Comment by pie_flavor

The 'some degree' is pretty important, though. The Rust language undergoes backwards incompatible changes sometimes, but the Rust tools do not. The 2024 edition has breaking changes since the 2021 edition, but all compilers can compile all historical editions and will do so forever, and new language features are available in as many editions as possible, and editions can be mixed in a dependency tree, so you do not ever have to update your 2015 edition code for anything.