My changes were based on the other generic directory functions ([`directory-empty?`](https://github.com/dylan-lang/opendylan/blob/master/sources/system/file-system/file-system.dylan#L418-L430), [`ensure-directories-exist`](https://github.com/dylan-lang/opendylan/blob/master/sources/system/file-system/file-system.dylan#L387-L414), [`delete-directory`](https://github.com/dylan-lang/opendylan/blob/master/sources/system/file-system/file-system.dylan#L353-L383), etc) that all contain the same three types of implementations, one accepting `<string>`, one accepting `<file-system-directory-locator>` and one accepting `<file-system-file-locator>`.

I don't know why this function's implementation differed, but after I saw it not-working I assumed it was incorrect, and then changing the impls to match the previous functions fixed it up.

Although, saying all of that, I can't say that this is the *correct* change, my edits mostly came from pattern matching on the previous fns to deduce a fix and then I saw that it worked.