diff -r 000000000000 -r 6474c204b198 js/src/jit-test/tests/basic/testReplaceWithLambda.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/jit-test/tests/basic/testReplaceWithLambda.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,50 @@
+// optimized
+(function(b) {
+    assertEq("abc".replace(/a|b/g, function(a) { return b[a] }), 'ABc');
+})({a:'A', b:'B' });
+(function() {
+    var b = {a:'A', b:'B' };
+    assertEq("abc".replace(/a|b/g, function(a) { return b[a] }), 'ABc');
+})();
+(function() {
+    let (b = {a:'A', b:'B' }) {
+        assertEq("abc".replace(/a|b/g, function(a) { return b[a] }), 'ABc');
+    }
+})();
+(function() {
+    var b = {a:'A', b:'B' };
+    (function () {
+        assertEq("abc".replace(/a|b/g, function(a) { return b[a] }), 'ABc');
+    })();
+})();
+(function() {
+    let (b = {a:'A', b:'B' }) {
+        (function () {
+            assertEq("abc".replace(/a|b/g, function(a) { return b[a] }), 'ABc');
+        })();
+    }
+})();
+(function() {
+    var b = {a:'A', b:'B' };
+    (function () {
+        (function () {
+            assertEq("abc".replace(/a|b/g, function(a) { return b[a] }), 'ABc');
+        })();
+    })();
+})();
+
+// not optimized:
+(function() {
+    var b = {a:'A', b:'B' };
+    with ({}) {
+        (function () {
+            assertEq("abc".replace(/a|b/g, function(a) { return b[a] }), 'ABc');
+        })();
+    }
+})();
+(function() {
+   var b = {a:'A', b:'B' };
+   var bad = function() { b = {a:1, b:2}; return 'X' }
+   Object.defineProperty(b, 'x', {get:bad});
+   assertEq("xabc".replace(/x|a|b/g, function(a) { return b[a] }), 'X12c');
+})();