OCaml and Haskell already have that nice type system (and even more nice). If OCaml's syntax bothers you, there is Reason [1] which is a different frontend to the same compiler suite.

Also in this space is Gleam [2] which targets Erlang / OTP, if high concurrency and fault tolerance is your cup of tea.

[1]: https://reasonml.github.io/

[2]: https://gleam.run/