What will happen if two potential difference is connected

If i have a voltage of 10 volts and a voltage regulator that drops the voltage to 5 volts, what will happen if i connected the 10 volts output of voltage regulator to the 10 voltage input and voltage regulator input to the 10 voltage also. And would have been any difference if it's a buck converter. My thought is that since it has different potential the current will flow to the regulator making it hot.