[Feature Request] Add support for vector<&T> as function return

[qiwihui]

🚀 Feature Request

Motivation

I would like to query a vector in a module with some filters, which return another vector with the same or less items in it. Is it possible to return vector<&T> without modifying the original vector. The following demo code contains errors.

public fun get<T: store>(container: &vector<T>): vector<&T> {
        let items = vector<&T>[];
        if (vector::length(container) != 0) {
            let container_len = vector::length<T>(container);
            let i = 0;
            while (i < container_len) {
                let item = vector::borrow(container, i);
                vector::push_back<T>(&mut items, item);
                i = i + 1;
            }
        };
        items
    }

Pitch

Describe the solution you'd like

Describe alternatives you've considered

Are you willing to open a pull request? (See CONTRIBUTING)

Additional context

[jolestar]

Can you simplify the example code, and make the code more useful and like a slice usage?

[sblackshear]

Move does not support storing references inside structs or vectors. Doing so would require significant changes to the borrow checker that would need to be carefully designed and implemented

[vgao1996]

Doing so would require significant changes to the borrow checker that would need to be carefully designed and implemented

Yeah if we want full-fledged support for references in structs or vectors then we'll likely need something like Rust's lifetime annotations. Although I heard @tnowacki was thinking about this issue or at least planning to relax the borrow checker a bit?