Move AST implementation out of generated

pkg/analyzer/lib/src/generated/ast.dart

 // Copyright (c) 2014, 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.
 
+/**
+ * This library is deprecated. Please convert all references to this library to
+ * reference one of the following public libraries:
+ * * package:analyzer/dart/ast/ast.dart
+ * * package:analyzer/dart/ast/visitor.dart
+ *
+ * If your code is using APIs not available in these public libraries, please
+ * contact the analyzer team to either find an alternate API or have the API you
+ * depend on added to the public API.
+ */
 library analyzer.src.generated.ast;

[scheglov, 2016/01/18 19:52:31]

Maybe @deprecated also?
Or this will cause hints and analysis failures of the clients?

[Brian Wilkerson, 2016/01/18 21:00:50]

It would cause hints, both in client code and in our code (because I haven't
cleaned up imports in our code yet). At some point we should do so, however, so
that clients are informed about the need to update.

 
-import 'dart:collection';
-
-import 'package:analyzer/dart/ast/ast.dart';
-import 'package:analyzer/dart/element/element.dart';
-import 'package:analyzer/dart/element/type.dart';
-import 'package:analyzer/src/dart/ast/utilities.dart';
-import 'package:analyzer/src/dart/element/element.dart';
-import 'package:analyzer/src/dart/element/type.dart';
-import 'package:analyzer/src/generated/engine.dart' show AnalysisEngine;
-import 'package:analyzer/src/generated/java_core.dart';
-import 'package:analyzer/src/generated/java_engine.dart';
-import 'package:analyzer/src/generated/parser.dart';
-import 'package:analyzer/src/generated/scanner.dart';
-import 'package:analyzer/src/generated/source.dart' show LineInfo, Source;
-import 'package:analyzer/src/generated/utilities_dart.dart';
-
 export 'package:analyzer/dart/ast/ast.dart';
 export 'package:analyzer/dart/ast/visitor.dart';
 export 'package:analyzer/src/dart/ast/utilities.dart';
-
-/**
- * Two or more string literals that are implicitly concatenated because of being
- * adjacent (separated only by whitespace).
- *
- * While the grammar only allows adjacent strings when all of the strings are of
- * the same kind (single line or multi-line), this class doesn't enforce that
- * restriction.
- *
- * > adjacentStrings ::=
- * >     [StringLiteral] [StringLiteral]+
- */
-class AdjacentStringsImpl extends StringLiteralImpl implements AdjacentStrings {
-  /**
-   * The strings that are implicitly concatenated.
-   */
-  NodeList<StringLiteral> _strings;
-
-  /**
-   * Initialize a newly created list of adjacent strings. To be syntactically
-   * valid, the list of [strings] must contain at least two elements.
-   */
-  AdjacentStringsImpl(List<StringLiteral> strings) {
-    _strings = new NodeList<StringLiteral>(this, strings);
-  }
-
-  @override
-  Token get beginToken => _strings.beginToken;
-
-  @override
-  Iterable get childEntities => new ChildEntities()..addAll(_strings);
-
-  @override
-  Token get endToken => _strings.endToken;
-
-  @override
-  NodeList<StringLiteral> get strings => _strings;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitAdjacentStrings(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _strings.accept(visitor);
-  }
-
-  @override
-  void _appendStringValue(StringBuffer buffer) {
-    for (StringLiteralImpl stringLiteral in strings) {
-      stringLiteral._appendStringValue(buffer);
-    }
-  }
-}
-
-/**
- * An AST node that can be annotated with both a documentation comment and a
- * list of annotations.
- */
-abstract class AnnotatedNodeImpl extends AstNodeImpl implements AnnotatedNode {
-  /**
-   * The documentation comment associated with this node, or `null` if this node
-   * does not have a documentation comment associated with it.
-   */
-  Comment _comment;
-
-  /**
-   * The annotations associated with this node.
-   */
-  NodeList<Annotation> _metadata;
-
-  /**
-   * Initialize a newly created annotated node. Either or both of the [comment]
-   * and [metadata] can be `null` if the node does not have the corresponding
-   * attribute.
-   */
-  AnnotatedNodeImpl(Comment comment, List<Annotation> metadata) {
-    _comment = _becomeParentOf(comment);
-    _metadata = new NodeList<Annotation>(this, metadata);
-  }
-
-  @override
-  Token get beginToken {
-    if (_comment == null) {
-      if (_metadata.isEmpty) {
-        return firstTokenAfterCommentAndMetadata;
-      }
-      return _metadata.beginToken;
-    } else if (_metadata.isEmpty) {
-      return _comment.beginToken;
-    }
-    Token commentToken = _comment.beginToken;
-    Token metadataToken = _metadata.beginToken;
-    if (commentToken.offset < metadataToken.offset) {
-      return commentToken;
-    }
-    return metadataToken;
-  }
-
-  @override
-  Comment get documentationComment => _comment;
-
-  @override
-  void set documentationComment(Comment comment) {
-    _comment = _becomeParentOf(comment);
-  }
-
-  @override
-  NodeList<Annotation> get metadata => _metadata;
-
-  @override
-  List<AstNode> get sortedCommentAndAnnotations {
-    return <AstNode>[]
-      ..add(_comment)
-      ..addAll(_metadata)
-      ..sort(AstNode.LEXICAL_ORDER);
-  }
-
-  /**
-   * Return a holder of child entities that subclasses can add to.
-   */
-  ChildEntities get _childEntities {
-    ChildEntities result = new ChildEntities();
-    if (_commentIsBeforeAnnotations()) {
-      result
-        ..add(_comment)
-        ..addAll(_metadata);
-    } else {
-      result.addAll(sortedCommentAndAnnotations);
-    }
-    return result;
-  }
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    if (_commentIsBeforeAnnotations()) {
-      _safelyVisitChild(_comment, visitor);
-      _metadata.accept(visitor);
-    } else {
-      for (AstNode child in sortedCommentAndAnnotations) {
-        child.accept(visitor);
-      }
-    }
-  }
-
-  /**
-   * Return `true` if there are no annotations before the comment. Note that a
-   * result of `true` does not imply that there is a comment, nor that there are
-   * annotations associated with this node.
-   */
-  bool _commentIsBeforeAnnotations() {
-    if (_comment == null || _metadata.isEmpty) {
-      return true;
-    }
-    Annotation firstAnnotation = _metadata[0];
-    return _comment.offset < firstAnnotation.offset;
-  }
-}
-
-/**
- * An annotation that can be associated with an AST node.
- *
- * > metadata ::=
- * >     annotation*
- * >
- * > annotation ::=
- * >     '@' [Identifier] ('.' [SimpleIdentifier])? [ArgumentList]?
- */
-class AnnotationImpl extends AstNodeImpl implements Annotation {
-  /**
-   * The at sign that introduced the annotation.
-   */
-  Token atSign;
-
-  /**
-   * The name of the class defining the constructor that is being invoked or the
-   * name of the field that is being referenced.
-   */
-  Identifier _name;
-
-  /**
-   * The period before the constructor name, or `null` if this annotation is not
-   * the invocation of a named constructor.
-   */
-  Token period;
-
-  /**
-   * The name of the constructor being invoked, or `null` if this annotation is
-   * not the invocation of a named constructor.
-   */
-  SimpleIdentifier _constructorName;
-
-  /**
-   * The arguments to the constructor being invoked, or `null` if this
-   * annotation is not the invocation of a constructor.
-   */
-  ArgumentList _arguments;
-
-  /**
-   * The element associated with this annotation, or `null` if the AST structure
-   * has not been resolved or if this annotation could not be resolved.
-   */
-  Element _element;
-
-  /**
-   * The element annotation representing this annotation in the element model.
-   */
-  ElementAnnotation elementAnnotation;
-
-  /**
-   * Initialize a newly created annotation. Both the [period] and the
-   * [constructorName] can be `null` if the annotation is not referencing a
-   * named constructor. The [arguments] can be `null` if the annotation is not
-   * referencing a constructor.
-   */
-  AnnotationImpl(this.atSign, Identifier name, this.period,
-      SimpleIdentifier constructorName, ArgumentList arguments) {
-    _name = _becomeParentOf(name);
-    _constructorName = _becomeParentOf(constructorName);
-    _arguments = _becomeParentOf(arguments);
-  }
-
-  @override
-  ArgumentList get arguments => _arguments;
-
-  @override
-  void set arguments(ArgumentList arguments) {
-    _arguments = _becomeParentOf(arguments);
-  }
-
-  @override
-  Token get beginToken => atSign;
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(atSign)
-    ..add(_name)
-    ..add(period)
-    ..add(_constructorName)
-    ..add(_arguments);
-
-  @override
-  SimpleIdentifier get constructorName => _constructorName;
-
-  @override
-  void set constructorName(SimpleIdentifier name) {
-    _constructorName = _becomeParentOf(name);
-  }
-
-  @override
-  Element get element {
-    if (_element != null) {
-      return _element;
-    } else if (_name != null) {
-      return _name.staticElement;
-    }
-    return null;
-  }
-
-  @override
-  void set element(Element element) {
-    _element = element;
-  }
-
-  @override
-  Token get endToken {
-    if (_arguments != null) {
-      return _arguments.endToken;
-    } else if (_constructorName != null) {
-      return _constructorName.endToken;
-    }
-    return _name.endToken;
-  }
-
-  @override
-  Identifier get name => _name;
-
-  @override
-  void set name(Identifier name) {
-    _name = _becomeParentOf(name);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitAnnotation(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_name, visitor);
-    _safelyVisitChild(_constructorName, visitor);
-    _safelyVisitChild(_arguments, visitor);
-  }
-}
-
-/**
- * A list of arguments in the invocation of an executable element (that is, a
- * function, method, or constructor).
- *
- * > argumentList ::=
- * >     '(' arguments? ')'
- * >
- * > arguments ::=
- * >     [NamedExpression] (',' [NamedExpression])*
- * >   | [Expression] (',' [Expression])* (',' [NamedExpression])*
- */
-class ArgumentListImpl extends AstNodeImpl implements ArgumentList {
-  /**
-   * The left parenthesis.
-   */
-  Token leftParenthesis;
-
-  /**
-   * The expressions producing the values of the arguments.
-   */
-  NodeList<Expression> _arguments;
-
-  /**
-   * The right parenthesis.
-   */
-  Token rightParenthesis;
-
-  /**
-   * A list containing the elements representing the parameters corresponding to
-   * each of the arguments in this list, or `null` if the AST has not been
-   * resolved or if the function or method being invoked could not be determined
-   * based on static type information. The list must be the same length as the
-   * number of arguments, but can contain `null` entries if a given argument
-   * does not correspond to a formal parameter.
-   */
-  List<ParameterElement> _correspondingStaticParameters;
-
-  /**
-   * A list containing the elements representing the parameters corresponding to
-   * each of the arguments in this list, or `null` if the AST has not been
-   * resolved or if the function or method being invoked could not be determined
-   * based on propagated type information. The list must be the same length as
-   * the number of arguments, but can contain `null` entries if a given argument
-   * does not correspond to a formal parameter.
-   */
-  List<ParameterElement> _correspondingPropagatedParameters;
-
-  /**
-   * Initialize a newly created list of arguments. The list of [arguments] can
-   * be `null` if there are no arguments.
-   */
-  ArgumentListImpl(
-      this.leftParenthesis, List<Expression> arguments, this.rightParenthesis) {
-    _arguments = new NodeList<Expression>(this, arguments);
-  }
-
-  @override
-  NodeList<Expression> get arguments => _arguments;
-
-  @override
-  Token get beginToken => leftParenthesis;
-
-  @override
-  // TODO(paulberry): Add commas.
-  Iterable get childEntities => new ChildEntities()
-    ..add(leftParenthesis)
-    ..addAll(_arguments)
-    ..add(rightParenthesis);
-
-  @override
-  void set correspondingPropagatedParameters(
-      List<ParameterElement> parameters) {
-    if (parameters.length != _arguments.length) {
-      throw new IllegalArgumentException(
-          "Expected ${_arguments.length} parameters, not ${parameters.length}");
-    }
-    _correspondingPropagatedParameters = parameters;
-  }
-
-  @override
-  void set correspondingStaticParameters(List<ParameterElement> parameters) {
-    if (parameters.length != _arguments.length) {
-      throw new IllegalArgumentException(
-          "Expected ${_arguments.length} parameters, not ${parameters.length}");
-    }
-    _correspondingStaticParameters = parameters;
-  }
-
-  @override
-  Token get endToken => rightParenthesis;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitArgumentList(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _arguments.accept(visitor);
-  }
-
-  /**
-   * If
-   * * the given [expression] is a child of this list,
-   * * the AST structure has been resolved,
-   * * the function being invoked is known based on propagated type information,
-   *   and
-   * * the expression corresponds to one of the parameters of the function being
-   *   invoked,
-   * then return the parameter element representing the parameter to which the
-   * value of the given expression will be bound. Otherwise, return `null`.
-   */
-  ParameterElement _getPropagatedParameterElementFor(Expression expression) {
-    if (_correspondingPropagatedParameters == null ||
-        _correspondingPropagatedParameters.length != _arguments.length) {
-      // Either the AST structure has not been resolved, the invocation of which
-      // this list is a part could not be resolved, or the argument list was
-      // modified after the parameters were set.
-      return null;
-    }
-    int index = _arguments.indexOf(expression);
-    if (index < 0) {
-      // The expression isn't a child of this node.
-      return null;
-    }
-    return _correspondingPropagatedParameters[index];
-  }
-
-  /**
-   * If
-   * * the given [expression] is a child of this list,
-   * * the AST structure has been resolved,
-   * * the function being invoked is known based on static type information, and
-   * * the expression corresponds to one of the parameters of the function being
-   *   invoked,
-   * then return the parameter element representing the parameter to which the
-   * value of the given expression will be bound. Otherwise, return `null`.
-   */
-  ParameterElement _getStaticParameterElementFor(Expression expression) {
-    if (_correspondingStaticParameters == null ||
-        _correspondingStaticParameters.length != _arguments.length) {
-      // Either the AST structure has not been resolved, the invocation of which
-      // this list is a part could not be resolved, or the argument list was
-      // modified after the parameters were set.
-      return null;
-    }
-    int index = _arguments.indexOf(expression);
-    if (index < 0) {
-      // The expression isn't a child of this node.
-      return null;
-    }
-    return _correspondingStaticParameters[index];
-  }
-}
-
-/**
- * An as expression.
- *
- * > asExpression ::=
- * >     [Expression] 'as' [TypeName]
- */
-class AsExpressionImpl extends ExpressionImpl implements AsExpression {
-  /**
-   * The expression used to compute the value being cast.
-   */
-  Expression _expression;
-
-  /**
-   * The 'as' operator.
-   */
-  Token asOperator;
-
-  /**
-   * The name of the type being cast to.
-   */
-  TypeName _type;
-
-  /**
-   * Initialize a newly created as expression.
-   */
-  AsExpressionImpl(Expression expression, this.asOperator, TypeName type) {
-    _expression = _becomeParentOf(expression);
-    _type = _becomeParentOf(type);
-  }
-
-  @override
-  Token get beginToken => _expression.beginToken;
-
-  @override
-  Iterable get childEntities =>
-      new ChildEntities()..add(_expression)..add(asOperator)..add(_type);
-
-  @override
-  Token get endToken => _type.endToken;
-
-  @override
-  Expression get expression => _expression;
-
-  @override
-  void set expression(Expression expression) {
-    _expression = _becomeParentOf(expression);
-  }
-
-  @override
-  int get precedence => 7;
-
-  @override
-  TypeName get type => _type;
-
-  @override
-  void set type(TypeName name) {
-    _type = _becomeParentOf(name);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitAsExpression(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_expression, visitor);
-    _safelyVisitChild(_type, visitor);
-  }
-}
-
-/**
- * An assert statement.
- *
- * > assertStatement ::=
- * >     'assert' '(' [Expression] ')' ';'
- */
-class AssertStatementImpl extends StatementImpl implements AssertStatement {
-  /**
-   * The token representing the 'assert' keyword.
-   */
-  Token assertKeyword;
-
-  /**
-   * The left parenthesis.
-   */
-  Token leftParenthesis;
-
-  /**
-   * The condition that is being asserted to be `true`.
-   */
-  Expression _condition;
-
-  /**
-   * The comma, if a message expression was supplied.  Otherwise `null`.
-   */
-  Token comma;
-
-  /**
-   * The message to report if the assertion fails.  `null` if no message was
-   * supplied.
-   */
-  Expression _message;
-
-  /**
-   * The right parenthesis.
-   */
-  Token rightParenthesis;
-
-  /**
-   * The semicolon terminating the statement.
-   */
-  Token semicolon;
-
-  /**
-   * Initialize a newly created assert statement.
-   */
-  AssertStatementImpl(
-      this.assertKeyword,
-      this.leftParenthesis,
-      Expression condition,
-      this.comma,
-      Expression message,
-      this.rightParenthesis,
-      this.semicolon) {
-    _condition = _becomeParentOf(condition);
-    _message = _becomeParentOf(message);
-  }
-
-  @override
-  Token get beginToken => assertKeyword;
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(assertKeyword)
-    ..add(leftParenthesis)
-    ..add(_condition)
-    ..add(comma)
-    ..add(_message)
-    ..add(rightParenthesis)
-    ..add(semicolon);
-
-  @override
-  Expression get condition => _condition;
-
-  @override
-  void set condition(Expression condition) {
-    _condition = _becomeParentOf(condition);
-  }
-
-  @override
-  Token get endToken => semicolon;
-
-  @override
-  Expression get message => _message;
-
-  @override
-  void set message(Expression expression) {
-    _message = _becomeParentOf(expression);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitAssertStatement(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_condition, visitor);
-    _safelyVisitChild(message, visitor);
-  }
-}
-
-/**
- * An assignment expression.
- *
- * > assignmentExpression ::=
- * >     [Expression] operator [Expression]
- */
-class AssignmentExpressionImpl extends ExpressionImpl
-    implements AssignmentExpression {
-  /**
-   * The expression used to compute the left hand side.
-   */
-  Expression _leftHandSide;
-
-  /**
-   * The assignment operator being applied.
-   */
-  Token operator;
-
-  /**
-   * The expression used to compute the right hand side.
-   */
-  Expression _rightHandSide;
-
-  /**
-   * The element associated with the operator based on the static type of the
-   * left-hand-side, or `null` if the AST structure has not been resolved, if
-   * the operator is not a compound operator, or if the operator could not be
-   * resolved.
-   */
-  MethodElement staticElement;
-
-  /**
-   * The element associated with the operator based on the propagated type of
-   * the left-hand-side, or `null` if the AST structure has not been resolved,
-   * if the operator is not a compound operator, or if the operator could not be
-   * resolved.
-   */
-  MethodElement propagatedElement;
-
-  /**
-   * Initialize a newly created assignment expression.
-   */
-  AssignmentExpressionImpl(
-      Expression leftHandSide, this.operator, Expression rightHandSide) {
-    if (leftHandSide == null || rightHandSide == null) {
-      String message;
-      if (leftHandSide == null) {
-        if (rightHandSide == null) {
-          message = "Both the left-hand and right-hand sides are null";
-        } else {
-          message = "The left-hand size is null";
-        }
-      } else {
-        message = "The right-hand size is null";
-      }
-      AnalysisEngine.instance.logger.logError(
-          message, new CaughtException(new AnalysisException(message), null));
-    }
-    _leftHandSide = _becomeParentOf(leftHandSide);
-    _rightHandSide = _becomeParentOf(rightHandSide);
-  }
-
-  @override
-  Token get beginToken => _leftHandSide.beginToken;
-
-  @override
-  MethodElement get bestElement {
-    MethodElement element = propagatedElement;
-    if (element == null) {
-      element = staticElement;
-    }
-    return element;
-  }
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(_leftHandSide)
-    ..add(operator)
-    ..add(_rightHandSide);
-
-  @override
-  Token get endToken => _rightHandSide.endToken;
-
-  @override
-  Expression get leftHandSide => _leftHandSide;
-
-  @override
-  void set leftHandSide(Expression expression) {
-    _leftHandSide = _becomeParentOf(expression);
-  }
-
-  @override
-  int get precedence => 1;
-
-  @override
-  Expression get rightHandSide => _rightHandSide;
-
-  @override
-  void set rightHandSide(Expression expression) {
-    _rightHandSide = _becomeParentOf(expression);
-  }
-
-  /**
-   * If the AST structure has been resolved, and the function being invoked is
-   * known based on propagated type information, then return the parameter
-   * element representing the parameter to which the value of the right operand
-   * will be bound. Otherwise, return `null`.
-   */
-  ParameterElement get _propagatedParameterElementForRightHandSide {
-    ExecutableElement executableElement = null;
-    if (propagatedElement != null) {
-      executableElement = propagatedElement;
-    } else {
-      if (_leftHandSide is Identifier) {
-        Identifier identifier = _leftHandSide as Identifier;
-        Element leftElement = identifier.propagatedElement;
-        if (leftElement is ExecutableElement) {
-          executableElement = leftElement;
-        }
-      }
-      if (_leftHandSide is PropertyAccess) {
-        SimpleIdentifier identifier =
-            (_leftHandSide as PropertyAccess).propertyName;
-        Element leftElement = identifier.propagatedElement;
-        if (leftElement is ExecutableElement) {
-          executableElement = leftElement;
-        }
-      }
-    }
-    if (executableElement == null) {
-      return null;
-    }
-    List<ParameterElement> parameters = executableElement.parameters;
-    if (parameters.length < 1) {
-      return null;
-    }
-    return parameters[0];
-  }
-
-  /**
-   * If the AST structure has been resolved, and the function being invoked is
-   * known based on static type information, then return the parameter element
-   * representing the parameter to which the value of the right operand will be
-   * bound. Otherwise, return `null`.
-   */
-  ParameterElement get _staticParameterElementForRightHandSide {
-    ExecutableElement executableElement = null;
-    if (staticElement != null) {
-      executableElement = staticElement;
-    } else {
-      if (_leftHandSide is Identifier) {
-        Element leftElement = (_leftHandSide as Identifier).staticElement;
-        if (leftElement is ExecutableElement) {
-          executableElement = leftElement;
-        }
-      }
-      if (_leftHandSide is PropertyAccess) {
-        Element leftElement =
-            (_leftHandSide as PropertyAccess).propertyName.staticElement;
-        if (leftElement is ExecutableElement) {
-          executableElement = leftElement;
-        }
-      }
-    }
-    if (executableElement == null) {
-      return null;
-    }
-    List<ParameterElement> parameters = executableElement.parameters;
-    if (parameters.length < 1) {
-      return null;
-    }
-    return parameters[0];
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitAssignmentExpression(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_leftHandSide, visitor);
-    _safelyVisitChild(_rightHandSide, visitor);
-  }
-}
-
-/**
- * A node in the AST structure for a Dart program.
- */
-abstract class AstNodeImpl implements AstNode {
-  /**
-   * The parent of the node, or `null` if the node is the root of an AST
-   * structure.
-   */
-  AstNode _parent;
-
-  /**
-   * A table mapping the names of properties to their values, or `null` if this
-   * node does not have any properties associated with it.
-   */
-  Map<String, Object> _propertyMap;
-
-  @override
-  int get end => offset + length;
-
-  @override
-  bool get isSynthetic => false;
-
-  @override
-  int get length {
-    Token beginToken = this.beginToken;
-    Token endToken = this.endToken;
-    if (beginToken == null || endToken == null) {
-      return -1;
-    }
-    return endToken.offset + endToken.length - beginToken.offset;
-  }
-
-  @override
-  int get offset {
-    Token beginToken = this.beginToken;
-    if (beginToken == null) {
-      return -1;
-    }
-    return beginToken.offset;
-  }
-
-  @override
-  AstNode get parent => _parent;
-
-  @override
-  AstNode get root {
-    AstNode root = this;
-    AstNode parent = this.parent;
-    while (parent != null) {
-      root = parent;
-      parent = root.parent;
-    }
-    return root;
-  }
-
-  @override
-  AstNode getAncestor(Predicate<AstNode> predicate) {
-    // TODO(brianwilkerson) It is a bug that this method can return `this`.
-    AstNode node = this;
-    while (node != null && !predicate(node)) {
-      node = node.parent;
-    }
-    return node;
-  }
-
-  @override
-  Object getProperty(String name) {
-    if (_propertyMap == null) {
-      return null;
-    }
-    return _propertyMap[name];
-  }
-
-  @override
-  void setProperty(String name, Object value) {
-    if (value == null) {
-      if (_propertyMap != null) {
-        _propertyMap.remove(name);
-        if (_propertyMap.isEmpty) {
-          _propertyMap = null;
-        }
-      }
-    } else {
-      if (_propertyMap == null) {
-        _propertyMap = new HashMap<String, Object>();
-      }
-      _propertyMap[name] = value;
-    }
-  }
-
-  @override
-  String toSource() {
-    PrintStringWriter writer = new PrintStringWriter();
-    accept(new ToSourceVisitor(writer));
-    return writer.toString();
-  }
-
-  @override
-  String toString() => toSource();
-
-  /**
-   * Make this node the parent of the given [child] node. Return the child node.
-   */
-  AstNode _becomeParentOf(AstNode child) {
-    if (child != null) {
-      (child as AstNodeImpl)._parent = this;
-    }
-    return child;
-  }
-
-  /**
-   * If the given [child] is not `null`, use the given [visitor] to visit it.
-   */
-  void _safelyVisitChild(AstNode child, AstVisitor visitor) {
-    if (child != null) {
-      child.accept(visitor);
-    }
-  }
-}
-
-/**
- * An await expression.
- *
- * > awaitExpression ::=
- * >     'await' [Expression]
- */
-class AwaitExpressionImpl extends ExpressionImpl implements AwaitExpression {
-  /**
-   * The 'await' keyword.
-   */
-  Token awaitKeyword;
-
-  /**
-   * The expression whose value is being waited on.
-   */
-  Expression _expression;
-
-  /**
-   * Initialize a newly created await expression.
-   */
-  AwaitExpressionImpl(this.awaitKeyword, Expression expression) {
-    _expression = _becomeParentOf(expression);
-  }
-
-  @override
-  Token get beginToken {
-    if (awaitKeyword != null) {
-      return awaitKeyword;
-    }
-    return _expression.beginToken;
-  }
-
-  @override
-  Iterable get childEntities =>
-      new ChildEntities()..add(awaitKeyword)..add(_expression);
-
-  @override
-  Token get endToken => _expression.endToken;
-
-  @override
-  Expression get expression => _expression;
-
-  @override
-  void set expression(Expression expression) {
-    _expression = _becomeParentOf(expression);
-  }
-
-  @override
-  int get precedence => 0;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitAwaitExpression(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_expression, visitor);
-  }
-}
-
-/**
- * A binary (infix) expression.
- *
- * > binaryExpression ::=
- * >     [Expression] [Token] [Expression]
- */
-class BinaryExpressionImpl extends ExpressionImpl implements BinaryExpression {
-  /**
-   * The expression used to compute the left operand.
-   */
-  Expression _leftOperand;
-
-  /**
-   * The binary operator being applied.
-   */
-  Token operator;
-
-  /**
-   * The expression used to compute the right operand.
-   */
-  Expression _rightOperand;
-
-  /**
-   * The element associated with the operator based on the static type of the
-   * left operand, or `null` if the AST structure has not been resolved, if the
-   * operator is not user definable, or if the operator could not be resolved.
-   */
-  MethodElement staticElement;
-
-  /**
-   * The element associated with the operator based on the propagated type of
-   * the left operand, or `null` if the AST structure has not been resolved, if
-   * the operator is not user definable, or if the operator could not be
-   * resolved.
-   */
-  MethodElement propagatedElement;
-
-  /**
-   * Initialize a newly created binary expression.
-   */
-  BinaryExpressionImpl(
-      Expression leftOperand, this.operator, Expression rightOperand) {
-    _leftOperand = _becomeParentOf(leftOperand);
-    _rightOperand = _becomeParentOf(rightOperand);
-  }
-
-  @override
-  Token get beginToken => _leftOperand.beginToken;
-
-  @override
-  MethodElement get bestElement {
-    MethodElement element = propagatedElement;
-    if (element == null) {
-      element = staticElement;
-    }
-    return element;
-  }
-
-  @override
-  Iterable get childEntities =>
-      new ChildEntities()..add(_leftOperand)..add(operator)..add(_rightOperand);
-
-  @override
-  Token get endToken => _rightOperand.endToken;
-
-  @override
-  Expression get leftOperand => _leftOperand;
-
-  @override
-  void set leftOperand(Expression expression) {
-    _leftOperand = _becomeParentOf(expression);
-  }
-
-  @override
-  int get precedence => operator.type.precedence;
-
-  @override
-  Expression get rightOperand => _rightOperand;
-
-  @override
-  void set rightOperand(Expression expression) {
-    _rightOperand = _becomeParentOf(expression);
-  }
-
-  /**
-   * If the AST structure has been resolved, and the function being invoked is
-   * known based on propagated type information, then return the parameter
-   * element representing the parameter to which the value of the right operand
-   * will be bound. Otherwise, return `null`.
-   */
-  ParameterElement get _propagatedParameterElementForRightOperand {
-    if (propagatedElement == null) {
-      return null;
-    }
-    List<ParameterElement> parameters = propagatedElement.parameters;
-    if (parameters.length < 1) {
-      return null;
-    }
-    return parameters[0];
-  }
-
-  /**
-   * If the AST structure has been resolved, and the function being invoked is
-   * known based on static type information, then return the parameter element
-   * representing the parameter to which the value of the right operand will be
-   * bound. Otherwise, return `null`.
-   */
-  ParameterElement get _staticParameterElementForRightOperand {
-    if (staticElement == null) {
-      return null;
-    }
-    List<ParameterElement> parameters = staticElement.parameters;
-    if (parameters.length < 1) {
-      return null;
-    }
-    return parameters[0];
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitBinaryExpression(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_leftOperand, visitor);
-    _safelyVisitChild(_rightOperand, visitor);
-  }
-}
-
-/**
- * A function body that consists of a block of statements.
- *
- * > blockFunctionBody ::=
- * >     ('async' | 'async' '*' | 'sync' '*')? [Block]
- */
-class BlockFunctionBodyImpl extends FunctionBodyImpl
-    implements BlockFunctionBody {
-  /**
-   * The token representing the 'async' or 'sync' keyword, or `null` if there is
-   * no such keyword.
-   */
-  Token keyword;
-
-  /**
-   * The star optionally following the 'async' or 'sync' keyword, or `null` if
-   * there is wither no such keyword or no star.
-   */
-  Token star;
-
-  /**
-   * The block representing the body of the function.
-   */
-  Block _block;
-
-  /**
-   * Initialize a newly created function body consisting of a block of
-   * statements. The [keyword] can be `null` if there is no keyword specified
-   * for the block. The [star] can be `null` if there is no star following the
-   * keyword (and must be `null` if there is no keyword).
-   */
-  BlockFunctionBodyImpl(this.keyword, this.star, Block block) {
-    _block = _becomeParentOf(block);
-  }
-
-  @override
-  Token get beginToken {
-    if (keyword != null) {
-      return keyword;
-    }
-    return _block.beginToken;
-  }
-
-  @override
-  Block get block => _block;
-
-  @override
-  void set block(Block block) {
-    _block = _becomeParentOf(block);
-  }
-
-  @override
-  Iterable get childEntities =>
-      new ChildEntities()..add(keyword)..add(star)..add(_block);
-
-  @override
-  Token get endToken => _block.endToken;
-
-  @override
-  bool get isAsynchronous => keyword != null && keyword.lexeme == Parser.ASYNC;
-
-  @override
-  bool get isGenerator => star != null;
-
-  @override
-  bool get isSynchronous => keyword == null || keyword.lexeme != Parser.ASYNC;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitBlockFunctionBody(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_block, visitor);
-  }
-}
-
-/**
- * A sequence of statements.
- *
- * > block ::=
- * >     '{' statement* '}'
- */
-class BlockImpl extends StatementImpl implements Block {
-  /**
-   * The left curly bracket.
-   */
-  Token leftBracket;
-
-  /**
-   * The statements contained in the block.
-   */
-  NodeList<Statement> _statements;
-
-  /**
-   * The right curly bracket.
-   */
-  Token rightBracket;
-
-  /**
-   * Initialize a newly created block of code.
-   */
-  BlockImpl(this.leftBracket, List<Statement> statements, this.rightBracket) {
-    _statements = new NodeList<Statement>(this, statements);
-  }
-
-  @override
-  Token get beginToken => leftBracket;
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(leftBracket)
-    ..addAll(_statements)
-    ..add(rightBracket);
-
-  @override
-  Token get endToken => rightBracket;
-
-  @override
-  NodeList<Statement> get statements => _statements;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitBlock(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _statements.accept(visitor);
-  }
-}
-
-/**
- * A boolean literal expression.
- *
- * > booleanLiteral ::=
- * >     'false' | 'true'
- */
-class BooleanLiteralImpl extends LiteralImpl implements BooleanLiteral {
-  /**
-   * The token representing the literal.
-   */
-  Token literal;
-
-  /**
-   * The value of the literal.
-   */
-  bool value = false;
-
-  /**
-   * Initialize a newly created boolean literal.
-   */
-  BooleanLiteralImpl(this.literal, this.value);
-
-  @override
-  Token get beginToken => literal;
-
-  @override
-  Iterable get childEntities => new ChildEntities()..add(literal);
-
-  @override
-  Token get endToken => literal;
-
-  @override
-  bool get isSynthetic => literal.isSynthetic;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitBooleanLiteral(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    // There are no children to visit.
-  }
-}
-
-/**
- * A break statement.
- *
- * > breakStatement ::=
- * >     'break' [SimpleIdentifier]? ';'
- */
-class BreakStatementImpl extends StatementImpl implements BreakStatement {
-  /**
-   * The token representing the 'break' keyword.
-   */
-  Token breakKeyword;
-
-  /**
-   * The label associated with the statement, or `null` if there is no label.
-   */
-  SimpleIdentifier _label;
-
-  /**
-   * The semicolon terminating the statement.
-   */
-  Token semicolon;
-
-  /**
-   * The AstNode which this break statement is breaking from.  This will be
-   * either a [Statement] (in the case of breaking out of a loop), a
-   * [SwitchMember] (in the case of a labeled break statement whose label
-   * matches a label on a switch case in an enclosing switch statement), or
-   * `null` if the AST has not yet been resolved or if the target could not be
-   * resolved. Note that if the source code has errors, the target might be
-   * invalid (e.g. trying to break to a switch case).
-   */
-  AstNode target;
-
-  /**
-   * Initialize a newly created break statement. The [label] can be `null` if
-   * there is no label associated with the statement.
-   */
-  BreakStatementImpl(
-      this.breakKeyword, SimpleIdentifier label, this.semicolon) {
-    _label = _becomeParentOf(label);
-  }
-
-  @override
-  Token get beginToken => breakKeyword;
-
-  @override
-  Iterable get childEntities =>
-      new ChildEntities()..add(breakKeyword)..add(_label)..add(semicolon);
-
-  @override
-  Token get endToken => semicolon;
-
-  @override
-  SimpleIdentifier get label => _label;
-
-  @override
-  void set label(SimpleIdentifier identifier) {
-    _label = _becomeParentOf(identifier);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitBreakStatement(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_label, visitor);
-  }
-}
-
-/**
- * A sequence of cascaded expressions: expressions that share a common target.
- * There are three kinds of expressions that can be used in a cascade
- * expression: [IndexExpression], [MethodInvocation] and [PropertyAccess].
- *
- * > cascadeExpression ::=
- * >     [Expression] cascadeSection*
- * >
- * > cascadeSection ::=
- * >     '..'  (cascadeSelector arguments*) (assignableSelector arguments*)*
- * >     (assignmentOperator expressionWithoutCascade)?
- * >
- * > cascadeSelector ::=
- * >     '[ ' expression '] '
- * >   | identifier
- */
-class CascadeExpressionImpl extends ExpressionImpl
-    implements CascadeExpression {
-  /**
-   * The target of the cascade sections.
-   */
-  Expression _target;
-
-  /**
-   * The cascade sections sharing the common target.
-   */
-  NodeList<Expression> _cascadeSections;
-
-  /**
-   * Initialize a newly created cascade expression. The list of
-   * [cascadeSections] must contain at least one element.
-   */
-  CascadeExpressionImpl(Expression target, List<Expression> cascadeSections) {
-    _target = _becomeParentOf(target);
-    _cascadeSections = new NodeList<Expression>(this, cascadeSections);
-  }
-
-  @override
-  Token get beginToken => _target.beginToken;
-
-  @override
-  NodeList<Expression> get cascadeSections => _cascadeSections;
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(_target)
-    ..addAll(_cascadeSections);
-
-  @override
-  Token get endToken => _cascadeSections.endToken;
-
-  @override
-  int get precedence => 2;
-
-  @override
-  Expression get target => _target;
-
-  @override
-  void set target(Expression target) {
-    _target = _becomeParentOf(target);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitCascadeExpression(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_target, visitor);
-    _cascadeSections.accept(visitor);
-  }
-}
-
-/**
- * A catch clause within a try statement.
- *
- * > onPart ::=
- * >     catchPart [Block]
- * >   | 'on' type catchPart? [Block]
- * >
- * > catchPart ::=
- * >     'catch' '(' [SimpleIdentifier] (',' [SimpleIdentifier])? ')'
- */
-class CatchClauseImpl extends AstNodeImpl implements CatchClause {
-  /**
-   * The token representing the 'on' keyword, or `null` if there is no 'on'
-   * keyword.
-   */
-  Token onKeyword;
-
-  /**
-   * The type of exceptions caught by this catch clause, or `null` if this catch
-   * clause catches every type of exception.
-   */
-  TypeName _exceptionType;
-
-  /**
-   * The token representing the 'catch' keyword, or `null` if there is no
-   * 'catch' keyword.
-   */
-  Token catchKeyword;
-
-  /**
-   * The left parenthesis, or `null` if there is no 'catch' keyword.
-   */
-  Token leftParenthesis;
-
-  /**
-   * The parameter whose value will be the exception that was thrown, or `null`
-   * if there is no 'catch' keyword.
-   */
-  SimpleIdentifier _exceptionParameter;
-
-  /**
-   * The comma separating the exception parameter from the stack trace
-   * parameter, or `null` if there is no stack trace parameter.
-   */
-  Token comma;
-
-  /**
-   * The parameter whose value will be the stack trace associated with the
-   * exception, or `null` if there is no stack trace parameter.
-   */
-  SimpleIdentifier _stackTraceParameter;
-
-  /**
-   * The right parenthesis, or `null` if there is no 'catch' keyword.
-   */
-  Token rightParenthesis;
-
-  /**
-   * The body of the catch block.
-   */
-  Block _body;
-
-  /**
-   * Initialize a newly created catch clause. The [onKeyword] and
-   * [exceptionType] can be `null` if the clause will catch all exceptions. The
-   * [comma] and [stackTraceParameter] can be `null` if the stack trace
-   * parameter is not defined.
-   */
-  CatchClauseImpl(
-      this.onKeyword,
-      TypeName exceptionType,
-      this.catchKeyword,
-      this.leftParenthesis,
-      SimpleIdentifier exceptionParameter,
-      this.comma,
-      SimpleIdentifier stackTraceParameter,
-      this.rightParenthesis,
-      Block body) {
-    _exceptionType = _becomeParentOf(exceptionType);
-    _exceptionParameter = _becomeParentOf(exceptionParameter);
-    _stackTraceParameter = _becomeParentOf(stackTraceParameter);
-    _body = _becomeParentOf(body);
-  }
-
-  @override
-  Token get beginToken {
-    if (onKeyword != null) {
-      return onKeyword;
-    }
-    return catchKeyword;
-  }
-
-  @override
-  Block get body => _body;
-
-  @override
-  void set body(Block block) {
-    _body = _becomeParentOf(block);
-  }
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(onKeyword)
-    ..add(_exceptionType)
-    ..add(catchKeyword)
-    ..add(leftParenthesis)
-    ..add(_exceptionParameter)
-    ..add(comma)
-    ..add(_stackTraceParameter)
-    ..add(rightParenthesis)
-    ..add(_body);
-
-  @override
-  Token get endToken => _body.endToken;
-
-  @override
-  SimpleIdentifier get exceptionParameter => _exceptionParameter;
-
-  @override
-  void set exceptionParameter(SimpleIdentifier parameter) {
-    _exceptionParameter = _becomeParentOf(parameter);
-  }
-
-  @override
-  TypeName get exceptionType => _exceptionType;
-
-  @override
-  void set exceptionType(TypeName exceptionType) {
-    _exceptionType = _becomeParentOf(exceptionType);
-  }
-
-  @override
-  SimpleIdentifier get stackTraceParameter => _stackTraceParameter;
-
-  @override
-  void set stackTraceParameter(SimpleIdentifier parameter) {
-    _stackTraceParameter = _becomeParentOf(parameter);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitCatchClause(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_exceptionType, visitor);
-    _safelyVisitChild(_exceptionParameter, visitor);
-    _safelyVisitChild(_stackTraceParameter, visitor);
-    _safelyVisitChild(_body, visitor);
-  }
-}
-
-/**
- * Helper class to allow iteration of child entities of an AST node.
- */
-class ChildEntities extends Object with IterableMixin implements Iterable {
-  /**
-   * The list of child entities to be iterated over.
-   */
-  List _entities = [];
-
-  @override
-  Iterator get iterator => _entities.iterator;
-
-  /**
-   * Add an AST node or token as the next child entity, if it is not null.
-   */
-  void add(entity) {
-    if (entity != null) {
-      assert(entity is Token || entity is AstNode);
-      _entities.add(entity);
-    }
-  }
-
-  /**
-   * Add the given items as the next child entities, if [items] is not null.
-   */
-  void addAll(Iterable items) {
-    if (items != null) {
-      _entities.addAll(items);
-    }
-  }
-}
-
-/**
- * The declaration of a class.
- *
- * > classDeclaration ::=
- * >     'abstract'? 'class' [SimpleIdentifier] [TypeParameterList]?
- * >     ([ExtendsClause] [WithClause]?)?
- * >     [ImplementsClause]?
- * >     '{' [ClassMember]* '}'
- */
-class ClassDeclarationImpl extends NamedCompilationUnitMemberImpl
-    implements ClassDeclaration {
-  /**
-   * The 'abstract' keyword, or `null` if the keyword was absent.
-   */
-  Token abstractKeyword;
-
-  /**
-   * The token representing the 'class' keyword.
-   */
-  Token classKeyword;
-
-  /**
-   * The type parameters for the class, or `null` if the class does not have any
-   * type parameters.
-   */
-  TypeParameterList _typeParameters;
-
-  /**
-   * The extends clause for the class, or `null` if the class does not extend
-   * any other class.
-   */
-  ExtendsClause _extendsClause;
-
-  /**
-   * The with clause for the class, or `null` if the class does not have a with
-   * clause.
-   */
-  WithClause _withClause;
-
-  /**
-   * The implements clause for the class, or `null` if the class does not
-   * implement any interfaces.
-   */
-  ImplementsClause _implementsClause;
-
-  /**
-   * The native clause for the class, or `null` if the class does not have a
-   * native clause.
-   */
-  NativeClause _nativeClause;
-
-  /**
-   * The left curly bracket.
-   */
-  Token leftBracket;
-
-  /**
-   * The members defined by the class.
-   */
-  NodeList<ClassMember> _members;
-
-  /**
-   * The right curly bracket.
-   */
-  Token rightBracket;
-
-  /**
-   * Initialize a newly created class declaration. Either or both of the
-   * [comment] and [metadata] can be `null` if the class does not have the
-   * corresponding attribute. The [abstractKeyword] can be `null` if the class
-   * is not abstract. The [typeParameters] can be `null` if the class does not
-   * have any type parameters. Any or all of the [extendsClause], [withClause],
-   * and [implementsClause] can be `null` if the class does not have the
-   * corresponding clause. The list of [members] can be `null` if the class does
-   * not have any members.
-   */
-  ClassDeclarationImpl(
-      Comment comment,
-      List<Annotation> metadata,
-      this.abstractKeyword,
-      this.classKeyword,
-      SimpleIdentifier name,
-      TypeParameterList typeParameters,
-      ExtendsClause extendsClause,
-      WithClause withClause,
-      ImplementsClause implementsClause,
-      this.leftBracket,
-      List<ClassMember> members,
-      this.rightBracket)
-      : super(comment, metadata, name) {
-    _typeParameters = _becomeParentOf(typeParameters);
-    _extendsClause = _becomeParentOf(extendsClause);
-    _withClause = _becomeParentOf(withClause);
-    _implementsClause = _becomeParentOf(implementsClause);
-    _members = new NodeList<ClassMember>(this, members);
-  }
-
-  @override
-  Iterable get childEntities => super._childEntities
-    ..add(abstractKeyword)
-    ..add(classKeyword)
-    ..add(_name)
-    ..add(_typeParameters)
-    ..add(_extendsClause)
-    ..add(_withClause)
-    ..add(_implementsClause)
-    ..add(_nativeClause)
-    ..add(leftBracket)
-    ..addAll(members)
-    ..add(rightBracket);
-
-  @override
-  ClassElement get element =>
-      _name != null ? (_name.staticElement as ClassElement) : null;
-
-  @override
-  Token get endToken => rightBracket;
-
-  @override
-  ExtendsClause get extendsClause => _extendsClause;
-
-  @override
-  void set extendsClause(ExtendsClause extendsClause) {
-    _extendsClause = _becomeParentOf(extendsClause);
-  }
-
-  @override
-  Token get firstTokenAfterCommentAndMetadata {
-    if (abstractKeyword != null) {
-      return abstractKeyword;
-    }
-    return classKeyword;
-  }
-
-  @override
-  ImplementsClause get implementsClause => _implementsClause;
-
-  @override
-  void set implementsClause(ImplementsClause implementsClause) {
-    _implementsClause = _becomeParentOf(implementsClause);
-  }
-
-  @override
-  bool get isAbstract => abstractKeyword != null;
-
-  @override
-  NodeList<ClassMember> get members => _members;
-
-  @override
-  NativeClause get nativeClause => _nativeClause;
-
-  @override
-  void set nativeClause(NativeClause nativeClause) {
-    _nativeClause = _becomeParentOf(nativeClause);
-  }
-
-  @override
-  TypeParameterList get typeParameters => _typeParameters;
-
-  @override
-  void set typeParameters(TypeParameterList typeParameters) {
-    _typeParameters = _becomeParentOf(typeParameters);
-  }
-
-  @override
-  WithClause get withClause => _withClause;
-
-  @override
-  void set withClause(WithClause withClause) {
-    _withClause = _becomeParentOf(withClause);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitClassDeclaration(this);
-
-  @override
-  ConstructorDeclaration getConstructor(String name) {
-    for (ClassMember classMember in _members) {
-      if (classMember is ConstructorDeclaration) {
-        ConstructorDeclaration constructor = classMember;
-        SimpleIdentifier constructorName = constructor.name;
-        if (name == null && constructorName == null) {
-          return constructor;
-        }
-        if (constructorName != null && constructorName.name == name) {
-          return constructor;
-        }
-      }
-    }
-    return null;
-  }
-
-  @override
-  VariableDeclaration getField(String name) {
-    for (ClassMember classMember in _members) {
-      if (classMember is FieldDeclaration) {
-        FieldDeclaration fieldDeclaration = classMember;
-        NodeList<VariableDeclaration> fields =
-            fieldDeclaration.fields.variables;
-        for (VariableDeclaration field in fields) {
-          SimpleIdentifier fieldName = field.name;
-          if (fieldName != null && name == fieldName.name) {
-            return field;
-          }
-        }
-      }
-    }
-    return null;
-  }
-
-  @override
-  MethodDeclaration getMethod(String name) {
-    for (ClassMember classMember in _members) {
-      if (classMember is MethodDeclaration) {
-        MethodDeclaration method = classMember;
-        SimpleIdentifier methodName = method.name;
-        if (methodName != null && name == methodName.name) {
-          return method;
-        }
-      }
-    }
-    return null;
-  }
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    super.visitChildren(visitor);
-    _safelyVisitChild(_name, visitor);
-    _safelyVisitChild(_typeParameters, visitor);
-    _safelyVisitChild(_extendsClause, visitor);
-    _safelyVisitChild(_withClause, visitor);
-    _safelyVisitChild(_implementsClause, visitor);
-    _safelyVisitChild(_nativeClause, visitor);
-    members.accept(visitor);
-  }
-}
-
-/**
- * A node that declares a name within the scope of a class.
- */
-abstract class ClassMemberImpl extends DeclarationImpl implements ClassMember {
-  /**
-   * Initialize a newly created member of a class. Either or both of the
-   * [comment] and [metadata] can be `null` if the member does not have the
-   * corresponding attribute.
-   */
-  ClassMemberImpl(Comment comment, List<Annotation> metadata)
-      : super(comment, metadata);
-}
-
-/**
- * A class type alias.
- *
- * > classTypeAlias ::=
- * >     [SimpleIdentifier] [TypeParameterList]? '=' 'abstract'? mixinApplication
- * >
- * > mixinApplication ::=
- * >     [TypeName] [WithClause] [ImplementsClause]? ';'
- */
-class ClassTypeAliasImpl extends TypeAliasImpl implements ClassTypeAlias {
-  /**
-   * The type parameters for the class, or `null` if the class does not have any
-   * type parameters.
-   */
-  TypeParameterList _typeParameters;
-
-  /**
-   * The token for the '=' separating the name from the definition.
-   */
-  Token equals;
-
-  /**
-   * The token for the 'abstract' keyword, or `null` if this is not defining an
-   * abstract class.
-   */
-  Token abstractKeyword;
-
-  /**
-   * The name of the superclass of the class being declared.
-   */
-  TypeName _superclass;
-
-  /**
-   * The with clause for this class.
-   */
-  WithClause _withClause;
-
-  /**
-   * The implements clause for this class, or `null` if there is no implements
-   * clause.
-   */
-  ImplementsClause _implementsClause;
-
-  /**
-   * Initialize a newly created class type alias. Either or both of the
-   * [comment] and [metadata] can be `null` if the class type alias does not
-   * have the corresponding attribute. The [typeParameters] can be `null` if the
-   * class does not have any type parameters. The [abstractKeyword] can be
-   * `null` if the class is not abstract. The [implementsClause] can be `null`
-   * if the class does not implement any interfaces.
-   */
-  ClassTypeAliasImpl(
-      Comment comment,
-      List<Annotation> metadata,
-      Token keyword,
-      SimpleIdentifier name,
-      TypeParameterList typeParameters,
-      this.equals,
-      this.abstractKeyword,
-      TypeName superclass,
-      WithClause withClause,
-      ImplementsClause implementsClause,
-      Token semicolon)
-      : super(comment, metadata, keyword, name, semicolon) {
-    _typeParameters = _becomeParentOf(typeParameters);
-    _superclass = _becomeParentOf(superclass);
-    _withClause = _becomeParentOf(withClause);
-    _implementsClause = _becomeParentOf(implementsClause);
-  }
-
-  @override
-  Iterable get childEntities => super._childEntities
-    ..add(typedefKeyword)
-    ..add(_name)
-    ..add(_typeParameters)
-    ..add(equals)
-    ..add(abstractKeyword)
-    ..add(_superclass)
-    ..add(_withClause)
-    ..add(_implementsClause)
-    ..add(semicolon);
-
-  @override
-  ClassElement get element =>
-      _name != null ? (_name.staticElement as ClassElement) : null;
-
-  @override
-  ImplementsClause get implementsClause => _implementsClause;
-
-  @override
-  void set implementsClause(ImplementsClause implementsClause) {
-    _implementsClause = _becomeParentOf(implementsClause);
-  }
-
-  @override
-  bool get isAbstract => abstractKeyword != null;
-
-  @override
-  TypeName get superclass => _superclass;
-
-  @override
-  void set superclass(TypeName superclass) {
-    _superclass = _becomeParentOf(superclass);
-  }
-
-  @override
-  TypeParameterList get typeParameters => _typeParameters;
-
-  @override
-  void set typeParameters(TypeParameterList typeParameters) {
-    _typeParameters = _becomeParentOf(typeParameters);
-  }
-
-  @override
-  WithClause get withClause => _withClause;
-
-  @override
-  void set withClause(WithClause withClause) {
-    _withClause = _becomeParentOf(withClause);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitClassTypeAlias(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    super.visitChildren(visitor);
-    _safelyVisitChild(_name, visitor);
-    _safelyVisitChild(_typeParameters, visitor);
-    _safelyVisitChild(_superclass, visitor);
-    _safelyVisitChild(_withClause, visitor);
-    _safelyVisitChild(_implementsClause, visitor);
-  }
-}
-
-/**
- * A combinator associated with an import or export directive.
- *
- * > combinator ::=
- * >     [HideCombinator]
- * >   | [ShowCombinator]
- */
-abstract class CombinatorImpl extends AstNodeImpl implements Combinator {
-  /**
-   * The 'hide' or 'show' keyword specifying what kind of processing is to be
-   * done on the names.
-   */
-  Token keyword;
-
-  /**
-   * Initialize a newly created combinator.
-   */
-  CombinatorImpl(this.keyword);
-
-  @override
-  Token get beginToken => keyword;
-}
-
-/**
- * A comment within the source code.
- *
- * > comment ::=
- * >     endOfLineComment
- * >   | blockComment
- * >   | documentationComment
- * >
- * > endOfLineComment ::=
- * >     '//' (CHARACTER - EOL)* EOL
- * >
- * > blockComment ::=
- * >     '/ *' CHARACTER* '&#42;/'
- * >
- * > documentationComment ::=
- * >     '/ **' (CHARACTER | [CommentReference])* '&#42;/'
- * >   | ('///' (CHARACTER - EOL)* EOL)+
- */
-class CommentImpl extends AstNodeImpl implements Comment {
-  /**
-   * The tokens representing the comment.
-   */
-  final List<Token> tokens;
-
-  /**
-   * The type of the comment.
-   */
-  final CommentType _type;
-
-  /**
-   * The references embedded within the documentation comment. This list will be
-   * empty unless this is a documentation comment that has references embedded
-   * within it.
-   */
-  NodeList<CommentReference> _references;
-
-  /**
-   * Initialize a newly created comment. The list of [tokens] must contain at
-   * least one token. The [type] is the type of the comment. The list of
-   * [references] can be empty if the comment does not contain any embedded
-   * references.
-   */
-  CommentImpl(this.tokens, this._type, List<CommentReference> references) {
-    _references = new NodeList<CommentReference>(this, references);
-  }
-
-  @override
-  Token get beginToken => tokens[0];
-
-  @override
-  Iterable get childEntities => new ChildEntities()..addAll(tokens);
-
-  @override
-  Token get endToken => tokens[tokens.length - 1];
-
-  @override
-  bool get isBlock => _type == CommentType.BLOCK;
-
-  @override
-  bool get isDocumentation => _type == CommentType.DOCUMENTATION;
-
-  @override
-  bool get isEndOfLine => _type == CommentType.END_OF_LINE;
-
-  @override
-  NodeList<CommentReference> get references => _references;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitComment(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _references.accept(visitor);
-  }
-
-  /**
-   * Create a block comment consisting of the given [tokens].
-   */
-  static Comment createBlockComment(List<Token> tokens) =>
-      new CommentImpl(tokens, CommentType.BLOCK, null);
-
-  /**
-   * Create a documentation comment consisting of the given [tokens].
-   */
-  static Comment createDocumentationComment(List<Token> tokens) =>
-      new CommentImpl(
-          tokens, CommentType.DOCUMENTATION, new List<CommentReference>());
-
-  /**
-   * Create a documentation comment consisting of the given [tokens] and having
-   * the given [references] embedded within it.
-   */
-  static Comment createDocumentationCommentWithReferences(
-          List<Token> tokens, List<CommentReference> references) =>
-      new CommentImpl(tokens, CommentType.DOCUMENTATION, references);
-
-  /**
-   * Create an end-of-line comment consisting of the given [tokens].
-   */
-  static Comment createEndOfLineComment(List<Token> tokens) =>
-      new CommentImpl(tokens, CommentType.END_OF_LINE, null);
-}
-
-/**
- * A reference to a Dart element that is found within a documentation comment.
- *
- * > commentReference ::=
- * >     '[' 'new'? [Identifier] ']'
- */
-class CommentReferenceImpl extends AstNodeImpl implements CommentReference {
-  /**
-   * The token representing the 'new' keyword, or `null` if there was no 'new'
-   * keyword.
-   */
-  Token newKeyword;
-
-  /**
-   * The identifier being referenced.
-   */
-  Identifier _identifier;
-
-  /**
-   * Initialize a newly created reference to a Dart element. The [newKeyword]
-   * can be `null` if the reference is not to a constructor.
-   */
-  CommentReferenceImpl(this.newKeyword, Identifier identifier) {
-    _identifier = _becomeParentOf(identifier);
-  }
-
-  @override
-  Token get beginToken => _identifier.beginToken;
-
-  @override
-  Iterable get childEntities =>
-      new ChildEntities()..add(newKeyword)..add(_identifier);
-
-  @override
-  Token get endToken => _identifier.endToken;
-
-  @override
-  Identifier get identifier => _identifier;
-
-  @override
-  void set identifier(Identifier identifier) {
-    _identifier = _becomeParentOf(identifier);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitCommentReference(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_identifier, visitor);
-  }
-}
-
-/**
- * The possible types of comments that are recognized by the parser.
- */
-class CommentType {
-  /**
-   * A block comment.
-   */
-  static const CommentType BLOCK = const CommentType('BLOCK');
-
-  /**
-   * A documentation comment.
-   */
-  static const CommentType DOCUMENTATION = const CommentType('DOCUMENTATION');
-
-  /**
-   * An end-of-line comment.
-   */
-  static const CommentType END_OF_LINE = const CommentType('END_OF_LINE');
-
-  /**
-   * The name of the comment type.
-   */
-  final String name;
-
-  /**
-   * Initialize a newly created comment type to have the given [name].
-   */
-  const CommentType(this.name);
-
-  @override
-  String toString() => name;
-}
-
-/**
- * A compilation unit.
- *
- * While the grammar restricts the order of the directives and declarations
- * within a compilation unit, this class does not enforce those restrictions.
- * In particular, the children of a compilation unit will be visited in lexical
- * order even if lexical order does not conform to the restrictions of the
- * grammar.
- *
- * > compilationUnit ::=
- * >     directives declarations
- * >
- * > directives ::=
- * >     [ScriptTag]? [LibraryDirective]? namespaceDirective* [PartDirective]*
- * >   | [PartOfDirective]
- * >
- * > namespaceDirective ::=
- * >     [ImportDirective]
- * >   | [ExportDirective]
- * >
- * > declarations ::=
- * >     [CompilationUnitMember]*
- */
-class CompilationUnitImpl extends AstNodeImpl implements CompilationUnit {
-  /**
-   * The first token in the token stream that was parsed to form this
-   * compilation unit.
-   */
-  Token beginToken;
-
-  /**
-   * The script tag at the beginning of the compilation unit, or `null` if there
-   * is no script tag in this compilation unit.
-   */
-  ScriptTag _scriptTag;
-
-  /**
-   * The directives contained in this compilation unit.
-   */
-  NodeList<Directive> _directives;
-
-  /**
-   * The declarations contained in this compilation unit.
-   */
-  NodeList<CompilationUnitMember> _declarations;
-
-  /**
-   * The last token in the token stream that was parsed to form this compilation
-   * unit. This token should always have a type of [TokenType.EOF].
-   */
-  Token endToken;
-
-  /**
-   * The element associated with this compilation unit, or `null` if the AST
-   * structure has not been resolved.
-   */
-  CompilationUnitElement element;
-
-  /**
-   * The line information for this compilation unit.
-   */
-  LineInfo lineInfo;
-
-  /**
-   * Initialize a newly created compilation unit to have the given directives
-   * and declarations. The [scriptTag] can be `null` if there is no script tag
-   * in the compilation unit. The list of [directives] can be `null` if there
-   * are no directives in the compilation unit. The list of [declarations] can
-   * be `null` if there are no declarations in the compilation unit.
-   */
-  CompilationUnitImpl(
-      this.beginToken,
-      ScriptTag scriptTag,
-      List<Directive> directives,
-      List<CompilationUnitMember> declarations,
-      this.endToken) {
-    _scriptTag = _becomeParentOf(scriptTag);
-    _directives = new NodeList<Directive>(this, directives);
-    _declarations = new NodeList<CompilationUnitMember>(this, declarations);
-  }
-
-  @override
-  Iterable get childEntities {
-    ChildEntities result = new ChildEntities()..add(_scriptTag);
-    if (_directivesAreBeforeDeclarations) {
-      result..addAll(_directives)..addAll(_declarations);
-    } else {
-      result.addAll(sortedDirectivesAndDeclarations);
-    }
-    return result;
-  }
-
-  @override
-  NodeList<CompilationUnitMember> get declarations => _declarations;
-
-  @override
-  NodeList<Directive> get directives => _directives;
-
-  @override
-  int get length {
-    Token endToken = this.endToken;
-    if (endToken == null) {
-      return 0;
-    }
-    return endToken.offset + endToken.length;
-  }
-
-  @override
-  int get offset => 0;
-
-  @override
-  ScriptTag get scriptTag => _scriptTag;
-
-  @override
-  void set scriptTag(ScriptTag scriptTag) {
-    _scriptTag = _becomeParentOf(scriptTag);
-  }
-
-  @override
-  List<AstNode> get sortedDirectivesAndDeclarations {
-    return <AstNode>[]
-      ..addAll(_directives)
-      ..addAll(_declarations)
-      ..sort(AstNode.LEXICAL_ORDER);
-  }
-
-  /**
-   * Return `true` if all of the directives are lexically before any
-   * declarations.
-   */
-  bool get _directivesAreBeforeDeclarations {
-    if (_directives.isEmpty || _declarations.isEmpty) {
-      return true;
-    }
-    Directive lastDirective = _directives[_directives.length - 1];
-    CompilationUnitMember firstDeclaration = _declarations[0];
-    return lastDirective.offset < firstDeclaration.offset;
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitCompilationUnit(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_scriptTag, visitor);
-    if (_directivesAreBeforeDeclarations) {
-      _directives.accept(visitor);
-      _declarations.accept(visitor);
-    } else {
-      for (AstNode child in sortedDirectivesAndDeclarations) {
-        child.accept(visitor);
-      }
-    }
-  }
-}
-
-/**
- * A node that declares one or more names within the scope of a compilation
- * unit.
- *
- * > compilationUnitMember ::=
- * >     [ClassDeclaration]
- * >   | [TypeAlias]
- * >   | [FunctionDeclaration]
- * >   | [MethodDeclaration]
- * >   | [VariableDeclaration]
- * >   | [VariableDeclaration]
- */
-abstract class CompilationUnitMemberImpl extends DeclarationImpl
-    implements CompilationUnitMember {
-  /**
-   * Initialize a newly created generic compilation unit member. Either or both
-   * of the [comment] and [metadata] can be `null` if the member does not have
-   * the corresponding attribute.
-   */
-  CompilationUnitMemberImpl(Comment comment, List<Annotation> metadata)
-      : super(comment, metadata);
-}
-
-/**
- * A conditional expression.
- *
- * > conditionalExpression ::=
- * >     [Expression] '?' [Expression] ':' [Expression]
- */
-class ConditionalExpressionImpl extends ExpressionImpl
-    implements ConditionalExpression {
-  /**
-   * The condition used to determine which of the expressions is executed next.
-   */
-  Expression _condition;
-
-  /**
-   * The token used to separate the condition from the then expression.
-   */
-  Token question;
-
-  /**
-   * The expression that is executed if the condition evaluates to `true`.
-   */
-  Expression _thenExpression;
-
-  /**
-   * The token used to separate the then expression from the else expression.
-   */
-  Token colon;
-
-  /**
-   * The expression that is executed if the condition evaluates to `false`.
-   */
-  Expression _elseExpression;
-
-  /**
-   * Initialize a newly created conditional expression.
-   */
-  ConditionalExpressionImpl(Expression condition, this.question,
-      Expression thenExpression, this.colon, Expression elseExpression) {
-    _condition = _becomeParentOf(condition);
-    _thenExpression = _becomeParentOf(thenExpression);
-    _elseExpression = _becomeParentOf(elseExpression);
-  }
-
-  @override
-  Token get beginToken => _condition.beginToken;
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(_condition)
-    ..add(question)
-    ..add(_thenExpression)
-    ..add(colon)
-    ..add(_elseExpression);
-
-  @override
-  Expression get condition => _condition;
-
-  @override
-  void set condition(Expression expression) {
-    _condition = _becomeParentOf(expression);
-  }
-
-  @override
-  Expression get elseExpression => _elseExpression;
-
-  @override
-  void set elseExpression(Expression expression) {
-    _elseExpression = _becomeParentOf(expression);
-  }
-
-  @override
-  Token get endToken => _elseExpression.endToken;
-
-  @override
-  int get precedence => 3;
-
-  @override
-  Expression get thenExpression => _thenExpression;
-
-  @override
-  void set thenExpression(Expression expression) {
-    _thenExpression = _becomeParentOf(expression);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitConditionalExpression(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_condition, visitor);
-    _safelyVisitChild(_thenExpression, visitor);
-    _safelyVisitChild(_elseExpression, visitor);
-  }
-}
-
-/**
- * A configuration in either an import or export directive.
- *
- *     configuration ::=
- *         'if' '(' test ')' uri
- *
- *     test ::=
- *         dottedName ('==' stringLiteral)?
- *
- *     dottedName ::=
- *         identifier ('.' identifier)*
- */
-class ConfigurationImpl extends AstNodeImpl implements Configuration {
-  Token ifKeyword;
-  Token leftParenthesis;
-  DottedName _name;
-  Token equalToken;
-  StringLiteral _value;
-  Token rightParenthesis;
-  StringLiteral _libraryUri;
-
-  ConfigurationImpl(
-      this.ifKeyword,
-      this.leftParenthesis,
-      DottedName name,
-      this.equalToken,
-      StringLiteral value,
-      this.rightParenthesis,
-      StringLiteral libraryUri) {
-    _name = _becomeParentOf(name);
-    _value = _becomeParentOf(value);
-    _libraryUri = _becomeParentOf(libraryUri);
-  }
-
-  @override
-  Token get beginToken => ifKeyword;
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(ifKeyword)
-    ..add(leftParenthesis)
-    ..add(_name)
-    ..add(equalToken)
-    ..add(_value)
-    ..add(rightParenthesis)
-    ..add(_libraryUri);
-
-  @override
-  Token get endToken => _libraryUri.endToken;
-
-  @override
-  StringLiteral get libraryUri => _libraryUri;
-
-  @override
-  void set libraryUri(StringLiteral libraryUri) {
-    _libraryUri = _becomeParentOf(libraryUri);
-  }
-
-  @override
-  DottedName get name => _name;
-
-  @override
-  void set name(DottedName name) {
-    _name = _becomeParentOf(name);
-  }
-
-  @override
-  StringLiteral get value => _value;
-
-  @override
-  void set value(StringLiteral value) {
-    _value = _becomeParentOf(value);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitConfiguration(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_name, visitor);
-    _safelyVisitChild(_value, visitor);
-    _safelyVisitChild(_libraryUri, visitor);
-  }
-}
-
-/**
- * A constructor declaration.
- *
- * > constructorDeclaration ::=
- * >     constructorSignature [FunctionBody]?
- * >   | constructorName formalParameterList ':' 'this' ('.' [SimpleIdentifier])? arguments
- * >
- * > constructorSignature ::=
- * >     'external'? constructorName formalParameterList initializerList?
- * >   | 'external'? 'factory' factoryName formalParameterList initializerList?
- * >   | 'external'? 'const'  constructorName formalParameterList initializerList?
- * >
- * > constructorName ::=
- * >     [SimpleIdentifier] ('.' [SimpleIdentifier])?
- * >
- * > factoryName ::=
- * >     [Identifier] ('.' [SimpleIdentifier])?
- * >
- * > initializerList ::=
- * >     ':' [ConstructorInitializer] (',' [ConstructorInitializer])*
- */
-class ConstructorDeclarationImpl extends ClassMemberImpl
-    implements ConstructorDeclaration {
-  /**
-   * The token for the 'external' keyword, or `null` if the constructor is not
-   * external.
-   */
-  Token externalKeyword;
-
-  /**
-   * The token for the 'const' keyword, or `null` if the constructor is not a
-   * const constructor.
-   */
-  Token constKeyword;
-
-  /**
-   * The token for the 'factory' keyword, or `null` if the constructor is not a
-   * factory constructor.
-   */
-  Token factoryKeyword;
-
-  /**
-   * The type of object being created. This can be different than the type in
-   * which the constructor is being declared if the constructor is the
-   * implementation of a factory constructor.
-   */
-  Identifier _returnType;
-
-  /**
-   * The token for the period before the constructor name, or `null` if the
-   * constructor being declared is unnamed.
-   */
-  Token period;
-
-  /**
-   * The name of the constructor, or `null` if the constructor being declared is
-   * unnamed.
-   */
-  SimpleIdentifier _name;
-
-  /**
-   * The parameters associated with the constructor.
-   */
-  FormalParameterList _parameters;
-
-  /**
-   * The token for the separator (colon or equals) before the initializer list
-   * or redirection, or `null` if there are no initializers.
-   */
-  Token separator;
-
-  /**
-   * The initializers associated with the constructor.
-   */
-  NodeList<ConstructorInitializer> _initializers;
-
-  /**
-   * The name of the constructor to which this constructor will be redirected,
-   * or `null` if this is not a redirecting factory constructor.
-   */
-  ConstructorName _redirectedConstructor;
-
-  /**
-   * The body of the constructor, or `null` if the constructor does not have a
-   * body.
-   */
-  FunctionBody _body;
-
-  /**
-   * The element associated with this constructor, or `null` if the AST
-   * structure has not been resolved or if this constructor could not be
-   * resolved.
-   */
-  ConstructorElement element;
-
-  /**
-   * Initialize a newly created constructor declaration. The [externalKeyword]
-   * can be `null` if the constructor is not external. Either or both of the
-   * [comment] and [metadata] can be `null` if the constructor does not have the
-   * corresponding attribute. The [constKeyword] can be `null` if the
-   * constructor cannot be used to create a constant. The [factoryKeyword] can
-   * be `null` if the constructor is not a factory. The [period] and [name] can
-   * both be `null` if the constructor is not a named constructor. The
-   * [separator] can be `null` if the constructor does not have any initializers
-   * and does not redirect to a different constructor. The list of
-   * [initializers] can be `null` if the constructor does not have any
-   * initializers. The [redirectedConstructor] can be `null` if the constructor
-   * does not redirect to a different constructor. The [body] can be `null` if
-   * the constructor does not have a body.
-   */
-  ConstructorDeclarationImpl(
-      Comment comment,
-      List<Annotation> metadata,
-      this.externalKeyword,
-      this.constKeyword,
-      this.factoryKeyword,
-      Identifier returnType,
-      this.period,
-      SimpleIdentifier name,
-      FormalParameterList parameters,
-      this.separator,
-      List<ConstructorInitializer> initializers,
-      ConstructorName redirectedConstructor,
-      FunctionBody body)
-      : super(comment, metadata) {
-    _returnType = _becomeParentOf(returnType);
-    _name = _becomeParentOf(name);
-    _parameters = _becomeParentOf(parameters);
-    _initializers = new NodeList<ConstructorInitializer>(this, initializers);
-    _redirectedConstructor = _becomeParentOf(redirectedConstructor);
-    _body = _becomeParentOf(body);
-  }
-
-  @override
-  FunctionBody get body => _body;
-
-  @override
-  void set body(FunctionBody functionBody) {
-    _body = _becomeParentOf(functionBody);
-  }
-
-  @override
-  Iterable get childEntities => super._childEntities
-    ..add(externalKeyword)
-    ..add(constKeyword)
-    ..add(factoryKeyword)
-    ..add(_returnType)
-    ..add(period)
-    ..add(_name)
-    ..add(_parameters)
-    ..add(separator)
-    ..addAll(initializers)
-    ..add(_redirectedConstructor)
-    ..add(_body);
-
-  @override
-  Token get endToken {
-    if (_body != null) {
-      return _body.endToken;
-    } else if (!_initializers.isEmpty) {
-      return _initializers.endToken;
-    }
-    return _parameters.endToken;
-  }
-
-  @override
-  Token get firstTokenAfterCommentAndMetadata {
-    Token leftMost =
-        Token.lexicallyFirst([externalKeyword, constKeyword, factoryKeyword]);
-    if (leftMost != null) {
-      return leftMost;
-    }
-    return _returnType.beginToken;
-  }
-
-  @override
-  NodeList<ConstructorInitializer> get initializers => _initializers;
-
-  @override
-  SimpleIdentifier get name => _name;
-
-  @override
-  void set name(SimpleIdentifier identifier) {
-    _name = _becomeParentOf(identifier);
-  }
-
-  @override
-  FormalParameterList get parameters => _parameters;
-
-  @override
-  void set parameters(FormalParameterList parameters) {
-    _parameters = _becomeParentOf(parameters);
-  }
-
-  @override
-  ConstructorName get redirectedConstructor => _redirectedConstructor;
-
-  @override
-  void set redirectedConstructor(ConstructorName redirectedConstructor) {
-    _redirectedConstructor = _becomeParentOf(redirectedConstructor);
-  }
-
-  @override
-  Identifier get returnType => _returnType;
-
-  @override
-  void set returnType(Identifier typeName) {
-    _returnType = _becomeParentOf(typeName);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitConstructorDeclaration(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    super.visitChildren(visitor);
-    _safelyVisitChild(_returnType, visitor);
-    _safelyVisitChild(_name, visitor);
-    _safelyVisitChild(_parameters, visitor);
-    _initializers.accept(visitor);
-    _safelyVisitChild(_redirectedConstructor, visitor);
-    _safelyVisitChild(_body, visitor);
-  }
-}
-
-/**
- * The initialization of a field within a constructor's initialization list.
- *
- * > fieldInitializer ::=
- * >     ('this' '.')? [SimpleIdentifier] '=' [Expression]
- */
-class ConstructorFieldInitializerImpl extends ConstructorInitializerImpl
-    implements ConstructorFieldInitializer {
-  /**
-   * The token for the 'this' keyword, or `null` if there is no 'this' keyword.
-   */
-  Token thisKeyword;
-
-  /**
-   * The token for the period after the 'this' keyword, or `null` if there is no
-   * 'this' keyword.
-   */
-  Token period;
-
-  /**
-   * The name of the field being initialized.
-   */
-  SimpleIdentifier _fieldName;
-
-  /**
-   * The token for the equal sign between the field name and the expression.
-   */
-  Token equals;
-
-  /**
-   * The expression computing the value to which the field will be initialized.
-   */
-  Expression _expression;
-
-  /**
-   * Initialize a newly created field initializer to initialize the field with
-   * the given name to the value of the given expression. The [thisKeyword] and
-   * [period] can be `null` if the 'this' keyword was not specified.
-   */
-  ConstructorFieldInitializerImpl(this.thisKeyword, this.period,
-      SimpleIdentifier fieldName, this.equals, Expression expression) {
-    _fieldName = _becomeParentOf(fieldName);
-    _expression = _becomeParentOf(expression);
-  }
-
-  @override
-  Token get beginToken {
-    if (thisKeyword != null) {
-      return thisKeyword;
-    }
-    return _fieldName.beginToken;
-  }
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(thisKeyword)
-    ..add(period)
-    ..add(_fieldName)
-    ..add(equals)
-    ..add(_expression);
-
-  @override
-  Token get endToken => _expression.endToken;
-
-  @override
-  Expression get expression => _expression;
-
-  @override
-  void set expression(Expression expression) {
-    _expression = _becomeParentOf(expression);
-  }
-
-  @override
-  SimpleIdentifier get fieldName => _fieldName;
-
-  @override
-  void set fieldName(SimpleIdentifier identifier) {
-    _fieldName = _becomeParentOf(identifier);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitConstructorFieldInitializer(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_fieldName, visitor);
-    _safelyVisitChild(_expression, visitor);
-  }
-}
-
-/**
- * A node that can occur in the initializer list of a constructor declaration.
- *
- * > constructorInitializer ::=
- * >     [SuperConstructorInvocation]
- * >   | [ConstructorFieldInitializer]
- * >   | [RedirectingConstructorInvocation]
- */
-abstract class ConstructorInitializerImpl extends AstNodeImpl
-    implements ConstructorInitializer {}
-
-/**
- * The name of the constructor.
- *
- * > constructorName ::=
- * >     type ('.' identifier)?
- */
-class ConstructorNameImpl extends AstNodeImpl implements ConstructorName {
-  /**
-   * The name of the type defining the constructor.
-   */
-  TypeName _type;
-
-  /**
-   * The token for the period before the constructor name, or `null` if the
-   * specified constructor is the unnamed constructor.
-   */
-  Token period;
-
-  /**
-   * The name of the constructor, or `null` if the specified constructor is the
-   * unnamed constructor.
-   */
-  SimpleIdentifier _name;
-
-  /**
-   * The element associated with this constructor name based on static type
-   * information, or `null` if the AST structure has not been resolved or if
-   * this constructor name could not be resolved.
-   */
-  ConstructorElement staticElement;
-
-  /**
-   * Initialize a newly created constructor name. The [period] and [name] can be
-   * `null` if the constructor being named is the unnamed constructor.
-   */
-  ConstructorNameImpl(TypeName type, this.period, SimpleIdentifier name) {
-    _type = _becomeParentOf(type);
-    _name = _becomeParentOf(name);
-  }
-
-  @override
-  Token get beginToken => _type.beginToken;
-
-  @override
-  Iterable get childEntities =>
-      new ChildEntities()..add(_type)..add(period)..add(_name);
-
-  @override
-  Token get endToken {
-    if (_name != null) {
-      return _name.endToken;
-    }
-    return _type.endToken;
-  }
-
-  @override
-  SimpleIdentifier get name => _name;
-
-  @override
-  void set name(SimpleIdentifier name) {
-    _name = _becomeParentOf(name);
-  }
-
-  @override
-  TypeName get type => _type;
-
-  @override
-  void set type(TypeName type) {
-    _type = _becomeParentOf(type);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitConstructorName(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_type, visitor);
-    _safelyVisitChild(_name, visitor);
-  }
-}
-
-/**
- * A continue statement.
- *
- * > continueStatement ::=
- * >     'continue' [SimpleIdentifier]? ';'
- */
-class ContinueStatementImpl extends StatementImpl implements ContinueStatement {
-  /**
-   * The token representing the 'continue' keyword.
-   */
-  Token continueKeyword;
-
-  /**
-   * The label associated with the statement, or `null` if there is no label.
-   */
-  SimpleIdentifier _label;
-
-  /**
-   * The semicolon terminating the statement.
-   */
-  Token semicolon;
-
-  /**
-   * The AstNode which this continue statement is continuing to.  This will be
-   * either a Statement (in the case of continuing a loop) or a SwitchMember
-   * (in the case of continuing from one switch case to another).  Null if the
-   * AST has not yet been resolved or if the target could not be resolved.
-   * Note that if the source code has errors, the target may be invalid (e.g.
-   * the target may be in an enclosing function).
-   */
-  AstNode target;
-
-  /**
-   * Initialize a newly created continue statement. The [label] can be `null` if
-   * there is no label associated with the statement.
-   */
-  ContinueStatementImpl(
-      this.continueKeyword, SimpleIdentifier label, this.semicolon) {
-    _label = _becomeParentOf(label);
-  }
-
-  @override
-  Token get beginToken => continueKeyword;
-
-  @override
-  Iterable get childEntities =>
-      new ChildEntities()..add(continueKeyword)..add(_label)..add(semicolon);
-
-  @override
-  Token get endToken => semicolon;
-
-  @override
-  SimpleIdentifier get label => _label;
-
-  @override
-  void set label(SimpleIdentifier identifier) {
-    _label = _becomeParentOf(identifier);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitContinueStatement(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_label, visitor);
-  }
-}
-
-/**
- * A node that represents the declaration of one or more names. Each declared
- * name is visible within a name scope.
- */
-abstract class DeclarationImpl extends AnnotatedNodeImpl
-    implements Declaration {
-  /**
-   * Initialize a newly created declaration. Either or both of the [comment] and
-   * [metadata] can be `null` if the declaration does not have the corresponding
-   * attribute.
-   */
-  DeclarationImpl(Comment comment, List<Annotation> metadata)
-      : super(comment, metadata);
-}
-
-/**
- * The declaration of a single identifier.
- *
- * > declaredIdentifier ::=
- * >     [Annotation] finalConstVarOrType [SimpleIdentifier]
- */
-class DeclaredIdentifierImpl extends DeclarationImpl
-    implements DeclaredIdentifier {
-  /**
-   * The token representing either the 'final', 'const' or 'var' keyword, or
-   * `null` if no keyword was used.
-   */
-  Token keyword;
-
-  /**
-   * The name of the declared type of the parameter, or `null` if the parameter
-   * does not have a declared type.
-   */
-  TypeName _type;
-
-  /**
-   * The name of the variable being declared.
-   */
-  SimpleIdentifier _identifier;
-
-  /**
-   * Initialize a newly created formal parameter. Either or both of the
-   * [comment] and [metadata] can be `null` if the declaration does not have the
-   * corresponding attribute. The [keyword] can be `null` if a type name is
-   * given. The [type] must be `null` if the keyword is 'var'.
-   */
-  DeclaredIdentifierImpl(Comment comment, List<Annotation> metadata,
-      this.keyword, TypeName type, SimpleIdentifier identifier)
-      : super(comment, metadata) {
-    _type = _becomeParentOf(type);
-    _identifier = _becomeParentOf(identifier);
-  }
-
-  @override
-  Iterable get childEntities =>
-      super._childEntities..add(keyword)..add(_type)..add(_identifier);
-
-  @override
-  LocalVariableElement get element {
-    if (_identifier == null) {
-      return null;
-    }
-    return _identifier.staticElement as LocalVariableElement;
-  }
-
-  @override
-  Token get endToken => _identifier.endToken;
-
-  @override
-  Token get firstTokenAfterCommentAndMetadata {
-    if (keyword != null) {
-      return keyword;
-    } else if (_type != null) {
-      return _type.beginToken;
-    }
-    return _identifier.beginToken;
-  }
-
-  @override
-  SimpleIdentifier get identifier => _identifier;
-
-  @override
-  void set identifier(SimpleIdentifier identifier) {
-    _identifier = _becomeParentOf(identifier);
-  }
-
-  @override
-  bool get isConst =>
-      (keyword is KeywordToken) &&
-      (keyword as KeywordToken).keyword == Keyword.CONST;
-
-  @override
-  bool get isFinal =>
-      (keyword is KeywordToken) &&
-      (keyword as KeywordToken).keyword == Keyword.FINAL;
-
-  @override
-  TypeName get type => _type;
-
-  @override
-  void set type(TypeName typeName) {
-    _type = _becomeParentOf(typeName);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitDeclaredIdentifier(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    super.visitChildren(visitor);
-    _safelyVisitChild(_type, visitor);
-    _safelyVisitChild(_identifier, visitor);
-  }
-}
-
-/**
- * A formal parameter with a default value. There are two kinds of parameters
- * that are both represented by this class: named formal parameters and
- * positional formal parameters.
- *
- * > defaultFormalParameter ::=
- * >     [NormalFormalParameter] ('=' [Expression])?
- * >
- * > defaultNamedParameter ::=
- * >     [NormalFormalParameter] (':' [Expression])?
- */
-class DefaultFormalParameterImpl extends FormalParameterImpl
-    implements DefaultFormalParameter {
-  /**
-   * The formal parameter with which the default value is associated.
-   */
-  NormalFormalParameter _parameter;
-
-  /**
-   * The kind of this parameter.
-   */
-  ParameterKind kind;
-
-  /**
-   * The token separating the parameter from the default value, or `null` if
-   * there is no default value.
-   */
-  Token separator;
-
-  /**
-   * The expression computing the default value for the parameter, or `null` if
-   * there is no default value.
-   */
-  Expression _defaultValue;
-
-  /**
-   * Initialize a newly created default formal parameter. The [separator] and
-   * [defaultValue] can be `null` if there is no default value.
-   */
-  DefaultFormalParameterImpl(NormalFormalParameter parameter, this.kind,
-      this.separator, Expression defaultValue) {
-    _parameter = _becomeParentOf(parameter);
-    _defaultValue = _becomeParentOf(defaultValue);
-  }
-
-  @override
-  Token get beginToken => _parameter.beginToken;
-
-  @override
-  Iterable get childEntities =>
-      new ChildEntities()..add(_parameter)..add(separator)..add(_defaultValue);
-
-  @override
-  Expression get defaultValue => _defaultValue;
-
-  @override
-  void set defaultValue(Expression expression) {
-    _defaultValue = _becomeParentOf(expression);
-  }
-
-  @override
-  Token get endToken {
-    if (_defaultValue != null) {
-      return _defaultValue.endToken;
-    }
-    return _parameter.endToken;
-  }
-
-  @override
-  SimpleIdentifier get identifier => _parameter.identifier;
-
-  @override
-  bool get isConst => _parameter != null && _parameter.isConst;
-
-  @override
-  bool get isFinal => _parameter != null && _parameter.isFinal;
-
-  @override
-  NodeList<Annotation> get metadata => _parameter.metadata;
-
-  @override
-  NormalFormalParameter get parameter => _parameter;
-
-  @override
-  void set parameter(NormalFormalParameter formalParameter) {
-    _parameter = _becomeParentOf(formalParameter);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitDefaultFormalParameter(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_parameter, visitor);
-    _safelyVisitChild(_defaultValue, visitor);
-  }
-}
-
-/**
- * A node that represents a directive.
- *
- * > directive ::=
- * >     [ExportDirective]
- * >   | [ImportDirective]
- * >   | [LibraryDirective]
- * >   | [PartDirective]
- * >   | [PartOfDirective]
- */
-abstract class DirectiveImpl extends AnnotatedNodeImpl implements Directive {
-  /**
-   * The element associated with this directive, or `null` if the AST structure
-   * has not been resolved or if this directive could not be resolved.
-   */
-  Element element;
-
-  /**
-   * Initialize a newly create directive. Either or both of the [comment] and
-   * [metadata] can be `null` if the directive does not have the corresponding
-   * attribute.
-   */
-  DirectiveImpl(Comment comment, List<Annotation> metadata)
-      : super(comment, metadata);
-}
-
-/**
- * A do statement.
- *
- * > doStatement ::=
- * >     'do' [Statement] 'while' '(' [Expression] ')' ';'
- */
-class DoStatementImpl extends StatementImpl implements DoStatement {
-  /**
-   * The token representing the 'do' keyword.
-   */
-  Token doKeyword;
-
-  /**
-   * The body of the loop.
-   */
-  Statement _body;
-
-  /**
-   * The token representing the 'while' keyword.
-   */
-  Token whileKeyword;
-
-  /**
-   * The left parenthesis.
-   */
-  Token leftParenthesis;
-
-  /**
-   * The condition that determines when the loop will terminate.
-   */
-  Expression _condition;
-
-  /**
-   * The right parenthesis.
-   */
-  Token rightParenthesis;
-
-  /**
-   * The semicolon terminating the statement.
-   */
-  Token semicolon;
-
-  /**
-   * Initialize a newly created do loop.
-   */
-  DoStatementImpl(
-      this.doKeyword,
-      Statement body,
-      this.whileKeyword,
-      this.leftParenthesis,
-      Expression condition,
-      this.rightParenthesis,
-      this.semicolon) {
-    _body = _becomeParentOf(body);
-    _condition = _becomeParentOf(condition);
-  }
-
-  @override
-  Token get beginToken => doKeyword;
-
-  @override
-  Statement get body => _body;
-
-  @override
-  void set body(Statement statement) {
-    _body = _becomeParentOf(statement);
-  }
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(doKeyword)
-    ..add(_body)
-    ..add(whileKeyword)
-    ..add(leftParenthesis)
-    ..add(_condition)
-    ..add(rightParenthesis)
-    ..add(semicolon);
-
-  @override
-  Expression get condition => _condition;
-
-  @override
-  void set condition(Expression expression) {
-    _condition = _becomeParentOf(expression);
-  }
-
-  @override
-  Token get endToken => semicolon;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitDoStatement(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_body, visitor);
-    _safelyVisitChild(_condition, visitor);
-  }
-}
-
-/**
- * A dotted name, used in a configuration within an import or export directive.
- *
- * > dottedName ::=
- * >     [SimpleIdentifier] ('.' [SimpleIdentifier])*
- */
-class DottedNameImpl extends AstNodeImpl implements DottedName {
-  /**
-   * The components of the identifier.
-   */
-  NodeList<SimpleIdentifier> _components;
-
-  /**
-   * Initialize a newly created dotted name.
-   */
-  DottedNameImpl(List<SimpleIdentifier> components) {
-    _components = new NodeList<SimpleIdentifier>(this, components);
-  }
-
-  @override
-  Token get beginToken => _components.beginToken;
-
-  @override
-  // TODO(paulberry): add "." tokens.
-  Iterable get childEntities => new ChildEntities()..addAll(_components);
-
-  @override
-  NodeList<SimpleIdentifier> get components => _components;
-
-  @override
-  Token get endToken => _components.endToken;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitDottedName(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _components.accept(visitor);
-  }
-}
-
-/**
- * A floating point literal expression.
- *
- * > doubleLiteral ::=
- * >     decimalDigit+ ('.' decimalDigit*)? exponent?
- * >   | '.' decimalDigit+ exponent?
- * >
- * > exponent ::=
- * >     ('e' | 'E') ('+' | '-')? decimalDigit+
- */
-class DoubleLiteralImpl extends LiteralImpl implements DoubleLiteral {
-  /**
-   * The token representing the literal.
-   */
-  Token literal;
-
-  /**
-   * The value of the literal.
-   */
-  double value;
-
-  /**
-   * Initialize a newly created floating point literal.
-   */
-  DoubleLiteralImpl(this.literal, this.value);
-
-  @override
-  Token get beginToken => literal;
-
-  @override
-  Iterable get childEntities => new ChildEntities()..add(literal);
-
-  @override
-  Token get endToken => literal;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitDoubleLiteral(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    // There are no children to visit.
-  }
-}
-
-/**
- * An empty function body, which can only appear in constructors or abstract
- * methods.
- *
- * > emptyFunctionBody ::=
- * >     ';'
- */
-class EmptyFunctionBodyImpl extends FunctionBodyImpl
-    implements EmptyFunctionBody {
-  /**
-   * The token representing the semicolon that marks the end of the function
-   * body.
-   */
-  Token semicolon;
-
-  /**
-   * Initialize a newly created function body.
-   */
-  EmptyFunctionBodyImpl(this.semicolon);
-
-  @override
-  Token get beginToken => semicolon;
-
-  @override
-  Iterable get childEntities => new ChildEntities()..add(semicolon);
-
-  @override
-  Token get endToken => semicolon;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitEmptyFunctionBody(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    // Empty function bodies have no children.
-  }
-}
-
-/**
- * An empty statement.
- *
- * > emptyStatement ::=
- * >     ';'
- */
-class EmptyStatementImpl extends StatementImpl implements EmptyStatement {
-  /**
-   * The semicolon terminating the statement.
-   */
-  Token semicolon;
-
-  /**
-   * Initialize a newly created empty statement.
-   */
-  EmptyStatementImpl(this.semicolon);
-
-  @override
-  Token get beginToken => semicolon;
-
-  @override
-  Iterable get childEntities => new ChildEntities()..add(semicolon);
-
-  @override
-  Token get endToken => semicolon;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitEmptyStatement(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    // There are no children to visit.
-  }
-}
-
-/**
- * The declaration of an enum constant.
- */
-class EnumConstantDeclarationImpl extends DeclarationImpl
-    implements EnumConstantDeclaration {
-  /**
-   * The name of the constant.
-   */
-  SimpleIdentifier _name;
-
-  /**
-   * Initialize a newly created enum constant declaration. Either or both of the
-   * [comment] and [metadata] can be `null` if the constant does not have the
-   * corresponding attribute. (Technically, enum constants cannot have metadata,
-   * but we allow it for consistency.)
-   */
-  EnumConstantDeclarationImpl(
-      Comment comment, List<Annotation> metadata, SimpleIdentifier name)
-      : super(comment, metadata) {
-    _name = _becomeParentOf(name);
-  }
-
-  @override
-  Iterable get childEntities => super._childEntities..add(_name);
-
-  @override
-  FieldElement get element =>
-      _name == null ? null : (_name.staticElement as FieldElement);
-
-  @override
-  Token get endToken => _name.endToken;
-
-  @override
-  Token get firstTokenAfterCommentAndMetadata => _name.beginToken;
-
-  @override
-  SimpleIdentifier get name => _name;
-
-  @override
-  void set name(SimpleIdentifier name) {
-    _name = _becomeParentOf(name);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitEnumConstantDeclaration(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    super.visitChildren(visitor);
-    _safelyVisitChild(_name, visitor);
-  }
-}
-
-/**
- * The declaration of an enumeration.
- *
- * > enumType ::=
- * >     metadata 'enum' [SimpleIdentifier] '{' [SimpleIdentifier] (',' [SimpleIdentifier])* (',')? '}'
- */
-class EnumDeclarationImpl extends NamedCompilationUnitMemberImpl
-    implements EnumDeclaration {
-  /**
-   * The 'enum' keyword.
-   */
-  Token enumKeyword;
-
-  /**
-   * The left curly bracket.
-   */
-  Token leftBracket;
-
-  /**
-   * The enumeration constants being declared.
-   */
-  NodeList<EnumConstantDeclaration> _constants;
-
-  /**
-   * The right curly bracket.
-   */
-  Token rightBracket;
-
-  /**
-   * Initialize a newly created enumeration declaration. Either or both of the
-   * [comment] and [metadata] can be `null` if the declaration does not have the
-   * corresponding attribute. The list of [constants] must contain at least one
-   * value.
-   */
-  EnumDeclarationImpl(
-      Comment comment,
-      List<Annotation> metadata,
-      this.enumKeyword,
-      SimpleIdentifier name,
-      this.leftBracket,
-      List<EnumConstantDeclaration> constants,
-      this.rightBracket)
-      : super(comment, metadata, name) {
-    _constants = new NodeList<EnumConstantDeclaration>(this, constants);
-  }
-
-  @override
-  // TODO(brianwilkerson) Add commas?
-  Iterable get childEntities => super._childEntities
-    ..add(enumKeyword)
-    ..add(_name)
-    ..add(leftBracket)
-    ..addAll(_constants)
-    ..add(rightBracket);
-
-  @override
-  NodeList<EnumConstantDeclaration> get constants => _constants;
-
-  @override
-  ClassElement get element =>
-      _name != null ? (_name.staticElement as ClassElement) : null;
-
-  @override
-  Token get endToken => rightBracket;
-
-  @override
-  Token get firstTokenAfterCommentAndMetadata => enumKeyword;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitEnumDeclaration(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    super.visitChildren(visitor);
-    _safelyVisitChild(_name, visitor);
-    _constants.accept(visitor);
-  }
-}
-
-/**
- * Ephemeral identifiers are created as needed to mimic the presence of an empty
- * identifier.
- */
-class EphemeralIdentifier extends SimpleIdentifierImpl {
-  EphemeralIdentifier(AstNode parent, int location)
-      : super(new StringToken(TokenType.IDENTIFIER, "", location)) {
-    (parent as AstNodeImpl)._becomeParentOf(this);
-  }
-}
-
-/**
- * An export directive.
- *
- * > exportDirective ::=
- * >     [Annotation] 'export' [StringLiteral] [Combinator]* ';'
- */
-class ExportDirectiveImpl extends NamespaceDirectiveImpl
-    implements ExportDirective {
-  /**
-   * Initialize a newly created export directive. Either or both of the
-   * [comment] and [metadata] can be `null` if the directive does not have the
-   * corresponding attribute. The list of [combinators] can be `null` if there
-   * are no combinators.
-   */
-  ExportDirectiveImpl(
-      Comment comment,
-      List<Annotation> metadata,
-      Token keyword,
-      StringLiteral libraryUri,
-      List<Configuration> configurations,
-      List<Combinator> combinators,
-      Token semicolon)
-      : super(comment, metadata, keyword, libraryUri, configurations,
-            combinators, semicolon);
-
-  @override
-  Iterable get childEntities => super._childEntities
-    ..add(_uri)
-    ..addAll(combinators)
-    ..add(semicolon);
-
-  @override
-  ExportElement get element => super.element as ExportElement;
-
-  @override
-  LibraryElement get uriElement {
-    if (element != null) {
-      return element.exportedLibrary;
-    }
-    return null;
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitExportDirective(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    super.visitChildren(visitor);
-    combinators.accept(visitor);
-  }
-}
-
-/**
- * A function body consisting of a single expression.
- *
- * > expressionFunctionBody ::=
- * >     'async'? '=>' [Expression] ';'
- */
-class ExpressionFunctionBodyImpl extends FunctionBodyImpl
-    implements ExpressionFunctionBody {
-  /**
-   * The token representing the 'async' keyword, or `null` if there is no such
-   * keyword.
-   */
-  Token keyword;
-
-  /**
-   * The token introducing the expression that represents the body of the
-   * function.
-   */
-  Token functionDefinition;
-
-  /**
-   * The expression representing the body of the function.
-   */
-  Expression _expression;
-
-  /**
-   * The semicolon terminating the statement.
-   */
-  Token semicolon;
-
-  /**
-   * Initialize a newly created function body consisting of a block of
-   * statements. The [keyword] can be `null` if the function body is not an
-   * async function body.
-   */
-  ExpressionFunctionBodyImpl(this.keyword, this.functionDefinition,
-      Expression expression, this.semicolon) {
-    _expression = _becomeParentOf(expression);
-  }
-
-  @override
-  Token get beginToken {
-    if (keyword != null) {
-      return keyword;
-    }
-    return functionDefinition;
-  }
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(keyword)
-    ..add(functionDefinition)
-    ..add(_expression)
-    ..add(semicolon);
-
-  @override
-  Token get endToken {
-    if (semicolon != null) {
-      return semicolon;
-    }
-    return _expression.endToken;
-  }
-
-  @override
-  Expression get expression => _expression;
-
-  @override
-  void set expression(Expression expression) {
-    _expression = _becomeParentOf(expression);
-  }
-
-  @override
-  bool get isAsynchronous => keyword != null;
-
-  @override
-  bool get isSynchronous => keyword == null;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitExpressionFunctionBody(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_expression, visitor);
-  }
-}
-
-/**
- * A node that represents an expression.
- *
- * > expression ::=
- * >     [AssignmentExpression]
- * >   | [ConditionalExpression] cascadeSection*
- * >   | [ThrowExpression]
- */
-abstract class ExpressionImpl extends AstNodeImpl implements Expression {
-  /**
-   * The static type of this expression, or `null` if the AST structure has not
-   * been resolved.
-   */
-  DartType staticType;
-
-  /**
-   * The propagated type of this expression, or `null` if type propagation has
-   * not been performed on the AST structure.
-   */
-  DartType propagatedType;
-
-  /**
-   * Return the best parameter element information available for this
-   * expression. If type propagation was able to find a better parameter element
-   * than static analysis, that type will be returned. Otherwise, the result of
-   * static analysis will be returned.
-   */
-  ParameterElement get bestParameterElement {
-    ParameterElement propagatedElement = propagatedParameterElement;
-    if (propagatedElement != null) {
-      return propagatedElement;
-    }
-    return staticParameterElement;
-  }
-
-  @override
-  DartType get bestType {
-    if (propagatedType != null) {
-      return propagatedType;
-    } else if (staticType != null) {
-      return staticType;
-    }
-    return DynamicTypeImpl.instance;
-  }
-
-  @override
-  bool get isAssignable => false;
-
-  @override
-  ParameterElement get propagatedParameterElement {
-    AstNode parent = this.parent;
-    if (parent is ArgumentListImpl) {
-      return parent._getPropagatedParameterElementFor(this);
-    } else if (parent is IndexExpressionImpl) {
-      if (identical(parent.index, this)) {
-        return parent._propagatedParameterElementForIndex;
-      }
-    } else if (parent is BinaryExpressionImpl) {
-      if (identical(parent.rightOperand, this)) {
-        return parent._propagatedParameterElementForRightOperand;
-      }
-    } else if (parent is AssignmentExpressionImpl) {
-      if (identical(parent.rightHandSide, this)) {
-        return parent._propagatedParameterElementForRightHandSide;
-      }
-    } else if (parent is PrefixExpressionImpl) {
-      return parent._propagatedParameterElementForOperand;
-    } else if (parent is PostfixExpressionImpl) {
-      return parent._propagatedParameterElementForOperand;
-    }
-    return null;
-  }
-
-  @override
-  ParameterElement get staticParameterElement {
-    AstNode parent = this.parent;
-    if (parent is ArgumentListImpl) {
-      return parent._getStaticParameterElementFor(this);
-    } else if (parent is IndexExpressionImpl) {
-      if (identical(parent.index, this)) {
-        return parent._staticParameterElementForIndex;
-      }
-    } else if (parent is BinaryExpressionImpl) {
-      if (identical(parent.rightOperand, this)) {
-        return parent._staticParameterElementForRightOperand;
-      }
-    } else if (parent is AssignmentExpressionImpl) {
-      if (identical(parent.rightHandSide, this)) {
-        return parent._staticParameterElementForRightHandSide;
-      }
-    } else if (parent is PrefixExpressionImpl) {
-      return parent._staticParameterElementForOperand;
-    } else if (parent is PostfixExpressionImpl) {
-      return parent._staticParameterElementForOperand;
-    }
-    return null;
-  }
-}
-
-/**
- * An expression used as a statement.
- *
- * > expressionStatement ::=
- * >     [Expression]? ';'
- */
-class ExpressionStatementImpl extends StatementImpl
-    implements ExpressionStatement {
-  /**
-   * The expression that comprises the statement.
-   */
-  Expression _expression;
-
-  /**
-   * The semicolon terminating the statement, or `null` if the expression is a
-   * function expression and therefore isn't followed by a semicolon.
-   */
-  Token semicolon;
-
-  /**
-   * Initialize a newly created expression statement.
-   */
-  ExpressionStatementImpl(Expression expression, this.semicolon) {
-    _expression = _becomeParentOf(expression);
-  }
-
-  @override
-  Token get beginToken => _expression.beginToken;
-
-  @override
-  Iterable get childEntities =>
-      new ChildEntities()..add(_expression)..add(semicolon);
-
-  @override
-  Token get endToken {
-    if (semicolon != null) {
-      return semicolon;
-    }
-    return _expression.endToken;
-  }
-
-  @override
-  Expression get expression => _expression;
-
-  @override
-  void set expression(Expression expression) {
-    _expression = _becomeParentOf(expression);
-  }
-
-  @override
-  bool get isSynthetic => _expression.isSynthetic && semicolon.isSynthetic;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitExpressionStatement(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_expression, visitor);
-  }
-}
-
-/**
- * The "extends" clause in a class declaration.
- *
- * > extendsClause ::=
- * >     'extends' [TypeName]
- */
-class ExtendsClauseImpl extends AstNodeImpl implements ExtendsClause {
-  /**
-   * The token representing the 'extends' keyword.
-   */
-  Token extendsKeyword;
-
-  /**
-   * The name of the class that is being extended.
-   */
-  TypeName _superclass;
-
-  /**
-   * Initialize a newly created extends clause.
-   */
-  ExtendsClauseImpl(this.extendsKeyword, TypeName superclass) {
-    _superclass = _becomeParentOf(superclass);
-  }
-
-  @override
-  Token get beginToken => extendsKeyword;
-
-  @override
-  Iterable get childEntities =>
-      new ChildEntities()..add(extendsKeyword)..add(_superclass);
-
-  @override
-  Token get endToken => _superclass.endToken;
-
-  @override
-  TypeName get superclass => _superclass;
-
-  @override
-  void set superclass(TypeName name) {
-    _superclass = _becomeParentOf(name);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitExtendsClause(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_superclass, visitor);
-  }
-}
-
-/**
- * The declaration of one or more fields of the same type.
- *
- * > fieldDeclaration ::=
- * >     'static'? [VariableDeclarationList] ';'
- */
-class FieldDeclarationImpl extends ClassMemberImpl implements FieldDeclaration {
-  /**
-   * The token representing the 'static' keyword, or `null` if the fields are
-   * not static.
-   */
-  Token staticKeyword;
-
-  /**
-   * The fields being declared.
-   */
-  VariableDeclarationList _fieldList;
-
-  /**
-   * The semicolon terminating the declaration.
-   */
-  Token semicolon;
-
-  /**
-   * Initialize a newly created field declaration. Either or both of the
-   * [comment] and [metadata] can be `null` if the declaration does not have the
-   * corresponding attribute. The [staticKeyword] can be `null` if the field is
-   * not a static field.
-   */
-  FieldDeclarationImpl(Comment comment, List<Annotation> metadata,
-      this.staticKeyword, VariableDeclarationList fieldList, this.semicolon)
-      : super(comment, metadata) {
-    _fieldList = _becomeParentOf(fieldList);
-  }
-
-  @override
-  Iterable get childEntities =>
-      super._childEntities..add(staticKeyword)..add(_fieldList)..add(semicolon);
-
-  @override
-  Element get element => null;
-
-  @override
-  Token get endToken => semicolon;
-
-  @override
-  VariableDeclarationList get fields => _fieldList;
-
-  @override
-  void set fields(VariableDeclarationList fields) {
-    _fieldList = _becomeParentOf(fields);
-  }
-
-  @override
-  Token get firstTokenAfterCommentAndMetadata {
-    if (staticKeyword != null) {
-      return staticKeyword;
-    }
-    return _fieldList.beginToken;
-  }
-
-  @override
-  bool get isStatic => staticKeyword != null;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitFieldDeclaration(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    super.visitChildren(visitor);
-    _safelyVisitChild(_fieldList, visitor);
-  }
-}
-
-/**
- * A field formal parameter.
- *
- * > fieldFormalParameter ::=
- * >     ('final' [TypeName] | 'const' [TypeName] | 'var' | [TypeName])?
- * >     'this' '.' [SimpleIdentifier] ([TypeParameterList]? [FormalParameterList])?
- */
-class FieldFormalParameterImpl extends NormalFormalParameterImpl
-    implements FieldFormalParameter {
-  /**
-   * The token representing either the 'final', 'const' or 'var' keyword, or
-   * `null` if no keyword was used.
-   */
-  Token keyword;
-
-  /**
-   * The name of the declared type of the parameter, or `null` if the parameter
-   * does not have a declared type.
-   */
-  TypeName _type;
-
-  /**
-   * The token representing the 'this' keyword.
-   */
-  Token thisKeyword;
-
-  /**
-   * The token representing the period.
-   */
-  Token period;
-
-  /**
-   * The type parameters associated with the method, or `null` if the method is
-   * not a generic method.
-   */
-  TypeParameterList _typeParameters;
-
-  /**
-   * The parameters of the function-typed parameter, or `null` if this is not a
-   * function-typed field formal parameter.
-   */
-  FormalParameterList _parameters;
-
-  /**
-   * Initialize a newly created formal parameter. Either or both of the
-   * [comment] and [metadata] can be `null` if the parameter does not have the
-   * corresponding attribute. The [keyword] can be `null` if there is a type.
-   * The [type] must be `null` if the keyword is 'var'. The [thisKeyword] and
-   * [period] can be `null` if the keyword 'this' was not provided.  The
-   * [parameters] can be `null` if this is not a function-typed field formal
-   * parameter.
-   */
-  FieldFormalParameterImpl(
-      Comment comment,
-      List<Annotation> metadata,
-      this.keyword,
-      TypeName type,
-      this.thisKeyword,
-      this.period,
-      SimpleIdentifier identifier,
-      TypeParameterList typeParameters,
-      FormalParameterList parameters)
-      : super(comment, metadata, identifier) {
-    _type = _becomeParentOf(type);
-    _typeParameters = _becomeParentOf(typeParameters);
-    _parameters = _becomeParentOf(parameters);
-  }
-
-  @override
-  Token get beginToken {
-    if (keyword != null) {
-      return keyword;
-    } else if (_type != null) {
-      return _type.beginToken;
-    }
-    return thisKeyword;
-  }
-
-  @override
-  Iterable get childEntities => super._childEntities
-    ..add(keyword)
-    ..add(_type)
-    ..add(thisKeyword)
-    ..add(period)
-    ..add(identifier)
-    ..add(_parameters);
-
-  @override
-  Token get endToken {
-    if (_parameters != null) {
-      return _parameters.endToken;
-    }
-    return identifier.endToken;
-  }
-
-  @override
-  bool get isConst =>
-      (keyword is KeywordToken) &&
-      (keyword as KeywordToken).keyword == Keyword.CONST;
-
-  @override
-  bool get isFinal =>
-      (keyword is KeywordToken) &&
-      (keyword as KeywordToken).keyword == Keyword.FINAL;
-
-  @override
-  FormalParameterList get parameters => _parameters;
-
-  @override
-  void set parameters(FormalParameterList parameters) {
-    _parameters = _becomeParentOf(parameters);
-  }
-
-  @override
-  TypeName get type => _type;
-
-  @override
-  void set type(TypeName typeName) {
-    _type = _becomeParentOf(typeName);
-  }
-
-  @override
-  TypeParameterList get typeParameters => _typeParameters;
-
-  @override
-  void set typeParameters(TypeParameterList typeParameters) {
-    _typeParameters = _becomeParentOf(typeParameters);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitFieldFormalParameter(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    super.visitChildren(visitor);
-    _safelyVisitChild(_type, visitor);
-    _safelyVisitChild(identifier, visitor);
-    _safelyVisitChild(_typeParameters, visitor);
-    _safelyVisitChild(_parameters, visitor);
-  }
-}
-
-/**
- * A for-each statement.
- *
- * > forEachStatement ::=
- * >     'await'? 'for' '(' [DeclaredIdentifier] 'in' [Expression] ')' [Block]
- * >   | 'await'? 'for' '(' [SimpleIdentifier] 'in' [Expression] ')' [Block]
- */
-class ForEachStatementImpl extends StatementImpl implements ForEachStatement {
-  /**
-   * The token representing the 'await' keyword, or `null` if there is no
-   * 'await' keyword.
-   */
-  Token awaitKeyword;
-
-  /**
-   * The token representing the 'for' keyword.
-   */
-  Token forKeyword;
-
-  /**
-   * The left parenthesis.
-   */
-  Token leftParenthesis;
-
-  /**
-   * The declaration of the loop variable, or `null` if the loop variable is a
-   * simple identifier.
-   */
-  DeclaredIdentifier _loopVariable;
-
-  /**
-   * The loop variable, or `null` if the loop variable is declared in the 'for'.
-   */
-  SimpleIdentifier _identifier;
-
-  /**
-   * The token representing the 'in' keyword.
-   */
-  Token inKeyword;
-
-  /**
-   * The expression evaluated to produce the iterator.
-   */
-  Expression _iterable;
-
-  /**
-   * The right parenthesis.
-   */
-  Token rightParenthesis;
-
-  /**
-   * The body of the loop.
-   */
-  Statement _body;
-
-  /**
-   * Initialize a newly created for-each statement whose loop control variable
-   * is declared internally (in the for-loop part). The [awaitKeyword] can be
-   * `null` if this is not an asynchronous for loop.
-   */
-  ForEachStatementImpl.withDeclaration(
-      this.awaitKeyword,
-      this.forKeyword,
-      this.leftParenthesis,
-      DeclaredIdentifier loopVariable,
-      this.inKeyword,
-      Expression iterator,
-      this.rightParenthesis,
-      Statement body) {
-    _loopVariable = _becomeParentOf(loopVariable);
-    _iterable = _becomeParentOf(iterator);
-    _body = _becomeParentOf(body);
-  }
-
-  /**
-   * Initialize a newly created for-each statement whose loop control variable
-   * is declared outside the for loop. The [awaitKeyword] can be `null` if this
-   * is not an asynchronous for loop.
-   */
-  ForEachStatementImpl.withReference(
-      this.awaitKeyword,
-      this.forKeyword,
-      this.leftParenthesis,
-      SimpleIdentifier identifier,
-      this.inKeyword,
-      Expression iterator,
-      this.rightParenthesis,
-      Statement body) {
-    _identifier = _becomeParentOf(identifier);
-    _iterable = _becomeParentOf(iterator);
-    _body = _becomeParentOf(body);
-  }
-
-  @override
-  Token get beginToken => forKeyword;
-
-  @override
-  Statement get body => _body;
-
-  @override
-  void set body(Statement statement) {
-    _body = _becomeParentOf(statement);
-  }
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(awaitKeyword)
-    ..add(forKeyword)
-    ..add(leftParenthesis)
-    ..add(_loopVariable)
-    ..add(_identifier)
-    ..add(inKeyword)
-    ..add(_iterable)
-    ..add(rightParenthesis)
-    ..add(_body);
-
-  @override
-  Token get endToken => _body.endToken;
-
-  @override
-  SimpleIdentifier get identifier => _identifier;
-
-  @override
-  void set identifier(SimpleIdentifier identifier) {
-    _identifier = _becomeParentOf(identifier);
-  }
-
-  @override
-  Expression get iterable => _iterable;
-
-  @override
-  void set iterable(Expression expression) {
-    _iterable = _becomeParentOf(expression);
-  }
-
-  @override
-  DeclaredIdentifier get loopVariable => _loopVariable;
-
-  @override
-  void set loopVariable(DeclaredIdentifier variable) {
-    _loopVariable = _becomeParentOf(variable);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitForEachStatement(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_loopVariable, visitor);
-    _safelyVisitChild(_identifier, visitor);
-    _safelyVisitChild(_iterable, visitor);
-    _safelyVisitChild(_body, visitor);
-  }
-}
-
-/**
- * A node representing a parameter to a function.
- *
- * > formalParameter ::=
- * >     [NormalFormalParameter]
- * >   | [DefaultFormalParameter]
- */
-abstract class FormalParameterImpl extends AstNodeImpl
-    implements FormalParameter {
-  @override
-  ParameterElement get element {
-    SimpleIdentifier identifier = this.identifier;
-    if (identifier == null) {
-      return null;
-    }
-    return identifier.staticElement as ParameterElement;
-  }
-}
-
-/**
- * The formal parameter list of a method declaration, function declaration, or
- * function type alias.
- *
- * While the grammar requires all optional formal parameters to follow all of
- * the normal formal parameters and at most one grouping of optional formal
- * parameters, this class does not enforce those constraints. All parameters are
- * flattened into a single list, which can have any or all kinds of parameters
- * (normal, named, and positional) in any order.
- *
- * > formalParameterList ::=
- * >     '(' ')'
- * >   | '(' normalFormalParameters (',' optionalFormalParameters)? ')'
- * >   | '(' optionalFormalParameters ')'
- * >
- * > normalFormalParameters ::=
- * >     [NormalFormalParameter] (',' [NormalFormalParameter])*
- * >
- * > optionalFormalParameters ::=
- * >     optionalPositionalFormalParameters
- * >   | namedFormalParameters
- * >
- * > optionalPositionalFormalParameters ::=
- * >     '[' [DefaultFormalParameter] (',' [DefaultFormalParameter])* ']'
- * >
- * > namedFormalParameters ::=
- * >     '{' [DefaultFormalParameter] (',' [DefaultFormalParameter])* '}'
- */
-class FormalParameterListImpl extends AstNodeImpl
-    implements FormalParameterList {
-  /**
-   * The left parenthesis.
-   */
-  Token leftParenthesis;
-
-  /**
-   * The parameters associated with the method.
-   */
-  NodeList<FormalParameter> _parameters;
-
-  /**
-   * The left square bracket ('[') or left curly brace ('{') introducing the
-   * optional parameters, or `null` if there are no optional parameters.
-   */
-  Token leftDelimiter;
-
-  /**
-   * The right square bracket (']') or right curly brace ('}') terminating the
-   * optional parameters, or `null` if there are no optional parameters.
-   */
-  Token rightDelimiter;
-
-  /**
-   * The right parenthesis.
-   */
-  Token rightParenthesis;
-
-  /**
-   * Initialize a newly created parameter list. The list of [parameters] can be
-   * `null` if there are no parameters. The [leftDelimiter] and [rightDelimiter]
-   * can be `null` if there are no optional parameters.
-   */
-  FormalParameterListImpl(
-      this.leftParenthesis,
-      List<FormalParameter> parameters,
-      this.leftDelimiter,
-      this.rightDelimiter,
-      this.rightParenthesis) {
-    _parameters = new NodeList<FormalParameter>(this, parameters);
-  }
-
-  @override
-  Token get beginToken => leftParenthesis;
-
-  @override
-  Iterable get childEntities {
-    // TODO(paulberry): include commas.
-    ChildEntities result = new ChildEntities()..add(leftParenthesis);
-    bool leftDelimiterNeeded = leftDelimiter != null;
-    for (FormalParameter parameter in _parameters) {
-      if (leftDelimiterNeeded && leftDelimiter.offset < parameter.offset) {
-        result.add(leftDelimiter);
-        leftDelimiterNeeded = false;
-      }
-      result.add(parameter);
-    }
-    return result..add(rightDelimiter)..add(rightParenthesis);
-  }
-
-  @override
-  Token get endToken => rightParenthesis;
-
-  @override
-  List<ParameterElement> get parameterElements {
-    int count = _parameters.length;
-    List<ParameterElement> types = new List<ParameterElement>(count);
-    for (int i = 0; i < count; i++) {
-      types[i] = _parameters[i].element;
-    }
-    return types;
-  }
-
-  @override
-  NodeList<FormalParameter> get parameters => _parameters;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitFormalParameterList(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _parameters.accept(visitor);
-  }
-}
-
-/**
- * A for statement.
- *
- * > forStatement ::=
- * >     'for' '(' forLoopParts ')' [Statement]
- * >
- * > forLoopParts ::=
- * >     forInitializerStatement ';' [Expression]? ';' [Expression]?
- * >
- * > forInitializerStatement ::=
- * >     [DefaultFormalParameter]
- * >   | [Expression]?
- */
-class ForStatementImpl extends StatementImpl implements ForStatement {
-  /**
-   * The token representing the 'for' keyword.
-   */
-  Token forKeyword;
-
-  /**
-   * The left parenthesis.
-   */
-  Token leftParenthesis;
-
-  /**
-   * The declaration of the loop variables, or `null` if there are no variables.
-   * Note that a for statement cannot have both a variable list and an
-   * initialization expression, but can validly have neither.
-   */
-  VariableDeclarationList _variableList;
-
-  /**
-   * The initialization expression, or `null` if there is no initialization
-   * expression. Note that a for statement cannot have both a variable list and
-   * an initialization expression, but can validly have neither.
-   */
-  Expression _initialization;
-
-  /**
-   * The semicolon separating the initializer and the condition.
-   */
-  Token leftSeparator;
-
-  /**
-   * The condition used to determine when to terminate the loop, or `null` if
-   * there is no condition.
-   */
-  Expression _condition;
-
-  /**
-   * The semicolon separating the condition and the updater.
-   */
-  Token rightSeparator;
-
-  /**
-   * The list of expressions run after each execution of the loop body.
-   */
-  NodeList<Expression> _updaters;
-
-  /**
-   * The right parenthesis.
-   */
-  Token rightParenthesis;
-
-  /**
-   * The body of the loop.
-   */
-  Statement _body;
-
-  /**
-   * Initialize a newly created for statement. Either the [variableList] or the
-   * [initialization] must be `null`. Either the [condition] and the list of
-   * [updaters] can be `null` if the loop does not have the corresponding
-   * attribute.
-   */
-  ForStatementImpl(
-      this.forKeyword,
-      this.leftParenthesis,
-      VariableDeclarationList variableList,
-      Expression initialization,
-      this.leftSeparator,
-      Expression condition,
-      this.rightSeparator,
-      List<Expression> updaters,
-      this.rightParenthesis,
-      Statement body) {
-    _variableList = _becomeParentOf(variableList);
-    _initialization = _becomeParentOf(initialization);
-    _condition = _becomeParentOf(condition);
-    _updaters = new NodeList<Expression>(this, updaters);
-    _body = _becomeParentOf(body);
-  }
-
-  @override
-  Token get beginToken => forKeyword;
-
-  @override
-  Statement get body => _body;
-
-  @override
-  void set body(Statement statement) {
-    _body = _becomeParentOf(statement);
-  }
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(forKeyword)
-    ..add(leftParenthesis)
-    ..add(_variableList)
-    ..add(_initialization)
-    ..add(leftSeparator)
-    ..add(_condition)
-    ..add(rightSeparator)
-    ..addAll(_updaters)
-    ..add(rightParenthesis)
-    ..add(_body);
-
-  @override
-  Expression get condition => _condition;
-
-  @override
-  void set condition(Expression expression) {
-    _condition = _becomeParentOf(expression);
-  }
-
-  @override
-  Token get endToken => _body.endToken;
-
-  @override
-  Expression get initialization => _initialization;
-
-  @override
-  void set initialization(Expression initialization) {
-    _initialization = _becomeParentOf(initialization);
-  }
-
-  @override
-  NodeList<Expression> get updaters => _updaters;
-
-  @override
-  VariableDeclarationList get variables => _variableList;
-
-  @override
-  void set variables(VariableDeclarationList variableList) {
-    _variableList = _becomeParentOf(variableList);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitForStatement(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_variableList, visitor);
-    _safelyVisitChild(_initialization, visitor);
-    _safelyVisitChild(_condition, visitor);
-    _updaters.accept(visitor);
-    _safelyVisitChild(_body, visitor);
-  }
-}
-
-/**
- * A node representing the body of a function or method.
- *
- * > functionBody ::=
- * >     [BlockFunctionBody]
- * >   | [EmptyFunctionBody]
- * >   | [ExpressionFunctionBody]
- */
-abstract class FunctionBodyImpl extends AstNodeImpl implements FunctionBody {
-  /**
-   * Return `true` if this function body is asynchronous.
-   */
-  bool get isAsynchronous => false;
-
-  /**
-   * Return `true` if this function body is a generator.
-   */
-  bool get isGenerator => false;
-
-  /**
-   * Return `true` if this function body is synchronous.
-   */
-  bool get isSynchronous => true;
-
-  /**
-   * Return the token representing the 'async' or 'sync' keyword, or `null` if
-   * there is no such keyword.
-   */
-  Token get keyword => null;
-
-  /**
-   * Return the star following the 'async' or 'sync' keyword, or `null` if there
-   * is no star.
-   */
-  Token get star => null;
-}
-
-/**
- * A top-level declaration.
- *
- * > functionDeclaration ::=
- * >     'external' functionSignature
- * >   | functionSignature [FunctionBody]
- * >
- * > functionSignature ::=
- * >     [Type]? ('get' | 'set')? [SimpleIdentifier] [FormalParameterList]
- */
-class FunctionDeclarationImpl extends NamedCompilationUnitMemberImpl
-    implements FunctionDeclaration {
-  /**
-   * The token representing the 'external' keyword, or `null` if this is not an
-   * external function.
-   */
-  Token externalKeyword;
-
-  /**
-   * The return type of the function, or `null` if no return type was declared.
-   */
-  TypeName _returnType;
-
-  /**
-   * The token representing the 'get' or 'set' keyword, or `null` if this is a
-   * function declaration rather than a property declaration.
-   */
-  Token propertyKeyword;
-
-  /**
-   * The function expression being wrapped.
-   */
-  FunctionExpression _functionExpression;
-
-  /**
-   * Initialize a newly created function declaration. Either or both of the
-   * [comment] and [metadata] can be `null` if the function does not have the
-   * corresponding attribute. The [externalKeyword] can be `null` if the
-   * function is not an external function. The [returnType] can be `null` if no
-   * return type was specified. The [propertyKeyword] can be `null` if the
-   * function is neither a getter or a setter.
-   */
-  FunctionDeclarationImpl(
-      Comment comment,
-      List<Annotation> metadata,
-      this.externalKeyword,
-      TypeName returnType,
-      this.propertyKeyword,
-      SimpleIdentifier name,
-      FunctionExpression functionExpression)
-      : super(comment, metadata, name) {
-    _returnType = _becomeParentOf(returnType);
-    _functionExpression = _becomeParentOf(functionExpression);
-  }
-
-  @override
-  Iterable get childEntities => super._childEntities
-    ..add(externalKeyword)
-    ..add(_returnType)
-    ..add(propertyKeyword)
-    ..add(_name)
-    ..add(_functionExpression);
-
-  @override
-  ExecutableElement get element =>
-      _name != null ? (_name.staticElement as ExecutableElement) : null;
-
-  @override
-  Token get endToken => _functionExpression.endToken;
-
-  @override
-  Token get firstTokenAfterCommentAndMetadata {
-    if (externalKeyword != null) {
-      return externalKeyword;
-    } else if (_returnType != null) {
-      return _returnType.beginToken;
-    } else if (propertyKeyword != null) {
-      return propertyKeyword;
-    } else if (_name != null) {
-      return _name.beginToken;
-    }
-    return _functionExpression.beginToken;
-  }
-
-  @override
-  FunctionExpression get functionExpression => _functionExpression;
-
-  @override
-  void set functionExpression(FunctionExpression functionExpression) {
-    _functionExpression = _becomeParentOf(functionExpression);
-  }
-
-  @override
-  bool get isGetter =>
-      propertyKeyword != null &&
-      (propertyKeyword as KeywordToken).keyword == Keyword.GET;
-
-  @override
-  bool get isSetter =>
-      propertyKeyword != null &&
-      (propertyKeyword as KeywordToken).keyword == Keyword.SET;
-
-  @override
-  TypeName get returnType => _returnType;
-
-  @override
-  void set returnType(TypeName returnType) {
-    _returnType = _becomeParentOf(returnType);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitFunctionDeclaration(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    super.visitChildren(visitor);
-    _safelyVisitChild(_returnType, visitor);
-    _safelyVisitChild(_name, visitor);
-    _safelyVisitChild(_functionExpression, visitor);
-  }
-}
-
-/**
- * A [FunctionDeclaration] used as a statement.
- */
-class FunctionDeclarationStatementImpl extends StatementImpl
-    implements FunctionDeclarationStatement {
-  /**
-   * The function declaration being wrapped.
-   */
-  FunctionDeclaration _functionDeclaration;
-
-  /**
-   * Initialize a newly created function declaration statement.
-   */
-  FunctionDeclarationStatementImpl(FunctionDeclaration functionDeclaration) {
-    _functionDeclaration = _becomeParentOf(functionDeclaration);
-  }
-
-  @override
-  Token get beginToken => _functionDeclaration.beginToken;
-
-  @override
-  Iterable get childEntities => new ChildEntities()..add(_functionDeclaration);
-
-  @override
-  Token get endToken => _functionDeclaration.endToken;
-
-  @override
-  FunctionDeclaration get functionDeclaration => _functionDeclaration;
-
-  @override
-  void set functionDeclaration(FunctionDeclaration functionDeclaration) {
-    _functionDeclaration = _becomeParentOf(functionDeclaration);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitFunctionDeclarationStatement(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_functionDeclaration, visitor);
-  }
-}
-
-/**
- * A function expression.
- *
- * > functionExpression ::=
- * >     [TypeParameterList]? [FormalParameterList] [FunctionBody]
- */
-class FunctionExpressionImpl extends ExpressionImpl
-    implements FunctionExpression {
-  /**
-   * The type parameters associated with the method, or `null` if the method is
-   * not a generic method.
-   */
-  TypeParameterList _typeParameters;
-
-  /**
-   * The parameters associated with the function.
-   */
-  FormalParameterList _parameters;
-
-  /**
-   * The body of the function, or `null` if this is an external function.
-   */
-  FunctionBody _body;
-
-  /**
-   * The element associated with the function, or `null` if the AST structure
-   * has not been resolved.
-   */
-  ExecutableElement element;
-
-  /**
-   * Initialize a newly created function declaration.
-   */
-  FunctionExpressionImpl(TypeParameterList typeParameters,
-      FormalParameterList parameters, FunctionBody body) {
-    _typeParameters = _becomeParentOf(typeParameters);
-    _parameters = _becomeParentOf(parameters);
-    _body = _becomeParentOf(body);
-  }
-
-  @override
-  Token get beginToken {
-    if (_typeParameters != null) {
-      return _typeParameters.beginToken;
-    } else if (_parameters != null) {
-      return _parameters.beginToken;
-    } else if (_body != null) {
-      return _body.beginToken;
-    }
-    // This should never be reached because external functions must be named,
-    // hence either the body or the name should be non-null.
-    throw new IllegalStateException("Non-external functions must have a body");
-  }
-
-  @override
-  FunctionBody get body => _body;
-
-  @override
-  void set body(FunctionBody functionBody) {
-    _body = _becomeParentOf(functionBody);
-  }
-
-  @override
-  Iterable get childEntities =>
-      new ChildEntities()..add(_parameters)..add(_body);
-
-  @override
-  Token get endToken {
-    if (_body != null) {
-      return _body.endToken;
-    } else if (_parameters != null) {
-      return _parameters.endToken;
-    }
-    // This should never be reached because external functions must be named,
-    // hence either the body or the name should be non-null.
-    throw new IllegalStateException("Non-external functions must have a body");
-  }
-
-  @override
-  FormalParameterList get parameters => _parameters;
-
-  @override
-  void set parameters(FormalParameterList parameters) {
-    _parameters = _becomeParentOf(parameters);
-  }
-
-  @override
-  int get precedence => 16;
-
-  @override
-  TypeParameterList get typeParameters => _typeParameters;
-
-  @override
-  void set typeParameters(TypeParameterList typeParameters) {
-    _typeParameters = _becomeParentOf(typeParameters);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitFunctionExpression(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_typeParameters, visitor);
-    _safelyVisitChild(_parameters, visitor);
-    _safelyVisitChild(_body, visitor);
-  }
-}
-
-/**
- * The invocation of a function resulting from evaluating an expression.
- * Invocations of methods and other forms of functions are represented by
- * [MethodInvocation] nodes. Invocations of getters and setters are represented
- * by either [PrefixedIdentifier] or [PropertyAccess] nodes.
- *
- * > functionExpressionInvocation ::=
- * >     [Expression] [TypeArgumentList]? [ArgumentList]
- */
-class FunctionExpressionInvocationImpl extends ExpressionImpl
-    implements FunctionExpressionInvocation {
-  /**
-   * The expression producing the function being invoked.
-   */
-  Expression _function;
-
-  /**
-   * The type arguments to be applied to the method being invoked, or `null` if
-   * no type arguments were provided.
-   */
-  TypeArgumentList _typeArguments;
-
-  /**
-   * The list of arguments to the function.
-   */
-  ArgumentList _argumentList;
-
-  /**
-   * The element associated with the function being invoked based on static type
-   * information, or `null` if the AST structure has not been resolved or the
-   * function could not be resolved.
-   */
-  ExecutableElement staticElement;
-
-  /**
-   * The function type of the method invocation, or `null` if the AST
-   * structure has not been resolved, or if the invoke could not be resolved.
-   *
-   * This will usually be a [FunctionType], but it can also be an
-   * [InterfaceType] with a `call` method, `dynamic`, `Function`, or a `@proxy`
-   * interface type that implements `Function`.
-   */
-  DartType staticInvokeType;
-
-  /**
-   * The element associated with the function being invoked based on propagated
-   * type information, or `null` if the AST structure has not been resolved or
-   * the function could not be resolved.
-   */
-  ExecutableElement propagatedElement;
-
-  /**
-   * Like [staticInvokeType], but reflects propagated type information.
-   */
-  DartType propagatedInvokeType;
-
-  /**
-   * Initialize a newly created function expression invocation.
-   */
-  FunctionExpressionInvocationImpl(Expression function,
-      TypeArgumentList typeArguments, ArgumentList argumentList) {
-    _function = _becomeParentOf(function);
-    _typeArguments = _becomeParentOf(typeArguments);
-    _argumentList = _becomeParentOf(argumentList);
-  }
-
-  @override
-  ArgumentList get argumentList => _argumentList;
-
-  @override
-  void set argumentList(ArgumentList argumentList) {
-    _argumentList = _becomeParentOf(argumentList);
-  }
-
-  @override
-  Token get beginToken => _function.beginToken;
-
-  @override
-  ExecutableElement get bestElement {
-    ExecutableElement element = propagatedElement;
-    if (element == null) {
-      element = staticElement;
-    }
-    return element;
-  }
-
-  @override
-  Iterable get childEntities =>
-      new ChildEntities()..add(_function)..add(_argumentList);
-
-  @override
-  Token get endToken => _argumentList.endToken;
-
-  @override
-  Expression get function => _function;
-
-  @override
-  void set function(Expression expression) {
-    _function = _becomeParentOf(expression);
-  }
-
-  @override
-  int get precedence => 15;
-
-  @override
-  TypeArgumentList get typeArguments => _typeArguments;
-
-  @override
-  void set typeArguments(TypeArgumentList typeArguments) {
-    _typeArguments = _becomeParentOf(typeArguments);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitFunctionExpressionInvocation(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_function, visitor);
-    _safelyVisitChild(_typeArguments, visitor);
-    _safelyVisitChild(_argumentList, visitor);
-  }
-}
-
-/**
- * A function type alias.
- *
- * > functionTypeAlias ::=
- * >     functionPrefix [TypeParameterList]? [FormalParameterList] ';'
- * >
- * > functionPrefix ::=
- * >     [TypeName]? [SimpleIdentifier]
- */
-class FunctionTypeAliasImpl extends TypeAliasImpl implements FunctionTypeAlias {
-  /**
-   * The name of the return type of the function type being defined, or `null`
-   * if no return type was given.
-   */
-  TypeName _returnType;
-
-  /**
-   * The type parameters for the function type, or `null` if the function type
-   * does not have any type parameters.
-   */
-  TypeParameterList _typeParameters;
-
-  /**
-   * The parameters associated with the function type.
-   */
-  FormalParameterList _parameters;
-
-  /**
-   * Initialize a newly created function type alias. Either or both of the
-   * [comment] and [metadata] can be `null` if the function does not have the
-   * corresponding attribute. The [returnType] can be `null` if no return type
-   * was specified. The [typeParameters] can be `null` if the function has no
-   * type parameters.
-   */
-  FunctionTypeAliasImpl(
-      Comment comment,
-      List<Annotation> metadata,
-      Token keyword,
-      TypeName returnType,
-      SimpleIdentifier name,
-      TypeParameterList typeParameters,
-      FormalParameterList parameters,
-      Token semicolon)
-      : super(comment, metadata, keyword, name, semicolon) {
-    _returnType = _becomeParentOf(returnType);
-    _typeParameters = _becomeParentOf(typeParameters);
-    _parameters = _becomeParentOf(parameters);
-  }
-
-  @override
-  Iterable get childEntities => super._childEntities
-    ..add(typedefKeyword)
-    ..add(_returnType)
-    ..add(_name)
-    ..add(_typeParameters)
-    ..add(_parameters)
-    ..add(semicolon);
-
-  @override
-  FunctionTypeAliasElement get element =>
-      _name != null ? (_name.staticElement as FunctionTypeAliasElement) : null;
-
-  @override
-  FormalParameterList get parameters => _parameters;
-
-  @override
-  void set parameters(FormalParameterList parameters) {
-    _parameters = _becomeParentOf(parameters);
-  }
-
-  @override
-  TypeName get returnType => _returnType;
-
-  @override
-  void set returnType(TypeName typeName) {
-    _returnType = _becomeParentOf(typeName);
-  }
-
-  @override
-  TypeParameterList get typeParameters => _typeParameters;
-
-  @override
-  void set typeParameters(TypeParameterList typeParameters) {
-    _typeParameters = _becomeParentOf(typeParameters);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitFunctionTypeAlias(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    super.visitChildren(visitor);
-    _safelyVisitChild(_returnType, visitor);
-    _safelyVisitChild(_name, visitor);
-    _safelyVisitChild(_typeParameters, visitor);
-    _safelyVisitChild(_parameters, visitor);
-  }
-}
-
-/**
- * A function-typed formal parameter.
- *
- * > functionSignature ::=
- * >     [TypeName]? [SimpleIdentifier] [TypeParameterList]? [FormalParameterList]
- */
-class FunctionTypedFormalParameterImpl extends NormalFormalParameterImpl
-    implements FunctionTypedFormalParameter {
-  /**
-   * The return type of the function, or `null` if the function does not have a
-   * return type.
-   */
-  TypeName _returnType;
-
-  /**
-   * The type parameters associated with the function, or `null` if the function
-   * is not a generic function.
-   */
-  TypeParameterList _typeParameters;
-
-  /**
-   * The parameters of the function-typed parameter.
-   */
-  FormalParameterList _parameters;
-
-  /**
-   * Initialize a newly created formal parameter. Either or both of the
-   * [comment] and [metadata] can be `null` if the parameter does not have the
-   * corresponding attribute. The [returnType] can be `null` if no return type
-   * was specified.
-   */
-  FunctionTypedFormalParameterImpl(
-      Comment comment,
-      List<Annotation> metadata,
-      TypeName returnType,
-      SimpleIdentifier identifier,
-      TypeParameterList typeParameters,
-      FormalParameterList parameters)
-      : super(comment, metadata, identifier) {
-    _returnType = _becomeParentOf(returnType);
-    _typeParameters = _becomeParentOf(typeParameters);
-    _parameters = _becomeParentOf(parameters);
-  }
-
-  @override
-  Token get beginToken {
-    if (_returnType != null) {
-      return _returnType.beginToken;
-    }
-    return identifier.beginToken;
-  }
-
-  @override
-  Iterable get childEntities =>
-      super._childEntities..add(_returnType)..add(identifier)..add(parameters);
-
-  @override
-  Token get endToken => _parameters.endToken;
-
-  @override
-  bool get isConst => false;
-
-  @override
-  bool get isFinal => false;
-
-  @override
-  FormalParameterList get parameters => _parameters;
-
-  @override
-  void set parameters(FormalParameterList parameters) {
-    _parameters = _becomeParentOf(parameters);
-  }
-
-  @override
-  TypeName get returnType => _returnType;
-
-  @override
-  void set returnType(TypeName type) {
-    _returnType = _becomeParentOf(type);
-  }
-
-  @override
-  TypeParameterList get typeParameters => _typeParameters;
-
-  @override
-  void set typeParameters(TypeParameterList typeParameters) {
-    _typeParameters = _becomeParentOf(typeParameters);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitFunctionTypedFormalParameter(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    super.visitChildren(visitor);
-    _safelyVisitChild(_returnType, visitor);
-    _safelyVisitChild(identifier, visitor);
-    _safelyVisitChild(_typeParameters, visitor);
-    _safelyVisitChild(_parameters, visitor);
-  }
-}
-
-/**
- * A combinator that restricts the names being imported to those that are not in
- * a given list.
- *
- * > hideCombinator ::=
- * >     'hide' [SimpleIdentifier] (',' [SimpleIdentifier])*
- */
-class HideCombinatorImpl extends CombinatorImpl implements HideCombinator {
-  /**
-   * The list of names from the library that are hidden by this combinator.
-   */
-  NodeList<SimpleIdentifier> _hiddenNames;
-
-  /**
-   * Initialize a newly created import show combinator.
-   */
-  HideCombinatorImpl(Token keyword, List<SimpleIdentifier> hiddenNames)
-      : super(keyword) {
-    _hiddenNames = new NodeList<SimpleIdentifier>(this, hiddenNames);
-  }
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(keyword)
-    ..addAll(_hiddenNames);
-
-  @override
-  Token get endToken => _hiddenNames.endToken;
-
-  @override
-  NodeList<SimpleIdentifier> get hiddenNames => _hiddenNames;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitHideCombinator(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _hiddenNames.accept(visitor);
-  }
-}
-
-/**
- * A node that represents an identifier.
- *
- * > identifier ::=
- * >     [SimpleIdentifier]
- * >   | [PrefixedIdentifier]
- */
-abstract class IdentifierImpl extends ExpressionImpl implements Identifier {
-  /**
-   * Return the best element available for this operator. If resolution was able
-   * to find a better element based on type propagation, that element will be
-   * returned. Otherwise, the element found using the result of static analysis
-   * will be returned. If resolution has not been performed, then `null` will be
-   * returned.
-   */
-  Element get bestElement;
-
-  @override
-  bool get isAssignable => true;
-}
-
-/**
- * An if statement.
- *
- * > ifStatement ::=
- * >     'if' '(' [Expression] ')' [Statement] ('else' [Statement])?
- */
-class IfStatementImpl extends StatementImpl implements IfStatement {
-  /**
-   * The token representing the 'if' keyword.
-   */
-  Token ifKeyword;
-
-  /**
-   * The left parenthesis.
-   */
-  Token leftParenthesis;
-
-  /**
-   * The condition used to determine which of the statements is executed next.
-   */
-  Expression _condition;
-
-  /**
-   * The right parenthesis.
-   */
-  Token rightParenthesis;
-
-  /**
-   * The statement that is executed if the condition evaluates to `true`.
-   */
-  Statement _thenStatement;
-
-  /**
-   * The token representing the 'else' keyword, or `null` if there is no else
-   * statement.
-   */
-  Token elseKeyword;
-
-  /**
-   * The statement that is executed if the condition evaluates to `false`, or
-   * `null` if there is no else statement.
-   */
-  Statement _elseStatement;
-
-  /**
-   * Initialize a newly created if statement. The [elseKeyword] and
-   * [elseStatement] can be `null` if there is no else clause.
-   */
-  IfStatementImpl(
-      this.ifKeyword,
-      this.leftParenthesis,
-      Expression condition,
-      this.rightParenthesis,
-      Statement thenStatement,
-      this.elseKeyword,
-      Statement elseStatement) {
-    _condition = _becomeParentOf(condition);
-    _thenStatement = _becomeParentOf(thenStatement);
-    _elseStatement = _becomeParentOf(elseStatement);
-  }
-
-  @override
-  Token get beginToken => ifKeyword;
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(ifKeyword)
-    ..add(leftParenthesis)
-    ..add(_condition)
-    ..add(rightParenthesis)
-    ..add(_thenStatement)
-    ..add(elseKeyword)
-    ..add(_elseStatement);
-
-  @override
-  Expression get condition => _condition;
-
-  @override
-  void set condition(Expression expression) {
-    _condition = _becomeParentOf(expression);
-  }
-
-  @override
-  Statement get elseStatement => _elseStatement;
-
-  @override
-  void set elseStatement(Statement statement) {
-    _elseStatement = _becomeParentOf(statement);
-  }
-
-  @override
-  Token get endToken {
-    if (_elseStatement != null) {
-      return _elseStatement.endToken;
-    }
-    return _thenStatement.endToken;
-  }
-
-  @override
-  Statement get thenStatement => _thenStatement;
-
-  @override
-  void set thenStatement(Statement statement) {
-    _thenStatement = _becomeParentOf(statement);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitIfStatement(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_condition, visitor);
-    _safelyVisitChild(_thenStatement, visitor);
-    _safelyVisitChild(_elseStatement, visitor);
-  }
-}
-
-/**
- * The "implements" clause in an class declaration.
- *
- * > implementsClause ::=
- * >     'implements' [TypeName] (',' [TypeName])*
- */
-class ImplementsClauseImpl extends AstNodeImpl implements ImplementsClause {
-  /**
-   * The token representing the 'implements' keyword.
-   */
-  Token implementsKeyword;
-
-  /**
-   * The interfaces that are being implemented.
-   */
-  NodeList<TypeName> _interfaces;
-
-  /**
-   * Initialize a newly created implements clause.
-   */
-  ImplementsClauseImpl(this.implementsKeyword, List<TypeName> interfaces) {
-    _interfaces = new NodeList<TypeName>(this, interfaces);
-  }
-
-  @override
-  Token get beginToken => implementsKeyword;
-
-  @override
-  // TODO(paulberry): add commas.
-  Iterable get childEntities => new ChildEntities()
-    ..add(implementsKeyword)
-    ..addAll(interfaces);
-
-  @override
-  Token get endToken => _interfaces.endToken;
-
-  @override
-  NodeList<TypeName> get interfaces => _interfaces;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitImplementsClause(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _interfaces.accept(visitor);
-  }
-}
-
-/**
- * An import directive.
- *
- * > importDirective ::=
- * >     [Annotation] 'import' [StringLiteral] ('as' identifier)? [Combinator]* ';'
- * >   | [Annotation] 'import' [StringLiteral] 'deferred' 'as' identifier [Combinator]* ';'
- */
-class ImportDirectiveImpl extends NamespaceDirectiveImpl
-    implements ImportDirective {
-  /**
-   * The token representing the 'deferred' keyword, or `null` if the imported is
-   * not deferred.
-   */
-  Token deferredKeyword;
-
-  /**
-   * The token representing the 'as' keyword, or `null` if the imported names are
-   * not prefixed.
-   */
-  Token asKeyword;
-
-  /**
-   * The prefix to be used with the imported names, or `null` if the imported
-   * names are not prefixed.
-   */
-  SimpleIdentifier _prefix;
-
-  /**
-   * Initialize a newly created import directive. Either or both of the
-   * [comment] and [metadata] can be `null` if the function does not have the
-   * corresponding attribute. The [deferredKeyword] can be `null` if the import
-   * is not deferred. The [asKeyword] and [prefix] can be `null` if the import
-   * does not specify a prefix. The list of [combinators] can be `null` if there
-   * are no combinators.
-   */
-  ImportDirectiveImpl(
-      Comment comment,
-      List<Annotation> metadata,
-      Token keyword,
-      StringLiteral libraryUri,
-      List<Configuration> configurations,
-      this.deferredKeyword,
-      this.asKeyword,
-      SimpleIdentifier prefix,
-      List<Combinator> combinators,
-      Token semicolon)
-      : super(comment, metadata, keyword, libraryUri, configurations,
-            combinators, semicolon) {
-    _prefix = _becomeParentOf(prefix);
-  }
-
-  @override
-  Iterable get childEntities => super._childEntities
-    ..add(_uri)
-    ..add(deferredKeyword)
-    ..add(asKeyword)
-    ..add(_prefix)
-    ..addAll(combinators)
-    ..add(semicolon);
-
-  @override
-  ImportElement get element => super.element as ImportElement;
-
-  @override
-  SimpleIdentifier get prefix => _prefix;
-
-  @override
-  void set prefix(SimpleIdentifier identifier) {
-    _prefix = _becomeParentOf(identifier);
-  }
-
-  @override
-  LibraryElement get uriElement {
-    ImportElement element = this.element;
-    if (element == null) {
-      return null;
-    }
-    return element.importedLibrary;
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitImportDirective(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    super.visitChildren(visitor);
-    _safelyVisitChild(_prefix, visitor);
-    combinators.accept(visitor);
-  }
-}
-
-/**
- * An index expression.
- *
- * > indexExpression ::=
- * >     [Expression] '[' [Expression] ']'
- */
-class IndexExpressionImpl extends ExpressionImpl implements IndexExpression {
-  /**
-   * The expression used to compute the object being indexed, or `null` if this
-   * index expression is part of a cascade expression.
-   */
-  Expression _target;
-
-  /**
-   * The period ("..") before a cascaded index expression, or `null` if this
-   * index expression is not part of a cascade expression.
-   */
-  Token period;
-
-  /**
-   * The left square bracket.
-   */
-  Token leftBracket;
-
-  /**
-   * The expression used to compute the index.
-   */
-  Expression _index;
-
-  /**
-   * The right square bracket.
-   */
-  Token rightBracket;
-
-  /**
-   * The element associated with the operator based on the static type of the
-   * target, or `null` if the AST structure has not been resolved or if the
-   * operator could not be resolved.
-   */
-  MethodElement staticElement;
-
-  /**
-   * The element associated with the operator based on the propagated type of
-   * the target, or `null` if the AST structure has not been resolved or if the
-   * operator could not be resolved.
-   */
-  MethodElement propagatedElement;
-
-  /**
-   * If this expression is both in a getter and setter context, the
-   * [AuxiliaryElements] will be set to hold onto the static and propagated
-   * information. The auxiliary element will hold onto the elements from the
-   * getter context.
-   */
-  AuxiliaryElements auxiliaryElements = null;
-
-  /**
-   * Initialize a newly created index expression.
-   */
-  IndexExpressionImpl.forCascade(
-      this.period, this.leftBracket, Expression index, this.rightBracket) {
-    _index = _becomeParentOf(index);
-  }
-
-  /**
-   * Initialize a newly created index expression.
-   */
-  IndexExpressionImpl.forTarget(Expression target, this.leftBracket,
-      Expression index, this.rightBracket) {
-    _target = _becomeParentOf(target);
-    _index = _becomeParentOf(index);
-  }
-
-  @override
-  Token get beginToken {
-    if (_target != null) {
-      return _target.beginToken;
-    }
-    return period;
-  }
-
-  @override
-  MethodElement get bestElement {
-    MethodElement element = propagatedElement;
-    if (element == null) {
-      element = staticElement;
-    }
-    return element;
-  }
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(_target)
-    ..add(period)
-    ..add(leftBracket)
-    ..add(_index)
-    ..add(rightBracket);
-
-  @override
-  Token get endToken => rightBracket;
-
-  @override
-  Expression get index => _index;
-
-  @override
-  void set index(Expression expression) {
-    _index = _becomeParentOf(expression);
-  }
-
-  @override
-  bool get isAssignable => true;
-
-  @override
-  bool get isCascaded => period != null;
-
-  @override
-  int get precedence => 15;
-
-  @override
-  Expression get realTarget {
-    if (isCascaded) {
-      AstNode ancestor = parent;
-      while (ancestor is! CascadeExpression) {
-        if (ancestor == null) {
-          return _target;
-        }
-        ancestor = ancestor.parent;
-      }
-      return (ancestor as CascadeExpression).target;
-    }
-    return _target;
-  }
-
-  @override
-  Expression get target => _target;
-
-  @override
-  void set target(Expression expression) {
-    _target = _becomeParentOf(expression);
-  }
-
-  /**
-   * If the AST structure has been resolved, and the function being invoked is
-   * known based on propagated type information, then return the parameter
-   * element representing the parameter to which the value of the index
-   * expression will be bound. Otherwise, return `null`.
-   */
-  ParameterElement get _propagatedParameterElementForIndex {
-    if (propagatedElement == null) {
-      return null;
-    }
-    List<ParameterElement> parameters = propagatedElement.parameters;
-    if (parameters.length < 1) {
-      return null;
-    }
-    return parameters[0];
-  }
-
-  /**
-   * If the AST structure has been resolved, and the function being invoked is
-   * known based on static type information, then return the parameter element
-   * representing the parameter to which the value of the index expression will
-   * be bound. Otherwise, return `null`.
-   */
-  ParameterElement get _staticParameterElementForIndex {
-    if (staticElement == null) {
-      return null;
-    }
-    List<ParameterElement> parameters = staticElement.parameters;
-    if (parameters.length < 1) {
-      return null;
-    }
-    return parameters[0];
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitIndexExpression(this);
-
-  @override
-  bool inGetterContext() {
-    // TODO(brianwilkerson) Convert this to a getter.
-    AstNode parent = this.parent;
-    if (parent is AssignmentExpression) {
-      AssignmentExpression assignment = parent;
-      if (identical(assignment.leftHandSide, this) &&
-          assignment.operator.type == TokenType.EQ) {
-        return false;
-      }
-    }
-    return true;
-  }
-
-  @override
-  bool inSetterContext() {
-    // TODO(brianwilkerson) Convert this to a getter.
-    AstNode parent = this.parent;
-    if (parent is PrefixExpression) {
-      return parent.operator.type.isIncrementOperator;
-    } else if (parent is PostfixExpression) {
-      return true;
-    } else if (parent is AssignmentExpression) {
-      return identical(parent.leftHandSide, this);
-    }
-    return false;
-  }
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_target, visitor);
-    _safelyVisitChild(_index, visitor);
-  }
-}
-
-/**
- * An instance creation expression.
- *
- * > newExpression ::=
- * >     ('new' | 'const') [TypeName] ('.' [SimpleIdentifier])? [ArgumentList]
- */
-class InstanceCreationExpressionImpl extends ExpressionImpl
-    implements InstanceCreationExpression {
-  /**
-   * The 'new' or 'const' keyword used to indicate how an object should be
-   * created.
-   */
-  Token keyword;
-
-  /**
-   * The name of the constructor to be invoked.
-   */
-  ConstructorName _constructorName;
-
-  /**
-   * The list of arguments to the constructor.
-   */
-  ArgumentList _argumentList;
-
-  /**
-   * The element associated with the constructor based on static type
-   * information, or `null` if the AST structure has not been resolved or if the
-   * constructor could not be resolved.
-   */
-  ConstructorElement staticElement;
-
-  /**
-   * Initialize a newly created instance creation expression.
-   */
-  InstanceCreationExpressionImpl(this.keyword, ConstructorName constructorName,
-      ArgumentList argumentList) {
-    _constructorName = _becomeParentOf(constructorName);
-    _argumentList = _becomeParentOf(argumentList);
-  }
-
-  @override
-  ArgumentList get argumentList => _argumentList;
-
-  @override
-  void set argumentList(ArgumentList argumentList) {
-    _argumentList = _becomeParentOf(argumentList);
-  }
-
-  @override
-  Token get beginToken => keyword;
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(keyword)
-    ..add(_constructorName)
-    ..add(_argumentList);
-
-  @override
-  ConstructorName get constructorName => _constructorName;
-
-  @override
-  void set constructorName(ConstructorName name) {
-    _constructorName = _becomeParentOf(name);
-  }
-
-  @override
-  Token get endToken => _argumentList.endToken;
-
-  @override
-  bool get isConst =>
-      keyword is KeywordToken &&
-      (keyword as KeywordToken).keyword == Keyword.CONST;
-
-  @override
-  int get precedence => 16;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitInstanceCreationExpression(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_constructorName, visitor);
-    _safelyVisitChild(_argumentList, visitor);
-  }
-}
-
-/**
- * An integer literal expression.
- *
- * > integerLiteral ::=
- * >     decimalIntegerLiteral
- * >   | hexadecimalIntegerLiteral
- * >
- * > decimalIntegerLiteral ::=
- * >     decimalDigit+
- * >
- * > hexadecimalIntegerLiteral ::=
- * >     '0x' hexadecimalDigit+
- * >   | '0X' hexadecimalDigit+
- */
-class IntegerLiteralImpl extends LiteralImpl implements IntegerLiteral {
-  /**
-   * The token representing the literal.
-   */
-  Token literal;
-
-  /**
-   * The value of the literal.
-   */
-  int value = 0;
-
-  /**
-   * Initialize a newly created integer literal.
-   */
-  IntegerLiteralImpl(this.literal, this.value);
-
-  @override
-  Token get beginToken => literal;
-
-  @override
-  Iterable get childEntities => new ChildEntities()..add(literal);
-
-  @override
-  Token get endToken => literal;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitIntegerLiteral(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    // There are no children to visit.
-  }
-}
-
-/**
- * A node within a [StringInterpolation].
- *
- * > interpolationElement ::=
- * >     [InterpolationExpression]
- * >   | [InterpolationString]
- */
-abstract class InterpolationElementImpl extends AstNodeImpl
-    implements InterpolationElement {}
-
-/**
- * An expression embedded in a string interpolation.
- *
- * > interpolationExpression ::=
- * >     '$' [SimpleIdentifier]
- * >   | '$' '{' [Expression] '}'
- */
-class InterpolationExpressionImpl extends InterpolationElementImpl
-    implements InterpolationExpression {
-  /**
-   * The token used to introduce the interpolation expression; either '$' if the
-   * expression is a simple identifier or '${' if the expression is a full
-   * expression.
-   */
-  Token leftBracket;
-
-  /**
-   * The expression to be evaluated for the value to be converted into a string.
-   */
-  Expression _expression;
-
-  /**
-   * The right curly bracket, or `null` if the expression is an identifier
-   * without brackets.
-   */
-  Token rightBracket;
-
-  /**
-   * Initialize a newly created interpolation expression.
-   */
-  InterpolationExpressionImpl(
-      this.leftBracket, Expression expression, this.rightBracket) {
-    _expression = _becomeParentOf(expression);
-  }
-
-  @override
-  Token get beginToken => leftBracket;
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(leftBracket)
-    ..add(_expression)
-    ..add(rightBracket);
-
-  @override
-  Token get endToken {
-    if (rightBracket != null) {
-      return rightBracket;
-    }
-    return _expression.endToken;
-  }
-
-  @override
-  Expression get expression => _expression;
-
-  @override
-  void set expression(Expression expression) {
-    _expression = _becomeParentOf(expression);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitInterpolationExpression(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_expression, visitor);
-  }
-}
-
-/**
- * A non-empty substring of an interpolated string.
- *
- * > interpolationString ::=
- * >     characters
- */
-class InterpolationStringImpl extends InterpolationElementImpl
-    implements InterpolationString {
-  /**
-   * The characters that will be added to the string.
-   */
-  Token contents;
-
-  /**
-   * The value of the literal.
-   */
-  String value;
-
-  /**
-   * Initialize a newly created string of characters that are part of a string
-   * interpolation.
-   */
-  InterpolationStringImpl(this.contents, this.value);
-
-  @override
-  Token get beginToken => contents;
-
-  @override
-  Iterable get childEntities => new ChildEntities()..add(contents);
-
-  @override
-  int get contentsEnd {
-    String lexeme = contents.lexeme;
-    return offset + new StringLexemeHelper(lexeme, true, true).end;
-  }
-
-  @override
-  int get contentsOffset {
-    int offset = contents.offset;
-    String lexeme = contents.lexeme;
-    return offset + new StringLexemeHelper(lexeme, true, true).start;
-  }
-
-  @override
-  Token get endToken => contents;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitInterpolationString(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {}
-}
-
-/**
- * An is expression.
- *
- * > isExpression ::=
- * >     [Expression] 'is' '!'? [TypeName]
- */
-class IsExpressionImpl extends ExpressionImpl implements IsExpression {
-  /**
-   * The expression used to compute the value whose type is being tested.
-   */
-  Expression _expression;
-
-  /**
-   * The is operator.
-   */
-  Token isOperator;
-
-  /**
-   * The not operator, or `null` if the sense of the test is not negated.
-   */
-  Token notOperator;
-
-  /**
-   * The name of the type being tested for.
-   */
-  TypeName _type;
-
-  /**
-   * Initialize a newly created is expression. The [notOperator] can be `null`
-   * if the sense of the test is not negated.
-   */
-  IsExpressionImpl(
-      Expression expression, this.isOperator, this.notOperator, TypeName type) {
-    _expression = _becomeParentOf(expression);
-    _type = _becomeParentOf(type);
-  }
-
-  @override
-  Token get beginToken => _expression.beginToken;
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(_expression)
-    ..add(isOperator)
-    ..add(notOperator)
-    ..add(_type);
-
-  @override
-  Token get endToken => _type.endToken;
-
-  @override
-  Expression get expression => _expression;
-
-  @override
-  void set expression(Expression expression) {
-    _expression = _becomeParentOf(expression);
-  }
-
-  @override
-  int get precedence => 7;
-
-  @override
-  TypeName get type => _type;
-
-  @override
-  void set type(TypeName name) {
-    _type = _becomeParentOf(name);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitIsExpression(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_expression, visitor);
-    _safelyVisitChild(_type, visitor);
-  }
-}
-
-/**
- * A statement that has a label associated with them.
- *
- * > labeledStatement ::=
- * >    [Label]+ [Statement]
- */
-class LabeledStatementImpl extends StatementImpl implements LabeledStatement {
-  /**
-   * The labels being associated with the statement.
-   */
-  NodeList<Label> _labels;
-
-  /**
-   * The statement with which the labels are being associated.
-   */
-  Statement _statement;
-
-  /**
-   * Initialize a newly created labeled statement.
-   */
-  LabeledStatementImpl(List<Label> labels, Statement statement) {
-    _labels = new NodeList<Label>(this, labels);
-    _statement = _becomeParentOf(statement);
-  }
-
-  @override
-  Token get beginToken {
-    if (!_labels.isEmpty) {
-      return _labels.beginToken;
-    }
-    return _statement.beginToken;
-  }
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..addAll(_labels)
-    ..add(_statement);
-
-  @override
-  Token get endToken => _statement.endToken;
-
-  @override
-  NodeList<Label> get labels => _labels;
-
-  @override
-  Statement get statement => _statement;
-
-  @override
-  void set statement(Statement statement) {
-    _statement = _becomeParentOf(statement);
-  }
-
-  @override
-  Statement get unlabeled => _statement.unlabeled;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitLabeledStatement(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _labels.accept(visitor);
-    _safelyVisitChild(_statement, visitor);
-  }
-}
-
-/**
- * A label on either a [LabeledStatement] or a [NamedExpression].
- *
- * > label ::=
- * >     [SimpleIdentifier] ':'
- */
-class LabelImpl extends AstNodeImpl implements Label {
-  /**
-   * The label being associated with the statement.
-   */
-  SimpleIdentifier _label;
-
-  /**
-   * The colon that separates the label from the statement.
-   */
-  Token colon;
-
-  /**
-   * Initialize a newly created label.
-   */
-  LabelImpl(SimpleIdentifier label, this.colon) {
-    _label = _becomeParentOf(label);
-  }
-
-  @override
-  Token get beginToken => _label.beginToken;
-
-  @override
-  Iterable get childEntities => new ChildEntities()..add(_label)..add(colon);
-
-  @override
-  Token get endToken => colon;
-
-  @override
-  SimpleIdentifier get label => _label;
-
-  @override
-  void set label(SimpleIdentifier label) {
-    _label = _becomeParentOf(label);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitLabel(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_label, visitor);
-  }
-}
-
-/**
- * A library directive.
- *
- * > libraryDirective ::=
- * >     [Annotation] 'library' [Identifier] ';'
- */
-class LibraryDirectiveImpl extends DirectiveImpl implements LibraryDirective {
-  /**
-   * The token representing the 'library' keyword.
-   */
-  Token libraryKeyword;
-
-  /**
-   * The name of the library being defined.
-   */
-  LibraryIdentifier _name;
-
-  /**
-   * The semicolon terminating the directive.
-   */
-  Token semicolon;
-
-  /**
-   * Initialize a newly created library directive. Either or both of the
-   * [comment] and [metadata] can be `null` if the directive does not have the
-   * corresponding attribute.
-   */
-  LibraryDirectiveImpl(Comment comment, List<Annotation> metadata,
-      this.libraryKeyword, LibraryIdentifier name, this.semicolon)
-      : super(comment, metadata) {
-    _name = _becomeParentOf(name);
-  }
-
-  @override
-  Iterable get childEntities =>
-      super._childEntities..add(libraryKeyword)..add(_name)..add(semicolon);
-
-  @override
-  Token get endToken => semicolon;
-
-  @override
-  Token get firstTokenAfterCommentAndMetadata => libraryKeyword;
-
-  @override
-  Token get keyword => libraryKeyword;
-
-  @override
-  LibraryIdentifier get name => _name;
-
-  @override
-  void set name(LibraryIdentifier name) {
-    _name = _becomeParentOf(name);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitLibraryDirective(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    super.visitChildren(visitor);
-    _safelyVisitChild(_name, visitor);
-  }
-}
-
-/**
- * The identifier for a library.
- *
- * > libraryIdentifier ::=
- * >     [SimpleIdentifier] ('.' [SimpleIdentifier])*
- */
-class LibraryIdentifierImpl extends IdentifierImpl
-    implements LibraryIdentifier {
-  /**
-   * The components of the identifier.
-   */
-  NodeList<SimpleIdentifier> _components;
-
-  /**
-   * Initialize a newly created prefixed identifier.
-   */
-  LibraryIdentifierImpl(List<SimpleIdentifier> components) {
-    _components = new NodeList<SimpleIdentifier>(this, components);
-  }
-
-  @override
-  Token get beginToken => _components.beginToken;
-
-  @override
-  Element get bestElement => staticElement;
-
-  @override
-  // TODO(paulberry): add "." tokens.
-  Iterable get childEntities => new ChildEntities()..addAll(_components);
-
-  @override
-  NodeList<SimpleIdentifier> get components => _components;
-
-  @override
-  Token get endToken => _components.endToken;
-
-  @override
-  String get name {
-    StringBuffer buffer = new StringBuffer();
-    bool needsPeriod = false;
-    for (SimpleIdentifier identifier in _components) {
-      if (needsPeriod) {
-        buffer.write(".");
-      } else {
-        needsPeriod = true;
-      }
-      buffer.write(identifier.name);
-    }
-    return buffer.toString();
-  }
-
-  @override
-  int get precedence => 15;
-
-  @override
-  Element get propagatedElement => null;
-
-  @override
-  Element get staticElement => null;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitLibraryIdentifier(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _components.accept(visitor);
-  }
-}
-
-/**
- * A list literal.
- *
- * > listLiteral ::=
- * >     'const'? ('<' [TypeName] '>')? '[' ([Expression] ','?)? ']'
- */
-class ListLiteralImpl extends TypedLiteralImpl implements ListLiteral {
-  /**
-   * The left square bracket.
-   */
-  Token leftBracket;
-
-  /**
-   * The expressions used to compute the elements of the list.
-   */
-  NodeList<Expression> _elements;
-
-  /**
-   * The right square bracket.
-   */
-  Token rightBracket;
-
-  /**
-   * Initialize a newly created list literal. The [constKeyword] can be `null`
-   * if the literal is not a constant. The [typeArguments] can be `null` if no
-   * type arguments were declared. The list of [elements] can be `null` if the
-   * list is empty.
-   */
-  ListLiteralImpl(Token constKeyword, TypeArgumentList typeArguments,
-      this.leftBracket, List<Expression> elements, this.rightBracket)
-      : super(constKeyword, typeArguments) {
-    _elements = new NodeList<Expression>(this, elements);
-  }
-
-  @override
-  Token get beginToken {
-    if (constKeyword != null) {
-      return constKeyword;
-    }
-    TypeArgumentList typeArguments = this.typeArguments;
-    if (typeArguments != null) {
-      return typeArguments.beginToken;
-    }
-    return leftBracket;
-  }
-
-  @override
-  // TODO(paulberry): add commas.
-  Iterable get childEntities => super._childEntities
-    ..add(leftBracket)
-    ..addAll(_elements)
-    ..add(rightBracket);
-
-  @override
-  NodeList<Expression> get elements => _elements;
-
-  @override
-  Token get endToken => rightBracket;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitListLiteral(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    super.visitChildren(visitor);
-    _elements.accept(visitor);
-  }
-}
-
-/**
- * A node that represents a literal expression.
- *
- * > literal ::=
- * >     [BooleanLiteral]
- * >   | [DoubleLiteral]
- * >   | [IntegerLiteral]
- * >   | [ListLiteral]
- * >   | [MapLiteral]
- * >   | [NullLiteral]
- * >   | [StringLiteral]
- */
-abstract class LiteralImpl extends ExpressionImpl implements Literal {
-  @override
-  int get precedence => 16;
-}
-
-/**
- * A single key/value pair in a map literal.
- *
- * > mapLiteralEntry ::=
- * >     [Expression] ':' [Expression]
- */
-class MapLiteralEntryImpl extends AstNodeImpl implements MapLiteralEntry {
-  /**
-   * The expression computing the key with which the value will be associated.
-   */
-  Expression _key;
-
-  /**
-   * The colon that separates the key from the value.
-   */
-  Token separator;
-
-  /**
-   * The expression computing the value that will be associated with the key.
-   */
-  Expression _value;
-
-  /**
-   * Initialize a newly created map literal entry.
-   */
-  MapLiteralEntryImpl(Expression key, this.separator, Expression value) {
-    _key = _becomeParentOf(key);
-    _value = _becomeParentOf(value);
-  }
-
-  @override
-  Token get beginToken => _key.beginToken;
-
-  @override
-  Iterable get childEntities =>
-      new ChildEntities()..add(_key)..add(separator)..add(_value);
-
-  @override
-  Token get endToken => _value.endToken;
-
-  @override
-  Expression get key => _key;
-
-  @override
-  void set key(Expression string) {
-    _key = _becomeParentOf(string);
-  }
-
-  @override
-  Expression get value => _value;
-
-  @override
-  void set value(Expression expression) {
-    _value = _becomeParentOf(expression);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitMapLiteralEntry(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_key, visitor);
-    _safelyVisitChild(_value, visitor);
-  }
-}
-
-/**
- * A literal map.
- *
- * > mapLiteral ::=
- * >     'const'? ('<' [TypeName] (',' [TypeName])* '>')?
- * >     '{' ([MapLiteralEntry] (',' [MapLiteralEntry])* ','?)? '}'
- */
-class MapLiteralImpl extends TypedLiteralImpl implements MapLiteral {
-  /**
-   * The left curly bracket.
-   */
-  Token leftBracket;
-
-  /**
-   * The entries in the map.
-   */
-  NodeList<MapLiteralEntry> _entries;
-
-  /**
-   * The right curly bracket.
-   */
-  Token rightBracket;
-
-  /**
-   * Initialize a newly created map literal. The [constKeyword] can be `null` if
-   * the literal is not a constant. The [typeArguments] can be `null` if no type
-   * arguments were declared. The [entries] can be `null` if the map is empty.
-   */
-  MapLiteralImpl(Token constKeyword, TypeArgumentList typeArguments,
-      this.leftBracket, List<MapLiteralEntry> entries, this.rightBracket)
-      : super(constKeyword, typeArguments) {
-    _entries = new NodeList<MapLiteralEntry>(this, entries);
-  }
-
-  @override
-  Token get beginToken {
-    if (constKeyword != null) {
-      return constKeyword;
-    }
-    TypeArgumentList typeArguments = this.typeArguments;
-    if (typeArguments != null) {
-      return typeArguments.beginToken;
-    }
-    return leftBracket;
-  }
-
-  @override
-  // TODO(paulberry): add commas.
-  Iterable get childEntities => super._childEntities
-    ..add(leftBracket)
-    ..addAll(entries)
-    ..add(rightBracket);
-
-  @override
-  Token get endToken => rightBracket;
-
-  @override
-  NodeList<MapLiteralEntry> get entries => _entries;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitMapLiteral(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    super.visitChildren(visitor);
-    _entries.accept(visitor);
-  }
-}
-
-/**
- * A method declaration.
- *
- * > methodDeclaration ::=
- * >     methodSignature [FunctionBody]
- * >
- * > methodSignature ::=
- * >     'external'? ('abstract' | 'static')? [Type]? ('get' | 'set')?
- * >     methodName [TypeParameterList] [FormalParameterList]
- * >
- * > methodName ::=
- * >     [SimpleIdentifier]
- * >   | 'operator' [SimpleIdentifier]
- */
-class MethodDeclarationImpl extends ClassMemberImpl
-    implements MethodDeclaration {
-  /**
-   * The token for the 'external' keyword, or `null` if the constructor is not
-   * external.
-   */
-  Token externalKeyword;
-
-  /**
-   * The token representing the 'abstract' or 'static' keyword, or `null` if
-   * neither modifier was specified.
-   */
-  Token modifierKeyword;
-
-  /**
-   * The return type of the method, or `null` if no return type was declared.
-   */
-  TypeName _returnType;
-
-  /**
-   * The token representing the 'get' or 'set' keyword, or `null` if this is a
-   * method declaration rather than a property declaration.
-   */
-  Token propertyKeyword;
-
-  /**
-   * The token representing the 'operator' keyword, or `null` if this method
-   * does not declare an operator.
-   */
-  Token operatorKeyword;
-
-  /**
-   * The name of the method.
-   */
-  SimpleIdentifier _name;
-
-  /**
-   * The type parameters associated with the method, or `null` if the method is
-   * not a generic method.
-   */
-  TypeParameterList _typeParameters;
-
-  /**
-   * The parameters associated with the method, or `null` if this method
-   * declares a getter.
-   */
-  FormalParameterList _parameters;
-
-  /**
-   * The body of the method.
-   */
-  FunctionBody _body;
-
-  /**
-   * Initialize a newly created method declaration. Either or both of the
-   * [comment] and [metadata] can be `null` if the declaration does not have the
-   * corresponding attribute. The [externalKeyword] can be `null` if the method
-   * is not external. The [modifierKeyword] can be `null` if the method is
-   * neither abstract nor static. The [returnType] can be `null` if no return
-   * type was specified. The [propertyKeyword] can be `null` if the method is
-   * neither a getter or a setter. The [operatorKeyword] can be `null` if the
-   * method does not implement an operator. The [parameters] must be `null` if
-   * this method declares a getter.
-   */
-  MethodDeclarationImpl(
-      Comment comment,
-      List<Annotation> metadata,
-      this.externalKeyword,
-      this.modifierKeyword,
-      TypeName returnType,
-      this.propertyKeyword,
-      this.operatorKeyword,
-      SimpleIdentifier name,
-      TypeParameterList typeParameters,
-      FormalParameterList parameters,
-      FunctionBody body)
-      : super(comment, metadata) {
-    _returnType = _becomeParentOf(returnType);
-    _name = _becomeParentOf(name);
-    _typeParameters = _becomeParentOf(typeParameters);
-    _parameters = _becomeParentOf(parameters);
-    _body = _becomeParentOf(body);
-  }
-
-  @override
-  FunctionBody get body => _body;
-
-  @override
-  void set body(FunctionBody functionBody) {
-    _body = _becomeParentOf(functionBody);
-  }
-
-  @override
-  Iterable get childEntities => super._childEntities
-    ..add(externalKeyword)
-    ..add(modifierKeyword)
-    ..add(_returnType)
-    ..add(propertyKeyword)
-    ..add(operatorKeyword)
-    ..add(_name)
-    ..add(_parameters)
-    ..add(_body);
-
-  /**
-   * Return the element associated with this method, or `null` if the AST
-   * structure has not been resolved. The element can either be a
-   * [MethodElement], if this represents the declaration of a normal method, or
-   * a [PropertyAccessorElement] if this represents the declaration of either a
-   * getter or a setter.
-   */
-  @override
-  ExecutableElement get element =>
-      _name != null ? (_name.staticElement as ExecutableElement) : null;
-
-  @override
-  Token get endToken => _body.endToken;
-
-  @override
-  Token get firstTokenAfterCommentAndMetadata {
-    if (modifierKeyword != null) {
-      return modifierKeyword;
-    } else if (_returnType != null) {
-      return _returnType.beginToken;
-    } else if (propertyKeyword != null) {
-      return propertyKeyword;
-    } else if (operatorKeyword != null) {
-      return operatorKeyword;
-    }
-    return _name.beginToken;
-  }
-
-  @override
-  bool get isAbstract {
-    FunctionBody body = _body;
-    return externalKeyword == null &&
-        (body is EmptyFunctionBody && !body.semicolon.isSynthetic);
-  }
-
-  @override
-  bool get isGetter =>
-      propertyKeyword != null &&
-      (propertyKeyword as KeywordToken).keyword == Keyword.GET;
-
-  @override
-  bool get isOperator => operatorKeyword != null;
-
-  @override
-  bool get isSetter =>
-      propertyKeyword != null &&
-      (propertyKeyword as KeywordToken).keyword == Keyword.SET;
-
-  @override
-  bool get isStatic =>
-      modifierKeyword != null &&
-      (modifierKeyword as KeywordToken).keyword == Keyword.STATIC;
-
-  @override
-  SimpleIdentifier get name => _name;
-
-  @override
-  void set name(SimpleIdentifier identifier) {
-    _name = _becomeParentOf(identifier);
-  }
-
-  @override
-  FormalParameterList get parameters => _parameters;
-
-  @override
-  void set parameters(FormalParameterList parameters) {
-    _parameters = _becomeParentOf(parameters);
-  }
-
-  @override
-  TypeName get returnType => _returnType;
-
-  @override
-  void set returnType(TypeName typeName) {
-    _returnType = _becomeParentOf(typeName);
-  }
-
-  @override
-  TypeParameterList get typeParameters => _typeParameters;
-
-  @override
-  void set typeParameters(TypeParameterList typeParameters) {
-    _typeParameters = _becomeParentOf(typeParameters);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitMethodDeclaration(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    super.visitChildren(visitor);
-    _safelyVisitChild(_returnType, visitor);
-    _safelyVisitChild(_name, visitor);
-    _safelyVisitChild(_typeParameters, visitor);
-    _safelyVisitChild(_parameters, visitor);
-    _safelyVisitChild(_body, visitor);
-  }
-}
-
-/**
- * The invocation of either a function or a method. Invocations of functions
- * resulting from evaluating an expression are represented by
- * [FunctionExpressionInvocation] nodes. Invocations of getters and setters are
- * represented by either [PrefixedIdentifier] or [PropertyAccess] nodes.
- *
- * > methodInvocation ::=
- * >     ([Expression] '.')? [SimpleIdentifier] [TypeArgumentList]? [ArgumentList]
- */
-class MethodInvocationImpl extends ExpressionImpl implements MethodInvocation {
-  /**
-   * The expression producing the object on which the method is defined, or
-   * `null` if there is no target (that is, the target is implicitly `this`).
-   */
-  Expression _target;
-
-  /**
-   * The operator that separates the target from the method name, or `null`
-   * if there is no target. In an ordinary method invocation this will be a
-   * period ('.'). In a cascade section this will be the cascade operator
-   * ('..').
-   */
-  Token operator;
-
-  /**
-   * The name of the method being invoked.
-   */
-  SimpleIdentifier _methodName;
-
-  /**
-   * The type arguments to be applied to the method being invoked, or `null` if
-   * no type arguments were provided.
-   */
-  TypeArgumentList _typeArguments;
-
-  /**
-   * The list of arguments to the method.
-   */
-  ArgumentList _argumentList;
-
-  /**
-   * The function type of the method invocation, or `null` if the AST
-   * structure has not been resolved, or if the invoke could not be resolved.
-   *
-   * This will usually be a [FunctionType], but it can also be an
-   * [InterfaceType] with a `call` method, `dynamic`, `Function`, or a `@proxy`
-   * interface type that implements `Function`.
-   */
-  DartType staticInvokeType;
-
-  /**
-   * Like [staticInvokeType], but reflects propagated type information.
-   */
-  DartType propagatedInvokeType;
-
-  /**
-   * Initialize a newly created method invocation. The [target] and [operator]
-   * can be `null` if there is no target.
-   */
-  MethodInvocationImpl(
-      Expression target,
-      this.operator,
-      SimpleIdentifier methodName,
-      TypeArgumentList typeArguments,
-      ArgumentList argumentList) {
-    _target = _becomeParentOf(target);
-    _methodName = _becomeParentOf(methodName);
-    _typeArguments = _becomeParentOf(typeArguments);
-    _argumentList = _becomeParentOf(argumentList);
-  }
-
-  @override
-  ArgumentList get argumentList => _argumentList;
-
-  @override
-  void set argumentList(ArgumentList argumentList) {
-    _argumentList = _becomeParentOf(argumentList);
-  }
-
-  @override
-  Token get beginToken {
-    if (_target != null) {
-      return _target.beginToken;
-    } else if (operator != null) {
-      return operator;
-    }
-    return _methodName.beginToken;
-  }
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(_target)
-    ..add(operator)
-    ..add(_methodName)
-    ..add(_argumentList);
-
-  @override
-  Token get endToken => _argumentList.endToken;
-
-  @override
-  bool get isCascaded =>
-      operator != null && operator.type == TokenType.PERIOD_PERIOD;
-
-  @override
-  SimpleIdentifier get methodName => _methodName;
-
-  @override
-  void set methodName(SimpleIdentifier identifier) {
-    _methodName = _becomeParentOf(identifier);
-  }
-
-  @override
-  int get precedence => 15;
-
-  @override
-  Expression get realTarget {
-    if (isCascaded) {
-      AstNode ancestor = parent;
-      while (ancestor is! CascadeExpression) {
-        if (ancestor == null) {
-          return _target;
-        }
-        ancestor = ancestor.parent;
-      }
-      return (ancestor as CascadeExpression).target;
-    }
-    return _target;
-  }
-
-  @override
-  Expression get target => _target;
-
-  @override
-  void set target(Expression expression) {
-    _target = _becomeParentOf(expression);
-  }
-
-  @override
-  TypeArgumentList get typeArguments => _typeArguments;
-
-  @override
-  void set typeArguments(TypeArgumentList typeArguments) {
-    _typeArguments = _becomeParentOf(typeArguments);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitMethodInvocation(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_target, visitor);
-    _safelyVisitChild(_methodName, visitor);
-    _safelyVisitChild(_typeArguments, visitor);
-    _safelyVisitChild(_argumentList, visitor);
-  }
-}
-
-/**
- * A node that declares a single name within the scope of a compilation unit.
- */
-abstract class NamedCompilationUnitMemberImpl extends CompilationUnitMemberImpl
-    implements NamedCompilationUnitMember {
-  /**
-   * The name of the member being declared.
-   */
-  SimpleIdentifier _name;
-
-  /**
-   * Initialize a newly created compilation unit member with the given [name].
-   * Either or both of the [comment] and [metadata] can be `null` if the member
-   * does not have the corresponding attribute.
-   */
-  NamedCompilationUnitMemberImpl(
-      Comment comment, List<Annotation> metadata, SimpleIdentifier name)
-      : super(comment, metadata) {
-    _name = _becomeParentOf(name);
-  }
-
-  @override
-  SimpleIdentifier get name => _name;
-
-  @override
-  void set name(SimpleIdentifier identifier) {
-    _name = _becomeParentOf(identifier);
-  }
-}
-
-/**
- * An expression that has a name associated with it. They are used in method
- * invocations when there are named parameters.
- *
- * > namedExpression ::=
- * >     [Label] [Expression]
- */
-class NamedExpressionImpl extends ExpressionImpl implements NamedExpression {
-  /**
-   * The name associated with the expression.
-   */
-  Label _name;
-
-  /**
-   * The expression with which the name is associated.
-   */
-  Expression _expression;
-
-  /**
-   * Initialize a newly created named expression..
-   */
-  NamedExpressionImpl(Label name, Expression expression) {
-    _name = _becomeParentOf(name);
-    _expression = _becomeParentOf(expression);
-  }
-
-  @override
-  Token get beginToken => _name.beginToken;
-
-  @override
-  Iterable get childEntities =>
-      new ChildEntities()..add(_name)..add(_expression);
-
-  @override
-  ParameterElement get element {
-    Element element = _name.label.staticElement;
-    if (element is ParameterElement) {
-      return element;
-    }
-    return null;
-  }
-
-  @override
-  Token get endToken => _expression.endToken;
-
-  @override
-  Expression get expression => _expression;
-
-  @override
-  void set expression(Expression expression) {
-    _expression = _becomeParentOf(expression);
-  }
-
-  @override
-  Label get name => _name;
-
-  @override
-  void set name(Label identifier) {
-    _name = _becomeParentOf(identifier);
-  }
-
-  @override
-  int get precedence => 0;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitNamedExpression(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_name, visitor);
-    _safelyVisitChild(_expression, visitor);
-  }
-}
-
-/**
- * A node that represents a directive that impacts the namespace of a library.
- *
- * > directive ::=
- * >     [ExportDirective]
- * >   | [ImportDirective]
- */
-abstract class NamespaceDirectiveImpl extends UriBasedDirectiveImpl
-    implements NamespaceDirective {
-  /**
-   * The token representing the 'import' or 'export' keyword.
-   */
-  Token keyword;
-
-  /**
-   * The configurations used to control which library will actually be loaded at
-   * run-time.
-   */
-  NodeList<Configuration> _configurations;
-
-  /**
-   * The combinators used to control which names are imported or exported.
-   */
-  NodeList<Combinator> _combinators;
-
-  /**
-   * The semicolon terminating the directive.
-   */
-  Token semicolon;
-
-  /**
-   * Initialize a newly created namespace directive. Either or both of the
-   * [comment] and [metadata] can be `null` if the directive does not have the
-   * corresponding attribute. The list of [combinators] can be `null` if there
-   * are no combinators.
-   */
-  NamespaceDirectiveImpl(
-      Comment comment,
-      List<Annotation> metadata,
-      this.keyword,
-      StringLiteral libraryUri,
-      List<Configuration> configurations,
-      List<Combinator> combinators,
-      this.semicolon)
-      : super(comment, metadata, libraryUri) {
-    _configurations = new NodeList<Configuration>(this, configurations);
-    _combinators = new NodeList<Combinator>(this, combinators);
-  }
-
-  @override
-  NodeList<Combinator> get combinators => _combinators;
-
-  @override
-  NodeList<Configuration> get configurations => _configurations;
-
-  @override
-  Token get endToken => semicolon;
-
-  @override
-  Token get firstTokenAfterCommentAndMetadata => keyword;
-
-  @override
-  LibraryElement get uriElement;
-}
-
-/**
- * The "native" clause in an class declaration.
- *
- * > nativeClause ::=
- * >     'native' [StringLiteral]
- */
-class NativeClauseImpl extends AstNodeImpl implements NativeClause {
-  /**
-   * The token representing the 'native' keyword.
-   */
-  Token nativeKeyword;
-
-  /**
-   * The name of the native object that implements the class.
-   */
-  StringLiteral _name;
-
-  /**
-   * Initialize a newly created native clause.
-   */
-  NativeClauseImpl(this.nativeKeyword, StringLiteral name) {
-    _name = _becomeParentOf(name);
-  }
-
-  @override
-  Token get beginToken => nativeKeyword;
-
-  @override
-  Iterable get childEntities =>
-      new ChildEntities()..add(nativeKeyword)..add(_name);
-
-  @override
-  Token get endToken => _name.endToken;
-
-  @override
-  StringLiteral get name => _name;
-
-  @override
-  void set name(StringLiteral name) {
-    _name = _becomeParentOf(name);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitNativeClause(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_name, visitor);
-  }
-}
-
-/**
- * A function body that consists of a native keyword followed by a string
- * literal.
- *
- * > nativeFunctionBody ::=
- * >     'native' [SimpleStringLiteral] ';'
- */
-class NativeFunctionBodyImpl extends FunctionBodyImpl
-    implements NativeFunctionBody {
-  /**
-   * The token representing 'native' that marks the start of the function body.
-   */
-  Token nativeKeyword;
-
-  /**
-   * The string literal, after the 'native' token.
-   */
-  StringLiteral _stringLiteral;
-
-  /**
-   * The token representing the semicolon that marks the end of the function
-   * body.
-   */
-  Token semicolon;
-
-  /**
-   * Initialize a newly created function body consisting of the 'native' token,
-   * a string literal, and a semicolon.
-   */
-  NativeFunctionBodyImpl(
-      this.nativeKeyword, StringLiteral stringLiteral, this.semicolon) {
-    _stringLiteral = _becomeParentOf(stringLiteral);
-  }
-
-  @override
-  Token get beginToken => nativeKeyword;
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(nativeKeyword)
-    ..add(_stringLiteral)
-    ..add(semicolon);
-
-  @override
-  Token get endToken => semicolon;
-
-  @override
-  StringLiteral get stringLiteral => _stringLiteral;
-
-  @override
-  void set stringLiteral(StringLiteral stringLiteral) {
-    _stringLiteral = _becomeParentOf(stringLiteral);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitNativeFunctionBody(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_stringLiteral, visitor);
-  }
-}
-
-/**
- * A list of AST nodes that have a common parent.
- */
-class NodeListImpl<E extends AstNode> extends Object
-    with ListMixin<E>
-    implements NodeList<E> {
-  /**
-   * The node that is the parent of each of the elements in the list.
-   */
-  AstNodeImpl owner;
-
-  /**
-   * The elements contained in the list.
-   */
-  List<E> _elements = <E>[];
-
-  /**
-   * Initialize a newly created list of nodes such that all of the nodes that
-   * are added to the list will have their parent set to the given [owner]. The
-   * list will initially be populated with the given [elements].
-   */
-  NodeListImpl(this.owner, [List<E> elements]) {
-    addAll(elements);
-  }
-
-  @override
-  Token get beginToken {
-    if (_elements.length == 0) {
-      return null;
-    }
-    return _elements[0].beginToken;
-  }
-
-  @override
-  Token get endToken {
-    int length = _elements.length;
-    if (length == 0) {
-      return null;
-    }
-    return _elements[length - 1].endToken;
-  }
-
-  int get length => _elements.length;
-
-  @deprecated // Never intended for public use.
-  @override
-  void set length(int newLength) {
-    throw new UnsupportedError("Cannot resize NodeList.");
-  }
-
-  E operator [](int index) {
-    if (index < 0 || index >= _elements.length) {
-      throw new RangeError("Index: $index, Size: ${_elements.length}");
-    }
-    return _elements[index];
-  }
-
-  void operator []=(int index, E node) {
-    if (index < 0 || index >= _elements.length) {
-      throw new RangeError("Index: $index, Size: ${_elements.length}");
-    }
-    owner._becomeParentOf(node);
-    _elements[index] = node;
-  }
-
-  @override
-  accept(AstVisitor visitor) {
-    int length = _elements.length;
-    for (var i = 0; i < length; i++) {
-      _elements[i].accept(visitor);
-    }
-  }
-
-  @override
-  void add(E node) {
-    insert(length, node);
-  }
-
-  @override
-  bool addAll(Iterable<E> nodes) {
-    if (nodes != null && !nodes.isEmpty) {
-      _elements.addAll(nodes);
-      for (E node in nodes) {
-        owner._becomeParentOf(node);
-      }
-      return true;
-    }
-    return false;
-  }
-
-  @override
-  void clear() {
-    _elements = <E>[];
-  }
-
-  @override
-  void insert(int index, E node) {
-    int length = _elements.length;
-    if (index < 0 || index > length) {
-      throw new RangeError("Index: $index, Size: ${_elements.length}");
-    }
-    owner._becomeParentOf(node);
-    if (length == 0) {
-      _elements.add(node);
-    } else {
-      _elements.insert(index, node);
-    }
-  }
-
-  @override
-  E removeAt(int index) {
-    if (index < 0 || index >= _elements.length) {
-      throw new RangeError("Index: $index, Size: ${_elements.length}");
-    }
-    E removedNode = _elements[index];
-    _elements.removeAt(index);
-    return removedNode;
-  }
-}
-
-/**
- * A formal parameter that is required (is not optional).
- *
- * > normalFormalParameter ::=
- * >     [FunctionTypedFormalParameter]
- * >   | [FieldFormalParameter]
- * >   | [SimpleFormalParameter]
- */
-abstract class NormalFormalParameterImpl extends FormalParameterImpl
-    implements NormalFormalParameter {
-  /**
-   * The documentation comment associated with this parameter, or `null` if this
-   * parameter does not have a documentation comment associated with it.
-   */
-  Comment _comment;
-
-  /**
-   * The annotations associated with this parameter.
-   */
-  NodeList<Annotation> _metadata;
-
-  /**
-   * The name of the parameter being declared.
-   */
-  SimpleIdentifier _identifier;
-
-  /**
-   * Initialize a newly created formal parameter. Either or both of the
-   * [comment] and [metadata] can be `null` if the parameter does not have the
-   * corresponding attribute.
-   */
-  NormalFormalParameterImpl(
-      Comment comment, List<Annotation> metadata, SimpleIdentifier identifier) {
-    _comment = _becomeParentOf(comment);
-    _metadata = new NodeList<Annotation>(this, metadata);
-    _identifier = _becomeParentOf(identifier);
-  }
-
-  @override
-  Comment get documentationComment => _comment;
-
-  @override
-  void set documentationComment(Comment comment) {
-    _comment = _becomeParentOf(comment);
-  }
-
-  @override
-  SimpleIdentifier get identifier => _identifier;
-
-  @override
-  void set identifier(SimpleIdentifier identifier) {
-    _identifier = _becomeParentOf(identifier);
-  }
-
-  @override
-  ParameterKind get kind {
-    AstNode parent = this.parent;
-    if (parent is DefaultFormalParameter) {
-      return parent.kind;
-    }
-    return ParameterKind.REQUIRED;
-  }
-
-  @override
-  NodeList<Annotation> get metadata => _metadata;
-
-  @override
-  void set metadata(List<Annotation> metadata) {
-    _metadata.clear();
-    _metadata.addAll(metadata);
-  }
-
-  @override
-  List<AstNode> get sortedCommentAndAnnotations {
-    return <AstNode>[]
-      ..add(_comment)
-      ..addAll(_metadata)
-      ..sort(AstNode.LEXICAL_ORDER);
-  }
-
-  ChildEntities get _childEntities {
-    ChildEntities result = new ChildEntities();
-    if (_commentIsBeforeAnnotations()) {
-      result
-        ..add(_comment)
-        ..addAll(_metadata);
-    } else {
-      result.addAll(sortedCommentAndAnnotations);
-    }
-    return result;
-  }
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    //
-    // Note that subclasses are responsible for visiting the identifier because
-    // they often need to visit other nodes before visiting the identifier.
-    //
-    if (_commentIsBeforeAnnotations()) {
-      _safelyVisitChild(_comment, visitor);
-      _metadata.accept(visitor);
-    } else {
-      for (AstNode child in sortedCommentAndAnnotations) {
-        child.accept(visitor);
-      }
-    }
-  }
-
-  /**
-   * Return `true` if the comment is lexically before any annotations.
-   */
-  bool _commentIsBeforeAnnotations() {
-    if (_comment == null || _metadata.isEmpty) {
-      return true;
-    }
-    Annotation firstAnnotation = _metadata[0];
-    return _comment.offset < firstAnnotation.offset;
-  }
-}
-
-/**
- * A null literal expression.
- *
- * > nullLiteral ::=
- * >     'null'
- */
-class NullLiteralImpl extends LiteralImpl implements NullLiteral {
-  /**
-   * The token representing the literal.
-   */
-  Token literal;
-
-  /**
-   * Initialize a newly created null literal.
-   */
-  NullLiteralImpl(this.literal);
-
-  @override
-  Token get beginToken => literal;
-
-  @override
-  Iterable get childEntities => new ChildEntities()..add(literal);
-
-  @override
-  Token get endToken => literal;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitNullLiteral(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    // There are no children to visit.
-  }
-}
-
-/**
- * A parenthesized expression.
- *
- * > parenthesizedExpression ::=
- * >     '(' [Expression] ')'
- */
-class ParenthesizedExpressionImpl extends ExpressionImpl
-    implements ParenthesizedExpression {
-  /**
-   * The left parenthesis.
-   */
-  Token leftParenthesis;
-
-  /**
-   * The expression within the parentheses.
-   */
-  Expression _expression;
-
-  /**
-   * The right parenthesis.
-   */
-  Token rightParenthesis;
-
-  /**
-   * Initialize a newly created parenthesized expression.
-   */
-  ParenthesizedExpressionImpl(
-      this.leftParenthesis, Expression expression, this.rightParenthesis) {
-    _expression = _becomeParentOf(expression);
-  }
-
-  @override
-  Token get beginToken => leftParenthesis;
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(leftParenthesis)
-    ..add(_expression)
-    ..add(rightParenthesis);
-
-  @override
-  Token get endToken => rightParenthesis;
-
-  @override
-  Expression get expression => _expression;
-
-  @override
-  void set expression(Expression expression) {
-    _expression = _becomeParentOf(expression);
-  }
-
-  @override
-  int get precedence => 15;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitParenthesizedExpression(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_expression, visitor);
-  }
-}
-
-/**
- * A part directive.
- *
- * > partDirective ::=
- * >     [Annotation] 'part' [StringLiteral] ';'
- */
-class PartDirectiveImpl extends UriBasedDirectiveImpl implements PartDirective {
-  /**
-   * The token representing the 'part' keyword.
-   */
-  Token partKeyword;
-
-  /**
-   * The semicolon terminating the directive.
-   */
-  Token semicolon;
-
-  /**
-   * Initialize a newly created part directive. Either or both of the [comment]
-   * and [metadata] can be `null` if the directive does not have the
-   * corresponding attribute.
-   */
-  PartDirectiveImpl(Comment comment, List<Annotation> metadata,
-      this.partKeyword, StringLiteral partUri, this.semicolon)
-      : super(comment, metadata, partUri);
-
-  @override
-  Iterable get childEntities =>
-      super._childEntities..add(partKeyword)..add(_uri)..add(semicolon);
-
-  @override
-  Token get endToken => semicolon;
-
-  @override
-  Token get firstTokenAfterCommentAndMetadata => partKeyword;
-
-  @override
-  Token get keyword => partKeyword;
-
-  @override
-  CompilationUnitElement get uriElement => element as CompilationUnitElement;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitPartDirective(this);
-}
-
-/**
- * A part-of directive.
- *
- * > partOfDirective ::=
- * >     [Annotation] 'part' 'of' [Identifier] ';'
- */
-class PartOfDirectiveImpl extends DirectiveImpl implements PartOfDirective {
-  /**
-   * The token representing the 'part' keyword.
-   */
-  Token partKeyword;
-
-  /**
-   * The token representing the 'of' keyword.
-   */
-  Token ofKeyword;
-
-  /**
-   * The name of the library that the containing compilation unit is part of.
-   */
-  LibraryIdentifier _libraryName;
-
-  /**
-   * The semicolon terminating the directive.
-   */
-  Token semicolon;
-
-  /**
-   * Initialize a newly created part-of directive. Either or both of the
-   * [comment] and [metadata] can be `null` if the directive does not have the
-   * corresponding attribute.
-   */
-  PartOfDirectiveImpl(
-      Comment comment,
-      List<Annotation> metadata,
-      this.partKeyword,
-      this.ofKeyword,
-      LibraryIdentifier libraryName,
-      this.semicolon)
-      : super(comment, metadata) {
-    _libraryName = _becomeParentOf(libraryName);
-  }
-
-  @override
-  Iterable get childEntities => super._childEntities
-    ..add(partKeyword)
-    ..add(ofKeyword)
-    ..add(_libraryName)
-    ..add(semicolon);
-
-  @override
-  Token get endToken => semicolon;
-
-  @override
-  Token get firstTokenAfterCommentAndMetadata => partKeyword;
-
-  @override
-  Token get keyword => partKeyword;
-
-  @override
-  LibraryIdentifier get libraryName => _libraryName;
-
-  @override
-  void set libraryName(LibraryIdentifier libraryName) {
-    _libraryName = _becomeParentOf(libraryName);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitPartOfDirective(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    super.visitChildren(visitor);
-    _safelyVisitChild(_libraryName, visitor);
-  }
-}
-
-/**
- * A postfix unary expression.
- *
- * > postfixExpression ::=
- * >     [Expression] [Token]
- */
-class PostfixExpressionImpl extends ExpressionImpl
-    implements PostfixExpression {
-  /**
-   * The expression computing the operand for the operator.
-   */
-  Expression _operand;
-
-  /**
-   * The postfix operator being applied to the operand.
-   */
-  Token operator;
-
-  /**
-   * The element associated with this the operator based on the propagated type
-   * of the operand, or `null` if the AST structure has not been resolved, if
-   * the operator is not user definable, or if the operator could not be
-   * resolved.
-   */
-  MethodElement propagatedElement;
-
-  /**
-   * The element associated with the operator based on the static type of the
-   * operand, or `null` if the AST structure has not been resolved, if the
-   * operator is not user definable, or if the operator could not be resolved.
-   */
-  MethodElement staticElement;
-
-  /**
-   * Initialize a newly created postfix expression.
-   */
-  PostfixExpressionImpl(Expression operand, this.operator) {
-    _operand = _becomeParentOf(operand);
-  }
-
-  @override
-  Token get beginToken => _operand.beginToken;
-
-  @override
-  MethodElement get bestElement {
-    MethodElement element = propagatedElement;
-    if (element == null) {
-      element = staticElement;
-    }
-    return element;
-  }
-
-  @override
-  Iterable get childEntities =>
-      new ChildEntities()..add(_operand)..add(operator);
-
-  @override
-  Token get endToken => operator;
-
-  @override
-  Expression get operand => _operand;
-
-  @override
-  void set operand(Expression expression) {
-    _operand = _becomeParentOf(expression);
-  }
-
-  @override
-  int get precedence => 15;
-
-  /**
-   * If the AST structure has been resolved, and the function being invoked is
-   * known based on propagated type information, then return the parameter
-   * element representing the parameter to which the value of the operand will
-   * be bound. Otherwise, return `null`.
-   */
-  ParameterElement get _propagatedParameterElementForOperand {
-    if (propagatedElement == null) {
-      return null;
-    }
-    List<ParameterElement> parameters = propagatedElement.parameters;
-    if (parameters.length < 1) {
-      return null;
-    }
-    return parameters[0];
-  }
-
-  /**
-   * If the AST structure has been resolved, and the function being invoked is
-   * known based on static type information, then return the parameter element
-   * representing the parameter to which the value of the operand will be bound.
-   * Otherwise, return `null`.
-   */
-  ParameterElement get _staticParameterElementForOperand {
-    if (staticElement == null) {
-      return null;
-    }
-    List<ParameterElement> parameters = staticElement.parameters;
-    if (parameters.length < 1) {
-      return null;
-    }
-    return parameters[0];
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitPostfixExpression(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_operand, visitor);
-  }
-}
-
-/**
- * An identifier that is prefixed or an access to an object property where the
- * target of the property access is a simple identifier.
- *
- * > prefixedIdentifier ::=
- * >     [SimpleIdentifier] '.' [SimpleIdentifier]
- */
-class PrefixedIdentifierImpl extends IdentifierImpl
-    implements PrefixedIdentifier {
-  /**
-   * The prefix associated with the library in which the identifier is defined.
-   */
-  SimpleIdentifier _prefix;
-
-  /**
-   * The period used to separate the prefix from the identifier.
-   */
-  Token period;
-
-  /**
-   * The identifier being prefixed.
-   */
-  SimpleIdentifier _identifier;
-
-  /**
-   * Initialize a newly created prefixed identifier.
-   */
-  PrefixedIdentifierImpl(
-      SimpleIdentifier prefix, this.period, SimpleIdentifier identifier) {
-    _prefix = _becomeParentOf(prefix);
-    _identifier = _becomeParentOf(identifier);
-  }
-
-  @override
-  Token get beginToken => _prefix.beginToken;
-
-  @override
-  Element get bestElement {
-    if (_identifier == null) {
-      return null;
-    }
-    return _identifier.bestElement;
-  }
-
-  @override
-  Iterable get childEntities =>
-      new ChildEntities()..add(_prefix)..add(period)..add(_identifier);
-
-  @override
-  Token get endToken => _identifier.endToken;
-
-  @override
-  SimpleIdentifier get identifier => _identifier;
-
-  @override
-  void set identifier(SimpleIdentifier identifier) {
-    _identifier = _becomeParentOf(identifier);
-  }
-
-  @override
-  bool get isDeferred {
-    Element element = _prefix.staticElement;
-    if (element is! PrefixElement) {
-      return false;
-    }
-    PrefixElement prefixElement = element as PrefixElement;
-    List<ImportElement> imports =
-        prefixElement.enclosingElement.getImportsWithPrefix(prefixElement);
-    if (imports.length != 1) {
-      return false;
-    }
-    return imports[0].isDeferred;
-  }
-
-  @override
-  String get name => "${_prefix.name}.${_identifier.name}";
-
-  @override
-  int get precedence => 15;
-
-  @override
-  SimpleIdentifier get prefix => _prefix;
-
-  @override
-  void set prefix(SimpleIdentifier identifier) {
-    _prefix = _becomeParentOf(identifier);
-  }
-
-  @override
-  Element get propagatedElement {
-    if (_identifier == null) {
-      return null;
-    }
-    return _identifier.propagatedElement;
-  }
-
-  @override
-  Element get staticElement {
-    if (_identifier == null) {
-      return null;
-    }
-    return _identifier.staticElement;
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitPrefixedIdentifier(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_prefix, visitor);
-    _safelyVisitChild(_identifier, visitor);
-  }
-}
-
-/**
- * A prefix unary expression.
- *
- * > prefixExpression ::=
- * >     [Token] [Expression]
- */
-class PrefixExpressionImpl extends ExpressionImpl implements PrefixExpression {
-  /**
-   * The prefix operator being applied to the operand.
-   */
-  Token operator;
-
-  /**
-   * The expression computing the operand for the operator.
-   */
-  Expression _operand;
-
-  /**
-   * The element associated with the operator based on the static type of the
-   * operand, or `null` if the AST structure has not been resolved, if the
-   * operator is not user definable, or if the operator could not be resolved.
-   */
-  MethodElement staticElement;
-
-  /**
-   * The element associated with the operator based on the propagated type of
-   * the operand, or `null` if the AST structure has not been resolved, if the
-   * operator is not user definable, or if the operator could not be resolved.
-   */
-  MethodElement propagatedElement;
-
-  /**
-   * Initialize a newly created prefix expression.
-   */
-  PrefixExpressionImpl(this.operator, Expression operand) {
-    _operand = _becomeParentOf(operand);
-  }
-
-  @override
-  Token get beginToken => operator;
-
-  @override
-  MethodElement get bestElement {
-    MethodElement element = propagatedElement;
-    if (element == null) {
-      element = staticElement;
-    }
-    return element;
-  }
-
-  @override
-  Iterable get childEntities =>
-      new ChildEntities()..add(operator)..add(_operand);
-
-  @override
-  Token get endToken => _operand.endToken;
-
-  @override
-  Expression get operand => _operand;
-
-  @override
-  void set operand(Expression expression) {
-    _operand = _becomeParentOf(expression);
-  }
-
-  @override
-  int get precedence => 14;
-
-  /**
-   * If the AST structure has been resolved, and the function being invoked is
-   * known based on propagated type information, then return the parameter
-   * element representing the parameter to which the value of the operand will
-   * be bound. Otherwise, return `null`.
-   */
-  ParameterElement get _propagatedParameterElementForOperand {
-    if (propagatedElement == null) {
-      return null;
-    }
-    List<ParameterElement> parameters = propagatedElement.parameters;
-    if (parameters.length < 1) {
-      return null;
-    }
-    return parameters[0];
-  }
-
-  /**
-   * If the AST structure has been resolved, and the function being invoked is
-   * known based on static type information, then return the parameter element
-   * representing the parameter to which the value of the operand will be bound.
-   * Otherwise, return `null`.
-   */
-  ParameterElement get _staticParameterElementForOperand {
-    if (staticElement == null) {
-      return null;
-    }
-    List<ParameterElement> parameters = staticElement.parameters;
-    if (parameters.length < 1) {
-      return null;
-    }
-    return parameters[0];
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitPrefixExpression(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_operand, visitor);
-  }
-}
-
-/**
- * The access of a property of an object.
- *
- * Note, however, that accesses to properties of objects can also be represented
- * as [PrefixedIdentifier] nodes in cases where the target is also a simple
- * identifier.
- *
- * > propertyAccess ::=
- * >     [Expression] '.' [SimpleIdentifier]
- */
-class PropertyAccessImpl extends ExpressionImpl implements PropertyAccess {
-  /**
-   * The expression computing the object defining the property being accessed.
-   */
-  Expression _target;
-
-  /**
-   * The property access operator.
-   */
-  Token operator;
-
-  /**
-   * The name of the property being accessed.
-   */
-  SimpleIdentifier _propertyName;
-
-  /**
-   * Initialize a newly created property access expression.
-   */
-  PropertyAccessImpl(
-      Expression target, this.operator, SimpleIdentifier propertyName) {
-    _target = _becomeParentOf(target);
-    _propertyName = _becomeParentOf(propertyName);
-  }
-
-  @override
-  Token get beginToken {
-    if (_target != null) {
-      return _target.beginToken;
-    }
-    return operator;
-  }
-
-  @override
-  Iterable get childEntities =>
-      new ChildEntities()..add(_target)..add(operator)..add(_propertyName);
-
-  @override
-  Token get endToken => _propertyName.endToken;
-
-  @override
-  bool get isAssignable => true;
-
-  @override
-  bool get isCascaded =>
-      operator != null && operator.type == TokenType.PERIOD_PERIOD;
-
-  @override
-  int get precedence => 15;
-
-  @override
-  SimpleIdentifier get propertyName => _propertyName;
-
-  @override
-  void set propertyName(SimpleIdentifier identifier) {
-    _propertyName = _becomeParentOf(identifier);
-  }
-
-  @override
-  Expression get realTarget {
-    if (isCascaded) {
-      AstNode ancestor = parent;
-      while (ancestor is! CascadeExpression) {
-        if (ancestor == null) {
-          return _target;
-        }
-        ancestor = ancestor.parent;
-      }
-      return (ancestor as CascadeExpression).target;
-    }
-    return _target;
-  }
-
-  @override
-  Expression get target => _target;
-
-  @override
-  void set target(Expression expression) {
-    _target = _becomeParentOf(expression);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitPropertyAccess(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_target, visitor);
-    _safelyVisitChild(_propertyName, visitor);
-  }
-}
-
-/**
- * The invocation of a constructor in the same class from within a constructor's
- * initialization list.
- *
- * > redirectingConstructorInvocation ::=
- * >     'this' ('.' identifier)? arguments
- */
-class RedirectingConstructorInvocationImpl extends ConstructorInitializerImpl
-    implements RedirectingConstructorInvocation {
-  /**
-   * The token for the 'this' keyword.
-   */
-  Token thisKeyword;
-
-  /**
-   * The token for the period before the name of the constructor that is being
-   * invoked, or `null` if the unnamed constructor is being invoked.
-   */
-  Token period;
-
-  /**
-   * The name of the constructor that is being invoked, or `null` if the unnamed
-   * constructor is being invoked.
-   */
-  SimpleIdentifier _constructorName;
-
-  /**
-   * The list of arguments to the constructor.
-   */
-  ArgumentList _argumentList;
-
-  /**
-   * The element associated with the constructor based on static type
-   * information, or `null` if the AST structure has not been resolved or if the
-   * constructor could not be resolved.
-   */
-  ConstructorElement staticElement;
-
-  /**
-   * Initialize a newly created redirecting invocation to invoke the constructor
-   * with the given name with the given arguments. The [constructorName] can be
-   * `null` if the constructor being invoked is the unnamed constructor.
-   */
-  RedirectingConstructorInvocationImpl(this.thisKeyword, this.period,
-      SimpleIdentifier constructorName, ArgumentList argumentList) {
-    _constructorName = _becomeParentOf(constructorName);
-    _argumentList = _becomeParentOf(argumentList);
-  }
-
-  @override
-  ArgumentList get argumentList => _argumentList;
-
-  @override
-  void set argumentList(ArgumentList argumentList) {
-    _argumentList = _becomeParentOf(argumentList);
-  }
-
-  @override
-  Token get beginToken => thisKeyword;
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(thisKeyword)
-    ..add(period)
-    ..add(_constructorName)
-    ..add(_argumentList);
-
-  @override
-  SimpleIdentifier get constructorName => _constructorName;
-
-  @override
-  void set constructorName(SimpleIdentifier identifier) {
-    _constructorName = _becomeParentOf(identifier);
-  }
-
-  @override
-  Token get endToken => _argumentList.endToken;
-
-  @override
-  accept(AstVisitor visitor) =>
-      visitor.visitRedirectingConstructorInvocation(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_constructorName, visitor);
-    _safelyVisitChild(_argumentList, visitor);
-  }
-}
-
-/**
- * A rethrow expression.
- *
- * > rethrowExpression ::=
- * >     'rethrow'
- */
-class RethrowExpressionImpl extends ExpressionImpl
-    implements RethrowExpression {
-  /**
-   * The token representing the 'rethrow' keyword.
-   */
-  Token rethrowKeyword;
-
-  /**
-   * Initialize a newly created rethrow expression.
-   */
-  RethrowExpressionImpl(this.rethrowKeyword);
-
-  @override
-  Token get beginToken => rethrowKeyword;
-
-  @override
-  Iterable get childEntities => new ChildEntities()..add(rethrowKeyword);
-
-  @override
-  Token get endToken => rethrowKeyword;
-
-  @override
-  int get precedence => 0;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitRethrowExpression(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    // There are no children to visit.
-  }
-}
-
-/**
- * A return statement.
- *
- * > returnStatement ::=
- * >     'return' [Expression]? ';'
- */
-class ReturnStatementImpl extends StatementImpl implements ReturnStatement {
-  /**
-   * The token representing the 'return' keyword.
-   */
-  Token returnKeyword;
-
-  /**
-   * The expression computing the value to be returned, or `null` if no explicit
-   * value was provided.
-   */
-  Expression _expression;
-
-  /**
-   * The semicolon terminating the statement.
-   */
-  Token semicolon;
-
-  /**
-   * Initialize a newly created return statement. The [expression] can be `null`
-   * if no explicit value was provided.
-   */
-  ReturnStatementImpl(
-      this.returnKeyword, Expression expression, this.semicolon) {
-    _expression = _becomeParentOf(expression);
-  }
-
-  @override
-  Token get beginToken => returnKeyword;
-
-  @override
-  Iterable get childEntities =>
-      new ChildEntities()..add(returnKeyword)..add(_expression)..add(semicolon);
-
-  @override
-  Token get endToken => semicolon;
-
-  @override
-  Expression get expression => _expression;
-
-  @override
-  void set expression(Expression expression) {
-    _expression = _becomeParentOf(expression);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitReturnStatement(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_expression, visitor);
-  }
-}
-
-/**
- * A script tag that can optionally occur at the beginning of a compilation unit.
- *
- * > scriptTag ::=
- * >     '#!' (~NEWLINE)* NEWLINE
- */
-class ScriptTagImpl extends AstNodeImpl implements ScriptTag {
-  /**
-   * The token representing this script tag.
-   */
-  Token scriptTag;
-
-  /**
-   * Initialize a newly created script tag.
-   */
-  ScriptTagImpl(this.scriptTag);
-
-  @override
-  Token get beginToken => scriptTag;
-
-  @override
-  Iterable get childEntities => new ChildEntities()..add(scriptTag);
-
-  @override
-  Token get endToken => scriptTag;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitScriptTag(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    // There are no children to visit.
-  }
-}
-
-/**
- * A combinator that restricts the names being imported to those in a given list.
- *
- * > showCombinator ::=
- * >     'show' [SimpleIdentifier] (',' [SimpleIdentifier])*
- */
-class ShowCombinatorImpl extends CombinatorImpl implements ShowCombinator {
-  /**
-   * The list of names from the library that are made visible by this combinator.
-   */
-  NodeList<SimpleIdentifier> _shownNames;
-
-  /**
-   * Initialize a newly created import show combinator.
-   */
-  ShowCombinatorImpl(Token keyword, List<SimpleIdentifier> shownNames)
-      : super(keyword) {
-    _shownNames = new NodeList<SimpleIdentifier>(this, shownNames);
-  }
-
-  @override
-  // TODO(paulberry): add commas.
-  Iterable get childEntities => new ChildEntities()
-    ..add(keyword)
-    ..addAll(_shownNames);
-
-  @override
-  Token get endToken => _shownNames.endToken;
-
-  @override
-  NodeList<SimpleIdentifier> get shownNames => _shownNames;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitShowCombinator(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _shownNames.accept(visitor);
-  }
-}
-
-/**
- * A simple formal parameter.
- *
- * > simpleFormalParameter ::=
- * >     ('final' [TypeName] | 'var' | [TypeName])? [SimpleIdentifier]
- */
-class SimpleFormalParameterImpl extends NormalFormalParameterImpl
-    implements SimpleFormalParameter {
-  /**
-   * The token representing either the 'final', 'const' or 'var' keyword, or
-   * `null` if no keyword was used.
-   */
-  Token keyword;
-
-  /**
-   * The name of the declared type of the parameter, or `null` if the parameter
-   * does not have a declared type.
-   */
-  TypeName _type;
-
-  /**
-   * Initialize a newly created formal parameter. Either or both of the
-   * [comment] and [metadata] can be `null` if the parameter does not have the
-   * corresponding attribute. The [keyword] can be `null` if a type was
-   * specified. The [type] must be `null` if the keyword is 'var'.
-   */
-  SimpleFormalParameterImpl(Comment comment, List<Annotation> metadata,
-      this.keyword, TypeName type, SimpleIdentifier identifier)
-      : super(comment, metadata, identifier) {
-    _type = _becomeParentOf(type);
-  }
-
-  @override
-  Token get beginToken {
-    NodeList<Annotation> metadata = this.metadata;
-    if (!metadata.isEmpty) {
-      return metadata.beginToken;
-    } else if (keyword != null) {
-      return keyword;
-    } else if (_type != null) {
-      return _type.beginToken;
-    }
-    return identifier.beginToken;
-  }
-
-  @override
-  Iterable get childEntities =>
-      super._childEntities..add(keyword)..add(_type)..add(identifier);
-
-  @override
-  Token get endToken => identifier.endToken;
-
-  @override
-  bool get isConst =>
-      (keyword is KeywordToken) &&
-      (keyword as KeywordToken).keyword == Keyword.CONST;
-
-  @override
-  bool get isFinal =>
-      (keyword is KeywordToken) &&
-      (keyword as KeywordToken).keyword == Keyword.FINAL;
-
-  @override
-  TypeName get type => _type;
-
-  @override
-  void set type(TypeName typeName) {
-    _type = _becomeParentOf(typeName);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitSimpleFormalParameter(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    super.visitChildren(visitor);
-    _safelyVisitChild(_type, visitor);
-    _safelyVisitChild(identifier, visitor);
-  }
-}
-
-/**
- * A simple identifier.
- *
- * > simpleIdentifier ::=
- * >     initialCharacter internalCharacter*
- * >
- * > initialCharacter ::= '_' | '$' | letter
- * >
- * > internalCharacter ::= '_' | '$' | letter | digit
- */
-class SimpleIdentifierImpl extends IdentifierImpl implements SimpleIdentifier {
-  /**
-   * The token representing the identifier.
-   */
-  Token token;
-
-  /**
-   * The element associated with this identifier based on static type
-   * information, or `null` if the AST structure has not been resolved or if
-   * this identifier could not be resolved.
-   */
-  Element _staticElement;
-
-  /**
-   * The element associated with this identifier based on propagated type
-   * information, or `null` if the AST structure has not been resolved or if
-   * this identifier could not be resolved.
-   */
-  Element _propagatedElement;
-
-  /**
-   * If this expression is both in a getter and setter context, the
-   * [AuxiliaryElements] will be set to hold onto the static and propagated
-   * information. The auxiliary element will hold onto the elements from the
-   * getter context.
-   */
-  AuxiliaryElements auxiliaryElements = null;
-
-  /**
-   * Initialize a newly created identifier.
-   */
-  SimpleIdentifierImpl(this.token);
-
-  @override
-  Token get beginToken => token;
-
-  @override
-  Element get bestElement {
-    if (_propagatedElement == null) {
-      return _staticElement;
-    }
-    return _propagatedElement;
-  }
-
-  @override
-  Iterable get childEntities => new ChildEntities()..add(token);
-
-  @override
-  Token get endToken => token;
-
-  @override
-  bool get isQualified {
-    AstNode parent = this.parent;
-    if (parent is PrefixedIdentifier) {
-      return identical(parent.identifier, this);
-    }
-    if (parent is PropertyAccess) {
-      return identical(parent.propertyName, this);
-    }
-    if (parent is MethodInvocation) {
-      MethodInvocation invocation = parent;
-      return identical(invocation.methodName, this) &&
-          invocation.realTarget != null;
-    }
-    return false;
-  }
-
-  @override
-  bool get isSynthetic => token.isSynthetic;
-
-  @override
-  String get name => token.lexeme;
-
-  @override
-  int get precedence => 16;
-
-  @override
-  Element get propagatedElement => _propagatedElement;
-
-  @override
-  void set propagatedElement(Element element) {
-    _propagatedElement = _validateElement(element);
-  }
-
-  @override
-  Element get staticElement => _staticElement;
-
-  @override
-  void set staticElement(Element element) {
-    _staticElement = _validateElement(element);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitSimpleIdentifier(this);
-
-  @override
-  bool inDeclarationContext() {
-    // TODO(brianwilkerson) Convert this to a getter.
-    AstNode parent = this.parent;
-    if (parent is CatchClause) {
-      CatchClause clause = parent;
-      return identical(this, clause.exceptionParameter) ||
-          identical(this, clause.stackTraceParameter);
-    } else if (parent is ClassDeclaration) {
-      return identical(this, parent.name);
-    } else if (parent is ClassTypeAlias) {
-      return identical(this, parent.name);
-    } else if (parent is ConstructorDeclaration) {
-      return identical(this, parent.name);
-    } else if (parent is DeclaredIdentifier) {
-      return identical(this, parent.identifier);
-    } else if (parent is EnumDeclaration) {
-      return identical(this, parent.name);
-    } else if (parent is EnumConstantDeclaration) {
-      return identical(this, parent.name);
-    } else if (parent is FunctionDeclaration) {
-      return identical(this, parent.name);
-    } else if (parent is FunctionTypeAlias) {
-      return identical(this, parent.name);
-    } else if (parent is ImportDirective) {
-      return identical(this, parent.prefix);
-    } else if (parent is Label) {
-      return identical(this, parent.label) &&
-          (parent.parent is LabeledStatement);
-    } else if (parent is MethodDeclaration) {
-      return identical(this, parent.name);
-    } else if (parent is FunctionTypedFormalParameter ||
-        parent is SimpleFormalParameter) {
-      return identical(this, (parent as NormalFormalParameter).identifier);
-    } else if (parent is TypeParameter) {
-      return identical(this, parent.name);
-    } else if (parent is VariableDeclaration) {
-      return identical(this, parent.name);
-    }
-    return false;
-  }
-
-  @override
-  bool inGetterContext() {
-    // TODO(brianwilkerson) Convert this to a getter.
-    AstNode parent = this.parent;
-    AstNode target = this;
-    // skip prefix
-    if (parent is PrefixedIdentifier) {
-      PrefixedIdentifier prefixed = parent as PrefixedIdentifier;
-      if (identical(prefixed.prefix, this)) {
-        return true;
-      }
-      parent = prefixed.parent;
-      target = prefixed;
-    } else if (parent is PropertyAccess) {
-      PropertyAccess access = parent as PropertyAccess;
-      if (identical(access.target, this)) {
-        return true;
-      }
-      parent = access.parent;
-      target = access;
-    }
-    // skip label
-    if (parent is Label) {
-      return false;
-    }
-    // analyze usage
-    if (parent is AssignmentExpression) {
-      if (identical(parent.leftHandSide, target) &&
-          parent.operator.type == TokenType.EQ) {
-        return false;
-      }
-    }
-    if (parent is ForEachStatement) {
-      if (identical(parent.identifier, target)) {
-        return false;
-      }
-    }
-    return true;
-  }
-
-  @override
-  bool inSetterContext() {
-    // TODO(brianwilkerson) Convert this to a getter.
-    AstNode parent = this.parent;
-    AstNode target = this;
-    // skip prefix
-    if (parent is PrefixedIdentifier) {
-      PrefixedIdentifier prefixed = parent as PrefixedIdentifier;
-      // if this is the prefix, then return false
-      if (identical(prefixed.prefix, this)) {
-        return false;
-      }
-      parent = prefixed.parent;
-      target = prefixed;
-    } else if (parent is PropertyAccess) {
-      PropertyAccess access = parent as PropertyAccess;
-      if (identical(access.target, this)) {
-        return false;
-      }
-      parent = access.parent;
-      target = access;
-    }
-    // analyze usage
-    if (parent is PrefixExpression) {
-      return parent.operator.type.isIncrementOperator;
-    } else if (parent is PostfixExpression) {
-      return true;
-    } else if (parent is AssignmentExpression) {
-      return identical(parent.leftHandSide, target);
-    } else if (parent is ForEachStatement) {
-      return identical(parent.identifier, target);
-    }
-    return false;
-  }
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    // There are no children to visit.
-  }
-
-  /**
-   * Return the given element if it is valid, or report the problem and return
-   * `null` if it is not appropriate.
-   *
-   * The [parent] is the parent of the element, used for reporting when there is
-   * a problem.
-   * The [isValid] is `true` if the element is appropriate.
-   * The [element] is the element to be associated with this identifier.
-   */
-  Element _returnOrReportElement(
-      AstNode parent, bool isValid, Element element) {
-    if (!isValid) {
-      AnalysisEngine.instance.logger.logInformation(
-          "Internal error: attempting to set the name of a ${parent.runtimeType} to a ${element.runtimeType}",
-          new CaughtException(new AnalysisException(), null));
-      return null;
-    }
-    return element;
-  }
-
-  /**
-   * Return the given [element] if it is an appropriate element based on the
-   * parent of this identifier, or `null` if it is not appropriate.
-   */
-  Element _validateElement(Element element) {
-    if (element == null) {
-      return null;
-    }
-    AstNode parent = this.parent;
-    if (parent is ClassDeclaration && identical(parent.name, this)) {
-      return _returnOrReportElement(parent, element is ClassElement, element);
-    } else if (parent is ClassTypeAlias && identical(parent.name, this)) {
-      return _returnOrReportElement(parent, element is ClassElement, element);
-    } else if (parent is DeclaredIdentifier &&
-        identical(parent.identifier, this)) {
-      return _returnOrReportElement(
-          parent, element is LocalVariableElement, element);
-    } else if (parent is FormalParameter &&
-        identical(parent.identifier, this)) {
-      return _returnOrReportElement(
-          parent, element is ParameterElement, element);
-    } else if (parent is FunctionDeclaration && identical(parent.name, this)) {
-      return _returnOrReportElement(
-          parent, element is ExecutableElement, element);
-    } else if (parent is FunctionTypeAlias && identical(parent.name, this)) {
-      return _returnOrReportElement(
-          parent, element is FunctionTypeAliasElement, element);
-    } else if (parent is MethodDeclaration && identical(parent.name, this)) {
-      return _returnOrReportElement(
-          parent, element is ExecutableElement, element);
-    } else if (parent is TypeParameter && identical(parent.name, this)) {
-      return _returnOrReportElement(
-          parent, element is TypeParameterElement, element);
-    } else if (parent is VariableDeclaration && identical(parent.name, this)) {
-      return _returnOrReportElement(
-          parent, element is VariableElement, element);
-    }
-    return element;
-  }
-}
-
-/**
- * A string literal expression that does not contain any interpolations.
- *
- * > simpleStringLiteral ::=
- * >     rawStringLiteral
- * >   | basicStringLiteral
- * >
- * > rawStringLiteral ::=
- * >     'r' basicStringLiteral
- * >
- * > simpleStringLiteral ::=
- * >     multiLineStringLiteral
- * >   | singleLineStringLiteral
- * >
- * > multiLineStringLiteral ::=
- * >     "'''" characters "'''"
- * >   | '"""' characters '"""'
- * >
- * > singleLineStringLiteral ::=
- * >     "'" characters "'"
- * >   | '"' characters '"'
- */
-class SimpleStringLiteralImpl extends SingleStringLiteralImpl
-    implements SimpleStringLiteral {
-  /**
-   * The token representing the literal.
-   */
-  Token literal;
-
-  /**
-   * The value of the literal.
-   */
-  String _value;
-
-  /**
-   * Initialize a newly created simple string literal.
-   */
-  SimpleStringLiteralImpl(this.literal, String value) {
-    _value = StringUtilities.intern(value);
-  }
-
-  @override
-  Token get beginToken => literal;
-
-  @override
-  Iterable get childEntities => new ChildEntities()..add(literal);
-
-  @override
-  int get contentsEnd => offset + _helper.end;
-
-  @override
-  int get contentsOffset => offset + _helper.start;
-
-  @override
-  Token get endToken => literal;
-
-  @override
-  bool get isMultiline => _helper.isMultiline;
-
-  @override
-  bool get isRaw => _helper.isRaw;
-
-  @override
-  bool get isSingleQuoted => _helper.isSingleQuoted;
-
-  @override
-  bool get isSynthetic => literal.isSynthetic;
-
-  @override
-  String get value => _value;
-
-  @override
-  void set value(String string) {
-    _value = StringUtilities.intern(_value);
-  }
-
-  StringLexemeHelper get _helper {
-    return new StringLexemeHelper(literal.lexeme, true, true);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitSimpleStringLiteral(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    // There are no children to visit.
-  }
-
-  @override
-  void _appendStringValue(StringBuffer buffer) {
-    buffer.write(value);
-  }
-}
-
-/**
- * A single string literal expression.
- *
- * > singleStringLiteral ::=
- * >     [SimpleStringLiteral]
- * >   | [StringInterpolation]
- */
-abstract class SingleStringLiteralImpl extends StringLiteralImpl
-    implements SingleStringLiteral {}
-
-/**
- * A node that represents a statement.
- *
- * > statement ::=
- * >     [Block]
- * >   | [VariableDeclarationStatement]
- * >   | [ForStatement]
- * >   | [ForEachStatement]
- * >   | [WhileStatement]
- * >   | [DoStatement]
- * >   | [SwitchStatement]
- * >   | [IfStatement]
- * >   | [TryStatement]
- * >   | [BreakStatement]
- * >   | [ContinueStatement]
- * >   | [ReturnStatement]
- * >   | [ExpressionStatement]
- * >   | [FunctionDeclarationStatement]
- */
-abstract class StatementImpl extends AstNodeImpl implements Statement {
-  @override
-  Statement get unlabeled => this;
-}
-
-/**
- * A string interpolation literal.
- *
- * > stringInterpolation ::=
- * >     ''' [InterpolationElement]* '''
- * >   | '"' [InterpolationElement]* '"'
- */
-class StringInterpolationImpl extends SingleStringLiteralImpl
-    implements StringInterpolation {
-  /**
-   * The elements that will be composed to produce the resulting string.
-   */
-  NodeList<InterpolationElement> _elements;
-
-  /**
-   * Initialize a newly created string interpolation expression.
-   */
-  StringInterpolationImpl(List<InterpolationElement> elements) {
-    _elements = new NodeList<InterpolationElement>(this, elements);
-  }
-
-  @override
-  Token get beginToken => _elements.beginToken;
-
-  @override
-  Iterable get childEntities => new ChildEntities()..addAll(_elements);
-
-  @override
-  int get contentsEnd {
-    InterpolationString element = _elements.last;
-    return element.contentsEnd;
-  }
-
-  @override
-  int get contentsOffset {
-    InterpolationString element = _elements.first;
-    return element.contentsOffset;
-  }
-
-  /**
-   * Return the elements that will be composed to produce the resulting string.
-   */
-  NodeList<InterpolationElement> get elements => _elements;
-
-  @override
-  Token get endToken => _elements.endToken;
-
-  @override
-  bool get isMultiline => _firstHelper.isMultiline;
-
-  @override
-  bool get isRaw => false;
-
-  @override
-  bool get isSingleQuoted => _firstHelper.isSingleQuoted;
-
-  StringLexemeHelper get _firstHelper {
-    InterpolationString lastString = _elements.first;
-    String lexeme = lastString.contents.lexeme;
-    return new StringLexemeHelper(lexeme, true, false);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitStringInterpolation(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _elements.accept(visitor);
-  }
-
-  @override
-  void _appendStringValue(StringBuffer buffer) {
-    throw new IllegalArgumentException();
-  }
-}
-
-/**
- * A helper for analyzing string lexemes.
- */
-class StringLexemeHelper {
-  final String lexeme;
-  final bool isFirst;
-  final bool isLast;
-
-  bool isRaw = false;
-  bool isSingleQuoted = false;
-  bool isMultiline = false;
-  int start = 0;
-  int end;
-
-  StringLexemeHelper(this.lexeme, this.isFirst, this.isLast) {
-    if (isFirst) {
-      isRaw = StringUtilities.startsWithChar(lexeme, 0x72);
-      if (isRaw) {
-        start++;
-      }
-      if (StringUtilities.startsWith3(lexeme, start, 0x27, 0x27, 0x27)) {
-        isSingleQuoted = true;
-        isMultiline = true;
-        start += 3;
-        start = _trimInitialWhitespace(start);
-      } else if (StringUtilities.startsWith3(lexeme, start, 0x22, 0x22, 0x22)) {
-        isSingleQuoted = false;
-        isMultiline = true;
-        start += 3;
-        start = _trimInitialWhitespace(start);
-      } else if (start < lexeme.length && lexeme.codeUnitAt(start) == 0x27) {
-        isSingleQuoted = true;
-        isMultiline = false;
-        start++;
-      } else if (start < lexeme.length && lexeme.codeUnitAt(start) == 0x22) {
-        isSingleQuoted = false;
-        isMultiline = false;
-        start++;
-      }
-    }
-    end = lexeme.length;
-    if (isLast) {
-      if (start + 3 <= end &&
-          (StringUtilities.endsWith3(lexeme, 0x22, 0x22, 0x22) ||
-              StringUtilities.endsWith3(lexeme, 0x27, 0x27, 0x27))) {
-        end -= 3;
-      } else if (start + 1 <= end &&
-          (StringUtilities.endsWithChar(lexeme, 0x22) ||
-              StringUtilities.endsWithChar(lexeme, 0x27))) {
-        end -= 1;
-      }
-    }
-  }
-
-  /**
-   * Given the [lexeme] for a multi-line string whose content begins at the
-   * given [start] index, return the index of the first character that is
-   * included in the value of the string. According to the specification:
-   *
-   * If the first line of a multiline string consists solely of the whitespace
-   * characters defined by the production WHITESPACE 20.1), possibly prefixed
-   * by \, then that line is ignored, including the new line at its end.
-   */
-  int _trimInitialWhitespace(int start) {
-    int length = lexeme.length;
-    int index = start;
-    while (index < length) {
-      int currentChar = lexeme.codeUnitAt(index);
-      if (currentChar == 0x0D) {
-        if (index + 1 < length && lexeme.codeUnitAt(index + 1) == 0x0A) {
-          return index + 2;
-        }
-        return index + 1;
-      } else if (currentChar == 0x0A) {
-        return index + 1;
-      } else if (currentChar == 0x5C) {
-        if (index + 1 >= length) {
-          return start;
-        }
-        currentChar = lexeme.codeUnitAt(index + 1);
-        if (currentChar != 0x0D &&
-            currentChar != 0x0A &&
-            currentChar != 0x09 &&
-            currentChar != 0x20) {
-          return start;
-        }
-      } else if (currentChar != 0x09 && currentChar != 0x20) {
-        return start;
-      }
-      index++;
-    }
-    return start;
-  }
-}
-
-/**
- * A string literal expression.
- *
- * > stringLiteral ::=
- * >     [SimpleStringLiteral]
- * >   | [AdjacentStrings]
- * >   | [StringInterpolation]
- */
-abstract class StringLiteralImpl extends LiteralImpl implements StringLiteral {
-  @override
-  String get stringValue {
-    StringBuffer buffer = new StringBuffer();
-    try {
-      _appendStringValue(buffer);
-    } on IllegalArgumentException {
-      return null;
-    }
-    return buffer.toString();
-  }
-
-  /**
-   * Append the value of this string literal to the given [buffer]. Throw an
-   * [IllegalArgumentException] if the string is not a constant string without
-   * any string interpolation.
-   */
-  void _appendStringValue(StringBuffer buffer);
-}
-
-/**
- * The invocation of a superclass' constructor from within a constructor's
- * initialization list.
- *
- * > superInvocation ::=
- * >     'super' ('.' [SimpleIdentifier])? [ArgumentList]
- */
-class SuperConstructorInvocationImpl extends ConstructorInitializerImpl
-    implements SuperConstructorInvocation {
-  /**
-   * The token for the 'super' keyword.
-   */
-  Token superKeyword;
-
-  /**
-   * The token for the period before the name of the constructor that is being
-   * invoked, or `null` if the unnamed constructor is being invoked.
-   */
-  Token period;
-
-  /**
-   * The name of the constructor that is being invoked, or `null` if the unnamed
-   * constructor is being invoked.
-   */
-  SimpleIdentifier _constructorName;
-
-  /**
-   * The list of arguments to the constructor.
-   */
-  ArgumentList _argumentList;
-
-  /**
-   * The element associated with the constructor based on static type
-   * information, or `null` if the AST structure has not been resolved or if the
-   * constructor could not be resolved.
-   */
-  ConstructorElement staticElement;
-
-  /**
-   * Initialize a newly created super invocation to invoke the inherited
-   * constructor with the given name with the given arguments. The [period] and
-   * [constructorName] can be `null` if the constructor being invoked is the
-   * unnamed constructor.
-   */
-  SuperConstructorInvocationImpl(this.superKeyword, this.period,
-      SimpleIdentifier constructorName, ArgumentList argumentList) {
-    _constructorName = _becomeParentOf(constructorName);
-    _argumentList = _becomeParentOf(argumentList);
-  }
-
-  @override
-  ArgumentList get argumentList => _argumentList;
-
-  @override
-  void set argumentList(ArgumentList argumentList) {
-    _argumentList = _becomeParentOf(argumentList);
-  }
-
-  @override
-  Token get beginToken => superKeyword;
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(superKeyword)
-    ..add(period)
-    ..add(_constructorName)
-    ..add(_argumentList);
-
-  @override
-  SimpleIdentifier get constructorName => _constructorName;
-
-  @override
-  void set constructorName(SimpleIdentifier identifier) {
-    _constructorName = _becomeParentOf(identifier);
-  }
-
-  @override
-  Token get endToken => _argumentList.endToken;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitSuperConstructorInvocation(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_constructorName, visitor);
-    _safelyVisitChild(_argumentList, visitor);
-  }
-}
-
-/**
- * A super expression.
- *
- * > superExpression ::=
- * >     'super'
- */
-class SuperExpressionImpl extends ExpressionImpl implements SuperExpression {
-  /**
-   * The token representing the 'super' keyword.
-   */
-  Token superKeyword;
-
-  /**
-   * Initialize a newly created super expression.
-   */
-  SuperExpressionImpl(this.superKeyword);
-
-  @override
-  Token get beginToken => superKeyword;
-
-  @override
-  Iterable get childEntities => new ChildEntities()..add(superKeyword);
-
-  @override
-  Token get endToken => superKeyword;
-
-  @override
-  int get precedence => 16;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitSuperExpression(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    // There are no children to visit.
-  }
-}
-
-/**
- * A case in a switch statement.
- *
- * > switchCase ::=
- * >     [SimpleIdentifier]* 'case' [Expression] ':' [Statement]*
- */
-class SwitchCaseImpl extends SwitchMemberImpl implements SwitchCase {
-  /**
-   * The expression controlling whether the statements will be executed.
-   */
-  Expression _expression;
-
-  /**
-   * Initialize a newly created switch case. The list of [labels] can be `null`
-   * if there are no labels.
-   */
-  SwitchCaseImpl(List<Label> labels, Token keyword, Expression expression,
-      Token colon, List<Statement> statements)
-      : super(labels, keyword, colon, statements) {
-    _expression = _becomeParentOf(expression);
-  }
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..addAll(labels)
-    ..add(keyword)
-    ..add(_expression)
-    ..add(colon)
-    ..addAll(statements);
-
-  @override
-  Expression get expression => _expression;
-
-  @override
-  void set expression(Expression expression) {
-    _expression = _becomeParentOf(expression);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitSwitchCase(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    labels.accept(visitor);
-    _safelyVisitChild(_expression, visitor);
-    statements.accept(visitor);
-  }
-}
-
-/**
- * The default case in a switch statement.
- *
- * > switchDefault ::=
- * >     [SimpleIdentifier]* 'default' ':' [Statement]*
- */
-class SwitchDefaultImpl extends SwitchMemberImpl implements SwitchDefault {
-  /**
-   * Initialize a newly created switch default. The list of [labels] can be
-   * `null` if there are no labels.
-   */
-  SwitchDefaultImpl(List<Label> labels, Token keyword, Token colon,
-      List<Statement> statements)
-      : super(labels, keyword, colon, statements);
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..addAll(labels)
-    ..add(keyword)
-    ..add(colon)
-    ..addAll(statements);
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitSwitchDefault(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    labels.accept(visitor);
-    statements.accept(visitor);
-  }
-}
-
-/**
- * An element within a switch statement.
- *
- * > switchMember ::=
- * >     switchCase
- * >   | switchDefault
- */
-abstract class SwitchMemberImpl extends AstNodeImpl implements SwitchMember {
-  /**
-   * The labels associated with the switch member.
-   */
-  NodeList<Label> _labels;
-
-  /**
-   * The token representing the 'case' or 'default' keyword.
-   */
-  Token keyword;
-
-  /**
-   * The colon separating the keyword or the expression from the statements.
-   */
-  Token colon;
-
-  /**
-   * The statements that will be executed if this switch member is selected.
-   */
-  NodeList<Statement> _statements;
-
-  /**
-   * Initialize a newly created switch member. The list of [labels] can be
-   * `null` if there are no labels.
-   */
-  SwitchMemberImpl(List<Label> labels, this.keyword, this.colon,
-      List<Statement> statements) {
-    _labels = new NodeList<Label>(this, labels);
-    _statements = new NodeList<Statement>(this, statements);
-  }
-
-  @override
-  Token get beginToken {
-    if (!_labels.isEmpty) {
-      return _labels.beginToken;
-    }
-    return keyword;
-  }
-
-  @override
-  Token get endToken {
-    if (!_statements.isEmpty) {
-      return _statements.endToken;
-    }
-    return colon;
-  }
-
-  @override
-  NodeList<Label> get labels => _labels;
-
-  @override
-  NodeList<Statement> get statements => _statements;
-}
-
-/**
- * A switch statement.
- *
- * > switchStatement ::=
- * >     'switch' '(' [Expression] ')' '{' [SwitchCase]* [SwitchDefault]? '}'
- */
-class SwitchStatementImpl extends StatementImpl implements SwitchStatement {
-  /**
-   * The token representing the 'switch' keyword.
-   */
-  Token switchKeyword;
-
-  /**
-   * The left parenthesis.
-   */
-  Token leftParenthesis;
-
-  /**
-   * The expression used to determine which of the switch members will be
-   * selected.
-   */
-  Expression _expression;
-
-  /**
-   * The right parenthesis.
-   */
-  Token rightParenthesis;
-
-  /**
-   * The left curly bracket.
-   */
-  Token leftBracket;
-
-  /**
-   * The switch members that can be selected by the expression.
-   */
-  NodeList<SwitchMember> _members;
-
-  /**
-   * The right curly bracket.
-   */
-  Token rightBracket;
-
-  /**
-   * Initialize a newly created switch statement. The list of [members] can be
-   * `null` if there are no switch members.
-   */
-  SwitchStatementImpl(
-      this.switchKeyword,
-      this.leftParenthesis,
-      Expression expression,
-      this.rightParenthesis,
-      this.leftBracket,
-      List<SwitchMember> members,
-      this.rightBracket) {
-    _expression = _becomeParentOf(expression);
-    _members = new NodeList<SwitchMember>(this, members);
-  }
-
-  @override
-  Token get beginToken => switchKeyword;
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(switchKeyword)
-    ..add(leftParenthesis)
-    ..add(_expression)
-    ..add(rightParenthesis)
-    ..add(leftBracket)
-    ..addAll(_members)
-    ..add(rightBracket);
-
-  @override
-  Token get endToken => rightBracket;
-
-  @override
-  Expression get expression => _expression;
-
-  @override
-  void set expression(Expression expression) {
-    _expression = _becomeParentOf(expression);
-  }
-
-  @override
-  NodeList<SwitchMember> get members => _members;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitSwitchStatement(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_expression, visitor);
-    _members.accept(visitor);
-  }
-}
-
-/**
- * A symbol literal expression.
- *
- * > symbolLiteral ::=
- * >     '#' (operator | (identifier ('.' identifier)*))
- */
-class SymbolLiteralImpl extends LiteralImpl implements SymbolLiteral {
-  /**
-   * The token introducing the literal.
-   */
-  Token poundSign;
-
-  /**
-   * The components of the literal.
-   */
-  final List<Token> components;
-
-  /**
-   * Initialize a newly created symbol literal.
-   */
-  SymbolLiteralImpl(this.poundSign, this.components);
-
-  @override
-  Token get beginToken => poundSign;
-
-  @override
-  // TODO(paulberry): add "." tokens.
-  Iterable get childEntities => new ChildEntities()
-    ..add(poundSign)
-    ..addAll(components);
-
-  @override
-  Token get endToken => components[components.length - 1];
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitSymbolLiteral(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    // There are no children to visit.
-  }
-}
-
-/**
- * A this expression.
- *
- * > thisExpression ::=
- * >     'this'
- */
-class ThisExpressionImpl extends ExpressionImpl implements ThisExpression {
-  /**
-   * The token representing the 'this' keyword.
-   */
-  Token thisKeyword;
-
-  /**
-   * Initialize a newly created this expression.
-   */
-  ThisExpressionImpl(this.thisKeyword);
-
-  @override
-  Token get beginToken => thisKeyword;
-
-  @override
-  Iterable get childEntities => new ChildEntities()..add(thisKeyword);
-
-  @override
-  Token get endToken => thisKeyword;
-
-  @override
-  int get precedence => 16;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitThisExpression(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    // There are no children to visit.
-  }
-}
-
-/**
- * A throw expression.
- *
- * > throwExpression ::=
- * >     'throw' [Expression]
- */
-class ThrowExpressionImpl extends ExpressionImpl implements ThrowExpression {
-  /**
-   * The token representing the 'throw' keyword.
-   */
-  Token throwKeyword;
-
-  /**
-   * The expression computing the exception to be thrown.
-   */
-  Expression _expression;
-
-  /**
-   * Initialize a newly created throw expression.
-   */
-  ThrowExpressionImpl(this.throwKeyword, Expression expression) {
-    _expression = _becomeParentOf(expression);
-  }
-
-  @override
-  Token get beginToken => throwKeyword;
-
-  @override
-  Iterable get childEntities =>
-      new ChildEntities()..add(throwKeyword)..add(_expression);
-
-  @override
-  Token get endToken {
-    if (_expression != null) {
-      return _expression.endToken;
-    }
-    return throwKeyword;
-  }
-
-  @override
-  Expression get expression => _expression;
-
-  @override
-  void set expression(Expression expression) {
-    _expression = _becomeParentOf(expression);
-  }
-
-  @override
-  int get precedence => 0;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitThrowExpression(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_expression, visitor);
-  }
-}
-
-/**
- * The declaration of one or more top-level variables of the same type.
- *
- * > topLevelVariableDeclaration ::=
- * >     ('final' | 'const') type? staticFinalDeclarationList ';'
- * >   | variableDeclaration ';'
- */
-class TopLevelVariableDeclarationImpl extends CompilationUnitMemberImpl
-    implements TopLevelVariableDeclaration {
-  /**
-   * The top-level variables being declared.
-   */
-  VariableDeclarationList _variableList;
-
-  /**
-   * The semicolon terminating the declaration.
-   */
-  Token semicolon;
-
-  /**
-   * Initialize a newly created top-level variable declaration. Either or both
-   * of the [comment] and [metadata] can be `null` if the variable does not have
-   * the corresponding attribute.
-   */
-  TopLevelVariableDeclarationImpl(Comment comment, List<Annotation> metadata,
-      VariableDeclarationList variableList, this.semicolon)
-      : super(comment, metadata) {
-    _variableList = _becomeParentOf(variableList);
-  }
-
-  @override
-  Iterable get childEntities =>
-      super._childEntities..add(_variableList)..add(semicolon);
-
-  @override
-  Element get element => null;
-
-  @override
-  Token get endToken => semicolon;
-
-  @override
-  Token get firstTokenAfterCommentAndMetadata => _variableList.beginToken;
-
-  @override
-  VariableDeclarationList get variables => _variableList;
-
-  @override
-  void set variables(VariableDeclarationList variables) {
-    _variableList = _becomeParentOf(variables);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitTopLevelVariableDeclaration(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    super.visitChildren(visitor);
-    _safelyVisitChild(_variableList, visitor);
-  }
-}
-
-/**
- * A try statement.
- *
- * > tryStatement ::=
- * >     'try' [Block] ([CatchClause]+ finallyClause? | finallyClause)
- * >
- * > finallyClause ::=
- * >     'finally' [Block]
- */
-class TryStatementImpl extends StatementImpl implements TryStatement {
-  /**
-   * The token representing the 'try' keyword.
-   */
-  Token tryKeyword;
-
-  /**
-   * The body of the statement.
-   */
-  Block _body;
-
-  /**
-   * The catch clauses contained in the try statement.
-   */
-  NodeList<CatchClause> _catchClauses;
-
-  /**
-   * The token representing the 'finally' keyword, or `null` if the statement
-   * does not contain a finally clause.
-   */
-  Token finallyKeyword;
-
-  /**
-   * The finally block contained in the try statement, or `null` if the
-   * statement does not contain a finally clause.
-   */
-  Block _finallyBlock;
-
-  /**
-   * Initialize a newly created try statement. The list of [catchClauses] can be
-   * `null` if there are no catch clauses. The [finallyKeyword] and
-   * [finallyBlock] can be `null` if there is no finally clause.
-   */
-  TryStatementImpl(this.tryKeyword, Block body, List<CatchClause> catchClauses,
-      this.finallyKeyword, Block finallyBlock) {
-    _body = _becomeParentOf(body);
-    _catchClauses = new NodeList<CatchClause>(this, catchClauses);
-    _finallyBlock = _becomeParentOf(finallyBlock);
-  }
-
-  @override
-  Token get beginToken => tryKeyword;
-
-  @override
-  Block get body => _body;
-
-  @override
-  void set body(Block block) {
-    _body = _becomeParentOf(block);
-  }
-
-  @override
-  NodeList<CatchClause> get catchClauses => _catchClauses;
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(tryKeyword)
-    ..add(_body)
-    ..addAll(_catchClauses)
-    ..add(finallyKeyword)
-    ..add(_finallyBlock);
-
-  @override
-  Token get endToken {
-    if (_finallyBlock != null) {
-      return _finallyBlock.endToken;
-    } else if (finallyKeyword != null) {
-      return finallyKeyword;
-    } else if (!_catchClauses.isEmpty) {
-      return _catchClauses.endToken;
-    }
-    return _body.endToken;
-  }
-
-  @override
-  Block get finallyBlock => _finallyBlock;
-
-  @override
-  void set finallyBlock(Block block) {
-    _finallyBlock = _becomeParentOf(block);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitTryStatement(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_body, visitor);
-    _catchClauses.accept(visitor);
-    _safelyVisitChild(_finallyBlock, visitor);
-  }
-}
-
-/**
- * The declaration of a type alias.
- *
- * > typeAlias ::=
- * >     'typedef' typeAliasBody
- * >
- * > typeAliasBody ::=
- * >     classTypeAlias
- * >   | functionTypeAlias
- */
-abstract class TypeAliasImpl extends NamedCompilationUnitMemberImpl
-    implements TypeAlias {
-  /**
-   * The token representing the 'typedef' keyword.
-   */
-  Token typedefKeyword;
-
-  /**
-   * The semicolon terminating the declaration.
-   */
-  Token semicolon;
-
-  /**
-   * Initialize a newly created type alias. Either or both of the [comment] and
-   * [metadata] can be `null` if the declaration does not have the corresponding
-   * attribute.
-   */
-  TypeAliasImpl(Comment comment, List<Annotation> metadata, this.typedefKeyword,
-      SimpleIdentifier name, this.semicolon)
-      : super(comment, metadata, name);
-
-  @override
-  Token get endToken => semicolon;
-
-  @override
-  Token get firstTokenAfterCommentAndMetadata => typedefKeyword;
-}
-
-/**
- * A list of type arguments.
- *
- * > typeArguments ::=
- * >     '<' typeName (',' typeName)* '>'
- */
-class TypeArgumentListImpl extends AstNodeImpl implements TypeArgumentList {
-  /**
-   * The left bracket.
-   */
-  Token leftBracket;
-
-  /**
-   * The type arguments associated with the type.
-   */
-  NodeList<TypeName> _arguments;
-
-  /**
-   * The right bracket.
-   */
-  Token rightBracket;
-
-  /**
-   * Initialize a newly created list of type arguments.
-   */
-  TypeArgumentListImpl(
-      this.leftBracket, List<TypeName> arguments, this.rightBracket) {
-    _arguments = new NodeList<TypeName>(this, arguments);
-  }
-
-  @override
-  NodeList<TypeName> get arguments => _arguments;
-
-  @override
-  Token get beginToken => leftBracket;
-
-  @override
-  // TODO(paulberry): Add commas.
-  Iterable get childEntities => new ChildEntities()
-    ..add(leftBracket)
-    ..addAll(_arguments)
-    ..add(rightBracket);
-
-  @override
-  Token get endToken => rightBracket;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitTypeArgumentList(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _arguments.accept(visitor);
-  }
-}
-
-/**
- * A literal that has a type associated with it.
- *
- * > typedLiteral ::=
- * >     [ListLiteral]
- * >   | [MapLiteral]
- */
-abstract class TypedLiteralImpl extends LiteralImpl implements TypedLiteral {
-  /**
-   * The token representing the 'const' keyword, or `null` if the literal is not
-   * a constant.
-   */
-  Token constKeyword;
-
-  /**
-   * The type argument associated with this literal, or `null` if no type
-   * arguments were declared.
-   */
-  TypeArgumentList _typeArguments;
-
-  /**
-   * Initialize a newly created typed literal. The [constKeyword] can be `null`\
-   * if the literal is not a constant. The [typeArguments] can be `null` if no
-   * type arguments were declared.
-   */
-  TypedLiteralImpl(this.constKeyword, TypeArgumentList typeArguments) {
-    _typeArguments = _becomeParentOf(typeArguments);
-  }
-
-  @override
-  TypeArgumentList get typeArguments => _typeArguments;
-
-  @override
-  void set typeArguments(TypeArgumentList typeArguments) {
-    _typeArguments = _becomeParentOf(typeArguments);
-  }
-
-  ChildEntities get _childEntities =>
-      new ChildEntities()..add(constKeyword)..add(_typeArguments);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_typeArguments, visitor);
-  }
-}
-
-/**
- * The name of a type, which can optionally include type arguments.
- *
- * > typeName ::=
- * >     [Identifier] typeArguments?
- */
-class TypeNameImpl extends AstNodeImpl implements TypeName {
-  /**
-   * The name of the type.
-   */
-  Identifier _name;
-
-  /**
-   * The type arguments associated with the type, or `null` if there are no type
-   * arguments.
-   */
-  TypeArgumentList _typeArguments;
-
-  /**
-   * The type being named, or `null` if the AST structure has not been resolved.
-   */
-  DartType type;
-
-  /**
-   * Initialize a newly created type name. The [typeArguments] can be `null` if
-   * there are no type arguments.
-   */
-  TypeNameImpl(Identifier name, TypeArgumentList typeArguments) {
-    _name = _becomeParentOf(name);
-    _typeArguments = _becomeParentOf(typeArguments);
-  }
-
-  @override
-  Token get beginToken => _name.beginToken;
-
-  @override
-  Iterable get childEntities =>
-      new ChildEntities()..add(_name)..add(_typeArguments);
-
-  @override
-  Token get endToken {
-    if (_typeArguments != null) {
-      return _typeArguments.endToken;
-    }
-    return _name.endToken;
-  }
-
-  @override
-  bool get isDeferred {
-    Identifier identifier = name;
-    if (identifier is! PrefixedIdentifier) {
-      return false;
-    }
-    return (identifier as PrefixedIdentifier).isDeferred;
-  }
-
-  @override
-  bool get isSynthetic => _name.isSynthetic && _typeArguments == null;
-
-  @override
-  Identifier get name => _name;
-
-  @override
-  void set name(Identifier identifier) {
-    _name = _becomeParentOf(identifier);
-  }
-
-  @override
-  TypeArgumentList get typeArguments => _typeArguments;
-
-  @override
-  void set typeArguments(TypeArgumentList typeArguments) {
-    _typeArguments = _becomeParentOf(typeArguments);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitTypeName(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_name, visitor);
-    _safelyVisitChild(_typeArguments, visitor);
-  }
-}
-
-/**
- * A type parameter.
- *
- * > typeParameter ::=
- * >     [SimpleIdentifier] ('extends' [TypeName])?
- */
-class TypeParameterImpl extends DeclarationImpl implements TypeParameter {
-  /**
-   * The name of the type parameter.
-   */
-  SimpleIdentifier _name;
-
-  /**
-   * The token representing the 'extends' keyword, or `null` if there is no
-   * explicit upper bound.
-   */
-  Token extendsKeyword;
-
-  /**
-   * The name of the upper bound for legal arguments, or `null` if there is no
-   * explicit upper bound.
-   */
-  TypeName _bound;
-
-  /**
-   * Initialize a newly created type parameter. Either or both of the [comment]
-   * and [metadata] can be `null` if the parameter does not have the
-   * corresponding attribute. The [extendsKeyword] and [bound] can be `null` if
-   * the parameter does not have an upper bound.
-   */
-  TypeParameterImpl(Comment comment, List<Annotation> metadata,
-      SimpleIdentifier name, this.extendsKeyword, TypeName bound)
-      : super(comment, metadata) {
-    _name = _becomeParentOf(name);
-    _bound = _becomeParentOf(bound);
-  }
-
-  @override
-  TypeName get bound => _bound;
-
-  @override
-  void set bound(TypeName typeName) {
-    _bound = _becomeParentOf(typeName);
-  }
-
-  @override
-  Iterable get childEntities =>
-      super._childEntities..add(_name)..add(extendsKeyword)..add(_bound);
-
-  @override
-  TypeParameterElement get element =>
-      _name != null ? (_name.staticElement as TypeParameterElement) : null;
-
-  @override
-  Token get endToken {
-    if (_bound == null) {
-      return _name.endToken;
-    }
-    return _bound.endToken;
-  }
-
-  @override
-  Token get firstTokenAfterCommentAndMetadata => _name.beginToken;
-
-  @override
-  SimpleIdentifier get name => _name;
-
-  @override
-  void set name(SimpleIdentifier identifier) {
-    _name = _becomeParentOf(identifier);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitTypeParameter(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    super.visitChildren(visitor);
-    _safelyVisitChild(_name, visitor);
-    _safelyVisitChild(_bound, visitor);
-  }
-}
-
-/**
- * Type parameters within a declaration.
- *
- * > typeParameterList ::=
- * >     '<' [TypeParameter] (',' [TypeParameter])* '>'
- */
-class TypeParameterListImpl extends AstNodeImpl implements TypeParameterList {
-  /**
-   * The left angle bracket.
-   */
-  final Token leftBracket;
-
-  /**
-   * The type parameters in the list.
-   */
-  NodeList<TypeParameter> _typeParameters;
-
-  /**
-   * The right angle bracket.
-   */
-  final Token rightBracket;
-
-  /**
-   * Initialize a newly created list of type parameters.
-   */
-  TypeParameterListImpl(
-      this.leftBracket, List<TypeParameter> typeParameters, this.rightBracket) {
-    _typeParameters = new NodeList<TypeParameter>(this, typeParameters);
-  }
-
-  @override
-  Token get beginToken => leftBracket;
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(leftBracket)
-    ..addAll(_typeParameters)
-    ..add(rightBracket);
-
-  @override
-  Token get endToken => rightBracket;
-
-  @override
-  NodeList<TypeParameter> get typeParameters => _typeParameters;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitTypeParameterList(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _typeParameters.accept(visitor);
-  }
-}
-
-/**
- * A directive that references a URI.
- *
- * > uriBasedDirective ::=
- * >     [ExportDirective]
- * >   | [ImportDirective]
- * >   | [PartDirective]
- */
-abstract class UriBasedDirectiveImpl extends DirectiveImpl
-    implements UriBasedDirective {
-  /**
-   * The prefix of a URI using the `dart-ext` scheme to reference a native code
-   * library.
-   */
-  static String _DART_EXT_SCHEME = "dart-ext:";
-
-  /**
-   * The URI referenced by this directive.
-   */
-  StringLiteral _uri;
-
-  /**
-   * The content of the URI.
-   */
-  String uriContent;
-
-  /**
-   * The source to which the URI was resolved.
-   */
-  Source source;
-
-  /**
-   * Initialize a newly create URI-based directive. Either or both of the
-   * [comment] and [metadata] can be `null` if the directive does not have the
-   * corresponding attribute.
-   */
-  UriBasedDirectiveImpl(
-      Comment comment, List<Annotation> metadata, StringLiteral uri)
-      : super(comment, metadata) {
-    _uri = _becomeParentOf(uri);
-  }
-
-  @override
-  StringLiteral get uri => _uri;
-
-  @override
-  void set uri(StringLiteral uri) {
-    _uri = _becomeParentOf(uri);
-  }
-
-  @override
-  UriValidationCode validate() {
-    StringLiteral uriLiteral = uri;
-    if (uriLiteral is StringInterpolation) {
-      return UriValidationCode.URI_WITH_INTERPOLATION;
-    }
-    String uriContent = this.uriContent;
-    if (uriContent == null) {
-      return UriValidationCode.INVALID_URI;
-    }
-    if (this is ImportDirective && uriContent.startsWith(_DART_EXT_SCHEME)) {
-      return UriValidationCode.URI_WITH_DART_EXT_SCHEME;
-    }
-    try {
-      parseUriWithException(Uri.encodeFull(uriContent));
-    } on URISyntaxException {
-      return UriValidationCode.INVALID_URI;
-    }
-    return null;
-  }
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    super.visitChildren(visitor);
-    _safelyVisitChild(_uri, visitor);
-  }
-}
-
-/**
- * Validation codes returned by [UriBasedDirective.validate].
- */
-class UriValidationCodeImpl implements UriValidationCode {
-  static const UriValidationCode INVALID_URI =
-      const UriValidationCodeImpl('INVALID_URI');
-
-  static const UriValidationCode URI_WITH_INTERPOLATION =
-      const UriValidationCodeImpl('URI_WITH_INTERPOLATION');
-
-  static const UriValidationCode URI_WITH_DART_EXT_SCHEME =
-      const UriValidationCodeImpl('URI_WITH_DART_EXT_SCHEME');
-
-  /**
-   * The name of the validation code.
-   */
-  final String name;
-
-  /**
-   * Initialize a newly created validation code to have the given [name].
-   */
-  const UriValidationCodeImpl(this.name);
-
-  @override
-  String toString() => name;
-}
-
-/**
- * An identifier that has an initial value associated with it. Instances of this
- * class are always children of the class [VariableDeclarationList].
- *
- * > variableDeclaration ::=
- * >     [SimpleIdentifier] ('=' [Expression])?
- *
- * TODO(paulberry): the grammar does not allow metadata to be associated with
- * a VariableDeclaration, and currently we don't record comments for it either.
- * Consider changing the class hierarchy so that [VariableDeclaration] does not
- * extend [Declaration].
- */
-class VariableDeclarationImpl extends DeclarationImpl
-    implements VariableDeclaration {
-  /**
-   * The name of the variable being declared.
-   */
-  SimpleIdentifier _name;
-
-  /**
-   * The equal sign separating the variable name from the initial value, or
-   * `null` if the initial value was not specified.
-   */
-  Token equals;
-
-  /**
-   * The expression used to compute the initial value for the variable, or
-   * `null` if the initial value was not specified.
-   */
-  Expression _initializer;
-
-  /**
-   * Initialize a newly created variable declaration. The [equals] and
-   * [initializer] can be `null` if there is no initializer.
-   */
-  VariableDeclarationImpl(
-      SimpleIdentifier name, this.equals, Expression initializer)
-      : super(null, null) {
-    _name = _becomeParentOf(name);
-    _initializer = _becomeParentOf(initializer);
-  }
-
-  @override
-  Iterable get childEntities =>
-      super._childEntities..add(_name)..add(equals)..add(_initializer);
-
-  /**
-   * This overridden implementation of getDocumentationComment() looks in the
-   * grandparent node for Dartdoc comments if no documentation is specifically
-   * available on the node.
-   */
-  @override
-  Comment get documentationComment {
-    Comment comment = super.documentationComment;
-    if (comment == null) {
-      if (parent != null && parent.parent != null) {
-        AstNode node = parent.parent;
-        if (node is AnnotatedNode) {
-          return node.documentationComment;
-        }
-      }
-    }
-    return comment;
-  }
-
-  @override
-  VariableElement get element =>
-      _name != null ? (_name.staticElement as VariableElement) : null;
-
-  @override
-  Token get endToken {
-    if (_initializer != null) {
-      return _initializer.endToken;
-    }
-    return _name.endToken;
-  }
-
-  @override
-  Token get firstTokenAfterCommentAndMetadata => _name.beginToken;
-
-  @override
-  Expression get initializer => _initializer;
-
-  @override
-  void set initializer(Expression expression) {
-    _initializer = _becomeParentOf(expression);
-  }
-
-  @override
-  bool get isConst {
-    AstNode parent = this.parent;
-    return parent is VariableDeclarationList && parent.isConst;
-  }
-
-  @override
-  bool get isFinal {
-    AstNode parent = this.parent;
-    return parent is VariableDeclarationList && parent.isFinal;
-  }
-
-  @override
-  SimpleIdentifier get name => _name;
-
-  @override
-  void set name(SimpleIdentifier identifier) {
-    _name = _becomeParentOf(identifier);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitVariableDeclaration(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    super.visitChildren(visitor);
-    _safelyVisitChild(_name, visitor);
-    _safelyVisitChild(_initializer, visitor);
-  }
-}
-
-/**
- * The declaration of one or more variables of the same type.
- *
- * > variableDeclarationList ::=
- * >     finalConstVarOrType [VariableDeclaration] (',' [VariableDeclaration])*
- * >
- * > finalConstVarOrType ::=
- * >   | 'final' [TypeName]?
- * >   | 'const' [TypeName]?
- * >   | 'var'
- * >   | [TypeName]
- */
-class VariableDeclarationListImpl extends AnnotatedNodeImpl
-    implements VariableDeclarationList {
-  /**
-   * The token representing the 'final', 'const' or 'var' keyword, or `null` if
-   * no keyword was included.
-   */
-  Token keyword;
-
-  /**
-   * The type of the variables being declared, or `null` if no type was provided.
-   */
-  TypeName _type;
-
-  /**
-   * A list containing the individual variables being declared.
-   */
-  NodeList<VariableDeclaration> _variables;
-
-  /**
-   * Initialize a newly created variable declaration list. Either or both of the
-   * [comment] and [metadata] can be `null` if the variable list does not have
-   * the corresponding attribute. The [keyword] can be `null` if a type was
-   * specified. The [type] must be `null` if the keyword is 'var'.
-   */
-  VariableDeclarationListImpl(Comment comment, List<Annotation> metadata,
-      this.keyword, TypeName type, List<VariableDeclaration> variables)
-      : super(comment, metadata) {
-    _type = _becomeParentOf(type);
-    _variables = new NodeList<VariableDeclaration>(this, variables);
-  }
-
-  @override
-  // TODO(paulberry): include commas.
-  Iterable get childEntities => super._childEntities
-    ..add(keyword)
-    ..add(_type)
-    ..addAll(_variables);
-
-  @override
-  Token get endToken => _variables.endToken;
-
-  @override
-  Token get firstTokenAfterCommentAndMetadata {
-    if (keyword != null) {
-      return keyword;
-    } else if (_type != null) {
-      return _type.beginToken;
-    }
-    return _variables.beginToken;
-  }
-
-  @override
-  bool get isConst =>
-      keyword is KeywordToken &&
-      (keyword as KeywordToken).keyword == Keyword.CONST;
-
-  @override
-  bool get isFinal =>
-      keyword is KeywordToken &&
-      (keyword as KeywordToken).keyword == Keyword.FINAL;
-
-  @override
-  TypeName get type => _type;
-
-  @override
-  void set type(TypeName typeName) {
-    _type = _becomeParentOf(typeName);
-  }
-
-  @override
-  NodeList<VariableDeclaration> get variables => _variables;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitVariableDeclarationList(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    super.visitChildren(visitor);
-    _safelyVisitChild(_type, visitor);
-    _variables.accept(visitor);
-  }
-}
-
-/**
- * A list of variables that are being declared in a context where a statement is
- * required.
- *
- * > variableDeclarationStatement ::=
- * >     [VariableDeclarationList] ';'
- */
-class VariableDeclarationStatementImpl extends StatementImpl
-    implements VariableDeclarationStatement {
-  /**
-   * The variables being declared.
-   */
-  VariableDeclarationList _variableList;
-
-  /**
-   * The semicolon terminating the statement.
-   */
-  Token semicolon;
-
-  /**
-   * Initialize a newly created variable declaration statement.
-   */
-  VariableDeclarationStatementImpl(
-      VariableDeclarationList variableList, this.semicolon) {
-    _variableList = _becomeParentOf(variableList);
-  }
-
-  @override
-  Token get beginToken => _variableList.beginToken;
-
-  @override
-  Iterable get childEntities =>
-      new ChildEntities()..add(_variableList)..add(semicolon);
-
-  @override
-  Token get endToken => semicolon;
-
-  @override
-  VariableDeclarationList get variables => _variableList;
-
-  @override
-  void set variables(VariableDeclarationList variables) {
-    _variableList = _becomeParentOf(variables);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitVariableDeclarationStatement(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_variableList, visitor);
-  }
-}
-
-/**
- * A while statement.
- *
- * > whileStatement ::=
- * >     'while' '(' [Expression] ')' [Statement]
- */
-class WhileStatementImpl extends StatementImpl implements WhileStatement {
-  /**
-   * The token representing the 'while' keyword.
-   */
-  Token whileKeyword;
-
-  /**
-   * The left parenthesis.
-   */
-  Token leftParenthesis;
-
-  /**
-   * The expression used to determine whether to execute the body of the loop.
-   */
-  Expression _condition;
-
-  /**
-   * The right parenthesis.
-   */
-  Token rightParenthesis;
-
-  /**
-   * The body of the loop.
-   */
-  Statement _body;
-
-  /**
-   * Initialize a newly created while statement.
-   */
-  WhileStatementImpl(this.whileKeyword, this.leftParenthesis,
-      Expression condition, this.rightParenthesis, Statement body) {
-    _condition = _becomeParentOf(condition);
-    _body = _becomeParentOf(body);
-  }
-
-  @override
-  Token get beginToken => whileKeyword;
-
-  @override
-  Statement get body => _body;
-
-  @override
-  void set body(Statement statement) {
-    _body = _becomeParentOf(statement);
-  }
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(whileKeyword)
-    ..add(leftParenthesis)
-    ..add(_condition)
-    ..add(rightParenthesis)
-    ..add(_body);
-
-  @override
-  Expression get condition => _condition;
-
-  @override
-  void set condition(Expression expression) {
-    _condition = _becomeParentOf(expression);
-  }
-
-  @override
-  Token get endToken => _body.endToken;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitWhileStatement(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_condition, visitor);
-    _safelyVisitChild(_body, visitor);
-  }
-}
-
-/**
- * The with clause in a class declaration.
- *
- * > withClause ::=
- * >     'with' [TypeName] (',' [TypeName])*
- */
-class WithClauseImpl extends AstNodeImpl implements WithClause {
-  /**
-   * The token representing the 'with' keyword.
-   */
-  Token withKeyword;
-
-  /**
-   * The names of the mixins that were specified.
-   */
-  NodeList<TypeName> _mixinTypes;
-
-  /**
-   * Initialize a newly created with clause.
-   */
-  WithClauseImpl(this.withKeyword, List<TypeName> mixinTypes) {
-    _mixinTypes = new NodeList<TypeName>(this, mixinTypes);
-  }
-
-  @override
-  Token get beginToken => withKeyword;
-
-  @override
-  // TODO(paulberry): add commas.
-  Iterable get childEntities => new ChildEntities()
-    ..add(withKeyword)
-    ..addAll(_mixinTypes);
-
-  @override
-  Token get endToken => _mixinTypes.endToken;
-
-  @override
-  NodeList<TypeName> get mixinTypes => _mixinTypes;
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitWithClause(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _mixinTypes.accept(visitor);
-  }
-}
-
-/**
- * A yield statement.
- *
- * > yieldStatement ::=
- * >     'yield' '*'? [Expression] ‘;’
- */
-class YieldStatementImpl extends StatementImpl implements YieldStatement {
-  /**
-   * The 'yield' keyword.
-   */
-  Token yieldKeyword;
-
-  /**
-   * The star optionally following the 'yield' keyword.
-   */
-  Token star;
-
-  /**
-   * The expression whose value will be yielded.
-   */
-  Expression _expression;
-
-  /**
-   * The semicolon following the expression.
-   */
-  Token semicolon;
-
-  /**
-   * Initialize a newly created yield expression. The [star] can be `null` if no
-   * star was provided.
-   */
-  YieldStatementImpl(
-      this.yieldKeyword, this.star, Expression expression, this.semicolon) {
-    _expression = _becomeParentOf(expression);
-  }
-
-  @override
-  Token get beginToken {
-    if (yieldKeyword != null) {
-      return yieldKeyword;
-    }
-    return _expression.beginToken;
-  }
-
-  @override
-  Iterable get childEntities => new ChildEntities()
-    ..add(yieldKeyword)
-    ..add(star)
-    ..add(_expression)
-    ..add(semicolon);
-
-  @override
-  Token get endToken {
-    if (semicolon != null) {
-      return semicolon;
-    }
-    return _expression.endToken;
-  }
-
-  @override
-  Expression get expression => _expression;
-
-  @override
-  void set expression(Expression expression) {
-    _expression = _becomeParentOf(expression);
-  }
-
-  @override
-  accept(AstVisitor visitor) => visitor.visitYieldStatement(this);
-
-  @override
-  void visitChildren(AstVisitor visitor) {
-    _safelyVisitChild(_expression, visitor);
-  }
-}