allow governance body on parachain to have sovereign account on Polkadot

runtime/kusama/src/xcm_config.rs

@@ -39,10 +39,10 @@ use xcm_builder::{
 	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
 	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, ChildParachainAsNative,
 	ChildParachainConvertsVia, ChildSystemParachainAsSuperuser,
-	CurrencyAdapter as XcmCurrencyAdapter, IsChildSystemParachain, IsConcrete, MintLocation,
-	OriginToPluralityVoice, SignedAccountId32AsNative, SignedToAccountId32,
-	SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId, UsingComponents,
-	WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	CurrencyAdapter as XcmCurrencyAdapter, DescribeBodyTerminal, DescribeFamily, HashedDescription,
+	IsChildSystemParachain, IsConcrete, MintLocation, OriginToPluralityVoice,
+	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
+	TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
 };
 use xcm_executor::traits::WithOriginFilter;
 
@@ -70,6 +70,8 @@ pub type SovereignAccountOf = (
 	ChildParachainConvertsVia<ParaId, AccountId>,
 	// We can directly alias an `AccountId32` into a local account.
 	AccountId32Aliases<ThisNetwork, AccountId>,
+	// Allow governance body to be used as a sovereign account.
+	HashedDescription<AccountId, DescribeFamily<DescribeBodyTerminal>>,
 );
 
 /// Our asset transactor. This is what allows us to interest with the runtime facilities from the

runtime/polkadot/src/xcm_config.rs

@@ -70,6 +70,9 @@ pub type SovereignAccountOf = (
 	ChildParachainConvertsVia<ParaId, AccountId>,
 	// We can directly alias an `AccountId32` into a local account.
 	AccountId32Aliases<ThisNetwork, AccountId>,
+	// TODO: enable this after https://github.com/paritytech/polkadot/pull/7518 is enacted and battle-tested.
+	// // Allow governance body to be used as a sovereign account.
+	// HashedDescription<AccountId, DescribeFamily<DescribeBodyTerminal>>,
 );
 
 /// Our asset transactor. This is what allows us to interact with the runtime assets from the point

runtime/westend/src/xcm_config.rs

@@ -37,9 +37,10 @@ use xcm_builder::{
 	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowKnownQueryResponses,
 	AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom, ChildParachainAsNative,
 	ChildParachainConvertsVia, ChildSystemParachainAsSuperuser,
-	CurrencyAdapter as XcmCurrencyAdapter, IsChildSystemParachain, IsConcrete, MintLocation,
-	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
-	TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	CurrencyAdapter as XcmCurrencyAdapter, DescribeBodyTerminal, DescribeFamily, HashedDescription,
+	IsChildSystemParachain, IsConcrete, MintLocation, SignedAccountId32AsNative,
+	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId,
+	UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
 };
 use xcm_executor::{traits::WithOriginFilter, XcmExecutor};
 
@@ -55,8 +56,14 @@ parameter_types! {
 	pub const BaseDeliveryFee: u128 = CENTS.saturating_mul(3);
 }
 
-pub type LocationConverter =
-	(ChildParachainConvertsVia<ParaId, AccountId>, AccountId32Aliases<ThisNetwork, AccountId>);
+pub type LocationConverter = (
+	// We can convert a child parachain using the standard `AccountId` conversion.
+	ChildParachainConvertsVia<ParaId, AccountId>,
+	// We can directly alias an `AccountId32` into a local account.
+	AccountId32Aliases<ThisNetwork, AccountId>,
+	// Allow governance body to be used as a sovereign account.
+	HashedDescription<AccountId, DescribeFamily<DescribeBodyTerminal>>,
+);
 
 pub type LocalAssetTransactor = XcmCurrencyAdapter<
 	// Use this currency:

xcm/xcm-builder/src/lib.rs

@@ -32,8 +32,8 @@ pub use location_conversion::ForeignChainAliasAccount;
 pub use location_conversion::{
 	Account32Hash, AccountId32Aliases, AccountKey20Aliases, AliasesIntoAccountId32,
 	ChildParachainConvertsVia, DescribeAccountId32Terminal, DescribeAccountIdTerminal,
-	DescribeAccountKey20Terminal, DescribeAllTerminal, DescribeFamily, DescribeLocation,
-	DescribePalletTerminal, DescribeTerminus, GlobalConsensusConvertsFor,
+	DescribeAccountKey20Terminal, DescribeAllTerminal, DescribeBodyTerminal, DescribeFamily,
+	DescribeLocation, DescribePalletTerminal, DescribeTerminus, GlobalConsensusConvertsFor,
 	GlobalConsensusParachainConvertsFor, HashedDescription, ParentIsPreset,
 	SiblingParachainConvertsVia,
 };

xcm/xcm-builder/src/location_conversion.rs

@@ -86,11 +86,22 @@ impl DescribeLocation for DescribeAccountKey20Terminal {
 
 pub type DescribeAccountIdTerminal = (DescribeAccountId32Terminal, DescribeAccountKey20Terminal);
 
+pub struct DescribeBodyTerminal;
+impl DescribeLocation for DescribeBodyTerminal {
+	fn describe_location(l: &MultiLocation) -> Option<Vec<u8>> {
+		match (l.parents, &l.interior) {
+			(0, X1(Plurality { id, part })) => Some((b"Body", id, part).encode()),
+			_ => return None,
+		}
+	}
+}
+
 pub type DescribeAllTerminal = (
 	DescribeTerminus,
 	DescribePalletTerminal,
 	DescribeAccountId32Terminal,
 	DescribeAccountKey20Terminal,
+	DescribeBodyTerminal,
 );
 
 pub struct DescribeFamily<DescribeInterior>(PhantomData<DescribeInterior>);