Second induction step of the completeness lemma for parse-concatenation.
Theorem:
(defthm parse-concatenation-when-tree-match-induction-step-2 (implies (and (not (mv-nth 0 (parse-repetition input))) (< (len (mv-nth 2 (parse-repetition input))) (len input)) (pred-repetition input) (pred-conc-rest (mv-nth 2 (parse-repetition input)))) (pred-concatenation input)))