False positive unused_lifetimes warning with an async fn

[Hawk777]

Given the following code:

#![warn(unused_lifetimes)]

use std::borrow::Cow;

pub async fn do_thing(s: Cow<'_, str>) -> Cow<'_, str> {
	s
}

The current output is:

warning: lifetime parameter `'_` never used
 --> src/main.rs:5:47
  |
5 | pub async fn do_thing(s: Cow<'_, str>) -> Cow<'_, str> {
  |                              -----------------^^
  |                              |
  |                              help: elide the unused lifetime
  |

Removing the word async makes the warning disappear. I am currently running 1.52.1, and this also happens in 1.53.0 on the playground, as well as 1.55.0 nightly on the playground.

[tmandry]

Someone interested in fixing this might find it helpful to look at #79689.

[Aaron1011]

This no longer warns as of the latest nightly.

[scottmcm]

Closing as the example in the OP no longer repros.

[Aaron1011]

Does this need a regression test?