Fix a bug in which we used propagate_on_container_copy_assignment in btree move assignment.

PiperOrigin-RevId: 565730754
Change-Id: Id828847d32c812736669803c179351433dda4aa6

absl/container/btree_test.cc

@@ -2515,14 +2515,14 @@ TEST(Btree, MoveAssignmentAllocatorPropagation) {
   InstanceTracker tracker;
 
   int64_t bytes1 = 0, bytes2 = 0;
-  PropagatingCountingAlloc<MovableOnlyInstance> allocator1(&bytes1);
-  PropagatingCountingAlloc<MovableOnlyInstance> allocator2(&bytes2);
+  MoveAssignPropagatingCountingAlloc<MovableOnlyInstance> allocator1(&bytes1);
+  MoveAssignPropagatingCountingAlloc<MovableOnlyInstance> allocator2(&bytes2);
   std::less<MovableOnlyInstance> cmp;
 
   // Test propagating allocator_type.
   {
     absl::btree_set<MovableOnlyInstance, std::less<MovableOnlyInstance>,
-                    PropagatingCountingAlloc<MovableOnlyInstance>>
+                    MoveAssignPropagatingCountingAlloc<MovableOnlyInstance>>
         set1(cmp, allocator1), set2(cmp, allocator2);
 
     for (int i = 0; i < 100; ++i) set1.insert(MovableOnlyInstance(i));

absl/container/internal/btree.h

@@ -2423,7 +2423,7 @@ auto btree<P>::operator=(btree &&other) noexcept -> btree & {
 
     using std::swap;
     if (absl::allocator_traits<
-            allocator_type>::propagate_on_container_copy_assignment::value) {
+            allocator_type>::propagate_on_container_move_assignment::value) {
       swap(root_, other.root_);
       // Note: `rightmost_` also contains the allocator and the key comparator.
       swap(rightmost_, other.rightmost_);