[gcc(refs/users/ppalka/heads/libstdcxx-constrained-algos)] add test (which currently fails)

[Patrick Palka]

https://gcc.gnu.org/g:42cac2d1b79e2e695321390d1904c76e948caf05

commit 42cac2d1b79e2e695321390d1904c76e948caf05
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Jan 15 17:20:27 2020 +0000

    add test (which currently fails)

Diff:
---
 .../testsuite/std/ranges/iota/difference_type.cc   | 57 ++++++++++++++++++++++
 1 file changed, 57 insertions(+)

diff --git a/libstdc++-v3/testsuite/std/ranges/iota/difference_type.cc b/libstdc++-v3/testsuite/std/ranges/iota/difference_type.cc
new file mode 100644
index 0000000..4a342de
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/ranges/iota/difference_type.cc
@@ -0,0 +1,57 @@
+// 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 run { target c++2a } }
+
+#include <ranges>
+#include <testsuite_hooks.h>
+
+void
+test01()
+{
+  using I = unsigned long long;
+  auto imax = std::numeric_limits<I>::max();
+  std::ranges::iota_view<I, I> i(0, imax);
+  auto begin = i.begin();
+  static_assert( std::input_or_output_iterator<decltype(begin)> );
+  auto size = std::ranges::end(i) - std::ranges::begin(i);
+  VERIFY( size > 0 );
+  VERIFY( size == imax );
+}
+
+void
+test02()
+{
+#if __SIZEOF_INT128__
+  using I = unsigned __int128;
+  auto imax = std::numeric_limits<I>::max();
+  std::ranges::iota_view<I, I> i(0, imax);
+  auto begin = i.begin();
+  static_assert( std::input_or_output_iterator<decltype(begin)> );
+  auto size = std::ranges::end(i) - std::ranges::begin(i);
+  VERIFY( size > 0 );
+  VERIFY( size == imax );
+#endif
+}
+
+int
+main()
+{
+  test01();
+  test02();
+}