Rollup of 4 pull requests#69417

Closed

Dylan-DPC-zz wants to merge 8 commits intorust-lang:masterfrom

Dylan-DPC-zz:rollup-1h781vo

Commits on Feb 22, 2020

Relax str::get_unchecked precondition to permit empty slicing
ridiculousfish
committed
Fix doc example for `MaybeUninit::get_mut()`

danielhenrymantilla
and
Frantisek Fladung
committed

Commits on Feb 23, 2020