registry: drop ::empty (deprecated function)

src/entt/entity/registry.hpp

@@ -481,14 +481,6 @@ public:
         return entities.capacity();
     }
 
-    /**
-     * @brief Checks whether the registry is empty (no entities still in use).
-     * @return True if the registry is empty, false otherwise.
-     */
-    [[deprecated("use .storage<Entity>().in_use() instead")]] [[nodiscard]] bool empty() const {
-        return !alive();
-    }
-
     /**
      * @brief Direct access to the list of entities of a registry.
      *

src/entt/entity/snapshot.hpp

@@ -172,7 +172,9 @@ public:
     basic_snapshot_loader(registry_type &source) noexcept
         : reg{&source} {
         // restoring a snapshot as a whole requires a clean registry
-        ENTT_ASSERT(reg->empty(), "Registry must be empty");
+        for([[maybe_unused]] auto [id, elem]: source.storage()) {
+            ENTT_ASSERT(elem.empty(), "Registry must be empty");
+        }
     }
 
     /*! @brief Default move constructor. */