I expect it should work:
```
:) select CAST(CAST('{"x" : 1}', 'Object(\'json\')'), 'Object(Nullable(\'json\'))')

SELECT CAST(CAST('{"x" : 1}', 'Object(\'json\')'), 'Object(Nullable(\'json\'))')

Query id: fb057b45-b72a-4d22-9b38-a3136cdf2465


0 rows in set. Elapsed: 0.002 sec.

Received exception from server (version 22.5.1):
Code: 53. DB::Exception: Received from localhost:9000. DB::Exception: Cast to Object can be performed only from flatten named Tuple, Map or String. Got: Object('json'): While processing CAST(CAST('{"x" : 1}', 'Object(\'json\')'), 'Object(Nullable(\'json\'))'). (TYPE_MISMATCH)
```

@CurtizJ what do you think?
if (requested_result_is_nullable)
                    {
                        
                        
                        
                        result_column = ConvertImpl<LeftDataType, RightDataType, FunctionName, ConvertReturnNullOnErrorTag>::execute(
                            arguments, result_type, input_rows_count, scale);
                        return true;
                    }
                }
                result_column = ConvertImpl<LeftDataType, RightDataType, FunctionName>::execute(arguments, result_type, input_rows_count, scale);
                return true;
            });
            
            if (!res)
            {
                if (wrapper_cast_type == CastType::accurateOrNull)
                {
                    auto nullable_column_wrapper = FunctionCast<FunctionName>::createToNullableColumnWrapper();
                    return nullable_column_wrapper(arguments, result_type, column_nullable, input_rows_count);
                }
                else
                    throw Exception(ErrorCodes::CANNOT_CONVERT_TYPE,
                        "Conversion from {} to {} is not supported",
                        type_index, to_type->getName());
            }
            return result_column;
        };
    }
    WrapperType createAggregateFunctionWrapper(const DataTypePtr & from_type_untyped, const DataTypeAggregateFunction * to_type) const