private function mount(array &$array, string $path, $message)
    {
        if ($path == '.') {
            throw new MapperException(
                "Unable to mount error `{$message}` to `{$path}` (root path is forbidden)"
            );
        }

        $step = explode('.', $path);
        while ($name = array_shift($step)) {
            $array = &$array[$name];
        }

        $array = $message;
    }