If you're updating a class then you're either (a) relying on existing functionality being maintained, or (b) changing functions that use instances of that class

If you're updating a class then you're either (a) relying on existing functionality being maintained, or (b) changing functions that use instances of that class. An `int` is likely a pathological example, btw; you most often work on classes that exist in your problem domain, like entities. It doesn't (generally) lead to problems in your type system because updates include both classes and the functions that operate on them.