use std::fmt::Debug;

fn foo() -> Vec<u32> {
    let mut xs = Vec::new();
    xs.push(8u32);
    xs.iter().map(|x| x * x).collect()
}

fn bar<T: Copy + Debug>(x: T) -> Vec<(T,T)> {
    let mut xs = Vec::new();
    xs.push(x);
    xs.iter().map(|&x| (x, x)).collect()
}

fn main() {
    println!("{:?}", foo());
    println!("{:?}", bar(()));
}