我应该使用哪种类型的declaration来创建我自己的包含

我正在努力理解Rust的类型系统。

use std::collections::HashSet;

fn hs_contains<T>(hs: &HashSet<T>, value: &T) -> bool
where 
    T: PartialEq,
{
    hs.iter().any(|v| v == value)
}

fn main() {
    // move strings into HashSet
    let known_values: HashSet<&str> = ["a", "b", "c"].iter().cloned().collect();

    // provided an Vec<String>
    let provided_values: Vec<String> = vec!["a".to_string(), "b".to_string(), "z".to_string()];

    // hash set of refrences
    let mut found: HashSet<&str> = HashSet::new();
    found.insert(&provided_values[0]);
    found.insert(&provided_values[1]);
    found.insert(&provided_values[2]);

    let missing: HashSet<_> = known_values.difference(&found).collect();

    let value: &String = &provided_values[1];

    hs_contains(&known_values, value);
    hs_contains(&missing, "c");

    println!("missing: {:#?}", missing);
}

( Playground )

示例代码无法编译,因为类型不强制。是否有可能为 hs_contains 这将满足示例底部的条件:

hs_contains(&known_values, value);
hs_contains(&missing, "c");

我为什么不直接用 HashSet::contains ?

更换 hs内容 具有 哈希集::包含

known_values.contains(value);
missing.contains(&"c");

导致以下编译错误

error[E0277]: the trait bound `&str: std::borrow::Borrow<std::string::String>` is not satisfied
  --> src/main.rs:38:18
   |
38 |     known_values.contains(value);
   |                  ^^^^^^^^ the trait `std::borrow::Borrow<std::string::String>` is not implemented for `&str`

我所知道的唯一其他方法是

known_values.iter().any(|v| v == value);

这激起了我对如何用类型声明定义一个可以封装上述内容的函数的兴趣。