From 9d80365d22b0923f255ced1f8433d7851094565b Mon Sep 17 00:00:00 2001
From: BlackMATov <blackmat@mail.ru>
Date: Mon, 20 Apr 2020 11:49:21 +0700
Subject: [PATCH] register traits in enum namespace

---
 README.md                 | 12 ++++++------
 headers/enum.hpp/enum.hpp | 11 +++--------
 untests/enum_examples.cpp |  4 ++--
 untests/enum_tests.cpp    | 11 ++++++-----
 4 files changed, 17 insertions(+), 21 deletions(-)

diff --git a/README.md b/README.md
index 7a546f4..6eb2572 100644
--- a/README.md
+++ b/README.md
@@ -142,10 +142,10 @@ namespace some_namespace
         (green = 0x00FF00)
         (blue = 0x0000FF)
         (white = red | green | blue))
-}
 
-// register traits in global namespace to generic access
-ENUM_HPP_REGISTER_TRAITS(some_namespace::color)
+    // register traits in enum namespace to generic access
+    ENUM_HPP_REGISTER_TRAITS(color)
+}
 
 int main() {
     using color = some_namespace::color;
@@ -176,9 +176,9 @@ namespace external_ns
         (a)
         (b)
         (c))
-}
 
-ENUM_HPP_REGISTER_TRAITS(external_ns::external_enum)
+    ENUM_HPP_REGISTER_TRAITS(external_enum)
+}
 
 int main() {
     using ee = external_ns::external_enum;
@@ -245,7 +245,7 @@ struct /*enum_name*/_traits {
 ### Generic functions
 
 ```cpp
-// should be in global namespace
+// should be in enum namespace
 ENUM_HPP_REGISTER_TRAITS(/*declared_enum_name*/)
 
 namespace enum_hpp
diff --git a/headers/enum.hpp/enum.hpp b/headers/enum.hpp/enum.hpp
index 455ef67..b66f5d8 100644
--- a/headers/enum.hpp/enum.hpp
+++ b/headers/enum.hpp/enum.hpp
@@ -7,6 +7,7 @@
 #pragma once
 
 #include <array>
+#include <utility>
 #include <optional>
 #include <stdexcept>
 #include <string_view>
@@ -27,10 +28,7 @@ namespace enum_hpp
 namespace enum_hpp
 {
     template < typename Enum >
-    struct traits;
-
-    template < typename Enum >
-    using traits_t = typename traits<Enum>::type;
+    using traits_t = decltype(enum_hpp_adl_find_registered_traits(std::declval<Enum>()));
 
     template < typename Enum >
     using underlying_type = typename traits_t<Enum>::underlying_type;
@@ -335,10 +333,7 @@ namespace enum_hpp::detail
 //
 
 #define ENUM_HPP_REGISTER_TRAITS(Enum)\
-    template <>\
-    struct enum_hpp::traits<Enum> {\
-        using type = Enum##_traits;\
-    };
+    [[maybe_unused]] Enum##_traits enum_hpp_adl_find_registered_traits(Enum) noexcept;
 
 // -----------------------------------------------------------------------------
 //
diff --git a/untests/enum_examples.cpp b/untests/enum_examples.cpp
index 602d5e0..b328613 100644
--- a/untests/enum_examples.cpp
+++ b/untests/enum_examples.cpp
@@ -19,9 +19,9 @@ namespace
         (green = 0x00FF00)
         (blue = 0x0000FF)
         (white = red | green | blue))
-}
 
-ENUM_HPP_REGISTER_TRAITS(color)
+    ENUM_HPP_REGISTER_TRAITS(color)
+}
 
 TEST_CASE("examples") {
     SECTION("traits_using") {
diff --git a/untests/enum_tests.cpp b/untests/enum_tests.cpp
index 26f63d2..a842df1 100644
--- a/untests/enum_tests.cpp
+++ b/untests/enum_tests.cpp
@@ -55,6 +55,10 @@ namespace some_namespace
         (_221)(_222)(_223)(_224)(_225)(_226)(_227)(_228)(_229)(_230)(_231)(_232)(_233)(_234)(_235)(_236)(_237)(_238)(_239)(_240)
         (_241)(_242)(_243)(_244)(_245)(_246)(_247)(_248)(_249)(_250)(_251)(_252)(_253)(_254)(_255))
 
+    ENUM_HPP_REGISTER_TRAITS(some_namespace::color)
+    ENUM_HPP_REGISTER_TRAITS(some_namespace::numbers)
+    ENUM_HPP_REGISTER_TRAITS(some_namespace::render::mask)
+
     namespace exns
     {
         enum class external_enum : unsigned short {
@@ -67,14 +71,11 @@ namespace some_namespace
             (a)
             (b)
             (c))
+
+        ENUM_HPP_REGISTER_TRAITS(external_enum)
     }
 }
 
-ENUM_HPP_REGISTER_TRAITS(some_namespace::color)
-ENUM_HPP_REGISTER_TRAITS(some_namespace::numbers)
-ENUM_HPP_REGISTER_TRAITS(some_namespace::render::mask)
-ENUM_HPP_REGISTER_TRAITS(some_namespace::exns::external_enum)
-
 TEST_CASE("enum") {
     namespace sn = some_namespace;