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.

library fasta.analyzer.ast_builder;

import 'package:analyzer/analyzer.dart';
import 'package:analyzer/dart/ast/ast_factory.dart' show AstFactory;
import 'package:analyzer/dart/ast/standard_ast_factory.dart' as standard;
import 'package:analyzer/dart/ast/token.dart' as analyzer show Token;
import 'package:analyzer/dart/ast/token.dart' show TokenType;
import 'package:analyzer/dart/element/element.dart' show Element;
import 'package:front_end/src/fasta/parser/parser.dart'
    show FormalParameterType, Parser;
import 'package:front_end/src/fasta/scanner/string_scanner.dart';
import 'package:front_end/src/fasta/scanner/token.dart'
    show BeginGroupToken, CommentToken, Token;

import 'package:front_end/src/fasta/errors.dart' show internalError;
import 'package:front_end/src/fasta/fasta_codes.dart'
    show FastaMessage, codeExpectedExpression, codeExpectedFunctionBody;
import 'package:front_end/src/fasta/kernel/kernel_builder.dart'
    show Builder, KernelLibraryBuilder, ProcedureBuilder, Scope;
import 'package:front_end/src/fasta/parser/identifier_context.dart'
    show IdentifierContext;
import 'package:front_end/src/fasta/quote.dart';
import 'package:front_end/src/fasta/source/scope_listener.dart'
    show JumpTargetKind, NullValue, ScopeListener;
import 'analyzer.dart' show toKernel;
import 'element_store.dart'
    show
        AnalyzerLocalVariableElemment,
        AnalyzerParameterElement,
        ElementStore,
        KernelClassElement;
import 'package:analyzer/src/dart/error/syntactic_errors.dart';
import 'token_utils.dart' show toAnalyzerToken, toAnalyzerCommentToken;

class AstBuilder extends ScopeListener {
  final AstFactory ast = standard.astFactory;

  final ErrorReporter errorReporter;
  final KernelLibraryBuilder library;
  final Builder member;
  final ElementStore elementStore;

  @override
  final Uri uri;

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

  bool parseGenericMethodComments = false;

  /// The name of the class currently being parsed, or `null` if no class is
  /// being parsed.
  String className;

  AstBuilder(this.errorReporter, this.library, this.member, this.elementStore,
      Scope scope,
      [Uri uri])
      : uri = uri ?? library.fileUri,
        super(scope);

  createJumpTarget(JumpTargetKind kind, int charOffset) {
    // TODO(ahe): Implement jump targets.
    return null;
  }

  void beginLiteralString(Token token) {
    debugEvent("beginLiteralString");
    push(token);
  }

  void handleNamedArgument(Token colon) {
    debugEvent("NamedArgument");
    Expression expression = pop();
    SimpleIdentifier name = pop();
    push(ast.namedExpression(
        ast.label(name, toAnalyzerToken(colon)), expression));
  }

  @override
  void handleNoConstructorReferenceContinuationAfterTypeArguments(Token token) {
    debugEvent("NoConstructorReferenceContinuationAfterTypeArguments");
    push(NullValue.ConstructorReferenceContinuationAfterTypeArguments);
  }

  @override
  void endConstructorReference(
      Token start, Token periodBeforeName, Token endToken) {
    debugEvent("ConstructorReference");
    SimpleIdentifier constructorName = pop();
    TypeArgumentList typeArguments = pop();
    Identifier typeNameIdentifier = pop();
    push(ast.constructorName(ast.typeName(typeNameIdentifier, typeArguments),
        toAnalyzerToken(periodBeforeName), constructorName));
  }

  @override
  void endConstExpression(Token token) {
    debugEvent("ConstExpression");
    _handleInstanceCreation(token);
  }

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

  void _handleInstanceCreation(Token token) {
    MethodInvocation arguments = pop();
    ConstructorName constructorName = pop();
    push(ast.instanceCreationExpression(
        toAnalyzerToken(token), constructorName, arguments.argumentList));
  }

  @override
  void endNewExpression(Token token) {
    debugEvent("NewExpression");
    _handleInstanceCreation(token);
  }

  @override
  void handleParenthesizedExpression(BeginGroupToken token) {
    debugEvent("ParenthesizedExpression");
    Expression expression = pop();
    push(ast.parenthesizedExpression(
        toAnalyzerToken(token), expression, toAnalyzerToken(token.endGroup)));
  }

  void handleStringPart(Token token) {
    debugEvent("StringPart");
    push(token);
  }

  void doStringPart(Token token) {
    push(ast.simpleStringLiteral(toAnalyzerToken(token), token.lexeme));
  }

  void endLiteralString(int interpolationCount, Token endToken) {
    debugEvent("endLiteralString");
    if (interpolationCount == 0) {
      Token token = pop();
      String value = unescapeString(token.lexeme);
      push(ast.simpleStringLiteral(toAnalyzerToken(token), value));
    } else {
      List parts = popList(1 + interpolationCount * 2);
      Token first = parts.first;
      Token last = parts.last;
      Quote quote = analyzeQuote(first.lexeme);
      List<InterpolationElement> elements = <InterpolationElement>[];
      elements.add(ast.interpolationString(toAnalyzerToken(first),
          unescapeFirstStringPart(first.lexeme, quote)));
      for (int i = 1; i < parts.length - 1; i++) {
        var part = parts[i];
        if (part is Token) {
          elements
              .add(ast.interpolationString(toAnalyzerToken(part), part.lexeme));
        } else if (part is Expression) {
          elements.add(ast.interpolationExpression(null, part, null));
        } else {
          internalError(
              "Unexpected part in string interpolation: ${part.runtimeType}");
        }
      }
      elements.add(ast.interpolationString(
          toAnalyzerToken(last), unescapeLastStringPart(last.lexeme, quote)));
      push(ast.stringInterpolation(elements));
    }
  }

  void handleScript(Token token) {
    debugEvent("Script");
    push(ast.scriptTag(toAnalyzerToken(token)));
  }

  void handleStringJuxtaposition(int literalCount) {
    debugEvent("StringJuxtaposition");
    push(ast.adjacentStrings(popList(literalCount)));
  }

  void endArguments(int count, Token beginToken, Token endToken) {
    debugEvent("Arguments");
    List expressions = popList(count);
    ArgumentList arguments = ast.argumentList(
        toAnalyzerToken(beginToken), expressions, toAnalyzerToken(endToken));
    push(ast.methodInvocation(null, null, null, null, arguments));
  }

  void handleIdentifier(Token token, IdentifierContext context) {
    debugEvent("handleIdentifier");
    analyzer.Token analyzerToken = toAnalyzerToken(token);

    if (context.inSymbol) {
      push(analyzerToken);
      return;
    }

    SimpleIdentifier identifier = ast.simpleIdentifier(analyzerToken,
        isDeclaration: context.inDeclaration);
    if (context.inLibraryOrPartOfDeclaration) {
      if (!context.isContinuation) {
        push([identifier]);
      } else {
        push(identifier);
      }
    } else if (context == IdentifierContext.enumValueDeclaration) {
      // TODO(paulberry): analyzer's ASTs allow for enumerated values to have
      // metadata, but the spec doesn't permit it.
      List<Annotation> metadata;
      Comment comment = _toAnalyzerComment(token.precedingCommentTokens);
      push(ast.enumConstantDeclaration(comment, metadata, identifier));
    } else {
      if (context.isScopeReference) {
        String name = token.lexeme;
        Builder builder = scope.lookup(name, token.charOffset, uri);
        if (builder != null) {
          Element element = elementStore[builder];
          assert(element != null);
          identifier.staticElement = element;
        }
      } else if (context == IdentifierContext.classDeclaration) {
        className = identifier.name;
      }
      push(identifier);
    }
  }

  void endSend(Token beginToken, Token endToken) {
    debugEvent("Send");
    MethodInvocation arguments = pop();
    TypeArgumentList typeArguments = pop();
    if (arguments != null) {
      doInvocation(endToken, typeArguments, arguments);
    } else {
      doPropertyGet(endToken);
    }
  }

  void doInvocation(
      Token token, TypeArgumentList typeArguments, MethodInvocation arguments) {
    Expression receiver = pop();
    if (receiver is SimpleIdentifier) {
      arguments.methodName = receiver;
      if (typeArguments != null) {
        arguments.typeArguments = typeArguments;
      }
      push(arguments);
    } else {
      push(ast.functionExpressionInvocation(
          receiver, typeArguments, arguments.argumentList));
    }
  }

  void doPropertyGet(Token token) {}

  void endExpressionStatement(Token token) {
    debugEvent("ExpressionStatement");
    push(ast.expressionStatement(pop(), toAnalyzerToken(token)));
  }

  @override
  void handleEmptyFunctionBody(Token semicolon) {
    debugEvent("EmptyFunctionBody");
    // TODO(scheglov) Change the parser to not produce these modifiers.
    pop(); // star
    pop(); // async
    push(ast.emptyFunctionBody(toAnalyzerToken(semicolon)));
  }

  @override
  void handleEmptyStatement(Token token) {
    debugEvent("EmptyStatement");
    push(ast.emptyStatement(toAnalyzerToken(token)));
  }

  void endBlockFunctionBody(int count, Token beginToken, Token endToken) {
    debugEvent("BlockFunctionBody");
    List statements = popList(count);
    if (beginToken != null) {
      exitLocalScope();
    }
    Block block = ast.block(
        toAnalyzerToken(beginToken), statements, toAnalyzerToken(endToken));
    analyzer.Token star = pop();
    analyzer.Token asyncKeyword = pop();
    push(ast.blockFunctionBody(asyncKeyword, star, block));
  }

  void finishFunction(formals, asyncModifier, FunctionBody body) {
    debugEvent("finishFunction");
    Statement bodyStatement;
    if (body is EmptyFunctionBody) {
      bodyStatement = ast.emptyStatement(body.semicolon);
    } else if (body is ExpressionFunctionBody) {
      bodyStatement = ast.returnStatement(null, body.expression, null);
    } else {
      bodyStatement = (body as BlockFunctionBody).block;
    }
    var kernel = toKernel(bodyStatement, elementStore, library.library, scope);
    if (member is ProcedureBuilder) {
      ProcedureBuilder builder = member;
      builder.body = kernel;
    } else {
      internalError("Internal error: expected procedure, but got: $member");
    }
  }

  void beginCascade(Token token) {
    debugEvent("beginCascade");
    Expression expression = pop();
    push(token);
    if (expression is CascadeExpression) {
      push(expression);
    } else {
      push(ast.cascadeExpression(expression, <Expression>[]));
    }
    push(NullValue.CascadeReceiver);
  }

  void endCascade() {
    debugEvent("Cascade");
    Expression expression = pop();
    CascadeExpression receiver = pop();
    pop(); // Token.
    receiver.cascadeSections.add(expression);
    push(receiver);
  }

  void handleOperator(Token token) {
    debugEvent("Operator");
    push(toAnalyzerToken(token));
  }

  void handleSymbolVoid(Token token) {
    debugEvent("SymbolVoid");
    push(toAnalyzerToken(token));
  }

  void handleBinaryExpression(Token token) {
    debugEvent("BinaryExpression");
    if (identical(".", token.stringValue) ||
        identical("?.", token.stringValue) ||
        identical("..", token.stringValue)) {
      doDotExpression(token);
    } else {
      Expression right = pop();
      Expression left = pop();
      push(ast.binaryExpression(left, toAnalyzerToken(token), right));
    }
  }

  void doDotExpression(Token token) {
    Expression identifierOrInvoke = pop();
    Expression receiver = pop();
    if (identifierOrInvoke is SimpleIdentifier) {
      if (receiver is SimpleIdentifier && identical('.', token.stringValue)) {
        push(ast.prefixedIdentifier(
            receiver, toAnalyzerToken(token), identifierOrInvoke));
      } else {
        push(ast.propertyAccess(
            receiver, toAnalyzerToken(token), identifierOrInvoke));
      }
    } else if (identifierOrInvoke is MethodInvocation) {
      assert(identifierOrInvoke.target == null);
      identifierOrInvoke
        ..target = receiver
        ..operator = toAnalyzerToken(token);
      push(identifierOrInvoke);
    } else {
      internalError(
          "Unhandled property access: ${identifierOrInvoke.runtimeType}");
    }
  }

  void handleLiteralInt(Token token) {
    debugEvent("LiteralInt");
    push(ast.integerLiteral(toAnalyzerToken(token), int.parse(token.lexeme)));
  }

  void handleExpressionFunctionBody(Token arrowToken, Token endToken) {
    debugEvent("ExpressionFunctionBody");
    Expression expression = pop();
    analyzer.Token star = pop();
    analyzer.Token asyncKeyword = pop();
    assert(star == null);
    push(ast.expressionFunctionBody(asyncKeyword, toAnalyzerToken(arrowToken),
        expression, toAnalyzerToken(endToken)));
  }

  void endReturnStatement(
      bool hasExpression, Token beginToken, Token endToken) {
    debugEvent("ReturnStatement");
    Expression expression = hasExpression ? pop() : null;
    push(ast.returnStatement(
        toAnalyzerToken(beginToken), expression, toAnalyzerToken(endToken)));
  }

  void endIfStatement(Token ifToken, Token elseToken) {
    Statement elsePart = popIfNotNull(elseToken);
    Statement thenPart = pop();
    Expression condition = pop();
    BeginGroupToken leftParenthesis = ifToken.next;
    push(ast.ifStatement(
        toAnalyzerToken(ifToken),
        toAnalyzerToken(ifToken.next),
        condition,
        toAnalyzerToken(leftParenthesis.endGroup),
        thenPart,
        toAnalyzerToken(elseToken),
        elsePart));
  }

  void prepareInitializers() {
    debugEvent("prepareInitializers");
  }

  void handleNoInitializers() {
    debugEvent("NoInitializers");
    push(NullValue.ConstructorInitializerSeparator);
    push(NullValue.ConstructorInitializers);
  }

  void endInitializers(int count, Token beginToken, Token endToken) {
    debugEvent("Initializers");
    List<Object> initializerObjects = popList(count) ?? const [];

    push(beginToken);

    var initializers = <ConstructorInitializer>[];
    for (Object initializerObject in initializerObjects) {
      if (initializerObject is FunctionExpressionInvocation) {
        Expression function = initializerObject.function;
        if (function is SuperExpression) {
          initializers.add(ast.superConstructorInvocation(function.superKeyword,
              null, null, initializerObject.argumentList));
        } else {
          initializers.add(ast.redirectingConstructorInvocation(
              (function as ThisExpression).thisKeyword,
              null,
              null,
              initializerObject.argumentList));
        }
      } else if (initializerObject is MethodInvocation) {
        Expression target = initializerObject.target;
        if (target is SuperExpression) {
          initializers.add(ast.superConstructorInvocation(
              target.superKeyword,
              initializerObject.operator,
              initializerObject.methodName,
              initializerObject.argumentList));
        } else {
          initializers.add(ast.redirectingConstructorInvocation(
              (target as ThisExpression).thisKeyword,
              initializerObject.operator,
              initializerObject.methodName,
              initializerObject.argumentList));
        }
      } else if (initializerObject is AssignmentExpression) {
        analyzer.Token thisKeyword;
        analyzer.Token period;
        SimpleIdentifier fieldName;
        Expression left = initializerObject.leftHandSide;
        if (left is PropertyAccess) {
          var thisExpression = left.target as ThisExpression;
          thisKeyword = thisExpression.thisKeyword;
          period = left.operator;
          fieldName = left.propertyName;
        } else {
          fieldName = left as SimpleIdentifier;
        }
        initializers.add(ast.constructorFieldInitializer(
            thisKeyword,
            period,
            fieldName,
            initializerObject.operator,
            initializerObject.rightHandSide));
      }
    }

    push(initializers);
  }

  void endVariableInitializer(Token assignmentOperator) {
    debugEvent("VariableInitializer");
    assert(assignmentOperator.stringValue == "=");
    Expression initializer = pop();
    Identifier identifier = pop();
    // TODO(ahe): Don't push initializers, instead install them.
    push(ast.variableDeclaration(
        identifier, toAnalyzerToken(assignmentOperator), initializer));
  }

  @override
  void endWhileStatement(Token whileKeyword, Token endToken) {
    debugEvent("WhileStatement");
    Statement body = pop();
    ParenthesizedExpression condition = pop();
    exitContinueTarget();
    exitBreakTarget();
    push(ast.whileStatement(
        toAnalyzerToken(whileKeyword),
        condition.leftParenthesis,
        condition.expression,
        condition.rightParenthesis,
        body));
  }

  @override
  void endYieldStatement(Token yieldToken, Token starToken, Token endToken) {
    debugEvent("YieldStatement");
    assert(endToken.lexeme == ';');
    Expression expression = pop();
    push(ast.yieldStatement(toAnalyzerToken(yieldToken),
        toAnalyzerToken(starToken), expression, toAnalyzerToken(endToken)));
  }

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

  void endInitializedIdentifier(Token nameToken) {
    debugEvent("InitializedIdentifier");
    AstNode node = pop();
    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 SimpleIdentifier) {
      variable = ast.variableDeclaration(node, null, null);
    } else {
      internalError("unhandled identifier: ${node.runtimeType}");
    }
    push(variable);
    scope[variable.name.name] = variable.name.staticElement =
        new AnalyzerLocalVariableElemment(variable);
  }

  void endVariablesDeclaration(int count, Token endToken) {
    debugEvent("VariablesDeclaration");
    List<VariableDeclaration> variables = popList(count);
    TypeAnnotation type = pop();
    _Modifiers modifiers = pop();
    Token keyword = modifiers?.finalConstOrVarKeyword;
    List<Annotation> metadata = pop();
    Comment comment = pop();
    push(ast.variableDeclarationStatement(
        ast.variableDeclarationList(
            comment, metadata, toAnalyzerToken(keyword), type, variables),
        toAnalyzerToken(endToken)));
  }

  void handleAssignmentExpression(Token token) {
    debugEvent("AssignmentExpression");
    Expression rhs = pop();
    Expression lhs = pop();
    push(ast.assignmentExpression(lhs, toAnalyzerToken(token), rhs));
  }

  void endBlock(int count, Token beginToken, Token endToken) {
    debugEvent("Block");
    List<Statement> statements = popList(count) ?? <Statement>[];
    exitLocalScope();
    push(ast.block(
        toAnalyzerToken(beginToken), statements, toAnalyzerToken(endToken)));
  }

  void endForStatement(Token forKeyword, Token leftSeparator,
      int updateExpressionCount, Token endToken) {
    debugEvent("ForStatement");
    Statement body = pop();
    List<Expression> updates = popList(updateExpressionCount);
    Statement conditionStatement = pop();
    Object initializerPart = pop();
    exitLocalScope();
    exitContinueTarget();
    exitBreakTarget();
    BeginGroupToken leftParenthesis = forKeyword.next;

    VariableDeclarationList variableList;
    Expression initializer;
    if (initializerPart is VariableDeclarationStatement) {
      variableList = initializerPart.variables;
    } else {
      initializer = initializerPart as Expression;
    }

    Expression condition;
    analyzer.Token rightSeparator;
    if (conditionStatement is ExpressionStatement) {
      condition = conditionStatement.expression;
      rightSeparator = conditionStatement.semicolon;
    } else {
      rightSeparator = (conditionStatement as EmptyStatement).semicolon;
    }

    push(ast.forStatement(
        toAnalyzerToken(forKeyword),
        toAnalyzerToken(leftParenthesis),
        variableList,
        initializer,
        toAnalyzerToken(leftSeparator),
        condition,
        rightSeparator,
        updates,
        toAnalyzerToken(leftParenthesis.endGroup),
        body));
  }

  void handleLiteralList(
      int count, Token beginToken, Token constKeyword, Token endToken) {
    debugEvent("LiteralList");
    List<Expression> expressions = popList(count);
    TypeArgumentList typeArguments = pop();
    push(ast.listLiteral(toAnalyzerToken(constKeyword), typeArguments,
        toAnalyzerToken(beginToken), expressions, toAnalyzerToken(endToken)));
  }

  void handleAsyncModifier(Token asyncToken, Token starToken) {
    debugEvent("AsyncModifier");
    push(toAnalyzerToken(asyncToken) ?? NullValue.FunctionBodyAsyncToken);
    push(toAnalyzerToken(starToken) ?? NullValue.FunctionBodyStarToken);
  }

  void endAwaitExpression(Token beginToken, Token endToken) {
    debugEvent("AwaitExpression");
    push(ast.awaitExpression(toAnalyzerToken(beginToken), pop()));
  }

  void handleLiteralBool(Token token) {
    debugEvent("LiteralBool");
    bool value = identical(token.stringValue, "true");
    assert(value || identical(token.stringValue, "false"));
    push(ast.booleanLiteral(toAnalyzerToken(token), value));
  }

  void handleLiteralDouble(Token token) {
    debugEvent("LiteralDouble");
    push(ast.doubleLiteral(toAnalyzerToken(token), double.parse(token.lexeme)));
  }

  void handleLiteralNull(Token token) {
    debugEvent("LiteralNull");
    push(ast.nullLiteral(toAnalyzerToken(token)));
  }

  void handleLiteralMap(
      int count, Token beginToken, Token constKeyword, Token endToken) {
    debugEvent("LiteralMap");
    List<MapLiteralEntry> entries = popList(count) ?? <MapLiteralEntry>[];
    TypeArgumentList typeArguments = pop();
    push(ast.mapLiteral(toAnalyzerToken(constKeyword), typeArguments,
        toAnalyzerToken(beginToken), entries, toAnalyzerToken(endToken)));
  }

  void endLiteralMapEntry(Token colon, Token endToken) {
    debugEvent("LiteralMapEntry");
    Expression value = pop();
    Expression key = pop();
    push(ast.mapLiteralEntry(key, toAnalyzerToken(colon), value));
  }

  void endLiteralSymbol(Token hashToken, int tokenCount) {
    debugEvent("LiteralSymbol");
    List<analyzer.Token> components = popList(tokenCount);
    push(ast.symbolLiteral(toAnalyzerToken(hashToken), components));
  }

  @override
  void handleSuperExpression(Token token, IdentifierContext context) {
    debugEvent("SuperExpression");
    push(ast.superExpression(toAnalyzerToken(token)));
  }

  @override
  void handleThisExpression(Token token, IdentifierContext context) {
    debugEvent("ThisExpression");
    push(ast.thisExpression(toAnalyzerToken(token)));
  }

  void handleType(Token beginToken, Token endToken) {
    debugEvent("Type");
    TypeArgumentList arguments = pop();
    Identifier name = pop();
    // TODO(paulberry,ahe): what if the type doesn't resolve to a class
    // element?  Try to share code with BodyBuilder.builderToFirstExpression.
    KernelClassElement cls = name.staticElement;
    push(ast.typeName(name, arguments)..type = cls?.rawType);
  }

  @override
  void handleAssertStatement(Token assertKeyword, Token leftParenthesis,
      Token comma, Token rightParenthesis, Token semicolon) {
    debugEvent("AssertStatement");
    Expression message = popIfNotNull(comma);
    Expression condition = pop();
    push(ast.assertStatement(
        toAnalyzerToken(assertKeyword),
        toAnalyzerToken(leftParenthesis),
        condition,
        toAnalyzerToken(comma),
        message,
        toAnalyzerToken(rightParenthesis),
        toAnalyzerToken(semicolon)));
  }

  void handleAsOperator(Token operator, Token endToken) {
    debugEvent("AsOperator");
    TypeAnnotation type = pop();
    Expression expression = pop();
    push(ast.asExpression(expression, toAnalyzerToken(operator), type));
  }

  @override
  void handleBreakStatement(
      bool hasTarget, Token breakKeyword, Token semicolon) {
    debugEvent("BreakStatement");
    SimpleIdentifier label = hasTarget ? pop() : null;
    push(ast.breakStatement(
        toAnalyzerToken(breakKeyword), label, toAnalyzerToken(semicolon)));
  }

  @override
  void handleContinueStatement(
      bool hasTarget, Token continueKeyword, Token semicolon) {
    debugEvent("ContinueStatement");
    SimpleIdentifier label = hasTarget ? pop() : null;
    push(ast.continueStatement(
        toAnalyzerToken(continueKeyword), label, toAnalyzerToken(semicolon)));
  }

  void handleIsOperator(Token operator, Token not, Token endToken) {
    debugEvent("IsOperator");
    TypeAnnotation type = pop();
    Expression expression = pop();
    push(ast.isExpression(
        expression, toAnalyzerToken(operator), toAnalyzerToken(not), type));
  }

  void handleConditionalExpression(Token question, Token colon) {
    debugEvent("ConditionalExpression");
    Expression elseExpression = pop();
    Expression thenExpression = pop();
    Expression condition = pop();
    push(ast.conditionalExpression(condition, toAnalyzerToken(question),
        thenExpression, toAnalyzerToken(colon), elseExpression));
  }

  @override
  void endRedirectingFactoryBody(Token equalToken, Token endToken) {
    debugEvent("RedirectingFactoryBody");
    ConstructorName constructorName = pop();
    Token starToken = pop();
    Token asyncToken = pop();
    push(new _RedirectingFactoryBody(
        asyncToken, starToken, equalToken, constructorName));
  }

  @override
  void endRethrowStatement(Token rethrowToken, Token endToken) {
    debugEvent("RethrowStatement");
    RethrowExpression expression =
        ast.rethrowExpression(toAnalyzerToken(rethrowToken));
    // TODO(scheglov) According to the specification, 'rethrow' is a statement.
    push(ast.expressionStatement(expression, toAnalyzerToken(endToken)));
  }

  void endThrowExpression(Token throwToken, Token endToken) {
    debugEvent("ThrowExpression");
    push(ast.throwExpression(toAnalyzerToken(throwToken), pop()));
  }

  @override
  void endOptionalFormalParameters(
      int count, Token beginToken, Token endToken) {
    debugEvent("OptionalFormalParameters");
    push(new _OptionalFormalParameters(popList(count), beginToken, endToken));
  }

  void handleValuedFormalParameter(Token equals, Token token) {
    debugEvent("ValuedFormalParameter");
    Expression value = pop();
    push(new _ParameterDefaultValue(equals, value));
  }

  void handleFunctionType(Token functionToken, Token semicolon) {
    debugEvent("FunctionType");
    FormalParameterList parameters = pop();
    TypeParameterList typeParameters = pop();
    TypeAnnotation returnType = pop();
    push(ast.genericFunctionType(returnType, toAnalyzerToken(functionToken),
        typeParameters, parameters));
  }

  void handleFormalParameterWithoutValue(Token token) {
    debugEvent("FormalParameterWithoutValue");
    push(NullValue.ParameterDefaultValue);
  }

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

  @override
  void endForIn(Token awaitToken, Token forToken, Token leftParenthesis,
      Token inKeyword, Token rightParenthesis, Token endToken) {
    debugEvent("ForInExpression");
    Statement body = pop();
    Expression iterator = pop();
    Object variableOrDeclaration = pop();
    exitLocalScope();
    exitContinueTarget();
    exitBreakTarget();
    if (variableOrDeclaration is SimpleIdentifier) {
      push(ast.forEachStatementWithReference(
          toAnalyzerToken(awaitToken),
          toAnalyzerToken(forToken),
          toAnalyzerToken(leftParenthesis),
          variableOrDeclaration,
          toAnalyzerToken(inKeyword),
          iterator,
          toAnalyzerToken(rightParenthesis),
          body));
    } else {
      var statement = variableOrDeclaration as VariableDeclarationStatement;
      VariableDeclarationList variableList = statement.variables;
      push(ast.forEachStatementWithDeclaration(
          toAnalyzerToken(awaitToken),
          toAnalyzerToken(forToken),
          toAnalyzerToken(leftParenthesis),
          ast.declaredIdentifier(
              variableList.documentationComment,
              variableList.metadata,
              variableList.keyword,
              variableList.type,
              variableList.variables.single.name),
          toAnalyzerToken(inKeyword),
          iterator,
          toAnalyzerToken(rightParenthesis),
          body));
    }
  }

  void endFormalParameter(Token covariantKeyword, Token thisKeyword,
      Token nameToken, FormalParameterType kind) {
    debugEvent("FormalParameter");
    _ParameterDefaultValue defaultValue = pop();

    AstNode nameOrFunctionTypedParameter = pop();

    FormalParameter node;
    SimpleIdentifier name;
    if (nameOrFunctionTypedParameter is FormalParameter) {
      node = nameOrFunctionTypedParameter;
      name = nameOrFunctionTypedParameter.identifier;
    } else {
      name = nameOrFunctionTypedParameter;
      TypeAnnotation type = pop();
      _Modifiers modifiers = pop();
      Token keyword = modifiers?.finalConstOrVarKeyword;
      pop(); // TODO(paulberry): Metadata.
      Comment comment = pop();
      if (thisKeyword == null) {
        node = ast.simpleFormalParameter2(
            comment: comment,
            covariantKeyword: toAnalyzerToken(covariantKeyword),
            keyword: toAnalyzerToken(keyword),
            type: type,
            identifier: name);
      } else {
        // TODO(scheglov): Ideally the period token should be passed in.
        Token period = identical('.', thisKeyword.next?.stringValue)
            ? thisKeyword.next
            : null;
        node = ast.fieldFormalParameter2(
            comment: comment,
            covariantKeyword: toAnalyzerToken(covariantKeyword),
            keyword: toAnalyzerToken(keyword),
            type: type,
            thisKeyword: toAnalyzerToken(thisKeyword),
            period: toAnalyzerToken(period),
            identifier: name);
      }
    }

    ParameterKind analyzerKind = _toAnalyzerParameterKind(kind);
    if (analyzerKind != ParameterKind.REQUIRED) {
      node = ast.defaultFormalParameter(node, analyzerKind,
          toAnalyzerToken(defaultValue?.separator), defaultValue?.value);
    }

    if (name != null) {
      scope[name.name] =
          name.staticElement = new AnalyzerParameterElement(node);
    }
    push(node);
  }

  @override
  void endFunctionTypedFormalParameter(
      Token covariantKeyword, Token thisKeyword, FormalParameterType kind) {
    debugEvent("FunctionTypedFormalParameter");

    FormalParameterList formalParameters = pop();
    TypeParameterList typeParameters = pop();
    SimpleIdentifier name = pop();
    TypeAnnotation returnType = pop();

    {
      _Modifiers modifiers = pop();
      if (modifiers != null) {
        // TODO(scheglov): Report error.
        internalError('Unexpected modifier. Report an error.');
      }
    }

    pop(); // TODO(paulberry): Metadata.
    Comment comment = pop();

    FormalParameter node;
    if (thisKeyword == null) {
      node = ast.functionTypedFormalParameter2(
          comment: comment,
          covariantKeyword: toAnalyzerToken(covariantKeyword),
          returnType: returnType,
          identifier: name,
          typeParameters: typeParameters,
          parameters: formalParameters);
    } else {
      // TODO(scheglov): Ideally the period token should be passed in.
      Token period = identical('.', thisKeyword?.next?.stringValue)
          ? thisKeyword.next
          : null;
      node = ast.fieldFormalParameter2(
          comment: comment,
          covariantKeyword: toAnalyzerToken(covariantKeyword),
          type: returnType,
          thisKeyword: toAnalyzerToken(thisKeyword),
          period: toAnalyzerToken(period),
          identifier: name,
          typeParameters: typeParameters,
          parameters: formalParameters);
    }

    scope[name.name] = name.staticElement = new AnalyzerParameterElement(node);
    push(node);
  }

  void endFormalParameters(int count, Token beginToken, Token endToken) {
    debugEvent("FormalParameters");
    List rawParameters = popList(count) ?? const <Object>[];
    List<FormalParameter> parameters = <FormalParameter>[];
    Token leftDelimiter;
    Token rightDelimiter;
    for (Object raw in rawParameters) {
      if (raw is _OptionalFormalParameters) {
        parameters.addAll(raw.parameters);
        leftDelimiter = raw.leftDelimiter;
        rightDelimiter = raw.rightDelimiter;
      } else {
        parameters.add(raw as FormalParameter);
      }
    }
    push(ast.formalParameterList(
        toAnalyzerToken(beginToken),
        parameters,
        toAnalyzerToken(leftDelimiter),
        toAnalyzerToken(rightDelimiter),
        toAnalyzerToken(endToken)));
  }

  @override
  void endSwitchBlock(int caseCount, Token leftBracket, Token rightBracket) {
    debugEvent("SwitchBlock");
    List<List<SwitchMember>> membersList = popList(caseCount);
    exitBreakTarget();
    exitLocalScope();
    List<SwitchMember> members =
        membersList?.expand((members) => members)?.toList() ?? <SwitchMember>[];
    push(leftBracket);
    push(members);
    push(rightBracket);
  }

  @override
  void handleSwitchCase(
      int labelCount,
      int expressionCount,
      Token defaultKeyword,
      int statementCount,
      Token firstToken,
      Token endToken) {
    debugEvent("SwitchCase");
    List<Statement> statements = popList(statementCount);
    List<SwitchMember> members = popList(expressionCount) ?? [];
    List<Label> labels = popList(labelCount);
    if (defaultKeyword != null) {
      members.add(ast.switchDefault(
          <Label>[], defaultKeyword, defaultKeyword.next, <Statement>[]));
    }
    members.last.statements.addAll(statements);
    members.first.labels.addAll(labels);
    push(members);
  }

  @override
  void handleCaseMatch(Token caseKeyword, Token colon) {
    debugEvent("CaseMatch");
    Expression expression = pop();
    push(ast.switchCase(
        <Label>[], caseKeyword, expression, colon, <Statement>[]));
  }

  @override
  void endSwitchStatement(Token switchKeyword, Token endToken) {
    debugEvent("SwitchStatement");
    Token rightBracket = pop();
    List<SwitchMember> members = pop();
    Token leftBracket = pop();
    ParenthesizedExpression expression = pop();
    push(ast.switchStatement(
        switchKeyword,
        expression.leftParenthesis,
        expression.expression,
        expression.rightParenthesis,
        leftBracket,
        members,
        rightBracket));
  }

  void handleCatchBlock(Token onKeyword, Token catchKeyword) {
    debugEvent("CatchBlock");
    Block body = pop();
    FormalParameterList catchParameterList = popIfNotNull(catchKeyword);
    TypeAnnotation type = popIfNotNull(onKeyword);
    SimpleIdentifier exception;
    SimpleIdentifier stackTrace;
    if (catchParameterList != null) {
      List<FormalParameter> catchParameters = catchParameterList.parameters;
      if (catchParameters.length > 0) {
        exception = catchParameters[0].identifier;
      }
      if (catchParameters.length > 1) {
        stackTrace = catchParameters[1].identifier;
      }
    }
    push(ast.catchClause(
        toAnalyzerToken(onKeyword),
        type,
        toAnalyzerToken(catchKeyword),
        catchParameterList?.leftParenthesis,
        exception,
        null,
        stackTrace,
        catchParameterList?.rightParenthesis,
        body));
  }

  @override
  void handleFinallyBlock(Token finallyKeyword) {
    debugEvent("FinallyBlock");
    // The finally block is popped in "endTryStatement".
  }

  void endTryStatement(int catchCount, Token tryKeyword, Token finallyKeyword) {
    Block finallyBlock = popIfNotNull(finallyKeyword);
    List<CatchClause> catchClauses = popList(catchCount);
    Block body = pop();
    push(ast.tryStatement(toAnalyzerToken(tryKeyword), body, catchClauses,
        toAnalyzerToken(finallyKeyword), finallyBlock));
  }

  @override
  void handleLabel(Token colon) {
    debugEvent("Label");
    SimpleIdentifier name = pop();
    push(ast.label(name, colon));
  }

  void handleNoExpression(Token token) {
    debugEvent("NoExpression");
    push(NullValue.Expression);
  }

  void handleIndexedExpression(
      Token openCurlyBracket, Token closeCurlyBracket) {
    debugEvent("IndexedExpression");
    Expression index = pop();
    Expression target = pop();
    if (target == null) {
      CascadeExpression receiver = pop();
      Token token = peek();
      push(receiver);
      IndexExpression expression = ast.indexExpressionForCascade(
          toAnalyzerToken(token),
          toAnalyzerToken(openCurlyBracket),
          index,
          toAnalyzerToken(closeCurlyBracket));
      assert(expression.isCascaded);
      push(expression);
    } else {
      push(ast.indexExpressionForTarget(
          target,
          toAnalyzerToken(openCurlyBracket),
          index,
          toAnalyzerToken(closeCurlyBracket)));
    }
  }

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

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

  @override
  Token handleUnrecoverableError(Token token, FastaMessage message) {
    if (message.code == codeExpectedFunctionBody) {
      if (identical('native', token.stringValue) && parser != null) {
        Token nativeKeyword = token;
        Token semicolon = parser.parseLiteralString(token.next);
        token = parser.expectSemicolon(semicolon);
        StringLiteral name = pop();
        pop(); // star
        pop(); // async
        push(ast.nativeFunctionBody(
            toAnalyzerToken(nativeKeyword), name, toAnalyzerToken(semicolon)));
        return token;
      }
    } else if (message.code == codeExpectedExpression) {
      String lexeme = token.lexeme;
      if (identical('async', lexeme) || identical('yield', lexeme)) {
        errorReporter?.reportErrorForOffset(
            ParserErrorCode.ASYNC_KEYWORD_USED_AS_IDENTIFIER,
            token.charOffset,
            token.charCount);
        push(ast.simpleIdentifier(toAnalyzerToken(token)));
        return token;
      }
    }
    return super.handleUnrecoverableError(token, message);
  }

  void handleUnaryPrefixExpression(Token token) {
    debugEvent("UnaryPrefixExpression");
    push(ast.prefixExpression(toAnalyzerToken(token), pop()));
  }

  void handleUnaryPrefixAssignmentExpression(Token token) {
    debugEvent("UnaryPrefixAssignmentExpression");
    push(ast.prefixExpression(toAnalyzerToken(token), pop()));
  }

  void handleUnaryPostfixAssignmentExpression(Token token) {
    debugEvent("UnaryPostfixAssignmentExpression");
    push(ast.postfixExpression(pop(), toAnalyzerToken(token)));
  }

  void handleModifier(Token token) {
    debugEvent("Modifier");
    push(token);
  }

  void handleModifiers(int count) {
    debugEvent("Modifiers");
    if (count == 0) {
      push(NullValue.Modifiers);
    } else {
      push(new _Modifiers(popList(count)));
    }
  }

  void endTopLevelMethod(Token beginToken, Token getOrSet, Token endToken) {
    // TODO(paulberry): set up scopes properly to resolve parameters and type
    // variables.
    debugEvent("TopLevelMethod");
    FunctionBody body = pop();
    FormalParameterList parameters = pop();
    TypeParameterList typeParameters = pop();
    SimpleIdentifier name = pop();
    analyzer.Token propertyKeyword = toAnalyzerToken(getOrSet);
    TypeAnnotation returnType = pop();
    _Modifiers modifiers = pop();
    Token externalKeyword = modifiers?.externalKeyword;
    List<Annotation> metadata = pop();
    Comment comment = pop();
    push(ast.functionDeclaration(
        comment,
        metadata,
        toAnalyzerToken(externalKeyword),
        returnType,
        propertyKeyword,
        name,
        ast.functionExpression(typeParameters, parameters, body)));
  }

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

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

  @override
  void endCompilationUnit(int count, Token endToken) {
    debugEvent("CompilationUnit");
    List<Object> elements = popList(count);
    Token beginToken = pop();

    ScriptTag scriptTag = null;
    var directives = <Directive>[];
    var declarations = <CompilationUnitMember>[];
    if (elements != null) {
      for (AstNode node in elements) {
        if (node is ScriptTag) {
          scriptTag = node;
        } else if (node is Directive) {
          directives.add(node);
        } else if (node is CompilationUnitMember) {
          declarations.add(node);
        } else {
          internalError(
              'Unrecognized compilation unit member: ${node.runtimeType}');
        }
      }
    }

    push(ast.compilationUnit(
        beginToken, scriptTag, directives, declarations, endToken));
  }

  void endImport(Token importKeyword, Token deferredKeyword, Token asKeyword,
      Token semicolon) {
    debugEvent("Import");
    List<Combinator> combinators = pop();
    SimpleIdentifier prefix;
    if (asKeyword != null) prefix = pop();
    List<Configuration> configurations = pop();
    StringLiteral uri = pop();
    List<Annotation> metadata = pop();
    assert(metadata == null); // TODO(paulberry): fix.
    Comment comment = pop();
    push(ast.importDirective(
        comment,
        metadata,
        toAnalyzerToken(importKeyword),
        uri,
        configurations,
        toAnalyzerToken(deferredKeyword),
        toAnalyzerToken(asKeyword),
        prefix,
        combinators,
        toAnalyzerToken(semicolon)));
  }

  void endExport(Token exportKeyword, Token semicolon) {
    debugEvent("Export");
    List<Combinator> combinators = pop();
    List<Configuration> configurations = pop();
    StringLiteral uri = pop();
    List<Annotation> metadata = pop();
    assert(metadata == null);
    Comment comment = pop();
    push(ast.exportDirective(comment, metadata, toAnalyzerToken(exportKeyword),
        uri, configurations, combinators, toAnalyzerToken(semicolon)));
  }

  @override
  void endDottedName(int count, Token firstIdentifier) {
    debugEvent("DottedName");
    List<SimpleIdentifier> components = popList(count);
    push(ast.dottedName(components));
  }

  @override
  void endDoWhileStatement(
      Token doKeyword, Token whileKeyword, Token semicolon) {
    debugEvent("DoWhileStatement");
    ParenthesizedExpression condition = pop();
    Statement body = pop();
    exitContinueTarget();
    exitBreakTarget();
    push(ast.doStatement(
        toAnalyzerToken(doKeyword),
        body,
        toAnalyzerToken(whileKeyword),
        condition.leftParenthesis,
        condition.expression,
        condition.rightParenthesis,
        toAnalyzerToken(semicolon)));
  }

  void endConditionalUri(Token ifKeyword, Token equalitySign) {
    debugEvent("ConditionalUri");
    StringLiteral libraryUri = pop();
    // TODO(paulberry,ahe): the parser should report the right paren token to
    // the listener.
    Token rightParen = null;
    StringLiteral value;
    if (equalitySign != null) {
      value = pop();
    }
    DottedName name = pop();
    // TODO(paulberry,ahe): what if there is no `(` token due to an error in the
    // file being parsed?  It seems like we need the parser to do adequate error
    // recovery and then report both the ifKeyword and leftParen tokens to the
    // listener.
    Token leftParen = ifKeyword.next;
    push(ast.configuration(
        toAnalyzerToken(ifKeyword),
        toAnalyzerToken(leftParen),
        name,
        toAnalyzerToken(equalitySign),
        value,
        toAnalyzerToken(rightParen),
        libraryUri));
  }

  @override
  void endConditionalUris(int count) {
    debugEvent("ConditionalUris");
    push(popList(count) ?? NullValue.ConditionalUris);
  }

  @override
  void endIdentifierList(int count) {
    debugEvent("IdentifierList");
    push(popList(count) ?? NullValue.IdentifierList);
  }

  @override
  void endShow(Token showKeyword) {
    debugEvent("Show");
    List<SimpleIdentifier> shownNames = pop();
    push(ast.showCombinator(toAnalyzerToken(showKeyword), shownNames));
  }

  @override
  void endHide(Token hideKeyword) {
    debugEvent("Hide");
    List<SimpleIdentifier> hiddenNames = pop();
    push(ast.hideCombinator(toAnalyzerToken(hideKeyword), hiddenNames));
  }

  @override
  void endTypeList(int count) {
    debugEvent("TypeList");
    push(popList(count) ?? NullValue.TypeList);
  }

  @override
  void endClassBody(int memberCount, Token beginToken, Token endToken) {
    debugEvent("ClassBody");
    push(new _ClassBody(
        beginToken, popList(memberCount) ?? <ClassMember>[], endToken));
  }

  @override
  void endClassDeclaration(
      int interfacesCount,
      Token beginToken,
      Token classKeyword,
      Token extendsKeyword,
      Token implementsKeyword,
      Token endToken) {
    debugEvent("ClassDeclaration");
    _ClassBody body = pop();
    ImplementsClause implementsClause;
    if (implementsKeyword != null) {
      List<TypeName> interfaces = popList(interfacesCount);
      implementsClause =
          ast.implementsClause(toAnalyzerToken(implementsKeyword), interfaces);
    }
    ExtendsClause extendsClause;
    WithClause withClause;
    var supertype = pop();
    if (supertype == null) {
      // No extends clause
    } else if (supertype is TypeName) {
      extendsClause =
          ast.extendsClause(toAnalyzerToken(extendsKeyword), supertype);
    } else if (supertype is _MixinApplication) {
      extendsClause = ast.extendsClause(
          toAnalyzerToken(extendsKeyword), supertype.supertype);
      withClause = ast.withClause(
          toAnalyzerToken(supertype.withKeyword), supertype.mixinTypes);
    } else {
      internalError('Unexpected kind of supertype ${supertype.runtimeType}');
    }
    TypeParameterList typeParameters = pop();
    SimpleIdentifier name = pop();
    assert(className == name.name);
    className = null;
    _Modifiers modifiers = pop();
    Token abstractKeyword = modifiers?.abstractKeyword;
    List<Annotation> metadata = pop();
    Comment comment = pop();
    push(ast.classDeclaration(
        comment,
        metadata,
        toAnalyzerToken(abstractKeyword),
        toAnalyzerToken(classKeyword),
        name,
        typeParameters,
        extendsClause,
        withClause,
        implementsClause,
        toAnalyzerToken(body.beginToken),
        body.members,
        toAnalyzerToken(body.endToken)));
  }

  @override
  void endMixinApplication(Token withKeyword) {
    debugEvent("MixinApplication");
    List<TypeName> mixinTypes = pop();
    TypeName supertype = pop();
    push(new _MixinApplication(supertype, withKeyword, mixinTypes));
  }

  @override
  void endNamedMixinApplication(Token beginToken, Token classKeyword,
      Token equalsToken, Token implementsKeyword, Token endToken) {
    debugEvent("NamedMixinApplication");
    ImplementsClause implementsClause;
    if (implementsKeyword != null) {
      List<TypeName> interfaces = pop();
      implementsClause =
          ast.implementsClause(toAnalyzerToken(implementsKeyword), interfaces);
    }
    _MixinApplication mixinApplication = pop();
    var superclass = mixinApplication.supertype;
    var withClause = ast.withClause(
        toAnalyzerToken(mixinApplication.withKeyword),
        mixinApplication.mixinTypes);
    analyzer.Token equals = toAnalyzerToken(equalsToken);
    TypeParameterList typeParameters = pop();
    SimpleIdentifier name = pop();
    _Modifiers modifiers = pop();
    Token abstractKeyword = modifiers?.abstractKeyword;
    List<Annotation> metadata = pop();
    Comment comment = pop();
    push(ast.classTypeAlias(
        comment,
        metadata,
        toAnalyzerToken(classKeyword),
        name,
        typeParameters,
        equals,
        toAnalyzerToken(abstractKeyword),
        superclass,
        withClause,
        implementsClause,
        toAnalyzerToken(endToken)));
  }

  @override
  void endLabeledStatement(int labelCount) {
    debugEvent("LabeledStatement");
    Statement statement = pop();
    List<Label> labels = popList(labelCount);
    push(ast.labeledStatement(labels, statement));
  }

  @override
  void endLibraryName(Token libraryKeyword, Token semicolon) {
    debugEvent("LibraryName");
    List<SimpleIdentifier> libraryName = pop();
    var name = ast.libraryIdentifier(libraryName);
    List<Annotation> metadata = pop();
    Comment comment = pop();
    push(ast.libraryDirective(comment, metadata,
        toAnalyzerToken(libraryKeyword), name, toAnalyzerToken(semicolon)));
  }

  @override
  void handleQualified(Token period) {
    SimpleIdentifier identifier = pop();
    var prefix = pop();
    if (prefix is List) {
      // We're just accumulating components into a list.
      prefix.add(identifier);
      push(prefix);
    } else if (prefix is SimpleIdentifier) {
      // TODO(paulberry): resolve [identifier].  Note that BodyBuilder handles
      // this situation using SendAccessor.
      push(ast.prefixedIdentifier(prefix, toAnalyzerToken(period), identifier));
    } else {
      // TODO(paulberry): implement.
      logEvent('Qualified with >1 dot');
    }
  }

  @override
  void endPart(Token partKeyword, Token semicolon) {
    debugEvent("Part");
    StringLiteral uri = pop();
    List<Annotation> metadata = pop();
    Comment comment = pop();
    push(ast.partDirective(comment, metadata, toAnalyzerToken(partKeyword), uri,
        toAnalyzerToken(semicolon)));
  }

  @override
  void endPartOf(Token partKeyword, Token semicolon, bool hasName) {
    debugEvent("PartOf");
    List<SimpleIdentifier> libraryName = pop();
    var name = ast.libraryIdentifier(libraryName);
    StringLiteral uri = null; // TODO(paulberry)
    // TODO(paulberry,ahe): seems hacky.  It would be nice if the parser passed
    // in a reference to the "of" keyword.
    var ofKeyword = partKeyword.next;
    List<Annotation> metadata = pop();
    Comment comment = pop();
    push(ast.partOfDirective(comment, metadata, toAnalyzerToken(partKeyword),
        toAnalyzerToken(ofKeyword), uri, name, toAnalyzerToken(semicolon)));
  }

  void endUnnamedFunction(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("UnnamedFunction");
    FunctionBody body = pop();
    FormalParameterList parameters = pop();
    TypeParameterList typeParameters = pop();
    push(ast.functionExpression(typeParameters, parameters, body));
  }

  @override
  void handleNoFieldInitializer(Token token) {
    debugEvent("NoFieldInitializer");
    SimpleIdentifier name = pop();
    push(ast.variableDeclaration(name, null, null));
  }

  @override
  void endFactoryMethod(
      Token beginToken, Token factoryKeyword, Token semicolon) {
    debugEvent("FactoryMethod");

    FunctionBody body;
    Token separator;
    ConstructorName redirectedConstructor;
    Object bodyObject = pop();
    if (bodyObject is FunctionBody) {
      body = bodyObject;
    } else if (bodyObject is _RedirectingFactoryBody) {
      separator = bodyObject.equalToken;
      redirectedConstructor = bodyObject.constructorName;
      body = ast.emptyFunctionBody(toAnalyzerToken(semicolon));
    } else {
      internalError('Unexpected body object: ${bodyObject.runtimeType}');
    }

    FormalParameterList parameters = pop();
    ConstructorName constructorName = pop();
    _Modifiers modifiers = pop();
    List<Annotation> metadata = pop();
    Comment comment = pop();

    // Decompose the preliminary ConstructorName into the type name and
    // the actual constructor name.
    SimpleIdentifier returnType;
    analyzer.Token period;
    SimpleIdentifier name;
    Identifier typeName = constructorName.type.name;
    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);
    }

    push(ast.constructorDeclaration(
        comment,
        metadata,
        toAnalyzerToken(modifiers?.externalKeyword),
        toAnalyzerToken(modifiers?.finalConstOrVarKeyword),
        toAnalyzerToken(factoryKeyword),
        ast.simpleIdentifier(returnType.token),
        period,
        name,
        parameters,
        toAnalyzerToken(separator),
        null,
        redirectedConstructor,
        body));
  }

  void endFieldInitializer(Token assignment, Token token) {
    debugEvent("FieldInitializer");
    Expression initializer = pop();
    SimpleIdentifier name = pop();
    push(ast.variableDeclaration(
        name, toAnalyzerToken(assignment), initializer));
  }

  @override
  void endFunction(Token getOrSet, Token endToken) {
    debugEvent("Function");
    FunctionBody body = pop();
    pop(); // constructor initializers
    pop(); // separator before constructor initializers
    FormalParameterList parameters = pop();
    TypeParameterList typeParameters = pop();
    // TODO(scheglov) It is an error if "getOrSet" is not null.
    push(ast.functionExpression(typeParameters, parameters, body));
  }

  @override
  void endFunctionDeclaration(Token token) {
    debugEvent("FunctionDeclaration");
    FunctionExpression functionExpression = pop();
    SimpleIdentifier name = pop();
    TypeAnnotation returnType = pop();
    pop(); // modifiers
    push(ast.functionDeclarationStatement(ast.functionDeclaration(
        null, null, null, returnType, null, name, functionExpression)));
  }

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

  void endTopLevelFields(int count, Token beginToken, Token endToken) {
    debugEvent("TopLevelFields");
    List<VariableDeclaration> variables = popList(count);
    TypeAnnotation type = pop();
    _Modifiers modifiers = pop();
    Token keyword = modifiers?.finalConstOrVarKeyword;
    var variableList = ast.variableDeclarationList(
        null, null, toAnalyzerToken(keyword), type, variables);
    List<Annotation> metadata = pop();
    Comment comment = pop();
    push(ast.topLevelVariableDeclaration(
        comment, metadata, variableList, toAnalyzerToken(endToken)));
  }

  @override
  void endTypeVariable(Token token, Token extendsOrSuper) {
    // 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("TypeVariable");
    TypeAnnotation bound = pop();
    SimpleIdentifier name = pop();
    List<Annotation> metadata = pop();
    Comment comment = pop();
    push(ast.typeParameter(
        comment, metadata, name, toAnalyzerToken(extendsOrSuper), bound));
  }

  @override
  void endTypeVariables(int count, Token beginToken, Token endToken) {
    debugEvent("TypeVariables");
    List<TypeParameter> typeParameters = popList(count);
    push(ast.typeParameterList(toAnalyzerToken(beginToken), typeParameters,
        toAnalyzerToken(endToken)));
  }

  @override
  void endMethod(Token getOrSet, Token beginToken, Token endToken) {
    debugEvent("Method");
    FunctionBody body = pop();
    ConstructorName redirectedConstructor = null; // TODO(paulberry)
    List<ConstructorInitializer> initializers = pop() ?? const [];
    Token separator = pop();
    FormalParameterList parameters = pop();
    TypeParameterList typeParameters = pop();
    var name = pop();
    TypeAnnotation returnType = pop();
    _Modifiers modifiers = pop();
    List<Annotation> metadata = pop();
    Comment comment = pop();

    void constructor(SimpleIdentifier returnType, analyzer.Token period,
        SimpleIdentifier name) {
      push(ast.constructorDeclaration(
          comment,
          metadata,
          toAnalyzerToken(modifiers?.externalKeyword),
          toAnalyzerToken(modifiers?.finalConstOrVarKeyword),
          null, // TODO(paulberry): factoryKeyword
          ast.simpleIdentifier(returnType.token),
          period,
          name,
          parameters,
          toAnalyzerToken(separator),
          initializers,
          redirectedConstructor,
          body));
    }

    void method(Token operatorKeyword, SimpleIdentifier name) {
      push(ast.methodDeclaration(
          comment,
          metadata,
          toAnalyzerToken(modifiers?.externalKeyword),
          toAnalyzerToken(
              modifiers?.abstractKeyword ?? modifiers?.staticKeyword),
          returnType,
          toAnalyzerToken(getOrSet),
          toAnalyzerToken(operatorKeyword),
          name,
          typeParameters,
          parameters,
          body));
    }

    if (name is SimpleIdentifier) {
      if (name.name == className) {
        constructor(name, null, null);
      } else {
        method(null, name);
      }
    } else if (name is _OperatorName) {
      method(name.operatorKeyword, name.name);
    } else if (name is PrefixedIdentifier) {
      constructor(name.prefix, name.period, name.identifier);
    } else {
      throw new UnimplementedError();
    }
  }

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

  @override
  void handleVoidKeyword(Token token) {
    debugEvent("VoidKeyword");
    // TODO(paulberry): is this sufficient, or do we need to hook the "void"
    // keyword up to an element?
    handleIdentifier(token, IdentifierContext.typeReference);
    handleNoTypeArguments(token);
    handleType(token, token);
  }

  @override
  void endFunctionTypeAlias(
      Token typedefKeyword, Token equals, Token endToken) {
    debugEvent("FunctionTypeAlias");
    if (equals == null) {
      FormalParameterList parameters = pop();
      TypeParameterList typeParameters = pop();
      SimpleIdentifier name = pop();
      TypeAnnotation returnType = pop();
      List<Annotation> metadata = pop();
      Comment comment = pop();
      push(ast.functionTypeAlias(
          comment,
          metadata,
          toAnalyzerToken(typedefKeyword),
          returnType,
          name,
          typeParameters,
          parameters,
          toAnalyzerToken(endToken)));
    } else {
      TypeAnnotation type = pop();
      TypeParameterList templateParameters = pop();
      SimpleIdentifier name = pop();
      List<Annotation> metadata = pop();
      Comment comment = pop();
      if (type is! GenericFunctionType) {
        // TODO(paulberry) Generate an error and recover (better than
        // this).
        type = null;
      }
      push(ast.genericTypeAlias(
          comment,
          metadata,
          toAnalyzerToken(typedefKeyword),
          name,
          templateParameters,
          toAnalyzerToken(equals),
          type,
          toAnalyzerToken(endToken)));
    }
  }

  @override
  void endEnum(Token enumKeyword, Token endBrace, int count) {
    debugEvent("Enum");
    List<EnumConstantDeclaration> constants = popList(count);
    // TODO(paulberry,ahe): the parser should pass in the openBrace token.
    var openBrace = enumKeyword.next.next as BeginGroupToken;
    // TODO(paulberry): what if the '}' is missing and the parser has performed
    // error recovery?
    Token closeBrace = openBrace.endGroup;
    SimpleIdentifier name = pop();
    List<Annotation> metadata = pop();
    Comment comment = pop();
    push(ast.enumDeclaration(
        comment,
        metadata,
        toAnalyzerToken(enumKeyword),
        name,
        toAnalyzerToken(openBrace),
        constants,
        toAnalyzerToken(closeBrace)));
  }

  @override
  void endTypeArguments(int count, Token beginToken, Token endToken) {
    debugEvent("TypeArguments");
    List<TypeAnnotation> arguments = popList(count);
    push(ast.typeArgumentList(
        toAnalyzerToken(beginToken), arguments, toAnalyzerToken(endToken)));
  }

  @override
  void endFields(
      int count, Token covariantKeyword, Token beginToken, Token endToken) {
    debugEvent("Fields");
    List<VariableDeclaration> variables = popList(count);
    TypeAnnotation type = pop();
    _Modifiers modifiers = pop();
    var variableList = ast.variableDeclarationList(null, null,
        toAnalyzerToken(modifiers?.finalConstOrVarKeyword), type, variables);
    List<Annotation> metadata = pop();
    Comment comment = pop();
    push(ast.fieldDeclaration2(
        comment: comment,
        metadata: metadata,
        covariantKeyword: toAnalyzerToken(covariantKeyword),
        staticKeyword: toAnalyzerToken(modifiers?.staticKeyword),
        fieldList: variableList,
        semicolon: toAnalyzerToken(endToken)));
  }

  @override
  void handleOperatorName(Token operatorKeyword, Token token) {
    debugEvent("OperatorName");
    push(new _OperatorName(operatorKeyword,
        ast.simpleIdentifier(toAnalyzerToken(token), isDeclaration: true)));
  }

  @override
  void beginMetadataStar(Token token) {
    debugEvent("beginMetadataStar");
    if (token.precedingComments != null) {
      push(_toAnalyzerComment(token.precedingCommentTokens));
    } else {
      push(NullValue.Comments);
    }
  }

  @override
  void endMetadata(Token beginToken, Token periodBeforeName, Token endToken) {
    debugEvent("Metadata");
    MethodInvocation invocation = pop();
    SimpleIdentifier constructorName = periodBeforeName != null ? pop() : null;
    pop(); // Type arguments, not allowed.
    Identifier name = pop();
    push(ast.annotation(
        toAnalyzerToken(beginToken),
        name,
        toAnalyzerToken(periodBeforeName),
        constructorName,
        invocation?.argumentList));
  }

  ParameterKind _toAnalyzerParameterKind(FormalParameterType type) {
    if (type == FormalParameterType.POSITIONAL) {
      return ParameterKind.POSITIONAL;
    } else if (type == FormalParameterType.NAMED) {
      return ParameterKind.NAMED;
    } else {
      return ParameterKind.REQUIRED;
    }
  }

  Comment _toAnalyzerComment(Token comments) {
    if (comments == null) return null;

    // This is temporary placeholder code to get tests to pass.
    // TODO(paulberry): after analyzer and fasta token representations are
    // unified, refactor the code in analyzer's parser that handles
    // documentation comments so that it is reusable, and reuse it here.
    // See Parser.parseCommentAndMetadata
    var tokens = <analyzer.Token>[toAnalyzerCommentToken(comments)];
    var references = <CommentReference>[];
    return ast.documentationComment(tokens, references);
  }

  @override
  void debugEvent(String name) {
    // printEvent(name);
  }

  @override
  Token injectGenericCommentTypeAssign(Token token) {
    // TODO(paulberry,scheglov,ahe): figure out how to share these generic
    // comment methods with BodyBuilder.
    return _injectGenericComment(
        token, TokenType.GENERIC_METHOD_TYPE_ASSIGN, 3);
  }

  @override
  Token injectGenericCommentTypeList(Token token) {
    return _injectGenericComment(token, TokenType.GENERIC_METHOD_TYPE_LIST, 2);
  }

  @override
  Token replaceTokenWithGenericCommentTypeAssign(
      Token tokenToStartReplacing, Token tokenWithComment) {
    Token injected = injectGenericCommentTypeAssign(tokenWithComment);
    if (!identical(injected, tokenWithComment)) {
      Token prev = tokenToStartReplacing.previous;
      prev.setNextWithoutSettingPrevious(injected);
      tokenToStartReplacing = injected;
      tokenToStartReplacing.previous = prev;
    }
    return tokenToStartReplacing;
  }

  /// Check if the given [token] has a comment token with the given [info],
  /// which should be either [TokenType.GENERIC_METHOD_TYPE_ASSIGN] or
  /// [TokenType.GENERIC_METHOD_TYPE_LIST].  If found, parse the comment
  /// into tokens and inject into the token stream before the [token].
  Token _injectGenericComment(Token token, TokenType info, int prefixLen) {
    if (parseGenericMethodComments) {
      CommentToken t = token.precedingCommentTokens;
      for (; t != null; t = t.next) {
        if (t.info == info) {
          String code = t.lexeme.substring(prefixLen, t.lexeme.length - 2);
          Token tokens = _scanGenericMethodComment(code, t.offset + prefixLen);
          if (tokens != null) {
            // Remove the token from the comment stream.
            t.remove();
            // Insert the tokens into the stream.
            _injectTokenList(token, tokens);
            return tokens;
          }
        }
      }
    }
    return token;
  }

  void _injectTokenList(Token beforeToken, Token firstToken) {
    // Scanner creates a cyclic EOF token.
    Token lastToken = firstToken;
    while (lastToken.next.info != TokenType.EOF) {
      lastToken = lastToken.next;
    }
    // Inject these new tokens into the stream.
    Token previous = beforeToken.previous;
    lastToken.setNext(beforeToken);
    previous.setNext(firstToken);
    beforeToken = firstToken;
  }

  /// Scans the given [code], and returns the tokens, otherwise returns `null`.
  Token _scanGenericMethodComment(String code, int offset) {
    var scanner = new SubStringScanner(offset, code);
    Token firstToken = scanner.tokenize();
    if (scanner.hasErrors) {
      return null;
    }
    return firstToken;
  }
}

/// Data structure placed on the stack to represent a class body.
///
/// This is needed because analyzer has no separate AST representation of a
/// class body; it simply stores all of the relevant data in the
/// [ClassDeclaration] object.
class _ClassBody {
  final Token beginToken;

  final List<ClassMember> members;

  final Token endToken;

  _ClassBody(this.beginToken, this.members, this.endToken);
}

/// Data structure placed on the stack to represent a mixin application (a
/// structure of the form "A with B, C").
///
/// This is needed because analyzer has no separate AST representation of a
/// mixin application; it simply stores all of the relevant data in the
/// [ClassDeclaration] or [ClassTypeAlias] object.
class _MixinApplication {
  final TypeName supertype;

  final Token withKeyword;

  final List<TypeName> mixinTypes;

  _MixinApplication(this.supertype, this.withKeyword, this.mixinTypes);
}

/// Data structure placed on the stack to represent the default parameter
/// value with the separator token.
class _ParameterDefaultValue {
  final Token separator;
  final Expression value;

  _ParameterDefaultValue(this.separator, this.value);
}

/// Data structure placed on stack to represent the redirected constructor.
class _RedirectingFactoryBody {
  final Token asyncKeyword;
  final Token starKeyword;
  final Token equalToken;
  final ConstructorName constructorName;

  _RedirectingFactoryBody(this.asyncKeyword, this.starKeyword, this.equalToken,
      this.constructorName);
}

/// Data structure placed on the stack as a container for optional parameters.
class _OptionalFormalParameters {
  final List<FormalParameter> parameters;
  final Token leftDelimiter;
  final Token rightDelimiter;

  _OptionalFormalParameters(
      this.parameters, this.leftDelimiter, this.rightDelimiter);
}

/// Data structure placed on the stack to represent the keyword "operator"
/// followed by a token.
class _OperatorName {
  final Token operatorKeyword;
  final SimpleIdentifier name;

  _OperatorName(this.operatorKeyword, this.name);
}

/// Data structure placed on the stack to represent a non-empty sequence
/// of modifiers.
class _Modifiers {
  Token abstractKeyword;
  Token externalKeyword;
  Token finalConstOrVarKeyword;
  Token staticKeyword;

  _Modifiers(List<Token> modifierTokens) {
    // No need to check the order and uniqueness of the modifiers, or that
    // disallowed modifiers are not used; the parser should do that.
    // TODO(paulberry,ahe): implement the necessary logic in the parser.
    for (var token in modifierTokens) {
      var s = token.lexeme;
      if (identical('abstract', s)) {
        abstractKeyword = token;
      } else if (identical('const', s)) {
        finalConstOrVarKeyword = token;
      } else if (identical('external', s)) {
        externalKeyword = token;
      } else if (identical('final', s)) {
        finalConstOrVarKeyword = token;
      } else if (identical('static', s)) {
        staticKeyword = token;
      } else if (identical('var', s)) {
        finalConstOrVarKeyword = token;
      } else {
        internalError('Unhandled modifier: $s');
      }
    }
  }
}