Slice iter cleanup

[hkBst]

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[rustbot]

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[hkBst]

r? libs

[ibraheemdev]

Going to pass this one along. r? libs

[hkBst]

@rustbot ready

Perhaps a perf run to see if I haven't regressed anything unwittingly?

[joboet]

I'd add that next must not be called if __get_unchecked was called, so invalidating previously returned items does not conflict with TrustedRandomAccess.

[hkBst]

While that is true, I don't see how this particular next method is special in that regard. So would you then like all next methods of iterators that impl TrustedRandomAccess to get such a comment?

[rustbot]

This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

[hkBst]

@joboet Thanks for reviewing so far; your comments have been very helpful!

I've removed all uses of overflowing_* and also switched all remaining conditions like if n >= len { code } else { code that needs the condition to be correct } to if n < len { code that needs the condition to be correct } else { code }.