[analyzer] Support C++23 static operator calls (llvm#84972)

Made by following:
llvm#83585 (comment)

Thanks for the details Tomek!

CPP-5080

clang/docs/ReleaseNotes.rst

@@ -576,6 +576,7 @@ Static Analyzer
 - Fixed crashing on loops if the loop variable was declared in switch blocks
   but not under any case blocks if ``unroll-loops=true`` analyzer config is
   set. (#GH68819)
+- Support C++23 static operator calls. (#GH84972)
 
 New features
 ^^^^^^^^^^^^

clang/include/clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h

@@ -59,6 +59,7 @@ namespace ento {
 
 enum CallEventKind {
   CE_Function,
+  CE_CXXStaticOperator,
   CE_CXXMember,
   CE_CXXMemberOperator,
   CE_CXXDestructor,
@@ -709,6 +710,77 @@ class CXXInstanceCall : public AnyFunctionCall {
   }
 };
 
+/// Represents a static C++ operator call.
+///
+/// "A" in this example.
+/// However, "B" and "C" are represented by SimpleFunctionCall.
+/// \code
+///   struct S {
+///     int pad;
+///     static void operator()(int x, int y);
+///   };
+///   S s{10};
+///   void (*fptr)(int, int) = &S::operator();
+///
+///   s(1, 2);  // A
+///   S::operator()(1, 2);  // B
+///   fptr(1, 2); // C
+/// \endcode
+class CXXStaticOperatorCall : public SimpleFunctionCall {
+  friend class CallEventManager;
+
+protected:
+  CXXStaticOperatorCall(const CXXOperatorCallExpr *CE, ProgramStateRef St,
+                        const LocationContext *LCtx,
+                        CFGBlock::ConstCFGElementRef ElemRef)
+      : SimpleFunctionCall(CE, St, LCtx, ElemRef) {}
+  CXXStaticOperatorCall(const CXXStaticOperatorCall &Other) = default;
+
+  void cloneTo(void *Dest) const override {
+    new (Dest) CXXStaticOperatorCall(*this);
+  }
+
+public:
+  const CXXOperatorCallExpr *getOriginExpr() const override {
+    return cast<CXXOperatorCallExpr>(SimpleFunctionCall::getOriginExpr());
+  }
+
+  unsigned getNumArgs() const override {
+    // Ignore the object parameter that is not used for static member functions.
+    assert(getOriginExpr()->getNumArgs() > 0);
+    return getOriginExpr()->getNumArgs() - 1;
+  }
+
+  const Expr *getArgExpr(unsigned Index) const override {
+    // Ignore the object parameter that is not used for static member functions.
+    return getOriginExpr()->getArg(Index + 1);
+  }
+
+  std::optional<unsigned>
+  getAdjustedParameterIndex(unsigned ASTArgumentIndex) const override {
+    // Ignore the object parameter that is not used for static member functions.
+    if (ASTArgumentIndex == 0)
+      return std::nullopt;
+    return ASTArgumentIndex - 1;
+  }
+
+  unsigned getASTArgumentIndex(unsigned CallArgumentIndex) const override {
+    // Account for the object parameter for the static member function.
+    return CallArgumentIndex + 1;
+  }
+
+  OverloadedOperatorKind getOverloadedOperator() const {
+    return getOriginExpr()->getOperator();
+  }
+
+  Kind getKind() const override { return CE_CXXStaticOperator; }
+  StringRef getKindAsString() const override { return "CXXStaticOperatorCall"; }
+
+  static bool classof(const CallEvent *CA) {
+    return CA->getKind() == CE_CXXStaticOperator;
+  }
+};
+
 /// Represents a non-static C++ member function call.
 ///
 /// Example: \c obj.fun()

clang/lib/StaticAnalyzer/Core/CallEvent.cpp

@@ -1408,9 +1408,12 @@ CallEventManager::getSimpleCall(const CallExpr *CE, ProgramStateRef State,
 
   if (const auto *OpCE = dyn_cast<CXXOperatorCallExpr>(CE)) {
     const FunctionDecl *DirectCallee = OpCE->getDirectCallee();
-    if (const auto *MD = dyn_cast<CXXMethodDecl>(DirectCallee))
+    if (const auto *MD = dyn_cast<CXXMethodDecl>(DirectCallee)) {
       if (MD->isImplicitObjectMemberFunction())
         return create<CXXMemberOperatorCall>(OpCE, State, LCtx, ElemRef);
+      if (MD->isStatic())
+        return create<CXXStaticOperatorCall>(OpCE, State, LCtx, ElemRef);
+    }
 
   } else if (CE->getCallee()->getType()->isBlockPointerType()) {
     return create<BlockCall>(CE, State, LCtx, ElemRef);

clang/lib/StaticAnalyzer/Core/ExprEngineCallAndReturn.cpp

@@ -846,6 +846,7 @@ ExprEngine::mayInlineCallKind(const CallEvent &Call, const ExplodedNode *Pred,
   const StackFrameContext *CallerSFC = CurLC->getStackFrame();
   switch (Call.getKind()) {
   case CE_Function:
+  case CE_CXXStaticOperator:
   case CE_Block:
     break;
   case CE_CXXMember:

clang/test/Analysis/cxx23-static-operator.cpp

@@ -0,0 +1,38 @@
+// RUN: %clang_analyze_cc1 -std=c++2b -verify %s \
+// RUN:   -analyzer-checker=core,debug.ExprInspection
+
+template <typename T> void clang_analyzer_dump(T);
+
+struct Adder {
+  int data;
+  static int operator()(int x, int y) {
+    clang_analyzer_dump(x); // expected-warning {{1}}
+    clang_analyzer_dump(y); // expected-warning {{2}}
+    return x + y;
+  }
+};
+
+void static_operator_call_inlines() {
+  Adder s{10};
+  clang_analyzer_dump(s(1, 2)); // expected-warning {{3}}
+}
+
+struct DataWithCtor {
+  int x;
+  int y;
+  DataWithCtor(int parm) : x(parm + 10), y(parm + 20) {
+    clang_analyzer_dump(this); // expected-warning {{&v}}
+  }
+};
+
+struct StaticSubscript {
+  static void operator[](DataWithCtor v) {
+    clang_analyzer_dump(v.x); // expected-warning {{20}}
+    clang_analyzer_dump(v.y); // expected-warning {{30}}
+  }
+};
+
+void top() {
+  StaticSubscript s;
+  s[DataWithCtor{10}];
+}