error[E0220]: associated type `Output` not found for `One<()>` --> $DIR/unboxed-closure-sugar-wrong-number-number-type-parameters-1.rs:5:16 | LL | fn foo(_: &dyn One()) | ^^^^^ associated type `Output` not found error: aborting due to previous error For more information about this error, try `rustc --explain E0220`.