// see comment about expecteds in ParseState.Error.cs
internal sealed override bool TryParse(ref ParseState <TToken> state, ref ExpectedCollector <TToken> expecteds, out T result)
{
var firstTime = true;
var err = new InternalError <TToken>(
Maybe.Nothing <TToken>(),
false,
state.Location,
"OneOf had no arguments"
);
var childExpecteds = new ExpectedCollector <TToken>(); // the expecteds for all loop iterations
var grandchildExpecteds = new ExpectedCollector <TToken>(); // the expecteds for the current loop iteration
foreach (var p in _parsers)
{
var thisStartLoc = state.Location;
var success = p.TryParse(ref state, ref grandchildExpecteds, out result);
if (success)
{
// throw out all expecteds
grandchildExpecteds.Dispose();
childExpecteds.Dispose();
return(true);
}
// we'll usually return the error from the first parser that didn't backtrack,
// even if other parsers had a longer match.
// There is some room for improvement here.
if (state.Location > thisStartLoc)
{
// throw out all expecteds except this one
expecteds.Add(ref grandchildExpecteds);
childExpecteds.Dispose();
grandchildExpecteds.Dispose();
result = default;
return(false);
}
childExpecteds.Add(ref grandchildExpecteds);
grandchildExpecteds.Clear();
// choose the longest match, preferring the left-most error in a tie,
// except the first time (avoid returning "OneOf had no arguments").
if (firstTime || state.Error.ErrorLocation > err.ErrorLocation)
{
err = state.Error;
}
firstTime = false;
}
state.Error = err;
expecteds.Add(ref childExpecteds);
childExpecteds.Dispose();
grandchildExpecteds.Dispose();
result = default;
return(false);
}
// see comment about expecteds in ParseState.Error.cs
internal sealed override InternalResult <T> Parse(ref ParseState <TToken> state)
{
var firstTime = true;
var err = new InternalError <TToken>(
Maybe.Nothing <TToken>(),
false,
state.Location,
"OneOf had no arguments"
);
state.BeginExpectedTran();
foreach (var p in _parsers)
{
state.BeginExpectedTran();
var thisResult = p.Parse(ref state);
if (thisResult.Success)
{
// throw out all expecteds
state.EndExpectedTran(false);
state.EndExpectedTran(false);
return(thisResult);
}
// we'll usually return the error from the first parser that didn't backtrack,
// even if other parsers had a longer match.
// There is some room for improvement here.
if (thisResult.ConsumedInput)
{
// throw out all expecteds except this one
var expected = state.ExpectedTranState();
state.EndExpectedTran(false);
state.EndExpectedTran(false);
state.AddExpected(expected.AsSpan());
expected.Dispose(clearArray: true);
return(thisResult);
}
state.EndExpectedTran(true);
// choose the longest match, preferring the left-most error in a tie,
// except the first time (avoid returning "OneOf had no arguments").
if (firstTime || state.Error.ErrorLocation > err.ErrorLocation)
{
err = state.Error;
}
firstTime = false;
}
state.Error = err;
state.EndExpectedTran(true);
return(InternalResult.Failure <T>(false));
}
