I've got some weird plans for variants. Basically, we'd represent an enum as a non-heap-allocated sealed interface with a struct for each "case". Basically, think of a Scala case class. Then, depending on where we put it (heap vs local/member/element), it will be compiled differently (a traditional interface vs a tagged variant, respectively). ...I don't expect that to make any sense.

Alas, I haven't started on sealed interfaces yet. Right now I'm occupied with the Rust interop; I'm hoping we can be able to seamlessly e.g. `import rust.std.collections.Vec<i32>;` and have it work. A lot of pieces have to fall into place for that to work though, especially since that's generic and Rust doesn't even have a stable ABI. It's kicking my ass, and I'm having a lot of fun with it!