How do I use a specific edition of Rust?

Question

I know there are currently two editions of Rust (2015 and 2018), how can I tell cargo and rustc which one I want to use?<

Answer 1

You can add the following to your Cargo.toml, it's documented on the edition 2018 guide:

[package]
edition = "2018"

---

If you directly use rustc you can use rustc --edition 2018, it's documented with rustc --help -v command.

--edition 2015|2018
  Specify which edition of the compiler to use when
  compiling code.