Add test for std::hash<std::error_code>

Copied from 19_diagnostics/error_condition/hash.cc added recently.

	* testsuite/19_diagnostics/error_code/hash.cc: New test.

From-SVN: r270951

libstdc++-v3/ChangeLog

+2019-05-07  Jonathan Wakely  <jwakely@redhat.com>
+
+	* testsuite/19_diagnostics/error_code/hash.cc: New test.
+
 2019-05-06  François Dumont  <fdumont@gcc.gnu.org>
 
 	* python/libstdcxx/v6/printers.py (add_one_template_type_printer):

libstdc++-v3/testsuite/19_diagnostics/error_code/hash.cc

+// 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/>.
+
+// { dg-do run { target c++11 } }
+
+#include <system_error>
+#include <testsuite_hooks.h>
+
+struct error_cat : std::error_category
+{
+  error_cat(std::string s) : _name(s) { }
+  std::string _name;
+  const char* name() const noexcept override { return _name.c_str(); }
+  std::string message(int) const override { return "error"; }
+};
+
+void
+test01()
+{
+  std::hash<std::error_code> h;
+  error_cat kitty("kitty"), moggy("moggy");
+  std::error_code cond1(99, kitty);
+  VERIFY( h(cond1) == h(cond1) );
+  std::error_code cond2(99, kitty);
+  VERIFY( h(cond1) == h(cond2) );
+  std::error_code cond3(88, kitty);
+  VERIFY( h(cond1) != h(cond3) );
+  std::error_code cond4(99, moggy);
+  VERIFY( h(cond1) != h(cond4) );
+}
+
+int
+main()
+{
+  test01();
+}