Tracking Issue for maybe_uninit_fill

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Feature gate: #![feature(maybe_uninit_fill)]

This is a tracking issue for ACP https://github.com/rust-lang/libs-team/issues/156

Public API

// in core

impl<T> [MaybeUninit<T>] {
    pub fn write_filled(&mut self, value: T) -> &mut [T]
    where
        T: Clone;

    pub fn write_with<F>(&mut self, mut f: F) -> &mut [T]
    where
        F: FnMut(usize) -> T;

    pub fn write_iter<I>(&mut self, it: I) -> (&mut [T], &mut [MaybeUninit<T>])
    where
        I: IntoIterator<Item = T>;
}

Steps / History

• Implementation: https://github.com/rust-lang/rust/pull/117426, https://github.com/rust-lang/rust/pull/121280
• Make slice methods inherent: https://github.com/rust-lang/rust/pull/135394
• Final comment period (FCP)^1
• Stabilization PR

Unresolved Questions

• Naming: these were originally named fill, fill_with, and fill_from to be consistent consistent with slice::{fill_with,fill_from}. Since changing to slice-inherent methods, these needed to be renamed to avoid conflict. Should we change to naming that keeps fill? Amanieu suggested fill_init at https://github.com/rust-lang/rust/pull/129259#issuecomment-2501783702.

Start with the public API and the linked implementation PRs for the maybe_uninit_fill feature gate. Review the unresolved naming question and the stabilization lifecycle guidance; done means resolving the open design work, completing the final comment period, and preparing the stabilization PR.