Tree matching theorem for parse-*digit-star-*digit.
Theorem:
(defthm tree-match-of-parse-*digit-star-*digit (b* (((mv error? tree? &) (parse-*digit-star-*digit input))) (implies (and (not error?) (equal element (!_ (/_ (*_ *digit*) "*" (*_ *digit*))))) (tree-match-element-p tree? element *grammar*))))