fix(arbitration): commit post first review. W_NATIVE has been made immutable

Author: hurstelm

contracts/src/arbitration/KlerosCoreBase.sol

@@ -101,7 +101,7 @@ abstract contract KlerosCoreBase is IArbitratorV2, Initializable, UUPSProxiable
     Dispute[] public disputes; // The disputes.
     mapping(IERC20 => CurrencyRate) public currencyRates; // The price of each token in ETH.
     bool public paused; // Whether asset withdrawals are paused.
-    address public wNative; // The address for WETH tranfers.
+    address immutable W_NATIVE; // The address for WETH tranfers.
 
     // ************************************* //
     // *              Events               * //
@@ -192,6 +192,17 @@ abstract contract KlerosCoreBase is IArbitratorV2, Initializable, UUPSProxiable
     // *            Constructor            * //
     // ************************************* //
 
+    /** 
+     * @dev This contract is deployed only once per chain, as the logic master contract.
+     *  New instances are created with minimal proxy from the factory.
+     *  This is only needed to set the wrapped native token, which is used in SafeSend.
+     *  Since it is constant per chain, it can be safely set as immutable to optimize gas usage.
+     * @param _wNative The Wrapped Native Token on this chain.
+     */
+    constructor(address _wNative) {
+        W_NATIVE = _wNative;
+}
+
     function __KlerosCoreBase_initialize(
         address _governor,
         address _guardian,
@@ -203,14 +214,12 @@ abstract contract KlerosCoreBase is IArbitratorV2, Initializable, UUPSProxiable
         uint256[4] memory _timesPerPeriod,
         bytes memory _sortitionExtraData,
         ISortitionModule _sortitionModuleAddress,
-        address _wNative
     ) internal onlyInitializing {
         governor = _governor;
         guardian = _guardian;
         pinakion = _pinakion;
         jurorProsecutionModule = _jurorProsecutionModule;
         sortitionModule = _sortitionModuleAddress;
-        wNative = _wNative;
 
         // NULL_DISPUTE_KIT: an empty element at index 0 to indicate when a dispute kit is not supported.
         disputeKits.push();
@@ -805,7 +814,7 @@ abstract contract KlerosCoreBase is IArbitratorV2, Initializable, UUPSProxiable
             // No one was coherent, send the rewards to the governor.
             if (round.feeToken == NATIVE_CURRENCY) {
                 // The dispute fees were paid in ETH
-                SafeSend.safeSend(payable(governor), round.totalFeesForJurors, wNative);
+                SafeSend.safeSend(payable(governor), round.totalFeesForJurors, W_NATIVE);
             } else {
                 // The dispute fees were paid in ERC20
                 round.feeToken.safeTransfer(governor, round.totalFeesForJurors);
@@ -862,7 +871,7 @@ abstract contract KlerosCoreBase is IArbitratorV2, Initializable, UUPSProxiable
         pinakion.safeTransfer(account, pnkReward);
         if (round.feeToken == NATIVE_CURRENCY) {
             // The dispute fees were paid in ETH
-            SafeSend.safeSend(payable(account), feeReward, wNative);
+            SafeSend.safeSend(payable(account), feeReward, W_NATIVE);
         } else {
             // The dispute fees were paid in ERC20
             round.feeToken.safeTransfer(account, feeReward);
@@ -888,7 +897,7 @@ abstract contract KlerosCoreBase is IArbitratorV2, Initializable, UUPSProxiable
                 if (leftoverFeeReward != 0) {
                     if (round.feeToken == NATIVE_CURRENCY) {
                         // The dispute fees were paid in ETH
-                        SafeSend.safeSend(payable(governor), leftoverFeeReward, wNative);
+                        SafeSend.safeSend(payable(governor), leftoverFeeReward, W_NATIVE);
                     } else {
                         // The dispute fees were paid in ERC20
                         round.feeToken.safeTransfer(governor, leftoverFeeReward);