From cafae0561920883f3269aa9a89aa4035b6a226e1 Mon Sep 17 00:00:00 2001
From: Christopher Di Bella <cjdb@google.com>
Date: Tue, 22 Jun 2021 19:21:46 +0000
Subject: [PATCH] [libcxx][NFC] prepares `<type_traits>` for moving out forward
 and swap

* `<type_traits>` depends on `std::forward`, so we replaced it with
  `static_cast<T&&>`.
* `swap`'s return type is confusing, so it's been rearranged to improve
   readabilitiy.
---
 libcxx/include/type_traits | 43 +++++++++++++++++++++----------------------
 libcxx/include/utility     | 22 +++++++++++-----------
 2 files changed, 32 insertions(+), 33 deletions(-)

diff --git a/libcxx/include/type_traits b/libcxx/include/type_traits
index 4e5a6ba..2593549 100644
--- a/libcxx/include/type_traits
+++ b/libcxx/include/type_traits
@@ -2855,7 +2855,7 @@ __decay_copy(_Tp&& __t)
 noexcept(is_nothrow_convertible_v<_Tp, remove_reference_t<_Tp>>)
 #endif
 {
-    return _VSTD::forward<_Tp>(__t);
+    return static_cast<_Tp&&>(__t);
 }
 
 template <class _MP, bool _IsMemberFunctionPtr, bool _IsMemberObjectPtr>
@@ -3866,42 +3866,42 @@ template <class _Fp, class _A0, class ..._Args,
 inline _LIBCPP_INLINE_VISIBILITY
 _LIBCPP_CONSTEXPR_AFTER_CXX17 auto
 __invoke(_Fp&& __f, _A0&& __a0, _Args&& ...__args)
-_LIBCPP_INVOKE_RETURN((_VSTD::forward<_A0>(__a0).*__f)(_VSTD::forward<_Args>(__args)...))
+_LIBCPP_INVOKE_RETURN((static_cast<_A0&&>(__a0).*__f)(static_cast<_Args&&>(__args)...))
 
 template <class _Fp, class _A0, class ..._Args,
           class = __enable_if_bullet1<_Fp, _A0>>
 inline _LIBCPP_INLINE_VISIBILITY
 _LIBCPP_CONSTEXPR auto
 __invoke_constexpr(_Fp&& __f, _A0&& __a0, _Args&& ...__args)
-_LIBCPP_INVOKE_RETURN((_VSTD::forward<_A0>(__a0).*__f)(_VSTD::forward<_Args>(__args)...))
+_LIBCPP_INVOKE_RETURN((static_cast<_A0&&>(__a0).*__f)(static_cast<_Args&&>(__args)...))
 
 template <class _Fp, class _A0, class ..._Args,
           class = __enable_if_bullet2<_Fp, _A0>>
 inline _LIBCPP_INLINE_VISIBILITY
 _LIBCPP_CONSTEXPR_AFTER_CXX17 auto
 __invoke(_Fp&& __f, _A0&& __a0, _Args&& ...__args)
-_LIBCPP_INVOKE_RETURN((__a0.get().*__f)(_VSTD::forward<_Args>(__args)...))
+_LIBCPP_INVOKE_RETURN((__a0.get().*__f)(static_cast<_Args&&>(__args)...))
 
 template <class _Fp, class _A0, class ..._Args,
           class = __enable_if_bullet2<_Fp, _A0>>
 inline _LIBCPP_INLINE_VISIBILITY
 _LIBCPP_CONSTEXPR auto
 __invoke_constexpr(_Fp&& __f, _A0&& __a0, _Args&& ...__args)
-_LIBCPP_INVOKE_RETURN((__a0.get().*__f)(_VSTD::forward<_Args>(__args)...))
+_LIBCPP_INVOKE_RETURN((__a0.get().*__f)(static_cast<_Args&&>(__args)...))
 
 template <class _Fp, class _A0, class ..._Args,
           class = __enable_if_bullet3<_Fp, _A0>>
 inline _LIBCPP_INLINE_VISIBILITY
 _LIBCPP_CONSTEXPR_AFTER_CXX17 auto
 __invoke(_Fp&& __f, _A0&& __a0, _Args&& ...__args)
-_LIBCPP_INVOKE_RETURN(((*_VSTD::forward<_A0>(__a0)).*__f)(_VSTD::forward<_Args>(__args)...))
+_LIBCPP_INVOKE_RETURN(((*static_cast<_A0&&>(__a0)).*__f)(static_cast<_Args&&>(__args)...))
 
 template <class _Fp, class _A0, class ..._Args,
           class = __enable_if_bullet3<_Fp, _A0>>
 inline _LIBCPP_INLINE_VISIBILITY
 _LIBCPP_CONSTEXPR auto
 __invoke_constexpr(_Fp&& __f, _A0&& __a0, _Args&& ...__args)
-_LIBCPP_INVOKE_RETURN(((*_VSTD::forward<_A0>(__a0)).*__f)(_VSTD::forward<_Args>(__args)...))
+_LIBCPP_INVOKE_RETURN(((*static_cast<_A0&&>(__a0)).*__f)(static_cast<_Args&&>(__args)...))
 
 // bullets 4, 5 and 6
 
@@ -3910,14 +3910,14 @@ template <class _Fp, class _A0,
 inline _LIBCPP_INLINE_VISIBILITY
 _LIBCPP_CONSTEXPR_AFTER_CXX17 auto
 __invoke(_Fp&& __f, _A0&& __a0)
-_LIBCPP_INVOKE_RETURN(_VSTD::forward<_A0>(__a0).*__f)
+_LIBCPP_INVOKE_RETURN(static_cast<_A0&&>(__a0).*__f)
 
 template <class _Fp, class _A0,
           class = __enable_if_bullet4<_Fp, _A0>>
 inline _LIBCPP_INLINE_VISIBILITY
 _LIBCPP_CONSTEXPR auto
 __invoke_constexpr(_Fp&& __f, _A0&& __a0)
-_LIBCPP_INVOKE_RETURN(_VSTD::forward<_A0>(__a0).*__f)
+_LIBCPP_INVOKE_RETURN(static_cast<_A0&&>(__a0).*__f)
 
 template <class _Fp, class _A0,
           class = __enable_if_bullet5<_Fp, _A0>>
@@ -3938,14 +3938,14 @@ template <class _Fp, class _A0,
 inline _LIBCPP_INLINE_VISIBILITY
 _LIBCPP_CONSTEXPR_AFTER_CXX17 auto
 __invoke(_Fp&& __f, _A0&& __a0)
-_LIBCPP_INVOKE_RETURN((*_VSTD::forward<_A0>(__a0)).*__f)
+_LIBCPP_INVOKE_RETURN((*static_cast<_A0&&>(__a0)).*__f)
 
 template <class _Fp, class _A0,
           class = __enable_if_bullet6<_Fp, _A0>>
 inline _LIBCPP_INLINE_VISIBILITY
 _LIBCPP_CONSTEXPR auto
 __invoke_constexpr(_Fp&& __f, _A0&& __a0)
-_LIBCPP_INVOKE_RETURN((*_VSTD::forward<_A0>(__a0)).*__f)
+_LIBCPP_INVOKE_RETURN((*static_cast<_A0&&>(__a0)).*__f)
 
 // bullet 7
 
@@ -3953,13 +3953,13 @@ template <class _Fp, class ..._Args>
 inline _LIBCPP_INLINE_VISIBILITY
 _LIBCPP_CONSTEXPR_AFTER_CXX17 auto
 __invoke(_Fp&& __f, _Args&& ...__args)
-_LIBCPP_INVOKE_RETURN(_VSTD::forward<_Fp>(__f)(_VSTD::forward<_Args>(__args)...))
+_LIBCPP_INVOKE_RETURN(static_cast<_Fp&&>(__f)(static_cast<_Args&&>(__args)...))
 
 template <class _Fp, class ..._Args>
 inline _LIBCPP_INLINE_VISIBILITY
 _LIBCPP_CONSTEXPR auto
 __invoke_constexpr(_Fp&& __f, _Args&& ...__args)
-_LIBCPP_INVOKE_RETURN(_VSTD::forward<_Fp>(__f)(_VSTD::forward<_Args>(__args)...))
+_LIBCPP_INVOKE_RETURN(static_cast<_Fp&&>(__f)(static_cast<_Args&&>(__args)...))
 
 #undef _LIBCPP_INVOKE_RETURN
 
@@ -4195,18 +4195,17 @@ inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 _ForwardIterator2
 swap_ranges(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2);
 
-template <class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY
 #ifndef _LIBCPP_CXX03_LANG
-typename enable_if
-<
-    is_move_constructible<_Tp>::value &&
-    is_move_assignable<_Tp>::value
->::type
+template <class _Tp>
+using __swap_result_t = typename enable_if<is_move_constructible<_Tp>::value && is_move_assignable<_Tp>::value>::type;
 #else
-void
+template <class>
+using __swap_result_t = void;
 #endif
-_LIBCPP_CONSTEXPR_AFTER_CXX17
+
+template <class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY
+_LIBCPP_CONSTEXPR_AFTER_CXX17 __swap_result_t<_Tp>
 swap(_Tp& __x, _Tp& __y) _NOEXCEPT_(is_nothrow_move_constructible<_Tp>::value &&
                                     is_nothrow_move_assignable<_Tp>::value)
 {
diff --git a/libcxx/include/utility b/libcxx/include/utility
index 1060b5c..c536a1a 100644
--- a/libcxx/include/utility
+++ b/libcxx/include/utility
@@ -272,19 +272,19 @@ operator>=(const _Tp& __x, const _Tp& __y)
 
 // move_if_noexcept
 
-template <class _Tp>
-_LIBCPP_NODISCARD_EXT inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 #ifndef _LIBCPP_CXX03_LANG
-typename conditional
-<
-    !is_nothrow_move_constructible<_Tp>::value && is_copy_constructible<_Tp>::value,
-    const _Tp&,
-    _Tp&&
->::type
-#else  // _LIBCPP_CXX03_LANG
-const _Tp&
+template <class _Tp>
+using __move_if_noexcept_result_t =
+    typename conditional<!is_nothrow_move_constructible<_Tp>::value && is_copy_constructible<_Tp>::value, const _Tp&,
+                         _Tp&&>::type;
+#else // _LIBCPP_CXX03_LANG
+template <class _Tp>
+using __move_if_noexcept_result_t = const _Tp&;
 #endif
-move_if_noexcept(_Tp& __x) _NOEXCEPT
+
+template <class _Tp>
+_LIBCPP_NODISCARD_EXT inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+__move_if_noexcept_result_t<_Tp> move_if_noexcept(_Tp& __x) _NOEXCEPT
 {
     return _VSTD::move(__x);
 }
-- 
2.7.4