1// -*- C++ -*-
2//===----------------------------------------------------------------------===//
3//
4// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
5// See https://llvm.org/LICENSE.txt for license information.
6// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7//
8//===----------------------------------------------------------------------===//
9
10#ifndef _LIBCPP___FUNCTIONAL_PERFECT_FORWARD_H
11#define _LIBCPP___FUNCTIONAL_PERFECT_FORWARD_H
12
13#include <__config>
14#include <__cstddef/size_t.h>
15#include <__type_traits/enable_if.h>
16#include <__type_traits/invoke.h>
17#include <__type_traits/is_constructible.h>
18#include <__utility/declval.h>
19#include <__utility/forward.h>
20#include <__utility/integer_sequence.h>
21#include <__utility/move.h>
22#include <tuple>
23
24#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
25# pragma GCC system_header
26#endif
27
28_LIBCPP_PUSH_MACROS
29#include <__undef_macros>
30
31_LIBCPP_BEGIN_NAMESPACE_STD
32
33#if _LIBCPP_STD_VER >= 17
34
35template <class _Op, class _Indices, class... _BoundArgs>
36struct __perfect_forward_impl;
37
38template <class _Op, size_t... _Idx, class... _BoundArgs>
39struct __perfect_forward_impl<_Op, index_sequence<_Idx...>, _BoundArgs...> {
40private:
41 tuple<_BoundArgs...> __bound_args_;
42
43public:
44 template <class... _Args, class = enable_if_t< is_constructible_v<tuple<_BoundArgs...>, _Args&&...> >>
45 _LIBCPP_HIDE_FROM_ABI explicit constexpr __perfect_forward_impl(_Args&&... __bound_args)
46 : __bound_args_(std::forward<_Args>(__bound_args)...) {}
47
48 _LIBCPP_HIDE_FROM_ABI __perfect_forward_impl(__perfect_forward_impl const&) = default;
49 _LIBCPP_HIDE_FROM_ABI __perfect_forward_impl(__perfect_forward_impl&&) = default;
50
51 _LIBCPP_HIDE_FROM_ABI __perfect_forward_impl& operator=(__perfect_forward_impl const&) = default;
52 _LIBCPP_HIDE_FROM_ABI __perfect_forward_impl& operator=(__perfect_forward_impl&&) = default;
53
54 template <class... _Args, class = enable_if_t<is_invocable_v<_Op, _BoundArgs&..., _Args...>>>
55 _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Args&&... __args) & noexcept(
56 noexcept(_Op()(std::get<_Idx>(__bound_args_)..., std::forward<_Args>(__args)...)))
57 -> decltype(_Op()(std::get<_Idx>(__bound_args_)..., std::forward<_Args>(__args)...)) {
58 return _Op()(std::get<_Idx>(__bound_args_)..., std::forward<_Args>(__args)...);
59 }
60
61 template <class... _Args, class = enable_if_t<!is_invocable_v<_Op, _BoundArgs&..., _Args...>>>
62 auto operator()(_Args&&...) & = delete;
63
64 template <class... _Args, class = enable_if_t<is_invocable_v<_Op, _BoundArgs const&..., _Args...>>>
65 _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Args&&... __args) const& noexcept(
66 noexcept(_Op()(std::get<_Idx>(__bound_args_)..., std::forward<_Args>(__args)...)))
67 -> decltype(_Op()(std::get<_Idx>(__bound_args_)..., std::forward<_Args>(__args)...)) {
68 return _Op()(std::get<_Idx>(__bound_args_)..., std::forward<_Args>(__args)...);
69 }
70
71 template <class... _Args, class = enable_if_t<!is_invocable_v<_Op, _BoundArgs const&..., _Args...>>>
72 auto operator()(_Args&&...) const& = delete;
73
74 template <class... _Args, class = enable_if_t<is_invocable_v<_Op, _BoundArgs..., _Args...>>>
75 _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Args&&... __args) && noexcept(
76 noexcept(_Op()(std::get<_Idx>(std::move(__bound_args_))..., std::forward<_Args>(__args)...)))
77 -> decltype(_Op()(std::get<_Idx>(std::move(__bound_args_))..., std::forward<_Args>(__args)...)) {
78 return _Op()(std::get<_Idx>(std::move(__bound_args_))..., std::forward<_Args>(__args)...);
79 }
80
81 template <class... _Args, class = enable_if_t<!is_invocable_v<_Op, _BoundArgs..., _Args...>>>
82 auto operator()(_Args&&...) && = delete;
83
84 template <class... _Args, class = enable_if_t<is_invocable_v<_Op, _BoundArgs const..., _Args...>>>
85 _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Args&&... __args) const&& noexcept(
86 noexcept(_Op()(std::get<_Idx>(std::move(__bound_args_))..., std::forward<_Args>(__args)...)))
87 -> decltype(_Op()(std::get<_Idx>(std::move(__bound_args_))..., std::forward<_Args>(__args)...)) {
88 return _Op()(std::get<_Idx>(std::move(__bound_args_))..., std::forward<_Args>(__args)...);
89 }
90
91 template <class... _Args, class = enable_if_t<!is_invocable_v<_Op, _BoundArgs const..., _Args...>>>
92 auto operator()(_Args&&...) const&& = delete;
93};
94
95// __perfect_forward implements a perfect-forwarding call wrapper as explained in [func.require].
96template <class _Op, class... _Args>
97using __perfect_forward _LIBCPP_NODEBUG = __perfect_forward_impl<_Op, index_sequence_for<_Args...>, _Args...>;
98
99#endif // _LIBCPP_STD_VER >= 17
100
101_LIBCPP_END_NAMESPACE_STD
102
103_LIBCPP_POP_MACROS
104
105#endif // _LIBCPP___FUNCTIONAL_PERFECT_FORWARD_H
106