code: void reportError(String msg, Element e) {
      messager.printMessage(Diagnostic.Kind.ERROR, msg, e);
      errorCount++;
    }
docs: 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 msg the text of the warning
  @param e the element to which it pertains