Weak's type parameter may dangle on drop

Author: dtolnay

library/alloc/src/rc.rs

@@ -2303,7 +2303,7 @@ impl<T: ?Sized> Weak<T> {
 }
 
 #[stable(feature = "rc_weak", since = "1.4.0")]
-impl<T: ?Sized> Drop for Weak<T> {
+unsafe impl<#[may_dangle] T: ?Sized> Drop for Weak<T> {
     /// Drops the `Weak` pointer.
     ///
     /// # Examples

library/alloc/src/sync.rs

@@ -2015,7 +2015,7 @@ impl<T> Default for Weak<T> {
 }
 
 #[stable(feature = "arc_weak", since = "1.4.0")]
-impl<T: ?Sized> Drop for Weak<T> {
+unsafe impl<#[may_dangle] T: ?Sized> Drop for Weak<T> {
     /// Drops the `Weak` pointer.
     ///
     /// # Examples