From 00dba3a6938fb996b5d3b7f67823fc5272b38f59 Mon Sep 17 00:00:00 2001
From: woppopo <woppopo@protonmail.com>
Date: Sun, 17 Oct 2021 00:02:42 +0900
Subject: [PATCH] Make Option::as_mut const

---
 library/core/src/option.rs   | 3 ++-
 library/core/tests/option.rs | 8 ++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/library/core/src/option.rs b/library/core/src/option.rs
index 401267f5613..88505832158 100644
--- a/library/core/src/option.rs
+++ b/library/core/src/option.rs
@@ -646,7 +646,8 @@ impl<T> Option<T> {
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn as_mut(&mut self) -> Option<&mut T> {
+    #[rustc_const_unstable(feature = "const_option", issue = "67441")]
+    pub const fn as_mut(&mut self) -> Option<&mut T> {
         match *self {
             Some(ref mut x) => Some(x),
             None => None,
diff --git a/library/core/tests/option.rs b/library/core/tests/option.rs
index 8995f96b123..c9508c14525 100644
--- a/library/core/tests/option.rs
+++ b/library/core/tests/option.rs
@@ -380,6 +380,14 @@ const fn option_const_mut() {
 
     let _take = option.take();
     let _replace = option.replace(42);
+
+    {
+        let as_mut = option.as_mut();
+        match as_mut {
+            Some(v) => *v = 32,
+            None => unreachable!(),
+        }
+    }
 }
 
 #[test]