Auction.userClaimableArbTokens claimablePerc calculations can be simplified

[code423n4]

Handle

hyh

Vulnerability details

Impact

Gas is overspent on access and operations.

Proof of Concept

claimablePerc is calculated in two steps, which can be made simpler.
https://github.com/code-423n4/2021-11-malt/blob/main/src/contracts/Auction.sol#L294

Recommended Mitigation Steps

Now:

uint256 totalTokens = auction.commitments.mul(auction.pegPrice).div(auction.finalPrice);
uint256 claimablePerc = auction.claimableTokens.mul(auction.pegPrice).div(totalTokens);

To be (totalTokens isn't used elsewhere):

uint256 claimablePerc = auction.claimableTokens.mul(auction.finalPrice).div(auction.commitments);

[GalloDaSballo]

Through the following symbolic replacements:

TT = (Ac * Ap) / Af
CP = (Act * Ap) / TT

CP = (Act * Ap) / (Ac * Ap) / Af
CP = (Act) / (Ac) / Af
CP = Af * Act / AC

I agree that the finding is valid and will save gas