[Quantlib-users] Why the scope of WesternImpl::isWeekend is changed from public from protected?

[Mike J. <ask...@gm...>]

    class Calendar {
      protected:
        //! abstract base class for calendar implementations
        class Impl {
          public:
            virtual bool isWeekend(Weekday) const = 0;
            ...
        };

        class WesternImpl : public Impl {
          protected:
            bool isWeekend(Weekday) const;
            ...
        };

If I were right, changing the virtual function scope is NOT a good
practice in c++. So why we decide to do so here?

Thank you