[alpha.webkit.UncountedCallArgsChecker] Avoid emitting warnings for Ref, RefPtr, and their variants. (#90153)

Skip the analysis of Ref, RefPtr, and their variant classes in
UncountedCallArgsChecker since these classes are "trusted" to not do
anything dangerous.

Author: rniwa

clang/lib/StaticAnalyzer/Checkers/WebKit/PtrTypesSemantics.h

@@ -50,6 +50,9 @@ std::optional<bool> isUncounted(const clang::CXXRecordDecl* Class);
 /// class, false if not, std::nullopt if inconclusive.
 std::optional<bool> isUncountedPtr(const clang::Type* T);
 
+/// \returns true if Name is a RefPtr, Ref, or its variant, false if not.
+bool isRefType(const std::string &Name);
+
 /// \returns true if \p F creates ref-countable object from uncounted parameter,
 /// false if not.
 bool isCtorOfRefCounted(const clang::FunctionDecl *F);

clang/lib/StaticAnalyzer/Checkers/WebKit/UncountedCallArgsChecker.cpp

@@ -53,6 +53,12 @@ class UncountedCallArgsChecker
       bool shouldVisitTemplateInstantiations() const { return true; }
       bool shouldVisitImplicitCode() const { return false; }
 
+      bool TraverseDecl(Decl *D) {
+        if (isa<ClassTemplateDecl>(D) && isRefType(safeGetName(D)))
+          return true;
+        return RecursiveASTVisitor<LocalVisitor>::TraverseDecl(D);
+      }
+
       bool VisitCallExpr(const CallExpr *CE) {
         Checker->visitCallExpr(CE);
         return true;

clang/test/Analysis/Checkers/WebKit/call-args.cpp

@@ -32,7 +32,7 @@ namespace ref_counted {
   void consume_ref_counted(Ref<RefCountable>) {}
 
   void foo() {
-    consume_refcntbl(provide_ref_counted().get());
+    consume_refcntbl(provide_ref_counted().ptr());
     // no warning
   }
 }

clang/test/Analysis/Checkers/WebKit/mock-types.h

@@ -1,24 +1,61 @@
 #ifndef mock_types_1103988513531
 #define mock_types_1103988513531
 
-template <typename T> struct Ref {
-  T *t;
+template<typename T>
+struct RawPtrTraits {
+  using StorageType = T*;
 
-  Ref() : t{} {};
-  Ref(T &t)
-    : t(t) {
-    if (t)
-      t->ref();
+  template<typename U>
+  static T* exchange(StorageType& ptr, U&& newValue)
+  {
+    StorageType oldValue = static_cast<StorageType&&>(ptr);
+    ptr = static_cast<U&&>(newValue);
+    return oldValue;
   }
-  ~Ref() {
-    if (t)
-      t->deref();
+
+  static void swap(StorageType& a, StorageType& b)
+  {
+    StorageType temp = static_cast<StorageType&&>(a);
+    a = static_cast<StorageType&&>(b);
+    b = static_cast<StorageType&&>(temp);
   }
-  T *get() { return t; }
-  T *ptr() { return t; }
-  T *operator->() { return t; }
-  operator const T &() const { return *t; }
-  operator T &() { return *t; }
+  static T* unwrap(const StorageType& ptr) { return ptr; }
+};
+
+template<typename T> struct DefaultRefDerefTraits {
+  static T* refIfNotNull(T* ptr)
+  {
+    if (ptr)
+      ptr->ref();
+    return ptr;
+  }
+
+  static T& ref(T& ref)
+  {
+    ref.ref();
+    return ref;
+  }
+
+  static void derefIfNotNull(T* ptr)
+  {
+    if (ptr)
+      ptr->deref();
+  }
+};
+
+template <typename T, typename PtrTraits = RawPtrTraits<T>, typename RefDerefTraits = DefaultRefDerefTraits<T>> struct Ref {
+  typename PtrTraits::StorageType t;
+
+  Ref() : t{} {};
+  Ref(T &t) : t(RefDerefTraits::refIfNotNull(t)) { }
+  Ref(const Ref& o) : t(RefDerefTraits::refIfNotNull(PtrTraits::unwrap(o.t))) { }
+  ~Ref() { RefDerefTraits::derefIfNotNull(PtrTraits::exchange(t, nullptr)); }
+  T &get() { return *PtrTraits::unwrap(t); }
+  T *ptr() { return PtrTraits::unwrap(t); }
+  T *operator->() { return PtrTraits::unwrap(t); }
+  operator const T &() const { return *PtrTraits::unwrap(t); }
+  operator T &() { return *PtrTraits::unwrap(t); }
+  T* leakRef() { PtrTraits::exchange(t, nullptr); }
 };
 
 template <typename T> struct RefPtr {