From 5b2076ff01c75d4b7e09dac5b5630ecb16d66255 Mon Sep 17 00:00:00 2001
From: Peter Todd <pete@petertodd.org>
Date: Thu, 27 May 2021 14:01:16 -0400
Subject: [PATCH] Revert #85176 addition of `clone_from` for `ManuallyDrop`

Forwarding `clone_from` to the inner value changes the observable
behavior, as previously the inner value would *not* be dropped by the
default implementation.
---
 library/core/src/mem/manually_drop.rs | 15 +--------------
 1 file changed, 1 insertion(+), 14 deletions(-)

diff --git a/library/core/src/mem/manually_drop.rs b/library/core/src/mem/manually_drop.rs
index 5b99f6954e62b..d86939454be5b 100644
--- a/library/core/src/mem/manually_drop.rs
+++ b/library/core/src/mem/manually_drop.rs
@@ -44,7 +44,7 @@ use crate::ptr;
 /// [`MaybeUninit<T>`]: crate::mem::MaybeUninit
 #[stable(feature = "manually_drop", since = "1.20.0")]
 #[lang = "manually_drop"]
-#[derive(Copy, Debug, Default, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[derive(Copy, Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord, Hash)]
 #[repr(transparent)]
 pub struct ManuallyDrop<T: ?Sized> {
     value: T,
@@ -160,16 +160,3 @@ impl<T: ?Sized> DerefMut for ManuallyDrop<T> {
         &mut self.value
     }
 }
-
-#[stable(feature = "manually_drop", since = "1.20.0")]
-impl<T: Clone> Clone for ManuallyDrop<T> {
-    #[inline]
-    fn clone(&self) -> ManuallyDrop<T> {
-        ManuallyDrop { value: self.value.clone() }
-    }
-
-    #[inline]
-    fn clone_from(&mut self, other: &Self) {
-        self.value.clone_from(&other.value)
-    }
-}