memur 0.3.4

Arena storage with bells and whistles.
Documentation 
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pub struct EmptyIfDeadIter<K, I: ExactSizeIterator<Item=K>> {
    pub is_alive: bool,
    pub inner: I,
}

impl<K, I: ExactSizeIterator<Item=K>> ExactSizeIterator for EmptyIfDeadIter<K, I> {
    fn len(&self) -> usize {
        if self.is_alive {
            0
        } else {
            self.inner.len()
        }
    }
}

impl<K, I: ExactSizeIterator<Item=K>> Iterator for EmptyIfDeadIter<K, I> {
    type Item = K;

    fn next(&mut self) -> Option<Self::Item> {
        if self.is_alive {
            self.inner.next()
        } else {
            None
        }
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        if self.is_alive {
            self.inner.size_hint()
        } else {
            (0, Some(0))
        }
    }
}