1 files changed, 29 insertions, 0 deletions
diff --git a/js/src/jit-test/tests/basic/__proto__-not-prototype-mutation.js b/js/src/jit-test/tests/basic/__proto__-not-prototype-mutation.js
new file mode 100644
index 0000000000..b940a229b2
--- /dev/null
+++ b/js/src/jit-test/tests/basic/__proto__-not-prototype-mutation.js
@@ -0,0 +1,29 @@
+/*
+ * Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/licenses/publicdomain/
+ */
+
+var __proto__ = "string value";
+
+var propdefs =
+  [{ c: "['__proto__']: null", t: "object" },
+   { c: "__proto__() {}", t: "function" },
+   { c: "['__proto__']() {}", t: "function" },
+   { c: "*__proto__() {}", t: "function" },
+   { c: "*['__proto__']() {}", t: "function" },
+   { c: "__proto__", t: "string" },
+   { c: "get __proto__() { return 42; }", t: "number" },
+   { c: "get ['__proto__']() { return undefined; }", t: "undefined" },
+   { c: "set __proto__(v) { }", t: "undefined" },
+   { c: "set ['__proto__'](v) { }", t: "undefined" }];
+
+for (var propdef of propdefs)
+{
+  var f = new Function("return { " + propdef.c + " };");
+  for (var i = 0; i < 100; i++)
+  {
+    var inst = f();
+    assertEq(typeof inst.__proto__, propdef.t);
+    assertEq(Object.getPrototypeOf(inst), Object.prototype);
+  }
+}