protected void reportAttemptingFullContext(DFA dfa, BitSet conflictingAlts, ATNConfigSet configs, int startIndex, int stopIndex) {
        if ( debug || retry_debug ) {
			Interval interval = Interval.of(startIndex, stopIndex);
			System.out.println("reportAttemptingFullContext decision="+dfa.decision+":"+configs+
                               ", input="+parser.getTokenStream().getText(interval));
        }
        if ( parser!=null ) parser.getErrorListenerDispatch().reportAttemptingFullContext(parser, dfa, startIndex, stopIndex, conflictingAlts, configs);
    }
Add state {@code D} to the DFA if it is not already present, and return
the actual instance stored in the DFA. If a state equivalent to {@code D}
is already in the DFA, the existing state is returned. Otherwise this
method returns {@code D} after adding it to the DFA.

<p>If {@code D} is {@link #ERROR}, this method returns {@link #ERROR} and
does not change the DFA.</p>

@param dfa The dfa
@param D The DFA state to add
@return The state stored in the DFA. This will be either the existing
state if {@code D} is already in the DFA, or {@code D} itself if the
state was not already present.
runtime/Java/src/org/antlr/v4/runtime/atn/ParserATNSimulator.java