offsetMap,
      metadata: metadata,
      beginToken: beginToken,
      endOffset: endToken.charOffset,
      initializersStartToken: beginInitializers,
      hasBody: methodBody != MethodBody.Abstract,
      bodyOffset: methodBodyToken.charOffset,
    );
  }

  @override
  void beginTopLevelMethod(
    Token lastConsumed,
    Token? augmentToken,
    Token? externalToken,
  ) {
    pushDeclarationContext(DeclarationContext.TopLevelMethod);
    _builderFactory.beginTopLevelMethod();
    Modifiers modifiers = Modifiers.from(
      augmentToken: augmentToken,
      externalToken: externalToken,
    );
    push(modifiers);
  }

  @override
  void endTopLevelMethod(Token beginToken, Token? getOrSet, Token endToken) {
    debugEvent("endTopLevelMethod");
    assert(
      checkState(beginToken, [
        /* method body token */ ValueKinds.Token,
        ValueKinds.MethodBody,
        ValueKinds.AsyncModifier,
        ValueKinds.FormalListOrNull,
        /* formalsOffset */ ValueKinds.Integer,
        ValueKinds.NominalTypeParametersOrNull,
        ValueKinds.IdentifierOrParserRecovery,
        ValueKinds.TypeBuilderOrNull,
        ValueKinds.Modifiers,
        ValueKinds.MetadataListOrNull,
      ]),
    );

    pop() as Token; // Method body token
    MethodBody kind = pop() as MethodBody;
    AsyncModifier asyncModifier = pop() as AsyncModifier;
    List<FormalParameterBuilder>? formals =
        pop() as List<FormalParameterBuilder>?;
    int formalsOffset = popCharOffset();
    NominalParameters? typeParameters =
        pop(NullValues.NominalParameters) as NominalParameters?;
    Object? identifier = pop();
    TypeBuilder? returnType = pop() as TypeBuilder?;
    bool isAbstract = kind == MethodBody.Abstract;
    if (getOrSet != null && getOrSet.isA(Keyword.SET)) {
      if (formals == null || formals.length != 1) {
        // This isn't abstract as we'll add an error-recovery node in
        // [BodyBuilder.finishFunction].
        isAbstract = false;
      }
    }
    Modifiers modifiers = pop() as Modifiers;
    if (isAbstract && !modifiers.isExternal) {
      modifiers |= Modifiers.Abstract;
    }
    if (nativeMethodName != null) {
      modifiers |= Modifiers.External;
    }
    List<MetadataBuilder>? metadata = pop() as List<MetadataBuilder>?;
    checkEmpty(beginToken.charOffset);
    if (identifier is Identifier) {
      final int startOffset = metadata?.first.atOffset ?? beginToken.charOffset;
      int nameOffset = identifier.nameOffset;
      int endOffset = endToken.charOffset;
      ProcedureKind kind = computeProcedureKind(getOrSet);
      switch (kind) {
        case ProcedureKind.Method:
        case ProcedureKind.Operator:
          _builderFactory.addMethod(
            offsetMap: _offsetMap,
            metadata: metadata,
            modifiers: modifiers,
            returnType: returnType,
            identifier: identifier,
            name: identifier.name,
            typeParameters: typeParameters?.fragments,
            formals: formals,
            isOperator: false,
            startOffset: startOffset,
            nameOffset: nameOffset,
            formalsOffset: formalsOffset,
            endOffset: endOffset,
            nativeMethodName: nativeMethodName,
            asyncModifier: asyncModifier,
            isInstanceMember: false,
            isExtensionMember: false,
            isExtensionTypeMember: false,
          );
        case ProcedureKind.Getter:
          _builderFactory.addGetter(
            offsetMap: _offsetMap,
            metadata: metadata,
            modifiers: modifiers,
            returnType: returnType,
            identifier: identifier,
            name: identifier.name,
            typeParameters: typeParameters
                // Coverage-ignore(suite): Not run.
                ?.fragments,
            formals: formals,
            startOffset: startOffset,
            nameOffset: nameOffset,
            formalsOffset: formalsOffset,
            endOffset: endOffset,
            nativeMethodName: nativeMethodName,
            asyncModifier: asyncModifier,
            isInstanceMember: false,
            isExtensionMember: false,
            isExtensionTypeMember: false,
          );
        case ProcedureKind.Setter:
          _builderFactory.addSetter(
            offsetMap: _offsetMap,
            metadata: metadata,
            modifiers: modifiers,
            returnType: returnType,
            identifier: identifier,
            name: identifier.name,
            typeParameters: typeParameters
                // Coverage-ignore(suite): Not run.
                ?.fragments,
            formals: formals,
            startOffset: startOffset,
            nameOffset: nameOffset,
            formalsOffset: formalsOffset,
            endOffset: endOffset,
            nativeMethodName: nativeMethodName,
            asyncModifier: asyncModifier,
            isInstanceMember: false,
            isExtensionMember: false,
            isExtensionTypeMember: false,
          );
        // Coverage-ignore(suite): Not run.
        case ProcedureKind.Factory:
          throw new UnsupportedError("Unexpected procedure kind: $kind");
      }
      nativeMethodName = null;
    } else {
      _builderFactory.endTopLevelMethodForParserRecovery(
        typeParameters
            // Coverage-ignore(suite): Not run.
            ?.fragments,
      );
    }
    popDeclarationContext(DeclarationContext.TopLevelMethod);
  }

  @override
  // Coverage-ignore(suite): Not run.
  void handleNativeFunctionBody(Token nativeToken, Token semicolon) {
    debugEvent("NativeFunctionBody");
    if (nativeMethodName != null) {
      push(MethodBody.Regular);
      push(nativeToken);
    } else {
      push(MethodBody.Abstract);
      push(semicolon);
    }
  }

  @override
  void handleNativeFunctionBodyIgnored(Token nativeToken, Token semicolon) {
    debugEvent("NativeFunctionBodyIgnored");
  }

  @override
  void handleNativeFunctionBodySkipped(Token nativeToken, Token semicolon) {
    if (!enableNative) {
      super.handleRecoverableError(
        diag.expectedBlockToSkip,
        nativeToken,
        nativeToken,
      );
    }
    push(MethodBody.Regular);
    push(nativeToken);
  }

  @override
  void handleNoFunctionBody(Token token) {
    debugEvent("NoFunctionBody");
    if (nativeMethodName != null) {
      // Coverage-ignore-block(suite): Not run.
      push(MethodBody.Regular);
    } else {
      push(MethodBody.Abstract);
    }
    push(token);
  }

  @override
  void handleFunctionBodySkipped(
    Token beginToken,
    Token endToken,
    bool isExpressionBody,
  ) {
    debugEvent("handleFunctionBodySkipped");
    push(MethodBody.Regular);
    push(beginToken);
  }

  @override
  void beginConstructor(
    DeclarationKind declarationKind,
    Token? augmentToken,
    Token? externalToken,
    Token? staticToken,
    Token? covariantToken,
    Token? varFinalOrConst,
    Token? getOrSet,
    Token? newToken,
    Token name,
    String? enclosingDeclarationName,
  ) {
    DeclarationContext declarationContext;
    switch (declarationKind) {
      case DeclarationKind.Class:
        declarationContext = DeclarationContext.ClassConstructor;
      case DeclarationKind.Mixin:
        declarationContext = DeclarationContext.MixinConstructor;
      case DeclarationKind.Extension:
        declarationContext = DeclarationContext.ExtensionConstructor;
      case DeclarationKind.ExtensionType:
        declarationContext = DeclarationContext.ExtensionTypeConstructor;
      case DeclarationKind.Enum:
        declarationContext = DeclarationContext.EnumConstructor;
      // Coverage-ignore(suite): Not run.
      case DeclarationKind.TopLevel:
        throw new UnsupportedError(
          "Unexpected constructor kind $declarationKind.",
        );
    }
    pushDeclarationContext(declarationContext);

    Modifiers modifiers = Modifiers.from(
      augmentToken: augmentToken,
      externalToken: externalToken,
      covariantToken: covariantToken,
      varFinalOrConst: varFinalOrConst,
    );
    push(varFinalOrConst?.charOffset ?? -1);
    push(modifiers);
    _builderFactory.beginConstructor();
  }

  @override
  void beginMethod(
    DeclarationKind declarationKind,
    Token? augmentToken,
    Token? externalToken,
    Token? staticToken,
    Token? covariantToken,
    Token? varFinalOrConst,
    Token? getOrSet,
    Token name,
    String? enclosingDeclarationName,
  ) {
    DeclarationContext declarationContext;
    switch (declarationKind) {
      case DeclarationKind.TopLevel:
        // Coverage-ignore(suite): Not run.
        assert(
          false,
          "Expected top level method to be handled by "
          "`beginTopLevelMethod`.",
        );
        declarationContext = DeclarationContext.TopLevelMethod;
        break;
      case DeclarationKind.Class:
        if (staticToken != null) {
          declarationContext = DeclarationContext.ClassStaticMethod;
        } else {
          declarationContext = DeclarationContext.ClassInstanceMethod;
        }
        break;
      case DeclarationKind.Mixin:
        if (staticToken != null) {
          declarationContext = DeclarationContext.MixinStaticMethod;
        } else {
          declarationContext = DeclarationContext.MixinInstanceMethod;
        }
        break;
      case DeclarationKind.Extension:
        if (staticToken != null) {
          declarationContext = DeclarationContext.ExtensionStaticMethod;
        } else {
          declarationContext = DeclarationContext.ExtensionInstanceMethod;
        }
        break;
      case DeclarationKind.ExtensionType:
        if (staticToken != null) {
          declarationContext = DeclarationContext.ExtensionTypeStaticMethod;
        } else {
          declarationContext = DeclarationContext.ExtensionTypeInstanceMethod;
        }
        break;
      case DeclarationKind.Enum:
        if (staticToken != null) {
          declarationContext = DeclarationContext.EnumStaticMethod;
        } else {
          declarationContext = DeclarationContext.EnumInstanceMethod;
        }
    }
    pushDeclarationContext(declarationContext);

    Modifiers modifiers = Modifiers.from(
      augmentToken: augmentToken,
      externalToken: externalToken,
      staticToken: staticToken,
      covariantToken: covariantToken,
      varFinalOrConst: varFinalOrConst,
    );
    push(varFinalOrConst?.charOffset ?? -1);
    push(modifiers);
    if (staticToken != null) {
      _builderFactory.beginStaticMethod();
    } else {
      _builderFactory.beginInstanceMethod();
    }
  }

  @override
  void endMethod(
    DeclarationKind kind,
    Token? getOrSet,
    Token beginToken,
    Token beginParam,
    Token? beginInitializers,
    Token endToken,
  ) {
    debugEvent("endClassMethod");

    if (kind == DeclarationKind.Enum) {
      reportIfNotEnabled(
        libraryFeatures.enhancedEnums,
        beginToken.charOffset,
        noLength,
      );
    }

    assert(
      checkState(beginToken, [
        /* method body token */ ValueKinds.Token,
        /* method body kind */ ValueKinds.MethodBody,
      ]),
    );
    pop() as Token; // Method body token
    MethodBody bodyKind = pop() as MethodBody;
    if (bodyKind == MethodBody.RedirectingFactoryBody) {
      // This will cause an error later.
      pop();
    }
    assert(
      checkState(beginToken, [
        ValueKinds.AsyncModifier,
        ValueKinds.FormalListOrNull,
        ValueKinds.Integer, // formals offset
        ValueKinds.NominalTypeParametersOrNull,
        ValueKinds.IdentifierOrParserRecovery,
        ValueKinds.TypeBuilderOrNull,
        ValueKinds.Modifiers,
        ValueKinds.Integer, // var/final/const offset
        ValueKinds.MetadataListOrNull,
      ]),
    );

    AsyncModifier asyncModifier = pop() as AsyncModifier;
    List<FormalParameterBuilder>? formals =
        pop() as List<FormalParameterBuilder>?;
    int formalsOffset = popCharOffset();
    NominalParameters? typeParameters =
        pop(NullValues.NominalParameters) as NominalParameters?;
    Object? identifier = pop();
    TypeBuilder? returnType = pop() as TypeBuilder?;
    Modifiers modifiers = pop() as Modifiers;
    popCharOffset(); // varFinalOrConstOffset
    List<MetadataBuilder>? metadata = pop() as List<MetadataBuilder>?;

    if (identifier is! Identifier) {
      assert(
        identifier is ParserRecovery,
        "Unexpected identifier $identifier (${identifier.runtimeType})",
      );

      if (modifiers.isStatic) {
        // Coverage-ignore-block(suite): Not run.
        _builderFactory.endStaticMethodForParserRecovery(
          typeParameters?.fragments,
        );
      } else {
        _builderFactory.endInstanceMethodForParserRecovery(
          typeParameters
              // Coverage-ignore(suite): Not run.
              ?.fragments,
        );
      }

      nativeMethodName = null;
      popDeclarationContext();
      return;
    }

    Operator? operator = identifier.operator;
    // TODO(johnniwinther): Find a uniform way to compute this.
    bool hasNoFormals = formals == null;
    if (Operator.subtract == operator && hasNoFormals) {
      operator = Operator.unaryMinus;
    }

    String name;
    ProcedureKind procedureKind;
    int nameOffset = identifier.qualifierOffset;
    if (operator != null) {
      name = operator.text;
      procedureKind = ProcedureKind.Operator;
      int requiredArgumentCount = operator.requiredArgumentCount;
      if ((formals?.length ?? 0) != requiredArgumentCount) {
        Template<Message Function({required String operatorName})> template;
        switch (requiredArgumentCount) {
          case 0:
            template = diag.operatorParameterMismatch0;
            break;

          case 1:
            if (Operator.subtract == operator) {
              template = diag.operatorMinusParameterMismatch;
            } else {
              template = diag.operatorParameterMismatch1;
            }
            break;

          case 2:
            template = diag.operatorParameterMismatch2;
            break;

          // Coverage-ignore(suite): Not run.
          default:
            unhandled(
              "$requiredArgumentCount",
              "operatorRequiredArgumentCount",
              identifier.nameOffset,
              uri,
            );
        }
        addProblem(
          template.withArguments(operatorName: name),
          nameOffset,
          name.length,
        );
      } else {
        if (formals != null) {
          for (FormalParameterBuilder formal in formals) {
            if (!formal.isRequiredPositional) {
              addProblem(
                diag.operatorWithOptionalFormals,
                formal.fileOffset,
                formal.name.length,
              );
            }
          }
        }
      }
      if (typeParameters != null) {
        addProblem(
          diag.operatorWithTypeParameters,
          typeParameters.charOffset,
          typeParameters.spanLength,
        );
      }
    } else {
      name = identifier.name;
      procedureKind = computeProcedureKind(getOrSet);
    }

    bool isAbstract = bodyKind == MethodBody.Abstract;
    if (isAbstract) {
      // An error has been reported if this wasn't already sync.
      asyncModifier = AsyncModifier.implicitSync;
    }
    if (getOrSet != null && getOrSet.isA(Keyword.SET)) {
      if (formals == null || formals.length != 1) {
        // This isn't abstract as we'll add an error-recovery node in
        // [BodyBuilder.finishFunction].
        isAbstract = false;
      }
    }

    if (isAbstract && !modifiers.isExternal) {
      modifiers |= Modifiers.Abstract;
    }
    if (nativeMethodName != null) {
      modifiers |= Modifiers.External;
    }

    bool isConst = modifiers.isConst;
    bool isStatic = modifiers.isStatic;

    if (isConst) {
      // TODO(danrubel): consider removing this
      // because it is an error to have a const method.
      modifiers -= Modifiers.Const;
    }

    int startOffset = metadata?.first.atOffset ?? beginToken.charOffset;

    int endOffset = endToken.charOffset;

    bool forAbstractClassOrMixin = inAbstractOrSealedClass;

    bool isExtensionMember = kind == DeclarationKind.Extension;
    bool isExtensionTypeMember = kind == DeclarationKind.ExtensionType;

    _builderFactory.addClassMethod(
      offsetMap: _offsetMap,
      metadata: metadata,
      identifier: identifier,
      name: name,
      returnType: returnType,
      formals: formals,
      typeParameters: typeParameters?.fragments,
      beginInitializers: beginInitializers,
      startOffset: startOffset,
      endOffset: endOffset,
      nameOffset: nameOffset,
      formalsOffset: formalsOffset,
      modifiers: modifiers,
      isStatic: isStatic,
      isExtensionMember: isExtensionMember,
      isExtensionTypeMember: isExtensionTypeMember,
      forAbstractClassOrMixin: forAbstractClassOrMixin,
      asyncModifier: asyncModifier,
      nativeMethodName: nativeMethodName,
      kind: procedureKind,
    );

    nativeMethodName = null;
    popDeclarationContext();
  }

  @override
  void endConstructor(
    DeclarationKind kind,
    Token beginToken,
    Token? newToken,
    Token beginParam,
    Token? beginInitializers,
    Token endToken,
  ) {
    debugEvent("endConstructor");

    if (kind == DeclarationKind.Enum) {
      reportIfNotEnabled(
        libraryFeatures.enhancedEnums,
        beginToken.charOffset,
        noLength,
      );
    }

    assert(
      checkState(beginToken, [
        /* method body token */ ValueKinds.Token,
        /* method body kind */ ValueKinds.MethodBody,
      ]),
    );
    Token bodyToken = pop() as Token;
    MethodBody bodyKind = pop() as MethodBody;
    if (bodyKind == MethodBody.RedirectingFactoryBody) {
      // This will cause an error later.
      pop();
    }
    assert(
      checkState(beginToken, [
        ValueKinds.AsyncModifier,
        ValueKinds.FormalListOrNull,
        ValueKinds.Integer, // formals offset
        ValueKinds.NominalTypeParametersOrNull,
        ValueKinds.IdentifierOrParserRecovery,
        ValueKinds.TypeBuilderOrNull,
        ValueKinds.Modifiers,
        ValueKinds.Integer, // var/final/const offset
        ValueKinds.MetadataListOrNull,
      ]),
    );

    pop() as AsyncModifier;
    List<FormalParameterBuilder>? formals =
        pop() as List<FormalParameterBuilder>?;
    int formalsOffset = popCharOffset();
    NominalParameters? typeParameters =
        pop(NullValues.NominalParameters) as NominalParameters?;
    Object? identifier = pop();
    TypeBuilder? returnType = pop() as TypeBuilder?;
    Modifiers modifiers = pop() as Modifiers;
    int varFinalOrConstOffset = popCharOffset();
    List<MetadataBuilder>? metadata = pop() as List<MetadataBuilder>?;

    if (typeParameters != null) {
      addProblem(
        diag.constructorWithTypeParameters,
        typeParameters.charOffset,
        typeParameters.spanLength,
      );
    }

    if (identifier is! Identifier) {
      assert(
        identifier is ParserRecovery,
        "Unexpected identifier $identifier (${identifier.runtimeType})",
      );

      _builderFactory.endConstructorForParserRecovery(
        typeParameters
            // Coverage-ignore(suite): Not run.
            ?.fragments,
      );

      nativeMethodName = null;
      popDeclarationContext();
      return;
    }

    bool isAbstract = bodyKind == MethodBody.Abstract;
    if (isAbstract && !modifiers.isExternal) {
      modifiers |= Modifiers.Abstract;
    }
    if (nativeMethodName != null) {
      modifiers |= Modifiers.External;
    }

    if (modifiers.isConst) {
      if (bodyKind != MethodBody.Abstract &&
          !libraryFeatures.constFunctions.isEnabled) {
        addProblem(diag.constConstructorWithBody, varFinalOrConstOffset, 5);
      }
    } else if (kind == DeclarationKind.Enum &&
        libraryFeatures.primaryConstructors.isEnabled) {
      modifiers |= Modifiers.Const;
      if (bodyKind != MethodBody.Abstract &&
          !libraryFeatures.constFunctions.isEnabled) {
        addProblem(
          diag.implicitlyConstEnumConstructorWithBody,
          bodyToken.charOffset,
          noLength,
        );
      }
    }

    if (returnType != null) {
      addProblem(
        diag.constructorWithReturnType,
        returnType.charOffset ?? // Coverage-ignore(suite): Not run.
            beginToken.offset,
        noLength,
      );
      returnType = null;
    }

    int startOffset = metadata?.first.atOffset ?? beginToken.charOffset;

    int endOffset = endToken.charOffset;

    bool forAbstractClassOrEnumOrMixin =
        inAbstractOrSealedClass ||
        kind == DeclarationKind.Mixin ||
        kind == DeclarationKind.Enum;

    // A constructor declaration is incomplete if all of:
    //   * It has no body.
    //   * It is not marked external.
    //   * There is no initializer list, initializing formals,
    //     or super parameters.
    // If a constructor is not incomplete then it is complete.
    bool isIncomplete =
        bodyKind == MethodBody.Abstract &&
        !modifiers.isExternal &&
        beginInitializers == null;
    if (isIncomplete && formals != null) {
      for (FormalParameterBuilder formal in formals) {
        if (formal.isInitializingFormal || formal.isSuperInitializingFormal) {
          isIncomplete = false;
          break;
        }
      }
    }

    _builderFactory.addConstructor(
      offsetMap: _offsetMap,
      metadata: metadata,
      modifiers: modifiers,
      identifier: identifier,
      typeParameters: typeParameters?.fragments,
      formals: formals,
      startOffset: startOffset,
      formalsOffset: formalsOffset,
      endOffset: endOffset,
      nativeMethodName: nativeMethodName,
      initializersStartToken: beginInitializers,
      hasNewKeyword: newToken != null,
      forAbstractClassOrEnumOrMixin: forAbstractClassOrEnumOrMixin,
      isComplete: !isIncomplete,
    );

    nativeMethodName = null;
    popDeclarationContext();
  }

  @override
  void handleNamedMixinApplicationWithClause(Token withKeyword) {
    debugEvent("NamedMixinApplicationWithClause");
    assert(
      checkState(withKeyword, [
        /* mixins */ unionOfKinds([
          ValueKinds.ParserRecovery,
          ValueKinds.TypeBuilderList,
        ]),
        /* supertype */ unionOfKinds([
          ValueKinds.ParserRecovery,
          ValueKinds.TypeBuilder,
        ]),
      ]),
    );
  }

  @override
  void handleNamedArgument(Token colon) {
    debugEvent("handleNamedArgument");
    assert(checkState(colon, [ValueKinds.IdentifierOrParserRecovery]));

    pop(); // Named argument name.
  }

  @override
  // Coverage-ignore(suite): Not run.
  void handleNamedRecordField(Token colon) {
    debugEvent("handleNamedRecordField");
    assert(checkState(colon, [ValueKinds.IdentifierOrParserRecovery]));

    pop(); // Named record field name.
  }

  @override
  void endNamedMixinApplication(
    Token beginToken,
    Token classKeyword,
    Token equals,
    Token? implementsKeyword,
    Token endToken,
  ) {
    debugEvent("endNamedMixinApplication");
    assert(
      checkState(beginToken, [
        if (implementsKeyword != null)
          /* interfaces */ unionOfKinds([
            ValueKinds.ParserRecovery,
            ValueKinds.TypeBuilderListOrNull,
          ]),
        /* mixins */ unionOfKinds([
          ValueKinds.ParserRecovery,
          ValueKinds.TypeBuilderList,
        ]),
        /* supertype */ unionOfKinds([
          ValueKinds.ParserRecovery,
          ValueKinds.TypeBuilder,
        ]),
        /* modifiers */ ValueKinds.Modifiers,
        /* type parameters */ ValueKinds.NominalTypeParametersOrNull,
        /* name */ ValueKinds.IdentifierOrParserRecovery,
        /* metadata */ ValueKinds.MetadataListOrNull,
      ]),
    );

    List<TypeBuilder>? interfaces = nullIfParserRecovery(
      popIfNotNull(implementsKeyword),
    ) as List<TypeBuilder>?;
    Object? mixinApplication = pop();
    Object? supertype = pop();
    Modifiers modifiers = pop() as Modifiers;
    NominalParameters? typeParameters =
        pop(NullValues.NominalParameters) as NominalParameters?;
    Object? name = pop();
    List<MetadataBuilder>? metadata = pop() as List<MetadataBuilder>?;
    checkEmpty(beginToken.charOffset);
    if (name is ParserRecovery ||
        supertype is ParserRecovery ||
        mixinApplication is ParserRecovery) {
      _builderFactory.endNamedMixinApplicationForParserRecovery(
        typeParameters?.fragments,
      );
    } else {
      Identifier identifier = name as Identifier;
      String classNameForErrors = identifier.name;
      List<TypeBuilder> mixins = mixinApplication as List<TypeBuilder>;
      supertype as TypeBuilder;
      if (supertype.nullabilityBuilder.build() == Nullability.nullable) {
        _compilationUnit.addProblem(
          diag.nullableSuperclassError.withArguments(
            supertypeName: supertype.fullNameForErrors,
          ),
          identifier.nameOffset,
          classNameForErrors.length,
          uri,
        );
      }
      for (TypeBuilder mixin in mixins) {
        if (mixin.nullabilityBuilder.build() == Nullability.nullable) {
          _compilationUnit.addProblem(
            diag.nullableMixinError.withArguments(
              mixinName: mixin.fullNameForErrors,
            ),
            identifier.nameOffset,
            classNameForErrors.length,
            uri,
          );
        }
      }
      if (interfaces != null) {
        for (TypeBuilder interface in interfaces) {
          if (interface.nullabilityBuilder.build() == Nullability.nullable) {
            _compilationUnit.addProblem(
              diag.nullableInterfaceError.withArguments(
                interfaceName: interface.fullNameForErrors,
              ),
              identifier.nameOffset,
              classNameForErrors.length,
              uri,
            );
          }
        }
      }

      if (modifiers.isSealed) {
        modifiers |= Modifiers.Abstract;
      }

      int startOffset = metadata?.first.atOffset ?? beginToken.charOffset;
      int endOffset = endToken.charOffset;
      _builderFactory.addNamedMixinApplication(
        metadata: metadata,
        name: identifier.name,
        typeParameters: typeParameters?.fragments,
        modifiers: modifiers,
        supertype: supertype,
        mixins: mixins,
        interfaces: interfaces,
        startOffset: startOffset,
        nameOffset: identifier.nameOffset,
        endOffset: endOffset,
      );
    }
    popDeclarationContext(DeclarationContext.NamedMixinApplication);
  }

  @override
  void endTypeArguments(int count, Token beginToken, Token endToken) {
    debugEvent("endTypeArguments");
    push(
      const FixedNullableList<TypeBuilder>().popNonNullable(
            stack,
            count,
            dummyTypeBuilder,
          ) ??
          NullValues.TypeArguments,
    );
  }

  @override
  void endArguments(int count, Token beginToken, Token endToken) {
    debugEvent("endArguments");
    push(beginToken);
  }

  @override
  // Coverage-ignore(suite): Not run.
  void handleInvalidTypeArguments(Token token) {
    debugEvent("handleInvalidTypeArguments");
    pop(NullValues.TypeArguments);
  }

  @override
  void handleScript(Token token) {
    debugEvent("handleScript");
    _builderFactory.addScriptToken(token.charOffset);
  }

  @override
  // Coverage-ignore(suite): Not run.
  void handleNonNullAssertExpression(Token bang) {}

  @override
  void handleType(Token beginToken, Token? questionMark) {
    debugEvent("handleType");
    assert(
      checkState(beginToken, [
        /* type arguments = */ ValueKinds.TypeArgumentsOrNull,
        /* identifier */ ValueKinds.IdentifierOrParserRecovery,
      ]),
    );
    bool isMarkedAsNullable = questionMark != null;
    List<TypeBuilder>? arguments = pop() as List<TypeBuilder>?;
    Object name = pop()!;
    if (name is ParserRecovery) {
      push(name);
    } else {
      Identifier identifier = name as Identifier;
      push(
        _builderFactory.addNamedType(
          identifier.typeName,
          isMarkedAsNullable
              ? const NullabilityBuilder.nullable()
              : const NullabilityBuilder.omitted(),
          arguments,
          identifier.qualifierOffset,
          instanceTypeParameterAccess:
              declarationContext.instanceTypeParameterAccessState,
        ),
      );
    }
  }

  @override
  void endTypeList(int count) {
    debugEvent("TypeList");
    push(
      const FixedNullableList<TypeBuilder>().popNonNullable(
            stack,
            count,
            dummyTypeBuilder,
          ) ??
          new ParserRecovery(-1),
    );
  }

  @override
  void handleNoArguments(Token token) {
    debugEvent("NoArguments");
    push(NullValues.Arguments);
  }

  @override
  void handleNoTypeVariables(Token token) {
    if (inFunctionType) {
      push(NullValues.StructuralParameters);
    } else {
      push(NullValues.NominalParameters);
    }
  }

  @override
  void handleNoTypeArguments(Token token) {
    debugEvent("NoTypeArguments");
    push(NullValues.TypeArguments);
  }

  @override
  // Coverage-ignore(suite): Not run.
  void handleSendWithoutArguments(
    Token beginToken,
    Token endToken,
    Token nextToken,
  ) {
    debugEvent("SendWithoutArguments");
  }

  @override
  // Coverage-ignore(suite): Not run.
  void handleInvocationWithoutTypeArguments(Token beginToken, Token endToken) {
    debugEvent("InvocationWithoutTypeArguments");
  }

  @override
  void handleNoTypeNameInConstructorReference(Token token) {
    debugEvent("NoTypeNameInConstructorReference");
    push(NullValues.Identifier);
  }

  @override
  void handleVoidKeyword(Token token) {
    debugEvent("VoidKeyword");
    push(_builderFactory.addVoidType(token.charOffset));
  }

  @override
  void handleVoidKeywordWithTypeArguments(Token token) {
    debugEvent("VoidKeyword");
    /*List<TypeBuilder> arguments =*/
    pop();
    push(_builderFactory.addVoidType(token.charOffset));
  }

  @override
  void beginFormalParameter(
    Token token,
    MemberKind kind,
    Token? requiredToken,
    Token? covariantToken,
    Token? varFinalOrConst,
  ) {
    _insideOfFormalParameterType = true;
    push(
      Modifiers.from(
        covariantToken: covariantToken,
        requiredToken: requiredToken,
        varFinalOrConst: varFinalOrConst,
      ),
    );
  }

  @override
  void endFormalParameter(
    Token? varOrFinal,
    Token? thisKeyword,
    Token? superKeyword,
    Token? periodAfterThisOrSuper,
    Token nameToken,
    Token? initializerStart,
    Token? initializerEnd,
    FormalParameterKind kind,
    MemberKind memberKind,
  ) {
    debugEvent("endFormalParameter");
    assert(
      checkState(nameToken, [
        ValueKinds.IdentifierOrParserRecoveryOrNull,
        unionOfKinds([ValueKinds.TypeBuilderOrNull, ValueKinds.ParserRecovery]),
        ValueKinds.Modifiers,
        ValueKinds.MetadataListOrNull,
      ]),
    );

    _insideOfFormalParameterType = false;

    if (superKeyword != null) {
      reportIfNotEnabled(
        libraryFeatures.superParameters,
        superKeyword.charOffset,
        superKeyword.length,
      );
    }

    Object? name = pop(NullValues.Identifier);
    TypeBuilder? type = nullIfParserRecovery(pop()) as TypeBuilder?;
    Modifiers modifiers = pop() as Modifiers;
    List<MetadataBuilder>? metadata = pop() as List<MetadataBuilder>?;
    if (name is ParserRecovery) {
      push(name);
    } else if (memberKind.isFunctionType) {
      Identifier? identifier = name as Identifier?;
      String? parameterName = identifier?.name;
      push(
        _builderFactory.addFunctionTypeParameter(
          kind: kind,
          type:
              type ??
              _createOmittedParameterTypeBuilder(
                memberKind,
                isDeclaringParameter: modifiers.isDeclaringParameter,
              ),
          name: parameterName,
          fileOffset: identifier?.nameOffset ?? nameToken.charOffset,
        ),
      );
    } else {
      if (memberKind == MemberKind.PrimaryConstructor &&
          (varOrFinal != null ||
              declarationContext == DeclarationContext.ExtensionType)) {
        modifiers |= Modifiers.DeclaringParameter;
      }

      Identifier identifier = name as Identifier;
      String parameterName = identifier.name;
      String? publicName = _problemReporting.checkPublicName(
        compilationUnit: _compilationUnit,
        kind: kind,
        parameterName: parameterName,
        nameToken: nameToken,
        thisKeyword: thisKeyword,
        isDeclaring: modifiers.isDeclaringParameter,
        libraryFeatures: libraryFeatures,
        fileUri: _compilationUnit.fileUri,
      );

      push(
        _builderFactory.addFormalParameter(
          metadata: metadata,
          kind: kind,
          modifiers: modifiers,
          type:
              type ??
              _createOmittedParameterTypeBuilder(
                memberKind,
                isDeclaringParameter: modifiers.isDeclaringParameter,
              ),
          name: parameterName,
          publicName: publicName,
          hasThis: thisKeyword != null,
          hasSuper: superKeyword != null,
          nameOffset: identifier.nameOffset,
          initializerToken: initializerStart,
        ),
      );
    }
  }

  /// Creates the [TypeBuilder] use for an omitted parameter type on the given
  /// member [kind].
  TypeBuilder _createOmittedParameterTypeBuilder(
    MemberKind kind, {
    bool isDeclaringParameter = false,
  }) {
    switch (kind) {
      case MemberKind.Catch:
      case MemberKind.FunctionTypeAlias:
      case MemberKind.Factory:
      case MemberKind.FunctionTypedParameter:
      case MemberKind.GeneralizedFunctionType:
      case MemberKind.Local:
      case MemberKind.StaticMethod:
      case MemberKind.TopLevelMethod:
      case MemberKind.ExtensionNonStaticMethod:
      case MemberKind.ExtensionStaticMethod:
      case MemberKind.ExtensionTypeStaticMethod:
        // Parameter type is not inferred.
        return const ImplicitTypeBuilder();
      case MemberKind.NonStaticMethod:
      case MemberKind.ExtensionTypeNonStaticMethod:
      // TODO(eernst): Write a test such that this does run.
      case MemberKind.AnonymousMethod:
      // These can be inferred but cannot hold parameters so the cases are
      // dead code:
      case MemberKind.NonStaticField:
      case MemberKind.StaticField:
      case MemberKind.TopLevelField:
        // Parameter type is inferred with `dynamic` as default.
        return _builderFactory.addInferableType(InferenceDefaultType.Dynamic);
      case MemberKind.PrimaryConstructor:
        if (libraryFeatures.primaryConstructors.isEnabled) {
          // Parameter type is inferred with `Object?` as default.
          return _builderFactory.addInferableType(
            isDeclaringParameter
                ? InferenceDefaultType.NullableObject
                : InferenceDefaultType.Dynamic,
          );
        } else {
          // Parameter type is not inferred.
          return const ImplicitTypeBuilder();
        }
    }
  }

  @override
  void beginFormalParameterDefaultValueExpression() {
    _insideOfFormalParameterType = false;
  }

  @override
  void endFormalParameterDefaultValueExpression() {
    debugEvent("endFormalParameterDefaultValueExpression");
    // Ignored for now.
  }

  @override
  void handleValuedFormalParameter(
    Token equals,
    Token token,
    FormalParameterKind kind,
  ) {
    debugEvent("handleValuedFormalParameter");
    // Ignored for now.
  }

  @override
  void handleFormalParameterWithoutValue(Token token) {
    debugEvent("handleFormalParameterWithoutValue");
    // Ignored for now.
  }

  @override
  void endOptionalFormalParameters(
    int count,
    Token beginToken,
    Token endToken,
    MemberKind kind,
  ) {
    debugEvent("endOptionalFormalParameters");
    if (kind.isFunctionType) {
      // When recovering from an empty list of optional arguments, count may be
      // 0. It might be simpler if the parser didn't call this method in that
      // case, however, then [beginOptionalFormalParameters] wouldn't always be
      // matched by this method.
      List<FunctionTypeParameterBuilder>? parameters =
          const FixedNullableList<FunctionTypeParameterBuilder>()
              .popNonNullable(stack, count, dummyFunctionTypeParameterBuilder);
      if (parameters == null) {
        push(new ParserRecovery(offsetForToken(beginToken)));
      } else {
        push(parameters);
      }
    } else {
      // When recovering from an empty list of optional arguments, count may be
      // 0. It might be simpler if the parser didn't call this method in that
      // case, however, then [beginOptionalFormalParameters] wouldn't always be
      // matched by this method.
      List<FormalParameterBuilder>? parameters =
          const FixedNullableList<FormalParameterBuilder>().popNonNullable(
            stack,
            count,
            dummyFormalParameterBuilder,
          );
      if (parameters == null) {
        push(new ParserRecovery(offsetForToken(beginToken)));
      } else {
        push(parameters);
      }
    }
  }

  @override
  void endFormalParameters(
    int count,
    Token beginToken,
    Token endToken,
    MemberKind kind,
  ) {
    debugEvent("FormalParameters");
    if (kind.isFunctionType) {
      List<FunctionTypeParameterBuilder>? formals;
      if (count == 1) {
        Object? last = pop();
        if (last is List<FunctionTypeParameterBuilder>) {
          formals = last;
        } else if (last is! ParserRecovery) {
          assert(last != null);
          formals = [last as FunctionTypeParameterBuilder];
        }
      } else if (count > 1) {
        Object? last = pop();
        count--;
        if (last is ParserRecovery) {
          // Coverage-ignore-block(suite): Not run.
          discard(count);
        } else if (last is List<FunctionTypeParameterBuilder>) {
          formals = const FixedNullableList<FunctionTypeParameterBuilder>()
              .popPaddedNonNullable(
                stack,
                count,
                last.length,
                dummyFunctionTypeParameterBuilder,
              );
          if (formals != null) {
            formals.setRange(count, formals.length, last);
          }
        } else {
          formals = const FixedNullableList<FunctionTypeParameterBuilder>()
              .popPaddedNonNullable(
                stack,
                count,
                1,
                dummyFunctionTypeParameterBuilder,
              );
          if (formals != null) {
            formals[count] = last as FunctionTypeParameterBuilder;
          }
        }
      }
      if (formals != null) {
        assert(formals.isNotEmpty);
        if (formals.length == 2) {
          // The name may be null for generalized function types.
          if (formals[0].name != null &&
              formals[0].name == formals[1].name &&
              !formals[0].isWildcard) {
            addProblem(
              diag.duplicatedParameterName.withArguments(
                name: formals[1].name!,
              ),
              formals[1].fileOffset,
              formals[1].name!.length,
              context: [
                diag.duplicatedParameterNameCause
                    .withArguments(name: formals[1].name!)
                    .withLocation(
                      uri,
                      formals[0].fileOffset,
                      formals[0].name!.length,
                    ),
              ],
            );
          }
        } else if (formals.length > 2) {
          Map<String, FunctionTypeParameterBuilder> seenNames =
              <String, FunctionTypeParameterBuilder>{};
          for (FunctionTypeParameterBuilder formal in formals) {
            if (formal.isWildcard) {
              continue;
            }
            String? name = formal.name;
            if (name == null) continue;
            if (seenNames.containsKey(formal.name)) {
              // Coverage-ignore-block(suite): Not run.
              addProblem(
                diag.duplicatedParameterName.withArguments(name: name),
                formal.fileOffset,
                name.length,
                context: [
                  diag.duplicatedParameterNameCause
                      .withArguments(name: name)
                      .withLocation(
                        uri,
                        seenNames[name]!.fileOffset,
                        seenNames[name]!.name!.length,
                      ),
                ],
              );
            } else {
              seenNames[name] = formal;
            }
          }
        }
      }
      push(beginToken.charOffset);
      push(formals ?? NullValues.FormalParameters);
    } else {
      List<FormalParameterBuilder>? formals;
      if (count == 1) {
        Object? last = pop();
        if (last is List<FormalParameterBuilder>) {
          formals = last;
        } else if (last is! ParserRecovery) {
          assert(last != null);
          formals = [last as FormalParameterBuilder];
        }
        if (!libraryFeatures.primaryConstructors.isEnabled) {
          Token? tokenBeforeEnd = endToken.previous;
          if (tokenBeforeEnd != null &&
              tokenBeforeEnd.isA(TokenType.COMMA) &&
              kind == MemberKind.PrimaryConstructor &&
              declarationContext == DeclarationContext.ExtensionType) {
            _compilationUnit.addProblem(
              diag.representationFieldTrailingComma,
              tokenBeforeEnd.charOffset,
              1,
              uri,
            );
          }
        }
      } else if (count > 1) {
        Object? last = pop();
        count--;
        if (last is ParserRecovery) {
          // Coverage-ignore-block(suite): Not run.
          discard(count);
        } else if (last is List<FormalParameterBuilder>) {
          formals = const FixedNullableList<FormalParameterBuilder>()
              .popPaddedNonNullable(
                stack,
                count,
                last.length,
                dummyFormalParameterBuilder,
              );
          if (formals != null) {
            formals.setRange(count, formals.length, last);
          }
        } else {
          formals = const FixedNullableList<FormalParameterBuilder>()
              .popPaddedNonNullable(
                stack,
                count,
                1,
                dummyFormalParameterBuilder,
              );
          if (formals != null) {
            formals[count] = last as FormalParameterBuilder;
          }
        }
      }
      if (formals != null) {
        assert(formals.isNotEmpty);
        if (formals.length == 2) {
          if (formals[0].name == formals[1].name && !formals[0].isWildcard) {
            addProblem(
              diag.duplicatedParameterName.withArguments(name: formals[1].name),
              formals[1].fileOffset,
              formals[1].name.length,
              context: [
                diag.duplicatedParameterNameCause
                    .withArguments(name: formals[1].name)
                    .withLocation(
                      uri,
                      formals[0].fileOffset,
                      formals[0].name.length,
                    ),
              ],
            );
          }

          // For private named parameters, also look for a collision between the
          // corresponding public name and another parameter's name.
          if (formals[0].publicName case var publicName?
              when publicName == formals[1].name) {
            _privateNamedParameterPublicNameCollision(
              publicName,
              formals[0],
              formals[1],
            );
          }

          if (formals[1].publicName case var publicName?
              when publicName == formals[0].name) {
            _privateNamedParameterPublicNameCollision(
              publicName,
              formals[1],
              formals[0],
            );
          }
        } else if (formals.length > 2) {
          Map<String, FormalParameterBuilder> seenNames =
              <String, FormalParameterBuilder>{};
          for (FormalParameterBuilder formal in formals) {
            if (formal.isWildcard) {
              continue;
            }
            if (seenNames.containsKey(formal.name)) {
              addProblem(
                diag.duplicatedParameterName.withArguments(name: formal.name),
                formal.fileOffset,
                formal.name.length,
                context: [
                  diag.duplicatedParameterNameCause
                      .withArguments(name: formal.name)
                      .withLocation(
                        uri,
                        seenNames[formal.name]!.fileOffset,
                        seenNames[formal.name]!.name.length,
                      ),
                ],
              );
            } else {
              seenNames[formal.name] = formal;
            }
          }

          // For private named parameters, also look for a collision between the
          // corresponding public name and another parameter's name.
          for (FormalParameterBuilder formal in formals) {
            if (formal.publicName case var publicName?) {
              if (seenNames[publicName] case var previous?) {
                _privateNamedParameterPublicNameCollision(
                  publicName,
                  formal,
                  previous,
                );
              }
            }
          }
        }
      }
      if (declarationContext == DeclarationContext.ExtensionType &&
          kind == MemberKind.PrimaryConstructor &&
          formals == null) {
        // In case of primary constructors of extension types, an error is
        // reported by the parser if the formals together with the parentheses
        // around them are missing. To distinguish that case from the case of
        // the formal parameters present, but lacking the representation field,
        // we pass the empty list further along instead of `null`.
        formals = const [];
      } else if ((declarationContext == DeclarationContext.ExtensionType &&
                  kind == MemberKind.PrimaryConstructor ||
              declarationContext ==
                  DeclarationContext.ExtensionTypeConstructor) &&
          formals != null) {
        for (FormalParameterBuilder formal in formals) {
          if (formal.isSuperInitializingFormal) {
            _compilationUnit.addProblem(
              diag.extensionTypeConstructorWithSuperFormalParameter,
              formal.fileOffset,
              formal.name.length,
              formal.fileUri,
            );
          }
        }
      }
      push(beginToken.charOffset);
      push(formals ?? NullValues.FormalParameters);
    }
  }

  /// Report a duplicate declaration error between a private named [formal]
  /// with [publicName] and another [previous] parameter.
  void _privateNamedParameterPublicNameCollision(
    String publicName,
    FormalParameterBuilder formal,
    FormalParameterBuilder previous,
  ) {
    addProblem(
      diag.privateNamedParameterDuplicatePublicName.withArguments(
        name: publicName,
      ),
      formal.fileOffset,
      formal.name.length,
      context: [
        diag.duplicatedParameterNameCause
            .withArguments(name: publicName)
            .withLocation(uri, previous.fileOffset, previous.name.length),
      ],
    );
  }

  @override
  void handleNoFormalParameters(Token token, MemberKind kind) {
    push(token.charOffset);
    super.handleNoFormalParameters(token, kind);
  }

  @override
  void endAssert(
    Token assertKeyword,
    Assert kind,
    Token leftParenthesis,
    Token? commaToken,
    Token endToken,
  ) {
    debugEvent("Assert");
    // Do nothing
  }

  @override
  void beginEnumDeclarationPrelude(Token enumKeyword) {
    pushDeclarationContext(DeclarationContext.Enum);
    _builderFactory.beginEnumDeclarationHeader();
  }

  @override
  void beginEnumDeclaration(
    Token beginToken,
    Token? augmentToken,
    Token enumKeyword,
    Token name,
  ) {
    assert(
      checkState(enumKeyword, [
        /* type parameters */ ValueKinds.NominalTypeParametersOrNull,
        /* name */ ValueKinds.IdentifierOrParserRecovery,
      ]),
    );
    debugEvent("EnumDeclaration");
    NominalParameters? typeParameters =
        peek(NullValues.NominalParameters) as NominalParameters?;

    _builderFactory.beginEnumDeclaration(
      name.lexeme,
      name.charOffset,
      typeParameters?.fragments,
    );

    Modifiers modifiers = Modifiers.from(augmentToken: augmentToken);
    push(modifiers);
  }

  @override
  void handleEnumHeader(
    Token? augmentToken,
    Token enumKeyword,
    Token leftBrace,
  ) {
    assert(
      checkState(enumKeyword, [
        /* interfaces */ ValueKinds.TypeBuilderListOrNull,
        /* mixins */ unionOfKinds([
          ValueKinds.TypeBuilderListOrNull,
          ValueKinds.ParserRecovery,
        ]),
        /* modifiers */ ValueKinds.Modifiers,
        /* type parameters */ ValueKinds.NominalTypeParametersOrNull,
        /* name */ ValueKinds.IdentifierOrParserRecovery,
      ]),
    );
    debugEvent("EnumHeader");
  }

  @override
  void beginEnumBody(Token token) {
    _builderFactory.beginEnumBody();
  }

  @override
  void handleEnumElement(Token beginToken, Token? augmentToken) {
    debugEvent("handleEnumElement");
    assert(
      checkState(beginToken, [
        /* argumentsBeginToken */ ValueKinds.ArgumentsTokenOrNull,
        ValueKinds.ConstructorReferenceBuilderOrNull,
        ValueKinds.EnumConstantInfoOrParserRecovery,
      ]),
    );

    Token? argumentsBeginToken = pop() as Token?;

    ConstructorReferenceBuilder? constructorReferenceBuilder =
        pop() as ConstructorReferenceBuilder?;
    Object? enumConstantInfo = pop();
    if (enumConstantInfo is EnumConstantInfo) {
      _builderFactory.addEnumElement(
        metadata: enumConstantInfo.metadata,
        name: enumConstantInfo.name,
        nameOffset: enumConstantInfo.nameOffset,
        constructorReferenceBuilder: constructorReferenceBuilder,
        argumentsBeginToken: argumentsBeginToken,
      );
    } else {
      assert(enumConstantInfo is ParserRecovery);
    }
  }

  @override
  void handleEnumElements(Token elementsEndToken, int elementsCount) {
    debugEvent("handleEnumElements");
  }

  @override
  void endEnumDeclaration(
    Token beginToken,
    Token enumKeyword,
    Token leftBrace,
    int memberCount,
    Token endToken,
  ) {
    debugEvent("endEnum");

    assert(
      checkState(beginToken, [
        /* interfaces */ ValueKinds.TypeBuilderListOrNull,
        /* mixins */ unionOfKinds([
          ValueKinds.TypeBuilderListOrNull,
          ValueKinds.ParserRecovery,
        ]),
        /* modifiers */ ValueKinds.Modifiers,
        /* type parameters */ ValueKinds.NominalTypeParametersOrNull,
        /* name */ ValueKinds.IdentifierOrParserRecovery,
        /* metadata */ ValueKinds.MetadataListOrNull,
      ]),
    );

    List<TypeBuilder>? interfaces =
        nullIfParserRecovery(pop()) as List<TypeBuilder>?;
    List<TypeBuilder>? mixins =
        nullIfParserRecovery(pop()) as List<TypeBuilder>?;
    Modifiers modifiers = pop() as Modifiers;
    NominalParameters? typeParameters =
        pop(NullValues.NominalParameters) as NominalParameters?;
    Object? identifier = pop();
    List<MetadataBuilder>? metadata = pop() as List<MetadataBuilder>?;
    checkEmpty(beginToken.charOffset);

    int startOffset = metadata?.first.atOffset ?? beginToken.charOffset;
    if (identifier is Identifier) {
      if (interfaces != null) {
        for (TypeBuilder interface in interfaces) {
          if (interface.nullabilityBuilder.build() == Nullability.nullable) {
            _compilationUnit.addProblem(
              diag.nullableInterfaceError.withArguments(
                interfaceName: interface.fullNameForErrors,
              ),
              interface.charOffset ?? startOffset,
              identifier.name.length,
              uri,
            );
          }
        }
      }

      _builderFactory.addEnum(
        offsetMap: _offsetMap,
        metadata: metadata,
        modifiers: modifiers,
        identifier: identifier,
        typeParameters: typeParameters?.fragments,
        mixins: mixins,
        interfaces: interfaces,
        startOffset: startOffset,
        endOffset: endToken.charOffset,
        hasErroneousBody: leftBrace.isSynthetic,
      );
    } else {
      _builderFactory.endEnumDeclarationForParserRecovery(
        typeParameters
            // Coverage-ignore(suite): Not run.
            ?.fragments,
      );
    }

    checkEmpty(enumKeyword.charOffset);
    popDeclarationContext(DeclarationContext.Enum);
  }

  @override
  void beginTypedef(Token token) {
    pushDeclarationContext(DeclarationContext.Typedef);
    _builderFactory.beginTypedef();
  }

  @override
  void beginFunctionType(Token beginToken) {
    debugEvent("beginFunctionType");
    _structuralParameterDepthLevel++;
    _builderFactory.beginFunctionType();
  }

  @override
  void beginFunctionTypedFormalParameter(Token token) {
    debugEvent("beginFunctionTypedFormalParameter");
    _insideOfFormalParameterType = false;
    _builderFactory.beginFunctionType();
  }

  @override
  void endRecordType(
    Token leftBracket,
    Token? questionMark,
    int count,
    bool hasNamedFields,
  ) {
    debugEvent("RecordType");
    assert(
      checkState(leftBracket, [
        if (hasNamedFields) ValueKinds.RecordTypeFieldBuilderListOrNull,
        ...repeatedKind(
          ValueKinds.RecordTypeFieldBuilder,
          hasNamedFields ? count - 1 : count,
        ),
      ]),
    );

    if (!libraryFeatures.records.isEnabled) {
      addProblem(
        diag.experimentNotEnabledOffByDefault.withArguments(
          featureName: ExperimentalFlag.records.name,
        ),
        leftBracket.offset,
        noLength,
      );
    }

    List<RecordTypeFieldBuilder>? namedFields;
    if (hasNamedFields) {
      namedFields =
          pop(NullValues.RecordTypeFieldList) as List<RecordTypeFieldBuilder>?;
    }
    List<RecordTypeFieldBuilder>? positionalFields =
        const FixedNullableList<RecordTypeFieldBuilder>().popNonNullable(
          stack,
          hasNamedFields ? count - 1 : count,
          dummyRecordTypeFieldBuilder,
        );

    push(
      new RecordTypeBuilderImpl(
        positionalFields,
        namedFields,
        questionMark != null
            ? const NullabilityBuilder.nullable()
            : const NullabilityBuilder.omitted(),
        uri,
        leftBracket.charOffset,
      ),
    );
  }

  @override
  void endRecordTypeEntry() {
    debugEvent("endRecordTypeEntry");
    assert(
      checkState(null, [
        ValueKinds.IdentifierOrParserRecoveryOrNull,
        unionOfKinds([ValueKinds.TypeBuilder, ValueKinds.ParserRecovery]),
        ValueKinds.MetadataListOrNull,
      ]),
    );

    // Offset of name of field (or next token if there's no name).
    Object? identifier = pop(NullValues.Identifier);
    Object? type = pop();
    List<MetadataBuilder>? metadata =
        pop(NullValues.Metadata) as List<MetadataBuilder>?;

    String? fieldName = identifier is Identifier ? identifier.name : null;
    push(
      new RecordTypeFieldBuilder(
        metadata,
        type is ParserRecovery
            ? new InvalidTypeBuilderImpl(uri, type.charOffset)
            : type as TypeBuilder,
        fieldName,
        identifier is Identifier ? identifier.nameOffset : -1,
        isWildcard:
            libraryFeatures.wildcardVariables.isEnabled && fieldName == '_',
      ),
    );
  }

  @override
  void endRecordTypeNamedFields(int count, Token leftBracket) {
    assert(
      checkState(leftBracket, [
        ...repeatedKind(ValueKinds.RecordTypeFieldBuilder, count),
      ]),
    );
    List<RecordTypeFieldBuilder>? fields =
        const FixedNullableList<RecordTypeFieldBuilder>().popNonNullable(
          stack,
          count,
          dummyRecordTypeFieldBuilder,
        );
    push(fields ?? NullValues.RecordTypeFieldList);
  }

  @override
  void endFunctionType(Token functionToken, Token? questionMark) {
    debugEvent("FunctionType");
    _structuralParameterDepthLevel--;
    List<FunctionTypeParameterBuilder>? formals =
        pop() as List<FunctionTypeParameterBuilder>?;
    pop(); // formals offset
    TypeBuilder? returnType = pop() as TypeBuilder?;
    StructuralParameters? typeParameters =
        pop(NullValues.StructuralParameters) as StructuralParameters?;
    push(
      _builderFactory.addFunctionType(
        returnType ?? const ImplicitTypeBuilder(),
        typeParameters?.builders,
        formals,
        questionMark != null
            ? const NullabilityBuilder.nullable()
            : const NullabilityBuilder.omitted(),
        uri,
        functionToken.charOffset,
        hasFunctionFormalParameterSyntax: false,
      ),
    );
  }

  @override
  void endFunctionTypedFormalParameter(Token nameToken, Token? question) {
    debugEvent("FunctionTypedFormalParameter");
    List<FunctionTypeParameterBuilder>? formals =
        pop() as List<FunctionTypeParameterBuilder>?;
    int formalsOffset = popCharOffset();
    TypeBuilder? returnType = pop() as TypeBuilder?;
    StructuralParameters? typeParameters =
        pop(NullValues.StructuralParameters) as StructuralParameters?;
    push(
      _builderFactory.addFunctionType(
        returnType ?? const ImplicitTypeBuilder(),
        typeParameters?.builders,
        formals,
        question != null
            ? const NullabilityBuilder.nullable()
            : const NullabilityBuilder.omitted(),
        uri,
        formalsOffset,
        hasFunctionFormalParameterSyntax: true,
      ),
    );
  }

  @override
  void endTypedef(
    Token? augmentToken,
    Token typedefKeyword,
    Token? equals,
    Token endToken,
  ) {
    debugEvent("endTypedef");
    assert(
      checkState(
        typedefKeyword,
        equals == null
            ? [
                /* formals */ ValueKinds.FunctionTypeParameterBuilderListOrNull,
                /* formals offset */ ValueKinds.Integer,
                /* type parameters */ ValueKinds.NominalTypeParametersOrNull,
                /* name */ ValueKinds.IdentifierOrParserRecovery,
                /* return type */ ValueKinds.TypeBuilderOrNull,
                /* metadata */ ValueKinds.MetadataListOrNull,
              ]
            : [
                /* type */ unionOfKinds([
                  ValueKinds.TypeBuilderOrNull,
                  ValueKinds.ParserRecovery,
                ]),
                /* type parameters */ ValueKinds.NominalTypeParametersOrNull,
                /* name */ ValueKinds.IdentifierOrParserRecovery,
                /* metadata */ ValueKinds.MetadataListOrNull,
              ],
      ),
    );

    NominalParameters? typeParameters;
    Object? name;
    Identifier identifier;
    TypeBuilder aliasedType;
    if (equals == null) {
      List<FunctionTypeParameterBuilder>? formals = pop(
        NullValues.FormalParameters,
      ) as List<FunctionTypeParameterBuilder>?;
      pop(); // formals offset
      typeParameters = pop(NullValues.NominalParameters) as NominalParameters?;
      name = pop();
      TypeBuilder? returnType = pop(NullValues.TypeBuilder) as TypeBuilder?;
      // Create a nested declaration that is ended below by
      // `library.addFunctionType`.
      if (name is ParserRecovery) {
        // Coverage-ignore-block(suite): Not run.
        pop(NullValues.Metadata); // Metadata.
        _builderFactory.endTypedefForParserRecovery(typeParameters?.fragments);
        popDeclarationContext(DeclarationContext.Typedef);
        return;
      }
      identifier = name as Identifier;
      _builderFactory.beginFunctionType();
      // TODO(cstefantsova): Make sure that RHS of typedefs can't have '?'.
      aliasedType = _builderFactory.addFunctionType(
        returnType ?? const ImplicitTypeBuilder(),
        null,
        formals,
        const NullabilityBuilder.omitted(),
        uri,
        identifier.nameOffset,
        hasFunctionFormalParameterSyntax: true,
      );
    } else {
      Object? type = pop(NullValues.TypeBuilder);
      typeParameters = pop(NullValues.NominalParameters) as NominalParameters?;
      name = pop();
      if (name is ParserRecovery) {
        // Coverage-ignore-block(suite): Not run.
        pop(NullValues.Metadata); // Metadata.
        _builderFactory.endTypedefForParserRecovery(typeParameters?.fragments);
        popDeclarationContext(DeclarationContext.Typedef);
        return;
      }
      identifier = name as Identifier;
      if (type is FunctionTypeBuilder &&
          !libraryFeatures.nonfunctionTypeAliases.isEnabled) {
        if (type.nullabilityBuilder.build() == Nullability.nullable) {
          addProblem(
            diag.typedefNullableType,
            equals.charOffset,
            equals.length,
          );
          aliasedType = new NamedTypeBuilderImpl.fromTypeDeclarationBuilder(
            new InvalidBuilder(
              identifier.name,
              diag.typedefNullableType.withLocation(
                uri,
                equals.charOffset,
                equals.length,
              ),
            ),
            const NullabilityBuilder.omitted(),
            instanceTypeParameterAccess:
                InstanceTypeParameterAccessState.Allowed,
          );
        } else {
          // TODO(ahe): We need to start a nested declaration when parsing the
          // formals and return type so we can correctly bind
          // `type.typeParameters`. A typedef can have type parameters, and a
          // new function type can also have type parameters (representing the
          // type of a generic function).
          aliasedType = type;
        }
      } else if (libraryFeatures.nonfunctionTypeAliases.isEnabled) {
        if (type is TypeBuilder) {
          aliasedType = type;
        } else {
          addProblem(diag.typedefNotType, equals.charOffset, equals.length);
          aliasedType = new NamedTypeBuilderImpl.fromTypeDeclarationBuilder(
            new InvalidBuilder(
              "${name}",
              diag.typedefNotType.withLocation(
                uri,
                equals.charOffset,
                equals.length,
              ),
            ),
            const NullabilityBuilder.omitted(),
            instanceTypeParameterAccess:
                InstanceTypeParameterAccessState.Allowed,
          );
        }
      } else {
        assert(type is! FunctionTypeBuilder);
        // TODO(ahe): Improve this error message.
        if (type is TypeBuilder) {
          addProblem(diag.typedefNotFunction, equals.charOffset, equals.length);
          aliasedType = new NamedTypeBuilderImpl.fromTypeDeclarationBuilder(
            new InvalidBuilder(
              identifier.name,
              diag.typedefNotFunction.withLocation(
                uri,
                equals.charOffset,
                equals.length,
              ),
            ),
            const NullabilityBuilder.omitted(),
            instanceTypeParameterAccess:
                InstanceTypeParameterAccessState.Allowed,
          );
        } else {
          addProblem(diag.typedefNotType, equals.charOffset, equals.length);
          aliasedType = new NamedTypeBuilderImpl.fromTypeDeclarationBuilder(
            new InvalidBuilder(
              identifier.name,
              diag.typedefNotType.withLocation(
                uri,
                equals.charOffset,
                equals.length,
              ),
            ),
            const NullabilityBuilder.omitted(),
            instanceTypeParameterAccess:
                InstanceTypeParameterAccessState.Allowed,
          );
        }
      }
    }
    List<MetadataBuilder>? metadata =
        pop(NullValues.Metadata) as List<MetadataBuilder>?;
    checkEmpty(typedefKeyword.charOffset);

    _builderFactory.addFunctionTypeAlias(
      metadata,
      identifier.name,
      typeParameters?.fragments,
      aliasedType,
      identifier.nameOffset,
    );
    popDeclarationContext(DeclarationContext.Typedef);
  }

  @override
  void beginFields(
    DeclarationKind declarationKind,
    Token? augmentToken,
    Token? abstractToken,
    Token? externalToken,
    Token? staticToken,
    Token? covariantToken,
    Token? lateToken,
    Token? varFinalOrConst,
    Token lastConsumed,
  ) {
    DeclarationContext declarationContext;
    switch (declarationKind) {
      case DeclarationKind.TopLevel:
        declarationContext = DeclarationContext.TopLevelField;
        break;
      case DeclarationKind.Class:
        if (staticToken != null) {
          declarationContext = DeclarationContext.ClassStaticField;
        } else {
          declarationContext = DeclarationContext.ClassInstanceField;
        }
        break;
      case DeclarationKind.Mixin:
        if (staticToken != null) {
          declarationContext = DeclarationContext.MixinStaticField;
        } else {
          declarationContext = DeclarationContext.MixinInstanceField;
        }
        break;
      case DeclarationKind.Extension:
        if (staticToken != null) {
          declarationContext = DeclarationContext.ExtensionStaticField;
        } else if (externalToken != null) {
          declarationContext =
              DeclarationContext.ExtensionExternalInstanceField;
        } else {
          declarationContext = DeclarationContext.ExtensionInstanceField;
        }
        break;
      case DeclarationKind.ExtensionType:
        if (staticToken != null) {
          declarationContext = DeclarationContext.ExtensionTypeStaticField;
        } else {
          declarationContext = DeclarationContext.ExtensionTypeInstanceField;
        }
        break;
      case DeclarationKind.Enum:
        if (staticToken != null) {
          declarationContext = DeclarationContext.EnumStaticMethod;
        } else {
          declarationContext = DeclarationContext.EnumInstanceMethod;
        }
    }
    pushDeclarationContext(declarationContext);
  }

  @override
  void endTopLevelFields(
    Token? augmentToken,
    Token? abstractToken,
    Token? externalToken,
    Token? staticToken,
    Token? covariantToken,
    Token? lateToken,
    Token? varFinalOrConst,
    int count,
    Token beginToken,
    Token endToken,
  ) {
    debugEvent("endTopLevelFields");
    assert(
      checkState(beginToken, [
        ...repeatedKinds([
          /* charEndOffset = */ ValueKinds.Integer,
          /* beforeLast = */ ValueKinds.FieldInitializerTokenOrNull,
          /* initializerTokenForInference = */ ValueKinds
              .FieldInitializerTokenOrNull,
          /* name = */ ValueKinds.IdentifierOrParserRecovery,
        ], count),
        /* type = */ unionOfKinds([
          ValueKinds.TypeBuilderOrNull,
          ValueKinds.ParserRecovery,
        ]),
        /* metadata = */ ValueKinds.MetadataListOrNull,
      ]),
    );
    if (externalToken != null && lateToken != null) {
      handleRecoverableError(
        diag.externalLateField,
        externalToken,
        externalToken,
      );
      externalToken = null;
    }
    List<FieldInfo>? fieldInfos = popFieldInfos(count);
    TypeBuilder? type = nullIfParserRecovery(pop()) as TypeBuilder?;
    Modifiers modifiers = Modifiers.from(
      abstractToken: abstractToken,
      augmentToken: augmentToken,
      externalToken: externalToken,
      staticToken: staticToken,
      covariantToken: covariantToken,
      lateToken: lateToken,
      varFinalOrConst: varFinalOrConst,
    );
    List<MetadataBuilder>? metadata = pop() as List<MetadataBuilder>?;
    checkEmpty(beginToken.charOffset);
    if (fieldInfos != null) {
      _builderFactory.addFields(
        _offsetMap,
        metadata,
        modifiers,
        /* isTopLevel = */ true,
        type,
        fieldInfos,
      );
    }
    popDeclarationContext();
  }

  @override
  void endFields(
    DeclarationKind kind,
    Token? abstractToken,
    Token? augmentToken,
    Token? externalToken,
    Token? staticToken,
    Token? covariantToken,
    Token? lateToken,
    Token? varFinalOrConst,
    int count,
    Token beginToken,
    Token endToken,
  ) {
    debugEvent("Fields");
    if (kind == DeclarationKind.Enum) {
      reportIfNotEnabled(
        libraryFeatures.enhancedEnums,
        beginToken.charOffset,
        noLength,
      );
    }
    _endClassFields(
      abstractToken,
      augmentToken,
      externalToken,
      staticToken,
      covariantToken,
      lateToken,
      varFinalOrConst,
      count,
      beginToken,
      endToken,
    );
  }

  void _endClassFields(
    Token? abstractToken,
    Token? augmentToken,
    Token? externalToken,
    Token? staticToken,
    Token? covariantToken,
    Token? lateToken,
    Token? varFinalOrConst,
    int count,
    Token beginToken,
    Token endToken,
  ) {
    assert(
      checkState(beginToken, [
        ...repeatedKinds([
          /* charEndOffset = */ ValueKinds.Integer,
          /* beforeLast = */ ValueKinds.FieldInitializerTokenOrNull,
          /* initializerTokenForInference = */ ValueKinds
              .FieldInitializerTokenOrNull,
          /* name = */ ValueKinds.IdentifierOrParserRecovery,
        ], count),
        /* type = */ ValueKinds.TypeBuilderOrNull,
        /* metadata = */ ValueKinds.MetadataListOrNull,
      ]),
    );
    if (!libraryFeatures.augmentations.isEnabled) {
      // TODO(johnniwinther): Move this check after applying augmentations.
      if (staticToken != null && abstractToken != null) {
        handleRecoverableError(
          diag.abstractStaticField,
          abstractToken,
          abstractToken,
        );
        abstractToken = null;
      }
    }
    if (abstractToken != null && lateToken != null) {
      handleRecoverableError(
        diag.abstractLateField,
        abstractToken,
        abstractToken,
      );
      abstractToken = null;
    } else if (externalToken != null && lateToken != null) {
      handleRecoverableError(
        diag.externalLateField,
        externalToken,
        externalToken,
      );
      externalToken = null;
    }

    List<FieldInfo>? fieldInfos = popFieldInfos(count);
    TypeBuilder? type = pop() as TypeBuilder?;
    Modifiers modifiers = Modifiers.from(
      abstractToken: abstractToken,
      augmentToken: augmentToken,
      externalToken: externalToken,
      staticToken: staticToken,
      covariantToken: covariantToken,
      lateToken: lateToken,
      varFinalOrConst: varFinalOrConst,
    );
    if (staticToken == null && modifiers.isConst) {
      // It is a compile-time error if an instance variable is declared to be
      // constant.
      addProblem(
        diag.constInstanceField,
        varFinalOrConst!.charOffset,
        varFinalOrConst.length,
      );
      modifiers -= Modifiers.Const;
    }
    List<MetadataBuilder>? metadata = pop() as List<MetadataBuilder>?;
    if (fieldInfos != null) {
      _builderFactory.addFields(
        _offsetMap,
        metadata,
        modifiers,
        /* isTopLevel = */ false,
        type,
        fieldInfos,
      );
    }
    popDeclarationContext();
  }

  List<FieldInfo>? popFieldInfos(int count) {
    assert(
      checkState(
        null,
        repeatedKinds([
          /* charEndOffset = */ ValueKinds.Integer,
          /* beforeLast = */ ValueKinds.FieldInitializerTokenOrNull,
          /* initializerTokenForInference = */ ValueKinds
              .FieldInitializerTokenOrNull,
          /* name = */ ValueKinds.IdentifierOrParserRecovery,
        ], count),
      ),
    );
    if (count == 0) return null;
    List<FieldInfo> fieldInfos = new List<FieldInfo>.filled(
      count,
      dummyFieldInfo,
    );
    bool isParserRecovery = false;
    for (int i = count - 1; i != -1; i--) {
      int charEndOffset = popCharOffset();
      Token? beforeLast = pop(NullValues.FieldInitializer) as Token?;
      Token? initializerTokenForInference =
          pop(NullValues.FieldInitializer) as Token?;
      Object? name = pop(NullValues.Identifier);
      if (name is ParserRecovery) {
        isParserRecovery = true;
      } else {
        fieldInfos[i] = new FieldInfo(
          name as Identifier,
          initializerTokenForInference,
          beforeLast,
          charEndOffset,
        );
      }
    }
    return isParserRecovery ? null : fieldInfos;
  }

  @override
  void beginTypeVariable(Token token) {
    assert(
      checkState(token, [
        ValueKinds.IdentifierOrParserRecovery,
        ValueKinds.MetadataListOrNull,
      ]),
    );
    debugEvent("beginTypeVariable");
    Object? name = pop();
    List<MetadataBuilder>? metadata = pop() as List<MetadataBuilder>?;
    if (name is ParserRecovery) {
      push(name);
    } else {
      Identifier identifier = name as Identifier;
      if (inFunctionType) {
        push(
          _builderFactory.addStructuralParameter(
            metadata: metadata,
            name: identifier.name,
            nameOffset: identifier.nameOffset,
            fileUri: uri,
          ),
        );
      } else {
        push(
          _builderFactory.addNominalParameter(
            metadata: metadata,
            name: identifier.name,
            nameOffset: identifier.nameOffset,
            fileUri: uri,
            kind: declarationContext.typeParameterKind,
          ),
        );
      }
    }
  }

  @override
  void handleTypeVariablesDefined(Token token, int count) {
    debugEvent("TypeVariablesDefined");
    assert(count > 0);
    if (inFunctionType) {
      push(
        const FixedNullableList<SourceStructuralParameterBuilder>()
                .popNonNullable(stack, count, dummyStructuralVariableBuilder) ??
            NullValues.StructuralParameters,
      );
    } else {
      push(
        const FixedNullableList<TypeParameterFragment>().popNonNullable(
              stack,
              count,
              dummyTypeParameterFragment,
            ) ??
            NullValues.NominalParameters,
      );
    }
  }

  @override
  void endTypeVariable(
    Token token,
    int index,
    Token? extendsOrSuper,
    Token? variance,
  ) {
    debugEvent("endTypeVariable");
    TypeBuilder? bound = nullIfParserRecovery(pop()) as TypeBuilder?;
    if (inFunctionType) {
      // Peek to leave type parameters on top of stack.
      List<SourceStructuralParameterBuilder>? typeParameters =
          peek() as List<SourceStructuralParameterBuilder>?;
      if (typeParameters != null) {
        typeParameters[index].bound = bound;
        if (variance != null) {
          // Coverage-ignore-block(suite): Not run.
          if (!libraryFeatures.variance.isEnabled) {
            reportVarianceModifierNotEnabled(variance);
          }
          typeParameters[index].variance = new Variance.fromKeywordString(
            variance.lexeme,
          );
        }
      }
    } else {
      // Peek to leave type parameters on top of stack.
      List<TypeParameterFragment>? typeParameters =
          peek() as List<TypeParameterFragment>?;
      if (typeParameters != null) {
        typeParameters[index].bound = bound;
        if (variance != null) {
          if (!libraryFeatures.variance.isEnabled) {
            reportVarianceModifierNotEnabled(variance);
          }
          typeParameters[index].variance = new Variance.fromKeywordString(
            variance.lexeme,
          );
        }
      }
    }
  }

  @override
  void endTypeVariables(Token beginToken, Token endToken) {
    debugEvent("endTypeVariables");

    if (declarationContext == DeclarationContext.Enum) {
      reportIfNotEnabled(
        libraryFeatures.enhancedEnums,
        beginToken.charOffset,
        noLength,
      );
    }

    if (inFunctionType) {
      List<SourceStructuralParameterBuilder>? builders =
          pop() as List<SourceStructuralParameterBuilder>?;
      push(
        new StructuralParameters(
          beginToken: beginToken,
          endToken: endToken,
          builders: builders,
        ),
      );
    } else {
      List<TypeParameterFragment>? fragments =
          pop() as List<TypeParameterFragment>?;
      push(
        new NominalParameters(
          beginToken: beginToken,
          endToken: endToken,
          fragments: fragments,
        ),
      );
    }
  }

  @override
  void endPartOf(
    Token partKeyword,
    Token ofKeyword,
    Token semicolon,
    bool hasName,
  ) {
    debugEvent("endPartOf");
    assert(
      checkState(
        partKeyword,
        hasName
            ? [
                /* library name */ ValueKinds.Identifier,
                /* metadata */ ValueKinds.MetadataListOrNull,
              ]
            : [
                /* offset */ ValueKinds.Integer,
                /* uri string */ ValueKinds.String,
                /* metadata */ ValueKinds.MetadataListOrNull,
              ],
      ),
    );

    if (hasName) {
      Identifier containingLibrary = pop() as Identifier;
      if (libraryFeatures.enhancedParts.isEnabled) {
        _compilationUnit.addProblem(
          diag.partOfName,
          containingLibrary.firstOffset,
          noLength,
          uri,
        );
      }
      List<MetadataBuilder>? metadata = pop() as List<MetadataBuilder>?;
      _builderFactory.addPartOfWithName(
        metadata: metadata,
        name: flattenName(
          containingLibrary,
          containingLibrary.firstOffset,
          uri,
        ),
        fileOffset: partKeyword.charOffset,
      );
    } else {
      int charOffset = popCharOffset();
      String uriString = pop() as String;
      List<MetadataBuilder>? metadata = pop() as List<MetadataBuilder>?;
      _builderFactory.addPartOfWithUri(
        metadata: metadata,
        uri: uriString,
        uriOffset: charOffset,
        fileOffset: partKeyword.charOffset,
      );
    }
  }

  @override
  void endConstructorReference(
    Token start,
    Token? periodBeforeName,
    Token endToken,
    ConstructorReferenceContext constructorReferenceContext,
  ) {
    debugEvent("ConstructorReference");
    assert(
      checkState(start, [
        if (periodBeforeName != null) /* suffix */ ValueKinds.Identifier,
        ValueKinds.TypeArgumentsOrNull,
        /* prefix */ ValueKinds.IdentifierOrParserRecoveryOrNull,
      ]),
    );

    Identifier? suffix = popIfNotNull(periodBeforeName) as Identifier?;
    List<TypeBuilder>? typeArguments = pop() as List<TypeBuilder>?;
    Object? name = pop();
    if (name is ParserRecovery) {
      push(name);
    } else if (name is Identifier) {
      push(
        _builderFactory.addConstructorReference(
          name.typeName,
          typeArguments,
          suffix?.name,
          name.qualifierOffset,
        ),
      );
    } else {
      assert(name == null);
      push(
        _builderFactory.addUnnamedConstructorReference(
              typeArguments,
              suffix,
              start.charOffset,
            ) ??
            NullValues.ConstructorReference,
      );
    }
  }

  @override
  void beginFactory(
    DeclarationKind declarationKind,
    Token lastConsumed,
    Token? augmentToken,
    Token? externalToken,
    Token? constToken,
  ) {
    DeclarationContext declarationContext;
    switch (declarationKind) {
      case DeclarationKind.TopLevel:
        // Coverage-ignore(suite): Not run.
        throw new UnsupportedError("Unexpected top level factory method.");
      case DeclarationKind.Class:
        declarationContext = DeclarationContext.ClassFactory;
        break;
      case DeclarationKind.Mixin:
        declarationContext = DeclarationContext.MixinFactory;
        break;
      case DeclarationKind.Extension:
        declarationContext = DeclarationContext.ExtensionFactory;
        break;
      case DeclarationKind.ExtensionType:
        declarationContext = DeclarationContext.ExtensionTypeFactory;
        break;
      case DeclarationKind.Enum:
        declarationContext = DeclarationContext.EnumFactory;
        break;
    }

    pushDeclarationContext(declarationContext);
    _builderFactory.beginFactoryMethod();
    push(
      Modifiers.from(
        augmentToken: augmentToken,
        externalToken: externalToken,
        constToken: constToken,
      ),
    );
  }

  void _endFactoryMethod(
    Token beginToken,
    Token factoryKeyword,
    Token endToken,
  ) {
    assert(
      checkState(beginToken, [
        /* method body token */ ValueKinds.Token,
        /* method body kind */ ValueKinds.MethodBody,
      ]),
    );

    pop() as Token; // Method body token
    MethodBody kind = pop() as MethodBody;

    assert(
      checkState(beginToken, [
        if (kind == MethodBody.RedirectingFactoryBody)
          unionOfKinds([
            ValueKinds.ConstructorReferenceBuilderOrNull,
            ValueKinds.ParserRecovery,
          ]),
        ValueKinds.AsyncModifier,
        ValueKinds.FormalListOrNull,
        /* formals offset */ ValueKinds.Integer,
        ValueKinds.NominalTypeParametersOrNull,
        ValueKinds.IdentifierOrParserRecovery,
        ValueKinds.Modifiers,
        ValueKinds.MetadataListOrNull,
      ]),
    );

    ConstructorReferenceBuilder? redirectionTarget;
    if (kind == MethodBody.RedirectingFactoryBody) {
      redirectionTarget =
          nullIfParserRecovery(pop()) as ConstructorReferenceBuilder?;
    }
    AsyncModifier asyncModifier = pop() as AsyncModifier;
    List<FormalParameterBuilder>? formals =
        pop() as List<FormalParameterBuilder>?;
    int formalsOffset = popCharOffset();
    NominalParameters? typeParameters = pop() as NominalParameters?;
    Object name = pop()!;
    Modifiers modifiers = pop() as Modifiers;
    if (nativeMethodName != null) {
      modifiers |= Modifiers.External;
    }
    List<MetadataBuilder>? metadata = pop() as List<MetadataBuilder>?;

    if (typeParameters != null) {
      addProblem(
        diag.constructorWithTypeParameters,
        typeParameters.charOffset,
        typeParameters.spanLength,
      );
    }

    if (name is! Identifier) {
      // Coverage-ignore-block(suite): Not run.
      assert(
        name is ParserRecovery,
        "Unexpected name $name (${name.runtimeType}).",
      );
      _builderFactory.endFactoryMethodForParserRecovery();
    } else {
      // A factory constructor declaration is incomplete if all of:
      //   * It has no body.
      //   * It is not marked external.
      //   * There is no redirection.
      // If a factory constructor is not incomplete then it is complete.
      bool isIncomplete = kind == MethodBody.Abstract && !modifiers.isExternal;

      _builderFactory.addFactoryMethod(
        offsetMap: _offsetMap,
        metadata: metadata,
        modifiers: modifiers,
        identifier: name,
        formals: formals,
        redirectionTarget: redirectionTarget,
        startOffset: metadata?.first.atOffset ?? beginToken.charOffset,
        nameOffset: name.qualifierOffset,
        formalsOffset: formalsOffset,
        endOffset: endToken.charOffset,
        nativeMethodName: nativeMethodName,
        asyncModifier: asyncModifier,
        isComplete: !isIncomplete,
      );
    }
    nativeMethodName = null;
    popDeclarationContext();
  }

  @override
  void endFactory(
    DeclarationKind kind,
    Token beginToken,
    Token factoryKeyword,
    Token endToken,
  ) {
    debugEvent("endClassFactoryMethod");

    if (kind == DeclarationKind.Enum) {
      reportIfNotEnabled(
        libraryFeatures.enhancedEnums,
        beginToken.charOffset,
        noLength,
      );
    }

    _endFactoryMethod(beginToken, factoryKeyword, endToken);
  }

  @override
  void endRedirectingFactoryBody(Token beginToken, Token endToken) {
    debugEvent("RedirectingFactoryBody");
    push(MethodBody.RedirectingFactoryBody);
    push(beginToken);
  }

  @override
  void handleConstFactory(Token constKeyword) {
    debugEvent("ConstFactory");
    if (!libraryFeatures.constFunctions.isEnabled &&
        !libraryFeatures.augmentations.isEnabled) {
      handleRecoverableError(diag.constFactory, constKeyword, constKeyword);
    }
  }

  @override
  void endFieldInitializer(Token assignmentOperator, Token endToken) {
    debugEvent("FieldInitializer");
    push(assignmentOperator.next);
    push(endToken);
    // TODO(jensj): Do we actually want the position of the "," or ";" here?
    push(endToken.next!.charOffset);
  }

  @override
  void handleNoFieldInitializer(Token token) {
    debugEvent("handleNoFieldInitializer");
    push(NullValues.FieldInitializer);
    push(NullValues.FieldInitializer);
    push(token.charOffset);
  }

  @override
  void endInitializers(int count, Token beginToken, Token endToken) {
    debugEvent("endInitializers");
    // Ignored for now.
  }

  @override
  void handleNoInitializers() {
    debugEvent("handleNoInitializers");
    // This is a constructor initializer and it's ignored for now.
  }

  @override
  void handleInvalidMember(Token endToken) {
    debugEvent("handleInvalidMember");
    pop(); // metadata star
  }

  @override
  void endMember() {
    debugEvent("endMember");
    assert(nativeMethodName == null);
  }

  @override
  void handleClassWithClause(Token withKeyword) {
    debugEvent("ClassWithClause");
    assert(
      checkState(withKeyword, [
        /* mixins */ unionOfKinds([
          ValueKinds.TypeBuilderList,
          ValueKinds.ParserRecovery,
        ]),
        /* supertype offset */ ValueKinds.Integer,
        /* supertype */ unionOfKinds([
          ValueKinds.TypeBuilderOrNull,
          ValueKinds.ParserRecovery,
        ]),
      ]),
    );

    Object? mixins = pop();
    int extendsOffset = popCharOffset();
    Object? supertype = peek();
    push(extendsOffset);
    if (supertype is ParserRecovery || mixins is ParserRecovery) {
      push(new ParserRecovery(withKeyword.charOffset));
    } else {
      push(mixins);
    }
    assert(
      checkState(withKeyword, [
        /* mixins */ unionOfKinds([
          ValueKinds.TypeBuilderListOrNull,
          ValueKinds.ParserRecovery,
        ]),
        /* supertype offset */ ValueKinds.Integer,
        /* supertype */ unionOfKinds([
          ValueKinds.TypeBuilderOrNull,
          ValueKinds.ParserRecovery,
        ]),
      ]),
    );
  }

  @override
  void handleClassNoWithClause() {
    debugEvent("ClassNoWithClause");
    assert(
      checkState(null, [
        /* supertype offset */ ValueKinds.Integer,
        /* supertype */ unionOfKinds([
          ValueKinds.TypeBuilderOrNull,
          ValueKinds.ParserRecovery,
        ]),
      ]),
    );
    push(NullValues.TypeBuilderList);
    assert(
      checkState(null, [
        /* mixins */ ValueKinds.TypeBuilderListOrNull,
        /* supertype offset */ ValueKinds.Integer,
        /* supertype */ unionOfKinds([
          ValueKinds.TypeBuilderOrNull,
          ValueKinds.ParserRecovery,
        ]),
      ]),
    );
  }

  @override
  void handleEnumWithClause(Token withKeyword) {
    debugEvent("EnumWithClause");
    assert(
      checkState(withKeyword, [
        /* mixins */ unionOfKinds([
          ValueKinds.TypeBuilderListOrNull,
          ValueKinds.ParserRecovery,
        ]),
      ]),
    );

    reportIfNotEnabled(
      libraryFeatures.enhancedEnums,
      withKeyword.charOffset,
      withKeyword.length,
    );

    Object? mixins = pop();
    if (mixins is ParserRecovery) {
      push(new ParserRecovery(withKeyword.charOffset));
    } else {
      push(mixins);
    }
    assert(
      checkState(withKeyword, [
        /* mixins */ unionOfKinds([
          ValueKinds.TypeBuilderListOrNull,
          ValueKinds.ParserRecovery,
        ]),
      ]),
    );
  }

  @override
  void handleEnumNoWithClause() {
    debugEvent("EnumNoWithClause");
    push(NullValues.TypeBuilderList);
  }

  @override
  void handleMixinWithClause(Token withKeyword) {
    debugEvent("MixinWithClause");
    assert(
      checkState(withKeyword, [
        /* mixins */ unionOfKinds([
          ValueKinds.TypeBuilderListOrNull,
          ValueKinds.ParserRecovery,
        ]),
      ]),
    );

    // This is an error case where the parser has already given an error.
    // We just discard the data.
    pop();
  }

  @override
  void handleClassHeader(Token begin, Token classKeyword, Token? nativeToken) {
    debugEvent("ClassHeader");
    nativeMethodName = null;
  }

  @override
  void handleMixinHeader(Token mixinKeyword) {
    debugEvent("handleMixinHeader");
    nativeMethodName = null;
  }

  @override
  void handleNoClassBody(Token semicolonToken) {
    debugEvent("NoClassBody");
    _builderFactory.beginClassBody();
  }

  @override
  void handleNoEnumBody(Token semicolon) {
    debugEvent("handleNoEnumBody");
    _builderFactory.beginEnumBody();
  }

  @override
  // Coverage-ignore(suite): Not run.
  void handleNoExtensionBody(Token semicolonToken) {
    debugEvent("handleNoExtensionBody");
    _builderFactory.beginExtensionBody();
  }

  @override
  void handleNoExtensionTypeBody(Token semicolonToken) {
    debugEvent("NoExtensionTypeBody");
    _builderFactory.beginExtensionTypeBody();
  }

  @override
  // Coverage-ignore(suite): Not run.
  void handleNoMixinBody(Token semicolonToken) {
    debugEvent("handleNoMixinBody");
    _builderFactory.beginMixinBody();
  }

  @override
  void endClassOrMixinOrExtensionBody(
    DeclarationKind kind,
    int memberCount,
    Token beginToken,
    Token endToken,
  ) {
    debugEvent("endClassOrMixinBody");
    popDeclarationContext();
  }

  @override
  void handleAsyncModifier(Token? asyncToken, Token? starToken) {
    debugEvent("AsyncModifier");
    push(asyncMarkerFromTokens(asyncToken, starToken));
  }

  @override
  void addProblem(
    Message message,
    int charOffset,
    int length, {
    bool wasHandled = false,
    List<LocatedMessage>? context,
  }) {
    _compilationUnit.addProblem(
      message,
      charOffset,
      length,
      uri,
      wasHandled: wasHandled,
      context: context,
    );
  }

  @override
  bool isIgnoredError(Code code, Token token) {
    return isIgnoredParserError(code, token) ||
        super.isIgnoredError(code, token);
  }

  @override
  void debugEvent(String name) {
    // printEvent('OutlineBuilder: $name');
  }

  @override
  void handleNewAsIdentifier(Token token) {
    reportIfNotEnabled(
      libraryFeatures.constructorTearoffs,
      token.charOffset,
      token.length,
    );
  }
}

class EnumConstantInfo {
  final List<MetadataBuilder>? metadata;
  final String name;
  final int nameOffset;

  new(this.metadata, this.name, this.nameOffset);
}

class NominalParameters {
  final Token beginToken;
  final Token endToken;
  final List<TypeParameterFragment>? fragments;

  new({
    required this.beginToken,
    required this.endToken,
    required this.fragments,
  });

  int get charOffset => beginToken.charOffset;

  int get spanLength => lengthOfSpan(beginToken, endToken);
}

class StructuralParameters {
  final Token beginToken;
  final Token endToken;
  final List<SourceStructuralParameterBuilder>? builders;

  new({
    required this.beginToken,
    required this.endToken,
    required this.builders,
  });
}