有没有办法将匿名类型引用为结构成员？

Question

Consider the following Rust code:

use std::future::Future;
use std::pin::Pin;

fn main() {
    let mut v: Vec<_> = Vec::new();
    for _ in 1..10 {
        v.push(wrap_future(Box::pin(async {})));
    }
}

fn wrap_future<T>(a: Pin<Box<dyn Future<Output=T>>>) -> impl Future<Output=T> {
    async {
        println!("doing stuff before awaiting");
        let result=a.await;
        println!("doing stuff after awaiting");
        result
    }
}

As you can see, the futures I'm putting into the Vec don't need to be boxed, since they are all the same type and the compiler can infer what that type is.

I would like to create a struct that has this Vec<...> type as one of its members, so that I could add a line at the end of main() :

let thing = MyStruct {myvec: v};

without any additional overhead (ie boxing).

Type inference and impl Trait syntax aren't allowed on struct members, and since the future type returned by an async block exists entirely within the compiler and is exclusive to that exact async block, there's no way to reference it by name. It seems to me that what I want to do is impossible. Is it? If so, will it become possible in a future version of Rust?

I am aware that it would be easy to sidestep this problem by simply boxing all the futures in the Vec as I did the argument to wrap_future() but I'd prefer not to do this if I can avoid it.

I am well aware that doing this would mean that there could be only one async block in my entire codebase whose result values could possibly be added to such a Vec , and thus that there could be only one function in my entire codebase that could create values that could possibly be pushed to it. I am okay with this limitation.

Answer 1

Nevermind, I'm stupid. I forgot that structs could have type parameters.

struct MyStruct<F> where F: Future<Output=()> {
     myvec: Vec<F>,
}