error: the `#[proc_macro_derive]` attribute is only usable with crates of the `proc-macro` crate type --> $DIR/illegal-proc-macro-derive-use.rs:3:1 | LL | #[proc_macro_derive(Foo)] | ^^^^^^^^^^^^^^^^^^^^^^^^^ error: the `#[proc_macro_derive]` attribute may only be used on bare functions --> $DIR/illegal-proc-macro-derive-use.rs:10:1 | LL | #[proc_macro_derive(Foo)] | ^^^^^^^^^^^^^^^^^^^^^^^^^ error: aborting due to 2 previous errors