1 error[E0593]: function is expected to take a single 0-tuple as argument, but it takes 2 distinct arguments
2 --> $DIR/issue-47706-trait.rs:3:24
4 LL | fn f(&self, _: ()) {
5 | ------------------ takes 2 distinct arguments
6 LL | None::<()>.map(Self::f);
7 | ^^^^^^^ expected function that takes a single 0-tuple as argument
9 error: aborting due to previous error
11 For more information about this error, try `rustc --explain E0593`.