nomicon/src/vec/vec.md

Example: Implementing Vec

To bring everything together, we're going to write std::Vec from scratch. We will limit ourselves to stable Rust. In particular we won't use any intrinsics that could make our code a little bit nicer or efficient because intrinsics are permanently unstable. Although many intrinsics do become stabilized elsewhere (std::ptr and std::mem consist of many intrinsics).

Ultimately this means our implementation may not take advantage of all possible optimizations, though it will be by no means naive. We will definitely get into the weeds over nitty-gritty details, even when the problem doesn't really merit it.

You wanted advanced. We're gonna go advanced.