error: invalid use of incomplete type 'struct QPaint

[Cremers]

Hello, I'm trying to implement a simple class to draw things:
Draw.h:

#ifndef DRAW_H
#define DRAW_H
#include <QWidget>
//------------------------------------
class Canvas : public QWidget
{
  Q_OBJECT
  public:
    Canvas(QWidget *parent = 0);
  protected:
    void paintEvent(QPaintEvent *e);
  private:
    QImage image;
};
#endif // DRAW_H

#ifndef DRAW_H
#define DRAW_H
#include <QWidget>
//------------------------------------
class Canvas : public QWidget
{
  Q_OBJECT
  public:
    Canvas(QWidget *parent = 0);
  protected:
    void paintEvent(QPaintEvent *e);
  private:
    QImage image;
};
#endif // DRAW_H

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Draw.cpp:

#include <QPainter>
#include "draw.h"
//-------------------------------------------
Canvas::Canvas(QWidget *parent) : QWidget(parent)
{
}
//-------------------------------------------
void Canvas::paintEvent(QPaintEvent *e)
{
QPainter p(this);
QRect r = e->rect();              // error: invalid use of incomplete type 'struct QPaintEvent'
p.drawImage(r, image, r);
}

#include <QPainter>
#include "draw.h"
//-------------------------------------------
Canvas::Canvas(QWidget *parent) : QWidget(parent)
{
}
//-------------------------------------------
void Canvas::paintEvent(QPaintEvent *e)
{
QPainter p(this);
QRect r = e->rect();              // error: invalid use of incomplete type 'struct QPaintEvent'
p.drawImage(r, image, r);
}

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I don't understand this error. Incomplete type??
What am I doing wrong?

Thank you.