Remove broken fmt::internal::format_enum (#818)

include/fmt/format.h

@@ -2322,10 +2322,6 @@ template <typename Context, typename T>
 struct format_type :
   std::integral_constant<bool, get_type<Context, T>::value != custom_type> {};
 
-// Specifies whether to format enums.
-template <typename T, typename Enable = void>
-struct format_enum : std::integral_constant<bool, std::is_enum<T>::value> {};
-
 template <template <typename> class Handler, typename Spec, typename Context>
 void handle_dynamic_spec(
     Spec &value, arg_ref<typename Context::char_type> ref, Context &ctx) {
@@ -3259,16 +3255,6 @@ struct formatter<
   internal::dynamic_format_specs<Char> specs_;
 };
 
-template <typename T, typename Char>
-struct formatter<T, Char,
-    typename std::enable_if<internal::format_enum<T>::value>::type>
-    : public formatter<int, Char> {
-  template <typename ParseContext>
-  auto parse(ParseContext &ctx) -> decltype(ctx.begin()) {
-    return ctx.begin();
-  }
-};
-
 // A formatter for types known only at run time such as variant alternatives.
 //
 // Usage:

include/fmt/ostream.h

@@ -106,11 +106,6 @@ void format_value(basic_buffer<Char> &buffer, const T &value) {
   output << value;
   buffer.resize(buffer.size());
 }
-
-// Disable builtin formatting of enums and use operator<< instead.
-template <typename T>
-struct format_enum<T,
-    typename std::enable_if<std::is_enum<T>::value>::type> : std::false_type {};
 }  // namespace internal
 
 // Formats an object of type T that has an overloaded ostream operator<<.

test/format-test.cc

@@ -1443,6 +1443,10 @@ TEST(FormatTest, Enum) {
   EXPECT_EQ("0", fmt::format("{}", A));
 }
 
+TEST(FormatTest, EnumFormatterUnambiguous) {
+  fmt::formatter<TestEnum> f;
+}
+
 #if FMT_HAS_FEATURE(cxx_strong_enums)
 enum TestFixedEnum : short { B };