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 <[email protected]>

Author: franciscoaguirre

Cargo.toml

@@ -18,7 +18,7 @@ log = { version = "0.4.17", default-features = false }
 parity-scale-codec = { version = "3.6.1", default-features = false, features = ["derive", "max-encoded-len"] }
 scale-info = { version = "2.10.0", default-features = false, features = ["derive", "serde"] }
 sp-weights = { path = "../../substrate/primitives/weights", default-features = false, features = ["serde"] }
-serde = { version = "1.0.195", default-features = false, features = ["alloc", "derive"] }
+serde = { version = "1.0.195", default-features = false, features = ["alloc", "derive", "rc"] }
 schemars = { version = "0.8.13", default-features = true, optional = true }
 xcm-procedural = { path = "procedural" }
 environmental = { version = "1.1.4", default-features = false }

pallet-xcm-benchmarks/src/fungible/benchmarking.rs

@@ -24,7 +24,7 @@ use frame_support::{
 };
 use sp_runtime::traits::{Bounded, Zero};
 use sp_std::{prelude::*, vec};
-use xcm::latest::{prelude::*, MAX_ITEMS_IN_MULTIASSETS};
+use xcm::latest::{prelude::*, MAX_ITEMS_IN_ASSETS};
 use xcm_executor::traits::{ConvertLocation, FeeReason, TransactAsset};
 
 benchmarks_instance_pallet! {
@@ -43,7 +43,7 @@ benchmarks_instance_pallet! {
 	withdraw_asset {
 		let (sender_account, sender_location) = account_and_location::<T>(1);
 		let worst_case_holding = T::worst_case_holding(0);
-		let asset = T::get_multi_asset();
+		let asset = T::get_asset();
 
 		<AssetTransactorOf<T>>::deposit_asset(&asset, &sender_location, None).unwrap();
 		// check the assets of origin.
@@ -63,8 +63,8 @@ benchmarks_instance_pallet! {
 
 	transfer_asset {
 		let (sender_account, sender_location) = account_and_location::<T>(1);
-		let asset = T::get_multi_asset();
-		let assets: MultiAssets = vec![ asset.clone() ].into();
+		let asset = T::get_asset();
+		let assets: Assets = vec![ asset.clone() ].into();
 		// this xcm doesn't use holding
 
 		let dest_location = T::valid_destination()?;
@@ -95,10 +95,10 @@ benchmarks_instance_pallet! {
 		);
 		let sender_account_balance_before = T::TransactAsset::balance(&sender_account);
 
-		let asset = T::get_multi_asset();
+		let asset = T::get_asset();
 		<AssetTransactorOf<T>>::deposit_asset(&asset, &sender_location, None).unwrap();
 		assert!(T::TransactAsset::balance(&sender_account) > sender_account_balance_before);
-		let assets: MultiAssets = vec![ asset ].into();
+		let assets: Assets = vec![asset].into();
 		assert!(T::TransactAsset::balance(&dest_account).is_zero());
 
 		let mut executor = new_executor::<T>(sender_location);
@@ -129,7 +129,7 @@ benchmarks_instance_pallet! {
 				BenchmarkResult::from_weight(Weight::MAX)
 			))?;
 
-		let assets: MultiAssets = vec![ transferable_reserve_asset ].into();
+		let assets: Assets = vec![ transferable_reserve_asset ].into();
 
 		let mut executor = new_executor::<T>(trusted_reserve);
 		let instruction = Instruction::ReserveAssetDeposited(assets.clone());
@@ -143,7 +143,7 @@ benchmarks_instance_pallet! {
 	initiate_reserve_withdraw {
 		let (sender_account, sender_location) = account_and_location::<T>(1);
 		let holding = T::worst_case_holding(1);
-		let assets_filter = MultiAssetFilter::Definite(holding.clone().into_inner().into_iter().take(MAX_ITEMS_IN_MULTIASSETS).collect::<Vec<_>>().into());
+		let assets_filter = AssetFilter::Definite(holding.clone().into_inner().into_iter().take(MAX_ITEMS_IN_ASSETS).collect::<Vec<_>>().into());
 		let reserve = T::valid_destination().map_err(|_| BenchmarkError::Skip)?;
 
 		let (expected_fees_mode, expected_assets_in_holding) = T::DeliveryHelper::ensure_successful_delivery(
@@ -188,7 +188,7 @@ benchmarks_instance_pallet! {
 			)?;
 		}
 
-		let assets: MultiAssets = vec![ teleportable_asset ].into();
+		let assets: Assets = vec![ teleportable_asset ].into();
 
 		let mut executor = new_executor::<T>(trusted_teleporter);
 		let instruction = Instruction::ReceiveTeleportedAsset(assets.clone());
@@ -204,7 +204,7 @@ benchmarks_instance_pallet! {
 	}
 
 	deposit_asset {
-		let asset = T::get_multi_asset();
+		let asset = T::get_asset();
 		let mut holding = T::worst_case_holding(1);
 
 		// Add our asset to the holding.
@@ -230,7 +230,7 @@ benchmarks_instance_pallet! {
 	}
 
 	deposit_reserve_asset {
-		let asset = T::get_multi_asset();
+		let asset = T::get_asset();
 		let mut holding = T::worst_case_holding(1);
 
 		// Add our asset to the holding.
@@ -257,7 +257,7 @@ benchmarks_instance_pallet! {
 	}
 
 	initiate_teleport {
-		let asset = T::get_multi_asset();
+		let asset = T::get_asset();
 		let mut holding = T::worst_case_holding(0);
 
 		// Add our asset to the holding.

pallet-xcm-benchmarks/src/fungible/mock.rs

@@ -93,10 +93,10 @@ parameter_types! {
 
 pub struct MatchAnyFungible;
 impl xcm_executor::traits::MatchesFungible<u64> for MatchAnyFungible {
-	fn matches_fungible(m: &MultiAsset) -> Option<u64> {
+	fn matches_fungible(m: &Asset) -> Option<u64> {
 		use sp_runtime::traits::SaturatedConversion;
 		match m {
-			MultiAsset { fun: Fungible(amount), .. } => Some((*amount).saturated_into::<u64>()),
+			Asset { fun: Fungible(amount), .. } => Some((*amount).saturated_into::<u64>()),
 			_ => None,
 		}
 	}
@@ -151,13 +151,12 @@ impl crate::Config for Test {
 	type XcmConfig = XcmConfig;
 	type AccountIdConverter = AccountIdConverter;
 	type DeliveryHelper = ();
-	fn valid_destination() -> Result<MultiLocation, BenchmarkError> {
-		let valid_destination: MultiLocation =
-			X1(AccountId32 { network: None, id: [0u8; 32] }).into();
+	fn valid_destination() -> Result<Location, BenchmarkError> {
+		let valid_destination: Location = [AccountId32 { network: None, id: [0u8; 32] }].into();
 
 		Ok(valid_destination)
 	}
-	fn worst_case_holding(depositable_count: u32) -> MultiAssets {
+	fn worst_case_holding(depositable_count: u32) -> Assets {
 		crate::mock_worst_case_holding(
 			depositable_count,
 			<XcmConfig as xcm_executor::Config>::MaxAssetsIntoHolding::get(),
@@ -170,19 +169,19 @@ pub type TrustedReserves = xcm_builder::Case<ReserveConcreteFungible>;
 
 parameter_types! {
 	pub const CheckingAccount: Option<(u64, MintLocation)> = Some((100, MintLocation::Local));
-	pub const ChildTeleporter: MultiLocation = Parachain(1000).into_location();
-	pub const TrustedTeleporter: Option<(MultiLocation, MultiAsset)> = Some((
+	pub ChildTeleporter: Location = Parachain(1000).into_location();
+	pub TrustedTeleporter: Option<(Location, Asset)> = Some((
 		ChildTeleporter::get(),
-		MultiAsset { id: Concrete(Here.into_location()), fun: Fungible(100) },
+		Asset { id: AssetId(Here.into_location()), fun: Fungible(100) },
 	));
-	pub const TrustedReserve: Option<(MultiLocation, MultiAsset)> = Some((
+	pub TrustedReserve: Option<(Location, Asset)> = Some((
 		ChildTeleporter::get(),
-		MultiAsset { id: Concrete(Here.into_location()), fun: Fungible(100) },
+		Asset { id: AssetId(Here.into_location()), fun: Fungible(100) },
 	));
-	pub const TeleportConcreteFungible: (MultiAssetFilter, MultiLocation) =
-		(Wild(AllOf { fun: WildFungible, id: Concrete(Here.into_location()) }), ChildTeleporter::get());
-	pub const ReserveConcreteFungible: (MultiAssetFilter, MultiLocation) =
-		(Wild(AllOf { fun: WildFungible, id: Concrete(Here.into_location()) }), ChildTeleporter::get());
+	pub TeleportConcreteFungible: (AssetFilter, Location) =
+		(Wild(AllOf { fun: WildFungible, id: AssetId(Here.into_location()) }), ChildTeleporter::get());
+	pub ReserveConcreteFungible: (AssetFilter, Location) =
+		(Wild(AllOf { fun: WildFungible, id: AssetId(Here.into_location()) }), ChildTeleporter::get());
 }
 
 impl xcm_balances_benchmark::Config for Test {
@@ -191,10 +190,10 @@ impl xcm_balances_benchmark::Config for Test {
 	type TrustedTeleporter = TrustedTeleporter;
 	type TrustedReserve = TrustedReserve;
 
-	fn get_multi_asset() -> MultiAsset {
+	fn get_asset() -> Asset {
 		let amount =
 			<Balances as frame_support::traits::fungible::Inspect<u64>>::minimum_balance() as u128;
-		MultiAsset { id: Concrete(Here.into()), fun: Fungible(amount) }
+		Asset { id: AssetId(Here.into()), fun: Fungible(amount) }
 	}
 }
 

pallet-xcm-benchmarks/src/fungible/mod.rs

@@ -37,14 +37,14 @@ pub mod pallet {
 		type CheckedAccount: Get<Option<(Self::AccountId, xcm_builder::MintLocation)>>;
 
 		/// A trusted location which we allow teleports from, and the asset we allow to teleport.
-		type TrustedTeleporter: Get<Option<(xcm::latest::MultiLocation, xcm::latest::MultiAsset)>>;
+		type TrustedTeleporter: Get<Option<(xcm::latest::Location, xcm::latest::Asset)>>;
 
 		/// A trusted location where reserve assets are stored, and the asset we allow to be
 		/// reserves.
-		type TrustedReserve: Get<Option<(xcm::latest::MultiLocation, xcm::latest::MultiAsset)>>;
+		type TrustedReserve: Get<Option<(xcm::latest::Location, xcm::latest::Asset)>>;
 
 		/// Give me a fungible asset that your asset transactor is going to accept.
-		fn get_multi_asset() -> xcm::latest::MultiAsset;
+		fn get_asset() -> xcm::latest::Asset;
 	}
 
 	#[pallet::pallet]

pallet-xcm-benchmarks/src/generic/benchmarking.rs

@@ -77,7 +77,7 @@ benchmarks! {
 		let mut executor = new_executor::<T>(Default::default());
 		executor.set_holding(holding);
 
-		let fee_asset = Concrete(Here.into());
+		let fee_asset = AssetId(Here.into());
 
 		let instruction = Instruction::<XcmCallOf<T>>::BuyExecution {
 			fees: (fee_asset, 100_000_000u128).into(), // should be something inside of holding
@@ -95,7 +95,7 @@ benchmarks! {
 		let mut executor = new_executor::<T>(Default::default());
 		let (query_id, response) = T::worst_case_response();
 		let max_weight = Weight::MAX;
-		let querier: Option<MultiLocation> = Some(Here.into());
+		let querier: Option<Location> = Some(Here.into());
 		let instruction = Instruction::QueryResponse { query_id, response, max_weight, querier };
 		let xcm = Xcm(vec![instruction]);
 	}: {
@@ -174,15 +174,15 @@ benchmarks! {
 
 	descend_origin {
 		let mut executor = new_executor::<T>(Default::default());
-		let who = X2(OnlyChild, OnlyChild);
-		let instruction = Instruction::DescendOrigin(who);
+		let who = Junctions::from([OnlyChild, OnlyChild]);
+		let instruction = Instruction::DescendOrigin(who.clone());
 		let xcm = Xcm(vec![instruction]);
 	} : {
 		executor.bench_process(xcm)?;
 	} verify {
 		assert_eq!(
 			executor.origin(),
-			&Some(MultiLocation {
+			&Some(Location {
 				parents: 0,
 				interior: who,
 			}),
@@ -242,7 +242,7 @@ benchmarks! {
 			&origin,
 			assets.clone().into(),
 			&XcmContext {
-				origin: Some(origin),
+				origin: Some(origin.clone()),
 				message_id: [0; 32],
 				topic: None,
 			},
@@ -279,7 +279,7 @@ benchmarks! {
 		let origin = T::subscribe_origin()?;
 		let query_id = Default::default();
 		let max_response_weight = Default::default();
-		let mut executor = new_executor::<T>(origin);
+		let mut executor = new_executor::<T>(origin.clone());
 		let instruction = Instruction::SubscribeVersion { query_id, max_response_weight };
 		let xcm = Xcm(vec![instruction]);
 	} : {
@@ -299,14 +299,14 @@ benchmarks! {
 			query_id,
 			max_response_weight,
 			&XcmContext {
-				origin: Some(origin),
+				origin: Some(origin.clone()),
 				message_id: [0; 32],
 				topic: None,
 			},
 		).map_err(|_| "Could not start subscription")?;
 		assert!(<T::XcmConfig as xcm_executor::Config>::SubscriptionService::is_subscribed(&origin));
 
-		let mut executor = new_executor::<T>(origin);
+		let mut executor = new_executor::<T>(origin.clone());
 		let instruction = Instruction::UnsubscribeVersion;
 		let xcm = Xcm(vec![instruction]);
 	} : {
@@ -545,7 +545,7 @@ benchmarks! {
 	} verify {
 		use frame_support::traits::Get;
 		let universal_location = <T::XcmConfig as xcm_executor::Config>::UniversalLocation::get();
-		assert_eq!(executor.origin(), &Some(X1(alias).relative_to(&universal_location)));
+		assert_eq!(executor.origin(), &Some(Junctions::from([alias]).relative_to(&universal_location)));
 	}
 
 	export_message {
@@ -561,8 +561,8 @@ benchmarks! {
 
 		let (expected_fees_mode, expected_assets_in_holding) = T::DeliveryHelper::ensure_successful_delivery(
 			&origin,
-			&destination.into(),
-			FeeReason::Export { network, destination },
+			&destination.clone().into(),
+			FeeReason::Export { network, destination: destination.clone() },
 		);
 		let sender_account = T::AccountIdConverter::convert_location(&origin).unwrap();
 		let sender_account_balance_before = T::TransactAsset::balance(&sender_account);
@@ -575,7 +575,7 @@ benchmarks! {
 			executor.set_holding(expected_assets_in_holding.into());
 		}
 		let xcm = Xcm(vec![ExportMessage {
-			network, destination, xcm: inner_xcm,
+			network, destination: destination.clone(), xcm: inner_xcm,
 		}]);
 	}: {
 		executor.bench_process(xcm)?;
@@ -632,13 +632,13 @@ benchmarks! {
 
 		let (unlocker, owner, asset) = T::unlockable_asset()?;
 
-		let mut executor = new_executor::<T>(unlocker);
+		let mut executor = new_executor::<T>(unlocker.clone());
 
 		// We first place the asset in lock first...
 		<T::XcmConfig as xcm_executor::Config>::AssetLocker::prepare_lock(
 			unlocker,
 			asset.clone(),
-			owner,
+			owner.clone(),
 		)
 		.map_err(|_| BenchmarkError::Skip)?
 		.enact()
@@ -658,13 +658,13 @@ benchmarks! {
 
 		let (unlocker, owner, asset) = T::unlockable_asset()?;
 
-		let mut executor = new_executor::<T>(unlocker);
+		let mut executor = new_executor::<T>(unlocker.clone());
 
 		// We first place the asset in lock first...
 		<T::XcmConfig as xcm_executor::Config>::AssetLocker::prepare_lock(
 			unlocker,
 			asset.clone(),
-			owner,
+			owner.clone(),
 		)
 		.map_err(|_| BenchmarkError::Skip)?
 		.enact()
@@ -686,9 +686,9 @@ benchmarks! {
 
 		// We first place the asset in lock first...
 		<T::XcmConfig as xcm_executor::Config>::AssetLocker::prepare_lock(
-			locker,
+			locker.clone(),
 			asset.clone(),
-			owner,
+			owner.clone(),
 		)
 		.map_err(|_| BenchmarkError::Skip)?
 		.enact()
@@ -739,7 +739,7 @@ benchmarks! {
 
 		let mut executor = new_executor::<T>(origin);
 
-		let instruction = Instruction::AliasOrigin(target);
+		let instruction = Instruction::AliasOrigin(target.clone());
 		let xcm = Xcm(vec![instruction]);
 	}: {
 		executor.bench_process(xcm)?;