From 8884eb9fcffb2ff207747bdaf7463791e1fd7af2 Mon Sep 17 00:00:00 2001
From: stvcisco <stvcisco@gmail.com>
Date: Fri, 27 Mar 2020 08:45:06 +0000
Subject: [PATCH] [[FIX]] TypeError accessing 'value' of undefined

Make sure that 'decl.first[0]' is defined before accessing its 'value'
attribute.

No breaking changes.

Fixes #3455
---
 src/jshint.js      |  2 +-
 tests/unit/core.js | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/jshint.js b/src/jshint.js
index 66193ba25c..8e235b0ba6 100644
--- a/src/jshint.js
+++ b/src/jshint.js
@@ -5219,7 +5219,7 @@ var JSHINT = (function() {
       }
       nolinebreak(state.tokens.curr);
       advance(";");
-      if (decl) {
+      if (decl && decl.first && decl.first[0]) {
         if (decl.value === "const"  && !decl.hasInitializer) {
           warning("E012", decl, decl.first[0].value);
         }
diff --git a/tests/unit/core.js b/tests/unit/core.js
index ba126e695b..a02be03154 100644
--- a/tests/unit/core.js
+++ b/tests/unit/core.js
@@ -2352,6 +2352,20 @@ exports.initializeCStyle = function(test) {
   test.done();
 };
 
+// regression test for gh-3455
+exports.constWithoutVar = function(test) {
+  TestRun(test)
+    .addError(1, 11, "Expected an identifier and instead saw ';'.")
+    .addError(1, 12, "Expected an identifier and instead saw ')'.")
+    .addError(1, 12, "Expected ';' and instead saw ''.")
+    .addError(1, 12, "Unrecoverable syntax error. (100% scanned).")
+    .test([
+      "for (const;)"
+    ], { esversion: 6 });
+
+  test.done();
+};
+
 exports.constWithoutInit = function(test) {
   TestRun(test, "single binding")
     .addError(1, 6, "const 'x' is initialized to 'undefined'.")