Deduce geometry tag from Traits::Access::get() return type

src/details/ArborX_DetailsTreeConstruction.hpp

@@ -213,6 +213,25 @@ inline void TreeConstruction<DeviceType>::calculateBoundingBoxOfTheScene(
   Kokkos::fence();
 }
 
+template <typename Primitives>
+struct GeometryTagHelper
+{
+private:
+  using accessor_return_type = std::decay_t<decltype(
+      Traits::Access<Primitives, Traits::PrimitivesTag>::get(
+          std::declval<Primitives const &>(), std::declval<int>()))>;
+
+  static_assert(std::is_same<accessor_return_type, Point>::value ||
+                    std::is_same<accessor_return_type, Box>::value,
+                "Invalid return type of "
+                "Traits::Access<Primitives,Traits::PrimitivesTag>::get()");
+
+public:
+  using tag =
+      std::conditional_t<std::is_same<accessor_return_type, Point>::value,
+                         PointTag, BoxTag>;
+};
+
 template <typename Primitives, typename MortonCodes>
 inline void assignMortonCodesDispatch(BoxTag, Primitives const &primitives,
                                       MortonCodes morton_codes,
@@ -262,7 +281,7 @@ inline void TreeConstruction<DeviceType>::assignMortonCodes(
   auto const n = Access::size(primitives);
   ARBORX_ASSERT(morton_codes.extent(0) == n);
 
-  using Tag = typename Access::Tag;
+  using Tag = typename GeometryTagHelper<Primitives>::tag;
   assignMortonCodesDispatch(Tag{}, primitives, morton_codes,
                             scene_bounding_box);
 }
@@ -322,7 +341,7 @@ inline void TreeConstruction<DeviceType>::initializeLeafNodes(
                 "Encoding leaf index in pointer to child is not safe if the "
                 "index and pointer types do not have the same size");
 
-  using Tag = typename Access::Tag;
+  using Tag = typename GeometryTagHelper<Primitives>::tag;
   initializeLeafNodesDispatch(Tag{}, primitives, permutation_indices,
                               leaf_nodes);
 }