From 96bc95d6d9025459b50b41674fa65f93b2428dde Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Thu, 30 Oct 2014 17:11:54 +1100
Subject: [PATCH] add blacklist syntax feature checking to 6to5/register

---
 lib/6to5/register.js | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/lib/6to5/register.js b/lib/6to5/register.js
index f09ea6396d..da10785944 100644
--- a/lib/6to5/register.js
+++ b/lib/6to5/register.js
@@ -20,6 +20,22 @@ sourceMapSupport.install({
 
 //
 
+var blacklist  = [];
+
+var blacklistTest = function (transformer, code) {
+  try {
+    eval(code);
+    blacklist.push(transformer);
+  } catch (err) {
+    if (err.name !== "SyntaxError") throw err;
+  }
+};
+
+blacklistTest("generators", "function test *() {}");
+blacklistTest("letScoping", "let test = 0;");
+
+//
+
 var ignoreRegex = /node_modules/;
 var exts        = {};
 var maps        = {};
@@ -31,6 +47,7 @@ var loader = function (m, filename) {
   }
 
   var result = to5.transformFileSync(filename, {
+    blacklist: blacklist,
     sourceMap: true
   });