bitmark-grammar/src/typescript-es6/antlr4es6/atn/AmbiguityInfo.ts

A bitmark parser

/*!
 * Copyright 2016 The ANTLR Project. All rights reserved.
 * Licensed under the BSD-3-Clause license. See LICENSE file in the project root for license information.
 */

// ConvertTo-TS run at 2016-10-04T11:26:24.8229279-07:00

import { BitSet } from "../misc/BitSet";
import { DecisionEventInfo } from "./DecisionEventInfo";
import { NotNull } from "../Decorators";
import { SimulatorState } from "./SimulatorState";
import { TokenStream } from "../TokenStream";

/**
 * This class represents profiling event information for an ambiguity.
 * Ambiguities are decisions where a particular input resulted in an SLL
 * conflict, followed by LL prediction also reaching a conflict state
 * (indicating a true ambiguity in the grammar).
 *
 * This event may be reported during SLL prediction in cases where the
 * conflicting SLL configuration set provides sufficient information to
 * determine that the SLL conflict is truly an ambiguity. For example, if none
 * of the ATN configurations in the conflicting SLL configuration set have
 * traversed a global follow transition (i.e.
 * {@link ATNConfig#getReachesIntoOuterContext} is `false` for all
 * configurations), then the result of SLL prediction for that input is known to
 * be equivalent to the result of LL prediction for that input.
 *
 * In some cases, the minimum represented alternative in the conflicting LL
 * configuration set is not equal to the minimum represented alternative in the
 * conflicting SLL configuration set. Grammars and inputs which result in this
 * scenario are unable to use {@link PredictionMode#SLL}, which in turn means
 * they cannot use the two-stage parsing strategy to improve parsing performance
 * for that input.
 *
 * @see ParserATNSimulator#reportAmbiguity
 * @see ParserErrorListener#reportAmbiguity
 *
 * @since 4.3
 */
export class AmbiguityInfo extends DecisionEventInfo {
	/** The set of alternative numbers for this decision event that lead to a valid parse. */
	@NotNull
	private ambigAlts: BitSet;

	/**
	 * Constructs a new instance of the {@link AmbiguityInfo} class with the
	 * specified detailed ambiguity information.
	 *
	 * @param decision The decision number
	 * @param state The final simulator state identifying the ambiguous
	 * alternatives for the current input
	 * @param ambigAlts The set of alternatives in the decision that lead to a valid parse.
	 *                  The predicted alt is the min(ambigAlts)
	 * @param input The input token stream
	 * @param startIndex The start index for the current prediction
	 * @param stopIndex The index at which the ambiguity was identified during
	 * prediction
	 */
	constructor(
		decision: number,
		@NotNull state: SimulatorState,
		@NotNull ambigAlts: BitSet,
		@NotNull input: TokenStream,
		startIndex: number,
		stopIndex: number) {
		super(decision, state, input, startIndex, stopIndex, state.useContext);
		this.ambigAlts = ambigAlts;
	}

	/**
	 * Gets the set of alternatives in the decision that lead to a valid parse.
	 *
	 * @since 4.5
	 */
	@NotNull
	get ambiguousAlternatives(): BitSet {
		return this.ambigAlts;
	}
}