From e6a0138004861bbb6360586892b988d00210e4ba Mon Sep 17 00:00:00 2001
From: Jeroen Ketema <jketema@github.com>
Date: Mon, 22 Sep 2025 11:02:21 +0200
Subject: [PATCH] Swift: Assign indexes to extensions looking at all the
 extensions of a type

---
 swift/extractor/mangler/SwiftMangler.cpp | 46 ++++++++++++++++++++----
 swift/extractor/mangler/SwiftMangler.h   |  4 ++-
 2 files changed, 42 insertions(+), 8 deletions(-)

diff --git a/swift/extractor/mangler/SwiftMangler.cpp b/swift/extractor/mangler/SwiftMangler.cpp
index 7e1f1f0bfe87..91e3359fc4de 100644
--- a/swift/extractor/mangler/SwiftMangler.cpp
+++ b/swift/extractor/mangler/SwiftMangler.cpp
@@ -112,12 +112,11 @@ unsigned SwiftMangler::getExtensionIndex(const swift::ExtensionDecl* decl,
   if (auto found = preloadedExtensionIndexes.extract(decl)) {
     return found.mapped();
   }
-  if (auto parentModule = llvm::dyn_cast<swift::ModuleDecl>(parent)) {
-    llvm::SmallVector<swift::Decl*> siblings;
-    parentModule->getTopLevelDecls(siblings);
-    indexExtensions(siblings);
+
+  if (llvm::isa<swift::ModuleDecl>(parent)) {
+    indexNominalTypeExtensions(decl->getExtendedNominal()->getExtensions(), parent);
   } else if (auto iterableParent = llvm::dyn_cast<swift::IterableDeclContext>(parent)) {
-    indexExtensions(iterableParent->getAllMembers());
+    indexIterableExtensions(iterableParent->getAllMembers());
   } else {
     // TODO use a generic logging handle for Swift entities here, once it's available
     CODEQL_ASSERT(false, "non-local context must be module or iterable decl context");
@@ -128,13 +127,46 @@ unsigned SwiftMangler::getExtensionIndex(const swift::ExtensionDecl* decl,
   return found.mapped();
 }
 
-void SwiftMangler::indexExtensions(llvm::ArrayRef<swift::Decl*> siblings) {
+void SwiftMangler::indexNominalTypeExtensions(swift::ExtensionRange unsortedExtensions,
+                                              const swift::Decl* parent) {
+  std::vector<const swift::ExtensionDecl*> extensions;
+  for (const auto& extension : unsortedExtensions) {
+    extensions.emplace_back(extension);
+  }
+
+  std::ranges::sort(extensions, [](const auto& e1, const auto& e2) {
+    if (auto f1 = e1->getSourceFileName()) {
+      if (auto f2 = e2->getSourceFileName()) {
+        int result = f1.value().compare(f2.value());
+        if (result != 0) {
+          return result < 0;
+        }
+      }
+    }
+    if (auto o1 = e1->getSourceOrder()) {
+      if (auto o2 = e2->getSourceOrder()) {
+        return o1.value() < o2.value();
+      }
+    }
+    return false;
+  });
+
+  auto index = 0u;
+  for (const auto& extension : extensions) {
+    if (getParent(extension) == parent) {
+      preloadedExtensionIndexes.emplace(extension, index);
+      index++;
+    }
+  }
+}
+
+void SwiftMangler::indexIterableExtensions(llvm::ArrayRef<swift::Decl*> siblings) {
   auto index = 0u;
   for (auto sibling : siblings) {
     if (sibling->getKind() == swift::DeclKind::Extension) {
       preloadedExtensionIndexes.emplace(sibling, index);
+      ++index;
     }
-    ++index;
   }
 }
 
diff --git a/swift/extractor/mangler/SwiftMangler.h b/swift/extractor/mangler/SwiftMangler.h
index 2e3acbb9103c..d0b1b12f7e8b 100644
--- a/swift/extractor/mangler/SwiftMangler.h
+++ b/swift/extractor/mangler/SwiftMangler.h
@@ -112,7 +112,9 @@ class SwiftMangler : private swift::TypeVisitor<SwiftMangler, SwiftMangledName>,
   virtual SwiftMangledName fetch(const swift::TypeBase* type) = 0;
   SwiftMangledName fetch(swift::Type type) { return fetch(type.getPointer()); }
 
-  void indexExtensions(llvm::ArrayRef<swift::Decl*> siblings);
+  void indexNominalTypeExtensions(swift::ExtensionRange unsortedExtensions,
+                                  const swift::Decl* parent);
+  void indexIterableExtensions(llvm::ArrayRef<swift::Decl*> siblings);
   unsigned int getExtensionIndex(const swift::ExtensionDecl* decl, const swift::Decl* parent);
   static SwiftMangledName initMangled(const swift::TypeBase* type);
   SwiftMangledName initMangled(const swift::Decl* decl);