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