pragma solidity ^0.4.10;

interface IToken {
    function transfer(address to, uint256 amount) public returns (bool);
}

contract BadToken {
    
    function transfer(address to, uint256 amount) public {
        // @do nothing
    }
    
}


contract GoodToken {
    
    function transfer(address to, uint256 amount) public returns (bool) {
        return true;
    }
}

contract Transferer {
    
    function transfer(address token, uint256 amount) {
        require(IToken(token).transfer(msg.sender, amount));
    }
    
}