Return type polymorphism has usecases where it is irreplaceable (see other comment threads). I am just pointing out an example of bad use, which is not a probl

Return type polymorphism has usecases where it is irreplaceable (see other comment threads). I am just pointing out an example of bad use, which is not a problem of the language, just of this specific API. As for APIs in general, sometimes they do need some leeway for future extension.