ICE in match statement at conditional catch-all

[Kimundi]

Reproduceable with this:

fn main() {
    let x = 5;
    match x {
        // 3 => (), // uncomment to get non-exhaustive patterns error
        _ if true => (),
        // _ => ()   // ICE if missing
    }
}

[catamorphism]

Looks like the same bug as #3121 , which I've had on my to-do list to finish for a long time. Thanks for the report!