add documentation for solidity selectors

precompiles/pallet-xcm/XcmInterface.sol

@@ -40,7 +40,7 @@ interface XCM {
     /// @custom:selector 9ea8ada7
     /// @param dest The destination chain.
     /// @param beneficiary The actual account that will receive the tokens on dest.
-    /// @param assets The combination (array) of assets to send.
+    /// @param assets The combination (array) of assets to send in Location format.
     /// @param feeAssetItem The index of the asset that will be used to pay for fees.
     function transferAssetsLocation(
         Location memory dest,
@@ -54,7 +54,7 @@ interface XCM {
     /// @custom:selector a0aeb5fe
     /// @param paraId The para-id of the destination chain.
     /// @param beneficiary The actual account that will receive the tokens on paraId destination.
-    /// @param assets The combination (array) of assets to send.
+    /// @param assets The combination (array) of assets to send in Address format.
     /// @param feeAssetItem The index of the asset that will be used to pay for fees.
     function transferAssetsToPara20(
         uint32 paraId,
@@ -68,7 +68,7 @@ interface XCM {
     /// @custom:selector f23032c3
     /// @param paraId The para-id of the destination chain.
     /// @param beneficiary The actual account that will receive the tokens on paraId destination.
-    /// @param assets The combination (array) of assets to send.
+    /// @param assets The combination (array) of assets to send in Address format.
     /// @param feeAssetItem The index of the asset that will be used to pay for fees.
     function transferAssetsToPara32(
         uint32 paraId,
@@ -81,15 +81,26 @@ interface XCM {
     /// using transfer_assets() pallet-xcm extrinsic.
     /// @custom:selector 6521cc2c
     /// @param beneficiary The actual account that will receive the tokens on the relay chain.
-    /// @param assets The combination (array) of assets to send.
+    /// @param assets The combination (array) of assets to send in Address format.
     /// @param feeAssetItem The index of the asset that will be used to pay for fees.
     function transferAssetsToRelay(
         bytes32 beneficiary,
         AssetAddressInfo[] memory assets,
         uint32 feeAssetItem
     ) external;
 
-    // No RemoteReserve at all
+    /// @dev Function to send assets through transfer_assets_using_type_and_then() pallet-xcm
+    /// extrinsic.
+    /// Important: in this selector RemoteReserve type (for either assets or fees) is not allowed.
+    /// If users want to send assets and fees (in Location format) with a remote reserve, 
+    /// they must use the selector fc19376c.
+    /// @custom:selector 8425d893
+    /// @param dest The destination chain.
+    /// @param assets The combination (array) of assets to send in Location format.
+    /// @param assetsTransferType The TransferType corresponding to assets being sent.
+    /// @param remoteFeesIdIndex The index of the asset (inside assets array) to use as fees.
+    /// @param feesTransferType The TransferType corresponding to the asset used as fees.
+    /// @param customXcmOnDest The XCM message to execute on destination chain.
     function transferAssetsUsingTypeAndThenLocation(
         Location memory dest,
         AssetLocationInfo[] memory assets,
@@ -99,7 +110,15 @@ interface XCM {
         bytes memory customXcmOnDest
     ) external;
 
-    // Remote reserve for assets and fees (must share same remote reserve)
+    /// @dev Function to send assets through transfer_assets_using_type_and_then() pallet-xcm
+    /// extrinsic.
+    /// @custom:selector fc19376c
+    /// @param dest The destination chain.
+    /// @param assets The combination (array) of assets to send in Location format.
+    /// @param remoteFeesIdIndex The index of the asset (inside assets array) to use as fees.
+    /// @param customXcmOnDest The XCM message to execute on destination chain.
+    /// @param remoteReserve The remote reserve corresponding for assets and fees. They MUST
+    /// share the same reserve.
     function transferAssetsUsingTypeAndThenLocation(
         Location memory dest,
         AssetLocationInfo[] memory assets,
@@ -108,7 +127,18 @@ interface XCM {
         Location memory remoteReserve
     ) external;
 
-    // No RemoteReserve at all
+    /// @dev Function to send assets through transfer_assets_using_type_and_then() pallet-xcm
+    /// extrinsic.
+    /// Important: in this selector RemoteReserve type (for either assets or fees) is not allowed.
+    /// If users want to send assets and fees (in Address format) with a remote reserve, 
+    /// they must use the selector aaecfc62.
+    /// @custom:selector 998093ee
+    /// @param dest The destination chain.
+    /// @param assets The combination (array) of assets to send in Address format.
+    /// @param assetsTransferType The TransferType corresponding to assets being sent.
+    /// @param remoteFeesIdIndex The index of the asset (inside assets array) to use as fees.
+    /// @param feesTransferType The TransferType corresponding to the asset used as fees.
+    /// @param customXcmOnDest The XCM message to execute on destination chain.
     function transferAssetsUsingTypeAndThenAddress(
         Location memory dest,
         AssetAddressInfo[] memory assets,
@@ -118,7 +148,15 @@ interface XCM {
         bytes memory customXcmOnDest
     ) external;
 
-    // Remote reserve for assets and fees (must share same reserve)
+    /// @dev Function to send assets through transfer_assets_using_type_and_then() pallet-xcm
+    /// extrinsic.
+    /// @custom:selector aaecfc62
+    /// @param dest The destination chain.
+    /// @param assets The combination (array) of assets to send in Address format.
+    /// @param remoteFeesIdIndex The index of the asset (inside assets array) to use as fees.
+    /// @param customXcmOnDest The XCM message to execute on destination chain.
+    /// @param remoteReserve The remote reserve corresponding for assets and fees. They MUST
+    /// share the same reserve.
     function transferAssetsUsingTypeAndThenAddress(
         Location memory dest,
         AssetAddressInfo[] memory assets,

precompiles/pallet-xcm/src/tests.rs

@@ -38,6 +38,10 @@ fn selectors() {
 	assert!(PCall::transfer_assets_to_para_20_selectors().contains(&0xa0aeb5fe));
 	assert!(PCall::transfer_assets_to_para_32_selectors().contains(&0xf23032c3));
 	assert!(PCall::transfer_assets_to_relay_selectors().contains(&0x6521cc2c));
+	assert!(PCall::transfer_assets_using_type_and_then_location_no_remote_reserve_selectors().contains(&0x8425d893));
+	assert!(PCall::transfer_assets_using_type_and_then_location_remote_reserve_selectors().contains(&0xfc19376c));
+	assert!(PCall::transfer_assets_using_type_and_then_address_no_remote_reserve_selectors().contains(&0x998093ee));
+	assert!(PCall::transfer_assets_using_type_and_then_address_remote_reserve_selectors().contains(&0xaaecfc62));
 }
 
 #[test]