diff --git a/lib/6to5/transformation/file.js b/lib/6to5/transformation/file.js
index 6d6d19fecc..aafe1399ad 100644
--- a/lib/6to5/transformation/file.js
+++ b/lib/6to5/transformation/file.js
@@ -443,30 +443,3 @@ File.prototype.generate = function () {
 
   return result;
 };
-
-File.prototype.generateUid = function (name, scope) {
-  name = t.toIdentifier(name).replace(/^_+/, "");
-
-  scope = scope || this.scope;
-
-  var uid;
-  var i = 0;
-  do {
-    uid = this._generateUid(name, i);
-    i++;
-  } while (scope.hasBinding(uid) || scope.hasGlobal(uid));
-  return uid;
-};
-
-File.prototype.generateUidIdentifier = function (name, scope) {
-  scope = scope || this.scope;
-  var id = t.identifier(this.generateUid(name, scope));
-  scope.getFunctionParent().registerBinding("uid", id);
-  return id;
-};
-
-File.prototype._generateUid = function (name, i) {
-  var id = name;
-  if (i > 1) id += i;
-  return "_" + id;
-};
diff --git a/lib/6to5/transformation/helpers/replace-supers.js b/lib/6to5/transformation/helpers/replace-supers.js
index 20479e3c10..f61be9b5a2 100644
--- a/lib/6to5/transformation/helpers/replace-supers.js
+++ b/lib/6to5/transformation/helpers/replace-supers.js
@@ -143,7 +143,7 @@ ReplaceSupers.prototype.getThisReference = function () {
   if (this.topLevelThisReference) {
     return this.topLevelThisReference;
   } else {
-    var ref = this.topLevelThisReference = this.file.generateUidIdentifier("this");
+    var ref = this.topLevelThisReference = this.scope.generateUidIdentifier("this");
     this.methodNode.value.body.body.unshift(t.variableDeclaration("var", [
       t.variableDeclarator(this.topLevelThisReference, t.thisExpression())
     ]));
diff --git a/lib/6to5/transformation/modules/_default.js b/lib/6to5/transformation/modules/_default.js
index 9a44d57791..93353752cd 100644
--- a/lib/6to5/transformation/modules/_default.js
+++ b/lib/6to5/transformation/modules/_default.js
@@ -9,8 +9,9 @@ var util     = require("../../util");
 var t        = require("../../types");
 
 function DefaultFormatter(file) {
-  this.file = file;
-  this.ids  = object();
+  this.scope = file.scope;
+  this.file  = file;
+  this.ids   = object();
 
   this.hasNonDefaultExports = false;
 
diff --git a/lib/6to5/transformation/modules/amd.js b/lib/6to5/transformation/modules/amd.js
index dc9c8162a9..d05567668c 100644
--- a/lib/6to5/transformation/modules/amd.js
+++ b/lib/6to5/transformation/modules/amd.js
@@ -70,7 +70,7 @@ AMDFormatter.prototype.getModuleName = function () {
 };
 
 AMDFormatter.prototype._getExternalReference = function (node) {
-  return this.file.generateUidIdentifier(node.source.value);
+  return this.scope.generateUidIdentifier(node.source.value);
 };
 
 AMDFormatter.prototype.importDeclaration = function (node) {
diff --git a/lib/6to5/transformation/modules/common.js b/lib/6to5/transformation/modules/common.js
index 73d2aeac31..d5c3d5d94e 100644
--- a/lib/6to5/transformation/modules/common.js
+++ b/lib/6to5/transformation/modules/common.js
@@ -93,7 +93,7 @@ CommonJSFormatter.prototype._getExternalReference = function (node, nodes) {
   var call = t.callExpression(t.identifier("require"), [node.source]);
 
   if (this.localImportOccurences[source] > 1) {
-    var uid = this.file.generateUidIdentifier(source);
+    var uid = this.scope.generateUidIdentifier(source);
     nodes.push(t.variableDeclaration("var", [
       t.variableDeclarator(uid, call)
     ]));
diff --git a/lib/6to5/transformation/modules/system.js b/lib/6to5/transformation/modules/system.js
index 0c5db72d55..192fff7799 100644
--- a/lib/6to5/transformation/modules/system.js
+++ b/lib/6to5/transformation/modules/system.js
@@ -12,7 +12,7 @@ var each             = require("lodash/collection/each");
 var map              = require("lodash/collection/map");
 
 function SystemFormatter(file) {
-  this.exportIdentifier = file.generateUidIdentifier("export");
+  this.exportIdentifier = file.scope.generateUidIdentifier("export");
   this.noInteropRequireExport = true;
   this.noInteropRequireImport = true;
 
@@ -29,7 +29,7 @@ SystemFormatter.prototype._addImportSource = function (node, exportNode) {
 };
 
 SystemFormatter.prototype.buildExportsWildcard = function (objectIdentifier, node) {
-  var leftIdentifier = this.file.generateUidIdentifier("key");
+  var leftIdentifier = this.scope.generateUidIdentifier("key");
   var valIdentifier  = t.memberExpression(objectIdentifier, leftIdentifier, true);
 
   var left = t.variableDeclaration("var", [
diff --git a/lib/6to5/transformation/transformers/playground/method-binding.js b/lib/6to5/transformation/transformers/playground/method-binding.js
index 085496a46b..3835d04543 100644
--- a/lib/6to5/transformation/transformers/playground/method-binding.js
+++ b/lib/6to5/transformation/transformers/playground/method-binding.js
@@ -34,7 +34,7 @@ exports.BindFunctionExpression = function (node, parent, scope, file) {
     ]));
   };
 
-  var temp = scope.generateTemp(file, "args");
+  var temp = scope.generateTemp("args");
 
   return t.sequenceExpression([
     t.assignmentExpression("=", temp, t.arrayExpression(node.arguments)),
diff --git a/lib/6to5/traversal/scope.js b/lib/6to5/traversal/scope.js
index d84bf38f36..d408fd5c22 100644
--- a/lib/6to5/traversal/scope.js
+++ b/lib/6to5/traversal/scope.js
@@ -50,12 +50,11 @@ Scope.prototype.traverse = function (node, opts, state) {
 /**
  * Description
  *
- * @param {File} file
  * @param {String} [name="temp"]
  */
 
-Scope.prototype.generateTemp = function (file, name) {
-  var id = file.generateUidIdentifier(name || "temp", this);
+Scope.prototype.generateTemp = function (name) {
+  var id = this.generateUidIdentifier(name || "temp");
   this.push({
     key: id.name,
     id: id
@@ -70,9 +69,36 @@ Scope.prototype.generateTemp = function (file, name) {
  */
 
 Scope.prototype.generateUidIdentifier = function (name) {
-  return this.file.generateUidIdentifier(name, this);
+  var id = t.identifier(this.generateUid(name));
+  this.getFunctionParent().registerBinding("uid", id);
+  return id;
 };
 
+/**
+ * Description
+ *
+ * @param {String} name
+ */
+
+Scope.prototype.generateUid = function (name) {
+  name = t.toIdentifier(name).replace(/^_+/, "");
+
+  var uid;
+  var i = 0;
+  do {
+    uid = this._generateUid(name, i);
+    i++;
+  } while (this.hasBinding(uid) || this.hasGlobal(uid));
+  return uid;
+};
+
+Scope.prototype._generateUid = function (name, i) {
+  var id = name;
+  if (i > 1) id += i;
+  return "_" + id;
+};
+
+
 /*
  * Description
  *
@@ -111,7 +137,7 @@ Scope.prototype.generateUidBasedOnNode = function (parent) {
   var id = parts.join("$");
   id = id.replace(/^_/, "") || "ref";
 
-  return this.file.generateUidIdentifier(id, this);
+  return this.generateUidIdentifier(id);
 };
 
 /**
@@ -197,8 +223,9 @@ Scope.prototype.inferType = function (node) {
     return;
   }
 
-  if (t.isCallExpression(target)) {
-    // todo: resolve this to a return type
+  if (t.isCallExpression(target) && t.isIdentifier(target.callee)) {
+    var funcInfo = this.getBindingInfo(target.callee.name);
+    if (funcInfo) return funcInfo.node.returnType;
   }
 
   if (t.isIdentifier(target)) {
@@ -329,6 +356,7 @@ Scope.prototype.registerBinding = function (kind, node) {
       reassigned:             false,
       identifier:             id,
       scope:                  this,
+      node:                   node,
       kind:                   kind
     };
   }