[clang] [Bounds-Safety] Add sized_by, counted_by_or_null & sized_by_or_null (PR #93231)

[Henrik G. Olsson via cfe-commits]

================
@@ -8641,22 +8641,33 @@ enum class CountedByInvalidPointeeTypeKind {
   VALID,
 };
 
-static bool CheckCountedByAttrOnField(
-    Sema &S, FieldDecl *FD, Expr *E,
-    llvm::SmallVectorImpl<TypeCoupledDeclRefInfo> &Decls) {
+static bool
+CheckCountedByAttrOnField(Sema &S, FieldDecl *FD, Expr *E,
+                          llvm::SmallVectorImpl<TypeCoupledDeclRefInfo> &Decls,
+                          bool CountInBytes, bool OrNull) {
   // Check the context the attribute is used in
 
+  unsigned Kind = CountInBytes;
+  if (OrNull)
+    Kind += 2;
+
   if (FD->getParent()->isUnion()) {
     S.Diag(FD->getBeginLoc(), diag::err_counted_by_attr_in_union)
-        << FD->getSourceRange();
+        << Kind << FD->getSourceRange();
     return true;
   }
 
   const auto FieldTy = FD->getType();
+  if (FieldTy->isArrayType() && (CountInBytes || OrNull)) {
+    S.Diag(FD->getBeginLoc(),
+           diag::err_counted_by_attr_not_on_ptr_or_flexible_array_member)
----------------
hnrklssn wrote:

>The diagnostic name is a little misleading here because CountInBytes suggested __sized_by but the diagnostic name has counted_by in its name

I kept it because it's the same family of attributes. Do you have a suggestion for a name that would imply that it's not just for `counted_by`, but more specific than `bounds_attribute`?

https://github.com/llvm/llvm-project/pull/93231