在symfony2中添加新名称空间时出错

Question

I'm developing an application using Symfony2 and Doctrine 2.

Technical Specs

I'm using Symfony 2.7.1

I'm using PostgreSQl 1.18.1

I'm trying to add a cast function using package called oro-crm doctrine extensions. I have that in app/config/config.yml:

dql:

                datetime_functions:
                    date:           Oro\ORM\Query\AST\Functions\SimpleFunction
                    time:           Oro\ORM\Query\AST\Functions\SimpleFunction
                    timestamp:      Oro\ORM\Query\AST\Functions\SimpleFunction
                    convert_tz:     Oro\ORM\Query\AST\Functions\DateTime\ConvertTz
                numeric_functions:
                    timestampdiff:  Oro\ORM\Query\AST\Functions\Numeric\TimestampDiff
                    dayofyear:      Oro\ORM\Query\AST\Functions\SimpleFunction
                    dayofmonth:     Oro\ORM\Query\AST\Functions\SimpleFunction
                    dayofweek:      Oro\ORM\Query\AST\Functions\SimpleFunction
                    week:           Oro\ORM\Query\AST\Functions\SimpleFunction
                    day:            Oro\ORM\Query\AST\Functions\SimpleFunction
                    hour:           Oro\ORM\Query\AST\Functions\SimpleFunction
                    minute:         Oro\ORM\Query\AST\Functions\SimpleFunction
                    month:          Oro\ORM\Query\AST\Functions\SimpleFunction
                    quarter:        Oro\ORM\Query\AST\Functions\SimpleFunction
                    second:         Oro\ORM\Query\AST\Functions\SimpleFunction
                    year:           Oro\ORM\Query\AST\Functions\SimpleFunction
                    sign:           Oro\ORM\Query\AST\Functions\Numeric\Sign
                    pow:            Oro\ORM\Query\AST\Functions\Numeric\Pow
                string_functions:
                    group_concat:   Oro\ORM\Query\AST\Functions\String\GroupConcat
                    concat_ws:      Oro\ORM\Query\AST\Functions\String\ConcatWs
                    cast:           Oro\ORM\Query\AST\Functions\Cast

This is the namespace of /oro/doctrine-extensions/src/Oro/ORM/Query/AST/Functions/Cast.php:

namespace Oro\ORM\Query\AST\Functions;

I have that in symfony2 composer.json

"oro/doctrine-extensions":"dev-master"

Well, the problem is that when I'm trying to add the configuration to Doctrine with this command:

$config=$this->em->getConfiguration();
$config->addCustomStringFunction('CAST', 'Oro\ORM\Query\AST\Functions\Cast');

I got that error:

Attempted to load class "Cast" from namespace "Oro\ORM\Query\AST\Functions". Did you forget a "use" statement for another namespace?