[im_down_w_otp]

There is static type checking/analysis available. Just use Dialyzer.

[Kexoth]

You're right. I've used it once as a part of an exercise in the "Programming Elixir" book and never again.

It should maybe come bundled with mix, as some other tools, that way it'll be more approachable.

Also there's a wrapper for it, which helps in the process.[0]

[0] - https://github.com/jeremyjh/dialyxir