Index: uspace/lib/cpp/include/impl/functional.hpp
===================================================================
--- uspace/lib/cpp/include/impl/functional.hpp	(revision 89bc64601cfdf838fc123ada605c9bae3dd2acbe)
+++ uspace/lib/cpp/include/impl/functional.hpp	(revision 8830faae3dc30d687ce5dbe1a747c51eb961fe2a)
@@ -260,4 +260,16 @@
          */
         struct transparent_t;
+
+        template<class T, class = void>
+        struct is_transparent: false_type
+        { /* DUMMY BODY */ };
+
+        template<class T>
+        struct is_transparent<T, void_t<typename T::is_transparent>>
+            : true_type
+        { /* DUMMY BODY */ };
+
+        template<class T>
+        inline constexpr bool is_transparent_v = is_transparent<T>::value;
     }