Removed fixed dependencies

packages/analyzer/lib/src/dart/ast/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.
+
+library analyzer.src.dart.ast.ast;
+
+import 'dart:collection';
+
+import 'package:analyzer/dart/ast/ast.dart';
+import 'package:analyzer/dart/ast/syntactic_entity.dart';
+import 'package:analyzer/dart/ast/token.dart';
+import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/dart/element/type.dart';
+import 'package:analyzer/exception/exception.dart';
+import 'package:analyzer/src/dart/ast/token.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/source.dart' show LineInfo, Source;
+import 'package:analyzer/src/generated/utilities_dart.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 NodeListImpl<StringLiteral>(this, strings);
+  }
+
+  @override
+  Token get beginToken => _strings.beginToken;
+
+  @override
+  Iterable<SyntacticEntity> get childEntities =>
+      new ChildEntities()..addAll(_strings);
+
+  @override
+  Token get endToken => _strings.endToken;
+
+  @override
+  NodeList<StringLiteral> get strings => _strings;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitAdjacentStrings(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _strings.accept(visitor);
+  }
+
+  @override
+  void _appendStringValue(StringBuffer buffer) {
+    int length = strings.length;
+    for (int i = 0; i < length; i++) {
+      StringLiteralImpl stringLiteral = strings[i];
+      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(CommentImpl comment, List<Annotation> metadata) {
+    _comment = _becomeParentOf(comment);
+    _metadata = new NodeListImpl<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 as AstNodeImpl);
+  }
+
+  @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()) {
+      _comment?.accept(visitor);
+      _metadata.accept(visitor);
+    } else {
+      List<AstNode> children = sortedCommentAndAnnotations;
+      int length = children.length;
+      for (int i = 0; i < length; i++) {
+        children[i].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.
+   */
+  @override
+  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.
+   */
+  @override
+  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.
+   */
+  @override
+  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, IdentifierImpl name, this.period,
+      SimpleIdentifierImpl constructorName, ArgumentListImpl arguments) {
+    _name = _becomeParentOf(name);
+    _constructorName = _becomeParentOf(constructorName);
+    _arguments = _becomeParentOf(arguments);
+  }
+
+  @override
+  ArgumentList get arguments => _arguments;
+
+  @override
+  void set arguments(ArgumentList arguments) {
+    _arguments = _becomeParentOf(arguments as AstNodeImpl);
+  }
+
+  @override
+  Token get beginToken => atSign;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  Element get element {
+    if (_element != null) {
+      return _element;
+    } else if (_constructorName == null && _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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitAnnotation(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _name?.accept(visitor);
+    _constructorName?.accept(visitor);
+    _arguments?.accept(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.
+   */
+  @override
+  Token leftParenthesis;
+
+  /**
+   * The expressions producing the values of the arguments.
+   */
+  NodeList<Expression> _arguments;
+
+  /**
+   * The right parenthesis.
+   */
+  @override
+  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 NodeListImpl<Expression>(this, arguments);
+  }
+
+  @override
+  NodeList<Expression> get arguments => _arguments;
+
+  @override
+  Token get beginToken => leftParenthesis;
+
+  @override
+  // TODO(paulberry): Add commas.
+  Iterable<SyntacticEntity> get childEntities => new ChildEntities()
+    ..add(leftParenthesis)
+    ..addAll(_arguments)
+    ..add(rightParenthesis);
+
+  List<ParameterElement> get correspondingPropagatedParameters =>
+      _correspondingPropagatedParameters;
+
+  @override
+  void set correspondingPropagatedParameters(
+      List<ParameterElement> parameters) {
+    if (parameters != null && parameters.length != _arguments.length) {
+      throw new ArgumentError(
+          "Expected ${_arguments.length} parameters, not ${parameters.length}");
+    }
+    _correspondingPropagatedParameters = parameters;
+  }
+
+  List<ParameterElement> get correspondingStaticParameters =>
+      _correspondingStaticParameters;
+
+  @override
+  void set correspondingStaticParameters(List<ParameterElement> parameters) {
+    if (parameters != null && parameters.length != _arguments.length) {
+      throw new ArgumentError(
+          "Expected ${_arguments.length} parameters, not ${parameters.length}");
+    }
+    _correspondingStaticParameters = parameters;
+  }
+
+  @override
+  Token get endToken => rightParenthesis;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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.
+   */
+  @override
+  Token asOperator;
+
+  /**
+   * The name of the type being cast to.
+   */
+  TypeName _type;
+
+  /**
+   * Initialize a newly created as expression.
+   */
+  AsExpressionImpl(
+      ExpressionImpl expression, this.asOperator, TypeNameImpl type) {
+    _expression = _becomeParentOf(expression);
+    _type = _becomeParentOf(type);
+  }
+
+  @override
+  Token get beginToken => _expression.beginToken;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  int get precedence => 7;
+
+  @override
+  TypeName get type => _type;
+
+  @override
+  void set type(TypeName name) {
+    _type = _becomeParentOf(name as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitAsExpression(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _expression?.accept(visitor);
+    _type?.accept(visitor);
+  }
+}
+
+/**
+ * An assert statement.
+ *
+ *    assertStatement ::=
+ *        'assert' '(' [Expression] ')' ';'
+ */
+class AssertStatementImpl extends StatementImpl implements AssertStatement {
+  /**
+   * The token representing the 'assert' keyword.
+   */
+  @override
+  Token assertKeyword;
+
+  /**
+   * The left parenthesis.
+   */
+  @override
+  Token leftParenthesis;
+
+  /**
+   * The condition that is being asserted to be `true`.
+   */
+  Expression _condition;
+
+  /**
+   * The comma, if a message expression was supplied.  Otherwise `null`.
+   */
+  @override
+  Token comma;
+
+  /**
+   * The message to report if the assertion fails.  `null` if no message was
+   * supplied.
+   */
+  Expression _message;
+
+  /**
+   * The right parenthesis.
+   */
+  @override
+  Token rightParenthesis;
+
+  /**
+   * The semicolon terminating the statement.
+   */
+  @override
+  Token semicolon;
+
+  /**
+   * Initialize a newly created assert statement.
+   */
+  AssertStatementImpl(
+      this.assertKeyword,
+      this.leftParenthesis,
+      ExpressionImpl condition,
+      this.comma,
+      ExpressionImpl message,
+      this.rightParenthesis,
+      this.semicolon) {
+    _condition = _becomeParentOf(condition);
+    _message = _becomeParentOf(message);
+  }
+
+  @override
+  Token get beginToken => assertKeyword;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  Token get endToken => semicolon;
+
+  @override
+  Expression get message => _message;
+
+  @override
+  void set message(Expression expression) {
+    _message = _becomeParentOf(expression as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitAssertStatement(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _condition?.accept(visitor);
+    message?.accept(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.
+   */
+  @override
+  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.
+   */
+  @override
+  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.
+   */
+  @override
+  MethodElement propagatedElement;
+
+  /**
+   * Initialize a newly created assignment expression.
+   */
+  AssignmentExpressionImpl(ExpressionImpl leftHandSide, this.operator,
+      ExpressionImpl 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<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  int get precedence => 1;
+
+  @override
+  Expression get rightHandSide => _rightHandSide;
+
+  @override
+  void set rightHandSide(Expression expression) {
+    _rightHandSide = _becomeParentOf(expression as AstNodeImpl);
+  }
+
+  /**
+   * 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 {
+      Expression left = _leftHandSide;
+      if (left is Identifier) {
+        Element leftElement = left.propagatedElement;
+        if (leftElement is ExecutableElement) {
+          executableElement = leftElement;
+        }
+      } else if (left is PropertyAccess) {
+        Element leftElement = left.propertyName.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 {
+      Expression left = _leftHandSide;
+      if (left is Identifier) {
+        Element leftElement = left.staticElement;
+        if (leftElement is ExecutableElement) {
+          executableElement = leftElement;
+        }
+      } else if (left is PropertyAccess) {
+        Element leftElement = left.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
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitAssignmentExpression(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _leftHandSide?.accept(visitor);
+    _rightHandSide?.accept(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/*=E*/ getAncestor/*<E extends AstNode>*/(
+      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 as AstNode/*=E*/;
+  }
+
+  @override
+  Object/*=E*/ getProperty/*<E>*/(String name) {
+    if (_propertyMap == null) {
+      return null;
+    }
+    return _propertyMap[name] as Object/*=E*/;
+  }
+
+  @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(AstNodeImpl child) {
+    if (child != null) {
+      child._parent = this;
+    }
+    return child;
+  }
+}
+
+/**
+ * An await expression.
+ *
+ *    awaitExpression ::=
+ *        'await' [Expression]
+ */
+class AwaitExpressionImpl extends ExpressionImpl implements AwaitExpression {
+  /**
+   * The 'await' keyword.
+   */
+  @override
+  Token awaitKeyword;
+
+  /**
+   * The expression whose value is being waited on.
+   */
+  Expression _expression;
+
+  /**
+   * Initialize a newly created await expression.
+   */
+  AwaitExpressionImpl(this.awaitKeyword, ExpressionImpl expression) {
+    _expression = _becomeParentOf(expression);
+  }
+
+  @override
+  Token get beginToken {
+    if (awaitKeyword != null) {
+      return awaitKeyword;
+    }
+    return _expression.beginToken;
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  int get precedence => 0;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitAwaitExpression(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _expression?.accept(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.
+   */
+  @override
+  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.
+   */
+  @override
+  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.
+   */
+  @override
+  MethodElement propagatedElement;
+
+  /**
+   * Initialize a newly created binary expression.
+   */
+  BinaryExpressionImpl(
+      ExpressionImpl leftOperand, this.operator, ExpressionImpl 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<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  int get precedence => operator.type.precedence;
+
+  @override
+  Expression get rightOperand => _rightOperand;
+
+  @override
+  void set rightOperand(Expression expression) {
+    _rightOperand = _becomeParentOf(expression as AstNodeImpl);
+  }
+
+  /**
+   * 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
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitBinaryExpression(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _leftOperand?.accept(visitor);
+    _rightOperand?.accept(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.
+   */
+  @override
+  Token keyword;
+
+  /**
+   * The star optionally following the 'async' or 'sync' keyword, or `null` if
+   * there is wither no such keyword or no star.
+   */
+  @override
+  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, BlockImpl 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 as AstNodeImpl);
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitBlockFunctionBody(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _block?.accept(visitor);
+  }
+}
+
+/**
+ * A sequence of statements.
+ *
+ *    block ::=
+ *        '{' statement* '}'
+ */
+class BlockImpl extends StatementImpl implements Block {
+  /**
+   * The left curly bracket.
+   */
+  @override
+  Token leftBracket;
+
+  /**
+   * The statements contained in the block.
+   */
+  NodeList<Statement> _statements;
+
+  /**
+   * The right curly bracket.
+   */
+  @override
+  Token rightBracket;
+
+  /**
+   * Initialize a newly created block of code.
+   */
+  BlockImpl(this.leftBracket, List<Statement> statements, this.rightBracket) {
+    _statements = new NodeListImpl<Statement>(this, statements);
+  }
+
+  @override
+  Token get beginToken => leftBracket;
+
+  @override
+  Iterable<SyntacticEntity> get childEntities => new ChildEntities()
+    ..add(leftBracket)
+    ..addAll(_statements)
+    ..add(rightBracket);
+
+  @override
+  Token get endToken => rightBracket;
+
+  @override
+  NodeList<Statement> get statements => _statements;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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.
+   */
+  @override
+  Token literal;
+
+  /**
+   * The value of the literal.
+   */
+  @override
+  bool value = false;
+
+  /**
+   * Initialize a newly created boolean literal.
+   */
+  BooleanLiteralImpl(this.literal, this.value);
+
+  @override
+  Token get beginToken => literal;
+
+  @override
+  Iterable<SyntacticEntity> get childEntities =>
+      new ChildEntities()..add(literal);
+
+  @override
+  Token get endToken => literal;
+
+  @override
+  bool get isSynthetic => literal.isSynthetic;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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.
+   */
+  @override
+  Token breakKeyword;
+
+  /**
+   * The label associated with the statement, or `null` if there is no label.
+   */
+  SimpleIdentifier _label;
+
+  /**
+   * The semicolon terminating the statement.
+   */
+  @override
+  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).
+   */
+  @override
+  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, SimpleIdentifierImpl label, this.semicolon) {
+    _label = _becomeParentOf(label);
+  }
+
+  @override
+  Token get beginToken => breakKeyword;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitBreakStatement(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _label?.accept(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(
+      ExpressionImpl target, List<Expression> cascadeSections) {
+    _target = _becomeParentOf(target);
+    _cascadeSections = new NodeListImpl<Expression>(this, cascadeSections);
+  }
+
+  @override
+  Token get beginToken => _target.beginToken;
+
+  @override
+  NodeList<Expression> get cascadeSections => _cascadeSections;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitCascadeExpression(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _target?.accept(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.
+   */
+  @override
+  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.
+   */
+  @override
+  Token catchKeyword;
+
+  /**
+   * The left parenthesis, or `null` if there is no 'catch' keyword.
+   */
+  @override
+  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.
+   */
+  @override
+  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.
+   */
+  @override
+  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,
+      TypeNameImpl exceptionType,
+      this.catchKeyword,
+      this.leftParenthesis,
+      SimpleIdentifierImpl exceptionParameter,
+      this.comma,
+      SimpleIdentifierImpl stackTraceParameter,
+      this.rightParenthesis,
+      BlockImpl 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 as AstNodeImpl);
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  TypeName get exceptionType => _exceptionType;
+
+  @override
+  void set exceptionType(TypeName exceptionType) {
+    _exceptionType = _becomeParentOf(exceptionType as AstNodeImpl);
+  }
+
+  @override
+  SimpleIdentifier get stackTraceParameter => _stackTraceParameter;
+
+  @override
+  void set stackTraceParameter(SimpleIdentifier parameter) {
+    _stackTraceParameter = _becomeParentOf(parameter as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitCatchClause(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _exceptionType?.accept(visitor);
+    _exceptionParameter?.accept(visitor);
+    _stackTraceParameter?.accept(visitor);
+    _body?.accept(visitor);
+  }
+}
+
+/**
+ * Helper class to allow iteration of child entities of an AST node.
+ */
+class ChildEntities extends Object
+    with IterableMixin<SyntacticEntity>
+    implements Iterable<SyntacticEntity> {
+  /**
+   * The list of child entities to be iterated over.
+   */
+  List<SyntacticEntity> _entities = [];
+
+  @override
+  Iterator<SyntacticEntity> get iterator => _entities.iterator;
+
+  /**
+   * Add an AST node or token as the next child entity, if it is not null.
+   */
+  void add(SyntacticEntity entity) {
+    if (entity != null) {
+      _entities.add(entity);
+    }
+  }
+
+  /**
+   * Add the given items as the next child entities, if [items] is not null.
+   */
+  void addAll(Iterable<SyntacticEntity> 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.
+   */
+  @override
+  Token abstractKeyword;
+
+  /**
+   * The token representing the 'class' keyword.
+   */
+  @override
+  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.
+   */
+  @override
+  Token leftBracket;
+
+  /**
+   * The members defined by the class.
+   */
+  NodeList<ClassMember> _members;
+
+  /**
+   * The right curly bracket.
+   */
+  @override
+  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,
+      SimpleIdentifierImpl name,
+      TypeParameterListImpl typeParameters,
+      ExtendsClauseImpl extendsClause,
+      WithClauseImpl withClause,
+      ImplementsClauseImpl 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 NodeListImpl<ClassMember>(this, members);
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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?.staticElement as ClassElement;
+
+  @override
+  Token get endToken => rightBracket;
+
+  @override
+  ExtendsClause get extendsClause => _extendsClause;
+
+  @override
+  void set extendsClause(ExtendsClause extendsClause) {
+    _extendsClause = _becomeParentOf(extendsClause as AstNodeImpl);
+  }
+
+  @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 as AstNodeImpl);
+  }
+
+  @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 as AstNodeImpl);
+  }
+
+  @override
+  TypeParameterList get typeParameters => _typeParameters;
+
+  @override
+  void set typeParameters(TypeParameterList typeParameters) {
+    _typeParameters = _becomeParentOf(typeParameters as AstNodeImpl);
+  }
+
+  @override
+  WithClause get withClause => _withClause;
+
+  @override
+  void set withClause(WithClause withClause) {
+    _withClause = _becomeParentOf(withClause as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitClassDeclaration(this);
+
+  @override
+  ConstructorDeclaration getConstructor(String name) {
+    int length = _members.length;
+    for (int i = 0; i < length; i++) {
+      ClassMember classMember = _members[i];
+      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) {
+    int memberLength = _members.length;
+    for (int i = 0; i < memberLength; i++) {
+      ClassMember classMember = _members[i];
+      if (classMember is FieldDeclaration) {
+        FieldDeclaration fieldDeclaration = classMember;
+        NodeList<VariableDeclaration> fields =
+            fieldDeclaration.fields.variables;
+        int fieldLength = fields.length;
+        for (int i = 0; i < fieldLength; i++) {
+          VariableDeclaration field = fields[i];
+          SimpleIdentifier fieldName = field.name;
+          if (fieldName != null && name == fieldName.name) {
+            return field;
+          }
+        }
+      }
+    }
+    return null;
+  }
+
+  @override
+  MethodDeclaration getMethod(String name) {
+    int length = _members.length;
+    for (int i = 0; i < length; i++) {
+      ClassMember classMember = _members[i];
+      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);
+    _name?.accept(visitor);
+    _typeParameters?.accept(visitor);
+    _extendsClause?.accept(visitor);
+    _withClause?.accept(visitor);
+    _implementsClause?.accept(visitor);
+    _nativeClause?.accept(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.
+   */
+  @override
+  Token equals;
+
+  /**
+   * The token for the 'abstract' keyword, or `null` if this is not defining an
+   * abstract class.
+   */
+  @override
+  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(
+      CommentImpl comment,
+      List<Annotation> metadata,
+      Token keyword,
+      SimpleIdentifierImpl name,
+      TypeParameterListImpl typeParameters,
+      this.equals,
+      this.abstractKeyword,
+      TypeNameImpl superclass,
+      WithClauseImpl withClause,
+      ImplementsClauseImpl implementsClause,
+      Token semicolon)
+      : super(comment, metadata, keyword, name, semicolon) {
+    _typeParameters = _becomeParentOf(typeParameters);
+    _superclass = _becomeParentOf(superclass);
+    _withClause = _becomeParentOf(withClause);
+    _implementsClause = _becomeParentOf(implementsClause);
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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?.staticElement as ClassElement;
+
+  @override
+  Token get firstTokenAfterCommentAndMetadata {
+    if (abstractKeyword != null) {
+      return abstractKeyword;
+    }
+    return typedefKeyword;
+  }
+
+  @override
+  ImplementsClause get implementsClause => _implementsClause;
+
+  @override
+  void set implementsClause(ImplementsClause implementsClause) {
+    _implementsClause = _becomeParentOf(implementsClause as AstNodeImpl);
+  }
+
+  @override
+  bool get isAbstract => abstractKeyword != null;
+
+  @override
+  TypeName get superclass => _superclass;
+
+  @override
+  void set superclass(TypeName superclass) {
+    _superclass = _becomeParentOf(superclass as AstNodeImpl);
+  }
+
+  @override
+  TypeParameterList get typeParameters => _typeParameters;
+
+  @override
+  void set typeParameters(TypeParameterList typeParameters) {
+    _typeParameters = _becomeParentOf(typeParameters as AstNodeImpl);
+  }
+
+  @override
+  WithClause get withClause => _withClause;
+
+  @override
+  void set withClause(WithClause withClause) {
+    _withClause = _becomeParentOf(withClause as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitClassTypeAlias(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    super.visitChildren(visitor);
+    _name?.accept(visitor);
+    _typeParameters?.accept(visitor);
+    _superclass?.accept(visitor);
+    _withClause?.accept(visitor);
+    _implementsClause?.accept(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.
+   */
+  @override
+  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.
+   */
+  @override
+  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 NodeListImpl<CommentReference>(this, references);
+  }
+
+  @override
+  Token get beginToken => tokens[0];
+
+  @override
+  Iterable<SyntacticEntity> 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
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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.
+   */
+  @override
+  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, IdentifierImpl identifier) {
+    _identifier = _becomeParentOf(identifier);
+  }
+
+  @override
+  Token get beginToken => _identifier.beginToken;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitCommentReference(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _identifier?.accept(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.
+   */
+  @override
+  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].
+   */
+  @override
+  Token endToken;
+
+  /**
+   * The element associated with this compilation unit, or `null` if the AST
+   * structure has not been resolved.
+   */
+  @override
+  CompilationUnitElement element;
+
+  /**
+   * The line information for this compilation unit.
+   */
+  @override
+  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,
+      ScriptTagImpl scriptTag,
+      List<Directive> directives,
+      List<CompilationUnitMember> declarations,
+      this.endToken) {
+    _scriptTag = _becomeParentOf(scriptTag);
+    _directives = new NodeListImpl<Directive>(this, directives);
+    _declarations = new NodeListImpl<CompilationUnitMember>(this, declarations);
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @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
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitCompilationUnit(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _scriptTag?.accept(visitor);
+    if (_directivesAreBeforeDeclarations) {
+      _directives.accept(visitor);
+      _declarations.accept(visitor);
+    } else {
+      int length = sortedDirectivesAndDeclarations.length;
+      for (int i = 0; i < length; i++) {
+        AstNode child = sortedDirectivesAndDeclarations[i];
+        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.
+   */
+  @override
+  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.
+   */
+  @override
+  Token colon;
+
+  /**
+   * The expression that is executed if the condition evaluates to `false`.
+   */
+  Expression _elseExpression;
+
+  /**
+   * Initialize a newly created conditional expression.
+   */
+  ConditionalExpressionImpl(
+      ExpressionImpl condition,
+      this.question,
+      ExpressionImpl thenExpression,
+      this.colon,
+      ExpressionImpl elseExpression) {
+    _condition = _becomeParentOf(condition);
+    _thenExpression = _becomeParentOf(thenExpression);
+    _elseExpression = _becomeParentOf(elseExpression);
+  }
+
+  @override
+  Token get beginToken => _condition.beginToken;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  Expression get elseExpression => _elseExpression;
+
+  @override
+  void set elseExpression(Expression expression) {
+    _elseExpression = _becomeParentOf(expression as AstNodeImpl);
+  }
+
+  @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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitConditionalExpression(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _condition?.accept(visitor);
+    _thenExpression?.accept(visitor);
+    _elseExpression?.accept(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 {
+  @override
+  Token ifKeyword;
+
+  @override
+  Token leftParenthesis;
+
+  DottedName _name;
+
+  @override
+  Token equalToken;
+
+  StringLiteral _value;
+
+  @override
+  Token rightParenthesis;
+
+  StringLiteral _uri;
+
+  @override
+  Source uriSource;
+
+  ConfigurationImpl(
+      this.ifKeyword,
+      this.leftParenthesis,
+      DottedNameImpl name,
+      this.equalToken,
+      StringLiteralImpl value,
+      this.rightParenthesis,
+      StringLiteralImpl libraryUri) {
+    _name = _becomeParentOf(name);
+    _value = _becomeParentOf(value);
+    _uri = _becomeParentOf(libraryUri);
+  }
+
+  @override
+  Token get beginToken => ifKeyword;
+
+  @override
+  Iterable<SyntacticEntity> get childEntities => new ChildEntities()
+    ..add(ifKeyword)
+    ..add(leftParenthesis)
+    ..add(_name)
+    ..add(equalToken)
+    ..add(_value)
+    ..add(rightParenthesis)
+    ..add(_uri);
+
+  @override
+  Token get endToken => _uri.endToken;
+
+  @deprecated
+  @override
+  StringLiteral get libraryUri => _uri;
+
+  @deprecated
+  @override
+  void set libraryUri(StringLiteral libraryUri) {
+    _uri = _becomeParentOf(libraryUri as AstNodeImpl);
+  }
+
+  @override
+  DottedName get name => _name;
+
+  @override
+  void set name(DottedName name) {
+    _name = _becomeParentOf(name as AstNodeImpl);
+  }
+
+  @override
+  StringLiteral get uri => _uri;
+
+  @override
+  void set uri(StringLiteral uri) {
+    _uri = _becomeParentOf(uri as AstNodeImpl);
+  }
+
+  @override
+  StringLiteral get value => _value;
+
+  @override
+  void set value(StringLiteral value) {
+    _value = _becomeParentOf(value as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitConfiguration(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _name?.accept(visitor);
+    _value?.accept(visitor);
+    _uri?.accept(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.
+   */
+  @override
+  Token externalKeyword;
+
+  /**
+   * The token for the 'const' keyword, or `null` if the constructor is not a
+   * const constructor.
+   */
+  @override
+  Token constKeyword;
+
+  /**
+   * The token for the 'factory' keyword, or `null` if the constructor is not a
+   * factory constructor.
+   */
+  @override
+  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.
+   */
+  @override
+  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.
+   */
+  @override
+  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.
+   */
+  @override
+  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(
+      CommentImpl comment,
+      List<Annotation> metadata,
+      this.externalKeyword,
+      this.constKeyword,
+      this.factoryKeyword,
+      IdentifierImpl returnType,
+      this.period,
+      SimpleIdentifierImpl name,
+      FormalParameterListImpl parameters,
+      this.separator,
+      List<ConstructorInitializer> initializers,
+      ConstructorNameImpl redirectedConstructor,
+      FunctionBodyImpl body)
+      : super(comment, metadata) {
+    _returnType = _becomeParentOf(returnType);
+    _name = _becomeParentOf(name);
+    _parameters = _becomeParentOf(parameters);
+    _initializers =
+        new NodeListImpl<ConstructorInitializer>(this, initializers);
+    _redirectedConstructor = _becomeParentOf(redirectedConstructor);
+    _body = _becomeParentOf(body);
+  }
+
+  @override
+  FunctionBody get body => _body;
+
+  @override
+  void set body(FunctionBody functionBody) {
+    _body = _becomeParentOf(functionBody as AstNodeImpl);
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  FormalParameterList get parameters => _parameters;
+
+  @override
+  void set parameters(FormalParameterList parameters) {
+    _parameters = _becomeParentOf(parameters as AstNodeImpl);
+  }
+
+  @override
+  ConstructorName get redirectedConstructor => _redirectedConstructor;
+
+  @override
+  void set redirectedConstructor(ConstructorName redirectedConstructor) {
+    _redirectedConstructor =
+        _becomeParentOf(redirectedConstructor as AstNodeImpl);
+  }
+
+  @override
+  Identifier get returnType => _returnType;
+
+  @override
+  void set returnType(Identifier typeName) {
+    _returnType = _becomeParentOf(typeName as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitConstructorDeclaration(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    super.visitChildren(visitor);
+    _returnType?.accept(visitor);
+    _name?.accept(visitor);
+    _parameters?.accept(visitor);
+    _initializers.accept(visitor);
+    _redirectedConstructor?.accept(visitor);
+    _body?.accept(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.
+   */
+  @override
+  Token thisKeyword;
+
+  /**
+   * The token for the period after the 'this' keyword, or `null` if there is no
+   * 'this' keyword.
+   */
+  @override
+  Token period;
+
+  /**
+   * The name of the field being initialized.
+   */
+  SimpleIdentifier _fieldName;
+
+  /**
+   * The token for the equal sign between the field name and the expression.
+   */
+  @override
+  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,
+      SimpleIdentifierImpl fieldName, this.equals, ExpressionImpl expression) {
+    _fieldName = _becomeParentOf(fieldName);
+    _expression = _becomeParentOf(expression);
+  }
+
+  @override
+  Token get beginToken {
+    if (thisKeyword != null) {
+      return thisKeyword;
+    }
+    return _fieldName.beginToken;
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  SimpleIdentifier get fieldName => _fieldName;
+
+  @override
+  void set fieldName(SimpleIdentifier identifier) {
+    _fieldName = _becomeParentOf(identifier as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitConstructorFieldInitializer(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _fieldName?.accept(visitor);
+    _expression?.accept(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.
+   */
+  @override
+  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.
+   */
+  @override
+  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(
+      TypeNameImpl type, this.period, SimpleIdentifierImpl name) {
+    _type = _becomeParentOf(type);
+    _name = _becomeParentOf(name);
+  }
+
+  @override
+  Token get beginToken => _type.beginToken;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  TypeName get type => _type;
+
+  @override
+  void set type(TypeName type) {
+    _type = _becomeParentOf(type as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitConstructorName(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _type?.accept(visitor);
+    _name?.accept(visitor);
+  }
+}
+
+/**
+ * A continue statement.
+ *
+ *    continueStatement ::=
+ *        'continue' [SimpleIdentifier]? ';'
+ */
+class ContinueStatementImpl extends StatementImpl implements ContinueStatement {
+  /**
+   * The token representing the 'continue' keyword.
+   */
+  @override
+  Token continueKeyword;
+
+  /**
+   * The label associated with the statement, or `null` if there is no label.
+   */
+  SimpleIdentifier _label;
+
+  /**
+   * The semicolon terminating the statement.
+   */
+  @override
+  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, SimpleIdentifierImpl label, this.semicolon) {
+    _label = _becomeParentOf(label);
+  }
+
+  @override
+  Token get beginToken => continueKeyword;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitContinueStatement(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _label?.accept(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.
+   */
+  @override
+  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(CommentImpl comment, List<Annotation> metadata,
+      this.keyword, TypeNameImpl type, SimpleIdentifierImpl identifier)
+      : super(comment, metadata) {
+    _type = _becomeParentOf(type);
+    _identifier = _becomeParentOf(identifier);
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  bool get isConst => keyword?.keyword == Keyword.CONST;
+
+  @override
+  bool get isFinal => keyword?.keyword == Keyword.FINAL;
+
+  @override
+  TypeName get type => _type;
+
+  @override
+  void set type(TypeName typeName) {
+    _type = _becomeParentOf(typeName as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitDeclaredIdentifier(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    super.visitChildren(visitor);
+    _type?.accept(visitor);
+    _identifier?.accept(visitor);
+  }
+}
+
+/**
+ * A simple identifier that declares a name.
+ */
+// TODO(rnystrom): Consider making this distinct from [SimpleIdentifier] and
+// get rid of all of the:
+//
+//     if (node.inDeclarationContext()) { ... }
+//
+// code and instead visit this separately. A declaration is semantically pretty
+// different from a use, so using the same node type doesn't seem to buy us
+// much.
+class DeclaredSimpleIdentifier extends SimpleIdentifierImpl {
+  DeclaredSimpleIdentifier(Token token) : super(token);
+
+  @override
+  bool inDeclarationContext() => true;
+}
+
+/**
+ * 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.
+   */
+  @override
+  ParameterKind kind;
+
+  /**
+   * The token separating the parameter from the default value, or `null` if
+   * there is no default value.
+   */
+  @override
+  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(NormalFormalParameterImpl parameter, this.kind,
+      this.separator, ExpressionImpl defaultValue) {
+    _parameter = _becomeParentOf(parameter);
+    _defaultValue = _becomeParentOf(defaultValue);
+  }
+
+  @override
+  Token get beginToken => _parameter.beginToken;
+
+  @override
+  Iterable<SyntacticEntity> get childEntities =>
+      new ChildEntities()..add(_parameter)..add(separator)..add(_defaultValue);
+
+  @override
+  Expression get defaultValue => _defaultValue;
+
+  @override
+  void set defaultValue(Expression expression) {
+    _defaultValue = _becomeParentOf(expression as AstNodeImpl);
+  }
+
+  @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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitDefaultFormalParameter(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _parameter?.accept(visitor);
+    _defaultValue?.accept(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);
+
+  @override
+  Element get element => _element;
+
+  /**
+   * Set the element associated with this directive to be the given [element].
+   */
+  void set element(Element element) {
+    _element = element;
+  }
+}
+
+/**
+ * A do statement.
+ *
+ *    doStatement ::=
+ *        'do' [Statement] 'while' '(' [Expression] ')' ';'
+ */
+class DoStatementImpl extends StatementImpl implements DoStatement {
+  /**
+   * The token representing the 'do' keyword.
+   */
+  @override
+  Token doKeyword;
+
+  /**
+   * The body of the loop.
+   */
+  Statement _body;
+
+  /**
+   * The token representing the 'while' keyword.
+   */
+  @override
+  Token whileKeyword;
+
+  /**
+   * The left parenthesis.
+   */
+  Token leftParenthesis;
+
+  /**
+   * The condition that determines when the loop will terminate.
+   */
+  Expression _condition;
+
+  /**
+   * The right parenthesis.
+   */
+  @override
+  Token rightParenthesis;
+
+  /**
+   * The semicolon terminating the statement.
+   */
+  @override
+  Token semicolon;
+
+  /**
+   * Initialize a newly created do loop.
+   */
+  DoStatementImpl(
+      this.doKeyword,
+      StatementImpl body,
+      this.whileKeyword,
+      this.leftParenthesis,
+      ExpressionImpl 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 as AstNodeImpl);
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  Token get endToken => semicolon;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitDoStatement(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _body?.accept(visitor);
+    _condition?.accept(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 NodeListImpl<SimpleIdentifier>(this, components);
+  }
+
+  @override
+  Token get beginToken => _components.beginToken;
+
+  @override
+  // TODO(paulberry): add "." tokens.
+  Iterable<SyntacticEntity> get childEntities =>
+      new ChildEntities()..addAll(_components);
+
+  @override
+  NodeList<SimpleIdentifier> get components => _components;
+
+  @override
+  Token get endToken => _components.endToken;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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.
+   */
+  @override
+  Token literal;
+
+  /**
+   * The value of the literal.
+   */
+  @override
+  double value;
+
+  /**
+   * Initialize a newly created floating point literal.
+   */
+  DoubleLiteralImpl(this.literal, this.value);
+
+  @override
+  Token get beginToken => literal;
+
+  @override
+  Iterable<SyntacticEntity> get childEntities =>
+      new ChildEntities()..add(literal);
+
+  @override
+  Token get endToken => literal;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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.
+   */
+  @override
+  Token semicolon;
+
+  /**
+   * Initialize a newly created function body.
+   */
+  EmptyFunctionBodyImpl(this.semicolon);
+
+  @override
+  Token get beginToken => semicolon;
+
+  @override
+  Iterable<SyntacticEntity> get childEntities =>
+      new ChildEntities()..add(semicolon);
+
+  @override
+  Token get endToken => semicolon;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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<SyntacticEntity> get childEntities =>
+      new ChildEntities()..add(semicolon);
+
+  @override
+  Token get endToken => semicolon;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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(
+      CommentImpl comment, List<Annotation> metadata, SimpleIdentifierImpl name)
+      : super(comment, metadata) {
+    _name = _becomeParentOf(name);
+  }
+
+  @override
+  Iterable<SyntacticEntity> get childEntities =>
+      super._childEntities..add(_name);
+
+  @override
+  FieldElement get element => _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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitEnumConstantDeclaration(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    super.visitChildren(visitor);
+    _name?.accept(visitor);
+  }
+}
+
+/**
+ * The declaration of an enumeration.
+ *
+ *    enumType ::=
+ *        metadata 'enum' [SimpleIdentifier] '{' [SimpleIdentifier] (',' [SimpleIdentifier])* (',')? '}'
+ */
+class EnumDeclarationImpl extends NamedCompilationUnitMemberImpl
+    implements EnumDeclaration {
+  /**
+   * The 'enum' keyword.
+   */
+  @override
+  Token enumKeyword;
+
+  /**
+   * The left curly bracket.
+   */
+  @override
+  Token leftBracket;
+
+  /**
+   * The enumeration constants being declared.
+   */
+  NodeList<EnumConstantDeclaration> _constants;
+
+  /**
+   * The right curly bracket.
+   */
+  @override
+  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 NodeListImpl<EnumConstantDeclaration>(this, constants);
+  }
+
+  @override
+  // TODO(brianwilkerson) Add commas?
+  Iterable<SyntacticEntity> 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?.staticElement as ClassElement;
+
+  @override
+  Token get endToken => rightBracket;
+
+  @override
+  Token get firstTokenAfterCommentAndMetadata => enumKeyword;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitEnumDeclaration(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    super.visitChildren(visitor);
+    _name?.accept(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<SyntacticEntity> 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
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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.
+   */
+  @override
+  Token keyword;
+
+  /**
+   * The token introducing the expression that represents the body of the
+   * function.
+   */
+  @override
+  Token functionDefinition;
+
+  /**
+   * The expression representing the body of the function.
+   */
+  Expression _expression;
+
+  /**
+   * The semicolon terminating the statement.
+   */
+  @override
+  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,
+      ExpressionImpl expression, this.semicolon) {
+    _expression = _becomeParentOf(expression);
+  }
+
+  @override
+  Token get beginToken {
+    if (keyword != null) {
+      return keyword;
+    }
+    return functionDefinition;
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  bool get isAsynchronous => keyword != null;
+
+  @override
+  bool get isSynchronous => keyword == null;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitExpressionFunctionBody(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _expression?.accept(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.
+   */
+  @override
+  DartType staticType;
+
+  /**
+   * The propagated type of this expression, or `null` if type propagation has
+   * not been performed on the AST structure.
+   */
+  @override
+  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;
+  }
+
+  @override
+  Expression get unParenthesized => this;
+}
+
+/**
+ * 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.
+   */
+  @override
+  Token semicolon;
+
+  /**
+   * Initialize a newly created expression statement.
+   */
+  ExpressionStatementImpl(ExpressionImpl expression, this.semicolon) {
+    _expression = _becomeParentOf(expression);
+  }
+
+  @override
+  Token get beginToken => _expression.beginToken;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  bool get isSynthetic => _expression.isSynthetic && semicolon.isSynthetic;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitExpressionStatement(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _expression?.accept(visitor);
+  }
+}
+
+/**
+ * The "extends" clause in a class declaration.
+ *
+ *    extendsClause ::=
+ *        'extends' [TypeName]
+ */
+class ExtendsClauseImpl extends AstNodeImpl implements ExtendsClause {
+  /**
+   * The token representing the 'extends' keyword.
+   */
+  @override
+  Token extendsKeyword;
+
+  /**
+   * The name of the class that is being extended.
+   */
+  TypeName _superclass;
+
+  /**
+   * Initialize a newly created extends clause.
+   */
+  ExtendsClauseImpl(this.extendsKeyword, TypeNameImpl superclass) {
+    _superclass = _becomeParentOf(superclass);
+  }
+
+  @override
+  Token get beginToken => extendsKeyword;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitExtendsClause(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _superclass?.accept(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.
+   */
+  @override
+  Token staticKeyword;
+
+  /**
+   * The fields being declared.
+   */
+  VariableDeclarationList _fieldList;
+
+  /**
+   * The semicolon terminating the declaration.
+   */
+  @override
+  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(CommentImpl comment, List<Annotation> metadata,
+      this.staticKeyword, VariableDeclarationListImpl fieldList, this.semicolon)
+      : super(comment, metadata) {
+    _fieldList = _becomeParentOf(fieldList);
+  }
+
+  @override
+  Iterable<SyntacticEntity> get childEntities =>
+      super._childEntities..add(staticKeyword)..add(_fieldList)..add(semicolon);
+
+  @override
+  Token get covariantKeyword => null;
+
+  @override
+  Element get element => null;
+
+  @override
+  Token get endToken => semicolon;
+
+  @override
+  VariableDeclarationList get fields => _fieldList;
+
+  @override
+  void set fields(VariableDeclarationList fields) {
+    _fieldList = _becomeParentOf(fields as AstNodeImpl);
+  }
+
+  @override
+  Token get firstTokenAfterCommentAndMetadata {
+    if (staticKeyword != null) {
+      return staticKeyword;
+    }
+    return _fieldList.beginToken;
+  }
+
+  @override
+  bool get isStatic => staticKeyword != null;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitFieldDeclaration(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    super.visitChildren(visitor);
+    _fieldList?.accept(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.
+   */
+  @override
+  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.
+   */
+  @override
+  Token thisKeyword;
+
+  /**
+   * The token representing the period.
+   */
+  @override
+  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(
+      CommentImpl comment,
+      List<Annotation> metadata,
+      this.keyword,
+      TypeNameImpl type,
+      this.thisKeyword,
+      this.period,
+      SimpleIdentifierImpl identifier,
+      TypeParameterListImpl typeParameters,
+      FormalParameterListImpl 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<SyntacticEntity> 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?.keyword == Keyword.CONST;
+
+  @override
+  bool get isFinal => keyword?.keyword == Keyword.FINAL;
+
+  @override
+  FormalParameterList get parameters => _parameters;
+
+  @override
+  void set parameters(FormalParameterList parameters) {
+    _parameters = _becomeParentOf(parameters as AstNodeImpl);
+  }
+
+  @override
+  TypeName get type => _type;
+
+  @override
+  void set type(TypeName typeName) {
+    _type = _becomeParentOf(typeName as AstNodeImpl);
+  }
+
+  @override
+  TypeParameterList get typeParameters => _typeParameters;
+
+  @override
+  void set typeParameters(TypeParameterList typeParameters) {
+    _typeParameters = _becomeParentOf(typeParameters as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitFieldFormalParameter(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    super.visitChildren(visitor);
+    _type?.accept(visitor);
+    identifier?.accept(visitor);
+    _typeParameters?.accept(visitor);
+    _parameters?.accept(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.
+   */
+  @override
+  Token awaitKeyword;
+
+  /**
+   * The token representing the 'for' keyword.
+   */
+  @override
+  Token forKeyword;
+
+  /**
+   * The left parenthesis.
+   */
+  @override
+  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.
+   */
+  @override
+  Token inKeyword;
+
+  /**
+   * The expression evaluated to produce the iterator.
+   */
+  Expression _iterable;
+
+  /**
+   * The right parenthesis.
+   */
+  @override
+  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,
+      DeclaredIdentifierImpl loopVariable,
+      this.inKeyword,
+      ExpressionImpl iterator,
+      this.rightParenthesis,
+      StatementImpl 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,
+      SimpleIdentifierImpl identifier,
+      this.inKeyword,
+      ExpressionImpl iterator,
+      this.rightParenthesis,
+      StatementImpl 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 as AstNodeImpl);
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  Expression get iterable => _iterable;
+
+  @override
+  void set iterable(Expression expression) {
+    _iterable = _becomeParentOf(expression as AstNodeImpl);
+  }
+
+  @override
+  DeclaredIdentifier get loopVariable => _loopVariable;
+
+  @override
+  void set loopVariable(DeclaredIdentifier variable) {
+    _loopVariable = _becomeParentOf(variable as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitForEachStatement(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _loopVariable?.accept(visitor);
+    _identifier?.accept(visitor);
+    _iterable?.accept(visitor);
+    _body?.accept(visitor);
+  }
+}
+
+/**
+ * A node representing a parameter to a function.
+ *
+ *    formalParameter ::=
+ *        [NormalFormalParameter]
+ *      | [DefaultFormalParameter]
+ */
+abstract class FormalParameterImpl extends AstNodeImpl
+    implements FormalParameter {
+  @override
+  Token get covariantKeyword => null;
+
+  @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.
+   */
+  @override
+  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.
+   */
+  @override
+  Token leftDelimiter;
+
+  /**
+   * The right square bracket (']') or right curly brace ('}') terminating the
+   * optional parameters, or `null` if there are no optional parameters.
+   */
+  @override
+  Token rightDelimiter;
+
+  /**
+   * The right parenthesis.
+   */
+  @override
+  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 NodeListImpl<FormalParameter>(this, parameters);
+  }
+
+  @override
+  Token get beginToken => leftParenthesis;
+
+  @override
+  Iterable<SyntacticEntity> get childEntities {
+    // TODO(paulberry): include commas.
+    ChildEntities result = new ChildEntities()..add(leftParenthesis);
+    bool leftDelimiterNeeded = leftDelimiter != null;
+    int length = _parameters.length;
+    for (int i = 0; i < length; i++) {
+      FormalParameter parameter = _parameters[i];
+      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
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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.
+   */
+  @override
+  Token forKeyword;
+
+  /**
+   * The left parenthesis.
+   */
+  @override
+  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.
+   */
+  @override
+  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.
+   */
+  @override
+  Token rightSeparator;
+
+  /**
+   * The list of expressions run after each execution of the loop body.
+   */
+  NodeList<Expression> _updaters;
+
+  /**
+   * The right parenthesis.
+   */
+  @override
+  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,
+      VariableDeclarationListImpl variableList,
+      ExpressionImpl initialization,
+      this.leftSeparator,
+      ExpressionImpl condition,
+      this.rightSeparator,
+      List<Expression> updaters,
+      this.rightParenthesis,
+      StatementImpl body) {
+    _variableList = _becomeParentOf(variableList);
+    _initialization = _becomeParentOf(initialization);
+    _condition = _becomeParentOf(condition);
+    _updaters = new NodeListImpl<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 as AstNodeImpl);
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  Token get endToken => _body.endToken;
+
+  @override
+  Expression get initialization => _initialization;
+
+  @override
+  void set initialization(Expression initialization) {
+    _initialization = _becomeParentOf(initialization as AstNodeImpl);
+  }
+
+  @override
+  NodeList<Expression> get updaters => _updaters;
+
+  @override
+  VariableDeclarationList get variables => _variableList;
+
+  @override
+  void set variables(VariableDeclarationList variableList) {
+    _variableList = _becomeParentOf(variableList as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitForStatement(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _variableList?.accept(visitor);
+    _initialization?.accept(visitor);
+    _condition?.accept(visitor);
+    _updaters.accept(visitor);
+    _body?.accept(visitor);
+  }
+}
+
+/**
+ * A node representing the body of a function or method.
+ *
+ *    functionBody ::=
+ *        [BlockFunctionBody]
+ *      | [EmptyFunctionBody]
+ *      | [ExpressionFunctionBody]
+ */
+abstract class FunctionBodyImpl extends AstNodeImpl implements FunctionBody {
+  /**
+   * Additional information about local variables and parameters that are
+   * declared within this function body or any enclosing function body.  `null`
+   * if resolution has not yet been performed.
+   */
+  LocalVariableInfo localVariableInfo;
+
+  /**
+   * Return `true` if this function body is asynchronous.
+   */
+  @override
+  bool get isAsynchronous => false;
+
+  /**
+   * Return `true` if this function body is a generator.
+   */
+  @override
+  bool get isGenerator => false;
+
+  /**
+   * Return `true` if this function body is synchronous.
+   */
+  @override
+  bool get isSynchronous => true;
+
+  /**
+   * Return the token representing the 'async' or 'sync' keyword, or `null` if
+   * there is no such keyword.
+   */
+  @override
+  Token get keyword => null;
+
+  /**
+   * Return the star following the 'async' or 'sync' keyword, or `null` if there
+   * is no star.
+   */
+  @override
+  Token get star => null;
+
+  @override
+  bool isPotentiallyMutatedInClosure(VariableElement variable) {
+    if (localVariableInfo == null) {
+      throw new StateError('Resolution has not yet been performed');
+    }
+    return localVariableInfo.potentiallyMutatedInClosure.contains(variable);
+  }
+
+  @override
+  bool isPotentiallyMutatedInScope(VariableElement variable) {
+    if (localVariableInfo == null) {
+      throw new StateError('Resolution has not yet been performed');
+    }
+    return localVariableInfo.potentiallyMutatedInScope.contains(variable);
+  }
+}
+
+/**
+ * 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.
+   */
+  @override
+  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.
+   */
+  @override
+  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(
+      CommentImpl comment,
+      List<Annotation> metadata,
+      this.externalKeyword,
+      TypeNameImpl returnType,
+      this.propertyKeyword,
+      SimpleIdentifierImpl name,
+      FunctionExpressionImpl functionExpression)
+      : super(comment, metadata, name) {
+    _returnType = _becomeParentOf(returnType);
+    _functionExpression = _becomeParentOf(functionExpression);
+  }
+
+  @override
+  Iterable<SyntacticEntity> get childEntities => super._childEntities
+    ..add(externalKeyword)
+    ..add(_returnType)
+    ..add(propertyKeyword)
+    ..add(_name)
+    ..add(_functionExpression);
+
+  @override
+  ExecutableElement get element => _name?.staticElement as ExecutableElement;
+
+  @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 as AstNodeImpl);
+  }
+
+  @override
+  bool get isGetter => propertyKeyword?.keyword == Keyword.GET;
+
+  @override
+  bool get isSetter => propertyKeyword?.keyword == Keyword.SET;
+
+  @override
+  TypeName get returnType => _returnType;
+
+  @override
+  void set returnType(TypeName returnType) {
+    _returnType = _becomeParentOf(returnType as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitFunctionDeclaration(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    super.visitChildren(visitor);
+    _returnType?.accept(visitor);
+    _name?.accept(visitor);
+    _functionExpression?.accept(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 as AstNodeImpl);
+  }
+
+  @override
+  Token get beginToken => _functionDeclaration.beginToken;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitFunctionDeclarationStatement(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _functionDeclaration?.accept(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.
+   */
+  @override
+  ExecutableElement element;
+
+  /**
+   * Initialize a newly created function declaration.
+   */
+  FunctionExpressionImpl(TypeParameterListImpl typeParameters,
+      FormalParameterListImpl parameters, FunctionBodyImpl 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 StateError("Non-external functions must have a body");
+  }
+
+  @override
+  FunctionBody get body => _body;
+
+  @override
+  void set body(FunctionBody functionBody) {
+    _body = _becomeParentOf(functionBody as AstNodeImpl);
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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 StateError("Non-external functions must have a body");
+  }
+
+  @override
+  FormalParameterList get parameters => _parameters;
+
+  @override
+  void set parameters(FormalParameterList parameters) {
+    _parameters = _becomeParentOf(parameters as AstNodeImpl);
+  }
+
+  @override
+  int get precedence => 16;
+
+  @override
+  TypeParameterList get typeParameters => _typeParameters;
+
+  @override
+  void set typeParameters(TypeParameterList typeParameters) {
+    _typeParameters = _becomeParentOf(typeParameters as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitFunctionExpression(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _typeParameters?.accept(visitor);
+    _parameters?.accept(visitor);
+    _body?.accept(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 InvocationExpressionImpl
+    implements FunctionExpressionInvocation {
+  /**
+   * The expression producing the function being invoked.
+   */
+  Expression _function;
+
+  /**
+   * 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.
+   */
+  @override
+  ExecutableElement staticElement;
+
+  /**
+   * 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.
+   */
+  @override
+  ExecutableElement propagatedElement;
+
+  /**
+   * Initialize a newly created function expression invocation.
+   */
+  FunctionExpressionInvocationImpl(ExpressionImpl function,
+      TypeArgumentListImpl typeArguments, ArgumentListImpl argumentList)
+      : super(typeArguments, argumentList) {
+    _function = _becomeParentOf(function);
+  }
+
+  @override
+  Token get beginToken => _function.beginToken;
+
+  @override
+  ExecutableElement get bestElement {
+    ExecutableElement element = propagatedElement;
+    if (element == null) {
+      element = staticElement;
+    }
+    return element;
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  int get precedence => 15;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitFunctionExpressionInvocation(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _function?.accept(visitor);
+    _typeArguments?.accept(visitor);
+    _argumentList?.accept(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(
+      CommentImpl comment,
+      List<Annotation> metadata,
+      Token keyword,
+      TypeNameImpl returnType,
+      SimpleIdentifierImpl name,
+      TypeParameterListImpl typeParameters,
+      FormalParameterListImpl parameters,
+      Token semicolon)
+      : super(comment, metadata, keyword, name, semicolon) {
+    _returnType = _becomeParentOf(returnType);
+    _typeParameters = _becomeParentOf(typeParameters);
+    _parameters = _becomeParentOf(parameters);
+  }
+
+  @override
+  Iterable<SyntacticEntity> get childEntities => super._childEntities
+    ..add(typedefKeyword)
+    ..add(_returnType)
+    ..add(_name)
+    ..add(_typeParameters)
+    ..add(_parameters)
+    ..add(semicolon);
+
+  @override
+  FunctionTypeAliasElement get element =>
+      _name?.staticElement as FunctionTypeAliasElement;
+
+  @override
+  FormalParameterList get parameters => _parameters;
+
+  @override
+  void set parameters(FormalParameterList parameters) {
+    _parameters = _becomeParentOf(parameters as AstNodeImpl);
+  }
+
+  @override
+  TypeName get returnType => _returnType;
+
+  @override
+  void set returnType(TypeName typeName) {
+    _returnType = _becomeParentOf(typeName as AstNodeImpl);
+  }
+
+  @override
+  TypeParameterList get typeParameters => _typeParameters;
+
+  @override
+  void set typeParameters(TypeParameterList typeParameters) {
+    _typeParameters = _becomeParentOf(typeParameters as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitFunctionTypeAlias(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    super.visitChildren(visitor);
+    _returnType?.accept(visitor);
+    _name?.accept(visitor);
+    _typeParameters?.accept(visitor);
+    _parameters?.accept(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;
+
+  @override
+  Token question;
+
+  /**
+   * 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(
+      CommentImpl comment,
+      List<Annotation> metadata,
+      TypeNameImpl returnType,
+      SimpleIdentifierImpl identifier,
+      TypeParameterListImpl typeParameters,
+      FormalParameterListImpl parameters,
+      this.question)
+      : 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<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  TypeName get returnType => _returnType;
+
+  @override
+  void set returnType(TypeName type) {
+    _returnType = _becomeParentOf(type as AstNodeImpl);
+  }
+
+  @override
+  TypeParameterList get typeParameters => _typeParameters;
+
+  @override
+  void set typeParameters(TypeParameterList typeParameters) {
+    _typeParameters = _becomeParentOf(typeParameters as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitFunctionTypedFormalParameter(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    super.visitChildren(visitor);
+    _returnType?.accept(visitor);
+    identifier?.accept(visitor);
+    _typeParameters?.accept(visitor);
+    _parameters?.accept(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 NodeListImpl<SimpleIdentifier>(this, hiddenNames);
+  }
+
+  @override
+  Iterable<SyntacticEntity> get childEntities => new ChildEntities()
+    ..add(keyword)
+    ..addAll(_hiddenNames);
+
+  @override
+  Token get endToken => _hiddenNames.endToken;
+
+  @override
+  NodeList<SimpleIdentifier> get hiddenNames => _hiddenNames;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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.
+   */
+  @override
+  Token ifKeyword;
+
+  /**
+   * The left parenthesis.
+   */
+  @override
+  Token leftParenthesis;
+
+  /**
+   * The condition used to determine which of the statements is executed next.
+   */
+  Expression _condition;
+
+  /**
+   * The right parenthesis.
+   */
+  @override
+  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.
+   */
+  @override
+  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,
+      ExpressionImpl condition,
+      this.rightParenthesis,
+      StatementImpl thenStatement,
+      this.elseKeyword,
+      StatementImpl elseStatement) {
+    _condition = _becomeParentOf(condition);
+    _thenStatement = _becomeParentOf(thenStatement);
+    _elseStatement = _becomeParentOf(elseStatement);
+  }
+
+  @override
+  Token get beginToken => ifKeyword;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  Statement get elseStatement => _elseStatement;
+
+  @override
+  void set elseStatement(Statement statement) {
+    _elseStatement = _becomeParentOf(statement as AstNodeImpl);
+  }
+
+  @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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitIfStatement(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _condition?.accept(visitor);
+    _thenStatement?.accept(visitor);
+    _elseStatement?.accept(visitor);
+  }
+}
+
+/**
+ * The "implements" clause in an class declaration.
+ *
+ *    implementsClause ::=
+ *        'implements' [TypeName] (',' [TypeName])*
+ */
+class ImplementsClauseImpl extends AstNodeImpl implements ImplementsClause {
+  /**
+   * The token representing the 'implements' keyword.
+   */
+  @override
+  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 NodeListImpl<TypeName>(this, interfaces);
+  }
+
+  @override
+  Token get beginToken => implementsKeyword;
+
+  @override
+  // TODO(paulberry): add commas.
+  Iterable<SyntacticEntity> get childEntities => new ChildEntities()
+    ..add(implementsKeyword)
+    ..addAll(interfaces);
+
+  @override
+  Token get endToken => _interfaces.endToken;
+
+  @override
+  NodeList<TypeName> get interfaces => _interfaces;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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.
+   */
+  @override
+  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(
+      CommentImpl comment,
+      List<Annotation> metadata,
+      Token keyword,
+      StringLiteralImpl libraryUri,
+      List<Configuration> configurations,
+      this.deferredKeyword,
+      this.asKeyword,
+      SimpleIdentifierImpl prefix,
+      List<Combinator> combinators,
+      Token semicolon)
+      : super(comment, metadata, keyword, libraryUri, configurations,
+            combinators, semicolon) {
+    _prefix = _becomeParentOf(prefix);
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  LibraryElement get uriElement {
+    ImportElement element = this.element;
+    if (element == null) {
+      return null;
+    }
+    return element.importedLibrary;
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitImportDirective(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    super.visitChildren(visitor);
+    _prefix?.accept(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.
+   */
+  @override
+  Token period;
+
+  /**
+   * The left square bracket.
+   */
+  @override
+  Token leftBracket;
+
+  /**
+   * The expression used to compute the index.
+   */
+  Expression _index;
+
+  /**
+   * The right square bracket.
+   */
+  @override
+  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.
+   */
+  @override
+  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.
+   */
+
+  @override
+  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, ExpressionImpl index, this.rightBracket) {
+    _index = _becomeParentOf(index);
+  }
+
+  /**
+   * Initialize a newly created index expression.
+   */
+  IndexExpressionImpl.forTarget(ExpressionImpl target, this.leftBracket,
+      ExpressionImpl 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<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @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 as AstNodeImpl);
+  }
+
+  /**
+   * 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
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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) {
+    _target?.accept(visitor);
+    _index?.accept(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.
+   */
+  @override
+  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.
+   */
+  @override
+  ConstructorElement staticElement;
+
+  /**
+   * Initialize a newly created instance creation expression.
+   */
+  InstanceCreationExpressionImpl(this.keyword,
+      ConstructorNameImpl constructorName, ArgumentListImpl argumentList) {
+    _constructorName = _becomeParentOf(constructorName);
+    _argumentList = _becomeParentOf(argumentList);
+  }
+
+  @override
+  ArgumentList get argumentList => _argumentList;
+
+  @override
+  void set argumentList(ArgumentList argumentList) {
+    _argumentList = _becomeParentOf(argumentList as AstNodeImpl);
+  }
+
+  @override
+  Token get beginToken => keyword;
+
+  @override
+  Iterable<SyntacticEntity> get childEntities => new ChildEntities()
+    ..add(keyword)
+    ..add(_constructorName)
+    ..add(_argumentList);
+
+  @override
+  ConstructorName get constructorName => _constructorName;
+
+  @override
+  void set constructorName(ConstructorName name) {
+    _constructorName = _becomeParentOf(name as AstNodeImpl);
+  }
+
+  @override
+  Token get endToken => _argumentList.endToken;
+
+  @override
+  bool get isConst => keyword?.keyword == Keyword.CONST;
+
+  @override
+  int get precedence => 16;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitInstanceCreationExpression(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _constructorName?.accept(visitor);
+    _argumentList?.accept(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.
+   */
+  @override
+  Token literal;
+
+  /**
+   * The value of the literal.
+   */
+  @override
+  int value = 0;
+
+  /**
+   * Initialize a newly created integer literal.
+   */
+  IntegerLiteralImpl(this.literal, this.value);
+
+  @override
+  Token get beginToken => literal;
+
+  @override
+  Iterable<SyntacticEntity> get childEntities =>
+      new ChildEntities()..add(literal);
+
+  @override
+  Token get endToken => literal;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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.
+   */
+  @override
+  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.
+   */
+  @override
+  Token rightBracket;
+
+  /**
+   * Initialize a newly created interpolation expression.
+   */
+  InterpolationExpressionImpl(
+      this.leftBracket, ExpressionImpl expression, this.rightBracket) {
+    _expression = _becomeParentOf(expression);
+  }
+
+  @override
+  Token get beginToken => leftBracket;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitInterpolationExpression(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _expression?.accept(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.
+   */
+  @override
+  Token contents;
+
+  /**
+   * The value of the literal.
+   */
+  @override
+  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<SyntacticEntity> 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
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitInterpolationString(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {}
+}
+
+/**
+ * Common base class for [FunctionExpressionInvocationImpl] and
+ * [MethodInvocationImpl].
+ */
+abstract class InvocationExpressionImpl extends ExpressionImpl
+    implements InvocationExpression {
+  /**
+   * The list of arguments to the function.
+   */
+  ArgumentList _argumentList;
+
+  /**
+   * The type arguments to be applied to the method being invoked, or `null` if
+   * no type arguments were provided.
+   */
+  TypeArgumentList _typeArguments;
+
+  @override
+  DartType propagatedInvokeType;
+
+  @override
+  DartType staticInvokeType;
+
+  /**
+   * Initialize a newly created invocation.
+   */
+  InvocationExpressionImpl(
+      TypeArgumentListImpl typeArguments, ArgumentListImpl argumentList) {
+    _typeArguments = _becomeParentOf(typeArguments);
+    _argumentList = _becomeParentOf(argumentList);
+  }
+
+  @override
+  ArgumentList get argumentList => _argumentList;
+
+  void set argumentList(ArgumentList argumentList) {
+    _argumentList = _becomeParentOf(argumentList as AstNodeImpl);
+  }
+
+  @override
+  TypeArgumentList get typeArguments => _typeArguments;
+
+  void set typeArguments(TypeArgumentList typeArguments) {
+    _typeArguments = _becomeParentOf(typeArguments as AstNodeImpl);
+  }
+}
+
+/**
+ * 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.
+   */
+  @override
+  Token isOperator;
+
+  /**
+   * The not operator, or `null` if the sense of the test is not negated.
+   */
+  @override
+  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(ExpressionImpl expression, this.isOperator, this.notOperator,
+      TypeNameImpl type) {
+    _expression = _becomeParentOf(expression);
+    _type = _becomeParentOf(type);
+  }
+
+  @override
+  Token get beginToken => _expression.beginToken;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  int get precedence => 7;
+
+  @override
+  TypeName get type => _type;
+
+  @override
+  void set type(TypeName name) {
+    _type = _becomeParentOf(name as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitIsExpression(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _expression?.accept(visitor);
+    _type?.accept(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, StatementImpl statement) {
+    _labels = new NodeListImpl<Label>(this, labels);
+    _statement = _becomeParentOf(statement);
+  }
+
+  @override
+  Token get beginToken {
+    if (!_labels.isEmpty) {
+      return _labels.beginToken;
+    }
+    return _statement.beginToken;
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  Statement get unlabeled => _statement.unlabeled;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitLabeledStatement(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _labels.accept(visitor);
+    _statement?.accept(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.
+   */
+  @override
+  Token colon;
+
+  /**
+   * Initialize a newly created label.
+   */
+  LabelImpl(SimpleIdentifierImpl label, this.colon) {
+    _label = _becomeParentOf(label);
+  }
+
+  @override
+  Token get beginToken => _label.beginToken;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitLabel(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _label?.accept(visitor);
+  }
+}
+
+/**
+ * A library directive.
+ *
+ *    libraryDirective ::=
+ *        [Annotation] 'library' [Identifier] ';'
+ */
+class LibraryDirectiveImpl extends DirectiveImpl implements LibraryDirective {
+  /**
+   * The token representing the 'library' keyword.
+   */
+  @override
+  Token libraryKeyword;
+
+  /**
+   * The name of the library being defined.
+   */
+  LibraryIdentifier _name;
+
+  /**
+   * The semicolon terminating the directive.
+   */
+  @override
+  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(CommentImpl comment, List<Annotation> metadata,
+      this.libraryKeyword, LibraryIdentifierImpl name, this.semicolon)
+      : super(comment, metadata) {
+    _name = _becomeParentOf(name);
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitLibraryDirective(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    super.visitChildren(visitor);
+    _name?.accept(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 NodeListImpl<SimpleIdentifier>(this, components);
+  }
+
+  @override
+  Token get beginToken => _components.beginToken;
+
+  @override
+  Element get bestElement => staticElement;
+
+  @override
+  // TODO(paulberry): add "." tokens.
+  Iterable<SyntacticEntity> 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;
+    int length = _components.length;
+    for (int i = 0; i < length; i++) {
+      SimpleIdentifier identifier = _components[i];
+      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
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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.
+   */
+  @override
+  Token leftBracket;
+
+  /**
+   * The expressions used to compute the elements of the list.
+   */
+  NodeList<Expression> _elements;
+
+  /**
+   * The right square bracket.
+   */
+  @override
+  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 NodeListImpl<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<SyntacticEntity> get childEntities => super._childEntities
+    ..add(leftBracket)
+    ..addAll(_elements)
+    ..add(rightBracket);
+
+  @override
+  NodeList<Expression> get elements => _elements;
+
+  @override
+  Token get endToken => rightBracket;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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;
+}
+
+/**
+ * Additional information about local variables within a function or method
+ * produced at resolution time.
+ */
+class LocalVariableInfo {
+  /**
+   * The set of local variables and parameters that are potentially mutated
+   * within a local function other than the function in which they are declared.
+   */
+  final Set<VariableElement> potentiallyMutatedInClosure =
+      new Set<VariableElement>();
+
+  /**
+   * The set of local variables and parameters that are potentiall mutated
+   * within the scope of their declarations.
+   */
+  final Set<VariableElement> potentiallyMutatedInScope =
+      new Set<VariableElement>();
+}
+
+/**
+ * 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.
+   */
+  @override
+  Token separator;
+
+  /**
+   * The expression computing the value that will be associated with the key.
+   */
+  Expression _value;
+
+  /**
+   * Initialize a newly created map literal entry.
+   */
+  MapLiteralEntryImpl(
+      ExpressionImpl key, this.separator, ExpressionImpl value) {
+    _key = _becomeParentOf(key);
+    _value = _becomeParentOf(value);
+  }
+
+  @override
+  Token get beginToken => _key.beginToken;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  Expression get value => _value;
+
+  @override
+  void set value(Expression expression) {
+    _value = _becomeParentOf(expression as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitMapLiteralEntry(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _key?.accept(visitor);
+    _value?.accept(visitor);
+  }
+}
+
+/**
+ * A literal map.
+ *
+ *    mapLiteral ::=
+ *        'const'? ('<' [TypeName] (',' [TypeName])* '>')?
+ *        '{' ([MapLiteralEntry] (',' [MapLiteralEntry])* ','?)? '}'
+ */
+class MapLiteralImpl extends TypedLiteralImpl implements MapLiteral {
+  /**
+   * The left curly bracket.
+   */
+  @override
+  Token leftBracket;
+
+  /**
+   * The entries in the map.
+   */
+  NodeList<MapLiteralEntry> _entries;
+
+  /**
+   * The right curly bracket.
+   */
+  @override
+  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 NodeListImpl<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<SyntacticEntity> get childEntities => super._childEntities
+    ..add(leftBracket)
+    ..addAll(entries)
+    ..add(rightBracket);
+
+  @override
+  Token get endToken => rightBracket;
+
+  @override
+  NodeList<MapLiteralEntry> get entries => _entries;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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.
+   */
+  @override
+  Token externalKeyword;
+
+  /**
+   * The token representing the 'abstract' or 'static' keyword, or `null` if
+   * neither modifier was specified.
+   */
+  @override
+  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.
+   */
+  @override
+  Token propertyKeyword;
+
+  /**
+   * The token representing the 'operator' keyword, or `null` if this method
+   * does not declare an operator.
+   */
+  @override
+  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(
+      CommentImpl comment,
+      List<Annotation> metadata,
+      this.externalKeyword,
+      this.modifierKeyword,
+      TypeNameImpl returnType,
+      this.propertyKeyword,
+      this.operatorKeyword,
+      SimpleIdentifierImpl name,
+      TypeParameterListImpl typeParameters,
+      FormalParameterListImpl parameters,
+      FunctionBodyImpl 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 as AstNodeImpl);
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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?.staticElement as ExecutableElement;
+
+  @override
+  Token get endToken => _body.endToken;
+
+  @override
+  Token get firstTokenAfterCommentAndMetadata {
+    if (externalKeyword != null) {
+      return externalKeyword;
+    } else 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?.keyword == Keyword.GET;
+
+  @override
+  bool get isOperator => operatorKeyword != null;
+
+  @override
+  bool get isSetter => propertyKeyword?.keyword == Keyword.SET;
+
+  @override
+  bool get isStatic => modifierKeyword?.keyword == Keyword.STATIC;
+
+  @override
+  SimpleIdentifier get name => _name;
+
+  @override
+  void set name(SimpleIdentifier identifier) {
+    _name = _becomeParentOf(identifier as AstNodeImpl);
+  }
+
+  @override
+  FormalParameterList get parameters => _parameters;
+
+  @override
+  void set parameters(FormalParameterList parameters) {
+    _parameters = _becomeParentOf(parameters as AstNodeImpl);
+  }
+
+  @override
+  TypeName get returnType => _returnType;
+
+  @override
+  void set returnType(TypeName typeName) {
+    _returnType = _becomeParentOf(typeName as AstNodeImpl);
+  }
+
+  @override
+  TypeParameterList get typeParameters => _typeParameters;
+
+  @override
+  void set typeParameters(TypeParameterList typeParameters) {
+    _typeParameters = _becomeParentOf(typeParameters as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitMethodDeclaration(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    super.visitChildren(visitor);
+    _returnType?.accept(visitor);
+    _name?.accept(visitor);
+    _typeParameters?.accept(visitor);
+    _parameters?.accept(visitor);
+    _body?.accept(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 InvocationExpressionImpl
+    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
+   * ('..').
+   */
+  @override
+  Token operator;
+
+  /**
+   * The name of the method being invoked.
+   */
+  SimpleIdentifier _methodName;
+
+  /**
+   * Initialize a newly created method invocation. The [target] and [operator]
+   * can be `null` if there is no target.
+   */
+  MethodInvocationImpl(
+      ExpressionImpl target,
+      this.operator,
+      SimpleIdentifierImpl methodName,
+      TypeArgumentListImpl typeArguments,
+      ArgumentListImpl argumentList)
+      : super(typeArguments, argumentList) {
+    _target = _becomeParentOf(target);
+    _methodName = _becomeParentOf(methodName);
+  }
+
+  @override
+  Token get beginToken {
+    if (_target != null) {
+      return _target.beginToken;
+    } else if (operator != null) {
+      return operator;
+    }
+    return _methodName.beginToken;
+  }
+
+  @override
+  Iterable<SyntacticEntity> get childEntities => new ChildEntities()
+    ..add(_target)
+    ..add(operator)
+    ..add(_methodName)
+    ..add(_argumentList);
+
+  @override
+  Token get endToken => _argumentList.endToken;
+
+  @override
+  Expression get function => methodName;
+
+  @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 as AstNodeImpl);
+  }
+
+  @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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitMethodInvocation(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _target?.accept(visitor);
+    _methodName?.accept(visitor);
+    _typeArguments?.accept(visitor);
+    _argumentList?.accept(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(
+      CommentImpl comment, List<Annotation> metadata, SimpleIdentifierImpl name)
+      : super(comment, metadata) {
+    _name = _becomeParentOf(name);
+  }
+
+  @override
+  SimpleIdentifier get name => _name;
+
+  @override
+  void set name(SimpleIdentifier identifier) {
+    _name = _becomeParentOf(identifier as AstNodeImpl);
+  }
+}
+
+/**
+ * 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(LabelImpl name, ExpressionImpl expression) {
+    _name = _becomeParentOf(name);
+    _expression = _becomeParentOf(expression);
+  }
+
+  @override
+  Token get beginToken => _name.beginToken;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  Label get name => _name;
+
+  @override
+  void set name(Label identifier) {
+    _name = _becomeParentOf(identifier as AstNodeImpl);
+  }
+
+  @override
+  int get precedence => 0;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitNamedExpression(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _name?.accept(visitor);
+    _expression?.accept(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.
+   */
+  @override
+  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.
+   */
+  @override
+  Token semicolon;
+
+  @override
+  String selectedUriContent;
+
+  @override
+  Source selectedSource;
+
+  /**
+   * 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 NodeListImpl<Configuration>(this, configurations);
+    _combinators = new NodeListImpl<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;
+
+  @deprecated
+  @override
+  Source get source => selectedSource;
+
+  @deprecated
+  @override
+  void set source(Source source) {
+    selectedSource = source;
+  }
+
+  @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.
+   */
+  @override
+  Token nativeKeyword;
+
+  /**
+   * The name of the native object that implements the class.
+   */
+  StringLiteral _name;
+
+  /**
+   * Initialize a newly created native clause.
+   */
+  NativeClauseImpl(this.nativeKeyword, StringLiteralImpl name) {
+    _name = _becomeParentOf(name);
+  }
+
+  @override
+  Token get beginToken => nativeKeyword;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitNativeClause(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _name?.accept(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.
+   */
+  @override
+  Token nativeKeyword;
+
+  /**
+   * The string literal, after the 'native' token.
+   */
+  StringLiteral _stringLiteral;
+
+  /**
+   * The token representing the semicolon that marks the end of the function
+   * body.
+   */
+  @override
+  Token semicolon;
+
+  /**
+   * Initialize a newly created function body consisting of the 'native' token,
+   * a string literal, and a semicolon.
+   */
+  NativeFunctionBodyImpl(
+      this.nativeKeyword, StringLiteralImpl stringLiteral, this.semicolon) {
+    _stringLiteral = _becomeParentOf(stringLiteral);
+  }
+
+  @override
+  Token get beginToken => nativeKeyword;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitNativeFunctionBody(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _stringLiteral?.accept(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.");
+  }
+
+  @override
+  AstNode get owner => _owner;
+
+  @override
+  void set owner(AstNode value) {
+    _owner = value as AstNodeImpl;
+  }
+
+  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 as AstNodeImpl);
+    _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) {
+      if (nodes is List<E>) {
+        int length = nodes.length;
+        for (int i = 0; i < length; i++) {
+          E node = nodes[i];
+          _elements.add(node);
+          _owner._becomeParentOf(node as AstNodeImpl);
+        }
+      } else {
+        for (E node in nodes) {
+          _elements.add(node);
+          _owner._becomeParentOf(node as AstNodeImpl);
+        }
+      }
+      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 as AstNodeImpl);
+    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(CommentImpl comment, List<Annotation> metadata,
+      SimpleIdentifierImpl identifier) {
+    _comment = _becomeParentOf(comment);
+    _metadata = new NodeListImpl<Annotation>(this, metadata);
+    _identifier = _becomeParentOf(identifier);
+  }
+
+  @override
+  Comment get documentationComment => _comment;
+
+  @override
+  void set documentationComment(Comment comment) {
+    _comment = _becomeParentOf(comment as AstNodeImpl);
+  }
+
+  @override
+  SimpleIdentifier get identifier => _identifier;
+
+  @override
+  void set identifier(SimpleIdentifier identifier) {
+    _identifier = _becomeParentOf(identifier as AstNodeImpl);
+  }
+
+  @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()) {
+      _comment?.accept(visitor);
+      _metadata.accept(visitor);
+    } else {
+      List<AstNode> children = sortedCommentAndAnnotations;
+      int length = children.length;
+      for (int i = 0; i < length; i++) {
+        children[i].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<SyntacticEntity> get childEntities =>
+      new ChildEntities()..add(literal);
+
+  @override
+  Token get endToken => literal;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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, ExpressionImpl expression, this.rightParenthesis) {
+    _expression = _becomeParentOf(expression);
+  }
+
+  @override
+  Token get beginToken => leftParenthesis;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  int get precedence => 15;
+
+  @override
+  Expression get unParenthesized {
+    // This is somewhat inefficient, but it avoids a stack overflow in the
+    // degenerate case.
+    Expression expression = _expression;
+    while (expression is ParenthesizedExpressionImpl) {
+      expression = (expression as ParenthesizedExpressionImpl)._expression;
+    }
+    return expression;
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitParenthesizedExpression(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _expression?.accept(visitor);
+  }
+}
+
+/**
+ * A part directive.
+ *
+ *    partDirective ::=
+ *        [Annotation] 'part' [StringLiteral] ';'
+ */
+class PartDirectiveImpl extends UriBasedDirectiveImpl implements PartDirective {
+  /**
+   * The token representing the 'part' keyword.
+   */
+  @override
+  Token partKeyword;
+
+  /**
+   * The semicolon terminating the directive.
+   */
+  @override
+  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<SyntacticEntity> 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
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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.
+   */
+  @override
+  Token partKeyword;
+
+  /**
+   * The token representing the 'of' keyword.
+   */
+  @override
+  Token ofKeyword;
+
+  /**
+   * The name of the library that the containing compilation unit is part of.
+   */
+  LibraryIdentifier _libraryName;
+
+  /**
+   * The semicolon terminating the directive.
+   */
+  @override
+  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(
+      CommentImpl comment,
+      List<Annotation> metadata,
+      this.partKeyword,
+      this.ofKeyword,
+      LibraryIdentifierImpl libraryName,
+      this.semicolon)
+      : super(comment, metadata) {
+    _libraryName = _becomeParentOf(libraryName);
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitPartOfDirective(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    super.visitChildren(visitor);
+    _libraryName?.accept(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.
+   */
+  @override
+  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.
+   */
+  @override
+  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.
+   */
+  @override
+  MethodElement staticElement;
+
+  /**
+   * Initialize a newly created postfix expression.
+   */
+  PostfixExpressionImpl(ExpressionImpl 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<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @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
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitPostfixExpression(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _operand?.accept(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(SimpleIdentifierImpl prefix, this.period,
+      SimpleIdentifierImpl identifier) {
+    _prefix = _becomeParentOf(prefix);
+    _identifier = _becomeParentOf(identifier);
+  }
+
+  /**
+   * Initialize a newly created prefixed identifier that does not take ownership
+   * of the components. The resulting node is only for temporary use, such as by
+   * resolution.
+   */
+  PrefixedIdentifierImpl.temp(this._prefix, this._identifier) : period = null;
+
+  @override
+  Token get beginToken => _prefix.beginToken;
+
+  @override
+  Element get bestElement {
+    if (_identifier == null) {
+      return null;
+    }
+    return _identifier.bestElement;
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  bool get isDeferred {
+    Element element = _prefix.staticElement;
+    if (element is PrefixElement) {
+      List<ImportElement> imports =
+          element.enclosingElement.getImportsWithPrefix(element);
+      if (imports.length != 1) {
+        return false;
+      }
+      return imports[0].isDeferred;
+    }
+    return false;
+  }
+
+  @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 as AstNodeImpl);
+  }
+
+  @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
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitPrefixedIdentifier(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _prefix?.accept(visitor);
+    _identifier?.accept(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, ExpressionImpl 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<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @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
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitPrefixExpression(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _operand?.accept(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(
+      ExpressionImpl target, this.operator, SimpleIdentifierImpl propertyName) {
+    _target = _becomeParentOf(target);
+    _propertyName = _becomeParentOf(propertyName);
+  }
+
+  @override
+  Token get beginToken {
+    if (_target != null) {
+      return _target.beginToken;
+    }
+    return operator;
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitPropertyAccess(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _target?.accept(visitor);
+    _propertyName?.accept(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,
+      SimpleIdentifierImpl constructorName, ArgumentListImpl argumentList) {
+    _constructorName = _becomeParentOf(constructorName);
+    _argumentList = _becomeParentOf(argumentList);
+  }
+
+  @override
+  ArgumentList get argumentList => _argumentList;
+
+  @override
+  void set argumentList(ArgumentList argumentList) {
+    _argumentList = _becomeParentOf(argumentList as AstNodeImpl);
+  }
+
+  @override
+  Token get beginToken => thisKeyword;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  Token get endToken => _argumentList.endToken;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitRedirectingConstructorInvocation(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _constructorName?.accept(visitor);
+    _argumentList?.accept(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<SyntacticEntity> get childEntities =>
+      new ChildEntities()..add(rethrowKeyword);
+
+  @override
+  Token get endToken => rethrowKeyword;
+
+  @override
+  int get precedence => 0;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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, ExpressionImpl expression, this.semicolon) {
+    _expression = _becomeParentOf(expression);
+  }
+
+  @override
+  Token get beginToken => returnKeyword;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitReturnStatement(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _expression?.accept(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<SyntacticEntity> get childEntities =>
+      new ChildEntities()..add(scriptTag);
+
+  @override
+  Token get endToken => scriptTag;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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 NodeListImpl<SimpleIdentifier>(this, shownNames);
+  }
+
+  @override
+  // TODO(paulberry): add commas.
+  Iterable<SyntacticEntity> get childEntities => new ChildEntities()
+    ..add(keyword)
+    ..addAll(_shownNames);
+
+  @override
+  Token get endToken => _shownNames.endToken;
+
+  @override
+  NodeList<SimpleIdentifier> get shownNames => _shownNames;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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(CommentImpl comment, List<Annotation> metadata,
+      this.keyword, TypeNameImpl type, SimpleIdentifierImpl 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<SyntacticEntity> get childEntities =>
+      super._childEntities..add(keyword)..add(_type)..add(identifier);
+
+  @override
+  Token get endToken => identifier.endToken;
+
+  @override
+  bool get isConst => keyword?.keyword == Keyword.CONST;
+
+  @override
+  bool get isFinal => keyword?.keyword == Keyword.FINAL;
+
+  @override
+  TypeName get type => _type;
+
+  @override
+  void set type(TypeName typeName) {
+    _type = _becomeParentOf(typeName as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitSimpleFormalParameter(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    super.visitChildren(visitor);
+    _type?.accept(visitor);
+    identifier?.accept(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<SyntacticEntity> 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);
+    } else if (parent is PropertyAccess) {
+      return identical(parent.propertyName, this);
+    } else 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 = element;
+  }
+
+  @override
+  Element get staticElement => _staticElement;
+
+  @override
+  void set staticElement(Element element) {
+    _staticElement = element;
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitSimpleIdentifier(this);
+
+  @override
+  bool inDeclarationContext() => false;
+
+  @override
+  bool inGetterContext() {
+    // TODO(brianwilkerson) Convert this to a getter.
+    AstNode initialParent = this.parent;
+    AstNode parent = initialParent;
+    AstNode target = this;
+    // skip prefix
+    if (initialParent is PrefixedIdentifier) {
+      if (identical(initialParent.prefix, this)) {
+        return true;
+      }
+      parent = initialParent.parent;
+      target = initialParent;
+    } else if (initialParent is PropertyAccess) {
+      if (identical(initialParent.target, this)) {
+        return true;
+      }
+      parent = initialParent.parent;
+      target = initialParent;
+    }
+    // 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 ConstructorFieldInitializer &&
+        identical(parent.fieldName, target)) {
+      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 initialParent = this.parent;
+    AstNode parent = initialParent;
+    AstNode target = this;
+    // skip prefix
+    if (initialParent is PrefixedIdentifier) {
+      // if this is the prefix, then return false
+      if (identical(initialParent.prefix, this)) {
+        return false;
+      }
+      parent = initialParent.parent;
+      target = initialParent;
+    } else if (initialParent is PropertyAccess) {
+      if (identical(initialParent.target, this)) {
+        return false;
+      }
+      parent = initialParent.parent;
+      target = initialParent;
+    }
+    // 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.
+  }
+}
+
+/**
+ * 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<SyntacticEntity> 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
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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 NodeListImpl<InterpolationElement>(this, elements);
+  }
+
+  @override
+  Token get beginToken => _elements.beginToken;
+
+  @override
+  Iterable<SyntacticEntity> 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
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitStringInterpolation(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _elements.accept(visitor);
+  }
+
+  @override
+  void _appendStringValue(StringBuffer buffer) {
+    throw new ArgumentError();
+  }
+}
+
+/**
+ * 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 ArgumentError {
+      return null;
+    }
+    return buffer.toString();
+  }
+
+  /**
+   * Append the value of this string literal to the given [buffer]. Throw an
+   * [ArgumentError] 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,
+      SimpleIdentifierImpl constructorName, ArgumentListImpl argumentList) {
+    _constructorName = _becomeParentOf(constructorName);
+    _argumentList = _becomeParentOf(argumentList);
+  }
+
+  @override
+  ArgumentList get argumentList => _argumentList;
+
+  @override
+  void set argumentList(ArgumentList argumentList) {
+    _argumentList = _becomeParentOf(argumentList as AstNodeImpl);
+  }
+
+  @override
+  Token get beginToken => superKeyword;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  Token get endToken => _argumentList.endToken;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitSuperConstructorInvocation(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _constructorName?.accept(visitor);
+    _argumentList?.accept(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<SyntacticEntity> get childEntities =>
+      new ChildEntities()..add(superKeyword);
+
+  @override
+  Token get endToken => superKeyword;
+
+  @override
+  int get precedence => 16;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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, ExpressionImpl expression,
+      Token colon, List<Statement> statements)
+      : super(labels, keyword, colon, statements) {
+    _expression = _becomeParentOf(expression);
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitSwitchCase(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    labels.accept(visitor);
+    _expression?.accept(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<SyntacticEntity> get childEntities => new ChildEntities()
+    ..addAll(labels)
+    ..add(keyword)
+    ..add(colon)
+    ..addAll(statements);
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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 NodeListImpl<Label>(this, labels);
+    _statements = new NodeListImpl<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,
+      ExpressionImpl expression,
+      this.rightParenthesis,
+      this.leftBracket,
+      List<SwitchMember> members,
+      this.rightBracket) {
+    _expression = _becomeParentOf(expression);
+    _members = new NodeListImpl<SwitchMember>(this, members);
+  }
+
+  @override
+  Token get beginToken => switchKeyword;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  NodeList<SwitchMember> get members => _members;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitSwitchStatement(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _expression?.accept(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<SyntacticEntity> get childEntities => new ChildEntities()
+    ..add(poundSign)
+    ..addAll(components);
+
+  @override
+  Token get endToken => components[components.length - 1];
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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<SyntacticEntity> get childEntities =>
+      new ChildEntities()..add(thisKeyword);
+
+  @override
+  Token get endToken => thisKeyword;
+
+  @override
+  int get precedence => 16;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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, ExpressionImpl expression) {
+    _expression = _becomeParentOf(expression);
+  }
+
+  @override
+  Token get beginToken => throwKeyword;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  int get precedence => 0;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitThrowExpression(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _expression?.accept(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(
+      CommentImpl comment,
+      List<Annotation> metadata,
+      VariableDeclarationListImpl variableList,
+      this.semicolon)
+      : super(comment, metadata) {
+    _variableList = _becomeParentOf(variableList);
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitTopLevelVariableDeclaration(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    super.visitChildren(visitor);
+    _variableList?.accept(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,
+      BlockImpl body,
+      List<CatchClause> catchClauses,
+      this.finallyKeyword,
+      BlockImpl finallyBlock) {
+    _body = _becomeParentOf(body);
+    _catchClauses = new NodeListImpl<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 as AstNodeImpl);
+  }
+
+  @override
+  NodeList<CatchClause> get catchClauses => _catchClauses;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitTryStatement(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _body?.accept(visitor);
+    _catchClauses.accept(visitor);
+    _finallyBlock?.accept(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 NodeListImpl<TypeName>(this, arguments);
+  }
+
+  @override
+  NodeList<TypeName> get arguments => _arguments;
+
+  @override
+  Token get beginToken => leftBracket;
+
+  @override
+  // TODO(paulberry): Add commas.
+  Iterable<SyntacticEntity> get childEntities => new ChildEntities()
+    ..add(leftBracket)
+    ..addAll(_arguments)
+    ..add(rightBracket);
+
+  @override
+  Token get endToken => rightBracket;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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, TypeArgumentListImpl typeArguments) {
+    _typeArguments = _becomeParentOf(typeArguments);
+  }
+
+  @override
+  TypeArgumentList get typeArguments => _typeArguments;
+
+  @override
+  void set typeArguments(TypeArgumentList typeArguments) {
+    _typeArguments = _becomeParentOf(typeArguments as AstNodeImpl);
+  }
+
+  ChildEntities get _childEntities =>
+      new ChildEntities()..add(constKeyword)..add(_typeArguments);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _typeArguments?.accept(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;
+
+  @override
+  Token question;
+
+  /**
+   * 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(
+      IdentifierImpl name, TypeArgumentListImpl typeArguments, this.question) {
+    _name = _becomeParentOf(name);
+    _typeArguments = _becomeParentOf(typeArguments);
+  }
+
+  @override
+  Token get beginToken => _name.beginToken;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  TypeArgumentList get typeArguments => _typeArguments;
+
+  @override
+  void set typeArguments(TypeArgumentList typeArguments) {
+    _typeArguments = _becomeParentOf(typeArguments as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitTypeName(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _name?.accept(visitor);
+    _typeArguments?.accept(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(CommentImpl comment, List<Annotation> metadata,
+      SimpleIdentifierImpl name, this.extendsKeyword, TypeNameImpl bound)
+      : super(comment, metadata) {
+    _name = _becomeParentOf(name);
+    _bound = _becomeParentOf(bound);
+  }
+
+  @override
+  TypeName get bound => _bound;
+
+  @override
+  void set bound(TypeName typeName) {
+    _bound = _becomeParentOf(typeName as AstNodeImpl);
+  }
+
+  @override
+  Iterable<SyntacticEntity> get childEntities =>
+      super._childEntities..add(_name)..add(extendsKeyword)..add(_bound);
+
+  @override
+  TypeParameterElement get element =>
+      _name?.staticElement as TypeParameterElement;
+
+  @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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitTypeParameter(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    super.visitChildren(visitor);
+    _name?.accept(visitor);
+    _bound?.accept(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 NodeListImpl<TypeParameter>(this, typeParameters);
+  }
+
+  @override
+  Token get beginToken => leftBracket;
+
+  @override
+  Iterable<SyntacticEntity> get childEntities => new ChildEntities()
+    ..add(leftBracket)
+    ..addAll(_typeParameters)
+    ..add(rightBracket);
+
+  @override
+  Token get endToken => rightBracket;
+
+  @override
+  NodeList<TypeParameter> get typeParameters => _typeParameters;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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;
+
+  @override
+  String uriContent;
+
+  @override
+  Source uriSource;
+
+  /**
+   * 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(
+      CommentImpl comment, List<Annotation> metadata, StringLiteralImpl uri)
+      : super(comment, metadata) {
+    _uri = _becomeParentOf(uri);
+  }
+
+  @deprecated
+  @override
+  Source get source => uriSource;
+
+  @deprecated
+  @override
+  void set source(Source source) {
+    uriSource = source;
+  }
+
+  @override
+  StringLiteral get uri => _uri;
+
+  @override
+  void set uri(StringLiteral uri) {
+    _uri = _becomeParentOf(uri as AstNodeImpl);
+  }
+
+  UriValidationCode validate() {
+    return validateUri(this is ImportDirective, uri, uriContent);
+  }
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    super.visitChildren(visitor);
+    _uri?.accept(visitor);
+  }
+
+  /**
+   * Validate this directive, but do not check for existence. Return a code
+   * indicating the problem if there is one, or `null` no problem.
+   */
+  static UriValidationCode validateUri(
+      bool isImport, StringLiteral uriLiteral, String uriContent) {
+    if (uriLiteral is StringInterpolation) {
+      return UriValidationCode.URI_WITH_INTERPOLATION;
+    }
+    if (uriContent == null) {
+      return UriValidationCode.INVALID_URI;
+    }
+    if (isImport && uriContent.startsWith(_DART_EXT_SCHEME)) {
+      return UriValidationCode.URI_WITH_DART_EXT_SCHEME;
+    }
+    Uri uri;
+    try {
+      uri = Uri.parse(Uri.encodeFull(uriContent));
+    } on FormatException {
+      return UriValidationCode.INVALID_URI;
+    }
+    if (uri.path.isEmpty) {
+      return UriValidationCode.INVALID_URI;
+    }
+    return null;
+  }
+}
+
+/**
+ * Validation codes returned by [UriBasedDirective.validate].
+ */
+class UriValidationCode {
+  static const UriValidationCode INVALID_URI =
+      const UriValidationCode('INVALID_URI');
+
+  static const UriValidationCode URI_WITH_INTERPOLATION =
+      const UriValidationCode('URI_WITH_INTERPOLATION');
+
+  static const UriValidationCode URI_WITH_DART_EXT_SCHEME =
+      const UriValidationCode('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 UriValidationCode(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(
+      SimpleIdentifierImpl name, this.equals, ExpressionImpl initializer)
+      : super(null, null) {
+    _name = _becomeParentOf(name);
+    _initializer = _becomeParentOf(initializer);
+  }
+
+  @override
+  Iterable<SyntacticEntity> get childEntities =>
+      super._childEntities..add(_name)..add(equals)..add(_initializer);
+
+  /**
+   * This overridden implementation of [documentationComment] 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) {
+      AstNode node = parent?.parent;
+      if (node is AnnotatedNode) {
+        return node.documentationComment;
+      }
+    }
+    return comment;
+  }
+
+  @override
+  VariableElement get element => _name?.staticElement as VariableElement;
+
+  @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 as AstNodeImpl);
+  }
+
+  @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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitVariableDeclaration(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    super.visitChildren(visitor);
+    _name?.accept(visitor);
+    _initializer?.accept(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(CommentImpl comment, List<Annotation> metadata,
+      this.keyword, TypeNameImpl type, List<VariableDeclaration> variables)
+      : super(comment, metadata) {
+    _type = _becomeParentOf(type);
+    _variables = new NodeListImpl<VariableDeclaration>(this, variables);
+  }
+
+  @override
+  // TODO(paulberry): include commas.
+  Iterable<SyntacticEntity> 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?.keyword == Keyword.CONST;
+
+  @override
+  bool get isFinal => keyword?.keyword == Keyword.FINAL;
+
+  @override
+  TypeName get type => _type;
+
+  @override
+  void set type(TypeName typeName) {
+    _type = _becomeParentOf(typeName as AstNodeImpl);
+  }
+
+  @override
+  NodeList<VariableDeclaration> get variables => _variables;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitVariableDeclarationList(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    super.visitChildren(visitor);
+    _type?.accept(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(
+      VariableDeclarationListImpl variableList, this.semicolon) {
+    _variableList = _becomeParentOf(variableList);
+  }
+
+  @override
+  Token get beginToken => _variableList.beginToken;
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitVariableDeclarationStatement(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _variableList?.accept(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,
+      ExpressionImpl condition, this.rightParenthesis, StatementImpl 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 as AstNodeImpl);
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  Token get endToken => _body.endToken;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitWhileStatement(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _condition?.accept(visitor);
+    _body?.accept(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 NodeListImpl<TypeName>(this, mixinTypes);
+  }
+
+  @override
+  Token get beginToken => withKeyword;
+
+  @override
+  // TODO(paulberry): add commas.
+  Iterable<SyntacticEntity> get childEntities => new ChildEntities()
+    ..add(withKeyword)
+    ..addAll(_mixinTypes);
+
+  @override
+  Token get endToken => _mixinTypes.endToken;
+
+  @override
+  NodeList<TypeName> get mixinTypes => _mixinTypes;
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ 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, ExpressionImpl expression, this.semicolon) {
+    _expression = _becomeParentOf(expression);
+  }
+
+  @override
+  Token get beginToken {
+    if (yieldKeyword != null) {
+      return yieldKeyword;
+    }
+    return _expression.beginToken;
+  }
+
+  @override
+  Iterable<SyntacticEntity> 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 as AstNodeImpl);
+  }
+
+  @override
+  dynamic/*=E*/ accept/*<E>*/(AstVisitor/*<E>*/ visitor) =>
+      visitor.visitYieldStatement(this);
+
+  @override
+  void visitChildren(AstVisitor visitor) {
+    _expression?.accept(visitor);
+  }
+}