(typecase last
(cif
(unless (proper-list-of-length-p succ 1 2)
- (barf "~S ends in an IF, but doesn't have one or two succesors."
+ (barf "~S ends in an IF, but doesn't have one or two successors."
block))
(unless (member (if-consequent last) succ)
(barf "The CONSEQUENT for ~S isn't in SUCC for ~S." last block))