AbstractRewardMine.getRewardOwnershipFraction shouldn't be used internally

[code423n4]

Handle

hyh

Vulnerability details

Impact

Gas is overspent on function calls.

Proof of Concept

earned function calls public getRewardOwnershipFraction function:
https://github.com/code-423n4/2021-11-malt/blob/main/src/contracts/AbstractRewardMine.sol#L144

Recommended Mitigation Steps

Now:

function totalDeclaredReward() virtual public view returns (uint256) {
	return rewardToken.balanceOf(address(this));
}
function getRewardOwnershipFraction(address account) public view returns(uint256 numerator, uint256 denominator) {
	numerator = balanceOfRewards(account);
	denominator = totalDeclaredReward();
}
...
function earned(address account) public view returns (uint256 earnedReward) {
	(uint256 rewardNumerator, uint256 rewardDenominator) = getRewardOwnershipFraction(account);

To be:

function earned(address account) public view returns (uint256 earnedReward) {
	uint256 rewardNumerator = balanceOfRewards(account);
	uint256 rewardDenominator = rewardToken.balanceOf(address(this));

[GalloDaSballo]

The finding is valid, using the same public functions instead of a new one would save the cost of an extra JUMP
I believe you could also save gas by using internal functions as the compiler will inline them.

That said, the finding saves gas, personally I wouldn't apply the improvement as I believe it would impair readability