libstdc++: LWG 3292 iota_view is under-constrained

Message ID 20200224232643.851356-1-ppalka@redhat.com
State New
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  • libstdc++: LWG 3292 iota_view is under-constrained
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Commit Message

Patrick Palka Feb. 24, 2020, 11:26 p.m.
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

-- 
2.25.1.291.ge68e29171c

Comments

Jonathan Wakely Feb. 25, 2020, 5:20 p.m. | #1
On 24/02/20 18:26 -0500, Patrick Palka wrote:
>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.


OK.

Patch

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" }