An easy way to get that is when you use a third-party library, update that to get some new feature, and get a new enum value for free, say because the html pars

An easy way to get that is when you use a third-party library, update that to get some new feature, and get a new enum value for free, say because the html parser library started supporting a new node type or added a new error type (the latter will be rare in go because of its lack of sum types). Ideally, of course, the release notes of the library would spell out the issue, and you’d read them, but even then, making sure you fix this everywhere is way easier if the compiler refuses to compile your code if it doesn’t handle the new case.