Make TypeMask an interface and start hiding implementation details of FlatTypeMask.

sdk/lib/_internal/compiler/implementation/world.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 dart2js;
 
 class World {
   final Compiler compiler;
   final Map<ClassElement, Set<MixinApplicationElement>> mixinUses;
   final Map<ClassElement, Set<ClassElement>> typesImplementedBySubclasses;
@@ skipping 130 matching lines @@
       allFunctions.add(element);
     }
   }
 
   VariableElement locateSingleField(Selector selector) {
     Element result = locateSingleElement(selector);
     return (result != null && result.isField()) ? result : null;
   }
 
   Element locateSingleElement(Selector selector) {
-    Iterable<Element> targets = allFunctions.filter(selector);
-    if (targets.length != 1) return null;
-    Element result = targets.first;
-    ClassElement enclosing = result.getEnclosingClass();
-    // TODO(kasperl): Move this code to the type mask.
-    ti.TypeMask mask = selector.mask;
-    ClassElement receiverTypeElement = (mask == null || mask.base == null)
-        ? compiler.objectClass
-        : mask.base.element;
-    // We only return the found element if it is guaranteed to be
-    // implemented on the exact receiver type. It could be found in a
-    // subclass or in an inheritance-wise unrelated class in case of
-    // subtype selectors.
-    return (receiverTypeElement.isSubclassOf(enclosing)) ? result : null;
+    ti.TypeMask mask = selector.mask == null
+        ? new ti.TypeMask.subclass(compiler.objectClass.rawType)
+        : selector.mask;
+    return mask.locateSingleElement(selector, compiler);
   }
 
   bool hasSingleMatch(Selector selector) {
     Iterable<Element> targets = allFunctions.filter(selector);
     return targets.length == 1;
   }
 
   Iterable<ClassElement> locateNoSuchMethodHolders(Selector selector) {
     Selector noSuchMethodSelector = compiler.noSuchMethodSelector;
     ti.TypeMask mask = selector.mask;
     if (mask != null) {
       noSuchMethodSelector = new TypedSelector(mask, noSuchMethodSelector);
     }
     ClassElement objectClass = compiler.objectClass;
     return allFunctions
         .filter(noSuchMethodSelector)
         .map((Element member) => member.getEnclosingClass())
         .where((ClassElement holder) => !identical(holder, objectClass));
   }
 
   void addFunctionCalledInLoop(Element element) {
     functionsCalledInLoop.add(element);
   }
 
   bool isCalledInLoop(Element element) {
     return functionsCalledInLoop.contains(element);
   }
 }