public int[] getRecursiveOpAlts() {
		if ( recOpAlts.size()==0 ) return null;
		int[] alts = new int[recOpAlts.size()+1];
		int alt = 1;
		for (LeftRecursiveRuleAltInfo altInfo : recOpAlts.values()) {
			alts[alt] = altInfo.altNum;
			alt++; // recOpAlts has alts possibly with gaps
		}
		return alts;
	}
Return an array that maps predicted alt from recursive op decision
 to original alt of rule. For following rule, return [0, 1, 3]

		e : e '*' e
		  | INT
		  | e '+' e
		  | ID
		  ;
 That maps predicted alt 1 to original alt 1 and predicted 2 to alt 3.

 @since 4.5.1
tool/src/org/antlr/v4/tool/LeftRecursiveRule.java