throw an error when destructuring a null or undefined value on an empty object pattern - fixes #681

lib/6to5/file.js

@@ -53,7 +53,8 @@ File.helpers = [
   "extends",
   "get",
   "set",
-  "class-call-check"
+  "class-call-check",
+  "object-destructuring-empty"
 ];
 
 File.validOptions = [

lib/6to5/transformation/templates/object-destructuring-empty.js

@@ -0,0 +1,3 @@
+(function (obj) {
+  if (obj == null) throw new TypeError("Cannot destructure undefined");
+});

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)) {

test/fixtures/transformation/es6-destructuring/empty-object-pattern/actual.js

@@ -0,0 +1 @@
+var {} = null;

test/fixtures/transformation/es6-destructuring/empty-object-pattern/exec.js

@@ -0,0 +1,3 @@
+assert.throws(function () {
+  var {} = null;
+}, /Cannot destructure undefined/);

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);