From 33f9a6d3609c7001afc7019c8308f4af8942ce0a Mon Sep 17 00:00:00 2001
From: Victor Zverovich <victor.zverovich@gmail.com>
Date: Thu, 3 Dec 2020 15:03:19 -0800
Subject: [PATCH] Fix handling of enums in to_string (#2036)

---
 include/fmt/format.h | 8 ++++++++
 test/format-test.cc  | 3 +++
 2 files changed, 11 insertions(+)

diff --git a/include/fmt/format.h b/include/fmt/format.h
index c8db0471e1a2..49fd93d28edc 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -2111,6 +2111,14 @@ FMT_CONSTEXPR OutputIt write(OutputIt out, T value) {
   return base_iterator(out, it);
 }
 
+template <typename Char, typename OutputIt, typename T,
+          FMT_ENABLE_IF(std::is_enum<T>::value &&
+                        !std::is_same<T, Char>::value)>
+FMT_CONSTEXPR OutputIt write(OutputIt out, T value) {
+  return write<Char>(
+      out, static_cast<typename std::underlying_type<T>::type>(value));
+}
+
 template <typename Char, typename OutputIt>
 constexpr OutputIt write(OutputIt out, bool value) {
   return write<Char>(out, string_view(value ? "true" : "false"));
diff --git a/test/format-test.cc b/test/format-test.cc
index bb10460f40f4..eecc0b0579d4 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -1987,6 +1987,9 @@ TEST(FormatTest, ToString) {
   EXPECT_EQ("42", fmt::to_string(42));
   EXPECT_EQ("0x1234", fmt::to_string(reinterpret_cast<void*>(0x1234)));
   EXPECT_EQ("foo", fmt::to_string(adl_test::fmt::detail::foo()));
+
+  enum test_enum : unsigned char { test_value };
+  EXPECT_EQ("0", fmt::to_string(test_value));
 }
 
 TEST(FormatTest, ToWString) { EXPECT_EQ(L"42", fmt::to_wstring(42)); }