Tracking issue for `#![feature(maybe_uninit_extra,const_maybe_uninit_write)]`

[Centril]

This is a tracking issue for the RFC "Deprecate uninitialized in favor of a new MaybeUninit type" (rust-lang/rfcs#1892).

This issue specifically tracks the following unstable methods:

impl<T> MaybeUninit<T> {
    pub unsafe fn assume_init_read(&self) -> T { ... }
    pub unsafe fn assume_init_drop(&mut self) { ... }
}

and it tracks const-ness of

impl<T> MaybeUninit<T> {
    pub const fn write(&mut self, val: T) -> &mut T { ... }
}

[RalfJung]

Latest status here:

I am beginning to think that read should probably be renamed to read_init or read_assume_init or so, something that indicates that this may only be done after initialization is complete.

[SimonSapin]

@RalfJung Should the same logic apply to get_ref and get_mut? #63568

[RalfJung]

That depends on whether references to invalid data are UB or not. If yes, then certainly. If not, then maybe.

Currently they are UB but that's just because it is the more conservative choice.