Fix a crash related to obsolete factory syntax.

dart/lib/compiler/implementation/tree/unparser.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.
 
 String unparse(Node node) {
   Unparser unparser = new Unparser();
   unparser.unparse(node);
   return unparser.result;
 }
 
@@ skipping 253 matching lines @@
     Operator op = node.selector.asOperator();
     String opString = op !== null ? op.source.stringValue : null;
     bool spacesNeeded = opString === 'is' || opString === 'as';
 
     if (node.isPrefix) visit(node.selector);
     unparseSendReceiver(node, spacesNeeded: spacesNeeded);
     if (!node.isPrefix && !node.isIndex) visit(node.selector);
     if (spacesNeeded) sb.add(' ');
     // Also add a space for sequences like x + +1 and y - -y.
     if (opString === '-' || opString === '+') {
-      Token beginToken = node.argumentsNode.getBeginToken();
-      if (beginToken !== null && beginToken.stringValue === opString) {
-        sb.add(' ');
+      if (node.argumentsNode != null) {

[karlklose, 2012/10/15 07:59:26]

You could add this condition to the if above.

[Lasse Reichstein Nielsen, 2012/10/15 08:34:37]

And eventually remove the '+' case when we drop support for that.

+        Token beginToken = node.argumentsNode.getBeginToken();
+        if (beginToken !== null && beginToken.stringValue === opString) {
+          sb.add(' ');
+        }
       }
     }
     visit(node.argumentsNode);
   }
 
   visitSendSet(SendSet node) {
     if (node.isPrefix) {
       sb.add(' ');
       visit(node.assignmentOperator);
     }
@@ skipping 301 matching lines @@
   }
 
   visitStatement(Statement node) {
     throw 'internal error'; // Should not be called.
   }
 
   visitStringNode(StringNode node) {
     throw 'internal error'; // Should not be called.
   }
 }