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[libc++] Deprecate and remove member types of hash in <variant> #127758

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Merged
merged 1 commit into from
Feb 19, 2025
Merged

[libc++] Deprecate and remove member types of hash in <variant> #127758

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8 changes: 5 additions & 3 deletions libcxx/include/__variant/monostate.h
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Original file line number Diff line number Diff line change
Expand Up @@ -49,10 +49,12 @@ _LIBCPP_HIDE_FROM_ABI inline constexpr bool operator>=(monostate, monostate) noe

template <>
struct _LIBCPP_TEMPLATE_VIS hash<monostate> {
using argument_type = monostate;
using result_type = size_t;
# if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
using argument_type _LIBCPP_DEPRECATED_IN_CXX17 = monostate;
using result_type _LIBCPP_DEPRECATED_IN_CXX17 = size_t;
# endif

inline _LIBCPP_HIDE_FROM_ABI result_type operator()(const argument_type&) const _NOEXCEPT {
inline _LIBCPP_HIDE_FROM_ABI size_t operator()(const monostate&) const noexcept {
return 66740831; // return a fundamentally attractive random value.
}
};
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8 changes: 5 additions & 3 deletions libcxx/include/variant
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Expand Up @@ -1585,10 +1585,12 @@ swap(variant<_Types...>& __lhs,

template <class... _Types>
struct _LIBCPP_TEMPLATE_VIS hash< __enable_hash_helper<variant<_Types...>, remove_const_t<_Types>...>> {
using argument_type = variant<_Types...>;
using result_type = size_t;
# if _LIBCPP_STD_VER <= 17 || defined(_LIBCPP_ENABLE_CXX20_REMOVED_BINDER_TYPEDEFS)
using argument_type _LIBCPP_DEPRECATED_IN_CXX17 = variant<_Types...>;
using result_type _LIBCPP_DEPRECATED_IN_CXX17 = size_t;
# endif

_LIBCPP_HIDE_FROM_ABI result_type operator()(const argument_type& __v) const {
_LIBCPP_HIDE_FROM_ABI size_t operator()(const variant<_Types...>& __v) const {
using __variant_detail::__visitation::__variant;
size_t __res =
__v.valueless_by_exception()
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33 changes: 33 additions & 0 deletions libcxx/test/std/utilities/variant/variant.hash/hash.depr.verify.cpp
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@@ -0,0 +1,33 @@
//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

// REQUIRES: std-at-least-c++17

#include <variant>

#include "test_macros.h"

using A1 [[maybe_unused]] = std::hash<std::variant<int, long>>::argument_type;
using R1 [[maybe_unused]] = std::hash<std::variant<int, long>>::result_type;
#if TEST_STD_VER >= 20
// expected-error@-3 {{no type named 'argument_type' in 'std::hash<std::variant<int, long>>'}}
// expected-error@-3 {{no type named 'result_type' in 'std::hash<std::variant<int, long>>'}}
#else
// expected-warning@-6 {{'argument_type' is deprecated}}
// expected-warning@-6 {{'result_type' is deprecated}}
#endif

using A2 [[maybe_unused]] = std::hash<std::monostate>::argument_type;
using R2 [[maybe_unused]] = std::hash<std::monostate>::result_type;
#if TEST_STD_VER >= 20
// expected-error@-3 {{no type named 'argument_type' in 'std::hash<monostate>'}}
// expected-error@-3 {{no type named 'result_type' in 'std::hash<monostate>'}}
#else
// expected-warning@-6 {{'argument_type' is deprecated}}
// expected-warning@-6 {{'result_type' is deprecated}}
#endif