@Override
	public String toString() {
		return "Message{" +
			   "errorType=" + getErrorType() +
			   ", args=" + Arrays.asList(getArgs()) +
			   ", e=" + getCause() +
			   ", fileName='" + fileName + '\'' +
			   ", line=" + line +
			   ", charPosition=" + charPosition +
			   '}';
	}
Most of the time, we'll have a token such as an undefined rule ref
 and so this will be set.
tool/src/org/antlr/v4/tool/ANTLRMessage.java