I read this as
Don't show the notes a) if there aren't any b) There are but they all have the location noted
a) makes sense to me b) doesn't. I keep getting a note that there is a warning but then have to switch to the repl to see what it is.
(defun slime-maybe-list-compiler-notes (notes) "Show the compiler notes if appropriate." (unless (or (null notes) (and (eq last-command 'slime-compile-defun) (every #'slime-note-has-location-p notes))) (slime-list-compiler-notes notes)))
-Alan