public ATNConfigSet getDeadEndConfigs() {
		return deadEndConfigs;
	}
The token object at the start index; the input stream might
	not be buffering tokens so get a reference to it. (At the
 time the error occurred, of course the stream needs to keep a
 buffer all of the tokens but later we might not have access to those.)
runtime/Java/src/org/antlr/v4/runtime/NoViableAltException.java