Not just pointers, it also has info such as alignment. (Shameless plug) I wrote a relevant article recently: https://ashdnazg.github.io/articles/26/Downcasting-

Not just pointers, it also has info such as alignment. (Shameless plug) I wrote a relevant article recently: https://ashdnazg.github.io/articles/26/Downcasting-Arcs-in-Rust https://ashdnazg.github.io/articles/26/Downcasting-Arcs-in-R...