| error[E0277]: the trait bound `(): std::ops::FnMut<(_, char)>` is not satisfied | |
| --> $DIR/issue-23966.rs:12:16 | |
| | | |
| LL | "".chars().fold(|_, _| (), ()); | |
| | ^^^^ 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`. |