From b4cd2df7454c7cd8d841d141bb8c592c564183af Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Mon, 18 May 2015 22:41:27 +0100
Subject: [PATCH] ignore this and arguments when performing TCO on shadowed
 functions - fixes #1564

---
 .../transformation/transformers/es6/tail-call.js    | 13 ++++++++-----
 .../transformation/es6.tail-call/shadow/actual.js   |  8 ++++++++
 .../transformation/es6.tail-call/shadow/expected.js | 13 +++++++++++++
 3 files changed, 29 insertions(+), 5 deletions(-)
 create mode 100644 test/core/fixtures/transformation/es6.tail-call/shadow/actual.js
 create mode 100644 test/core/fixtures/transformation/es6.tail-call/shadow/expected.js

diff --git a/src/babel/transformation/transformers/es6/tail-call.js b/src/babel/transformation/transformers/es6/tail-call.js
index 00bce9ffff..247d408754 100644
--- a/src/babel/transformation/transformers/es6/tail-call.js
+++ b/src/babel/transformation/transformers/es6/tail-call.js
@@ -44,12 +44,14 @@ var visitor = {
   },
 
   ThisExpression(node, parent, scope, state) {
-    state.needsThis = true;
-    state.thisPaths.push(this);
+    if (!state.isShadowed) {
+      state.needsThis = true;
+      state.thisPaths.push(this);
+    }
   },
 
   ReferencedIdentifier(node, parent, scope, state) {
-    if (node.name === "arguments") {
+    if (node.name === "arguments" && !state.isShadowed) {
       state.needsArguments = true;
       state.argumentsPaths.push(this);
     }
@@ -67,8 +69,9 @@ class TailCallTransformer {
     this.needsThis = false;
     this.thisPaths = [];
 
-    this.ownerId = path.node.id;
-    this.vars    = [];
+    this.isShadowed = path.isArrowFunctionExpression() || path.is("shadow");
+    this.ownerId    = path.node.id;
+    this.vars       = [];
 
     this.scope = scope;
     this.path  = path;
diff --git a/test/core/fixtures/transformation/es6.tail-call/shadow/actual.js b/test/core/fixtures/transformation/es6.tail-call/shadow/actual.js
new file mode 100644
index 0000000000..2fa228077d
--- /dev/null
+++ b/test/core/fixtures/transformation/es6.tail-call/shadow/actual.js
@@ -0,0 +1,8 @@
+(function(){
+  var foo = () => {
+    this;
+    arguments;
+    foo();
+  };
+  foo();
+});
diff --git a/test/core/fixtures/transformation/es6.tail-call/shadow/expected.js b/test/core/fixtures/transformation/es6.tail-call/shadow/expected.js
new file mode 100644
index 0000000000..82f39882d9
--- /dev/null
+++ b/test/core/fixtures/transformation/es6.tail-call/shadow/expected.js
@@ -0,0 +1,13 @@
+"use strict";
+
+(function () {
+  var _this = this,
+      _arguments = arguments;
+
+  var foo = function foo() {
+    _this;
+    _arguments;
+    foo();
+  };
+  foo();
+});