Tracking Issue for `core_slice_as_array`.

[bjoernager]

Feature gate: #![feature(core_slice_as_array)]

This is a tracking issue for adding conversion functions going from slices to arrays.

_{This tracking issue has been branched into #148082.}

Public API

// core::slice

impl<T> [T] {
    pub const fn as_array<const N: usize>(&self) -> Option<&[T; N]>;

    pub const fn as_mut_array<const N: usize>(&mut self) -> Option<&mut [T; N]>;
}

// core::ptr

impl<T> *const [T] {
    pub const fn as_array<const N: usize>(self) -> Option<*const [T; N]>;
}

impl<T> *mut [T] {
    pub const fn as_mut_array<const N: usize>(self) -> Option<*mut [T; N]>;
}

Steps / History

• API change proposal (ACP): #496
• Implementation:
  • ... for [_], *const [_], and *mut [_]: Add as_array and as_mut_array conversion methods to slices. #133512
  • Fix docs for <[_]>::as_array: Fix docs for <[T]>::as_array. #133743
• Final comment period (FCP)
• Stabilisation: Stabilise as_array in [_] and *const [_]; stabilise as_mut_array in [_] and *mut [_]. #147540

Unresolved Questions

• None yet.

[bjoernager]

@RustyYato suggests the following signature for the alloc-typed slices:

pub fn into_array<const N: usize>(self) -> Result<Self<[T; N]>, Self<[T]>>;

to prevent accidental leaks if conversion fails. Would this be preferred as-is or would a new error type (e.g. SliceIntoArrayError) have to be defined?

[programmerjake]

well, if you use Rc::<dyn Any>::downcast as precedence, just returning Result<Rc<[T; N]>, Rc<[T]>> (and likewise for other owning types) should be good imo

[bjoernager]

It seems I messed up the docs entry for <[T]>::as_array. I'll make a follow-up PR addressing this when I can.

[bjoernager]

I am aware that they mostly do not specialise any methods, but could (and should) we extend this to also include Mutex and RwLock?