Tracking Issue for const_borrow

[lilasta]

Feature gate: #![feature(const_borrow)]

This is a tracking issue for implementing const Borrow/BorrowMut.

Public API

// core::borrow
impl<T: ?Sized> const Borrow<T> for T
impl<T: ?Sized> const BorrowMut<T> for T
impl<T: ?Sized> const Borrow<T> for &T
impl<T: ?Sized> const Borrow<T> for &mut T
impl<T: ?Sized> const BorrowMut<T> for &mut T

// core::array
impl<T, const N: usize> const Borrow<[T]> for [T; N]
impl<T, const N: usize> const BorrowMut<[T]> for [T; N]

Steps / History

• Implementation: Make Borrow and BorrowMut impls const #90270
• Final comment period (FCP)
• Stabilization PR

Unresolved Questions

• None yet.

[DavidSkrundz]

It appears the implementation was removed in 76dbe29#diff-b8d90f158b67cb63e13a53302629ba287759aed739f9e10ee524d5ef8592b9ca. Is there an alternative or a plan to reintroduce the feature?

[lilasta]

According to #110395, it will be restored after `~const' trait is reimplemented.

[RalfJung]

Is any part of this feature left after #110393? Cc @fee1-dead

That PR removed a lot of rustc_const_unstable, likely all those tracking issues are outdated now.

[RalfJung]

I can't find any mention of 91522 in the codebase, so I''ll close this issue -- this feature has been removed.