1 files changed, 71 insertions, 0 deletions
diff --git a/tests/ui/nullable-pointer-iotareduction.rs b/tests/ui/nullable-pointer-iotareduction.rs
new file mode 100644
index 00000000000..d345fec8118
--- /dev/null
+++ b/tests/ui/nullable-pointer-iotareduction.rs
@@ -0,0 +1,71 @@
+// run-pass
+
+// Iota-reduction is a rule in the Calculus of (Co-)Inductive Constructions,
+// which "says that a destructor applied to an object built from a constructor
+// behaves as expected".  -- https://coq.inria.fr/doc/language/core/conversion.html#iota-reduction
+//
+// It's a little more complicated here, because of pointers and regions and
+// trying to get assert failure messages that at least identify which case
+// failed.
+
+enum E<T> { Thing(isize, T), #[allow(unused_tuple_struct_fields)] Nothing((), ((), ()), [i8; 0]) }
+impl<T> E<T> {
+    fn is_none(&self) -> bool {
+        match *self {
+            E::Thing(..) => false,
+            E::Nothing(..) => true
+        }
+    }
+    fn get_ref(&self) -> (isize, &T) {
+        match *self {
+            E::Nothing(..) => panic!("E::get_ref(Nothing::<{}>)",  stringify!(T)),
+            E::Thing(x, ref y) => (x, y)
+        }
+    }
+}
+
+macro_rules! check_option {
+    ($e:expr, $T:ty) => {{
+        check_option!($e, $T, |ptr| assert_eq!(*ptr, $e));
+    }};
+    ($e:expr, $T:ty, |$v:ident| $chk:expr) => {{
+        assert!(None::<$T>.is_none());
+        let e = $e;
+        let s_ = Some::<$T>(e);
+        let $v = s_.as_ref().unwrap();
+        $chk
+    }}
+}
+
+macro_rules! check_fancy {
+    ($e:expr, $T:ty) => {{
+        check_fancy!($e, $T, |ptr| assert_eq!(*ptr, $e));
+    }};
+    ($e:expr, $T:ty, |$v:ident| $chk:expr) => {{
+        assert!(E::Nothing::<$T>((), ((), ()), [23; 0]).is_none());
+        let e = $e;
+        let t_ = E::Thing::<$T>(23, e);
+        match t_.get_ref() {
+            (23, $v) => { $chk }
+            _ => panic!("Thing::<{}>(23, {}).get_ref() != (23, _)",
+                       stringify!($T), stringify!($e))
+        }
+    }}
+}
+
+macro_rules! check_type {
+    ($($a:tt)*) => {{
+        check_option!($($a)*);
+        check_fancy!($($a)*);
+    }}
+}
+
+pub fn main() {
+    check_type!(&17, &isize);
+    check_type!(Box::new(18), Box<isize>);
+    check_type!("foo".to_string(), String);
+    check_type!(vec![20, 22], Vec<isize>);
+    check_type!(main, fn(), |pthing| {
+        assert_eq!(main as fn(), *pthing as fn())
+    });
+}