diff -r 000000000000 -r 6474c204b198 js/src/tests/js1_8/regress/regress-499524.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/js1_8/regress/regress-499524.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,50 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+
+/*
+ * Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/licenses/publicdomain/
+ */
+
+function isSyntaxError(code) {
+  try {
+    eval(code);
+    return false;
+  } catch (exception) {
+    if (SyntaxError.prototype.isPrototypeOf(exception))
+      return true;
+    throw exception;
+  };
+};
+
+/* 
+ * Duplicate parameter names must be tolerated (as per ES3), unless
+ * the parameter list uses destructuring, in which case we claim the
+ * user has opted in to a modicum of sanity, and we forbid duplicate
+ * parameter names.
+ */
+assertEq(isSyntaxError("function f(x,x){}"),                false);
+
+assertEq(isSyntaxError("function f(x,[x]){})"),             true);
+assertEq(isSyntaxError("function f(x,{y:x}){})"),           true);
+assertEq(isSyntaxError("function f(x,{x}){})"),             true);
+
+assertEq(isSyntaxError("function f([x],x){})"),             true);
+assertEq(isSyntaxError("function f({y:x},x){})"),           true);
+assertEq(isSyntaxError("function f({x},x){})"),             true);
+
+assertEq(isSyntaxError("function f([x,x]){}"),              true);
+assertEq(isSyntaxError("function f({x,x}){}"),              true);
+assertEq(isSyntaxError("function f({y:x,z:x}){}"),          true);
+
+assertEq(isSyntaxError("function f(x,x,[y]){}"),            true);
+assertEq(isSyntaxError("function f(x,x,{y}){}"),            true);
+assertEq(isSyntaxError("function f([y],x,x){}"),            true);
+assertEq(isSyntaxError("function f({y},x,x){}"),            true);
+
+assertEq(isSyntaxError("function f(a,b,c,d,e,f,g,h,b,[y]){}"),  true);
+assertEq(isSyntaxError("function f([y],a,b,c,d,e,f,g,h,a){}"),  true);
+assertEq(isSyntaxError("function f([a],b,c,d,e,f,g,h,i,a){}"),  true);
+assertEq(isSyntaxError("function f(a,b,c,d,e,f,g,h,i,[a]){}"),  true);
+assertEq(isSyntaxError("function f(a,b,c,d,e,f,g,h,i,[a]){}"),  true);
+
+reportCompare(true, true);