diff --git a/libcxx/include/__flat_set/flat_set.h b/libcxx/include/__flat_set/flat_set.h
index 0c8fdb5a803c8..1be38f10ea9f3 100644
--- a/libcxx/include/__flat_set/flat_set.h
+++ b/libcxx/include/__flat_set/flat_set.h
@@ -339,38 +339,42 @@ class flat_set {
   }
 
   // iterators
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator begin() noexcept {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator begin() noexcept {
     return iterator(std::as_const(__keys_).begin());
   }
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator begin() const noexcept {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator begin() const noexcept {
     return const_iterator(__keys_.begin());
   }
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator end() noexcept {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator end() noexcept {
     return iterator(std::as_const(__keys_).end());
   }
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator end() const noexcept {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator end() const noexcept {
     return const_iterator(__keys_.end());
   }
 
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 reverse_iterator rbegin() noexcept {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 reverse_iterator rbegin() noexcept {
     return reverse_iterator(end());
   }
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_reverse_iterator rbegin() const noexcept {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_reverse_iterator rbegin() const noexcept {
     return const_reverse_iterator(end());
   }
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 reverse_iterator rend() noexcept {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 reverse_iterator rend() noexcept {
     return reverse_iterator(begin());
   }
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_reverse_iterator rend() const noexcept {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_reverse_iterator rend() const noexcept {
     return const_reverse_iterator(begin());
   }
 
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator cbegin() const noexcept { return begin(); }
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator cend() const noexcept { return end(); }
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_reverse_iterator crbegin() const noexcept {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator cbegin() const noexcept {
+    return begin();
+  }
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator cend() const noexcept {
+    return end();
+  }
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_reverse_iterator crbegin() const noexcept {
     return const_reverse_iterator(end());
   }
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_reverse_iterator crend() const noexcept {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_reverse_iterator crend() const noexcept {
     return const_reverse_iterator(begin());
   }
 
@@ -379,9 +383,13 @@ class flat_set {
     return __keys_.empty();
   }
 
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 size_type size() const noexcept { return __keys_.size(); }
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 size_type size() const noexcept {
+    return __keys_.size();
+  }
 
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 size_type max_size() const noexcept { return __keys_.max_size(); }
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 size_type max_size() const noexcept {
+    return __keys_.max_size();
+  }
 
   // [flat.set.modifiers], modifiers
   template <class... _Args>
@@ -466,7 +474,7 @@ class flat_set {
     insert(sorted_unique, __il.begin(), __il.end());
   }
 
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 container_type extract() && {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 container_type extract() && {
     auto __guard = std::__make_scope_guard([&]() noexcept { clear() /* noexcept */; });
     auto __ret   = std::move(__keys_);
     return __ret;
@@ -528,111 +536,117 @@ class flat_set {
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 void clear() noexcept { __keys_.clear(); }
 
   // observers
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 key_compare key_comp() const { return __compare_; }
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 value_compare value_comp() const { return __compare_; }
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 key_compare key_comp() const { return __compare_; }
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 value_compare value_comp() const {
+    return __compare_;
+  }
 
   // set operations
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator find(const key_type& __x) {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator find(const key_type& __x) {
     return __find_impl(*this, __x);
   }
 
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator find(const key_type& __x) const {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator find(const key_type& __x) const {
     return __find_impl(*this, __x);
   }
 
   template <class _Kp>
     requires __is_transparent_v<_Compare>
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator find(const _Kp& __x) {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator find(const _Kp& __x) {
     return __find_impl(*this, __x);
   }
 
   template <class _Kp>
     requires __is_transparent_v<_Compare>
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator find(const _Kp& __x) const {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator find(const _Kp& __x) const {
     return __find_impl(*this, __x);
   }
 
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 size_type count(const key_type& __x) const {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 size_type count(const key_type& __x) const {
     return contains(__x) ? 1 : 0;
   }
 
   template <class _Kp>
     requires __is_transparent_v<_Compare>
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 size_type count(const _Kp& __x) const {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 size_type count(const _Kp& __x) const {
     return contains(__x) ? 1 : 0;
   }
 
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 bool contains(const key_type& __x) const {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 bool contains(const key_type& __x) const {
     return find(__x) != end();
   }
 
   template <class _Kp>
     requires __is_transparent_v<_Compare>
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 bool contains(const _Kp& __x) const {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 bool contains(const _Kp& __x) const {
     return find(__x) != end();
   }
 
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator lower_bound(const key_type& __x) {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator lower_bound(const key_type& __x) {
     const auto& __keys = __keys_;
     return iterator(std::lower_bound(__keys.begin(), __keys.end(), __x, __compare_));
   }
 
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator lower_bound(const key_type& __x) const {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator
+  lower_bound(const key_type& __x) const {
     return const_iterator(std::lower_bound(__keys_.begin(), __keys_.end(), __x, __compare_));
   }
 
   template <class _Kp>
     requires __is_transparent_v<_Compare>
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator lower_bound(const _Kp& __x) {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator lower_bound(const _Kp& __x) {
     const auto& __keys = __keys_;
     return iterator(std::lower_bound(__keys.begin(), __keys.end(), __x, __compare_));
   }
 
   template <class _Kp>
     requires __is_transparent_v<_Compare>
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator lower_bound(const _Kp& __x) const {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator lower_bound(const _Kp& __x) const {
     return const_iterator(std::lower_bound(__keys_.begin(), __keys_.end(), __x, __compare_));
   }
 
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator upper_bound(const key_type& __x) {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator upper_bound(const key_type& __x) {
     const auto& __keys = __keys_;
     return iterator(std::upper_bound(__keys.begin(), __keys.end(), __x, __compare_));
   }
 
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator upper_bound(const key_type& __x) const {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator
+  upper_bound(const key_type& __x) const {
     return const_iterator(std::upper_bound(__keys_.begin(), __keys_.end(), __x, __compare_));
   }
 
   template <class _Kp>
     requires __is_transparent_v<_Compare>
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator upper_bound(const _Kp& __x) {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 iterator upper_bound(const _Kp& __x) {
     const auto& __keys = __keys_;
     return iterator(std::upper_bound(__keys.begin(), __keys.end(), __x, __compare_));
   }
 
   template <class _Kp>
     requires __is_transparent_v<_Compare>
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator upper_bound(const _Kp& __x) const {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 const_iterator upper_bound(const _Kp& __x) const {
     return const_iterator(std::upper_bound(__keys_.begin(), __keys_.end(), __x, __compare_));
   }
 
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 pair<iterator, iterator> equal_range(const key_type& __x) {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 pair<iterator, iterator>
+  equal_range(const key_type& __x) {
     return __equal_range_impl(*this, __x);
   }
 
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 pair<const_iterator, const_iterator>
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 pair<const_iterator, const_iterator>
   equal_range(const key_type& __x) const {
     return __equal_range_impl(*this, __x);
   }
 
   template <class _Kp>
     requires __is_transparent_v<_Compare>
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 pair<iterator, iterator> equal_range(const _Kp& __x) {
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 pair<iterator, iterator>
+  equal_range(const _Kp& __x) {
     return __equal_range_impl(*this, __x);
   }
   template <class _Kp>
     requires __is_transparent_v<_Compare>
-  _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 pair<const_iterator, const_iterator>
+  [[nodiscard]] _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX26 pair<const_iterator, const_iterator>
   equal_range(const _Kp& __x) const {
     return __equal_range_impl(*this, __x);
   }
diff --git a/libcxx/test/libcxx/diagnostics/flat_map.nodiscard.verify.cpp b/libcxx/test/libcxx/diagnostics/flat_map.nodiscard.verify.cpp
index d569616b99bf4..7d75083157aef 100644
--- a/libcxx/test/libcxx/diagnostics/flat_map.nodiscard.verify.cpp
+++ b/libcxx/test/libcxx/diagnostics/flat_map.nodiscard.verify.cpp
@@ -10,7 +10,7 @@
 
 // <flat_map>
 
-// [[nodiscard]] bool empty() const noexcept;
+// Check that functions are marked [[nodiscard]]
 
 #include <flat_map>
 #include <utility>
diff --git a/libcxx/test/libcxx/diagnostics/flat_set.nodiscard.verify.cpp b/libcxx/test/libcxx/diagnostics/flat_set.nodiscard.verify.cpp
index 161fe533eabac..89d60456a20c1 100644
--- a/libcxx/test/libcxx/diagnostics/flat_set.nodiscard.verify.cpp
+++ b/libcxx/test/libcxx/diagnostics/flat_set.nodiscard.verify.cpp
@@ -6,15 +6,93 @@
 //
 //===----------------------------------------------------------------------===//
 
-// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+// REQUIRES: std-at-least-c++23
 
 // <flat_set>
 
-// [[nodiscard]] bool empty() const noexcept;
+// Check that functions are marked [[nodiscard]]
 
 #include <flat_set>
+#include <utility>
 
-void f() {
-  std::flat_set<int> c;
-  c.empty(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+template <typename T>
+struct TransparentKey {
+  T t;
+
+  constexpr explicit operator T() const { return t; }
+};
+
+struct TransparentCompare {
+  using is_transparent = void; // This makes the comparator transparent
+
+  template <typename T>
+  constexpr bool operator()(const T& t, const TransparentKey<T>& transparent) const {
+    return t < transparent.t;
+  }
+
+  template <typename T>
+  constexpr bool operator()(const TransparentKey<T>& transparent, const T& t) const {
+    return transparent.t < t;
+  }
+
+  template <typename T>
+  constexpr bool operator()(const T& t1, const T& t2) const {
+    return t1 < t2;
+  }
+};
+
+void test() {
+  std::flat_set<int, TransparentCompare> fs;
+  const std::flat_set<int, TransparentCompare> cfs;
+
+  fs.begin();    // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  cfs.begin();   // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  fs.end();      // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  cfs.end();     // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  fs.rbegin();   // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  cfs.rbegin();  // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  fs.rend();     // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  cfs.rend();    // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  cfs.cbegin();  // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  cfs.cend();    // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  cfs.crbegin(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  cfs.crend();   // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+
+  fs.empty();    // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  fs.size();     // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  fs.max_size(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+
+  std::move(fs).extract(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+
+  fs.key_comp();   // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  fs.value_comp(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+
+  int key = 0;
+  TransparentKey<int> tkey;
+
+  fs.find(key);   // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  cfs.find(key);  // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  fs.find(tkey);  // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  cfs.find(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+
+  fs.count(key);  // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  fs.count(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+
+  fs.contains(key);  // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  fs.contains(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+
+  fs.lower_bound(key);   // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  cfs.lower_bound(key);  // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  fs.lower_bound(tkey);  // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  cfs.lower_bound(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+
+  fs.upper_bound(key);   // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  cfs.upper_bound(key);  // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  fs.upper_bound(tkey);  // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  cfs.upper_bound(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+
+  fs.equal_range(key);   // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  cfs.equal_range(key);  // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  fs.equal_range(tkey);  // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+  cfs.equal_range(tkey); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
 }