Rollup merge of rust-lang#124678 - UserIsntAvailable:feat/stabilize-split-at-checked, r=jhpratt

Stabilize `split_at_checked`

Closes rust-lang#119128

For the const version of `slice::split_at_mut_checked`, I'm reusing the `const_slice_split_at_mut` feature flag (rust-lang#101804). I don't if it okay to reuse tracking issues or if it preferred to create new ones...

Author: compiler-errors

library/core/src/lib.rs

@@ -186,7 +186,6 @@
 #![feature(ptr_metadata)]
 #![feature(set_ptr_value)]
 #![feature(slice_ptr_get)]
-#![feature(split_at_checked)]
 #![feature(str_internals)]
 #![feature(str_split_inclusive_remainder)]
 #![feature(str_split_remainder)]

library/core/src/slice/mod.rs

@@ -2051,8 +2051,6 @@ impl<T> [T] {
     /// # Examples
     ///
     /// ```
-    /// #![feature(split_at_checked)]
-    ///
     /// let v = [1, -2, 3, -4, 5, -6];
     ///
     /// {
@@ -2075,8 +2073,8 @@ impl<T> [T] {
     ///
     /// assert_eq!(None, v.split_at_checked(7));
     /// ```
-    #[unstable(feature = "split_at_checked", reason = "new API", issue = "119128")]
-    #[rustc_const_unstable(feature = "split_at_checked", issue = "119128")]
+    #[stable(feature = "split_at_checked", since = "CURRENT_RUSTC_VERSION")]
+    #[rustc_const_stable(feature = "split_at_checked", since = "CURRENT_RUSTC_VERSION")]
     #[inline]
     #[must_use]
     pub const fn split_at_checked(&self, mid: usize) -> Option<(&[T], &[T])> {
@@ -2102,8 +2100,6 @@ impl<T> [T] {
     /// # Examples
     ///
     /// ```
-    /// #![feature(split_at_checked)]
-    ///
     /// let mut v = [1, 0, 3, 0, 5, 6];
     ///
     /// if let Some((left, right)) = v.split_at_mut_checked(2) {
@@ -2116,8 +2112,8 @@ impl<T> [T] {
     ///
     /// assert_eq!(None, v.split_at_mut_checked(7));
     /// ```
-    #[unstable(feature = "split_at_checked", reason = "new API", issue = "119128")]
-    #[rustc_const_unstable(feature = "split_at_checked", issue = "119128")]
+    #[stable(feature = "split_at_checked", since = "CURRENT_RUSTC_VERSION")]
+    #[rustc_const_unstable(feature = "const_slice_split_at_mut", issue = "101804")]
     #[inline]
     #[must_use]
     pub const fn split_at_mut_checked(&mut self, mid: usize) -> Option<(&mut [T], &mut [T])> {

library/core/src/str/mod.rs

@@ -721,8 +721,6 @@ impl str {
     /// # Examples
     ///
     /// ```
-    /// #![feature(split_at_checked)]
-    ///
     /// let s = "Per Martin-Löf";
     ///
     /// let (first, last) = s.split_at_checked(3).unwrap();
@@ -734,7 +732,7 @@ impl str {
     /// ```
     #[inline]
     #[must_use]
-    #[unstable(feature = "split_at_checked", reason = "new API", issue = "119128")]
+    #[stable(feature = "split_at_checked", since = "CURRENT_RUSTC_VERSION")]
     pub fn split_at_checked(&self, mid: usize) -> Option<(&str, &str)> {
         // is_char_boundary checks that the index is in [0, .len()]
         if self.is_char_boundary(mid) {
@@ -761,8 +759,6 @@ impl str {
     /// # Examples
     ///
     /// ```
-    /// #![feature(split_at_checked)]
-    ///
     /// let mut s = "Per Martin-Löf".to_string();
     /// if let Some((first, last)) = s.split_at_mut_checked(3) {
     ///     first.make_ascii_uppercase();
@@ -776,7 +772,7 @@ impl str {
     /// ```
     #[inline]
     #[must_use]
-    #[unstable(feature = "split_at_checked", reason = "new API", issue = "119128")]
+    #[stable(feature = "split_at_checked", since = "CURRENT_RUSTC_VERSION")]
     pub fn split_at_mut_checked(&mut self, mid: usize) -> Option<(&mut str, &mut str)> {
         // is_char_boundary checks that the index is in [0, .len()]
         if self.is_char_boundary(mid) {