error[E0308]: mismatched types
  --> $DIR/issue-99914.rs:9:27
   |
LL |     t.and_then(|t| -> _ { bar(t) });
   |                           ^^^^^^ expected `Result<_, Error>`, found opaque type
   |
note: while checking the return type of the `async fn`
  --> $DIR/issue-99914.rs:13:23
   |
LL | async fn bar(t: Okay) {}
   |                       ^ checked the `Output` of this `async fn`, found opaque type
   = note:     expected enum `Result<_, Error>`
           found opaque type `impl Future<Output = ()>`
help: try wrapping the expression in `Ok`
   |
LL |     t.and_then(|t| -> _ { Ok(bar(t)) });
   |                           +++      +

error: aborting due to previous error

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