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'.
I was definitely using the old syntax. I uses the proper, newer syntax and this got rid of the errors:
setTimeout(() => this.matchNotifications(), 5000);