error[E0277]: expected a `Fn()` closure, found `()` --> $DIR/issue-22034.rs:8:16 | LL | &mut *(ptr as *mut dyn Fn()) | ^^^ expected an `Fn()` closure, found `()` | = help: the trait `Fn<()>` is not implemented for `()` = note: wrap the `()` in a closure with no arguments: `|| { /* code */ }` = note: required for the cast from `*mut ()` to `*mut dyn Fn()` error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0277`.