error: derive proc macro has incorrect signature --> $DIR/signature.rs:10:1 | LL | pub unsafe extern "C" fn foo(a: i32, b: u32) -> u32 { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected normal fn, found unsafe fn | = note: expected signature `fn(proc_macro::TokenStream) -> proc_macro::TokenStream` found signature `unsafe extern "C" fn(i32, u32) -> u32` error: aborting due to 1 previous error