[libc++] Extension: Make move and forward constexpr in C++11.

Summary:
`std::move` and `std::forward` were not marked constexpr in C++11.  This can be very damaging because it makes otherwise constant expressions non-constant. For example:

```
#include <utility>
template <class T>
struct Foo {
  constexpr Foo(T&& tx) :  t(std::move(tx)) {}
  T t;
};
[[clang::require_constant_initialization]] Foo<int> f(42); // Foo should be constant initialized but C++11 move is not constexpr. As a result `f` is an unsafe global.
```

This patch applies `constexpr` to `move` and `forward` as an extension in C++11. Normally the library is not allowed to add `constexpr` because it may be observable to the user. In particular adding constexpr may cause valid code to stop compiling. However these problems only happen in more complex situations, like making `__invoke(...)` constexpr. `forward` and `move` are simply enough that applying `constexpr` is safe. 

Note that libstdc++ has offered this extension since at least 4.8.1.

Most of the changes in this patch are simply test cleanups or additions. The main changes in the tests are:

* Fold all `forward_N.fail.cpp` tests into a single `forward.fail.cpp` test using -verify.
* Delete most `move_only_N.fail.cpp` tests because they weren't actually testing anything.
* Fold `move_copy.pass.cpp` and `move_only.pass.cpp` into a single `move.pass.cpp` test.
* Add return type and noexcept tests for `forward` and `move`.




Reviewers: rsmith, mclow.lists, EricWF

Subscribers: K-ballo, loladiro

Differential Revision: https://reviews.llvm.org/D24637

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@282439 91177308-0d34-0410-b5e6-96231b3b80d8

include/type_traits

@@ -2155,7 +2155,7 @@ template <class _Tp> _LIBCPP_CONSTEXPR bool is_destructible_v
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 
 template <class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
 typename remove_reference<_Tp>::type&&
 move(_Tp&& __t) _NOEXCEPT
 {
@@ -2164,7 +2164,7 @@ move(_Tp&& __t) _NOEXCEPT
 }
 
 template <class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
 _Tp&&
 forward(typename remove_reference<_Tp>::type& __t) _NOEXCEPT
 {
@@ -2172,12 +2172,12 @@ forward(typename remove_reference<_Tp>::type& __t) _NOEXCEPT
 }
 
 template <class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
 _Tp&&
 forward(typename remove_reference<_Tp>::type&& __t) _NOEXCEPT
 {
     static_assert(!is_lvalue_reference<_Tp>::value,
-                  "Can not forward an rvalue as an lvalue.");
+                  "can not forward an rvalue as an lvalue");
     return static_cast<_Tp&&>(__t);
 }
 

test/std/utilities/utility/forward/forward.fail.cpp

@@ -0,0 +1,53 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// test forward
+
+#include <utility>
+
+#include "test_macros.h"
+
+struct A
+{
+};
+
+A source() {return A();}
+const A csource() {return A();}
+
+int main()
+{
+#if TEST_STD_VER >= 11
+    {
+        std::forward<A&>(source());  // expected-note {{requested here}}
+        // expected-error@type_traits:* 1 {{static_assert failed "can not forward an rvalue as an lvalue"}}
+    }
+#else
+    {
+        std::forward<A&>(source()); // expected-error {{no matching function for call to 'forward'}}
+    }
+#endif
+    {
+        const A ca = A();
+        std::forward<A&>(ca); // expected-error {{no matching function for call to 'forward'}}
+    }
+    {
+        std::forward<A&>(csource());  // expected-error {{no matching function for call to 'forward'}}
+    }
+    {
+        const A ca = A();
+        std::forward<A>(ca); // expected-error {{no matching function for call to 'forward'}}
+    }
+    {
+        std::forward<A>(csource()); // expected-error {{no matching function for call to 'forward'}}
+    }
+    {
+        A a;
+        std::forward(a); // expected-error {{no matching function for call to 'forward'}}
+    }
+}

test/std/utilities/utility/forward/forward.pass.cpp

@@ -7,32 +7,40 @@
 //
 //===----------------------------------------------------------------------===//
 
+// UNSUPPORTED: c++98, c++03
+
 // test forward
 
 #include <utility>
+#include <type_traits>
 #include <cassert>
 
+#include "test_macros.h"
+
 struct A
 {
 };
 
-A source() {return A();}
+A source() noexcept {return A();}
-const A csource() {return A();}
+const A csource() noexcept {return A();}
 
-typedef char one;
-struct two {one _[2];};
-struct four {one _[4];};
-struct eight {one _[8];};
 
-one test(A&);
+constexpr bool test_constexpr_forward() {
-two test(const A&);
+#if TEST_STD_VER > 11
-
+    int x = 42;
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+    const int cx = 101;
-
+    return std::forward<int&>(x)        == 42
-four test(A&&);
+        && std::forward<int>(x)         == 42
-eight test(const A&&);
+        && std::forward<const int&>(x)  == 42
-
+        && std::forward<const int>(x)   == 42
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+        && std::forward<int&&>(x)       == 42
+        && std::forward<const int&&>(x) == 42
+        && std::forward<const int&>(cx) == 101
+        && std::forward<const int>(cx)  == 101;
+#else
+    return true;
+#endif
+}
 
 int main()
 {
@@ -42,42 +50,42 @@ int main()
     ((void)a); // Prevent unused warning
     ((void)ca); // Prevent unused warning
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+    static_assert(std::is_same<decltype(std::forward<A&>(a)), A&>::value, "");
-    static_assert(sizeof(test(std::forward<A&>(a))) == 1, "");
+    static_assert(std::is_same<decltype(std::forward<A>(a)), A&&>::value, "");
-    static_assert(sizeof(test(std::forward<A>(a))) == 4, "");
+    static_assert(std::is_same<decltype(std::forward<A>(source())), A&&>::value, "");
-    static_assert(sizeof(test(std::forward<A>(source()))) == 4, "");
+    static_assert(noexcept(std::forward<A&>(a)), "");
+    static_assert(noexcept(std::forward<A>(a)), "");
+    static_assert(noexcept(std::forward<A>(source())), "");
 
-    static_assert(sizeof(test(std::forward<const A&>(a))) == 2, "");
+    static_assert(std::is_same<decltype(std::forward<const A&>(a)), const A&>::value, "");
-//    static_assert(sizeof(test(std::forward<const A&>(source()))) == 2, "");
+    static_assert(std::is_same<decltype(std::forward<const A>(a)), const A&&>::value, "");
-    static_assert(sizeof(test(std::forward<const A>(a))) == 8, "");
+    static_assert(std::is_same<decltype(std::forward<const A>(source())), const A&&>::value, "");
-    static_assert(sizeof(test(std::forward<const A>(source()))) == 8, "");
+    static_assert(noexcept(std::forward<const A&>(a)), "");
+    static_assert(noexcept(std::forward<const A>(a)), "");
+    static_assert(noexcept(std::forward<const A>(source())), "");
 
-    static_assert(sizeof(test(std::forward<const A&>(ca))) == 2, "");
+    static_assert(std::is_same<decltype(std::forward<const A&>(ca)), const A&>::value, "");
-//    static_assert(sizeof(test(std::forward<const A&>(csource()))) == 2, "");
+    static_assert(std::is_same<decltype(std::forward<const A>(ca)), const A&&>::value, "");
-    static_assert(sizeof(test(std::forward<const A>(ca))) == 8, "");
+    static_assert(std::is_same<decltype(std::forward<const A>(csource())), const A&&>::value, "");
-    static_assert(sizeof(test(std::forward<const A>(csource()))) == 8, "");
+    static_assert(noexcept(std::forward<const A&>(ca)), "");
+    static_assert(noexcept(std::forward<const A>(ca)), "");
+    static_assert(noexcept(std::forward<const A>(csource())), "");
 
-#else  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#if TEST_STD_VER > 11
-
+    {
-    static_assert(sizeof(test(std::forward<A&>(a))) == 1, "");
-    static_assert(sizeof(test(std::forward<A>(a))) == 1, "");
-//    static_assert(sizeof(test(std::forward<A>(source()))) == 2, "");
-
-    static_assert(sizeof(test(std::forward<const A&>(a))) == 2, "");
-    static_assert(sizeof(test(std::forward<const A&>(source()))) == 2, "");
-    static_assert(sizeof(test(std::forward<const A>(a))) == 2, "");
-    static_assert(sizeof(test(std::forward<const A>(source()))) == 2, "");
-
-    static_assert(sizeof(test(std::forward<const A&>(ca))) == 2, "");
-    static_assert(sizeof(test(std::forward<const A&>(csource()))) == 2, "");
-    static_assert(sizeof(test(std::forward<const A>(ca))) == 2, "");
-    static_assert(sizeof(test(std::forward<const A>(csource()))) == 2, "");
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-#if _LIBCPP_STD_VER > 11
-    constexpr int i1 = std::move(23);
-    static_assert(i1 == 23, "" );
     constexpr int i2 = std::forward<int>(42);
-    static_assert(i2 == 42, "" );
+    static_assert(std::forward<int>(42) == 42, "");
+    static_assert(std::forward<const int&>(i2) == 42, "");
+    static_assert(test_constexpr_forward(), "");
+    }
+#endif
+#if TEST_STD_VER == 11 && defined(_LIBCPP_VERSION)
+    // Test that std::forward is constexpr in C++11. This is an extension
+    // provided by both libc++ and libstdc++.
+    {
+    constexpr int i2 = std::forward<int>(42);
+    static_assert(std::forward<int>(42) == 42, "" );
+    static_assert(std::forward<const int&>(i2) == 42, "");
+    }
 #endif
 }

test/std/utilities/utility/forward/forward1.fail.cpp

@@ -1,24 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is dual licensed under the MIT and the University of Illinois Open
-// Source Licenses. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-
-// test forward
-
-#include <utility>
-
-struct A
-{
-};
-
-A source() {return A();}
-const A csource() {return A();}
-
-int main()
-{
-    std::forward<A&>(source());  // error
-}

test/std/utilities/utility/forward/forward2.fail.cpp

@@ -1,25 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is dual licensed under the MIT and the University of Illinois Open
-// Source Licenses. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-
-// test forward
-
-#include <utility>
-
-struct A
-{
-};
-
-A source() {return A();}
-const A csource() {return A();}
-
-int main()
-{
-    const A ca = A();
-    std::forward<A&>(ca);  // error
-}

test/std/utilities/utility/forward/forward3.fail.cpp

@@ -1,24 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is dual licensed under the MIT and the University of Illinois Open
-// Source Licenses. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-
-// test forward
-
-#include <utility>
-
-struct A
-{
-};
-
-A source() {return A();}
-const A csource() {return A();}
-
-int main()
-{
-    std::forward<A&>(csource());  // error
-}

test/std/utilities/utility/forward/forward4.fail.cpp

@@ -1,25 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is dual licensed under the MIT and the University of Illinois Open
-// Source Licenses. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-
-// test forward
-
-#include <utility>
-
-struct A
-{
-};
-
-A source() {return A();}
-const A csource() {return A();}
-
-int main()
-{
-    const A ca = A();
-    std::forward<A>(ca);  // error
-}

test/std/utilities/utility/forward/forward5.fail.cpp

@@ -1,25 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is dual licensed under the MIT and the University of Illinois Open
-// Source Licenses. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-
-// test forward
-
-#include <utility>
-
-struct A
-{
-};
-
-A source() {return A();}
-const A csource() {return A();}
-
-int main()
-{
-    const A ca = A();
-    std::forward<A>(csource());  // error
-}

test/std/utilities/utility/forward/forward6.fail.cpp

@@ -1,22 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is dual licensed under the MIT and the University of Illinois Open
-// Source Licenses. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-
-// test forward
-
-#include <utility>
-
-struct A
-{
-};
-
-int main()
-{
-    A a;
-    std::forward(a);  // error
-}

test/std/utilities/utility/forward/forward_03.pass.cpp

@@ -0,0 +1,58 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// test forward
+
+#include <utility>
+#include <cassert>
+
+#include "test_macros.h"
+
+struct A
+{
+};
+
+A source() {return A();}
+const A csource() {return A();}
+
+typedef char one;
+struct two {one _[2];};
+struct four {one _[4];};
+struct eight {one _[8];};
+
+one test(A&);
+two test(const A&);
+
+int main()
+{
+    A a;
+    const A ca = A();
+
+    ((void)a); // Prevent unused warning
+    ((void)ca); // Prevent unused warning
+
+#if TEST_STD_VER < 11
+    static_assert(sizeof(test(std::forward<A&>(a))) == 1, "");
+    static_assert(sizeof(test(std::forward<A>(a))) == 1, "");
+
+    // Libc++'s C++03 implementation of 'forward' cannot accept true non-const
+    // rvalues.
+    // static_assert(sizeof(test(std::forward<A>(source()))) == 2, "");
+
+    static_assert(sizeof(test(std::forward<const A&>(a))) == 2, "");
+    static_assert(sizeof(test(std::forward<const A&>(source()))) == 2, "");
+    static_assert(sizeof(test(std::forward<const A>(a))) == 2, "");
+    static_assert(sizeof(test(std::forward<const A>(source()))) == 2, "");
+
+    static_assert(sizeof(test(std::forward<const A&>(ca))) == 2, "");
+    static_assert(sizeof(test(std::forward<const A&>(csource()))) == 2, "");
+    static_assert(sizeof(test(std::forward<const A>(ca))) == 2, "");
+    static_assert(sizeof(test(std::forward<const A>(csource()))) == 2, "");
+#endif
+}

test/std/utilities/utility/forward/move.fail.cpp

@@ -7,22 +7,17 @@
 //
 //===----------------------------------------------------------------------===//
 
-// test move
-
 // UNSUPPORTED: c++98, c++03
 
+// test move
+
 #include <utility>
 #include <cassert>
 
-class move_only
+struct move_only {
-{
-    move_only(const move_only&);
-    move_only& operator=(const move_only&);
-public:
-    move_only(move_only&&) {}
-    move_only& operator=(move_only&&) {return *this;}
-
     move_only() {}
+    move_only(move_only&&) = default;
+    move_only& operator=(move_only&&) = default;
 };
 
 move_only source() {return move_only();}
@@ -32,8 +27,8 @@ void test(move_only) {}
 
 int main()
 {
-    move_only mo;
+    move_only a;
+    const move_only ca = move_only();
 
-    test(std::move(mo));
+    test(std::move(ca)); // c
-    test(source());
 }

test/std/utilities/utility/forward/move.pass.cpp

@@ -0,0 +1,121 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// test move
+
+// UNSUPPORTED: c++98, c++03
+
+#include <utility>
+#include <type_traits>
+#include <cassert>
+
+#include "test_macros.h"
+
+class move_only
+{
+    move_only(const move_only&);
+    move_only& operator=(const move_only&);
+public:
+    move_only(move_only&&) {}
+    move_only& operator=(move_only&&) {return *this;}
+
+    move_only() {}
+};
+
+move_only source() {return move_only();}
+const move_only csource() {return move_only();}
+
+void test(move_only) {}
+
+int x = 42;
+const int& cx = x;
+
+template <class QualInt>
+QualInt get() noexcept { return static_cast<QualInt>(x); }
+
+
+int copy_ctor = 0;
+int move_ctor = 0;
+
+struct A {
+    A() {}
+    A(const A&) {++copy_ctor;}
+    A(A&&) {++move_ctor;}
+    A& operator=(const A&) = delete;
+};
+
+constexpr bool test_constexpr_move() {
+#if TEST_STD_VER > 11
+    int x = 42;
+    const int cx = x;
+    return std::move(x) == 42
+        && std::move(cx) == 42
+        && std::move(static_cast<int&&>(x)) == 42
+        && std::move(static_cast<int const&&>(x)) == 42;
+#else
+    return true;
+#endif
+}
+
+int main()
+{
+    { // Test return type and noexcept.
+        static_assert(std::is_same<decltype(std::move(x)), int&&>::value, "");
+        static_assert(noexcept(std::move(x)), "");
+        static_assert(std::is_same<decltype(std::move(cx)), const int&&>::value, "");
+        static_assert(noexcept(std::move(cx)), "");
+        static_assert(std::is_same<decltype(std::move(42)), int&&>::value, "");
+        static_assert(noexcept(std::move(42)), "");
+        static_assert(std::is_same<decltype(std::move(get<const int&&>())), const int&&>::value, "");
+        static_assert(noexcept(std::move(get<int const&&>())), "");
+    }
+    { // test copy and move semantics
+        A a;
+        const A ca = A();
+
+        assert(copy_ctor == 0);
+        assert(move_ctor == 0);
+
+        A a2 = a;
+        assert(copy_ctor == 1);
+        assert(move_ctor == 0);
+
+        A a3 = std::move(a);
+        assert(copy_ctor == 1);
+        assert(move_ctor == 1);
+
+        A a4 = ca;
+        assert(copy_ctor == 2);
+        assert(move_ctor == 1);
+
+        A a5 = std::move(ca);
+        assert(copy_ctor == 3);
+        assert(move_ctor == 1);
+    }
+    { // test on a move only type
+        move_only mo;
+        test(std::move(mo));
+        test(source());
+    }
+#if TEST_STD_VER > 11
+    {
+        constexpr int x = 42;
+        static_assert(std::move(x) == 42, "");
+        static_assert(test_constexpr_move(), "");
+    }
+#endif
+#if TEST_STD_VER == 11 && defined(_LIBCPP_VERSION)
+    // Test that std::forward is constexpr in C++11. This is an extension
+    // provided by both libc++ and libstdc++.
+    {
+        constexpr int x = 42;
+        static_assert(std::move(x) == 42, "");
+    }
+#endif
+}

test/std/utilities/utility/forward/move_copy.pass.cpp

@@ -1,61 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is dual licensed under the MIT and the University of Illinois Open
-// Source Licenses. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-
-// test move
-
-// UNSUPPORTED: c++98, c++03
-
-#include <utility>
-#include <cassert>
-
-int copy_ctor = 0;
-int move_ctor = 0;
-
-class A
-{
-public:
-
-    A(const A&) {++copy_ctor;}
-    A& operator=(const A&);
-
-    A(A&&) {++move_ctor;}
-    A& operator=(A&&);
-
-    A() {}
-};
-
-A source() {return A();}
-const A csource() {return A();}
-
-void test(A) {}
-
-int main()
-{
-    A a;
-    const A ca = A();
-
-    assert(copy_ctor == 0);
-    assert(move_ctor == 0);
-
-    A a2 = a;
-    assert(copy_ctor == 1);
-    assert(move_ctor == 0);
-
-    A a3 = std::move(a);
-    assert(copy_ctor == 1);
-    assert(move_ctor == 1);
-
-    A a4 = ca;
-    assert(copy_ctor == 2);
-    assert(move_ctor == 1);
-
-    A a5 = std::move(ca);
-    assert(copy_ctor == 3);
-    assert(move_ctor == 1);
-}

test/std/utilities/utility/forward/move_only1.fail.cpp

@@ -1,52 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is dual licensed under the MIT and the University of Illinois Open
-// Source Licenses. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-
-// test move
-
-#include <utility>
-#include <cassert>
-
-#include <typeinfo>
-#include <stdio.h>
-
-class move_only
-{
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    move_only(const move_only&);
-    move_only& operator=(const move_only&);
-#else  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    move_only(move_only&);
-    move_only& operator=(move_only&);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-public:
-
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    move_only(move_only&&) {}
-    move_only& operator=(move_only&&) {}
-#else  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    operator std::__rv<move_only> () {return std::__rv<move_only>(*this);}
-    move_only(std::__rv<move_only>) {}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-    move_only() {}
-};
-
-move_only source() {return move_only();}
-const move_only csource() {return move_only();}
-
-void test(move_only) {}
-
-int main()
-{
-    move_only a;
-    const move_only ca = move_only();
-
-    test(a);
-}

test/std/utilities/utility/forward/move_only2.fail.cpp

@@ -1,52 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is dual licensed under the MIT and the University of Illinois Open
-// Source Licenses. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-
-// test move
-
-#include <utility>
-#include <cassert>
-
-#include <typeinfo>
-#include <stdio.h>
-
-class move_only
-{
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    move_only(const move_only&);
-    move_only& operator=(const move_only&);
-#else  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    move_only(move_only&);
-    move_only& operator=(move_only&);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-public:
-
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    move_only(move_only&&) {}
-    move_only& operator=(move_only&&) {}
-#else  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    operator std::__rv<move_only> () {return std::__rv<move_only>(*this);}
-    move_only(std::__rv<move_only>) {}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-    move_only() {}
-};
-
-move_only source() {return move_only();}
-const move_only csource() {return move_only();}
-
-void test(move_only) {}
-
-int main()
-{
-    move_only a;
-    const move_only ca = move_only();
-
-    test(ca);
-}

test/std/utilities/utility/forward/move_only3.fail.cpp

@@ -1,49 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is dual licensed under the MIT and the University of Illinois Open
-// Source Licenses. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-
-// test move
-
-#include <utility>
-#include <cassert>
-
-class move_only
-{
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    move_only(const move_only&);
-    move_only& operator=(const move_only&);
-#else  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    move_only(move_only&);
-    move_only& operator=(move_only&);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-public:
-
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    move_only(move_only&&) {}
-    move_only& operator=(move_only&&) {}
-#else  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    operator std::__rv<move_only> () {return std::__rv<move_only>(*this);}
-    move_only(std::__rv<move_only>) {}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-    move_only() {}
-};
-
-move_only source() {return move_only();}
-const move_only csource() {return move_only();}
-
-void test(move_only) {}
-
-int main()
-{
-    move_only a;
-    const move_only ca = move_only();
-
-    test(std::move(ca));
-}

test/std/utilities/utility/forward/move_only4.fail.cpp

@@ -1,52 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is dual licensed under the MIT and the University of Illinois Open
-// Source Licenses. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-
-// test move
-
-#include <utility>
-#include <cassert>
-
-#include <typeinfo>
-#include <stdio.h>
-
-class move_only
-{
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    move_only(const move_only&);
-    move_only& operator=(const move_only&);
-#else  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    move_only(move_only&);
-    move_only& operator=(move_only&);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-public:
-
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    move_only(move_only&&) {}
-    move_only& operator=(move_only&&) {}
-#else  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    operator std::__rv<move_only> () {return std::__rv<move_only>(*this);}
-    move_only(std::__rv<move_only>) {}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-    move_only() {}
-};
-
-move_only source() {return move_only();}
-const move_only csource() {return move_only();}
-
-void test(move_only) {}
-
-int main()
-{
-    move_only a;
-    const move_only ca = move_only();
-
-    test(csource());
-}