From ecb8dadde5af8b442f60204585b9ac680edfb822 Mon Sep 17 00:00:00 2001
From: tylerjenningsw <tylerjennings2@outlook.com>
Date: Sun, 25 Oct 2026 14:17:41 -0400
Subject: [PATCH] Expressions: an expression can't delete or redefine
 thisLayer, thisComp or the other unqualified names

---
 crates/expr/src/prelude.js | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/crates/expr/src/prelude.js b/crates/expr/src/prelude.js
index 06757ec79..5671d3ec2 100644
--- a/crates/expr/src/prelude.js
+++ b/crates/expr/src/prelude.js
@@ -1056,11 +1056,11 @@ Markers.prototype = {
 // ---------------------------------------------------------------------------------------------
 // Unqualified names: thisLayer / thisProperty attributes and the `this*` objects. They're
 // accessors on the global object; assigning one (`var width = 10`) shadows it for the current
-// evaluation only.
+// evaluation only. They can't be deleted or redefined, so an expression can't take one away from
+// the evaluations after it.
 
 function __global(name, get) {
   Object.defineProperty(globalThis, name, {
-    configurable: true,
     get: function () { return name in __S.vars ? __S.vars[name] : get(); },
     set: function (v) { __S.vars[name] = v; },
   });