- ;; effects except possibly CONS. If a function is defined to signal
- ;; errors, then it is not flushable even if it is movable or
- ;; foldable.
+ ;; effects except possibly cons. If a function might signal errors,
+ ;; then it is not flushable even if it is movable, foldable or
+ ;; unsafely-flushable. Implies UNSAFELY-FLUSHABLE. (In safe code
+ ;; type checking of arguments is always performed by the caller, so
+ ;; a function which SHOULD signal an error if arguments are not of
+ ;; declared types may be FLUSHABLE.)