No, it's referring to formal methods. Elm will prevent you from writing a binary search that returns a string, but will happily admit a broken binary search tha

No, it's referring to formal methods. Elm will prevent you from writing a binary search that returns a string, but will happily admit a broken binary search that (say) never terminates, or always returns 0. Formal methods allow you to catch that class of mistakes. I don't see any case for a functional-programming inspired change now. 30 years ago programmers were enlighten by LISP, 15 years ago I was enlightened by OCaml, and today's generation is enlightened by Haskell, or in your case Elm. What's different now? If anything I think we're moving in the opposite direction. Development speed is now king, and deployment is easier than it's ever been, which means that bugs are less costly to fix. Bondage-and-discipline type languages that promise fewer bugs for more work are just less relevant.