1 files changed, 16 insertions, 13 deletions
diff --git a/deimos/core/format.h b/deimos/core/format.h
index ba1a3e2..8a2c850 100644
--- a/deimos/core/format.h
+++ b/deimos/core/format.h
@@ -15,6 +15,12 @@ struct CustomFormatter
     Callback    callback;
 };
 
+template<typename T>
+concept CustomFormattable = requires(IWriter* writer, const T& value)
+{
+    DeimosFormat(writer, value);
+};
+
 struct FormatArg
 {
     enum Type : uint8_t
@@ -50,29 +56,26 @@ struct FormatArg
         string{value}
     {}
 
-    template<typename T>
-    constexpr explicit FormatArg(const T& payload, CustomFormatter::Callback callback) :
+    template<CustomFormattable T>
+    constexpr explicit FormatArg(const T& payload) :
         type{kCustom},
-        custom{CustomFormatter{&payload, callback}}
-    {}
+        custom{CustomFormatter{&payload, [](IWriter* writer, const void* raw)
+        {
+            DeimosFormat(writer, *(const T*)raw);
+        }}}
+    {
+    }
 };
 
 template<typename T>
-deimos::FormatArg DeimosMakeFormatArg(T&& value)
-    requires std::is_constructible_v<deimos::FormatArg, T>
-{
-    return deimos::FormatArg(value);
-}
-
-template<typename T>
-concept Formattable = std::same_as<deimos::FormatArg, decltype(DeimosMakeFormatArg(std::declval<T>()))>;
+concept Formattable = std::is_constructible_v<FormatArg, T>;
 
 void FormatVa(IWriter*, gsl::czstring fmt, Span<const FormatArg>);
 
 template<Formattable... Args>
 void Format(IWriter* writer, gsl::czstring fmt, Args&&... args)
 {
-    FormatVa(writer, fmt, { DeimosMakeFormatArg(std::forward<Args>(args))... });
+    FormatVa(writer, fmt, { FormatArg(std::forward<Args>(args))... });
 }
 
 } // namespace deimos