From 5fbb3f27b2f034b5c1fcdf6355700540db4aab3a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Manuel=20B=C3=A4renz?= <m.baerenz@sonnen.de>
Date: Wed, 9 Dec 2020 10:45:41 +0100
Subject: [PATCH] Expand `alias __MODULE__` manually. Fixes #27

---
 lib/ex_type/custom_env.ex | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/lib/ex_type/custom_env.ex b/lib/ex_type/custom_env.ex
index 691d4ef..ec4b054 100644
--- a/lib/ex_type/custom_env.ex
+++ b/lib/ex_type/custom_env.ex
@@ -102,6 +102,13 @@ defmodule ExType.CustomEnv do
   defmacro defmodule(alias, do: block) do
     {:__aliases__, meta, tokens} = alias
 
+    # Manually expand `alias __MODULE__`, see https://github.com/gyson/ex_type/issues/27
+    block = block
+      |> Macro.prewalk(fn
+          {:alias, meta_alias, [{:__MODULE__, meta_module, nil}]} -> {:alias, meta_alias, [{:__aliases__, meta_module, tokens}]}
+          token -> token
+        end)
+
     # Don't move nested modules into custom env (https://github.com/gyson/ex_type/issues/23)
     env = __CALLER__
     new_alias_prefix = case env.module do