Tracking Issue for raw slice getters (slice_ptr_get)

[RalfJung]

This is a tracking issue for indexing methods on raw slices: get_unchecked(_mut) and as_(mut_/non_null_)ptr on raw slices (mutable and const raw pointers and NonNull).

The feature gate for the issue is #![feature(slice_ptr_get)].

Public API

impl<T> *mut [T] {
    pub const fn as_mut_ptr(self) -> *mut T {}
    pub unsafe fn get_unchecked_mut<I>(self, index: I) -> *mut I::Output where I: SliceIndex<[T]>;
}

impl<T> *const [T] {
    pub const fn as_ptr(self) -> *const T {}
    pub unsafe fn get_unchecked<I>(self, index: I) -> *const I::Output where I: SliceIndex<[T]>;
}

impl<T> NonNull<[T]> {
    pub const fn as_non_null_ptr(self) -> NonNull<T> {}
    pub const fn as_mut_ptr(self) -> *mut T {}
    pub unsafe fn get_unchecked_mut<I>(self, index: I) -> NonNull<I::Output> where I: SliceIndex<[T]>;
}

History / Steps

• Initial PR: add (unchecked) indexing methods to raw (and NonNull) slices #73986
• Add NonNull::as_mut_ptr: Add as_mut_ptr to NonNull<[T]> #75248
• Final commenting period (FCP)
• Stabilization PR

Open questions

• Potential blockers: rustc performs auto-ref when a raw pointer would be enough #73987, Missing unsizing coercions for raw slice pointers #74679
• Should this use arbitrary_self_types (Arbitrary self types v2 rfcs#3519)

[RalfJung]

#74679 is a potential blocker for this.

[RalfJung]

With #75152, the allocator trait started making use of this.

[TimDiekmann]

Especially with AllocRef using it, it would come in handy if we could also add

impl<T> NonNull<[T]> {
    #[inline]
    fn as_mut_ptr(self) -> *mut T {
        self.as_non_null_ptr().as_ptr()
    }
}

If we want this I'd make a PR.

[RalfJung]

Seems reasonable to me -- @Amanieu what do you think?

[TimDiekmann]

An alternative name would be as_raw_ptr to avoid confusion with as_ptr, which already returns *mut T. This would also apply to *const [T] and *mut [T].

[Amanieu]

I don't particularly care for the name bikeshed but I agree that this method would be useful.

[TimDiekmann]

This issue now also tracks NonNull::<[T]>::as_mut_ptr(). I can't edit the OP as I'm not a collaborator of this repository.

At "Implementation history" this has to be added:

• as_mut_ptr for NonNull<[T]>: Add as_mut_ptr to NonNull<[T]> #75248.