Is there any way to use GATs to achieve a particular use case of ah-hoc/anonymous enums[0]? Say if library L1 returns enum A|B, L2 operates on enum A|B, and main wants to pass enum A|B from L1 to L2, with the kicker being A, B are concrete in main.
I'm not interested in distinguishing between multiple appearances of the same type as in the RFC example, so rather like:
let foo: (~str|int) = (_|666);
match foo {
(s: str|_) => println(fmt!("string: %?", s)),
(_|n: int) => println(fmt!("int: %?", n))
}