error[E0277]: `{integer}` is not a future
  --> $DIR/issue-83919.rs:22:9
   |
LL | /         async move {
LL | |             42
LL | |             // 42 does not impl Future and rustc does actually point out the error,
LL | |             // but rustc used to panic.
LL | |             // Putting a valid Future here always worked fine.
LL | |         }
   | |_________^ `{integer}` is not a future
   |
   = help: the trait `Future` is not implemented for `{integer}`
   = note: {integer} must be a future or must implement `IntoFuture` to be awaited

error: aborting due to previous error

For more information about this error, try `rustc --explain E0277`.