diff -r 000000000000 -r 6474c204b198 js/src/tests/ecma_5/RegExp/instance-property-storage-introspection.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/tests/ecma_5/RegExp/instance-property-storage-introspection.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,153 @@
+/*
+ * Any copyright is dedicated to the Public Domain.
+ * http://creativecommons.org/licenses/publicdomain/
+ */
+
+var BUGNUMBER = 640072;
+var summary =
+  "Represent /a/.{lastIndex,global,source,multiline,sticky,ignoreCase} with " +
+  "plain old data properties";
+
+print(BUGNUMBER + ": " + summary);
+
+/**************
+ * BEGIN TEST *
+ **************/
+
+function checkDataProperty(obj, p, expect, msg)
+{
+  var d = Object.getOwnPropertyDescriptor(obj, p);
+
+  assertEq(d.value, expect.value, msg + ": bad value for " + p);
+  assertEq(d.writable, expect.writable, msg + ": bad writable for " + p);
+  assertEq(d.enumerable, expect.enumerable, msg + ": bad enumerable for " + p);
+  assertEq(d.configurable, expect.configurable, msg + ": bad configurable for " + p);
+
+  // Try redefining the property using its initial values: these should all be
+  // silent no-ops.
+  Object.defineProperty(obj, p, { value: expect.value });
+  Object.defineProperty(obj, p, { writable: expect.writable });
+  Object.defineProperty(obj, p, { enumerable: expect.enumerable });
+  Object.defineProperty(obj, p, { configurable: expect.configurable });
+
+  var d2 = Object.getOwnPropertyDescriptor(obj, p);
+  assertEq(d.value, d2.value, msg + ": value changed on redefinition of " + p + "?");
+  assertEq(d.writable, d2.writable, msg + ": writable changed on redefinition of " + p + "?");
+  assertEq(d.enumerable, d2.enumerable, msg + ": enumerable changed on redefinition of " + p + "?");
+  assertEq(d.configurable, d2.configurable, msg + ": configurable changed on redefinition of " + p + "?");
+}
+
+
+// Check a bunch of "empty" regular expressions first.
+
+var choices = [{ msg: "RegExp.prototype",
+                 get: function() { return RegExp.prototype; } },
+               { msg: "new RegExp()",
+                 get: function() { return new RegExp(); } },
+               { msg: "/(?:)/",
+                 get: Function("return /(?:)/;") }];
+
+function checkRegExp(r, msg, lastIndex, global, ignoreCase, multiline)
+{
+  var expect;
+
+  expect = { value: lastIndex, enumerable: false, configurable: false, writable: true };
+  checkDataProperty(r, "lastIndex", expect, msg);
+
+  // check source specially: its value is under-defined in the spec
+  var d = Object.getOwnPropertyDescriptor(r, "source");
+  assertEq(d.writable, false, "bad writable: " + msg);
+  assertEq(d.enumerable, false, "bad enumerable: " + msg);
+  assertEq(d.configurable, false, "bad configurable: " + msg);
+
+  expect = { value: global, enumerable: false, configurable: false, writable: false };
+  checkDataProperty(r, "global", expect, msg);
+
+  expect = { value: ignoreCase, enumerable: false, configurable: false, writable: false };
+  checkDataProperty(r, "ignoreCase", expect, msg);
+
+  expect = { value: multiline, enumerable: false, configurable: false, writable: false };
+  checkDataProperty(r, "multiline", expect, msg);
+}
+
+checkRegExp(RegExp.prototype, "RegExp.prototype", 0, false, false, false);
+checkRegExp(new RegExp(), "new RegExp()", 0, false, false, false);
+checkRegExp(/(?:)/, "/(?:)/", 0, false, false, false);
+checkRegExp(Function("return /(?:)/;")(), 'Function("return /(?:)/;")()', 0, false, false, false);
+
+for (var i = 0; i < choices.length; i++)
+{
+  var choice = choices[i];
+  var msg = choice.msg;
+  var r = choice.get();
+
+  checkRegExp(r, msg, 0, false, false, false);
+}
+
+// Now test less generic regular expressions
+
+checkRegExp(/a/gim, "/a/gim", 0, true, true, true);
+
+var r;
+
+do
+{
+  r = /abcd/mg;
+  checkRegExp(r, "/abcd/mg initially", 0, true, false, true);
+  r.exec("abcdefg");
+  checkRegExp(r, "/abcd/mg step 1", 4, true, false, true);
+  r.exec("abcdabcd");
+  checkRegExp(r, "/abcd/mg step 2", 8, true, false, true);
+  r.exec("abcdabcd");
+  checkRegExp(r, "/abcd/mg end", 0, true, false, true);
+
+  r = /cde/ig;
+  checkRegExp(r, "/cde/ig initially", 0, true, true, false);
+  var obj = r.lastIndex = { valueOf: function() { return 2; } };
+  checkRegExp(r, "/cde/ig after lastIndex", obj, true, true, false);
+  r.exec("aaacdef");
+  checkRegExp(r, "/cde/ig after exec", 6, true, true, false);
+  Object.defineProperty(r, "lastIndex", { value: 3 });
+  checkRegExp(r, "/cde/ig after define 3", 3, true, true, false);
+  Object.defineProperty(r, "lastIndex", { value: obj });
+  checkRegExp(r, "/cde/ig after lastIndex", obj, true, true, false);
+
+
+  // Tricky bits of testing: make sure that redefining lastIndex doesn't change
+  // the slot where the lastIndex property is initially stored, even if
+  // the redefinition also changes writability.
+  r = /a/g;
+  checkRegExp(r, "/a/g initially", 0, true, false, false);
+  Object.defineProperty(r, "lastIndex", { value: 2 });
+  r.exec("aabbbba");
+  checkRegExp(r, "/a/g after first exec", 7, true, false, false);
+  assertEq(r.lastIndex, 7);
+  r.lastIndex = 2;
+  checkRegExp(r, "/a/g after assign", 2, true, false, false);
+  r.exec("aabbbba");
+  assertEq(r.lastIndex, 7); // check in reverse order
+  checkRegExp(r, "/a/g after second exec", 7, true, false, false);
+
+  r = /c/g;
+  r.lastIndex = 2;
+  checkRegExp(r, "/c/g initially", 2, true, false, false);
+  Object.defineProperty(r, "lastIndex", { writable: false });
+  assertEq(Object.getOwnPropertyDescriptor(r, "lastIndex").writable, false);
+  try { r.exec("aabbbba"); } catch (e) { /* swallow error if thrown */ }
+  assertEq(Object.getOwnPropertyDescriptor(r, "lastIndex").writable, false);
+  assertEq(Object.getOwnPropertyDescriptor(r, "source").writable, false);
+  assertEq(Object.getOwnPropertyDescriptor(r, "global").value, true);
+  assertEq(Object.getOwnPropertyDescriptor(r, "global").writable, false);
+  assertEq(Object.getOwnPropertyDescriptor(r, "ignoreCase").value, false);
+  assertEq(Object.getOwnPropertyDescriptor(r, "ignoreCase").writable, false);
+  assertEq(Object.getOwnPropertyDescriptor(r, "multiline").value, false);
+  assertEq(Object.getOwnPropertyDescriptor(r, "multiline").writable, false);
+}
+while (Math.random() > 17); // fake loop to discourage RegExp object caching
+
+/******************************************************************************/
+
+if (typeof reportCompare === "function")
+  reportCompare(true, true);
+
+print("All tests passed!");