unsafe async fn -> async unsafe fn + error

[Proximyst]

The reordering of the signature pub unsafe async fn test(&mut self) in an impl block breaks compilation, given it makes it pub async unsafe fn test(&mut self). I have no clue if this applies to any and all functions with unsafe async fn, but it breaks with this simple case:

#![feature(async_await)]

struct A;

impl A {
    pub unsafe async fn thing(&mut self) -> Result<(), ()> {
        Err(())
    }
}

If you now use the newest rustfmt (i.e. from latest nightly), it breaks compilation:

error: missing `fn`, `type`, or `const` for impl-item declaration
 --> a.rs:5:8
  |
5 |     pub async unsafe fn thing(&mut self) -> Result<(), ()> {
  |        ^ missing `fn`, `type`, or `const`

A simple case for making this work is just creating a file called a.rs, copy+paste that, run rustfmt a.rs, then rustc a.rs to get the error.

[topecongiro]

Hmm, I thought the correct ordering has changed to async unsafe fn in rust-lang/rust#61319, but that doesn't apply to methods in impl? That's strange.

[topecongiro]

This is a bug in the rustc parser. It will be fixed in rust-lang/rust#62241.

Closing as this is not a rustfmt issue. @Proximyst Thank you for reporting!