What this means is that when one evaluates M-x slime-macroexpand-again in a lisp file which is not a macroexpansion-buffer e.g. some-file-i-do-not-want-clobbered.lisp the contents of the file _are_ clobbered by slime-macroexpand-again and left in a more or less unrecoverable state! This happens easily when one uses values of `minibuffer-history' for M-x command completion esp. b/c `slime-macroexpand-*' is a prefix for at least seven different interactive macro-expansion related commands including:
The Interactive `slime-macroexpand-*' commands which might potentially clobber the contents of current-buffer should check that current-buffer is in fact a macro-expansion buffer before proceeding...