Tracking Issue for `borrowed_buf_init`

Feature gate: #![feature(borrowed_buf_init)]

This is a tracking issue for borrowed_buf_init

Public API

impl<'data, T> BorrowedBuf<'data, T> {
    pub fn is_init(&self) -> bool;
}

impl<'data, T: Copy> BorrowedBuf<'data, T> {
    pub unsafe fn set_init(&mut self) -> &mut Self;
}

impl<'a, T: Copy> BorrowedCursor<'a, T> {
    pub fn is_init(&self) -> bool;
    pub unsafe fn set_init(&mut self);
    pub fn advance_checked(&mut self, n: usize) -> &mut Self;
}

impl<'a> BorrowedCursor<'a, u8> {
    pub fn ensure_init(&mut self) -> &mut [u8];
}

Steps / History

• Implementation on the preexisting tracking issues: https://github.com/rust-lang/rust/issues/78485, https://github.com/rust-lang/rust/issues/117693
• Make ensure_init generic over T: Default: #160432
• Final comment period (FCP)^1
• Stabilization PR

Unresolved Questions

• Can the bounds for ensure_init be weakened to T: Default? Or should we have API more similar to [T: Clone]::fill(&mut self, value: T) / [T]::fill_with<F: FnMut() -> T>(&mut self, f: F)?

Read the listed BorrowedBuf and BorrowedCursor API and issue #160432 first, then review the feature-lifecycle stabilization guidance linked in the tracking issue. Done means resolving the ensure_init bounds question, completing the final comment period, and producing the stabilization PR.