XCM: Allow reclaim of assets dropped from holding (#3727)

* XCM: Introduce AssetTrap

* Revert reversions

* Remove attempts at weighing and add test

* Less storage use for asset trapping

* Add missing file

* Fixes

* Fixes

* Formatting

* Fixes

* Docs

* Filter types to allow runtimes to dictate which assets/origins should be trapped

* Formatting

* Tests

* Formatting

* Fixes

* Docs

polkadot/runtime/common/src/claims.rs

@@ -1044,7 +1044,7 @@ mod tests {
 	}
 
 	#[test]
-	fn invalid_attest_transactions_are_recognised() {
+	fn invalid_attest_transactions_are_recognized() {
 		new_test_ext().execute_with(|| {
 			let p = PrevalidateAttests::<Test>::new();
 			let c = Call::Claims(ClaimsCall::attest(StatementKind::Regular.to_text().to_vec()));

polkadot/runtime/kusama/src/lib.rs

@@ -1296,7 +1296,9 @@ impl xcm_executor::Config for XcmConfig {
 	type Weigher = FixedWeightBounds<BaseXcmWeight, Call, MaxInstructions>;
 	// The weight trader piggybacks on the existing transaction-fee conversion logic.
 	type Trader = UsingComponents<WeightToFee, KsmLocation, AccountId, Balances, ToAuthor<Runtime>>;
-	type ResponseHandler = ();
+	type ResponseHandler = XcmPallet;
+	type AssetTrap = XcmPallet;
+	type AssetClaims = XcmPallet;
 }
 
 parameter_types! {

polkadot/runtime/rococo/src/lib.rs

@@ -669,7 +669,9 @@ impl xcm_executor::Config for XcmConfig {
 	type Barrier = Barrier;
 	type Weigher = FixedWeightBounds<BaseXcmWeight, Call, MaxInstructions>;
 	type Trader = UsingComponents<WeightToFee, RocLocation, AccountId, Balances, ToAuthor<Runtime>>;
-	type ResponseHandler = ();
+	type ResponseHandler = XcmPallet;
+	type AssetTrap = XcmPallet;
+	type AssetClaims = XcmPallet;
 }
 
 parameter_types! {

polkadot/runtime/test-runtime/src/xcm_config.rs

@@ -86,4 +86,6 @@ impl xcm_executor::Config for XcmConfig {
 	type Weigher = FixedWeightBounds<super::BaseXcmWeight, super::Call, MaxInstructions>;
 	type Trader = DummyWeightTrader;
 	type ResponseHandler = super::Xcm;
+	type AssetTrap = super::Xcm;
+	type AssetClaims = super::Xcm;
 }

polkadot/runtime/westend/src/lib.rs

@@ -938,7 +938,9 @@ impl xcm_executor::Config for XcmConfig {
 	type Barrier = Barrier;
 	type Weigher = FixedWeightBounds<BaseXcmWeight, Call, MaxInstructions>;
 	type Trader = UsingComponents<WeightToFee, WndLocation, AccountId, Balances, ToAuthor<Runtime>>;
-	type ResponseHandler = ();
+	type ResponseHandler = XcmPallet;
+	type AssetTrap = XcmPallet;
+	type AssetClaims = XcmPallet;
 }
 
 /// Type to convert an `Origin` type value into a `MultiLocation` value which represents an interior location