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.

library fasta.outline_builder;

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/type_inference/type_analyzer_operations.dart'
    show Variance;
import 'package:_fe_analyzer_shared/src/util/link.dart';
import 'package:_fe_analyzer_shared/src/util/value_kind.dart';
import 'package:kernel/ast.dart'
    show AsyncMarker, 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;
import '../base/ignored_parser_errors.dart' show isIgnoredParserError;
import '../base/messages.dart';
import '../base/modifiers.dart' show Modifiers;
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/library_builder.dart';
import '../builder/metadata_builder.dart';
import '../builder/mixin_application_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 '../base/operator.dart' show Operator;
import '../base/problems.dart' show unhandled;
import '../base/uris.dart';
import '../kernel/utils.dart';
import 'builder_factory.dart';
import 'offset_map.dart';
import 'source_enum_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 variables 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 {
  InstanceTypeVariableAccessState get instanceTypeVariableAccessState {
    switch (this) {
      case DeclarationContext.Library:
      case DeclarationContext.Typedef:
      case DeclarationContext.TopLevelMethod:
      case DeclarationContext.TopLevelField:
        return InstanceTypeVariableAccessState.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 InstanceTypeVariableAccessState.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 InstanceTypeVariableAccessState.Disallowed;
      case DeclarationContext.MixinConstructor:
      case DeclarationContext.MixinFactory:
      case DeclarationContext.ExtensionConstructor:
      case DeclarationContext.ExtensionFactory:
      case DeclarationContext.ExtensionInstanceField:
      case DeclarationContext.EnumFactory:
        return InstanceTypeVariableAccessState.Invalid;
    }
  }

  /// Returns the kind of type variable created in the current context.
  TypeVariableKind get typeVariableKind {
    switch (this) {
      case DeclarationContext.Class:
      case DeclarationContext.ClassOrMixinOrNamedMixinApplication:
      case DeclarationContext.Mixin:
      case DeclarationContext.NamedMixinApplication:
        return TypeVariableKind.classMixinOrEnum;
      case DeclarationContext.ExtensionOrExtensionType:
      case DeclarationContext.Extension:
      case DeclarationContext.ExtensionBody:
      case DeclarationContext.ExtensionType:
      case DeclarationContext.ExtensionTypeBody:
        return TypeVariableKind.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 TypeVariableKind.function;
    }
  }
}

class OutlineBuilder extends StackListenerImpl {
  final SourceCompilationUnit _compilationUnit;
  final BuilderFactory _builderFactory;

  final bool enableNative;
  bool inAbstractOrSealedClass = false;
  bool inConstructor = false;
  bool inConstructorName = 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 variables should be interpreted differently: as structural and
  /// nominal correspondingly.
  bool _insideOfFormalParameterType = false;

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

  OffsetMap _offsetMap;

  OutlineBuilder(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));
  }

  @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>,
          hideKeyword.charOffset, _compilationUnit.fileUri));
    }
  }

  @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>,
          showKeyword.charOffset, _compilationUnit.fileUri));
    }
  }

  @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? augmentToken, 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;
    }

    if (augmentToken != null) {
      if (reportIfNotEnabled(libraryFeatures.macros, augmentToken.charOffset,
          augmentToken.length)) {
        augmentToken = null;
      }
    }
    bool isAugmentationImport = augmentToken != null;
    _builderFactory.addImport(
        offsetMap: _offsetMap,
        importKeyword: importKeyword,
        metadata: metadata,
        isAugmentationImport: isAugmentationImport,
        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, [
      /* uri string */ ValueKinds.ConfigurationListOrNull,
      /* offset */ ValueKinds.Integer,
      /* uri string */ ValueKinds.String,
      /* metadata */ ValueKinds.MetadataListOrNull,
    ]));

    pop(); // configurations
    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
  // Coverage-ignore(suite): Not run.
  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));
      }
    }
    if (inConstructor && context == IdentifierContext.methodDeclaration) {
      inConstructorName = true;
    }
  }

  @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(messageInterpolationInUri, 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 handleStringJuxtaposition(Token startToken, int literalCount) {
    debugEvent("StringJuxtaposition");
    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, metadata: metadata, isAugment: false);
  }

  @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, metadata: metadata, isAugment: true);
  }

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

  @override
  void beginClassDeclaration(
      Token begin,
      Token? abstractToken,
      Token? macroToken,
      Token? sealedToken,
      Token? baseToken,
      Token? interfaceToken,
      Token? finalToken,
      Token? augmentToken,
      Token? mixinToken,
      Token name) {
    debugEvent("beginClassDeclaration");
    popDeclarationContext(
        DeclarationContext.ClassOrMixinOrNamedMixinApplication);
    pushDeclarationContext(DeclarationContext.Class);
    List<NominalVariableBuilder>? typeVariables =
        pop() as List<NominalVariableBuilder>?;
    push(typeVariables ?? NullValues.NominalVariables);
    if (macroToken != null) {
      if (reportIfNotEnabled(
          libraryFeatures.macros, macroToken.charOffset, macroToken.length)) {
        macroToken = null;
      }
    }
    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, typeVariables);
    Modifiers modifiers = Modifiers.from(
        abstractToken: abstractToken,
        macroToken: macroToken,
        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);
    List<NominalVariableBuilder>? typeVariables =
        pop() as List<NominalVariableBuilder>?;
    if (baseToken != null) {
      if (reportIfNotEnabled(libraryFeatures.classModifiers,
          baseToken.charOffset, baseToken.length)) {
        baseToken = null;
      }
    }
    Modifiers modifiers =
        Modifiers.from(augmentToken: augmentToken, baseToken: baseToken);
    push(modifiers);
    push(typeVariables ?? NullValues.NominalVariables);
    _builderFactory.beginMixinDeclaration(
        name.lexeme, name.charOffset, typeVariables);
  }

  @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])
        ]));

        Object? extensionThisType = peek();
        // TODO(johnniwinther): Supply an invalid type as the extension on type.
        _builderFactory.beginExtensionBody(
            extensionThisType is TypeBuilder ? extensionThisType : null);
        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? macroToken,
      Token? sealedToken,
      Token? baseToken,
      Token? interfaceToken,
      Token? finalToken,
      Token? augmentToken,
      Token? mixinToken,
      Token name) {
    debugEvent("beginNamedMixinApplication");
    popDeclarationContext(
        DeclarationContext.ClassOrMixinOrNamedMixinApplication);
    pushDeclarationContext(DeclarationContext.NamedMixinApplication);
    List<NominalVariableBuilder>? typeVariables =
        pop() as List<NominalVariableBuilder>?;
    push(typeVariables ?? NullValues.NominalVariables);
    _builderFactory.beginNamedMixinApplication(
        name.lexeme, name.charOffset, typeVariables);
    if (macroToken != null) {
      if (reportIfNotEnabled(
          libraryFeatures.macros, macroToken.charOffset, macroToken.length)) {
        macroToken = null;
      }
    }
    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,
        macroToken: macroToken,
        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.MixinApplicationBuilderOrNull,
        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.MixinApplicationBuilder); // Mixin applications.
    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.MixinApplicationBuilderOrNull,
        ValueKinds.ParserRecovery,
      ]),
      /* supertype offset */ ValueKinds.Integer,
      /* supertype */ unionOfKinds([
        ValueKinds.TypeBuilderOrNull,
        ValueKinds.ParserRecovery,
      ]),
      /* modifiers */ ValueKinds.Modifiers,
      /* type variables */ ValueKinds.NominalVariableListOrNull,
      /* name */ ValueKinds.IdentifierOrParserRecovery,
      /* metadata */ ValueKinds.MetadataListOrNull,
    ]));

    List<TypeBuilder>? interfaces =
        pop(NullValues.TypeBuilderList) as List<TypeBuilder>?;
    MixinApplicationBuilder? mixinApplication =
        nullIfParserRecovery(pop(NullValues.MixinApplicationBuilder))
            as MixinApplicationBuilder?;
    int supertypeOffset = popCharOffset();
    TypeBuilder? supertype = nullIfParserRecovery(pop()) as TypeBuilder?;
    Modifiers modifiers = pop() as Modifiers;
    List<NominalVariableBuilder>? typeVariables =
        pop() as List<NominalVariableBuilder>?;
    Object? name = pop();
    if (typeVariables != null && mixinApplication != null) {
      mixinApplication.typeVariables = typeVariables;
    }
    List<MetadataBuilder>? metadata = pop() as List<MetadataBuilder>?;
    inAbstractOrSealedClass = false;
    checkEmpty(beginToken.charOffset);
    if (name is ParserRecovery) {
      // Coverage-ignore-block(suite): Not run.
      _builderFactory.endClassDeclarationForParserRecovery(typeVariables);
    } else {
      Identifier identifier = name as Identifier;
      final int startCharOffset =
          metadata == null ? beginToken.charOffset : metadata.first.charOffset;

      String classNameForErrors = identifier.name;
      if (supertype != null) {
        if (supertype.nullabilityBuilder.build() == Nullability.nullable) {
          _compilationUnit.addProblem(
              templateNullableSuperclassError
                  .withArguments(supertype.fullNameForErrors),
              identifier.nameOffset,
              classNameForErrors.length,
              uri);
        }
      }
      if (mixinApplication != null) {
        List<TypeBuilder>? mixins = mixinApplication.mixins;
        for (TypeBuilder mixin in mixins) {
          if (mixin.nullabilityBuilder.build() == Nullability.nullable) {
            _compilationUnit.addProblem(
                templateNullableMixinError
                    .withArguments(mixin.fullNameForErrors),
                identifier.nameOffset,
                classNameForErrors.length,
                uri);
          }
        }
      }
      if (interfaces != null) {
        for (TypeBuilder interface in interfaces) {
          if (interface.nullabilityBuilder.build() == Nullability.nullable) {
            _compilationUnit.addProblem(
                templateNullableInterfaceError
                    .withArguments(interface.fullNameForErrors),
                identifier.nameOffset,
                classNameForErrors.length,
                uri);
          }
        }
      }

      if (modifiers.isSealed) {
        modifiers |= Modifiers.Abstract;
      }
      _builderFactory.addClass(
          _offsetMap,
          metadata,
          modifiers,
          identifier,
          typeVariables,
          supertype,
          mixinApplication,
          interfaces,
          startCharOffset,
          identifier.nameOffset,
          endToken.charOffset,
          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 variables */ ValueKinds.NominalVariableListOrNull,
      /* 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>?;
    List<NominalVariableBuilder>? typeVariables =
        pop(NullValues.NominalVariables) as List<NominalVariableBuilder>?;
    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(typeVariables);
    } else {
      Identifier identifier = name as Identifier;
      int startOffset = metadata == null
          ? beginToken.charOffset
          :
          // Coverage-ignore(suite): Not run.
          metadata.first.charOffset;
      String classNameForErrors = identifier.name;
      if (supertypeConstraints != null) {
        for (TypeBuilder supertype in supertypeConstraints) {
          if (supertype.nullabilityBuilder.build() == Nullability.nullable) {
            _compilationUnit.addProblem(
                templateNullableSuperclassError
                    .withArguments(supertype.fullNameForErrors),
                identifier.nameOffset,
                classNameForErrors.length,
                uri);
          }
        }
      }
      if (interfaces != null) {
        for (TypeBuilder interface in interfaces) {
          if (interface.nullabilityBuilder.build() == Nullability.nullable) {
            _compilationUnit.addProblem(
                templateNullableInterfaceError
                    .withArguments(interface.fullNameForErrors),
                identifier.nameOffset,
                classNameForErrors.length,
                uri);
          }
        }
      }

      _builderFactory.addMixinDeclaration(
          _offsetMap,
          metadata,
          modifiers,
          identifier,
          typeVariables,
          supertypeConstraints,
          interfaces,
          startOffset,
          identifier.nameOffset,
          endToken.charOffset,
          -1);
    }
    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.NominalVariableListOrNull, ValueKinds.MetadataListOrNull]));
    debugEvent("beginExtensionDeclaration");
    popDeclarationContext(DeclarationContext.ExtensionOrExtensionType);
    pushDeclarationContext(DeclarationContext.Extension);
    List<NominalVariableBuilder>? typeVariables =
        pop() as List<NominalVariableBuilder>?;
    int offset = nameToken?.charOffset ?? extensionKeyword.charOffset;
    push(nameToken != null
        ? new SimpleIdentifier(nameToken)
        : NullValues.Identifier);
    push(typeVariables ?? NullValues.NominalVariables);
    _builderFactory.beginExtensionDeclaration(
        nameToken?.lexeme, offset, typeVariables);
  }

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

    Object? onType = pop();
    if (onType is ParserRecovery) {
      ParserRecovery parserRecovery = onType;
      onType = new FixedTypeBuilderImpl(
          const InvalidType(), uri, parserRecovery.charOffset);
    }
    List<NominalVariableBuilder>? typeVariables =
        pop(NullValues.NominalVariables) as List<NominalVariableBuilder>?;
    Identifier? name = pop(NullValues.Identifier) as Identifier?;
    int nameOffset = name?.nameOffset ?? extensionKeyword.charOffset;
    List<MetadataBuilder>? metadata =
        pop(NullValues.Metadata) as List<MetadataBuilder>?;
    checkEmpty(extensionKeyword.charOffset);
    int startOffset = metadata == null
        ? extensionKeyword.charOffset
        : metadata.first.charOffset;
    _builderFactory.addExtensionDeclaration(
        _offsetMap,
        beginToken,
        metadata,
        // TODO(johnniwinther): Support modifiers on extensions?
        Modifiers.empty,
        name,
        typeVariables,
        onType as TypeBuilder,
        startOffset,
        nameOffset,
        endToken.charOffset);
    popDeclarationContext(DeclarationContext.Extension);
  }

  @override
  void beginExtensionTypeDeclaration(
      Token? augmentToken, Token extensionKeyword, Token nameToken) {
    assert(checkState(extensionKeyword,
        [ValueKinds.NominalVariableListOrNull, ValueKinds.MetadataListOrNull]));
    debugEvent("beginExtensionTypeDeclaration");
    popDeclarationContext(DeclarationContext.ExtensionOrExtensionType);
    pushDeclarationContext(DeclarationContext.ExtensionType);
    List<NominalVariableBuilder>? typeVariables =
        pop() as List<NominalVariableBuilder>?;
    String name = nameToken.lexeme;
    int offset = nameToken.charOffset;
    push(new SimpleIdentifier(nameToken));
    push(typeVariables ?? NullValues.NominalVariables);
    _builderFactory.beginExtensionTypeDeclaration(name, offset, typeVariables);
  }

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

    List<TypeBuilder>? interfaces =
        pop(NullValues.TypeBuilderList) as List<TypeBuilder>?;
    List<NominalVariableBuilder>? typeVariables =
        pop(NullValues.NominalVariables) as List<NominalVariableBuilder>?;
    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 == null
        ? extensionKeyword.charOffset
        : metadata.first.charOffset;
    _builderFactory.addExtensionTypeDeclaration(
        _offsetMap,
        metadata,
        // TODO(johnniwinther): Support modifiers on extension types?
        Modifiers.empty,
        identifier,
        typeVariables,
        interfaces,
        startOffset,
        endToken.charOffset);

    popDeclarationContext(DeclarationContext.ExtensionType);
  }

  @override
  void beginPrimaryConstructor(Token beginToken) {}

  @override
  void endPrimaryConstructor(
      Token beginToken, 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
    String constructorName = '';
    if (hasConstructorName) {
      // TODO(johnniwinther): Handle [ParserRecovery].
      Identifier identifier = pop() as Identifier;
      charOffset = identifier.nameOffset;
      constructorName = identifier.name;
    }
    bool inExtensionType =
        declarationContext == DeclarationContext.ExtensionType;
    if (formals != null) {
      int requiredPositionalCount = 0;
      int? firstNamedParameterOffset;
      int? firstOptionalPositionalParameterOffset;
      for (int i = 0; i < formals.length; i++) {
        FormalParameterBuilder formal = formals[i];
        if (inExtensionType) {
          TypeBuilder type = formal.type;
          if (type is FunctionTypeBuilder &&
              type.hasFunctionFormalParameterSyntax) {
            _compilationUnit.addProblem(
                // ignore: lines_longer_than_80_chars
                messageExtensionTypePrimaryConstructorFunctionFormalParameterSyntax,
                formal.charOffset,
                formal.name.length,
                formal.fileUri);
          }
          if (type is ImplicitTypeBuilder) {
            _compilationUnit.addProblem(messageExpectedRepresentationType,
                formal.charOffset, formal.name.length, formal.fileUri);
            formal.type =
                new InvalidTypeBuilderImpl(formal.fileUri, formal.charOffset);
          }
          if (formal.modifiers.containsSyntacticModifiers(
              ignoreCovariant: true, ignoreRequired: true)) {
            _compilationUnit.addProblem(messageRepresentationFieldModifier,
                formal.charOffset, formal.name.length, formal.fileUri);
          }
          if (formal.isInitializingFormal) {
            _compilationUnit.addProblem(
                messageExtensionTypePrimaryConstructorWithInitializingFormal,
                formal.charOffset,
                formal.name.length,
                formal.fileUri);
          }
        }

        if (formal.isPositional) {
          if (formal.isOptionalPositional) {
            firstOptionalPositionalParameterOffset = formal.charOffset;
          } else {
            requiredPositionalCount++;
          }
        }
        if (formal.isNamed) {
          firstNamedParameterOffset = formal.charOffset;
        }
        _builderFactory.addPrimaryConstructorField(
            // TODO(johnniwinther): Support annotations on annotations on fields
            // defined through a primary constructor. This is not needed for
            // extension types where the field is not part of the AST but will
            // be needed when primary constructors are generally supported.
            metadata: null,
            type: formal.type,
            name: formal.name,
            charOffset: formal.charOffset);
        formals[i] = formal.forPrimaryConstructor(_builderFactory);
      }
      if (inExtensionType) {
        if (firstOptionalPositionalParameterOffset != null) {
          _compilationUnit.addProblem(
              messageOptionalParametersInExtensionTypeDeclaration,
              firstOptionalPositionalParameterOffset,
              1,
              uri);
        } else if (firstNamedParameterOffset != null) {
          _compilationUnit.addProblem(
              messageNamedParametersInExtensionTypeDeclaration,
              firstNamedParameterOffset,
              1,
              uri);
        } else if (requiredPositionalCount == 0) {
          _compilationUnit.addProblem(
              messageExpectedRepresentationField, charOffset, 1, uri);
        } else if (formals.length > 1) {
          _compilationUnit.addProblem(
              messageMultipleRepresentationFields, charOffset, 1, uri);
        }
      }
    }

    _builderFactory.addPrimaryConstructor(
        offsetMap: _offsetMap,
        beginToken: beginToken,
        constructorName: constructorName == "new" ? "" : constructorName,
        charOffset: charOffset,
        formals: formals,
        isConst: constKeyword != null);
  }

  ProcedureKind computeProcedureKind(Token? token) {
    if (token == null) return ProcedureKind.Method;
    if (token.isA2(Keyword.GET)) return ProcedureKind.Getter;
    if (token.isA2(Keyword.SET)) return ProcedureKind.Setter;
    return unhandled(
        token.lexeme, "computeProcedureKind", token.charOffset, uri);
  }

  @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, [
      ValueKinds.MethodBody,
      ValueKinds.AsyncMarker,
      ValueKinds.FormalListOrNull,
      /* formalsOffset */ ValueKinds.Integer,
      ValueKinds.NominalVariableListOrNull,
      ValueKinds.IdentifierOrParserRecovery,
      ValueKinds.TypeBuilderOrNull,
      ValueKinds.Modifiers,
      ValueKinds.MetadataListOrNull,
    ]));

    MethodBody kind = pop() as MethodBody;
    AsyncMarker asyncModifier = pop() as AsyncMarker;
    List<FormalParameterBuilder>? formals =
        pop() as List<FormalParameterBuilder>?;
    int formalsOffset = popCharOffset();
    List<NominalVariableBuilder>? typeVariables =
        pop() as List<NominalVariableBuilder>?;
    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;
      }
      if (returnType != null && !returnType.isVoidType) {
        addProblem(messageNonVoidReturnSetter, beginToken.charOffset, noLength);
        // Use implicit void as recovery.
        returnType = null;
      }
    }
    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) {
      _builderFactory.endTopLevelMethod();
      final int startCharOffset =
          metadata == null ? beginToken.charOffset : metadata.first.charOffset;
      _builderFactory.addProcedure(
          _offsetMap,
          metadata,
          modifiers,
          returnType,
          identifier,
          identifier.name,
          typeVariables,
          formals,
          computeProcedureKind(getOrSet),
          startCharOffset,
          identifier.nameOffset,
          formalsOffset,
          endToken.charOffset,
          nativeMethodName,
          asyncModifier,
          isInstanceMember: false,
          isExtensionMember: false,
          isExtensionTypeMember: false);
      nativeMethodName = null;
    } else {
      _builderFactory.endTopLevelMethodForParserRecovery(typeVariables);
    }
    popDeclarationContext(DeclarationContext.TopLevelMethod);
  }

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

  @override
  // Coverage-ignore(suite): Not run.
  void handleNativeFunctionBodyIgnored(Token nativeToken, Token semicolon) {
    debugEvent("NativeFunctionBodyIgnored");
  }

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

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

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

  @override
  void beginMethod(
      DeclarationKind declarationKind,
      Token? augmentToken,
      Token? externalToken,
      Token? staticToken,
      Token? covariantToken,
      Token? varFinalOrConst,
      Token? getOrSet,
      Token name,
      String? enclosingDeclarationName) {
    inConstructor = name.lexeme == enclosingDeclarationName && getOrSet == null;
    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 (inConstructor) {
          declarationContext = DeclarationContext.ClassConstructor;
        } else if (staticToken != null) {
          declarationContext = DeclarationContext.ClassStaticMethod;
        } else {
          declarationContext = DeclarationContext.ClassInstanceMethod;
        }
        break;
      case DeclarationKind.Mixin:
        if (inConstructor) {
          declarationContext = DeclarationContext.MixinConstructor;
        } else if (staticToken != null) {
          declarationContext = DeclarationContext.MixinStaticMethod;
        } else {
          declarationContext = DeclarationContext.MixinInstanceMethod;
        }
        break;
      case DeclarationKind.Extension:
        if (inConstructor) {
          declarationContext = DeclarationContext.ExtensionConstructor;
        } else if (staticToken != null) {
          declarationContext = DeclarationContext.ExtensionStaticMethod;
        } else {
          declarationContext = DeclarationContext.ExtensionInstanceMethod;
        }
        break;
      case DeclarationKind.ExtensionType:
        if (inConstructor) {
          declarationContext = DeclarationContext.ExtensionTypeConstructor;
        } else if (staticToken != null) {
          declarationContext = DeclarationContext.ExtensionTypeStaticMethod;
        } else {
          declarationContext = DeclarationContext.ExtensionTypeInstanceMethod;
        }
        break;
      case DeclarationKind.Enum:
        if (inConstructor) {
          declarationContext = DeclarationContext.EnumConstructor;
        } else if (staticToken != null) {
          declarationContext = DeclarationContext.EnumStaticMethod;
        } else {
          declarationContext = DeclarationContext.EnumInstanceMethod;
        }
    }
    pushDeclarationContext(declarationContext);

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

  @override
  void endClassMethod(Token? getOrSet, Token beginToken, Token beginParam,
      Token? beginInitializers, Token endToken) {
    debugEvent("endClassMethod");
    _endClassMethod(getOrSet, beginToken, beginParam, beginInitializers,
        endToken, _MethodKind.classMethod);
  }

  @override
  void endClassConstructor(Token? getOrSet, Token beginToken, Token beginParam,
      Token? beginInitializers, Token endToken) {
    debugEvent("endClassConstructor");
    _endClassMethod(getOrSet, beginToken, beginParam, beginInitializers,
        endToken, _MethodKind.classConstructor);
  }

  @override
  void endMixinMethod(Token? getOrSet, Token beginToken, Token beginParam,
      Token? beginInitializers, Token endToken) {
    debugEvent("endMixinMethod");
    _endClassMethod(getOrSet, beginToken, beginParam, beginInitializers,
        endToken, _MethodKind.mixinMethod);
  }

  @override
  void endExtensionMethod(Token? getOrSet, Token beginToken, Token beginParam,
      Token? beginInitializers, Token endToken) {
    debugEvent("endExtensionMethod");
    _endClassMethod(getOrSet, beginToken, beginParam, beginInitializers,
        endToken, _MethodKind.extensionMethod);
  }

  @override
  void endExtensionTypeMethod(Token? getOrSet, Token beginToken,
      Token beginParam, Token? beginInitializers, Token endToken) {
    debugEvent("endExtensionTypeMethod");
    _endClassMethod(getOrSet, beginToken, beginParam, beginInitializers,
        endToken, _MethodKind.extensionTypeMethod);
  }

  @override
  void endMixinConstructor(Token? getOrSet, Token beginToken, Token beginParam,
      Token? beginInitializers, Token endToken) {
    debugEvent("endMixinConstructor");
    _endClassMethod(getOrSet, beginToken, beginParam, beginInitializers,
        endToken, _MethodKind.mixinConstructor);
  }

  @override
  void endExtensionConstructor(Token? getOrSet, Token beginToken,
      Token beginParam, Token? beginInitializers, Token endToken) {
    debugEvent("endExtensionConstructor");
    _endClassMethod(getOrSet, beginToken, beginParam, beginInitializers,
        endToken, _MethodKind.extensionConstructor);
  }

  @override
  void endExtensionTypeConstructor(Token? getOrSet, Token beginToken,
      Token beginParam, Token? beginInitializers, Token endToken) {
    debugEvent("endExtensionTypeConstructor");
    _endClassMethod(getOrSet, beginToken, beginParam, beginInitializers,
        endToken, _MethodKind.extensionTypeConstructor);
  }

  void _endClassMethod(Token? getOrSet, Token beginToken, Token beginParam,
      Token? beginInitializers, Token endToken, _MethodKind methodKind) {
    assert(checkState(beginToken, [ValueKinds.MethodBody]));
    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.NominalVariableListOrNull,
      ValueKinds.IdentifierOrParserRecovery,
      ValueKinds.TypeBuilderOrNull,
      ValueKinds.Modifiers,
      ValueKinds.Integer, // var/final/const offset
      ValueKinds.MetadataListOrNull,
    ]));

    AsyncMarker asyncModifier = pop() as AsyncMarker;
    List<FormalParameterBuilder>? formals =
        pop() as List<FormalParameterBuilder>?;
    int formalsOffset = popCharOffset();
    List<NominalVariableBuilder>? typeVariables =
        pop() as List<NominalVariableBuilder>?;
    Object? identifier = pop();
    TypeBuilder? returnType = pop() as TypeBuilder?;
    Modifiers modifiers = pop() as Modifiers;
    int varFinalOrConstOffset = popCharOffset();
    List<MetadataBuilder>? metadata = pop() as List<MetadataBuilder>?;

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

      if (inConstructor) {
        _builderFactory.endConstructorForParserRecovery(typeVariables);
      } else if (modifiers.isStatic) {
        // Coverage-ignore-block(suite): Not run.
        _builderFactory.endStaticMethodForParserRecovery(typeVariables);
      } else {
        _builderFactory.endInstanceMethodForParserRecovery(typeVariables);
      }

      nativeMethodName = null;
      inConstructor = false;
      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? kind;
    int charOffset = identifier.qualifierOffset;
    if (operator != null) {
      name = operator.text;
      kind = ProcedureKind.Operator;
      int requiredArgumentCount = operator.requiredArgumentCount;
      if ((formals?.length ?? 0) != requiredArgumentCount) {
        Template<Message Function(String name)> template;
        switch (requiredArgumentCount) {
          case 0:
            template = templateOperatorParameterMismatch0;
            break;

          case 1:
            if (Operator.subtract == operator) {
              template = templateOperatorMinusParameterMismatch;
            } else {
              template = templateOperatorParameterMismatch1;
            }
            break;

          case 2:
            template = templateOperatorParameterMismatch2;
            break;

          // Coverage-ignore(suite): Not run.
          default:
            unhandled("$requiredArgumentCount", "operatorRequiredArgumentCount",
                identifier.nameOffset, uri);
        }
        addProblem(template.withArguments(name), charOffset, name.length);
      } else {
        if (formals != null) {
          for (FormalParameterBuilder formal in formals) {
            if (!formal.isRequiredPositional) {
              addProblem(messageOperatorWithOptionalFormals, formal.charOffset,
                  formal.name.length);
            }
          }
        }
      }
      if (typeVariables != null) {
        NominalVariableBuilder typeVariableBuilder = typeVariables.first;
        addProblem(messageOperatorWithTypeParameters,
            typeVariableBuilder.charOffset, typeVariableBuilder.name.length);
      }
    } else {
      name = identifier.name;
      kind = computeProcedureKind(getOrSet);
    }

    bool isAbstract = bodyKind == MethodBody.Abstract;
    if (isAbstract) {
      // An error has been reported if this wasn't already sync.
      asyncModifier = AsyncMarker.Sync;
    }
    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 (returnType != null && !returnType.isVoidType) {
        addProblem(
            messageNonVoidReturnSetter,
            returnType.charOffset ?? // Coverage-ignore(suite): Not run.
                beginToken.charOffset,
            noLength);
        // Use implicit void as recovery.
        returnType = null;
      }
    }
    if (operator == Operator.indexSet &&
        returnType != null &&
        !returnType.isVoidType) {
      addProblem(
          messageNonVoidReturnOperator,
          returnType.charOffset ?? // Coverage-ignore(suite): Not run.
              beginToken.offset,
          noLength);
      // Use implicit void as recovery.
      returnType = null;
    }

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

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

    bool isConstructor = switch (methodKind) {
      _MethodKind.classConstructor => true,
      _MethodKind.mixinConstructor => true,
      _MethodKind.extensionConstructor => true,
      _MethodKind.extensionTypeConstructor => true,
      _MethodKind.enumConstructor => true,
      _MethodKind.classMethod => false,
      _MethodKind.mixinMethod => false,
      _MethodKind.extensionMethod => false,
      _MethodKind.extensionTypeMethod => false,
      _MethodKind.enumMethod => false,
    };
    if (isConstructor) {
      if (isConst &&
          bodyKind != MethodBody.Abstract &&
          !libraryFeatures.constFunctions.isEnabled) {
        addProblem(messageConstConstructorWithBody, varFinalOrConstOffset, 5);
        modifiers -= Modifiers.Const;
      }
      if (returnType != null) {
        addProblem(
            messageConstructorWithReturnType,
            returnType.charOffset ?? // Coverage-ignore(suite): Not run.
                beginToken.offset,
            noLength);
        returnType = null;
      }
    } else {
      // Coverage-ignore-block(suite): Not run.
      if (isConst) {
        // TODO(danrubel): consider removing this
        // because it is an error to have a const method.
        modifiers -= Modifiers.Const;
      }
    }

    int startCharOffset =
        metadata == null ? beginToken.charOffset : metadata.first.charOffset;

    int endCharOffset = endToken.charOffset;

    bool forAbstractClassOrMixin =
        inAbstractOrSealedClass || methodKind == _MethodKind.mixinConstructor;

    bool isExtensionMember = methodKind == _MethodKind.extensionMethod;
    bool isExtensionTypeMember = methodKind == _MethodKind.extensionTypeMethod;

    _builderFactory.addClassMethod(
        offsetMap: _offsetMap,
        metadata: metadata,
        identifier: identifier,
        name: name,
        returnType: returnType,
        formals: formals,
        typeVariables: typeVariables,
        beginInitializers: beginInitializers,
        startCharOffset: startCharOffset,
        endCharOffset: endCharOffset,
        charOffset: charOffset,
        formalsOffset: formalsOffset,
        modifiers: modifiers,
        inConstructor: inConstructor,
        isStatic: isStatic,
        isConstructor: isConstructor,
        isExtensionMember: isExtensionMember,
        isExtensionTypeMember: isExtensionTypeMember,
        forAbstractClassOrMixin: forAbstractClassOrMixin,
        asyncModifier: asyncModifier,
        nativeMethodName: nativeMethodName,
        kind: kind);

    nativeMethodName = null;
    inConstructor = false;
    popDeclarationContext();
  }

  @override
  void handleNamedMixinApplicationWithClause(Token withKeyword) {
    debugEvent("NamedMixinApplicationWithClause");
    assert(checkState(withKeyword, [
      /* mixins */ unionOfKinds([
        ValueKinds.ParserRecovery,
        ValueKinds.TypeBuilderListOrNull,
      ]),
      /* supertype */ unionOfKinds([
        ValueKinds.ParserRecovery,
        ValueKinds.TypeBuilder,
      ]),
    ]));
    Object? mixins = pop();
    if (mixins is ParserRecovery) {
      push(mixins);
    } else {
      push(_builderFactory.addMixinApplication(
          mixins as List<TypeBuilder>, withKeyword.charOffset));
    }
    assert(checkState(withKeyword, [
      /* mixin application */ unionOfKinds([
        ValueKinds.ParserRecovery,
        ValueKinds.MixinApplicationBuilder,
      ]),
      /* 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,
        ]),
      /* mixin application */ unionOfKinds([
        ValueKinds.ParserRecovery,
        ValueKinds.MixinApplicationBuilder,
      ]),
      /* supertype */ unionOfKinds([
        ValueKinds.ParserRecovery,
        ValueKinds.TypeBuilder,
      ]),
      /* modifiers */ ValueKinds.Modifiers,
      /* type variables */ ValueKinds.NominalVariableListOrNull,
      /* 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;
    List<NominalVariableBuilder>? typeVariables =
        pop() as List<NominalVariableBuilder>?;
    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(typeVariables);
    } else {
      Identifier identifier = name as Identifier;
      String classNameForErrors = identifier.name;
      MixinApplicationBuilder mixinApplicationBuilder =
          mixinApplication as MixinApplicationBuilder;
      List<TypeBuilder> mixins = mixinApplicationBuilder.mixins;
      if (supertype is TypeBuilder && supertype is! MixinApplicationBuilder) {
        if (supertype.nullabilityBuilder.build() == Nullability.nullable) {
          _compilationUnit.addProblem(
              templateNullableSuperclassError
                  .withArguments(supertype.fullNameForErrors),
              identifier.nameOffset,
              classNameForErrors.length,
              uri);
        }
      }
      for (TypeBuilder mixin in mixins) {
        if (mixin.nullabilityBuilder.build() == Nullability.nullable) {
          _compilationUnit.addProblem(
              templateNullableMixinError.withArguments(mixin.fullNameForErrors),
              identifier.nameOffset,
              classNameForErrors.length,
              uri);
        }
      }
      if (interfaces != null) {
        for (TypeBuilder interface in interfaces) {
          if (interface.nullabilityBuilder.build() == Nullability.nullable) {
            _compilationUnit.addProblem(
                templateNullableInterfaceError
                    .withArguments(interface.fullNameForErrors),
                identifier.nameOffset,
                classNameForErrors.length,
                uri);
          }
        }
      }

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

      int startCharOffset = beginToken.charOffset;
      int charEndOffset = endToken.charOffset;
      _builderFactory.addNamedMixinApplication(
          metadata,
          identifier.name,
          typeVariables,
          modifiers,
          supertype as TypeBuilder?,
          mixinApplication,
          interfaces,
          startCharOffset,
          identifier.nameOffset,
          charEndOffset);
    }
    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,
          instanceTypeVariableAccess:
              declarationContext.instanceTypeVariableAccessState));
    }
  }

  @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) {
    super.handleNoTypeVariables(token);
    inConstructorName = false;
  }

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

  @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? 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 {
      Identifier? identifier = name as Identifier?;
      push(_builderFactory.addFormalParameter(
          metadata,
          kind,
          modifiers,
          type ??
              (memberKind.isParameterInferable
                  ? _builderFactory.addInferableType()
                  : const ImplicitTypeBuilder()),
          identifier == null
              ? FormalParameterBuilder.noNameSentinel
              : identifier.name,
          thisKeyword != null,
          superKeyword != null,
          identifier?.nameOffset ?? nameToken.charOffset,
          initializerStart,
          // Extension type parameters should not have a lowered name for
          // wildcard variables.
          lowerWildcard:
              declarationContext != DeclarationContext.ExtensionType));
    }
  }

  @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");
    // 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");
    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];
      }

      Token? tokenBeforeEnd = endToken.previous;
      if (tokenBeforeEnd != null &&
          tokenBeforeEnd.isA(TokenType.COMMA) &&
          kind == MemberKind.PrimaryConstructor &&
          declarationContext == DeclarationContext.ExtensionType) {
        _compilationUnit.addProblem(messageRepresentationFieldTrailingComma,
            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) {
        // The name may be null for generalized function types.
        if (formals[0].name != FormalParameterBuilder.noNameSentinel &&
            formals[0].name == formals[1].name &&
            !formals[0].isWildcard) {
          addProblem(
              templateDuplicatedParameterName.withArguments(formals[1].name),
              formals[1].charOffset,
              formals[1].name.length,
              context: [
                templateDuplicatedParameterNameCause
                    .withArguments(formals[1].name)
                    .withLocation(
                        uri, formals[0].charOffset, formals[0].name.length)
              ]);
        }
      } else if (formals.length > 2) {
        Map<String, FormalParameterBuilder> seenNames =
            <String, FormalParameterBuilder>{};
        for (FormalParameterBuilder formal in formals) {
          if (formal.isWildcard) {
            continue;
          }
          if (formal.name == FormalParameterBuilder.noNameSentinel) continue;
          if (seenNames.containsKey(formal.name)) {
            // Coverage-ignore-block(suite): Not run.
            addProblem(
                templateDuplicatedParameterName.withArguments(formal.name),
                formal.charOffset,
                formal.name.length,
                context: [
                  templateDuplicatedParameterNameCause
                      .withArguments(formal.name)
                      .withLocation(uri, seenNames[formal.name]!.charOffset,
                          seenNames[formal.name]!.name.length)
                ]);
          } else {
            seenNames[formal.name] = formal;
          }
        }
      }
    }
    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(
              messageExtensionTypeConstructorWithSuperFormalParameter,
              formal.charOffset,
              formal.name.length,
              formal.fileUri);
        }
      }
    }
    push(beginToken.charOffset);
    push(formals ?? NullValues.FormalParameters);
  }

  @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 beginEnum(Token enumKeyword) {
    assert(checkState(enumKeyword, [
      ValueKinds.IdentifierOrParserRecovery,
    ]));
    Object? identifier = peek();

    String declarationName;
    if (identifier is Identifier) {
      declarationName = identifier.name;
    } else {
      declarationName = '#enum';
    }
    pushDeclarationContext(DeclarationContext.Enum);
    _builderFactory.beginEnumDeclarationHeader(declarationName);
  }

  @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) {
      push(enumConstantInfo
        ..constructorReferenceBuilder = constructorReferenceBuilder
        ..argumentsBeginToken = argumentsBeginToken);
    } else {
      assert(enumConstantInfo is ParserRecovery);
      push(NullValues.EnumConstantInfo);
    }
  }

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

    // We pop more values than needed to reach typeVariables, offset and name.
    List<TypeBuilder>? interfaces =
        pop(NullValues.TypeBuilderList) as List<TypeBuilder>?;
    Object? mixins = pop(NullValues.MixinApplicationBuilder);
    List<NominalVariableBuilder>? typeVariables =
        pop() as List<NominalVariableBuilder>?;

    Object? identifier = peek();
    if (identifier is Identifier) {
      _builderFactory.beginEnumDeclaration(
          identifier.name, identifier.nameOffset, typeVariables);
    } else {
      identifier as ParserRecovery;
      _builderFactory.beginEnumDeclaration(
          "<syntax-error>", identifier.charOffset, typeVariables);
    }
    _builderFactory.beginEnumBody();

    push(typeVariables ?? NullValues.NominalVariables);
    push(mixins ?? NullValues.MixinApplicationBuilder);
    push(interfaces ?? NullValues.TypeBuilderList);

    push(enumKeyword.charOffset); // start char offset.
    push(leftBrace.endGroup!.charOffset); // end char offset.
  }

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

  @override
  void endEnum(Token beginToken, Token enumKeyword, Token leftBrace,
      int memberCount, Token endToken) {
    assert(checkState(beginToken, [
      /* element count */ ValueKinds.Integer,
    ]));
    debugEvent("endEnum");

    int elementsCount = pop() as int;

    assert(checkState(beginToken, [
      /* enum constants */ ...repeatedKind(
          ValueKinds.EnumConstantInfoOrNull, elementsCount),
      /* endCharOffset */ ValueKinds.Integer,
      /* startCharOffset */ ValueKinds.Integer,
      /* interfaces */ ValueKinds.TypeBuilderListOrNull,
      /* mixins */ unionOfKinds([
        ValueKinds.MixinApplicationBuilderOrNull,
        ValueKinds.ParserRecovery,
      ]),
      /* type variables */ ValueKinds.NominalVariableListOrNull,
      /* name */ ValueKinds.IdentifierOrParserRecovery,
      /* metadata */ ValueKinds.MetadataListOrNull,
    ]));

    List<EnumConstantInfo?>? enumConstantInfos =
        const FixedNullableList<EnumConstantInfo>().pop(stack, elementsCount);

    if (enumConstantInfos != null) {
      List<EnumConstantInfo?>? parsedEnumConstantInfos;
      for (int index = 0; index < enumConstantInfos.length; index++) {
        EnumConstantInfo? info = enumConstantInfos[index];
        if (info == null) {
          parsedEnumConstantInfos = enumConstantInfos.take(index).toList();
        }
        // Coverage-ignore(suite): Not run.
        else if (parsedEnumConstantInfos != null) {
          parsedEnumConstantInfos.add(info);
        }
      }
      if (parsedEnumConstantInfos != null) {
        if (parsedEnumConstantInfos.isEmpty) {
          enumConstantInfos = null;
        } else {
          enumConstantInfos = parsedEnumConstantInfos;
        }
      }
    }

    int endCharOffset = popCharOffset();
    int startCharOffset = popCharOffset();
    List<TypeBuilder>? interfaces =
        nullIfParserRecovery(pop()) as List<TypeBuilder>?;
    MixinApplicationBuilder? mixinBuilder =
        nullIfParserRecovery(pop()) as MixinApplicationBuilder?;
    List<NominalVariableBuilder>? typeVariables =
        pop() as List<NominalVariableBuilder>?;
    Object? identifier = pop();
    List<MetadataBuilder>? metadata = pop() as List<MetadataBuilder>?;
    checkEmpty(startCharOffset);

    if (identifier is Identifier) {
      if (enumConstantInfos == null) {
        if (!leftBrace.isSynthetic) {
          // Coverage-ignore-block(suite): Not run.
          addProblem(messageEnumDeclarationEmpty, identifier.token.offset,
              identifier.token.length);
        }
      }
      if (interfaces != null) {
        for (TypeBuilder interface in interfaces) {
          if (interface.nullabilityBuilder.build() == Nullability.nullable) {
            _compilationUnit.addProblem(
                templateNullableInterfaceError
                    .withArguments(interface.fullNameForErrors),
                interface.charOffset ?? startCharOffset,
                identifier.name.length,
                uri);
          }
        }
      }

      _builderFactory.addEnum(
          _offsetMap,
          metadata,
          identifier,
          typeVariables,
          mixinBuilder,
          interfaces,
          enumConstantInfos,
          startCharOffset,
          endCharOffset);
    } else {
      _builderFactory.endEnumDeclarationForParserRecovery(typeVariables);
    }

    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(
          templateExperimentNotEnabledOffByDefault
              .withArguments(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<FormalParameterBuilder>? formals =
        pop() as List<FormalParameterBuilder>?;
    pop(); // formals offset
    TypeBuilder? returnType = pop() as TypeBuilder?;
    List<StructuralVariableBuilder>? typeVariables =
        pop() as List<StructuralVariableBuilder>?;
    push(_builderFactory.addFunctionType(
        returnType ?? const ImplicitTypeBuilder(),
        typeVariables,
        formals,
        questionMark != null
            ? const NullabilityBuilder.nullable()
            : const NullabilityBuilder.omitted(),
        uri,
        functionToken.charOffset,
        hasFunctionFormalParameterSyntax: false));
  }

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

  @override
  void endTypedef(Token? augmentToken, Token typedefKeyword, Token? equals,
      Token endToken) {