First stab at parsing redirecting constructors.

lib/compiler/implementation/tree/nodes.dart

 // 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.
 
 abstract class Visitor<R> {
   const Visitor();
 
   abstract R visitNode(Node node);
 
   R visitBlock(Block node) => visitStatement(node);
@@ skipping 894 matching lines @@
 
 class Operator extends Identifier {
   Operator(Token token) : super(token);
 
   Operator asOperator() => this;
 
   accept(Visitor visitor) => visitor.visitOperator(this);
 }
 
 class Return extends Statement {
-  final Expression expression;
+  final Node expression;
   final Token beginToken;
   final Token endToken;
 
   Return(this.beginToken, this.endToken, this.expression);
 
   Return asReturn() => this;
 
   bool get hasExpression => expression !== null;
 
+  bool get isRedirectingConstructorBody => beginToken.stringValue == '=';
+
   accept(Visitor visitor) => visitor.visitReturn(this);
 
   visitChildren(Visitor visitor) {
     if (expression !== null) expression.accept(visitor);
   }
 
   Token getBeginToken() => beginToken;
 
   Token getEndToken() {
     if (endToken === null) return expression.getEndToken();
@@ skipping 1041 matching lines @@
  * argument).
  *
  * TODO(ahe): This method is controversial, the team needs to discuss
  * if top-level methods are acceptable and what naming conventions to
  * use.
  */
 initializerDo(Node node, f(Node node)) {
   SendSet send = node.asSendSet();
   if (send !== null) return f(send.arguments.head);
 }