latest Rust needs a patch

Author: RalfJung

rust-src.diff

@@ -0,0 +1,36 @@
+diff --git a/library/core/tests/mem.rs b/library/core/tests/mem.rs
+index 5e24fa690ef52..5d0fedd4d9ccc 100644
+--- a/library/core/tests/mem.rs
++++ b/library/core/tests/mem.rs
+@@ -1,5 +1,6 @@
+ use core::mem::*;
+ 
++#[cfg(panic = "unwind")]
+ use std::rc::Rc;
+ 
+ #[test]
+@@ -250,14 +251,19 @@ fn uninit_write_slice_cloned_mid_panic() {
+ 
+ #[test]
+ fn uninit_write_slice_cloned_no_drop() {
+-    let rc = Rc::new(());
++    #[derive(Clone)]
++    struct Bomb;
++
++    impl Drop for Bomb {
++        fn drop(&mut self) {
++            panic!("dropped a bomb! kaboom")
++        }
++    }
+ 
+     let mut dst = [MaybeUninit::uninit()];
+-    let src = [rc.clone()];
++    let src = [Bomb];
+ 
+     MaybeUninit::write_slice_cloned(&mut dst, &src);
+ 
+-    drop(src);
+-
+-    assert_eq!(Rc::strong_count(&rc), 2);
++    forget(src);
+ }

rust-version

@@ -1 +1 @@
-nightly-2020-11-30
+nightly-2020-12-19