1 files changed, 29 insertions, 0 deletions
diff --git a/tests/ui/unsafe/union-assignop.rs b/tests/ui/unsafe/union-assignop.rs
new file mode 100644
index 00000000000..5e667cd10d5
--- /dev/null
+++ b/tests/ui/unsafe/union-assignop.rs
@@ -0,0 +1,29 @@
+// revisions: mirunsafeck thirunsafeck
+// [thirunsafeck]compile-flags: -Z thir-unsafeck
+
+use std::ops::AddAssign;
+use std::mem::ManuallyDrop;
+
+struct NonCopy;
+impl AddAssign for NonCopy {
+    fn add_assign(&mut self, _: Self) {}
+}
+
+union Foo {
+    a: u8, // non-dropping
+    b: ManuallyDrop<NonCopy>,
+}
+
+fn main() {
+    let mut foo = Foo { a: 42 };
+    foo.a += 5; //~ ERROR access to union field is unsafe
+    *foo.b += NonCopy; //~ ERROR access to union field is unsafe
+    *foo.b = NonCopy; //~ ERROR access to union field is unsafe
+    foo.b = ManuallyDrop::new(NonCopy);
+    foo.a; //~ ERROR access to union field is unsafe
+    let foo = Foo { a: 42 };
+    foo.b; //~ ERROR access to union field is unsafe
+    let mut foo = Foo { a: 42 };
+    foo.b = foo.b;
+    //~^ ERROR access to union field is unsafe
+}