Sync implementation constraints for RawOccupiedEntryMut

[ajtribick]

The implementation of sync for RawOccupiedEntryMut looks like

unsafe impl<K, V, S, A> Sync for RawOccupiedEntryMut<'_, K, V, S, A>
where
    K: Sync,
    V: Sync,
    A: Send + Allocator + Clone,
{
}

Is the requirement that A be Send correct here, or should this be Sync? E.g. the equivalent implementation on OccupiedEntry requires A: Sync + Allocator + Clone.

[Amanieu]

Nice catch, that should be A: Sync + Allocator + Clone.

[Amanieu]

In fact, this is also missing a S: Sync bound (and for the Send impl too).

[Amanieu]

I've opened #303 which should fix all existing Send/Sync` bounds.