From 06c4c7f4a0fa53928a057782490b83ccd0f02ef5 Mon Sep 17 00:00:00 2001
From: Vladislav Shchapov <vladislav@shchapov.ru>
Date: Mon, 7 Aug 2023 20:08:33 +0500
Subject: [PATCH] to_string supports types with format_as

Signed-off-by: Vladislav Shchapov <vladislav@shchapov.ru>
---
 include/fmt/format.h | 9 ++++++++-
 test/format-test.cc  | 7 +++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/include/fmt/format.h b/include/fmt/format.h
index e5bd8b110efe..a311fd9f9649 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -4287,7 +4287,8 @@ auto join(Range&& range, string_view sep)
     std::string answer = fmt::to_string(42);
   \endrst
  */
-template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value)>
+template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value &&
+                                    !detail::has_format_as<T>::value)>
 inline auto to_string(const T& value) -> std::string {
   auto buffer = memory_buffer();
   detail::write<char>(appender(buffer), value);
@@ -4312,6 +4313,12 @@ FMT_NODISCARD auto to_string(const basic_memory_buffer<Char, SIZE>& buf)
   return std::basic_string<Char>(buf.data(), size);
 }
 
+template <typename T, FMT_ENABLE_IF(!std::is_integral<T>::value &&
+                                    detail::has_format_as<T>::value)>
+inline auto to_string(const T& value) -> std::string {
+  return to_string(format_as(value));
+}
+
 namespace detail {
 
 template <typename Char>
diff --git a/test/format-test.cc b/test/format-test.cc
index d148e743ea5f..dd3881716c95 100644
--- a/test/format-test.cc
+++ b/test/format-test.cc
@@ -2141,6 +2141,13 @@ TEST(format_test, format_as) {
   EXPECT_EQ(fmt::format("{}", test::struct_as_int()), "42");
 }
 
+TEST(format_test, format_as_to_string) {
+  EXPECT_EQ(fmt::to_string(test::scoped_enum_as_int()), "42");
+  EXPECT_EQ(fmt::to_string(test::scoped_enum_as_string_view()), "foo");
+  EXPECT_EQ(fmt::to_string(test::scoped_enum_as_string()), "foo");
+  EXPECT_EQ(fmt::to_string(test::struct_as_int()), "42");
+}
+
 template <typename Char, typename T> bool check_enabled_formatter() {
   static_assert(std::is_default_constructible<fmt::formatter<T, Char>>::value,
                 "");