Behavioral subtyping is undecidable in general , so it can not be implemented by a program ( compiler ) .
Subtype polymorphism as enforced by the type checker in OOP languages ( with mutable objects ) can not guarantee behavioral subtyping in any context .
Behavioral subtyping is undecidable in general , so OOP can not be implemented by a program ( compiler ) .
Subtype polymorphism as enforced by the type checker in OOP languages ( with mutable objects ) can not guarantee behavioral subtyping in any context .