| error[E0277]: expected a `std::ops::FnMut<(_, char)>` closure, found `()` | |
| --> $DIR/issue-23966.rs:2:32 | |
| | | |
| LL | "".chars().fold(|_, _| (), ()); | |
| | ^^ expected an `FnMut<(_, char)>` closure, found `()` | |
| | | |
| = help: the trait `std::ops::FnMut<(_, char)>` is not implemented for `()` | |
| error: aborting due to previous error | |
| For more information about this error, try `rustc --explain E0277`. |