elixir’s simple module produces only argument errors

This is an issue of using Erlang/OTP 23 and Elixir 1.9.4 simultaneously.

Elixir 1.9 is older than OTP 23, but elixir fully leverages OTP, so it relies on some warnings/messages coming from erlang compiler during compilation.

That said, downgrading OTP to the version Elixir 1.9 is aware of (21 would be fine, I believe,) or upgrading Elixir to the recent 1.11.1 would fix the issue producing fancy

== Compilation error in file /tmp/test.ex ==
** (CompileError) /tmp/test.ex:3: undefined function do_addition_problems/1
    (elixir 1.11.1) src/elixir_locals.erl:114: anonymous fn/3 in :elixir_locals.ensure_no_undefined_local/3
    (stdlib 3.13.2) erl_eval.erl:680: :erl_eval.do_apply/6