[PATCH] Add C++17 deduction guide for std::basic_regex (P0433R2, partial)

[Jonathan Wakely]

C++17 deduction guide for std::basic_regex.

        * include/bits/regex.h (basic_regex): Add deduction guide from P0433.
        * testsuite/28_regex/basic_regex/ctors/deduction.cc: New.

Tested powerpc64le-linux, committed to trunk.


commit 9f523df8e7338b52277b6f4942b85cb75de1cb6a
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Wed Jun 7 14:28:58 2017 +0100

    Add C++17 deduction guide for std::basic_regex (P0433R2, partial)
    
        * include/bits/regex.h (basic_regex): Add deduction guide from P0433.
        * testsuite/28_regex/basic_regex/ctors/deduction.cc: New.

diff --git a/libstdc++-v3/include/bits/regex.h 
b/libstdc++-v3/include/bits/regex.h
index 1710db9..0bb88cb 100644
--- a/libstdc++-v3/include/bits/regex.h
+++ b/libstdc++-v3/include/bits/regex.h
@@ -787,6 +787,13 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
       _AutomatonPtr          _M_automaton;
     };
 
+#if __cpp_deduction_guides >= 201606
+  template<typename _ForwardIterator>
+    basic_regex(_ForwardIterator, _ForwardIterator,
+               regex_constants::syntax_option_type = {})
+      -> basic_regex<typename iterator_traits<_ForwardIterator>::value_type>;
+#endif
+
   /** @brief Standard regular expressions. */
   typedef basic_regex<char>    regex;
 
diff --git a/libstdc++-v3/testsuite/28_regex/basic_regex/ctors/deduction.cc 
b/libstdc++-v3/testsuite/28_regex/basic_regex/ctors/deduction.cc
new file mode 100644
index 0000000..63b3f67
--- /dev/null
+++ b/libstdc++-v3/testsuite/28_regex/basic_regex/ctors/deduction.cc
@@ -0,0 +1,61 @@
+// Copyright (C) 2017 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++17" }
+// { dg-do compile { target c++1z } }
+
+#include <regex>
+#include <testsuite_iterators.h>
+
+template<typename T, typename U> struct require_same;
+template<typename T> struct require_same<T, T> { using type = void; };
+
+template<typename T, typename U>
+  typename require_same<T, U>::type
+  check_type(U&) { }
+
+void
+test01()
+{
+  std::basic_regex x("");
+  check_type<std::basic_regex<char>>(x);
+  char s[1] = {};
+  std::basic_regex x2(s);
+  check_type<std::basic_regex<char>>(x2);
+  std::basic_regex x3(U"");
+  check_type<std::basic_regex<char32_t>>(x3);
+  std::basic_regex x4(U"", std::regex_constants::grep);
+  check_type<std::basic_regex<char32_t>>(x4);
+
+  // Test explicit guide:
+  std::basic_regex x5(s, s+1);
+  check_type<std::basic_regex<char>>(x5);
+  std::basic_regex x6((const char*)s, (const char*)s+1);
+  check_type<std::basic_regex<char>>(x6);
+  std::basic_regex x7(s, s+1, std::regex_constants::grep);
+  check_type<std::basic_regex<char>>(x7);
+  __gnu_test::test_container<char, __gnu_test::forward_iterator_wrapper> f(s);
+  std::basic_regex x8(f.begin(), f.end());
+  check_type<std::basic_regex<char>>(x8);
+  std::basic_regex x9(f.begin(), f.end(), std::regex_constants::grep);
+  check_type<std::basic_regex<char>>(x9);
+
+  std::basic_regex copy = x;
+  check_type<std::basic_regex<char>>(copy);
+  std::basic_regex move = std::move(x);
+  check_type<std::basic_regex<char>>(move);
+}