Hijacking your comment because this is a common point that's made on the superiority of Swift syntax against the union syntax.

At least with |, you're attempting to model the state space. You're saying "this is one of these things." You might get the exhaustiveness wrong, but you're in the right ballpark. As it's normally done right now, the Swift developer with five optional properties is modeling state as "maybe this, maybe that, maybe both, who knows, good luck." which is just worse than a bar. If you need to discriminate explicitly, add a `__kind` field!