2.8.1 泛型 Generics 中的示例代码存在所有权问题

[miranquil]

fn largest<T>(list: &[T]) -> T {
    let mut largest = list[0];

    for &item in list.iter() {
        if item > largest {
            largest = item;
        }
    }

    largest
}

fn main() {
    let number_list = vec![34, 50, 25, 100, 65];

    let result = largest(&number_list);
    println!("The largest number is {}", result);

    let char_list = vec!['y', 'm', 'a', 'q'];

    let result = largest(&char_list);
    println!("The largest char is {}", result);
}

这段代码即使补充上后文所述的 : std::cmp::PartialOrd 也仍会报下面的错误：

error[E0508]: cannot move out of type `[T]`, a non-copy slice
 --> src/main.rs:2:23
  |
2 |     let mut largest = list[0];
  |                       ^^^^^^^
  |                       |
  |                       cannot move out of here
  |                       move occurs because `list[_]` has type `T`, which does not implement the `Copy` trait
  |                       help: consider borrowing here: `&list[0]`

一个可行的示例：

fn largest<T: std::cmp::PartialOrd>(list: &[T]) -> &T {
    let mut largest = &list[0];
    for item in list.iter() {
        if item > largest {
            largest = item
        }
    }
    largest
}

fn main() {
    let number_list = vec![34, 50, 25, 100, 65];

    let result = largest(&number_list);
    println!("The largest number is {}", result);

    let char_list = vec!['y', 'm', 'a', 'q'];

    let result = largest(&char_list);
    println!("The largest char is {}", result);
}

Rust 版本：rustc 1.59.0 (9d1b2106e 2022-02-23)