normal8781

struct Defer<F: FnOnce()>(Option<F>);

impl<F: FnOnce()> Drop for Defer<F> { fn drop(&mut self) { self.0.take().unwrap()(); } }

pub fn y_defer<F: FnOnce()>(f: F) -> impl Drop { Defer(Some(f)) }

#[macro_export]
macro_rules! defer { ($f:expr) => { $crate::y_defer(|| $f); }; } 

#[test]

normal8781

#[macro_export]
macro_rules! linq {
    (from $r:ident in $d:ident; select $s:expr;) =>
        { $d.map(|$r| $s) };
    (from $r:ident in $d:ident; $(where $w:expr;)* select $s:expr;)
        => { $d.filter(|&$r| (true $(&$w)*)).map(|$r| $s) };
}

fn main() {
    let x = [1, 2, 3, 4, 5, 6, 7, 8, 9].iter();