cyber: make DEFINE_TYPE_TRAITS more readale

cyber/base/macros.h

@@ -30,20 +30,22 @@
 
 #define CACHELINE_SIZE 64
 
-#define DEFINE_TYPE_TRAIT(name, func)                            \
-  template <typename T>                                          \
-  class name {                                                   \
-   private:                                                      \
-    template <typename Class>                                    \
-    static char Test(decltype(&Class::func)*);                   \
-    template <typename>                                          \
-    static int Test(...);                                        \
-                                                                 \
-   public:                                                       \
-    static constexpr bool value = sizeof(Test<T>(nullptr)) == 1; \
-  };                                                             \
-                                                                 \
-  template <typename T>                                          \
+#define DEFINE_TYPE_TRAIT(name, func)                     \
+  template <typename T>                                   \
+  struct name {                                           \
+    template <typename Class>                             \
+    static constexpr bool Test(decltype(&Class::func)*) { \
+      return true;                                        \
+    }                                                     \
+    template <typename>                                   \
+    static constexpr bool Test(...) {                     \
+      return false;                                       \
+    }                                                     \
+                                                          \
+    static constexpr bool value = Test<T>(nullptr);       \
+  };                                                      \
+                                                          \
+  template <typename T>                                   \
   constexpr bool name<T>::value;
 
 inline void cpu_relax() {