When we want to extract the value inside the Arc, we usually use:
pub fn get_mut(this: &mut Self) -> Option<&mut T>;
It's very rare to me that using a &mut Arc<T>, I wondered why this function must take a &mut Self? What's the danger if it takes a &Self?
If it took &self then you would still be able to dereference the Arc with deref and get another another reference to the same T, thus breaking the borrowing rules.
It would also be possible to clone the Arc and get simultaneous access that way.
Sorry for asking a silly question, I'v been coding for hours without sleeping, and now I'm experiencing some serious brain fog 