From 3de2ea519ec01817b45cf5e30a81fc38e4b7670e Mon Sep 17 00:00:00 2001
From: Mathieu Hofman <mathieu@agoric.com>
Date: Thu, 12 Jan 2023 17:20:36 +0000
Subject: [PATCH] fixup! bad(Swingset): Releasing a constrained Zalgo on
 syscall replay Address feedback: better isThenable check

---
 packages/SwingSet/src/kernel/vat-loader/async-helper.js | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/packages/SwingSet/src/kernel/vat-loader/async-helper.js b/packages/SwingSet/src/kernel/vat-loader/async-helper.js
index 709899c40197..281fa6802fa2 100644
--- a/packages/SwingSet/src/kernel/vat-loader/async-helper.js
+++ b/packages/SwingSet/src/kernel/vat-loader/async-helper.js
@@ -19,7 +19,7 @@
  * @returns {T extends PromiseLike<any> ? Promise<Awaited<R>> : R}
  */
 export function maybeAsync(v, handle) {
-  if (typeof v === 'object' && v !== null && 'then' in v) {
+  if (Object(v) === v && typeof v.then === 'function') {
     return Promise.resolve(v).then(handle);
   } else {
     return handle(v);
@@ -37,7 +37,7 @@ export function ensureSync(fn) {
   // eslint-disable-next-line func-names
   return function (...args) {
     const result = Reflect.apply(fn, this, args);
-    if (typeof result === 'object' && result !== null && 'then' in result) {
+    if (Object(result) === result && typeof result.then === 'function') {
       throw new Error('Unexpected async result');
     } else {
       return result;