anchor.diff:      List elements = _getElements(context);
   
       if (!_isList) {
  -      if (elements.isEmpty && !_isNullable) {
  +      if (elements.isEmpty && !_isOptional) {
           throw new StateError('Unable to find element for non-nullable, non-list'
               ' field $_fieldName');
         }
  
positive.code:       this._filters,
        this._instanceType,
        this._isList,
        this._isNullable);
  
    @override
    void setField(
  
negative.code:     }
  
      if (finder != null) {
        return new _FinderFieldInfo(name, finder, filters, type, isList, isOptional);
      } else if (type.simpleName == const Symbol('PageLoader')) {
        return new _InjectedPageLoaderInfo(name);
      } else if (type.simpleName == const Symbol('WebDriver')) {
  