From 58fac2e2beb92f0e0a1b373e8531c378ef00ff44 Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Sat, 15 Nov 2014 02:49:49 +1100
Subject: [PATCH] support duplicate constants within different block scopes -
 fixes #161

---
 lib/6to5/transformation/transformers/constants.js | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/lib/6to5/transformation/transformers/constants.js b/lib/6to5/transformation/transformers/constants.js
index 9fe817e1ab..7c342edee7 100644
--- a/lib/6to5/transformation/transformers/constants.js
+++ b/lib/6to5/transformation/transformers/constants.js
@@ -9,11 +9,12 @@ exports.ForOfStatement =
 exports.ForStatement = function (node, parent, file) {
   var constants = [];
 
-  var check = function (node, names) {
+  var check = function (node, names, parent) {
     _.each(names, function (name) {
-      if (constants.indexOf(name) >= 0) {
-        throw file.errorWithNode(node, name + " is read-only");
-      }
+      if (!_.has(constants, name)) return;
+      if (t.isBlockStatement(parent) && parent !== constants[name]) return;
+
+      throw file.errorWithNode(node, name + " is read-only");
     });
   };
 
@@ -21,12 +22,12 @@ exports.ForStatement = function (node, parent, file) {
     return t.getIds(node, false, ["MemberExpression"]);
   };
 
-  _.each(node.body, function (child) {
+  _.each(node.body, function (child, parent) {
     if (child && t.isVariableDeclaration(child, { kind: "const" })) {
       _.each(child.declarations, function (declar) {
         _.each(getIds(declar), function (name) {
-          check(declar, [name]);
-          constants.push(name);
+          check(declar, [name], parent);
+          constants[name] = parent;
         });
 
         declar._ignoreConstant = true;