The move: assignment is a transfer of title

fn main() {
    let s1 = String::from("hello");
    let s2 = s1; // ownership moves; s1 is retired at compile time

    // println!("{s1}");  // <- uncomment: error[E0382] borrow of moved value
    println!("s2 owns it: {s2} (len {})", s2.len());

    let a = 5;
    let b = a; // i32 is Copy: duplicated, not moved
    println!("both fine: a = {a}, b = {b}");
}

fn main() {
    let s1 = String::from("hello");
    let s2 = s1.clone(); // copies the HEAP bytes, not just the 3 stack words

    // both alive, and provably independent storage:
    println!("s1 = {s1}, s2 = {s2}");
    println!("separate heap allocations: {}", s1.as_ptr() != s2.as_ptr());
    println!("a String is {} bytes on the stack", std::mem::size_of::<String>());
}

fn shout(s: String) -> String {
    // takes ownership, transforms, RETURNS ownership
    s.to_uppercase()
}

fn measure(s: String) -> (String, usize) {
    let n = s.len();
    (s, n) // hand the string back alongside the answer
}

fn main() {
    let name = String::from("ferris");
    let loud = shout(name);
    // println!("{name}");  // <- E0382: `name` moved into shout()
    println!("loud = {loud}");

    let (back, n) = measure(loud);
    println!("still ours: {back} (len {n})");
}