diff mbox series

[1/2] libstdc++/pair: Define _S_const_assignable helper for C++20

Message ID 20240123235303.1540890-1-ppalka@redhat.com
State Accepted
Headers
Series [1/2] libstdc++/pair: Define _S_const_assignable helper for C++20 |

Checks

Context Check Description
snail/gcc-patch-check success Github commit url

Commit Message

Patrick Palka Jan. 23, 2024, 11:53 p.m. UTC 
  This is consistent with std::tuple's __const_assignable member function,
and will be reused when implementing the new pair::operator= overloads
from P2165R4.

libstdc++-v3/ChangeLog:

	* include/bits/stl_pair.h (pair::_S_const_assignable): Define,
	factored out from ...
	(pair::operator=): ... the constraints of the const overloads.
---
 libstdc++-v3/include/bits/stl_pair.h | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

Comments

Jonathan Wakely Jan. 24, 2024, 12:21 a.m. UTC | #1 
On Tue, 23 Jan 2024, 23:53 Patrick Palka, <ppalka@redhat.com> wrote:

> This is consistent with std::tuple's __const_assignable member function,
> and will be reused when implementing the new pair::operator= overloads
> from P2165R4.
>


OK



> libstdc++-v3/ChangeLog:
>
>         * include/bits/stl_pair.h (pair::_S_const_assignable): Define,
>         factored out from ...
>         (pair::operator=): ... the constraints of the const overloads.
> ---
>  libstdc++-v3/include/bits/stl_pair.h | 21 +++++++++++++--------
>  1 file changed, 13 insertions(+), 8 deletions(-)
>
> diff --git a/libstdc++-v3/include/bits/stl_pair.h
> b/libstdc++-v3/include/bits/stl_pair.h
> index acd0c7b58f9..b81b479ad43 100644
> --- a/libstdc++-v3/include/bits/stl_pair.h
> +++ b/libstdc++-v3/include/bits/stl_pair.h
> @@ -404,6 +404,15 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>           return false;
>         }
>
> +      template<typename _U1, typename _U2>
> +       static constexpr bool
> +       _S_const_assignable()
> +       {
> +         if constexpr (is_assignable_v<const _T1&, _U1>)
> +           return is_assignable_v<const _T2&, _U2>;
> +         return false;
> +       }
> +
>        template<typename _U1, typename _U2>
>         static constexpr bool
>         _S_nothrow_assignable()
> @@ -468,8 +477,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        /// Copy assignment operator (const)
>        constexpr const pair&
>        operator=(const pair& __p) const
> -      requires is_copy_assignable_v<const first_type>
> -       && is_copy_assignable_v<const second_type>
> +      requires (_S_const_assignable<const first_type&, const
> second_type&>())
>        {
>         first = __p.first;
>         second = __p.second;
> @@ -479,8 +487,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        /// Move assignment operator (const)
>        constexpr const pair&
>        operator=(pair&& __p) const
> -      requires is_assignable_v<const first_type&, first_type>
> -       && is_assignable_v<const second_type&, second_type>
> +      requires (_S_const_assignable<first_type, second_type>())
>        {
>         first = std::forward<first_type>(__p.first);
>         second = std::forward<second_type>(__p.second);
> @@ -491,8 +498,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        template<typename _U1, typename _U2>
>         constexpr const pair&
>         operator=(const pair<_U1, _U2>& __p) const
> -       requires is_assignable_v<const first_type&, const _U1&>
> -         && is_assignable_v<const second_type&, const _U2&>
> +       requires (_S_const_assignable<const _U1&, const _U2&>())
>         {
>           first = __p.first;
>           second = __p.second;
> @@ -503,8 +509,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
>        template<typename _U1, typename _U2>
>         constexpr const pair&
>         operator=(pair<_U1, _U2>&& __p) const
> -       requires is_assignable_v<const first_type&, _U1>
> -         && is_assignable_v<const second_type&, _U2>
> +       requires (_S_const_assignable<_U1, _U2>())
>         {
>           first = std::forward<_U1>(__p.first);
>           second = std::forward<_U2>(__p.second);
> --
> 2.43.0.386.ge02ecfcc53
>
>
diff mbox series

Patch

diff --git a/libstdc++-v3/include/bits/stl_pair.h b/libstdc++-v3/include/bits/stl_pair.h
index acd0c7b58f9..b81b479ad43 100644
--- a/libstdc++-v3/include/bits/stl_pair.h
+++ b/libstdc++-v3/include/bits/stl_pair.h
@@ -404,6 +404,15 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	  return false;
 	}
 
+      template<typename _U1, typename _U2>
+	static constexpr bool
+	_S_const_assignable()
+	{
+	  if constexpr (is_assignable_v<const _T1&, _U1>)
+	    return is_assignable_v<const _T2&, _U2>;
+	  return false;
+	}
+
       template<typename _U1, typename _U2>
 	static constexpr bool
 	_S_nothrow_assignable()
@@ -468,8 +477,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
       /// Copy assignment operator (const)
       constexpr const pair&
       operator=(const pair& __p) const
-      requires is_copy_assignable_v<const first_type>
-	&& is_copy_assignable_v<const second_type>
+      requires (_S_const_assignable<const first_type&, const second_type&>())
       {
 	first = __p.first;
 	second = __p.second;
@@ -479,8 +487,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
       /// Move assignment operator (const)
       constexpr const pair&
       operator=(pair&& __p) const
-      requires is_assignable_v<const first_type&, first_type>
-	&& is_assignable_v<const second_type&, second_type>
+      requires (_S_const_assignable<first_type, second_type>())
       {
 	first = std::forward<first_type>(__p.first);
 	second = std::forward<second_type>(__p.second);
@@ -491,8 +498,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
       template<typename _U1, typename _U2>
 	constexpr const pair&
 	operator=(const pair<_U1, _U2>& __p) const
-	requires is_assignable_v<const first_type&, const _U1&>
-	  && is_assignable_v<const second_type&, const _U2&>
+	requires (_S_const_assignable<const _U1&, const _U2&>())
 	{
 	  first = __p.first;
 	  second = __p.second;
@@ -503,8 +509,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
       template<typename _U1, typename _U2>
 	constexpr const pair&
 	operator=(pair<_U1, _U2>&& __p) const
-	requires is_assignable_v<const first_type&, _U1>
-	  && is_assignable_v<const second_type&, _U2>
+	requires (_S_const_assignable<_U1, _U2>())
 	{
 	  first = std::forward<_U1>(__p.first);
 	  second = std::forward<_U2>(__p.second);