Invalid compiler warning?

Question

I've got:
class A<Type1>
  public A<Type1> getValue();
class B<Type1, Type2> extends A<Type1>
  public B<Type1, Type2> getValue()
    return (B<Type1, Type2>) super.getValue(); // compiler complains of unchecked cast
}Thing is, I really don't see why the above is an unchecked cast. We know that B extends A. When B is constructed, it passes its parameter-types down so when getValue() returns A<Type1> it is really returning a superclass-view of B<Type1, Type2> -- at least that's what I think is going on. Am I wrong?
Gili

Answer 1

Thing is, I really don't see why the above is an
unchecked cast.A.getType returns an A. B.getType returns a B. Just because 'this' is a B doesn't mean that super.getType will return a B.
For example, we could have:
class A
  public A getValue()
    return new A();
class B extends A
    public B getType()
        return super.getType();
}Would you expect the above to work?