i made the javascripts faster with a transformer prepass to check what transformers actually have to be ran

test/_helper.js

@@ -1,7 +1,8 @@
-var util = require("../lib/6to5/util");
-var path = require("path");
-var fs   = require("fs");
-var _    = require("lodash");
+var esvalid = require("esvalid");
+var util    = require("../lib/6to5/util");
+var path    = require("path");
+var fs      = require("fs");
+var _       = require("lodash");
 
 var humanize = function (val, noext) {
   if (noext) val = path.basename(val, path.extname(val));
@@ -18,6 +19,17 @@ var readFile = exports.readFile = function (filename) {
   }
 };
 
+exports.esvalid = function (ast, loc) {
+  var errors = esvalid.errors(ast);
+  if (errors.length) {
+    var msg = [];
+    _.each(errors, function (err) {
+      msg.push(err.message + " - " + JSON.stringify(err.node));
+    });
+    throw new Error(loc + ": " + msg.join(". "));
+  }
+};
+
 exports.assertVendor = function (name) {
   if (!fs.existsSync(__dirname + "/../vendor/" + name)) {
     console.error("No vendor/" + name + " - run `make bootstrap`");

test/_transformation-helper.js

@@ -2,7 +2,6 @@ var genHelpers = require("./_generator-helpers");
 var transform  = require("../lib/6to5/transformation");
 var sourceMap  = require("source-map");
 var codeFrame  = require("../lib/6to5/helpers/code-frame");
-var esvalid    = require("esvalid");
 var Module     = require("module");
 var helper     = require("./_helper");
 var assert     = require("assert");
@@ -55,15 +54,7 @@ var run = function (task, done) {
 
   var checkAst = function (result, opts) {
     if (noCheckAst) return;
-
-    var errors = esvalid.errors(result.ast.program);
-    if (errors.length) {
-      var msg = [];
-      _.each(errors, function (err) {
-        msg.push(err.message + " - " + JSON.stringify(err.node));
-      });
-      throw new Error(opts.loc + ": " + msg.join(". "));
-    }
+    helper.esvalid(result.ast.program, opts.loc);
   };
 
   if (execCode) {

test/test262.js

@@ -4,6 +4,7 @@ require("./_helper").assertVendor("test262");
 
 var transform = require("../lib/6to5/transformation");
 var readdir   = require("fs-readdir-recursive");
+var helper    = require("./_helper");
 var path      = require("path");
 var fs        = require("fs");
 var _         = require("lodash");
@@ -16,7 +17,7 @@ var read = function (loc) {
   });
 };
 
-var exec = function (loc) {
+var check = function (loc) {
   try {
     var file = fs.readFileSync(loc, "utf8");
 
@@ -26,25 +27,21 @@ var exec = function (loc) {
     // ReferenceError: 1++; (runtime)
     var lazyError = /negative: (\S+)/.test(file);
 
-    var compiled = transform(file, {
+    transform(file, {
       filename: loc,
-      blacklist: ["useStrict"]
+      blacklist: ["useStrict"],
+      _anal: true
     });
-
-    global.eval(compiled);
   } catch (err) {
     if (err && lazyError && err instanceof SyntaxError) {
       return;
     } else {
+      err.stack = loc + ": " + err.stack;
       throw err;
     }
   }
 };
 
-// harness
-var harness = read(test262Loc + "/harness");
-_.each(harness, exec);
-
 // tests!
 var tests = read(test262Loc + "/test");
 _.each(tests, function (loc) {
@@ -52,6 +49,6 @@ _.each(tests, function (loc) {
   alias = alias.replace(/\.([^\.]+)$/g, "");
   test(alias, function () {
     this.timeout(0);
-    exec(loc);
+    check(loc);
   });
 });