[brundolf]

I've actually been playing with a similar idea in JavaScript, having pure functions generate "Plans" for async actions which are then executed later by other code. They can be thought of as Promises that haven't happened yet.

A neat side-effect (no pun intended) of doing things this way is that, unlike Promises, Plans can be stored as constants (or cached) and re-used multiple times.

I'm sure it's nowhere near as advanced or flexible as the OP, but it seems to be in the same general spirit

[mirekrusin]

Yes, you "can" somehow emulate it with async generators everywhere but your js code will look more like brainfuck than js. It really requires language construct, similar to how yield, try/catch or pattern matching can be simulated without those constructs but it's going to be total disaster with no language support.