Automatic registration of custom types?

[CJha]

Hi, I am using Qt 6.5 and C++20. I am getting my own type automatically registered without using either Q_DECLARE_METATYPE or qRegisterMetaType. Here is the full code:

MainWindow.h

#include <QWidget>
#include <QDebug>
#include <memory>
#include "ui_MainWindow.h"

struct Type
{
  int value;
  std::unique_ptr<QString> ptr = std::make_unique<QString>("One"); // just to make Type struct a bit more complex
};

class MainWindow : public QWidget
{
  Q_OBJECT

public:
  MainWindow(QWidget* parent = nullptr);
  ~MainWindow();

private:
  Ui::MainWindowClass ui;
};

MainWindow.cpp

#include "MainWindow.h"

MainWindow::MainWindow(QWidget* parent)
  : QWidget(parent)
{
  ui.setupUi(this);

  Type type;
  int id = qMetaTypeId<Type>();
  qDebug() << "ID =" << id << QMetaType::isRegistered(id) << *type.ptr;
}

MainWindow::~MainWindow()
{}

I was expecting to get a compilation error as explained in the qMetaTypeId() documentation: Returns the meta type id of type T at compile time. If the type was not declared with Q_DECLARE_METATYPE(), compilation will fail. But there is no error when I run the project and I am getting the output as: ID = 65537 true "One" . What is happening?

[Pl45m4]

@CJha

Look here.

:)