From b6e83108482aec1d6a4e68d42993c59a7271eeee Mon Sep 17 00:00:00 2001
From: Marijn Haverbeke <marijnh@gmail.com>
Date: Thu, 19 Mar 2015 12:46:36 +0100
Subject: [PATCH] Require an initalization value when let/var/const-declaring a
 complex pattern

Closes #222
---
 acorn.js              | 2 ++
 test/tests-harmony.js | 2 ++
 2 files changed, 4 insertions(+)

diff --git a/acorn.js b/acorn.js
index 17ca02ce82..0e9845a2d5 100644
--- a/acorn.js
+++ b/acorn.js
@@ -2134,6 +2134,8 @@
         decl.init = this.parseMaybeAssign(noIn);
       } else if (kind === tt._const && !(this.type === tt._in || (this.options.ecmaVersion >= 6 && this.isContextual("of")))) {
         this.unexpected();
+      } else if (decl.id.type != "Identifier") {
+        this.raise(this.lastTokEnd, "Complex binding patterns require an initialization value")
       } else {
         decl.init = null;
       }
diff --git a/test/tests-harmony.js b/test/tests-harmony.js
index 3a8c55db7c..e4b0ee4ff8 100644
--- a/test/tests-harmony.js
+++ b/test/tests-harmony.js
@@ -15466,6 +15466,8 @@ test("let {x} = y", {
   "end": 11
 }, {ecmaVersion: 6})
 
+testFail("let [x]", "Complex binding patterns require an initialization value (1:7)", {ecmaVersion: 6})
+testFail("var [x]", "Complex binding patterns require an initialization value (1:7)", {ecmaVersion: 6})
 testFail("var _𖫵 = 11;", "Unexpected character '𖫵' (1:5)", {ecmaVersion: 6});
 testFail("var 𫠞_ = 12;", "Unexpected character '𫠞' (1:4)", {ecmaVersion: 6});
 testFail("var 𫠝_ = 10;", "Unexpected character '𫠝' (1:4)", {ecmaVersion: 5});