~~Yes,~~ `SO_REUSEADDR` is a valid option on AF_UNIX sockets and is supported by this patch. I'll add a test for it. It looks like this is only true for abstract AF_UNIX sockets, which are expressly unsupported due to Windows' own lack of support for them.
Okay, I think I was assuming that "unbinding" meant doing the opposite of bind(), rather than "allowing other sockets to use that address". It'd be nice to have some tests for that functionality, then:
* test that trying to use the same address *without* deleting the socket fails (even if you close the socket handle? That part is very surprising to me.)
* test that trying to use the same address after deleting the socket succeeds, which currently isn't actually tested.
* Can the socket be used normally after deleting it?