parabellum
bubbers is right
just being switched to tower doesn't mean you are not IFR anymore...with visual apch clearance or any other apch clearance.
tower is part of ATC, many have radar repeaters or ''bright scopes'' and a direct line to apch control...indeed, at times certain up //down towers only one person is on duty (until they fell asleep that is) and they do it all, apch, dpch, tower, ground etc.
once you are in radar contact, you remain in radar contact until advised (beyond massive failures)
about separation...if you are on a visual apch you have the same responsibilities for see and avoid as any other time in VMC.
there is a little known requirement of ATC which is to point out traffic to all jet powered aircraft