gistfile1.txt

fn main() {
    let mut x = 1;
    wat(|i| { x += i; return x; });
    println!("{}", x);
}

fn wat<F>(f: F) -> u32 where F: FnMut(u32) -> u32 {
    foo(f)
}

fn foo<F>(mut f: F) -> u32 where F: FnMut(u32) -> u32 {
    f(1) + f(2)
}