error[E0597]: `x` does not live long enough
  --> $DIR/async-borrowck-escaping-closure-error.rs:5:24
   |
LL |     Box::new((async || x)())
   |     -------------------^----
   |     |         |        |
   |     |         |        borrowed value does not live long enough
   |     |         value captured here
   |     borrow later used here
LL |
LL | }
   | - `x` dropped here while still borrowed

error: aborting due to previous error

For more information about this error, try `rustc --explain E0597`.