#![crate_type = "lib"] // bbb
#![allow(unused_variables)] // aaa

fn main() {
// General metadata applied to the enclosing module or crate.
    #![crate_type = "lib"]

    // A function marked as a unit test
    #[test]
    fn test_foo() {
        /* ... */
    }

    // A conditionally-compiled module
    #[cfg(target_os = "linux")]
    mod bar {
        /* ... */
    }

    // A lint attribute used to suppress a warning/error
    #[allow(non_camel_case_types)]
    type int8_t = i8;

    // Inner attribute applies to the entire function.
    fn some_unused_variables() {
        #![allow(unused_variables)]

        let x = ();
        let y = ();
        let z = ();
    }
}