I had this timeout function calling a method after 500ms:

    setTimeout(
      this.matchNotifications(),
      5000
    );

This was the error I was getting:

 error TS2345: Argument of type 'void' is not assignable to parameter of type 'TimerHandler'.

Solution

I was definitely using the old syntax. I uses the proper, newer syntax and this got rid of the errors:

    setTimeout(() => this.matchNotifications(), 5000);