From 0cda6230210add2bbedc40100dbfe8f0f8e98826 Mon Sep 17 00:00:00 2001
From: Chip Morningstar <chip@fudco.com>
Date: Thu, 29 Jul 2021 14:17:41 -0700
Subject: [PATCH] feat: require that buildRootObject always returns a Far
 reference

---
 packages/SwingSet/src/kernel/liveSlots.js | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/packages/SwingSet/src/kernel/liveSlots.js b/packages/SwingSet/src/kernel/liveSlots.js
index 00169af3f20..525959ee62c 100644
--- a/packages/SwingSet/src/kernel/liveSlots.js
+++ b/packages/SwingSet/src/kernel/liveSlots.js
@@ -1,6 +1,11 @@
 /* global HandledPromise */
 
-import { Remotable, passStyleOf, makeMarshal } from '@agoric/marshal';
+import {
+  Remotable,
+  passStyleOf,
+  getInterfaceOf,
+  makeMarshal,
+} from '@agoric/marshal';
 import { assert, details as X } from '@agoric/assert';
 import { isPromise } from '@agoric/promise-kit';
 import { insistVatType, makeVatSlot, parseVatSlot } from '../parseVatSlots.js';
@@ -973,7 +978,11 @@ function build(
     assert.equal(
       passStyleOf(rootObject),
       'remotable',
-      `buildRootObject() (${buildRootObject}) returned ${rootObject}, which is not Far`,
+      X`buildRootObject() for vat ${forVatID} returned ${rootObject}, which is not Far`,
+    );
+    assert(
+      getInterfaceOf(rootObject) !== undefined,
+      X`buildRootObject() for vat ${forVatID} returned ${rootObject} with no interface`,
     );
 
     const rootSlot = makeVatSlot('object', true, BigInt(0));