Macro id 

macro_rules! id {
    ($($x:ident).+) => { ... };
    (@ $root:ident . $($x:ident).+) => { ... };
}

Make a identifier string with the given path

use gom::id;

const MY_ID: &str = id!(my.module.MyType);
const OTHER_ID: &str = id!(@MY_ID.other.OtherType);

assert_eq!(MY_ID, ".my.module.MyType");
assert_eq!(OTHER_ID, ".my.module.MyType.other.OtherType");