> Static typing lets you build very large rigid structures where types ensure constraints. However, these constraints get in the way of moving quickly. If you change a signature of a function, you have to first change every piece of code that calls the function.

I strongly disagree that this sort of refactoring is "quicker" with dynamically typed languages, particularly with non-trivial (i.e. large) code bases.

You have zero feedback and no indication of how disruptive such a change is when working with a dynamically typed language. In fact, you have no feedback on whether you've actually finished the change at all.

While with static type checking, you have immediate and valuable feedback guiding you through such a change. Each line of code which requires updating is identified for you and communicated to you.