| error[E0658]: attributes starting with `rustc` are reserved for use by the `rustc` compiler | |
| --> $DIR/expand-to-unstable-2.rs:10:10 | |
| | | |
| LL | #[derive(Unstable)] | |
| | ^^^^^^^^ | |
| | | |
| = note: for more information, see https://github.com/rust-lang/rust/issues/29642 | |
| = help: add `#![feature(rustc_attrs)]` to the crate attributes to enable | |
| error: aborting due to previous error | |
| For more information about this error, try `rustc --explain E0658`. |