Compiler fails to find the struct module

Questions & Help Questions
1

Hey folks.

I’ve got a simple use case for macros based on the following example module:

defmodule StructTestWorking do
  defmodule State do
    defstruct []
  end

  def foo(%State{}), do: nil
end

I want to extract the function foo into a “template module” and then use that module:

defmodule StructTestCommonUsing do
  defmacro __using__(_opts) do
    quote do
      def foo(%State{}), do: nil
    end
  end
end

defmodule StructTestFailingUsing do
  defmodule State do
    defstruct []
  end

  use StructTestCommonUsing
end

As the module name suggests, this doesn’t work. I’m getting this compilation error:

== Compilation error on file lib/struct_test_failing_using.ex ==
** (CompileError) lib/struct_test_failing_using.ex:14: State.__struct__/0 is undefined, cannot expand struct State
    (stdlib) lists.erl:1353: :lists.mapfoldl/3

It doesn’t work when using a @before_compile hook either:

defmodule StructTestCommonBeforeCompile do
  defmacro __using__(_opts) do
    quote do
      @before_compile unquote(__MODULE__)
    end
  end

  defmacro __before_compile__(_env) do
    quote do
      def foo(%State{}), do: nil
    end
  end
end

defmodule StructTestFailingBeforeCompile do
  defmodule State do
    defstruct []
  end

  use StructTestCommonBeforeCompile
end

This is using Elixir v1.3.1. Would you expect this to work?

I’ve also pushed the code to a repo – https://github.com/alco/struct_test.