It'd be nice if OwningRefMut could share ownership, but…

[Rufflewind]

It'd be nice if OwningRefMut could share ownership through Arc, but turns out that doesn't really work because it would cause safety issues due to the presence of .owner() :(

Here's what I wanted to implement for OwningRefMut:

pub fn split<F, U: ?Sized, V: ?Sized>(mut self, f: F) -> (OwningRefMut<O, U>, OwningRefMut<O, V>)
    where F: FnOnce(&mut T) -> (&mut U, &mut V),
          O: stable_deref_trait::CloneStableDeref

But this is not safe, because you could use owner() of OwningRefMut<O, U> to get an immutable reference while holding a mutable reference from the OwningRefMut<O, V>.

This means the API would have to be limited to something like Arc<Erased>, from which you can't take extract any immutable references.

Edit: My current workaround is to wrap the inner object inside an opaque wrapper to prevent the user from acquiring any references from it: Rufflewind@e9ab08f