I do too, but I feel like TypeScript stands alone as an unusually effective and pleasant to use bolted-on type system. I've not seen any other approach come close. (My sample size is Python, Ruby and Elixir)
I really like PHP's type hints (I think they were the first I used) though it's somewhat limited (can't type hint complex/nested structures last time I checked).
Flow for Javascript was okay but Typescript I've found to be much nicer (last used flow years ago but occasionally I'd encounter bugs in Flow).
you don't think the elixir type system is effective? I've never seen a bolted-on type system get so much acceptance from the hardcore "you can add types into my dead hands" crowd
