[clang][bytecode] Address review comments by added more code comments and use Invalid()

Signed-off-by: yronglin <[email protected]>

Author: yronglin

clang/lib/AST/ByteCode/Interp.cpp

@@ -348,11 +348,12 @@ bool CheckConstant(InterpState &S, CodePtr OpPC, const Descriptor *Desc) {
   if (D->isConstexpr())
     return true;
 
+  // If we're evaluating the initializer for a constexpr variable in C23, we may
+  // only read other contexpr variables. Abort here since this one isn't
+  // constexpr.
   if (const auto *VD = dyn_cast_if_present<VarDecl>(S.EvaluatingDecl);
-      VD && VD->isConstexpr() && S.getLangOpts().C23) {
-    S.FFDiag(S.Current->getExpr(OpPC));
-    return false;
-  }
+      VD && VD->isConstexpr() && S.getLangOpts().C23)
+    return Invalid(S, OpPC);
 
   QualType T = D->getType();
   bool IsConstant = T.isConstant(S.getASTContext());