From 888ab5473a2acc22aad9880e70cbc71d04e9101e Mon Sep 17 00:00:00 2001
From: James Kyle <me@thejameskyle.com>
Date: Tue, 2 Dec 2014 16:26:18 -0800
Subject: [PATCH] Only slice arguments when necessary - fixes #239

---
 lib/6to5/transformation/transformers/es6-spread.js   |  7 ++++++-
 .../es6-spread/arguments-array/actual.js             |  9 +++++++++
 .../es6-spread/arguments-array/expected.js           | 12 ++++++++++++
 .../es6-spread/arguments-concat/actual.js            |  9 +++++++++
 .../es6-spread/arguments-concat/expected.js          | 12 ++++++++++++
 .../transformation/es6-spread/arguments/actual.js    |  2 +-
 .../transformation/es6-spread/arguments/expected.js  |  3 +--
 7 files changed, 50 insertions(+), 4 deletions(-)
 create mode 100644 test/fixtures/transformation/es6-spread/arguments-array/actual.js
 create mode 100644 test/fixtures/transformation/es6-spread/arguments-array/expected.js
 create mode 100644 test/fixtures/transformation/es6-spread/arguments-concat/actual.js
 create mode 100644 test/fixtures/transformation/es6-spread/arguments-concat/expected.js

diff --git a/lib/6to5/transformation/transformers/es6-spread.js b/lib/6to5/transformation/transformers/es6-spread.js
index 20f2165bda..8e07127db2 100644
--- a/lib/6to5/transformation/transformers/es6-spread.js
+++ b/lib/6to5/transformation/transformers/es6-spread.js
@@ -64,7 +64,12 @@ exports.CallExpression = function (node, parent, file) {
 
   node.arguments = [];
 
-  var nodes = build(args, file);
+  var nodes;
+  if (args.length === 1 && args[0].argument.name === 'arguments') {
+    nodes = [args[0].argument];
+  } else {
+    nodes = build(args, file);
+  }
   var first = nodes.shift();
 
   if (nodes.length) {
diff --git a/test/fixtures/transformation/es6-spread/arguments-array/actual.js b/test/fixtures/transformation/es6-spread/arguments-array/actual.js
new file mode 100644
index 0000000000..e18c362b1b
--- /dev/null
+++ b/test/fixtures/transformation/es6-spread/arguments-array/actual.js
@@ -0,0 +1,9 @@
+function foo() {
+  return bar([...arguments]);
+}
+
+function bar(one, two, three) {
+  return [one, two, three];
+}
+
+foo("foo", "bar");
diff --git a/test/fixtures/transformation/es6-spread/arguments-array/expected.js b/test/fixtures/transformation/es6-spread/arguments-array/expected.js
new file mode 100644
index 0000000000..705f37c31e
--- /dev/null
+++ b/test/fixtures/transformation/es6-spread/arguments-array/expected.js
@@ -0,0 +1,12 @@
+"use strict";
+
+var _slice = Array.prototype.slice;
+function foo() {
+  return bar([].concat(_slice.call(arguments)));
+}
+
+function bar(one, two, three) {
+  return [one, two, three];
+}
+
+foo("foo", "bar");
diff --git a/test/fixtures/transformation/es6-spread/arguments-concat/actual.js b/test/fixtures/transformation/es6-spread/arguments-concat/actual.js
new file mode 100644
index 0000000000..a6fdb21bef
--- /dev/null
+++ b/test/fixtures/transformation/es6-spread/arguments-concat/actual.js
@@ -0,0 +1,9 @@
+function foo() {
+  return bar("test", ...arguments);
+}
+
+function bar(one, two, three) {
+  return [one, two, three];
+}
+
+foo("foo", "bar");
diff --git a/test/fixtures/transformation/es6-spread/arguments-concat/expected.js b/test/fixtures/transformation/es6-spread/arguments-concat/expected.js
new file mode 100644
index 0000000000..1ba8c3aeb2
--- /dev/null
+++ b/test/fixtures/transformation/es6-spread/arguments-concat/expected.js
@@ -0,0 +1,12 @@
+"use strict";
+
+var _slice = Array.prototype.slice;
+function foo() {
+  return bar.apply(null, ["test"].concat(_slice.call(arguments)));
+}
+
+function bar(one, two, three) {
+  return [one, two, three];
+}
+
+foo("foo", "bar");
diff --git a/test/fixtures/transformation/es6-spread/arguments/actual.js b/test/fixtures/transformation/es6-spread/arguments/actual.js
index a6fdb21bef..476da431e8 100644
--- a/test/fixtures/transformation/es6-spread/arguments/actual.js
+++ b/test/fixtures/transformation/es6-spread/arguments/actual.js
@@ -1,5 +1,5 @@
 function foo() {
-  return bar("test", ...arguments);
+  return bar(...arguments);
 }
 
 function bar(one, two, three) {
diff --git a/test/fixtures/transformation/es6-spread/arguments/expected.js b/test/fixtures/transformation/es6-spread/arguments/expected.js
index 1ba8c3aeb2..c78c808ef0 100644
--- a/test/fixtures/transformation/es6-spread/arguments/expected.js
+++ b/test/fixtures/transformation/es6-spread/arguments/expected.js
@@ -1,8 +1,7 @@
 "use strict";
 
-var _slice = Array.prototype.slice;
 function foo() {
-  return bar.apply(null, ["test"].concat(_slice.call(arguments)));
+  return bar.apply(null, arguments);
 }
 
 function bar(one, two, three) {