The challenge with async code is that the state across yield points is put into a struct and if a reference to a stack variable is used across yield points, then that struct is self-referential which Rust can't reason about (yet?). I honestly do not know who much can be recreated with `unsafe` and `Pin` vs how much is built-in.

I'd love for Rust to eventually get a Move trait (something like C=+ move constructors) to resolve this. Besides some complexity in designing it, there is resistance from some corners about having anything execute on a move.