libstdc++-v3/ChangeLog:
LWG 3292 iota_view is under-constrained
* include/std/ranges (iota_view): Require that _Winc models semiregular
as per LWG 3292.
* testsuite/std/ranges/iota/lwg3292_neg.cc: New test.
---
libstdc++-v3/include/std/ranges | 1 +
.../testsuite/std/ranges/iota/lwg3292_neg.cc | 40 +++++++++++++++++++
2 files changed, 41 insertions(+)
create mode 100644 libstdc++-v3/testsuite/std/ranges/iota/lwg3292_neg.cc
diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index 0b2057c9661..ab8fbaca38f 100644
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -615,6 +615,7 @@ namespace ranges
template<weakly_incrementable _Winc,
semiregular _Bound = unreachable_sentinel_t>
requires std::__detail::__weakly_eq_cmp_with<_Winc, _Bound>
+ && semiregular<_Winc>
class iota_view : public view_interface<iota_view<_Winc, _Bound>>
{
private:
diff --git a/libstdc++-v3/testsuite/std/ranges/iota/lwg3292_neg.cc
b/libstdc++-v3/testsuite/std/ranges/iota/lwg3292_neg.cc
new file mode 100644
index 00000000000..80c392729b3
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/ranges/iota/lwg3292_neg.cc
@@ -0,0 +1,40 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library. This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3. If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <sstream>
+#include <ranges>
+
+namespace ranges = std::ranges;
+namespace views = std::views;
+
+void
+test01()
+{
+ std::istringstream s("1 2 3 4 5");
+ auto v = ranges::istream_view<int>(s);
+ auto i = v.begin();
+ static_assert(!std::semiregular<decltype(i)>);
+ auto o = views::iota(std::move(i));
+ static_assert(false); // { dg-error "" }
+}
+
+// { dg-prune-output "no match" }
+// { dg-prune-output "deduction failed" }
+// { dg-prune-output "constraint failure" }
--
2.25.1.291.ge68e29171c
