Comment by kibwen

> The functions have the same calling conventions regardless of IO implementation.

Okay, then by that definition, Rust doesn't have colored functions either, because `async fn foo() -> Bar {` in Rust is just syntax sugar for `fn foo() -> impl Future<Output=Bar> {` (that's a normal function that returns a future), and `Future` is just a normal trait that provides a `poll` method; there's no different calling convention anywhere. So which is it? Either Rust and Zig both have colored functions, or neither do.