Custom zero copy collections

[armaniferrante]

We should create zero copy collections so that we can use vec, map, etc in zero copy types.

[jarry-xiao]

+1 This would be huge

[archseer]

I have an arrayvec-like implementation here: https://github.com/smartcontractkit/chainlink-solana/blob/develop/contracts/crates/arrayvec/src/lib.rs

Had to strip out the generics (and define the type outside the macro) to make the IDL generator happy.

[lidatong]

We should create zero copy collections so that we can use vec, map, etc in zero copy types.

it's worth noting these types are not Copy, and the ZeroCopy trait does have an explicit Copy bound:

pub trait ZeroCopy: Discriminator + Copy + Clone + Zeroable + Pod { }

what do you think of dropping the explicit Copy bound to make this possible?

• bytemuck's Pod also includes this bound, but it can be unsafe impl'd

[archseer]

There's a good reason for this: https://github.com/Lokathor/bytemuck/issues/87#issuecomment-1007577400

[lidatong]

There's a good reason for this: Lokathor/bytemuck#87 (comment)

i understand why Pod needs it, but you can unsafe impl Pod. here to satisfy #[account(zero_copy)] we would additionally need something like unsafe impl Copy which doesn't exist

[lidatong]

nvm, i was totally wrong here. bytemuck will yell at you if you unsafe impl Pod without the type being Copy. i had a misunderstanding about unsafe impl Pod vs. #[derive(Pod)] but saw in the source the macro is generating unsafe impl. sorry