[clang] static operators should evaluate object argument (reland)

clang-tools-extra/clangd/InlayHints.cpp

@@ -651,16 +651,12 @@ class InlayHintVisitor : public RecursiveASTVisitor<InlayHintVisitor> {
     // implied object argument ([over.call.func]), the list of provided
     // arguments is preceded by the implied object argument for the purposes of
     // this correspondence...
-    //
-    // However, we don't have the implied object argument
-    // for static operator() per clang::Sema::BuildCallToObjectOfClassType.
     llvm::ArrayRef<const Expr *> Args = {E->getArgs(), E->getNumArgs()};
     // We don't have the implied object argument through a function pointer
     // either.
     if (const CXXMethodDecl *Method =
             dyn_cast_or_null<CXXMethodDecl>(Callee.Decl))
-      if (Method->isInstance() &&
-          (IsFunctor || Method->hasCXXExplicitFunctionObjectParameter()))
+      if (IsFunctor || Method->hasCXXExplicitFunctionObjectParameter())
         Args = Args.drop_front(1);
     processCall(Callee, Args);
     return true;

clang/docs/ReleaseNotes.rst

@@ -147,6 +147,8 @@ Bug Fixes to C++ Support
 - Fix for crash when using a erroneous type in a return statement.
   Fixes (`#63244 <https://github.com/llvm/llvm-project/issues/63244>`_)
   and (`#79745 <https://github.com/llvm/llvm-project/issues/79745>`_)
+- Fix incorrect code generation caused by the object argument of ``static operator()`` and ``static operator[]`` calls not being evaluated.
+  Fixes (`#67976 <https://github.com/llvm/llvm-project/issues/67976>`_)
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^

clang/lib/AST/ExprConstant.cpp

@@ -7951,7 +7951,8 @@ class ExprEvaluatorBase
       // Overloaded operator calls to member functions are represented as normal
       // calls with '*this' as the first argument.
       const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD);
-      if (MD && MD->isImplicitObjectMemberFunction()) {
+      if (MD &&
+          (MD->isImplicitObjectMemberFunction() || (OCE && MD->isStatic()))) {
         // FIXME: When selecting an implicit conversion for an overloaded
         // operator delete, we sometimes try to evaluate calls to conversion
         // operators without a 'this' parameter!
@@ -7960,7 +7961,11 @@ class ExprEvaluatorBase
 
         if (!EvaluateObjectArgument(Info, Args[0], ThisVal))
           return false;
-        This = &ThisVal;
+
+        // If we are calling a static operator, the 'this' argument needs to be
+        // ignored after being evaluated.
+        if (MD->isInstance())
+          This = &ThisVal;
 
         // If this is syntactically a simple assignment using a trivial
         // assignment operator, start the lifetimes of union members as needed,

clang/lib/CodeGen/CGExpr.cpp

@@ -5848,6 +5848,7 @@ RValue CodeGenFunction::EmitCall(QualType CalleeType, const CGCallee &OrigCallee
   // destruction order is not necessarily reverse construction order.
   // FIXME: Revisit this based on C++ committee response to unimplementability.
   EvaluationOrder Order = EvaluationOrder::Default;
+  bool StaticOperator = false;
   if (auto *OCE = dyn_cast<CXXOperatorCallExpr>(E)) {
     if (OCE->isAssignmentOp())
       Order = EvaluationOrder::ForceRightToLeft;
@@ -5865,10 +5866,22 @@ RValue CodeGenFunction::EmitCall(QualType CalleeType, const CGCallee &OrigCallee
         break;
       }
     }
+
+    if (const auto *MD =
+            dyn_cast_if_present<CXXMethodDecl>(OCE->getCalleeDecl());
+        MD && MD->isStatic())
+      StaticOperator = true;
   }
 
-  EmitCallArgs(Args, dyn_cast<FunctionProtoType>(FnType), E->arguments(),
-               E->getDirectCallee(), /*ParamsToSkip*/ 0, Order);
+  auto Arguments = E->arguments();
+  if (StaticOperator) {
+    // If we're calling a static operator, we need to emit the object argument
+    // and ignore it.
+    EmitIgnoredExpr(E->getArg(0));
+    Arguments = drop_begin(Arguments, 1);
+  }
+  EmitCallArgs(Args, dyn_cast<FunctionProtoType>(FnType), Arguments,
+               E->getDirectCallee(), /*ParamsToSkip=*/0, Order);
 
   const CGFunctionInfo &FnInfo = CGM.getTypes().arrangeFreeFunctionCall(
       Args, FnType, /*ChainCall=*/Chain);

clang/lib/Sema/SemaChecking.cpp

@@ -7611,9 +7611,8 @@ bool Sema::CheckFunctionCall(FunctionDecl *FDecl, CallExpr *TheCall,
   unsigned NumArgs = TheCall->getNumArgs();
 
   Expr *ImplicitThis = nullptr;
-  if (IsMemberOperatorCall && !FDecl->isStatic() &&
-      !FDecl->hasCXXExplicitFunctionObjectParameter()) {
-    // If this is a call to a non-static member operator, hide the first
+  if (IsMemberOperatorCall && !FDecl->hasCXXExplicitFunctionObjectParameter()) {
+    // If this is a call to a member operator, hide the first
     // argument from checkCall.
     // FIXME: Our choice of AST representation here is less than ideal.
     ImplicitThis = Args[0];

clang/lib/Sema/SemaOverload.cpp

@@ -5664,10 +5664,15 @@ static ImplicitConversionSequence TryObjectArgumentInitialization(
   assert(FromType->isRecordType());
 
   QualType ClassType = S.Context.getTypeDeclType(ActingContext);
-  // [class.dtor]p2: A destructor can be invoked for a const, volatile or
-  //                 const volatile object.
+  // C++98 [class.dtor]p2:
+  //   A destructor can be invoked for a const, volatile or const volatile
+  //   object.
+  // C++98 [over.match.funcs]p4:
+  //   For static member functions, the implicit object parameter is considered
+  //   to match any object (since if the function is selected, the object is
+  //   discarded).
   Qualifiers Quals = Method->getMethodQualifiers();
-  if (isa<CXXDestructorDecl>(Method)) {
+  if (isa<CXXDestructorDecl>(Method) || Method->isStatic()) {
     Quals.addConst();
     Quals.addVolatile();
   }
@@ -15061,15 +15066,15 @@ ExprResult Sema::CreateOverloadedArraySubscriptExpr(SourceLocation LLoc,
         CXXMethodDecl *Method = cast<CXXMethodDecl>(FnDecl);
         SmallVector<Expr *, 2> MethodArgs;
 
-        // Handle 'this' parameter if the selected function is not static.
+        // Initialize the object parameter.
         if (Method->isExplicitObjectMemberFunction()) {
           ExprResult Res =
               InitializeExplicitObjectArgument(*this, Args[0], Method);
           if (Res.isInvalid())
             return ExprError();
           Args[0] = Res.get();
           ArgExpr = Args;
-        } else if (Method->isInstance()) {
+        } else {
           ExprResult Arg0 = PerformImplicitObjectArgumentInitialization(
               Args[0], /*Qualifier=*/nullptr, Best->FoundDecl, Method);
           if (Arg0.isInvalid())
@@ -15097,15 +15102,9 @@ ExprResult Sema::CreateOverloadedArraySubscriptExpr(SourceLocation LLoc,
         ExprValueKind VK = Expr::getValueKindForType(ResultTy);
         ResultTy = ResultTy.getNonLValueExprType(Context);
 
-        CallExpr *TheCall;
-        if (Method->isInstance())
-          TheCall = CXXOperatorCallExpr::Create(
-              Context, OO_Subscript, FnExpr.get(), MethodArgs, ResultTy, VK,
-              RLoc, CurFPFeatureOverrides());
-        else
-          TheCall =
-              CallExpr::Create(Context, FnExpr.get(), MethodArgs, ResultTy, VK,
-                               RLoc, CurFPFeatureOverrides());
+        CallExpr *TheCall = CXXOperatorCallExpr::Create(
+            Context, OO_Subscript, FnExpr.get(), MethodArgs, ResultTy, VK, RLoc,
+            CurFPFeatureOverrides());
 
         if (CheckCallReturnType(FnDecl->getReturnType(), LLoc, TheCall, FnDecl))
           return ExprError();
@@ -15733,15 +15732,13 @@ Sema::BuildCallToObjectOfClassType(Scope *S, Expr *Obj,
 
   bool IsError = false;
 
-  // Initialize the implicit object parameter if needed.
-  // Since C++23, this could also be a call to a static call operator
-  // which we emit as a regular CallExpr.
+  // Initialize the object parameter.
   llvm::SmallVector<Expr *, 8> NewArgs;
   if (Method->isExplicitObjectMemberFunction()) {
     // FIXME: we should do that during the definition of the lambda when we can.
     DiagnoseInvalidExplicitObjectParameterInLambda(Method);
     PrepareExplicitObjectArgument(*this, Method, Obj, Args, NewArgs);
-  } else if (Method->isInstance()) {
+  } else {
     ExprResult ObjRes = PerformImplicitObjectArgumentInitialization(
         Object.get(), /*Qualifier=*/nullptr, Best->FoundDecl, Method);
     if (ObjRes.isInvalid())
@@ -15775,14 +15772,9 @@ Sema::BuildCallToObjectOfClassType(Scope *S, Expr *Obj,
   ExprValueKind VK = Expr::getValueKindForType(ResultTy);
   ResultTy = ResultTy.getNonLValueExprType(Context);
 
-  CallExpr *TheCall;
-  if (Method->isInstance())
-    TheCall = CXXOperatorCallExpr::Create(Context, OO_Call, NewFn.get(),
-                                          MethodArgs, ResultTy, VK, RParenLoc,
-                                          CurFPFeatureOverrides());
-  else
-    TheCall = CallExpr::Create(Context, NewFn.get(), MethodArgs, ResultTy, VK,
-                               RParenLoc, CurFPFeatureOverrides());
+  CallExpr *TheCall = CXXOperatorCallExpr::Create(
+      Context, OO_Call, NewFn.get(), MethodArgs, ResultTy, VK, RParenLoc,
+      CurFPFeatureOverrides());
 
   if (CheckCallReturnType(Method->getReturnType(), LParenLoc, TheCall, Method))
     return true;

clang/test/AST/ast-dump-static-operators.cpp

@@ -0,0 +1,55 @@
+// RUN: %clang_cc1 -std=c++23 %s -ast-dump -triple x86_64-unknown-unknown -o - | FileCheck -strict-whitespace %s
+
+struct Functor {
+  static int operator()(int x, int y) {
+    return x + y;
+  }
+  static int operator[](int x, int y) {
+    return x + y;
+  }
+};
+
+Functor& get_functor() {
+  static Functor functor;
+  return functor;
+}
+
+void call_static_operators() {
+  Functor functor;
+
+  int z1 = functor(1, 2);
+  // CHECK:      CXXOperatorCallExpr {{.*}} 'int' '()'
+  // CHECK-NEXT: |-ImplicitCastExpr {{.*}} <col:19, col:24> 'int (*)(int, int)' <FunctionToPointerDecay>
+  // CHECK-NEXT: | `-DeclRefExpr {{.*}} <col:19, col:24> 'int (int, int)' lvalue CXXMethod {{.*}} 'operator()' 'int (int, int)'
+  // CHECK-NEXT: |-DeclRefExpr {{.*}} <col:12> 'Functor' lvalue Var {{.*}} 'functor' 'Functor'
+  // CHECK-NEXT: |-IntegerLiteral {{.*}} <col:20> 'int' 1
+  // CHECK-NEXT: `-IntegerLiteral {{.*}} <col:23> 'int' 2
+
+  int z2 = functor[1, 2];
+  // CHECK:      CXXOperatorCallExpr {{.*}} 'int' '[]'
+  // CHECK-NEXT: |-ImplicitCastExpr {{.*}} <col:19, col:24> 'int (*)(int, int)' <FunctionToPointerDecay>
+  // CHECK-NEXT: | `-DeclRefExpr {{.*}} <col:19, col:24> 'int (int, int)' lvalue CXXMethod {{.*}} 'operator[]' 'int (int, int)'
+  // CHECK-NEXT: |-DeclRefExpr {{.*}} <col:12> 'Functor' lvalue Var {{.*}} 'functor' 'Functor'
+  // CHECK-NEXT: |-IntegerLiteral {{.*}} <col:20> 'int' 1
+  // CHECK-NEXT: `-IntegerLiteral {{.*}} <col:23> 'int' 2
+
+  int z3 = get_functor()(1, 2);
+  // CHECK:      CXXOperatorCallExpr {{.*}} 'int' '()'
+  // CHECK-NEXT: |-ImplicitCastExpr {{.*}} <col:25, col:30> 'int (*)(int, int)' <FunctionToPointerDecay>
+  // CHECK-NEXT: | `-DeclRefExpr {{.*}} <col:25, col:30> 'int (int, int)' lvalue CXXMethod {{.*}} 'operator()' 'int (int, int)'
+  // CHECK-NEXT: |-CallExpr {{.*}} <col:12, col:24> 'Functor' lvalue
+  // CHECK-NEXT: | `-ImplicitCastExpr {{.*}} <col:12> 'Functor &(*)()' <FunctionToPointerDecay>
+  // CHECK-NEXT: |   `-DeclRefExpr {{.*}} <col:12> 'Functor &()' lvalue Function {{.*}} 'get_functor' 'Functor &()'
+  // CHECK-NEXT: |-IntegerLiteral {{.*}} <col:26> 'int' 1
+  // CHECK-NEXT: `-IntegerLiteral {{.*}} <col:29> 'int' 2
+
+  int z4 = get_functor()[1, 2];
+  // CHECK:      CXXOperatorCallExpr {{.*}} 'int' '[]'
+  // CHECK-NEXT: |-ImplicitCastExpr {{.*}} <col:25, col:30> 'int (*)(int, int)' <FunctionToPointerDecay>
+  // CHECK-NEXT: | `-DeclRefExpr {{.*}} <col:25, col:30> 'int (int, int)' lvalue CXXMethod {{.*}} 'operator[]' 'int (int, int)'
+  // CHECK-NEXT: |-CallExpr {{.*}} <col:12, col:24> 'Functor' lvalue
+  // CHECK-NEXT: | `-ImplicitCastExpr {{.*}} <col:12> 'Functor &(*)()' <FunctionToPointerDecay>
+  // CHECK-NEXT: |   `-DeclRefExpr {{.*}} <col:12> 'Functor &()' lvalue Function {{.*}} 'get_functor' 'Functor &()'
+  // CHECK-NEXT: |-IntegerLiteral {{.*}} <col:26> 'int' 1
+  // CHECK-NEXT: `-IntegerLiteral {{.*}} <col:29> 'int' 2
+}

clang/test/CodeGenCXX/cxx2b-static-call-operator.cpp

@@ -19,16 +19,22 @@ void CallsTheLambda() {
 
 // CHECK:      define {{.*}}CallsTheLambda{{.*}}
 // CHECK-NEXT: entry:
-// CHECK-NEXT:   %call = call noundef i32 {{.*}}(i32 noundef 1, i32 noundef 2)
+// CHECK:        {{.*}}call {{.*}}GetALambda{{.*}}()
+// CHECK-NEXT:   {{.*}} = call noundef i32 {{.*}}(i32 noundef 1, i32 noundef 2)
 // CHECK-NEXT:   ret void
 // CHECK-NEXT: }
 
+Functor GetAFunctor() {
+  return {};
+}
+
 void call_static_call_operator() {
   Functor f;
   f(101, 102);
   f.operator()(201, 202);
   Functor{}(301, 302);
   Functor::operator()(401, 402);
+  GetAFunctor()(501, 502);
 }
 
 // CHECK:      define {{.*}}call_static_call_operator{{.*}}
@@ -37,6 +43,8 @@ void call_static_call_operator() {
 // CHECK-NEXT:   {{.*}} = call noundef i32 {{.*}}Functor{{.*}}(i32 noundef 201, i32 noundef 202)
 // CHECK-NEXT:   {{.*}} = call noundef i32 {{.*}}Functor{{.*}}(i32 noundef 301, i32 noundef 302)
 // CHECK-NEXT:   {{.*}} = call noundef i32 {{.*}}Functor{{.*}}(i32 noundef 401, i32 noundef 402)
+// CHECK:        {{.*}}call {{.*}}GetAFunctor{{.*}}()
+// CHECK-NEXT:   {{.*}} = call noundef i32 {{.*}}Functor{{.*}}(i32 noundef 501, i32 noundef 502)
 // CHECK-NEXT:   ret void
 // CHECK-NEXT: }
 
@@ -106,12 +114,16 @@ void test_dep_functors() {
 
 // CHECK:      define {{.*}}test_dep_functors{{.*}}
 // CHECK-NEXT: entry:
-// CHECK:        %call = call noundef i32 {{.*}}DepFunctor{{.*}}(float noundef 1.000000e+00)
-// CHECK:        %call1 = call noundef i32 {{.*}}DepFunctor{{.*}}(i1 noundef zeroext true)
-// CHECK:        %call2 = call noundef i32 {{.*}}dep_lambda1{{.*}}(float noundef 1.000000e+00)
-// CHECK:        %call3 = call noundef i32 {{.*}}dep_lambda1{{.*}}(i1 noundef zeroext true)
-// CHECK:        %call4 = call noundef i32 {{.*}}dep_lambda2{{.*}}(float noundef 1.000000e+00)
-// CHECK:        %call5 = call noundef i32 {{.*}}dep_lambda2{{.*}}(i1 noundef zeroext true)
+// CHECK:        {{.*}} = call noundef i32 {{.*}}DepFunctor{{.*}}(float noundef 1.000000e+00)
+// CHECK:        {{.*}} = call noundef i32 {{.*}}DepFunctor{{.*}}(i1 noundef zeroext true)
+// CHECK:        {{.*}}call {{.*}}dep_lambda1{{.*}}()
+// CHECK:        {{.*}} = call noundef i32 {{.*}}dep_lambda1{{.*}}(float noundef 1.000000e+00)
+// CHECK:        {{.*}}call {{.*}}dep_lambda1{{.*}}()
+// CHECK:        {{.*}} = call noundef i32 {{.*}}dep_lambda1{{.*}}(i1 noundef zeroext true)
+// CHECK:        {{.*}}call {{.*}}dep_lambda2{{.*}}()
+// CHECK:        {{.*}} = call noundef i32 {{.*}}dep_lambda2{{.*}}(float noundef 1.000000e+00)
+// CHECK:        {{.*}}call {{.*}}dep_lambda2{{.*}}()
+// CHECK:        {{.*}} = call noundef i32 {{.*}}dep_lambda2{{.*}}(i1 noundef zeroext true)
 // CHECK:        ret void
 // CHECK-NEXT: }
 

clang/test/CodeGenCXX/cxx2b-static-subscript-operator.cpp

@@ -7,12 +7,17 @@ struct Functor {
   }
 };
 
+Functor GetAFunctor() {
+  return {};
+}
+
 void call_static_subscript_operator() {
   Functor f;
   f[101, 102];
   f.operator[](201, 202);
   Functor{}[301, 302];
   Functor::operator[](401, 402);
+  GetAFunctor()[501, 502];
 }
 
 // CHECK:      define {{.*}}call_static_subscript_operator{{.*}}
@@ -21,6 +26,8 @@ void call_static_subscript_operator() {
 // CHECK-NEXT:   {{.*}} = call noundef i32 {{.*}}Functor{{.*}}(i32 noundef 201, i32 noundef 202)
 // CHECK-NEXT:   {{.*}} = call noundef i32 {{.*}}Functor{{.*}}(i32 noundef 301, i32 noundef 302)
 // CHECK-NEXT:   {{.*}} = call noundef i32 {{.*}}Functor{{.*}}(i32 noundef 401, i32 noundef 402)
+// CHECK:        {{.*}}call {{.*}}GetAFunctor{{.*}}()
+// CHECK-NEXT:   {{.*}} = call noundef i32 {{.*}}Functor{{.*}}(i32 noundef 501, i32 noundef 502)
 // CHECK-NEXT:   ret void
 // CHECK-NEXT: }
 
@@ -60,7 +67,7 @@ void test_dep_functors() {
 
 // CHECK:      define {{.*}}test_dep_functors{{.*}}
 // CHECK-NEXT: entry:
-// CHECK:        %call = call noundef i32 {{.*}}DepFunctor{{.*}}(float noundef 1.000000e+00)
-// CHECK:        %call1 = call noundef i32 {{.*}}DepFunctor{{.*}}(i1 noundef zeroext true)
+// CHECK:        {{.*}} = call noundef i32 {{.*}}DepFunctor{{.*}}(float noundef 1.000000e+00)
+// CHECK:        {{.*}} = call noundef i32 {{.*}}DepFunctor{{.*}}(i1 noundef zeroext true)
 // CHECK:        ret void
 // CHECK-NEXT: }

clang/test/SemaCXX/cxx2b-static-operator.cpp

@@ -0,0 +1,31 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -std=c++23 %s
+
+// expected-no-diagnostics
+
+namespace A {
+
+struct Foo {
+  static int operator()(int a, int b) { return a + b; }
+  static int operator[](int a, int b) { return a + b; }
+};
+
+void ok() {
+  // Should pass regardless of const / volatile
+  Foo foo;
+  foo(1, 2);
+  foo[1, 2];
+
+  const Foo fooC;
+  fooC(1, 2);
+  fooC[1, 2];
+
+  const Foo fooV;
+  fooV(1, 2);
+  fooV[1, 2];
+
+  const volatile Foo fooCV;
+  fooCV(1, 2);
+  fooCV[1, 2];
+}
+
+}