[clang] [Clang] allow restrict qualifier for array types with pointer types as element types (PR #120896)

[Eli Friedman via cfe-commits]

================
@@ -1593,35 +1593,38 @@ QualType Sema::BuildQualifiedType(QualType T, SourceLocation Loc,
   // object or incomplete types shall not be restrict-qualified."
   if (Qs.hasRestrict()) {
     unsigned DiagID = 0;
-    QualType ProblemTy;
-
-    if (T->isAnyPointerType() || T->isReferenceType() ||
-        T->isMemberPointerType()) {
-      QualType EltTy;
-      if (T->isObjCObjectPointerType())
-        EltTy = T;
-      else if (const MemberPointerType *PTy = T->getAs<MemberPointerType>())
+    QualType EltTy = Context.getBaseElementType(T);
+
+    if (EltTy->isAnyPointerType() || EltTy->isReferenceType() ||
+        EltTy->isMemberPointerType()) {
+
+      if (const MemberPointerType *PTy = EltTy->getAs<MemberPointerType>())
         EltTy = PTy->getPointeeType();
       else
-        EltTy = T->getPointeeType();
+        EltTy = EltTy->getPointeeType();
 
       // If we have a pointer or reference, the pointee must have an object
       // incomplete type.
-      if (!EltTy->isIncompleteOrObjectType()) {
+      if (!EltTy->isIncompleteOrObjectType())
         DiagID = diag::err_typecheck_invalid_restrict_invalid_pointee;
-        ProblemTy = EltTy;
-      }
+
     } else if (!isDependentOrGNUAutoType(T)) {
       // For an __auto_type variable, we may not have seen the initializer yet
       // and so have no idea whether the underlying type is a pointer type or
       // not.
       DiagID = diag::err_typecheck_invalid_restrict_not_pointer;
-      ProblemTy = T;
+      EltTy = T;
     }
 
+    Loc = DS ? DS->getRestrictSpecLoc() : Loc;
     if (DiagID) {
-      Diag(DS ? DS->getRestrictSpecLoc() : Loc, DiagID) << ProblemTy;
+      Diag(Loc, DiagID) << EltTy;
       Qs.removeRestrict();
+    } else {
+      if (!getLangOpts().C23 && T->isArrayType()) {
+        Diag(Loc, diag::ext_restrict_on_array_of_pointers_c23);
+        Diag(Loc, diag::warn_c23_compat_restrict_on_array_of_pointers);
+      }
----------------
efriedma-quic wrote:

```suggestion
      if (T->isArrayType()) {
        if (getLangOpts().C23)
          Diag(Loc, diag::warn_c23_compat_restrict_on_array_of_pointers);
        else
          Diag(Loc, diag::ext_restrict_on_array_of_pointers_c23);
      }
```

https://github.com/llvm/llvm-project/pull/120896