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* [gcc r14-8709] libstdc++/pair: Factor out const-assignability helper for C++20
@ 2024-02-01 20:03 Patrick Palka
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From: Patrick Palka @ 2024-02-01 20:03 UTC (permalink / raw)
To: gcc-cvs, libstdc++-cvs
https://gcc.gnu.org/g:87d162383ed68c55311a55784f6b40e979945c00
commit r14-8709-g87d162383ed68c55311a55784f6b40e979945c00
Author: Patrick Palka <ppalka@redhat.com>
Date: Thu Feb 1 14:56:02 2024 -0500
libstdc++/pair: Factor out const-assignability helper for C++20
This is consistent with std::tuple's __const_assignable helper, and will
be useful for 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.
Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
Diff:
---
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 acd0c7b58f91..b81b479ad43a 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);
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