missing trait impl suggestion is not async-aware

[ehuss]

I tried this code:

#![allow(incomplete_features)]
#![feature(async_fn_in_trait)]

trait Trait {
    async fn foo();
}

struct S;

impl Trait for S {

}

When compiled will provide a (tool-only) suggestion that is not valid:

rustc --edition 2021 --error-format=json foo.rs 2>&1 | jq '.children[0].spans[0].suggested_replacement'

shows the suggestion is:

fn foo() -> impl Future<Output = ()> { todo!() }

I would expect the signature to more closely match the original trait:

async fn foo() { todo!() }

Note: The console output is:

error[E0046]: not all trait items implemented, missing: `foo`
  --> foo.rs:10:1
   |
5  |     async fn foo();
   |     --------------- `foo` from trait
...
10 | impl Trait for S {
   | ^^^^^^^^^^^^^^^^ missing `foo` in implementation

Meta

rustc --version --verbose:

rustc 1.69.0-nightly (9a7cc6c32 2023-02-16)
binary: rustc
commit-hash: 9a7cc6c32f1a690f86827e4724bcda85e506ef35
commit-date: 2023-02-16
host: aarch64-apple-darwin
release: 1.69.0-nightly
LLVM version: 15.0.7