public override Parse <TFuture> BuildParse <TFuture>(Future <string, TFuture> future)
{
Parse <TFuture> parse = null;
parse = scanner =>
{
// 保存读取当前单词之前的位置
ForkableScanner prevScanner = scanner.Fork();
Lexeme l = scanner.Read();
if (l.TokenIndex == m_token.Index)
{
return(new StepResult <TFuture>(0, () => future(l.Value.Content)(scanner)));
}
Lexeme recovery = l.GetErrorCorrectionLexeme(m_token.Index, m_token.Description);
SyntaxError insertionErr = Grammar.RecoverByInsertion(recovery);
if (l.IsEndOfStream)
{
// 已经到了输入的末尾
// 插入预期的Token进行恢复
return(new StepResult <TFuture>(1,
() => future(recovery.Value.Content)(prevScanner), insertionErr));
}
else
{
// 同时尝试插入预期的Token，以及删除当前字符
// 在未来的解析中选取更好的路线
return(Grammar.Best(
new StepResult <TFuture>(1, () => future(recovery.Value.Content)(prevScanner), insertionErr),
new StepResult <TFuture>(1, () => parse(scanner), Grammar.RecoverByDeletion(l))));
}
};
return(parse);
}
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);
}
}
}
}
}
private void RecoverError(Lexeme z)
{
List <ParserHead> shiftedHeads = m_shiftedHeads;
m_heads.Clear();
int errorHeadCount = m_errorCandidates.Count;
Debug.Assert(errorHeadCount > 0);
for (int i = 0; i < errorHeadCount; i++)
{
var head = m_errorCandidates[i];
//option 1: remove
//remove current token and continue
if (!z.IsEndOfStream)
{
var deleteHead = head.Clone();
deleteHead.IncreaseErrorRecoverLevel();
deleteHead.AddError(new ErrorRecord(m_errorDef.TokenUnexpectedId, z.Value.Span)
{
ErrorArgument = z.Value
});
shiftedHeads.Add(deleteHead);
}
//option 2: insert
//insert all possible shifts token and continue
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);
int tokenIndex;
if (shiftLexer == null)
{
tokenIndex = z.TokenIndex;
}
else
{
tokenIndex = z.GetTokenIndex(shiftLexer.Value);
}
var recoverShifts = m_transitions.GetShift(recoverStateNumber, j);
var recoverShift = recoverShifts;
while (recoverShift != null)
{
var insertHead = recoverHead.Clone();
var insertLexeme = z.GetErrorCorrectionLexeme(j, m_transitions.GetTokenDescription(j));
insertHead.Shift(insertLexeme, recoverShift.Value);
insertHead.IncreaseErrorRecoverLevel();
insertHead.AddError(new ErrorRecord(m_errorDef.TokenMissingId, z.Value.Span)
{
ErrorArgument = insertLexeme.Value
});
m_heads.Add(insertHead);
recoverShift = recoverShift.GetNext();
}
var reduceLexer = m_transitions.GetLexersInReducing(recoverStateNumber);
if (reduceLexer == null)
{
tokenIndex = z.TokenIndex;
}
else
{
tokenIndex = z.GetTokenIndex(reduceLexer.Value);
}
var recoverReduces = m_transitions.GetReduce(recoverStateNumber, j);
var recoverReduce = recoverReduces;
while (recoverReduce != null)
{
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);
}
}
}
}
}
}
