Package org.antlr.v4.runtime

Interface ParserErrorListener

All Superinterfaces:

ANTLRErrorListener<Token>

All Known Implementing Classes:

BaseErrorListener, DiagnosticErrorListener, ProxyParserErrorListener

public interface ParserErrorListener
extends ANTLRErrorListener<Token>

How to emit recognition errors for parsers.

Method Summary

Modifier and Type	Method	Description
void	reportAmbiguity(Parser recognizer, DFA dfa, int startIndex, int stopIndex, boolean exact, BitSet ambigAlts, ATNConfigSet configs)	This method is called by the parser when a full-context prediction results in an ambiguity.
void	reportAttemptingFullContext(Parser recognizer, DFA dfa, int startIndex, int stopIndex, BitSet conflictingAlts, SimulatorState conflictState)	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.
void	reportContextSensitivity(Parser recognizer, DFA dfa, int startIndex, int stopIndex, int prediction, SimulatorState acceptState)	This method is called by the parser when a full-context prediction has a unique result.

Methods inherited from interface org.antlr.v4.runtime.ANTLRErrorListener

syntaxError

Method Details

reportAmbiguity

void reportAmbiguity(@NotNull
 Parser recognizer,
 @NotNull
 DFA dfa,
 int startIndex,
 int stopIndex,
 boolean exact,
 @Nullable
 BitSet ambigAlts,
 @NotNull
 ATNConfigSet configs)

This method is called by the parser when a full-context prediction results in an ambiguity.

Each full-context prediction which does not result in a syntax error will call either reportContextSensitivity(org.antlr.v4.runtime.Parser, org.antlr.v4.runtime.dfa.DFA, int, int, int, org.antlr.v4.runtime.atn.SimulatorState) or reportAmbiguity(org.antlr.v4.runtime.Parser, org.antlr.v4.runtime.dfa.DFA, int, int, boolean, java.util.BitSet, org.antlr.v4.runtime.atn.ATNConfigSet).

When ambigAlts is not null, it contains the set of potentially viable alternatives identified by the prediction algorithm. When ambigAlts is null, use ATNConfigSet.getRepresentedAlternatives() to obtain the represented alternatives from the configs argument.

When exact is true, all of the potentially viable alternatives are truly viable, i.e. this is reporting an exact ambiguity. When exact is false, at least two 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 minimum potentially viable alternative is truly viable.

When the PredictionMode.LL_EXACT_AMBIG_DETECTION prediction mode is used, the parser is required to identify exact ambiguities so exact will always be true.

Parameters:

recognizer - the parser instance

dfa - the DFA for the current decision

startIndex - the input index where the decision started

stopIndex - the input input where the ambiguity was identified

exact - true if the ambiguity is exactly known, otherwise false. This is always true when PredictionMode.LL_EXACT_AMBIG_DETECTION is used.

ambigAlts - the potentially ambiguous alternatives, or null to indicate that the potentially ambiguous alternatives are the complete set of represented alternatives in configs

configs - the ATN configuration set where the ambiguity was identified

reportAttemptingFullContext

void reportAttemptingFullContext(@NotNull
 Parser recognizer,
 @NotNull
 DFA dfa,
 int startIndex,
 int stopIndex,
 @Nullable
 BitSet conflictingAlts,
 @NotNull
 SimulatorState conflictState)

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.

If one or more configurations in 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 conflictingAlts.

Parameters:

recognizer - the parser instance

dfa - the DFA for the current decision

startIndex - the input index where the decision started

stopIndex - the input index where the SLL conflict occurred

conflictingAlts - The specific conflicting alternatives. If this is null, the conflicting alternatives are all alternatives represented in configs.

conflictState - the simulator state when the SLL conflict was detected

reportContextSensitivity

void reportContextSensitivity(@NotNull
 Parser recognizer,
 @NotNull
 DFA dfa,
 int startIndex,
 int stopIndex,
 int prediction,
 @NotNull
 SimulatorState acceptState)

This method is called by the parser when a full-context prediction has a unique result.

Each full-context prediction which does not result in a syntax error will call either reportContextSensitivity(org.antlr.v4.runtime.Parser, org.antlr.v4.runtime.dfa.DFA, int, int, int, org.antlr.v4.runtime.atn.SimulatorState) or reportAmbiguity(org.antlr.v4.runtime.Parser, org.antlr.v4.runtime.dfa.DFA, int, int, boolean, java.util.BitSet, org.antlr.v4.runtime.atn.ATNConfigSet).

For prediction implementations that only evaluate full-context predictions when an SLL conflict is found (including the default 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.

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 prediction argument.

Note that the definition of "context sensitivity" in this method differs from the concept in 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.

Parameters:

recognizer - the parser instance

dfa - the DFA for the current decision

startIndex - the input index where the decision started

stopIndex - the input index where the context sensitivity was finally determined

prediction - the unambiguous result of the full-context prediction

acceptState - the simulator state when the unambiguous prediction was determined