rustfmt reorders for and async in impl for<'chk> async Fn

[nikomatsakis]

I tried formatting this code:

#![feature(async_closure)]

async fn my_func(op: impl for<'x> async Fn(&'x String)) {
    let s = String::new();
    op(&s).await
}

fn main() { }

I expected to see this happen: nothing

Instead, this happened: rustfmt reorders for and async incorrectly...

#![feature(async_closure)]

async fn my_func(op: impl async for<'x> Fn(&'x String)) {
    let s = String::new();
    op(&s).await
}

fn main() {}

This formatted code does not compile.

[nikomatsakis]

cc @compiler-errors I imagine this blocks stabilization.

[compiler-errors]

Ah, I definitely forgot to reorder these bounds after we settled the ordering.