From f03f45d8c25f5f0d9813b93feea20efe4df6a4f8 Mon Sep 17 00:00:00 2001
From: Yevgeny Tomenko <skie@mail.ru>
Date: Fri, 12 Feb 2016 03:47:39 +0300
Subject: [PATCH] Added check for input parameters types in
 QueryExpression::equalFields.

---
 src/Database/Expression/QueryExpression.php | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/Database/Expression/QueryExpression.php b/src/Database/Expression/QueryExpression.php
index f3c500b7916..54115c0115b 100644
--- a/src/Database/Expression/QueryExpression.php
+++ b/src/Database/Expression/QueryExpression.php
@@ -447,7 +447,13 @@ public function count()
      */
     public function equalFields($left, $right)
     {
-        return $this->eq(new IdentifierExpression($left), new IdentifierExpression($right));
+        $wrapIdentifier = function($field) {
+            if ($field instanceof ExpressionInterface) {
+                return $field;
+            }
+            return new IdentifierExpression($field);
+        };
+        return $this->eq($wrapIdentifier($left), $wrapIdentifier($right));
     }
 
     /**