to_string supports types with format_as

Signed-off-by: Vladislav Shchapov <[email protected]>

include/fmt/format.h

@@ -4286,13 +4286,22 @@ 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);
   return {buffer.data(), buffer.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 {
+  auto buffer = memory_buffer();
+  detail::write<char>(appender(buffer), format_as(value));
+  return {buffer.data(), buffer.size()};
+}
+
 template <typename T, FMT_ENABLE_IF(std::is_integral<T>::value)>
 FMT_NODISCARD inline auto to_string(T value) -> std::string {
   // The buffer should be large enough to store the number including the sign

test/format-test.cc

@@ -2140,6 +2140,13 @@ 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,
                 "");