IMHO type checking for dynamically typed languages should be done by the IDE instead of messing up the language itself. Fortunately at some point there will be an addon for your favorite IDE that does the type checking without touching your code. Microsoft could have developed such a rigorous type check addon for VSCode, but (unfortunately) instead they went for Typescript, no clue why they preferred to do the latter, maybe another throw to dominate the no1 browser language?