QWeakPointer d pointer is private

#include <QMap>
#include <QObject>
#include <QWeakPointer>

class Example
	: public QObject
{
	Q_OBJECT
};

int main(int argc, char** argv)
{

	QMap<QString, QWeakPointer<QObject>> instances;
	auto shared = QSharedPointer<Example>::create();

        // broken
	instances.insert(QStringLiteral("1"), shared.toWeakRef());

        // works        
	auto tmp = shared.toWeakRef();
	instances.insert(QStringLiteral("2"), tmp);

	return 0;
}

#include "main.moc"

/.../libs/qt6/dist/include/QtCore/qsharedpointer_impl.h: In instantiation of 'QWeakPointer<T>::QWeakPointer(QWeakPointer<X>&&) [with X = Example; typename std::enable_if<std::is_convertible<_Up*, _Tp*>::value, bool>::type <anonymous> = true; T = QObject]':

/.../libs/qt6/dist/include/QtCore/qsharedpointer_impl.h:589:19: error: 'QWeakPointer<Example>::Data* QWeakPointer<Example>::d' is private within this context
  589 |         : d(other.d), value(other.value)
      |             ~~~~~~^
/.../libs/qt6/dist/include/QtCore/qsharedpointer_impl.h:719:11: note: declared private here
  719 |     Data *d;
      |           ^
/.../libs/qt6/dist/include/QtCore/qsharedpointer_impl.h:589:35: error: 'Example* QWeakPointer<Example>::value' is private within this context
  589 |         : d(other.d), value(other.value)
      |                             ~~~~~~^~~~~
/.../libs/qt6/dist/include/QtCore/qsharedpointer_impl.h:720:8: note: declared private here
  720 |     T *value;
      |        ^~~~~
/.../libs/qt6/dist/include/QtCore/qsharedpointer_impl.h:591:15: error: 'QWeakPointer<Example>::Data* QWeakPointer<Example>::d' is private within this context
  591 |         other.d = nullptr;
      |         ~~~~~~^
/.../libs/qt6/dist/include/QtCore/qsharedpointer_impl.h:719:11: note: declared private here
  719 |     Data *d;
      |           ^
/.../libs/qt6/dist/include/QtCore/qsharedpointer_impl.h:592:15: error: 'Example* QWeakPointer<Example>::value' is private within this context
  592 |         other.value = nullptr;
      |         ~~~~~~^~~~~
/.../libs/qt6/dist/include/QtCore/qsharedpointer_impl.h:720:8: note: declared private here
  720 |     T *value;
      |        ^~~~~