Error Pada saat seting Login

Helo coach David,
pada materi fluter auth, ini setelah setting handler lalu setting login.dart. dan pada saat menambahkan toggleVIew di key error. berikut kodedan errornya :
code :
import ‘package:flutter/material.dart’;

class Login extends StatefulWidget {
final Function? toggleView();
const Login({super.key,this.toggleView});

@override
State<Login> createState() => _LoginState();
}

class _LoginState extends State<Login> {
@override
Widget build(BuildContext context) {
return const Placeholder();
}
}

Keterangan Errornya :
Can’t have modifier ‘final’ here.
‘toggleView’ must have a method body because ‘Login’ isn’t abstract.
‘super’ can’t be used as an identifier because it’s a keyword.
Expected to find ‘}’.