Add elaboration on interface use

[ilikesymmetry]

Interfaces are a critical way solidity devs across teams can easily build on top of each other and therefore I think the current "Avoid writing interfaces" is too reductionist. I agree with the intention of avoiding unnecessary interfaces and making known the potential downsides of them though, but think there are still many cases where writing an interface will save external developers the hassle and risk of writing their own custom interfaces to interact with your contract. Additionally, I wanted to call out that using interfaces to call contracts is preferable to manual encoding methods.

[wilsoncusack]

You don't need an interface for this, right? You can just do ERC20(address).transfer are you assuming here there is some pragma conflict?

[ilikesymmetry]

You can just do Contract(address).function, but then you bring the entire bytecode of Contract into your deployed contract, boosting the size. In extreme cases, you could overflow the 24kb limit without noticing. If you use IContract, then you are typically bringing much less bytecode into your contract, saving on deploy costs and also leaving more room for the 24kb limit if needed.

[wilsoncusack]

Using a contract or interface here is a compiler level thing and doesn't impact bytecode. These will print them exact same thing

contract T is Test {
    function test() public {
        console2.logBytes(type(UseContract).creationCode);
        console2.logBytes(type(UseInterface).creationCode);
    }
}

contract MyContract {
    function call() external {

    }
}

interface MyInterface {
    function call() external;
}

contract UseContract {
    function x() external {
        MyContract(address(1)).call();
    }
}

contract UseInterface {
    function x() external {
        MyInterface(address(1)).call();
    }
}

[wilsoncusack]

It would only be included in bytecode if you did like new MyContract()

[wilsoncusack]

Going to close this for now @ilikesymmetry, but I do want to make some clarifying statement around interfaces. In particular, that I think they can be used but documentation should not be there.