diff --git a/CMakeLists.txt b/CMakeLists.txt
index d21a29a1..f7282a3f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -21,7 +21,7 @@ target_include_directories(
         "$<BUILD_INTERFACE:${CMAKE_CURRENT_LIST_DIR}/include>"
 )
 
-target_compile_features(fplus INTERFACE cxx_std_14)
+target_compile_features(fplus INTERFACE cxx_std_17)
 
 find_package(Threads REQUIRED)
 target_link_libraries(fplus INTERFACE Threads::Threads)
diff --git a/include/fplus/function_traits.hpp b/include/fplus/function_traits.hpp
index 9598f748..9c0bac76 100644
--- a/include/fplus/function_traits.hpp
+++ b/include/fplus/function_traits.hpp
@@ -100,7 +100,6 @@ namespace utils {
                     R (C::*)(A...)>::type>::type type;
         };
     }
-
     template <typename ReturnType, typename... Args>
     struct function_traits<ReturnType(Args...)> {
         /**
@@ -441,7 +440,7 @@ namespace internal {
     };
 
     template <typename ReturnType, typename ClassType, typename... Args>
-    struct has_function_traits<ReturnType (ClassType::*)(Args...)&> : std::true_type {
+    struct has_function_traits<ReturnType (ClassType::*)(Args...) &> : std::true_type {
     };
 
     template <typename ReturnType, typename ClassType, typename... Args>
diff --git a/include/fplus/variant.hpp b/include/fplus/variant.hpp
index 732ffa38..6e7f866f 100644
--- a/include/fplus/variant.hpp
+++ b/include/fplus/variant.hpp
@@ -93,23 +93,21 @@ namespace internal {
         typedef std::shared_ptr<T> type;
     };
 
-    // http://stackoverflow.com/a/27588263/1866775
-
-    template <typename T, typename... Ts>
-    struct get_index;
-
-    template <typename T, typename... Ts>
-    struct get_index<T, T, Ts...> : std::integral_constant<std::size_t, 0> {
+    template <typename What, typename... Ts>
+    struct contains {
+        /// True if T is in Ts...
+        constexpr static bool value = (std::is_same_v<What, Ts> || ...);
     };
 
-    template <typename T, typename Tail, typename... Ts>
-    struct get_index<T, Tail, Ts...> : std::integral_constant<std::size_t, 1 + get_index<T, Ts...>::value> {
-    };
-
-    template <typename T>
-    struct get_index<T> {
-        // condition is always false, but should be dependant of T
-        static_assert(sizeof(T) == 0, "element not found");
+    template <typename What, typename... Ts>
+    struct get_index {
+        /// Index of type T in List.
+        static_assert(contains<What, Ts...>::value, "element is not in list");
+        constexpr static auto value = []() {
+            return ([]() {std::size_t i = 0;
+            (... && (!std::is_same_v<What, Ts> && ++i));
+            return i; }());
+        }();
     };
 
     template <typename T, typename... Ts>
diff --git a/include_all_in_one/include/fplus/fplus.hpp b/include_all_in_one/include/fplus/fplus.hpp
index 80894cdd..bf290851 100644
--- a/include_all_in_one/include/fplus/fplus.hpp
+++ b/include_all_in_one/include/fplus/fplus.hpp
@@ -344,22 +344,6 @@ namespace utils {
         : public function_traits<decltype(&T::operator())> {
     };
 
-    namespace xx_impl {
-        template <typename C, typename R, typename... A>
-        struct memfn_type {
-            typedef typename std::conditional<
-                std::is_const<C>::value,
-                typename std::conditional<
-                    std::is_volatile<C>::value,
-                    R (C::*)(A...) const volatile,
-                    R (C::*)(A...) const>::type,
-                typename std::conditional<
-                    std::is_volatile<C>::value,
-                    R (C::*)(A...) volatile,
-                    R (C::*)(A...)>::type>::type type;
-        };
-    }
-
     template <typename ReturnType, typename... Args>
     struct function_traits<ReturnType(Args...)> {
         /**
@@ -404,6 +388,22 @@ namespace utils {
         };
     };
 
+    namespace xx_impl {
+        template <typename C, typename R, typename... A>
+        struct memfn_type {
+            typedef typename std::conditional<
+                std::is_const<C>::value,
+                typename std::conditional<
+                    std::is_volatile<C>::value,
+                    R (C::*)(A...) const volatile,
+                    R (C::*)(A...) const>::type,
+                typename std::conditional<
+                    std::is_volatile<C>::value,
+                    R (C::*)(A...) volatile,
+                    R (C::*)(A...)>::type>::type type;
+        };
+    }
+
 #if __cplusplus > 201510L
 
     template <typename ReturnType, typename... Args>
@@ -700,7 +700,7 @@ namespace internal {
     };
 
     template <typename ReturnType, typename ClassType, typename... Args>
-    struct has_function_traits<ReturnType (ClassType::*)(Args...)&> : std::true_type {
+    struct has_function_traits<ReturnType (ClassType::*)(Args...) &> : std::true_type {
     };
 
     template <typename ReturnType, typename ClassType, typename... Args>
@@ -3295,7 +3295,7 @@ namespace internal {
         std::size_t pos_;
     };
 
-#if defined(_MSC_VER) && _MSC_VER >= 1900
+#if defined(_MSC_VER) && _MSC_VER >= 1900 && _MSC_VER < 1915
     template <typename T, std::size_t N>
     struct std::_Is_checked_helper<array_back_insert_iterator<T, N>>
         : public true_type { // mark array_back_insert_iterator as checked
@@ -14329,23 +14329,21 @@ namespace internal {
         typedef std::shared_ptr<T> type;
     };
 
-    // http://stackoverflow.com/a/27588263/1866775
-
-    template <typename T, typename... Ts>
-    struct get_index;
-
-    template <typename T, typename... Ts>
-    struct get_index<T, T, Ts...> : std::integral_constant<std::size_t, 0> {
-    };
-
-    template <typename T, typename Tail, typename... Ts>
-    struct get_index<T, Tail, Ts...> : std::integral_constant<std::size_t, 1 + get_index<T, Ts...>::value> {
+    template <typename What, typename... Ts>
+    struct contains {
+        /// True if T is in Ts...
+        constexpr static bool value = (std::is_same_v<What, Ts> || ...);
     };
 
-    template <typename T>
-    struct get_index<T> {
-        // condition is always false, but should be dependant of T
-        static_assert(sizeof(T) == 0, "element not found");
+    template <typename What, typename... Ts>
+    struct get_index {
+        /// Index of type T in List.
+        static_assert(contains<What, Ts...>::value, "element is not in list");
+        constexpr static auto value = []() {
+            return ([]() {std::size_t i = 0;
+            (... && (!std::is_same_v<What, Ts> && ++i));
+            return i; }());
+        }();
     };
 
     template <typename T, typename... Ts>
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 0a10914a..025344cf 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -15,9 +15,7 @@ include(../cmake/warnings.cmake)
 find_package(doctest 2.4.11 CONFIG REQUIRED)
 # for doctest_discover_tests
 include(doctest)
-
 enable_testing()
-
 set(
         tests
         show_versions
@@ -75,6 +73,6 @@ foreach (name IN LISTS tests)
             FunctionalPlus::fplus
             doctest::doctest
     )
-    target_compile_features("${name}" PRIVATE cxx_std_14)
+    target_compile_features("${name}" PRIVATE cxx_std_17)
     doctest_discover_tests("${name}")
 endforeach ()