https://github.com/philnik777 created 
https://github.com/llvm/llvm-project/pull/155565

This reverts commit 72c04bb882ad70230bce309c3013d9cc2c99e9a7.


>From d6988b99004c3c4c53f4d0c100f6cd8b94b7fefa Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklau...@berlin.de>
Date: Wed, 27 Aug 2025 08:57:17 +0200
Subject: [PATCH] Reapply "[libc++] Refactor key extraction for __hash_table
 and __tree (#154512)"

This reverts commit 72c04bb882ad70230bce309c3013d9cc2c99e9a7.
---
 libcxx/include/CMakeLists.txt                 |   2 +-
 libcxx/include/__fwd/tuple.h                  |   6 +
 libcxx/include/__hash_table                   | 168 ++++++---------
 libcxx/include/__tree                         | 199 +++++-------------
 .../include/__type_traits/can_extract_key.h   |  53 -----
 libcxx/include/__utility/try_key_extraction.h | 114 ++++++++++
 libcxx/include/map                            |  38 ++--
 libcxx/include/module.modulemap.in            |   2 +-
 libcxx/include/set                            |   6 +-
 libcxx/include/tuple                          |   6 -
 libcxx/include/unordered_map                  |  18 +-
 .../associative/multiset/emplace.pass.cpp     |  10 +-
 .../associative/set/emplace.pass.cpp          |  11 +-
 .../unord/unord.multiset/emplace.pass.cpp     |  13 +-
 .../unord/unord.set/emplace.pass.cpp          |  14 +-
 .../TestLibcxxInternalsRecognizer.py          |   1 +
 16 files changed, 309 insertions(+), 352 deletions(-)
 delete mode 100644 libcxx/include/__type_traits/can_extract_key.h
 create mode 100644 libcxx/include/__utility/try_key_extraction.h

diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index c6b87a34a43e9..6fd16419f0c49 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -792,7 +792,6 @@ set(files
   __type_traits/aligned_storage.h
   __type_traits/aligned_union.h
   __type_traits/alignment_of.h
-  __type_traits/can_extract_key.h
   __type_traits/common_reference.h
   __type_traits/common_type.h
   __type_traits/conditional.h
@@ -933,6 +932,7 @@ set(files
   __utility/small_buffer.h
   __utility/swap.h
   __utility/to_underlying.h
+  __utility/try_key_extraction.h
   __utility/unreachable.h
   __variant/monostate.h
   __vector/comparison.h
diff --git a/libcxx/include/__fwd/tuple.h b/libcxx/include/__fwd/tuple.h
index 39ed94d9806e5..b3cac4e2a633d 100644
--- a/libcxx/include/__fwd/tuple.h
+++ b/libcxx/include/__fwd/tuple.h
@@ -26,6 +26,12 @@ struct tuple_element;
 template <class...>
 class tuple;
 
+template <class>
+inline const bool __is_tuple_v = false;
+
+template <class... _Tp>
+inline const bool __is_tuple_v<tuple<_Tp...>> = true;
+
 template <size_t _Ip, class... _Tp>
 struct tuple_element<_Ip, tuple<_Tp...> > {
   using type _LIBCPP_NODEBUG = __type_pack_element<_Ip, _Tp...>;
diff --git a/libcxx/include/__hash_table b/libcxx/include/__hash_table
index f0f335a4d5cab..91f660d3491e8 100644
--- a/libcxx/include/__hash_table
+++ b/libcxx/include/__hash_table
@@ -29,7 +29,6 @@
 #include <__memory/swap_allocator.h>
 #include <__memory/unique_ptr.h>
 #include <__new/launder.h>
-#include <__type_traits/can_extract_key.h>
 #include <__type_traits/copy_cvref.h>
 #include <__type_traits/enable_if.h>
 #include <__type_traits/invoke.h>
@@ -46,6 +45,7 @@
 #include <__utility/move.h>
 #include <__utility/pair.h>
 #include <__utility/swap.h>
+#include <__utility/try_key_extraction.h>
 #include <limits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -797,40 +797,66 @@ public:
   _LIBCPP_HIDE_FROM_ABI iterator __node_insert_multi(__node_pointer __nd);
   _LIBCPP_HIDE_FROM_ABI iterator __node_insert_multi(const_iterator __p, 
__node_pointer __nd);
 
-  template <class _Key, class... _Args>
-  _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> __emplace_unique_key_args(_Key 
const& __k, _Args&&... __args);
-
-  template <class... _Args>
-  _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> __emplace_unique_impl(_Args&&... 
__args);
-
-  template <class _Pp>
-  _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> __emplace_unique(_Pp&& __x) {
-    return __emplace_unique_extract_key(std::forward<_Pp>(__x), 
__can_extract_key<_Pp, key_type>());
-  }
-
-  template <class _First,
-            class _Second,
-            __enable_if_t<__can_extract_map_key<_First, key_type, 
value_type>::value, int> = 0>
-  _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> __emplace_unique(_First&& __f, 
_Second&& __s) {
-    return __emplace_unique_key_args(__f, std::forward<_First>(__f), 
std::forward<_Second>(__s));
-  }
-
   template <class... _Args>
   _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> __emplace_unique(_Args&&... 
__args) {
-    return __emplace_unique_impl(std::forward<_Args>(__args)...);
-  }
-
-  template <class _Pp>
-  _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> 
__emplace_unique_extract_key(_Pp&& __x, __extract_key_fail_tag) {
-    return __emplace_unique_impl(std::forward<_Pp>(__x));
-  }
-  template <class _Pp>
-  _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> 
__emplace_unique_extract_key(_Pp&& __x, __extract_key_self_tag) {
-    return __emplace_unique_key_args(__x, std::forward<_Pp>(__x));
-  }
-  template <class _Pp>
-  _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> 
__emplace_unique_extract_key(_Pp&& __x, __extract_key_first_tag) {
-    return __emplace_unique_key_args(__x.first, std::forward<_Pp>(__x));
+    return std::__try_key_extraction<key_type>(
+        [this](const key_type& __key, _Args&&... __args2) {
+          size_t __hash   = hash_function()(__key);
+          size_type __bc  = bucket_count();
+          bool __inserted = false;
+          __next_pointer __nd;
+          size_t __chash;
+          if (__bc != 0) {
+            __chash = std::__constrain_hash(__hash, __bc);
+            __nd    = __bucket_list_[__chash];
+            if (__nd != nullptr) {
+              for (__nd = __nd->__next_;
+                   __nd != nullptr &&
+                   (__nd->__hash() == __hash || 
std::__constrain_hash(__nd->__hash(), __bc) == __chash);
+                   __nd = __nd->__next_) {
+                if ((__nd->__hash() == __hash) && 
key_eq()(__nd->__upcast()->__get_value(), __key))
+                  goto __done;
+              }
+            }
+          }
+          {
+            __node_holder __h = __construct_node_hash(__hash, 
std::forward<_Args>(__args2)...);
+            if (size() + 1 > __bc * max_load_factor() || __bc == 0) {
+              __rehash_unique(std::max<size_type>(2 * __bc + 
!std::__is_hash_power2(__bc),
+                                                  
size_type(__math::ceil(float(size() + 1) / max_load_factor()))));
+              __bc    = bucket_count();
+              __chash = std::__constrain_hash(__hash, __bc);
+            }
+            // insert_after __bucket_list_[__chash], or __first_node if bucket 
is null
+            __next_pointer __pn = __bucket_list_[__chash];
+            if (__pn == nullptr) {
+              __pn          = __first_node_.__ptr();
+              __h->__next_  = __pn->__next_;
+              __pn->__next_ = __h.get()->__ptr();
+              // fix up __bucket_list_
+              __bucket_list_[__chash] = __pn;
+              if (__h->__next_ != nullptr)
+                __bucket_list_[std::__constrain_hash(__h->__next_->__hash(), 
__bc)] = __h.get()->__ptr();
+            } else {
+              __h->__next_  = __pn->__next_;
+              __pn->__next_ = static_cast<__next_pointer>(__h.get());
+            }
+            __nd = static_cast<__next_pointer>(__h.release());
+            // increment size
+            ++size();
+            __inserted = true;
+          }
+        __done:
+          return pair<iterator, bool>(iterator(__nd), __inserted);
+        },
+        [this](_Args&&... __args2) {
+          __node_holder __h        = 
__construct_node(std::forward<_Args>(__args2)...);
+          pair<iterator, bool> __r = __node_insert_unique(__h.get());
+          if (__r.second)
+            __h.release();
+          return __r;
+        },
+        std::forward<_Args>(__args)...);
   }
 
   template <class... _Args>
@@ -999,8 +1025,8 @@ private:
   template <class... _Args>
   _LIBCPP_HIDE_FROM_ABI __node_holder __construct_node(_Args&&... __args);
 
-  template <class _First, class... _Rest>
-  _LIBCPP_HIDE_FROM_ABI __node_holder __construct_node_hash(size_t __hash, 
_First&& __f, _Rest&&... __rest);
+  template <class... _Args>
+  _LIBCPP_HIDE_FROM_ABI __node_holder __construct_node_hash(size_t __hash, 
_Args&&... __args);
 
   _LIBCPP_HIDE_FROM_ABI void __copy_assign_alloc(const __hash_table& __u) {
     __copy_assign_alloc(__u, integral_constant<bool, 
__node_traits::propagate_on_container_copy_assignment::value>());
@@ -1614,69 +1640,6 @@ __hash_table<_Tp, _Hash, _Equal, 
_Alloc>::__node_insert_multi(const_iterator __p
   return __node_insert_multi(__cp);
 }
 
-template <class _Tp, class _Hash, class _Equal, class _Alloc>
-template <class _Key, class... _Args>
-pair<typename __hash_table<_Tp, _Hash, _Equal, _Alloc>::iterator, bool>
-__hash_table<_Tp, _Hash, _Equal, _Alloc>::__emplace_unique_key_args(_Key 
const& __k, _Args&&... __args) {
-  size_t __hash   = hash_function()(__k);
-  size_type __bc  = bucket_count();
-  bool __inserted = false;
-  __next_pointer __nd;
-  size_t __chash;
-  if (__bc != 0) {
-    __chash = std::__constrain_hash(__hash, __bc);
-    __nd    = __bucket_list_[__chash];
-    if (__nd != nullptr) {
-      for (__nd = __nd->__next_;
-           __nd != nullptr && (__nd->__hash() == __hash || 
std::__constrain_hash(__nd->__hash(), __bc) == __chash);
-           __nd = __nd->__next_) {
-        if ((__nd->__hash() == __hash) && 
key_eq()(__nd->__upcast()->__get_value(), __k))
-          goto __done;
-      }
-    }
-  }
-  {
-    __node_holder __h = __construct_node_hash(__hash, 
std::forward<_Args>(__args)...);
-    if (size() + 1 > __bc * max_load_factor() || __bc == 0) {
-      __rehash_unique(std::max<size_type>(
-          2 * __bc + !std::__is_hash_power2(__bc), 
size_type(__math::ceil(float(size() + 1) / max_load_factor()))));
-      __bc    = bucket_count();
-      __chash = std::__constrain_hash(__hash, __bc);
-    }
-    // insert_after __bucket_list_[__chash], or __first_node if bucket is null
-    __next_pointer __pn = __bucket_list_[__chash];
-    if (__pn == nullptr) {
-      __pn          = __first_node_.__ptr();
-      __h->__next_  = __pn->__next_;
-      __pn->__next_ = __h.get()->__ptr();
-      // fix up __bucket_list_
-      __bucket_list_[__chash] = __pn;
-      if (__h->__next_ != nullptr)
-        __bucket_list_[std::__constrain_hash(__h->__next_->__hash(), __bc)] = 
__h.get()->__ptr();
-    } else {
-      __h->__next_  = __pn->__next_;
-      __pn->__next_ = static_cast<__next_pointer>(__h.get());
-    }
-    __nd = static_cast<__next_pointer>(__h.release());
-    // increment size
-    ++size();
-    __inserted = true;
-  }
-__done:
-  return pair<iterator, bool>(iterator(__nd), __inserted);
-}
-
-template <class _Tp, class _Hash, class _Equal, class _Alloc>
-template <class... _Args>
-pair<typename __hash_table<_Tp, _Hash, _Equal, _Alloc>::iterator, bool>
-__hash_table<_Tp, _Hash, _Equal, _Alloc>::__emplace_unique_impl(_Args&&... 
__args) {
-  __node_holder __h        = __construct_node(std::forward<_Args>(__args)...);
-  pair<iterator, bool> __r = __node_insert_unique(__h.get());
-  if (__r.second)
-    __h.release();
-  return __r;
-}
-
 template <class _Tp, class _Hash, class _Equal, class _Alloc>
 template <class... _Args>
 typename __hash_table<_Tp, _Hash, _Equal, _Alloc>::iterator
@@ -1928,15 +1891,14 @@ __hash_table<_Tp, _Hash, _Equal, 
_Alloc>::__construct_node(_Args&&... __args) {
 }
 
 template <class _Tp, class _Hash, class _Equal, class _Alloc>
-template <class _First, class... _Rest>
+template <class... _Args>
 typename __hash_table<_Tp, _Hash, _Equal, _Alloc>::__node_holder
-__hash_table<_Tp, _Hash, _Equal, _Alloc>::__construct_node_hash(size_t __hash, 
_First&& __f, _Rest&&... __rest) {
-  static_assert(!__is_hash_value_type<_First, _Rest...>::value, "Construct 
cannot be called with a hash value type");
+__hash_table<_Tp, _Hash, _Equal, _Alloc>::__construct_node_hash(size_t __hash, 
_Args&&... __args) {
+  static_assert(!__is_hash_value_type<_Args...>::value, "Construct cannot be 
called with a hash value type");
   __node_allocator& __na = __node_alloc();
   __node_holder __h(__node_traits::allocate(__na, 1), _Dp(__na));
   std::__construct_at(std::addressof(*__h), /* next = */ nullptr, /* hash = */ 
__hash);
-  __node_traits::construct(
-      __na, std::addressof(__h->__get_value()), std::forward<_First>(__f), 
std::forward<_Rest>(__rest)...);
+  __node_traits::construct(__na, std::addressof(__h->__get_value()), 
std::forward<_Args>(__args)...);
   __h.get_deleter().__value_constructed = true;
   return __h;
 }
diff --git a/libcxx/include/__tree b/libcxx/include/__tree
index 0f3640ef6a834..3ad2129ba9ddf 100644
--- a/libcxx/include/__tree
+++ b/libcxx/include/__tree
@@ -23,7 +23,6 @@
 #include <__memory/pointer_traits.h>
 #include <__memory/swap_allocator.h>
 #include <__memory/unique_ptr.h>
-#include <__type_traits/can_extract_key.h>
 #include <__type_traits/copy_cvref.h>
 #include <__type_traits/enable_if.h>
 #include <__type_traits/invoke.h>
@@ -38,6 +37,7 @@
 #include <__utility/move.h>
 #include <__utility/pair.h>
 #include <__utility/swap.h>
+#include <__utility/try_key_extraction.h>
 #include <limits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -900,88 +900,74 @@ public:
       _NOEXCEPT_(__is_nothrow_swappable_v<value_compare>);
 #endif
 
-  template <class _Key, class... _Args>
-  _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> __emplace_unique_key_args(_Key 
const&, _Args&&... __args);
-  template <class _Key, class... _Args>
-  _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> 
__emplace_hint_unique_key_args(const_iterator, _Key const&, _Args&&...);
-
-  template <class... _Args>
-  _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> __emplace_unique_impl(_Args&&... 
__args);
-
-  template <class... _Args>
-  _LIBCPP_HIDE_FROM_ABI iterator __emplace_hint_unique_impl(const_iterator 
__p, _Args&&... __args);
-
   template <class... _Args>
   _LIBCPP_HIDE_FROM_ABI iterator __emplace_multi(_Args&&... __args);
 
   template <class... _Args>
   _LIBCPP_HIDE_FROM_ABI iterator __emplace_hint_multi(const_iterator __p, 
_Args&&... __args);
 
-  template <class _Pp>
-  _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> __emplace_unique(_Pp&& __x) {
-    return __emplace_unique_extract_key(std::forward<_Pp>(__x), 
__can_extract_key<_Pp, key_type>());
-  }
-
-  template <class _First,
-            class _Second,
-            __enable_if_t<__can_extract_map_key<_First, key_type, 
value_type>::value, int> = 0>
-  _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> __emplace_unique(_First&& __f, 
_Second&& __s) {
-    return __emplace_unique_key_args(__f, std::forward<_First>(__f), 
std::forward<_Second>(__s));
-  }
-
   template <class... _Args>
   _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> __emplace_unique(_Args&&... 
__args) {
-    return __emplace_unique_impl(std::forward<_Args>(__args)...);
-  }
-
-  template <class _Pp>
-  _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> 
__emplace_unique_extract_key(_Pp&& __x, __extract_key_fail_tag) {
-    return __emplace_unique_impl(std::forward<_Pp>(__x));
-  }
-
-  template <class _Pp>
-  _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> 
__emplace_unique_extract_key(_Pp&& __x, __extract_key_self_tag) {
-    return __emplace_unique_key_args(__x, std::forward<_Pp>(__x));
-  }
-
-  template <class _Pp>
-  _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> 
__emplace_unique_extract_key(_Pp&& __x, __extract_key_first_tag) {
-    return __emplace_unique_key_args(__x.first, std::forward<_Pp>(__x));
-  }
-
-  template <class _Pp>
-  _LIBCPP_HIDE_FROM_ABI iterator __emplace_hint_unique(const_iterator __p, 
_Pp&& __x) {
-    return __emplace_hint_unique_extract_key(__p, std::forward<_Pp>(__x), 
__can_extract_key<_Pp, key_type>());
-  }
-
-  template <class _First,
-            class _Second,
-            __enable_if_t<__can_extract_map_key<_First, key_type, 
value_type>::value, int> = 0>
-  _LIBCPP_HIDE_FROM_ABI iterator __emplace_hint_unique(const_iterator __p, 
_First&& __f, _Second&& __s) {
-    return __emplace_hint_unique_key_args(__p, __f, std::forward<_First>(__f), 
std::forward<_Second>(__s)).first;
+    return std::__try_key_extraction<key_type>(
+        [this](const key_type& __key, _Args&&... __args2) {
+          __end_node_pointer __parent;
+          __node_base_pointer& __child = __find_equal(__parent, __key);
+          __node_pointer __r           = static_cast<__node_pointer>(__child);
+          bool __inserted              = false;
+          if (__child == nullptr) {
+            __node_holder __h = 
__construct_node(std::forward<_Args>(__args2)...);
+            __insert_node_at(__parent, __child, 
static_cast<__node_base_pointer>(__h.get()));
+            __r        = __h.release();
+            __inserted = true;
+          }
+          return pair<iterator, bool>(iterator(__r), __inserted);
+        },
+        [this](_Args&&... __args2) {
+          __node_holder __h = 
__construct_node(std::forward<_Args>(__args2)...);
+          __end_node_pointer __parent;
+          __node_base_pointer& __child = __find_equal(__parent, 
__h->__get_value());
+          __node_pointer __r           = static_cast<__node_pointer>(__child);
+          bool __inserted              = false;
+          if (__child == nullptr) {
+            __insert_node_at(__parent, __child, 
static_cast<__node_base_pointer>(__h.get()));
+            __r        = __h.release();
+            __inserted = true;
+          }
+          return pair<iterator, bool>(iterator(__r), __inserted);
+        },
+        std::forward<_Args>(__args)...);
   }
 
   template <class... _Args>
-  _LIBCPP_HIDE_FROM_ABI iterator __emplace_hint_unique(const_iterator __p, 
_Args&&... __args) {
-    return __emplace_hint_unique_impl(__p, std::forward<_Args>(__args)...);
-  }
-
-  template <class _Pp>
-  _LIBCPP_HIDE_FROM_ABI iterator
-  __emplace_hint_unique_extract_key(const_iterator __p, _Pp&& __x, 
__extract_key_fail_tag) {
-    return __emplace_hint_unique_impl(__p, std::forward<_Pp>(__x));
-  }
-
-  template <class _Pp>
-  _LIBCPP_HIDE_FROM_ABI iterator
-  __emplace_hint_unique_extract_key(const_iterator __p, _Pp&& __x, 
__extract_key_self_tag) {
-    return __emplace_hint_unique_key_args(__p, __x, 
std::forward<_Pp>(__x)).first;
-  }
-
-  template <class _Pp>
-  _LIBCPP_HIDE_FROM_ABI iterator
-  __emplace_hint_unique_extract_key(const_iterator __p, _Pp&& __x, 
__extract_key_first_tag) {
-    return __emplace_hint_unique_key_args(__p, __x.first, 
std::forward<_Pp>(__x)).first;
+  _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> 
__emplace_hint_unique(const_iterator __p, _Args&&... __args) {
+    return std::__try_key_extraction<key_type>(
+        [this, __p](const key_type& __key, _Args&&... __args2) {
+          __end_node_pointer __parent;
+          __node_base_pointer __dummy;
+          __node_base_pointer& __child = __find_equal(__p, __parent, __dummy, 
__key);
+          __node_pointer __r           = static_cast<__node_pointer>(__child);
+          bool __inserted              = false;
+          if (__child == nullptr) {
+            __node_holder __h = 
__construct_node(std::forward<_Args>(__args2)...);
+            __insert_node_at(__parent, __child, 
static_cast<__node_base_pointer>(__h.get()));
+            __r        = __h.release();
+            __inserted = true;
+          }
+          return pair<iterator, bool>(iterator(__r), __inserted);
+        },
+        [this, __p](_Args&&... __args2) {
+          __node_holder __h = 
__construct_node(std::forward<_Args>(__args2)...);
+          __end_node_pointer __parent;
+          __node_base_pointer __dummy;
+          __node_base_pointer& __child = __find_equal(__p, __parent, __dummy, 
__h->__get_value());
+          __node_pointer __r           = static_cast<__node_pointer>(__child);
+          if (__child == nullptr) {
+            __insert_node_at(__parent, __child, 
static_cast<__node_base_pointer>(__h.get()));
+            __r = __h.release();
+          }
+          return pair<iterator, bool>(iterator(__r), __child == nullptr);
+        },
+        std::forward<_Args>(__args)...);
   }
 
   template <class _ValueT = _Tp, 
__enable_if_t<__is_tree_value_type_v<_ValueT>, int> = 0>
@@ -1801,42 +1787,6 @@ void __tree<_Tp, _Compare, _Allocator>::__insert_node_at(
   ++__size_;
 }
 
-template <class _Tp, class _Compare, class _Allocator>
-template <class _Key, class... _Args>
-pair<typename __tree<_Tp, _Compare, _Allocator>::iterator, bool>
-__tree<_Tp, _Compare, _Allocator>::__emplace_unique_key_args(_Key const& __k, 
_Args&&... __args) {
-  __end_node_pointer __parent;
-  __node_base_pointer& __child = __find_equal(__parent, __k);
-  __node_pointer __r           = static_cast<__node_pointer>(__child);
-  bool __inserted              = false;
-  if (__child == nullptr) {
-    __node_holder __h = __construct_node(std::forward<_Args>(__args)...);
-    __insert_node_at(__parent, __child, 
static_cast<__node_base_pointer>(__h.get()));
-    __r        = __h.release();
-    __inserted = true;
-  }
-  return pair<iterator, bool>(iterator(__r), __inserted);
-}
-
-template <class _Tp, class _Compare, class _Allocator>
-template <class _Key, class... _Args>
-pair<typename __tree<_Tp, _Compare, _Allocator>::iterator, bool>
-__tree<_Tp, _Compare, _Allocator>::__emplace_hint_unique_key_args(
-    const_iterator __p, _Key const& __k, _Args&&... __args) {
-  __end_node_pointer __parent;
-  __node_base_pointer __dummy;
-  __node_base_pointer& __child = __find_equal(__p, __parent, __dummy, __k);
-  __node_pointer __r           = static_cast<__node_pointer>(__child);
-  bool __inserted              = false;
-  if (__child == nullptr) {
-    __node_holder __h = __construct_node(std::forward<_Args>(__args)...);
-    __insert_node_at(__parent, __child, 
static_cast<__node_base_pointer>(__h.get()));
-    __r        = __h.release();
-    __inserted = true;
-  }
-  return pair<iterator, bool>(iterator(__r), __inserted);
-}
-
 template <class _Tp, class _Compare, class _Allocator>
 template <class... _Args>
 typename __tree<_Tp, _Compare, _Allocator>::__node_holder
@@ -1848,39 +1798,6 @@ __tree<_Tp, _Compare, 
_Allocator>::__construct_node(_Args&&... __args) {
   return __h;
 }
 
-template <class _Tp, class _Compare, class _Allocator>
-template <class... _Args>
-pair<typename __tree<_Tp, _Compare, _Allocator>::iterator, bool>
-__tree<_Tp, _Compare, _Allocator>::__emplace_unique_impl(_Args&&... __args) {
-  __node_holder __h = __construct_node(std::forward<_Args>(__args)...);
-  __end_node_pointer __parent;
-  __node_base_pointer& __child = __find_equal(__parent, __h->__get_value());
-  __node_pointer __r           = static_cast<__node_pointer>(__child);
-  bool __inserted              = false;
-  if (__child == nullptr) {
-    __insert_node_at(__parent, __child, 
static_cast<__node_base_pointer>(__h.get()));
-    __r        = __h.release();
-    __inserted = true;
-  }
-  return pair<iterator, bool>(iterator(__r), __inserted);
-}
-
-template <class _Tp, class _Compare, class _Allocator>
-template <class... _Args>
-typename __tree<_Tp, _Compare, _Allocator>::iterator
-__tree<_Tp, _Compare, _Allocator>::__emplace_hint_unique_impl(const_iterator 
__p, _Args&&... __args) {
-  __node_holder __h = __construct_node(std::forward<_Args>(__args)...);
-  __end_node_pointer __parent;
-  __node_base_pointer __dummy;
-  __node_base_pointer& __child = __find_equal(__p, __parent, __dummy, 
__h->__get_value());
-  __node_pointer __r           = static_cast<__node_pointer>(__child);
-  if (__child == nullptr) {
-    __insert_node_at(__parent, __child, 
static_cast<__node_base_pointer>(__h.get()));
-    __r = __h.release();
-  }
-  return iterator(__r);
-}
-
 template <class _Tp, class _Compare, class _Allocator>
 template <class... _Args>
 typename __tree<_Tp, _Compare, _Allocator>::iterator
diff --git a/libcxx/include/__type_traits/can_extract_key.h 
b/libcxx/include/__type_traits/can_extract_key.h
deleted file mode 100644
index b8359d0708810..0000000000000
--- a/libcxx/include/__type_traits/can_extract_key.h
+++ /dev/null
@@ -1,53 +0,0 @@
-//===----------------------------------------------------------------------===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef _LIBCPP___TYPE_TRAITS_CAN_EXTRACT_KEY_H
-#define _LIBCPP___TYPE_TRAITS_CAN_EXTRACT_KEY_H
-
-#include <__config>
-#include <__fwd/pair.h>
-#include <__type_traits/conditional.h>
-#include <__type_traits/integral_constant.h>
-#include <__type_traits/is_same.h>
-#include <__type_traits/remove_const.h>
-#include <__type_traits/remove_const_ref.h>
-
-#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#  pragma GCC system_header
-#endif
-
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-// These traits are used in __tree and __hash_table
-struct __extract_key_fail_tag {};
-struct __extract_key_self_tag {};
-struct __extract_key_first_tag {};
-
-template <class _ValTy, class _Key, class _RawValTy = 
__remove_const_ref_t<_ValTy> >
-struct __can_extract_key
-    : __conditional_t<_IsSame<_RawValTy, _Key>::value, __extract_key_self_tag, 
__extract_key_fail_tag> {};
-
-template <class _Pair, class _Key, class _First, class _Second>
-struct __can_extract_key<_Pair, _Key, pair<_First, _Second> >
-    : __conditional_t<_IsSame<__remove_const_t<_First>, _Key>::value, 
__extract_key_first_tag, __extract_key_fail_tag> {
-};
-
-// __can_extract_map_key uses true_type/false_type instead of the tags.
-// It returns true if _Key != _ContainerValueTy (the container is a map not a 
set)
-// and _ValTy == _Key.
-template <class _ValTy, class _Key, class _ContainerValueTy, class _RawValTy = 
__remove_const_ref_t<_ValTy> >
-struct __can_extract_map_key : integral_constant<bool, _IsSame<_RawValTy, 
_Key>::value> {};
-
-// This specialization returns __extract_key_fail_tag for non-map containers
-// because _Key == _ContainerValueTy
-template <class _ValTy, class _Key, class _RawValTy>
-struct __can_extract_map_key<_ValTy, _Key, _Key, _RawValTy> : false_type {};
-
-_LIBCPP_END_NAMESPACE_STD
-
-#endif // _LIBCPP___TYPE_TRAITS_CAN_EXTRACT_KEY_H
diff --git a/libcxx/include/__utility/try_key_extraction.h 
b/libcxx/include/__utility/try_key_extraction.h
new file mode 100644
index 0000000000000..755c08214019f
--- /dev/null
+++ b/libcxx/include/__utility/try_key_extraction.h
@@ -0,0 +1,114 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM 
Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___UTILITY_TRY_EXTRACT_KEY_H
+#define _LIBCPP___UTILITY_TRY_EXTRACT_KEY_H
+
+#include <__config>
+#include <__fwd/pair.h>
+#include <__fwd/tuple.h>
+#include <__type_traits/enable_if.h>
+#include <__type_traits/is_same.h>
+#include <__type_traits/remove_const.h>
+#include <__type_traits/remove_const_ref.h>
+#include <__utility/declval.h>
+#include <__utility/forward.h>
+#include <__utility/piecewise_construct.h>
+#include <__utility/priority_tag.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _KeyT, class _Ret, class _WithKey, class _WithoutKey, class... 
_Args>
+_LIBCPP_HIDE_FROM_ABI _Ret
+__try_key_extraction_impl(__priority_tag<0>, _WithKey, _WithoutKey 
__without_key, _Args&&... __args) {
+  return __without_key(std::forward<_Args>(__args)...);
+}
+
+template <class _KeyT,
+          class _Ret,
+          class _WithKey,
+          class _WithoutKey,
+          class _Arg,
+          __enable_if_t<is_same<_KeyT, __remove_const_ref_t<_Arg> >::value, 
int> = 0>
+_LIBCPP_HIDE_FROM_ABI _Ret
+__try_key_extraction_impl(__priority_tag<1>, _WithKey __with_key, _WithoutKey, 
_Arg&& __arg) {
+  return __with_key(__arg, std::forward<_Arg>(__arg));
+}
+
+template <class _KeyT,
+          class _Ret,
+          class _WithKey,
+          class _WithoutKey,
+          class _Arg,
+          __enable_if_t<__is_pair_v<__remove_const_ref_t<_Arg> > &&
+                            is_same<__remove_const_t<typename 
__remove_const_ref_t<_Arg>::first_type>, _KeyT>::value,
+                        int> = 0>
+_LIBCPP_HIDE_FROM_ABI _Ret
+__try_key_extraction_impl(__priority_tag<1>, _WithKey __with_key, _WithoutKey, 
_Arg&& __arg) {
+  return __with_key(__arg.first, std::forward<_Arg>(__arg));
+}
+
+template <class _KeyT,
+          class _Ret,
+          class _WithKey,
+          class _WithoutKey,
+          class _Arg1,
+          class _Arg2,
+          __enable_if_t<is_same<_KeyT, __remove_const_ref_t<_Arg1> >::value, 
int> = 0>
+_LIBCPP_HIDE_FROM_ABI _Ret
+__try_key_extraction_impl(__priority_tag<1>, _WithKey __with_key, _WithoutKey, 
_Arg1&& __arg1, _Arg2&& __arg2) {
+  return __with_key(__arg1, std::forward<_Arg1>(__arg1), 
std::forward<_Arg2>(__arg2));
+}
+
+#ifndef _LIBCPP_CXX03_LANG
+template <class _KeyT,
+          class _Ret,
+          class _WithKey,
+          class _WithoutKey,
+          class _PiecewiseConstruct,
+          class _Tuple1,
+          class _Tuple2,
+          __enable_if_t<is_same<__remove_const_ref_t<_PiecewiseConstruct>, 
piecewise_construct_t>::value &&
+                            __is_tuple_v<_Tuple1> && 
tuple_size<_Tuple1>::value == 1 &&
+                            is_same<__remove_const_ref_t<typename 
tuple_element<0, _Tuple1>::type>, _KeyT>::value,
+                        int> = 0>
+_LIBCPP_HIDE_FROM_ABI _Ret __try_key_extraction_impl(
+    __priority_tag<1>,
+    _WithKey __with_key,
+    _WithoutKey,
+    _PiecewiseConstruct&& __pc,
+    _Tuple1&& __tuple1,
+    _Tuple2&& __tuple2) {
+  return __with_key(
+      std::get<0>(__tuple1),
+      std::forward<_PiecewiseConstruct>(__pc),
+      std::forward<_Tuple1>(__tuple1),
+      std::forward<_Tuple2>(__tuple2));
+}
+#endif // _LIBCPP_CXX03_LANG
+
+// This function tries extracting the given _KeyT from _Args...
+// If it succeeds to extract the key, it calls the `__with_key` function with 
the extracted key and all of the
+// arguments. Otherwise it calls the `__without_key` function with all of the 
arguments.
+//
+// Both `__with_key` and `__without_key` must take all arguments by reference.
+template <class _KeyT, class _WithKey, class _WithoutKey, class... _Args>
+_LIBCPP_HIDE_FROM_ABI 
decltype(std::declval<_WithoutKey>()(std::declval<_Args>()...))
+__try_key_extraction(_WithKey __with_key, _WithoutKey __without_key, 
_Args&&... __args) {
+  using _Ret = decltype(__without_key(std::forward<_Args>(__args)...));
+  return std::__try_key_extraction_impl<_KeyT, _Ret>(
+      __priority_tag<1>(), __with_key, __without_key, 
std::forward<_Args>(__args)...);
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___UTILITY_TRY_EXTRACT_KEY_H
diff --git a/libcxx/include/map b/libcxx/include/map
index 9bd2282e77a3c..b53e1c4213487 100644
--- a/libcxx/include/map
+++ b/libcxx/include/map
@@ -1055,7 +1055,7 @@ public:
 
   template <class... _Args>
   _LIBCPP_HIDE_FROM_ABI iterator emplace_hint(const_iterator __p, _Args&&... 
__args) {
-    return __tree_.__emplace_hint_unique(__p.__i_, 
std::forward<_Args>(__args)...);
+    return __tree_.__emplace_hint_unique(__p.__i_, 
std::forward<_Args>(__args)...).first;
   }
 
   template <class _Pp, __enable_if_t<is_constructible<value_type, _Pp>::value, 
int> = 0>
@@ -1065,7 +1065,7 @@ public:
 
   template <class _Pp, __enable_if_t<is_constructible<value_type, _Pp>::value, 
int> = 0>
   _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __pos, _Pp&& __p) {
-    return __tree_.__emplace_hint_unique(__pos.__i_, std::forward<_Pp>(__p));
+    return __tree_.__emplace_hint_unique(__pos.__i_, 
std::forward<_Pp>(__p)).first;
   }
 
 #  endif // _LIBCPP_CXX03_LANG
@@ -1073,7 +1073,7 @@ public:
   _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> insert(const value_type& __v) { 
return __tree_.__emplace_unique(__v); }
 
   _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __p, const value_type& 
__v) {
-    return __tree_.__emplace_hint_unique(__p.__i_, __v);
+    return __tree_.__emplace_hint_unique(__p.__i_, __v).first;
   }
 
 #  ifndef _LIBCPP_CXX03_LANG
@@ -1082,7 +1082,7 @@ public:
   }
 
   _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __p, value_type&& __v) {
-    return __tree_.__emplace_hint_unique(__p.__i_, std::move(__v));
+    return __tree_.__emplace_hint_unique(__p.__i_, std::move(__v)).first;
   }
 
   _LIBCPP_HIDE_FROM_ABI void insert(initializer_list<value_type> __il) { 
insert(__il.begin(), __il.end()); }
@@ -1108,17 +1108,13 @@ public:
 
   template <class... _Args>
   _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> try_emplace(const key_type& __k, 
_Args&&... __args) {
-    return __tree_.__emplace_unique_key_args(
-        __k,
-        std::piecewise_construct,
-        std::forward_as_tuple(__k),
-        std::forward_as_tuple(std::forward<_Args>(__args)...));
+    return __tree_.__emplace_unique(
+        std::piecewise_construct, std::forward_as_tuple(__k), 
std::forward_as_tuple(std::forward<_Args>(__args)...));
   }
 
   template <class... _Args>
   _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> try_emplace(key_type&& __k, 
_Args&&... __args) {
-    return __tree_.__emplace_unique_key_args(
-        __k,
+    return __tree_.__emplace_unique(
         std::piecewise_construct,
         std::forward_as_tuple(std::move(__k)),
         std::forward_as_tuple(std::forward<_Args>(__args)...));
@@ -1127,9 +1123,8 @@ public:
   template <class... _Args>
   _LIBCPP_HIDE_FROM_ABI iterator try_emplace(const_iterator __h, const 
key_type& __k, _Args&&... __args) {
     return __tree_
-        .__emplace_hint_unique_key_args(
+        .__emplace_hint_unique(
             __h.__i_,
-            __k,
             std::piecewise_construct,
             std::forward_as_tuple(__k),
             std::forward_as_tuple(std::forward<_Args>(__args)...))
@@ -1139,9 +1134,8 @@ public:
   template <class... _Args>
   _LIBCPP_HIDE_FROM_ABI iterator try_emplace(const_iterator __h, key_type&& 
__k, _Args&&... __args) {
     return __tree_
-        .__emplace_hint_unique_key_args(
+        .__emplace_hint_unique(
             __h.__i_,
-            __k,
             std::piecewise_construct,
             std::forward_as_tuple(std::move(__k)),
             std::forward_as_tuple(std::forward<_Args>(__args)...))
@@ -1170,7 +1164,7 @@ public:
 
   template <class _Vp>
   _LIBCPP_HIDE_FROM_ABI iterator insert_or_assign(const_iterator __h, const 
key_type& __k, _Vp&& __v) {
-    auto [__r, __inserted] = __tree_.__emplace_hint_unique_key_args(__h.__i_, 
__k, __k, std::forward<_Vp>(__v));
+    auto [__r, __inserted] = __tree_.__emplace_hint_unique(__h.__i_, __k, 
std::forward<_Vp>(__v));
 
     if (!__inserted)
       __r->second = std::forward<_Vp>(__v);
@@ -1180,8 +1174,7 @@ public:
 
   template <class _Vp>
   _LIBCPP_HIDE_FROM_ABI iterator insert_or_assign(const_iterator __h, 
key_type&& __k, _Vp&& __v) {
-    auto [__r, __inserted] =
-        __tree_.__emplace_hint_unique_key_args(__h.__i_, __k, std::move(__k), 
std::forward<_Vp>(__v));
+    auto [__r, __inserted] = __tree_.__emplace_hint_unique(__h.__i_, 
std::move(__k), std::forward<_Vp>(__v));
 
     if (!__inserted)
       __r->second = std::forward<_Vp>(__v);
@@ -1398,20 +1391,15 @@ map<_Key, _Tp, _Compare, _Allocator>::map(map&& __m, 
const allocator_type& __a)
 
 template <class _Key, class _Tp, class _Compare, class _Allocator>
 _Tp& map<_Key, _Tp, _Compare, _Allocator>::operator[](const key_type& __k) {
-  return __tree_
-      .__emplace_unique_key_args(__k, std::piecewise_construct, 
std::forward_as_tuple(__k), std::forward_as_tuple())
+  return __tree_.__emplace_unique(std::piecewise_construct, 
std::forward_as_tuple(__k), std::forward_as_tuple())
       .first->second;
 }
 
 template <class _Key, class _Tp, class _Compare, class _Allocator>
 _Tp& map<_Key, _Tp, _Compare, _Allocator>::operator[](key_type&& __k) {
-  // TODO investigate this clang-tidy warning.
-  // NOLINTBEGIN(bugprone-use-after-move)
   return __tree_
-      .__emplace_unique_key_args(
-          __k, std::piecewise_construct, 
std::forward_as_tuple(std::move(__k)), std::forward_as_tuple())
+      .__emplace_unique(std::piecewise_construct, 
std::forward_as_tuple(std::move(__k)), std::forward_as_tuple())
       .first->second;
-  // NOLINTEND(bugprone-use-after-move)
 }
 
 #  else // _LIBCPP_CXX03_LANG
diff --git a/libcxx/include/module.modulemap.in 
b/libcxx/include/module.modulemap.in
index c431c0cb407f3..ee18d04c78d0e 100644
--- a/libcxx/include/module.modulemap.in
+++ b/libcxx/include/module.modulemap.in
@@ -70,7 +70,6 @@ module std_core [system] {
     module aligned_storage                            { header 
"__type_traits/aligned_storage.h" }
     module aligned_union                              { header 
"__type_traits/aligned_union.h" }
     module alignment_of                               { header 
"__type_traits/alignment_of.h" }
-    module can_extract_key                            { header 
"__type_traits/can_extract_key.h" }
     module common_reference                           { header 
"__type_traits/common_reference.h" }
     module common_type {
       header "__type_traits/common_type.h"
@@ -2178,6 +2177,7 @@ module std [system] {
     module small_buffer               { header "__utility/small_buffer.h" }
     module swap                       { header "__utility/swap.h" }
     module to_underlying              { header "__utility/to_underlying.h" }
+    module try_key_extraction         { header 
"__utility/try_key_extraction.h" }
     module unreachable                { header "__utility/unreachable.h" }
 
     header "utility"
diff --git a/libcxx/include/set b/libcxx/include/set
index 5190fc1f406ba..b444e8357052a 100644
--- a/libcxx/include/set
+++ b/libcxx/include/set
@@ -732,13 +732,13 @@ public:
   }
   template <class... _Args>
   _LIBCPP_HIDE_FROM_ABI iterator emplace_hint(const_iterator __p, _Args&&... 
__args) {
-    return __tree_.__emplace_hint_unique(__p, std::forward<_Args>(__args)...);
+    return __tree_.__emplace_hint_unique(__p, 
std::forward<_Args>(__args)...).first;
   }
 #  endif // _LIBCPP_CXX03_LANG
 
   _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> insert(const value_type& __v) { 
return __tree_.__emplace_unique(__v); }
   _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __p, const value_type& 
__v) {
-    return __tree_.__emplace_hint_unique(__p, __v);
+    return __tree_.__emplace_hint_unique(__p, __v).first;
   }
 
   template <class _InputIterator>
@@ -763,7 +763,7 @@ public:
   }
 
   _LIBCPP_HIDE_FROM_ABI iterator insert(const_iterator __p, value_type&& __v) {
-    return __tree_.__emplace_hint_unique(__p, std::move(__v));
+    return __tree_.__emplace_hint_unique(__p, std::move(__v)).first;
   }
 
   _LIBCPP_HIDE_FROM_ABI void insert(initializer_list<value_type> __il) { 
insert(__il.begin(), __il.end()); }
diff --git a/libcxx/include/tuple b/libcxx/include/tuple
index 8cc061c70b891..d2cc0f55cb2c8 100644
--- a/libcxx/include/tuple
+++ b/libcxx/include/tuple
@@ -324,12 +324,6 @@ _LIBCPP_HIDE_FROM_ABI constexpr _Ret 
__tuple_compare_three_way(const _Tp& __x, c
 #    endif // _LIBCPP_STD_VER >= 20
 
 #    if _LIBCPP_STD_VER >= 23
-template <class>
-inline constexpr bool __is_tuple_v = false;
-
-template <class... _Tp>
-inline constexpr bool __is_tuple_v<tuple<_Tp...>> = true;
-
 template <class _Tp>
 concept __tuple_like_no_tuple = __tuple_like<_Tp> && !__is_tuple_v<_Tp>;
 
diff --git a/libcxx/include/unordered_map b/libcxx/include/unordered_map
index a934953674967..9b02ecf0393d0 100644
--- a/libcxx/include/unordered_map
+++ b/libcxx/include/unordered_map
@@ -1172,14 +1172,13 @@ public:
 #  if _LIBCPP_STD_VER >= 17
   template <class... _Args>
   _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> try_emplace(const key_type& __k, 
_Args&&... __args) {
-    return __table_.__emplace_unique_key_args(
-        __k, piecewise_construct, std::forward_as_tuple(__k), 
std::forward_as_tuple(std::forward<_Args>(__args)...));
+    return __table_.__emplace_unique(
+        piecewise_construct, std::forward_as_tuple(__k), 
std::forward_as_tuple(std::forward<_Args>(__args)...));
   }
 
   template <class... _Args>
   _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> try_emplace(key_type&& __k, 
_Args&&... __args) {
-    return __table_.__emplace_unique_key_args(
-        __k,
+    return __table_.__emplace_unique(
         piecewise_construct,
         std::forward_as_tuple(std::move(__k)),
         std::forward_as_tuple(std::forward<_Args>(__args)...));
@@ -1197,7 +1196,7 @@ public:
 
   template <class _Vp>
   _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> insert_or_assign(const key_type& 
__k, _Vp&& __v) {
-    pair<iterator, bool> __res = __table_.__emplace_unique_key_args(__k, __k, 
std::forward<_Vp>(__v));
+    pair<iterator, bool> __res = __table_.__emplace_unique(__k, 
std::forward<_Vp>(__v));
     if (!__res.second) {
       __res.first->second = std::forward<_Vp>(__v);
     }
@@ -1206,7 +1205,7 @@ public:
 
   template <class _Vp>
   _LIBCPP_HIDE_FROM_ABI pair<iterator, bool> insert_or_assign(key_type&& __k, 
_Vp&& __v) {
-    pair<iterator, bool> __res = __table_.__emplace_unique_key_args(__k, 
std::move(__k), std::forward<_Vp>(__v));
+    pair<iterator, bool> __res = __table_.__emplace_unique(std::move(__k), 
std::forward<_Vp>(__v));
     if (!__res.second) {
       __res.first->second = std::forward<_Vp>(__v);
     }
@@ -1612,16 +1611,13 @@ inline void unordered_map<_Key, _Tp, _Hash, _Pred, 
_Alloc>::insert(_InputIterato
 
 template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
 _Tp& unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::operator[](const 
key_type& __k) {
-  return __table_
-      .__emplace_unique_key_args(__k, piecewise_construct, 
std::forward_as_tuple(__k), std::forward_as_tuple())
+  return __table_.__emplace_unique(piecewise_construct, 
std::forward_as_tuple(__k), std::forward_as_tuple())
       .first->second;
 }
 
 template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
 _Tp& unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::operator[](key_type&& 
__k) {
-  return __table_
-      .__emplace_unique_key_args(
-          __k, piecewise_construct, std::forward_as_tuple(std::move(__k)), 
std::forward_as_tuple())
+  return __table_.__emplace_unique(piecewise_construct, 
std::forward_as_tuple(std::move(__k)), std::forward_as_tuple())
       .first->second;
 }
 #  else // _LIBCPP_CXX03_LANG
diff --git a/libcxx/test/std/containers/associative/multiset/emplace.pass.cpp 
b/libcxx/test/std/containers/associative/multiset/emplace.pass.cpp
index bddfd8f621437..97cae1c565216 100644
--- a/libcxx/test/std/containers/associative/multiset/emplace.pass.cpp
+++ b/libcxx/test/std/containers/associative/multiset/emplace.pass.cpp
@@ -15,12 +15,12 @@
 // template <class... Args>
 //   iterator emplace(Args&&... args);
 
-#include <set>
 #include <cassert>
+#include <set>
 
-#include "test_macros.h"
 #include "../../Emplaceable.h"
 #include "DefaultOnly.h"
+#include "MoveOnly.h"
 #include "min_allocator.h"
 
 int main(int, char**) {
@@ -77,6 +77,12 @@ int main(int, char**) {
     assert(m.size() == 1);
     assert(*r == 2);
   }
+  { // We're unwrapping pairs for `{,multi}map`. Make sure we're not trying to 
do that for multiset.
+    using Set = std::multiset<std::pair<MoveOnly, MoveOnly>>;
+    Set set;
+    auto iter = set.emplace(std::pair<MoveOnly, MoveOnly>(2, 4));
+    assert(set.begin() == iter);
+  }
 
   return 0;
 }
diff --git a/libcxx/test/std/containers/associative/set/emplace.pass.cpp 
b/libcxx/test/std/containers/associative/set/emplace.pass.cpp
index e038de77d48a6..e5a9f9590aad0 100644
--- a/libcxx/test/std/containers/associative/set/emplace.pass.cpp
+++ b/libcxx/test/std/containers/associative/set/emplace.pass.cpp
@@ -15,12 +15,12 @@
 // template <class... Args>
 //   pair<iterator, bool> emplace(Args&&... args);
 
-#include <set>
 #include <cassert>
+#include <set>
 
-#include "test_macros.h"
 #include "../../Emplaceable.h"
 #include "DefaultOnly.h"
+#include "MoveOnly.h"
 #include "min_allocator.h"
 
 int main(int, char**) {
@@ -84,6 +84,13 @@ int main(int, char**) {
     assert(m.size() == 1);
     assert(*r.first == 2);
   }
+  { // We're unwrapping pairs for `{,multi}map`. Make sure we're not trying to 
do that for set.
+    using Set = std::set<std::pair<MoveOnly, MoveOnly>>;
+    Set set;
+    auto res = set.emplace(std::pair<MoveOnly, MoveOnly>(2, 4));
+    assert(std::get<1>(res));
+    assert(set.begin() == std::get<0>(res));
+  }
 
   return 0;
 }
diff --git a/libcxx/test/std/containers/unord/unord.multiset/emplace.pass.cpp 
b/libcxx/test/std/containers/unord/unord.multiset/emplace.pass.cpp
index 886ddd74efd45..434f205f90b98 100644
--- a/libcxx/test/std/containers/unord/unord.multiset/emplace.pass.cpp
+++ b/libcxx/test/std/containers/unord/unord.multiset/emplace.pass.cpp
@@ -17,11 +17,11 @@
 // template <class... Args>
 //     iterator emplace(Args&&... args);
 
-#include <unordered_set>
 #include <cassert>
+#include <unordered_set>
 
-#include "test_macros.h"
 #include "../../Emplaceable.h"
+#include "MoveOnly.h"
 #include "min_allocator.h"
 
 int main(int, char**) {
@@ -59,6 +59,15 @@ int main(int, char**) {
     assert(c.size() == 3);
     assert(*r == Emplaceable(5, 6));
   }
+  { // We're unwrapping pairs for `unordered_{,multi}map`. Make sure we're not 
trying to do that for unordered_multiset.
+    struct PairHasher {
+      size_t operator()(const std::pair<MoveOnly, MoveOnly>& val) const { 
return std::hash<MoveOnly>()(val.first); }
+    };
+    using Set = std::unordered_multiset<std::pair<MoveOnly, MoveOnly>, 
PairHasher>;
+    Set set;
+    auto iter = set.emplace(std::pair<MoveOnly, MoveOnly>(2, 4));
+    assert(set.begin() == iter);
+  }
 
   return 0;
 }
diff --git a/libcxx/test/std/containers/unord/unord.set/emplace.pass.cpp 
b/libcxx/test/std/containers/unord/unord.set/emplace.pass.cpp
index 8972f03f2d2a8..24e85a1ab7f54 100644
--- a/libcxx/test/std/containers/unord/unord.set/emplace.pass.cpp
+++ b/libcxx/test/std/containers/unord/unord.set/emplace.pass.cpp
@@ -17,11 +17,11 @@
 // template <class... Args>
 //     pair<iterator, bool> emplace(Args&&... args);
 
-#include <unordered_set>
 #include <cassert>
+#include <unordered_set>
 
-#include "test_macros.h"
 #include "../../Emplaceable.h"
+#include "MoveOnly.h"
 #include "min_allocator.h"
 
 int main(int, char**) {
@@ -65,6 +65,16 @@ int main(int, char**) {
     assert(*r.first == Emplaceable(5, 6));
     assert(!r.second);
   }
+  { // We're unwrapping pairs for `unordered_{,multi}map`. Make sure we're not 
trying to do that for unordered_set.
+    struct PairHasher {
+      size_t operator()(const std::pair<MoveOnly, MoveOnly>& val) const { 
return std::hash<MoveOnly>()(val.first); }
+    };
+    using Set = std::unordered_set<std::pair<MoveOnly, MoveOnly>, PairHasher>;
+    Set set;
+    auto res = set.emplace(std::pair<MoveOnly, MoveOnly>(2, 4));
+    assert(std::get<1>(res));
+    assert(set.begin() == std::get<0>(res));
+  }
 
   return 0;
 }
diff --git 
a/lldb/test/API/lang/cpp/libcxx-internals-recognizer/TestLibcxxInternalsRecognizer.py
 
b/lldb/test/API/lang/cpp/libcxx-internals-recognizer/TestLibcxxInternalsRecognizer.py
index 8efa53bdbf722..aaee45b608193 100644
--- 
a/lldb/test/API/lang/cpp/libcxx-internals-recognizer/TestLibcxxInternalsRecognizer.py
+++ 
b/lldb/test/API/lang/cpp/libcxx-internals-recognizer/TestLibcxxInternalsRecognizer.py
@@ -40,6 +40,7 @@ def test_frame_recognizer(self):
             "Callable::operator()(int) const": ["::invoke", "test_invoke"],
             # Containers
             "MyKey::operator<(MyKey const&) const": [
+                "::operator()",
                 "less",
                 "::emplace",
                 "test_containers",

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