review

library/core/src/lib.rs

@@ -137,7 +137,6 @@
 #![feature(const_size_of_val)]
 #![feature(const_slice_from_raw_parts_mut)]
 #![feature(const_slice_ptr_len)]
-#![feature(const_slice_split_at_not_mut)]
 #![feature(const_str_from_utf8_unchecked_mut)]
 #![feature(const_swap)]
 #![feature(const_trait_impl)]
@@ -150,6 +149,7 @@
 #![feature(maybe_uninit_uninit_array)]
 #![feature(ptr_metadata)]
 #![feature(slice_ptr_get)]
+#![feature(slice_split_at_unchecked)]
 #![feature(str_internals)]
 #![feature(utf16_extra)]
 #![feature(utf16_extra_const)]

library/core/src/slice/mod.rs

@@ -1624,10 +1624,14 @@ impl<T> [T] {
     /// }
     /// ```
     #[unstable(feature = "slice_split_at_unchecked", reason = "new API", issue = "76014")]
-    #[rustc_const_unstable(feature = "const_slice_split_at_not_mut", issue = "none")]
+    #[rustc_const_unstable(feature = "slice_split_at_unchecked", issue = "76014")]
     #[inline]
     #[must_use]
     pub const unsafe fn split_at_unchecked(&self, mid: usize) -> (&[T], &[T]) {
+        // HACK: the const function `from_raw_parts` is used to make this
+        // function const; previously the implementation used
+        // `(self.get_unchecked(..mid), self.get_unchecked(mid..))`
+
         let len = self.len();
         let ptr = self.as_ptr();