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