Maybe I don't understand the complexity, but in good old Ruby I can easily stop a thread if I don't need result anymore. No async needed and no yield points necessary. Doesn't it apply to Rust too?
I assume that Ruby does in fact have yield points in some form, such as a global lock. Killing a thread is only possible (for a pthread) via the `pthread_cancel` API. That API is very dangerous and is generally not something you'd ever want to use manually - the thread will not clean up any memory or other resources, any shared memory is left in a tricky state.
To gracefully shut a thread down you need yielding of some kind.
