2 files changed, 30 insertions, 4 deletions
diff --git a/absl/container/btree_test.cc b/absl/container/btree_test.cc
index 1bfa0c20..b6c11ea1 100644
--- a/absl/container/btree_test.cc
+++ b/absl/container/btree_test.cc
@@ -55,6 +55,7 @@ using ::testing::ElementsAreArray;
 using ::testing::IsEmpty;
 using ::testing::IsNull;
 using ::testing::Pair;
+using ::testing::SizeIs;
 
 template <typename T, typename U>
 void CheckPairEquals(const T &x, const U &y) {
@@ -2109,6 +2110,31 @@ TEST(Btree, MergeIntoMultiMapsWithDifferentComparators) {
                                Pair(4, 1), Pair(4, 4), Pair(5, 5)));
 }
 
+TEST(Btree, MergeIntoSetMovableOnly) {
+  absl::btree_set<MovableOnlyInstance> src;
+  src.insert(MovableOnlyInstance(1));
+  absl::btree_multiset<MovableOnlyInstance> dst1;
+  dst1.insert(MovableOnlyInstance(2));
+  absl::btree_set<MovableOnlyInstance> dst2;
+
+  // Test merge into multiset.
+  dst1.merge(src);
+
+  EXPECT_TRUE(src.empty());
+  // ElementsAre/ElementsAreArray don't work with move-only types.
+  ASSERT_THAT(dst1, SizeIs(2));
+  EXPECT_EQ(*dst1.begin(), MovableOnlyInstance(1));
+  EXPECT_EQ(*std::next(dst1.begin()), MovableOnlyInstance(2));
+
+  // Test merge into set.
+  dst2.merge(dst1);
+
+  EXPECT_TRUE(dst1.empty());
+  ASSERT_THAT(dst2, SizeIs(2));
+  EXPECT_EQ(*dst2.begin(), MovableOnlyInstance(1));
+  EXPECT_EQ(*std::next(dst2.begin()), MovableOnlyInstance(2));
+}
+
 struct KeyCompareToWeakOrdering {
   template <typename T>
   absl::weak_ordering operator()(const T &a, const T &b) const {
diff --git a/absl/container/internal/btree_container.h b/absl/container/internal/btree_container.h
index 137614f8..279024d3 100644
--- a/absl/container/internal/btree_container.h
+++ b/absl/container/internal/btree_container.h
@@ -151,7 +151,6 @@ class btree_container {
     return extract(iterator(position));
   }
 
- public:
   // Utility routines.
   void clear() { tree_.clear(); }
   void swap(btree_container &other) { tree_.swap(other.tree_); }
@@ -344,7 +343,7 @@ class btree_set_container : public btree_container<Tree> {
           int> = 0>
   void merge(btree_container<T> &src) {  // NOLINT
     for (auto src_it = src.begin(); src_it != src.end();) {
-      if (insert(std::move(*src_it)).second) {
+      if (insert(std::move(params_type::element(src_it.slot()))).second) {
         src_it = src.erase(src_it);
       } else {
         ++src_it;
@@ -627,8 +626,9 @@ class btree_multiset_container : public btree_container<Tree> {
                            typename T::params_type::is_map_container>>::value,
           int> = 0>
   void merge(btree_container<T> &src) {  // NOLINT
-    insert(std::make_move_iterator(src.begin()),
-           std::make_move_iterator(src.end()));
+    for (auto src_it = src.begin(), end = src.end(); src_it != end; ++src_it) {
+      insert(std::move(params_type::element(src_it.slot())));
+    }
     src.clear();
   }