private void PerformPanicRecovery(Lexeme z, List <ParserHead> shiftedHeads)
{
//Panic recovery
//to the 1st head:
//pop stack until there's a state S, which has a Goto action of a non-terminal A
//discard input until there's an token a in Follow(A)
//push Goto(s, A) into stack
//discard all other heads
m_heads.Clear();
m_heads.AddRange(shiftedHeads.Where(h => h.ErrorRecoverLevel == 0));
shiftedHeads.Clear();
ParserHead errorHead1 = m_errorCandidates[0];
m_errorCandidates.Clear();
IProduction p = errorHead1.PanicRecover(m_transitions, z.Value.Span, z.IsEndOfStream);
ProductionBase productionBase = p as ProductionBase;
if (productionBase != null)
{
var follow = productionBase.Info.Follow;
m_heads.Add(errorHead1);
throw new PanicRecoverException(follow);
}
}
public static bool ShareSameParent(ParserHead h1, ParserHead h2)
{
var prev1 = h1.m_topStack.PrevNode;
var prev2 = h2.m_topStack.PrevNode;
if (prev1 != null && prev2 != null && ReferenceEquals(prev1, prev2))
{
return(true);
}
return(false);
}
public bool HasSameErrorsWith(ParserHead other)
{
if (other.m_errors == null && m_errors == null)
{
return(true);
}
if (other.m_errors == null || m_errors == null)
{
return(false);
}
HashSet <ErrorRecord> myErrors = new HashSet <ErrorRecord>(m_errors);
HashSet <ErrorRecord> otherErrors = new HashSet <ErrorRecord>(other.m_errors);
return(myErrors.SetEquals(otherErrors));
}
private void PerformPanicRecovery(Lexeme z, List <ParserHead> shiftedHeads)
{
//Panic recovery
//to the 1st head:
//pop stack until there's a state S, which has a Goto action of a non-terminal A
//discard input until there's an token a in Follow(A)
//push Goto(s, A) into stack
//discard all other heads
m_heads.Clear();
m_heads.AddRange(shiftedHeads.Where(h => h.ErrorRecoverLevel == 0));
shiftedHeads.Clear();
ParserHead errorHead1 = m_errorCandidates[0];
m_errorCandidates.Clear();
var candidates = errorHead1.PanicRecover(m_transitions, z.Value.Span, z.IsEndOfStream);
ISet <IProduction> follows = new HashSet <IProduction>();
foreach (var candidate in candidates)
{
ProductionBase p = candidate.Item2 as ProductionBase;
follows.UnionWith(p.Info.Follow);
m_heads.Add(candidate.Item1);
}
if (m_heads.Count > 0)
{
throw new PanicRecoverException(follows);
}
else
{
throw new ParsingFailureException("There's no way to recover from parser error");
}
}
private void ReduceAndShiftForRecovery(Lexeme z, ParserHead head, IList<ParserHead> shiftTarget, int syntaxError, CancellationToken ctoken)
{
Queue<ParserHead> recoverQueue = new Queue<ParserHead>();
for (int j = 0; j < m_transitions.TokenCount - 1; j++)
{
recoverQueue.Enqueue(head);
while (recoverQueue.Count > 0)
{
var recoverHead = recoverQueue.Dequeue();
int recoverStateNumber = recoverHead.TopStackStateIndex;
var shiftLexer = m_transitions.GetLexersInShifting(recoverStateNumber);
var recoverShifts = m_transitions.GetShift(recoverStateNumber, j);
var recoverShift = recoverShifts;
while (recoverShift != null)
{
ctoken.ThrowIfCancellationRequested();
var insertHead = recoverHead.Clone();
var insertLexeme = z.GetErrorCorrectionLexeme(j, m_transitions.GetTokenDescription(j));
insertHead.Shift(insertLexeme, recoverShift.Value);
insertHead.IncreaseErrorRecoverLevel();
insertHead.AddError(new ErrorRecord(syntaxError, z.Value.Span)
{
ErrorArgument = insertLexeme.Value,
ErrorArgument2 = z.Value
});
shiftTarget.Add(insertHead);
recoverShift = recoverShift.GetNext();
}
var reduceLexer = m_transitions.GetLexersInReducing(recoverStateNumber);
var recoverReduces = m_transitions.GetReduce(recoverStateNumber, j);
var recoverReduce = recoverReduces;
while (recoverReduce != null)
{
ctoken.ThrowIfCancellationRequested();
int productionIndex = recoverReduce.Value;
IProduction production = m_transitions.NonTerminals[productionIndex];
var reducedHead = recoverHead.Clone();
reducedHead.Reduce(production, m_reducer, z);
//add back to queue, until shifted
m_recoverReducedHeads.Add(reducedHead);
//get next reduce
recoverReduce = recoverReduce.GetNext();
}
if (m_recoverReducedHeads.Count > 0)
{
m_tempHeads.Clear();
m_cleaner.CleanHeads(m_recoverReducedHeads, m_tempHeads);
m_recoverReducedHeads.Clear();
foreach (var recoveredHead in m_tempHeads)
{
recoverQueue.Enqueue(recoveredHead);
}
}
}
}
}
public bool HasSameErrorsWith(ParserHead other)
{
if (other.m_errors == null && m_errors == null)
{
return true;
}
if (other.m_errors == null || m_errors == null)
{
return false;
}
HashSet<ErrorRecord> myErrors = new HashSet<ErrorRecord>(m_errors);
HashSet<ErrorRecord> otherErrors = new HashSet<ErrorRecord>(other.m_errors);
return myErrors.SetEquals(otherErrors);
}
public static bool ShareSameParent(ParserHead h1, ParserHead h2)
{
var prev1 = h1.m_topStack.PrevNode;
var prev2 = h2.m_topStack.PrevNode;
if (prev1 != null && prev2 != null && ReferenceEquals(prev1, prev2))
{
return true;
}
return false;
}
private void ReduceAndShiftForRecovery(Lexeme z, ParserHead head, IList <ParserHead> shiftTarget, int syntaxError, CancellationToken ctoken)
{
Queue <ParserHead> recoverQueue = new Queue <ParserHead>();
for (int j = 0; j < m_transitions.TokenCount - 1; j++)
{
recoverQueue.Enqueue(head);
while (recoverQueue.Count > 0)
{
var recoverHead = recoverQueue.Dequeue();
int recoverStateNumber = recoverHead.TopStackStateIndex;
var shiftLexer = m_transitions.GetLexersInShifting(recoverStateNumber);
var recoverShifts = m_transitions.GetShift(recoverStateNumber, j);
var recoverShift = recoverShifts;
while (recoverShift != null)
{
ctoken.ThrowIfCancellationRequested();
var insertHead = recoverHead.Clone();
var insertLexeme = z.GetErrorCorrectionLexeme(j, m_transitions.GetTokenDescription(j));
insertHead.Shift(insertLexeme, recoverShift.Value);
insertHead.IncreaseErrorRecoverLevel();
insertHead.AddError(new ErrorRecord(syntaxError, z.Value.Span)
{
ErrorArgument = insertLexeme.Value,
ErrorArgument2 = z.Value
});
shiftTarget.Add(insertHead);
recoverShift = recoverShift.GetNext();
}
var reduceLexer = m_transitions.GetLexersInReducing(recoverStateNumber);
var recoverReduces = m_transitions.GetReduce(recoverStateNumber, j);
var recoverReduce = recoverReduces;
while (recoverReduce != null)
{
ctoken.ThrowIfCancellationRequested();
int productionIndex = recoverReduce.Value;
IProduction production = m_transitions.NonTerminals[productionIndex];
var reducedHead = recoverHead.Clone();
reducedHead.Reduce(production, m_reducer, z);
//add back to queue, until shifted
m_recoverReducedHeads.Add(reducedHead);
//get next reduce
recoverReduce = recoverReduce.GetNext();
}
if (m_recoverReducedHeads.Count > 0)
{
m_tempHeads.Clear();
m_cleaner.CleanHeads(m_recoverReducedHeads, m_tempHeads);
m_recoverReducedHeads.Clear();
foreach (var recoveredHead in m_tempHeads)
{
recoverQueue.Enqueue(recoveredHead);
}
}
}
}
}
public void CleanHeads(IList <ParserHead> sourceHeads, IList <ParserHead> targetHeads)
{
int minErrorLevel = sourceHeads[0].ErrorRecoverLevel;
//int minErrorCount = sourceHeads[0].Errors != null ? sourceHeads[0].Errors.Count : 0;
for (int i = 0; i < sourceHeads.Count; i++)
{
var head = sourceHeads[i];
var errorLevel = head.ErrorRecoverLevel;
if (errorLevel < minErrorLevel)
{
minErrorLevel = errorLevel;
}
//var errorCount = head.Errors != null ? head.Errors.Count : 0;
//if (errorCount < minErrorCount)
//{
// minErrorCount = errorCount;
//}
}
foreach (var head in sourceHeads)
{
if (head.ErrorRecoverLevel > minErrorLevel)
{
//discard heads with higher error level
continue;
}
//var errorCount = head.Errors != null ? head.Errors.Count : 0;
//if (errorCount > minErrorCount)
//{
// //discard heads with more errors
// continue;
//}
if (head.AmbiguityAggregator == null)
{
targetHeads.Add(head);
continue;
}
//aggregate ambiguities
bool isAggregated = false;
foreach (var ambhead in m_aggregatingHeads)
{
if (ambhead.TopStackStateIndex == head.TopStackStateIndex &&
ambhead.AmbiguityAggregator.ProductionIndex == head.AmbiguityAggregator.ProductionIndex &&
ParserHead.ShareSameParent(ambhead, head))
{
var aggregator = ambhead.AmbiguityAggregator;
//if the head have different errors, they are probably came from error recovery
//in this case, the aggregation just keep the first one and discard others
//this way won't increase the total amount of errors
if (ambhead.HasSameErrorsWith(head))
{
//update aggregate value
ambhead.TopStackValue = aggregator.Aggregate(ambhead.TopStackValue, head.TopStackValue);
}
//discard he aggregated head
isAggregated = true;
break;
}
}
if (!isAggregated)
{
m_aggregatingHeads.Add(head);
targetHeads.Add(head);
}
}
foreach (var aggHead in m_aggregatingHeads)
{
aggHead.AmbiguityAggregator = null;
}
m_aggregatingHeads.Clear();
}
private void RecoverError(Lexeme z)
{
List <ParserHead> shiftedHeads = m_shiftedHeads;
m_heads.Clear();
int errorHeadCount = m_errorCandidates.Count;
Debug.Assert(errorHeadCount > 0);
if (errorHeadCount > c_panicRecoveryThreshold)
{
//Panic recovery
//to the 1st head:
//pop stack until there's a state S, which has a Goto action of a non-terminal A
//discard input until there's an token a in Follow(A)
//push Goto(s, A) into stack
//discard all other heads
m_heads.Clear();
m_heads.AddRange(shiftedHeads.Where(h => h.ErrorRecoverLevel == 0));
shiftedHeads.Clear();
ParserHead errorHead1 = m_errorCandidates[0];
m_errorCandidates.Clear();
IProduction p = errorHead1.PanicRecover(m_transitions, z.Value.Span);
var follow = (p as ProductionBase).Info.Follow;
m_heads.Add(errorHead1);
throw new PanicRecoverException(follow);
}
for (int i = 0; i < errorHeadCount; i++)
{
var head = m_errorCandidates[i];
if (!z.IsEndOfStream)
{
//option 1: remove
//remove current token and continue
var deleteHead = head.Clone();
deleteHead.IncreaseErrorRecoverLevel();
deleteHead.AddError(new ErrorRecord(m_errorDef.TokenUnexpectedId, z.Value.Span)
{
ErrorArgument = z.Value
});
shiftedHeads.Add(deleteHead);
//option 2: replace
//replace the current input char with all possible shifts token and continue
ReduceAndShiftForRecovery(z, head, shiftedHeads, m_errorDef.TokenMistakeId);
}
//option 3: insert
//insert all possible shifts token and continue
ReduceAndShiftForRecovery(z, head, m_heads, m_errorDef.TokenMissingId);
}
}
