org.antlr.v4.runtime

Interface ANTLRErrorListener

All Known Implementing Classes:

BaseErrorListener, ConsoleErrorListener, DiagnosticErrorListener, ProxyErrorListener

public interface ANTLRErrorListener

How to emit recognition errors

Method Summary

Methods

Modifier and Type	Method and Description
void	reportAmbiguity(Parser recognizer, DFA dfa, int startIndex, int stopIndex, BitSet ambigAlts, ATNConfigSet configs) Called when the parser detects a true ambiguity: an input sequence can be matched literally by two or more pass through the grammar.
void	reportAttemptingFullContext(Parser recognizer, DFA dfa, int startIndex, int stopIndex, ATNConfigSet configs)
void	reportContextSensitivity(Parser recognizer, DFA dfa, int startIndex, int stopIndex, ATNConfigSet configs) Called by the parser when it find a conflict that is resolved by retrying the parse with full context.
void	syntaxError(Recognizer<?,?> recognizer, Object offendingSymbol, int line, int charPositionInLine, String msg, RecognitionException e) Upon syntax error, notify any interested parties.

Method Detail

syntaxError

void syntaxError(Recognizer<?,?> recognizer,
               @Nullable
               Object offendingSymbol,
               int line,
               int charPositionInLine,
               String msg,
               @Nullable
               RecognitionException e)

Upon syntax error, notify any interested parties. This is not how to recover from errors or compute error messages. The parser 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. The 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).

Parameters:

recognizer - What parser got the error. From this object, you can access the context as well as the input stream.

offendingSymbol - The offending token in the input token stream, unless recognizer is a lexer (then it's null) If no viable alternative error, e has token at which we started production for the decision.

line - At what line in input to the error occur? This always refers to stopTokenIndex

charPositionInLine - At what character position within that line did the error occur.

msg - The message to emit

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.

reportAmbiguity

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

Called when the parser detects a true ambiguity: an input sequence can be matched literally by two or more pass through the grammar. ANTLR resolves the ambiguity in favor of the alternative appearing first in the grammar. The start and stop index are zero-based absolute indices into the token stream. ambigAlts is a set of alternative numbers that can match the input sequence. This method is only called when we are parsing with full context.

reportAttemptingFullContext

void reportAttemptingFullContext(@NotNull
                               Parser recognizer,
                               @NotNull
                               DFA dfa,
                               int startIndex,
                               int stopIndex,
                               @NotNull
                               ATNConfigSet configs)

reportContextSensitivity

void reportContextSensitivity(@NotNull
                            Parser recognizer,
                            @NotNull
                            DFA dfa,
                            int startIndex,
                            int stopIndex,
                            @NotNull
                            ATNConfigSet configs)

Called by the parser when it find a conflict that is resolved by retrying the parse with full context. This is not a warning; it simply notifies you that your grammar is more complicated than Strong LL can handle. The parser moved up to full context parsing for that input sequence.