The promise of better type systems os that more of your code will be secured by types, not that everything will be covered. That is why there are still people w

The promise of better type systems os that more of your code will be secured by types, not that everything will be covered. That is why there are still people working on newer type systems (e.g. dependent types, linear types, etc). For the specific example you give, you can either use liquid haskell, which is an annotation system bringing richer types to haskell, or use another lang that has dependent types off the shelf.