From f4eecc9fbab2bac81d60ed9aa04c441f4e7f5777 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Crazy=E5=87=A1?=
 <15794964+CrazyFanFan@users.noreply.github.com>
Date: Thu, 13 Nov 2025 00:25:48 +0800
Subject: [PATCH] optimize contains method in CxxSet

---
 .../ClangDerivedConformances.cpp              | 11 +++++----
 stdlib/public/Cxx/CxxSet.swift                | 24 +++++++------------
 2 files changed, 15 insertions(+), 20 deletions(-)

diff --git a/lib/ClangImporter/ClangDerivedConformances.cpp b/lib/ClangImporter/ClangDerivedConformances.cpp
index 593ea94c26667..d6799817c4bbd 100644
--- a/lib/ClangImporter/ClangDerivedConformances.cpp
+++ b/lib/ClangImporter/ClangDerivedConformances.cpp
@@ -996,11 +996,6 @@ void swift::conformToCxxSetIfNeeded(ClangImporter::Implementation &impl,
                                insert->getResultInterfaceType());
   impl.addSynthesizedProtocolAttrs(decl, {KnownProtocolKind::CxxSet});
 
-  // If this isn't a std::multiset, try to also synthesize the conformance to
-  // CxxUniqueSet.
-  if (!isStdDecl(clangDecl, {"set", "unordered_set"}))
-    return;
-
   ProtocolDecl *cxxInputIteratorProto =
       ctx.getProtocol(KnownProtocolKind::UnsafeCxxInputIterator);
   if (!cxxInputIteratorProto)
@@ -1025,6 +1020,12 @@ void swift::conformToCxxSetIfNeeded(ClangImporter::Implementation &impl,
                                rawIteratorTy);
   impl.addSynthesizedTypealias(decl, ctx.getIdentifier("RawMutableIterator"),
                                rawMutableIteratorTy);
+
+  // If this isn't a std::multiset, try to also synthesize the conformance to
+  // CxxUniqueSet.
+  if (!isStdDecl(clangDecl, {"set", "unordered_set"}))
+    return;
+
   impl.addSynthesizedProtocolAttrs(decl, {KnownProtocolKind::CxxUniqueSet});
 }
 
diff --git a/stdlib/public/Cxx/CxxSet.swift b/stdlib/public/Cxx/CxxSet.swift
index eb8c169536abc..80306ca1237a4 100644
--- a/stdlib/public/Cxx/CxxSet.swift
+++ b/stdlib/public/Cxx/CxxSet.swift
@@ -19,16 +19,22 @@
 public protocol CxxSet<Element>: ExpressibleByArrayLiteral {
   associatedtype Element
   associatedtype Size: BinaryInteger
+  associatedtype RawIterator: UnsafeCxxInputIterator
+    where RawIterator.Pointee == Element
+  associatedtype RawMutableIterator: UnsafeCxxInputIterator
+    where RawMutableIterator.Pointee == Element
 
   // std::pair<iterator, bool> for std::set and std::unordered_set
   // iterator for std::multiset
-  associatedtype InsertionResult 
+  associatedtype InsertionResult
 
   init()
 
+  func __endUnsafe() -> RawIterator
+  func __findUnsafe(_ value: Element) -> RawIterator
+
   @discardableResult
   mutating func __insertUnsafe(_ element: Element) -> InsertionResult
-
   func count(_ element: Element) -> Size
 }
 
@@ -56,7 +62,7 @@ extension CxxSet {
   /// in the set.
   @inlinable
   public func contains(_ element: Element) -> Bool {
-    return count(element) > 0
+    return self.__findUnsafe(element) != self.__endUnsafe()
   }
 }
 
@@ -65,23 +71,11 @@ extension CxxSet {
 /// C++ standard library types such as `std::set` and `std::unordered_set`
 /// conform to this protocol.
 public protocol CxxUniqueSet<Element>: CxxSet {
-  override associatedtype Element
-  override associatedtype Size: BinaryInteger
-  associatedtype RawIterator: UnsafeCxxInputIterator
-    where RawIterator.Pointee == Element
-  associatedtype RawMutableIterator: UnsafeCxxInputIterator
-    where RawMutableIterator.Pointee == Element
   override associatedtype InsertionResult
     where InsertionResult: CxxPair<RawMutableIterator, Bool>
 
-  @discardableResult
-  mutating func __findUnsafe(_ value: Element) -> RawIterator
-
   @discardableResult
   mutating func __eraseUnsafe(_ iter: RawIterator) -> RawMutableIterator
-
-  @discardableResult
-  mutating func __endUnsafe() -> RawIterator
 }
 
 extension CxxUniqueSet {