1 files changed, 16 insertions, 0 deletions
diff --git a/js/src/tests/non262/object/setPrototypeOf-cycle.js b/js/src/tests/non262/object/setPrototypeOf-cycle.js
new file mode 100644
index 0000000000..a8b5aa75cd
--- /dev/null
+++ b/js/src/tests/non262/object/setPrototypeOf-cycle.js
@@ -0,0 +1,16 @@
+// The cycle check in 9.1.2 [[SetPrototypeOf]] does not walk proxies.
+// Therefore it's very easy to create prototype chain cycles involving proxies,
+// and the spec requires us to accept this.
+
+var t = {};
+var p = new Proxy(t, {});
+Object.setPrototypeOf(t, p);  // 🙈
+
+// Actually doing anything that searches this object's prototype chain
+// technically should not terminate. We instead throw "too much recursion".
+for (var obj of [t, p]) {
+    assertThrowsInstanceOf(() => "x" in obj, InternalError);
+    assertThrowsInstanceOf(() => obj.x, InternalError);
+    assertThrowsInstanceOf(() => { obj.x = 1; }, InternalError);
+}
+reportCompare(0, 0);