According to current Canon Law, is a pastor permitted to deny communion to someone he privately knows to be in a state of grave sin?

Canon 843 says >Can. 843 §1. Sacred ministers cannot deny the sacraments to those who seek them at appropriate times, are properly disposed, and are not prohibited by law from receiving them. > >§2. Pastors of souls and other members of the Christian faithful, according to their respective ecclesiastical function, have the duty to take care that those who seek the sacraments are prepared to receive them by proper evangelization and catechetical instruction, attentive to the norms issued by competent authority. This seems to me to entail that priests may deny communion to those they know to be improperly disposed. If someone seeks communion at an inappropriate time, or while improperly disposed, or is prohibited by law from receiving communion, then there does not appear to be any requirement for the pastor to give that person communion. Yet, there are those who say that a priest can only deny communion to someone who is in "manifest grave sin." This is a reference to canon 915, which says >Can. 915 Those who have been excommunicated or interdicted after the imposition or declaration of the penalty and others obstinately persevering in manifest grave sin are not to be admitted to holy communion. But this canon says the priest *may not* admit such people to communion, not that the priest must admit anyone who does not meet these criteria to communion. If, hypothetically, I walked up to the priest just before Mass, and told him that I had committed some grave sin and had not yet repented of it in Confession, but the sin is private, known only to me and the priest, it seems common sense to me that if I then approach to receive communion during Mass, the priest should deny me. Even if I did not tell him the particulars of the sin, but merely that it was grave or mortal, it seems common sense that he ought to deny communion to me. I would very much like to see the reasoning from a trained canon lawyer as to how the law as written requires priests, especially pastors, to give communion to someone they know is in unrepentant mortal sin as long as the sin isn't publicly manifest. Or, if that is incorrect, are there any canon lawyers who say that the priest in my hypothetical scenario is permitted to refuse someone communion?