Adam was not a sinner , he only made a mistake, he felt sorry for that and repented before GodAllahYHWH, and He accepted his repentance and forgave him; so Adam was as clean as before he was at the time of his birth.
This is like Jonah, who also made a mistake, accepted his mistake, repented before GodAllahYHWH, resolved not to do it again and he was also forgiven.
Jesus was more like Adam that is why he often used to say Son of Man, or Son of Adam , so if one believes that Jesus was a sinless person,( at least I believe this) this tantamount to saying that Adam was sinless and innocent.
If Jesus would have thought that Adam was a sinful person , then Jesus would have never said that he was Son of Man i.e., Son of Adam. What relation an innocent man had with a sinful person? Jesus would never have imagined that Adam was sinful that is why he took him as his father or grand father and announced it publicly.