Tested powerpc64le-linux. Pushed to trunk.
This LWG issue was approved at the October 2021 plenary and can be implemented now that std::optional is fully constexpr. libstdc++-v3/ChangeLog: * include/std/ranges (ranges::__detail::__box): Add constexpr to assignment operators (LWG 3572). * testsuite/std/ranges/adaptors/filter.cc: Check assignment of a view that uses copyable-box. --- libstdc++-v3/include/std/ranges | 5 ++-- .../testsuite/std/ranges/adaptors/filter.cc | 28 +++++++++++++++++++ 2 files changed, 31 insertions(+), 2 deletions(-) diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges index c90d33c89fb..780a3633417 100644 --- a/libstdc++-v3/include/std/ranges +++ b/libstdc++-v3/include/std/ranges @@ -109,7 +109,8 @@ namespace ranges // _GLIBCXX_RESOLVE_LIB_DEFECTS // 3477. Simplify constraints for semiregular-box - __box& + // 3572. copyable-box should be fully constexpr + constexpr __box& operator=(const __box& __that) noexcept(is_nothrow_copy_constructible_v<_Tp>) requires (!copyable<_Tp>) @@ -124,7 +125,7 @@ namespace ranges return *this; } - __box& + constexpr __box& operator=(__box&& __that) noexcept(is_nothrow_move_constructible_v<_Tp>) requires (!movable<_Tp>) diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/filter.cc b/libstdc++-v3/testsuite/std/ranges/adaptors/filter.cc index b8d081e1d5e..ed5a01ca595 100644 --- a/libstdc++-v3/testsuite/std/ranges/adaptors/filter.cc +++ b/libstdc++-v3/testsuite/std/ranges/adaptors/filter.cc @@ -140,6 +140,33 @@ test06() static_assert(!requires { views::all | filter; }); } +constexpr bool +test07() +{ + struct Pred + { + constexpr Pred() { } + constexpr Pred(const Pred&) { } + constexpr Pred(Pred&&) { } + // These make it non-copyable, so non-copyable-box<Pred> will provide + // assignment. + Pred& operator=(const Pred&) = delete; + Pred& operator=(Pred&&) = delete; + + bool operator()(int i) const { return i < 10; } + }; + + int i = 0; + ranges::filter_view v(views::single(i), Pred{}); + // LWG 3572. copyable-box should be fully constexpr + v = v; + v = std::move(v); + + return true; +} + +static_assert( test07() ); + int main() { @@ -150,4 +177,5 @@ main() test05<forward_iterator_wrapper>(); test05<random_access_iterator_wrapper>(); test06(); + test07(); } -- 2.31.1