Yield Witch v2 contest - sashik_eth's results

G01 - unchecked block can be used for gas efficiency of the expression that can't overflow/underflow

L332 could be unchecked since if overflow happens it would be reverted on L319:

contracts/Witch.sol:319 liquidatorCut + auctioneerCut,
...
contracts/Witch.sol:332 _collateralBought(vaultId, to, liquidatorCut + auctioneerCut, artIn); 

https://github.com/code-423n4/2022-07-yield/blob/main/contracts/Witch.sol#L332 Same here: https://github.com/code-423n4/2022-07-yield/blob/main/contracts/Witch.sol#L382

L598 could be unchecked since auctioneerCut always be less than liquidatorCut, because auctioneerReward can't be grather than 1e18 (check on L162):

contracts/Witch.sol:597 auctioneerCut = liquidatorCut.wmul(auctioneerReward);
contracts/Witch.sol:598 liquidatorCut -= auctioneerCut; 

https://github.com/code-423n4/2022-07-yield/blob/main/contracts/Witch.sol#L598

L444 could be unchecked since if artIn < auction_.art it would reverted on L438

contracts/Witch.sol:438 auction_.art - artIn >= debt.min * (10**debt.dec),
...
contracts/Witch.sol:444 auction_.art -= artIn.u128();  

https://github.com/code-423n4/2022-07-yield/blob/main/contracts/Witch.sol#L444

G02 - Using custom error instead of require() string

Custom errors are available from solidity version 0.8.4. They cost cheaper than require/revert strings.

contracts/Witch.sol:84  require(param == "ladle", "Unrecognized"); 
contracts/Witch.sol:102 require(initialOffer <= 1e18, "InitialOffer above 100%"); 
contracts/Witch.sol:103 require(proportion <= 1e18, "Proportion above 100%"); 
contracts/Witch.sol:106 "InitialOffer below 1%" 
contracts/Witch.sol:108 require(proportion >= 0.01e18, "Proportion below 1%"); 
contracts/Witch.sol:189 require(cauldron.level(vaultId) < 0, "Not undercollateralized"); 
contracts/Witch.sol:200 require(limits_.sum <= limits_.max, "Collateral limit reached"); 
contracts/Witch.sol:255 require(auction_.start > 0, "Vault not under auction"); 
contracts/Witch.sol:256 require(cauldron.level(vaultId) >= 0, "Undercollateralized"); 
contracts/Witch.sol:300 require(auction_.start > 0, "Vault not under auction"); 
contracts/Witch.sol:313 require(liquidatorCut >= minInkOut, "Not enough bought"); 
contracts/Witch.sol:328 require(baseJoin != IJoin(address(0)), "Join not found"); 
contracts/Witch.sol:358 require(auction_.start > 0, "Vault not under auction"); 
contracts/Witch.sol:365 require(liquidatorCut >= minInkOut, "Not enough bought"); 
contracts/Witch.sol:395 require(ilkJoin != IJoin(address(0)), "Join not found"); 
contracts/Witch.sol:416 require(auction_.start > 0, "Vault not under auction"); 
contracts/Witch.sol:439 "Leaves dust" 

G03 - Using >0 costs more gas than !=0 when used with uint in require statement

contracts/Witch.sol:255 require(auction_.start > 0, "Vault not under auction");
contracts/Witch.sol:300 require(auction_.start > 0, "Vault not under auction"); 
contracts/Witch.sol:358 require(auction_.start > 0, "Vault not under auction"); 
contracts/Witch.sol:416 require(auction_.start > 0, "Vault not under auction");