Initial support for extended FP types

Author: vitaut

Diff for: include/fmt/base.h

@@ -1505,12 +1505,14 @@ template <typename Context> struct arg_mapper {
     return {};
   }
 
+  // is_fundamental is used to allow formatters for extended FP types.
   template <typename T, typename U = remove_const_t<T>,
-            FMT_ENABLE_IF((std::is_class<U>::value || std::is_enum<U>::value ||
-                           std::is_union<U>::value) &&
-                          !has_to_string_view<U>::value && !is_char<U>::value &&
-                          !is_named_arg<U>::value &&
-                          !std::is_arithmetic<format_as_t<U>>::value)>
+            FMT_ENABLE_IF(
+                (std::is_class<U>::value || std::is_enum<U>::value ||
+                 std::is_union<U>::value || std::is_fundamental<U>::value) &&
+                !has_to_string_view<U>::value && !is_char<U>::value &&
+                !is_named_arg<U>::value && !std::is_integral<U>::value &&
+                !std::is_arithmetic<format_as_t<U>>::value)>
   FMT_MAP_API auto map(T& val) -> decltype(FMT_DECLTYPE_THIS do_map(val)) {
     return do_map(val);
   }

Diff for: include/fmt/format.h

@@ -3716,7 +3716,9 @@ FMT_CONSTEXPR auto write(OutputIt out, const T& value) -> enable_if_t<
 template <typename Char, typename OutputIt, typename T,
           typename Context = basic_format_context<OutputIt, Char>>
 FMT_CONSTEXPR auto write(OutputIt out, const T& value)
-    -> enable_if_t<mapped_type_constant<T, Context>::value == type::custom_type,
+    -> enable_if_t<mapped_type_constant<T, Context>::value ==
+                           type::custom_type &&
+                       !std::is_fundamental<T>::value,
                    OutputIt> {
   auto formatter = typename Context::template formatter_type<T>();
   auto parse_ctx = typename Context::parse_context_type({});