i know that using RefCell has a runtime cost, and also i’ve learn that i can avoid using it by replacing it with Cell<Option<T>> or Cell<T>(T impl Default) and use take or replace to get the instance, mutate it then put it back.

but there’s also some cost, i have to wrap T with Some and use if let Some(t) & .set(Some(t)) to get and put it back. i don’t know if it worth replacing RefCell with Cell<Option>