code: public Content getTagletOutput(Element holder, DocTree tag, TagletWriter writer) {
          Utils utils = writer.configuration().utils;
          Messages messages = writer.configuration().getMessages();
          VariableElement field = getVariableElement(holder, writer.configuration(), tag);
          if (field == null) {
              if (tag.toString().isEmpty()) {
                  //Invalid use of @value
                  messages.warning(holder,
                          "doclet.value_tag_invalid_use");
              } else {
                  //Reference is unknown.
                  messages.warning(holder,
                          "doclet.value_tag_invalid_reference", tag.toString());
              }
          } else if (field.getConstantValue() != null) {
              return writer.valueTagOutput(field,
                  utils.constantValueExpresion(field),
                  // TODO: investigate and cleanup
                  // in the j.l.m world, equals will not be accurate
                  // !field.equals(tag.holder())
                  !utils.elementsEqual(field, holder)
              );
          } else {
              //Referenced field is not a constant.
              messages.warning(holder,
                  "doclet.value_tag_invalid_constant", utils.getSimpleName(field));
          }
          return writer.getOutputInstance();
      }
docs: {@inheritDoc}