1 files changed, 78 insertions, 0 deletions
diff --git a/src/test/ui/union/union-unsafe.rs b/src/test/ui/union/union-unsafe.rs
new file mode 100644
index 000000000..5e1837a90
--- /dev/null
+++ b/src/test/ui/union/union-unsafe.rs
@@ -0,0 +1,78 @@
+// revisions: mir thir
+// [thir]compile-flags: -Z thir-unsafeck
+
+use std::mem::ManuallyDrop;
+use std::cell::RefCell;
+
+union U1 {
+    a: u8
+}
+
+union U2 {
+    a: ManuallyDrop<String>
+}
+
+union U3<T> {
+    a: ManuallyDrop<T>
+}
+
+union U4<T: Copy> {
+    a: T
+}
+
+union URef {
+    p: &'static mut i32,
+}
+
+union URefCell { // field that does not drop but is not `Copy`, either
+    a: (ManuallyDrop<RefCell<i32>>, i32),
+}
+
+fn deref_union_field(mut u: URef) {
+    // Not an assignment but an access to the union field!
+    *(u.p) = 13; //~ ERROR access to union field is unsafe
+}
+
+fn assign_noncopy_union_field(mut u: URefCell) {
+    // FIXME(thir-unsafeck)
+    u.a = (ManuallyDrop::new(RefCell::new(0)), 1); // OK (assignment does not drop)
+    u.a.0 = ManuallyDrop::new(RefCell::new(0)); // OK (assignment does not drop)
+    u.a.1 = 1; // OK
+}
+
+fn generic_noncopy<T: Default>() {
+    let mut u3 = U3 { a: ManuallyDrop::new(T::default()) };
+    u3.a = ManuallyDrop::new(T::default()); // OK (assignment does not drop)
+    *u3.a = T::default(); //~ ERROR access to union field is unsafe
+}
+
+fn generic_copy<T: Copy + Default>() {
+    let mut u3 = U3 { a: ManuallyDrop::new(T::default()) };
+    u3.a = ManuallyDrop::new(T::default()); // OK
+    *u3.a = T::default(); //~ ERROR access to union field is unsafe
+
+    let mut u4 = U4 { a: T::default() };
+    u4.a = T::default(); // OK
+}
+
+fn main() {
+    let mut u1 = U1 { a: 10 }; // OK
+    let a = u1.a; //~ ERROR access to union field is unsafe
+    u1.a = 11; // OK
+
+    let U1 { a } = u1; //~ ERROR access to union field is unsafe
+    if let U1 { a: 12 } = u1 {} //~ ERROR access to union field is unsafe
+    // let U1 { .. } = u1; // OK
+
+    let mut u2 = U2 { a: ManuallyDrop::new(String::from("old")) }; // OK
+    u2.a = ManuallyDrop::new(String::from("new")); // OK (assignment does not drop)
+    *u2.a = String::from("new"); //~ ERROR access to union field is unsafe
+
+    let mut u3 = U3 { a: ManuallyDrop::new(0) }; // OK
+    u3.a = ManuallyDrop::new(1); // OK
+    *u3.a = 1; //~ ERROR access to union field is unsafe
+
+    let mut u3 = U3 { a: ManuallyDrop::new(String::from("old")) }; // OK
+    u3.a = ManuallyDrop::new(String::from("new")); // OK (assignment does not drop)
+    *u3.a = String::from("new"); //~ ERROR access to union field is unsafe
+}