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 <__utility/declval.h>
  15 #include <__utility/forward.h>
  16 #include <__utility/move.h>
  17 #include <tuple>
  18 #include <type_traits>
  19
  20 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
  21 #pragma GCC system_header
  22 #endif
  23
  24 _LIBCPP_BEGIN_NAMESPACE_STD
  25
  26 #if _LIBCPP_STD_VER > 14
  27
  28 template <class _Op, class _Indices, class ..._Bound>
  29 struct __perfect_forward_impl;
  30
  31 template <class _Op, size_t ..._Idx, class ..._Bound>
  32 struct __perfect_forward_impl<_Op, index_sequence<_Idx...>, _Bound...> {
  33 private:
  34     tuple<_Bound...> __bound_;
  35
  36 public:
  37     template <class ..._BoundArgs, class = enable_if_t<
  38         is_constructible_v<tuple<_Bound...>, _BoundArgs&&...>
  39     >>
  40     explicit constexpr __perfect_forward_impl(_BoundArgs&& ...__bound)
  41         : __bound_(_VSTD::forward<_BoundArgs>(__bound)...)
  42     { }
  43
  44     __perfect_forward_impl(__perfect_forward_impl const&) = default;
  45     __perfect_forward_impl(__perfect_forward_impl&&) = default;
  46
  47     __perfect_forward_impl& operator=(__perfect_forward_impl const&) = default;
  48     __perfect_forward_impl& operator=(__perfect_forward_impl&&) = default;
  49
  50     template <class ..._Args, class = enable_if_t<is_invocable_v<_Op, _Bound&..., _Args...>>>
  51     _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Args&&... __args) &
  52         noexcept(noexcept(_Op()(_VSTD::get<_Idx>(__bound_)..., _VSTD::forward<_Args>(__args)...)))
  53         -> decltype(      _Op()(_VSTD::get<_Idx>(__bound_)..., _VSTD::forward<_Args>(__args)...))
  54         { return          _Op()(_VSTD::get<_Idx>(__bound_)..., _VSTD::forward<_Args>(__args)...); }
  55
  56     template <class ..._Args, class = enable_if_t<!is_invocable_v<_Op, _Bound&..., _Args...>>>
  57     auto operator()(_Args&&...) & = delete;
  58
  59     template <class ..._Args, class = enable_if_t<is_invocable_v<_Op, _Bound const&..., _Args...>>>
  60     _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Args&&... __args) const&
  61         noexcept(noexcept(_Op()(_VSTD::get<_Idx>(__bound_)..., _VSTD::forward<_Args>(__args)...)))
  62         -> decltype(      _Op()(_VSTD::get<_Idx>(__bound_)..., _VSTD::forward<_Args>(__args)...))
  63         { return          _Op()(_VSTD::get<_Idx>(__bound_)..., _VSTD::forward<_Args>(__args)...); }
  64
  65     template <class ..._Args, class = enable_if_t<!is_invocable_v<_Op, _Bound const&..., _Args...>>>
  66     auto operator()(_Args&&...) const& = delete;
  67
  68     template <class ..._Args, class = enable_if_t<is_invocable_v<_Op, _Bound..., _Args...>>>
  69     _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Args&&... __args) &&
  70         noexcept(noexcept(_Op()(_VSTD::get<_Idx>(_VSTD::move(__bound_))..., _VSTD::forward<_Args>(__args)...)))
  71         -> decltype(      _Op()(_VSTD::get<_Idx>(_VSTD::move(__bound_))..., _VSTD::forward<_Args>(__args)...))
  72         { return          _Op()(_VSTD::get<_Idx>(_VSTD::move(__bound_))..., _VSTD::forward<_Args>(__args)...); }
  73
  74     template <class ..._Args, class = enable_if_t<!is_invocable_v<_Op, _Bound..., _Args...>>>
  75     auto operator()(_Args&&...) && = delete;
  76
  77     template <class ..._Args, class = enable_if_t<is_invocable_v<_Op, _Bound const..., _Args...>>>
  78     _LIBCPP_HIDE_FROM_ABI constexpr auto operator()(_Args&&... __args) const&&
  79         noexcept(noexcept(_Op()(_VSTD::get<_Idx>(_VSTD::move(__bound_))..., _VSTD::forward<_Args>(__args)...)))
  80         -> decltype(      _Op()(_VSTD::get<_Idx>(_VSTD::move(__bound_))..., _VSTD::forward<_Args>(__args)...))
  81         { return          _Op()(_VSTD::get<_Idx>(_VSTD::move(__bound_))..., _VSTD::forward<_Args>(__args)...); }
  82
  83     template <class ..._Args, class = enable_if_t<!is_invocable_v<_Op, _Bound const..., _Args...>>>
  84     auto operator()(_Args&&...) const&& = delete;
  85 };
  86
  87 // __perfect_forward implements a perfect-forwarding call wrapper as explained in [func.require].
  88 template <class _Op, class ..._Args>
  89 using __perfect_forward = __perfect_forward_impl<_Op, index_sequence_for<_Args...>, _Args...>;
  90
  91 #endif // _LIBCPP_STD_VER > 14
  92
  93 _LIBCPP_END_NAMESPACE_STD
  94
  95 #endif // _LIBCPP___FUNCTIONAL_PERFECT_FORWARD_H