To be clear, cyclic references are just as much an issue in GCed languages. In Python I had to use weakref lib to ensure cyclically referenced objects are still GCed. Rust is the same in that aspect, you use the Rc builtin type and create a weakref for one of them.
No, GCs can handle cyclic references. You don't need weak references merely in order to ensure that a cyclic structure is eventually freed once it's become inaccessible. That's not to say that there might not sometimes be good reasons for using weak references in a GCed language, however.
