The point is that if you change the type, existing calls to country.toString() will still compile. (Normally, fixing compile errors is a fairly reliable way to

The point is that if you change the type, existing calls to country.toString() will still compile. (Normally, fixing compile errors is a fairly reliable way to do this kind of refactoring.) That means you can’t guarantee to catch them all, so there’s a risk of modified behavior escaping into production.