Antlr4.Runtime.Atn.ParserATNSimulator.ApplyPrecedenceFilter C# (CSharp) Метод

        protected ATNConfigSet ApplyPrecedenceFilter(ATNConfigSet configSet)
        {
            Dictionary<int, PredictionContext> statesFromAlt1 = new Dictionary<int, PredictionContext>();
            ATNConfigSet result = new ATNConfigSet(configSet.fullCtx);
            foreach (ATNConfig config in configSet.configs)
            {
                // handle alt 1 first
                if (config.alt != 1)
                {
                    continue;
                }

                SemanticContext updatedContext = config.semanticContext.EvalPrecedence(parser, context);
                if (updatedContext == null)
                {
                    // the configuration was eliminated
                    continue;
                }

                statesFromAlt1[config.state.stateNumber] = config.context;
                if (updatedContext != config.semanticContext)
                {
                    result.Add(new ATNConfig(config, updatedContext), mergeCache);
                }
                else {
                    result.Add(config, mergeCache);
                }
            }

            foreach (ATNConfig config in configSet.configs)
            {
                if (config.alt == 1)
                {
                    // already handled
                    continue;
                }

                if (!config.IsPrecedenceFilterSuppressed)
                {
                    /* In the future, this elimination step could be updated to also
                     * filter the prediction context for alternatives predicting alt>1
                     * (basically a graph subtraction algorithm).
                     */
                    PredictionContext ctx;
                    if (statesFromAlt1.TryGetValue(config.state.stateNumber, out ctx))
                    {
                        if (ctx != null && ctx.Equals(config.context))
                        {
                            // eliminated
                            continue;
                        }
                    }
                }

                result.Add(config, mergeCache);
            }

            return result;
        }