I hope this gets better uptake than Clojure's Core.typed -- for instance, see CircleCI's experience with it
https://circleci.com/blog/why-were-no-longer-using-core-type... (though it seems the issues are getting addressed,
https://theholyjava.wordpress.com/2015/10/06/an-answer-to-ci... )
Guido supporting this certainly helps.