error[E0277]: expected a `Fn<(&'w (),)>` closure, found `fn(&'w ())` --> $DIR/fn-ptr.rs:12:5 | LL | ice(); | ^^^ expected an `Fn<(&'w (),)>` closure, found `fn(&'w ())` | = help: the trait `for<'w> Fn<(&'w (),)>` is not implemented for `fn(&'w ())` note: required by a bound in `ice` --> $DIR/fn-ptr.rs:7:25 | LL | fn ice() | --- required by a bound in this function LL | where LL | for<'w> fn(&'w ()): Fn(&'w ()), | ^^^^^^^^^^ required by this bound in `ice` error: aborting due to previous error For more information about this error, try `rustc --explain E0277`.