Cyclic mutable graphs are very hard to model in _safe_ Rust (without arena). They can be implemented easily in unsafe Rust, using pointers instead of references, like in C.

They can also be implemented by not using pointer spaghetti ;)

Even in C++ I generally prefer to use handles over pointers for cases like that because graphs are just plain hard to get right, and if you use handles you can get a nice error message when something goes wrong instead of a segfault.