Unused Named Returns

[code423n4]

Handle

ye0lde

Vulnerability details

Impact

Removing unused named return variables can reduce gas usage and improve code clarity.

Proof of Concept

Unused named returns
https://github.com/code-423n4/2021-11-yaxis/blob/146febcb61ae7fe20b0920849c4f4bbe111c6ba7/contracts/v3/alchemix/Transmuter.sol#L394-L397
https://github.com/code-423n4/2021-11-yaxis/blob/146febcb61ae7fe20b0920849c4f4bbe111c6ba7/contracts/v3/alchemix/Transmuter.sol#L424

Tools Used

Visual Studio Code, Remix

Recommended Mitigation Steps

Either remove the named variables or
Delete the similar local variables that were created and used instead of the named variables.
The return statement can also be deleted.

For example, refactor the userInfo function
https://github.com/code-423n4/2021-11-yaxis/blob/146febcb61ae7fe20b0920849c4f4bbe111c6ba7/contracts/v3/alchemix/Transmuter.sol#L394-L397
like this:

    function userInfo(address user)  
        public
        view
        returns (
            uint256 depositedAl,
            uint256 pendingdivs,
            uint256 inbucket,
            uint256 realised
        )
    {
        depositedAl = depositedAlTokens[user];
        uint256 _toDistribute = buffer.mul(block.number.sub(lastDepositBlock)).div(TRANSMUTATION_PERIOD);
        if(block.number.sub(lastDepositBlock) > TRANSMUTATION_PERIOD){
            _toDistribute = buffer;
        }
        pendingdivs = _toDistribute.mul(depositedAlTokens[user]).div(totalSupplyAltokens);
        inbucket = tokensInBucket[user].add(dividendsOwing(user));
        realised = realisedTokens[user];
    }

getMultipleUserInfo can be refactored in the same way.

[Xuefeng-Zhu]

I think this is for readability

[0xleastwood]

This is a valid finding. As far as I'm aware, declaring named returns uses memory to store the created state variables. As this is unnecessary, there are a number of memory operations which can be removed, slightly improving gas costs for affected function calls.