fn main() {
    let x = generic(0);
    match x {
        Generic::F64(o) => println!("{}", o),
        Generic::Usize(o) => println!("{}", o),
    }
}

#[derive(Clone, Copy, Debug)]
enum Generic {
    F64(f64),
    Usize(usize),
}

fn generic(n: usize) -> Generic {
    match n {
        0 => Generic::F64(2.0f64),
        _ => Generic::Usize(3usize),
    }
}