private void reportMissingElements(Set<ElementFactory> missingElementFactories) {
    for (ElementFactory missingElementFactory : missingElementFactories) {
      Element missingElement = missingElementFactory.getElement(elementUtils);
      if (missingElement != null) {
        messager.printMessage(
            ERROR,
            processingErrorMessage("this " + Ascii.toLowerCase(missingElement.getKind().name())),
            missingElement);
      } else {
        messager.printMessage(ERROR, processingErrorMessage(missingElementFactory.toString));
      }
    }
  }
Processes the valid elements, including those previously deferred by each step.
common/src/main/java/com/google/auto/common/BasicAnnotationProcessor.java