libcxx/include/__functional/perfect_forward.h

   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
  34 template <class _Op, class _Indices, class... _BoundArgs>
  35 struct __perfect_forward_impl;
  36
  37 template <class _Op, size_t... _Idx, class... _BoundArgs>
  38 struct __perfect_forward_impl<_Op, index_sequence<_Idx...>, _BoundArgs...> {
  39 private:
  40   tuple<_BoundArgs...> __bound_args_;
  41
  42 public:
  43   template <class... _Args, class = enable_if_t<
  44     is_constructible_v<tuple<_BoundArgs...>, _Args&&...>
  45   >>
  46   _LIBCPP_HIDE_FROM_ABI explicit constexpr __perfect_forward_impl(_Args&&... __bound_args)
  47     : __bound_args_(_VSTD::forward<_Args>(__bound_args)...) {}
  48
  49   _LIBCPP_HIDE_FROM_ABI __perfect_forward_impl(__perfect_forward_impl const&) = default;
  50   _LIBCPP_HIDE_FROM_ABI __perfect_forward_impl(__perfect_forward_impl&&) = default;
  51
  52   _LIBCPP_HIDE_FROM_ABI __perfect_forward_impl& operator=(__perfect_forward_impl const&) = default;
  53   _LIBCPP_HIDE_FROM_ABI __perfect_forward_impl& operator=(__perfect_forward_impl&&) = default;
  54
  55   template <class... _Args, class = enable_if_t<is_invocable_v<_Op, _BoundArgs&..., _Args...>>>
  56   _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Args&&... __args) &
  57     noexcept(noexcept(_Op()(_VSTD::get<_Idx>(__bound_args_)..., _VSTD::forward<_Args>(__args)...)))
  58     -> decltype(      _Op()(_VSTD::get<_Idx>(__bound_args_)..., _VSTD::forward<_Args>(__args)...))
  59     { return          _Op()(_VSTD::get<_Idx>(__bound_args_)..., _VSTD::forward<_Args>(__args)...); }
  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&
  66     noexcept(noexcept(_Op()(_VSTD::get<_Idx>(__bound_args_)..., _VSTD::forward<_Args>(__args)...)))
  67     -> decltype(      _Op()(_VSTD::get<_Idx>(__bound_args_)..., _VSTD::forward<_Args>(__args)...))
  68     { return          _Op()(_VSTD::get<_Idx>(__bound_args_)..., _VSTD::forward<_Args>(__args)...); }
  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) &&
  75     noexcept(noexcept(_Op()(_VSTD::get<_Idx>(_VSTD::move(__bound_args_))..., _VSTD::forward<_Args>(__args)...)))
  76     -> decltype(      _Op()(_VSTD::get<_Idx>(_VSTD::move(__bound_args_))..., _VSTD::forward<_Args>(__args)...))
  77     { return          _Op()(_VSTD::get<_Idx>(_VSTD::move(__bound_args_))..., _VSTD::forward<_Args>(__args)...); }
  78
  79   template <class... _Args, class = enable_if_t<!is_invocable_v<_Op, _BoundArgs..., _Args...>>>
  80   auto operator()(_Args&&...) && = delete;
  81
  82   template <class... _Args, class = enable_if_t<is_invocable_v<_Op, _BoundArgs const..., _Args...>>>
  83   _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Args&&... __args) const&&
  84     noexcept(noexcept(_Op()(_VSTD::get<_Idx>(_VSTD::move(__bound_args_))..., _VSTD::forward<_Args>(__args)...)))
  85     -> decltype(      _Op()(_VSTD::get<_Idx>(_VSTD::move(__bound_args_))..., _VSTD::forward<_Args>(__args)...))
  86     { return          _Op()(_VSTD::get<_Idx>(_VSTD::move(__bound_args_))..., _VSTD::forward<_Args>(__args)...); }
  87
  88   template <class... _Args, class = enable_if_t<!is_invocable_v<_Op, _BoundArgs const..., _Args...>>>
  89   auto operator()(_Args&&...) const&& = delete;
  90 };
  91
  92 // __perfect_forward implements a perfect-forwarding call wrapper as explained in [func.require].
  93 template <class _Op, class ..._Args>
  94 using __perfect_forward = __perfect_forward_impl<_Op, index_sequence_for<_Args...>, _Args...>;
  95
  96 #endif // _LIBCPP_STD_VER >= 17
  97
  98 _LIBCPP_END_NAMESPACE_STD
  99
 100 _LIBCPP_POP_MACROS
 101
 102 #endif // _LIBCPP___FUNCTIONAL_PERFECT_FORWARD_H