This is a continuation of
https://github.com/polkadot-fellows/xcm-format/pull/63 following the
migration of XCM RFCs to this repo.
# Summary
This RFC proposes a new instruction that provides a way to initiate
asset transfers which transfer multiple types (teleports, local-reserve,
destination-reserve) of assets, on remote chains using XCM alone.
The currently existing instructions are too opinionated and force each
XCM asset transfer to a single transfer type (teleport, local-reserve,
destination-reserve). This results in inability to combine different
types of transfers in single transfer which results in overall poor UX
when trying to move assets across chains.
# Example usage
```rust
// pay remote fees with ROCs
let remote_fees = Some(
AssetTransferFilter::ReserveWithdraw(
AssetFilter::Wild(AllOf { id: rocs_id.into(), fun: WildFungibility::Fungible })
)
);
// XCM to be executed locally
let xcm = Xcm::<penpal_runtime::RuntimeCall>(vec![
// Withdraw both ROCs and PENs from origin account
WithdrawAsset(assets.clone().into()),
// Execute the transfers while paying remote fees with ROCs
InitiateAssetsTransfer {
dest: local_asset_hub,
assets: vec![
// ROCs are reserve-withdrawn on AHR
ReserveWithdraw(rocs.into()),
// PENs are teleported to AHR
Teleport(pens.into()),
],
remote_fees,
remote_xcm: xcm_on_ahr,
},
]);
```
I also have a [proof-of-concept
implementation](https://github.com/acatangiu/polkadot-sdk/blob/1738f8eebd33d87c9c09c7a6bcd7c42fc1a8aa9e/polkadot/xcm/xcm-executor/src/lib.rs#L717C4-L831C6)
and a [proof-of-concept asset transfer
test](https://github.com/acatangiu/polkadot-sdk/blob/1738f8eebd33d87c9c09c7a6bcd7c42fc1a8aa9e/cumulus/parachains/integration-tests/emulated/tests/bridges/bridge-hub-rococo/src/tests/asset_transfers.rs#L484C1-L489C60),
transferring 2 different types of assets across 3 chains.
Adrian Catangiu