I’m not convinced that this can help in a meaningful way.
Fundamentally, if you have two coroutines (or cooperatively scheduled threads or whatever), and one of them holds a lock, and the other one is awaiting the lock, and you don’t schedule the first one, you’re stuck.
I wonder if there’s a form of structured concurrency that would help. If I create two futures and start both of them (in Rust this means polling each one once) but do not continue to poll both, then I’m sort of making a mistake.
So imagine a world where, to poll a future at all, I need to have a nursery, and the nursery is passed in from my task and down the call stack. When I create a future, I can pass in my nursery, but that future then gets an exclusive reference to my future until it’s complete or cancelled. If I want to create more than one future that are live concurrently, I need to create a FutureGroup (that gets an exclusive reference to my nursery) and that allows me to create multiple sub-nurseries that can be used to make futures but cannot be used to poll them — instead I poll the FutureGroup.
(I have yet to try using an async/await system or a reactor or anything of the sort that is not very easy to screw up. My current pet peeve is this pattern:
data = await thingy.read()