code: @Override
      public void sawOpcode(int seen) {
          try {
              stack.precomputation(this);
  
              if ((seen == Const.ARETURN) && (stack.getStackDepth() > 0)) {
                  OpcodeStack.Item itm = stack.getStackItem(0);
                  if (!itm.isNull()) {
                      returnTypes.put(itm.getJavaClass(), Integer.valueOf(getPC()));
                  }
              }
          } catch (ClassNotFoundException cnfe) {
              bugReporter.reportMissingClass(cnfe);
          } finally {
              stack.sawOpcode(this, seen);
          }
      }
docs: implements the visitor to find return values where the types of objects returned from the method are related only by object.
  
  @param seen
  the opcode of the currently parsed instruction