@FormatMethod
  void reportError(Element e, String format, Object... args) {
    messager.printMessage(Diagnostic.Kind.ERROR, String.format(format, args), e);
    errorCount++;
  }
Issue a compilation error. This method does not throw an exception, since we want to continue
processing and perhaps report other errors. It is a good idea to introduce a test case in
CompilationTest for any new call to reportError(...) to ensure that we continue correctly after
an error.

@param e the element to which it pertains
@param format the format string for the text of the warning
@param args arguments for the format string
value/src/main/java/com/google/auto/value/processor/ErrorReporter.java