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?
{
        if (const auto * from_tuple = checkAndGetDataType<DataTypeTuple>(from_type.get()))
        {
            return createTupleToObjectWrapper(*from_tuple, to_type->hasNullableSubcolumns());
        }
        else if (const auto * from_map = checkAndGetDataType<DataTypeMap>(from_type.get()))
        {
            return createMapToObjectWrapper(*from_map, to_type->hasNullableSubcolumns());
        }
        else if (checkAndGetDataType<DataTypeString>(from_type.get()))
        {
            return [] (ColumnsWithTypeAndName & arguments, const DataTypePtr & result_type, const ColumnNullable * nullable_source, size_t input_rows_count)
            {
                auto res = ConvertImplGenericFromString<ColumnString>::execute(arguments, result_type, nullable_source, input_rows_count);
                auto & res_object = assert_cast<ColumnObject &>(res->assumeMutableRef());
                res_object.finalize();
                return res;
            };
        }
        throw Exception(ErrorCodes::TYPE_MISMATCH,
            "Cast to Object can be performed only from flatten named Tuple, Map or String. Got: {}", from_type->getName());
    }
    template <typename FieldType>
    WrapperType createEnumWrapper(const DataTypePtr & from_type, const DataTypeEnum<FieldType> * to_type) const