hello everyone.
I am trying to learn metaprogramming and start with simple project. in this road I this weird situation.
I want to implement interface like action_fallback macro in Phoenix controller(inside UseSample module).

defmodule GuardModule do
  def test() do
    IO.inspect("TEST")
  end
end

defmodule Sample do

  defmacro guard(module_name) do
    quote do
      @guard unquote(module_name)
    end
  end

  defmacro __using__(_opts) do
    quote do
      import unquote(__MODULE__)
      Module.register_attribute(__MODULE__, :guard, accumulate: :false, persist: :false)

      @before_compile unquote(__MODULE__)
    end
  end

  defmacro __before_compile__(env) do
    custom_guard = Module.get_attribute(env.module, :guard)
    custom_guard.test()
    # quote do
    #   def test_inside_use_sample() do
    #     custom_guard.test()
    #   end
    # end
  end
end

defmodule UseSample do
  use Sample

  guard GuardModule
end

now I have some questions.

1. in Sample.__before_compile__ macro i can call external module functions. but i can’t generate function that call this external function inside its body(commented section not compile). how can I do that?
2. in this situation GuardModule compiles before others because it’s in the beginning of file. how can I force elixir compiler to compile this module before Sample module?
3. and finally am i have right solving strategy for this problem or should do something else?

thanks a lot.