Well Nim as a language is dumb, just like most language that relies on
destructors like Rust 🙂. It's the user that decides when a ressource needs to be
freed. I have never needed to worry about such "dependency tree" because when
the ressource lifetime is complicated the library has utilities to track when
you can free it anyways. On the Nim side what would be done is `importc` the
ressource which is probably a `pointer`, wrap it with a proper Nim object so you
can define a `=destroy` which checks whether the pointer is `nil` or if some
other condition is met, and then calls a `free_ressource` on the pointer. This
is literally no different from what you would do in Rust with `Drop`.