From c550e9e55f4e385bf068a55429d2996d2c360107 Mon Sep 17 00:00:00 2001
From: Kevin Schaaf <kschaaf@google.com>
Date: Thu, 21 Jun 2018 18:25:30 -0700
Subject: [PATCH] Add comment

---
 lib/legacy/legacy-data-mixin.html | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/legacy/legacy-data-mixin.html b/lib/legacy/legacy-data-mixin.html
index af367a3e3b..21124629ca 100644
--- a/lib/legacy/legacy-data-mixin.html
+++ b/lib/legacy/legacy-data-mixin.html
@@ -59,6 +59,8 @@
         if (this._legacyUndefinedCheck && args.length > 1) {
           for (let i=0; i<args.length; i++) {
             if (vals[i] === undefined) {
+              // Break out of effect's control flow; will be caught in
+              // wrapped property effect function below
               throw new UndefinedArgumentError(`argument '${args[i].name}' is undefined; ensure it has an undefined check`);
             }
           }