Good luck implementing "peer pointers" in Rust. Zero allocation involved, trivial to do safely in C++. class A { /* can be NULL if detached */ B *p

Good luck implementing "peer pointers" in Rust. Zero allocation involved, trivial to do safely in C++. class A { /* can be NULL if detached */ B *peer; /* other fields generally exist in one of the classes. */ /* useful objects are typically created in pairs, but can be constructed detached if needed */ /* move ctor and swap keep the (value) objects pointing at each other */ /* move assignment and dtor call detach() on the overwritten/expiring object */ /* Often separate "detach and cancel" and "detach without canceling" are useful */ void detach(); /* other functions specific to the peerage */ }; class B { A *peer; /* same API as `class A`, but usually most of it is only used via one owner. */ /* In my experience, generally one class's instance goes in some collection of centralized objects like an event loop, and the other is used as a handle to it. */ }; I guess we could always use the usual Rust solution of "screw ownership and efficiency, just shove everything in an `Rc<RefCell<>>`".