Rust has two ways of ensuring forwards compatibility (or incompatibility): The first is the `stable`/`nightly` system. Anything in `stable` gets compatibility

Rust has two ways of ensuring forwards compatibility (or incompatibility): The first is the `stable`/`nightly` system. Anything in `stable` gets compatibility guarantees, anything in `nightly` can change or be removed at any time. Nightly also has feature-gates: using an unstable feature requires an opt-in to enable it. The old `asm!` syntax which got renamed was only ever in `nightly`. The compatibility guarantees for `stable` are based on editions: each year there's an edition, your project's `cargo.toml` specifies which edition your code is for, and compilers will continue to support old edition code. New editions might require changes to existing code, but as long as you don't update the edition in your `cargo.toml` you can freely update your compiler (to a new stable version) without worrying about it breaking. You can use crates (packages) from any edition with any other edition, as long as the compiler is new enough to support the latest edition used.