Thanks a lot for the insight. I think if I do it the way shifgrethor did, I can have GC at arbitrary time. But I'm not so sure about that. With the way Rust ma

Thanks a lot for the insight. I think if I do it the way shifgrethor did, I can have GC at arbitrary time. But I'm not so sure about that. With the way Rust may perform optimizations on the assumption of no alias, I guess there's currently no way to avoid RefCell if we want to be 100% on the safe side.