void shift(IteratorT begin, IteratorT end, int offset)
{
  while (begin != end)
  {
    *begin++ = (*begin).addDays(offset * 7);
  }
}

template <typename IteratorT>
void shift(IteratorT begin, IteratorT end, typename std::iterator_traits<IteratorT>::difference_type offset)

Q_PROPERTY(QQmlListProperty<const QObjectDerived> items READ items NOTIFY updated)

Q_PROPERTY(QQmlListProperty<QObjectDerived> items READ items NOTIFY updated)

...
                Button {
                    id: openButton
                    text: qsTr("Open")
                    onClicked: root.click(StandardButton.Open)
                    visible: root.standardButtons & StandardButton.Open
                }
                Button {
                    id: saveButton
                    text: qsTr("Save")
                    onClicked: root.click(StandardButton.Save)
                    visible: root.standardButtons & StandardButton.Save
                }
...

    /// \file
    /// \brief Application main file
    /// \author John Doe
    /// \date 27.Mar.2021

...
                    //##note: When the main window is closing at the dialog opened, here the dialog 
                    // itself is already destroyed, and its properties are 'undefined'.
                    if (typeof object.parent !== 'undefined')
                        object.destroy()
...

ApplicationWindow {
    id: appWindow
	
    Menu {
        MenuItem {
            text: qsTr("About...")
            onTriggered: {
                function destroyAboutWindow() {
		    //##note: When the main window is closing at the dialog opened, here the main
                    // window ref. is already nulled. The main window will destroy the dialog while
                    // its own destruction.
		    if (appWindow)
			object.destroy()
                }

                var component = Qt.createComponent("AboutWindow.qml")
                var object = component.createObject(appWindow)
                console.assert(object)
                object.open()
                object.closed.connect(destroyAboutWindow)
            }
        }
    }
}

#include <iostream>

enum Param {
	First,
	Second,
	Third
};

template <Param> const char* ParamName = "Not associated!";
template <> const char* ParamName<First> = "First parameter name";
template <> const char* ParamName<Second> = "Second parameter name";

// Для третьего параметра "забыли" специализацию, поэтому будет "Not associated!".

int main()
{
	std::cout << ParamName<First> << std::endl;
	std::cout << ParamName<Second> << std::endl;
	std::cout << ParamName<Third> << std::endl;  // Not associated!

	return 0;
}

template <Param> const char* ParamName = "Not associated!";
заменить на
template <Param> const char* ParamName = [](){ static_assert(0, "Not associated!"); return nullptr; }();

template <typename IteratorT>
static void shiftWeeks(IteratorT begin, IteratorT end)
{
    ....
    static const int DayStep = 7 * (IsReverseIterator<IteratorT> ? -1 : 1);
    ....
}

template <typename, typename = void>
inline constexpr bool IsReverseIterator = false;

template <typename T>
inline constexpr bool IsReverseIterator<T, std::void_t<decltype(std::declval<T>().base())>> = true;

ApplicationWindow {
    Menu {
        MenuItem {
            text: qsTr("About...")
            onTriggered: {
                //TODO: At open dialog and app closing: TypeError: Property 'destroy' of object TypeError: Type error is not a function
                function destroyAboutWindow() {
                    object.destroy()
                }

                var component = Qt.createComponent("AboutWindow.qml")
                var object = component.createObject(appWindow)
                console.assert(object)
                object.open()
                object.closed.connect(destroyAboutWindow)
            }
        }
    }
}

void showAboutDialog()
{
	auto dialog = new QDialog;
	dialog->deleteLater(); 
	dialog->exec();  // blocking call, shows modal dialog with its own event loop
}