pub trait ListArcSafe<const ID: u64 = 0> {
// Required methods
unsafe fn on_create_list_arc_from_unique(self: Pin<&mut Self>);
unsafe fn on_drop_list_arc(&self);
}Expand description
Declares that this type has some way to ensure that there is exactly one ListArc instance for
this id.
Types that implement this trait should include some kind of logic for keeping track of whether
a ListArc exists or not. We refer to this logic as “the tracking inside T”.
We allow the case where the tracking inside T thinks that a ListArc exists, but actually,
there isn’t a ListArc. However, we do not allow the opposite situation where a ListArc
exists, but the tracking thinks it doesn’t. This is because the former can at most result in us
failing to create a ListArc when the operation could succeed, whereas the latter can result
in the creation of two ListArc references. Only the latter situation can lead to memory
safety issues.
A consequence of the above is that you may implement the tracking inside T by not actually
keeping track of anything. To do this, you always claim that a ListArc exists, even if
there isn’t one. This implementation is allowed by the above rule, but it means that
ListArc references can only be created if you have ownership of all references to the
refcounted object, as you otherwise have no way of knowing whether a ListArc exists.