1 files changed, 32 insertions, 0 deletions
diff --git a/src/test/ui/typeck/typeck-unsafe-always-share.rs b/src/test/ui/typeck/typeck-unsafe-always-share.rs
new file mode 100644
index 000000000..be87ab172
--- /dev/null
+++ b/src/test/ui/typeck/typeck-unsafe-always-share.rs
@@ -0,0 +1,32 @@
+// Verify that UnsafeCell is *always* !Sync regardless if `T` is sync.
+
+#![feature(negative_impls)]
+
+use std::cell::UnsafeCell;
+use std::marker::Sync;
+
+struct MySync<T> {
+    u: UnsafeCell<T>
+}
+
+struct NoSync;
+impl !Sync for NoSync {}
+
+fn test<T: Sync>(s: T) {}
+
+fn main() {
+    let us = UnsafeCell::new(MySync{u: UnsafeCell::new(0)});
+    test(us);
+    //~^ ERROR `UnsafeCell<MySync<{integer}>>` cannot be shared between threads safely
+
+    let uns = UnsafeCell::new(NoSync);
+    test(uns);
+    //~^ ERROR `UnsafeCell<NoSync>` cannot be shared between threads safely [E0277]
+
+    let ms = MySync{u: uns};
+    test(ms);
+    //~^ ERROR `UnsafeCell<NoSync>` cannot be shared between threads safely [E0277]
+
+    test(NoSync);
+    //~^ ERROR `NoSync` cannot be shared between threads safely [E0277]
+}