Add null check.

lib/compiler/implementation/tree/unparser.dart

Index: lib/compiler/implementation/tree/unparser.dart
diff --git a/lib/compiler/implementation/tree/unparser.dart b/lib/compiler/implementation/tree/unparser.dart
index b1ca8d66721bec5f2f2e90a71937cfe7b5e949e7..ea3473a514d4ce734bc9b476dd850c94d5278950 100644
--- a/lib/compiler/implementation/tree/unparser.dart
+++ b/lib/compiler/implementation/tree/unparser.dart
@@ -90,7 +90,7 @@ class Unparser implements Visitor {
     // names are modelled with Send and it emits operator[] as only
     // operator, without [] which are expected to be emitted with
     // arguments.
-    Send send = node.name.asSend();
+    Send send = node.name !== null ? node.name.asSend() : null;

[ahe, 2012/06/20 19:25:45]

Perhaps you should change this to use:

if (node.name is Send) {
  ...
}

Also, indentation seems weird. 

[Anton Muhin, 2012/06/20 19:34:49]

Done.  What's wrong w/ indentation?

     if (send !== null) {
       assert(send is !SendSet);
       visit(send.receiver);