Adding unchecked directive can save gas

[code423n4]

Handle

WatchPug

Vulnerability details

For the arithmetic operations that will never over/underflow, using the unchecked directive (Solidity v0.8 has default overflow/underflow checks) can save some gas from the unnecessary internal over/underflow checks.

For example:

https://github.com/code-423n4/2022-01-trader-joe/blob/a1579f6453bc4bf9fb0db9c627beaa41135438ed/contracts/LaunchEvent.sol#L327-L333

if (newAllocation > user.allocation) {
    // Burn tokens and update allocation.
    rJoeNeeded = getRJoeAmount(newAllocation - user.allocation);
    // ...
}

newAllocation - user.allocation will never underflow.

https://github.com/code-423n4/2022-01-trader-joe/blob/a1579f6453bc4bf9fb0db9c627beaa41135438ed/contracts/RocketJoeStaking.sol#L116-L135

    function withdraw(uint256 _amount) external {
        UserInfo storage user = userInfo[msg.sender];
        require(
            user.amount >= _amount,
            "RocketJoeStaking: withdraw amount exceeds balance"
        );

        updatePool();

        uint256 pending = (user.amount * accRJoePerShare) /
            PRECISION -
            user.rewardDebt;

        user.amount = user.amount - _amount;
        // ...
    }

user.amount - _amount will never underflow.