Remove a variable template usage

Because it’s only supported in gcc>=5.0

src/database/row.hpp

@@ -30,13 +30,13 @@ struct Row
   }
 
   template <bool Coucou=true>
-  void save(std::unique_ptr<DatabaseEngine>& db,  typename std::enable_if<!is_one_of<Id, T...> && Coucou>::type* = nullptr)
+  void save(std::unique_ptr<DatabaseEngine>& db,  typename std::enable_if<!is_one_of<Id, T...>::value && Coucou>::type* = nullptr)
   {
     this->insert(*db);
   }
 
   template <bool Coucou=true>
-  void save(std::unique_ptr<DatabaseEngine>& db,  typename std::enable_if<is_one_of<Id, T...> && Coucou>::type* = nullptr)
+  void save(std::unique_ptr<DatabaseEngine>& db,  typename std::enable_if<is_one_of<Id, T...>::value && Coucou>::type* = nullptr)
   {
     const Id& id = std::get<Id>(this->columns);
     if (id.value == Id::unset_value)

src/utils/is_one_of.hpp

@@ -3,15 +3,12 @@
 #include <type_traits>
 
 template <typename...>
-struct is_one_of_implem {
+struct is_one_of {
     static constexpr bool value = false;
 };
 
 template <typename F, typename S, typename... T>
-struct is_one_of_implem<F, S, T...> {
+struct is_one_of<F, S, T...> {
     static constexpr bool value =
-        std::is_same<F, S>::value || is_one_of_implem<F, T...>::value;
+        std::is_same<F, S>::value || is_one_of<F, T...>::value;
 };
-
-template<typename... T>
-constexpr bool is_one_of = is_one_of_implem<T...>::value;

tests/utils.cpp

@@ -175,11 +175,11 @@ TEST_CASE("dirname")
 
 TEST_CASE("is_in")
 {
-  CHECK((is_one_of<int, float, std::string, int>) == true);
-  CHECK((is_one_of<int, float, std::string>) == false);
-  CHECK((is_one_of<int>) == false);
-  CHECK((is_one_of<int, int>) == true);
-  CHECK((is_one_of<bool, int>) == false);
-  CHECK((is_one_of<bool, bool>) == true);
-  CHECK((is_one_of<bool, bool, bool, bool, bool, int>) == true);
+  CHECK((is_one_of<int, float, std::string, int>::value) == true);
+  CHECK((is_one_of<int, float, std::string>::value) == false);
+  CHECK((is_one_of<int>::value) == false);
+  CHECK((is_one_of<int, int>::value) == true);
+  CHECK((is_one_of<bool, int>::value) == false);
+  CHECK((is_one_of<bool, bool>::value) == true);
+  CHECK((is_one_of<bool, bool, bool, bool, bool, int>::value) == true);
 }