Added TODO.

lib/compiler/implementation/compiler.dart

Index: lib/compiler/implementation/compiler.dart
diff --git a/lib/compiler/implementation/compiler.dart b/lib/compiler/implementation/compiler.dart
index 39ca6fe83e74ad3e26b2268ea1579667d0d5622b..f2dbc25ef8caac3b115b7b26f9ee79801749a098 100644
--- a/lib/compiler/implementation/compiler.dart
+++ b/lib/compiler/implementation/compiler.dart
@@ -841,8 +841,11 @@ class Compiler implements DiagnosticListener {
     // TODO(ager,johnniwinther): The patch support should be
     // reworked to allow us to get rid of this.
     if (element.isPatched) {
-      position = element.patch.position();
-      uri = element.patch.getCompilationUnit().script.uri;
+      // TODO(johnniwinther,karlklose): create a subtype of Element for
+      // patchable elements or move the patch field to Element.
+      var patched = element;
+      position = patched.patch.position();
+      uri = patched.patch.getCompilationUnit().script.uri;
     }
 
     return (position === null)