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 <__type_traits/enable_if.h>
15#include <__type_traits/invoke.h>
16#include <__type_traits/is_constructible.h>
17#include <__utility/declval.h>
18#include <__utility/forward.h>
19#include <__utility/integer_sequence.h>
20#include <__utility/move.h>
21#include <tuple>
22
23#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
24# pragma GCC system_header
25#endif
26
27_LIBCPP_PUSH_MACROS
28#include <__undef_macros>
29
30_LIBCPP_BEGIN_NAMESPACE_STD
31
32#if _LIBCPP_STD_VER >= 17
33
34template <class _Op, class _Indices, class... _BoundArgs>
35struct __perfect_forward_impl;
36
37template <class _Op, size_t... _Idx, class... _BoundArgs>
38struct __perfect_forward_impl<_Op, index_sequence<_Idx...>, _BoundArgs...> {
39private:
40 tuple<_BoundArgs...> __bound_args_;
41
42public:
43 template <class... _Args, class = enable_if_t< is_constructible_v<tuple<_BoundArgs...>, _Args&&...> >>
44 _LIBCPP_HIDE_FROM_ABI explicit constexpr __perfect_forward_impl(_Args&&... __bound_args)
45 : __bound_args_(std::forward<_Args>(__bound_args)...) {}
46
47 _LIBCPP_HIDE_FROM_ABI __perfect_forward_impl(__perfect_forward_impl const&) = default;
48 _LIBCPP_HIDE_FROM_ABI __perfect_forward_impl(__perfect_forward_impl&&) = default;
49
50 _LIBCPP_HIDE_FROM_ABI __perfect_forward_impl& operator=(__perfect_forward_impl const&) = default;
51 _LIBCPP_HIDE_FROM_ABI __perfect_forward_impl& operator=(__perfect_forward_impl&&) = default;
52
53 template <class... _Args, class = enable_if_t<is_invocable_v<_Op, _BoundArgs&..., _Args...>>>
54 _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Args&&... __args) & noexcept(
55 noexcept(_Op()(std::get<_Idx>(__bound_args_)..., std::forward<_Args>(__args)...)))
56 -> decltype(_Op()(std::get<_Idx>(__bound_args_)..., std::forward<_Args>(__args)...)) {
57 return _Op()(std::get<_Idx>(__bound_args_)..., std::forward<_Args>(__args)...);
58 }
59
60 template <class... _Args, class = enable_if_t<!is_invocable_v<_Op, _BoundArgs&..., _Args...>>>
61 auto operator()(_Args&&...) & = delete;
62
63 template <class... _Args, class = enable_if_t<is_invocable_v<_Op, _BoundArgs const&..., _Args...>>>
64 _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Args&&... __args) const& noexcept(
65 noexcept(_Op()(std::get<_Idx>(__bound_args_)..., std::forward<_Args>(__args)...)))
66 -> decltype(_Op()(std::get<_Idx>(__bound_args_)..., std::forward<_Args>(__args)...)) {
67 return _Op()(std::get<_Idx>(__bound_args_)..., std::forward<_Args>(__args)...);
68 }
69
70 template <class... _Args, class = enable_if_t<!is_invocable_v<_Op, _BoundArgs const&..., _Args...>>>
71 auto operator()(_Args&&...) const& = delete;
72
73 template <class... _Args, class = enable_if_t<is_invocable_v<_Op, _BoundArgs..., _Args...>>>
74 _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Args&&... __args) && noexcept(
75 noexcept(_Op()(std::get<_Idx>(std::move(__bound_args_))..., std::forward<_Args>(__args)...)))
76 -> decltype(_Op()(std::get<_Idx>(std::move(__bound_args_))..., std::forward<_Args>(__args)...)) {
77 return _Op()(std::get<_Idx>(std::move(__bound_args_))..., std::forward<_Args>(__args)...);
78 }
79
80 template <class... _Args, class = enable_if_t<!is_invocable_v<_Op, _BoundArgs..., _Args...>>>
81 auto operator()(_Args&&...) && = delete;
82
83 template <class... _Args, class = enable_if_t<is_invocable_v<_Op, _BoundArgs const..., _Args...>>>
84 _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Args&&... __args) const&& noexcept(
85 noexcept(_Op()(std::get<_Idx>(std::move(__bound_args_))..., std::forward<_Args>(__args)...)))
86 -> decltype(_Op()(std::get<_Idx>(std::move(__bound_args_))..., std::forward<_Args>(__args)...)) {
87 return _Op()(std::get<_Idx>(std::move(__bound_args_))..., std::forward<_Args>(__args)...);
88 }
89
90 template <class... _Args, class = enable_if_t<!is_invocable_v<_Op, _BoundArgs const..., _Args...>>>
91 auto operator()(_Args&&...) const&& = delete;
92};
93
94// __perfect_forward implements a perfect-forwarding call wrapper as explained in [func.require].
95template <class _Op, class... _Args>
96using __perfect_forward = __perfect_forward_impl<_Op, index_sequence_for<_Args...>, _Args...>;
97
98#endif // _LIBCPP_STD_VER >= 17
99
100_LIBCPP_END_NAMESPACE_STD
101
102_LIBCPP_POP_MACROS
103
104#endif // _LIBCPP___FUNCTIONAL_PERFECT_FORWARD_H
105