匹配枚举引用并返回字符串会导致“match arms have compatible types”(匹配臂具有不兼容的类型)

我该怎么做 match 在枚举引用上?我使用的依赖项返回对枚举的引用,我需要读取枚举包含的值。在下面的示例中,我关心的是分配 final_val 具有 x :

fn main() {
    let test_string = String::from("test");
    let option: std::option::Option<String> = Some(test_string);
    let ref_option = &option;

    let final_val = match ref_option {
        Some(x) => x,
        _ => String::from("not Set"),
    };

    println!("{:?}", final_val);
}

如果我按照编译器的建议添加 & 到类型 Some 和 ref x :

fn main() {
    let test_string = String::from("test");
    let option: std::option::Option<String> = Some(test_string);
    let ref_option = &option;

    let final_val = match ref_option {
        &Some(ref x) => x,
        _ => String::from("not Set"),
    };

    println!("{:?}", final_val);
}

我遇到以下错误,我不知道如何解决:

error[E0308]: match arms have incompatible types
  --> src\main.rs:6:21
   |
6  |       let final_val = match ref_option
   |  _____________________^
7  | |     {
8  | |         &Some(ref x) => x,
9  | |         _ => String::from("not Set" ),
   | |              ------------------------ match arm with an incompatible type

10 | |     };
   | |_____^ expected reference, found struct `std::string::String`
   |
   = note: expected type `&std::string::String`
              found type `std::string::String`