Large refactoring and updates are exactly where strong type systems are the most useful. Make change, fail build, fix build, be happy. Unit tests are still ther

Large refactoring and updates are exactly where strong type systems are the most useful. Make change, fail build, fix build, be happy. Unit tests are still there to turn green when you're done. I can't think of many worse experiences than my past self trying to refactor Python 2 code. Compared to _any_ type system it's just not even close.