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[libc++] Simplify the tuple constructors a bit #150405

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merged 1 commit into from
Aug 1, 2025
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[libc++] Simplify the tuple constructors a bit #150405

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70 changes: 20 additions & 50 deletions libcxx/include/tuple
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Original file line number Diff line number Diff line change
Expand Up @@ -454,33 +454,28 @@ struct __all_default_constructible<__tuple_types<_Tp...>> : __all<is_default_con
template <class _Indx, class... _Tp>
struct __tuple_impl;

struct __forward_args {};
struct __value_init {};

template <size_t... _Indx, class... _Tp>
struct _LIBCPP_DECLSPEC_EMPTY_BASES
__tuple_impl<__index_sequence<_Indx...>, _Tp...> : public __tuple_leaf<_Indx, _Tp>... {
_LIBCPP_HIDE_FROM_ABI constexpr __tuple_impl() noexcept(
__all<is_nothrow_default_constructible<_Tp>::value...>::value) {}

template <size_t... _Uf, class... _Tf, size_t... _Ul, class... _Tl, class... _Up>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 explicit __tuple_impl(
__index_sequence<_Uf...>,
__tuple_types<_Tf...>,
__index_sequence<_Ul...>,
__tuple_types<_Tl...>,
_Up&&... __u) noexcept(__all<is_nothrow_constructible<_Tf, _Up>::value...>::value &&
__all<is_nothrow_default_constructible<_Tl>::value...>::value)
: __tuple_leaf<_Uf, _Tf>(std::forward<_Up>(__u))..., __tuple_leaf<_Ul, _Tl>()... {}

template <class _Alloc, size_t... _Uf, class... _Tf, size_t... _Ul, class... _Tl, class... _Up>
template <class... _Args>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 explicit __tuple_impl(__forward_args, _Args&&... __args)
: __tuple_leaf<_Indx, _Tp>(std::forward<_Args>(__args))... {}

template <class _Alloc>
_LIBCPP_HIDE_FROM_ABI
_LIBCPP_CONSTEXPR_SINCE_CXX14 explicit __tuple_impl(allocator_arg_t, const _Alloc& __alloc, __value_init)
: __tuple_leaf<_Indx, _Tp>(__uses_alloc_ctor<_Tp, _Alloc>(), __alloc)... {}

template <class _Alloc, class... _Args>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 explicit __tuple_impl(
allocator_arg_t,
const _Alloc& __a,
__index_sequence<_Uf...>,
__tuple_types<_Tf...>,
__index_sequence<_Ul...>,
__tuple_types<_Tl...>,
_Up&&... __u)
: __tuple_leaf<_Uf, _Tf>(__uses_alloc_ctor<_Tf, _Alloc, _Up>(), __a, std::forward<_Up>(__u))...,
__tuple_leaf<_Ul, _Tl>(__uses_alloc_ctor<_Tl, _Alloc>(), __a)... {}
allocator_arg_t, const _Alloc& __alloc, __forward_args, _Args&&... __args)
: __tuple_leaf<_Indx, _Tp>(__uses_alloc_ctor<_Tp, _Alloc, _Args>(), __alloc, std::forward<_Args>(__args))... {}

template <class _Tuple, __enable_if_t<__tuple_constructible<_Tuple, tuple<_Tp...> >::value, int> = 0>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 __tuple_impl(_Tuple&& __t) noexcept(
Expand Down Expand Up @@ -565,38 +560,23 @@ public:
__enable_if_t< _And< _IsDefault<_Tp>... >::value, int> = 0>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 explicit(_Not<_Lazy<_And, _IsImpDefault<_Tp>...> >::value)
tuple(allocator_arg_t, _Alloc const& __a)
: __base_(allocator_arg_t(),
__a,
__index_sequence<>(),
__tuple_types<>(),
__make_index_sequence<sizeof...(_Tp)>(),
__tuple_types<_Tp...>()) {}
: __base_(allocator_arg_t(), __a, __value_init{}) {}

// tuple(const T&...) constructors (including allocator_arg_t variants)
template <template <class...> class _And = _And,
__enable_if_t< _And< _BoolConstant<sizeof...(_Tp) >= 1>, is_copy_constructible<_Tp>... >::value, int> = 0>
_LIBCPP_HIDE_FROM_ABI
_LIBCPP_CONSTEXPR_SINCE_CXX14 explicit(_Not<_Lazy<_And, is_convertible<const _Tp&, _Tp>...> >::value)
tuple(const _Tp&... __t) noexcept(_And<is_nothrow_copy_constructible<_Tp>...>::value)
: __base_(__make_index_sequence<sizeof...(_Tp)>(),
__tuple_types<_Tp...>(),
__index_sequence<>(),
__tuple_types<>(),
__t...) {}
: __base_(__forward_args{}, __t...) {}

template <class _Alloc,
template <class...> class _And = _And,
__enable_if_t< _And< _BoolConstant<sizeof...(_Tp) >= 1>, is_copy_constructible<_Tp>... >::value, int> = 0>
_LIBCPP_HIDE_FROM_ABI
_LIBCPP_CONSTEXPR_SINCE_CXX20 explicit(_Not<_Lazy<_And, is_convertible<const _Tp&, _Tp>...> >::value)
tuple(allocator_arg_t, const _Alloc& __a, const _Tp&... __t)
: __base_(allocator_arg_t(),
__a,
__make_index_sequence<sizeof...(_Tp)>(),
__tuple_types<_Tp...>(),
__index_sequence<>(),
__tuple_types<>(),
__t...) {}
: __base_(allocator_arg_t(), __a, __forward_args{}, __t...) {}

// tuple(U&& ...) constructors (including allocator_arg_t variants)
template <class... _Up>
Expand All @@ -615,25 +595,15 @@ public:
int> = 0>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX14 explicit(_Not<_Lazy<_And, is_convertible<_Up, _Tp>...> >::value)
tuple(_Up&&... __u) noexcept(_And<is_nothrow_constructible<_Tp, _Up>...>::value)
: __base_(__make_index_sequence<sizeof...(_Up)>(),
__tuple_types<_Tp...>(),
__index_sequence<>(),
__tuple_types<>(),
std::forward<_Up>(__u)...) {}
: __base_(__forward_args{}, std::forward<_Up>(__u)...) {}

template <class _Alloc,
class... _Up,
__enable_if_t< _And< _BoolConstant<sizeof...(_Up) == sizeof...(_Tp)>, _EnableUTypesCtor<_Up...> >::value,
int> = 0>
_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 explicit(_Not<_Lazy<_And, is_convertible<_Up, _Tp>...> >::value)
tuple(allocator_arg_t, const _Alloc& __a, _Up&&... __u)
: __base_(allocator_arg_t(),
__a,
__make_index_sequence<sizeof...(_Up)>(),
__tuple_types<_Tp...>(),
__index_sequence<>(),
__tuple_types<>(),
std::forward<_Up>(__u)...) {}
: __base_(allocator_arg_t(), __a, __forward_args{}, std::forward<_Up>(__u)...) {}

// Copy and move constructors (including the allocator_arg_t variants)
tuple(const tuple&) = default;
Expand Down
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