struct CandyMachine<'a, T: 'a> {
    candyfn: &'a (Fn() -> T)
}
impl<'a,T> CandyMachine<'a,T> {
    fn new<Map>(f: &'a Map) -> CandyMachine<'a,T> where Map: Fn() -> T { CandyMachine { candyfn: f } }
    fn candy(&self) -> T { (self.candyfn)() }
}

struct Candy {}
impl Candy {
    fn candy() -> String { "shleck".to_string() }
}

fn main() {
    let m = CandyMachine::new(&Candy::candy);
    println!("Candy is {}.", m.candy());
}