17c94b5f12
Add invariant to VecDeque::pop_* that len < cap if pop successful Similar to #114370 for VecDeque instead of Vec. I initially come from https://github.com/rust-itertools/itertools/pull/899 where we noticed that `pop_front;push_back;` was slower than expected so `@scottmcm` suggested I file an issue which lead to https://internals.rust-lang.org/t/vecdeque-pop-front-push-back/20483 where **kornel** mentionned #114334 (fixed by #114370). This is my first time with codegen tests, I based the test on what was done for Vec.