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?
{
    x = time;
}
template <>
inline void convertFromTime<DataTypeDateTime>(DataTypeDateTime::FieldType & x, time_t & time)
{
    if (unlikely(time < 0))
        x = 0;
    else if (unlikely(time > 0xFFFFFFFF))
        x = 0xFFFFFFFF;
    else
        x = time;
}
/** Conversion of strings to numbers, dates, datetimes: through parsing.
  */
template <typename DataType>
void parseImpl(typename DataType::FieldType & x, ReadBuffer & rb, const DateLUTImpl *)
{
    readText(x, rb);
}
template <>
inline void parseImpl<DataTypeDate>(DataTypeDate::FieldType & x, ReadBuffer & rb, const DateLUTImpl *)
{
    DayNum tmp(0);
    readDateText(tmp, rb);
    x = tmp;
}
template <>
inline void parseImpl<DataTypeDate32>(DataTypeDate32::FieldType & x, ReadBuffer & rb, const DateLUTImpl *)