stabilize ptr_cast_slice

[malezjaa]

Stabilization report

Closes #149103

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.

Implementation

1. Implementation PR: Implement cast_slice for raw pointer types #149110
2. Migrated std to use ptr.cast_slice: Migrate libraries from ptr::slice_from_raw_parts to .cast_slice #156109

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]>;
}

r? @nia-e

@rustbot modify labels: +T-libs

[rustbot]

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[nia-e]

seems fine. i think it's small enough that we can const-stabilise it too yeah.

@rfcbot merge libs

[rust-rfcbot]

@nia-e has proposed to merge this. The next step is review by the rest of the tagged team members:

• @ChrisDenton
• @Mark-Simulacrum
• @cuviper
• @dtolnay
• @joshtriplett
• @nia-e
• @the8472
• @thomcc

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[Paladynee]

i'd like to change the documentation to point to ptr::slice_from_raw_parts instead of inlining it before we stabilize, like ptr.copy_from_nonoverlapping pointing to ptr::copy_nonoverlapping