Updated issue to #75027
Update to rm oob access
And hopefully fix docs as well
Fixed naming conflict in test
Fix test which used 1-indexing
Nth starts from 0, woops
Fix a bunch of off by 1 errors
See https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=757b311987e3fae1ca47122969acda5a
Add even more off by 1 errors
And also write `next` and `next_back` in terms of `nth` and `nth_back`.
Run fmt
Fix forgetting to change fn name in test
add nth_back test & document unsafe
Remove as_ref().unwrap()
Documented occurrences of unsafe, noting what invariants are maintained