fn main() {
    // Fall For type 'String'
    let s1 = String::from("hello");
    let s2 = s1.clone();
    //let s2 = &s1; // OK
    //let s2 = s1; // ERROR

    // Fall For type 'str'
    //let s1 = "hello";
    //let s2 = s1;
    // let s2 = &s1; // OK
    //let s2 = s1.clone();  // OK

    println!("s1: the value of variable s1 is {}", s1);
    println!("s1: the stack address of variable s1 is {:p}", &s1);
    println!("s2: the value of variable s2 is {}", s2);
    println!("s2: the stack address of variable s2 is {:p}", &s2);
}