(progn
  (defgeneric foo (bar))
  (declaim (ftype (function (number) boolean) foo)))
  
; compiling (DEFGENERIC FOO ...)
; compiling (DECLAIM (FTYPE # ...))
STYLE-WARNING:
   Generic function GATEWAY/PROTOCOLS::FOO clobbers an earlier FTYPE
   proclamation (FUNCTION (NUMBER) (VALUES &OPTIONAL BOOLEAN &REST T)) for the
   same name with (FUNCTION (T) *).