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/* Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
* Use of this file is governed by the BSD 3-clause license that
* can be found in the LICENSE.txt file in the project root.
*/
#pragma once
#include "RecognitionException.h"
namespace antlrcpp {
class BitSet;
}
namespace antlr4 {
/// How to emit recognition errors (an interface in Java).
class ANTLR4CPP_PUBLIC ANTLRErrorListener {
public:
virtual ~ANTLRErrorListener();
/// <summary>
/// Upon syntax error, notify any interested parties. This is not how to
/// recover from errors or compute error messages. <seealso
/// cref="ANTLRErrorStrategy"/> specifies how to recover from syntax errors
/// and how to compute error messages. This listener's job is simply to emit a
/// computed message, though it has enough information to create its own
/// message in many cases. <p/> The <seealso cref="RecognitionException"/> is
/// non-null for all syntax errors except when we discover mismatched token
/// errors that we can recover from in-line, without returning from the
/// surrounding rule (via the single token insertion and deletion mechanism).
/// </summary>
/// <param name="recognizer">
/// What parser got the error. From this
/// object, you can access the context as well
/// as the input stream. </param>
/// <param name="offendingSymbol">
/// The offending token in the input token
/// stream, unless recognizer is a lexer (then it's null). If
/// no viable alternative error, {@code e} has token at which we
/// started production for the decision. </param>
/// <param name="line">
/// The line number in the input where the error occurred.
/// </param> <param name="charPositionInLine"> The character
/// position within that line where the error occurred. </param> <param
/// name="msg"> The message to emit. </param> <param name="e">
/// The exception generated by the parser that led to
/// the reporting of an error. It is null in the case where
/// the parser was able to recover in line without exiting the
/// surrounding rule. </param>
virtual void syntaxError(Recognizer* recognizer, Token* offendingSymbol,
size_t line, size_t charPositionInLine,
const std::string& msg, std::exception_ptr e) = 0;
/**
* This method is called by the parser when a full-context prediction
* results in an ambiguity.
*
* <p>Each full-context prediction which does not result in a syntax error
* will call either {@link #reportContextSensitivity} or
* {@link #reportAmbiguity}.</p>
*
* <p>When {@code ambigAlts} is not null, it contains the set of potentially
* viable alternatives identified by the prediction algorithm. When
* {@code ambigAlts} is null, use {@link ATNConfigSet#getAlts} to obtain the
* represented alternatives from the {@code configs} argument.</p>
*
* <p>When {@code exact} is {@code true}, <em>all</em> of the potentially
* viable alternatives are truly viable, i.e. this is reporting an exact
* ambiguity. When {@code exact} is {@code false}, <em>at least two</em> of
* the potentially viable alternatives are viable for the current input, but
* the prediction algorithm terminated as soon as it determined that at
* least the <em>minimum</em> potentially viable alternative is truly
* viable.</p>
*
* <p>When the {@link PredictionMode#LL_EXACT_AMBIG_DETECTION} prediction
* mode is used, the parser is required to identify exact ambiguities so
* {@code exact} will always be {@code true}.</p>
*
* <p>This method is not used by lexers.</p>
*
* @param recognizer the parser instance
* @param dfa the DFA for the current decision
* @param startIndex the input index where the decision started
* @param stopIndex the input input where the ambiguity was identified
* @param exact {@code true} if the ambiguity is exactly known, otherwise
* {@code false}. This is always {@code true} when
* {@link PredictionMode#LL_EXACT_AMBIG_DETECTION} is used.
* @param ambigAlts the potentially ambiguous alternatives, or {@code null}
* to indicate that the potentially ambiguous alternatives are the complete
* set of represented alternatives in {@code configs}
* @param configs the ATN configuration set where the ambiguity was
* identified
*/
virtual void reportAmbiguity(Parser* recognizer, const dfa::DFA& dfa,
size_t startIndex, size_t stopIndex, bool exact,
const antlrcpp::BitSet& ambigAlts,
atn::ATNConfigSet* configs) = 0;
/**
* This method is called when an SLL conflict occurs and the parser is about
* to use the full context information to make an LL decision.
*
* <p>If one or more configurations in {@code configs} contains a semantic
* predicate, the predicates are evaluated before this method is called. The
* subset of alternatives which are still viable after predicates are
* evaluated is reported in {@code conflictingAlts}.</p>
*
* <p>This method is not used by lexers.</p>
*
* @param recognizer the parser instance
* @param dfa the DFA for the current decision
* @param startIndex the input index where the decision started
* @param stopIndex the input index where the SLL conflict occurred
* @param conflictingAlts The specific conflicting alternatives. If this is
* {@code null}, the conflicting alternatives are all alternatives
* represented in {@code configs}. At the moment, conflictingAlts is non-null
* (for the reference implementation, but Sam's optimized version can see this
* as null).
* @param configs the ATN configuration set where the SLL conflict was
* detected
*/
virtual void reportAttemptingFullContext(
Parser* recognizer, const dfa::DFA& dfa, size_t startIndex,
size_t stopIndex, const antlrcpp::BitSet& conflictingAlts,
atn::ATNConfigSet* configs) = 0;
/**
* This method is called by the parser when a full-context prediction has a
* unique result.
*
* <p>Each full-context prediction which does not result in a syntax error
* will call either {@link #reportContextSensitivity} or
* {@link #reportAmbiguity}.</p>
*
* <p>For prediction implementations that only evaluate full-context
* predictions when an SLL conflict is found (including the default
* {@link ParserATNSimulator} implementation), this method reports cases
* where SLL conflicts were resolved to unique full-context predictions,
* i.e. the decision was context-sensitive. This report does not necessarily
* indicate a problem, and it may appear even in completely unambiguous
* grammars.</p>
*
* <p>{@code configs} may have more than one represented alternative if the
* full-context prediction algorithm does not evaluate predicates before
* beginning the full-context prediction. In all cases, the final prediction
* is passed as the {@code prediction} argument.</p>
*
* <p>Note that the definition of "context sensitivity" in this method
* differs from the concept in {@link DecisionInfo#contextSensitivities}.
* This method reports all instances where an SLL conflict occurred but LL
* parsing produced a unique result, whether or not that unique result
* matches the minimum alternative in the SLL conflicting set.</p>
*
* <p>This method is not used by lexers.</p>
*
* @param recognizer the parser instance
* @param dfa the DFA for the current decision
* @param startIndex the input index where the decision started
* @param stopIndex the input index where the context sensitivity was
* finally determined
* @param prediction the unambiguous result of the full-context prediction
* @param configs the ATN configuration set where the unambiguous prediction
* was determined
*/
virtual void reportContextSensitivity(Parser* recognizer, const dfa::DFA& dfa,
size_t startIndex, size_t stopIndex,
size_t prediction,
atn::ATNConfigSet* configs) = 0;
};
} // namespace antlr4
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