The solution for the slither exercise 1 is not general enough

[ggrieco-tob]

The proposed solution fails to work when the exercise is made a little harder, using the following contract:

contract Coin{

    address owner = msg.sender;

    mapping(address => uint) balances;


    // _mint must not be overriden
    function _mint(address dst, uint val) internal{
        require(msg.sender == owner);
        balances[dst] += val;
    }

    function mint(address dst, uint val) public{
        _mint(dst, val);
    }

}

contract MyCoin is Coin{

    event Mint(address, uint);

    function _mint(address dst, uint val) internal{
        balances[dst] += val;
        emit Mint(dst, val);
    }

}

contract MyCoin2 is MyCoin{

    function set(address dst, uint val) internal{
        balances[dst] = val;
    }
    
}

contract MyCoin3 is Coin{

    function set(address dst, uint val) internal{
        balances[dst] = val;
    }
}

contract MyCoin4 {
   
    function _mint(address dst, int val) public{}

}

contract NotCoin {
    address notowner;
    function _mint(address dst, uint val) internal{}


}

Running the solution results in this output:

$ python3 solution.py 
Error, MyCoin overrides _mint
Error, MyCoin2 overrides _mint
Error, MyCoin3 overrides _mint

However, MyCoin3 should not be detected as overriding the _mint function.