revert result handling

contracts/contracts/lib/CrossMsgHelper.sol

@@ -181,11 +181,13 @@ library CrossMsgHelper {
         }
 
         address recipient = crossMsg.to.rawAddress.extractEvmAddress().normalize();
-        // If the cross msg kind is Result, create result message should have handled the value correctly.
-        // If the execution is ok, value should be 0, else one should perform refund.
-        if (crossMsg.kind == IpcMsgKind.Transfer || crossMsg.kind == IpcMsgKind.Result) {
+        if (crossMsg.kind == IpcMsgKind.Transfer) {
             return supplySource.transferFunds({recipient: payable(recipient), value: crossMsg.value});
-        } else if (crossMsg.kind == IpcMsgKind.Call) {
+        } else if (crossMsg.kind == IpcMsgKind.Call || crossMsg.kind == IpcMsgKind.Result) {
+            // For a Result message, the idea is to perform a call as this returns control back to the caller.
+            // If it's an account, there will be no code to invoke, so this will be have like a bare transfer.
+            // But if the original caller was a contract, this give it control so it can handle the result
+
             // send the envelope directly to the entrypoint
             // use supplySource so the tokens in the message are handled successfully
             // and by the right supply source

contracts/test/integration/L2PlusXNet.t.sol

@@ -35,6 +35,7 @@ import {ActivityHelper} from "../helpers/ActivityHelper.sol";
 import {EnumerableSet} from "@openzeppelin/contracts/utils/structs/EnumerableSet.sol";
 import {ISubnetActor} from "../../contracts/interfaces/ISubnetActor.sol";
 import {IPCMsgType} from "../../contracts/enums/IPCMsgType.sol";
+import {IIpcHandler} from "../../sdk/interfaces/IIpcHandler.sol";
 
 import "forge-std/console.sol";
 
@@ -137,7 +138,7 @@ interface IGateway {
     function fundWithToken(SubnetID calldata subnetId, FvmAddress calldata to, uint256 amount) external;
 }
 
-contract L2PlusSubnetTest is Test, IntegrationTestBase {
+contract L2PlusSubnetTest is Test, IntegrationTestBase, IIpcHandler {
     using SubnetIDHelper for SubnetID;
     using CrossMsgHelper for IpcEnvelope;
     using GatewayFacetsHelper for GatewayDiamond;
@@ -161,6 +162,17 @@ contract L2PlusSubnetTest is Test, IntegrationTestBase {
         vm.deal(address(this), 10 ether);
     }
 
+    // ======= implements ipc handler =======
+
+    /* solhint-disable-next-line unused-vars */
+    function handleIpcMessage(IpcEnvelope calldata envelope) external payable returns (bytes memory ret) {
+        ret = bytes("");
+    }
+
+    receive() external payable {}
+
+    // ======= internal util methods ========
+
     function executeTopdownMessages(IpcEnvelope[] memory msgs, GatewayDiamond gw) internal {
         uint256 minted_tokens;
 

contracts/test/integration/MultiSubnet.t.sol

@@ -1150,16 +1150,18 @@ contract MultiSubnetTest is Test, IntegrationTestBase {
         vm.deal(tokenSubnet.subnetActorAddr, DEFAULT_COLLATERAL_AMOUNT);
         vm.deal(caller, 1 ether);
 
-        uint256 fundToSend = 10;
+        uint256 balance = 100;
 
         // Fund an account in the subnet.
-        token.transfer(caller, fundToSend);
+        token.transfer(caller, balance);
         vm.prank(caller);
-        token.approve(rootSubnet.gatewayAddr, fundToSend);
+        token.approve(rootSubnet.gatewayAddr, balance);
 
         vm.prank(tokenSubnet.subnetActorAddr);
         registerSubnetGW(DEFAULT_COLLATERAL_AMOUNT, tokenSubnet.subnetActorAddr, rootSubnet.gateway);
 
+        uint256 fundToSend = 10;
+
         vm.prank(caller);
         rootSubnet.gateway.manager().fundWithToken(tokenSubnet.id, FvmAddressHelper.from(address(caller)), fundToSend);
 
@@ -1190,14 +1192,14 @@ contract MultiSubnetTest is Test, IntegrationTestBase {
         // but the caller is MockIpcContractRevert, which reverts whatever
         // call made to `handleIpcMessage`, we should make sure:
         // 1. The submission of checkpoint is never blocked
+        // 2. The fund is locked in the gateway as execution is rejected
         submitBottomUpCheckpoint(checkpoint, tokenSubnet.subnetActor);
 
-        // because error result xnet message should have refunded the token
-        require(token.balanceOf(caller) == amount, "caller fund should not be locked in gateway");
         require(
-            token.balanceOf(address(rootSubnet.gateway.manager())) == fundToSend - amount,
-            "fund should not be locked in gateway"
+            token.balanceOf(address(rootSubnet.gateway.manager())) == fundToSend,
+            "fund should still be locked in gateway"
         );
+        require(token.balanceOf(caller) == balance - fundToSend, "fund should still be locked in gateway");
     }
 
     function testMultiSubnet_Token_CallFromChildToParent() public {