Get rid of not_same_as concept

Author: aprokop

src/spatial/detail/ArborX_AccessTraits.hpp

@@ -74,9 +74,6 @@ struct AccessTraits<
 namespace Concepts
 {
 
-template <class T, class U>
-concept not_same_as = !std::same_as<T, U>;
-
 template <typename T>
 concept AccessTraits = requires() {
   typename ArborX::AccessTraits<T>::memory_space;
@@ -86,9 +83,13 @@ concept AccessTraits = requires() {
   {
     AccessTraits<T>::size(v)
   } -> std::integral;
+  // Cannot check return type of get() here as we need to test for non-void, but
+  // there's no not_same_as concept, and !std::same_as<void> does not work
+  AccessTraits<T>::get(v, 0);
+} && !requires(T const &v) {
   {
     AccessTraits<T>::get(v, 0)
-  } -> not_same_as<void>;
+  } -> std::same_as<void>;
 };
 
 template <typename T>