From 58bed088f512e3387b34812ff6f412026b7a7bc0 Mon Sep 17 00:00:00 2001
From: Sebastian McKenzie <sebmck@gmail.com>
Date: Wed, 4 Feb 2015 17:35:24 +1100
Subject: [PATCH] throw an error when destructuring a null or undefined value
 on an empty object pattern - fixes #681

---
 lib/6to5/file.js                                           | 3 ++-
 .../transformation/templates/object-destructuring-empty.js | 3 +++
 lib/6to5/transformation/transformers/es6/destructuring.js  | 6 ++++++
 .../es6-destructuring/empty-object-pattern/actual.js       | 1 +
 .../es6-destructuring/empty-object-pattern/exec.js         | 3 +++
 .../es6-destructuring/empty-object-pattern/expected.js     | 7 +++++++
 6 files changed, 22 insertions(+), 1 deletion(-)
 create mode 100644 lib/6to5/transformation/templates/object-destructuring-empty.js
 create mode 100644 test/fixtures/transformation/es6-destructuring/empty-object-pattern/actual.js
 create mode 100644 test/fixtures/transformation/es6-destructuring/empty-object-pattern/exec.js
 create mode 100644 test/fixtures/transformation/es6-destructuring/empty-object-pattern/expected.js

diff --git a/lib/6to5/file.js b/lib/6to5/file.js
index dce01a04cc..cd2d34a6ac 100644
--- a/lib/6to5/file.js
+++ b/lib/6to5/file.js
@@ -53,7 +53,8 @@ File.helpers = [
   "extends",
   "get",
   "set",
-  "class-call-check"
+  "class-call-check",
+  "object-destructuring-empty"
 ];
 
 File.validOptions = [
diff --git a/lib/6to5/transformation/templates/object-destructuring-empty.js b/lib/6to5/transformation/templates/object-destructuring-empty.js
new file mode 100644
index 0000000000..b2252a935a
--- /dev/null
+++ b/lib/6to5/transformation/templates/object-destructuring-empty.js
@@ -0,0 +1,3 @@
+(function (obj) {
+  if (obj == null) throw new TypeError("Cannot destructure undefined");
+});
diff --git a/lib/6to5/transformation/transformers/es6/destructuring.js b/lib/6to5/transformation/transformers/es6/destructuring.js
index 6dc61bfd6e..34e9895a81 100644
--- a/lib/6to5/transformation/transformers/es6/destructuring.js
+++ b/lib/6to5/transformation/transformers/es6/destructuring.js
@@ -66,6 +66,12 @@ var pushAssignmentPattern = function (opts, nodes, pattern, parentId) {
 };
 
 var pushObjectPattern = function (opts, nodes, pattern, parentId) {
+  if (!pattern.properties.length) {
+    nodes.push(t.expressionStatement(
+      t.callExpression(opts.file.addHelper("object-destructuring-empty"), [parentId])
+    ));
+  }
+
   for (var i = 0; i < pattern.properties.length; i++) {
     var prop = pattern.properties[i];
     if (t.isSpreadProperty(prop)) {
diff --git a/test/fixtures/transformation/es6-destructuring/empty-object-pattern/actual.js b/test/fixtures/transformation/es6-destructuring/empty-object-pattern/actual.js
new file mode 100644
index 0000000000..c216969cbd
--- /dev/null
+++ b/test/fixtures/transformation/es6-destructuring/empty-object-pattern/actual.js
@@ -0,0 +1 @@
+var {} = null;
diff --git a/test/fixtures/transformation/es6-destructuring/empty-object-pattern/exec.js b/test/fixtures/transformation/es6-destructuring/empty-object-pattern/exec.js
new file mode 100644
index 0000000000..5cb51af584
--- /dev/null
+++ b/test/fixtures/transformation/es6-destructuring/empty-object-pattern/exec.js
@@ -0,0 +1,3 @@
+assert.throws(function () {
+  var {} = null;
+}, /Cannot destructure undefined/);
diff --git a/test/fixtures/transformation/es6-destructuring/empty-object-pattern/expected.js b/test/fixtures/transformation/es6-destructuring/empty-object-pattern/expected.js
new file mode 100644
index 0000000000..93c853b604
--- /dev/null
+++ b/test/fixtures/transformation/es6-destructuring/empty-object-pattern/expected.js
@@ -0,0 +1,7 @@
+"use strict";
+
+var _objectDestructuringEmpty = function (obj) { if (obj == null) throw new TypeError("Cannot destructure undefined"); };
+
+var _ref = null;
+
+_objectDestructuringEmpty(_ref);