abstract contract Hevm {
    function label(address addr, string calldata label) external virtual;
}

contract C {
    constructor() public {
        Hevm(0x7109709ECfa91a80626fF3989D68f67F5b1DD12D).label(
            address(0x20000),
            "hacker"
        );
    }
    bool hacked;
    function hack() public {
        if (msg.sender == address(0x20000)) hacked = true;
    }

    function hack2(address x) public {
        if (msg.sender == address(0x10000) && x == address(0x20000))
            assert(!hacked);
    }
}