| error[E0059]: cannot use call notation; the first type parameter for the function trait is neither a tuple nor unit | |
| --> $DIR/E0059.rs:3:41 | |
| | | |
| LL | fn foo<F: Fn<i32>>(f: F) -> F::Output { f(3) } | |
| | ^^^^ | |
| error: aborting due to previous error | |
| For more information about this error, try `rustc --explain E0059`. |