Revert "[Clang][Sema] access checking of friend declaration should not be delayed (#91430)"

This reverts commit 200f3bd.

Author: zyn0217

clang/include/clang/Sema/Scope.h

@@ -160,9 +160,6 @@ class Scope {
 
     /// This is a scope of type alias declaration.
     TypeAliasScope = 0x20000000,
-
-    /// This is a scope of friend declaration.
-    FriendScope = 0x40000000,
   };
 
 private:
@@ -590,9 +587,6 @@ class Scope {
   /// Determine whether this scope is a type alias scope.
   bool isTypeAliasScope() const { return getFlags() & Scope::TypeAliasScope; }
 
-  /// Determine whether this scope is a friend scope.
-  bool isFriendScope() const { return getFlags() & Scope::FriendScope; }
-
   /// Returns if rhs has a higher scope depth than this.
   ///
   /// The caller is responsible for calling this only if one of the two scopes

clang/lib/Parse/ParseDecl.cpp

@@ -4219,12 +4219,9 @@ void Parser::ParseDeclarationSpecifiers(
 
     // friend
     case tok::kw_friend:
-      if (DSContext == DeclSpecContext::DSC_class) {
+      if (DSContext == DeclSpecContext::DSC_class)
         isInvalid = DS.SetFriendSpec(Loc, PrevSpec, DiagID);
-        Scope *CurS = getCurScope();
-        if (!isInvalid && CurS)
-          CurS->setFlags(CurS->getFlags() | Scope::FriendScope);
-      } else {
+      else {
         PrevSpec = ""; // not actually used by the diagnostic
         DiagID = diag::err_friend_invalid_in_context;
         isInvalid = true;

clang/lib/Sema/Scope.cpp

@@ -233,7 +233,6 @@ void Scope::dumpImpl(raw_ostream &OS) const {
       {LambdaScope, "LambdaScope"},
       {OpenACCComputeConstructScope, "OpenACCComputeConstructScope"},
       {TypeAliasScope, "TypeAliasScope"},
-      {FriendScope, "FriendScope"},
   };
 
   for (auto Info : FlagInfo) {

clang/lib/Sema/SemaAccess.cpp

@@ -1469,32 +1469,12 @@ static Sema::AccessResult CheckAccess(Sema &S, SourceLocation Loc,
   // specifier, like this:
   //   A::private_type A::foo() { ... }
   //
-  // friend declaration should not be delayed because it may lead to incorrect
-  // redeclaration chain, such as:
-  //   class D {
-  //    class E{
-  //     class F{};
-  //     friend  void foo(D::E::F& q);
-  //    };
-  //    friend  void foo(D::E::F& q);
-  //   };
+  // Or we might be parsing something that will turn out to be a friend:
+  //   void foo(A::private_type);
+  //   void B::foo(A::private_type);
   if (S.DelayedDiagnostics.shouldDelayDiagnostics()) {
-    // [class.friend]p9:
-    // A member nominated by a friend declaration shall be accessible in the
-    // class containing the friend declaration. The meaning of the friend
-    // declaration is the same whether the friend declaration appears in the
-    // private, protected, or public ([class.mem]) portion of the class
-    // member-specification.
-    Scope *TS = S.getCurScope();
-    bool IsFriendDeclaration = false;
-    while (TS && !IsFriendDeclaration) {
-      IsFriendDeclaration = TS->isFriendScope();
-      TS = TS->getParent();
-    }
-    if (!IsFriendDeclaration) {
-      S.DelayedDiagnostics.add(DelayedDiagnostic::makeAccess(Loc, Entity));
-      return Sema::AR_delayed;
-    }
+    S.DelayedDiagnostics.add(DelayedDiagnostic::makeAccess(Loc, Entity));
+    return Sema::AR_delayed;
   }
 
   EffectiveContext EC(S.CurContext);