Symfony\Component\Config\Definition\Builder\ArrayNodeDefinition::validateConcreteNode PHP Method

    protected function validateConcreteNode(ArrayNode $node)
    {
        $path = $node->getPath();
        if (null !== $this->key) {
            throw new InvalidDefinitionException(sprintf('->useAttributeAsKey() is not applicable to concrete nodes at path "%s"', $path));
        }
        if (true === $this->atLeastOne) {
            throw new InvalidDefinitionException(sprintf('->requiresAtLeastOneElement() is not applicable to concrete nodes at path "%s"', $path));
        }
        if ($this->default) {
            throw new InvalidDefinitionException(sprintf('->defaultValue() is not applicable to concrete nodes at path "%s"', $path));
        }
        if (false !== $this->addDefaultChildren) {
            throw new InvalidDefinitionException(sprintf('->addDefaultChildrenIfNoneSet() is not applicable to concrete nodes at path "%s"', $path));
        }
    }