struct User {	age: i32,	nick: String,}impl User {	fn new(age: i32, nick: String) -> User {		User{age: age,  nick: nick}	}		fn setAge(&mut self, age: i32) {		self.age = age;	}	fn printInfo(&self) {		println!("My name is: {}, my age is: {}.", self.nick, self.age);	}}fn main() {	let mut jim = User::new(99, "jim".to_string());	jim.printInfo();	let jimPtr = &mut jim as *mut User;	unsafe {		(*jimPtr).setAge(100);	}	jim.printInfo();    //这里是按值传递，下面会证明	let jimCopy = jim;	jimCopy.printInfo();	unsafe {		(*jimPtr).setAge(200);	}    //上面的一行代码其实已经把年龄修改成了200，但是这里打印还是100，说明let jimCopy=jim;是按值传递	jimCopy.printInfo();}