#![feature(async_closure)] use anyhow::Error; use futures::{stream::repeat_with, StreamExt}; fn accept_str(_: &str) {} fn accept_string(_: &String) {} #[tokio::main(flavor = "current_thread")] async fn main() -> Result<(), Error> { // when using closure returning async block - everything works repeat_with(|| "foo".to_owned()) .take(1) .for_each(|value| async move { accept_str(&value); // ok accept_str(value.as_str()); // ok accept_string(&value); // ok }) .await; // when using async closure, most options fail repeat_with(|| "foo".to_owned()) .take(1) .for_each(async move |value| { // error on whole closure, rust thinks that type of value is `str` // accept_str(&value); // type annotations needed, cannot infer type // accept_str(value.as_str()); // this works accept_string(&value); // ok }) .await; // can be fixed by providing type hint on async closure parameter repeat_with(|| "foo".to_owned()) .take(1) .for_each(async move |value: String| { accept_str(&value); // ok accept_str(value.as_str()); // ok accept_string(&value); // ok }) .await; Ok(()) }