Backwards compatibility is more difficult in Rust for many reasons. For example, you can't add a new item to an enum without creating missing-case errors everywhere it is used.
That's a true effect, although I'd question whether it makes it harder or easier for things to be backwards compatible. I use Rust because I trust it to throw up a bunch of errors when I make changes; if I handle all the cases of an enum somewhere, and suddenly there's a new enum variant, the answer is probably that I need to handle the new variant there too.
Adding an enum variant can be backwards incompatible just as easily in languages that don't do this, you just don't get to see the error at compile time.
Right. This even tidily forbids the exhaustive matching for other people's code (ie requires them to write a default) using your crate but still allows it within the crate, reasoning that you should know which values you added even if you never promise an exhaustive list to your users.
