Reland: [clang] Fix missing diagnostic of declaration use when accessing TypeDecls through typename access

clang/docs/ReleaseNotes.rst

@@ -35,6 +35,9 @@ Potentially Breaking Changes
 ============================
 
 - The Objective-C ARC migrator (ARCMigrate) has been removed.
+- Fix missing diagnostics for uses of declarations when performing typename access,
+  such as when performing member access on a '[[deprecated]]' type alias.
+  (#GH58547)
 
 C/C++ Language Potentially Breaking Changes
 -------------------------------------------

clang/include/clang/Sema/Sema.h

@@ -3168,6 +3168,13 @@ class Sema final : public SemaBase {
 
   DeclGroupPtrTy ConvertDeclToDeclGroup(Decl *Ptr, Decl *OwnedType = nullptr);
 
+  enum class DiagCtorKind { None, Implicit, Typename };
+  /// Returns the TypeDeclType for the given type declaration,
+  /// as ASTContext::getTypeDeclType would, but
+  /// performs the required semantic checks for name lookup of said entity.
+  QualType getTypeDeclType(DeclContext *LookupCtx, DiagCtorKind DCK,
+                           TypeDecl *TD, SourceLocation NameLoc);
+
   /// If the identifier refers to a type name within this scope,
   /// return the declaration of that type.
   ///

clang/lib/Sema/SemaAvailability.cpp

@@ -99,16 +99,29 @@ ShouldDiagnoseAvailabilityOfDecl(Sema &S, const NamedDecl *D,
   // For typedefs, if the typedef declaration appears available look
   // to the underlying type to see if it is more restrictive.
   while (const auto *TD = dyn_cast<TypedefNameDecl>(D)) {
-    if (Result == AR_Available) {
-      if (const auto *TT = TD->getUnderlyingType()->getAs<TagType>()) {
+    if (Result != AR_Available)
+      break;
+    for (const Type *T = TD->getUnderlyingType().getTypePtr(); /**/; /**/) {
+      if (auto *TT = dyn_cast<TagType>(T)) {
         D = TT->getDecl();
-        Result = D->getAvailability(Message);
+      } else if (isa<SubstTemplateTypeParmType>(T)) {
+        // A Subst* node represents a use through a template.
+        // Any uses of the underlying declaration happened through it's template
+        // specialization.
+        goto done;
+      } else {
+        const Type *NextT =
+            T->getLocallyUnqualifiedSingleStepDesugaredType().getTypePtr();
+        if (NextT == T)
+          goto done;
+        T = NextT;
         continue;
       }
+      Result = D->getAvailability(Message);
+      break;
     }
-    break;
   }
-
+done:
   // For alias templates, get the underlying declaration.
   if (const auto *ADecl = dyn_cast<TypeAliasTemplateDecl>(D)) {
     D = ADecl->getTemplatedDecl();

clang/lib/Sema/SemaDecl.cpp

@@ -139,6 +139,26 @@ class TypeNameValidatorCCC final : public CorrectionCandidateCallback {
 
 } // end anonymous namespace
 
+QualType Sema::getTypeDeclType(DeclContext *LookupCtx, DiagCtorKind DCK,
+                               TypeDecl *TD, SourceLocation NameLoc) {
+  auto *LookupRD = dyn_cast_or_null<CXXRecordDecl>(LookupCtx);
+  auto *FoundRD = dyn_cast<CXXRecordDecl>(TD);
+  if (DCK != DiagCtorKind::None && LookupRD && FoundRD &&
+      FoundRD->isInjectedClassName() &&
+      declaresSameEntity(LookupRD, cast<Decl>(FoundRD->getParent()))) {
+    Diag(NameLoc,
+         DCK == DiagCtorKind::Typename
+             ? diag::ext_out_of_line_qualified_id_type_names_constructor
+             : diag::err_out_of_line_qualified_id_type_names_constructor)
+        << TD->getIdentifier() << /*Type=*/1
+        << 0 /*if any keyword was present, it was 'typename'*/;
+  }
+
+  DiagnoseUseOfDecl(TD, NameLoc);
+  MarkAnyDeclReferenced(TD->getLocation(), TD, /*OdrUse=*/false);
+  return Context.getTypeDeclType(TD);
+}
+
 namespace {
 enum class UnqualifiedTypeNameLookupResult {
   NotFound,
@@ -295,10 +315,11 @@ ParsedType Sema::getTypeName(const IdentifierInfo &II, SourceLocation NameLoc,
                              bool IsClassTemplateDeductionContext,
                              ImplicitTypenameContext AllowImplicitTypename,
                              IdentifierInfo **CorrectedII) {
+  bool IsImplicitTypename = !isClassName && !IsCtorOrDtorName;
   // FIXME: Consider allowing this outside C++1z mode as an extension.
   bool AllowDeducedTemplate = IsClassTemplateDeductionContext &&
-                              getLangOpts().CPlusPlus17 && !IsCtorOrDtorName &&
-                              !isClassName && !HasTrailingDot;
+                              getLangOpts().CPlusPlus17 && IsImplicitTypename &&
+                              !HasTrailingDot;
 
   // Determine where we will perform name lookup.
   DeclContext *LookupCtx = nullptr;
@@ -322,11 +343,9 @@ ParsedType Sema::getTypeName(const IdentifierInfo &II, SourceLocation NameLoc,
         // refer to a member of an unknown specialization.
         // In C++2a, in several contexts a 'typename' is not required. Also
         // allow this as an extension.
-        if (AllowImplicitTypename == ImplicitTypenameContext::No &&
-            !isClassName && !IsCtorOrDtorName)
-          return nullptr;
-        bool IsImplicitTypename = !isClassName && !IsCtorOrDtorName;
         if (IsImplicitTypename) {
+          if (AllowImplicitTypename == ImplicitTypenameContext::No)
+            return nullptr;
           SourceLocation QualifiedLoc = SS->getRange().getBegin();
           if (getLangOpts().CPlusPlus20)
             Diag(QualifiedLoc, diag::warn_cxx17_compat_implicit_typename);
@@ -515,18 +534,10 @@ ParsedType Sema::getTypeName(const IdentifierInfo &II, SourceLocation NameLoc,
     // C++ [class.qual]p2: A lookup that would find the injected-class-name
     // instead names the constructors of the class, except when naming a class.
     // This is ill-formed when we're not actually forming a ctor or dtor name.
-    auto *LookupRD = dyn_cast_or_null<CXXRecordDecl>(LookupCtx);
-    auto *FoundRD = dyn_cast<CXXRecordDecl>(TD);
-    if (!isClassName && !IsCtorOrDtorName && LookupRD && FoundRD &&
-        FoundRD->isInjectedClassName() &&
-        declaresSameEntity(LookupRD, cast<Decl>(FoundRD->getParent())))
-      Diag(NameLoc, diag::err_out_of_line_qualified_id_type_names_constructor)
-          << &II << /*Type*/1;
-
-    DiagnoseUseOfDecl(IIDecl, NameLoc);
-
-    T = Context.getTypeDeclType(TD);
-    MarkAnyDeclReferenced(TD->getLocation(), TD, /*OdrUse=*/false);
+    T = getTypeDeclType(LookupCtx,
+                        IsImplicitTypename ? DiagCtorKind::Implicit
+                                           : DiagCtorKind::None,
+                        TD, NameLoc);
   } else if (ObjCInterfaceDecl *IDecl = dyn_cast<ObjCInterfaceDecl>(IIDecl)) {
     (void)DiagnoseUseOfDecl(IDecl, NameLoc);
     if (!HasTrailingDot)

clang/lib/Sema/SemaTemplate.cpp

@@ -10930,20 +10930,15 @@ Sema::CheckTypenameType(ElaboratedTypeKeyword Keyword,
       //
       // FIXME: That's not strictly true: mem-initializer-id lookup does not
       // ignore functions, but that appears to be an oversight.
-      auto *LookupRD = dyn_cast_or_null<CXXRecordDecl>(Ctx);
-      auto *FoundRD = dyn_cast<CXXRecordDecl>(Type);
-      if (Keyword == ElaboratedTypeKeyword::Typename && LookupRD && FoundRD &&
-          FoundRD->isInjectedClassName() &&
-          declaresSameEntity(LookupRD, cast<Decl>(FoundRD->getParent())))
-        Diag(IILoc, diag::ext_out_of_line_qualified_id_type_names_constructor)
-            << &II << 1 << 0 /*'typename' keyword used*/;
-
+      QualType T = getTypeDeclType(Ctx,
+                                   Keyword == ElaboratedTypeKeyword::Typename
+                                       ? DiagCtorKind::Typename
+                                       : DiagCtorKind::None,
+                                   Type, IILoc);
       // We found a type. Build an ElaboratedType, since the
       // typename-specifier was just sugar.
-      MarkAnyDeclReferenced(Type->getLocation(), Type, /*OdrUse=*/false);
-      return Context.getElaboratedType(Keyword,
-                                       QualifierLoc.getNestedNameSpecifier(),
-                                       Context.getTypeDeclType(Type));
+      return Context.getElaboratedType(
+          Keyword, QualifierLoc.getNestedNameSpecifier(), T);
     }
 
     // C++ [dcl.type.simple]p2:

clang/test/CXX/dcl.dcl/dcl.attr/dcl.attr.deprecated/p1.cpp

@@ -58,3 +58,17 @@ template <typename T>
   FunS2 f;// No warning, entire function is deprecated, so usage here should be fine.
 
 }
+
+namespace GH58547 {
+struct A {
+  using ta [[deprecated]] = int; // expected-note 2{{marked deprecated here}}
+};
+
+using t1 = typename A::ta; // expected-warning {{'ta' is deprecated}}
+
+template <class B1> struct B {
+  using tb = typename B1::ta; // expected-warning {{'ta' is deprecated}}
+};
+
+template struct B<A>; // expected-note {{requested here}}
+} // namespace GH58547

clang/test/Sema/attr-availability-macosx.cpp

@@ -14,4 +14,17 @@ bool try_acquire_for(T duration) { // expected-note{{'try_acquire_for<int>' has
 int main() {
   try_acquire_for(1); // expected-warning{{'try_acquire_for<int>' is only available on macOS 11 or newer}}
   // expected-note@-1{{enclose 'try_acquire_for<int>' in a __builtin_available check to silence this warning}}
-}
+}
+
+namespace typename_template {
+  struct [[clang::availability(macos, introduced = 16)]] A {};
+
+  template<class T> struct B { using type = T; };
+  template <class T> struct C {
+    typename B<T>::type v;
+  };
+
+  struct [[clang::availability(macos, introduced = 16)]] D {
+    C<A> c;
+  };
+} // namespace typename_template