So I glanced at it, expecting something much much worse, but I was surprised to see it wasn't that bad. Even if you look at the final code for the final implementation, it doesn't seem much more complex than what you'd have to write in C. And a good chunk of the code is implementing traits from the stdlib, stuff that isn't strictly necessary, but makes it easier to make the API of the deque idiomatic and work well with other stdlib (and non-stdlib) APIs.

And regardless, this book is teaching from the perspective of intentional super-hard-mode. Most Rust developers will never have to write that much unsafe code.