Guideline idea: Blanket ban on use of "unchecked_" functions in the standard library

[vapdrs]

Following this discussion thread it should be investigated which if any of this functions are useful in a safety critical context. Otherwise their use should be discouraged.

[AchimKriso]

Is there a reason to single out unchecked_ functions over other unsafe operations?
IMO, a rule for banning unsafe operations in general makes more sense (where you then can deviate where necessary).

Unless we're only talking unchecked arithmetic, which appears was the trigger for this issue in the first place, but is not reflected in the ticket description.
I'd agree that it is rarely if ever worth it to use unchecked arithmetic over safe alternatives.

But other unchecked functions are sometimes simply necessary like Pin::new_unchecked. And banning those, unless under the umbrella of a more general guideline, does not seem worth it to me.