Interesting mistakes while programming

if (A) {

   Do1();

}

if (A && B) {

   Do2();

} else {

   Do3();

}

after some refactoring has changed to:

if (A) {

   Do1();

   if (B) {

      Do2();

   } else {

      Do3();

   }

}

These two fragments obviously aren't the same.