anchor.diff:        _checkImplementsSuperClass(implementsClause);
         _checkMixinInference(node, withClause);
         _checkForMixinWithConflictingPrivateMember(withClause, superclass);
  -      if (!disableConflictingGenericsCheck) {
  -        _checkForConflictingGenerics(node);
  -      }
  +      _checkForConflictingGenerics(node);
       }
     }
   
  
positive.code: 
    final _UninstantiatedBoundChecker _uninstantiatedBoundChecker;
  
    /// Setting this flag to `true` disables the check for conflicting generics.
    /// This is used when running with the old task model to work around
    /// dartbug.com/32421.
    ///
    /// TODO(paulberry): remove this flag once dartbug.com/32421 is properly
    /// fixed.
    final bool disableConflictingGenericsCheck;
  
    /// The features enabled in the unit currently being checked for errors.
    FeatureSet _featureSet;
  
  
negative.code:    * Initialize a newly created error verifier.
     */
    ErrorVerifier(ErrorReporter errorReporter, this._currentLibrary,
        this._typeProvider, this._inheritanceManager, bool enableSuperMixins)
        : _errorReporter = errorReporter,
          _uninstantiatedBoundChecker =
              _UninstantiatedBoundChecker(errorReporter),
  