Use immutable variables can save gas

[code423n4]

Handle

WatchPug

Vulnerability details

https://github.com/code-423n4/2021-12-mellow/blob/6679e2dd118b33481ee81ad013ece4ea723327b5/mellow-vaults/contracts/LpIssuer.sol#L20-L20

IVaultGovernance internal _vaultGovernance;

constructor(
    IVaultGovernance vaultGovernance_,
    address[] memory vaultTokens_,
    string memory name_,
    string memory symbol_
) ERC20(name_, symbol_) {
    require(CommonLibrary.isSortedAndUnique(vaultTokens_), ExceptionsLibrary.SORTED_AND_UNIQUE);
    _vaultGovernance = vaultGovernance_;
    _vaultTokens = vaultTokens_;
    // ...
}

_vaultGovernance will never change, use immutable variable instead of storage variable can save gas.

https://github.com/code-423n4/2021-12-mellow/blob/6679e2dd118b33481ee81ad013ece4ea723327b5/mellow-vaults/contracts/trader/UniV3Trader.sol#L26-L30

ISwapRouter public swapRouter;

constructor(address _swapRouter) {
    swapRouter = ISwapRouter(_swapRouter);
}

swapRouter will never change, use immutable variable instead of storage variable can save gas.