From a531c98cd2bdc53e62011b9836f34aea41975c55 Mon Sep 17 00:00:00 2001
From: Jonas Jenwald <jonas.jenwald@gmail.com>
Date: Mon, 14 Sep 2020 13:21:55 +0200
Subject: [PATCH] Ensure that the empty dictionary won't be accidentally
 modified

Currently there's nothing that prevents modification of the `Dict.empty` primitive, which obviously needs to be *truly* empty to prevent any future (hard to find) bugs.
---
 src/core/primitives.js | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/core/primitives.js b/src/core/primitives.js
index 39eddf984..a1e83b165 100644
--- a/src/core/primitives.js
+++ b/src/core/primitives.js
@@ -171,7 +171,14 @@ var Dict = (function DictClosure() {
     },
   };
 
-  Dict.empty = new Dict(null);
+  Dict.empty = (function () {
+    const emptyDict = new Dict(null);
+
+    emptyDict.set = (key, value) => {
+      unreachable("Should not call `set` on the empty dictionary.");
+    };
+    return emptyDict;
+  })();
 
   Dict.merge = function ({ xref, dictArray, mergeSubDicts = false }) {
     const mergedDict = new Dict(xref);