Six swank back-ends implement the RESTART-FRAME interface. Yet only two of these back-ends implements FRAME-RESTARTABLE-P, which is used by the BACKTRACE slimefun to identify whether a frame is restartable.
Allegro and SBCL implement both restart-frame and frame-restartable- p. ABCL, CCL, CLISP and LispWorks only implement restart-frame.
For consistency, perhaps back-ends that implement restart-frame also could implement frame-restartable-p?
-- Terje Norderhaug terje@in-progress.com