private ParserNode CreateNode(ParserContext context)
{
var node = new ParserNode(context, Reduction.Product);
node.Children.AddRange(PopChildren(context).Reverse());
node.EnsureResultComputed();
return node;
}
public ParseResult Parse(Lexer lexer, ParserState initialState)
{
var context = new ParserContext(this, Automaton.Grammar, lexer);
context.CurrentState = initialState;
context.ParserStack.Push(new ParserNode(context, new GrammarDefinition("init"))
{
State = initialState
});
ReadNextToken(context);
context.CurrentNode = new ParserNode(context, Automaton.Grammar.ToElement(lexer.Current.GetTokenCode()), lexer.Current);
while (lexer.Current != null && context.Root == null && context.CurrentState != null)
{
// If no input and no default action (e.g. a grammar reduction),
// that means we have to read the next token.
if (context.CurrentNode == null && context.CurrentState.DefaultAction == null)
ReadNextToken(context);
var action = GetNextAction(context);
action.Execute(context);
}
lexer.SpecialBag.InsertNodesIntoAstNode(context.Root.Result);
return ParseResult.FromContext(context);
}
public override void Execute(ParserContext context)
{
context.SendLogMessage(MessageSeverity.Message, ToString());
CustomAction?.Invoke(context);
context.ParserStack.Push(context.CurrentNode);
context.CurrentState = context.CurrentNode.State = NextState;
context.CurrentNode = null;
}
public override void Execute(ParserContext context)
{
context.SendLogMessage(MessageSeverity.Message, ToString());
context.Root = context.ParserStack.Pop();
context.CurrentNode = null;
context.CurrentState = context.ParserStack.Peek().State;
}
public override void Execute(ParserContext context)
{
ReportSyntaxError(context);
if (!TryRecover(context))
{
context.SendLogMessage(MessageSeverity.Error, "Failed to recover from syntax error.");
context.CurrentState = null;
}
}
private static void ReportSyntaxError(ParserContext context)
{
var expectedTokens = context.CurrentState.Actions.Keys.OfType<TokenGrammarElement>().ToArray();
var node = context.CurrentNode;
var message = string.Format("Unexpected {0} token. Expected {1}.",
node.GrammarElement.Name,
string.Join(" or ", expectedTokens.Select(x => x.Name)));
context.SyntaxErrors.Add(new SyntaxError(node.Result.Range.Start, message, MessageSeverity.Error));
context.SendLogMessage(MessageSeverity.Error, message);
}
public override void Execute(ParserContext context)
{
context.SendLogMessage(MessageSeverity.Message, ToString());
var temp = context.CurrentNode;
var node = context.CurrentNode = CreateNode(context);
context.CurrentState = context.ParserStack.Peek().State;
var action = context.CurrentState.Actions[node.GrammarElement];
action.Execute(context);
context.CurrentNode = temp;
}
public ParserAction GetNextAction(ParserContext context)
{
if (context.CurrentState.DefaultAction != null)
return context.CurrentState.DefaultAction;
ParserAction parserAction;
if (!context.CurrentState.Actions.TryGetValue(context.CurrentNode.GrammarElement, out parserAction))
{
// Unexpected token or grammar pattern. Try to recover.
return ErrorParserAction.Instance;
}
return parserAction;
}
private static ShiftParserAction PopToErrorShifter(ParserContext context)
{
ParserAction action = null;
while (context.ParserStack.Any())
{
var state = context.ParserStack.Peek().State;
context.SendLogMessage(MessageSeverity.Message, "Going back to state " + state.Id + ".");
state.Actions.TryGetValue(Grammar.Error, out action);
if (action is ShiftParserAction)
break;
context.ParserStack.Pop();
}
return action as ShiftParserAction;
}
private static bool TryRecover(ParserContext context)
{
// Find shifter for error token, or fail recovery.
var errorShifter = PopToErrorShifter(context);
if (errorShifter == null)
return false;
// Execute shift.
var currentNode = context.CurrentNode;
context.CurrentNode = new ParserNode(context, Grammar.Error);
errorShifter.Execute(context);
context.CurrentNode = currentNode;
while (true)
{
if (context.CurrentNode == null && context.CurrentState.DefaultAction == null)
context.Parser.ReadNextToken(context);
var action = context.Parser.GetNextAction(context);
// Discard tokens until legal action can be made.
if (action is ErrorParserAction)
{
if (context.CurrentNode.GrammarElement == Grammar.Eof)
return false;
context.Parser.ReadNextToken(context);
}
else
{
action.Execute(context);
}
// If we found a synchronize token (i.e. a reduction with an error token), we have recovered.
if (action is ReduceParserAction)
return true;
}
}
private void WarningEmptyStatement(ParserContext context, TextLocation location)
{
context.SyntaxErrors.Add(new SyntaxError(location,
"Possible mistaken empty statement.",
MessageSeverity.Warning));
}
public abstract void Execute(ParserContext context);
public static ParseResult FromContext(ParserContext context)
{
return new ParseResult(context.Root, context.SyntaxErrors);
}
private IEnumerable<ParserNode> PopChildren(ParserContext context)
{
var childCount = Reduction.Sequence.Count;
for (int i = 0; i < childCount; i++)
yield return context.ParserStack.Pop();
}
internal void SendLogMessage(ParserContext parserContext, MessageSeverity severity, string message)
{
if (EnableLogging)
LogMessageReceived?.Invoke(this, new SourceParserLogEventArgs(parserContext, severity, message));
}
public void ReadNextToken(ParserContext context)
{
context.SendLogMessage(MessageSeverity.Message, "Read next token.");
var lexer = context.Lexer;
lexer.Advance();
context.CurrentNode = new ParserNode(context, Automaton.Grammar.ToElement(lexer.Current.GetTokenCode()), lexer.Current);
}
public SourceParserLogEventArgs(ParserContext parserContext, MessageSeverity messageSeverity, string message)
{
ParserContext = parserContext;
MessageSeverity = messageSeverity;
Message = message;
}