Access specifiers in nested class

[Ganado]

This is probably a really basic question, but I'm confused by why this code compiles

class Foo {
public:

    Foo()
    : value(100) { }
 
private:

    class Bar {
    public:      
        Bar(Foo& foo)
        : foo(foo) { }
        
        void Update()
        {
            foo.value = 42;
        }
        
    private:
        Foo& foo;
    };
            
    int value;
};

int main()
{

}

Specifically, line 16.
Isn't foo.value a private member?
I assume it's something special with it being a nested class?

[Peter87]

https://en.cppreference.com/w/cpp/language/nested_types.html

Like any member of its enclosing class, the nested class has access to all names (private, protected, etc) to which the enclosing class has access, but it is otherwise independent and has no special access to the this pointer of the enclosing class.

[Ganado]

Thanks Peter.