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?
UInt32 scale = extractToDecimalScale(scale_column);
                result_column = ConvertImpl<LeftDataType, RightDataType, Name, SpecialTag>::execute(arguments, result_type, input_rows_count, scale);
            }
            else if constexpr (IsDataTypeDateOrDateTime<RightDataType> && std::is_same_v<LeftDataType, DataTypeDateTime64>)
            {
                const auto * dt64 = assert_cast<const DataTypeDateTime64 *>(arguments[0].type.get());
                result_column = ConvertImpl<LeftDataType, RightDataType, Name, SpecialTag>::execute(arguments, result_type, input_rows_count, dt64->getScale());
            }
            else if constexpr (IsDataTypeDecimalOrNumber<LeftDataType> && IsDataTypeDecimalOrNumber<RightDataType>)
            {
                using LeftT = typename LeftDataType::FieldType;
                using RightT = typename RightDataType::FieldType;
                static constexpr bool bad_left =
                    is_decimal<LeftT> || std::is_floating_point_v<LeftT> || is_big_int_v<LeftT> || is_signed_v<LeftT>;
                static constexpr bool bad_right =
                    is_decimal<RightT> || std::is_floating_point_v<RightT> || is_big_int_v<RightT> || is_signed_v<RightT>;
                
                if constexpr ((bad_left && std::is_same_v<RightDataType, DataTypeUUID>) ||
                              (bad_right && std::is_same_v<LeftDataType, DataTypeUUID>))
                {
                    throw Exception("Wrong UUID conversion", ErrorCodes::CANNOT_CONVERT_TYPE);
                }
                else
                {
                    result_column
                        = ConvertImpl<LeftDataType, RightDataType, Name, SpecialTag>::execute(arguments, result_type, input_rows_count);
                }
            }
            else
            {