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fix universal: make ForwardLike conform to the standard #1222

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fix universal: make ForwardLike conform to the standard #1222

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33 changes: 21 additions & 12 deletions universal/include/userver/utils/forward_like.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4,26 +4,35 @@
/// @brief @copybrief utils::ForwardLike

#include <type_traits>
#include <utility>

USERVER_NAMESPACE_BEGIN

namespace utils {

// Analogue of std::forward_like from c++23.
template <typename TOwner, typename TMember>
decltype(auto) ForwardLike(TMember& member) {
if constexpr (std::is_lvalue_reference_v<TOwner> || std::is_lvalue_reference_v<TMember>) {
return member;
} else {
return std::move(member);
}
}
namespace impl {

template <typename T, typename U>
struct ForwardLikeHelper;

template <typename T, typename U>
struct ForwardLikeHelper<T&, U&> : std::type_identity<U&> {};

template <typename T, typename U>
struct ForwardLikeHelper<const T&, U&> : std::type_identity<const U&> {};

template <typename T, typename U>
struct ForwardLikeHelper<T&&, U&> : std::type_identity<U&&> {};

template <typename T, typename U>
struct ForwardLikeHelper<const T&&, U&> : std::type_identity<const U&&> {};

} // namespace impl

// Analogue of std::forward_like from c++23.
template <typename TOwner, typename TMember>
decltype(auto) ForwardLike(const TMember& member) {
return member;
constexpr auto&& ForwardLike(TMember&& member) noexcept {
using RType = impl::ForwardLikeHelper<TOwner&&, TMember&>::type;
return static_cast<RType>(member);
}

} // namespace utils
Expand Down
35 changes: 27 additions & 8 deletions universal/include/userver/utils/struct_subsets.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -34,15 +34,34 @@ constexpr auto IsDefinedAndAggregate(Args...) -> bool {
return false;
}

template <typename Superset, typename Field, typename T>
auto&& GetSupersetField(T &t, InternalTag) noexcept {
if constexpr (std::is_reference_v<Field>) {
return std::forward<Field>(t);
} else {
return utils::ForwardLike<Superset>(t);
}
}

template <typename T>
struct SubsetField : std::type_identity<T> {};

template <typename T>
struct SubsetFieldRef : std::type_identity<const T&> {};

template <typename T>
struct SubsetFieldRef<T&&> : std::type_identity<T&&> {};

} // namespace utils::impl

USERVER_NAMESPACE_END

/// @cond

// NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
#define USERVER_IMPL_STRUCT_MAP(r, data, elem) \
USERVER_NAMESPACE::utils::ForwardLike<OtherDeps, decltype(other.elem)>(other.elem),
#define USERVER_IMPL_STRUCT_MAP(r, data, elem) \
USERVER_NAMESPACE::utils::impl::GetSupersetField<OtherDeps, decltype(other.elem)>( \
other.elem, USERVER_NAMESPACE::utils::impl::InternalTag{}),

// NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
#define USERVER_IMPL_MAKE_FROM_SUPERSET(Self, ...) \
Expand All @@ -56,14 +75,14 @@ USERVER_NAMESPACE_END
}

// NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
#define USERVER_IMPL_STRUCT_SUBSET_MAP(r, data, elem) \
/* NOLINTNEXTLINE(bugprone-macro-parentheses) */ \
decltype(data::elem) elem;
#define USERVER_IMPL_STRUCT_SUBSET_MAP(r, data, elem) \
/* NOLINTNEXTLINE(bugprone-macro-parentheses) */ \
USERVER_NAMESPACE::utils::impl::SubsetField<decltype(data::elem)>::type elem;

// NOLINTNEXTLINE(cppcoreguidelines-macro-usage)
#define USERVER_IMPL_STRUCT_SUBSET_REF_MAP(r, data, elem) \
/* NOLINTNEXTLINE(bugprone-macro-parentheses) */ \
std::add_const_t<decltype(data::elem)>& elem;
#define USERVER_IMPL_STRUCT_SUBSET_REF_MAP(r, data, elem) \
/* NOLINTNEXTLINE(bugprone-macro-parentheses) */ \
USERVER_NAMESPACE::utils::impl::SubsetFieldRef<decltype(data::elem)>::type elem;

/// @endcond

Expand Down
171 changes: 171 additions & 0 deletions universal/src/utils/forward_like_test.cpp
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@ddvamp ddvamp Apr 29, 2026

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Test has been run on std::forward_like from gcc and clang.

Original file line number Diff line number Diff line change
@@ -0,0 +1,171 @@
#include <userver/utils/forward_like.hpp>

#include <type_traits>
#include <utility>

USERVER_NAMESPACE_BEGIN

namespace {

template <typename T, typename U>
using ForwardLikeResult = decltype(utils::ForwardLike<T>(std::declval<U>()));

static_assert(std::is_same_v<ForwardLikeResult<int, int>, int&&>);
static_assert(std::is_same_v<ForwardLikeResult<int, const int>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<int, volatile int>, volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<int, const volatile int>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<int, int&>, int&&>);
static_assert(std::is_same_v<ForwardLikeResult<int, const int&>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<int, volatile int&>, volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<int, const volatile int&>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<int, int&&>, int&&>);
static_assert(std::is_same_v<ForwardLikeResult<int, const int&&>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<int, volatile int&&>, volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<int, const volatile int&&>, const volatile int&&>);

static_assert(std::is_same_v<ForwardLikeResult<const int, int>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const int, const int>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const int, volatile int>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const int, const volatile int>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const int, int&>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const int, const int&>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const int, volatile int&>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const int, const volatile int&>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const int, int&&>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const int, const int&&>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const int, volatile int&&>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const int, const volatile int&&>, const volatile int&&>);

static_assert(std::is_same_v<ForwardLikeResult<volatile int, int>, int&&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int, const int>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int, volatile int>, volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int, const volatile int>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int, int&>, int&&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int, const int&>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int, volatile int&>, volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int, const volatile int&>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int, int&&>, int&&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int, const int&&>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int, volatile int&&>, volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int, const volatile int&&>, const volatile int&&>);

static_assert(std::is_same_v<ForwardLikeResult<const volatile int, int>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int, const int>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int, volatile int>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int, const volatile int>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int, int&>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int, const int&>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int, volatile int&>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int, const volatile int&>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int, int&&>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int, const int&&>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int, volatile int&&>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int, const volatile int&&>, const volatile int&&>);

static_assert(std::is_same_v<ForwardLikeResult<int&, int>, int&>);
static_assert(std::is_same_v<ForwardLikeResult<int&, const int>, const int&>);
static_assert(std::is_same_v<ForwardLikeResult<int&, volatile int>, volatile int&>);
static_assert(std::is_same_v<ForwardLikeResult<int&, const volatile int>, const volatile int&>);
static_assert(std::is_same_v<ForwardLikeResult<int&, int&>, int&>);
static_assert(std::is_same_v<ForwardLikeResult<int&, const int&>, const int&>);
static_assert(std::is_same_v<ForwardLikeResult<int&, volatile int&>, volatile int&>);
static_assert(std::is_same_v<ForwardLikeResult<int&, const volatile int&>, const volatile int&>);
static_assert(std::is_same_v<ForwardLikeResult<int&, int&&>, int&>);
static_assert(std::is_same_v<ForwardLikeResult<int&, const int&&>, const int&>);
static_assert(std::is_same_v<ForwardLikeResult<int&, volatile int&&>, volatile int&>);
static_assert(std::is_same_v<ForwardLikeResult<int&, const volatile int&&>, const volatile int&>);

static_assert(std::is_same_v<ForwardLikeResult<const int&, int>, const int&>);
static_assert(std::is_same_v<ForwardLikeResult<const int&, const int>, const int&>);
static_assert(std::is_same_v<ForwardLikeResult<const int&, volatile int>, const volatile int&>);
static_assert(std::is_same_v<ForwardLikeResult<const int&, const volatile int>, const volatile int&>);
static_assert(std::is_same_v<ForwardLikeResult<const int&, int&>, const int&>);
static_assert(std::is_same_v<ForwardLikeResult<const int&, const int&>, const int&>);
static_assert(std::is_same_v<ForwardLikeResult<const int&, volatile int&>, const volatile int&>);
static_assert(std::is_same_v<ForwardLikeResult<const int&, const volatile int&>, const volatile int&>);
static_assert(std::is_same_v<ForwardLikeResult<const int&, int&&>, const int&>);
static_assert(std::is_same_v<ForwardLikeResult<const int&, const int&&>, const int&>);
static_assert(std::is_same_v<ForwardLikeResult<const int&, volatile int&&>, const volatile int&>);
static_assert(std::is_same_v<ForwardLikeResult<const int&, const volatile int&&>, const volatile int&>);

static_assert(std::is_same_v<ForwardLikeResult<volatile int&, int>, int&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int&, const int>, const int&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int&, volatile int>, volatile int&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int&, const volatile int>, const volatile int&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int&, int&>, int&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int&, const int&>, const int&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int&, volatile int&>, volatile int&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int&, const volatile int&>, const volatile int&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int&, int&&>, int&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int&, const int&&>, const int&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int&, volatile int&&>, volatile int&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int&, const volatile int&&>, const volatile int&>);

static_assert(std::is_same_v<ForwardLikeResult<const volatile int&, int>, const int&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int&, const int>, const int&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int&, volatile int>, const volatile int&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int&, const volatile int>, const volatile int&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int&, int&>, const int&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int&, const int&>, const int&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int&, volatile int&>, const volatile int&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int&, const volatile int&>, const volatile int&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int&, int&&>, const int&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int&, const int&&>, const int&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int&, volatile int&&>, const volatile int&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int&, const volatile int&&>, const volatile int&>);

static_assert(std::is_same_v<ForwardLikeResult<int&&, int>, int&&>);
static_assert(std::is_same_v<ForwardLikeResult<int&&, const int>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<int&&, volatile int>, volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<int&&, const volatile int>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<int&&, int&>, int&&>);
static_assert(std::is_same_v<ForwardLikeResult<int&&, const int&>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<int&&, volatile int&>, volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<int&&, const volatile int&>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<int&&, int&&>, int&&>);
static_assert(std::is_same_v<ForwardLikeResult<int&&, const int&&>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<int&&, volatile int&&>, volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<int&&, const volatile int&&>, const volatile int&&>);

static_assert(std::is_same_v<ForwardLikeResult<const int&&, int>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const int&&, const int>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const int&&, volatile int>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const int&&, const volatile int>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const int&&, int&>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const int&&, const int&>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const int&&, volatile int&>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const int&&, const volatile int&>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const int&&, int&&>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const int&&, const int&&>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const int&&, volatile int&&>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const int&&, const volatile int&&>, const volatile int&&>);

static_assert(std::is_same_v<ForwardLikeResult<volatile int&&, int>, int&&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int&&, const int>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int&&, volatile int>, volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int&&, const volatile int>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int&&, int&>, int&&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int&&, const int&>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int&&, volatile int&>, volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int&&, const volatile int&>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int&&, int&&>, int&&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int&&, const int&&>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int&&, volatile int&&>, volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<volatile int&&, const volatile int&&>, const volatile int&&>);

static_assert(std::is_same_v<ForwardLikeResult<const volatile int&&, int>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int&&, const int>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int&&, volatile int>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int&&, const volatile int>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int&&, int&>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int&&, const int&>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int&&, volatile int&>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int&&, const volatile int&>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int&&, int&&>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int&&, const int&&>, const int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int&&, volatile int&&>, const volatile int&&>);
static_assert(std::is_same_v<ForwardLikeResult<const volatile int&&, const volatile int&&>, const volatile int&&>);

} // namespace

USERVER_NAMESPACE_END
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