iso C++ forbids declaration of ""with no type 是什么原因 怒了,该怎么解决

iso C++ forbids declaration of ""with no type 是什么原因 怒了
#include <QtGui/QApplication>
#include "mainwindow.h"
#include <qwidget.h>
#include <qpushbutton.h>
#include <qfont.h>
#include <qlineedit.h>
#include <qstring.h>
class MyMainWindow : public QWidget
{
  Q_OBJECT
public:
  MyMainWindow();
public slots:
  void CopyEdit(int);
private:
  QPushButton *b1;
  QPushButton *b2;
  QPushButton *b3;
  QLineEdit *ledit;
signals:
  void valueChanged(int);
};
 MyMainWindow::CopyEdit(int)
{
ledit->setText("this is a line of text!");
emit valueChanged(int);
connect(b2,SIGNAL(clicked()),ledit,SLOT(valueChanged(int)));
};
MyMainWindow::MyMainWindow()
{
this->setGeometry(300,300,400,400);
b1=new QPushButton("Click here to mark the tsxt",this);
b1->setGeometry(0,0,400,20);
b1->setFont(QFont("Times",10,QFont::Bold));
b2=new QPushButton("click here to unmark the text",this);
b2->setGeometry(0,25,400,20);
b2->setFont(QFont("Times",10,QFont::Bold));
b3=new QPushButton("click here to remove the text",this);
b3->setGeometry(0,50,400,20);
b3->setFont(QFont("Times",10,QFont::Bold));
ledit=new QLineEdit("this is a line of text!",this);
ledit->setGeometry(0,80,400,40);
connect(b1,SIGNAL(clicked()),ledit,SLOT(selectAll()));
//connect(b2,SIGNAL(clicked()),ledit,SLOT(CopyEdit()));
connect(b3,SIGNAL(clicked()),ledit,SLOT(clear()));

};

int main(int argc, char *argv[])
{
  QApplication a(argc, argv);
  MyMainWindow w;
  w.show();

  return a.exec();
}

------解决方案--------------------
好像是说父类里面（QWidget？）是int CopyEdit(int)而子类里面（MyMainWindow）是void CopyEdit(int)，这个两个函数不匹配，把MyMainWindow里面改成int CopyEdit(int)应该就好了。
------解决方案--------------------

探讨

void MyMainWindow::CopyEdit(int)
{
ledit->setText("this is a line of text!");
emit valueChanged(int);
connect(b2,SIGNAL(clicked()),ledit,SLOT(valueChanged(int)));
};

------解决方案--------------------
没指定返回值.
------解决方案--------------------

探讨

提示如下:
iso C++ forbids declaration of "CopyEdit"with no type QT
prototype for "int MyMainWindow::CopyEdit(int)"dose not match any class"MyMainWindow"
cabdidate is "void MyMainWindow::CopyEdit(int)"……