I love peeking into the Rust standard library's source code. Every (commonly used) function is so carefully and lovingly optimized, it feels like a bonsai garden. Every line of code has received at least an hour of attention.
If you're curious as to what inspired this post: https://doc.rust-lang.org/nightly/src/core/slice/iter/macros.rs.html. Feel free to share anything similar you've run into, from std or otherwise.
