From 44061c8499f63b04061cb2a35801acb93bbf98c7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jos=C3=A9=20Valim?= <jose.valim@dashbit.co>
Date: Fri, 22 May 2020 09:59:42 +0200
Subject: [PATCH] Do not crash when checking empty receive

---
 lib/elixir/lib/module/types/expr.ex               | 3 +++
 lib/elixir/test/elixir/module/types/expr_test.exs | 9 +++++++++
 2 files changed, 12 insertions(+)

diff --git a/lib/elixir/lib/module/types/expr.ex b/lib/elixir/lib/module/types/expr.ex
index 75962652da..35f6fb4ecc 100644
--- a/lib/elixir/lib/module/types/expr.ex
+++ b/lib/elixir/lib/module/types/expr.ex
@@ -264,6 +264,9 @@ defmodule Module.Types.Expr do
 
     result =
       each_ok(blocks, fn
+        {:do, {:__block__, _, []}} ->
+          :ok
+
         {:do, clauses} ->
           of_clauses(clauses, stack, context)
 
diff --git a/lib/elixir/test/elixir/module/types/expr_test.exs b/lib/elixir/test/elixir/module/types/expr_test.exs
index d1eaa96ef7..6a5188b75e 100644
--- a/lib/elixir/test/elixir/module/types/expr_test.exs
+++ b/lib/elixir/test/elixir/module/types/expr_test.exs
@@ -288,6 +288,15 @@ defmodule Module.Types.ExprTest do
     assert {:error, _} = quoted_expr(fn :foo = b -> :bar = b end)
   end
 
+  test "receive" do
+    assert quoted_expr(
+             receive do
+             after
+               0 -> :ok
+             end
+           ) == {:ok, :dynamic}
+  end
+
   test "with" do
     assert quoted_expr(
              [a, b],