pkg/compiler/lib/src/parser/node_listener.dart

// Copyright (c) 2015, 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 dart2js.parser.node_listener;

import '../common.dart';
import '../elements/elements.dart' show
    CompilationUnitElement;
import '../native/native.dart' as native;
import '../tokens/precedence_constants.dart' as Precedence show
    BAD_INPUT_INFO,
    EOF_INFO,
    INDEX_INFO;
import '../tokens/token.dart' show
    ErrorToken,
    StringToken,
    Token;
import '../tree/tree.dart';
import '../util/util.dart' show
    Link;

import 'element_listener.dart' show
    ElementListener,
    ScannerOptions;
import 'partial_elements.dart' show
    PartialFunctionElement;

class NodeListener extends ElementListener {
  NodeListener(
      ScannerOptions scannerOptions,
      DiagnosticReporter reporter,
      CompilationUnitElement element)
    : super(scannerOptions, reporter, element, null);

  void addLibraryTag(LibraryTag tag) {
    pushNode(tag);
  }

  void addPartOfTag(PartOf tag) {
    pushNode(tag);
  }

  void endClassDeclaration(int interfacesCount, Token beginToken,
                           Token extendsKeyword, Token implementsKeyword,
                           Token endToken) {
    NodeList body = popNode();
    NodeList interfaces =
        makeNodeList(interfacesCount, implementsKeyword, null, ",");
    Node supertype = popNode();
    NodeList typeParameters = popNode();
    Identifier name = popNode();
    Modifiers modifiers = popNode();
    pushNode(new ClassNode(modifiers, name, typeParameters, supertype,
                           interfaces, beginToken, extendsKeyword, body,
                           endToken));
  }

  void endCompilationUnit(int count, Token token) {
    pushNode(makeNodeList(count, null, null, '\n'));
  }

  void endFunctionTypeAlias(Token typedefKeyword, Token endToken) {
    NodeList formals = popNode();
    NodeList typeParameters = popNode();
    Identifier name = popNode();
    TypeAnnotation returnType = popNode();
    pushNode(new Typedef(returnType, name, typeParameters, formals,
                         typedefKeyword, endToken));
  }

  void endNamedMixinApplication(Token classKeyword,
                                Token implementsKeyword,
                                Token endToken) {
    NodeList interfaces = (implementsKeyword != null) ? popNode() : null;
    Node mixinApplication = popNode();
    Modifiers modifiers = popNode();
    NodeList typeParameters = popNode();
    Identifier name = popNode();
    pushNode(new NamedMixinApplication(name, typeParameters,
                                       modifiers, mixinApplication,
                                       interfaces,
                                       classKeyword, endToken));
  }

  void endEnum(Token enumKeyword, Token endBrace, int count) {
    NodeList names = makeNodeList(count, enumKeyword.next.next, endBrace, ",");
    Identifier name = popNode();
    pushNode(new Enum(enumKeyword, name, names));
  }

  void endClassBody(int memberCount, Token beginToken, Token endToken) {
    pushNode(makeNodeList(memberCount, beginToken, endToken, null));
  }

  void endTopLevelFields(int count, Token beginToken, Token endToken) {
    NodeList variables = makeNodeList(count, null, endToken, ",");
    TypeAnnotation type = popNode();
    Modifiers modifiers = popNode();
    pushNode(new VariableDefinitions(type, modifiers, variables));
  }

  void endTopLevelMethod(Token beginToken, Token getOrSet, Token endToken) {
    popNode(); // body
    popNode(); // formalParameters
    Identifier name = popNode();
    popNode(); // type
    Modifiers modifiers = popNode();
    PartialFunctionElement element = new PartialFunctionElement(
        name.source, beginToken, getOrSet, endToken,
        modifiers, compilationUnitElement);
    pushElement(element);
  }

  void endFormalParameter(Token thisKeyword) {
    Expression name = popNode();
    if (thisKeyword != null) {
      Identifier thisIdentifier = new Identifier(thisKeyword);
      if (name.asSend() == null) {
        name = new Send(thisIdentifier, name);
      } else {
        name = name.asSend().copyWithReceiver(thisIdentifier, false);
      }
    }
    TypeAnnotation type = popNode();
    Modifiers modifiers = popNode();
    NodeList metadata = popNode();
    pushNode(new VariableDefinitions.forParameter(
        metadata, type, modifiers, new NodeList.singleton(name)));
  }

  void endFormalParameters(int count, Token beginToken, Token endToken) {
    pushNode(makeNodeList(count, beginToken, endToken, ","));
  }

  void handleNoFormalParameters(Token token) {
    pushNode(null);
  }

  void endArguments(int count, Token beginToken, Token endToken) {
    pushNode(makeNodeList(count, beginToken, endToken, ","));
  }

  void handleNoArguments(Token token) {
    pushNode(null);
  }

  void endConstructorReference(Token start, Token periodBeforeName,
                               Token endToken) {
    Identifier name = null;
    if (periodBeforeName != null) {
      name = popNode();
    }
    NodeList typeArguments = popNode();
    Node classReference = popNode();
    if (typeArguments != null) {
      classReference = new TypeAnnotation(classReference, typeArguments);
    } else {
      Identifier identifier = classReference.asIdentifier();
      Send send = classReference.asSend();
      if (identifier != null) {
        // TODO(ahe): Should be:
        // classReference = new Send(null, identifier);
        classReference = identifier;
      } else if (send != null) {
        classReference = send;
      } else {
        internalError(node: classReference);
      }
    }
    Node constructor = classReference;
    if (name != null) {
      // Either typeName<args>.name or x.y.name.
      constructor = new Send(classReference, name);
    }
    pushNode(constructor);
  }

  void endRedirectingFactoryBody(Token beginToken,
                                 Token endToken) {
    pushNode(new RedirectingFactoryBody(beginToken, endToken, popNode()));
  }

  void endReturnStatement(bool hasExpression,
                          Token beginToken, Token endToken) {
    Expression expression = hasExpression ? popNode() : null;
    pushNode(new Return(beginToken, endToken, expression));
  }

  void endYieldStatement(Token yieldToken, Token starToken, Token endToken) {
    Expression expression = popNode();
    pushNode(new Yield(yieldToken, starToken, expression, endToken));
  }

  void endExpressionStatement(Token token) {
    pushNode(new ExpressionStatement(popNode(), token));
  }

  void handleOnError(Token token, var errorInformation) {
    reporter.internalError(token, "'${token.value}': ${errorInformation}");
  }

  Token expectedFunctionBody(Token token) {
    if (identical(token.stringValue, 'native')) {
      return native.handleNativeFunctionBody(this, token);
    } else if (token is ErrorToken) {
      pushNode(null);
      reportErrorToken(token);
    } else {
      reportFatalError(token,
                       "Expected a function body, but got '${token.value}'.");
    }
    return skipToEof(token);
  }

  Token expectedClassBody(Token token) {
    if (token is ErrorToken) {
      reportErrorToken(token);
      return skipToEof(token);
    } else {
      reportFatalError(token,
                       "Expected a class body, but got '${token.value}'.");
      return skipToEof(token);
    }
  }

  void handleLiteralInt(Token token) {
    pushNode(new LiteralInt(token, (t, e) => handleOnError(t, e)));
  }

  void handleLiteralDouble(Token token) {
    pushNode(new LiteralDouble(token, (t, e) => handleOnError(t, e)));
  }

  void handleLiteralBool(Token token) {
    pushNode(new LiteralBool(token, (t, e) => handleOnError(t, e)));
  }

  void handleLiteralNull(Token token) {
    pushNode(new LiteralNull(token));
  }

  void endLiteralSymbol(Token hashToken, int identifierCount) {
    NodeList identifiers = makeNodeList(identifierCount, null, null, '.');
    pushNode(new LiteralSymbol(hashToken, identifiers));
  }

  void handleBinaryExpression(Token token) {
    Node argument = popNode();
    Node receiver = popNode();
    String tokenString = token.stringValue;
    if (identical(tokenString, '.') ||
        identical(tokenString, '..') ||
        identical(tokenString, '?.')) {
      Send argumentSend = argument.asSend();
      if (argumentSend == null) {
        // TODO(ahe): The parser should diagnose this problem, not
        // this listener.
        reportFatalError(argument,
                         'Expected an identifier.');
      }
      if (argumentSend.receiver != null) internalError(node: argument);
      if (argument is SendSet) internalError(node: argument);
      pushNode(argument.asSend().copyWithReceiver(receiver,
            identical(tokenString, '?.')));
    } else {
      NodeList arguments = new NodeList.singleton(argument);
      pushNode(new Send(receiver, new Operator(token), arguments));
    }
    if (identical(tokenString, '===')) {
      reporter.reportErrorMessage(
          token,
          MessageKind.UNSUPPORTED_EQ_EQ_EQ,
          {'lhs': receiver, 'rhs': argument});
    }
    if (identical(tokenString, '!==')) {
      reporter.reportErrorMessage(
          token,
          MessageKind.UNSUPPORTED_BANG_EQ_EQ,
          {'lhs': receiver, 'rhs': argument});
    }
  }

  void beginCascade(Token token) {
    pushNode(new CascadeReceiver(popNode(), token));
  }

  void endCascade() {
    pushNode(new Cascade(popNode()));
  }

  void handleAsOperator(Token operathor, Token endToken) {
    TypeAnnotation type = popNode();
    Expression expression = popNode();
    NodeList arguments = new NodeList.singleton(type);
    pushNode(new Send(expression, new Operator(operathor), arguments));
  }

  void handleAssignmentExpression(Token token) {
    Node arg = popNode();
    Node node = popNode();
    Send send = node.asSend();
    if (send == null || !(send.isPropertyAccess || send.isIndex)) {
      reportNotAssignable(node);
    }
    if (send.asSendSet() != null) internalError(node: send);
    NodeList arguments;
    if (send.isIndex) {
      Link<Node> link = const Link<Node>().prepend(arg);
      link = link.prepend(send.arguments.head);
      arguments = new NodeList(null, link);
    } else {
      arguments = new NodeList.singleton(arg);
    }
    Operator op = new Operator(token);
    pushNode(new SendSet(send.receiver, send.selector, op, arguments,
        send.isConditional));
  }

  void reportNotAssignable(Node node) {
    // TODO(ahe): The parser should diagnose this problem, not this
    // listener.
    reportFatalError(node,
                     'Not assignable.');
  }

  void handleConditionalExpression(Token question, Token colon) {
    Node elseExpression = popNode();
    Node thenExpression = popNode();
    Node condition = popNode();
    pushNode(new Conditional(
        condition, thenExpression, elseExpression, question, colon));
  }

  void endSend(Token token) {
    NodeList arguments = popNode();
    Node selector = popNode();
    // TODO(ahe): Handle receiver.
    pushNode(new Send(null, selector, arguments));
  }

  void endFunctionBody(int count, Token beginToken, Token endToken) {
    if (count == 0 && beginToken == null) {
      pushNode(new EmptyStatement(endToken));
    } else {
      pushNode(new Block(makeNodeList(count, beginToken, endToken, null)));
    }
  }

  void handleAsyncModifier(Token asyncToken, Token starToken) {
    if (asyncToken != null) {
      pushNode(new AsyncModifier(asyncToken, starToken));
    } else {
      pushNode(null);
    }
  }

  void skippedFunctionBody(Token token) {
    pushNode(new Block(new NodeList.empty()));
  }

  void handleNoFunctionBody(Token token) {
    pushNode(new EmptyStatement(token));
  }

  void endFunction(Token getOrSet, Token endToken) {
    Statement body = popNode();
    AsyncModifier asyncModifier = popNode();
    NodeList initializers = popNode();
    NodeList formals = popNode();
    // The name can be an identifier or a send in case of named constructors.
    Expression name = popNode();
    TypeAnnotation type = popNode();
    Modifiers modifiers = popNode();
    pushNode(new FunctionExpression(name, formals, body, type,
                                    modifiers, initializers, getOrSet,
                                    asyncModifier));
  }

  void endFunctionDeclaration(Token endToken) {
    pushNode(new FunctionDeclaration(popNode()));
  }

  void endVariablesDeclaration(int count, Token endToken) {
    // TODO(ahe): Pick one name for this concept, either
    // VariablesDeclaration or VariableDefinitions.
    NodeList variables = makeNodeList(count, null, endToken, ",");
    TypeAnnotation type = popNode();
    Modifiers modifiers = popNode();
    pushNode(new VariableDefinitions(type, modifiers, variables));
  }

  void endInitializer(Token assignmentOperator) {
    Expression initializer = popNode();
    NodeList arguments =
        initializer == null ? null : new NodeList.singleton(initializer);
    Expression name = popNode();
    Operator op = new Operator(assignmentOperator);
    pushNode(new SendSet(null, name, op, arguments));
  }

  void endIfStatement(Token ifToken, Token elseToken) {
    Statement elsePart = (elseToken == null) ? null : popNode();
    Statement thenPart = popNode();
    ParenthesizedExpression condition = popNode();
    pushNode(new If(condition, thenPart, elsePart, ifToken, elseToken));
  }

  void endForStatement(int updateExpressionCount,
                       Token beginToken, Token endToken) {
    Statement body = popNode();
    NodeList updates = makeNodeList(updateExpressionCount, null, null, ',');
    Statement condition = popNode();
    Node initializer = popNode();
    pushNode(new For(initializer, condition, updates, body, beginToken));
  }

  void handleNoExpression(Token token) {
    pushNode(null);
  }

  void endDoWhileStatement(Token doKeyword, Token whileKeyword,
                           Token endToken) {
    Expression condition = popNode();
    Statement body = popNode();
    pushNode(new DoWhile(body, condition, doKeyword, whileKeyword, endToken));
  }

  void endWhileStatement(Token whileKeyword, Token endToken) {
    Statement body = popNode();
    Expression condition = popNode();
    pushNode(new While(condition, body, whileKeyword));
  }

  void endBlock(int count, Token beginToken, Token endToken) {
    pushNode(new Block(makeNodeList(count, beginToken, endToken, null)));
  }

  void endThrowExpression(Token throwToken, Token endToken) {
    Expression expression = popNode();
    pushNode(new Throw(expression, throwToken, endToken));
  }

  void endAwaitExpression(Token awaitToken, Token endToken) {
    Expression expression = popNode();
    pushNode(new Await(awaitToken, expression));
  }

  void endRethrowStatement(Token throwToken, Token endToken) {
    pushNode(new Rethrow(throwToken, endToken));
    if (identical(throwToken.stringValue, 'throw')) {
      reporter.reportErrorMessage(
          throwToken, MessageKind.UNSUPPORTED_THROW_WITHOUT_EXP);
    }
  }

  void handleUnaryPrefixExpression(Token token) {
    pushNode(new Send.prefix(popNode(), new Operator(token)));
  }

  void handleSuperExpression(Token token) {
    pushNode(new Identifier(token));
  }

  void handleThisExpression(Token token) {
    pushNode(new Identifier(token));
  }

  void handleUnaryAssignmentExpression(Token token, bool isPrefix) {
    Node node = popNode();
    Send send = node.asSend();
    if (send == null) {
      reportNotAssignable(node);
    }
    if (!(send.isPropertyAccess || send.isIndex)) {
      reportNotAssignable(node);
    }
    if (send.asSendSet() != null) internalError(node: send);
    Node argument = null;
    if (send.isIndex) argument = send.arguments.head;
    Operator op = new Operator(token);

    if (isPrefix) {
      pushNode(new SendSet.prefix(send.receiver, send.selector, op, argument,
          send.isConditional));
    } else {
      pushNode(new SendSet.postfix(send.receiver, send.selector, op, argument,
          send.isConditional));
    }
  }

  void handleUnaryPostfixAssignmentExpression(Token token) {
    handleUnaryAssignmentExpression(token, false);
  }

  void handleUnaryPrefixAssignmentExpression(Token token) {
    handleUnaryAssignmentExpression(token, true);
  }

  void endInitializers(int count, Token beginToken, Token endToken) {
    pushNode(makeNodeList(count, beginToken, null, ','));
  }

  void handleNoInitializers() {
    pushNode(null);
  }

  void endFields(int count, Token beginToken, Token endToken) {
    NodeList variables = makeNodeList(count, null, endToken, ",");
    TypeAnnotation type = popNode();
    Modifiers modifiers = popNode();
    pushNode(new VariableDefinitions(type, modifiers, variables));
  }

  void endMethod(Token getOrSet, Token beginToken, Token endToken) {
    Statement body = popNode();
    AsyncModifier asyncModifier = popNode();
    NodeList initializers = popNode();
    NodeList formalParameters = popNode();
    Expression name = popNode();
    TypeAnnotation returnType = popNode();
    Modifiers modifiers = popNode();
    pushNode(new FunctionExpression(name, formalParameters, body, returnType,
                                    modifiers, initializers, getOrSet,
                                    asyncModifier));
  }

  void handleLiteralMap(int count, Token beginToken, Token constKeyword,
                        Token endToken) {
    NodeList entries = makeNodeList(count, beginToken, endToken, ',');
    NodeList typeArguments = popNode();
    pushNode(new LiteralMap(typeArguments, entries, constKeyword));
  }

  void endLiteralMapEntry(Token colon, Token endToken) {
    Expression value = popNode();
    Expression key = popNode();
    pushNode(new LiteralMapEntry(key, colon, value));
  }

  void handleLiteralList(int count, Token beginToken, Token constKeyword,
                         Token endToken) {
    NodeList elements = makeNodeList(count, beginToken, endToken, ',');
    pushNode(new LiteralList(popNode(), elements, constKeyword));
  }

  void handleIndexedExpression(Token openSquareBracket,
                               Token closeSquareBracket) {
    NodeList arguments =
        makeNodeList(1, openSquareBracket, closeSquareBracket, null);
    Node receiver = popNode();
    Token token = new StringToken.fromString(Precedence.INDEX_INFO, '[]',
                                  openSquareBracket.charOffset);
    Node selector = new Operator(token);
    pushNode(new Send(receiver, selector, arguments));
  }

  void handleNewExpression(Token token) {
    NodeList arguments = popNode();
    Node name = popNode();
    pushNode(new NewExpression(token, new Send(null, name, arguments)));
  }

  void handleConstExpression(Token token) {
    // [token] carries the 'const' information.
    handleNewExpression(token);
  }

  void handleOperator(Token token) {
    pushNode(new Operator(token));
  }

  void handleOperatorName(Token operatorKeyword, Token token) {
    Operator op = new Operator(token);
    pushNode(new Send(new Identifier(operatorKeyword), op, null));
  }

  void handleNamedArgument(Token colon) {
    Expression expression = popNode();
    Identifier name = popNode();
    pushNode(new NamedArgument(name, colon, expression));
  }

  void endOptionalFormalParameters(int count,
                                   Token beginToken, Token endToken) {
    pushNode(makeNodeList(count, beginToken, endToken, ','));
  }

  void handleFunctionTypedFormalParameter(Token endToken) {
    NodeList formals = popNode();
    Identifier name = popNode();
    TypeAnnotation returnType = popNode();
    pushNode(null); // Signal "no type" to endFormalParameter.
    pushNode(new FunctionExpression(name, formals, null, returnType,
                                    Modifiers.EMPTY, null, null, null));
  }

  void handleValuedFormalParameter(Token equals, Token token) {
    Expression defaultValue = popNode();
    Expression parameterName = popNode();
    pushNode(new SendSet(null, parameterName, new Operator(equals),
                         new NodeList.singleton(defaultValue)));
  }

  void endTryStatement(int catchCount, Token tryKeyword, Token finallyKeyword) {
    Block finallyBlock = null;
    if (finallyKeyword != null) {
      finallyBlock = popNode();
    }
    NodeList catchBlocks = makeNodeList(catchCount, null, null, null);
    Block tryBlock = popNode();
    pushNode(new TryStatement(tryBlock, catchBlocks, finallyBlock,
                              tryKeyword, finallyKeyword));
  }

  void handleCaseMatch(Token caseKeyword, Token colon) {
    pushNode(new CaseMatch(caseKeyword, popNode(), colon));
  }

  void handleCatchBlock(Token onKeyword, Token catchKeyword) {
    Block block = popNode();
    NodeList formals = catchKeyword != null? popNode(): null;
    TypeAnnotation type = onKeyword != null ? popNode() : null;
    pushNode(new CatchBlock(type, formals, block, onKeyword, catchKeyword));
  }

  void endSwitchStatement(Token switchKeyword, Token endToken) {
    NodeList cases = popNode();
    ParenthesizedExpression expression = popNode();
    pushNode(new SwitchStatement(expression, cases, switchKeyword));
  }

  void endSwitchBlock(int caseCount, Token beginToken, Token endToken) {
    Link<Node> caseNodes = const Link<Node>();
    while (caseCount > 0) {
      SwitchCase switchCase = popNode();
      caseNodes = caseNodes.prepend(switchCase);
      caseCount--;
    }
    pushNode(new NodeList(beginToken, caseNodes, endToken, null));
  }

  void handleSwitchCase(int labelCount, int caseCount,
                        Token defaultKeyword, int statementCount,
                        Token firstToken, Token endToken) {
    NodeList statements = makeNodeList(statementCount, null, null, null);
    NodeList labelsAndCases =
        makeNodeList(labelCount + caseCount, null, null, null);
    pushNode(new SwitchCase(labelsAndCases, defaultKeyword, statements,
                            firstToken));
  }

  void handleBreakStatement(bool hasTarget,
                            Token breakKeyword, Token endToken) {
    Identifier target = null;
    if (hasTarget) {
      target = popNode();
    }
    pushNode(new BreakStatement(target, breakKeyword, endToken));
  }

  void handleContinueStatement(bool hasTarget,
                               Token continueKeyword, Token endToken) {
    Identifier target = null;
    if (hasTarget) {
      target = popNode();
    }
    pushNode(new ContinueStatement(target, continueKeyword, endToken));
  }

  void handleEmptyStatement(Token token) {
    pushNode(new EmptyStatement(token));
  }

  void endFactoryMethod(Token beginToken, Token endToken) {
    super.endFactoryMethod(beginToken, endToken);
    Statement body = popNode();
    AsyncModifier asyncModifier = popNode();
    NodeList formals = popNode();
    Node name = popNode();

    // TODO(ahe): Move this parsing to the parser.
    int modifierCount = 0;
    Token modifier = beginToken;
    if (modifier.stringValue == "external") {
      handleModifier(modifier);
      modifierCount++;
      modifier = modifier.next;
    }
    if (modifier.stringValue == "const") {
      handleModifier(modifier);
      modifierCount++;
      modifier = modifier.next;
    }
    assert(modifier.stringValue == "factory");
    handleModifier(modifier);
    modifierCount++;
    handleModifiers(modifierCount);
    Modifiers modifiers = popNode();

    pushNode(new FunctionExpression(name, formals, body, null,
                                    modifiers, null, null, asyncModifier));
  }

  void endForIn(Token awaitToken, Token forToken,
                Token inKeyword, Token endToken) {
    Statement body = popNode();
    Expression expression = popNode();
    Node declaredIdentifier = popNode();
    if (awaitToken == null) {
      pushNode(new SyncForIn(declaredIdentifier, expression, body,
                             forToken, inKeyword));
    } else {
      pushNode(new AsyncForIn(declaredIdentifier, expression, body, awaitToken,
                              forToken, inKeyword));
    }
  }

  void endMetadataStar(int count, bool forParameter) {
    // TODO(johnniwinther): Handle metadata for all node kinds.
    if (forParameter) {
      if (0 == count) {
        pushNode(null);
      } else {
        pushNode(makeNodeList(count, null, null, ' '));
      }
    }
  }

  void endMetadata(Token beginToken, Token periodBeforeName, Token endToken) {
    NodeList arguments = popNode();
    if (arguments == null) {
      // This is a constant expression.
      Identifier name;
      if (periodBeforeName != null) {
        name = popNode();
      }
      NodeList typeArguments = popNode();
      Node receiver = popNode();
      if (typeArguments != null) {
        receiver = new TypeAnnotation(receiver, typeArguments);
        recoverableError(typeArguments,
                         'Type arguments are not allowed here.');
      } else {
        Identifier identifier = receiver.asIdentifier();
        Send send = receiver.asSend();
        if (identifier != null) {
          receiver = new Send(null, identifier);
        } else if (send == null) {
          internalError(node: receiver);
        }
      }
      Send send = receiver;
      if (name != null) {
        send = new Send(receiver, name);
      }
      pushNode(new Metadata(beginToken, send));
    } else {
      // This is a const constructor call.
      endConstructorReference(beginToken, periodBeforeName, endToken);
      Node constructor = popNode();
      pushNode(new Metadata(beginToken,
          new NewExpression(null,
              new Send(null, constructor, arguments))));
    }
  }

  void handleAssertStatement(Token assertKeyword,
                             Token commaToken, Token semicolonToken) {
    Node message;
    Node condition;
    if (commaToken != null) {
      message = popNode();
    }
    condition = popNode();
    pushNode(new Assert(assertKeyword, condition,
                        message, semicolonToken));
  }

  void endUnnamedFunction(Token token) {
    Statement body = popNode();
    AsyncModifier asyncModifier = popNode();
    NodeList formals = popNode();
    pushNode(new FunctionExpression(null, formals, body, null,
                                    Modifiers.EMPTY, null, null,
                                    asyncModifier));
  }

  void handleIsOperator(Token operathor, Token not, Token endToken) {
    TypeAnnotation type = popNode();
    Expression expression = popNode();
    Node argument;
    if (not != null) {
      argument = new Send.prefix(type, new Operator(not));
    } else {
      argument = type;
    }

    NodeList arguments = new NodeList.singleton(argument);
    pushNode(new Send(expression, new Operator(operathor), arguments));
  }

  void handleLabel(Token colon) {
    Identifier name = popNode();
    pushNode(new Label(name, colon));
  }

  void endLabeledStatement(int labelCount) {
    Statement statement = popNode();
    NodeList labels = makeNodeList(labelCount, null, null, null);
    pushNode(new LabeledStatement(labels, statement));
  }

  void log(message) {
    reporter.log(message);
  }

  void internalError({Token token, Node node}) {
    // TODO(ahe): This should call reporter.internalError.
    Spannable spannable = (token == null) ? node : token;
    throw new SpannableAssertionFailure(spannable, 'Internal error in parser.');
  }
}