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use std::mem;

pub struct Defer<F: FnOnce()> {
    f: Option<F>,
}

impl<F: FnOnce()> Drop for Defer<F> {
    fn drop(&mut self) {
        if let Some(f) = mem::replace(&mut self.f, None) {
            f();
        }
    }
}

pub fn defer<F: FnOnce()>(f: F) -> Defer<F> {
    Defer { f: Some(f) }
}