> You get into trouble because of the self-recursion.
Which is why (savvy) object-oriented programmers have largely moved on to interface polymorphism. Inheritance polymorphism has its uses, which is why there hasn't been a whole lot of effort to rally behind languages that lack it, but the general consensus is that you should really only use inheritance when inheritance is what you really want to use.
Unfortunately it's true that there's a whole lot of OO code out there that was written before people learned this lesson. And OO's popularity with pragmatists combined with its relative lack of popularity with academics means that a lot of code doesn't reflect lessons related to the pitfalls of inheritance polymorphism that academics figured out a very long time ago, such as the Liskov Substitution Principle.
Which is why (savvy) object-oriented programmers have largely moved on to interface polymorphism. Inheritance polymorphism has its uses, which is why there hasn't been a whole lot of effort to rally behind languages that lack it, but the general consensus is that you should really only use inheritance when inheritance is what you really want to use.
Unfortunately it's true that there's a whole lot of OO code out there that was written before people learned this lesson. And OO's popularity with pragmatists combined with its relative lack of popularity with academics means that a lot of code doesn't reflect lessons related to the pitfalls of inheritance polymorphism that academics figured out a very long time ago, such as the Liskov Substitution Principle.