Factorize code in isEmptySelf()

Author: BenMorel

lib/Doctrine/DBAL/Query/Expression/CompositeExpression.php

@@ -79,7 +79,7 @@ public function add($part)
             return $this;
         }
 
-        if ($part instanceof self && count($part) === 0) {
+        if ($this->isEmptySelf($part)) {
             return $this;
         }
 
@@ -100,12 +100,12 @@ public function with($part, ...$parts) : self
     {
         $that = clone $this;
 
-        if (! ($part instanceof self && count($part) === 0)) {
+        if (! $this->isEmptySelf($part)) {
             $that->parts[] = $part;
         }
 
         foreach ($parts as $part) {
-            if ($part instanceof self && count($part) === 0) {
+            if ($this->isEmptySelf($part)) {
                 continue;
             }
 
@@ -115,6 +115,14 @@ public function with($part, ...$parts) : self
         return $that;
     }
 
+    /**
+     * @param self|string $part
+     */
+    private function isEmptySelf($part) : bool
+    {
+        return $part instanceof self && count($part) === 0;
+    }
+
     /**
      * Retrieves the amount of expressions on composite expression.
      *