operator + method

Evaluation operator + (Evaluation other)

Combines two evaluation results.

The reason will be concatenated with a newline, and passed will be combined with an && operator.

Implementation 

Evaluation operator +(Evaluation other) {
  if (other == null)
    return this;
  final StringBuffer buffer = StringBuffer();
  if (reason != null) {
    buffer.write(reason);
    buffer.write(' ');
  }
  if (other.reason != null)
    buffer.write(other.reason);
  return Evaluation._(passed && other.passed, buffer.isEmpty ? null : buffer.toString());
}