error[E0121]: the type placeholder `_` is not allowed within types on item signatures --> $DIR/self-infer.rs:4:16 | LL | fn f(self: _) {} | ^ | help: use type parameters instead | LL | fn f(self: T) {} | ^^^ ^ error[E0121]: the type placeholder `_` is not allowed within types on item signatures --> $DIR/self-infer.rs:5:17 | LL | fn g(self: &_) {} | ^ | help: use type parameters instead | LL | fn g(self: &T) {} | ^^^ ^ error: aborting due to 2 previous errors For more information about this error, try `rustc --explain E0121`.