Rollup merge of rust-lang#111453 - scottmcm:constify-as-slice, r=Mark…

…-Simulacrum

constify `slice_as_chunks` (unstable)

Tracking issue: rust-lang#74985

Nothing complicated required; just adding `const` to the declarations.

library/core/src/lib.rs

@@ -153,6 +153,7 @@
 #![feature(const_slice_is_ascii)]
 #![feature(const_slice_ptr_len)]
 #![feature(const_slice_split_at_mut)]
+#![feature(const_slice_split_at_not_mut)]
 #![feature(const_str_from_utf8_unchecked_mut)]
 #![feature(const_swap)]
 #![feature(const_transmute_copy)]

library/core/src/slice/mod.rs

@@ -995,7 +995,7 @@ impl<T> [T] {
     #[unstable(feature = "slice_as_chunks", issue = "74985")]
     #[inline]
     #[must_use]
-    pub unsafe fn as_chunks_unchecked<const N: usize>(&self) -> &[[T; N]] {
+    pub const unsafe fn as_chunks_unchecked<const N: usize>(&self) -> &[[T; N]] {
         let this = self;
         // SAFETY: Caller must guarantee that `N` is nonzero and exactly divides the slice length
         let new_len = unsafe {
@@ -1043,7 +1043,7 @@ impl<T> [T] {
     #[inline]
     #[track_caller]
     #[must_use]
-    pub fn as_chunks<const N: usize>(&self) -> (&[[T; N]], &[T]) {
+    pub const fn as_chunks<const N: usize>(&self) -> (&[[T; N]], &[T]) {
         assert!(N != 0, "chunk size must be non-zero");
         let len = self.len() / N;
         let (multiple_of_n, remainder) = self.split_at(len * N);
@@ -1075,7 +1075,7 @@ impl<T> [T] {
     #[inline]
     #[track_caller]
     #[must_use]
-    pub fn as_rchunks<const N: usize>(&self) -> (&[T], &[[T; N]]) {
+    pub const fn as_rchunks<const N: usize>(&self) -> (&[T], &[[T; N]]) {
         assert!(N != 0, "chunk size must be non-zero");
         let len = self.len() / N;
         let (remainder, multiple_of_n) = self.split_at(self.len() - len * N);
@@ -1152,7 +1152,7 @@ impl<T> [T] {
     #[unstable(feature = "slice_as_chunks", issue = "74985")]
     #[inline]
     #[must_use]
-    pub unsafe fn as_chunks_unchecked_mut<const N: usize>(&mut self) -> &mut [[T; N]] {
+    pub const unsafe fn as_chunks_unchecked_mut<const N: usize>(&mut self) -> &mut [[T; N]] {
         let this = &*self;
         // SAFETY: Caller must guarantee that `N` is nonzero and exactly divides the slice length
         let new_len = unsafe {
@@ -1195,7 +1195,7 @@ impl<T> [T] {
     #[inline]
     #[track_caller]
     #[must_use]
-    pub fn as_chunks_mut<const N: usize>(&mut self) -> (&mut [[T; N]], &mut [T]) {
+    pub const fn as_chunks_mut<const N: usize>(&mut self) -> (&mut [[T; N]], &mut [T]) {
         assert!(N != 0, "chunk size must be non-zero");
         let len = self.len() / N;
         let (multiple_of_n, remainder) = self.split_at_mut(len * N);
@@ -1233,7 +1233,7 @@ impl<T> [T] {
     #[inline]
     #[track_caller]
     #[must_use]
-    pub fn as_rchunks_mut<const N: usize>(&mut self) -> (&mut [T], &mut [[T; N]]) {
+    pub const fn as_rchunks_mut<const N: usize>(&mut self) -> (&mut [T], &mut [[T; N]]) {
         assert!(N != 0, "chunk size must be non-zero");
         let len = self.len() / N;
         let (remainder, multiple_of_n) = self.split_at_mut(self.len() - len * N);