/**
  * @param SQLTransformer $transformer
  * @param Expression     $expression
  * @param Configuration  $config
  *
  * @return Clause
  */
 public function __invoke(SQLTransformer $transformer, Expression $expression, Configuration $config)
 {
     switch ($config->getPlaceholderStyle()) {
         case self::STYLE_NAMED:
             $name = 'P' . spl_object_hash($expression);
             return new Clause(':' . $name, [$name => $expression->getValue()]);
     }
     return new Clause('?', [$expression->getValue()]);
 }