From 78b4e9b8bb6374ab669e4c44433dbf71b508b8cb Mon Sep 17 00:00:00 2001
From: Hannes Vogt <vogt@hey.com>
Date: Wed, 30 Jun 2021 13:40:15 +0200
Subject: [PATCH] Allow empty Type<> type list

---
 googletest/include/gtest/internal/gtest-type-util.h | 13 ++++++++++++-
 googletest/test/gtest-typed-test_test.cc            | 13 +++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/googletest/include/gtest/internal/gtest-type-util.h b/googletest/include/gtest/internal/gtest-type-util.h
index b87a2e2c..59c8582b 100644
--- a/googletest/include/gtest/internal/gtest-type-util.h
+++ b/googletest/include/gtest/internal/gtest-type-util.h
@@ -147,11 +147,22 @@ struct Types<Head_> {
   using Tail = None;
 };
 
+// Helper metafunction to convert an empty ::testing::Types list to None
+template <typename... Ts>
+struct types_or_none {
+  using type = Types<Ts...>;
+};
+
+template <>
+struct types_or_none<> {
+  using type = None;
+};
+
 // Helper metafunctions to tell apart a single type from types
 // generated by ::testing::Types
 template <typename... Ts>
 struct ProxyTypeList {
-  using type = Types<Ts...>;
+  using type = typename types_or_none<Ts...>::type;
 };
 
 template <typename>
diff --git a/googletest/test/gtest-typed-test_test.cc b/googletest/test/gtest-typed-test_test.cc
index 5fc678cb..35f3cc0c 100644
--- a/googletest/test/gtest-typed-test_test.cc
+++ b/googletest/test/gtest-typed-test_test.cc
@@ -150,6 +150,19 @@ TYPED_TEST_SUITE(TypedTest2, Types<int>);
 // share the same name.
 TYPED_TEST(TypedTest2, A) {}
 
+template <typename T>
+class TypedTest3 : public Test {
+};
+
+// Verifies that an empty Types<> type list works.
+// This is useful in case Types<> is constructed conditionally, e.g.
+// `my_types = typename std::conditional<have_types, some_types, Types<>>::type;`
+TYPED_TEST_SUITE(TypedTest3, Types<>);
+
+TYPED_TEST(TypedTest3, A) {
+  ASSERT_TRUE(false); // Make sure this test is never executed.
+}
+
 // Tests that a typed test case can be defined in a namespace.
 
 namespace library1 {