CEI violation in FxERC20ChildTunnel.sol

[b0gdaniy]

There is a CEI (Checks-Effects-Interactions) pattern violation in FxERC20ChildTunnel.sol.
In costructor() assignment value tokenTemplate = _tokenTemplate; before _isContract(_tokenTemplate) check:

    constructor(address _fxChild, address _tokenTemplate) FxBaseChildTunnel(_fxChild) {
        tokenTemplate = _tokenTemplate; // Effect on state variable
        require(_isContract(_tokenTemplate), "Token template is not contract"); // Check
    }

so the code should look like this:

    constructor(address _fxChild, address _tokenTemplate) FxBaseChildTunnel(_fxChild) {
        require(_isContract(_tokenTemplate), "Token template is not contract"); // Check
        tokenTemplate = _tokenTemplate; // Interaction with state variable
    }

Also in _mapToken() function where
IFxERC20(childToken).initialize() called before rootToChildToken[rootToken] = childToken:

function _mapToken(bytes memory syncData) internal returns (address) {
        (address rootToken, string memory name, string memory symbol, uint8 decimals) = abi.decode(
            syncData,
            (address, string, string, uint8)
        );

        // get root to child token
        address childToken = rootToChildToken[rootToken];

        // check if it's already mapped
        require(childToken == address(0x0), "FxERC20ChildTunnel: ALREADY_MAPPED");

        // deploy new child token
        bytes32 salt = keccak256(abi.encodePacked(rootToken));
        childToken = createClone(salt, tokenTemplate);
        // slither-disable-next-line reentrancy-no-eth
        IFxERC20(childToken).initialize(
            address(this),
            rootToken,
            string(abi.encodePacked(name, SUFFIX_NAME)),
            string(abi.encodePacked(PREFIX_SYMBOL, symbol)),
            decimals
        ); // Interaction with childToken

        // map the token
        rootToChildToken[rootToken] = childToken; // Effect on state variable
        emit TokenMapped(rootToken, childToken);

        // return new child token
        return childToken;
    }

and code should look like:

function _mapToken(bytes memory syncData) internal returns (address) {
        (address rootToken, string memory name, string memory symbol, uint8 decimals) = abi.decode(
            syncData,
            (address, string, string, uint8)
        );

        // get root to child token
        address childToken = rootToChildToken[rootToken];

        // check if it's already mapped
        require(childToken == address(0x0), "FxERC20ChildTunnel: ALREADY_MAPPED");

        // deploy new child token
        bytes32 salt = keccak256(abi.encodePacked(rootToken));
        childToken = createClone(salt, tokenTemplate);

        // map the token
        rootToChildToken[rootToken] = childToken; // Effect on state variable
        
        // slither-disable-next-line reentrancy-no-eth
        IFxERC20(childToken).initialize(
            address(this),
            rootToken,
            string(abi.encodePacked(name, SUFFIX_NAME)),
            string(abi.encodePacked(PREFIX_SYMBOL, symbol)),
            decimals
        ); // Interaction with childToken
        
        emit TokenMapped(rootToken, childToken);

        // return new child token
        return childToken;
    }

These changes reduce gas cost if some of these checks will revert an error, before effects/interactions.