struct Defer<'a, F>
    where F: FnOnce() + 'a
{
    f: Option<F>,
    _t: ::std::marker::PhantomData<&'a F>,
}

impl <'a, F> Drop for Defer<'a, F>
    where F: FnOnce() + 'a
{
    fn drop(&mut self) {
        if let Some(f) = self.f.take() {
            (f)();
        }
    }
}

macro_rules! defer {
    ($func:block) => {
        let _defer = Defer {
            f: Some(|| $func),
            _t: ::std::marker::PhantomData,
        };
    }
}
fn main() {
    defer!({println!("End!")});

    println!("Running")
}