Return type of getClass method

Question

The documentation for the method getClass() in Object says:

The actual result type is Class<? extends |X|> where |X| is the erasure of the static type of the expression on which getClass is called.

So why does foo compile but not bar?

static void foo(String s) {
    try {
        Class<? extends String> clazz = s.getClass();
    } catch (Exception e) {

    }
}

static <T> void bar(T t) {
    try {
        Class<? extends T> clazz = t.getClass();
    } catch (Exception e) {

    }
}

Edit

I've accepted yshavit's answer, as it clearly answers my question, but I'm still curious to know why they defined it like this. They could have defined it to have type Class<? extends T> where T is the static type of the expression. It isn't clear to me why it's necessary to erase the type information at this stage. It makes sense if the type is List<String>, but not if it's T. I'll up-vote any answer that explains this.

Answer 1

where |X| is the erasure of the static type of the expression (emphasis added)

The erasure of T t is Object, so |X| is Object in that case. That means that the result type is Class<? extends Object> (which is essentially equivalent to Class<?>).

The erasure of String s, on the other hand, is String (since String is a reifiable type -- ie, not generic).