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 (result_is_bool)
                    {
                        vec_to[i] = vec_from[i] != FromFieldType(0);
                        continue;
                    }
                }
                if constexpr (std::is_same_v<FromDataType, DataTypeUUID> != std::is_same_v<ToDataType, DataTypeUUID>)
                {
                    throw Exception("Conversion between numeric types and UUID is not supported", ErrorCodes::NOT_IMPLEMENTED);
                }
                else
                {
                    if constexpr (IsDataTypeDecimal<FromDataType> || IsDataTypeDecimal<ToDataType>)
                    {
                        if constexpr (std::is_same_v<Additions, AccurateOrNullConvertStrategyAdditions>)
                        {
                            ToFieldType result;
                            bool convert_result = false;
                            if constexpr (IsDataTypeDecimal<FromDataType> && IsDataTypeDecimal<ToDataType>)
                                convert_result = tryConvertDecimals<FromDataType, ToDataType>(vec_from[i], col_from->getScale(), col_to->getScale(), result);
                            else if constexpr (IsDataTypeDecimal<FromDataType> && IsDataTypeNumber<ToDataType>)
                                convert_result = tryConvertFromDecimal<FromDataType, ToDataType>(vec_from[i], col_from->getScale(), result);
                            else if constexpr (IsDataTypeNumber<FromDataType> && IsDataTypeDecimal<ToDataType>)
                                convert_result = tryConvertToDecimal<FromDataType, ToDataType>(vec_from[i], col_to->getScale(), result);
                            if (convert_result)
                                vec_to[i] = result;
                            else
                            {
                                vec_to[i] = static_cast<ToFieldType>(0);
                                (*vec_null_map_to)[i] = true;