From aad44f28396b8cf9722d74027b94840820f7c3dc Mon Sep 17 00:00:00 2001
From: Victor Zverovich <viz@fb.com>
Date: Sat, 19 Feb 2022 08:03:42 -0800
Subject: [PATCH] Add fmt::enums::format_as

---
 include/fmt/format.h | 7 +++++++
 test/format-test.cc  | 6 ++++++
 2 files changed, 13 insertions(+)

diff --git a/include/fmt/format.h b/include/fmt/format.h
index dcd1d58a..1db4528d 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -2891,6 +2891,13 @@ constexpr auto underlying(Enum e) noexcept -> underlying_t<Enum> {
   return static_cast<underlying_t<Enum>>(e);
 }
 
+namespace enums {
+template <typename Enum, FMT_ENABLE_IF(std::is_enum<Enum>::value)>
+constexpr auto format_as(Enum e) noexcept -> underlying_t<Enum> {
+  return static_cast<underlying_t<Enum>>(e);
+}
+}
+
 #ifdef __cpp_lib_byte
 inline auto format_as(std::byte b) -> unsigned char { return underlying(b); }
 FMT_FORMAT_AS(std::byte, unsigned char);
diff --git a/test/format-test.cc b/test/format-test.cc
index c7a468ad..3b540ab8 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -1459,8 +1459,14 @@ TEST(format_test, write_uintptr_fallback) {
 
 enum class color { red, green, blue };
 
+namespace test_ns {
+enum class color { red, green, blue };
+using fmt::enums::format_as;
+}  // namespace test_ns
+
 TEST(format_test, format_enum_class) {
   EXPECT_EQ(fmt::format("{}", fmt::underlying(color::red)), "0");
+  EXPECT_EQ(fmt::format("{}", test_ns::color::red), "0");
 }
 
 TEST(format_test, format_string) {