Avoid creating invalid TypeMask.nonNullExact

pkg/compiler/lib/src/elements/common.dart

 // Copyright (c) 2015, 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.
 
 /// Mixins that implement convenience methods on [Element] subclasses.
 
 library elements.common;
 
 import '../common/names.dart' show
     Names,
@@ skipping 388 matching lines @@
           }
         }
       }
       lookupClass = lookupClass.superclass;
     }
     return false;
   }
 
   @override
   bool implementsInterface(ClassElement intrface) {
-    for (DartType implementedInterfaceType in allSupertypes) {
-      ClassElement implementedInterface = implementedInterfaceType.element;
-      if (identical(implementedInterface, intrface)) {
-        return true;
-      }
-    }
-    return false;
+    return this != intrface &&
+        allSupertypesAndSelf.asInstanceOf(intrface) != null;

[Johnni Winther, 2015/10/13 10:14:55]

Optimization

   }
 
   @override
   bool isSubclassOf(ClassElement cls) {
     // Use [declaration] for both [this] and [cls], because
     // declaration classes hold the superclass hierarchy.
     cls = cls.declaration;
     for (ClassElement s = declaration; s != null; s = s.superclass) {
       if (identical(s, cls)) return true;
     }
@@ skipping 63 matching lines @@
       // this signature must not have more required parameters.  Having more
       // optional parameters is not a problem, they simply are never provided
       // by call sites of a call to a method with the other signature.
       int otherTotalCount = signature.parameterCount;
       return requiredParameterCount <= otherTotalCount
           && parameterCount >= otherTotalCount;
     }
     return true;
   }
 }