Recognizer for function-option structures.
(function-optionp x) → *
Function:
(defun function-optionp (x) (declare (xargs :guard t)) (let ((__function__ 'function-optionp)) (declare (ignorable __function__)) (cond ((not x) (b* nil t)) (t (b* ((fty::val x)) (functionp fty::val))))))