Added TODO.

lib/compiler/implementation/elements/elements.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.
 
 #library('elements');
 
 #import('dart:uri');
 
 #import('../tree/tree.dart');
 #import('../scanner/scannerlib.dart');
@@ skipping 1113 matching lines @@
       return 'origin ${super.toString()}';
     } else {
       return super.toString();
     }
   }
 
   Scope buildScope() {
     Scope result =
         new MethodScope(enclosingElement.buildScope(), this);
     if (enclosingElement.isClass()) {
-      Scope clsScope = result.parent;
+      ClassScope clsScope = result.parent;
       clsScope.inStaticContext = !isInstanceMember() && !isConstructor();
     }
     return result;
   }
 }
 
 class ConstructorBodyElement extends FunctionElement {
   FunctionElement constructor;
 
   ConstructorBodyElement(FunctionElement constructor)
@@ skipping 667 matching lines @@
  * class Bar {}
  * :]
  *
  * In this example, there are three instances of [MetadataAnnotation]
  * and they correspond each to a location in the source code where
  * there is an at-sign, '@'. The [value] of each of these instances
  * are the same compile-time constant, [: const Data() :].
  *
  * The mirror system does not have a concept matching this class.
  */
-class MetadataAnnotation {
+abstract class MetadataAnnotation {
   /**
    * The compile-time constant which this annotation resolves to.
    * In the mirror system, this would be an object mirror.
    */
   abstract Constant get value;
   Element annotatedElement;
   int resolutionState;
 
   MetadataAnnotation([this.resolutionState = STATE_NOT_STARTED]);
 
   MetadataAnnotation ensureResolved(Compiler compiler) {
     if (resolutionState == STATE_NOT_STARTED) {
       compiler.resolver.resolveMetadataAnnotation(this);
     }
     return this;
   }
 
   String toString() => 'MetadataAnnotation($value, $resolutionState)';
 }