anchor.diff:  /// fields.
   class BoxLocal extends Local {
     final String name;
  -  final ExecutableElement executableContext;
  +  final Entity executableContext;
  +  final MemberEntity memberContext;
   
     final int hashCode = _nextHashCode = (_nextHashCode + 10007).toUnsigned(30);
     static int _nextHashCode = 0;
   
  -  BoxLocal(this.name, this.executableContext);
  -
  -  @override
  -  MemberElement get memberContext => executableContext.memberContext;
  +  BoxLocal(this.name, this.executableContext, this.memberContext);
   
     String toString() => 'BoxLocal($name)';
   }
  
positive.code:   }
  
    @override
    MemberElement get memberContext => box.executableContext.memberContext;
  
    @override
    List<FunctionElement> get nestedClosures => const <FunctionElement>[];
  
negative.code:         if (box == null) {
            // TODO(floitsch): construct better box names.
            String boxName = getBoxFieldName(closureFieldCounter++);
            box = new BoxLocal(
                boxName, executableContext, executableContext.memberContext);
          }
          String elementName = variable.name;
          String boxedName =
  