``` enum what { } fn what_to_str(x: what) -> ~str { alt x { } } fn main() { } ``` gives me ``` /Users/jruderman/Desktop/unlikely_non-exhaustive.rs:5:4: 6:5 error: non-exhaustive patterns /Users/jruderman/Desktop/unlikely_non-exhaustive.rs:5 alt x { /Users/jruderman/Desktop/unlikely_non-exhaustive.rs:6 } ``` I did exhaust all the cases of the `what` enum, however vacuously :)