public class ParserATNSimulator extends ATNSimulator
The basic complexity of the adaptive strategy makes it harder to understand. We begin with ATN simulation to build paths in a DFA. Subsequent prediction requests go through the DFA first. If they reach a state without an edge for the current symbol, the algorithm fails over to the ATN simulation to complete the DFA path for the current input (until it finds a conflict state or uniquely predicting state).
All of that is done without using the outer context because we want to create a DFA that is not dependent upon the rule invocation stack when we do a prediction. One DFA works in all contexts. We avoid using context not necessarily because it's slower, although it can be, but because of the DFA caching problem. The closure routine only considers the rule invocation stack created during prediction beginning in the decision rule. For example, if prediction occurs without invoking another rule's ATN, there are no context stacks in the configurations. When lack of context leads to a conflict, we don't know if it's an ambiguity or a weakness in the strong LL(*) parsing strategy (versus full LL(*)).
When SLL yields a configuration set with conflict, we rewind the input and retry the ATN simulation, this time using full outer context without adding to the DFA. Configuration context stacks will be the full invocation stacks from the start rule. If we get a conflict using full context, then we can definitively say we have a true ambiguity for that input sequence. If we don't get a conflict, it implies that the decision is sensitive to the outer context. (It is not context-sensitive in the sense of context-sensitive grammars.)
The next time we reach this DFA state with an SLL conflict, through DFA simulation, we will again retry the ATN simulation using full context mode. This is slow because we can't save the results and have to "interpret" the ATN each time we get that input.
CACHING FULL CONTEXT PREDICTIONS
We could cache results from full context to predicted alternative easily and that saves a lot of time but doesn't work in presence of predicates. The set of visible predicates from the ATN start state changes depending on the context, because closure can fall off the end of a rule. I tried to cache tuples (stack context, semantic context, predicted alt) but it was slower than interpreting and much more complicated. Also required a huge amount of memory. The goal is not to create the world's fastest parser anyway. I'd like to keep this algorithm simple. By launching multiple threads, we can improve the speed of parsing across a large number of files.
There is no strict ordering between the amount of input used by SLL vs LL, which makes it really hard to build a cache for full context. Let's say that we have input A B C that leads to an SLL conflict with full context X. That implies that using X we might only use A B but we could also use A B C D to resolve conflict. Input A B C D could predict alternative 1 in one position in the input and A B C E could predict alternative 2 in another position in input. The conflicting SLL configurations could still be non-unique in the full context prediction, which would lead us to requiring more input than the original A B C. To make a prediction cache work, we have to track the exact input used during the previous prediction. That amounts to a cache that maps X to a specific DFA for that context.
Something should be done for left-recursive expression predictions. They are likely LL(1) + pred eval. Easier to do the whole SLL unless error and retry with full LL thing Sam does.
AVOIDING FULL CONTEXT PREDICTION
We avoid doing full context retry when the outer context is empty, we did not dip into the outer context by falling off the end of the decision state rule, or when we force SLL mode.
As an example of the not dip into outer context case, consider as super constructor calls versus function calls. One grammar might look like this:
ctorBody
: '{' superCall? stat* '}'
;
Or, you might see something like
stat : superCall ';' | expression ';' | ... ;
In both cases I believe that no closure operations will dip into the outer context. In the first case ctorBody in the worst case will stop at the '}'. In the 2nd case it should stop at the ';'. Both cases should stay within the entry rule and not dip into the outer context.
PREDICATES
Predicates are always evaluated if present in either SLL or LL both. SLL and LL simulation deals with predicates differently. SLL collects predicates as it performs closure operations like ANTLR v3 did. It delays predicate evaluation until it reaches and accept state. This allows us to cache the SLL ATN simulation whereas, if we had evaluated predicates on-the-fly during closure, the DFA state configuration sets would be different and we couldn't build up a suitable DFA.
When building a DFA accept state during ATN simulation, we evaluate any predicates and return the sole semantically valid alternative. If there is more than 1 alternative, we report an ambiguity. If there are 0 alternatives, we throw an exception. Alternatives without predicates act like they have true predicates. The simple way to think about it is to strip away all alternatives with false predicates and choose the minimum alternative that remains.
When we start in the DFA and reach an accept state that's predicated, we test those and return the minimum semantically viable alternative. If no alternatives are viable, we throw an exception.
During full LL ATN simulation, closure always evaluates predicates and on-the-fly. This is crucial to reducing the configuration set size during closure. It hits a landmine when parsing with the Java grammar, for example, without this on-the-fly evaluation.
SHARING DFA
All instances of the same parser share the same decision DFAs through a
static field. Each instance gets its own ATN simulator but they share the
same decisionToDFA field. They also share a
PredictionContextCache object that makes sure that all
PredictionContext objects are shared among the DFA states. This makes
a big size difference.
THREAD SAFETY
The ParserATNSimulator locks on the decisionToDFA field when
it adds a new DFA object to that array. addDFAEdge(org.antlr.v4.runtime.dfa.DFA, org.antlr.v4.runtime.dfa.DFAState, int, org.antlr.v4.runtime.dfa.DFAState)
locks on the DFA for the current decision when setting the
DFAState.edges field. addDFAState(org.antlr.v4.runtime.dfa.DFA, org.antlr.v4.runtime.dfa.DFAState) locks on
the DFA for the current decision when looking up a DFA state to see if it
already exists. We must make sure that all requests to add DFA states that
are equivalent result in the same shared DFA object. This is because lots of
threads will be trying to update the DFA at once. The
addDFAState(org.antlr.v4.runtime.dfa.DFA, org.antlr.v4.runtime.dfa.DFAState) method also locks inside the DFA lock
but this time on the shared context cache when it rebuilds the
configurations' PredictionContext objects using cached
subgraphs/nodes. No other locking occurs, even during DFA simulation. This is
safe as long as we can guarantee that all threads referencing
s.edge[t] get the same physical target DFAState, or
null. Once into the DFA, the DFA simulation does not reference the
DFA.states map. It follows the DFAState.edges field to new
targets. The DFA simulator will either find DFAState.edges to be
null, to be non-null and dfa.edges[t] null, or
dfa.edges[t] to be non-null. The
addDFAEdge(org.antlr.v4.runtime.dfa.DFA, org.antlr.v4.runtime.dfa.DFAState, int, org.antlr.v4.runtime.dfa.DFAState) method could be racing to set the field
but in either case the DFA simulator works; if null, and requests ATN
simulation. It could also race trying to get dfa.edges[t], but either
way it will work because it's not doing a test and set operation.
Starting with SLL then failing to combined SLL/LL (Two-Stage Parsing)
Sam pointed out that if SLL does not give a syntax error, then there is no
point in doing full LL, which is slower. We only have to try LL if we get a
syntax error. For maximum speed, Sam starts the parser set to pure SLL
mode with the BailErrorStrategy:
parser.getInterpreter().setPredictionMode(PredictionMode.SLL); parser.setErrorHandler(newBailErrorStrategy());
If it does not get a syntax error, then we're done. If it does get a syntax error, we need to retry with the combined SLL/LL strategy.
The reason this works is as follows. If there are no SLL conflicts, then the grammar is SLL (at least for that input set). If there is an SLL conflict, the full LL analysis must yield a set of viable alternatives which is a subset of the alternatives reported by SLL. If the LL set is a singleton, then the grammar is LL but not SLL. If the LL set is the same size as the SLL set, the decision is SLL. If the LL set has size > 1, then that decision is truly ambiguous on the current input. If the LL set is smaller, then the SLL conflict resolution might choose an alternative that the full LL would rule out as a possibility based upon better context information. If that's the case, then the SLL parse will definitely get an error because the full LL analysis says it's not viable. If SLL conflict resolution chooses an alternative within the LL set, them both SLL and LL would choose the same alternative because they both choose the minimum of multiple conflicting alternatives.
Let's say we have a set of SLL conflicting alternatives {1, 2, 3} and
a smaller LL set called s. If s is {2, 3}, then SLL
parsing will get an error because SLL will pursue alternative 1. If
s is {1, 2} or {1, 3} then both SLL and LL will
choose the same alternative because alternative one is the minimum of either
set. If s is {2} or {3} then SLL will get a syntax
error. If s is {1} then SLL will succeed.
Of course, if the input is invalid, then we will get an error for sure in both SLL and LL parsing. Erroneous input will therefore require 2 passes over the input.
| Modifier and Type | Field and Description |
|---|---|
protected DFA |
_dfa |
protected TokenStream |
_input |
protected ParserRuleContext |
_outerContext |
protected int |
_startIndex |
static boolean |
debug |
static boolean |
debug_list_atn_decisions |
DFA[] |
decisionToDFA |
static boolean |
dfa_debug |
protected DoubleKeyMap<PredictionContext,PredictionContext,PredictionContext> |
mergeCache
Each prediction operation uses a cache for merge of prediction contexts.
|
protected Parser |
parser |
static boolean |
retry_debug |
atn, ERROR, SERIALIZED_UUID, SERIALIZED_VERSION, sharedContextCache| Constructor and Description |
|---|
ParserATNSimulator(ATN atn,
DFA[] decisionToDFA,
PredictionContextCache sharedContextCache)
Testing only!
|
ParserATNSimulator(Parser parser,
ATN atn,
DFA[] decisionToDFA,
PredictionContextCache sharedContextCache) |
| Modifier and Type | Method and Description |
|---|---|
protected ATNConfig |
actionTransition(ATNConfig config,
ActionTransition t) |
int |
adaptivePredict(TokenStream input,
int decision,
ParserRuleContext outerContext) |
protected DFAState |
addDFAEdge(DFA dfa,
DFAState from,
int t,
DFAState to)
Add an edge to the DFA, if possible.
|
protected DFAState |
addDFAState(DFA dfa,
DFAState D)
Add state
D to the DFA if it is not already present, and return
the actual instance stored in the DFA. |
protected ATNConfigSet |
applyPrecedenceFilter(ATNConfigSet configs)
This method transforms the start state computed by
computeStartState(org.antlr.v4.runtime.atn.ATNState, org.antlr.v4.runtime.RuleContext, boolean) to the special start state used by a
precedence DFA for a particular precedence value. |
void |
clearDFA()
Clear the DFA cache used by the current instance.
|
protected void |
closure_(ATNConfig config,
ATNConfigSet configs,
Set<ATNConfig> closureBusy,
boolean collectPredicates,
boolean fullCtx,
int depth,
boolean treatEofAsEpsilon)
Do the actual work of walking epsilon edges
|
protected void |
closure(ATNConfig config,
ATNConfigSet configs,
Set<ATNConfig> closureBusy,
boolean collectPredicates,
boolean fullCtx,
boolean treatEofAsEpsilon) |
protected void |
closureCheckingStopState(ATNConfig config,
ATNConfigSet configs,
Set<ATNConfig> closureBusy,
boolean collectPredicates,
boolean fullCtx,
int depth,
boolean treatEofAsEpsilon) |
protected ATNConfigSet |
computeReachSet(ATNConfigSet closure,
int t,
boolean fullCtx) |
protected ATNConfigSet |
computeStartState(ATNState p,
RuleContext ctx,
boolean fullCtx) |
protected DFAState |
computeTargetState(DFA dfa,
DFAState previousD,
int t)
Compute a target state for an edge in the DFA, and attempt to add the
computed state and corresponding edge to the DFA.
|
void |
dumpDeadEndConfigs(NoViableAltException nvae)
Used for debugging in adaptivePredict around execATN but I cut
it out for clarity now that alg.
|
protected BitSet |
evalSemanticContext(DFAState.PredPrediction[] predPredictions,
ParserRuleContext outerContext,
boolean complete)
Look through a list of predicate/alt pairs, returning alts for the
pairs that win.
|
protected boolean |
evalSemanticContext(SemanticContext pred,
ParserRuleContext parserCallStack,
int alt,
boolean fullCtx)
Evaluate a semantic context within a specific parser context.
|
protected int |
execATN(DFA dfa,
DFAState s0,
TokenStream input,
int startIndex,
ParserRuleContext outerContext)
Performs ATN simulation to compute a predicted alternative based
upon the remaining input, but also updates the DFA cache to avoid
having to traverse the ATN again for the same input sequence.
|
protected int |
execATNWithFullContext(DFA dfa,
DFAState D,
ATNConfigSet s0,
TokenStream input,
int startIndex,
ParserRuleContext outerContext) |
protected int |
getAltThatFinishedDecisionEntryRule(ATNConfigSet configs) |
protected BitSet |
getConflictingAlts(ATNConfigSet configs)
Gets a
BitSet containing the alternatives in configs
which are part of one or more conflicting alternative subsets. |
protected BitSet |
getConflictingAltsOrUniqueAlt(ATNConfigSet configs)
Sam pointed out a problem with the previous definition, v3, of
ambiguous states.
|
protected ATNConfig |
getEpsilonTarget(ATNConfig config,
Transition t,
boolean collectPredicates,
boolean inContext,
boolean fullCtx,
boolean treatEofAsEpsilon) |
protected DFAState |
getExistingTargetState(DFAState previousD,
int t)
Get an existing target state for an edge in the DFA.
|
String |
getLookaheadName(TokenStream input) |
Parser |
getParser() |
protected DFAState.PredPrediction[] |
getPredicatePredictions(BitSet ambigAlts,
SemanticContext[] altToPred) |
PredictionMode |
getPredictionMode() |
protected SemanticContext[] |
getPredsForAmbigAlts(BitSet ambigAlts,
ATNConfigSet configs,
int nalts) |
protected ATNState |
getReachableTarget(Transition trans,
int ttype) |
String |
getRuleName(int index) |
protected int |
getSynValidOrSemInvalidAltThatFinishedDecisionEntryRule(ATNConfigSet configs,
ParserRuleContext outerContext)
This method is used to improve the localization of error messages by
choosing an alternative rather than throwing a
NoViableAltException in particular prediction scenarios where the
ATNSimulator.ERROR state was reached during ATN simulation. |
String |
getTokenName(int t) |
protected static int |
getUniqueAlt(ATNConfigSet configs) |
protected NoViableAltException |
noViableAlt(TokenStream input,
ParserRuleContext outerContext,
ATNConfigSet configs,
int startIndex) |
ATNConfig |
precedenceTransition(ATNConfig config,
PrecedencePredicateTransition pt,
boolean collectPredicates,
boolean inContext,
boolean fullCtx) |
protected void |
predicateDFAState(DFAState dfaState,
DecisionState decisionState) |
protected ATNConfig |
predTransition(ATNConfig config,
PredicateTransition pt,
boolean collectPredicates,
boolean inContext,
boolean fullCtx) |
protected ATNConfigSet |
removeAllConfigsNotInRuleStopState(ATNConfigSet configs,
boolean lookToEndOfRule)
Return a configuration set containing only the configurations from
configs which are in a RuleStopState. |
protected void |
reportAmbiguity(DFA dfa,
DFAState D,
int startIndex,
int stopIndex,
boolean exact,
BitSet ambigAlts,
ATNConfigSet configs)
If context sensitive parsing, we know it's ambiguity not conflict
|
protected void |
reportAttemptingFullContext(DFA dfa,
BitSet conflictingAlts,
ATNConfigSet configs,
int startIndex,
int stopIndex) |
protected void |
reportContextSensitivity(DFA dfa,
int prediction,
ATNConfigSet configs,
int startIndex,
int stopIndex) |
void |
reset() |
protected ATNConfig |
ruleTransition(ATNConfig config,
RuleTransition t) |
void |
setPredictionMode(PredictionMode mode) |
protected Pair<ATNConfigSet,ATNConfigSet> |
splitAccordingToSemanticValidity(ATNConfigSet configs,
ParserRuleContext outerContext)
Walk the list of configurations and split them according to
those that have preds evaluating to true/false.
|
checkCondition, checkCondition, deserialize, edgeFactory, getCachedContext, getSharedContextCache, stateFactory, toInt, toInt32, toLong, toUUIDpublic static final boolean debug
public static final boolean debug_list_atn_decisions
public static final boolean dfa_debug
public static final boolean retry_debug
protected final Parser parser
public final DFA[] decisionToDFA
protected DoubleKeyMap<PredictionContext,PredictionContext,PredictionContext> mergeCache
protected TokenStream _input
protected int _startIndex
protected ParserRuleContext _outerContext
protected DFA _dfa
public ParserATNSimulator(ATN atn, DFA[] decisionToDFA, PredictionContextCache sharedContextCache)
public ParserATNSimulator(Parser parser, ATN atn, DFA[] decisionToDFA, PredictionContextCache sharedContextCache)
public void reset()
reset in class ATNSimulatorpublic void clearDFA()
ATNSimulatorclearDFA in class ATNSimulatorpublic int adaptivePredict(TokenStream input, int decision, ParserRuleContext outerContext)
protected int execATN(DFA dfa, DFAState s0, TokenStream input, int startIndex, ParserRuleContext outerContext)
protected DFAState getExistingTargetState(DFAState previousD, int t)
null.previousD - The current DFA statet - The next input symbolt, or null if the target state for this edge is not
already cachedprotected DFAState computeTargetState(DFA dfa, DFAState previousD, int t)
dfa - The DFApreviousD - The current DFA statet - The next input symbolt. If t does not lead to a valid DFA state, this method
returns ATNSimulator.ERROR.protected void predicateDFAState(DFAState dfaState, DecisionState decisionState)
protected int execATNWithFullContext(DFA dfa, DFAState D, ATNConfigSet s0, TokenStream input, int startIndex, ParserRuleContext outerContext)
protected ATNConfigSet computeReachSet(ATNConfigSet closure, int t, boolean fullCtx)
protected ATNConfigSet removeAllConfigsNotInRuleStopState(ATNConfigSet configs, boolean lookToEndOfRule)
configs which are in a RuleStopState. If all
configurations in configs are already in a rule stop state, this
method simply returns configs.
When lookToEndOfRule is true, this method uses
ATN.nextTokens(org.antlr.v4.runtime.atn.ATNState, org.antlr.v4.runtime.RuleContext) for each configuration in configs which is
not already in a rule stop state to see if a rule stop state is reachable
from the configuration via epsilon-only transitions.
configs - the configuration set to updatelookToEndOfRule - when true, this method checks for rule stop states
reachable by epsilon-only transitions from each configuration in
configs.configs if all configurations in configs are in a
rule stop state, otherwise return a new configuration set containing only
the configurations from configs which are in a rule stop stateprotected ATNConfigSet computeStartState(ATNState p, RuleContext ctx, boolean fullCtx)
protected ATNConfigSet applyPrecedenceFilter(ATNConfigSet configs)
computeStartState(org.antlr.v4.runtime.atn.ATNState, org.antlr.v4.runtime.RuleContext, boolean) to the special start state used by a
precedence DFA for a particular precedence value. The transformation
process applies the following changes to the start state's configuration
set.
SemanticContext.evalPrecedence(org.antlr.v4.runtime.Recognizer<?, ?>, org.antlr.v4.runtime.RuleContext).ATNConfig.isPrecedenceFilterSuppressed() is false,
remove all configurations which predict an alternative greater than 1,
for which another configuration that predicts alternative 1 is in the
same ATN state with the same prediction context. This transformation is
valid for the following reasons:
ATNConfig.isPrecedenceFilterSuppressed() property marks ATN
configurations which do not meet this condition, and therefore are not
eligible for elimination during the filtering process.The prediction context must be considered by this filter to address situations like the following.
grammar TA;
prog: statement* EOF;
statement: letterA | statement letterA 'b' ;
letterA: 'a';
If the above grammar, the ATN state immediately before the token
reference 'a' in letterA is reachable from the left edge
of both the primary and closure blocks of the left-recursive rule
statement. The prediction context associated with each of these
configurations distinguishes between them, and prevents the alternative
which stepped out to prog (and then back in to statement
from being eliminated by the filter.
configs - The configuration set computed by
computeStartState(org.antlr.v4.runtime.atn.ATNState, org.antlr.v4.runtime.RuleContext, boolean) as the start state for the DFA.Parser.getPrecedence()).protected ATNState getReachableTarget(Transition trans, int ttype)
protected SemanticContext[] getPredsForAmbigAlts(BitSet ambigAlts, ATNConfigSet configs, int nalts)
protected DFAState.PredPrediction[] getPredicatePredictions(BitSet ambigAlts, SemanticContext[] altToPred)
protected int getSynValidOrSemInvalidAltThatFinishedDecisionEntryRule(ATNConfigSet configs, ParserRuleContext outerContext)
NoViableAltException in particular prediction scenarios where the
ATNSimulator.ERROR state was reached during ATN simulation.
The default implementation of this method uses the following
algorithm to identify an ATN configuration which successfully parsed the
decision entry rule. Choosing such an alternative ensures that the
ParserRuleContext returned by the calling rule will be complete
and valid, and the syntax error will be reported later at a more
localized location.
ATN.INVALID_ALT_NUMBER.
In some scenarios, the algorithm described above could predict an
alternative which will result in a FailedPredicateException in
the parser. Specifically, this could occur if the only configuration
capable of successfully parsing to the end of the decision rule is
blocked by a semantic predicate. By choosing this alternative within
adaptivePredict(org.antlr.v4.runtime.TokenStream, int, org.antlr.v4.runtime.ParserRuleContext) instead of throwing a
NoViableAltException, the resulting
FailedPredicateException in the parser will identify the specific
predicate which is preventing the parser from successfully parsing the
decision rule, which helps developers identify and correct logic errors
in semantic predicates.
configs - The ATN configurations which were valid immediately before
the ATNSimulator.ERROR state was reachedouterContext - The is the \gamma_0 initial parser context from the paper
or the parser stack at the instant before prediction commences.adaptivePredict(org.antlr.v4.runtime.TokenStream, int, org.antlr.v4.runtime.ParserRuleContext), or
ATN.INVALID_ALT_NUMBER if a suitable alternative was not
identified and adaptivePredict(org.antlr.v4.runtime.TokenStream, int, org.antlr.v4.runtime.ParserRuleContext) should report an error instead.protected int getAltThatFinishedDecisionEntryRule(ATNConfigSet configs)
protected Pair<ATNConfigSet,ATNConfigSet> splitAccordingToSemanticValidity(ATNConfigSet configs, ParserRuleContext outerContext)
protected BitSet evalSemanticContext(DFAState.PredPrediction[] predPredictions, ParserRuleContext outerContext, boolean complete)
NONE predicate indicates an alt containing an
unpredicated config which behaves as "always true." If !complete
then we stop at the first predicate that evaluates to true. This
includes pairs with null predicates.protected boolean evalSemanticContext(SemanticContext pred, ParserRuleContext parserCallStack, int alt, boolean fullCtx)
This method might not be called for every semantic context evaluated during the prediction process. In particular, we currently do not evaluate the following but it may change in the future:
SemanticContext.PrecedencePredicate) are not currently evaluated
through this method.SemanticContext.AND and
SemanticContext.OR) are evaluated as a single semantic
context, rather than evaluating the operands individually.
Implementations which require evaluation results from individual
predicates should override this method to explicitly handle evaluation of
the operands within operator predicates.pred - The semantic context to evaluateparserCallStack - The parser context in which to evaluate the
semantic contextalt - The alternative which is guarded by predfullCtx - true if the evaluation is occurring during LL
prediction; otherwise, false if the evaluation is occurring
during SLL predictionprotected void closure(ATNConfig config, ATNConfigSet configs, Set<ATNConfig> closureBusy, boolean collectPredicates, boolean fullCtx, boolean treatEofAsEpsilon)
protected void closureCheckingStopState(ATNConfig config, ATNConfigSet configs, Set<ATNConfig> closureBusy, boolean collectPredicates, boolean fullCtx, int depth, boolean treatEofAsEpsilon)
protected void closure_(ATNConfig config, ATNConfigSet configs, Set<ATNConfig> closureBusy, boolean collectPredicates, boolean fullCtx, int depth, boolean treatEofAsEpsilon)
public String getRuleName(int index)
protected ATNConfig getEpsilonTarget(ATNConfig config, Transition t, boolean collectPredicates, boolean inContext, boolean fullCtx, boolean treatEofAsEpsilon)
protected ATNConfig actionTransition(ATNConfig config, ActionTransition t)
public ATNConfig precedenceTransition(ATNConfig config, PrecedencePredicateTransition pt, boolean collectPredicates, boolean inContext, boolean fullCtx)
protected ATNConfig predTransition(ATNConfig config, PredicateTransition pt, boolean collectPredicates, boolean inContext, boolean fullCtx)
protected ATNConfig ruleTransition(ATNConfig config, RuleTransition t)
protected BitSet getConflictingAlts(ATNConfigSet configs)
BitSet containing the alternatives in configs
which are part of one or more conflicting alternative subsets.configs - The ATNConfigSet to analyze.configs which are part of one or more
conflicting alternative subsets. If configs does not contain any
conflicting subsets, this method returns an empty BitSet.protected BitSet getConflictingAltsOrUniqueAlt(ATNConfigSet configs)
public String getTokenName(int t)
public String getLookaheadName(TokenStream input)
public void dumpDeadEndConfigs(NoViableAltException nvae)
protected NoViableAltException noViableAlt(TokenStream input, ParserRuleContext outerContext, ATNConfigSet configs, int startIndex)
protected static int getUniqueAlt(ATNConfigSet configs)
protected DFAState addDFAEdge(DFA dfa, DFAState from, int t, DFAState to)
addDFAState(org.antlr.v4.runtime.dfa.DFA, org.antlr.v4.runtime.dfa.DFAState) to ensure the to state is present in the
DFA. If from is null, or if t is outside the
range of edges that can be represented in the DFA tables, this method
returns without adding the edge to the DFA.
If to is null, this method returns null.
Otherwise, this method returns the DFAState returned by calling
addDFAState(org.antlr.v4.runtime.dfa.DFA, org.antlr.v4.runtime.dfa.DFAState) for the to state.
dfa - The DFAfrom - The source state for the edget - The input symbolto - The target state for the edgeto is null, this method returns null;
otherwise this method returns the result of calling addDFAState(org.antlr.v4.runtime.dfa.DFA, org.antlr.v4.runtime.dfa.DFAState)
on toprotected DFAState addDFAState(DFA dfa, DFAState D)
D to the DFA if it is not already present, and return
the actual instance stored in the DFA. If a state equivalent to D
is already in the DFA, the existing state is returned. Otherwise this
method returns D after adding it to the DFA.
If D is ATNSimulator.ERROR, this method returns ATNSimulator.ERROR and
does not change the DFA.
dfa - The dfaD - The DFA state to addD is already in the DFA, or D itself if the
state was not already present.protected void reportAttemptingFullContext(DFA dfa, BitSet conflictingAlts, ATNConfigSet configs, int startIndex, int stopIndex)
protected void reportContextSensitivity(DFA dfa, int prediction, ATNConfigSet configs, int startIndex, int stopIndex)
protected void reportAmbiguity(DFA dfa, DFAState D, int startIndex, int stopIndex, boolean exact, BitSet ambigAlts, ATNConfigSet configs)
public final void setPredictionMode(PredictionMode mode)
public final PredictionMode getPredictionMode()
public Parser getParser()
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