> "The only 'assembly' required is creating the associated promise"

Again, that is only true for one step. For a state machine with N states you need explicit state enums or a long chain of .then() continuations. You also need to the manage the shared state across continuations (normally on the heap). You need to manage manual error propagation across each boundary and handle the cancellation tokens.

You only get a "A nice readable linear flow" using std:future when 1) using a blocking .get() on a thread, or 2) .then() chaining, which isn't "nice" by any means.

Lastly, you seem to be conflating a co_yield (generator, pull-based) with co_await (event-driven, push-based). With co_await, the coroutine is resumed by whoever completes the awaitable.

But what do I know... I only worked on implementing coroutines in cl.exe for 4 years. ;-)