Editor placeholder in source file (viewController)

import UIKit
import AVFoundation

class ViewController: UIViewController {

    @IBAction func buttonPressed(_ sender: Any) {
        let device = AVCaptureDevice.default(for: AVMediaType.video)
        

        if device!.hasTorch {
            do {
                try device?.lockForConfiguration()
                device?.torchMode = device!.torchMode == AVCaptureDevice.TorchMode.on ? .off : .on
                device?.unlockForConfiguration()
            } catch {
                print(error)
            }
        }
    }
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
    }


}

Что за ошибка и как исправить?