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?
{
        writeText(x, type->getScale(), wb, false);
        return ReturnType(true);
    }
};
template <typename FieldType, typename Name>
struct ConvertImpl<DataTypeEnum<FieldType>, DataTypeNumber<FieldType>, Name, ConvertDefaultBehaviorTag>
{
    static ColumnPtr execute(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t )
    {
        return arguments[0].column;
    }
};
static ColumnUInt8::MutablePtr copyNullMap(ColumnPtr col)
{
    ColumnUInt8::MutablePtr null_map = nullptr;
    if (const auto * col_null = checkAndGetColumn<ColumnNullable>(col.get()))
    {
        null_map = ColumnUInt8::create();
        null_map->insertRangeFrom(col_null->getNullMapColumn(), 0, col_null->size());
    }
    return null_map;
}
template <typename FromDataType, typename Name>
requires (!std::is_same_v<FromDataType, DataTypeString>)
struct ConvertImpl<FromDataType, DataTypeString, Name, ConvertDefaultBehaviorTag>
{
    using FromFieldType = typename FromDataType::FieldType;
    using ColVecType = ColumnVectorOrDecimal<FromFieldType>;
    static ColumnPtr execute(const ColumnsWithTypeAndName & arguments, const DataTypePtr &, size_t )