fix(exo): methods might be non-enumerable

packages/exo/src/exo-tools.js

@@ -22,7 +22,8 @@ import {
 
 const { quote: q, Fail } = assert;
 const { apply, ownKeys } = Reflect;
-const { defineProperties, fromEntries } = Object;
+const { defineProperties, fromEntries, getOwnPropertyDescriptors, create } =
+  Object;
 
 /**
  * A method guard, for inclusion in an interface guard, that enforces only that
@@ -285,12 +286,19 @@ export const defendPrototype = (
   interfaceGuard = undefined,
 ) => {
   const prototype = {};
-  if (hasOwnPropertyOf(behaviorMethods, 'constructor')) {
-    // By ignoring any method named "constructor", we can use a
-    // class.prototype as a behaviorMethods.
-    const { constructor: _, ...methods } = behaviorMethods;
-    // @ts-expect-error TS misses that hasOwn check makes this safe
-    behaviorMethods = harden(methods);
+  if (
+    hasOwnPropertyOf(behaviorMethods, 'constructor') &&
+    typeof behaviorMethods.constructor === 'function' &&
+    hasOwnPropertyOf(behaviorMethods.constructor, 'prototype')
+  ) {
+    // By ignoring any method named "constructor" that might be a
+    // class, we can use a class.prototype as a behaviorMethods.
+    // TODO: Because this looks only at own properties, it is
+    // currently useful only on base classes. Better would be
+    // for it to deal with subclasses as well.
+    const { constructor: _, ...methodDescs } =
+      getOwnPropertyDescriptors(behaviorMethods);
+    behaviorMethods = create(Object.prototype, methodDescs);
   }
   /** @type {Record<PropertyKey, MethodGuard> | undefined} */
   let methodGuards;