1 files changed, 34 insertions, 22 deletions
diff --git a/libcxx/include/__algorithm/ranges_inplace_merge.h b/libcxx/include/__algorithm/ranges_inplace_merge.h
index a0867e486c3a..88171a65c8e9 100644
--- a/libcxx/include/__algorithm/ranges_inplace_merge.h
+++ b/libcxx/include/__algorithm/ranges_inplace_merge.h
@@ -10,6 +10,7 @@
 #define _LIBCPP___ALGORITHM_RANGES_INPLACE_MERGE_H
 
 #include <__algorithm/inplace_merge.h>
+#include <__algorithm/iterator_operations.h>
 #include <__algorithm/make_projected.h>
 #include <__config>
 #include <__functional/identity.h>
@@ -17,6 +18,7 @@
 #include <__functional/ranges_operations.h>
 #include <__iterator/concepts.h>
 #include <__iterator/iterator_traits.h>
+#include <__iterator/next.h>
 #include <__iterator/projected.h>
 #include <__iterator/sortable.h>
 #include <__ranges/access.h>
@@ -29,35 +31,45 @@
 #  pragma GCC system_header
 #endif
 
-#if _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
+#if _LIBCPP_STD_VER > 17
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 namespace ranges {
 namespace __inplace_merge {
 
-struct __fn {
+  struct __fn {
+    template <class _Iter, class _Sent, class _Comp, class _Proj>
+    _LIBCPP_HIDE_FROM_ABI static constexpr auto
+    __inplace_merge_impl(_Iter __first, _Iter __middle, _Sent __last, _Comp&& __comp, _Proj&& __proj) {
+      auto __last_iter = ranges::next(__middle, __last);
+      std::__inplace_merge<_RangeAlgPolicy>(
+          std::move(__first), std::move(__middle), __last_iter, std::__make_projected(__comp, __proj));
+      return __last_iter;
+    }
 
-  template <bidirectional_iterator _Iter, sentinel_for<_Iter> _Sent, class _Comp = ranges::less, class _Proj = identity>
-  requires sortable<_Iter, _Comp, _Proj>
-  _LIBCPP_HIDE_FROM_ABI
-  _Iter operator()(_Iter __first, _Iter __middle, _Sent __last, _Comp __comp = {}, _Proj __proj = {}) const {
-    // TODO: implement
-    (void)__first; (void)__middle; (void)__last; (void)__comp; (void)__proj;
-    return {};
-  }
+    template <
+        bidirectional_iterator _Iter,
+        sentinel_for<_Iter> _Sent,
+        class _Comp = ranges::less,
+        class _Proj = identity>
+      requires sortable<_Iter, _Comp, _Proj>
+    _LIBCPP_HIDE_FROM_ABI _Iter
+    operator()(_Iter __first, _Iter __middle, _Sent __last, _Comp __comp = {}, _Proj __proj = {}) const {
+      return __inplace_merge_impl(
+          std::move(__first), std::move(__middle), std::move(__last), std::move(__comp), std::move(__proj));
+    }
 
-  template <bidirectional_range _Range, class _Comp = ranges::less, class _Proj = identity>
-  requires sortable<iterator_t<_Range>, _Comp, _Proj>
-  _LIBCPP_HIDE_FROM_ABI
-  borrowed_iterator_t<_Range> operator()(_Range&& __range, iterator_t<_Range> __middle,
-                                            _Comp __comp = {}, _Proj __proj = {}) const {
-    // TODO: implement
-    (void)__range; (void)__middle; (void)__comp; (void)__proj;
-    return {};
-  }
-
-};
+    template <bidirectional_range _Range, class _Comp = ranges::less, class _Proj = identity>
+      requires sortable<
+          iterator_t<_Range>,
+          _Comp,
+          _Proj> _LIBCPP_HIDE_FROM_ABI borrowed_iterator_t<_Range>
+      operator()(_Range&& __range, iterator_t<_Range> __middle, _Comp __comp = {}, _Proj __proj = {}) const {
+      return __inplace_merge_impl(
+          ranges::begin(__range), std::move(__middle), ranges::end(__range), std::move(__comp), std::move(__proj));
+    }
+  };
 
 } // namespace __inplace_merge
 
@@ -68,6 +80,6 @@ inline namespace __cpo {
 
 _LIBCPP_END_NAMESPACE_STD
 
-#endif // _LIBCPP_STD_VER > 17 && !defined(_LIBCPP_HAS_NO_INCOMPLETE_RANGES)
+#endif // _LIBCPP_STD_VER > 17
 
 #endif // _LIBCPP___ALGORITHM_RANGES_INPLACE_MERGE_H