+ (;; sequence is not guaranteed to be an exhaustive
+ ;; partition, but it includes at least lists and vectors.
+ (target-type-is-in '(sequence))
+ (if (or (vectorp host-object) (listp host-object))
+ (values t t)
+ (if (typep host-object target-type)
+ (warn-and-give-up)
+ (values nil t))))