error[E0050]: method `bar` has 1 parameter but the declaration in trait `Foo::bar` has 2 --> $DIR/impl-different-num-params.rs:5:12 | LL | fn bar(&self, x: usize) -> Self; | --------------- trait requires 2 parameters ... LL | fn bar(&self) -> isize { | ^^^^^ expected 2 parameters, found 1 error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0050`.