wtf.el

  (with-eval-after-load 'flycheck
    (flycheck-define-checker elixir-dialyzer
      "Erlang syntax checker based on dialyzer."
      :command ("mix" "dialyzer")
      :default-directory (lambda ()
                           (locate-dominating-file default-directory "mix.exs"))
      :error-patterns
      ((error line-start
              (file-name)
              ":"
              line
              ":"
              (message)
              line-end))
      :modes elixir-mode)

    (add-to-list 'flycheck-checkers 'elixir-dialyzer t))
  )