anchor.diff:    }
   
     set bound(DartType bound) {
  -    _bound = _checkElementOfType(bound);
  +    _bound = bound;
     }
   
     @override
  
positive.code:   /// [returnType].
    @override
    set returnType(DartType returnType) {
      _returnType = _checkElementOfType(returnType);
    }
  
    @override
  
negative.code:     if (linkedNode != null) {
        return linkedContext.setVariableType(linkedNode, type);
      }
      _type = type;
    }
  
    /// Return the error reported during type inference for this variable, or
  