How do I apply swank update coming with GNU Emacs SLIME melpa update without
restarting Lisp?

Initially I just tried to

(asdf:load-system "swank")

which signalled a SIMPLE-FILE-ERROR while attempting to WRITE-FILE
located at a previous slime directory which directory does not exist
anymore after SLIME update.

Restarting SLIME signalled the same error, only now I'm not connected to
Lisp image at all. At this point, I don't know what to do sans
restarting Lisp which would be unwelcome.

What should I have done and what do I do now? (Clearly, at least I
should have started a different SLIME connection for this attempt at
restart.)

Note regarding ASDF version: Gentoo says ASDF 3.1.5, manual shipped with
current SBCL (1.4.5) says 3.3.1. Without connection to Lisp, I can't say
much more.