Handling unknown cases in enums [RE: SE-0192]

[Chris_Lattner3 (Chris Lattner)]

@jrose

Once you do that, this concept makes perfect sense (though would be extremely unusual to see in practice!!) in an if case:

if case (42, unknown default) = foo() {

Again, this does not make sense because unknown default-or-whatever is a catch-all. It’s true that this match does not always succeed, but there is no way to prevent it from producing a warning.

I don't know what you mean. Of course "unknown default" matches everything - its runtime behavior is the same as default. "case (42, default):" doesn't always match because the first value may not be 42.