//Line 62 WETH contract
function transferFrom(address src, address dst, uint wad)
        public
        returns (bool)
    {
        require(balanceOf[src] >= wad);

        if (src != msg.sender && allowance[src][msg.sender] != uint(-1)) { 
            require(allowance[src][msg.sender] >= wad); 
            allowance[src][msg.sender] -= wad; // <----------- this line won't executed
        }

        balanceOf[src] -= wad;
        balanceOf[dst] += wad;

        Transfer(src, dst, wad);

        return true;
    }
