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[libcxx] Implement P0318: unwrap_ref_decay and unwrap_reference

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Summary:
This was voted into C++20 in San Diego. Note that there was a revision
D0318R2 which did include unwrap_reference_t, but we mistakingly voted
P0318R1 into the C++20 Working Draft (which does not include
unwrap_reference_t). This patch implements D0318R2, which is what
we'll end up with in the Working Draft once this mistake has been
fixed.

Reviewers: EricWF, mclow.lists

Subscribers: christof, dexonsmith, libcxx-commits

Differential Revision: https://reviews.llvm.org/D54485

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@348138 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Louis Dionne 2018-12-03 14:03:27 +00:00
parent a815a3f8cc
commit 604afd7688
6 changed files with 150 additions and 41 deletions
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13
include/functional
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@ -68,6 +68,11 @@ template <class T> reference_wrapper<const T> cref(const T& t) noexcept;
template <class T> void cref(const T&& t) = delete;
template <class T> reference_wrapper<const T> cref(reference_wrapper<T> t) noexcept;
template <class T> struct unwrap_reference; // since C++20
template <class T> struct unwrap_ref_decay : unwrap_reference<decay_t<T>> { }; // since C++20
template <class T> using unwrap_reference_t = typename unwrap_reference<T>::type; // since C++20
template <class T> using unwrap_ref_decay_t = typename unwrap_ref_decay<T>::type; // since C++20
template <class T> // <class T=void> in C++14
struct plus : binary_function<T, T, T>
{
@ -2527,6 +2532,14 @@ private:
#endif // _LIBCPP_STD_VER > 14
#if _LIBCPP_STD_VER > 17
template <class _Tp>
using unwrap_reference_t = typename unwrap_reference<_Tp>::type;
template <class _Tp>
using unwrap_ref_decay_t = typename unwrap_ref_decay<_Tp>::type;
#endif // > C++17
_LIBCPP_END_NAMESPACE_STD
#endif // _LIBCPP_FUNCTIONAL

22
include/tuple
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@ -1078,30 +1078,12 @@ namespace {
_LIBCPP_INLINE_VAR constexpr __ignore_t<unsigned char> ignore = __ignore_t<unsigned char>();
}
template <class _Tp>
struct __make_tuple_return_impl
{
typedef _Tp type;
};
template <class _Tp>
struct __make_tuple_return_impl<reference_wrapper<_Tp> >
{
typedef _Tp& type;
};
template <class _Tp>
struct __make_tuple_return
{
typedef typename __make_tuple_return_impl<typename decay<_Tp>::type>::type type;
};
template <class... _Tp>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
tuple<typename __make_tuple_return<_Tp>::type...>
tuple<typename __unwrap_ref_decay<_Tp>::type...>
make_tuple(_Tp&&... __t)
{
return tuple<typename __make_tuple_return<_Tp>::type...>(_VSTD::forward<_Tp>(__t)...);
return tuple<typename __unwrap_ref_decay<_Tp>::type...>(_VSTD::forward<_Tp>(__t)...);
}
template <class... _Tp>

45
include/utility
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@ -616,32 +616,37 @@ swap(pair<_T1, _T2>& __x, pair<_T1, _T2>& __y)
__x.swap(__y);
}
template <class _Tp>
struct __unwrap_reference { typedef _Tp type; };
template <class _Tp>
struct __unwrap_reference<reference_wrapper<_Tp> > { typedef _Tp& type; };
#if _LIBCPP_STD_VER > 17
template <class _Tp>
struct unwrap_reference : __unwrap_reference<_Tp> { };
template <class _Tp>
struct unwrap_ref_decay : unwrap_reference<typename decay<_Tp>::type> { };
#endif // > C++17
template <class _Tp>
struct __unwrap_ref_decay
#if _LIBCPP_STD_VER > 17
: unwrap_ref_decay<_Tp>
#else
: __unwrap_reference<typename decay<_Tp>::type>
#endif
{ };
#ifndef _LIBCPP_CXX03_LANG
template <class _Tp>
struct __make_pair_return_impl
{
typedef _Tp type;
};
template <class _Tp>
struct __make_pair_return_impl<reference_wrapper<_Tp>>
{
typedef _Tp& type;
};
template <class _Tp>
struct __make_pair_return
{
typedef typename __make_pair_return_impl<typename decay<_Tp>::type>::type type;
};
template <class _T1, class _T2>
inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
pair<typename __make_pair_return<_T1>::type, typename __make_pair_return<_T2>::type>
pair<typename __unwrap_ref_decay<_T1>::type, typename __unwrap_ref_decay<_T2>::type>
make_pair(_T1&& __t1, _T2&& __t2)
{
return pair<typename __make_pair_return<_T1>::type, typename __make_pair_return<_T2>::type>
return pair<typename __unwrap_ref_decay<_T1>::type, typename __unwrap_ref_decay<_T2>::type>
(_VSTD::forward<_T1>(__t1), _VSTD::forward<_T2>(__t2));
}

58
test/std/utilities/function.objects/refwrap/unwrap_ref_decay.pass.cpp Normal file
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@ -0,0 +1,58 @@
//===----------------------------------------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
// <functional>
//
// template <class T>
// struct unwrap_ref_decay;
//
// template <class T>
// using unwrap_ref_decay_t = typename unwrap_ref_decay<T>::type;
// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
#include <functional>
#include <type_traits>
template <typename T, typename Result>
void check() {
static_assert(std::is_same_v<typename std::unwrap_ref_decay<T>::type, Result>);
static_assert(std::is_same_v<typename std::unwrap_ref_decay<T>::type, std::unwrap_ref_decay_t<T>>);
}
struct T { };
int main() {
check<T, T>();
check<T&, T>();
check<T const, T>();
check<T const&, T>();
check<T*, T*>();
check<T const*, T const*>();
check<T[3], T*>();
check<T const [3], T const*>();
check<T (), T (*)()>();
check<T (int) const, T (int) const>();
check<T (int) &, T (int) &>();
check<T (int) &&, T (int) &&>();
check<std::reference_wrapper<T>, T&>();
check<std::reference_wrapper<T>&, T&>();
check<std::reference_wrapper<T const>, T const&>();
check<std::reference_wrapper<T const>&, T const&>();
check<std::reference_wrapper<T*>, T*&>();
check<std::reference_wrapper<T*>&, T*&>();
check<std::reference_wrapper<T const*>, T const*&>();
check<std::reference_wrapper<T const*>&, T const*&>();
check<std::reference_wrapper<T[3]>, T (&)[3]>();
check<std::reference_wrapper<T[3]>&, T (&)[3]>();
check<std::reference_wrapper<T ()>, T (&)()>();
check<std::reference_wrapper<T ()>&, T (&)()>();
}

51
test/std/utilities/function.objects/refwrap/unwrap_reference.pass.cpp Normal file
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@ -0,0 +1,51 @@
//===----------------------------------------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
// <functional>
//
// template <class T>
// struct unwrap_reference;
//
// template <class T>
// using unwrap_reference_t = typename unwrap_reference<T>::type;
// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
#include <functional>
#include <type_traits>
template <typename T, typename Expected>
void check_equal() {
static_assert(std::is_same_v<typename std::unwrap_reference<T>::type, Expected>);
static_assert(std::is_same_v<typename std::unwrap_reference<T>::type, std::unwrap_reference_t<T>>);
}
template <typename T>
void check() {
check_equal<T, T>();
check_equal<T&, T&>();
check_equal<T const, T const>();
check_equal<T const&, T const&>();
check_equal<std::reference_wrapper<T>, T&>();
check_equal<std::reference_wrapper<T const>, T const&>();
}
struct T { };
int main() {
check<T>();
check<int>();
check<float>();
check<T*>();
check<int*>();
check<float*>();
}

2
www/cxx2a_status.html
View File

@ -108,7 +108,7 @@
<tr><td><a href="https://wg21.link/P1120R0">P1120R0</a></td><td>CWG</td><td>Consistency improvements for &lt;=&gt; and other comparison operators</td><td>Rapperswil</td><td></td><td></td></tr>
<tr><td></td><td></td><td></td><td></td><td></td><td></td></tr>
<tr><td><a href="https://wg21.link/P0318R1">P0318R1</a></td><td>LWG</td><td>unwrap_ref_decay and unwrap_reference</td><td>San Diego</td><td><i> </i></td><td></td></tr>
<tr><td><a href="https://wg21.link/P0318R1">P0318R1</a></td><td>LWG</td><td>unwrap_ref_decay and unwrap_reference</td><td>San Diego</td><td>Complete</td><td>8.0</td></tr>
<tr><td><a href="https://wg21.link/P0356R5">P0356R5</a></td><td>LWG</td><td>Simplified partial function application</td><td>San Diego</td><td><i> </i></td><td></td></tr>
<tr><td><a href="https://wg21.link/P0357R3">P0357R3</a></td><td>LWG</td><td>reference_wrapper for incomplete types</td><td>San Diego</td><td><i> </i></td><td></td></tr>
<tr><td><a href="https://wg21.link/P0482R6">P0482R6</a></td><td>CWG</td><td>char8_t: A type for UTF-8 characters and strings</td><td>San Diego</td><td><i> </i></td><td></td></tr>