| error[E0774]: `derive` may only be applied to `struct`s, `enum`s and `union`s | |
| --> $DIR/macros-in-extern-derive.rs:2:5 | |
| | | |
| LL | #[derive(Copy)] | |
| | ^^^^^^^^^^^^^^^ not applicable here | |
| LL | fn f(); | |
| | ------- not a `struct`, `enum` or `union` | |
| error: aborting due to 1 previous error | |
| For more information about this error, try `rustc --explain E0774`. |