error[E0277]: expected a `FnOnce<(&i32,)>` closure, found `i32`
  --> $DIR/check-trait-object-bounds-2.rs:13:5
   |
LL | fn f<T: for<'r> X<'r> + ?Sized>() {
   |         ------------- required by this bound in `f`
...
LL |     f::<dyn for<'x> X<'x, F = i32>>();
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected an `FnOnce<(&i32,)>` closure, found `i32`
   |
   = help: the trait `for<'r> FnOnce<(&'r i32,)>` is not implemented for `i32`

error: aborting due to previous error

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