error: attributes starting with `rustc` are reserved for use by the `rustc` compiler --> $DIR/expand-to-unstable-2.rs:10:10 | LL | #[derive(Unstable)] | ^^^^^^^^ | = note: this error originates in the derive macro `Unstable` (in Nightly builds, run with -Z macro-backtrace for more info) error: aborting due to previous error