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?
data_to.resize(size * (strlen("YYYY-MM-DD") + 1));
            else if constexpr (std::is_same_v<FromDataType, DataTypeDateTime>)
                data_to.resize(size * (strlen("YYYY-MM-DD hh:mm:ss") + 1));
            else if constexpr (std::is_same_v<FromDataType, DataTypeDateTime64>)
                data_to.resize(size * (strlen("YYYY-MM-DD hh:mm:ss.") + col_from->getScale() + 1));
            else
                data_to.resize(size * 3);   
            offsets_to.resize(size);
            WriteBufferFromVector<ColumnString::Chars> write_buffer(data_to);
            if (null_map)
            {
                for (size_t i = 0; i < size; ++i)
                {
                    bool is_ok = FormatImpl<FromDataType>::template execute<bool>(vec_from[i], write_buffer, &type, time_zone);
                    null_map->getData()[i] |= !is_ok;
                    writeChar(0, write_buffer);
                    offsets_to[i] = write_buffer.count();
                }
            }
            else
            {
                for (size_t i = 0; i < size; ++i)
                {
                    FormatImpl<FromDataType>::template execute<void>(vec_from[i], write_buffer, &type, time_zone);
                    writeChar(0, write_buffer);
                    offsets_to[i] = write_buffer.count();
                }
            }
            write_buffer.finalize();
            if (null_map)