canndrew2016
I interpreted OP's comment as complaining about the lack of more general abstractions in Rust that would allow you to implement async/await. Your comment specifically mentioned Haskell-style monads (eg. a `Monad` trait), but that's not the only way to implement something like this.
> the last part is offensive & wrong
Quoting steveklabnik:
> it’s an open research problem if do notation can work in Rust. Until that’s solved at all, we’re just not sure it’s possible. ... "Open question" doesn't mean "impossible", mind you. But nobody has ever come up with a design. In the meantime, we have users to support...
Isn't this what I was saying? "We don't know how to do it, so we're going with the easier option."
Edit: To be clear, I don't think async/await we've ended up with is necessarily in the wrong direction. But I also don't think that "we thoroughly explored the design space of do/monads/effects and concluded that they were impossible to implement ergonomically/efficiently" is really true.
Sorry, but I don't buy it. I had a half-baked, unfinished proposal for an effects system that would have allowed Rust to implement async/await just as efficiently (no stackful coroutines) along with any number of other effects [0]. Maybe it wouldn't have been a good idea due to stretching Rust's complexity budget too far, but that's very different from saying it's impossible. Having watched the development of Rust closely I really think that the design team just didn't understand the theory side well enough to be able explore the design space here. (I'm not being as critical as I might sound, PL theory is hard and the Rust devs have wielded it much more competently than the designers of any other non-research language).
[0] https://internals.rust-lang.org/t/start-of-an-effects-system...
http://www.potaroo.net/ietf/idref/draft-grothoff-iesg-specia...
They were trying to get .gns, .zkey, .onion, .exit, .i2p and .bit recognized.