Alternate definition of Impl::is_nothrow_swappable_v for NVCC version…

… less than 11.4

core/src/Kokkos_Swap.hpp

@@ -37,6 +37,26 @@ kokkos_swap(T& a, T& b) noexcept(std::is_nothrow_move_constructible_v<T>&&
 
 namespace Impl {
 
+// Workaround for the definition of is_nothrow_swappable_v
+#if defined(KOKKOS_COMPILER_NVCC) && (KOKKOS_COMPILER_NVCC < 1140)
+template <class T>
+struct is_swappable {
+  template <class U>
+  static decltype(kokkos_swap(std::declval<T&>(), std::declval<T&>()))
+  test_swap(int) noexcept(noexcept(kokkos_swap(std::declval<T&>(),
+                                               std::declval<T&>())));
+  struct Nope {};  // test_swap must return a complete type for the definition
+                   // of nothrow below
+  template <class U>
+  static Nope test_swap(long);
+  static constexpr bool value =
+      !std::is_same_v<decltype(test_swap<T>(0)), Nope>;
+  static constexpr bool nothrow = noexcept(test_swap<T>(0));
+};
+
+template <class T>
+inline constexpr bool is_nothrow_swappable_v = is_swappable<T>::nothrow;
+#else
 template <class T>
 struct is_swappable {
   template <class U>
@@ -52,6 +72,7 @@ struct is_swappable {
 template <class T>
 inline constexpr bool is_nothrow_swappable_v =
     noexcept(kokkos_swap(std::declval<T&>(), std::declval<T&>()));
+#endif
 
 }  // namespace Impl