FileCollection and addDirectory

That gives me Class "CodeIgniter\Files\FileCollection" not found....

This is a grep for "FileCollection" in my project's home:

Code:

system/HTTP/IncomingRequest.php:use CodeIgniter\HTTP\Files\FileCollection;
system/HTTP/IncomingRequest.php:    * @var FileCollection|null
system/HTTP/IncomingRequest.php:            $this->files = new FileCollection();
system/HTTP/IncomingRequest.php:            $this->files = new FileCollection();
system/HTTP/IncomingRequest.php:            $this->files = new FileCollection();
system/HTTP/Files/FileCollection.php: * Class FileCollection
system/HTTP/Files/FileCollection.php:class FileCollection

I don't see any system/Files/FileCollection.php..... ?