Sorry, I made an ambiguous comment. I meant continuation as in "continuation passing style" not as in "first class continuation"
It looks like the proactive IO in Bastion is using Rust's async/await, which I know nothing about, but in most languages async/await exists as sugar to make CPS look like linear flow.
It looks like the proactive IO in Bastion is using Rust's async/await, which I know nothing about, but in most languages async/await exists as sugar to make CPS look like linear flow.