P0758R1 Implicit conversion traits

Extend __is_convertible_helper to also detect whether the conversion is
non-throwing, for std::is_nothrow_convertible in C++2a,

	* include/std/type_traits [__cplusplus > 201703]
	(__is_convertible_helper::__is_nothrow_type): Define new member.
	(__is_convertible_helper<_From, _To, false>::__test_aux1): Add
	noexcept.
	(__is_convertible_helper<_From, _To, false>::__test_nothrow)
	(__is_convertible_helper<_From, _To, false>::__is_nothrow_type): Add
	new members.
	(is_nothrow_convertible, is_nothrow_convertible_v): Define for C++2a.
	* testsuite/20_util/is_nothrow_convertible/value.cc: New.
	* testsuite/20_util/is_nothrow_convertible/requirements/
	explicit_instantiation.cc: New.
	* testsuite/20_util/is_nothrow_convertible/requirements/typedefs.cc:
	New.

From-SVN: r262322

libstdc++-v3/ChangeLog

@@ -1,5 +1,20 @@
 2018-07-02  Jonathan Wakely  <jwakely@redhat.com>
 
+	P0758R1 Implicit conversion traits
+	* include/std/type_traits [__cplusplus > 201703]
+	(__is_convertible_helper::__is_nothrow_type): Define new member.
+	(__is_convertible_helper<_From, _To, false>::__test_aux1): Add
+	noexcept.
+	(__is_convertible_helper<_From, _To, false>::__test_nothrow)
+	(__is_convertible_helper<_From, _To, false>::__is_nothrow_type): Add
+	new members.
+	(is_nothrow_convertible, is_nothrow_convertible_v): Define for C++2a.
+	* testsuite/20_util/is_nothrow_convertible/value.cc: New.
+	* testsuite/20_util/is_nothrow_convertible/requirements/
+	explicit_instantiation.cc: New.
+	* testsuite/20_util/is_nothrow_convertible/requirements/typedefs.cc:
+	New.
+
 	P0887R1 The identity metafunction
 	* include/std/type_traits (type_identity, type_identity_t): Define
 	for C++2a.

libstdc++-v3/include/std/type_traits

@@ -1341,13 +1341,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
            bool = __or_<is_void<_From>, is_function<_To>,
                         is_array<_To>>::value>
     struct __is_convertible_helper
-    { typedef typename is_void<_To>::type type; };
+    {
+      typedef typename is_void<_To>::type type;
+#if __cplusplus > 201703L
+      typedef type __is_nothrow_type;
+#endif
+    };
 
   template<typename _From, typename _To>
     class __is_convertible_helper<_From, _To, false>
     {
-       template<typename _To1>
-	static void __test_aux(_To1);
+      template<typename _To1>
+	static void __test_aux(_To1) noexcept;
 
       template<typename _From1, typename _To1,
 	       typename = decltype(__test_aux<_To1>(std::declval<_From1>()))>
@@ -1358,8 +1363,23 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	static false_type
 	__test(...);
 
+#if __cplusplus > 201703L
+      template<typename _From1, typename _To1,
+	       bool _NoEx = noexcept(__test_aux<_To1>(std::declval<_From1>()))>
+	static __bool_constant<_NoEx>
+	__test_nothrow(int);
+
+      template<typename, typename>
+	static false_type
+	__test_nothrow(...);
+#endif
+
     public:
       typedef decltype(__test<_From, _To>(0)) type;
+
+#if __cplusplus > 201703L
+      typedef decltype(__test_nothrow<_From, _To>(0)) __is_nothrow_type;
+#endif
     };
 
 
@@ -1369,6 +1389,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     : public __is_convertible_helper<_From, _To>::type
     { };
 
+#if __cplusplus > 201703L
+  /// is_nothrow_convertible
+  template<typename _From, typename _To>
+    struct is_nothrow_convertible
+    : public __is_convertible_helper<_From, _To>::__is_nothrow_type
+    { };
+
+  /// is_nothrow_convertible_v
+  template<typename _From, typename _To>
+    inline constexpr bool is_nothrow_convertible_v
+      = is_nothrow_convertible<_From, _To>::value;
+#endif // C++2a
 
   // Const-volatile modifications.
 

libstdc++-v3/testsuite/20_util/is_nothrow_convertible/requirements/explicit_instantiation.cc

@@ -0,0 +1,29 @@
+// Copyright (C) 2018 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 } }
+
+// NB: This file is for testing type_traits with NO OTHER INCLUDES.
+
+#include <type_traits>
+
+namespace std
+{
+  typedef short test_type;
+  template struct is_nothrow_convertible<test_type, test_type>;
+}

libstdc++-v3/testsuite/20_util/is_nothrow_convertible/requirements/typedefs.cc

@@ -0,0 +1,33 @@
+// Copyright (C) 2018 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 } }
+
+// NB: This file is for testing type_traits with NO OTHER INCLUDES.
+
+#include <type_traits>
+
+void test01()
+{
+  // Check for required typedefs
+  typedef std::is_nothrow_convertible<int, int> test_type;
+  typedef test_type::value_type               value_type;
+  typedef test_type::type                     type;
+  typedef test_type::type::value_type         type_value_type;
+  typedef test_type::type::type               type_type;
+}

libstdc++-v3/testsuite/20_util/is_nothrow_convertible/value.cc

@@ -0,0 +1,177 @@
+// Copyright (C) 2018 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 <type_traits>
+#include <testsuite_tr1.h>
+
+void test01()
+{
+  using std::is_nothrow_convertible;
+  using namespace __gnu_test;
+
+  // Positive conversion tests.
+  static_assert(test_relationship<is_nothrow_convertible,
+				  int, int>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  int, const int>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  volatile int, const int>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  int, float>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  double, float>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  float, int>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  int*, const int*>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  int*, void*>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  int[4], int*>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  float&, int>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  int, const int&>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  const int&, int>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  float, const int&>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  int(int), int(*)(int)>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  int(&)(int), int(*)(int)>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  EnumType, int>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  ClassType, ClassType>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  DerivedType, ClassType>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  DerivedType*, ClassType*>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  DerivedType&, ClassType&>(true));
+
+  static_assert(test_relationship<is_nothrow_convertible,
+				  const int, const int&>(true));
+
+  static_assert(test_relationship<is_nothrow_convertible,
+				  void, void>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  const void, void>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  void, volatile void>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  double&, NoexceptExplicitClass>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  NoexceptCopyConsClass,
+				  NoexceptCopyConsClass>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  const NoexceptCopyConsClass,
+				  NoexceptCopyConsClass>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  const NoexceptCopyConsClass&,
+				  NoexceptCopyConsClass>(true));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  NoexceptMoveConsClass,
+				  NoexceptMoveConsClass>(true));
+
+  static_assert(test_relationship<is_nothrow_convertible,
+				  int(int), int(&)(int)>(true));
+
+  // Negative conversion tests.
+  static_assert(test_relationship<is_nothrow_convertible,
+				  const int*, int*>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  int*, float*>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  const int[4], int*>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  int[4], int[4]>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  const int&, int&>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  float&, int&>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  float, volatile int&>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  int(int), int(int)>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  int(int), int(*)(void)>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  int(*)(int), int(&)(int)>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  int, EnumType>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  int, ClassType>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  ClassType, DerivedType>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  ClassType*, DerivedType*>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  ClassType&, DerivedType&>(false));
+
+  static_assert(test_relationship<is_nothrow_convertible,
+				  void, int>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  void, float>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  void, int(*)(int)>(false));
+
+  // C++0x
+  static_assert(test_relationship<is_nothrow_convertible,
+				  int, void>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  int[4], void>(false));
+
+  static_assert(test_relationship<is_nothrow_convertible,
+				  int, int&>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  float, volatile float&>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  const volatile int,
+				  const volatile int&>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  volatile int, volatile int&>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  double&, ExplicitClass>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  int&, ExplicitClass>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  void*, ExplicitClass>(false));
+
+  static_assert(test_relationship<is_nothrow_convertible,
+				  ExceptCopyConsClass,
+				  ExceptCopyConsClass>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  const ExceptCopyConsClass,
+				  ExceptCopyConsClass>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  const ExceptCopyConsClass&,
+				  ExceptCopyConsClass>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  ExceptMoveConsClass,
+				  ExceptMoveConsClass>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  ExceptMoveConsClass&,
+				  ExceptMoveConsClass>(false));
+  static_assert(test_relationship<is_nothrow_convertible,
+				  NoexceptMoveConsClass&,
+				  NoexceptMoveConsClass>(false));
+}

libstdc++-v3/testsuite/20_util/make_signed/requirements/typedefs_neg.cc

@@ -47,4 +47,4 @@ void test01()
 // { dg-error "required from here" "" { target *-*-* } 39 }
 // { dg-error "required from here" "" { target *-*-* } 41 }
 
-// { dg-error "invalid use of incomplete type" "" { target *-*-* } 1793 }
+// { dg-error "invalid use of incomplete type" "" { target *-*-* } 1825 }

libstdc++-v3/testsuite/20_util/make_unsigned/requirements/typedefs_neg.cc

@@ -47,5 +47,5 @@ void test01()
 // { dg-error "required from here" "" { target *-*-* } 39 }
 // { dg-error "required from here" "" { target *-*-* } 41 }
 
-// { dg-error "invalid use of incomplete type" "" { target *-*-* } 1676 }
+// { dg-error "invalid use of incomplete type" "" { target *-*-* } 1708 }