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Tracking Issue for maybe_uninit_array_assume_init #80908
Description
Feature gate: #![feature(maybe_uninit_array_assume_init)]
This is a tracking issue for MaybeUninit::array_assume_init.
Public API
// core::mem::maybe_uninit
impl<T> MaybeUninit<T> {
pub unsafe fn array_assume_init<const N: usize>(array: [Self; N]) -> [T; N];
}Steps / History
- Implementation: Add
MaybeUninitmethodarray_assume_init#80600 - Final commenting period (FCP)
- Stabilization PR
Unresolved Questions
- Should this be a const function?
- Should this be a method of array?
- Should this method be replaced by a conversion method from
[MaybeUninit<T>; N]toMaybeUninit<[T; N]>(see comment).
Activity
joboet commentedon Jan 11, 2021
hellow554 commentedon Jan 11, 2021
joboet commentedon Jan 11, 2021
hellow554 commentedon Jan 11, 2021
Rollup merge of rust-lang#81412 - hyd-dev:array-assume-init-wrong-ass…
bstrie commentedon Jan 31, 2021
The documentation for this item suggests that it should be used with another unstable API,
MaybeUninit::uninit_array. However that API is not contained under this feature flag, and furthermore I can't find a tracking issue for it. Should we use this issue to track that one as well?cole-miller commentedon Feb 18, 2021
Fwiw, this function is now used by hashbrown (
nightlycrate feature only, introduced in rust-lang/hashbrown#239). I'd love to see it stabilized soon! (Along withmaybe_uninit_uninit_array.)the8472 commentedon Oct 27, 2021
A possible alternative is to have a conversion method from
[MaybeUninit<T>; N]toMaybeUninit<[T; N]>and thenassume_init()the latter. Then a separatearray_assume_init()function isn't needed.joboet commentedon Dec 12, 2021
That's a good idea!
MaybeUninit::from(_).assume_init()is about the same length asMaybeUninit::array_assume_init(_)and allows for better integration with the other methods.Kixunil commentedon Feb 2, 2022
Converting in the other direction could be useful too as well as between
MaybeUninit<[MaybeUninit<T>; N]>and the rest.clarfonthey commentedon Feb 18, 2022
Would very much like some version of
uninit_arrayandarray_assume_initto be stable; right now there's not really a stable equivalent.IMHO, we should at least collect the array-based issues into a single issue (likely this one) like what's already done with the slice methods in #63569.
Raekye commentedon Apr 14, 2022
MaybeUninit::assume_initis const as of 1.59, and I'd like to see this be const as wellOne issue with the conversion traits (
FromandInto) is that they can't be used in const contexts, so I'd like this function to exist as wellclarfonthey commentedon Apr 16, 2022
I filed #96097 since
MaybeUninit::uninit_arraydidn't have a tracking issue, and linked to this one. So, stuff that doesn't specifically apply toMaybeUninit::array_assume_initand concerns uninit arrays in general can probably go there instead of here.Also created #96099 which adds constness to this method + links everything to the new issue so people are funnelled in the same place. If you think
array_assume_initshould still point here, I would voice so there.joboet commentedon Apr 16, 2022
Thank you! I'll close this issue then. For future readers: please go to #96097 for further discussion of this feature.