Comment by dkarapetyan

Yes, type erasure is neat and a bit of thinking will make it obvious why proving static properties does not require run time checks if the transformations you perform on your program preserve those static properties. I disagree with the author's claim though that types are everywhere. Types in fact are extra structure that is hoisted onto programs. At the end of the day the machine knows nothing about the types and will shuttle bytes back and forth all day long. Furthermore, types restrict the universe of computation and there are examples of programs that are not well-typed but don't go wrong when evaluated.