Simplify the selector map and get rid of the partial type tree.

sdk/lib/_internal/compiler/implementation/universe/function_set.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.
 
 part of universe;
 
 // TODO(kasperl): This actually holds getters and setters just fine
 // too and stricly they aren't functions. Maybe this needs a better
 // name -- something like ElementSet seems a bit too generic.
 class FunctionSet {
@@ skipping 71 matching lines @@
     assert(element.name == name);
     // We try to avoid clearing the cache unless we have to. For that
     // reason we keep the explicit contains check even though the add
     // method ends up doing the work again (for sets).
     if (!elements.contains(element)) {
       if (isList && elements.length >= MAX_ELEMENTS_IN_LIST) {
         elements = elements.toSet();
         isList = false;
       }
       elements.add(element);
-      cache.clear();
+      if (!cache.isEmpty) cache.clear();

[ngeoffray, 2013/02/14 10:14:33]

Why adding this?

     }
   }
 
   void remove(Element element) {
     assert(element.name == name);
     if (isList) {
       List list = elements;
       int index = list.indexOf(element);
       if (index < 0) return;
       Element last = list.removeLast();
       if (index != list.length) {
         list[index] = last;
       }
-      cache.clear();
+      if (!cache.isEmpty) cache.clear();
     } else {
       Set set = elements;
       if (set.remove(element)) {
         // To avoid wobbling between the two representations, we do
         // not transition back to the list representation even if we
         // end up with few enough elements at this point.
-        cache.clear();
+        if (!cache.isEmpty) cache.clear();
       }
     }
   }
 
   bool contains(Element element) {
     assert(element.name == name);
     return elements.contains(element);
   }
 
   void forEach(Function action) {
@@ skipping 13 matching lines @@
           result = <Element>[];
         }
         result.add(element);
       }
     }
     if (result == null) result = const <Element>[];
     cache[selector] = result;
     return result;
   }
 }