add block scoped functions - fixes #514

lib/6to5/transformation/transform.js

@@ -44,6 +44,7 @@ transform.moduleFormatters = {
 _.each({
   specNoForInOfAssignment:   require("./transformers/spec-no-for-in-of-assignment"),
   specSetters:               require("./transformers/spec-setters"),
+  specBlockScopedFunctions:  require("./transformers/spec-block-scoped-functions"),
 
   // playground
   malletOperator:            require("./transformers/playground-mallet-operator"),

lib/6to5/transformation/transformers/spec-block-scoped-functions.js

@@ -0,0 +1,19 @@
+var t = require("../../types");
+
+exports.FunctionDeclaration = function (node, parent) {
+  if (t.isProgram(parent) || t.isExportDeclaration(parent)) {
+    return;
+  }
+
+  var declar = t.variableDeclaration("let", [
+    t.variableDeclarator(node.id, t.toExpression(node))
+  ]);
+
+  // hoist it up above everything else
+  declar._blockHoist = 2;
+
+  // todo: name this
+  node.id = null;
+
+  return declar;
+};