This final chapter leads us to the most important experimental features in Rust, provided on the newest nightly toolchain. As of the time of writing, this is rustc 1.25.0-nightly. If you are using rustup (https://rustup.rs/), you can set it as your default toolchain like this:

rustup default nightly

These recipes will ensure that you stay ahead in your knowledge of Rust, and are ready to use them effectively once they are stabilized, or right now in your own unstable apps.

All of the recipes in this chapter have varying stability guarantees. Many will undergo drastic changes before they land in the stable toolchain, and others are nearly done. This means that some of the example code provided is expected not to work on your newest nightly. When this happens, you can find help in two places:

• If the feature is still experimental, it will have an entry in The Unstable Book (https://doc.rust-lang.org/unstable-book/), and a link to the relevant GitHub issue and its surrounding discussion
• If the feature has been stabilized, there is a good chance you will find it listed in the appendix of The Rust Programming Language, Second Edition (https://doc.rust-lang.org/stable/book/second-edition/appendix-06-newest-features.html)