pkg/analyzer/lib/src/fasta/ast_builder.dart

// Copyright (c) 2016, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import 'package:_fe_analyzer_shared/src/messages/codes.dart'
    show
        LocatedMessage,
        Message,
        MessageCode,
        codeBuiltInIdentifierInDeclaration,
        messageAbstractClassMember,
        messageAbstractLateField,
        messageAbstractStaticField,
        messageConstConstructorWithBody,
        messageConstFactory,
        messageConstructorWithTypeParameters,
        messageDirectiveAfterDeclaration,
        messageExpectedStatement,
        messageExternalField,
        messageExternalLateField,
        messageFieldInitializerOutsideConstructor,
        messageIllegalAssignmentToNonAssignable,
        messageInterpolationInUri,
        messageInvalidInitializer,
        messageInvalidSuperInInitializer,
        messageInvalidThisInInitializer,
        messageMissingAssignableSelector,
        messageNativeClauseShouldBeAnnotation,
        messageOperatorWithTypeParameters,
        messagePositionalAfterNamedArgument,
        templateDuplicateLabelInSwitchStatement,
        templateExpectedButGot,
        templateExpectedIdentifier,
        templateExperimentNotEnabled,
        templateExtraneousModifier,
        templateInternalProblemUnhandled,
        templateUnexpectedToken;
import 'package:_fe_analyzer_shared/src/parser/parser.dart'
    show
        Assert,
        BlockKind,
        ConstructorReferenceContext,
        DeclarationKind,
        FormalParameterKind,
        IdentifierContext,
        MemberKind,
        optional,
        Parser;
import 'package:_fe_analyzer_shared/src/parser/quote.dart';
import 'package:_fe_analyzer_shared/src/parser/stack_listener.dart'
    show NullValue, StackListener;
import 'package:_fe_analyzer_shared/src/scanner/errors.dart'
    show translateErrorToken;
import 'package:_fe_analyzer_shared/src/scanner/scanner.dart';
import 'package:_fe_analyzer_shared/src/scanner/token.dart'
    show KeywordToken, StringToken, SyntheticStringToken, SyntheticToken;
import 'package:_fe_analyzer_shared/src/scanner/token_constants.dart';
import 'package:analyzer/dart/analysis/features.dart';
import 'package:analyzer/dart/ast/ast.dart';
import 'package:analyzer/dart/ast/token.dart' show Token, TokenType;
import 'package:analyzer/error/listener.dart';
import 'package:analyzer/source/line_info.dart';
import 'package:analyzer/src/dart/analysis/experiments.dart';
import 'package:analyzer/src/dart/ast/ast.dart';
import 'package:analyzer/src/dart/ast/ast_factory.dart';
import 'package:analyzer/src/fasta/error_converter.dart';
import 'package:analyzer/src/generated/utilities_dart.dart';
import 'package:analyzer/src/summary2/ast_binary_tokens.dart';
import 'package:collection/collection.dart';
import 'package:pub_semver/pub_semver.dart';

const _invalidCollectionElement = _InvalidCollectionElement._();

/// A parser listener that builds the analyzer's AST structure.
class AstBuilder extends StackListener {
  final AstFactoryImpl ast = astFactory;

  final FastaErrorReporter errorReporter;
  final Uri fileUri;
  ScriptTag? scriptTag;
  final List<Directive> directives = <Directive>[];
  final List<CompilationUnitMember> declarations = <CompilationUnitMember>[];

  @override
  final Uri uri;

  /// The parser that uses this listener, used to parse optional parts, e.g.
  /// `native` support.
  late Parser parser;

  /// The class currently being parsed, or `null` if no class is being parsed.
  ClassDeclarationImpl? classDeclaration;

  /// The mixin currently being parsed, or `null` if no mixin is being parsed.
  MixinDeclarationImpl? mixinDeclaration;

  /// The extension currently being parsed, or `null` if none.
  ExtensionDeclarationImpl? extensionDeclaration;

  /// The enum currently being parsed, or `null` if none.
  EnumDeclarationImpl? enumDeclaration;

  /// If true, this is building a full AST. Otherwise, only create method
  /// bodies.
  final bool isFullAst;

  /// `true` if the `native` clause is allowed
  /// in class, method, and function declarations.
  ///
  /// This is being replaced by the @native(...) annotation.
  //
  // TODO(danrubel) Move this flag to a better location
  // and should only be true if either:
  // * The current library is a platform library
  // * The current library has an import that uses the scheme "dart-ext".
  bool allowNativeClause = false;

  StringLiteral? nativeName;

  bool parseFunctionBodies = true;

  /// `true` if non-nullable behavior is enabled.
  final bool enableNonNullable;

  /// `true` if spread-collections behavior is enabled
  final bool enableSpreadCollections;

  /// `true` if control-flow-collections behavior is enabled
  final bool enableControlFlowCollections;

  /// `true` if triple-shift behavior is enabled
  final bool enableTripleShift;

  /// `true` if nonfunction-type-aliases behavior is enabled
  final bool enableNonFunctionTypeAliases;

  /// `true` if variance behavior is enabled
  final bool enableVariance;

  /// `true` if constructor tearoffs are enabled
  final bool enableConstructorTearoffs;

  /// `true` if extension types are enabled
  final bool enableExtensionTypes;

  /// `true` if named arguments anywhere are enabled
  final bool enableNamedArgumentsAnywhere;

  /// `true` if super parameters are enabled
  final bool enableSuperParameters;

  /// `true` if enhanced enums are enabled
  final bool enableEnhancedEnums;

  /// `true` if macros are enabled
  final bool enableMacros;

  /// `true` if records are enabled
  final bool enableRecords;

  final FeatureSet _featureSet;

  final LineInfo _lineInfo;

  AstBuilder(ErrorReporter? errorReporter, this.fileUri, this.isFullAst,
      this._featureSet, this._lineInfo,
      [Uri? uri])
      : errorReporter = FastaErrorReporter(errorReporter),
        enableNonNullable = _featureSet.isEnabled(Feature.non_nullable),
        enableSpreadCollections =
            _featureSet.isEnabled(Feature.spread_collections),
        enableControlFlowCollections =
            _featureSet.isEnabled(Feature.control_flow_collections),
        enableTripleShift = _featureSet.isEnabled(Feature.triple_shift),
        enableNonFunctionTypeAliases =
            _featureSet.isEnabled(Feature.nonfunction_type_aliases),
        enableVariance = _featureSet.isEnabled(Feature.variance),
        enableConstructorTearoffs =
            _featureSet.isEnabled(Feature.constructor_tearoffs),
        enableExtensionTypes = _featureSet.isEnabled(Feature.extension_types),
        enableNamedArgumentsAnywhere =
            _featureSet.isEnabled(Feature.named_arguments_anywhere),
        enableSuperParameters = _featureSet.isEnabled(Feature.super_parameters),
        enableEnhancedEnums = _featureSet.isEnabled(Feature.enhanced_enums),
        enableMacros = _featureSet.isEnabled(Feature.macros),
        enableRecords = _featureSet.isEnabled(Feature.records),
        uri = uri ?? fileUri;

  NodeList<ClassMember> get currentDeclarationMembers {
    if (classDeclaration != null) {
      return classDeclaration!.members;
    } else if (mixinDeclaration != null) {
      return mixinDeclaration!.members;
    } else if (extensionDeclaration != null) {
      return extensionDeclaration!.members;
    } else {
      return enumDeclaration!.members;
    }
  }

  Token? get currentDeclarationName {
    if (classDeclaration != null) {
      return classDeclaration!.name2;
    } else if (mixinDeclaration != null) {
      return mixinDeclaration!.name2;
    } else if (extensionDeclaration != null) {
      return extensionDeclaration!.name2;
    } else {
      return enumDeclaration!.name2;
    }
  }

  @override
  Uri get importUri => uri;

  @override
  void addProblem(Message message, int charOffset, int length,
      {bool wasHandled = false, List<LocatedMessage>? context}) {
    if (directives.isEmpty &&
        (message.code.analyzerCodes
                ?.contains('NON_PART_OF_DIRECTIVE_IN_PART') ??
            false)) {
      message = messageDirectiveAfterDeclaration;
    }
    errorReporter.reportMessage(message, charOffset, length);
  }

  @override
  void beginAsOperatorType(Token asOperator) {}

  @override
  void beginCascade(Token token) {
    assert(optional('..', token) || optional('?..', token));
    debugEvent("beginCascade");

    var expression = pop() as ExpressionImpl;
    push(token);
    if (expression is CascadeExpression) {
      push(expression);
    } else {
      push(
        CascadeExpressionImpl(
          target: expression,
          cascadeSections: <Expression>[],
        ),
      );
    }
    push(NullValue.CascadeReceiver);
  }

  @override
  void beginClassDeclaration(Token begin, Token? abstractToken,
      Token? macroToken, Token? augmentToken, Token name) {
    assert(classDeclaration == null &&
        mixinDeclaration == null &&
        extensionDeclaration == null);
    push(_Modifiers()..abstractKeyword = abstractToken);
    if (!enableMacros) {
      if (macroToken != null) {
        _reportFeatureNotEnabled(
          feature: ExperimentalFeatures.macros,
          startToken: macroToken,
        );
        // Pretend that 'macro' didn't occur while this feature is incomplete.
        macroToken = null;
      }
    }
    push(macroToken ?? NullValue.Token);
    push(augmentToken ?? NullValue.Token);
  }

  @override
  void beginCompilationUnit(Token token) {
    push(token);
  }

  @override
  void beginEnum(Token enumKeyword) {}

  @override
  void beginExtensionDeclaration(Token extensionKeyword, Token? nameToken) {
    assert(optional('extension', extensionKeyword));
    assert(classDeclaration == null &&
        mixinDeclaration == null &&
        extensionDeclaration == null);
    debugEvent("ExtensionHeader");

    var typeParameters = pop() as TypeParameterListImpl?;
    var metadata = pop() as List<Annotation>?;
    var comment = _findComment(metadata, extensionKeyword);

    SimpleIdentifierImpl? name;
    if (nameToken != null) {
      name = ast.simpleIdentifier(nameToken, isDeclaration: true);
    }

    extensionDeclaration = ExtensionDeclarationImpl(
      comment: comment,
      metadata: metadata,
      extensionKeyword: extensionKeyword,
      typeKeyword: null,
      name: name,
      typeParameters: typeParameters,
      onKeyword: Tokens.on_(),
      extendedType: ast.namedType(
        name: _tmpSimpleIdentifier(),
      ), // extendedType is set in [endExtensionDeclaration]
      showClause: null,
      hideClause: null,
      leftBracket: Tokens.openCurlyBracket(),
      rightBracket: Tokens.closeCurlyBracket(),
      members: [],
    );

    declarations.add(extensionDeclaration!);
  }

  @override
  void beginFactoryMethod(DeclarationKind declarationKind, Token lastConsumed,
      Token? externalToken, Token? constToken) {
    push(_Modifiers()
      ..externalKeyword = externalToken
      ..finalConstOrVarKeyword = constToken);
  }

  @override
  void beginFormalParameter(Token token, MemberKind kind, Token? requiredToken,
      Token? covariantToken, Token? varFinalOrConst) {
    push(_Modifiers()
      ..covariantKeyword = covariantToken
      ..finalConstOrVarKeyword = varFinalOrConst
      ..requiredToken = requiredToken);
  }

  @override
  void beginFormalParameterDefaultValueExpression() {}

  @override
  void beginIfControlFlow(Token ifToken) {
    push(ifToken);
  }

  @override
  void beginIsOperatorType(Token asOperator) {}

  @override
  void beginLibraryAugmentation(Token libraryKeyword, Token augmentKeyword) {}

  @override
  void beginLiteralString(Token literalString) {
    assert(identical(literalString.kind, STRING_TOKEN));
    debugEvent("beginLiteralString");

    push(literalString);
  }

  @override
  void beginMetadataStar(Token token) {
    debugEvent("beginMetadataStar");
  }

  @override
  void beginMethod(
      DeclarationKind declarationKind,
      Token? augmentToken,
      Token? externalToken,
      Token? staticToken,
      Token? covariantToken,
      Token? varFinalOrConst,
      Token? getOrSet,
      Token name) {
    _Modifiers modifiers = _Modifiers();
    if (augmentToken != null) {
      assert(augmentToken.isModifier);
      modifiers.augmentKeyword = augmentToken;
    }
    if (externalToken != null) {
      assert(externalToken.isModifier);
      modifiers.externalKeyword = externalToken;
    }
    if (staticToken != null) {
      assert(staticToken.isModifier);
      String? className = currentDeclarationName?.lexeme;
      if (name.lexeme != className || getOrSet != null) {
        modifiers.staticKeyword = staticToken;
      }
    }
    if (covariantToken != null) {
      assert(covariantToken.isModifier);
      modifiers.covariantKeyword = covariantToken;
    }
    if (varFinalOrConst != null) {
      assert(varFinalOrConst.isModifier);
      modifiers.finalConstOrVarKeyword = varFinalOrConst;
    }
    push(modifiers);
  }

  @override
  void beginMixinDeclaration(
      Token? augmentToken, Token mixinKeyword, Token name) {
    assert(classDeclaration == null &&
        mixinDeclaration == null &&
        extensionDeclaration == null);
    push(augmentToken ?? NullValue.Token);
  }

  @override
  void beginNamedMixinApplication(Token begin, Token? abstractToken,
      Token? macroToken, Token? augmentToken, Token name) {
    push(_Modifiers()..abstractKeyword = abstractToken);
    if (!enableMacros) {
      if (macroToken != null) {
        _reportFeatureNotEnabled(
          feature: ExperimentalFeatures.macros,
          startToken: macroToken,
        );
        // Pretend that 'macro' didn't occur while this feature is incomplete.
        macroToken = null;
      }
    }
    push(macroToken ?? NullValue.Token);
    push(augmentToken ?? NullValue.Token);
  }

  @override
  void beginTopLevelMethod(
      Token lastConsumed, Token? augmentToken, Token? externalToken) {
    push(_Modifiers()
      ..augmentKeyword = augmentToken
      ..externalKeyword = externalToken);
  }

  @override
  void beginTypeVariable(Token token) {
    debugEvent("beginTypeVariable");
    var name = pop() as SimpleIdentifierImpl;
    var metadata = pop() as List<Annotation>?;

    var comment = _findComment(metadata, name.beginToken);
    var typeParameter = TypeParameterImpl(
      comment: comment,
      metadata: metadata,
      name: name,
      extendsKeyword: null,
      bound: null,
    );
    push(typeParameter);
  }

  @override
  void beginVariablesDeclaration(
      Token token, Token? lateToken, Token? varFinalOrConst) {
    debugEvent("beginVariablesDeclaration");
    if (varFinalOrConst != null || lateToken != null) {
      push(_Modifiers()
        ..finalConstOrVarKeyword = varFinalOrConst
        ..lateToken = lateToken);
    } else {
      push(NullValue.Modifiers);
    }
  }

  ConstructorInitializer? buildInitializer(Object initializerObject) {
    if (initializerObject is FunctionExpressionInvocation) {
      Expression function = initializerObject.function;
      if (function is SuperExpression) {
        return ast.superConstructorInvocation(
            function.superKeyword, null, null, initializerObject.argumentList);
      }
      if (function is ThisExpression) {
        return ast.redirectingConstructorInvocation(
            function.thisKeyword, null, null, initializerObject.argumentList);
      }
      return null;
    }

    if (initializerObject is MethodInvocation) {
      var target = initializerObject.target;
      if (target is SuperExpression) {
        return ast.superConstructorInvocation(
            target.superKeyword,
            initializerObject.operator,
            initializerObject.methodName,
            initializerObject.argumentList);
      }
      if (target is ThisExpression) {
        return ast.redirectingConstructorInvocation(
            target.thisKeyword,
            initializerObject.operator,
            initializerObject.methodName,
            initializerObject.argumentList);
      }
      return buildInitializerTargetExpressionRecovery(
          target, initializerObject);
    }

    if (initializerObject is PropertyAccess) {
      return buildInitializerTargetExpressionRecovery(
          initializerObject.target, initializerObject);
    }

    if (initializerObject is AssignmentExpressionImpl) {
      Token? thisKeyword;
      Token? period;
      SimpleIdentifierImpl fieldName;
      Expression left = initializerObject.leftHandSide;
      if (left is PropertyAccessImpl) {
        var target = left.target;
        if (target is ThisExpressionImpl) {
          thisKeyword = target.thisKeyword;
          period = left.operator;
        } else {
          assert(target is SuperExpression);
          // Recovery:
          // Parser has reported FieldInitializedOutsideDeclaringClass.
        }
        fieldName = left.propertyName;
      } else if (left is SimpleIdentifierImpl) {
        fieldName = left;
      } else {
        // Recovery:
        // Parser has reported invalid assignment.
        var superExpression = left as SuperExpression;
        fieldName = ast.simpleIdentifier(superExpression.superKeyword);
      }
      return ConstructorFieldInitializerImpl(
        thisKeyword: thisKeyword,
        period: period,
        fieldName: fieldName,
        equals: initializerObject.operator,
        expression: initializerObject.rightHandSide,
      );
    }

    if (initializerObject is AssertInitializer) {
      return initializerObject;
    }

    if (initializerObject is IndexExpression) {
      return buildInitializerTargetExpressionRecovery(
          initializerObject.target, initializerObject);
    }

    if (initializerObject is CascadeExpression) {
      return buildInitializerTargetExpressionRecovery(
          initializerObject.target, initializerObject);
    }

    return null;
  }

  ConstructorInitializer? buildInitializerTargetExpressionRecovery(
      Expression? target, Object initializerObject) {
    ArgumentList? argumentList;
    while (true) {
      if (target is FunctionExpressionInvocation) {
        argumentList = target.argumentList;
        target = target.function;
      } else if (target is MethodInvocation) {
        argumentList = target.argumentList;
        target = target.target;
      } else if (target is PropertyAccess) {
        argumentList = null;
        target = target.target;
      } else {
        break;
      }
    }
    if (target is SuperExpression) {
      // TODO(danrubel): Consider generating this error in the parser
      // This error is also reported in the body builder
      handleRecoverableError(messageInvalidSuperInInitializer,
          target.superKeyword, target.superKeyword);
      return ast.superConstructorInvocation(target.superKeyword, null, null,
          argumentList ?? _syntheticArgumentList(target.superKeyword));
    } else if (target is ThisExpression) {
      // TODO(danrubel): Consider generating this error in the parser
      // This error is also reported in the body builder
      handleRecoverableError(messageInvalidThisInInitializer,
          target.thisKeyword, target.thisKeyword);
      return ast.redirectingConstructorInvocation(target.thisKeyword, null,
          null, argumentList ?? _syntheticArgumentList(target.thisKeyword));
    }
    return null;
  }

  void checkFieldFormalParameters(FormalParameterList? parameterList) {
    var parameters = parameterList?.parameters;
    if (parameters != null) {
      for (var parameter in parameters) {
        if (parameter is FieldFormalParameter) {
          // This error is reported in the BodyBuilder.endFormalParameter.
          handleRecoverableError(messageFieldInitializerOutsideConstructor,
              parameter.thisKeyword, parameter.thisKeyword);
        }
      }
    }
  }

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

  void doDotExpression(Token dot) {
    var identifierOrInvoke = pop() as Expression;
    var receiver = pop() as Expression?;
    if (identifierOrInvoke is SimpleIdentifier) {
      if (receiver is SimpleIdentifier && identical('.', dot.stringValue)) {
        push(ast.prefixedIdentifier(receiver, dot, identifierOrInvoke));
      } else {
        push(ast.propertyAccess(receiver, dot, identifierOrInvoke));
      }
    } else if (identifierOrInvoke is MethodInvocationImpl) {
      assert(identifierOrInvoke.target == null);
      identifierOrInvoke
        ..target = receiver
        ..operator = dot;
      push(identifierOrInvoke);
    } else {
      // This same error is reported in BodyBuilder.doDotOrCascadeExpression
      Token token = identifierOrInvoke.beginToken;
      // TODO(danrubel): Consider specializing the error message based
      // upon the type of expression. e.g. "x.this" -> templateThisAsIdentifier
      handleRecoverableError(
          templateExpectedIdentifier.withArguments(token), token, token);
      SimpleIdentifier identifier =
          ast.simpleIdentifier(token, isDeclaration: false);
      push(ast.propertyAccess(receiver, dot, identifier));
    }
  }

  void doInvocation(
      TypeArgumentList? typeArguments, MethodInvocationImpl arguments) {
    var receiver = pop() as Expression;
    if (receiver is SimpleIdentifierImpl) {
      arguments.methodName = receiver;
      if (typeArguments != null) {
        arguments.typeArguments = typeArguments;
      }
      push(arguments);
    } else {
      push(ast.functionExpressionInvocation(
          receiver, typeArguments, arguments.argumentList));
    }
  }

  void doPropertyGet() {}

  @override
  void endArguments(int count, Token leftParenthesis, Token rightParenthesis) {
    assert(optional('(', leftParenthesis));
    assert(optional(')', rightParenthesis));
    debugEvent("Arguments");

    var expressions = popTypedList2<Expression>(count);
    ArgumentList arguments = ArgumentListImpl(
      leftParenthesis: leftParenthesis,
      arguments: expressions,
      rightParenthesis: rightParenthesis,
    );

    if (!enableNamedArgumentsAnywhere) {
      bool hasSeenNamedArgument = false;
      for (Expression expression in expressions) {
        if (expression is NamedExpression) {
          hasSeenNamedArgument = true;
        } else if (hasSeenNamedArgument) {
          // Positional argument after named argument.
          handleRecoverableError(messagePositionalAfterNamedArgument,
              expression.beginToken, expression.endToken);
        }
      }
    }

    push(ast.methodInvocation(
        null, null, _tmpSimpleIdentifier(), null, arguments));
  }

  @override
  void endAsOperatorType(Token asOperator) {
    debugEvent("AsOperatorType");
  }

  @override
  void endAssert(Token assertKeyword, Assert kind, Token leftParenthesis,
      Token? comma, Token semicolon) {
    assert(optional('assert', assertKeyword));
    assert(optional('(', leftParenthesis));
    assert(optionalOrNull(',', comma));
    assert(kind != Assert.Statement || optionalOrNull(';', semicolon));
    debugEvent("Assert");

    var message = popIfNotNull(comma) as ExpressionImpl?;
    var condition = pop() as ExpressionImpl;
    switch (kind) {
      case Assert.Expression:
        // The parser has already reported an error indicating that assert
        // cannot be used in an expression. Insert a placeholder.
        List<Expression> arguments = <Expression>[condition];
        if (message != null) {
          arguments.add(message);
        }
        push(
          ast.functionExpressionInvocation(
            ast.simpleIdentifier(assertKeyword),
            null,
            ArgumentListImpl(
              leftParenthesis: leftParenthesis,
              arguments: arguments,
              rightParenthesis: leftParenthesis.endGroup!,
            ),
          ),
        );
        break;
      case Assert.Initializer:
        push(
          AssertInitializerImpl(
            assertKeyword: assertKeyword,
            leftParenthesis: leftParenthesis,
            condition: condition,
            comma: comma,
            message: message,
            rightParenthesis: leftParenthesis.endGroup!,
          ),
        );
        break;
      case Assert.Statement:
        push(
          AssertStatementImpl(
            assertKeyword: assertKeyword,
            leftParenthesis: leftParenthesis,
            condition: condition,
            comma: comma,
            message: message,
            rightParenthesis: leftParenthesis.endGroup!,
            semicolon: semicolon,
          ),
        );
        break;
    }
  }

  @override
  void endAwaitExpression(Token awaitKeyword, Token endToken) {
    assert(optional('await', awaitKeyword));
    debugEvent("AwaitExpression");

    var expression = pop() as ExpressionImpl;
    push(
      AwaitExpressionImpl(
        awaitKeyword: awaitKeyword,
        expression: expression,
      ),
    );
  }

  @override
  void endBinaryExpression(Token operatorToken) {
    assert(operatorToken.isOperator ||
        optional('.', operatorToken) ||
        optional('?.', operatorToken) ||
        optional('..', operatorToken) ||
        optional('?..', operatorToken) ||
        optional('===', operatorToken) ||
        optional('!==', operatorToken));
    debugEvent("BinaryExpression");

    if (identical(".", operatorToken.stringValue) ||
        identical("?.", operatorToken.stringValue) ||
        identical("..", operatorToken.stringValue) ||
        identical("?..", operatorToken.stringValue)) {
      doDotExpression(operatorToken);
    } else {
      var right = pop() as ExpressionImpl;
      var left = pop() as ExpressionImpl;
      reportErrorIfSuper(right);
      push(
        BinaryExpressionImpl(
          leftOperand: left,
          operator: operatorToken,
          rightOperand: right,
        ),
      );
      if (!enableTripleShift && operatorToken.type == TokenType.GT_GT_GT) {
        _reportFeatureNotEnabled(
          feature: ExperimentalFeatures.triple_shift,
          startToken: operatorToken,
        );
      }
    }
  }

  @override
  void endBlock(
      int count, Token leftBracket, Token rightBracket, BlockKind blockKind) {
    assert(optional('{', leftBracket));
    assert(optional('}', rightBracket));
    debugEvent("Block");

    var statements = popTypedList2<Statement>(count);
    push(
      BlockImpl(
        leftBracket: leftBracket,
        statements: statements,
        rightBracket: rightBracket,
      ),
    );
  }

  @override
  void endBlockFunctionBody(int count, Token leftBracket, Token rightBracket) {
    assert(optional('{', leftBracket));
    assert(optional('}', rightBracket));
    debugEvent("BlockFunctionBody");

    var statements = popTypedList2<Statement>(count);
    final block = BlockImpl(
      leftBracket: leftBracket,
      statements: statements,
      rightBracket: rightBracket,
    );
    var star = pop() as Token?;
    var asyncKeyword = pop() as Token?;
    if (parseFunctionBodies) {
      push(
        BlockFunctionBodyImpl(
          keyword: asyncKeyword,
          star: star,
          block: block,
        ),
      );
    } else {
      // TODO(danrubel): Skip the block rather than parsing it.
      push(
        EmptyFunctionBodyImpl(
          semicolon: SyntheticToken(
            TokenType.SEMICOLON,
            leftBracket.charOffset,
          ),
        ),
      );
    }
  }

  @override
  void endCascade() {
    debugEvent("Cascade");

    var expression = pop() as Expression;
    var receiver = pop() as CascadeExpression;
    pop(); // Token.
    receiver.cascadeSections.add(expression);
    push(receiver);
  }

  @override
  void endClassConstructor(Token? getOrSet, Token beginToken, Token beginParam,
      Token? beginInitializers, Token endToken) {
    assert(getOrSet == null ||
        optional('get', getOrSet) ||
        optional('set', getOrSet));
    debugEvent("ClassConstructor");

    var bodyObject = pop();
    var initializers = (pop() as List<ConstructorInitializer>?) ?? const [];
    var separator = pop() as Token?;
    var parameters = pop() as FormalParameterListImpl;
    var typeParameters = pop() as TypeParameterList?;
    var name = pop();
    pop(); // return type
    var modifiers = pop() as _Modifiers?;
    var metadata = pop() as List<Annotation>?;
    var comment = _findComment(metadata, beginToken);

    ConstructorNameImpl? redirectedConstructor;
    FunctionBodyImpl body;
    if (bodyObject is FunctionBodyImpl) {
      body = bodyObject;
    } else if (bodyObject is _RedirectingFactoryBody) {
      separator = bodyObject.equalToken;
      redirectedConstructor = bodyObject.constructorName;
      body = EmptyFunctionBodyImpl(
        semicolon: endToken,
      );
    } else {
      internalProblem(
          templateInternalProblemUnhandled.withArguments(
              "${bodyObject.runtimeType}", "bodyObject"),
          beginToken.charOffset,
          uri);
    }

    SimpleIdentifier prefixOrName;
    Token? period;
    SimpleIdentifierImpl? nameOrNull;
    if (name is SimpleIdentifierImpl) {
      prefixOrName = name;
    } else if (name is PrefixedIdentifierImpl) {
      prefixOrName = name.prefix;
      period = name.period;
      nameOrNull = name.identifier;
    } else if (name is _OperatorName) {
      prefixOrName = name.name;
    } else {
      throw UnimplementedError(
          'name is an instance of ${name.runtimeType} in endClassConstructor');
    }

    if (typeParameters != null) {
      // Outline builder also reports this error message.
      handleRecoverableError(messageConstructorWithTypeParameters,
          typeParameters.beginToken, typeParameters.endToken);
    }
    if (modifiers?.constKeyword != null &&
        (body.length > 1 || body.beginToken.lexeme != ';')) {
      // This error is also reported in BodyBuilder.finishFunction
      Token bodyToken = body.beginToken;
      // Token bodyToken = body.beginToken ?? modifiers.constKeyword;
      handleRecoverableError(
          messageConstConstructorWithBody, bodyToken, bodyToken);
    }
    ConstructorDeclaration constructor = ConstructorDeclarationImpl(
      comment: comment,
      metadata: metadata,
      externalKeyword: modifiers?.externalKeyword,
      constKeyword: modifiers?.finalConstOrVarKeyword,
      factoryKeyword: null,
      returnType: ast.simpleIdentifier(prefixOrName.token),
      period: period,
      name: nameOrNull,
      parameters: parameters,
      separator: separator,
      initializers: initializers,
      redirectedConstructor: redirectedConstructor,
      body: body,
    );
    currentDeclarationMembers.add(constructor);
    if (mixinDeclaration != null) {
      // TODO (danrubel): Report an error if this is a mixin declaration.
    }
  }

  @override
  void endClassDeclaration(Token beginToken, Token endToken) {
    debugEvent("ClassDeclaration");
    classDeclaration = null;
  }

  @override
  void endClassFactoryMethod(
      Token beginToken, Token factoryKeyword, Token endToken) {
    assert(optional('factory', factoryKeyword));
    assert(optional(';', endToken) || optional('}', endToken));
    debugEvent("ClassFactoryMethod");

    FunctionBodyImpl body;
    Token? separator;
    ConstructorNameImpl? redirectedConstructor;
    var bodyObject = pop();
    if (bodyObject is FunctionBodyImpl) {
      body = bodyObject;
    } else if (bodyObject is _RedirectingFactoryBody) {
      separator = bodyObject.equalToken;
      redirectedConstructor = bodyObject.constructorName;
      body = EmptyFunctionBodyImpl(
        semicolon: endToken,
      );
    } else {
      internalProblem(
          templateInternalProblemUnhandled.withArguments(
              "${bodyObject.runtimeType}", "bodyObject"),
          beginToken.charOffset,
          uri);
    }

    var parameters = pop() as FormalParameterListImpl;
    var typeParameters = pop() as TypeParameterList?;
    var constructorName = pop() as Identifier;
    var modifiers = pop() as _Modifiers?;
    var metadata = pop() as List<Annotation>?;
    var comment = _findComment(metadata, beginToken);

    if (typeParameters != null) {
      // TODO(danrubel): Update OutlineBuilder to report this error message.
      handleRecoverableError(messageConstructorWithTypeParameters,
          typeParameters.beginToken, typeParameters.endToken);
    }

    // Decompose the preliminary ConstructorName into the type name and
    // the actual constructor name.
    SimpleIdentifier returnType;
    Token? period;
    SimpleIdentifierImpl? name;
    Identifier typeName = constructorName;
    if (typeName is SimpleIdentifier) {
      returnType = typeName;
    } else if (typeName is PrefixedIdentifier) {
      returnType = typeName.prefix;
      period = typeName.period;
      name =
          ast.simpleIdentifier(typeName.identifier.token, isDeclaration: true);
    } else {
      throw UnimplementedError();
    }

    currentDeclarationMembers.add(
      ConstructorDeclarationImpl(
        comment: comment,
        metadata: metadata,
        externalKeyword: modifiers?.externalKeyword,
        constKeyword: modifiers?.finalConstOrVarKeyword,
        factoryKeyword: factoryKeyword,
        returnType: ast.simpleIdentifier(returnType.token),
        period: period,
        name: name,
        parameters: parameters,
        separator: separator,
        initializers: null,
        redirectedConstructor: redirectedConstructor,
        body: body,
      ),
    );
  }

  @override
  void endClassFields(
      Token? abstractToken,
      Token? augmentToken,
      Token? externalToken,
      Token? staticToken,
      Token? covariantToken,
      Token? lateToken,
      Token? varFinalOrConst,
      int count,
      Token beginToken,
      Token semicolon) {
    assert(optional(';', semicolon));
    debugEvent("Fields");

    if (abstractToken != null) {
      if (!enableNonNullable) {
        handleRecoverableError(
            messageAbstractClassMember, abstractToken, abstractToken);
      } else {
        if (staticToken != null) {
          handleRecoverableError(
              messageAbstractStaticField, abstractToken, abstractToken);
        }
        if (lateToken != null) {
          handleRecoverableError(
              messageAbstractLateField, abstractToken, abstractToken);
        }
      }
    }
    if (externalToken != null) {
      if (!enableNonNullable) {
        handleRecoverableError(
            messageExternalField, externalToken, externalToken);
      } else if (lateToken != null) {
        handleRecoverableError(
            messageExternalLateField, externalToken, externalToken);
      }
    }

    var variables = popTypedList2<VariableDeclaration>(count);
    var type = pop() as TypeAnnotationImpl?;
    var variableList = VariableDeclarationListImpl(
      comment: null,
      metadata: null,
      lateKeyword: lateToken,
      keyword: varFinalOrConst,
      type: type,
      variables: variables,
    );
    var covariantKeyword = covariantToken;
    var metadata = pop() as List<Annotation>?;
    var comment = _findComment(metadata, beginToken);
    currentDeclarationMembers.add(
      FieldDeclarationImpl(
        comment: comment,
        metadata: metadata,
        abstractKeyword: abstractToken,
        augmentKeyword: augmentToken,
        covariantKeyword: covariantKeyword,
        externalKeyword: externalToken,
        staticKeyword: staticToken,
        fieldList: variableList,
        semicolon: semicolon,
      ),
    );
  }

  @override
  void endClassMethod(Token? getOrSet, Token beginToken, Token beginParam,
      Token? beginInitializers, Token endToken) {
    assert(getOrSet == null ||
        optional('get', getOrSet) ||
        optional('set', getOrSet));
    debugEvent("ClassMethod");

    var bodyObject = pop();
    pop(); // initializers
    pop(); // separator
    var parameters = pop() as FormalParameterListImpl?;
    var typeParameters = pop() as TypeParameterListImpl?;
    var name = pop();
    var returnType = pop() as TypeAnnotationImpl?;
    var modifiers = pop() as _Modifiers?;
    var metadata = pop() as List<Annotation>?;
    var comment = _findComment(metadata, beginToken);

    assert(parameters != null || optional('get', getOrSet!));

    FunctionBodyImpl body;
    if (bodyObject is FunctionBodyImpl) {
      body = bodyObject;
    } else if (bodyObject is _RedirectingFactoryBody) {
      body = EmptyFunctionBodyImpl(
        semicolon: endToken,
      );
    } else {
      internalProblem(
          templateInternalProblemUnhandled.withArguments(
              "${bodyObject.runtimeType}", "bodyObject"),
          beginToken.charOffset,
          uri);
    }

    Token? operatorKeyword;
    SimpleIdentifierImpl nameId;
    if (name is SimpleIdentifierImpl) {
      nameId = name;
    } else if (name is _OperatorName) {
      operatorKeyword = name.operatorKeyword;
      nameId = name.name;
      if (typeParameters != null) {
        handleRecoverableError(messageOperatorWithTypeParameters,
            typeParameters.beginToken, typeParameters.endToken);
      }
    } else {
      throw UnimplementedError(
          'name is an instance of ${name.runtimeType} in endClassMethod');
    }

    checkFieldFormalParameters(parameters);
    currentDeclarationMembers.add(
      MethodDeclarationImpl(
        comment: comment,
        metadata: metadata,
        externalKeyword: modifiers?.externalKeyword,
        modifierKeyword: modifiers?.abstractKeyword ?? modifiers?.staticKeyword,
        returnType: returnType,
        propertyKeyword: getOrSet,
        operatorKeyword: operatorKeyword,
        name: nameId,
        typeParameters: typeParameters,
        parameters: parameters,
        body: body,
      ),
    );
  }

  @override
  void endClassOrMixinOrExtensionBody(DeclarationKind kind, int memberCount,
      Token leftBracket, Token rightBracket) {
    // TODO(danrubel): consider renaming endClassOrMixinBody
    // to endClassOrMixinOrExtensionBody
    assert(optional('{', leftBracket));
    assert(optional('}', rightBracket));
    debugEvent("ClassOrMixinBody");

    if (classDeclaration != null) {
      classDeclaration!
        ..leftBracket = leftBracket
        ..rightBracket = rightBracket;
    } else if (mixinDeclaration != null) {
      mixinDeclaration!
        ..leftBracket = leftBracket
        ..rightBracket = rightBracket;
    } else {
      extensionDeclaration!
        ..leftBracket = leftBracket
        ..rightBracket = rightBracket;
    }
  }

  @override
  void endCombinators(int count) {
    debugEvent("Combinators");
    push(popTypedList<Combinator>(count) ?? NullValue.Combinators);
  }

  @override
  void endCompilationUnit(int count, Token endToken) {
    debugEvent("CompilationUnit");

    var beginToken = pop() as Token;
    checkEmpty(endToken.charOffset);

    CompilationUnitImpl unit = ast.compilationUnit(
        beginToken: beginToken,
        scriptTag: scriptTag,
        directives: directives,
        declarations: declarations,
        endToken: endToken,
        featureSet: _featureSet,
        lineInfo: _lineInfo);
    push(unit);
  }

  @override
  void endConditionalExpression(Token question, Token colon) {
    assert(optional('?', question));
    assert(optional(':', colon));
    debugEvent("ConditionalExpression");

    var elseExpression = pop() as ExpressionImpl;
    var thenExpression = pop() as ExpressionImpl;
    var condition = pop() as ExpressionImpl;
    reportErrorIfSuper(elseExpression);
    reportErrorIfSuper(thenExpression);
    push(
      ConditionalExpressionImpl(
        condition: condition,
        question: question,
        thenExpression: thenExpression,
        colon: colon,
        elseExpression: elseExpression,
      ),
    );
  }

  @override
  void endConditionalUri(Token ifKeyword, Token leftParen, Token? equalSign) {
    assert(optional('if', ifKeyword));
    assert(optionalOrNull('(', leftParen));
    assert(optionalOrNull('==', equalSign));
    debugEvent("ConditionalUri");

    var libraryUri = pop() as StringLiteralImpl;
    var value = popIfNotNull(equalSign) as StringLiteralImpl?;
    if (value is StringInterpolationImpl) {
      for (var child in value.childEntities) {
        if (child is InterpolationExpression) {
          // This error is reported in OutlineBuilder.endLiteralString
          handleRecoverableError(
              messageInterpolationInUri, child.beginToken, child.endToken);
          break;
        }
      }
    }
    var name = pop() as DottedNameImpl;
    push(
      ConfigurationImpl(
        ifKeyword: ifKeyword,
        leftParenthesis: leftParen,
        name: name,
        equalToken: equalSign,
        value: value,
        rightParenthesis: leftParen.endGroup!,
        uri: libraryUri,
      ),
    );
  }

  @override
  void endConditionalUris(int count) {
    debugEvent("ConditionalUris");

    push(popTypedList<Configuration>(count) ?? NullValue.ConditionalUris);
  }

  @override
  void endConstExpression(Token constKeyword) {
    assert(optional('const', constKeyword));
    debugEvent("ConstExpression");

    _handleInstanceCreation(constKeyword);
  }

  @override
  void endConstLiteral(Token token) {
    debugEvent("endConstLiteral");
  }

  @override
  void endConstructorReference(Token start, Token? periodBeforeName,
      Token endToken, ConstructorReferenceContext constructorReferenceContext) {
    assert(optionalOrNull('.', periodBeforeName));
    debugEvent("ConstructorReference");

    var constructorName = pop() as SimpleIdentifierImpl?;
    var typeArguments = pop() as TypeArgumentListImpl?;
    var typeNameIdentifier = pop() as IdentifierImpl;
    push(
      ConstructorNameImpl(
        type: ast.namedType(
          name: typeNameIdentifier,
          typeArguments: typeArguments,
        ),
        period: periodBeforeName,
        name: constructorName,
      ),
    );
  }

  @override
  void endDoWhileStatement(
      Token doKeyword, Token whileKeyword, Token semicolon) {
    assert(optional('do', doKeyword));
    assert(optional('while', whileKeyword));
    assert(optional(';', semicolon));
    debugEvent("DoWhileStatement");

    var condition = pop() as ParenthesizedExpressionImpl;
    var body = pop() as StatementImpl;
    push(
      DoStatementImpl(
        doKeyword: doKeyword,
        body: body,
        whileKeyword: whileKeyword,
        leftParenthesis: condition.leftParenthesis,
        condition: condition.expression,
        rightParenthesis: condition.rightParenthesis,
        semicolon: semicolon,
      ),
    );
  }

  @override
  void endDoWhileStatementBody(Token token) {
    debugEvent("endDoWhileStatementBody");
  }

  @override
  void endElseStatement(Token token) {
    debugEvent("endElseStatement");
  }

  @override
  void endEnum(Token enumKeyword, Token leftBrace, int memberCount) {
    assert(optional('enum', enumKeyword));
    assert(optional('{', leftBrace));
    debugEvent("Enum");
  }

  @override
  void endEnumConstructor(Token? getOrSet, Token beginToken, Token beginParam,
      Token? beginInitializers, Token endToken) {
    debugEvent("endEnumConstructor");
    endClassConstructor(
        getOrSet, beginToken, beginParam, beginInitializers, endToken);
  }

  @override
  void endExport(Token exportKeyword, Token semicolon) {
    assert(optional('export', exportKeyword));
    assert(optional(';', semicolon));
    debugEvent("Export");

    var combinators = pop() as List<Combinator>?;
    var configurations = pop() as List<Configuration>?;
    var uri = pop() as StringLiteralImpl;
    var metadata = pop() as List<Annotation>?;
    var comment = _findComment(metadata, exportKeyword);
    directives.add(
      ExportDirectiveImpl(
        comment: comment,
        metadata: metadata,
        exportKeyword: exportKeyword,
        uri: uri,
        configurations: configurations,
        combinators: combinators,
        semicolon: semicolon,
      ),
    );
  }

  @override
  void endExtensionConstructor(Token? getOrSet, Token beginToken,
      Token beginParam, Token? beginInitializers, Token endToken) {
    debugEvent("ExtensionConstructor");
    // TODO(danrubel) Decide how to handle constructor declarations within
    // extensions. They are invalid and the parser has already reported an
    // error at this point. In the future, we should include them in order
    // to get navigation, search, etc.
    pop(); // body
    pop(); // initializers
    pop(); // separator
    pop(); // parameters
    pop(); // typeParameters
    pop(); // name
    pop(); // returnType
    pop(); // modifiers
    pop(); // metadata
  }

  @override
  void endExtensionDeclaration(Token extensionKeyword, Token? typeKeyword,
      Token onKeyword, Token? showKeyword, Token? hideKeyword, Token token) {
    if (typeKeyword != null && !enableExtensionTypes) {
      _reportFeatureNotEnabled(
        feature: ExperimentalFeatures.extension_types,
        startToken: typeKeyword,
      );
    }

    final showOrHideKeyword = showKeyword ?? hideKeyword;
    if (showOrHideKeyword != null && !enableExtensionTypes) {
      _reportFeatureNotEnabled(
        feature: ExperimentalFeatures.extension_types,
        startToken: showOrHideKeyword,
      );
    }

    ShowClause? showClause = pop(NullValue.ShowClause) as ShowClause?;
    HideClause? hideClause = pop(NullValue.HideClause) as HideClause?;

    var type = pop() as TypeAnnotation;

    extensionDeclaration!
      ..extendedType = type
      ..onKeyword = onKeyword
      ..typeKeyword = typeKeyword
      ..showClause = showClause
      ..hideClause = hideClause;
    extensionDeclaration = null;
  }

  @override
  void endExtensionFactoryMethod(
      Token beginToken, Token factoryKeyword, Token endToken) {
    assert(optional('factory', factoryKeyword));
    assert(optional(';', endToken) || optional('}', endToken));
    debugEvent("ExtensionFactoryMethod");

    var bodyObject = pop();
    var parameters = pop() as FormalParameterListImpl;
    var typeParameters = pop() as TypeParameterListImpl?;
    var constructorName = pop();
    var modifiers = pop() as _Modifiers?;
    var metadata = pop() as List<Annotation>?;

    FunctionBodyImpl body;
    if (bodyObject is FunctionBodyImpl) {
      body = bodyObject;
    } else if (bodyObject is _RedirectingFactoryBody) {
      body = EmptyFunctionBodyImpl(
        semicolon: endToken,
      );
    } else {
      // Unhandled situation which should never happen.
      // Since this event handler is just a recovery attempt,
      // don't bother adding this declaration to the AST.
      return;
    }
    var comment = _findComment(metadata, beginToken);

    // Constructor declarations within extensions are invalid and the parser
    // has already reported an error at this point, but we include them in as
    // a method declaration in order to get navigation, search, etc.

    SimpleIdentifierImpl methodName;
    if (constructorName is SimpleIdentifierImpl) {
      methodName = constructorName;
    } else if (constructorName is PrefixedIdentifierImpl) {
      methodName = constructorName.identifier;
    } else {
      // Unsure what the method name should be in this situation.
      // Since this event handler is just a recovery attempt,
      // don't bother adding this declaration to the AST.
      return;
    }
    currentDeclarationMembers.add(
      MethodDeclarationImpl(
        comment: comment,
        metadata: metadata,
        externalKeyword: modifiers?.externalKeyword,
        modifierKeyword: modifiers?.abstractKeyword ?? modifiers?.staticKeyword,
        returnType: null,
        propertyKeyword: null,
        operatorKeyword: null,
        name: methodName,
        typeParameters: typeParameters,
        parameters: parameters,
        body: body,
      ),
    );
  }

  @override
  void endExtensionFields(
      Token? abstractToken,
      Token? augmentToken,
      Token? externalToken,
      Token? staticToken,
      Token? covariantToken,
      Token? lateToken,
      Token? varFinalOrConst,
      int count,
      Token beginToken,
      Token endToken) {
    if (staticToken == null) {
      // TODO(danrubel) Decide how to handle instance field declarations
      // within extensions. They are invalid and the parser has already reported
      // an error at this point, but we include them in order to get navigation,
      // search, etc.
    }
    endClassFields(
        abstractToken,
        augmentToken,
        externalToken,
        staticToken,
        covariantToken,
        lateToken,
        varFinalOrConst,
        count,
        beginToken,
        endToken);
  }

  @override
  void endExtensionMethod(Token? getOrSet, Token beginToken, Token beginParam,
      Token? beginInitializers, Token endToken) {
    debugEvent("ExtensionMethod");
    endClassMethod(
        getOrSet, beginToken, beginParam, beginInitializers, endToken);
  }

  @override
  void endFieldInitializer(Token assignment, Token token) {
    assert(optional('=', assignment));
    debugEvent("FieldInitializer");

    var initializer = pop() as ExpressionImpl;
    var name = pop() as SimpleIdentifierImpl;
    push(
      _makeVariableDeclaration(
        name: name,
        equals: assignment,
        initializer: initializer,
      ),
    );
  }

  @override
  void endForControlFlow(Token token) {
    debugEvent("endForControlFlow");
    var entry = pop() as Object;
    var forLoopParts = pop() as ForParts;
    var leftParen = pop() as Token;
    var forToken = pop() as Token;

    pushForControlFlowInfo(null, forToken, leftParen, forLoopParts, entry);
  }

  @override
  void endForIn(Token endToken) {
    debugEvent("ForInExpression");

    var body = pop() as Statement;
    var forLoopParts = pop() as ForEachParts;
    var leftParenthesis = pop() as Token;
    var forToken = pop() as Token;
    var awaitToken = pop(NullValue.AwaitToken) as Token?;

    push(ast.forStatement(
      awaitKeyword: awaitToken,
      forKeyword: forToken,
      leftParenthesis: leftParenthesis,
      forLoopParts: forLoopParts,
      rightParenthesis: leftParenthesis.endGroup!,
      body: body,
    ));
  }

  @override
  void endForInBody(Token token) {
    debugEvent("endForInBody");
  }

  @override
  void endForInControlFlow(Token token) {
    debugEvent("endForInControlFlow");

    var entry = pop() as Object;
    var forLoopParts = pop() as ForEachParts;
    var leftParenthesis = pop() as Token;
    var forToken = pop() as Token;
    var awaitToken = pop(NullValue.AwaitToken) as Token?;

    pushForControlFlowInfo(
        awaitToken, forToken, leftParenthesis, forLoopParts, entry);
  }

  @override
  void endForInExpression(Token token) {
    debugEvent("ForInExpression");
  }

  @override
  void endFormalParameter(
      Token? thisKeyword,
      Token? superKeyword,
      Token? periodAfterThisOrSuper,
      Token nameToken,
      Token? initializerStart,
      Token? initializerEnd,
      FormalParameterKind kind,
      MemberKind memberKind) {
    assert(optionalOrNull('this', thisKeyword));
    assert(optionalOrNull('super', superKeyword));
    assert(thisKeyword == null && superKeyword == null
        ? periodAfterThisOrSuper == null
        : optional('.', periodAfterThisOrSuper!));
    debugEvent("FormalParameter");

    if (superKeyword != null && !enableSuperParameters) {
      _reportFeatureNotEnabled(
        feature: ExperimentalFeatures.super_parameters,
        startToken: superKeyword,
      );
    }

    var defaultValue = pop() as _ParameterDefaultValue?;
    var name = pop() as SimpleIdentifier?;
    var typeOrFunctionTypedParameter = pop() as AstNode?;
    var modifiers = pop() as _Modifiers?;
    var keyword = modifiers?.finalConstOrVarKeyword;
    var covariantKeyword = modifiers?.covariantKeyword;
    var requiredKeyword = modifiers?.requiredToken;
    if (!enableNonNullable && requiredKeyword != null) {
      _reportFeatureNotEnabled(
        feature: ExperimentalFeatures.non_nullable,
        startToken: requiredKeyword,
      );
    }
    var metadata = pop() as List<Annotation>?;
    var comment = _findComment(metadata,
        thisKeyword ?? typeOrFunctionTypedParameter?.beginToken ?? nameToken);

    NormalFormalParameterImpl node;
    if (typeOrFunctionTypedParameter is FunctionTypedFormalParameterImpl) {
      // This is a temporary AST node that was constructed in
      // [endFunctionTypedFormalParameter]. We now deconstruct it and create
      // the final AST node.
      if (superKeyword != null) {
        assert(thisKeyword == null,
            "Can't have both 'this' and 'super' in a parameter.");
        node = ast.superFormalParameter(
            identifier: name!,
            comment: comment,
            metadata: metadata,
            covariantKeyword: covariantKeyword,
            requiredKeyword: requiredKeyword,
            type: typeOrFunctionTypedParameter.returnType,
            superKeyword: superKeyword,
            period: periodAfterThisOrSuper!,
            typeParameters: typeOrFunctionTypedParameter.typeParameters,
            parameters: typeOrFunctionTypedParameter.parameters,
            question: typeOrFunctionTypedParameter.question);
      } else if (thisKeyword != null) {
        assert(superKeyword == null,
            "Can't have both 'this' and 'super' in a parameter.");
        node = ast.fieldFormalParameter2(
            identifier: name!,
            comment: comment,
            metadata: metadata,
            covariantKeyword: covariantKeyword,
            requiredKeyword: requiredKeyword,
            type: typeOrFunctionTypedParameter.returnType,
            thisKeyword: thisKeyword,
            period: periodAfterThisOrSuper!,
            typeParameters: typeOrFunctionTypedParameter.typeParameters,
            parameters: typeOrFunctionTypedParameter.parameters,
            question: typeOrFunctionTypedParameter.question);
      } else {
        node = ast.functionTypedFormalParameter2(
            identifier: name!,
            comment: comment,
            metadata: metadata,
            covariantKeyword: covariantKeyword,
            requiredKeyword: requiredKeyword,
            returnType: typeOrFunctionTypedParameter.returnType,
            typeParameters: typeOrFunctionTypedParameter.typeParameters,
            parameters: typeOrFunctionTypedParameter.parameters,
            question: typeOrFunctionTypedParameter.question);
      }
    } else {
      var type = typeOrFunctionTypedParameter as TypeAnnotation?;
      if (superKeyword != null) {
        assert(thisKeyword == null,
            "Can't have both 'this' and 'super' in a parameter.");
        if (keyword is KeywordToken && keyword.keyword == Keyword.VAR) {
          handleRecoverableError(
            templateExtraneousModifier.withArguments(keyword),
            keyword,
            keyword,
          );
        }
        node = ast.superFormalParameter(
            comment: comment,
            metadata: metadata,
            covariantKeyword: covariantKeyword,
            requiredKeyword: requiredKeyword,
            keyword: keyword,
            type: type,
            superKeyword: superKeyword,
            period: periodAfterThisOrSuper!,
            identifier: name!);
      } else if (thisKeyword != null) {
        assert(superKeyword == null,
            "Can't have both 'this' and 'super' in a parameter.");
        node = ast.fieldFormalParameter2(
            comment: comment,
            metadata: metadata,
            covariantKeyword: covariantKeyword,
            requiredKeyword: requiredKeyword,
            keyword: keyword,
            type: type,
            thisKeyword: thisKeyword,
            period: thisKeyword.next!,
            identifier: name!);
      } else {
        node = ast.simpleFormalParameter2(
            comment: comment,
            metadata: metadata,
            covariantKeyword: covariantKeyword,
            requiredKeyword: requiredKeyword,
            keyword: keyword,
            type: type,
            identifier: name);
      }
    }

    ParameterKind analyzerKind = _toAnalyzerParameterKind(kind);
    FormalParameter parameter = node;
    if (analyzerKind != ParameterKind.REQUIRED) {
      parameter = DefaultFormalParameterImpl(
        parameter: node,
        kind: analyzerKind,
        separator: defaultValue?.separator,
        defaultValue: defaultValue?.value,
      );
    } else if (defaultValue != null) {
      // An error is reported if a required parameter has a default value.
      // Record it as named parameter for recovery.
      parameter = DefaultFormalParameterImpl(
        parameter: node,
        kind: ParameterKind.NAMED,
        separator: defaultValue.separator,
        defaultValue: defaultValue.value,
      );
    }
    push(parameter);
  }

  @override
  void endFormalParameterDefaultValueExpression() {
    debugEvent("FormalParameterDefaultValueExpression");
  }

  @override
  void endFormalParameters(
      int count, Token leftParen, Token rightParen, MemberKind kind) {
    assert(optional('(', leftParen));
    assert(optional(')', rightParen));
    debugEvent("FormalParameters");

    var rawParameters = popTypedList(count) ?? const <Object>[];
    List<FormalParameter> parameters = <FormalParameter>[];
    Token? leftDelimiter;
    Token? rightDelimiter;
    for (Object raw in rawParameters) {
      if (raw is _OptionalFormalParameters) {
        parameters.addAll(raw.parameters ?? const <FormalParameter>[]);
        leftDelimiter = raw.leftDelimiter;
        rightDelimiter = raw.rightDelimiter;
      } else {
        parameters.add(raw as FormalParameter);
      }
    }
    push(ast.formalParameterList(
        leftParen, parameters, leftDelimiter, rightDelimiter, rightParen));
  }

  @override
  void endForStatement(Token endToken) {
    debugEvent("ForStatement");
    var body = pop() as Statement;
    var forLoopParts = pop() as ForParts;
    var leftParen = pop() as Token;
    var forToken = pop() as Token;

    push(ast.forStatement(
      forKeyword: forToken,
      leftParenthesis: leftParen,
      forLoopParts: forLoopParts,
      rightParenthesis: leftParen.endGroup!,
      body: body,
    ));
  }

  @override
  void endForStatementBody(Token token) {
    debugEvent("endForStatementBody");
  }

  @override
  void endFunctionExpression(Token beginToken, Token token) {
    // TODO(paulberry): set up scopes properly to resolve parameters and type
    // variables.  Note that this is tricky due to the handling of initializers
    // in constructors, so the logic should be shared with BodyBuilder as much
    // as possible.
    debugEvent("FunctionExpression");

    var body = pop() as FunctionBody;
    var parameters = pop() as FormalParameterList?;
    var typeParameters = pop() as TypeParameterList?;
    push(ast.functionExpression(typeParameters, parameters, body));
  }

  @override
  void endFunctionName(Token beginToken, Token token) {
    debugEvent("FunctionName");
  }

  @override
  void endFunctionType(Token functionToken, Token? questionMark) {
    assert(optional('Function', functionToken));
    debugEvent("FunctionType");
    if (!enableNonNullable) {
      reportErrorIfNullableType(questionMark);
    }

    var parameters = pop() as FormalParameterList;
    var returnType = pop() as TypeAnnotation?;
    var typeParameters = pop() as TypeParameterList?;
    push(ast.genericFunctionType(
        returnType, functionToken, typeParameters, parameters,
        question: questionMark));
  }

  @override
  void endFunctionTypedFormalParameter(Token nameToken, Token? question) {
    debugEvent("FunctionTypedFormalParameter");
    if (!enableNonNullable) {
      reportErrorIfNullableType(question);
    }

    var formalParameters = pop() as FormalParameterList;
    var returnType = pop() as TypeAnnotation?;
    var typeParameters = pop() as TypeParameterList?;

    // Create a temporary formal parameter that will be dissected later in
    // [endFormalParameter].
    push(ast.functionTypedFormalParameter2(
        identifier: ast.simpleIdentifier(
          StringToken(TokenType.IDENTIFIER, '', 0),
        ),
        returnType: returnType,
        typeParameters: typeParameters,
        parameters: formalParameters,
        question: question));
  }

  @override
  void endHide(Token hideKeyword) {
    assert(optional('hide', hideKeyword));
    debugEvent("Hide");

    var hiddenNames = pop() as List<SimpleIdentifier>;
    push(ast.hideCombinator(hideKeyword, hiddenNames));
  }

  @override
  void endIfControlFlow(Token token) {
    var thenElement = pop() as CollectionElement;
    var condition = pop() as ParenthesizedExpression;
    var ifToken = pop() as Token;
    pushIfControlFlowInfo(ifToken, condition, thenElement, null, null);
  }

  @override
  void endIfElseControlFlow(Token token) {
    var elseElement = pop() as CollectionElement;
    var elseToken = pop() as Token;
    var thenElement = pop() as CollectionElement;
    var condition = pop() as ParenthesizedExpression;
    var ifToken = pop() as Token;
    pushIfControlFlowInfo(
        ifToken, condition, thenElement, elseToken, elseElement);
  }

  @override
  void endIfStatement(Token ifToken, Token? elseToken) {
    assert(optional('if', ifToken));
    assert(optionalOrNull('else', elseToken));

    var elsePart = popIfNotNull(elseToken) as Statement?;
    var thenPart = pop() as Statement;
    var condition = pop() as ParenthesizedExpression;
    push(ast.ifStatement(
        ifToken,
        condition.leftParenthesis,
        condition.expression,
        condition.rightParenthesis,
        thenPart,
        elseToken,
        elsePart));
  }

  @override
  void endImplicitCreationExpression(Token token, Token openAngleBracket) {
    debugEvent("ImplicitCreationExpression");

    _handleInstanceCreation(null);
  }

  @override
  void endImport(Token importKeyword, Token? augmentToken, Token? semicolon) {
    assert(optional('import', importKeyword));
    assert(optionalOrNull(';', semicolon));
    debugEvent("Import");

    var combinators = pop() as List<Combinator>?;
    var deferredKeyword = pop(NullValue.Deferred) as Token?;
    var asKeyword = pop(NullValue.As) as Token?;
    var prefix = pop(NullValue.Prefix) as SimpleIdentifierImpl?;
    var configurations = pop() as List<Configuration>?;
    var uri = pop() as StringLiteralImpl;
    var metadata = pop() as List<Annotation>?;
    var comment = _findComment(metadata, importKeyword);

    if (!enableMacros) {
      if (augmentToken != null) {
        _reportFeatureNotEnabled(
          feature: ExperimentalFeatures.macros,
          startToken: augmentToken,
        );
        // Pretend that 'augment' didn't occur while this feature is incomplete.
        augmentToken = null;
      }
    }

    if (augmentToken != null) {
      directives.add(
        AugmentationImportDirectiveImpl(
          comment: comment,
          uri: uri,
          importKeyword: importKeyword,
          augmentKeyword: augmentToken,
          metadata: metadata,
          semicolon: semicolon ?? Tokens.semicolon(),
        ),
      );
    } else {
      directives.add(
        ImportDirectiveImpl(
          comment: comment,
          metadata: metadata,
          importKeyword: importKeyword,
          uri: uri,
          configurations: configurations,
          deferredKeyword: deferredKeyword,
          asKeyword: asKeyword,
          prefix: prefix,
          combinators: combinators,
          semicolon: semicolon ?? Tokens.semicolon(),
        ),
      );
    }
  }

  @override
  void endInitializedIdentifier(Token nameToken) {
    debugEvent("InitializedIdentifier");

    var node = pop() as AstNode?;
    VariableDeclaration variable;
    // TODO(paulberry): This seems kludgy.  It would be preferable if we
    // could respond to a "handleNoVariableInitializer" event by converting a
    // SimpleIdentifier into a VariableDeclaration, and then when this code was
    // reached, node would always be a VariableDeclaration.
    if (node is VariableDeclaration) {
      variable = node;
    } else if (node is SimpleIdentifierImpl) {
      variable = _makeVariableDeclaration(
        name: node,
        equals: null,
        initializer: null,
      );
    } else {
      internalProblem(
          templateInternalProblemUnhandled.withArguments(
              "${node.runtimeType}", "identifier"),
          nameToken.charOffset,
          uri);
    }
    push(variable);
  }

  @override
  void endInitializers(int count, Token colon, Token endToken) {
    assert(optional(':', colon));
    debugEvent("Initializers");

    var initializerObjects = popTypedList(count) ?? const [];
    if (!isFullAst) return;

    push(colon);

    var initializers = <ConstructorInitializer>[];
    for (Object initializerObject in initializerObjects) {
      var initializer = buildInitializer(initializerObject);
      if (initializer != null) {
        initializers.add(initializer);
      } else {
        handleRecoverableError(
            messageInvalidInitializer,
            initializerObject is AstNode ? initializerObject.beginToken : colon,
            initializerObject is AstNode ? initializerObject.endToken : colon);
      }
    }

    push(initializers);
  }

  @override
  void endInvalidAwaitExpression(
      Token awaitKeyword, Token endToken, MessageCode errorCode) {
    debugEvent("InvalidAwaitExpression");
    endAwaitExpression(awaitKeyword, endToken);
  }

  @override
  void endInvalidYieldStatement(Token yieldKeyword, Token? starToken,
      Token endToken, MessageCode errorCode) {
    debugEvent("InvalidYieldStatement");
    endYieldStatement(yieldKeyword, starToken, endToken);
  }

  @override
  void endIsOperatorType(Token asOperator) {
    debugEvent("IsOperatorType");
  }

  @override
  void endLabeledStatement(int labelCount) {
    debugEvent("LabeledStatement");

    var statement = pop() as Statement;
    var labels = popTypedList2<Label>(labelCount);
    push(ast.labeledStatement(labels, statement));
  }

  @override
  void endLibraryAugmentation(
      Token libraryKeyword, Token augmentKeyword, Token semicolon) {
    final uri = pop() as StringLiteralImpl;
    final metadata = pop() as List<Annotation>?;
    final comment = _findComment(metadata, libraryKeyword);
    directives.add(
      LibraryAugmentationDirectiveImpl(
        comment: comment,
        metadata: metadata,
        libraryKeyword: libraryKeyword,
        augmentKeyword: augmentKeyword,
        uri: uri,
        semicolon: semicolon,
      ),
    );
  }

  @override
  void endLibraryName(Token libraryKeyword, Token semicolon) {
    assert(optional('library', libraryKeyword));
    assert(optional(';', semicolon));
    debugEvent("LibraryName");

    var libraryName = pop() as List<SimpleIdentifier>;
    var name = ast.libraryIdentifier(libraryName);
    var metadata = pop() as List<Annotation>?;
    var comment = _findComment(metadata, libraryKeyword);
    directives.add(
      LibraryDirectiveImpl(
        comment: comment,
        metadata: metadata,
        libraryKeyword: libraryKeyword,
        name: name,
        semicolon: semicolon,
      ),
    );
  }

  @override
  void endLiteralString(int interpolationCount, Token endToken) {
    debugEvent("endLiteralString");

    if (interpolationCount == 0) {
      var token = pop() as Token;
      String value = unescapeString(token.lexeme, token, this);
      push(ast.simpleStringLiteral(token, value));
    } else {
      var parts = popTypedList(1 + interpolationCount * 2)!;
      var first = parts.first as Token;
      var last = parts.last as Token;
      Quote quote = analyzeQuote(first.lexeme);
      List<InterpolationElement> elements = <InterpolationElement>[];
      elements.add(ast.interpolationString(
          first, unescapeFirstStringPart(first.lexeme, quote, first, this)));
      for (int i = 1; i < parts.length - 1; i++) {
        var part = parts[i];
        if (part is Token) {
          elements.add(ast.interpolationString(
              part, unescape(part.lexeme, quote, part, this)));
        } else if (part is InterpolationExpression) {
          elements.add(part);
        } else {
          internalProblem(
              templateInternalProblemUnhandled.withArguments(
                  "${part.runtimeType}", "string interpolation"),
              first.charOffset,
              uri);
        }
      }
      elements.add(ast.interpolationString(
          last,
          unescapeLastStringPart(
              last.lexeme, quote, last, last.isSynthetic, this)));
      push(ast.stringInterpolation(elements));
    }
  }

  @override
  void endLiteralSymbol(Token hashToken, int tokenCount) {
    assert(optional('#', hashToken));
    debugEvent("LiteralSymbol");

    var components = popTypedList2<Token>(tokenCount);
    push(ast.symbolLiteral(hashToken, components));
  }

  @override
  void endLocalFunctionDeclaration(Token token) {
    debugEvent("LocalFunctionDeclaration");
    var body = pop() as FunctionBody;
    if (isFullAst) {
      pop(); // constructor initializers
      pop(); // separator before constructor initializers
    }
    var parameters = pop() as FormalParameterList;
    checkFieldFormalParameters(parameters);
    var name = pop() as SimpleIdentifierImpl;
    var returnType = pop() as TypeAnnotationImpl?;
    var typeParameters = pop() as TypeParameterList?;
    var metadata = pop(NullValue.Metadata) as List<Annotation>?;
    final functionExpression =
        ast.functionExpression(typeParameters, parameters, body);
    var functionDeclaration = FunctionDeclarationImpl(
      comment: null,
      metadata: metadata,
      augmentKeyword: null,
      externalKeyword: null,
      returnType: returnType,
      propertyKeyword: null,
      name: name,
      functionExpression: functionExpression,
    );
    push(ast.functionDeclarationStatement(functionDeclaration));
  }

  @override
  void endMember() {
    debugEvent("Member");
  }

  @override
  void endMetadata(Token atSign, Token? periodBeforeName, Token endToken) {
    assert(optional('@', atSign));
    assert(optionalOrNull('.', periodBeforeName));
    debugEvent("Metadata");

    var invocation = pop() as MethodInvocationImpl?;
    var constructorName =
        periodBeforeName != null ? pop() as SimpleIdentifierImpl : null;
    var typeArguments = pop() as TypeArgumentListImpl?;
    if (typeArguments != null &&
        !_featureSet.isEnabled(Feature.generic_metadata)) {
      _reportFeatureNotEnabled(
        feature: ExperimentalFeatures.generic_metadata,
        startToken: typeArguments.beginToken,
      );
    }
    var name = pop() as IdentifierImpl;
    push(
      AnnotationImpl(
        atSign: atSign,
        name: name,
        typeArguments: typeArguments,
        period: periodBeforeName,
        constructorName: constructorName,
        arguments: invocation?.argumentList,
      ),
    );
  }

  @override
  void endMetadataStar(int count) {
    debugEvent("MetadataStar");

    push(popTypedList<Annotation>(count) ?? NullValue.Metadata);
  }

  @override
  void endMixinConstructor(Token? getOrSet, Token beginToken, Token beginParam,
      Token? beginInitializers, Token endToken) {
    debugEvent("MixinConstructor");
    // TODO(danrubel) Decide how to handle constructor declarations within
    // mixins. They are invalid, but we include them in order to get navigation,
    // search, etc. Currently the error is reported by multiple listeners,
    // but should be moved into the parser.
    endClassConstructor(
        getOrSet, beginToken, beginParam, beginInitializers, endToken);
  }

  @override
  void endMixinDeclaration(Token mixinKeyword, Token endToken) {
    debugEvent("MixinDeclaration");
    mixinDeclaration = null;
  }

  @override
  void endMixinFactoryMethod(
      Token beginToken, Token factoryKeyword, Token endToken) {
    debugEvent("MixinFactoryMethod");
    endClassFactoryMethod(beginToken, factoryKeyword, endToken);
  }

  @override
  void endMixinFields(
      Token? abstractToken,
      Token? augmentToken,
      Token? externalToken,
      Token? staticToken,
      Token? covariantToken,
      Token? lateToken,
      Token? varFinalOrConst,
      int count,
      Token beginToken,
      Token endToken) {
    endClassFields(
        abstractToken,
        augmentToken,
        externalToken,
        staticToken,
        covariantToken,
        lateToken,
        varFinalOrConst,
        count,
        beginToken,
        endToken);
  }

  @override
  void endMixinMethod(Token? getOrSet, Token beginToken, Token beginParam,
      Token? beginInitializers, Token endToken) {
    debugEvent("MixinMethod");
    endClassMethod(
        getOrSet, beginToken, beginParam, beginInitializers, endToken);
  }

  @override
  void endNamedFunctionExpression(Token endToken) {
    debugEvent("NamedFunctionExpression");
    var body = pop() as FunctionBody;
    if (isFullAst) {
      pop(); // constructor initializers
      pop(); // separator before constructor initializers
    }
    var parameters = pop() as FormalParameterList;
    pop(); // name
    pop(); // returnType
    var typeParameters = pop() as TypeParameterList?;
    push(ast.functionExpression(typeParameters, parameters, body));
  }

  @override
  void endNamedMixinApplication(Token beginToken, Token classKeyword,
      Token equalsToken, Token? implementsKeyword, Token semicolon) {
    assert(optional('class', classKeyword));
    assert(optionalOrNull('=', equalsToken));
    assert(optionalOrNull('implements', implementsKeyword));
    assert(optional(';', semicolon));
    debugEvent("NamedMixinApplication");

    ImplementsClauseImpl? implementsClause;
    if (implementsKeyword != null) {
      var interfaces = pop() as List<NamedType>;
      implementsClause = ast.implementsClause(implementsKeyword, interfaces);
    }
    var withClause = pop(NullValue.WithClause) as WithClauseImpl;
    var superclass = pop() as NamedTypeImpl;
    var augmentKeyword = pop(NullValue.Token) as Token?;
    var macroKeyword = pop(NullValue.Token) as Token?;
    var modifiers = pop() as _Modifiers?;
    var typeParameters = pop() as TypeParameterListImpl?;
    var name = pop() as SimpleIdentifierImpl;
    var abstractKeyword = modifiers?.abstractKeyword;
    var metadata = pop() as List<Annotation>?;
    var comment = _findComment(metadata, beginToken);
    declarations.add(
      ClassTypeAliasImpl(
        comment: comment,
        metadata: metadata,
        typedefKeyword: classKeyword,
        name: name,
        typeParameters: typeParameters,
        equals: equalsToken,
        abstractKeyword: abstractKeyword,
        macroKeyword: macroKeyword,
        augmentKeyword: augmentKeyword,
        superclass: superclass,
        withClause: withClause,
        implementsClause: implementsClause,
        semicolon: semicolon,
      ),
    );
  }

  @override
  void endNewExpression(Token newKeyword) {
    assert(optional('new', newKeyword));
    debugEvent("NewExpression");

    _handleInstanceCreation(newKeyword);
  }

  @override
  void endOptionalFormalParameters(
      int count, Token leftDelimeter, Token rightDelimeter) {
    assert((optional('[', leftDelimeter) && optional(']', rightDelimeter)) ||
        (optional('{', leftDelimeter) && optional('}', rightDelimeter)));
    debugEvent("OptionalFormalParameters");

    push(_OptionalFormalParameters(
        popTypedList2<FormalParameter>(count), leftDelimeter, rightDelimeter));
  }

  @override
  void endParenthesizedExpression(Token leftParenthesis) {
    assert(optional('(', leftParenthesis));
    debugEvent("ParenthesizedExpression");

    var expression = pop() as Expression;
    push(ast.parenthesizedExpression(
        leftParenthesis, expression, leftParenthesis.endGroup!));
  }

  @override
  void endPart(Token partKeyword, Token semicolon) {
    assert(optional('part', partKeyword));
    assert(optional(';', semicolon));
    debugEvent("Part");

    var uri = pop() as StringLiteralImpl;
    var metadata = pop() as List<Annotation>?;
    var comment = _findComment(metadata, partKeyword);
    directives.add(
      PartDirectiveImpl(
        comment: comment,
        metadata: metadata,
        partKeyword: partKeyword,
        uri: uri,
        semicolon: semicolon,
      ),
    );
  }

  @override
  void endPartOf(
      Token partKeyword, Token ofKeyword, Token semicolon, bool hasName) {
    assert(optional('part', partKeyword));
    assert(optional('of', ofKeyword));
    assert(optional(';', semicolon));
    debugEvent("PartOf");
    var libraryNameOrUri = pop();
    LibraryIdentifierImpl? name;
    StringLiteralImpl? uri;
    if (libraryNameOrUri is StringLiteralImpl) {
      uri = libraryNameOrUri;
    } else {
      name = ast.libraryIdentifier(libraryNameOrUri as List<SimpleIdentifier>);
    }
    var metadata = pop() as List<Annotation>?;
    var comment = _findComment(metadata, partKeyword);
    directives.add(
      PartOfDirectiveImpl(
        comment: comment,
        metadata: metadata,
        partKeyword: partKeyword,
        ofKeyword: ofKeyword,
        uri: uri,
        libraryName: name,
        semicolon: semicolon,
      ),
    );
  }

  @override
  void endRecordLiteral(Token token, int count) {
    debugEvent("RecordLiteral");

    if (!enableRecords) {
      _reportFeatureNotEnabled(
        feature: ExperimentalFeatures.records,
        startToken: token,
      );
    }

    var elements = popTypedList<Expression>(count) ?? const [];
    List<Expression> expressions = <Expression>[];
    for (var elem in elements) {
      expressions.add(elem);
    }

    push(RecordLiteralImpl(
      leftParenthesis: token,
      fields: expressions,
      rightParenthesis: token.endGroup!,
    ));
  }

  @override
  void endRedirectingFactoryBody(Token equalToken, Token endToken) {
    assert(optional('=', equalToken));
    debugEvent("RedirectingFactoryBody");

    var constructorName = pop() as ConstructorNameImpl;
    var starToken = pop() as Token?;
    var asyncToken = pop() as Token?;
    push(_RedirectingFactoryBody(
        asyncToken, starToken, equalToken, constructorName));
  }

  @override
  void endRethrowStatement(Token rethrowToken, Token semicolon) {
    assert(optional('rethrow', rethrowToken));
    assert(optional(';', semicolon));
    debugEvent("RethrowStatement");

    RethrowExpression expression = ast.rethrowExpression(rethrowToken);
    // TODO(scheglov) According to the specification, 'rethrow' is a statement.
    push(ast.expressionStatement(expression, semicolon));
  }

  @override
  void endReturnStatement(
      bool hasExpression, Token returnKeyword, Token semicolon) {
    assert(optional('return', returnKeyword));
    assert(optional(';', semicolon));
    debugEvent("ReturnStatement");

    var expression = hasExpression ? pop() as Expression : null;
    push(ast.returnStatement(returnKeyword, expression, semicolon));
  }

  @override
  void endShow(Token showKeyword) {
    assert(optional('show', showKeyword));
    debugEvent("Show");

    var shownNames = pop() as List<SimpleIdentifier>;
    push(ast.showCombinator(showKeyword, shownNames));
  }

  @override
  void endSwitchBlock(int caseCount, Token leftBracket, Token rightBracket) {
    assert(optional('{', leftBracket));
    assert(optional('}', rightBracket));
    debugEvent("SwitchBlock");

    var membersList = popTypedList2<List<SwitchMember>>(caseCount);
    List<SwitchMember> members =
        membersList.expand((members) => members).toList();

    Set<String> labels = <String>{};
    for (SwitchMember member in members) {
      for (Label label in member.labels) {
        if (!labels.add(label.label.name)) {
          handleRecoverableError(
              templateDuplicateLabelInSwitchStatement
                  .withArguments(label.label.name),
              label.beginToken,
              label.beginToken);
        }
      }
    }

    push(leftBracket);
    push(members);
    push(rightBracket);
  }

  @override
  void endSwitchCase(
      int labelCount,
      int expressionCount,
      Token? defaultKeyword,
      Token? colonAfterDefault,
      int statementCount,
      Token firstToken,
      Token endToken) {
    assert(optionalOrNull('default', defaultKeyword));
    assert(defaultKeyword == null
        ? colonAfterDefault == null
        : optional(':', colonAfterDefault!));
    debugEvent("SwitchCase");

    var statements = popTypedList2<Statement>(statementCount);
    List<SwitchMember?> members;

    if (labelCount == 0 && defaultKeyword == null) {
      // Common situation: case with no default and no labels.
      members = popTypedList2<SwitchMember>(expressionCount);
    } else {
      // Labels and case statements may be intertwined
      if (defaultKeyword != null) {
        SwitchDefault member = ast.switchDefault(
            <Label>[], defaultKeyword, colonAfterDefault!, <Statement>[]);
        while (peek() is Label) {
          member.labels.insert(0, pop() as Label);
          --labelCount;
        }
        members = List<SwitchMember?>.filled(expressionCount + 1, null);
        members[expressionCount] = member;
      } else {
        members = List<SwitchMember?>.filled(expressionCount, null);
      }
      for (int index = expressionCount - 1; index >= 0; --index) {
        var member = pop() as SwitchMember;
        while (peek() is Label) {
          member.labels.insert(0, pop() as Label);
          --labelCount;
        }
        members[index] = member;
      }
      assert(labelCount == 0);
    }
    var members2 = members.whereNotNull().toList();
    if (members2.isNotEmpty) {
      members2.last.statements.addAll(statements);
    }
    push(members2);
  }

  @override
  void endSwitchStatement(Token switchKeyword, Token endToken) {
    assert(optional('switch', switchKeyword));
    debugEvent("SwitchStatement");

    var rightBracket = pop() as Token;
    var members = pop() as List<SwitchMember>;
    var leftBracket = pop() as Token;
    var expression = pop() as ParenthesizedExpression;
    push(ast.switchStatement(
        switchKeyword,
        expression.leftParenthesis,
        expression.expression,
        expression.rightParenthesis,
        leftBracket,
        members,
        rightBracket));
  }

  @override
  void endThenStatement(Token token) {
    debugEvent("endThenStatement");
  }

  @override
  void endTopLevelDeclaration(Token token) {
    debugEvent("TopLevelDeclaration");
  }

  @override
  void endTopLevelFields(
      Token? externalToken,
      Token? staticToken,
      Token? covariantToken,
      Token? lateToken,
      Token? varFinalOrConst,
      int count,
      Token beginToken,
      Token semicolon) {
    assert(optional(';', semicolon));
    debugEvent("TopLevelFields");

    if (externalToken != null) {
      if (!enableNonNullable) {
        handleRecoverableError(
            messageExternalField, externalToken, externalToken);
      } else if (lateToken != null) {
        handleRecoverableError(
            messageExternalLateField, externalToken, externalToken);
      }
    }

    var variables = popTypedList2<VariableDeclaration>(count);
    var type = pop() as TypeAnnotationImpl?;
    var variableList = VariableDeclarationListImpl(
      comment: null,
      metadata: null,
      lateKeyword: lateToken,
      keyword: varFinalOrConst,
      type: type,
      variables: variables,
    );
    var metadata = pop() as List<Annotation>?;
    var comment = _findComment(metadata, beginToken);
    declarations.add(
      TopLevelVariableDeclarationImpl(
        comment: comment,
        metadata: metadata,
        externalKeyword: externalToken,
        variableList: variableList,
        semicolon: semicolon,
      ),
    );
  }

  @override
  void endTopLevelMethod(Token beginToken, Token? getOrSet, Token endToken) {
    // TODO(paulberry): set up scopes properly to resolve parameters and type
    // variables.
    assert(getOrSet == null ||
        optional('get', getOrSet) ||
        optional('set', getOrSet));
    debugEvent("TopLevelMethod");

    var body = pop() as FunctionBody;
    var parameters = pop() as FormalParameterList?;
    var typeParameters = pop() as TypeParameterList?;
    var name = pop() as SimpleIdentifierImpl;
    var returnType = pop() as TypeAnnotationImpl?;
    var modifiers = pop() as _Modifiers?;
    var augmentKeyword = modifiers?.augmentKeyword;
    var externalKeyword = modifiers?.externalKeyword;
    var metadata = pop() as List<Annotation>?;
    var comment = _findComment(metadata, beginToken);
    declarations.add(
      FunctionDeclarationImpl(
        comment: comment,
        metadata: metadata,
        augmentKeyword: augmentKeyword,
        externalKeyword: externalKeyword,
        returnType: returnType,
        propertyKeyword: getOrSet,
        name: name,
        functionExpression:
            ast.functionExpression(typeParameters, parameters, body),
      ),
    );
  }

  @override
  void endTryStatement(
      int catchCount, Token tryKeyword, Token? finallyKeyword) {
    assert(optional('try', tryKeyword));
    assert(optionalOrNull('finally', finallyKeyword));
    debugEvent("TryStatement");

    var finallyBlock = popIfNotNull(finallyKeyword) as Block?;
    var catchClauses = popTypedList2<CatchClause>(catchCount);
    var body = pop() as Block;
    push(ast.tryStatement(
        tryKeyword, body, catchClauses, finallyKeyword, finallyBlock));
  }

  @override
  void endTypeArguments(int count, Token leftBracket, Token rightBracket) {
    assert(optional('<', leftBracket));
    assert(optional('>', rightBracket));
    debugEvent("TypeArguments");

    var arguments = popTypedList2<TypeAnnotation>(count);
    push(ast.typeArgumentList(leftBracket, arguments, rightBracket));
  }

  @override
  void endTypedef(Token typedefKeyword, Token? equals, Token semicolon) {
    assert(optional('typedef', typedefKeyword));
    assert(optionalOrNull('=', equals));
    assert(optional(';', semicolon));
    debugEvent("FunctionTypeAlias");

    if (equals == null) {
      var parameters = pop() as FormalParameterListImpl;
      var typeParameters = pop() as TypeParameterListImpl?;
      var name = pop() as SimpleIdentifierImpl;
      var returnType = pop() as TypeAnnotationImpl?;
      var metadata = pop() as List<Annotation>?;
      var comment = _findComment(metadata, typedefKeyword);
      declarations.add(
        FunctionTypeAliasImpl(
          comment: comment,
          metadata: metadata,
          typedefKeyword: typedefKeyword,
          returnType: returnType,
          name: name,
          typeParameters: typeParameters,
          parameters: parameters,
          semicolon: semicolon,
        ),
      );
    } else {
      var type = pop() as TypeAnnotationImpl;
      var templateParameters = pop() as TypeParameterListImpl?;
      var name = pop() as SimpleIdentifierImpl;
      var metadata = pop() as List<Annotation>?;
      var comment = _findComment(metadata, typedefKeyword);
      if (type is! GenericFunctionType && !enableNonFunctionTypeAliases) {
        _reportFeatureNotEnabled(
          feature: ExperimentalFeatures.nonfunction_type_aliases,
          startToken: equals,
        );
      }
      declarations.add(
        GenericTypeAliasImpl(
          comment: comment,
          metadata: metadata,
          typedefKeyword: typedefKeyword,
          name: name,
          typeParameters: templateParameters,
          equals: equals,
          type: type,
          semicolon: semicolon,
        ),
      );
    }
  }

  @override
  void endTypeList(int count) {
    debugEvent("TypeList");
    push(popTypedList<NamedType>(count) ?? NullValue.TypeList);
  }

  @override
  void endTypeVariable(
      Token token, int index, Token? extendsOrSuper, Token? variance) {
    debugEvent("TypeVariable");
    assert(extendsOrSuper == null ||
        optional('extends', extendsOrSuper) ||
        optional('super', extendsOrSuper));

    // TODO (kallentu): Implement variance behaviour for the analyzer.
    assert(variance == null ||
        optional('in', variance) ||
        optional('out', variance) ||
        optional('inout', variance));
    if (!enableVariance) {
      reportVarianceModifierNotEnabled(variance);
    }

    var bound = pop() as TypeAnnotation?;

    // Peek to leave type parameters on top of stack.
    var typeParameters = peek() as List<TypeParameter>;

    // TODO (kallentu) : Clean up TypeParameterImpl casting once variance is
    // added to the interface.
    (typeParameters[index] as TypeParameterImpl)
      ..extendsKeyword = extendsOrSuper
      ..bound = bound
      ..varianceKeyword = variance;
  }

  @override
  void endTypeVariables(Token beginToken, Token endToken) {
    assert(optional('<', beginToken));
    assert(optional('>', endToken));
    debugEvent("TypeVariables");

    var typeParameters = pop() as List<TypeParameter>;
    push(ast.typeParameterList(beginToken, typeParameters, endToken));
  }

  @override
  void endVariableInitializer(Token assignmentOperator) {
    assert(optionalOrNull('=', assignmentOperator));
    debugEvent("VariableInitializer");

    var initializer = pop() as ExpressionImpl;
    var identifier = pop() as SimpleIdentifierImpl;
    // TODO(ahe): Don't push initializers, instead install them.
    push(
      _makeVariableDeclaration(
        name: identifier,
        equals: assignmentOperator,
        initializer: initializer,
      ),
    );
  }

  @override
  void endVariablesDeclaration(int count, Token? semicolon) {
    assert(optionalOrNull(';', semicolon));
    debugEvent("VariablesDeclaration");

    var variables = popTypedList2<VariableDeclaration>(count);
    var modifiers = pop(NullValue.Modifiers) as _Modifiers?;
    var type = pop() as TypeAnnotationImpl?;
    var keyword = modifiers?.finalConstOrVarKeyword;
    var metadata = pop() as List<Annotation>?;
    var comment = _findComment(metadata, variables[0].beginToken);
    // var comment = _findComment(metadata,
    //     variables[0].beginToken ?? type?.beginToken ?? modifiers.beginToken);
    push(
      ast.variableDeclarationStatement(
        VariableDeclarationListImpl(
          comment: comment,
          metadata: metadata,
          lateKeyword: modifiers?.lateToken,
          keyword: keyword,
          type: type,
          variables: variables,
        ),
        semicolon ?? Tokens.semicolon(),
      ),
    );
  }

  @override
  void endWhileStatement(Token whileKeyword, Token endToken) {
    assert(optional('while', whileKeyword));
    debugEvent("WhileStatement");

    var body = pop() as Statement;
    var condition = pop() as ParenthesizedExpression;
    push(ast.whileStatement(whileKeyword, condition.leftParenthesis,
        condition.expression, condition.rightParenthesis, body));
  }

  @override
  void endWhileStatementBody(Token token) {
    debugEvent("endWhileStatementBody");
  }

  @override
  void endYieldStatement(Token yieldToken, Token? starToken, Token semicolon) {
    assert(optional('yield', yieldToken));
    assert(optionalOrNull('*', starToken));
    assert(optional(';', semicolon));
    debugEvent("YieldStatement");

    var expression = pop() as Expression;
    push(ast.yieldStatement(yieldToken, starToken, expression, semicolon));
  }

  @override
  void handleAsOperator(Token asOperator) {
    assert(optional('as', asOperator));
    debugEvent("AsOperator");

    var type = pop() as TypeAnnotationImpl;
    var expression = pop() as ExpressionImpl;
    push(
      AsExpressionImpl(
        expression: expression,
        asOperator: asOperator,
        type: type,
      ),
    );
  }

  @override
  void handleAssignmentExpression(Token token) {
    assert(token.type.isAssignmentOperator);
    debugEvent("AssignmentExpression");

    var rhs = pop() as ExpressionImpl;
    var lhs = pop() as ExpressionImpl;
    if (!lhs.isAssignable) {
      // TODO(danrubel): Update the BodyBuilder to report this error.
      handleRecoverableError(
          messageMissingAssignableSelector, lhs.beginToken, lhs.endToken);
    }
    push(
      AssignmentExpressionImpl(
        leftHandSide: lhs,
        operator: token,
        rightHandSide: rhs,
      ),
    );
    if (!enableTripleShift && token.type == TokenType.GT_GT_GT_EQ) {
      _reportFeatureNotEnabled(
        feature: ExperimentalFeatures.triple_shift,
        startToken: token,
      );
    }
  }

  @override
  void handleAsyncModifier(Token? asyncToken, Token? starToken) {
    assert(asyncToken == null ||
        optional('async', asyncToken) ||
        optional('sync', asyncToken));
    assert(optionalOrNull('*', starToken));
    debugEvent("AsyncModifier");

    push(asyncToken ?? NullValue.FunctionBodyAsyncToken);
    push(starToken ?? NullValue.FunctionBodyStarToken);
  }

  @override
  void handleAugmentSuperExpression(
      Token augmentKeyword, Token superKeyword, IdentifierContext context) {
    assert(optional('augment', augmentKeyword));
    assert(optional('super', superKeyword));
    debugEvent("AugmentSuperExpression");
    throw UnimplementedError('AstBuilder.handleAugmentSuperExpression');
  }

  @override
  void handleBreakStatement(
      bool hasTarget, Token breakKeyword, Token semicolon) {
    assert(optional('break', breakKeyword));
    assert(optional(';', semicolon));
    debugEvent("BreakStatement");

    var label = hasTarget ? pop() as SimpleIdentifierImpl : null;
    push(
      BreakStatementImpl(
        breakKeyword: breakKeyword,
        label: label,
        semicolon: semicolon,
      ),
    );
  }

  @override
  void handleCaseMatch(Token caseKeyword, Token colon) {
    assert(optional('case', caseKeyword));
    assert(optional(':', colon));
    debugEvent("CaseMatch");

    var expression = pop() as Expression;
    push(ast.switchCase(
        <Label>[], caseKeyword, expression, colon, <Statement>[]));
  }

  @override
  void handleCatchBlock(Token? onKeyword, Token? catchKeyword, Token? comma) {
    assert(optionalOrNull('on', onKeyword));
    assert(optionalOrNull('catch', catchKeyword));
    assert(optionalOrNull(',', comma));
    debugEvent("CatchBlock");

    var body = pop() as Block;
    var catchParameterList = popIfNotNull(catchKeyword) as FormalParameterList?;
    var type = popIfNotNull(onKeyword) as TypeAnnotation?;
    SimpleIdentifier? exception;
    SimpleIdentifier? stackTrace;
    if (catchParameterList != null) {
      List<FormalParameter> catchParameters = catchParameterList.parameters;
      if (catchParameters.isNotEmpty) {
        // ignore: deprecated_member_use_from_same_package
        exception = catchParameters[0].identifier;
      }
      if (catchParameters.length > 1) {
        // ignore: deprecated_member_use_from_same_package
        stackTrace = catchParameters[1].identifier;
      }
    }
    push(
      CatchClauseImpl(
        onKeyword: onKeyword,
        exceptionType: type as TypeAnnotationImpl?,
        catchKeyword: catchKeyword,
        leftParenthesis: catchParameterList?.leftParenthesis,
        exceptionParameter: exception != null
            ? CatchClauseParameterImpl(
                nameNode: exception as SimpleIdentifierImpl,
              )
            : null,
        comma: comma,
        stackTraceParameter: stackTrace != null
            ? CatchClauseParameterImpl(
                nameNode: stackTrace as SimpleIdentifierImpl,
              )
            : null,
        rightParenthesis: catchParameterList?.rightParenthesis,
        body: body as BlockImpl,
      ),
    );
  }

  @override
  void handleClassExtends(Token? extendsKeyword, int typeCount) {
    assert(extendsKeyword == null || extendsKeyword.isKeywordOrIdentifier);
    debugEvent("ClassExtends");

    // If more extends clauses was specified (parser has already issued an
    // error) throw them away for now and pick the first one.
    while (typeCount > 1) {
      pop();
      typeCount--;
    }
    var supertype = pop() as NamedType?;
    if (supertype != null) {
      push(ast.extendsClause(extendsKeyword!, supertype));
    } else {
      push(NullValue.ExtendsClause);
    }
  }

  @override
  void handleClassHeader(Token begin, Token classKeyword, Token? nativeToken) {
    assert(optional('class', classKeyword));
    assert(optionalOrNull('native', nativeToken));
    assert(classDeclaration == null && mixinDeclaration == null);
    debugEvent("ClassHeader");

    NativeClause? nativeClause;
    if (nativeToken != null) {
      nativeClause = ast.nativeClause(nativeToken, nativeName);
    }
    var implementsClause =
        pop(NullValue.IdentifierList) as ImplementsClauseImpl?;
    var withClause = pop(NullValue.WithClause) as WithClauseImpl?;