The 'slime-asdf' contribution always reports "Compilation failed" in the minibuffer for all of the various REPL shortcut commands (i.e. those prefixed with the "'" character) dealing with ASDF (tested this under SBCL, ABCL, and CLISP). This is occurring because the value of ASDF:OPERATE (aka ASDF:OOS) is seemingly always NIL. COLLECT-NOTES in swank.lisp:2461 is passing this result back to SLIME in the COMPILATION-RESULT to be reported in the minibuffer as status.
Did something get lost in a refactoring somewhere? Or did the ASDF hooks always have this behavior? I can't see a plausible way to assign a meaningful status from ASDF:OPERATE anyways (my understanding is that it always returns nil), so my suggestion would be to change the minibuffer message for COMPILATION-RESULTs from ASDF invocations, but that didn't look like a fast fix, so I wanted to solicit advice.
In the scale of things, this is a minor cosmetic problem with SLIME, but it was bugging me (and would be confusing for new users)…