XCMv4 (#1230)

# Note for reviewer

Most changes are just syntax changes necessary for the new version.
Most important files should be the ones under the `xcm` folder.

# Description 

Added XCMv4.

## Removed `Multi` prefix
The following types have been renamed:
- MultiLocation -> Location
- MultiAsset -> Asset
- MultiAssets -> Assets
- InteriorMultiLocation -> InteriorLocation
- MultiAssetFilter -> AssetFilter
- VersionedMultiAsset -> VersionedAsset
- WildMultiAsset -> WildAsset
- VersionedMultiLocation -> VersionedLocation

In order to fix a name conflict, the `Assets` in `xcm-executor` were
renamed to `HoldingAssets`, as they represent assets in holding.

## Removed `Abstract` asset id

It was not being used anywhere and this simplifies the code.

Now assets are just constructed as follows:

```rust
let asset: Asset = (AssetId(Location::new(1, Here)), 100u128).into();
```

No need for specifying `Concrete` anymore.

## Outcome is now a named fields struct

Instead of

```rust
pub enum Outcome {
  Complete(Weight),
  Incomplete(Weight, Error),
  Error(Error),
}
```

we now have

```rust
pub enum Outcome {
  Complete { used: Weight },
  Incomplete { used: Weight, error: Error },
  Error { error: Error },
}
```

## Added Reanchorable trait

Now both locations and assets implement this trait, making it easier to
reanchor both.

## New syntax for building locations and junctions

Now junctions are built using the following methods:

```rust
let location = Location {
    parents: 1,
    interior: [Parachain(1000), PalletInstance(50), GeneralIndex(1984)].into()
};
```

or

```rust
let location = Location::new(1, [Parachain(1000), PalletInstance(50), GeneralIndex(1984)]);
```

And they are matched like so:

```rust
match location.unpack() {
  (1, [Parachain(id)]) => ...
  (0, Here) => ...,
  (1, [_]) => ...,
}
```

This syntax is mandatory in v4, and has been also implemented for v2 and
v3 for easier migration.

This was needed to make all sizes smaller.

# TODO
- [x] Scaffold v4
- [x] Port github.com/paritytech/polkadot/pull/7236
- [x] Remove `Multi` prefix
- [x] Remove `Abstract` asset id

---------

Co-authored-by: command-bot <>
Co-authored-by: Keith Yeung <kungfukeith11@gmail.com>

cumulus/parachains/integration-tests/emulated/tests/bridges/bridge-hub-rococo/src/lib.rs

@@ -22,7 +22,7 @@ pub use xcm::{
 	latest::ParentThen,
 	prelude::{AccountId32 as AccountId32Junction, *},
 	v3::{
-		Error,
+		self, Error,
 		NetworkId::{Rococo as RococoId, Westend as WestendId},
 	},
 };

cumulus/parachains/integration-tests/emulated/tests/bridges/bridge-hub-rococo/src/tests/asset_transfers.rs

@@ -15,14 +15,14 @@
 
 use crate::tests::*;
 
-fn send_asset_from_asset_hub_rococo_to_asset_hub_westend(id: MultiLocation, amount: u128) {
+fn send_asset_from_asset_hub_rococo_to_asset_hub_westend(id: Location, amount: u128) {
 	let destination = asset_hub_westend_location();
 
 	// fund the AHR's SA on BHR for paying bridge transport fees
 	BridgeHubRococo::fund_para_sovereign(AssetHubRococo::para_id(), 10_000_000_000_000u128);
 
 	// set XCM versions
-	AssetHubRococo::force_xcm_version(destination, XCM_VERSION);
+	AssetHubRococo::force_xcm_version(destination.clone(), XCM_VERSION);
 	BridgeHubRococo::force_xcm_version(bridge_hub_westend_location(), XCM_VERSION);
 
 	// send message over bridge
@@ -33,9 +33,9 @@ fn send_asset_from_asset_hub_rococo_to_asset_hub_westend(id: MultiLocation, amou
 
 #[test]
 fn send_rocs_from_asset_hub_rococo_to_asset_hub_westend() {
-	let roc_at_asset_hub_rococo: MultiLocation = Parent.into();
+	let roc_at_asset_hub_rococo: v3::Location = v3::Parent.into();
 	let roc_at_asset_hub_westend =
-		MultiLocation { parents: 2, interior: X1(GlobalConsensus(NetworkId::Rococo)) };
+		v3::Location::new(2, [v3::Junction::GlobalConsensus(v3::NetworkId::Rococo)]);
 	let owner: AccountId = AssetHubWestend::account_id_of(ALICE);
 	AssetHubWestend::force_create_foreign_asset(
 		roc_at_asset_hub_westend,
@@ -62,7 +62,7 @@ fn send_rocs_from_asset_hub_rococo_to_asset_hub_westend() {
 
 		assert_ok!(<AssetHubWestend as AssetHubWestendPallet>::AssetConversion::create_pool(
 			<AssetHubWestend as Chain>::RuntimeOrigin::signed(AssetHubWestendSender::get()),
-			Box::new(Parent.into()),
+			Box::new(xcm::v3::Parent.into()),
 			Box::new(roc_at_asset_hub_westend),
 		));
 
@@ -75,7 +75,7 @@ fn send_rocs_from_asset_hub_rococo_to_asset_hub_westend() {
 
 		assert_ok!(<AssetHubWestend as AssetHubWestendPallet>::AssetConversion::add_liquidity(
 			<AssetHubWestend as Chain>::RuntimeOrigin::signed(AssetHubWestendSender::get()),
-			Box::new(Parent.into()),
+			Box::new(xcm::v3::Parent.into()),
 			Box::new(roc_at_asset_hub_westend),
 			1_000_000_000_000,
 			2_000_000_000_000,
@@ -101,8 +101,9 @@ fn send_rocs_from_asset_hub_rococo_to_asset_hub_westend() {
 		<Assets as Inspect<_>>::balance(roc_at_asset_hub_westend, &AssetHubWestendReceiver::get())
 	});
 
+	let roc_at_asset_hub_rococo_latest: Location = roc_at_asset_hub_rococo.try_into().unwrap();
 	let amount = ASSET_HUB_ROCOCO_ED * 1_000_000;
-	send_asset_from_asset_hub_rococo_to_asset_hub_westend(roc_at_asset_hub_rococo, amount);
+	send_asset_from_asset_hub_rococo_to_asset_hub_westend(roc_at_asset_hub_rococo_latest, amount);
 	AssetHubWestend::execute_with(|| {
 		type RuntimeEvent = <AssetHubWestend as Chain>::RuntimeEvent;
 		assert_expected_events!(
@@ -142,7 +143,7 @@ fn send_rocs_from_asset_hub_rococo_to_asset_hub_westend() {
 fn send_wnds_from_asset_hub_rococo_to_asset_hub_westend() {
 	let prefund_amount = 10_000_000_000_000u128;
 	let wnd_at_asset_hub_rococo =
-		MultiLocation { parents: 2, interior: X1(GlobalConsensus(NetworkId::Westend)) };
+		v3::Location::new(2, [v3::Junction::GlobalConsensus(v3::NetworkId::Westend)]);
 	let owner: AccountId = AssetHubWestend::account_id_of(ALICE);
 	AssetHubRococo::force_create_foreign_asset(
 		wnd_at_asset_hub_rococo,
@@ -170,8 +171,12 @@ fn send_wnds_from_asset_hub_rococo_to_asset_hub_westend() {
 	let receiver_wnds_before =
 		<AssetHubWestend as Chain>::account_data_of(AssetHubWestendReceiver::get()).free;
 
+	let wnd_at_asset_hub_rococo_latest: Location = wnd_at_asset_hub_rococo.try_into().unwrap();
 	let amount_to_send = ASSET_HUB_WESTEND_ED * 1_000;
-	send_asset_from_asset_hub_rococo_to_asset_hub_westend(wnd_at_asset_hub_rococo, amount_to_send);
+	send_asset_from_asset_hub_rococo_to_asset_hub_westend(
+		wnd_at_asset_hub_rococo_latest.clone(),
+		amount_to_send,
+	);
 	AssetHubWestend::execute_with(|| {
 		type RuntimeEvent = <AssetHubWestend as Chain>::RuntimeEvent;
 		assert_expected_events!(

cumulus/parachains/integration-tests/emulated/tests/bridges/bridge-hub-rococo/src/tests/mod.rs

@@ -20,37 +20,31 @@ mod send_xcm;
 mod snowbridge;
 mod teleport;
 
-pub(crate) fn asset_hub_westend_location() -> MultiLocation {
-	MultiLocation {
-		parents: 2,
-		interior: X2(
-			GlobalConsensus(NetworkId::Westend),
-			Parachain(AssetHubWestend::para_id().into()),
-		),
-	}
+pub(crate) fn asset_hub_westend_location() -> Location {
+	Location::new(
+		2,
+		[GlobalConsensus(NetworkId::Westend), Parachain(AssetHubWestend::para_id().into())],
+	)
 }
 
-pub(crate) fn bridge_hub_westend_location() -> MultiLocation {
-	MultiLocation {
-		parents: 2,
-		interior: X2(
-			GlobalConsensus(NetworkId::Westend),
-			Parachain(BridgeHubWestend::para_id().into()),
-		),
-	}
+pub(crate) fn bridge_hub_westend_location() -> Location {
+	Location::new(
+		2,
+		[GlobalConsensus(NetworkId::Westend), Parachain(BridgeHubWestend::para_id().into())],
+	)
 }
 
 pub(crate) fn send_asset_from_asset_hub_rococo(
-	destination: MultiLocation,
-	(id, amount): (MultiLocation, u128),
+	destination: Location,
+	(id, amount): (Location, u128),
 ) -> DispatchResult {
 	let signed_origin =
 		<AssetHubRococo as Chain>::RuntimeOrigin::signed(AssetHubRococoSender::get().into());
 
-	let beneficiary: MultiLocation =
+	let beneficiary: Location =
 		AccountId32Junction { network: None, id: AssetHubWestendReceiver::get().into() }.into();
 
-	let assets: MultiAssets = (id, amount).into();
+	let assets: Assets = (id, amount).into();
 	let fee_asset_item = 0;
 
 	AssetHubRococo::execute_with(|| {

cumulus/parachains/integration-tests/emulated/tests/bridges/bridge-hub-rococo/src/tests/send_xcm.rs

@@ -29,8 +29,8 @@ fn send_xcm_from_rococo_relay_to_westend_asset_hub_should_fail_on_not_applicable
 	let xcm = VersionedXcm::from(Xcm(vec![
 		UnpaidExecution { weight_limit, check_origin },
 		ExportMessage {
-			network: WestendId,
-			destination: X1(Parachain(AssetHubWestend::para_id().into())),
+			network: WestendId.into(),
+			destination: [Parachain(AssetHubWestend::para_id().into())].into(),
 			xcm: remote_xcm,
 		},
 	]));
@@ -68,7 +68,7 @@ fn send_xcm_through_opened_lane_with_different_xcm_version_on_hops_works() {
 
 	// prepare data
 	let destination = asset_hub_westend_location();
-	let native_token = MultiLocation::parent();
+	let native_token = Location::parent();
 	let amount = ASSET_HUB_ROCOCO_ED * 1_000;
 
 	// fund the AHR's SA on BHR for paying bridge transport fees
@@ -78,7 +78,7 @@ fn send_xcm_through_opened_lane_with_different_xcm_version_on_hops_works() {
 
 	// send XCM from AssetHubRococo - fails - destination version not known
 	assert_err!(
-		send_asset_from_asset_hub_rococo(destination, (native_token, amount)),
+		send_asset_from_asset_hub_rococo(destination.clone(), (native_token.clone(), amount)),
 		DispatchError::Module(sp_runtime::ModuleError {
 			index: 31,
 			error: [1, 0, 0, 0],
@@ -87,7 +87,7 @@ fn send_xcm_through_opened_lane_with_different_xcm_version_on_hops_works() {
 	);
 
 	// set destination version
-	AssetHubRococo::force_xcm_version(destination, xcm::v3::prelude::XCM_VERSION);
+	AssetHubRococo::force_xcm_version(destination.clone(), xcm::v3::prelude::XCM_VERSION);
 
 	// TODO: remove this block, when removing `xcm:v2`
 	{
@@ -95,7 +95,7 @@ fn send_xcm_through_opened_lane_with_different_xcm_version_on_hops_works() {
 		// version, which does not have the `ExportMessage` instruction. If the default `2` is
 		// changed to `3`, then this assert can go away"
 		assert_err!(
-			send_asset_from_asset_hub_rococo(destination, (native_token, amount)),
+			send_asset_from_asset_hub_rococo(destination.clone(), (native_token.clone(), amount)),
 			DispatchError::Module(sp_runtime::ModuleError {
 				index: 31,
 				error: [1, 0, 0, 0],
@@ -110,7 +110,7 @@ fn send_xcm_through_opened_lane_with_different_xcm_version_on_hops_works() {
 		);
 		// send XCM from AssetHubRococo - fails - `ExportMessage` is not in `2`
 		assert_err!(
-			send_asset_from_asset_hub_rococo(destination, (native_token, amount)),
+			send_asset_from_asset_hub_rococo(destination.clone(), (native_token.clone(), amount)),
 			DispatchError::Module(sp_runtime::ModuleError {
 				index: 31,
 				error: [1, 0, 0, 0],
@@ -125,7 +125,10 @@ fn send_xcm_through_opened_lane_with_different_xcm_version_on_hops_works() {
 		xcm::v3::prelude::XCM_VERSION,
 	);
 	// send XCM from AssetHubRococo - ok
-	assert_ok!(send_asset_from_asset_hub_rococo(destination, (native_token, amount)));
+	assert_ok!(send_asset_from_asset_hub_rococo(
+		destination.clone(),
+		(native_token.clone(), amount)
+	));
 
 	// `ExportMessage` on local BridgeHub - fails - remote BridgeHub version not known
 	assert_bridge_hub_rococo_message_accepted(false);
@@ -142,7 +145,10 @@ fn send_xcm_through_opened_lane_with_different_xcm_version_on_hops_works() {
 	);
 
 	// send XCM from AssetHubRococo - ok
-	assert_ok!(send_asset_from_asset_hub_rococo(destination, (native_token, amount)));
+	assert_ok!(send_asset_from_asset_hub_rococo(
+		destination.clone(),
+		(native_token.clone(), amount)
+	));
 	assert_bridge_hub_rococo_message_accepted(true);
 	assert_bridge_hub_westend_message_received();
 	// message delivered and processed at destination

cumulus/parachains/integration-tests/emulated/tests/bridges/bridge-hub-rococo/src/tests/snowbridge.rs

@@ -61,7 +61,7 @@ fn create_agent() {
 
 	let remote_xcm = VersionedXcm::from(Xcm(vec![
 		UnpaidExecution { weight_limit: Unlimited, check_origin: None },
-		DescendOrigin(X1(Parachain(origin_para))),
+		DescendOrigin(Parachain(origin_para).into()),
 		Transact {
 			require_weight_at_most: 3000000000.into(),
 			origin_kind: OriginKind::Xcm,
@@ -109,14 +109,14 @@ fn create_channel() {
 	BridgeHubRococo::fund_para_sovereign(origin_para.into(), INITIAL_FUND);
 
 	let sudo_origin = <Rococo as Chain>::RuntimeOrigin::root();
-	let destination: VersionedMultiLocation =
+	let destination: VersionedLocation =
 		Rococo::child_location_of(BridgeHubRococo::para_id()).into();
 
 	let create_agent_call = SnowbridgeControl::Control(ControlCall::CreateAgent {});
 
 	let create_agent_xcm = VersionedXcm::from(Xcm(vec![
 		UnpaidExecution { weight_limit: Unlimited, check_origin: None },
-		DescendOrigin(X1(Parachain(origin_para))),
+		DescendOrigin(Parachain(origin_para).into()),
 		Transact {
 			require_weight_at_most: 3000000000.into(),
 			origin_kind: OriginKind::Xcm,
@@ -129,7 +129,7 @@ fn create_channel() {
 
 	let create_channel_xcm = VersionedXcm::from(Xcm(vec![
 		UnpaidExecution { weight_limit: Unlimited, check_origin: None },
-		DescendOrigin(X1(Parachain(origin_para))),
+		DescendOrigin(Parachain(origin_para).into()),
 		Transact {
 			require_weight_at_most: 3000000000.into(),
 			origin_kind: OriginKind::Xcm,
@@ -218,10 +218,10 @@ fn register_weth_token_from_ethereum_to_asset_hub() {
 
 #[test]
 fn send_token_from_ethereum_to_penpal() {
-	let asset_hub_sovereign = BridgeHubRococo::sovereign_account_id_of(MultiLocation {
-		parents: 1,
-		interior: X1(Parachain(AssetHubRococo::para_id().into())),
-	});
+	let asset_hub_sovereign = BridgeHubRococo::sovereign_account_id_of(Location::new(
+		1,
+		[Parachain(AssetHubRococo::para_id().into())],
+	));
 	BridgeHubRococo::fund_accounts(vec![(asset_hub_sovereign.clone(), INITIAL_FUND)]);
 
 	PenpalA::fund_accounts(vec![
@@ -229,9 +229,9 @@ fn send_token_from_ethereum_to_penpal() {
 		(PenpalASender::get(), INITIAL_FUND),
 	]);
 
-	let weth_asset_location: MultiLocation =
+	let weth_asset_location: Location =
 		(Parent, Parent, EthereumNetwork::get(), AccountKey20 { network: None, key: WETH }).into();
-	let weth_asset_id = weth_asset_location.into();
+	let weth_asset_id: v3::Location = weth_asset_location.try_into().unwrap();
 
 	let origin_location = (Parent, Parent, EthereumNetwork::get()).into();
 
@@ -375,18 +375,15 @@ fn send_token_from_ethereum_to_asset_hub() {
 #[test]
 fn send_weth_asset_from_asset_hub_to_ethereum() {
 	use asset_hub_rococo_runtime::xcm_config::bridging::to_ethereum::DefaultBridgeHubEthereumBaseFee;
-	let assethub_sovereign = BridgeHubRococo::sovereign_account_id_of(MultiLocation {
-		parents: 1,
-		interior: X1(Parachain(AssetHubRococo::para_id().into())),
-	});
+	let assethub_sovereign = BridgeHubRococo::sovereign_account_id_of(Location::new(
+		1,
+		[Parachain(AssetHubRococo::para_id().into())],
+	));
 
 	AssetHubRococo::force_default_xcm_version(Some(XCM_VERSION));
 	BridgeHubRococo::force_default_xcm_version(Some(XCM_VERSION));
 	AssetHubRococo::force_xcm_version(
-		MultiLocation {
-			parents: 2,
-			interior: X1(GlobalConsensus(Ethereum { chain_id: CHAIN_ID })),
-		},
+		Location::new(2, [GlobalConsensus(Ethereum { chain_id: CHAIN_ID })]),
 		XCM_VERSION,
 	);
 
@@ -437,27 +434,27 @@ fn send_weth_asset_from_asset_hub_to_ethereum() {
 				RuntimeEvent::ForeignAssets(pallet_assets::Event::Issued { .. }) => {},
 			]
 		);
-		let assets = vec![MultiAsset {
-			id: Concrete(MultiLocation {
-				parents: 2,
-				interior: X2(
+		let assets = vec![Asset {
+			id: AssetId(Location::new(
+				2,
+				[
 					GlobalConsensus(Ethereum { chain_id: CHAIN_ID }),
 					AccountKey20 { network: None, key: WETH },
-				),
-			}),
+				],
+			)),
 			fun: Fungible(WETH_AMOUNT),
 		}];
-		let multi_assets = VersionedMultiAssets::V3(MultiAssets::from(assets));
+		let multi_assets = VersionedAssets::V4(Assets::from(assets));
 
-		let destination = VersionedMultiLocation::V3(MultiLocation {
-			parents: 2,
-			interior: X1(GlobalConsensus(Ethereum { chain_id: CHAIN_ID })),
-		});
+		let destination = VersionedLocation::V4(Location::new(
+			2,
+			[GlobalConsensus(Ethereum { chain_id: CHAIN_ID })],
+		));
 
-		let beneficiary = VersionedMultiLocation::V3(MultiLocation {
-			parents: 0,
-			interior: X1(AccountKey20 { network: None, key: ETHEREUM_DESTINATION_ADDRESS.into() }),
-		});
+		let beneficiary = VersionedLocation::V4(Location::new(
+			0,
+			[AccountKey20 { network: None, key: ETHEREUM_DESTINATION_ADDRESS.into() }],
+		));
 
 		let free_balance_before = <AssetHubRococo as AssetHubRococoPallet>::Balances::free_balance(
 			AssetHubRococoReceiver::get(),

cumulus/parachains/integration-tests/emulated/tests/bridges/bridge-hub-rococo/src/tests/teleport.rs

@@ -19,7 +19,7 @@ use bridge_hub_rococo_runtime::xcm_config::XcmConfig;
 #[test]
 fn teleport_to_other_system_parachains_works() {
 	let amount = BRIDGE_HUB_ROCOCO_ED * 100;
-	let native_asset: MultiAssets = (Parent, amount).into();
+	let native_asset: Assets = (Parent, amount).into();
 
 	test_parachain_is_trusted_teleporter!(
 		BridgeHubRococo,      // Origin