Fix move assignment from the same object

include/rcp.h

@@ -81,7 +81,7 @@ public:
 
     rcp & operator=(rcp && other) noexcept
     {
-        if (ptr != other.ptr)
+        if (this != &other)
         {
             if (ptr)
             {

tests.cpp

@@ -191,6 +191,18 @@ void test_move_assignment()
     assert(mybase_destruct == destructed_before + 1);
 }
 
+void test_move_assignment_same_object()
+{
+    MyB a = MyB::create(1, 2);
+    MyB b = a;
+    assert(a.use_count() == 2);
+    b = std::move(a);
+    assert(!a);
+    assert(b);
+    assert(b->x == 1);
+    assert(b.use_count() == 1);
+}
+
 void test_move_assignment_releases_existing()
 {
     int constructed_before = mybase_construct;
@@ -395,6 +407,7 @@ int main(int argc, char * argv[])
     test_reset();
     test_move_constructor();
     test_move_assignment();
+    test_move_assignment_same_object();
     test_move_assignment_releases_existing();
     test_upcast();
     test_move_upcast();