Since the soul is in a state of mortal sin at the time of death for someone who commits suicide, it would seem that the consequence must necessarily be damnation.
However here is what the catechism says:
2280 Everyone is responsible for his life before God who has given it
to him. It is God who remains the sovereign Master of life. We are
obliged to accept life gratefully and preserve it for his honor and
the salvation of our souls. We are stewards, not owners, of the life
God has entrusted to us. It is not ours to dispose of.
2281 Suicide contradicts the natural inclination of the human being to
preserve and perpetuate his life. It is gravely contrary to the just
love of self. It likewise offends love of neighbor because it unjustly
breaks the ties of solidarity with family, nation, and other human
societies to which we continue to have obligations. Suicide is
contrary to love for the living God.
2282 If suicide is committed with the intention of setting an example,
especially to the young, it also takes on the gravity of scandal.
Voluntary co-operation in suicide is contrary to the moral law.
Grave psychological disturbances, anguish, or grave fear of hardship,
suffering, or torture can diminish the responsibility of the one
2283 We should not despair of the eternal salvation of persons who
have taken their own lives. By ways known to him alone, God can
provide the opportunity for salutary repentance. The Church prays for
persons who have taken their own lives.