Add a type kind to TypedSelector. A typed selector can either be

sdk/lib/_internal/compiler/implementation/enqueue.dart

Index: sdk/lib/_internal/compiler/implementation/enqueue.dart
===================================================================
--- sdk/lib/_internal/compiler/implementation/enqueue.dart	(revision 18306)
+++ sdk/lib/_internal/compiler/implementation/enqueue.dart	(working copy)
@@ -354,9 +354,10 @@
                            DartType type) {
     task.measure(() {
       Selector getter = new Selector.getter(getterName, library);
-      registerNewSelector(getterName,
-                          new TypedSelector(type, getter),
-                          universe.fieldGetters);
+      registerNewSelector(
+          getterName,
+          new TypedSelector.subclass(type, getter),

[kasperl, 2013/02/11 13:11:50]

Aren't we throwing away information at this point? Couldn't this take a selector
instead of a getterName, a library, and a type? The same goes for the setter.

[ngeoffray, 2013/02/11 14:20:29]

Actually, we should just take an element. Done.

+          universe.fieldGetters);
     });
   }
 
@@ -365,9 +366,10 @@
                            DartType type) {
     task.measure(() {
       Selector setter = new Selector.setter(setterName, library);
-      registerNewSelector(setterName,
-                          new TypedSelector(type, setter),
-                          universe.fieldSetters);
+      registerNewSelector(
+          setterName,
+          new TypedSelector.subclass(type, setter),
+          universe.fieldSetters);
     });
   }