anchor.diff:          }
           isList = true;
           type = reflectClass(datum.type);
  -      } else if (datum is _Nullable) {
  -        isNullable = true;
  +      } else if (datum is _Optional) {
  +        isOptional = true;
         }
   
         if (datum is HasFilterFinderOptions &&
  
positive.code:     var name;
  
      if (field is VariableMirror) {
        type = field.type;
        name = field.simpleName;
      } else if (field is MethodMirror && field.isSetter) {
        type = field.parameters.first.type;
        // HACK to get correct symbol name for operating with setField.
        name = field.simpleName.toString();
        name = new Symbol(name.substring(8, name.length - 3));
  
negative.code:   final List<Filter> _filters;
    final ClassMirror _instanceType;
    final bool _isList;
    final bool _isOptional;
  
    _FinderFieldInfo(
        this._fieldName,
  