Index double assert?

[tower120]

id-arena/src/lib.rs

Line 510 in 473ce26

fn index(&self, id: A::Id) -> &T {

Since you already do safety check assert_eq!(self.arena_id, A::arena_id(id));, maybe it is possible to use self.items.get instead of []?
In order to omit Vec's assert inside Index.

[LindonKelley]

If I'm understanding the issue correctly, I believe you are confusing the arena_id check as being equivalent to the Vec index check, or were you actually implying that if the arena_id is equivalent then id must be inside the range of self.items?