Add is_swappable/is_nothrow_swappable traits

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@267079 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/utilities/utility/utility.swap/swap_array.pass.cpp

@@ -16,50 +16,86 @@
 
 #include <utility>
 #include <cassert>
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 #include <memory>
+
+#include "test_macros.h"
+
+
+#if TEST_STD_VER >= 11
+struct CopyOnly {
+    CopyOnly() {}
+    CopyOnly(CopyOnly const&) noexcept {}
+    CopyOnly& operator=(CopyOnly const&) { return *this; }
+};
+
+
+struct NoexceptMoveOnly {
+    NoexceptMoveOnly() {}
+    NoexceptMoveOnly(NoexceptMoveOnly&&) noexcept {}
+    NoexceptMoveOnly& operator=(NoexceptMoveOnly&&) noexcept { return *this; }
+};
+
+struct NotMoveConstructible {
+    NotMoveConstructible() {}
+    NotMoveConstructible& operator=(NotMoveConstructible&&) { return *this; }
+private:
+    NotMoveConstructible(NotMoveConstructible&&);
+};
+
+template <class Tp>
+auto can_swap_test(int) -> decltype(std::swap(std::declval<Tp>(), std::declval<Tp>()));
+
+template <class Tp>
+auto can_swap_test(...) -> std::false_type;
+
+template <class Tp>
+constexpr bool can_swap() {
+    return std::is_same<decltype(can_swap_test<Tp>(0)), void>::value;
+}
 #endif
 
-void
-test()
-{
-    int i[3] = {1, 2, 3};
-    int j[3] = {4, 5, 6};
-    std::swap(i, j);
-    assert(i[0] == 4);
-    assert(i[1] == 5);
-    assert(i[2] == 6);
-    assert(j[0] == 1);
-    assert(j[1] == 2);
-    assert(j[2] == 3);
-}
-
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-void
-test1()
-{
-    std::unique_ptr<int> i[3];
-    for (int k = 0; k < 3; ++k)
-        i[k].reset(new int(k+1));
-    std::unique_ptr<int> j[3];
-    for (int k = 0; k < 3; ++k)
-        j[k].reset(new int(k+4));
-    std::swap(i, j);
-    assert(*i[0] == 4);
-    assert(*i[1] == 5);
-    assert(*i[2] == 6);
-    assert(*j[0] == 1);
-    assert(*j[1] == 2);
-    assert(*j[2] == 3);
-}
-
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 
 int main()
 {
-    test();
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    test1();
+    {
+        int i[3] = {1, 2, 3};
+        int j[3] = {4, 5, 6};
+        std::swap(i, j);
+        assert(i[0] == 4);
+        assert(i[1] == 5);
+        assert(i[2] == 6);
+        assert(j[0] == 1);
+        assert(j[1] == 2);
+        assert(j[2] == 3);
+    }
+#if TEST_STD_VER >= 11
+    {
+        std::unique_ptr<int> i[3];
+        for (int k = 0; k < 3; ++k)
+            i[k].reset(new int(k+1));
+        std::unique_ptr<int> j[3];
+        for (int k = 0; k < 3; ++k)
+            j[k].reset(new int(k+4));
+        std::swap(i, j);
+        assert(*i[0] == 4);
+        assert(*i[1] == 5);
+        assert(*i[2] == 6);
+        assert(*j[0] == 1);
+        assert(*j[1] == 2);
+        assert(*j[2] == 3);
+    }
+    {
+        using CA = CopyOnly[42];
+        using MA = NoexceptMoveOnly[42];
+        using NA = NotMoveConstructible[42];
+        static_assert(can_swap<CA&>(), "");
+        static_assert(can_swap<MA&>(), "");
+        static_assert(!can_swap<NA&>(), "");
+
+        CA ca;
+        MA ma;
+        static_assert(!noexcept(std::swap(ca, ca)), "");
+        static_assert(noexcept(std::swap(ma, ma)), "");
+    }
 #endif
 }