| error[E0412]: cannot find type `Oper` in this scope | |
| --> $DIR/issue-54966.rs:3:27 | |
| | | |
| LL | fn generate_duration() -> Oper<impl FnMut()> {} | |
| | ^^^^ not found in this scope | |
| error: aborting due to previous error | |
| For more information about this error, try `rustc --explain E0412`. |