enum MyOption<T> {
    Some(T),
    None
}

impl<T> MyOption<T> {
    fn unwrap(self) -> T {
        match self {
            MyOption::Some(v) => v,
            MyOption::None => panic!("unwrap failed"),
        }
    }

    fn from_option(v: Option<T>) -> Self {
        match v {
            None => MyOption::None,
            Some(v) => MyOption::Some(v),
        }
    }
}

fn main() {
    let mut v = vec![1,2,3];
    while let MyOption::Some(v) = MyOption::from_option(v.pop()) {
        println!("{}", v);
    }
    let w: MyOption<i32> = MyOption::None;
    println!("{}", w.unwrap());
}