QT新手问题信号槽连接失败

求助！！！运行的时候出现错误提示：QObject::connect: signal not found in QPushButton，哪位大佬愿意帮助一下嘛哭了

定义的窗口类

//widget.cpp
#include "mywidget.h"
#include<QPushButton>

mainWidget::mainWidget(QWidget *parent)
    : QWidget(parent)
{
    //设置固定窗口大小
    setFixedSize(1080,640);

    //创建按钮
    QPushButton * btn = new QPushButton;
    btn->setText("search");
    btn->setParent(this);
    connect(btn, &QPushButton::click, this, &QWidget::close);

    //查询按钮功能设置
    connect(search_btn, &QPushButton::click, this, &QWidget::close);
}

主函数

//main.cpp
#include "mywidget.h"
#include"bookwidget.h"

#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    mainWidget mainwiget;
//    BookWIDGET bookwidget;
    mainwiget.show();
//    bookwidget.show();
    return a.exec();
}

QPushButton没有click信号
connect(btn, &QPushButton::clicked, this, &QWidget::close);
connect(search_btn, &QPushButton::clicked, this, &QWidget::close);