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