Avoid forcing to define the choices_as_values option when using choic…

…e_loader

When using the choice loader, choices are ignored entirely. Forcing the dev
to add the choices_as_values just to avoid the deprecation warning (and then
to remove the option again at some point in 3.x due to deprecation) is a bad
developer experience.

src/Symfony/Component/Form/Extension/Core/Type/ChoiceType.php

@@ -357,7 +357,7 @@ public function configureOptions(OptionsResolver $resolver)
         };
 
         $choicesAsValuesNormalizer = function (Options $options, $choicesAsValues) use ($that) {
-            if (true !== $choicesAsValues) {
+            if (true !== $choicesAsValues && null === $options['choice_loader']) {
                 @trigger_error(sprintf('The value "false" for the "choices_as_values" option of the "%s" form type (%s) is deprecated since version 2.8 and will not be supported anymore in 3.0. Set this option to "true" and flip the contents of the "choices" option instead.', $that->getName(), __CLASS__), E_USER_DEPRECATED);
             }