Kathryn-cat commented on code in PR #649: URL: https://github.com/apache/tvm-ffi/pull/649#discussion_r3733708105
########## include/tvm/ffi/extra/structural_mutate.h: ########## @@ -0,0 +1,904 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance + * with the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, + * software distributed under the License is distributed on an + * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY + * KIND, either express or implied. See the License for the + * specific language governing permissions and limitations + * under the License. + */ +/*! + * \file tvm/ffi/extra/structural_mutate.h + * \brief Structural mutation API with optional in-place optimization. + */ +#ifndef TVM_FFI_EXTRA_STRUCTURAL_MUTATE_H_ +#define TVM_FFI_EXTRA_STRUCTURAL_MUTATE_H_ + +#include <tvm/ffi/any.h> +#include <tvm/ffi/c_api.h> +#include <tvm/ffi/cast.h> +#include <tvm/ffi/container/array.h> +#include <tvm/ffi/container/map.h> +#include <tvm/ffi/container/tuple.h> +#include <tvm/ffi/container/variant.h> +#include <tvm/ffi/expected.h> +#include <tvm/ffi/extra/structural_visit.h> +#include <tvm/ffi/extra/visit_error_context.h> +#include <tvm/ffi/function.h> +#include <tvm/ffi/function_details.h> +#include <tvm/ffi/optional.h> +#include <tvm/ffi/reflection/accessor.h> + +#include <cstddef> +#include <exception> +#include <optional> +#include <string> +#include <tuple> +#include <type_traits> +#include <utility> + +namespace tvm { +namespace ffi { + +class StructuralMutatorObj; + +/*! + * \brief ABI callback type for structural mutation. + * + * \param mutator The active structural mutator. + * \param value The borrowed value to transform. + * \return Raw ``TVMFFIAny`` containing the transformed value or an Error. + */ +using FStructuralMutate = TVMFFIAny (*)(StructuralMutatorObj* mutator, AnyView value) noexcept; + +/*! + * \brief ABI callback type for looking up an identity substitution. + * + * \param mutator The active structural mutator. + * \param var The borrowed variable identity to look up. + * \return Raw ``TVMFFIAny`` containing the owning mapped value, FFI None when no mapping exists, + * or an Error. + */ +using FStructuralVarRemapGet = TVMFFIAny (*)(StructuralMutatorObj* mutator, AnyView var) noexcept; + +/*! + * \brief ABI callback type for recording an identity substitution. + * + * \param mutator The active structural mutator. + * \param var The borrowed variable identity to bind. + * \param mapped_value The borrowed replacement value. + * \return Raw ``TVMFFIAny`` containing FFI None on success or an Error. + */ +using FStructuralVarRemapSet = TVMFFIAny (*)(StructuralMutatorObj* mutator, AnyView var, + AnyView mapped_value) noexcept; + +namespace details { + +// Copy and structurally mutate the reflected fields of an object-backed value. +TVM_FFI_INLINE static Expected<Any> MutateReflectedFieldsExpected(StructuralMutatorObj* mutator, + AnyView value) noexcept; + +} // namespace details + +/*! + * \brief VTable ABI for \ref StructuralMutator dispatch. + */ +struct StructuralMutatorVTable { + /*! + * \brief Mutate a value without modifying the source in place. + * + * \param mutator The active structural mutator. + * \param value The borrowed value to mutate. + * \return Raw ``TVMFFIAny`` carrying the transformed value or Error. + */ + FStructuralMutate mutate = nullptr; + /*! + * \brief Mutate a value, permitting an in-place implementation when it is safe. + * + * \param mutator The active structural mutator. + * \param value The borrowed value to transform. + * \return Raw ``TVMFFIAny`` carrying the mutated value or Error. + * + * The returned value may refer to the same object as \p value when the implementation mutates + * that object in place. + */ + FStructuralMutate maybe_inplace_mutate = nullptr; + /*! + * \brief Look up the replacement for a variable identity. + * + * \param mutator The active structural mutator. + * \param var The borrowed variable identity to look up. + * \return Raw ``TVMFFIAny`` carrying the owning replacement, FFI None on a miss, or Error. + */ + FStructuralVarRemapGet var_remap_get = nullptr; + /*! + * \brief Record the replacement for a variable identity. + * + * \param mutator The active structural mutator. + * \param var The borrowed variable identity to bind. + * \param mapped_value The borrowed replacement value. + * \return Raw ``TVMFFIAny`` carrying None or Error. + */ + FStructuralVarRemapSet var_remap_set = nullptr; +}; + +/*! + * \brief Object node of a structural mutator. + */ +class StructuralMutatorObj : public Object { + public: + /*! + * \brief Mutate a value through the mutator vtable. + * + * \param value The value to mutate. + * \return The mutated owning value. + * \throws Error if mutation fails. + * + * This entry point never intentionally mutates \p value in place. Recursive transformations + * also use \ref Mutate. + */ + TVM_FFI_INLINE Any Mutate(AnyView value) { return MutateExpected(value).value(); } + + /*! + * \brief Exception-free form of \ref Mutate. + * + * \param value The value to mutate. + * \return The mutated owning value, or an Error if mutation failed. + */ + TVM_FFI_INLINE Expected<Any> MutateExpected(AnyView value) noexcept { + return details::ExpectedUnsafe::MoveFromTVMFFIAny<Any>((*vtable_->mutate)(this, value)); + } + + /*! + * \brief Mutate a value, permitting an in-place implementation when it is safe. + * + * \param value The borrowed value to transform. + * \return The transformed owning value. + * \throws Error if transformation fails. + * + * The returned value may refer to the same object as \p value. Callers must use the return value + * as the result of the transformation rather than assuming that the input object was reused. + */ + TVM_FFI_INLINE Any MaybeInplaceMutate(AnyView value) { + return MaybeInplaceMutateExpected(value).value(); + } + + /*! + * \brief Exception-free form of \ref MaybeInplaceMutate. + * + * \param value The borrowed value to transform. + * \return The transformed owning value, or an Error if transformation failed. + */ + TVM_FFI_INLINE Expected<Any> MaybeInplaceMutateExpected(AnyView value) noexcept { + return details::ExpectedUnsafe::MoveFromTVMFFIAny<Any>( + (*vtable_->maybe_inplace_mutate)(this, value)); + } + + /*! + * \brief Mutate a value, in-place mutate only when it is uniquely owned. + * + * \param value The borrowed value to transform. + * \return The transformed owning value, or an Error if transformation failed. + */ + TVM_FFI_INLINE Expected<Any> MaybeInplaceMutateIfUniqueExpected(AnyView value) noexcept { + const Object* obj = value.as<Object>(); + if (obj == nullptr || obj->unique()) { + return MaybeInplaceMutateExpected(value); + } + return MutateExpected(value); + } + + /*! + * \brief Apply the default structural mutation with copy-on-write behavior. + * + * \param value The value to mutate. + * \return The mutated value, or an Error if hook dispatch, copying, or field mutation failed. + * + * \note A registered ``__s_mutate__`` hook is dispatched before the reflected fallback and is + * responsible for variable-remap lookup and insertion when it represents a FreeVar + * identity. Automatic FreeVar remapping applies only to the reflected fallback. + */ + TVM_FFI_INLINE Expected<Any> DefaultMutateExpected(AnyView value) noexcept { + int32_t type_index = value.type_index(); + static reflection::TypeAttrColumn column(reflection::type_attr::kStructuralMutate); + AnyView attr = column[type_index]; + if (attr.type_index() != TypeIndex::kTVMFFINone) { + if (attr.type_index() == TypeIndex::kTVMFFIOpaquePtr) { + auto* hook = reinterpret_cast<FStructuralMutate>(attr.cast<void*>()); + return details::ExpectedUnsafe::MoveFromTVMFFIAny<Any>((*hook)(this, value)); + } + if (attr.type_index() == TypeIndex::kTVMFFIFunction) { + return attr.cast<Function>().CallExpected<Any>(this, value); + } + return Unexpected(Error("TypeError", + std::string(reflection::type_attr::kStructuralMutate) + + " must be an opaque function pointer or ffi.Function", + "")); + } + if (type_index < TypeIndex::kTVMFFIStaticObjectBegin) { + return Any(value); + } + + const TVMFFITypeInfo* type_info = TVMFFIGetTypeInfo(type_index); + bool is_free_var = type_info->metadata != nullptr && + type_info->metadata->structural_eq_hash_kind == kTVMFFISEqHashKindFreeVar; + if (is_free_var) { + Expected<Any> mapped_value = VarRemapGetExpected(value); + if (TVM_FFI_PREDICT_FALSE(mapped_value.is_err())) { + return Unexpected(std::move(mapped_value).error()); + } + if (details::ExpectedUnsafe::GetData(mapped_value).type_index() != TypeIndex::kTVMFFINone) { + return mapped_value; + } + } + + Expected<Any> result = details::MutateReflectedFieldsExpected(this, value); + if (TVM_FFI_PREDICT_FALSE(result.is_err()) || !is_free_var) { + return result; + } + + Expected<void> set_result = + VarRemapSetExpected(value, details::ExpectedUnsafe::GetData(result)); + if (TVM_FFI_PREDICT_FALSE(set_result.is_err())) { + return Unexpected(std::move(set_result).error()); + } + return result; + } + + /*! + * \brief Apply custom maybe-in-place mutation, or fall back to non-in-place mutation. + * + * \param value The borrowed value to transform. + * \return The transformed owning value, or an Error if transformation failed. In-place changes + * completed before an Error are not rolled back. + * + * \note In-place mutation is explicitly opt-in. A registered + * ``__s_maybe_inplace_mutate__`` hook may rely on its input being safe to mutate and owns + * any variable-remap handling. When the hook is absent, this method calls + * \ref DefaultMutateExpected. + */ + TVM_FFI_INLINE Expected<Any> DefaultMaybeInplaceMutateExpected(AnyView value) noexcept { + int32_t type_index = value.type_index(); + static reflection::TypeAttrColumn maybe_inplace_mutate_column( + reflection::type_attr::kStructuralMaybeInplaceMutate); + AnyView maybe_inplace_mutate_attr = maybe_inplace_mutate_column[type_index]; + if (maybe_inplace_mutate_attr.type_index() == TypeIndex::kTVMFFIOpaquePtr) { + auto* hook = reinterpret_cast<FStructuralMutate>(maybe_inplace_mutate_attr.cast<void*>()); + return details::ExpectedUnsafe::MoveFromTVMFFIAny<Any>((*hook)(this, value)); + } + if (maybe_inplace_mutate_attr.type_index() == TypeIndex::kTVMFFIFunction) { + return maybe_inplace_mutate_attr.cast<Function>().CallExpected<Any>(this, value); + } + if (maybe_inplace_mutate_attr.type_index() == TypeIndex::kTVMFFINone) { + return DefaultMutateExpected(value); + } + return Unexpected(Error("TypeError", + std::string(reflection::type_attr::kStructuralMaybeInplaceMutate) + + " must be an opaque function pointer or ffi.Function", + "")); + } + + /*! + * \brief Look up the replacement recorded for a variable identity. + * + * \param var The borrowed variable identity to look up. + * \return The owning replacement, FFI None if no replacement exists, or an Error if lookup + * fails. + * + * \note The variable identity must have + * ``kTVMFFISEqHashKindFreeVar`` structural-equality metadata. + */ + TVM_FFI_INLINE Expected<Any> VarRemapGetExpected(AnyView var) noexcept { + return details::ExpectedUnsafe::MoveFromTVMFFIAny<Any>((*vtable_->var_remap_get)(this, var)); + } + + /*! + * \brief Record the replacement for a variable identity. + * + * \param var The borrowed variable identity to bind. + * \param mapped_value The borrowed replacement value. + * \return Successful completion, or an Error if the binding is invalid or cannot be stored. + * + * \note The variable identity must have + * ``kTVMFFISEqHashKindFreeVar`` structural-equality metadata. + */ + TVM_FFI_INLINE Expected<void> VarRemapSetExpected(AnyView var, AnyView mapped_value) noexcept { + return details::ExpectedUnsafe::MoveFromTVMFFIAny<void>( + (*vtable_->var_remap_set)(this, var, mapped_value)); + } + + /*! + * \brief Return the current def-region context. + * \return The active def-region kind. + */ + TVM_FFI_INLINE TVMFFIDefRegionKind def_region_kind() const { return def_region_mode_; } + + /*! + * \brief Temporarily switch the def-region context while invoking \p callback. + * + * \param kind The def-region kind to set during the callback. + * \param callback A nullary callable that performs recursive transformation. + * \return The value returned by \p callback. + */ + template <typename Callback> + TVM_FFI_INLINE auto WithDefRegionKind(TVMFFIDefRegionKind kind, Callback&& callback) + -> decltype(std::forward<Callback>(callback)()) { + class Scope { + public: + Scope(StructuralMutatorObj* mutator, TVMFFIDefRegionKind kind) + : mutator_(mutator), old_kind_(mutator->def_region_mode_) { + mutator_->def_region_mode_ = kind; + } + ~Scope() { mutator_->def_region_mode_ = old_kind_; } + Scope(const Scope&) = delete; + Scope& operator=(const Scope&) = delete; + + private: + StructuralMutatorObj* mutator_; + TVMFFIDefRegionKind old_kind_; + }; + Scope scope(this, kind); + return std::forward<Callback>(callback)(); + } + + /// \cond Doxygen_Suppress + static constexpr const bool _type_mutable = true; + TVM_FFI_DECLARE_OBJECT_INFO("ffi.StructuralMutator", StructuralMutatorObj, Object); + /// \endcond + + protected: + /*! + * \brief Construct a structural mutator from an immutable dispatch vtable. + * \param vtable The non-null dispatch table for this mutator. It must outlive this object. + */ + explicit StructuralMutatorObj(const StructuralMutatorVTable* vtable) : vtable_(vtable) {} + + /*! + * \brief Non-owning pointer to the required ABI dispatch table. + */ + const StructuralMutatorVTable* vtable_ = nullptr; + + /*! + * \brief Current def-region context for def-region-aware structural transformation. + */ + TVMFFIDefRegionKind def_region_mode_ = kTVMFFIDefRegionKindNone; +}; + +/*! + * \brief ObjectRef wrapper for \ref StructuralMutatorObj. + * + * \sa StructuralMutatorObj + */ +class StructuralMutator : public ObjectRef { + public: + /*! + * \brief Construct from an existing mutator object pointer. + * \param n The object pointer to wrap. + */ + explicit StructuralMutator(ObjectPtr<StructuralMutatorObj> n) : ObjectRef(std::move(n)) {} + + /// \cond Doxygen_Suppress + TVM_FFI_DEFINE_OBJECT_REF_METHODS_NOTNULLABLE(StructuralMutator, ObjectRef, StructuralMutatorObj); + /// \endcond +}; + +namespace details { + +/*! + * \brief Mutate the reflected structural fields of an object-backed value. + * + * \param mutator The active structural mutator. + * \param value The object-backed value to mutate. + * \return The original value when no field changes, a transformed shallow copy otherwise, or an + * Error if copying or mutation failed. + */ +TVM_FFI_INLINE static Expected<Any> MutateReflectedFieldsExpected(StructuralMutatorObj* mutator, + AnyView value) noexcept { + const Object* obj = value.as<Object>(); + int32_t type_index = obj->type_index(); + + static reflection::TypeAttrColumn column(reflection::type_attr::kShallowCopy); + AnyView attr = column[type_index]; + if (TVM_FFI_PREDICT_FALSE(attr.type_index() != TypeIndex::kTVMFFIFunction)) { + return Unexpected( + Error("TypeError", + std::string(reflection::type_attr::kShallowCopy) + " must be an ffi.Function", "")); + } + + Expected<Any> result = attr.cast<Function>().CallExpected<Any>(value); + if (TVM_FFI_PREDICT_FALSE(result.is_err())) { + return result; + } + + const Any& result_value = details::ExpectedUnsafe::GetData(result); + Object* new_obj = const_cast<Object*>(result_value.as<Object>()); + // Copy-on-write mutation requires a distinct target so partial updates cannot modify the source. + if (TVM_FFI_PREDICT_FALSE(new_obj == nullptr || result.type_index() != value.type_index() || + new_obj == obj)) { + return Unexpected(Error( + "TypeError", + "Shallow copy callback must return a distinct object with the same type as its input", "")); + } + + const TVMFFITypeInfo* type_info = TVMFFIGetTypeInfo(new_obj->type_index()); + // A non-recursive definition applies to a FreeVar itself, but not to its children. All other + // inherited modes propagate until an explicit field annotation overrides them. + TVMFFIDefRegionKind inherited_kind = mutator->def_region_kind(); + if (inherited_kind == kTVMFFIDefRegionKindNonRecursive && type_info->metadata != nullptr && + type_info->metadata->structural_eq_hash_kind == kTVMFFISEqHashKindFreeVar) { + inherited_kind = kTVMFFIDefRegionKindNone; + } + + bool field_changed = false; + reflection::ForEachFieldInfoWithEarlyStop( + type_info, [&](const TVMFFIFieldInfo* field_info) -> bool { + if (field_info->flags & kTVMFFIFieldFlagBitMaskSEqHashIgnore) { + return false; + } + + Any field_value; + void* field_addr = reinterpret_cast<char*>(new_obj) + field_info->offset; + int ret_code = field_info->getter(field_addr, reinterpret_cast<TVMFFIAny*>(&field_value)); + if (TVM_FFI_PREDICT_FALSE(ret_code != 0)) { + result = Unexpected(details::MoveFromSafeCallRaised()); + return true; + } + + TVMFFIDefRegionKind kind = inherited_kind; + if (field_info->flags & kTVMFFIFieldFlagBitMaskSEqHashDefNonRecursive) { + kind = kTVMFFIDefRegionKindNonRecursive; + } else if (field_info->flags & kTVMFFIFieldFlagBitMaskSEqHashDefRecursive) { + kind = kTVMFFIDefRegionKindRecursive; + } + + Expected<Any> transformed_field = mutator->WithDefRegionKind( + kind, [&]() { return mutator->MutateExpected(field_value); }); + if (TVM_FFI_PREDICT_FALSE(transformed_field.is_err())) { + result = Unexpected(std::move(transformed_field).error()); + return true; + } + const Any& new_field = details::ExpectedUnsafe::GetData(transformed_field); + if (field_value.same_as(new_field)) { + return false; + } + + if (TVM_FFI_PREDICT_FALSE(field_info->setter == nullptr)) { + result = Unexpected( + Error("TypeError", + "Cannot structurally mutate field `" + + std::string(field_info->name.data, field_info->name.size) + "` of type `" + + std::string(type_info->type_key.data, type_info->type_key.size) + + "` because it does not define a setter", + "")); + return true; + } + + ret_code = reflection::CallFieldSetter(field_info, field_addr, + reinterpret_cast<const TVMFFIAny*>(&new_field)); + if (TVM_FFI_PREDICT_FALSE(ret_code != 0)) { + result = Unexpected(details::MoveFromSafeCallRaised()); + return true; + } + field_changed = true; + return false; + }); + + if (TVM_FFI_PREDICT_FALSE(result.is_err())) { + return result; + } + if (!field_changed) { + return Any(value); + } + return result; +} + +} // namespace details + +// --------------------------------------------------------------------------- +// Structural Map API. +// --------------------------------------------------------------------------- + +namespace details { + +/// \cond Doxygen_Suppress +// Return from the current mutation function if Result is an Error. +// Append Node to the mutate error context before returning. +#define TVM_FFI_S_MUTATE_MAYBE_EARLY_RETURN_WITH_ERROR_CONTEXT(Result, Node) \ + do { \ + auto&& tvm_ffi_res_ = (Result); \ + if (TVM_FFI_PREDICT_FALSE(tvm_ffi_res_.type_index() == ::tvm::ffi::TypeIndex::kTVMFFIError)) { \ + if ((Node).type_index() >= ::tvm::ffi::TypeIndex::kTVMFFIStaticObjectBegin) { \ + ::tvm::ffi::Error tvm_ffi_mutate_err_ = tvm_ffi_res_.error(); \ + ::tvm::ffi::details::UpdateVisitErrorContext(tvm_ffi_mutate_err_, \ + (Node).cast<::tvm::ffi::ObjectRef>()); \ + } \ + return ::std::move(tvm_ffi_res_); \ + } \ + } while (0) +/// \endcond + +/*! + * \brief Structural mutator that invokes typed callbacks during recursive mapping. + * + * \tparam order Callback placement relative to child mapping. + * \tparam Dispatch Callback dispatcher with signature + * ``Expected<Any>(AnyView, TVMFFIDefRegionKind)``. + * \sa StructuralMapCallbackChain + */ +template <WalkOrder order, typename Dispatch> +class StructuralMapMutatorObj : public StructuralMutatorObj { + public: + /*! + * \brief Construct a callback-aware mutator. + * \param dispatch The composed callback dispatcher. + */ + explicit StructuralMapMutatorObj(Dispatch dispatch) + : StructuralMutatorObj(VTable()), dispatch_(std::move(dispatch)) {} + + private: + /*! + * \brief Return the shared callback-aware mutator vtable. + * \return Pointer to the immutable mutator vtable for this specialization. + */ + static const StructuralMutatorVTable* VTable() { + static const StructuralMutatorVTable vtable{ + &StructuralMapMutatorObj::DispatchMutate, + &StructuralMapMutatorObj::DispatchMaybeInplaceMutate, + &StructuralMapMutatorObj::DispatchVarRemapGet, + &StructuralMapMutatorObj::DispatchVarRemapSet, + }; + return &vtable; + } + + /*! + * \brief Dispatch variable-remap lookup through this mutator's vtable. + * \param mutator The erased callback-aware mutator. + * \param var The borrowed variable identity to look up. + * \return Raw ``TVMFFIAny`` containing the owning replacement, FFI None, or Error. + */ + static TVMFFIAny DispatchVarRemapGet(StructuralMutatorObj* mutator, AnyView var) noexcept { + auto* self = static_cast<StructuralMapMutatorObj*>(mutator); + Expected<Any> result = self->VarRemapGetImpl(var); + return ExpectedUnsafe::MoveToTVMFFIAny(std::move(result)); + } + + /*! + * \brief Dispatch variable-remap insertion through this mutator's vtable. + * \param mutator The erased callback-aware mutator. + * \param var The borrowed variable identity to bind. + * \param mapped_value The borrowed replacement value. + * \return Raw ``TVMFFIAny`` containing FFI None or Error. + */ + static TVMFFIAny DispatchVarRemapSet(StructuralMutatorObj* mutator, AnyView var, + AnyView mapped_value) noexcept { + auto* self = static_cast<StructuralMapMutatorObj*>(mutator); + Expected<void> result = self->VarRemapSetImpl(var, mapped_value); + return ExpectedUnsafe::MoveToTVMFFIAny(std::move(result)); + } + + /*! + * \brief Look up a replacement in this mutator's identity-substitution environment. + * \param var The borrowed variable identity to look up. + * \return The owning replacement, FFI None on a miss, or an Error. + */ + Expected<Any> VarRemapGetImpl(AnyView var) noexcept { + if (var.type_index() < TypeIndex::kTVMFFIStaticObjectBegin) { + return Unexpected( + Error("TypeError", "Variable-remap key must be an object-backed value", "")); + } + try { + ObjectRef var_ref = var.cast<ObjectRef>(); + std::optional<Any> result = var_remap_.Get(var_ref); + if (!result.has_value()) { + return Any(nullptr); + } + return *std::move(result); + } catch (const Error& err) { + return Unexpected(err); + } + } + + /*! + * \brief Record a replacement in this mutator's identity-substitution environment. + * \param var The borrowed variable identity to bind. + * \param mapped_value The borrowed replacement value. + * \return Successful completion, or an Error if the binding cannot be stored. + */ + Expected<void> VarRemapSetImpl(AnyView var, AnyView mapped_value) noexcept { + if (var.type_index() < TypeIndex::kTVMFFIStaticObjectBegin) { + return Unexpected( + Error("TypeError", "Variable-remap key must be an object-backed value", "")); + } + try { + ObjectRef var_ref = var.cast<ObjectRef>(); + Any owned_mapped_value(mapped_value); + var_remap_.Set(var_ref, owned_mapped_value); + return Expected<void>(); + } catch (const Error& err) { + return Unexpected(err); + } + } + + /*! + * \brief Dispatch callback-aware optional in-place mutation through the ABI vtable. + * \param mutator The erased callback-aware mutator. + * \param value The borrowed value to transform. + * \return Raw ``TVMFFIAny`` containing the transformed value or Error. + */ + static TVMFFIAny DispatchMaybeInplaceMutate(StructuralMutatorObj* mutator, + AnyView value) noexcept { + auto* self = static_cast<StructuralMapMutatorObj*>(mutator); + return ExpectedUnsafe::MoveToTVMFFIAny(self->MaybeInplaceMutateImpl(value)); + } + + /*! + * \brief Dispatch callback-aware mutation through the ABI vtable. + * \param mutator The erased callback-aware mutator. + * \param value The borrowed value to mutate. + * \return Raw ``TVMFFIAny`` containing the mutated value or Error. + */ + static TVMFFIAny DispatchMutate(StructuralMutatorObj* mutator, AnyView value) noexcept { + auto* self = static_cast<StructuralMapMutatorObj*>(mutator); + return ExpectedUnsafe::MoveToTVMFFIAny(self->MutateImpl(value)); + } + + /*! + * \brief Invoke the callback and select mutation according to its result and walk order. + * + * \param value The borrowed value to transform. + * \return The transformed value or an Error. + */ + Expected<Any> MaybeInplaceMutateImpl(AnyView value) noexcept { + if (TVM_FFI_PREDICT_FALSE(value.type_index() == TypeIndex::kTVMFFINone)) { + return Any(value); + } + + if constexpr (order == WalkOrder::kPreOrder) { + Expected<Any> callback_result = dispatch_(value, def_region_kind()); + TVM_FFI_S_MUTATE_MAYBE_EARLY_RETURN_WITH_ERROR_CONTEXT(callback_result, value); + + const Any& mapped_value = ExpectedUnsafe::GetData(callback_result); + if (!mapped_value.same_as(Any(value))) { + const Object* mapped_obj = mapped_value.as<Object>(); + bool can_mutate_mapped_value_inplace = mapped_obj != nullptr && mapped_obj->unique(); + Expected<Any> result = can_mutate_mapped_value_inplace + ? DefaultMaybeInplaceMutateExpected(mapped_value) + : DefaultMutateExpected(mapped_value); + TVM_FFI_S_MUTATE_MAYBE_EARLY_RETURN_WITH_ERROR_CONTEXT(result, mapped_value); + return result; + } + + // Release the callback result's temporary ownership before a maybe-in-place hook observes + // the input's reference count. + Expected<Any> result = DefaultMaybeInplaceMutateExpected(value); + TVM_FFI_S_MUTATE_MAYBE_EARLY_RETURN_WITH_ERROR_CONTEXT(result, value); Review Comment: I prefer the existing impl mimicing visitor side, because it updates the error context at the precise propagation boundary and returns the error, and keeps success path explicitly not returning. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. 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