I can agree with the author's premise that types are essentially great, but it would be useful to have control over when (if ever) in the development stage I ne

I can agree with the author's premise that types are essentially great, but it would be useful to have control over when (if ever) in the development stage I need to bring them, much like we do with testing. I guess there is an underlying analogy between TDD and strong static typing. I think this is one of the motivations for typed/racket, which is a lot of fun to use.