登录、登出后重定向到来源页面

目标：
A页(未登录)->登录页->登录->A页(已登录)
B页(已登录)->登出->B页(未登录)

代码：
app/Http/Controllers/Auth/LoginController.php

...
use URL;

class LoginController extends Controller
{
    use AuthenticatesUsers {
        showLoginForm as laravelShowLoginForm;
        logout as laravelLogout;
    }

    protected $redirectToSessionKey = 'redirect_to';

    public function __construct()
    {
        $this->middleware('guest')->except('logout');
    }

    public function showLoginForm(Request $request)
    {
        $request->session()->put($this->redirectToSessionKey, URL::previous());

        return $this->laravelShowLoginForm();
    }

    public function redirectTo()
    {
        $request = app(Request::class);
        $redirectTo = $request->session()->get($this->redirectToSessionKey);
        $request->session()->forget($this->redirectToSessionKey);

        return $redirectTo;
    }

    public function logout(Request $request)
    {
        $this->laravelLogout($request);

        return redirect(URL::previous());
    }
}