C の内部クラスは、外部クラスのプライベート メンバーにアクセスできますか?

#include <string>
#include <iostream>

class Outer {
public:
    class Inner {
    public:
        Inner(Outer& x): parent(x) {}  // Pass a reference to the outer class

        void func() {
            std::string a = "myconst1";
            std::cout << parent.var << std::endl;

            if (a == Outer::MYCONST)
                std::cout << "string same" << std::endl;
            else
                std::cout << "string not same" << std::endl;
        }

    private:
        Outer& parent;
    };

    public:
        Outer(): i(*this), var(4) {}
        Outer(Outer& other): i(other), var(22) {}
        void func() {
            i.func();
        }

    private:
        static const char* const MYCONST;
        Inner i;
        int var;
};

const char* const Outer::MYCONST = "myconst";

int main() {
    Outer o1;
    Outer o2(o1);
    o1.func();
    o2.func();

    return 0;
}