[2.0] Commiting missing file

lib/Doctrine/ORM/Query/AST/EmptyCollectionComparisonExpression.php

+<?php
+
+namespace Doctrine\ORM\Query\AST;
+
+/**
+ * EmptyCollectionComparisonExpression ::= CollectionValuedPathExpression "IS" ["NOT"] "EMPTY"
+ *
+ * @author Guilherme Blanco <guilhermeblanco@hotmail.com>
+ */
+class EmptyCollectionComparisonExpression extends Node
+{
+    private $_expression;
+    private $_not;
+
+    public function __construct($expression)
+    {
+        $this->_expression = $expression;
+    }
+
+    public function getExpression()
+    {
+        return $this->_expression;
+    }
+
+    public function setNot($bool)
+    {
+        $this->_not = $bool;
+    }
+
+    public function isNot()
+    {
+        return $this->_not;
+    }
+
+    public function dispatch($sqlWalker)
+    {
+        return $sqlWalker->walkEmptyCollectionComparisonExpression($this);
+    }
+}
+