fix some slither issues

v2/src/evm/ERC20Custody.sol

@@ -17,10 +17,7 @@ contract ERC20Custody is IERC20CustodyEvents, IERC20CustodyErrors, ReentrancyGua
     using SafeERC20 for IERC20;
 
     /// @notice Gateway contract.
-    IGatewayEVM public gateway;
-    /// @notice TSS address.
-    address public tssAddress;
-
+    IGatewayEVM public immutable gateway;
     /// @notice New role identifier for pauser role.
     bytes32 public constant PAUSER_ROLE = keccak256("PAUSER_ROLE");
     /// @notice New role identifier for withdrawer role.
@@ -29,11 +26,10 @@ contract ERC20Custody is IERC20CustodyEvents, IERC20CustodyErrors, ReentrancyGua
     /// @notice Constructor for ERC20Custody.
     /// @dev Set admin as default admin and pauser, and tssAddress as tss role.
     constructor(address _gateway, address _tssAddress, address _admin) {
-        if (_gateway == address(0) || _tssAddress == address(0)) {
+        if (_gateway == address(0) || _tssAddress == address(0) || _admin == address(0)) {
             revert ZeroAddress();
         }
         gateway = IGatewayEVM(_gateway);
-        tssAddress = _tssAddress;
         _grantRole(DEFAULT_ADMIN_ROLE, _admin);
         _grantRole(PAUSER_ROLE, _admin);
         _grantRole(WITHDRAWER_ROLE, _tssAddress);

v2/src/evm/GatewayEVM.sol

@@ -19,6 +19,7 @@ contract GatewayEVM is
     Initializable,
     AccessControlUpgradeable,
     UUPSUpgradeable,
+    IGatewayEVM,
     IGatewayEVMErrors,
     IGatewayEVMEvents,
     ReentrancyGuardUpgradeable,
@@ -96,7 +97,8 @@ contract GatewayEVM is
     /// @param destination Address to call.
     /// @param data Calldata to pass to the call.
     function executeRevert(address destination, bytes calldata data) public payable onlyRole(TSS_ROLE) whenNotPaused {
-        (bool success, bytes memory result) = destination.call{ value: msg.value }("");
+        if (destination == address(0)) revert ZeroAddress();
+        (bool success,) = destination.call{ value: msg.value }("");
         if (!success) revert ExecutionFailed();
         Revertable(destination).onRevert(data);
 
@@ -193,7 +195,7 @@ contract GatewayEVM is
         if (msg.value == 0) revert InsufficientETHAmount();
         (bool deposited,) = tssAddress.call{ value: msg.value }("");
 
-        if (deposited == false) revert DepositFailed();
+        if (!deposited) revert DepositFailed();
 
         emit Deposit(msg.sender, receiver, msg.value, address(0), "");
     }
@@ -217,7 +219,7 @@ contract GatewayEVM is
         if (msg.value == 0) revert InsufficientETHAmount();
         (bool deposited,) = tssAddress.call{ value: msg.value }("");
 
-        if (deposited == false) revert DepositFailed();
+        if (!deposited) revert DepositFailed();
 
         emit Deposit(msg.sender, receiver, msg.value, address(0), payload);
     }
@@ -291,7 +293,7 @@ contract GatewayEVM is
             // transfer amount to gateway
             IERC20(token).safeTransferFrom(from, address(this), amount);
             // approve connector to handle tokens depending on connector version (eg. lock or burn)
-            IERC20(token).approve(zetaConnector, amount);
+            if (!IERC20(token).approve(zetaConnector, amount)) revert ApprovalFailed();
             // send tokens to connector
             ZetaConnectorBase(zetaConnector).receiveTokens(amount);
         } else {
@@ -309,7 +311,7 @@ contract GatewayEVM is
         if (token == zetaToken) {
             // transfer to connector
             // approve connector to handle tokens depending on connector version (eg. lock or burn)
-            IERC20(token).approve(zetaConnector, amount);
+            if (!IERC20(token).approve(zetaConnector, amount)) revert ApprovalFailed();
             // send tokens to connector
             ZetaConnectorBase(zetaConnector).receiveTokens(amount);
         } else {

v2/src/evm/ZetaConnectorBase.sol

@@ -23,8 +23,6 @@ abstract contract ZetaConnectorBase is IZetaConnectorEvents, ReentrancyGuard, Pa
     IGatewayEVM public immutable gateway;
     /// @notice The address of the Zeta token.
     address public immutable zetaToken;
-    /// @notice The address of the TSS (Threshold Signature Scheme) contract.
-    address public tssAddress;
 
     /// @notice New role identifier for withdrawer role.
     bytes32 public constant WITHDRAWER_ROLE = keccak256("WITHDRAWER_ROLE");
@@ -39,7 +37,6 @@ abstract contract ZetaConnectorBase is IZetaConnectorEvents, ReentrancyGuard, Pa
         }
         gateway = IGatewayEVM(_gateway);
         zetaToken = _zetaToken;
-        tssAddress = _tssAddress;
 
         _grantRole(DEFAULT_ADMIN_ROLE, _admin);
         _grantRole(WITHDRAWER_ROLE, _tssAddress);

v2/src/evm/ZetaConnectorNonNative.sol

@@ -3,7 +3,6 @@ pragma solidity 0.8.26;
 
 import "./ZetaConnectorBase.sol";
 import "./interfaces/IZetaNonEthNew.sol";
-import "@openzeppelin/contracts/token/ERC20/extensions/ERC20Burnable.sol";
 
 /// @title ZetaConnectorNonNative
 /// @notice Implementation of ZetaConnectorBase for non-native token handling.

v2/src/evm/interfaces/IGatewayEVM.sol

@@ -80,6 +80,12 @@ interface IGatewayEVM {
     /// @param data The calldata to pass to the contract call.
     function executeWithERC20(address token, address to, uint256 amount, bytes calldata data) external;
 
+    /// @notice Transfers msg.value to destination contract and executes it's onRevert function.
+    /// @dev This function can only be called by the TSS address and it is payable.
+    /// @param destination Address to call.
+    /// @param data Calldata to pass to the call.
+    function executeRevert(address destination, bytes calldata data) external payable;
+
     /// @notice Executes a call to a contract.
     /// @param destination The address of the contract to call.
     /// @param data The calldata to pass to the contract call.
@@ -92,6 +98,38 @@ interface IGatewayEVM {
     /// @param amount The amount of tokens to transfer.
     /// @param data The calldata to pass to the contract call.
     function revertWithERC20(address token, address to, uint256 amount, bytes calldata data) external;
+
+    /// @notice Deposits ETH to the TSS address.
+    /// @param receiver Address of the receiver.
+    function deposit(address receiver) external payable;
+
+    /// @notice Deposits ERC20 tokens to the custody or connector contract.
+    /// @param receiver Address of the receiver.
+    /// @param amount Amount of tokens to deposit.
+    /// @param asset Address of the ERC20 token.
+    function deposit(address receiver, uint256 amount, address asset) external;
+
+    /// @notice Deposits ETH to the TSS address and calls an omnichain smart contract.
+    /// @param receiver Address of the receiver.
+    /// @param payload Calldata to pass to the call.
+    function depositAndCall(address receiver, bytes calldata payload) external payable;
+
+    /// @notice Deposits ERC20 tokens to the custody or connector contract and calls an omnichain smart contract.
+    /// @param receiver Address of the receiver.
+    /// @param amount Amount of tokens to deposit.
+    /// @param asset Address of the ERC20 token.
+    /// @param payload Calldata to pass to the call.
+    function depositAndCall(
+        address receiver,
+        uint256 amount,
+        address asset,
+        bytes calldata payload
+    ) external;
+
+    /// @notice Calls an omnichain smart contract without asset transfer.
+    /// @param receiver Address of the receiver.
+    /// @param payload Calldata to pass to the call.
+    function call(address receiver, bytes calldata payload) external;
 }
 
 /// @title Revertable

v2/src/zevm/GatewayZEVM.sol

@@ -16,6 +16,7 @@ import "@openzeppelin/contracts-upgradeable/utils/ReentrancyGuardUpgradeable.sol
 /// @notice The GatewayZEVM contract is the endpoint to call smart contracts on omnichain.
 /// @dev The contract doesn't hold any funds and should never have active allowances.
 contract GatewayZEVM is
+    IGatewayZEVM,
     IGatewayZEVMEvents,
     IGatewayZEVMErrors,
     Initializable,
@@ -182,7 +183,7 @@ contract GatewayZEVM is
     function deposit(address zrc20, uint256 amount, address target) external onlyFungible whenNotPaused {
         if (target == FUNGIBLE_MODULE_ADDRESS || target == address(this)) revert InvalidTarget();
 
-        IZRC20(zrc20).deposit(target, amount);
+        if (!IZRC20(zrc20).deposit(target, amount)) revert ZRC20DepositFailed();
     }
 
     /// @notice Execute a user-specified contract on ZEVM.
@@ -224,7 +225,7 @@ contract GatewayZEVM is
     {
         if (target == FUNGIBLE_MODULE_ADDRESS || target == address(this)) revert InvalidTarget();
 
-        IZRC20(zrc20).deposit(target, amount);
+        if (!IZRC20(zrc20).deposit(target, amount)) revert ZRC20DepositFailed();
         UniversalContract(target).onCrossChainCall(context, zrc20, amount, message);
     }
 
@@ -288,7 +289,7 @@ contract GatewayZEVM is
     {
         if (target == FUNGIBLE_MODULE_ADDRESS || target == address(this)) revert InvalidTarget();
 
-        IZRC20(zrc20).deposit(target, amount);
+        if (!IZRC20(zrc20).deposit(target, amount)) revert ZRC20DepositFailed();
         UniversalContract(target).onRevert(context, zrc20, amount, message);
     }
 }

v2/src/zevm/ZRC20.sol

@@ -42,16 +42,12 @@ contract ZRC20 is IZRC20Metadata, ZRC20Errors, ZRC20Events {
     uint256 private _totalSupply;
     string private _name;
     string private _symbol;
-    uint8 private _decimals;
+    uint8 private immutable _decimals;
 
     function _msgSender() internal view virtual returns (address) {
         return msg.sender;
     }
 
-    function _msgData() internal view virtual returns (bytes calldata) {
-        return msg.data;
-    }
-
     /**
      * @dev Only fungible module modifier.
      */
@@ -74,6 +70,7 @@ contract ZRC20 is IZRC20Metadata, ZRC20Errors, ZRC20Events {
         address gatewayAddress_
     ) {
         if (msg.sender != FUNGIBLE_MODULE_ADDRESS) revert CallerIsNotFungibleModule();
+        if (systemContractAddress_ == address(0) || gatewayAddress_ == address(0)) revert ZeroAddress();
         _name = name_;
         _symbol = symbol_;
         _decimals = decimals_;
@@ -279,6 +276,7 @@ contract ZRC20 is IZRC20Metadata, ZRC20Errors, ZRC20Events {
      * @param addr, new system contract address.
      */
     function updateSystemContractAddress(address addr) external onlyFungible {
+        if (addr == address(0)) revert ZeroAddress();
         systemContractAddress = addr;
         emit UpdatedSystemContract(addr);
     }
@@ -288,6 +286,7 @@ contract ZRC20 is IZRC20Metadata, ZRC20Errors, ZRC20Events {
      * @param addr, new gateway contract address.
      */
     function updateGatewayAddress(address addr) external onlyFungible {
+        if (addr == address(0)) revert ZeroAddress();
         gatewayAddress = addr;
         emit UpdatedGateway(addr);
     }

v2/src/zevm/interfaces/IGatewayZEVM.sol

@@ -71,6 +71,49 @@ interface IGatewayZEVM {
         bytes calldata message
     )
         external;
+
+    /// @notice Deposit ZETA and call a user-specified contract on ZEVM.
+    /// @param context The context of the cross-chain call.
+    /// @param amount The amount of tokens to transfer.
+    /// @param target The target contract to call.
+    /// @param message The calldata to pass to the contract call.
+    function depositAndCall(
+        zContext calldata context,
+        uint256 amount,
+        address target,
+        bytes calldata message
+    )
+        external;
+
+    /// @notice Revert a user-specified contract on ZEVM.
+    /// @param context The context of the revert call.
+    /// @param zrc20 The address of the ZRC20 token.
+    /// @param amount The amount of tokens to revert.
+    /// @param target The target contract to call.
+    /// @param message The calldata to pass to the contract call.
+    function executeRevert(
+        revertContext calldata context,
+        address zrc20,
+        uint256 amount,
+        address target,
+        bytes calldata message
+    )
+        external;
+
+    /// @notice Deposit foreign coins into ZRC20 and revert a user-specified contract on ZEVM.
+    /// @param context The context of the revert call.
+    /// @param zrc20 The address of the ZRC20 token.
+    /// @param amount The amount of tokens to revert.
+    /// @param target The target contract to call.
+    /// @param message The calldata to pass to the contract call.
+    function depositAndRevert(
+        revertContext calldata context,
+        address zrc20,
+        uint256 amount,
+        address target,
+        bytes calldata message
+    )
+        external;
 }
 
 /// @title IGatewayZEVMEvents
@@ -119,6 +162,9 @@ interface IGatewayZEVMErrors {
     /// @notice Error indicating a failure to transfer ZRC20 tokens.
     error ZRC20TransferFailed();
 
+    /// @notice Error indicating a failure to deposit ZRC20 tokens.
+    error ZRC20DepositFailed();
+
     /// @notice Error indicating a failure to transfer gas fee.
     error GasFeeTransferFailed();