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?
{
        static_assert(std::is_same_v<StringColumnType, ColumnString> || std::is_same_v<StringColumnType, ColumnFixedString>,
                "Can be used only to parse from ColumnString or ColumnFixedString");
        const IColumn & col_from = *arguments[0].column;
        const IDataType & data_type_to = *result_type;
        if (const StringColumnType * col_from_string = checkAndGetColumn<StringColumnType>(&col_from))
        {
            auto res = data_type_to.createColumn();
            IColumn & column_to = *res;
            column_to.reserve(input_rows_count);
            FormatSettings format_settings;
            auto serialization = data_type_to.getDefaultSerialization();