I agree that `async` and other “effects” (we could also mention const, unsafe, etc.) are not very composable in present-day Rust.

I will note, though, that this particular example (iterating over a list asynchronously) is actually where you might really want to do something else, because async allows you to do something fundamentally different: run all in parallel.

Async really shines when you have code that does two or more things and you don’t care about the order in which they finish, and that isn’t really feasible without it.