windowState() doesn't retrun the enum Qt::WindowState?

[shawnlau]

From the documentation:

"Qt::WindowState QWindow::windowState() const
the screen-occupation state of the window
See also setWindowState() and windowStates()."

So isn't it supposed to return a Qt::WindowState?

Well this code fails.
.pro

QT+= widgets
HEADERS += \
    mainwindow.h
 
SOURCES += \
    main.cpp

QT+= widgets
HEADERS += \
    mainwindow.h

SOURCES += \
    main.cpp

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mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H
 
#include <QMainWindow>
 
class MainWindow : public QMainWindow
{
    Q_OBJECT
public:
    explicit MainWindow(QWidget *parent = nullptr);
    void getState();
signals:
 
public slots:
private:
    Qt::WindowState m_state;
};
 
#endif // MAINWINDOW_H

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

class MainWindow : public QMainWindow
{
    Q_OBJECT
public:
    explicit MainWindow(QWidget *parent = nullptr);
    void getState();
signals:

public slots:
private:
    Qt::WindowState m_state;
};

#endif // MAINWINDOW_H

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main.cpp

#include <QApplication>
 
#include "mainwindow.h"
 
MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent)
{
    resize(400,400);
}
 
void MainWindow::getState()
{
    m_state = windowState();
}
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    MainWindow window;
    window.show();
 
    return app.exec();
}

#include <QApplication>

#include "mainwindow.h"

MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent)
{
    resize(400,400);
}

void MainWindow::getState()
{
    m_state = windowState();
}

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    MainWindow window;
    window.show();

    return app.exec();
}

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Compiler error:

Y:\QTProjects\Problems\myWindowState\main.cpp:12: error: C2440: '=': cannot convert from 'Qt::WindowStates' to 'Qt::WindowState'
Y:\QTProjects\Problems\myWindowState\main.cpp:12: No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called

What am I missing?
I need to be able to save m_state, and use it to setWindowState(m_state)