Land 'Fix a crash related to obsolete factory syntax.'.

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 252 matching lines @@
   visitSend(Send node) {
     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 === '+') {
+    // TODO(ahe): remove case for '+' when we drop the support for it.
+    if (node.argumentsNode != null && (opString === '-' || opString === '+')) {
       Token beginToken = node.argumentsNode.getBeginToken();
       if (beginToken !== null && beginToken.stringValue === opString) {
         sb.add(' ');
       }
     }
     visit(node.argumentsNode);
   }
 
   visitSendSet(SendSet node) {
     if (node.isPrefix) {
@@ skipping 304 matching lines @@
   }
 
   visitStatement(Statement node) {
     throw 'internal error'; // Should not be called.
   }
 
   visitStringNode(StringNode node) {
     throw 'internal error'; // Should not be called.
   }
 }