Proposal to add equivalent of the Vec type

[emilyaherbert]

When writing Sway code I have been finding myself wanting the Vec type, it would be awesome if we had it 😄

Dependent on this issue (#428) and on dynamic size arrays

Rust's implemenation of Vec: https://doc.rust-lang.org/std/vec/struct.Vec.html

[AlicanC]

How would this be represented in the ABI and coded?

From the impl at #1118:

struct RawVec<T> {
    ptr: u64,
    cap: u64,
}
pub struct Vec<T> {
    buf: RawVec,
    len: u64,
}

This would be coded like (ptr: u64, cap: u64, len: u64) which lacks the actual data.

[otrho]

Do we plan to send heap oriented data across the FFI? This will be very tricky, fairly brittle IMO, easy to get wrong, other than for raw pointers to individual heap allocations.

[AlicanC]

I have to send data from the heap in my Multicall script which was the reason for mem::Buffer. Currently the MC script has a fixed-length section that can be represented in the ABI (and can be coded with our AbiCoder) and a dynamic-length part managed with a Buffer.

[adlerjohn]

Yes, we plan to support heap types across the ABI. The SDKs will have to be smart enough to know about particular heap types and set their pointers correctly. The data can be somewhere in scriptData, it doesn't have to be on the actual heap.

[mohammadfawaz]

TIL! But yeah that makes sense.