From a70b24018936fe59f0a037adfa13f2255d8aa5d2 Mon Sep 17 00:00:00 2001
From: Konrad Borowski <konrad@borowski.pw>
Date: Sat, 18 Jan 2020 18:35:36 +0100
Subject: [PATCH 1/2] Make iter::Empty<T> implement Send and Sync for any T

---
 src/libcore/iter/sources.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/libcore/iter/sources.rs b/src/libcore/iter/sources.rs
index a65d47cc2c1f0..25dfc573e416a 100644
--- a/src/libcore/iter/sources.rs
+++ b/src/libcore/iter/sources.rs
@@ -208,6 +208,11 @@ pub fn repeat_with<A, F: FnMut() -> A>(repeater: F) -> RepeatWith<F> {
 #[stable(feature = "iter_empty", since = "1.2.0")]
 pub struct Empty<T>(marker::PhantomData<T>);
 
+#[stable(feature = "iter_empty_send_sync", since = "1.42.0")]
+unsafe impl<T> Send for Empty<T> {}
+#[stable(feature = "iter_empty_send_sync", since = "1.42.0")]
+unsafe impl<T> Sync for Empty<T> {}
+
 #[stable(feature = "core_impl_debug", since = "1.9.0")]
 impl<T> fmt::Debug for Empty<T> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

From d7a18f89864a4360230e3cbbdcbf22d9864a86e0 Mon Sep 17 00:00:00 2001
From: Konrad Borowski <konrad@borowski.pw>
Date: Thu, 17 Jan 2019 00:07:22 +0100
Subject: [PATCH 2/2] Add a test for iter::empty::<*mut i32> being Sync and
 Send

---
 src/test/ui/threads-sendsync/sync-send-iterators-in-libcore.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/test/ui/threads-sendsync/sync-send-iterators-in-libcore.rs b/src/test/ui/threads-sendsync/sync-send-iterators-in-libcore.rs
index 44beb9dc1e534..2f6d35f01be62 100644
--- a/src/test/ui/threads-sendsync/sync-send-iterators-in-libcore.rs
+++ b/src/test/ui/threads-sendsync/sync-send-iterators-in-libcore.rs
@@ -88,6 +88,7 @@ fn main() {
     is_sync_send!((1..));
     is_sync_send!(repeat(1));
     is_sync_send!(empty::<usize>());
+    is_sync_send!(empty::<*mut i32>());
     is_sync_send!(once(1));
 
     // for option.rs