Check in the test for PR#24890 that I forgot in previous commit

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@248305 91177308-0d34-0410-b5e6-96231b3b80d8

test/std/utilities/utility/pairs/pairs.pair/swap.pass.cpp

@@ -16,6 +16,14 @@
 #include <utility>
 #include <cassert>
 
+struct S {
+    int i; 
+    S() : i(0) {}
+    S(int j) : i(j) {}
+    S const * operator& () const { assert(false); return this; }
+    bool operator==(int x) const { return i == x; }
+    };
+
 int main()
 {
     {
@@ -28,4 +36,14 @@ int main()
         assert(p2.first == 3);
         assert(p2.second == 4);
     }
+    {
+        typedef std::pair<int, S> P1;
+        P1 p1(3, S(4));
+        P1 p2(5, S(6));
+        p1.swap(p2);
+        assert(p1.first == 5);
+        assert(p1.second == 6);
+        assert(p2.first == 3);
+        assert(p2.second == 4);
+    }
 }