Got stuck here. Unhandled Exception: type '(String, int) => Future<Null>' is not a subtype of type '(String, int?) => void' in type cast

[Prime-Ext]

class AuthProvider with ChangeNotifier{

FirebaseAuth _auth = FirebaseAuth.instance; late String smsOtp; late String verificationId; String error = ''; UserServices _userServices = UserServices();

FutureverifyPhone(BuildContext context, String number)async { final PhoneVerificationCompleted verificationCompleted = (PhoneAuthCredential credential) async { await _auth.signInWithCredential(credential); };

final PhoneVerificationFailed verificationFailed = (FirebaseAuthException e){
  print(e.code);
};

final PhoneCodeSent smsOtpSend = (String verId, int resendToken)async {
  this.verificationId = verId;
} as PhoneCodeSent;

smsOtpDialog(context,number);

  try{
    _auth.verifyPhoneNumber(
        phoneNumber: number,
        verificationCompleted: verificationCompleted,
        verificationFailed: verificationFailed,
        codeSent: smsOtpSend,
        codeAutoRetrievalTimeout: (String verId){
          this.verificationId = verId;
        },
    );

  }catch(e){
    print(e);
  }
}

Future<bool?> smsOtpDialog(BuildContext context, String number){
  return showDialog(
      context: context,
      builder: (BuildContext context) {
        return AlertDialog(
          title: Column(
            children: [
              Text('Verification Code'),
              SizedBox(height: 6,),
              Text('Enter the 6 didgit Code received by sms',
                style: TextStyle(color: Colors.grey,fontSize: 10),
              ),
            ],
          ),
          content: Container(
            height: 85,
            child: TextField(
              textAlign: TextAlign.center,
              keyboardType: TextInputType.number,
              maxLength: 6,
              onChanged: (value) {
                this.smsOtp = value;
              },
            ),
          ),
          actions: [
            FlatButton(
              onPressed: ()async{
                (context);
                try{
                  PhoneAuthCredential phoneAuthCredential =
                      PhoneAuthProvider.credential(
                          verificationId: verificationId,
                          smsCode: smsOtp,

                   );

                  final User? user  = (await _auth.signInWithCredential(phoneAuthCredential)).user;

                  //create user data in fireStore after successful login
                  _createUser(id: user?.uid,number: user?.phoneNumber );
                  //navigate to homepage after login
                  if(user!=null){
                    Navigator.of(context).pop();

                    //dont want to come back to welcome screen after login
                    Navigator.of(context).pushReplacement(MaterialPageRoute(
                        builder: (context)=>HomeScreen(),
                    ));
                  }else{
                    print('Login Failed');
                  }

                }catch (e){
                  this.error = 'Invalid Code';
                  print(e.toString());
                  notifyListeners();
                  Navigator.of(context).pop();
                }
              },
              child: Text('DONE',style: TextStyle(color: Theme.of(context).primaryColor),),
            ),
          ],
        );
      });
}

  void _createUser({String? id, String? number}){
_userServices.createUserData({
  'id':id,
  'number':number,
});

} }