struct Stdout;
In order to See https://github.com/rcore-os/rCore-Tutorial-Book-v3/issues/100#issuecomment-1127614678
char
write!
TypeId
self
Returns the argument unchanged.
Calls U::from(self).
U::from(self)
That is, this conversion is whatever the implementation of From<T> for U chooses to do.
From<T> for U