Ok that reference-counted interior mutability stuff got a little out of control. Surely Rust doesn't really expect you to do that sort of thing in general? Well, yes and no. Rc and Refcell can be great for handling simple cases, but they can get unwieldy. Especially if you want to hide that it's happening. There's gotta be a better way!
In this chapter we're going to roll back to singly linked lists and implement a singly-linked queue to dip our toes into raw pointers and Unsafe Rust.
Let's add a new file called fifth.rs:
// in lib.rs pub mod first; pub mod second; pub mod third; pub mod fourth; pub mod fifth;
Our code is largely going to be derived from second.rs, since a queue is mostly an augmentation of a stack in the world of linked lists. Still, we're going to go from scratch because there's some fundamental issues we want to address with layout and what-not.