error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds about async-trait

[dtolnay]

This looks like it affects any function with a signature resembling async fn<'a>(&A, &'static B) -> &'a C, not anything about async-trait. Could you make sure there is an issue filed for this in rust-lang/rust?

Minimized further:

async fn test<'a>(_: &(), _: &'static ()) -> &'a () {
    unimplemented!()
}

error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
 --> src/main.rs:1:46
  |
1 | async fn test<'a>(_: &(), _: &'static ()) -> &'a () {
  |                                              ^^^^^^
  |
note: hidden type `impl std::future::Future` captures the scope of call-site for function at 1:53
 --> src/main.rs:1:53
  |
1 |   async fn test<'a>(_: &(), _: &'static ()) -> &'a () {
  |  _____________________________________________________^
2 | |     unimplemented!()
3 | | }
  | |_^

[nirui]

async fn test<'a>(_: &(), _: &'static ()) -> &'a () { unimplemented!() }

Nice catch! I'll investigate some more into the language itself.

Thank you for your time! And sorry for the bothering.

[fzzzy]

I just hit this same rust compiler bug in some code that doesn't use async trait. Did this ever get filed as a bug against rustc?

[jrconlin]

Looks like rust-lang/rust#64552 might be related?