code: private void nullConvert(Label end) {
          LocalVariable temp = createLocalVariable("temp", TypeDesc.OBJECT);
          storeLocal(temp);
          loadLocal(temp);
          Label notNull = createLabel();
          ifNullBranch(notNull, false);
          loadNull();
          branch(end);
          notNull.setLocation();
          loadLocal(temp);
      }
docs: a NullPointerException. Assumes that from type and to type are objects.