warning: the feature `async_fn_in_trait` is incomplete and may not be safe to use and/or cause compiler crashes
  --> $DIR/return-type-suggestion.rs:3:12
   |
LL | #![feature(async_fn_in_trait)]
   |            ^^^^^^^^^^^^^^^^^
   |
   = note: see issue #91611 <https://github.com/rust-lang/rust/issues/91611> for more information
   = note: `#[warn(incomplete_features)]` on by default

error[E0308]: mismatched types
  --> $DIR/return-type-suggestion.rs:8:9
   |
LL |         Ok(())
   |         ^^^^^^- help: consider using a semicolon here: `;`
   |         |
   |         expected `()`, found enum `Result`
   |
   = note: expected unit type `()`
                   found enum `Result<(), _>`

error: aborting due to previous error; 1 warning emitted

For more information about this error, try `rustc --explain E0308`.