Fix XCM Weights on Westend (#4066)

* found issue

* fix up

* remove printlns

polkadot/runtime/westend/src/tests.rs

@@ -49,3 +49,21 @@ fn call_size() {
 		If the limit is too strong, maybe consider increase the limit to 300.",
 	);
 }
+
+#[test]
+fn sanity_check_teleport_assets_weight() {
+	// This test sanity checks that at least 50 teleports can exist in a block.
+	// Usually when XCM runs into an issue, it will return a weight of `Weight::MAX`,
+	// so this test will certainly ensure that this problem does not occur.
+	use frame_support::dispatch::GetDispatchInfo;
+	let weight = pallet_xcm::Call::<Runtime>::teleport_assets {
+		dest: Box::new(xcm::VersionedMultiLocation::V1(MultiLocation::here())),
+		beneficiary: Box::new(xcm::VersionedMultiLocation::V1(MultiLocation::here())),
+		assets: Box::new((Concrete(MultiLocation::here()), Fungible(200_000)).into()),
+		fee_asset_item: 0,
+	}
+	.get_dispatch_info()
+	.weight;
+
+	assert!(weight * 50 < BlockWeights::get().max_block);
+}

polkadot/runtime/westend/src/weights/xcm/mod.rs

@@ -31,7 +31,9 @@ trait WeighMultiAssets {
 	fn weigh_multi_assets(&self, balances_weight: Weight) -> Weight;
 }
 
-// TODO wild case
+// Westend only knows about one asset, the balances pallet.
+const MAX_ASSETS: u32 = 1;
+
 impl WeighMultiAssets for MultiAssetFilter {
 	fn weigh_multi_assets(&self, balances_weight: Weight) -> Weight {
 		match self {
@@ -44,7 +46,7 @@ impl WeighMultiAssets for MultiAssetFilter {
 					AssetTypes::Unknown => Weight::MAX,
 				})
 				.fold(0, |acc, x| acc.saturating_add(x)),
-			_ => Weight::MAX,
+			Self::Wild(_) => (MAX_ASSETS as Weight).saturating_mul(balances_weight),
 		}
 	}
 }