Move js_ast library to its own package under pkg

pkg/compiler/lib/src/js/nodes.dart

Index: pkg/compiler/lib/src/js/nodes.dart
diff --git a/pkg/compiler/lib/src/js/nodes.dart b/pkg/compiler/lib/src/js/nodes.dart
deleted file mode 100644
index 92446fa8bf48b3d4faeefcfa0a2013d7b8ec4343..0000000000000000000000000000000000000000
--- a/pkg/compiler/lib/src/js/nodes.dart
+++ /dev/null
@@ -1,1148 +0,0 @@
-// Copyright (c) 2012, 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.
-
-part of js_ast;
-
-abstract class NodeVisitor<T> {
-  T visitProgram(Program node);
-
-  T visitBlock(Block node);
-  T visitExpressionStatement(ExpressionStatement node);
-  T visitEmptyStatement(EmptyStatement node);
-  T visitIf(If node);
-  T visitFor(For node);
-  T visitForIn(ForIn node);
-  T visitWhile(While node);
-  T visitDo(Do node);
-  T visitContinue(Continue node);
-  T visitBreak(Break node);
-  T visitReturn(Return node);
-  T visitThrow(Throw node);
-  T visitTry(Try node);
-  T visitCatch(Catch node);
-  T visitSwitch(Switch node);
-  T visitCase(Case node);
-  T visitDefault(Default node);
-  T visitFunctionDeclaration(FunctionDeclaration node);
-  T visitLabeledStatement(LabeledStatement node);
-  T visitLiteralStatement(LiteralStatement node);
-  T visitDartYield(DartYield node);
-
-  T visitLiteralExpression(LiteralExpression node);
-  T visitVariableDeclarationList(VariableDeclarationList node);
-  T visitAssignment(Assignment node);
-  T visitVariableInitialization(VariableInitialization node);
-  T visitConditional(Conditional cond);
-  T visitNew(New node);
-  T visitCall(Call node);
-  T visitBinary(Binary node);
-  T visitPrefix(Prefix node);
-  T visitPostfix(Postfix node);
-
-  T visitVariableUse(VariableUse node);
-  T visitThis(This node);
-  T visitVariableDeclaration(VariableDeclaration node);
-  T visitParameter(Parameter node);
-  T visitAccess(PropertyAccess node);
-
-  T visitNamedFunction(NamedFunction node);
-  T visitFun(Fun node);
-
-  T visitLiteralBool(LiteralBool node);
-  T visitLiteralString(LiteralString node);
-  T visitLiteralNumber(LiteralNumber node);
-  T visitLiteralNull(LiteralNull node);
-
-  T visitArrayInitializer(ArrayInitializer node);
-  T visitArrayHole(ArrayHole node);
-  T visitObjectInitializer(ObjectInitializer node);
-  T visitProperty(Property node);
-  T visitRegExpLiteral(RegExpLiteral node);
-
-  T visitAwait(Await node);
-
-  T visitComment(Comment node);
-
-  T visitInterpolatedExpression(InterpolatedExpression node);
-  T visitInterpolatedLiteral(InterpolatedLiteral node);
-  T visitInterpolatedParameter(InterpolatedParameter node);
-  T visitInterpolatedSelector(InterpolatedSelector node);
-  T visitInterpolatedStatement(InterpolatedStatement node);
-}
-
-class BaseVisitor<T> implements NodeVisitor<T> {
-  T visitNode(Node node) {
-    node.visitChildren(this);
-    return null;
-  }
-
-  T visitProgram(Program node) => visitNode(node);
-
-  T visitStatement(Statement node) => visitNode(node);
-  T visitLoop(Loop node) => visitStatement(node);
-  T visitJump(Statement node) => visitStatement(node);
-
-  T visitBlock(Block node) => visitStatement(node);
-  T visitExpressionStatement(ExpressionStatement node)
-      => visitStatement(node);
-  T visitEmptyStatement(EmptyStatement node) => visitStatement(node);
-  T visitIf(If node) => visitStatement(node);
-  T visitFor(For node) => visitLoop(node);
-  T visitForIn(ForIn node) => visitLoop(node);
-  T visitWhile(While node) => visitLoop(node);
-  T visitDo(Do node) => visitLoop(node);
-  T visitContinue(Continue node) => visitJump(node);
-  T visitBreak(Break node) => visitJump(node);
-  T visitReturn(Return node) => visitJump(node);
-  T visitThrow(Throw node) => visitJump(node);
-  T visitTry(Try node) => visitStatement(node);
-  T visitSwitch(Switch node) => visitStatement(node);
-  T visitFunctionDeclaration(FunctionDeclaration node)
-      => visitStatement(node);
-  T visitLabeledStatement(LabeledStatement node) => visitStatement(node);
-  T visitLiteralStatement(LiteralStatement node) => visitStatement(node);
-
-  T visitCatch(Catch node) => visitNode(node);
-  T visitCase(Case node) => visitNode(node);
-  T visitDefault(Default node) => visitNode(node);
-
-  T visitExpression(Expression node) => visitNode(node);
-  T visitVariableReference(VariableReference node) => visitExpression(node);
-
-  T visitLiteralExpression(LiteralExpression node) => visitExpression(node);
-  T visitVariableDeclarationList(VariableDeclarationList node)
-      => visitExpression(node);
-  T visitAssignment(Assignment node) => visitExpression(node);
-  T visitVariableInitialization(VariableInitialization node) {
-    if (node.value != null) {
-      return visitAssignment(node);
-    } else {
-      return visitExpression(node);
-    }
-  }
-  T visitConditional(Conditional node) => visitExpression(node);
-  T visitNew(New node) => visitExpression(node);
-  T visitCall(Call node) => visitExpression(node);
-  T visitBinary(Binary node) => visitExpression(node);
-  T visitPrefix(Prefix node) => visitExpression(node);
-  T visitPostfix(Postfix node) => visitExpression(node);
-  T visitAccess(PropertyAccess node) => visitExpression(node);
-
-  T visitVariableUse(VariableUse node) => visitVariableReference(node);
-  T visitVariableDeclaration(VariableDeclaration node)
-      => visitVariableReference(node);
-  T visitParameter(Parameter node) => visitVariableDeclaration(node);
-  T visitThis(This node) => visitParameter(node);
-
-  T visitNamedFunction(NamedFunction node) => visitExpression(node);
-  T visitFun(Fun node) => visitExpression(node);
-
-  T visitLiteral(Literal node) => visitExpression(node);
-
-  T visitLiteralBool(LiteralBool node) => visitLiteral(node);
-  T visitLiteralString(LiteralString node) => visitLiteral(node);
-  T visitLiteralNumber(LiteralNumber node) => visitLiteral(node);
-  T visitLiteralNull(LiteralNull node) => visitLiteral(node);
-
-  T visitArrayInitializer(ArrayInitializer node) => visitExpression(node);
-  T visitArrayHole(ArrayHole node) => visitExpression(node);
-  T visitObjectInitializer(ObjectInitializer node) => visitExpression(node);
-  T visitProperty(Property node) => visitNode(node);
-  T visitRegExpLiteral(RegExpLiteral node) => visitExpression(node);
-
-  T visitInterpolatedNode(InterpolatedNode node) => visitNode(node);
-
-  T visitInterpolatedExpression(InterpolatedExpression node)
-      => visitInterpolatedNode(node);
-  T visitInterpolatedLiteral(InterpolatedLiteral node)
-      => visitInterpolatedNode(node);
-  T visitInterpolatedParameter(InterpolatedParameter node)
-      => visitInterpolatedNode(node);
-  T visitInterpolatedSelector(InterpolatedSelector node)
-      => visitInterpolatedNode(node);
-  T visitInterpolatedStatement(InterpolatedStatement node)
-      => visitInterpolatedNode(node);
-
-  // Ignore comments by default.
-  T visitComment(Comment node) => null;
-
-  T visitAwait(Await node) => visitExpression(node);
-  T visitDartYield(DartYield node) => visitStatement(node);
-}
-
-/// This tag interface has no behaviour but must be implemented by any class
-/// that is to be stored on a [Node] as source information.
-abstract class JavaScriptNodeSourceInformation {}
-
-abstract class Node {
-  JavaScriptNodeSourceInformation get sourceInformation => _sourceInformation;
-
-  JavaScriptNodeSourceInformation _sourceInformation;
-
-  accept(NodeVisitor visitor);
-  void visitChildren(NodeVisitor visitor);
-
-  // Shallow clone of node.  Does not clone positions since the only use of this
-  // private method is create a copy with a new position.
-  Node _clone();
-
-  // Returns a node equivalent to [this], but with new source position and end
-  // source position.
-  Node withSourceInformation(
-      JavaScriptNodeSourceInformation sourceInformation) {
-    if (sourceInformation == _sourceInformation) {
-      return this;
-    }
-    Node clone = _clone();
-    // TODO(sra): Should existing data be 'sticky' if we try to overwrite with
-    // `null`?
-    clone._sourceInformation = sourceInformation;
-    return clone;
-  }
-
-  VariableUse asVariableUse() => null;
-
-  bool get isCommaOperator => false;
-
-  Statement toStatement() {
-    throw new UnsupportedError('toStatement');
-  }
-}
-
-class Program extends Node {
-  final List<Statement> body;
-  Program(this.body);
-
-  accept(NodeVisitor visitor) => visitor.visitProgram(this);
-  void visitChildren(NodeVisitor visitor) {
-    for (Statement statement in body) statement.accept(visitor);
-  }
-  Program _clone() => new Program(body);
-}
-
-abstract class Statement extends Node {
-  Statement toStatement() => this;
-}
-
-class Block extends Statement {
-  final List<Statement> statements;
-  Block(this.statements);
-  Block.empty() : this.statements = <Statement>[];
-
-  accept(NodeVisitor visitor) => visitor.visitBlock(this);
-  void visitChildren(NodeVisitor visitor) {
-    for (Statement statement in statements) statement.accept(visitor);
-  }
-  Block _clone() => new Block(statements);
-}
-
-class ExpressionStatement extends Statement {
-  final Expression expression;
-  ExpressionStatement(this.expression);
-
-  accept(NodeVisitor visitor) => visitor.visitExpressionStatement(this);
-  void visitChildren(NodeVisitor visitor) { expression.accept(visitor); }
-  ExpressionStatement _clone() => new ExpressionStatement(expression);
-}
-
-class EmptyStatement extends Statement {
-  EmptyStatement();
-
-  accept(NodeVisitor visitor) => visitor.visitEmptyStatement(this);
-  void visitChildren(NodeVisitor visitor) {}
-  EmptyStatement _clone() => new EmptyStatement();
-}
-
-class If extends Statement {
-  final Expression condition;
-  final Node then;
-  final Node otherwise;
-
-  If(this.condition, this.then, this.otherwise);
-  If.noElse(this.condition, this.then) : this.otherwise = new EmptyStatement();
-
-  bool get hasElse => otherwise is !EmptyStatement;
-
-  accept(NodeVisitor visitor) => visitor.visitIf(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    condition.accept(visitor);
-    then.accept(visitor);
-    otherwise.accept(visitor);
-  }
-
-  If _clone() => new If(condition, then, otherwise);
-}
-
-abstract class Loop extends Statement {
-  final Statement body;
-  Loop(this.body);
-}
-
-class For extends Loop {
-  final Expression init;
-  final Expression condition;
-  final Expression update;
-
-  For(this.init, this.condition, this.update, Statement body) : super(body);
-
-  accept(NodeVisitor visitor) => visitor.visitFor(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    if (init != null) init.accept(visitor);
-    if (condition != null) condition.accept(visitor);
-    if (update != null) update.accept(visitor);
-    body.accept(visitor);
-  }
-
-  For _clone() => new For(init, condition, update, body);
-}
-
-class ForIn extends Loop {
-  // Note that [VariableDeclarationList] is a subclass of [Expression].
-  // Therefore we can type the leftHandSide as [Expression].
-  final Expression leftHandSide;
-  final Expression object;
-
-  ForIn(this.leftHandSide, this.object, Statement body) : super(body);
-
-  accept(NodeVisitor visitor) => visitor.visitForIn(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    leftHandSide.accept(visitor);
-    object.accept(visitor);
-    body.accept(visitor);
-  }
-
-  ForIn _clone() => new ForIn(leftHandSide, object, body);
-}
-
-class While extends Loop {
-  final Node condition;
-
-  While(this.condition, Statement body) : super(body);
-
-  accept(NodeVisitor visitor) => visitor.visitWhile(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    condition.accept(visitor);
-    body.accept(visitor);
-  }
-
-  While _clone() => new While(condition, body);
-}
-
-class Do extends Loop {
-  final Expression condition;
-
-  Do(Statement body, this.condition) : super(body);
-
-  accept(NodeVisitor visitor) => visitor.visitDo(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    body.accept(visitor);
-    condition.accept(visitor);
-  }
-
-  Do _clone() => new Do(body, condition);
-}
-
-class Continue extends Statement {
-  final String targetLabel;  // Can be null.
-
-  Continue(this.targetLabel);
-
-  accept(NodeVisitor visitor) => visitor.visitContinue(this);
-  void visitChildren(NodeVisitor visitor) {}
-
-  Continue _clone() => new Continue(targetLabel);
-}
-
-class Break extends Statement {
-  final String targetLabel;  // Can be null.
-
-  Break(this.targetLabel);
-
-  accept(NodeVisitor visitor) => visitor.visitBreak(this);
-  void visitChildren(NodeVisitor visitor) {}
-
-  Break _clone() => new Break(targetLabel);
-}
-
-class Return extends Statement {
-  final Expression value;  // Can be null.
-
-  Return([this.value = null]);
-
-  accept(NodeVisitor visitor) => visitor.visitReturn(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    if (value != null) value.accept(visitor);
-  }
-
-  Return _clone() => new Return(value);
-}
-
-class Throw extends Statement {
-  final Expression expression;
-
-  Throw(this.expression);
-
-  accept(NodeVisitor visitor) => visitor.visitThrow(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    expression.accept(visitor);
-  }
-
-  Throw _clone() => new Throw(expression);
-}
-
-class Try extends Statement {
-  final Block body;
-  final Catch catchPart;  // Can be null if [finallyPart] is non-null.
-  final Block finallyPart;  // Can be null if [catchPart] is non-null.
-
-  Try(this.body, this.catchPart, this.finallyPart) {
-    assert(catchPart != null || finallyPart != null);
-  }
-
-  accept(NodeVisitor visitor) => visitor.visitTry(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    body.accept(visitor);
-    if (catchPart != null) catchPart.accept(visitor);
-    if (finallyPart != null) finallyPart.accept(visitor);
-  }
-
-  Try _clone() => new Try(body, catchPart, finallyPart);
-}
-
-class Catch extends Node {
-  final VariableDeclaration declaration;
-  final Block body;
-
-  Catch(this.declaration, this.body);
-
-  accept(NodeVisitor visitor) => visitor.visitCatch(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    declaration.accept(visitor);
-    body.accept(visitor);
-  }
-
-  Catch _clone() => new Catch(declaration, body);
-}
-
-class Switch extends Statement {
-  final Expression key;
-  final List<SwitchClause> cases;
-
-  Switch(this.key, this.cases);
-
-  accept(NodeVisitor visitor) => visitor.visitSwitch(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    key.accept(visitor);
-    for (SwitchClause clause in cases) clause.accept(visitor);
-  }
-
-  Switch _clone() => new Switch(key, cases);
-}
-
-abstract class SwitchClause extends Node {
-  final Block body;
-
-  SwitchClause(this.body);
-}
-
-class Case extends SwitchClause {
-  final Expression expression;
-
-  Case(this.expression, Block body) : super(body);
-
-  accept(NodeVisitor visitor) => visitor.visitCase(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    expression.accept(visitor);
-    body.accept(visitor);
-  }
-
-  Case _clone() => new Case(expression, body);
-}
-
-class Default extends SwitchClause {
-  Default(Block body) : super(body);
-
-  accept(NodeVisitor visitor) => visitor.visitDefault(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    body.accept(visitor);
-  }
-
-  Default _clone() => new Default(body);
-}
-
-class FunctionDeclaration extends Statement {
-  final VariableDeclaration name;
-  final Fun function;
-
-  FunctionDeclaration(this.name, this.function);
-
-  accept(NodeVisitor visitor) => visitor.visitFunctionDeclaration(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    name.accept(visitor);
-    function.accept(visitor);
-  }
-
-  FunctionDeclaration _clone() => new FunctionDeclaration(name, function);
-}
-
-class LabeledStatement extends Statement {
-  final String label;
-  final Statement body;
-
-  LabeledStatement(this.label, this.body);
-
-  accept(NodeVisitor visitor) => visitor.visitLabeledStatement(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    body.accept(visitor);
-  }
-
-  LabeledStatement _clone() => new LabeledStatement(label, body);
-}
-
-class LiteralStatement extends Statement {
-  final String code;
-
-  LiteralStatement(this.code);
-
-  accept(NodeVisitor visitor) => visitor.visitLiteralStatement(this);
-  void visitChildren(NodeVisitor visitor) { }
-
-  LiteralStatement _clone() => new LiteralStatement(code);
-}
-
-// Not a real JavaScript node, but represents the yield statement from a dart
-// program translated to JavaScript.
-class DartYield extends Statement {
-  final Expression expression;
-
-  final bool hasStar;
-
-  DartYield(this.expression, this.hasStar);
-
-  accept(NodeVisitor visitor) => visitor.visitDartYield(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    expression.accept(visitor);
-  }
-
-  DartYield _clone() => new DartYield(expression, hasStar);
-}
-
-abstract class Expression extends Node {
-  int get precedenceLevel;
-
-  Statement toStatement() => new ExpressionStatement(this);
-}
-
-class LiteralExpression extends Expression {
-  final String template;
-  final List<Expression> inputs;
-
-  LiteralExpression(this.template) : inputs = const [];
-  LiteralExpression.withData(this.template, this.inputs);
-
-  accept(NodeVisitor visitor) => visitor.visitLiteralExpression(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    if (inputs != null) {
-      for (Expression expr in inputs) expr.accept(visitor);
-    }
-  }
-
-  LiteralExpression _clone() =>
-      new LiteralExpression.withData(template, inputs);
-
-  // Code that uses JS must take care of operator precedences, and
-  // put parenthesis if needed.
-  int get precedenceLevel => PRIMARY;
-}
-
-/**
- * [VariableDeclarationList] is a subclass of [Expression] to simplify the
- * AST.
- */
-class VariableDeclarationList extends Expression {
-  final List<VariableInitialization> declarations;
-
-  VariableDeclarationList(this.declarations);
-
-  accept(NodeVisitor visitor) => visitor.visitVariableDeclarationList(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    for (VariableInitialization declaration in declarations) {
-      declaration.accept(visitor);
-    }
-  }
-
-  VariableDeclarationList _clone() => new VariableDeclarationList(declarations);
-
-  int get precedenceLevel => EXPRESSION;
-}
-
-class Assignment extends Expression {
-  final Expression leftHandSide;
-  final String op;         // Null, if the assignment is not compound.
-  final Expression value;  // May be null, for [VariableInitialization]s.
-
-  Assignment(leftHandSide, value)
-      : this.compound(leftHandSide, null, value);
-  Assignment.compound(this.leftHandSide, this.op, this.value);
-
-  int get precedenceLevel => ASSIGNMENT;
-
-  bool get isCompound => op != null;
-
-  accept(NodeVisitor visitor) => visitor.visitAssignment(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    leftHandSide.accept(visitor);
-    if (value != null) value.accept(visitor);
-  }
-
-  Assignment _clone() =>
-      new Assignment.compound(leftHandSide, op, value);
-}
-
-class VariableInitialization extends Assignment {
-  /** [value] may be null. */
-  VariableInitialization(VariableDeclaration declaration, Expression value)
-      : super(declaration, value);
-
-  VariableDeclaration get declaration => leftHandSide;
-
-  accept(NodeVisitor visitor) => visitor.visitVariableInitialization(this);
-
-  VariableInitialization _clone() =>
-      new VariableInitialization(declaration, value);
-}
-
-class Conditional extends Expression {
-  final Expression condition;
-  final Expression then;
-  final Expression otherwise;
-
-  Conditional(this.condition, this.then, this.otherwise);
-
-  accept(NodeVisitor visitor) => visitor.visitConditional(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    condition.accept(visitor);
-    then.accept(visitor);
-    otherwise.accept(visitor);
-  }
-
-  Conditional _clone() => new Conditional(condition, then, otherwise);
-
-  int get precedenceLevel => ASSIGNMENT;
-}
-
-class Call extends Expression {
-  Expression target;
-  List<Expression> arguments;
-
-  Call(this.target, this.arguments);
-
-  accept(NodeVisitor visitor) => visitor.visitCall(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    target.accept(visitor);
-    for (Expression arg in arguments) arg.accept(visitor);
-  }
-
-  Call _clone() => new Call(target, arguments);
-
-  int get precedenceLevel => CALL;
-}
-
-class New extends Call {
-  New(Expression cls, List<Expression> arguments) : super(cls, arguments);
-
-  accept(NodeVisitor visitor) => visitor.visitNew(this);
-
-  New _clone() => new New(target, arguments);
-}
-
-class Binary extends Expression {
-  final String op;
-  final Expression left;
-  final Expression right;
-
-  Binary(this.op, this.left, this.right);
-
-  accept(NodeVisitor visitor) => visitor.visitBinary(this);
-
-  Binary _clone() => new Binary(op, left, right);
-
-  void visitChildren(NodeVisitor visitor) {
-    left.accept(visitor);
-    right.accept(visitor);
-  }
-
-  bool get isCommaOperator => op == ',';
-
-  int get precedenceLevel {
-    // TODO(floitsch): switch to constant map.
-    switch (op) {
-      case "*":
-      case "/":
-      case "%":
-        return MULTIPLICATIVE;
-      case "+":
-      case "-":
-        return ADDITIVE;
-      case "<<":
-      case ">>":
-      case ">>>":
-        return SHIFT;
-      case "<":
-      case ">":
-      case "<=":
-      case ">=":
-      case "instanceof":
-      case "in":
-        return RELATIONAL;
-      case "==":
-      case "===":
-      case "!=":
-      case "!==":
-        return EQUALITY;
-      case "&":
-        return BIT_AND;
-      case "^":
-        return BIT_XOR;
-      case "|":
-        return BIT_OR;
-      case "&&":
-        return LOGICAL_AND;
-      case "||":
-        return LOGICAL_OR;
-      case ',':
-        return EXPRESSION;
-      default:
-        throw "Internal Error: Unhandled binary operator: $op";
-    }
-  }
-}
-
-class Prefix extends Expression {
-  final String op;
-  final Expression argument;
-
-  Prefix(this.op, this.argument);
-
-  accept(NodeVisitor visitor) => visitor.visitPrefix(this);
-
-  Prefix _clone() => new Prefix(op, argument);
-
-  void visitChildren(NodeVisitor visitor) {
-    argument.accept(visitor);
-  }
-
-  int get precedenceLevel => UNARY;
-}
-
-class Postfix extends Expression {
-  final String op;
-  final Expression argument;
-
-  Postfix(this.op, this.argument);
-
-  accept(NodeVisitor visitor) => visitor.visitPostfix(this);
-
-  Postfix _clone() => new Postfix(op, argument);
-
-  void visitChildren(NodeVisitor visitor) {
-    argument.accept(visitor);
-  }
-
-
-  int get precedenceLevel => UNARY;
-}
-
-abstract class VariableReference extends Expression {
-  final String name;
-
-  VariableReference(this.name) {
-    assert(_identifierRE.hasMatch(name));
-  }
-  static RegExp _identifierRE = new RegExp(r'^[A-Za-z_$][A-Za-z_$0-9]*$');
-
-  accept(NodeVisitor visitor);
-  int get precedenceLevel => PRIMARY;
-  void visitChildren(NodeVisitor visitor) {}
-}
-
-class VariableUse extends VariableReference {
-  VariableUse(String name) : super(name);
-
-  accept(NodeVisitor visitor) => visitor.visitVariableUse(this);
-  VariableUse _clone() => new VariableUse(name);
-
-  VariableUse asVariableUse() => this;
-
-  toString() => 'VariableUse($name)';
-}
-
-class VariableDeclaration extends VariableReference {
-  final bool allowRename;
-  VariableDeclaration(String name, {this.allowRename: true}) : super(name);
-
-  accept(NodeVisitor visitor) => visitor.visitVariableDeclaration(this);
-  VariableDeclaration _clone() => new VariableDeclaration(name);
-}
-
-class Parameter extends VariableDeclaration {
-  Parameter(String name) : super(name);
-
-  accept(NodeVisitor visitor) => visitor.visitParameter(this);
-  Parameter _clone() => new Parameter(name);
-}
-
-class This extends Parameter {
-  This() : super("this");
-
-  accept(NodeVisitor visitor) => visitor.visitThis(this);
-  This _clone() => new This();
-}
-
-class NamedFunction extends Expression {
-  final VariableDeclaration name;
-  final Fun function;
-
-  NamedFunction(this.name, this.function);
-
-  accept(NodeVisitor visitor) => visitor.visitNamedFunction(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    name.accept(visitor);
-    function.accept(visitor);
-  }
-  NamedFunction _clone() => new NamedFunction(name, function);
-
-  int get precedenceLevel => CALL;
-}
-
-class Fun extends Expression {
-  final List<Parameter> params;
-  final Block body;
-  final AsyncModifier asyncModifier;
-
-  Fun(this.params, this.body, {this.asyncModifier: const AsyncModifier.sync()});
-
-  accept(NodeVisitor visitor) => visitor.visitFun(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    for (Parameter param in params) param.accept(visitor);
-    body.accept(visitor);
-  }
-
-  Fun _clone() => new Fun(params, body, asyncModifier: asyncModifier);
-
-  int get precedenceLevel => CALL;
-}
-
-class AsyncModifier {
-  final bool isAsync;
-  final bool isYielding;
-  final String description;
-
-  const AsyncModifier.sync()
-      : isAsync = false,
-        isYielding = false,
-        description = "sync";
-  const AsyncModifier.async()
-      : isAsync = true,
-        isYielding = false,
-        description = "async";
-  const AsyncModifier.asyncStar()
-      : isAsync = true,
-        isYielding = true,
-        description = "async*";
-  const AsyncModifier.syncStar()
-      : isAsync = false,
-        isYielding = true,
-        description = "sync*";
-  toString() => description;
-}
-
-class PropertyAccess extends Expression {
-  final Expression receiver;
-  final Expression selector;
-
-  PropertyAccess(this.receiver, this.selector);
-  PropertyAccess.field(this.receiver, String fieldName)
-      : selector = new LiteralString('"$fieldName"');
-  PropertyAccess.indexed(this.receiver, int index)
-      : selector = new LiteralNumber('$index');
-
-  accept(NodeVisitor visitor) => visitor.visitAccess(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    receiver.accept(visitor);
-    selector.accept(visitor);
-  }
-
-  PropertyAccess _clone() => new PropertyAccess(receiver, selector);
-
-  int get precedenceLevel => CALL;
-}
-
-abstract class Literal extends Expression {
-  void visitChildren(NodeVisitor visitor) {}
-
-  int get precedenceLevel => PRIMARY;
-}
-
-class LiteralBool extends Literal {
-  final bool value;
-
-  LiteralBool(this.value);
-
-  accept(NodeVisitor visitor) => visitor.visitLiteralBool(this);
-  // [visitChildren] inherited from [Literal].
-  LiteralBool _clone() => new LiteralBool(value);
-}
-
-class LiteralNull extends Literal {
-  LiteralNull();
-
-  accept(NodeVisitor visitor) => visitor.visitLiteralNull(this);
-  LiteralNull _clone() => new LiteralNull();
-}
-
-class LiteralString extends Literal {
-  final String value;
-
-  /**
-   * Constructs a LiteralString from a string value.
-   *
-   * The constructor does not add the required quotes.  If [value] is not
-   * surrounded by quotes and property escaped, the resulting object is invalid
-   * as a JS value.
-   *
-   * TODO(sra): Introduce variants for known valid strings that don't allocate a
-   * new string just to add quotes.
-   */
-  LiteralString(this.value);
-
-  accept(NodeVisitor visitor) => visitor.visitLiteralString(this);
-  LiteralString _clone() => new LiteralString(value);
-}
-
-class LiteralNumber extends Literal {
-  final String value;  // Must be a valid JavaScript number literal.
-
-  LiteralNumber(this.value);
-
-  accept(NodeVisitor visitor) => visitor.visitLiteralNumber(this);
-  LiteralNumber _clone() => new LiteralNumber(value);
-}
-
-class ArrayInitializer extends Expression {
-  final List<Expression> elements;
-
-  ArrayInitializer(this.elements);
-
-  accept(NodeVisitor visitor) => visitor.visitArrayInitializer(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    for (Expression element in elements) element.accept(visitor);
-  }
-
-  ArrayInitializer _clone() => new ArrayInitializer(elements);
-
-  int get precedenceLevel => PRIMARY;
-}
-
-/**
- * An empty place in an [ArrayInitializer].
- * For example the list [1, , , 2] would contain two holes.
- */
-class ArrayHole extends Expression {
-  accept(NodeVisitor visitor) => visitor.visitArrayHole(this);
-
-  void visitChildren(NodeVisitor visitor) {}
-
-  ArrayHole _clone() => new ArrayHole();
-
-  int get precedenceLevel => PRIMARY;
-}
-
-class ObjectInitializer extends Expression {
-  final List<Property> properties;
-  final bool isOneLiner;
-
-  /**
-   * Constructs a new object-initializer containing the given [properties].
-   *
-   * [isOneLiner] describes the behaviour when pretty-printing (non-minified).
-   * If true print all properties on the same line.
-   * If false print each property on a seperate line.
-   */
-  ObjectInitializer(this.properties, {this.isOneLiner: true});
-
-  accept(NodeVisitor visitor) => visitor.visitObjectInitializer(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    for (Property init in properties) init.accept(visitor);
-  }
-
-  ObjectInitializer _clone() =>
-      new ObjectInitializer(properties, isOneLiner: isOneLiner);
-
-  int get precedenceLevel => PRIMARY;
-}
-
-class Property extends Node {
-  final Literal name;
-  final Expression value;
-
-  Property(this.name, this.value);
-
-  accept(NodeVisitor visitor) => visitor.visitProperty(this);
-
-  void visitChildren(NodeVisitor visitor) {
-    name.accept(visitor);
-    value.accept(visitor);
-  }
-
-  Property _clone() => new Property(name, value);
-}
-
-/// Tag class for all interpolated positions.
-abstract class InterpolatedNode implements Node {
-  get nameOrPosition;
-
-  bool get isNamed => nameOrPosition is String;
-  bool get isPositional => nameOrPosition is int;
-}
-
-class InterpolatedExpression extends Expression with InterpolatedNode {
-  final nameOrPosition;
-
-  InterpolatedExpression(this.nameOrPosition);
-
-  accept(NodeVisitor visitor) => visitor.visitInterpolatedExpression(this);
-  void visitChildren(NodeVisitor visitor) {}
-  InterpolatedExpression _clone() =>
-      new InterpolatedExpression(nameOrPosition);
-
-  int get precedenceLevel => PRIMARY;
-}
-
-class InterpolatedLiteral extends Literal with InterpolatedNode {
-  final nameOrPosition;
-
-  InterpolatedLiteral(this.nameOrPosition);
-
-  accept(NodeVisitor visitor) => visitor.visitInterpolatedLiteral(this);
-  void visitChildren(NodeVisitor visitor) {}
-  InterpolatedLiteral _clone() => new InterpolatedLiteral(nameOrPosition);
-}
-
-class InterpolatedParameter extends Expression with InterpolatedNode
-    implements Parameter {
-  final nameOrPosition;
-
-  String get name { throw "InterpolatedParameter.name must not be invoked"; }
-  bool get allowRename => false;
-
-  InterpolatedParameter(this.nameOrPosition);
-
-  accept(NodeVisitor visitor) => visitor.visitInterpolatedParameter(this);
-  void visitChildren(NodeVisitor visitor) {}
-  InterpolatedParameter _clone() => new InterpolatedParameter(nameOrPosition);
-
-  int get precedenceLevel => PRIMARY;
-}
-
-class InterpolatedSelector extends Expression with InterpolatedNode {
-  final nameOrPosition;
-
-  InterpolatedSelector(this.nameOrPosition);
-
-  accept(NodeVisitor visitor) => visitor.visitInterpolatedSelector(this);
-  void visitChildren(NodeVisitor visitor) {}
-  InterpolatedSelector _clone() => new InterpolatedSelector(nameOrPosition);
-
-  int get precedenceLevel => PRIMARY;
-}
-
-class InterpolatedStatement extends Statement with InterpolatedNode {
-  final nameOrPosition;
-
-  InterpolatedStatement(this.nameOrPosition);
-
-  accept(NodeVisitor visitor) => visitor.visitInterpolatedStatement(this);
-  void visitChildren(NodeVisitor visitor) {}
-  InterpolatedStatement _clone() => new InterpolatedStatement(nameOrPosition);
-}
-
-/**
- * [RegExpLiteral]s, despite being called "Literal", do not inherit from
- * [Literal]. Indeed, regular expressions in JavaScript have a side-effect and
- * are thus not in the same category as numbers or strings.
- */
-class RegExpLiteral extends Expression {
-  /** Contains the pattern and the flags.*/
-  final String pattern;
-
-  RegExpLiteral(this.pattern);
-
-  accept(NodeVisitor visitor) => visitor.visitRegExpLiteral(this);
-  void visitChildren(NodeVisitor visitor) {}
-  RegExpLiteral _clone() => new RegExpLiteral(pattern);
-
-  int get precedenceLevel => PRIMARY;
-}
-
-/**
- * An asynchronous await.
- *
- * Not part of JavaScript. We desugar this expression before outputting.
- * Should only occur in a [Fun] with `asyncModifier` async or asyncStar.
- */
-class Await extends Expression {
-  /** The awaited expression. */
-  final Expression expression;
-
-  Await(this.expression);
-
-  int get precedenceLevel => UNARY;
-  accept(NodeVisitor visitor) => visitor.visitAwait(this);
-  void visitChildren(NodeVisitor visitor) => expression.accept(visitor);
-  Await _clone() => new Await(expression);
-
-}
-
-/**
- * A comment.
- *
- * Extends [Statement] so we can add comments before statements in
- * [Block] and [Program].
- */
-class Comment extends Statement {
-  final String comment;
-
-  Comment(this.comment);
-
-  accept(NodeVisitor visitor) => visitor.visitComment(this);
-  Comment _clone() => new Comment(comment);
-
-  void visitChildren(NodeVisitor visitor) {}
-}