Tree matching theorem for parse-ichar2.
Theorem:
(defthm tree-match-of-parse-ichar2 (b* (((mv error? tree? &) (parse-ichar2 char1 char2 input))) (implies (and (not error?) (element-case element :char-val) (char-val-case (element-char-val->get element) :insensitive) (equal (char-val-insensitive->get (element-char-val->get element)) (implode (list char1 char2)))) (tree-match-element-p tree? element *grammar*))))