Rust 中使用 :: 这种语法的几种情况

mod utils {
    pub fn do_something() { /* ... */ }
}

let result = utils::do_something();

struct MyStruct;

impl MyStruct {
    fn new() -> Self {
        MyStruct
    }
}

let instance = MyStruct::new();

trait MyTrait {
    type Output;
    const VALUE: u32 = 42;
}

impl MyTrait for i32 {
    type Output = String;
}

let value = <i32 as MyTrait>::VALUE;

fn test3<T: AsRef<str>>(s: T) -> T {
    s
}

let result = test3::<&str>("hello");