Better PrettyPrinter output for Return nodes, display tokens and expression.

lib/compiler/implementation/tree/prettyprint.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.
 
 /**
  * Pretty-prints Node tree in XML-like format.
  *
  * TODO(smok): Add main() to run from command-line to print out tree for given
  * .dart file.
  */
@@ skipping 223 matching lines @@
 
   visitOperator(Operator node) {
     openAndCloseNode("Operator", {"value" : node.token.slowToString()});
   }
 
   visitParenthesizedExpression(ParenthesizedExpression node) {
     visitNodeWithChildren(node, "ParenthesizedExpression");
   }
 
   visitReturn(Return node) {
-    visitNodeWithChildren(node, "Return");
+    var beginToken =
+        node.beginToken !== null ? node.beginToken.stringValue : "null";
+    var endToken = node.endToken !== null ? node.endToken.stringValue : "null";
+    openNode("Return", {"beginToken" : beginToken, "endToken" : endToken});
+    if (node.hasExpression) visitWithPrefix(node.expression, "expression:");
+    closeNode("Return");
   }
 
   visitScriptTag(ScriptTag node) {
     visitNodeWithChildren(node, "ScriptTag");
   }
 
   /** Custom helper to visit given node and print its type with prefix. */
   visitWithPrefix(Node node, String prefix) {
     nextTypePrefix = prefix;
     node.accept(this);
@@ skipping 64 matching lines @@
   }
 
   visitVariableDefinitions(VariableDefinitions node) {
     visitNodeWithChildren(node, "VariableDefinitions");
   }
 
   visitWhile(While node) {
     visitNodeWithChildren(node, "While");
   }
 }