Stabilize feature sort_unstable

Author: Stjepan Glavina

src/doc/unstable-book/src/library-features/sort-unstable.md

@@ -1144,6 +1144,10 @@ impl<T> [T] {
     ///
     /// This sort is stable (i.e. does not reorder equal elements) and `O(n log n)` worst-case.
     ///
+    /// When applicable, unstable sorting is preferred because it is generally faster than stable
+    /// sorting and it doesn't allocate auxiliary memory.
+    /// See [`sort_unstable`](#method.sort_unstable).
+    ///
     /// # Current implementation
     ///
     /// The current algorithm is an adaptive, iterative merge sort inspired by
@@ -1174,6 +1178,10 @@ impl<T> [T] {
     ///
     /// This sort is stable (i.e. does not reorder equal elements) and `O(n log n)` worst-case.
     ///
+    /// When applicable, unstable sorting is preferred because it is generally faster than stable
+    /// sorting and it doesn't allocate auxiliary memory.
+    /// See [`sort_unstable_by`](#method.sort_unstable_by).
+    ///
     /// # Current implementation
     ///
     /// The current algorithm is an adaptive, iterative merge sort inspired by
@@ -1207,6 +1215,10 @@ impl<T> [T] {
     ///
     /// This sort is stable (i.e. does not reorder equal elements) and `O(n log n)` worst-case.
     ///
+    /// When applicable, unstable sorting is preferred because it is generally faster than stable
+    /// sorting and it doesn't allocate auxiliary memory.
+    /// See [`sort_unstable_by_key`](#method.sort_unstable_by_key).
+    ///
     /// # Current implementation
     ///
     /// The current algorithm is an adaptive, iterative merge sort inspired by
@@ -1251,17 +1263,14 @@ impl<T> [T] {
     /// # Examples
     ///
     /// ```
-    /// #![feature(sort_unstable)]
-    ///
     /// let mut v = [-5, 4, 1, -3, 2];
     ///
     /// v.sort_unstable();
     /// assert!(v == [-5, -3, 1, 2, 4]);
     /// ```
     ///
     /// [pdqsort]: https://github.com/orlp/pdqsort
-    // FIXME #40585: Mention `sort_unstable` in the documentation for `sort`.
-    #[unstable(feature = "sort_unstable", issue = "40585")]
+    #[stable(feature = "sort_unstable", since = "1.20.0")]
     #[inline]
     pub fn sort_unstable(&mut self)
         where T: Ord
@@ -1288,8 +1297,6 @@ impl<T> [T] {
     /// # Examples
     ///
     /// ```
-    /// #![feature(sort_unstable)]
-    ///
     /// let mut v = [5, 4, 1, 3, 2];
     /// v.sort_unstable_by(|a, b| a.cmp(b));
     /// assert!(v == [1, 2, 3, 4, 5]);
@@ -1300,8 +1307,7 @@ impl<T> [T] {
     /// ```
     ///
     /// [pdqsort]: https://github.com/orlp/pdqsort
-    // FIXME #40585: Mention `sort_unstable_by` in the documentation for `sort_by`.
-    #[unstable(feature = "sort_unstable", issue = "40585")]
+    #[stable(feature = "sort_unstable", since = "1.20.0")]
     #[inline]
     pub fn sort_unstable_by<F>(&mut self, compare: F)
         where F: FnMut(&T, &T) -> Ordering
@@ -1328,17 +1334,14 @@ impl<T> [T] {
     /// # Examples
     ///
     /// ```
-    /// #![feature(sort_unstable)]
-    ///
     /// let mut v = [-5i32, 4, 1, -3, 2];
     ///
     /// v.sort_unstable_by_key(|k| k.abs());
     /// assert!(v == [1, 2, -3, 4, -5]);
     /// ```
     ///
     /// [pdqsort]: https://github.com/orlp/pdqsort
-    // FIXME #40585: Mention `sort_unstable_by_key` in the documentation for `sort_by_key`.
-    #[unstable(feature = "sort_unstable", issue = "40585")]
+    #[stable(feature = "sort_unstable", since = "1.20.0")]
     #[inline]
     pub fn sort_unstable_by_key<B, F>(&mut self, f: F)
         where F: FnMut(&T) -> B,

src/liballoc/slice.rs

@@ -351,7 +351,7 @@ fn partition_in_blocks<T, F>(v: &mut [T], pivot: &T, is_less: &mut F) -> usize
 
     if start_l < end_l {
         // The left block remains.
-        // Move it's remaining out-of-order elements to the far right.
+        // Move its remaining out-of-order elements to the far right.
         debug_assert_eq!(width(l, r), block_l);
         while start_l < end_l {
             unsafe {
@@ -363,7 +363,7 @@ fn partition_in_blocks<T, F>(v: &mut [T], pivot: &T, is_less: &mut F) -> usize
         width(v.as_mut_ptr(), r)
     } else if start_r < end_r {
         // The right block remains.
-        // Move it's remaining out-of-order elements to the far left.
+        // Move its remaining out-of-order elements to the far left.
         debug_assert_eq!(width(l, r), block_r);
         while start_r < end_r {
             unsafe {