Tracking Issue for `#![feature(ptr_cast_slice)]`

Feature gate: #![feature(ptr_cast_slice)]

This is a tracking issue for https://github.com/rust-lang/libs-team/issues/693

This feature adds method calls on raw pointers that call into the respective ptr::slice_from_raw_parts{_mut} method for the types *const T, *mut T and NonNull<T> to make using raw pointers more ergonomic in Rust by supporting postfix method chain syntax while creating slices.

Public API

// core::ptr::const_ptr
impl<T> *const T {
    pub const fn cast_slice(self, len: usize) -> *const [T];
}

// core::ptr::mut_ptr
impl<T> *mut T {
    pub const fn cast_slice(self, len: usize) -> *mut [T];
}

// core::ptr::non_null
impl<T> NonNull<T> {
    pub const fn cast_slice(self, len: usize) -> NonNull<[T]>;
}

Steps / History

(Remember to update the S-tracking-* label when checking boxes.)

• ACP: rust-lang/libs-team#693
• Implementation: https://github.com/rust-lang/rust/pull/149110
• Final comment period (FCP)^1
• Stabilization PR

Unresolved Questions

• the inference problem
  • infers: let null10: *const [u8] = ptr::slice_from_raw_parts(ptr::null(), 10);
  • does not infer: let null10: *const [u8] = ptr::null().cast_slice(10);
  • deemed okay to have https://github.com/rust-lang/rust/issues/149103#issuecomment-4972276661

Start with the implementation PR #149110 and the public API in core::ptr::const_ptr, core::ptr::mut_ptr, and core::ptr::non_null, then read the stabilization process linked in the issue. Done means completing the final comment period and opening the stabilization PR once unresolved questions are addressed.