Baptism of Desire isn't heretical. But neither is it a dogma. Many of XavierSems quotes are from the 19th century and onwards when this issue first started.
I will provide a few quotes of my own.
[color=rgba(0, 0, 0, 0.87)]Pope Pelagius II[/color][color=rgba(0, 0, 0, 0.87)]
(A.D. 578 – 590): “Consider the fact that whoever has not been in the peace and unity of the Church cannot have the Lord. …Although given over to flames and fires, they burn, or, thrown to wild beasts, they lay down their lives, there will not be (for them) that crown of faith but the punishment of faithlessness. …Such a one can be slain, he cannot be crowned. …[If] slain outside the Church, he cannot attain the rewards of the Church.” ([/color]
[color=rgba(0, 0, 0, 0.87)]Denzinger[/color][color=rgba(0, 0, 0, 0.87)]
246-247)[/color]
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[color=rgba(0, 0, 0, 0.87)]Pope Saint Gregory the Great[/color][color=rgba(0, 0, 0, 0.87)]
(A.D. 590 – 604): “Now the holy Church universal proclaims that God cannot be truly worshipped saving within herself, asserting that all they that are without her shall never be saved.” ([/color]
[color=rgba(0, 0, 0, 0.87)]Moralia[/color][color=rgba(0, 0, 0, 0.87)]
)[/color][/font][/size][/color]
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[color=rgba(0, 0, 0, 0.87)][color=rgba(0, 0, 0, 0.87)]Pope Innocent III[/color][color=rgba(0, 0, 0, 0.87)]
(A.D. 1198 – 1216): “With our hearts we believe and with our lips we confess but one Church, not that of the heretics, but the Holy Roman Catholic and Apostolic Church, outside which we believe that no one is saved.” ([/color]
[color=rgba(0, 0, 0, 0.87)]Denzinger[/color][color=rgba(0, 0, 0, 0.87)]
423)[/color][/font][/size][/color][/font][/size][/color]
[color=rgba(0, 0, 0, 0.87)]
[color=rgba(0, 0, 0, 0.87)][color=rgba(0, 0, 0, 0.87)][color=rgba(0, 0, 0, 0.87)]Pope Pius IX[/color][color=rgba(0, 0, 0, 0.87)]
(A.D. 1846 – 1878): “It must be held by faith that outside the Apostolic Roman Church, no one can be saved; that this is the only ark of salvation; that he who shall not have entered therein will perish in the flood.” ([/color]
[color=rgba(0, 0, 0, 0.87)]Denzinger[/color][color=rgba(0, 0, 0, 0.87)]
1647)[/color][/font][/size][/color][/font][/size][/color][/font][/size][/color]
[color=rgba(0, 0, 0, 0.87)]
[color=rgba(0, 0, 0, 0.87)][color=rgba(0, 0, 0, 0.87)][color=rgba(0, 0, 0, 0.87)][color=rgba(0, 0, 0, 0.87)]Pope Pius XI[/color][color=rgba(0, 0, 0, 0.87)]
(A.D. 1922 – 1939): “The Catholic Church alone is keeping the true worship. This is the font of truth, this is the house of faith, this is the temple of God; if any man enter not here, or if any man go forth from it, he is a stranger to the hope of life and salvation….Furthermore, in this one Church of Christ, no man can be or remain who does not accept, recognize and obey the authority and supremacy of Peter and his legitimate successors.” (Encyclical, [/color]
[color=rgba(0, 0, 0, 0.87)]Mortalium Animos[/color][color=rgba(0, 0, 0, 0.87)]
)[/color][/font][/size][/color][/font][/size][/color][/font][/size][/color][/font][/size][/color]
[color=rgba(0, 0, 0, 0.87)]
[color=rgba(0, 0, 0, 0.87)][color=rgba(0, 0, 0, 0.87)][color=rgba(0, 0, 0, 0.87)][color=rgba(0, 0, 0, 0.87)][color=rgba(0, 0, 0, 0.87)]Pope Eugene IV[/color][color=rgba(0, 0, 0, 0.87)]
and the [/color]
Council of Florence[color=rgba(0, 0, 0, 0.87)]
(A.D. 1438 – 1445): “[The most Holy Roman Church] firmly believes, professes, and proclaims that those not living within the Catholic Church, not only pagans, but also Jєωs and heretics and schismatics cannot become participants in eternal life, but will depart `into everlasting fire which was prepared for the devil and his angels’ (Matt. 25:41), unless before the end of life the same have been added to the flock; and that the unity of the ecclesiastical body is so strong that only to those remaining in it are the sacraments of the Church of benefit for salvation, and do fastings, almsgiving, and other functions of piety and exercises of Christian service produce eternal reward, and that no one, whatever almsgiving he has practiced, even if he has shed blood for the name of Christ, can be saved, unless he has remained in the bosom and unity of the Catholic Church.”[/color][/font][/size][/color][/font][/size][/color][/font][/size][/color][/font][/size][/color][/font][/size][/color]
[color=rgba(0, 0, 0, 0.87)]
[color=rgba(0, 0, 0, 0.87)][color=rgba(0, 0, 0, 0.87)][color=rgba(0, 0, 0, 0.87)][color=rgba(0, 0, 0, 0.87)][color=rgba(0, 0, 0, 0.87)][color=rgba(0, 0, 0, 0.87)]Pope Boniface VIII[/color][color=rgba(0, 0, 0, 0.87)]
in his Papal Bull [/color]
Unam Sanctam[color=rgba(0, 0, 0, 0.87)]
(A.D. 1302): “We declare, say, define, and pronounce that it is absolutely necessary for the salvation of every human creature to be subject to the Roman Pontiff.”[/color][/font][/size][/color][/font][/size][/color][/font][/size][/color][/font][/size][/color][/font][/size][/color][/font][/size][/color]