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use core::mem::ManuallyDrop;
use core::ptr;
#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
pub struct OnDrop<F: FnOnce()>(ManuallyDrop<F>);
impl<F: FnOnce()> OnDrop<F> {
pub fn new(f: F) -> Self {
Self(ManuallyDrop::new(f))
}
pub fn into_inner(self) -> F {
let this = ManuallyDrop::new(self);
unsafe { ptr::read(&*this.0) }
}
}
impl<F: FnOnce()> Drop for OnDrop<F> {
#[inline(always)]
fn drop(&mut self) {
unsafe {
let f: F = core::ptr::read(&*self.0);
f()
}
}
}
#[cfg(test)]
mod tests {
use super::*;
use std::cell::Cell;
use dropcheck::{DropCheck, DropToken};
#[test]
fn drops_closure_once() {
let check = DropCheck::new();
let (token, state) = check.pair();
let mut dst = Cell::new(None);
let ondrop = OnDrop::new(|| {
dst.set(Some(token));
});
assert!(state.is_not_dropped());
ondrop.into_inner();
assert!(state.is_dropped());
assert!(dst.take().is_none());
let (token, state) = check.pair();
let ondrop = OnDrop::new(|| {
dst.set(Some(token));
});
assert!(state.is_not_dropped());
drop(ondrop);
assert!(state.is_not_dropped());
assert!(dst.take().is_some());
}
}