Reapply "[Clang][Sema] Fix crash when 'this' is used in a dependent class scope function template specialization that instantiates to a static member function (#87541, #88311)"

clang/docs/ReleaseNotes.rst

@@ -538,6 +538,8 @@ Bug Fixes to C++ Support
 - Fix an issue caused by not handling invalid cases when substituting into the parameter mapping of a constraint. Fixes (#GH86757).
 - Fixed a bug that prevented member function templates of class templates declared with a deduced return type
   from being explicitly specialized for a given implicit instantiation of the class template.
+- Fixed a crash when ``this`` is used in a dependent class scope function template specialization
+  that instantiates to a static member function.
 
 - Fix crash when inheriting from a cv-qualified type. Fixes #GH35603
 - Fix a crash when the using enum declaration uses an anonymous enumeration. Fixes (#GH86790).

clang/include/clang/AST/ExprCXX.h

@@ -3198,7 +3198,6 @@ class UnresolvedLookupExpr final
                        NestedNameSpecifierLoc QualifierLoc,
                        SourceLocation TemplateKWLoc,
                        const DeclarationNameInfo &NameInfo, bool RequiresADL,
-                       bool Overloaded,
                        const TemplateArgumentListInfo *TemplateArgs,
                        UnresolvedSetIterator Begin, UnresolvedSetIterator End,
                        bool KnownDependent);
@@ -3218,8 +3217,9 @@ class UnresolvedLookupExpr final
   static UnresolvedLookupExpr *
   Create(const ASTContext &Context, CXXRecordDecl *NamingClass,
          NestedNameSpecifierLoc QualifierLoc,
-         const DeclarationNameInfo &NameInfo, bool RequiresADL, bool Overloaded,
-         UnresolvedSetIterator Begin, UnresolvedSetIterator End);
+         const DeclarationNameInfo &NameInfo, bool RequiresADL,
+         UnresolvedSetIterator Begin, UnresolvedSetIterator End,
+         bool KnownDependent);
 
   // After canonicalization, there may be dependent template arguments in
   // CanonicalConverted But none of Args is dependent. When any of
@@ -3240,9 +3240,6 @@ class UnresolvedLookupExpr final
   /// argument-dependent lookup.
   bool requiresADL() const { return UnresolvedLookupExprBits.RequiresADL; }
 
-  /// True if this lookup is overloaded.
-  bool isOverloaded() const { return UnresolvedLookupExprBits.Overloaded; }
-
   /// Gets the 'naming class' (in the sense of C++0x
   /// [class.access.base]p5) of the lookup.  This is the scope
   /// that was looked in to find these results.

clang/include/clang/AST/Stmt.h

@@ -1067,11 +1067,6 @@ class alignas(void *) Stmt {
     /// argument-dependent lookup if this is the operand of a function call.
     LLVM_PREFERRED_TYPE(bool)
     unsigned RequiresADL : 1;
-
-    /// True if these lookup results are overloaded.  This is pretty trivially
-    /// rederivable if we urgently need to kill this field.
-    LLVM_PREFERRED_TYPE(bool)
-    unsigned Overloaded : 1;
   };
   static_assert(sizeof(UnresolvedLookupExprBitfields) <= 4,
                 "UnresolvedLookupExprBitfields must be <= than 4 bytes to"

clang/include/clang/Sema/Sema.h

@@ -6527,7 +6527,10 @@ class Sema final : public SemaBase {
                             SourceLocation RParenLoc);
 
   //// ActOnCXXThis -  Parse 'this' pointer.
-  ExprResult ActOnCXXThis(SourceLocation loc);
+  ExprResult ActOnCXXThis(SourceLocation Loc);
+
+  /// Check whether the type of 'this' is valid in the current context.
+  bool CheckCXXThisType(SourceLocation Loc, QualType Type);
 
   /// Build a CXXThisExpr and mark it referenced in the current context.
   Expr *BuildCXXThisExpr(SourceLocation Loc, QualType Type, bool IsImplicit);
@@ -6949,10 +6952,14 @@ class Sema final : public SemaBase {
   ///@{
 
 public:
+  /// Check whether an expression might be an implicit class member access.
+  bool isPotentialImplicitMemberAccess(const CXXScopeSpec &SS, LookupResult &R,
+                                       bool IsAddressOfOperand);
+
   ExprResult BuildPossibleImplicitMemberExpr(
       const CXXScopeSpec &SS, SourceLocation TemplateKWLoc, LookupResult &R,
-      const TemplateArgumentListInfo *TemplateArgs, const Scope *S,
-      UnresolvedLookupExpr *AsULE = nullptr);
+      const TemplateArgumentListInfo *TemplateArgs, const Scope *S);
+
   ExprResult
   BuildImplicitMemberExpr(const CXXScopeSpec &SS, SourceLocation TemplateKWLoc,
                           LookupResult &R,

clang/lib/AST/ASTImporter.cpp

@@ -8574,8 +8574,8 @@ ASTNodeImporter::VisitUnresolvedLookupExpr(UnresolvedLookupExpr *E) {
 
   return UnresolvedLookupExpr::Create(
       Importer.getToContext(), *ToNamingClassOrErr, *ToQualifierLocOrErr,
-      ToNameInfo, E->requiresADL(), E->isOverloaded(), ToDecls.begin(),
-      ToDecls.end());
+      ToNameInfo, E->requiresADL(), ToDecls.begin(), ToDecls.end(),
+      /*KnownDependent=*/E->isTypeDependent());
 }
 
 ExpectedStmt

clang/lib/AST/ExprCXX.cpp

@@ -353,15 +353,14 @@ SourceLocation CXXPseudoDestructorExpr::getEndLoc() const {
 UnresolvedLookupExpr::UnresolvedLookupExpr(
     const ASTContext &Context, CXXRecordDecl *NamingClass,
     NestedNameSpecifierLoc QualifierLoc, SourceLocation TemplateKWLoc,
-    const DeclarationNameInfo &NameInfo, bool RequiresADL, bool Overloaded,
+    const DeclarationNameInfo &NameInfo, bool RequiresADL,
     const TemplateArgumentListInfo *TemplateArgs, UnresolvedSetIterator Begin,
     UnresolvedSetIterator End, bool KnownDependent)
     : OverloadExpr(UnresolvedLookupExprClass, Context, QualifierLoc,
                    TemplateKWLoc, NameInfo, TemplateArgs, Begin, End,
                    KnownDependent, false, false),
       NamingClass(NamingClass) {
   UnresolvedLookupExprBits.RequiresADL = RequiresADL;
-  UnresolvedLookupExprBits.Overloaded = Overloaded;
 }
 
 UnresolvedLookupExpr::UnresolvedLookupExpr(EmptyShell Empty,
@@ -373,15 +372,16 @@ UnresolvedLookupExpr::UnresolvedLookupExpr(EmptyShell Empty,
 UnresolvedLookupExpr *UnresolvedLookupExpr::Create(
     const ASTContext &Context, CXXRecordDecl *NamingClass,
     NestedNameSpecifierLoc QualifierLoc, const DeclarationNameInfo &NameInfo,
-    bool RequiresADL, bool Overloaded, UnresolvedSetIterator Begin,
-    UnresolvedSetIterator End) {
+    bool RequiresADL, UnresolvedSetIterator Begin, UnresolvedSetIterator End,
+    bool KnownDependent) {
   unsigned NumResults = End - Begin;
   unsigned Size = totalSizeToAlloc<DeclAccessPair, ASTTemplateKWAndArgsInfo,
                                    TemplateArgumentLoc>(NumResults, 0, 0);
   void *Mem = Context.Allocate(Size, alignof(UnresolvedLookupExpr));
-  return new (Mem) UnresolvedLookupExpr(Context, NamingClass, QualifierLoc,
-                                        SourceLocation(), NameInfo, RequiresADL,
-                                        Overloaded, nullptr, Begin, End, false);
+  return new (Mem) UnresolvedLookupExpr(
+      Context, NamingClass, QualifierLoc,
+      /*TemplateKWLoc=*/SourceLocation(), NameInfo, RequiresADL,
+      /*TemplateArgs=*/nullptr, Begin, End, KnownDependent);
 }
 
 UnresolvedLookupExpr *UnresolvedLookupExpr::Create(
@@ -390,16 +390,16 @@ UnresolvedLookupExpr *UnresolvedLookupExpr::Create(
     const DeclarationNameInfo &NameInfo, bool RequiresADL,
     const TemplateArgumentListInfo *Args, UnresolvedSetIterator Begin,
     UnresolvedSetIterator End, bool KnownDependent) {
-  assert(Args || TemplateKWLoc.isValid());
   unsigned NumResults = End - Begin;
+  bool HasTemplateKWAndArgsInfo = Args || TemplateKWLoc.isValid();
   unsigned NumTemplateArgs = Args ? Args->size() : 0;
-  unsigned Size =
-      totalSizeToAlloc<DeclAccessPair, ASTTemplateKWAndArgsInfo,
-                       TemplateArgumentLoc>(NumResults, 1, NumTemplateArgs);
+  unsigned Size = totalSizeToAlloc<DeclAccessPair, ASTTemplateKWAndArgsInfo,
+                                   TemplateArgumentLoc>(
+      NumResults, HasTemplateKWAndArgsInfo, NumTemplateArgs);
   void *Mem = Context.Allocate(Size, alignof(UnresolvedLookupExpr));
-  return new (Mem) UnresolvedLookupExpr(
-      Context, NamingClass, QualifierLoc, TemplateKWLoc, NameInfo, RequiresADL,
-      /*Overloaded=*/true, Args, Begin, End, KnownDependent);
+  return new (Mem) UnresolvedLookupExpr(Context, NamingClass, QualifierLoc,
+                                        TemplateKWLoc, NameInfo, RequiresADL,
+                                        Args, Begin, End, KnownDependent);
 }
 
 UnresolvedLookupExpr *UnresolvedLookupExpr::CreateEmpty(

clang/lib/Sema/SemaCoroutine.cpp

@@ -817,13 +817,10 @@ ExprResult Sema::BuildOperatorCoawaitLookupExpr(Scope *S, SourceLocation Loc) {
 
   assert(!Operators.isAmbiguous() && "Operator lookup cannot be ambiguous");
   const auto &Functions = Operators.asUnresolvedSet();
-  bool IsOverloaded =
-      Functions.size() > 1 ||
-      (Functions.size() == 1 && isa<FunctionTemplateDecl>(*Functions.begin()));
   Expr *CoawaitOp = UnresolvedLookupExpr::Create(
       Context, /*NamingClass*/ nullptr, NestedNameSpecifierLoc(),
-      DeclarationNameInfo(OpName, Loc), /*RequiresADL*/ true, IsOverloaded,
-      Functions.begin(), Functions.end());
+      DeclarationNameInfo(OpName, Loc), /*RequiresADL*/ true, Functions.begin(),
+      Functions.end(), /*KnownDependent=*/false);
   assert(CoawaitOp);
   return CoawaitOp;
 }

clang/lib/Sema/SemaDecl.cpp

@@ -1240,8 +1240,8 @@ Sema::NameClassification Sema::ClassifyName(Scope *S, CXXScopeSpec &SS,
   Result.suppressDiagnostics();
   return NameClassification::OverloadSet(UnresolvedLookupExpr::Create(
       Context, Result.getNamingClass(), SS.getWithLocInContext(Context),
-      Result.getLookupNameInfo(), ADL, Result.isOverloadedResult(),
-      Result.begin(), Result.end()));
+      Result.getLookupNameInfo(), ADL, Result.begin(), Result.end(),
+      /*KnownDependent=*/false));
 }
 
 ExprResult

clang/lib/Sema/SemaDeclCXX.cpp

@@ -1302,7 +1302,7 @@ static bool checkTupleLikeDecomposition(Sema &S,
       //   in the associated namespaces.
       Expr *Get = UnresolvedLookupExpr::Create(
           S.Context, nullptr, NestedNameSpecifierLoc(), SourceLocation(),
-          DeclarationNameInfo(GetDN, Loc), /*RequiresADL*/ true, &Args,
+          DeclarationNameInfo(GetDN, Loc), /*RequiresADL=*/true, &Args,
           UnresolvedSetIterator(), UnresolvedSetIterator(),
           /*KnownDependent=*/false);
 

clang/lib/Sema/SemaExpr.cpp

@@ -2918,26 +2918,9 @@ Sema::ActOnIdExpression(Scope *S, CXXScopeSpec &SS,
   // to get this right here so that we don't end up making a
   // spuriously dependent expression if we're inside a dependent
   // instance method.
-  if (getLangOpts().CPlusPlus && !R.empty() &&
-      (*R.begin())->isCXXClassMember()) {
-    bool MightBeImplicitMember;
-    if (!IsAddressOfOperand)
-      MightBeImplicitMember = true;
-    else if (!SS.isEmpty())
-      MightBeImplicitMember = false;
-    else if (R.isOverloadedResult())
-      MightBeImplicitMember = false;
-    else if (R.isUnresolvableResult())
-      MightBeImplicitMember = true;
-    else
-      MightBeImplicitMember = isa<FieldDecl>(R.getFoundDecl()) ||
-                              isa<IndirectFieldDecl>(R.getFoundDecl()) ||
-                              isa<MSPropertyDecl>(R.getFoundDecl());
-
-    if (MightBeImplicitMember)
-      return BuildPossibleImplicitMemberExpr(SS, TemplateKWLoc,
-                                             R, TemplateArgs, S);
-  }
+  if (isPotentialImplicitMemberAccess(SS, R, IsAddressOfOperand))
+    return BuildPossibleImplicitMemberExpr(SS, TemplateKWLoc, R, TemplateArgs,
+                                           S);
 
   if (TemplateArgs || TemplateKWLoc.isValid()) {
 
@@ -3471,12 +3454,10 @@ ExprResult Sema::BuildDeclarationNameExpr(const CXXScopeSpec &SS,
   // we've picked a target.
   R.suppressDiagnostics();
 
-  UnresolvedLookupExpr *ULE
-    = UnresolvedLookupExpr::Create(Context, R.getNamingClass(),
-                                   SS.getWithLocInContext(Context),
-                                   R.getLookupNameInfo(),
-                                   NeedsADL, R.isOverloadedResult(),
-                                   R.begin(), R.end());
+  UnresolvedLookupExpr *ULE = UnresolvedLookupExpr::Create(
+      Context, R.getNamingClass(), SS.getWithLocInContext(Context),
+      R.getLookupNameInfo(), NeedsADL, R.begin(), R.end(),
+      /*KnownDependent=*/false);
 
   return ULE;
 }

clang/lib/Sema/SemaExprCXX.cpp

@@ -1416,26 +1416,42 @@ bool Sema::CheckCXXThisCapture(SourceLocation Loc, const bool Explicit,
 }
 
 ExprResult Sema::ActOnCXXThis(SourceLocation Loc) {
-  /// C++ 9.3.2: In the body of a non-static member function, the keyword this
-  /// is a non-lvalue expression whose value is the address of the object for
-  /// which the function is called.
+  // C++20 [expr.prim.this]p1:
+  //   The keyword this names a pointer to the object for which an
+  //   implicit object member function is invoked or a non-static
+  //   data member's initializer is evaluated.
   QualType ThisTy = getCurrentThisType();
 
-  if (ThisTy.isNull()) {
-    DeclContext *DC = getFunctionLevelDeclContext();
+  if (CheckCXXThisType(Loc, ThisTy))
+    return ExprError();
 
-    if (const auto *Method = dyn_cast<CXXMethodDecl>(DC);
-        Method && Method->isExplicitObjectMemberFunction()) {
-      return Diag(Loc, diag::err_invalid_this_use) << 1;
-    }
+  return BuildCXXThisExpr(Loc, ThisTy, /*IsImplicit=*/false);
+}
 
-    if (isLambdaCallWithExplicitObjectParameter(CurContext))
-      return Diag(Loc, diag::err_invalid_this_use) << 1;
+bool Sema::CheckCXXThisType(SourceLocation Loc, QualType Type) {
+  if (!Type.isNull())
+    return false;
 
-    return Diag(Loc, diag::err_invalid_this_use) << 0;
+  // C++20 [expr.prim.this]p3:
+  //   If a declaration declares a member function or member function template
+  //   of a class X, the expression this is a prvalue of type
+  //   "pointer to cv-qualifier-seq X" wherever X is the current class between
+  //   the optional cv-qualifier-seq and the end of the function-definition,
+  //   member-declarator, or declarator. It shall not appear within the
+  //   declaration of either a static member function or an explicit object
+  //   member function of the current class (although its type and value
+  //   category are defined within such member functions as they are within
+  //   an implicit object member function).
+  DeclContext *DC = getFunctionLevelDeclContext();
+  if (const auto *Method = dyn_cast<CXXMethodDecl>(DC);
+      Method && Method->isExplicitObjectMemberFunction()) {
+    Diag(Loc, diag::err_invalid_this_use) << 1;
+  } else if (isLambdaCallWithExplicitObjectParameter(CurContext)) {
+    Diag(Loc, diag::err_invalid_this_use) << 1;
+  } else {
+    Diag(Loc, diag::err_invalid_this_use) << 0;
   }
-
-  return BuildCXXThisExpr(Loc, ThisTy, /*IsImplicit=*/false);
+  return true;
 }
 
 Expr *Sema::BuildCXXThisExpr(SourceLocation Loc, QualType Type,
@@ -8644,21 +8660,8 @@ static ExprResult attemptRecovery(Sema &SemaRef,
 
       // Detect and handle the case where the decl might be an implicit
       // member.
-      bool MightBeImplicitMember;
-      if (!Consumer.isAddressOfOperand())
-        MightBeImplicitMember = true;
-      else if (!NewSS.isEmpty())
-        MightBeImplicitMember = false;
-      else if (R.isOverloadedResult())
-        MightBeImplicitMember = false;
-      else if (R.isUnresolvableResult())
-        MightBeImplicitMember = true;
-      else
-        MightBeImplicitMember = isa<FieldDecl>(ND) ||
-                                isa<IndirectFieldDecl>(ND) ||
-                                isa<MSPropertyDecl>(ND);
-
-      if (MightBeImplicitMember)
+      if (SemaRef.isPotentialImplicitMemberAccess(
+              NewSS, R, Consumer.isAddressOfOperand()))
         return SemaRef.BuildPossibleImplicitMemberExpr(
             NewSS, /*TemplateKWLoc*/ SourceLocation(), R,
             /*TemplateArgs*/ nullptr, /*S*/ nullptr);