1 files changed, 53 insertions, 0 deletions
diff --git a/tests/ui/unsafe/union.rs b/tests/ui/unsafe/union.rs
new file mode 100644
index 00000000000..4338d78eabb
--- /dev/null
+++ b/tests/ui/unsafe/union.rs
@@ -0,0 +1,53 @@
+// revisions: mir thir
+// [thir]compile-flags: -Z thir-unsafeck
+
+union Foo {
+    bar: i8,
+    zst: (),
+    pizza: Pizza,
+}
+
+#[derive(Clone, Copy)]
+struct Pizza {
+    topping: Option<PizzaTopping>
+}
+
+#[allow(dead_code)]
+#[derive(Clone, Copy)]
+enum PizzaTopping {
+    Cheese,
+    Pineapple,
+}
+
+fn do_nothing(_x: &mut Foo) {}
+
+pub fn main() {
+    let mut foo = Foo { bar: 5 };
+    do_nothing(&mut foo);
+
+    // This is UB, so this test isn't run
+    match foo {
+        Foo { bar: _a } => {}, //~ ERROR access to union field is unsafe
+    }
+    match foo { //[mir]~ ERROR access to union field is unsafe
+        Foo {
+            pizza: Pizza { //[thir]~ ERROR access to union field is unsafe
+                topping: Some(PizzaTopping::Cheese) | Some(PizzaTopping::Pineapple) | None
+            }
+        } => {},
+    }
+
+    // MIR unsafeck incorrectly thinks that no unsafe block is needed to do these
+    match foo {
+        Foo { zst: () } => {}, //[thir]~ ERROR access to union field is unsafe
+    }
+    match foo {
+        Foo { pizza: Pizza { .. } } => {}, //[thir]~ ERROR access to union field is unsafe
+    }
+
+    // binding to wildcard is okay
+    match foo {
+        Foo { bar: _ } => {},
+    }
+    let Foo { bar: _ } = foo;
+}