Add remaining changes from P1065R2 "constexpr INVOKE"

	* include/bits/refwrap.h (reference_wrapper, ref, cref): Add constexpr
	specifiers for C++20.
	* include/std/functional (_Mem_fn, mem_fn, _Bind, _Bind_result, bind)
	(bind_front, _Not_fn, not_fn): Likewise.
	* testsuite/20_util/bind/constexpr.cc: New test.
	* testsuite/20_util/function_objects/bind_front/constexpr.cc: New test.
	* testsuite/20_util/function_objects/mem_fn/constexpr.cc: New test.
	* testsuite/20_util/function_objects/not_fn/constexpr.cc: New test.
	* testsuite/20_util/reference_wrapper/constexpr.cc: New test.

From-SVN: r277698

5 files changed, 203 insertions, 0 deletions

diff --git a/libstdc++-v3/testsuite/20_util/bind/constexpr.cc b/libstdc++-v3/testsuite/20_util/bind/constexpr.cc
new file mode 100644
index 00000000000..6761c2c92a1
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/bind/constexpr.cc
@@ -0,0 +1,43 @@
+// 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-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <functional>
+
+struct add
+{
+  constexpr int operator()(int i, int j) const { return i + j; }
+};
+
+constexpr int
+test01(int i, int j)
+{
+  add a;
+  return std::bind(a, i, std::placeholders::_1)(j);
+}
+
+static_assert( test01(1, 2) == 3 );
+
+constexpr int
+test02(int i, int j)
+{
+  return std::bind<int>(add{}, i, std::placeholders::_1)(j);
+}
+
+static_assert( test02(4, 5) == 9 );
diff --git a/libstdc++-v3/testsuite/20_util/function_objects/bind_front/constexpr.cc b/libstdc++-v3/testsuite/20_util/function_objects/bind_front/constexpr.cc
new file mode 100644
index 00000000000..ee82745ddb7
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/function_objects/bind_front/constexpr.cc
@@ -0,0 +1,35 @@
+// 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-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <functional>
+
+struct add
+{
+  constexpr int operator()(int i, int j) const { return i + j; }
+};
+
+constexpr int
+test01(int i, int j)
+{
+  add a;
+  return std::bind_front(a, i)(j);
+}
+
+static_assert( test01(1, 2) == 3 );
diff --git a/libstdc++-v3/testsuite/20_util/function_objects/mem_fn/constexpr.cc b/libstdc++-v3/testsuite/20_util/function_objects/mem_fn/constexpr.cc
new file mode 100644
index 00000000000..6a0d0616baa
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/function_objects/mem_fn/constexpr.cc
@@ -0,0 +1,45 @@
+// 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-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <functional>
+
+struct F
+{
+  int i;
+  constexpr int add(int j) { return i + j; }
+};
+
+constexpr int
+test01(int i)
+{
+  F f{i};
+  return std::mem_fn(&F::i)(f);
+}
+
+static_assert( test01(2) == 2 );
+
+constexpr int
+test02(int i, int j)
+{
+  F f{i};
+  return std::mem_fn(&F::add)(&f, j);
+}
+
+static_assert( test02(3, 4) == 7 );
diff --git a/libstdc++-v3/testsuite/20_util/function_objects/not_fn/constexpr.cc b/libstdc++-v3/testsuite/20_util/function_objects/not_fn/constexpr.cc
new file mode 100644
index 00000000000..1c0e737fb7d
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/function_objects/not_fn/constexpr.cc
@@ -0,0 +1,35 @@
+// 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-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <functional>
+
+struct F
+{
+  constexpr bool operator()(int i, int j) const { return i == j; }
+};
+
+constexpr int
+test01(int i, int j)
+{
+  F f;
+  return std::not_fn(f)(1, 2);
+}
+
+static_assert( test01(1, 2) );
diff --git a/libstdc++-v3/testsuite/20_util/reference_wrapper/constexpr.cc b/libstdc++-v3/testsuite/20_util/reference_wrapper/constexpr.cc
new file mode 100644
index 00000000000..8a1c54eea7f
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/reference_wrapper/constexpr.cc
@@ -0,0 +1,45 @@
+// 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-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <functional>
+
+struct F
+{
+  constexpr int operator()(int i, int j) { return i + j; }
+  constexpr int operator()(int i, int j) const { return i * j; }
+};
+
+constexpr int
+test01(int i, int j)
+{
+  F f;
+  return std::ref(std::ref(f))(i, j);
+}
+
+static_assert( test01(1, 2) == 3 );
+
+constexpr int
+test02(int i, int j)
+{
+  F f;
+  return std::cref(std::cref(f))(i, j);
+}
+
+static_assert( test02(4, 5) == 20 );