registry: [[nodiscard]] as it should be

src/entt/entity/registry.hpp

@@ -1092,7 +1092,7 @@ public:
 
     /*! @copydoc group */
     template<typename... Owned, typename... Get, typename... Exclude>
-    basic_group<owned_t<storage_for_type<const Owned>...>, get_t<storage_for_type<const Get>...>, exclude_t<storage_for_type<const Exclude>...>>
+    [[nodiscard]] basic_group<owned_t<storage_for_type<const Owned>...>, get_t<storage_for_type<const Get>...>, exclude_t<storage_for_type<const Exclude>...>>
     group_if_exists(get_t<Get...> = get_t{}, exclude_t<Exclude...> = exclude_t{}) const {
         using group_type = basic_group<owned_t<storage_for_type<const Owned>...>, get_t<storage_for_type<const Get>...>, exclude_t<storage_for_type<const Exclude>...>>;
         using handler_type = typename group_type::handler;