storage:

* move storage_type[_t] and storage_for[_t] to fwd.hpp
* no need to include storage.hpp when forward defining views

src/entt/entity/fwd.hpp

@@ -17,15 +17,47 @@ class basic_sparse_set;
 template<typename Type, typename = entity, typename = std::allocator<Type>, typename = void>
 class basic_storage;
 
-template<typename Type, typename = entity, typename = std::allocator<Type>, typename = void>
-struct storage_type;
-
-template<typename Type, typename = entity, typename = std::allocator<std::remove_const_t<Type>>>
-struct storage_for;
-
 template<typename Type>
 class sigh_storage_mixin;
 
+/**
+ * @brief Provides a common way to define storage types.
+ * @tparam Type Storage value type.
+ * @tparam Entity A valid entity type (see entt_traits for more details).
+ * @tparam Allocator Type of allocator used to manage memory and elements.
+ */
+template<typename Type, typename Entity = entity, typename Allocator = std::allocator<Type>, typename = void>
+struct storage_type {
+    /*! @brief Type-to-storage conversion result. */
+    using type = sigh_storage_mixin<basic_storage<Type, Entity, Allocator>>;
+};
+
+/**
+ * @brief Helper type.
+ * @tparam Args Arguments to forward.
+ */
+template<typename... Args>
+using storage_type_t = typename storage_type<Args...>::type;
+
+/**
+ * Type-to-storage conversion utility that preserves constness.
+ * @tparam Type Storage value type, eventually const.
+ * @tparam Entity A valid entity type (see entt_traits for more details).
+ * @tparam Allocator Type of allocator used to manage memory and elements.
+ */
+template<typename Type, typename Entity = entity, typename Allocator = std::allocator<std::remove_const_t<Type>>>
+struct storage_for {
+    /*! @brief Type-to-storage conversion result. */
+    using type = constness_as_t<storage_type_t<std::remove_const_t<Type>, Entity, Allocator>, Type>;
+};
+
+/**
+ * @brief Helper type.
+ * @tparam Args Arguments to forward.
+ */
+template<typename... Args>
+using storage_for_t = typename storage_for<Args...>::type;
+
 template<typename Entity = entity, typename = std::allocator<Entity>>
 class basic_registry;
 

src/entt/entity/storage.hpp

@@ -898,44 +898,6 @@ public:
     }
 };
 
-/**
- * @brief Provides a common way to define storage types.
- * @tparam Type Storage value type.
- * @tparam Entity A valid entity type (see entt_traits for more details).
- * @tparam Allocator Type of allocator used to manage memory and elements.
- */
-template<typename Type, typename Entity, typename Allocator, typename>
-struct storage_type {
-    /*! @brief Type-to-storage conversion result. */
-    using type = sigh_storage_mixin<basic_storage<Type, Entity, Allocator>>;
-};
-
-/**
- * @brief Helper type.
- * @tparam Args Arguments to forward.
- */
-template<typename... Args>
-using storage_type_t = typename storage_type<Args...>::type;
-
-/**
- * Type-to-storage conversion utility that preserves constness.
- * @tparam Type Storage value type, eventually const.
- * @tparam Entity A valid entity type (see entt_traits for more details).
- * @tparam Allocator Type of allocator used to manage memory and elements.
- */
-template<typename Type, typename Entity, typename Allocator>
-struct storage_for {
-    /*! @brief Type-to-storage conversion result. */
-    using type = constness_as_t<storage_type_t<std::remove_const_t<Type>, Entity, Allocator>, Type>;
-};
-
-/**
- * @brief Helper type.
- * @tparam Args Arguments to forward.
- */
-template<typename... Args>
-using storage_for_t = typename storage_for<Args...>::type;
-
 } // namespace entt
 
 #endif