Rust's compiler/library interface is still much simpler than C++'s. An `async fn` call gives you an anonymous-typed object (much like a lambda) which implements the `Future` trait, which has a single method `poll`.
`Generator` and `GeneratorState` are not exposed or usable. There are no knobs to turn like C++'s `await_ready` or `early_suspend`/`final_suspend`. There is no implicit heap allocation or corresponding elision optimization, and thus no need to map between `coroutine_handle`s and promise objects.
To be fair, C++'s design is a bit more flexible in that it supports passing data in and out of a coroutine. But even if you look at Rust's (unstable work-in-progress) approach to supporting this, the compiler/library interface is still way simpler. The difference is really not related to how much functionality is stabilized, but how scattered and ad-hoc the C++ interface is.
`Generator` and `GeneratorState` are not exposed or usable. There are no knobs to turn like C++'s `await_ready` or `early_suspend`/`final_suspend`. There is no implicit heap allocation or corresponding elision optimization, and thus no need to map between `coroutine_handle`s and promise objects.
To be fair, C++'s design is a bit more flexible in that it supports passing data in and out of a coroutine. But even if you look at Rust's (unstable work-in-progress) approach to supporting this, the compiler/library interface is still way simpler. The difference is really not related to how much functionality is stabilized, but how scattered and ad-hoc the C++ interface is.