Revert "[clang] Fix missing diagnostic of declaration use when accessing TypeDecls through typename access (#129681)"

This caused incorrect -Wunguarded-availability warnings. See comment on
the pull request.

> We were missing a call to DiagnoseUseOfDecl when performing typename
> access.
>
> This refactors the code so that TypeDecl lookups funnel through a helper
> which performs all the necessary checks, removing some related
> duplication on the way.
>
> Fixes #58547
>
> Differential Revision: https://reviews.llvm.org/D136533

This reverts commit 4c4fd6b03149348cf11af245ad2603d24144a9d5.

clang/docs/ReleaseNotes.rst

@@ -35,9 +35,6 @@ 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

@@ -3168,13 +3168,6 @@ public:
 
   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/SemaDecl.cpp

@@ -139,26 +139,6 @@ 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,
@@ -315,11 +295,10 @@ 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 && IsImplicitTypename &&
-                              !HasTrailingDot;
+                              getLangOpts().CPlusPlus17 && !IsCtorOrDtorName &&
+                              !isClassName && !HasTrailingDot;
 
   // Determine where we will perform name lookup.
   DeclContext *LookupCtx = nullptr;
@@ -343,9 +322,11 @@ 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);
@@ -534,10 +515,18 @@ 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.
-    T = getTypeDeclType(LookupCtx,
-                        IsImplicitTypename ? DiagCtorKind::Implicit
-                                           : DiagCtorKind::None,
-                        TD, NameLoc);
+    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);
   } else if (ObjCInterfaceDecl *IDecl = dyn_cast<ObjCInterfaceDecl>(IIDecl)) {
     (void)DiagnoseUseOfDecl(IDecl, NameLoc);
     if (!HasTrailingDot)

clang/lib/Sema/SemaTemplate.cpp

@@ -10918,15 +10918,20 @@ 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.
-      QualType T = getTypeDeclType(Ctx,
-                                   Keyword == ElaboratedTypeKeyword::Typename
-                                       ? DiagCtorKind::Typename
-                                       : DiagCtorKind::None,
-                                   Type, IILoc);
+      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*/;
+
       // We found a type. Build an ElaboratedType, since the
       // typename-specifier was just sugar.
-      return Context.getElaboratedType(
-          Keyword, QualifierLoc.getNestedNameSpecifier(), T);
+      MarkAnyDeclReferenced(Type->getLocation(), Type, /*OdrUse=*/false);
+      return Context.getElaboratedType(Keyword,
+                                       QualifierLoc.getNestedNameSpecifier(),
+                                       Context.getTypeDeclType(Type));
     }
 
     // C++ [dcl.type.simple]p2:

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

@@ -58,17 +58,3 @@ 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