@Override
    @Nullable
    public Invokable invoke(Invokation invokation, Object... parameters) {
      Messager messager = EnvironmentState.processing().getMessager();
      String message = CharMatcher.whitespace().trimFrom(parameters[parameters.length - 1].toString());
      Element element = (Element) Iterators.find(
          Iterators.forArray(parameters),
          Predicates.instanceOf(Element.class),
          null);
      if (element != null) {
        messager.printMessage(Diagnostic.Kind.ERROR, message, Delegated.unwrap(element));
      } else {
        messager.printMessage(Diagnostic.Kind.ERROR, message);
      }
      return null;
    }
Pragma-like comment indicator just at beginning of the source file used to disable import
post-processing.
generator/src/org/immutables/generator/Output.java