What state(s) are iterator adapters allowed to be in after a panic, @rust-lang/libs? Obviously they need to memory safe, but how many items are they expected to have consumed? Is it even allowed to call .next() on an (un-fused) iterator after you called, say, .find() on it with a closure that panicked?

Asking because this has just come up in two PRs:

• RangeInclusive internal iteration performance improvement. #58122 (comment)
• override VecDeque::try_rfold, also update iterator #58064 (comment)