Removed a FIXME, added some comments linking to std source

const_sort_rs/src/const_slice_sort_ext.rs

@@ -423,13 +423,15 @@ impl<T: ~const Destruct> const ConstSliceSortExt<T> for [T] {
   where
     T: ~const PartialOrd + Ord,
   {
+    // https://doc.rust-lang.org/nightly/src/core/slice/mod.rs.html#2539
     const_sort::const_quicksort(self, const_pred_lt);
   }
   #[inline]
   fn const_sort_unstable_by<F>(&mut self, mut compare: F)
   where
     F: ~const FnMut(&T, &T) -> Ordering + ~const Destruct,
   {
+    // https://doc.rust-lang.org/nightly/src/core/slice/mod.rs.html#2594
     // sort::const_quicksort(self, |a, b| compare(a, b) == Ordering::Less);
     const fn imp<T, F>(compare: &mut F, (a, b): (&T, &T)) -> bool
     where
@@ -445,6 +447,7 @@ impl<T: ~const Destruct> const ConstSliceSortExt<T> for [T] {
     F: ~const FnMut(&T) -> K + ~const Destruct,
     K: Ord + ~const PartialOrd + ~const Destruct,
   {
+    // https://doc.rust-lang.org/nightly/src/core/slice/mod.rs.html#2632
     // sort::quicksort(self, |a, b| f(a).lt(&f(b)));
     const fn imp<T, F, K: ~const PartialOrd + ~const Destruct>(f: &mut F, (a, b): (&T, &T)) -> bool
     where
@@ -460,6 +463,7 @@ impl<T: ~const Destruct> const ConstSliceSortExt<T> for [T] {
   where
     T: ~const PartialOrd + Ord,
   {
+    // https://doc.rust-lang.org/nightly/src/core/slice/mod.rs.html#2678
     // let mut f = |a: &T, b: &T| a.lt(b);
     // sort::partition_at_index(self, index, &mut f)
     const_sort::const_partition_at_index(self, index, const_pred_lt)
@@ -473,6 +477,7 @@ impl<T: ~const Destruct> const ConstSliceSortExt<T> for [T] {
   where
     F: ~const FnMut(&T, &T) -> Ordering + ~const Destruct,
   {
+    // https://doc.rust-lang.org/nightly/src/core/slice/mod.rs.html#2725
     // let mut f = |a: &T, b: &T| compare(a, b) == Less;
     // sort::partition_at_index(self, index, &mut f)
     const fn imp<T, F>(compare: &mut F, (a, b): (&T, &T)) -> bool
@@ -493,6 +498,7 @@ impl<T: ~const Destruct> const ConstSliceSortExt<T> for [T] {
     F: ~const FnMut(&T) -> K + ~const Destruct,
     K: Ord + ~const PartialOrd + ~const Destruct,
   {
+    // https://doc.rust-lang.org/nightly/src/core/slice/mod.rs.html#2776
     // let mut g = |a: &T, b: &T| f(a).lt(&f(b));
     // sort::partition_at_index(self, index, &mut g)
     const fn imp<T, F, K: ~const PartialOrd + ~const Destruct>(f: &mut F, (a, b): (&T, &T)) -> bool
@@ -522,8 +528,7 @@ impl<T: ~const Destruct> const ConstSliceSortExt<T> for [T] {
     let mut i = 1;
     while i < self.len() {
       let ord_opt = compare(&self[i - 1], &self[i]);
-      if matches!(ord_opt, None) {
-        // FIXME: Once the matches can be replaced with `==`.
+      if ord_opt.is_none() {
         return false;
       }
       if ord_opt.unwrap() == Ordering::Greater {
@@ -547,6 +552,8 @@ impl<T: ~const Destruct> const ConstSliceSortExt<T> for [T] {
       T: ~const Destruct,
       for<'r> F: ~const FnMut(&'r T) -> K + ~const Destruct,
     {
+      // https://doc.rust-lang.org/nightly/src/core/iter/traits/iterator.rs.html#3840
+      // self.map(f).is_sorted()
       f(a).partial_cmp(&f(b))
     }
     self.const_is_sorted_by(ConstFnMutClosure::new(&mut f, imp))

const_sort_rs/src/slice_const_split_at_mut.rs

@@ -70,6 +70,7 @@ impl<T> const ConstSplitAtMutExtensions<T> for [T] {
   #[inline]
   #[track_caller]
   fn const_split_at_mut(&mut self, mid: usize) -> (&mut [T], &mut [T]) {
+    // https://doc.rust-lang.org/nightly/src/core/slice/mod.rs.html#1583
     assert!(mid <= self.len());
     // SAFETY: `[ptr; mid]` and `[mid; len]` are inside `self`, which
     // fulfils the requirements of `from_raw_parts_mut`.
@@ -78,6 +79,7 @@ impl<T> const ConstSplitAtMutExtensions<T> for [T] {
 
   #[inline]
   unsafe fn const_split_at_mut_unchecked(&mut self, mid: usize) -> (&mut [T], &mut [T]) {
+    // https://doc.rust-lang.org/nightly/src/core/slice/mod.rs.html#1684
     let len = self.len();
     let ptr = self.as_mut_ptr();