Revert "Normalize type masks to use the least upper instantiated subclass/type."

pkg/compiler/lib/src/types/flat_type_mask.dart

 // Copyright (c) 2013, 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 types;
 
 /**
  * A flat type mask is a type mask that has been flattened to contain a
  * base type.
  */
@@ skipping 528 matching lines @@
         || classWorld.hasAnySubclassThatMixes(mixinApplication, other));
     }
   }
 
   /**
    * Returns whether a [selector] call on an instance of [cls]
    * will hit a method at runtime, and not go through [noSuchMethod].
    */
   static bool hasConcreteMatch(ClassElement cls,
                                Selector selector,
-                               ClassWorld world) {
-    assert(invariant(cls, world.isInstantiated(cls),
+                               World world) {
+    assert(invariant(cls,
+        world.compiler.resolverWorld.isInstantiated(cls),
         message: '$cls has not been instantiated.'));
     Element element = findMatchIn(cls, selector);
     if (element == null) return false;
 
     if (element.isAbstract) {
       ClassElement enclosingClass = element.enclosingClass;
       return hasConcreteMatch(enclosingClass.superclass, selector, world);
     }
     return selector.appliesUntyped(element, world);
   }
@@ skipping 142 matching lines @@
     if (x.isExact) {
       return null;
     } else if (x.isSubclass) {
       return classWorld.strictSubclassesOf(element);
     } else {
       assert(x.isSubtype);
       return classWorld.strictSubtypesOf(element);
     }
   }
 }