Rust external library macro : I have a project tree like this:

main.rs:

    external crate lib;
    mod a;
    fn main() {
        a::some_func();
    }

a.rs:

    use lib;
    fn some_func() {
        lib::func();
    }

this works ok.
but when i try to use a macro from 'lib', it gives me an error of macro undefined. 

I tried putting #[macro_use] in front of the 'external crate lib', then i get a lot of unresolved errors inside of the external crate. And i have already looked inside of the external crate, there is nothing wrong. Also, the fact that i can use functions from the library kinda proves (to me, im a rust noob) that the library is ok, and i'm doing something wrong.