From e19fc282624f914919f83e2746769b4ebebff42d Mon Sep 17 00:00:00 2001
From: Konrad Borowski <konrad@borowski.pw>
Date: Thu, 17 Jan 2019 06:50:14 +0100
Subject: [PATCH 1/2] Make iter::Empty<T> Send, Sync and Unpin for any T

---
 src/libcore/iter/sources.rs | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/libcore/iter/sources.rs b/src/libcore/iter/sources.rs
index 2590fa6023a53..f6a3bdea40cab 100644
--- a/src/libcore/iter/sources.rs
+++ b/src/libcore/iter/sources.rs
@@ -198,7 +198,10 @@ pub fn repeat_with<A, F: FnMut() -> A>(repeater: F) -> RepeatWith<F> {
 ///
 /// [`empty`]: fn.empty.html
 #[stable(feature = "iter_empty", since = "1.2.0")]
-pub struct Empty<T>(marker::PhantomData<T>);
+pub struct Empty<T>(marker::PhantomData<PhantomFnWorkaround<T>>);
+
+// Workaround for PhantomData<fn() -> T> not being allowed in const fn.
+struct PhantomFnWorkaround<T>(fn() -> T);
 
 #[stable(feature = "core_impl_debug", since = "1.9.0")]
 impl<T> fmt::Debug for Empty<T> {

From 313c628592452b6e4072eaad41242f16aa303077 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

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

diff --git a/src/test/run-pass/threads-sendsync/sync-send-iterators-in-libcore.rs b/src/test/run-pass/threads-sendsync/sync-send-iterators-in-libcore.rs
index 903bbf5163443..3e9d1a8f702d8 100644
--- a/src/test/run-pass/threads-sendsync/sync-send-iterators-in-libcore.rs
+++ b/src/test/run-pass/threads-sendsync/sync-send-iterators-in-libcore.rs
@@ -91,6 +91,7 @@ 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