From 88fe83765bc2f8b4b10d284bda3a031e4398f9a8 Mon Sep 17 00:00:00 2001
From: timsong-cpp <rs2740@gmail.com>
Date: Fri, 18 Mar 2022 12:58:57 -0500
Subject: [PATCH] Only use format_as if no formatter is available

---
 include/fmt/core.h |  4 +++-
 test/core-test.cc  | 20 ++++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/include/fmt/core.h b/include/fmt/core.h
index 106fd6fe..6d30bc41 100644
--- a/include/fmt/core.h
+++ b/include/fmt/core.h
@@ -1423,7 +1423,9 @@ template <typename Context> struct arg_mapper {
   }
 
   template <typename T, typename U = decltype(format_as(T())),
-            FMT_ENABLE_IF(std::is_enum<T>::value&& std::is_integral<U>::value)>
+            FMT_ENABLE_IF(std::is_enum<T>::value && std::is_integral<U>::value &&
+                !has_formatter<T, Context>::value &&
+                !has_fallback_formatter<T, char_type>::value)>
   FMT_CONSTEXPR FMT_INLINE auto map(const T& val)
       -> decltype(std::declval<arg_mapper>().map(U())) {
     return map(format_as(val));
diff --git a/test/core-test.cc b/test/core-test.cc
index a040d241..76d09d47 100644
--- a/test/core-test.cc
+++ b/test/core-test.cc
@@ -761,11 +761,28 @@ namespace test {
 enum class formattable_scoped_enum {};
 auto format_as(formattable_scoped_enum) -> int { return 42; }
 
+enum class formattable_formatter_scoped_enum {};
+auto format_as(formattable_formatter_scoped_enum) -> int { return 24; }
+
 struct convertible_to_enum {
   operator formattable_scoped_enum() const { return {}; }
 };
 }  // namespace test
 
+FMT_BEGIN_NAMESPACE
+template <> struct formatter<::test::formattable_formatter_scoped_enum> {
+  auto parse(format_parse_context& ctx) -> decltype(ctx.begin()) {
+    return ctx.begin();
+  }
+
+  auto format(::test::formattable_formatter_scoped_enum, format_context& ctx) const
+      -> decltype(ctx.out()) {
+    auto name = string_view("formattable_formatter_scoped_enum");
+    return std::copy_n(name.data(), name.size(), ctx.out());
+  }
+};
+FMT_END_NAMESPACE
+
 TEST(core_test, is_formattable) {
 #if 0
   // This should be enabled once corresponding map overloads are gone.
@@ -820,6 +837,9 @@ TEST(core_test, format_to) {
 
 TEST(core_test, format_as) {
   EXPECT_EQ(fmt::format("{}", test::formattable_scoped_enum()), "42");
+  EXPECT_EQ(fmt::format("{}", test::formattable_formatter_scoped_enum()), "formattable_formatter_scoped_enum");
+  const test::formattable_formatter_scoped_enum x{};
+  EXPECT_EQ(fmt::format("{}", x), "formattable_formatter_scoped_enum");
 }
 
 struct convertible_to_int {