如何匹配 Rust 中的数据类型

我试图匹配 struct 的泛型字段的数据类型，并做出相应的react .我的总体 idea 是这样的(代码不编译):

struct Foo<T> {
    bar: T,
}

fn main() {
    let x = Foo::<String> {
        bar: "world".to_string(),
    };

    match x.bar {
        String => println!("It's a string!"),
        u32 => println!("It's a u32!"),
        _ => println!("Something else"),
    };

    println!("end of program!");
}

来自编译器的错误消息:

warning: unreachable pattern
  --> src/main.rs:12:9
   |
11 |         String => println!("It's a string!"),
   |         ------ matches any value
12 |         u32 => println!("It's a u32!"),
   |         ^^^ unreachable pattern
   |
   = note: `#[warn(unreachable_patterns)]` on by default

warning: unreachable pattern
  --> src/main.rs:13:9
   |
11 |         String => println!("It's a string!"),
   |         ------ matches any value
12 |         u32 => println!("It's a u32!"),
13 |         _ => println!("Something else"),
   |         ^ unreachable pattern

warning: unused variable: `String`
  --> src/main.rs:11:9
   |
11 |         String => println!("It's a string!"),
   |         ^^^^^^ help: consider prefixing with an underscore: `_String`
   |
   = note: `#[warn(unused_variables)]` on by default

warning: unused variable: `u32`
  --> src/main.rs:12:9
   |
12 |         u32 => println!("It's a u32!"),
   |         ^^^ help: consider prefixing with an underscore: `_u32`

warning: variable `String` should have a snake case name
  --> src/main.rs:11:9
   |
11 |         String => println!("It's a string!"),
   |         ^^^^^^ help: convert the identifier to snake case: `string`
   |
   = note: `#[warn(non_snake_case)]` on by default

我想要的是x美元来匹配第一个.实际上我不确定我想做什么可以做到，但什么能达到预期的效果呢？