[davidclark]

Well written typespecs + dialyzer catches most things you’d want to catch with a type system: https://hexdocs.pm/elixir/typespecs.html

There is also pattern matching and guard clauses so you can write something like:

def add(a, b) when is_integer(a) and is_integer(b), do: a + b

def add(_, _), do: :error

It’s up to personal preference and the exact context if you want a fall through case like this. Could also have it raise an error if that is preferred. Not including the fallback case will cause an error if the conditions aren’t met for values passed to the function.

[conradfr]

Writing typespecs (+ guards) feels really outdated and a drag, especially in a language that wants you to write a lot of functions.

It reminds of the not-missed phpspec, in a worst way because at least with PHP the IDE was mostly writing it itself and you didn't need to add the function name to them (easily missed when copy/pasting).

[bevr1337]

I wouldn't lump guards and typespecs together. Guards are a runtime feature of erlang/elixir's excellent pattern matching.

Typespec is an opt-in type hint for develop and build time.