private function invalidType($name, $provided)
    {
        $expected = implode('|', $this->argDefinitions[$name]['valid']);
        $msg = "Invalid configuration value "
            . "provided for \"{$name}\". Expected {$expected}, but got "
            . describe_type($provided) . "\n\n"
            . $this->getArgMessage($name);
        throw new IAE($msg);
    }