add in custom acorn node constructor

lib/6to5/patch.js

@@ -3,6 +3,8 @@
 var t = require("./types");
 var _ = require("lodash");
 
+require("./types/node");
+
 // estraverse
 
 var estraverse = require("estraverse");

lib/6to5/types/index.js

@@ -2,6 +2,7 @@
 
 var toFastProperties = require("../helpers/to-fast-properties");
 var esutils          = require("esutils");
+var Node             = require("./node");
 var _                = require("lodash");
 
 var t = exports;
@@ -100,7 +101,9 @@ t.BUILDER_KEYS = _.defaults(require("./builder-keys"), t.VISITOR_KEYS);
 _.each(t.BUILDER_KEYS, function (keys, type) {
   t[type[0].toLowerCase() + type.slice(1)] = function () {
     var args = arguments;
-    var node = { type: type };
+    var node = new Node;
+    node.start = null;
+    node.type = type;
     _.each(keys, function (key, i) {
       node[key] = args[i];
     });

lib/6to5/types/node.js

@@ -0,0 +1,11 @@
+module.exports = Node;
+
+var object = require("../helpers/object");
+var acorn  = require("acorn-6to5");
+
+var oldNode = acorn.Node;
+acorn.Node = Node;
+
+function Node() {
+  oldNode.apply(this);
+}