anchor.diff:  
   import '../messages.dart'
       show
  -        messageInternalProblemBodyOnAbstractMethod,
           messageNonInstanceTypeVariableUse,
           messagePatchDeclarationMismatch,
           messagePatchDeclarationOrigin,
  
positive.code: 
  import '../parser.dart' show noLength;
  
  import '../problems.dart' show internalProblem, unexpected;
  
  import '../deprecated_problems.dart' show deprecated_inputError;
  
  
negative.code:   KernelFunctionBuilder get actualOrigin;
  
    void set body(Statement newBody) {
  //    if (newBody != null) {
  //      if (isAbstract) {
  //        // TODO(danrubel): Is this check needed?
  //        return internalProblem(messageInternalProblemBodyOnAbstractMethod,
  //            newBody.fileOffset, fileUri);
  //      }
  //    }
      actualBody = newBody;
      if (function != null) {
        // A forwarding semi-stub is a method that is abstract in the source code,
  