Test for C++20 p0858 - ConstexprIterator requirements.

2019-06-08  Edward Smith-Rowland  <3dw4rd@verizon.net>

	Test for C++20 p0858 - ConstexprIterator requirements.
	* testsuite/21_strings/basic_string_view/requirements/constexpr_iter.cc:
	New test.
	* testsuite/23_containers/array/requirements/constexpr_iter.cc:
	New test.

From-SVN: r272085

libstdc++-v3/ChangeLog

+2019-06-08  Edward Smith-Rowland  <3dw4rd@verizon.net>
+
+	Test for C++20 p0858 - ConstexprIterator requirements.
+	* testsuite/21_strings/basic_string_view/requirements/constexpr_iter.cc:
+	New test.
+	* testsuite/23_containers/array/requirements/constexpr_iter.cc:
+	New test.
+
 2019-06-07  Thomas Rodgers  <trodgers@redhat.com>
 
 	Rename PSTL macro's consistent with libstdc++ (and llvm upstream

libstdc++-v3/testsuite/21_strings/basic_string_view/requirements/constexpr_iter.cc

+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+//
+// Copyright (C) 2019 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/>.
+
+#include <string_view>
+#include <array>
+
+constexpr char
+test()
+{
+  constexpr std::string_view hw("Hello, World!");
+  static_assert('H' == *hw.begin());
+  auto ch = hw[4];
+  static_assert('W' == *(hw.cbegin() + 7));
+
+  std::array<int, hw.size()> a2{{0,0,0,0,0,0,0,0,0,0,0,0,0}};
+  std::copy(hw.begin(), hw.end(), a2.begin());
+
+  return *(hw.cbegin() + 3);
+}
+
+void
+run_test()
+{
+  constexpr char ch = test();
+}

libstdc++-v3/testsuite/23_containers/array/requirements/constexpr_iter.cc

+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+//
+// Copyright (C) 2019 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/>.
+
+#include <array>
+
+constexpr int
+test()
+{
+  constexpr std::array<int, 3> a1{{1, 2, 3}};
+  static_assert(1 == *a1.begin());
+  auto n = a1[0] * a1[1]* a1[2];
+  static_assert(1 == *a1.cbegin());
+
+  std::array<int, 3> a2{{0, 0, 0}};
+  std::copy(a1.begin(), a1.end(), a2.begin());
+
+  return n;
+}
+
+void
+run_test()
+{
+  constexpr int n = test();
+}