移動語意

An assignment will transfer ownership between variables:

fn main() {
    let s1: String = String::from("Hello!");
    let s2: String = s1;
    println!("s2: {s2}");
    // println!("s1: {s1}");
}

• 將 s1 指派給 s2 會轉移所有權。
• When s1 goes out of scope, nothing happens: it does not own anything.
• 當 s2 超出範圍時，系統會釋放字串資料。
• 一律「只有」一個變數綁定會擁有值。