meta: avoid invoking .data() more than once

TODO

@@ -14,7 +14,6 @@ TODO (high prio):
 * further optimize exclusion lists in multi type views (no existence check)
 * doc: bump entities
 * deprecate/drop snapshot orphans function, make it a general purpose one
-* avoid invoking ::data twice if possible ie within meta_associative_container::begin()
 
 WIP:
 * get rid of observers, storage based views made them pointless - document alternatives

src/entt/meta/container.hpp

@@ -58,13 +58,14 @@ struct basic_meta_sequence_container_traits {
         }
     }
 
-    [[nodiscard]] static iterator iter(const meta_ctx &ctx, void *container, const void *as_const, const bool as_end) {
-        if(auto *const cont = static_cast<Type *>(container); cont) {
-            return iterator{ctx, as_end ? cont->end() : cont->begin()};
+    [[nodiscard]] static iterator iter(const meta_ctx &ctx, const void *container, const bool as_const, const bool as_end) {
+        if(as_const) {
+            const auto it = as_end ? static_cast<const Type *>(container)->end() : static_cast<const Type *>(container)->begin();
+            return iterator{ctx, it};
+        } else {
+            const auto it = as_end ? static_cast<Type *>(const_cast<void *>(container))->end() : static_cast<Type *>(const_cast<void *>(container))->begin();
+            return iterator{ctx, it};
         }
-
-        auto *const cont = static_cast<const Type *>(as_const);
-        return iterator{ctx, as_end ? cont->end() : cont->begin()};
     }
 
     [[nodiscard]] static iterator insert_or_erase([[maybe_unused]] const meta_ctx &ctx, [[maybe_unused]] void *container, [[maybe_unused]] const any &handle, [[maybe_unused]] meta_any &value) {
@@ -110,13 +111,14 @@ struct basic_meta_associative_container_traits {
         return true;
     }
 
-    [[nodiscard]] static iterator iter(const meta_ctx &ctx, void *container, const void *as_const, const bool as_end) {
-        if(auto *const cont = static_cast<Type *>(container); cont) {
-            return iterator{ctx, std::bool_constant<key_only>{}, as_end ? cont->end() : cont->begin()};
+    [[nodiscard]] static iterator iter(const meta_ctx &ctx, const void *container, const bool as_const, const bool as_end) {
+        if(as_const) {
+            const auto it = as_end ? static_cast<const Type *>(container)->end() : static_cast<const Type *>(container)->begin();
+            return iterator{ctx, std::bool_constant<key_only>{}, it};
+        } else {
+            const auto it = as_end ? static_cast<Type *>(const_cast<void *>(container))->end() : static_cast<Type *>(const_cast<void *>(container))->begin();
+            return iterator{ctx, std::bool_constant<key_only>{}, it};
         }
-
-        auto *const cont = static_cast<const Type *>(as_const);
-        return iterator{ctx, std::bool_constant<key_only>{}, as_end ? cont->end() : cont->begin()};
     }
 
     [[nodiscard]] static size_type insert_or_erase(void *container, meta_any &key, meta_any &value) {
@@ -135,13 +137,10 @@ struct basic_meta_associative_container_traits {
         return 0u;
     }
 
-    [[nodiscard]] static iterator find(const meta_ctx &ctx, void *container, const void *as_const, meta_any &key) {
+    [[nodiscard]] static iterator find(const meta_ctx &ctx, const void *container, const bool as_const, meta_any &key) {
         if(key.allow_cast<const typename Type::key_type &>()) {
-            if(auto *const cont = static_cast<Type *>(container); cont) {
-                return iterator{ctx, std::bool_constant<key_only>{}, cont->find(key.cast<const typename Type::key_type &>())};
-            }
-
-            return iterator{ctx, std::bool_constant<key_only>{}, static_cast<const Type *>(as_const)->find(key.cast<const typename Type::key_type &>())};
+            return as_const ? iterator{ctx, std::bool_constant<key_only>{}, static_cast<const Type *>(container)->find(key.cast<const typename Type::key_type &>())}
+                            : iterator{ctx, std::bool_constant<key_only>{}, static_cast<Type *>(const_cast<void *>(container))->find(key.cast<const typename Type::key_type &>())};
         }
 
         return iterator{};

src/entt/meta/meta.hpp

@@ -75,7 +75,7 @@ private:
     internal::meta_type_node (*value_type_node)(const internal::meta_context &){};
     size_type (*size_fn)(const void *) noexcept {};
     bool (*resize_fn)(void *, size_type){};
-    iterator (*iter_fn)(const meta_ctx &, void *, const void *, const bool){};
+    iterator (*iter_fn)(const meta_ctx &, const void *, const bool, const bool){};
     iterator (*insert_or_erase_fn)(const meta_ctx &, void *, const any &, meta_any &){};
     any storage{};
 };
@@ -143,9 +143,9 @@ private:
     internal::meta_type_node (*value_type_node)(const internal::meta_context &){};
     size_type (*size_fn)(const void *) noexcept {};
     bool (*clear_fn)(void *){};
-    iterator (*iter_fn)(const meta_ctx &, void *, const void *, const bool){};
+    iterator (*iter_fn)(const meta_ctx &, const void *, const bool, const bool){};
     size_type (*insert_or_erase_fn)(void *, meta_any &, meta_any &){};
-    iterator (*find_fn)(const meta_ctx &, void *, const void *, meta_any &){};
+    iterator (*find_fn)(const meta_ctx &, const void *, const bool, meta_any &){};
     any storage{};
 };
 
@@ -1867,7 +1867,7 @@ inline bool meta_sequence_container::clear() {
  * @return An iterator to the first element of the container.
  */
 [[nodiscard]] inline meta_sequence_container::iterator meta_sequence_container::begin() {
-    return iter_fn(*ctx, storage.data(), std::as_const(storage).data(), false);
+    return iter_fn(*ctx, std::as_const(storage).data(), (storage.policy() == any_policy::cref), false);
 }
 
 /**
@@ -1875,7 +1875,7 @@ inline bool meta_sequence_container::clear() {
  * @return An iterator that is past the last element of the container.
  */
 [[nodiscard]] inline meta_sequence_container::iterator meta_sequence_container::end() {
-    return iter_fn(*ctx, storage.data(), std::as_const(storage).data(), true);
+    return iter_fn(*ctx, std::as_const(storage).data(), (storage.policy() == any_policy::cref), true);
 }
 
 /**
@@ -1958,12 +1958,12 @@ inline bool meta_associative_container::clear() {
 
 /*! @copydoc meta_sequence_container::begin */
 [[nodiscard]] inline meta_associative_container::iterator meta_associative_container::begin() {
-    return iter_fn(*ctx, storage.data(), std::as_const(storage).data(), false);
+    return iter_fn(*ctx, std::as_const(storage).data(), (storage.policy() == any_policy::cref), false);
 }
 
 /*! @copydoc meta_sequence_container::end */
 [[nodiscard]] inline meta_associative_container::iterator meta_associative_container::end() {
-    return iter_fn(*ctx, storage.data(), std::as_const(storage).data(), true);
+    return iter_fn(*ctx, std::as_const(storage).data(), (storage.policy() == any_policy::cref), true);
 }
 
 /**
@@ -2001,7 +2001,7 @@ inline meta_associative_container::size_type meta_associative_container::erase(m
  * @return An iterator to the element with the given key, if any.
  */
 [[nodiscard]] inline meta_associative_container::iterator meta_associative_container::find(meta_any key) {
-    return find_fn(*ctx, storage.data(), std::as_const(storage).data(), key);
+    return find_fn(*ctx, std::as_const(storage).data(), (storage.policy() == any_policy::cref), key);
 }
 
 /**