From ca909e703495cb685c5894f7a8d9f945bd8eeb31 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@nuwen.net>
Date: Thu, 15 Jan 2026 15:30:15 -0800
Subject: [PATCH 1/3] Drop unnecessary `this->`.

---
 stl/inc/flat_map | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/stl/inc/flat_map b/stl/inc/flat_map
index 394fa0394ad..5b4c52c4676 100644
--- a/stl/inc/flat_map
+++ b/stl/inc/flat_map
@@ -902,19 +902,19 @@ protected:
         if constexpr (_IsUnique) {
             if (_Key_it != _Data.keys.begin() && !_Key_compare(*(_Key_it - 1), _STD forward<_OtherKey>(_Key_val))) {
                 // Previous element is equivalent to key, no insert needed
-                return {this->begin() + (_Index - 1), false};
+                return {begin() + (_Index - 1), false};
             }
         }
 
         // Need to insert
         key_type _Key_to_insert(_STD forward<_OtherKey>(_Key_val));
         mapped_type _Mapped_to_insert(_STD forward<_MappedArgTypes>(_Mapped_args)...);
-        _Insert_exact(this->cbegin() + _Index, _STD move(_Key_to_insert), _STD move(_Mapped_to_insert));
+        _Insert_exact(cbegin() + _Index, _STD move(_Key_to_insert), _STD move(_Mapped_to_insert));
 
         if constexpr (_IsUnique) {
-            return {this->begin() + _Index, true};
+            return {begin() + _Index, true};
         } else {
-            return this->begin() + _Index;
+            return begin() + _Index;
         }
     }
 
@@ -986,7 +986,7 @@ protected:
             }
         }
 
-        const auto _Dist = _New_position - this->begin();
+        const auto _Dist = _New_position - begin();
         {
             key_type _Key_to_insert(_STD forward<_OtherKey>(_Key_val));
             mapped_type _Mapped_to_insert(_STD forward<_MappedArgTypes>(_Args)...);
@@ -1260,12 +1260,12 @@ public:
     mapped_type& operator[](const key_type& _Key_val)
         requires is_default_constructible_v<mapped_type>
     {
-        return this->try_emplace(_Key_val).first->second;
+        return try_emplace(_Key_val).first->second;
     }
     mapped_type& operator[](key_type&& _Key_val)
         requires is_default_constructible_v<mapped_type>
     {
-        return this->try_emplace(_STD move(_Key_val)).first->second;
+        return try_emplace(_STD move(_Key_val)).first->second;
     }
 
     template <class _OtherKey>
@@ -1273,7 +1273,7 @@ public:
         requires _Transparent<key_compare> && is_constructible_v<key_type, _OtherKey>
               && is_default_constructible_v<mapped_type>
     {
-        return this->try_emplace(_STD forward<_OtherKey>(_Key_val)).first->second;
+        return try_emplace(_STD forward<_OtherKey>(_Key_val)).first->second;
     }
 
     _NODISCARD mapped_type& at(const key_type& _Key_val) {

From 18611d0dc288ed428003ce6feee7de4104dc7596 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@nuwen.net>
Date: Thu, 15 Jan 2026 15:36:31 -0800
Subject: [PATCH 2/3] `typename` => `class` in tests.

---
 tests/std/tests/P0429R9_flat_map/test.cpp          | 14 +++++++-------
 .../test.compile.pass.cpp                          |  2 +-
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/tests/std/tests/P0429R9_flat_map/test.cpp b/tests/std/tests/P0429R9_flat_map/test.cpp
index c7e0aba31d0..e2a4a9b8733 100644
--- a/tests/std/tests/P0429R9_flat_map/test.cpp
+++ b/tests/std/tests/P0429R9_flat_map/test.cpp
@@ -30,7 +30,7 @@ constexpr bool is_specialization_v = false;
 template <template <class...> class Tmpl, class... Ts>
 constexpr bool is_specialization_v<Tmpl<Ts...>, Tmpl> = true;
 
-template <typename T>
+template <class T>
 concept IsFlatMap =
     is_specialization_v<remove_cvref_t<T>, flat_map> || is_specialization_v<remove_cvref_t<T>, flat_multimap>;
 
@@ -120,7 +120,7 @@ template <IsFlatMap T>
     });
 }
 
-template <typename T>
+template <class T>
 class MyAllocator : public allocator<T> {
 public:
     using value_type = T;
@@ -169,14 +169,14 @@ namespace std {
     };
 } // namespace std
 
-template <typename T>
+template <class T>
 class Packaged {
 private:
     T value;
 
 public:
     Packaged() : value() {}
-    template <typename U>
+    template <class U>
         requires constructible_from<T, U&&>
     Packaged(U&& u) : value(forward<U>(u)) {}
 
@@ -197,10 +197,10 @@ class Packaged {
     friend auto operator<=>(const Packaged&, const Packaged&) = default;
 };
 
-template <typename T>
+template <class T>
 struct PackagedCompare : less<Packaged<T>> {};
 
-template <typename T>
+template <class T>
 struct TransparentPackagedCompare : PackagedCompare<T> {
     using is_transparent = void;
 
@@ -1183,7 +1183,7 @@ void test_throwing_compare_swap_single() {
 }
 
 // Test that changes in GH-5987 did not break calls of lookup member functions by using deducing this.
-template <typename T>
+template <class T>
 void test_lookup_call_on_temporaries_single() {
     (void) T{}.lower_bound(42);
     (void) T{}.lower_bound('a');
diff --git a/tests/std/tests/P0429R9_flat_map_ms_specific/test.compile.pass.cpp b/tests/std/tests/P0429R9_flat_map_ms_specific/test.compile.pass.cpp
index 335c8e14326..fd39e6a478c 100644
--- a/tests/std/tests/P0429R9_flat_map_ms_specific/test.compile.pass.cpp
+++ b/tests/std/tests/P0429R9_flat_map_ms_specific/test.compile.pass.cpp
@@ -51,7 +51,7 @@ struct flat_map_unique_if_impl<false> {
 template <bool IsUnique, class Key, class Mapped, class Comp, class KeyCont, class MappedCont>
 using flat_map_unique_if = flat_map_unique_if_impl<IsUnique>::template type<Key, Mapped, Comp, KeyCont, MappedCont>;
 
-template <typename A, typename B>
+template <class A, class B>
 constexpr bool has_different_nested_types = !is_same_v<typename A::value_compare, typename B::value_compare>
                                          && !is_same_v<typename A::containers, typename B::containers>;
 

From 76b8c7102f5823405458a13fb63d3a7f059ef009 Mon Sep 17 00:00:00 2001
From: "Stephan T. Lavavej" <stl@nuwen.net>
Date: Thu, 15 Jan 2026 16:02:47 -0800
Subject: [PATCH 3/3] flat_map: value_compare should be a class, with a private
 ctor, avoiding an unnecessary copy of key_compare.

---
 stl/inc/flat_map | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/stl/inc/flat_map b/stl/inc/flat_map
index 5b4c52c4676..2e294d5c822 100644
--- a/stl/inc/flat_map
+++ b/stl/inc/flat_map
@@ -318,15 +318,17 @@ public:
         "mapped_container_type must support random-access iterators in order to be adapted. "
         "(N5014 [flat.map.overview]/7, [flat.multimap.overview]/7)");
 
-    struct value_compare {
+    class value_compare {
     public:
         _NODISCARD bool operator()(const_reference _Left, const_reference _Right) const {
             return _Key_comparator(_Left.first, _Right.first);
         }
 
-        value_compare(key_compare _Comp) : _Key_comparator(_Comp) {}
-
     private:
+        friend _Flat_map_base;
+
+        value_compare(const key_compare& _Comp) : _Key_comparator(_Comp) {}
+
         key_compare _Key_comparator;
     };