protected NoViableAltException noViableAlt(TokenStream input,
											ParserRuleContext outerContext,
											ATNConfigSet configs,
											int startIndex)
	{
		return new NoViableAltException(parser, input,
											input.get(startIndex),
											input.LT(1),
											configs, outerContext);
	}
Used for debugging in adaptivePredict around execATN but I cut
 it out for clarity now that alg. works well. We can leave this
 "dead" code for a bit.
runtime/Java/src/org/antlr/v4/runtime/atn/ParserATNSimulator.java