Reapply "[Clang][Sema] Diagnose class member access expressions naming non-existent members of the current instantiation prior to instantiation in the absence of dependent base classes (#84050)" (#90152)

Reapplies #84050, addressing a bug which cases a crash when an
expression with the type of the current instantiation is used as the
_postfix-expression_ in a class member access expression (arrow form).

11 files changed, 276 insertions, 221 deletions

diff --git a/clang/lib/Sema/HLSLExternalSemaSource.cpp b/clang/lib/Sema/HLSLExternalSemaSource.cpp
index 1a1febf..bb283c5 100644
--- a/clang/lib/Sema/HLSLExternalSemaSource.cpp
+++ b/clang/lib/Sema/HLSLExternalSemaSource.cpp
@@ -126,12 +126,15 @@ struct BuiltinTypeDeclBuilder {
 
   static DeclRefExpr *lookupBuiltinFunction(ASTContext &AST, Sema &S,
                                             StringRef Name) {
-    CXXScopeSpec SS;
     IdentifierInfo &II = AST.Idents.get(Name, tok::TokenKind::identifier);
     DeclarationNameInfo NameInfo =
         DeclarationNameInfo(DeclarationName(&II), SourceLocation());
     LookupResult R(S, NameInfo, Sema::LookupOrdinaryName);
-    S.LookupParsedName(R, S.getCurScope(), &SS, false);
+    // AllowBuiltinCreation is false but LookupDirect will create
+    // the builtin when searching the global scope anyways...
+    S.LookupName(R, S.getCurScope());
+    // FIXME: If the builtin function was user-declared in global scope,
+    // this assert *will* fail. Should this call LookupBuiltin instead?
     assert(R.isSingleResult() &&
            "Since this is a builtin it should always resolve!");
     auto *VD = cast<ValueDecl>(R.getFoundDecl());
diff --git a/clang/lib/Sema/SemaAttr.cpp b/clang/lib/Sema/SemaAttr.cpp
index a5dd158..a83b1e8 100644
--- a/clang/lib/Sema/SemaAttr.cpp
+++ b/clang/lib/Sema/SemaAttr.cpp
@@ -837,7 +837,7 @@ void Sema::ActOnPragmaUnused(const Token &IdTok, Scope *curScope,
 
   IdentifierInfo *Name = IdTok.getIdentifierInfo();
   LookupResult Lookup(*this, Name, IdTok.getLocation(), LookupOrdinaryName);
-  LookupParsedName(Lookup, curScope, nullptr, true);
+  LookupName(Lookup, curScope, /*AllowBuiltinCreation=*/true);
 
   if (Lookup.empty()) {
     Diag(PragmaLoc, diag::warn_pragma_unused_undeclared_var)
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index 671752b..79fb6c0 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -832,7 +832,7 @@ static bool isTagTypeWithMissingTag(Sema &SemaRef, LookupResult &Result,
                                     IdentifierInfo *&Name,
                                     SourceLocation NameLoc) {
   LookupResult R(SemaRef, Name, NameLoc, Sema::LookupTagName);
-  SemaRef.LookupParsedName(R, S, &SS);
+  SemaRef.LookupParsedName(R, S, &SS, /*ObjectType=*/QualType());
   if (TagDecl *Tag = R.getAsSingle<TagDecl>()) {
     StringRef FixItTagName;
     switch (Tag->getTagKind()) {
@@ -869,7 +869,7 @@ static bool isTagTypeWithMissingTag(Sema &SemaRef, LookupResult &Result,
 
     // Replace lookup results with just the tag decl.
     Result.clear(Sema::LookupTagName);
-    SemaRef.LookupParsedName(Result, S, &SS);
+    SemaRef.LookupParsedName(Result, S, &SS, /*ObjectType=*/QualType());
     return true;
   }
 
@@ -896,7 +896,8 @@ Sema::NameClassification Sema::ClassifyName(Scope *S, CXXScopeSpec &SS,
   }
 
   LookupResult Result(*this, Name, NameLoc, LookupOrdinaryName);
-  LookupParsedName(Result, S, &SS, !CurMethod);
+  LookupParsedName(Result, S, &SS, /*ObjectType=*/QualType(),
+                   /*AllowBuiltinCreation=*/!CurMethod);
 
   if (SS.isInvalid())
     return NameClassification::Error();
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index 83155c3..157d42c 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -4519,7 +4519,7 @@ Sema::BuildMemInitializer(Decl *ConstructorD,
                               DS.getBeginLoc(), DS.getEllipsisLoc());
   } else {
     LookupResult R(*this, MemberOrBase, IdLoc, LookupOrdinaryName);
-    LookupParsedName(R, S, &SS);
+    LookupParsedName(R, S, &SS, /*ObjectType=*/QualType());
 
     TypeDecl *TyD = R.getAsSingle<TypeDecl>();
     if (!TyD) {
@@ -12270,7 +12270,7 @@ Decl *Sema::ActOnUsingDirective(Scope *S, SourceLocation UsingLoc,
 
   // Lookup namespace name.
   LookupResult R(*this, NamespcName, IdentLoc, LookupNamespaceName);
-  LookupParsedName(R, S, &SS);
+  LookupParsedName(R, S, &SS, /*ObjectType=*/QualType());
   if (R.isAmbiguous())
     return nullptr;
 
@@ -13729,7 +13729,7 @@ Decl *Sema::ActOnNamespaceAliasDef(Scope *S, SourceLocation NamespaceLoc,
 
   // Lookup the namespace name.
   LookupResult R(*this, Ident, IdentLoc, LookupNamespaceName);
-  LookupParsedName(R, S, &SS);
+  LookupParsedName(R, S, &SS, /*ObjectType=*/QualType());
 
   if (R.isAmbiguous())
     return nullptr;
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 50f92c4..0c37f43f7 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -673,8 +673,9 @@ ExprResult Sema::DefaultLvalueConversion(Expr *E) {
   // expressions of certain types in C++.
   if (getLangOpts().CPlusPlus &&
       (E->getType() == Context.OverloadTy ||
-       T->isDependentType() ||
-       T->isRecordType()))
+       // FIXME: This is a hack! We want the lvalue-to-rvalue conversion applied
+       // to pointer types even if the pointee type is dependent.
+       (T->isDependentType() && !T->isPointerType()) || T->isRecordType()))
     return E;
 
   // The C standard is actually really unclear on this point, and
@@ -2751,8 +2752,8 @@ Sema::ActOnIdExpression(Scope *S, CXXScopeSpec &SS,
   if (isBoundsAttrContext() && !getLangOpts().CPlusPlus && S->isClassScope()) {
     // See if this is reference to a field of struct.
     LookupResult R(*this, NameInfo, LookupMemberName);
-    // LookupParsedName handles a name lookup from within anonymous struct.
-    if (LookupParsedName(R, S, &SS)) {
+    // LookupName handles a name lookup from within anonymous struct.
+    if (LookupName(R, S)) {
       if (auto *VD = dyn_cast<ValueDecl>(R.getFoundDecl())) {
         QualType type = VD->getType().getNonReferenceType();
         // This will eventually be translated into MemberExpr upon
@@ -2773,20 +2774,19 @@ Sema::ActOnIdExpression(Scope *S, CXXScopeSpec &SS,
     // lookup to determine that it was a template name in the first place. If
     // this becomes a performance hit, we can work harder to preserve those
     // results until we get here but it's likely not worth it.
-    bool MemberOfUnknownSpecialization;
     AssumedTemplateKind AssumedTemplate;
-    if (LookupTemplateName(R, S, SS, QualType(), /*EnteringContext=*/false,
-                           MemberOfUnknownSpecialization, TemplateKWLoc,
+    if (LookupTemplateName(R, S, SS, /*ObjectType=*/QualType(),
+                           /*EnteringContext=*/false, TemplateKWLoc,
                            &AssumedTemplate))
       return ExprError();
 
-    if (MemberOfUnknownSpecialization ||
-        (R.getResultKind() == LookupResult::NotFoundInCurrentInstantiation))
+    if (R.wasNotFoundInCurrentInstantiation())
       return ActOnDependentIdExpression(SS, TemplateKWLoc, NameInfo,
                                         IsAddressOfOperand, TemplateArgs);
   } else {
     bool IvarLookupFollowUp = II && !SS.isSet() && getCurMethodDecl();
-    LookupParsedName(R, S, &SS, !IvarLookupFollowUp);
+    LookupParsedName(R, S, &SS, /*ObjectType=*/QualType(),
+                     /*AllowBuiltinCreation=*/!IvarLookupFollowUp);
 
     // If the result might be in a dependent base class, this is a dependent
     // id-expression.
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index 779a416..c1cb03e 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -9157,7 +9157,7 @@ Sema::CheckMicrosoftIfExistsSymbol(Scope *S,
   // Do the redeclaration lookup in the current scope.
   LookupResult R(*this, TargetNameInfo, Sema::LookupAnyName,
                  RedeclarationKind::NotForRedeclaration);
-  LookupParsedName(R, S, &SS);
+  LookupParsedName(R, S, &SS, /*ObjectType=*/QualType());
   R.suppressDiagnostics();
 
   switch (R.getResultKind()) {
diff --git a/clang/lib/Sema/SemaExprMember.cpp b/clang/lib/Sema/SemaExprMember.cpp
index 6e30716..5facb14 100644
--- a/clang/lib/Sema/SemaExprMember.cpp
+++ b/clang/lib/Sema/SemaExprMember.cpp
@@ -667,8 +667,8 @@ namespace {
 // classes, one of its base classes.
 class RecordMemberExprValidatorCCC final : public CorrectionCandidateCallback {
 public:
-  explicit RecordMemberExprValidatorCCC(const RecordType *RTy)
-      : Record(RTy->getDecl()) {
+  explicit RecordMemberExprValidatorCCC(QualType RTy)
+      : Record(RTy->getAsRecordDecl()) {
     // Don't add bare keywords to the consumer since they will always fail
     // validation by virtue of not being associated with any decls.
     WantTypeSpecifiers = false;
@@ -713,58 +713,36 @@ private:
 }
 
 static bool LookupMemberExprInRecord(Sema &SemaRef, LookupResult &R,
-                                     Expr *BaseExpr,
-                                     const RecordType *RTy,
+                                     Expr *BaseExpr, QualType RTy,
                                      SourceLocation OpLoc, bool IsArrow,
                                      CXXScopeSpec &SS, bool HasTemplateArgs,
                                      SourceLocation TemplateKWLoc,
                                      TypoExpr *&TE) {
   SourceRange BaseRange = BaseExpr ? BaseExpr->getSourceRange() : SourceRange();
-  RecordDecl *RDecl = RTy->getDecl();
-  if (!SemaRef.isThisOutsideMemberFunctionBody(QualType(RTy, 0)) &&
-      SemaRef.RequireCompleteType(OpLoc, QualType(RTy, 0),
-                                  diag::err_typecheck_incomplete_tag,
-                                  BaseRange))
+  if (!RTy->isDependentType() &&
+      !SemaRef.isThisOutsideMemberFunctionBody(RTy) &&
+      SemaRef.RequireCompleteType(
+          OpLoc, RTy, diag::err_typecheck_incomplete_tag, BaseRange))
     return true;
 
-  if (HasTemplateArgs || TemplateKWLoc.isValid()) {
-    // LookupTemplateName doesn't expect these both to exist simultaneously.
-    QualType ObjectType = SS.isSet() ? QualType() : QualType(RTy, 0);
+  // LookupTemplateName/LookupParsedName don't expect these both to exist
+  // simultaneously.
+  QualType ObjectType = SS.isSet() ? QualType() : RTy;
+  if (HasTemplateArgs || TemplateKWLoc.isValid())
+    return SemaRef.LookupTemplateName(R,
+                                      /*S=*/nullptr, SS, ObjectType,
+                                      /*EnteringContext=*/false, TemplateKWLoc);
 
-    bool MOUS;
-    return SemaRef.LookupTemplateName(R, nullptr, SS, ObjectType, false, MOUS,
-                                      TemplateKWLoc);
-  }
-
-  DeclContext *DC = RDecl;
-  if (SS.isSet()) {
-    // If the member name was a qualified-id, look into the
-    // nested-name-specifier.
-    DC = SemaRef.computeDeclContext(SS, false);
-
-    if (SemaRef.RequireCompleteDeclContext(SS, DC)) {
-      SemaRef.Diag(SS.getRange().getEnd(), diag::err_typecheck_incomplete_tag)
-          << SS.getRange() << DC;
-      return true;
-    }
-
-    assert(DC && "Cannot handle non-computable dependent contexts in lookup");
-
-    if (!isa<TypeDecl>(DC)) {
-      SemaRef.Diag(R.getNameLoc(), diag::err_qualified_member_nonclass)
-          << DC << SS.getRange();
-      return true;
-    }
-  }
-
-  // The record definition is complete, now look up the member.
-  SemaRef.LookupQualifiedName(R, DC, SS);
+  SemaRef.LookupParsedName(R, /*S=*/nullptr, &SS, ObjectType);
 
-  if (!R.empty())
+  if (!R.empty() || R.wasNotFoundInCurrentInstantiation())
     return false;
 
   DeclarationName Typo = R.getLookupName();
   SourceLocation TypoLoc = R.getNameLoc();
+  // Recompute the lookup context.
+  DeclContext *DC = SS.isSet() ? SemaRef.computeDeclContext(SS)
+                               : SemaRef.computeDeclContext(RTy);
 
   struct QueryState {
     Sema &SemaRef;
@@ -788,7 +766,8 @@ static bool LookupMemberExprInRecord(Sema &SemaRef, LookupResult &R,
                                        << Typo << DC << DroppedSpecifier
                                        << SS.getRange());
         } else {
-          SemaRef.Diag(TypoLoc, diag::err_no_member) << Typo << DC << BaseRange;
+          SemaRef.Diag(TypoLoc, diag::err_no_member)
+              << Typo << DC << (SS.isSet() ? SS.getRange() : BaseRange);
         }
       },
       [=](Sema &SemaRef, TypoExpr *TE, TypoCorrection TC) mutable {
@@ -814,34 +793,25 @@ static ExprResult LookupMemberExpr(Sema &S, LookupResult &R,
                                    Decl *ObjCImpDecl, bool HasTemplateArgs,
                                    SourceLocation TemplateKWLoc);
 
-ExprResult
-Sema::BuildMemberReferenceExpr(Expr *Base, QualType BaseType,
-                               SourceLocation OpLoc, bool IsArrow,
-                               CXXScopeSpec &SS,
-                               SourceLocation TemplateKWLoc,
-                               NamedDecl *FirstQualifierInScope,
-                               const DeclarationNameInfo &NameInfo,
-                               const TemplateArgumentListInfo *TemplateArgs,
-                               const Scope *S,
-                               ActOnMemberAccessExtraArgs *ExtraArgs) {
-  if (BaseType->isDependentType() ||
-      (SS.isSet() && isDependentScopeSpecifier(SS)) ||
-      NameInfo.getName().isDependentName())
-    return ActOnDependentMemberExpr(Base, BaseType,
-                                    IsArrow, OpLoc,
-                                    SS, TemplateKWLoc, FirstQualifierInScope,
-                                    NameInfo, TemplateArgs);
-
+ExprResult Sema::BuildMemberReferenceExpr(
+    Expr *Base, QualType BaseType, SourceLocation OpLoc, bool IsArrow,
+    CXXScopeSpec &SS, SourceLocation TemplateKWLoc,
+    NamedDecl *FirstQualifierInScope, const DeclarationNameInfo &NameInfo,
+    const TemplateArgumentListInfo *TemplateArgs, const Scope *S,
+    ActOnMemberAccessExtraArgs *ExtraArgs) {
   LookupResult R(*this, NameInfo, LookupMemberName);
 
+  if (SS.isInvalid())
+    return ExprError();
+
   // Implicit member accesses.
   if (!Base) {
     TypoExpr *TE = nullptr;
     QualType RecordTy = BaseType;
     if (IsArrow) RecordTy = RecordTy->castAs<PointerType>()->getPointeeType();
-    if (LookupMemberExprInRecord(
-            *this, R, nullptr, RecordTy->castAs<RecordType>(), OpLoc, IsArrow,
-            SS, TemplateArgs != nullptr, TemplateKWLoc, TE))
+    if (LookupMemberExprInRecord(*this, R, nullptr, RecordTy, OpLoc, IsArrow,
+                                 SS, TemplateArgs != nullptr, TemplateKWLoc,
+                                 TE))
       return ExprError();
     if (TE)
       return TE;
@@ -969,19 +939,6 @@ BuildMSPropertyRefExpr(Sema &S, Expr *BaseExpr, bool IsArrow,
 }
 
 MemberExpr *Sema::BuildMemberExpr(
-    Expr *Base, bool IsArrow, SourceLocation OpLoc, const CXXScopeSpec *SS,
-    SourceLocation TemplateKWLoc, ValueDecl *Member, DeclAccessPair FoundDecl,
-    bool HadMultipleCandidates, const DeclarationNameInfo &MemberNameInfo,
-    QualType Ty, ExprValueKind VK, ExprObjectKind OK,
-    const TemplateArgumentListInfo *TemplateArgs) {
-  NestedNameSpecifierLoc NNS =
-      SS ? SS->getWithLocInContext(Context) : NestedNameSpecifierLoc();
-  return BuildMemberExpr(Base, IsArrow, OpLoc, NNS, TemplateKWLoc, Member,
-                         FoundDecl, HadMultipleCandidates, MemberNameInfo, Ty,
-                         VK, OK, TemplateArgs);
-}
-
-MemberExpr *Sema::BuildMemberExpr(
     Expr *Base, bool IsArrow, SourceLocation OpLoc, NestedNameSpecifierLoc NNS,
     SourceLocation TemplateKWLoc, ValueDecl *Member, DeclAccessPair FoundDecl,
     bool HadMultipleCandidates, const DeclarationNameInfo &MemberNameInfo,
@@ -1033,6 +990,17 @@ Sema::BuildMemberReferenceExpr(Expr *BaseExpr, QualType BaseExprType,
                                const Scope *S,
                                bool SuppressQualifierCheck,
                                ActOnMemberAccessExtraArgs *ExtraArgs) {
+  assert(!SS.isInvalid() && "nested-name-specifier cannot be invalid");
+  // If the member wasn't found in the current instantiation, or if the
+  // arrow operator was used with a dependent non-pointer object expression,
+  // build a CXXDependentScopeMemberExpr.
+  if (R.wasNotFoundInCurrentInstantiation() ||
+      (IsArrow && !BaseExprType->isPointerType() &&
+       BaseExprType->isDependentType()))
+    return ActOnDependentMemberExpr(BaseExpr, BaseExprType, IsArrow, OpLoc, SS,
+                                    TemplateKWLoc, FirstQualifierInScope,
+                                    R.getLookupNameInfo(), TemplateArgs);
+
   QualType BaseType = BaseExprType;
   if (IsArrow) {
     assert(BaseType->isPointerType());
@@ -1040,6 +1008,11 @@ Sema::BuildMemberReferenceExpr(Expr *BaseExpr, QualType BaseExprType,
   }
   R.setBaseObjectType(BaseType);
 
+  assert((SS.isEmpty()
+              ? !BaseType->isDependentType() || computeDeclContext(BaseType)
+              : !isDependentScopeSpecifier(SS) || computeDeclContext(SS)) &&
+         "dependent lookup context that isn't the current instantiation?");
+
   // C++1z [expr.ref]p2:
   //   For the first option (dot) the first expression shall be a glvalue [...]
   if (!IsArrow && BaseExpr && BaseExpr->isPRValue()) {
@@ -1068,40 +1041,39 @@ Sema::BuildMemberReferenceExpr(Expr *BaseExpr, QualType BaseExprType,
         << isa<CXXDestructorDecl>(FD);
 
   if (R.empty()) {
-    // Rederive where we looked up.
-    DeclContext *DC = (SS.isSet()
-                       ? computeDeclContext(SS, false)
-                       : BaseType->castAs<RecordType>()->getDecl());
-
-    if (ExtraArgs) {
-      ExprResult RetryExpr;
-      if (!IsArrow && BaseExpr) {
-        SFINAETrap Trap(*this, true);
-        ParsedType ObjectType;
-        bool MayBePseudoDestructor = false;
-        RetryExpr = ActOnStartCXXMemberReference(getCurScope(), BaseExpr,
-                                                 OpLoc, tok::arrow, ObjectType,
-                                                 MayBePseudoDestructor);
-        if (RetryExpr.isUsable() && !Trap.hasErrorOccurred()) {
-          CXXScopeSpec TempSS(SS);
-          RetryExpr = ActOnMemberAccessExpr(
-              ExtraArgs->S, RetryExpr.get(), OpLoc, tok::arrow, TempSS,
-              TemplateKWLoc, ExtraArgs->Id, ExtraArgs->ObjCImpDecl);
-        }
-        if (Trap.hasErrorOccurred())
-          RetryExpr = ExprError();
-      }
-      if (RetryExpr.isUsable()) {
-        Diag(OpLoc, diag::err_no_member_overloaded_arrow)
-          << MemberName << DC << FixItHint::CreateReplacement(OpLoc, "->");
-        return RetryExpr;
+    ExprResult RetryExpr = ExprError();
+    if (ExtraArgs && !IsArrow && BaseExpr && !BaseExpr->isTypeDependent()) {
+      SFINAETrap Trap(*this, true);
+      ParsedType ObjectType;
+      bool MayBePseudoDestructor = false;
+      RetryExpr = ActOnStartCXXMemberReference(getCurScope(), BaseExpr, OpLoc,
+                                               tok::arrow, ObjectType,
+                                               MayBePseudoDestructor);
+      if (RetryExpr.isUsable() && !Trap.hasErrorOccurred()) {
+        CXXScopeSpec TempSS(SS);
+        RetryExpr = ActOnMemberAccessExpr(
+            ExtraArgs->S, RetryExpr.get(), OpLoc, tok::arrow, TempSS,
+            TemplateKWLoc, ExtraArgs->Id, ExtraArgs->ObjCImpDecl);
       }
+      if (Trap.hasErrorOccurred())
+        RetryExpr = ExprError();
     }
 
-    Diag(R.getNameLoc(), diag::err_no_member)
-      << MemberName << DC
-      << (BaseExpr ? BaseExpr->getSourceRange() : SourceRange());
-    return ExprError();
+    // Rederive where we looked up.
+    DeclContext *DC =
+        (SS.isSet() ? computeDeclContext(SS) : computeDeclContext(BaseType));
+    assert(DC);
+
+    if (RetryExpr.isUsable())
+      Diag(OpLoc, diag::err_no_member_overloaded_arrow)
+          << MemberName << DC << FixItHint::CreateReplacement(OpLoc, "->");
+    else
+      Diag(R.getNameLoc(), diag::err_no_member)
+          << MemberName << DC
+          << (SS.isSet()
+                  ? SS.getRange()
+                  : (BaseExpr ? BaseExpr->getSourceRange() : SourceRange()));
+    return RetryExpr;
   }
 
   // Diagnose lookups that find only declarations from a non-base
@@ -1186,7 +1158,8 @@ Sema::BuildMemberReferenceExpr(Expr *BaseExpr, QualType BaseExprType,
                                                     OpLoc);
 
   if (VarDecl *Var = dyn_cast<VarDecl>(MemberDecl)) {
-    return BuildMemberExpr(BaseExpr, IsArrow, OpLoc, &SS, TemplateKWLoc, Var,
+    return BuildMemberExpr(BaseExpr, IsArrow, OpLoc,
+                           SS.getWithLocInContext(Context), TemplateKWLoc, Var,
                            FoundDecl, /*HadMultipleCandidates=*/false,
                            MemberNameInfo, Var->getType().getNonReferenceType(),
                            VK_LValue, OK_Ordinary);
@@ -1203,17 +1176,18 @@ Sema::BuildMemberReferenceExpr(Expr *BaseExpr, QualType BaseExprType,
       type = MemberFn->getType();
     }
 
-    return BuildMemberExpr(BaseExpr, IsArrow, OpLoc, &SS, TemplateKWLoc,
+    return BuildMemberExpr(BaseExpr, IsArrow, OpLoc,
+                           SS.getWithLocInContext(Context), TemplateKWLoc,
                            MemberFn, FoundDecl, /*HadMultipleCandidates=*/false,
                            MemberNameInfo, type, valueKind, OK_Ordinary);
   }
   assert(!isa<FunctionDecl>(MemberDecl) && "member function not C++ method?");
 
   if (EnumConstantDecl *Enum = dyn_cast<EnumConstantDecl>(MemberDecl)) {
-    return BuildMemberExpr(BaseExpr, IsArrow, OpLoc, &SS, TemplateKWLoc, Enum,
-                           FoundDecl, /*HadMultipleCandidates=*/false,
-                           MemberNameInfo, Enum->getType(), VK_PRValue,
-                           OK_Ordinary);
+    return BuildMemberExpr(
+        BaseExpr, IsArrow, OpLoc, SS.getWithLocInContext(Context),
+        TemplateKWLoc, Enum, FoundDecl, /*HadMultipleCandidates=*/false,
+        MemberNameInfo, Enum->getType(), VK_PRValue, OK_Ordinary);
   }
 
   if (VarTemplateDecl *VarTempl = dyn_cast<VarTemplateDecl>(MemberDecl)) {
@@ -1237,7 +1211,8 @@ Sema::BuildMemberReferenceExpr(Expr *BaseExpr, QualType BaseExprType,
     if (!Var->getTemplateSpecializationKind())
       Var->setTemplateSpecializationKind(TSK_ImplicitInstantiation, MemberLoc);
 
-    return BuildMemberExpr(BaseExpr, IsArrow, OpLoc, &SS, TemplateKWLoc, Var,
+    return BuildMemberExpr(BaseExpr, IsArrow, OpLoc,
+                           SS.getWithLocInContext(Context), TemplateKWLoc, Var,
                            FoundDecl, /*HadMultipleCandidates=*/false,
                            MemberNameInfo, Var->getType().getNonReferenceType(),
                            VK_LValue, OK_Ordinary, TemplateArgs);
@@ -1330,7 +1305,6 @@ static ExprResult LookupMemberExpr(Sema &S, LookupResult &R,
     return ExprError();
 
   QualType BaseType = BaseExpr.get()->getType();
-  assert(!BaseType->isDependentType());
 
   DeclarationName MemberName = R.getLookupName();
   SourceLocation MemberLoc = R.getNameLoc();
@@ -1342,29 +1316,31 @@ static ExprResult LookupMemberExpr(Sema &S, LookupResult &R,
   if (IsArrow) {
     if (const PointerType *Ptr = BaseType->getAs<PointerType>())
       BaseType = Ptr->getPointeeType();
-    else if (const ObjCObjectPointerType *Ptr
-               = BaseType->getAs<ObjCObjectPointerType>())
+    else if (const ObjCObjectPointerType *Ptr =
+                 BaseType->getAs<ObjCObjectPointerType>())
       BaseType = Ptr->getPointeeType();
-    else if (BaseType->isRecordType()) {
-      // Recover from arrow accesses to records, e.g.:
-      //   struct MyRecord foo;
-      //   foo->bar
-      // This is actually well-formed in C++ if MyRecord has an
-      // overloaded operator->, but that should have been dealt with
-      // by now--or a diagnostic message already issued if a problem
-      // was encountered while looking for the overloaded operator->.
-      if (!S.getLangOpts().CPlusPlus) {
-        S.Diag(OpLoc, diag::err_typecheck_member_reference_suggestion)
-          << BaseType << int(IsArrow) << BaseExpr.get()->getSourceRange()
-          << FixItHint::CreateReplacement(OpLoc, ".");
+    else if (!BaseType->isDependentType()) {
+      if (BaseType->isRecordType()) {
+        // Recover from arrow accesses to records, e.g.:
+        //   struct MyRecord foo;
+        //   foo->bar
+        // This is actually well-formed in C++ if MyRecord has an
+        // overloaded operator->, but that should have been dealt with
+        // by now--or a diagnostic message already issued if a problem
+        // was encountered while looking for the overloaded operator->.
+        if (!S.getLangOpts().CPlusPlus) {
+          S.Diag(OpLoc, diag::err_typecheck_member_reference_suggestion)
+              << BaseType << int(IsArrow) << BaseExpr.get()->getSourceRange()
+              << FixItHint::CreateReplacement(OpLoc, ".");
+        }
+        IsArrow = false;
+      } else if (BaseType->isFunctionType()) {
+        goto fail;
+      } else {
+        S.Diag(MemberLoc, diag::err_typecheck_member_reference_arrow)
+            << BaseType << BaseExpr.get()->getSourceRange();
+        return ExprError();
       }
-      IsArrow = false;
-    } else if (BaseType->isFunctionType()) {
-      goto fail;
-    } else {
-      S.Diag(MemberLoc, diag::err_typecheck_member_reference_arrow)
-        << BaseType << BaseExpr.get()->getSourceRange();
-      return ExprError();
     }
   }
 
@@ -1384,10 +1360,10 @@ static ExprResult LookupMemberExpr(Sema &S, LookupResult &R,
   }
 
   // Handle field access to simple records.
-  if (const RecordType *RTy = BaseType->getAs<RecordType>()) {
+  if (BaseType->getAsRecordDecl() || BaseType->isDependentType()) {
     TypoExpr *TE = nullptr;
-    if (LookupMemberExprInRecord(S, R, BaseExpr.get(), RTy, OpLoc, IsArrow, SS,
-                                 HasTemplateArgs, TemplateKWLoc, TE))
+    if (LookupMemberExprInRecord(S, R, BaseExpr.get(), BaseType, OpLoc, IsArrow,
+                                 SS, HasTemplateArgs, TemplateKWLoc, TE))
       return ExprError();
 
     // Returning valid-but-null is how we indicate to the caller that
@@ -1810,7 +1786,6 @@ ExprResult Sema::ActOnMemberAccessExpr(Scope *S, Expr *Base,
   DecomposeUnqualifiedId(Id, TemplateArgsBuffer,
                          NameInfo, TemplateArgs);
 
-  DeclarationName Name = NameInfo.getName();
   bool IsArrow = (OpKind == tok::arrow);
 
   if (getLangOpts().HLSL && IsArrow)
@@ -1824,13 +1799,6 @@ ExprResult Sema::ActOnMemberAccessExpr(Scope *S, Expr *Base,
   if (Result.isInvalid()) return ExprError();
   Base = Result.get();
 
-  if (Base->getType()->isDependentType() || Name.isDependentName() ||
-      isDependentScopeSpecifier(SS)) {
-    return ActOnDependentMemberExpr(Base, Base->getType(), IsArrow, OpLoc, SS,
-                                    TemplateKWLoc, FirstQualifierInScope,
-                                    NameInfo, TemplateArgs);
-  }
-
   ActOnMemberAccessExtraArgs ExtraArgs = {S, Id, ObjCImpDecl};
   ExprResult Res = BuildMemberReferenceExpr(
       Base, Base->getType(), OpLoc, IsArrow, SS, TemplateKWLoc,
@@ -1949,10 +1917,10 @@ Sema::BuildFieldReferenceExpr(Expr *BaseExpr, bool IsArrow,
     }
   }
 
-  return BuildMemberExpr(Base.get(), IsArrow, OpLoc, &SS,
-                         /*TemplateKWLoc=*/SourceLocation(), Field, FoundDecl,
-                         /*HadMultipleCandidates=*/false, MemberNameInfo,
-                         MemberType, VK, OK);
+  return BuildMemberExpr(
+      Base.get(), IsArrow, OpLoc, SS.getWithLocInContext(Context),
+      /*TemplateKWLoc=*/SourceLocation(), Field, FoundDecl,
+      /*HadMultipleCandidates=*/false, MemberNameInfo, MemberType, VK, OK);
 }
 
 /// Builds an implicit member access expression.  The current context
diff --git a/clang/lib/Sema/SemaLookup.cpp b/clang/lib/Sema/SemaLookup.cpp
index 55af414..2f6ad49 100644
--- a/clang/lib/Sema/SemaLookup.cpp
+++ b/clang/lib/Sema/SemaLookup.cpp
@@ -1282,6 +1282,31 @@ bool Sema::CppLookupName(LookupResult &R, Scope *S) {
       if (DeclContext *DC = PreS->getEntity())
         DeclareImplicitMemberFunctionsWithName(*this, Name, R.getNameLoc(), DC);
   }
+  // C++23 [temp.dep.general]p2:
+  //   The component name of an unqualified-id is dependent if
+  //   - it is a conversion-function-id whose conversion-type-id
+  //     is dependent, or
+  //   - it is operator= and the current class is a templated entity, or
+  //   - the unqualified-id is the postfix-expression in a dependent call.
+  if (Name.getNameKind() == DeclarationName::CXXConversionFunctionName &&
+      Name.getCXXNameType()->isDependentType()) {
+    R.setNotFoundInCurrentInstantiation();
+    return false;
+  }
+
+  // If this is the name of an implicitly-declared special member function,
+  // go through the scope stack to implicitly declare
+  if (isImplicitlyDeclaredMemberFunctionName(Name)) {
+    for (Scope *PreS = S; PreS; PreS = PreS->getParent())
+      if (DeclContext *DC = PreS->getEntity()) {
+        if (DC->isDependentContext() && isa<CXXRecordDecl>(DC) &&
+            Name.getCXXOverloadedOperator() == OO_Equal) {
+          R.setNotFoundInCurrentInstantiation();
+          return false;
+        }
+        DeclareImplicitMemberFunctionsWithName(*this, Name, R.getNameLoc(), DC);
+      }
+  }
 
   // Implicitly declare member functions with the name we're looking for, if in
   // fact we are in a scope where it matters.
@@ -2446,10 +2471,33 @@ bool Sema::LookupQualifiedName(LookupResult &R, DeclContext *LookupCtx,
     }
   } QL(LookupCtx);
 
+  CXXRecordDecl *LookupRec = dyn_cast<CXXRecordDecl>(LookupCtx);
+  // FIXME: Per [temp.dep.general]p2, an unqualified name is also dependent
+  // if it's a dependent conversion-function-id or operator= where the current
+  // class is a templated entity. This should be handled in LookupName.
+  if (!InUnqualifiedLookup && !R.isForRedeclaration()) {
+    // C++23 [temp.dep.type]p5:
+    //   A qualified name is dependent if
+    //   - it is a conversion-function-id whose conversion-type-id
+    //     is dependent, or
+    //   - [...]
+    //   - its lookup context is the current instantiation and it
+    //     is operator=, or
+    //   - [...]
+    if (DeclarationName Name = R.getLookupName();
+        (Name.getNameKind() == DeclarationName::CXXConversionFunctionName &&
+         Name.getCXXNameType()->isDependentType()) ||
+        (Name.getCXXOverloadedOperator() == OO_Equal && LookupRec &&
+         LookupRec->isDependentContext())) {
+      R.setNotFoundInCurrentInstantiation();
+      return false;
+    }
+  }
+
   if (LookupDirect(*this, R, LookupCtx)) {
     R.resolveKind();
-    if (isa<CXXRecordDecl>(LookupCtx))
-      R.setNamingClass(cast<CXXRecordDecl>(LookupCtx));
+    if (LookupRec)
+      R.setNamingClass(LookupRec);
     return true;
   }
 
@@ -2471,7 +2519,6 @@ bool Sema::LookupQualifiedName(LookupResult &R, DeclContext *LookupCtx,
 
   // If this isn't a C++ class, we aren't allowed to look into base
   // classes, we're done.
-  CXXRecordDecl *LookupRec = dyn_cast<CXXRecordDecl>(LookupCtx);
   if (!LookupRec || !LookupRec->getDefinition())
     return false;
 
@@ -2718,38 +2765,54 @@ bool Sema::LookupQualifiedName(LookupResult &R, DeclContext *LookupCtx,
 ///
 /// @returns True if any decls were found (but possibly ambiguous)
 bool Sema::LookupParsedName(LookupResult &R, Scope *S, CXXScopeSpec *SS,
-                            bool AllowBuiltinCreation, bool EnteringContext) {
-  if (SS && SS->isInvalid()) {
-    // When the scope specifier is invalid, don't even look for
-    // anything.
+                            QualType ObjectType, bool AllowBuiltinCreation,
+                            bool EnteringContext) {
+  // When the scope specifier is invalid, don't even look for anything.
+  if (SS && SS->isInvalid())
     return false;
-  }
 
-  if (SS && SS->isSet()) {
-    NestedNameSpecifier *NNS = SS->getScopeRep();
-    if (NNS->getKind() == NestedNameSpecifier::Super)
+  // Determine where to perform name lookup
+  DeclContext *DC = nullptr;
+  bool IsDependent = false;
+  if (!ObjectType.isNull()) {
+    // This nested-name-specifier occurs in a member access expression, e.g.,
+    // x->B::f, and we are looking into the type of the object.
+    assert((!SS || SS->isEmpty()) &&
+           "ObjectType and scope specifier cannot coexist");
+    DC = computeDeclContext(ObjectType);
+    IsDependent = !DC && ObjectType->isDependentType();
+    assert(((!DC && ObjectType->isDependentType()) ||
+            !ObjectType->isIncompleteType() || !ObjectType->getAs<TagType>() ||
+            ObjectType->castAs<TagType>()->isBeingDefined()) &&
+           "Caller should have completed object type");
+  } else if (SS && SS->isNotEmpty()) {
+    if (NestedNameSpecifier *NNS = SS->getScopeRep();
+        NNS->getKind() == NestedNameSpecifier::Super)
       return LookupInSuper(R, NNS->getAsRecordDecl());
-
-    if (DeclContext *DC = computeDeclContext(*SS, EnteringContext)) {
-      // We have resolved the scope specifier to a particular declaration
-      // contex, and will perform name lookup in that context.
+    // This nested-name-specifier occurs after another nested-name-specifier,
+    // so long into the context associated with the prior nested-name-specifier.
+    if ((DC = computeDeclContext(*SS, EnteringContext))) {
+      // The declaration context must be complete.
       if (!DC->isDependentContext() && RequireCompleteDeclContext(*SS, DC))
         return false;
-
       R.setContextRange(SS->getRange());
-      return LookupQualifiedName(R, DC);
     }
+    IsDependent = !DC && isDependentScopeSpecifier(*SS);
+  } else {
+    // Perform unqualified name lookup starting in the given scope.
+    return LookupName(R, S, AllowBuiltinCreation);
+  }
 
+  // If we were able to compute a declaration context, perform qualified name
+  // lookup in that context.
+  if (DC)
+    return LookupQualifiedName(R, DC);
+  else if (IsDependent)
     // We could not resolve the scope specified to a specific declaration
     // context, which means that SS refers to an unknown specialization.
     // Name lookup can't find anything in this case.
     R.setNotFoundInCurrentInstantiation();
-    R.setContextRange(SS->getRange());
-    return false;
-  }
-
-  // Perform unqualified name lookup starting in the given scope.
-  return LookupName(R, S, AllowBuiltinCreation);
+  return false;
 }
 
 /// Perform qualified name lookup into all base classes of the given
@@ -5018,8 +5081,9 @@ static void LookupPotentialTypoResult(Sema &SemaRef,
     return;
   }
 
-  SemaRef.LookupParsedName(Res, S, SS, /*AllowBuiltinCreation=*/false,
-                           EnteringContext);
+  SemaRef.LookupParsedName(Res, S, SS,
+                           /*ObjectType=*/QualType(),
+                           /*AllowBuiltinCreation=*/false, EnteringContext);
 
   // Fake ivar lookup; this should really be part of
   // LookupParsedName.
diff --git a/clang/lib/Sema/SemaOpenMP.cpp b/clang/lib/Sema/SemaOpenMP.cpp
index cee8da4..cf5447f 100644
--- a/clang/lib/Sema/SemaOpenMP.cpp
+++ b/clang/lib/Sema/SemaOpenMP.cpp
@@ -3061,7 +3061,9 @@ ExprResult SemaOpenMP::ActOnOpenMPIdExpression(Scope *CurScope,
                                                OpenMPDirectiveKind Kind) {
   ASTContext &Context = getASTContext();
   LookupResult Lookup(SemaRef, Id, Sema::LookupOrdinaryName);
-  SemaRef.LookupParsedName(Lookup, CurScope, &ScopeSpec, true);
+  SemaRef.LookupParsedName(Lookup, CurScope, &ScopeSpec,
+                           /*ObjectType=*/QualType(),
+                           /*AllowBuiltinCreation=*/true);
 
   if (Lookup.isAmbiguous())
     return ExprError();
@@ -7407,7 +7409,8 @@ void SemaOpenMP::ActOnStartOfFunctionDefinitionInOpenMPDeclareVariantScope(
   const IdentifierInfo *BaseII = D.getIdentifier();
   LookupResult Lookup(SemaRef, DeclarationName(BaseII), D.getIdentifierLoc(),
                       Sema::LookupOrdinaryName);
-  SemaRef.LookupParsedName(Lookup, S, &D.getCXXScopeSpec());
+  SemaRef.LookupParsedName(Lookup, S, &D.getCXXScopeSpec(),
+                           /*ObjectType=*/QualType());
 
   TypeSourceInfo *TInfo = SemaRef.GetTypeForDeclarator(D);
   QualType FType = TInfo->getType();
@@ -19311,7 +19314,8 @@ buildDeclareReductionRef(Sema &SemaRef, SourceLocation Loc, SourceRange Range,
   if (S) {
     LookupResult Lookup(SemaRef, ReductionId, Sema::LookupOMPReductionName);
     Lookup.suppressDiagnostics();
-    while (S && SemaRef.LookupParsedName(Lookup, S, &ReductionIdScopeSpec)) {
+    while (S && SemaRef.LookupParsedName(Lookup, S, &ReductionIdScopeSpec,
+                                         /*ObjectType=*/QualType())) {
       NamedDecl *D = Lookup.getRepresentativeDecl();
       do {
         S = S->getParent();
@@ -22180,7 +22184,8 @@ static ExprResult buildUserDefinedMapperRef(Sema &SemaRef, Scope *S,
   LookupResult Lookup(SemaRef, MapperId, Sema::LookupOMPMapperName);
   Lookup.suppressDiagnostics();
   if (S) {
-    while (S && SemaRef.LookupParsedName(Lookup, S, &MapperIdScopeSpec)) {
+    while (S && SemaRef.LookupParsedName(Lookup, S, &MapperIdScopeSpec,
+                                         /*ObjectType=*/QualType())) {
       NamedDecl *D = Lookup.getRepresentativeDecl();
       while (S && !S->isDeclScope(D))
         S = S->getParent();
@@ -23497,7 +23502,9 @@ void SemaOpenMP::DiagnoseUnterminatedOpenMPDeclareTarget() {
 NamedDecl *SemaOpenMP::lookupOpenMPDeclareTargetName(
     Scope *CurScope, CXXScopeSpec &ScopeSpec, const DeclarationNameInfo &Id) {
   LookupResult Lookup(SemaRef, Id, Sema::LookupOrdinaryName);
-  SemaRef.LookupParsedName(Lookup, CurScope, &ScopeSpec, true);
+  SemaRef.LookupParsedName(Lookup, CurScope, &ScopeSpec,
+                           /*ObjectType=*/QualType(),
+                           /*AllowBuiltinCreation=*/true);
 
   if (Lookup.isAmbiguous())
     return nullptr;
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 3c2a5a4..7f18631 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -210,10 +210,11 @@ TemplateNameKind Sema::isTemplateName(Scope *S,
   AssumedTemplateKind AssumedTemplate;
   LookupResult R(*this, TName, Name.getBeginLoc(), LookupOrdinaryName);
   if (LookupTemplateName(R, S, SS, ObjectType, EnteringContext,
-                         MemberOfUnknownSpecialization, SourceLocation(),
+                         /*RequiredTemplate=*/SourceLocation(),
                          &AssumedTemplate,
                          /*AllowTypoCorrection=*/!Disambiguation))
     return TNK_Non_template;
+  MemberOfUnknownSpecialization = R.wasNotFoundInCurrentInstantiation();
 
   if (AssumedTemplate != AssumedTemplateKind::None) {
     TemplateResult = TemplateTy::make(Context.getAssumedTemplateName(TName));
@@ -320,15 +321,12 @@ TemplateNameKind Sema::isTemplateName(Scope *S,
 bool Sema::isDeductionGuideName(Scope *S, const IdentifierInfo &Name,
                                 SourceLocation NameLoc, CXXScopeSpec &SS,
                                 ParsedTemplateTy *Template /*=nullptr*/) {
-  bool MemberOfUnknownSpecialization = false;
-
   // We could use redeclaration lookup here, but we don't need to: the
   // syntactic form of a deduction guide is enough to identify it even
   // if we can't look up the template name at all.
   LookupResult R(*this, DeclarationName(&Name), NameLoc, LookupOrdinaryName);
   if (LookupTemplateName(R, S, SS, /*ObjectType*/ QualType(),
-                         /*EnteringContext*/ false,
-                         MemberOfUnknownSpecialization))
+                         /*EnteringContext*/ false))
     return false;
 
   if (R.empty()) return false;
@@ -374,11 +372,8 @@ bool Sema::DiagnoseUnknownTemplateName(const IdentifierInfo &II,
   return true;
 }
 
-bool Sema::LookupTemplateName(LookupResult &Found,
-                              Scope *S, CXXScopeSpec &SS,
-                              QualType ObjectType,
-                              bool EnteringContext,
-                              bool &MemberOfUnknownSpecialization,
+bool Sema::LookupTemplateName(LookupResult &Found, Scope *S, CXXScopeSpec &SS,
+                              QualType ObjectType, bool EnteringContext,
                               RequiredTemplateKind RequiredTemplate,
                               AssumedTemplateKind *ATK,
                               bool AllowTypoCorrection) {
@@ -391,7 +386,6 @@ bool Sema::LookupTemplateName(LookupResult &Found,
   Found.setTemplateNameLookup(true);
 
   // Determine where to perform name lookup
-  MemberOfUnknownSpecialization = false;
   DeclContext *LookupCtx = nullptr;
   bool IsDependent = false;
   if (!ObjectType.isNull()) {
@@ -548,7 +542,7 @@ bool Sema::LookupTemplateName(LookupResult &Found,
   FilterAcceptableTemplateNames(Found, AllowFunctionTemplatesInLookup);
   if (Found.empty()) {
     if (IsDependent) {
-      MemberOfUnknownSpecialization = true;
+      Found.setNotFoundInCurrentInstantiation();
       return false;
     }
 
@@ -5595,11 +5589,9 @@ Sema::BuildQualifiedTemplateIdExpr(CXXScopeSpec &SS,
       RequireCompleteDeclContext(SS, DC))
     return BuildDependentDeclRefExpr(SS, TemplateKWLoc, NameInfo, TemplateArgs);
 
-  bool MemberOfUnknownSpecialization;
   LookupResult R(*this, NameInfo, LookupOrdinaryName);
   if (LookupTemplateName(R, (Scope *)nullptr, SS, QualType(),
-                         /*Entering*/false, MemberOfUnknownSpecialization,
-                         TemplateKWLoc))
+                         /*Entering*/ false, TemplateKWLoc))
     return ExprError();
 
   if (R.isAmbiguous())
@@ -5720,14 +5712,13 @@ TemplateNameKind Sema::ActOnTemplateName(Scope *S,
     DeclarationNameInfo DNI = GetNameFromUnqualifiedId(Name);
     LookupResult R(*this, DNI.getName(), Name.getBeginLoc(),
                    LookupOrdinaryName);
-    bool MOUS;
     // Tell LookupTemplateName that we require a template so that it diagnoses
     // cases where it finds a non-template.
     RequiredTemplateKind RTK = TemplateKWLoc.isValid()
                                    ? RequiredTemplateKind(TemplateKWLoc)
                                    : TemplateNameIsRequired;
-    if (!LookupTemplateName(R, S, SS, ObjectType.get(), EnteringContext, MOUS,
-                            RTK, nullptr, /*AllowTypoCorrection=*/false) &&
+    if (!LookupTemplateName(R, S, SS, ObjectType.get(), EnteringContext, RTK,
+                            /*ATK=*/nullptr, /*AllowTypoCorrection=*/false) &&
         !R.isAmbiguous()) {
       if (LookupCtx)
         Diag(Name.getBeginLoc(), diag::err_no_member)
@@ -5816,7 +5807,7 @@ bool Sema::CheckTemplateTypeArgument(
 
     if (auto *II = NameInfo.getName().getAsIdentifierInfo()) {
       LookupResult Result(*this, NameInfo, LookupOrdinaryName);
-      LookupParsedName(Result, CurScope, &SS);
+      LookupParsedName(Result, CurScope, &SS, /*ObjectType=*/QualType());
 
       if (Result.getAsSingle<TypeDecl>() ||
           Result.getResultKind() ==
@@ -11190,7 +11181,8 @@ DeclResult Sema::ActOnExplicitInstantiation(Scope *S,
                            : TSK_ExplicitInstantiationDeclaration;
 
   LookupResult Previous(*this, NameInfo, LookupOrdinaryName);
-  LookupParsedName(Previous, S, &D.getCXXScopeSpec());
+  LookupParsedName(Previous, S, &D.getCXXScopeSpec(),
+                   /*ObjectType=*/QualType());
 
   if (!R->isFunctionType()) {
     // C++ [temp.explicit]p1:
diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index f47bc21..28d3d1b 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -13217,6 +13217,26 @@ bool TreeTransform<Derived>::TransformOverloadExprDecls(OverloadExpr *Old,
   // Resolve a kind, but don't do any further analysis.  If it's
   // ambiguous, the callee needs to deal with it.
   R.resolveKind();
+
+  if (Old->hasTemplateKeyword() && !R.empty()) {
+    NamedDecl *FoundDecl = R.getRepresentativeDecl()->getUnderlyingDecl();
+    getSema().FilterAcceptableTemplateNames(R,
+                                            /*AllowFunctionTemplates=*/true,
+                                            /*AllowDependent=*/true);
+    if (R.empty()) {
+      // If a 'template' keyword was used, a lookup that finds only non-template
+      // names is an error.
+      getSema().Diag(R.getNameLoc(),
+                     diag::err_template_kw_refers_to_non_template)
+          << R.getLookupName() << Old->getQualifierLoc().getSourceRange()
+          << Old->hasTemplateKeyword() << Old->getTemplateKeywordLoc();
+      getSema().Diag(FoundDecl->getLocation(),
+                     diag::note_template_kw_refers_to_non_template)
+          << R.getLookupName();
+      return true;
+    }
+  }
+
   return false;
 }