Panics on drop will cause double drops.

[Stebalien]

IntoIter and ArrayVec need to be poisoned to prevent dropping before being drained; otherwise, if one of the elements panics on drop, it will be dropped twice. I've worked on a couple of solutions but they all have design tradeoffs so I figured I'd just let you fix it.

Drain doesn't have this issue because the ArrayVec's length is set to 0 when the Drain is initialized.

[Stebalien]

Test cases (abusing rust's panic on drop -> abort).

#[test]
#[should_panic]
fn test_drop_panic() {
    struct DropPanic;

    impl Drop for DropPanic {
        fn drop(&mut self) {
            panic!("drop");
        }
    }

    let mut array = ArrayVec::<[DropPanic; 1]>::new();
    array.push(DropPanic);
}

#[test]
#[should_panic]
fn test_drop_panic_into_iter() {
    struct DropPanic;

    impl Drop for DropPanic {
        fn drop(&mut self) {
            panic!("drop");
        }
    }

    let mut array = ArrayVec::<[DropPanic; 1]>::new();
    array.push(DropPanic);
    array.into_iter();
}

[bluss]

Thanks! I guess this won't be easy..

[bluss]

For the lols, please read #5. Hey you said you would leave it for me to fix! But I do think you have the sane version, and I the insane..

[bluss]

Fixed in version 0.3.10. Use (unstable) feature flag nodrop/no_drop_flag to recover size. (However, it's not completely equivalent in terms of overhead, even if the size is the same.)

[bluss]

Great, now it's fixed in smallvec too.