From 5e1730fd17145fd9db5c042b127e2f400c83738a Mon Sep 17 00:00:00 2001
From: ltdk <usr@ltdk.xyz>
Date: Wed, 17 Aug 2022 02:01:32 -0400
Subject: [PATCH 1/2] Make slice::reverse const

---
 library/core/src/slice/mod.rs | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/library/core/src/slice/mod.rs b/library/core/src/slice/mod.rs
index e79d47c9f98cd..361862cdd5257 100644
--- a/library/core/src/slice/mod.rs
+++ b/library/core/src/slice/mod.rs
@@ -674,8 +674,9 @@ impl<T> [T] {
     /// assert!(v == [3, 2, 1]);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[rustc_const_unstable(feature = "const_reverse", issue = "none")]
     #[inline]
-    pub fn reverse(&mut self) {
+    pub const fn reverse(&mut self) {
         let half_len = self.len() / 2;
         let Range { start, end } = self.as_mut_ptr_range();
 
@@ -698,9 +699,9 @@ impl<T> [T] {
         revswap(front_half, back_half, half_len);
 
         #[inline]
-        fn revswap<T>(a: &mut [T], b: &mut [T], n: usize) {
-            debug_assert_eq!(a.len(), n);
-            debug_assert_eq!(b.len(), n);
+        const fn revswap<T>(a: &mut [T], b: &mut [T], n: usize) {
+            debug_assert!(a.len() == n);
+            debug_assert!(b.len() == n);
 
             // Because this function is first compiled in isolation,
             // this check tells LLVM that the indexing below is
@@ -708,8 +709,10 @@ impl<T> [T] {
             // lengths of the slices are known -- it's removed.
             let (a, b) = (&mut a[..n], &mut b[..n]);
 
-            for i in 0..n {
+            let mut i = 0;
+            while i < n {
                 mem::swap(&mut a[i], &mut b[n - 1 - i]);
+                i += 1;
             }
         }
     }

From ae2b1dbc8915c2a41bc3555cceb65a07c0032b05 Mon Sep 17 00:00:00 2001
From: ltdk <usr@ltdk.xyz>
Date: Fri, 19 Aug 2022 20:38:32 -0400
Subject: [PATCH 2/2] Tracking issue for const_reverse

---
 library/core/src/slice/mod.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/library/core/src/slice/mod.rs b/library/core/src/slice/mod.rs
index 361862cdd5257..75c7c4d5581d9 100644
--- a/library/core/src/slice/mod.rs
+++ b/library/core/src/slice/mod.rs
@@ -674,7 +674,7 @@ impl<T> [T] {
     /// assert!(v == [3, 2, 1]);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_const_unstable(feature = "const_reverse", issue = "none")]
+    #[rustc_const_unstable(feature = "const_reverse", issue = "100784")]
     #[inline]
     pub const fn reverse(&mut self) {
         let half_len = self.len() / 2;