tqchen commented on code in PR #647:
URL: https://github.com/apache/tvm-ffi/pull/647#discussion_r3486258225
##########
include/tvm/ffi/type_traits.h:
##########
@@ -118,22 +118,39 @@ inline std::string TypeIndexToTypeKey(int32_t type_index)
{
return std::string(type_info->type_key.data, type_info->type_key.size);
}
-namespace details {
/*!
- * \brief Check whether `Derived` can reuse `Base` storage directly.
+ * \brief Whether TargetType subsumes SourceType for direct storage reuse.
*
- * \tparam Base The base type.
- * \tparam Derived The derived type.
- * \return True if Derived's storage can be used as Base's storage, false
otherwise.
+ * The target type is first and the source type is second. The result is true
+ * exactly when every SourceType value can reuse TargetType storage without
+ * conversion.
+ *
+ * \tparam TargetType The target storage type.
+ * \tparam SourceType The source value type.
*/
-template <typename Base, typename Derived>
-inline constexpr bool type_contains_v =
- std::is_base_of_v<Base, Derived> || std::is_same_v<Base, Derived>;
+template <typename TargetType, typename SourceType>
+inline constexpr bool type_subsumes_v =
+ std::is_base_of_v<TargetType, SourceType> || std::is_same_v<TargetType,
SourceType>;
// Special case for Any, which can store any compatible value directly.
-template <typename Derived>
-inline constexpr bool type_contains_v<Any, Derived> = true;
-} // namespace details
+template <typename SourceType>
+inline constexpr bool type_subsumes_v<Any, SourceType> = true;
+
+/*!
+ * \brief Whether RefType contains every ObjectType instance.
+ *
+ * The containing reference type is first and the contained object type is
+ * second. The default is true exactly when RefType has an exact container type
+ * and ObjectType derives from that container type. Direct specializations can
+ * provide the proof for non-exact reference types.
+ *
+ * \tparam RefType The object reference type.
+ * \tparam ObjectType The object type.
+ */
+template <typename RefType, typename ObjectType>
+inline constexpr bool object_ref_contains_v =
+ RefType::_type_container_is_exact &&
+ std::is_base_of_v<typename RefType::ContainerType, ObjectType>;
Review Comment:
Follow-up from the careful review in 2c522a6: `GetRef` now places its
implementation in the successful `if constexpr` branch and keeps the
containment assertion in the rejected branch. Invalid ref and object categories
therefore stop at the intended `object_ref_contains_v` assertion instead of
also instantiating `_type_is_nullable` or an invalid object-pointer cast. GCC
negative probes with `-Werror=return-type` confirm a single focused diagnostic
for both cases.
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