error[E0050]: method `foo` has 2 parameters but the declaration in trait `Foo::foo` has 3 --> $DIR/trait-method-number-parameters.rs:7:9 | LL | fn foo(&mut self, x: i32, y: i32) -> i32; | ------------------------- trait requires 3 parameters ... LL | / &mut self, //~ ERROR LL | | x: i32, | |______________^ expected 3 parameters, found 2 error: aborting due to previous error For more information about this error, try `rustc --explain E0050`.