> [1] I'd really like to see F# Computation Expressions instead of async/await. I know the language experts have said Haskell-like do notation doesn't work in Rust but I'm not sure if the F# tweaks would make it work or not.

I'd prefer a systems-y, zero-cost take on algebraic effects, similar to what OCaml is going to get. Could be much more extensible, and open things up to annotating whether functions panic or not, access global state, etc. Alas it's still a tricky research problem, even after all these years. There were some nice discussions from ICFP here - the comments strayed into talking about how effects might be implemented without a GC: https://www.youtube.com/watch?v=DNp3ifNpgPM