private string ComputeRecursiveExitLabel(LabelGroupData data, string label)
{
var labelData = data[label];
var recursiveExit = labelData.DirectExitLabel;
if (recursiveExit == null)
{
return(null);
}
while (recursiveExit != null)
{
LabelGroupLabelData targetLabelData;
if (!data.TryGetValue(recursiveExit, out targetLabelData))
{
// The label is part of another label group.
return(null);
}
if (targetLabelData.DirectExitLabel == null)
{
if (
(targetLabelData.ExitTargetLabels.Count == 0) /* &&
* FIXME: Is this right?
* (targetLabelData.UntargettedExitCount <= 1) */
)
{
return(recursiveExit);
}
else
{
return(null);
}
}
else
{
// Cycle detected
if (recursiveExit == targetLabelData.DirectExitLabel)
{
return(null);
}
recursiveExit = targetLabelData.DirectExitLabel;
}
// Cycle detected
if (recursiveExit == label)
{
return(null);
}
}
return(null);
}
public void VisitNode(JSLabelGroupStatement lgs)
{
CheckForFallthrough(lgs);
var data = new LabelGroupData();
LabelGroupStack.Push(data);
foreach (var key in lgs.Labels.Keys)
{
data.Add(key.Value, new LabelGroupLabelData());
}
VisitChildren(lgs);
// Scan all the labels to determine their direct exit label, if any
foreach (var kvp in data)
{
var targetLabels = kvp.Value.ExitTargetLabels.Distinct().ToArray();
if (
(targetLabels.Length == 1) &&
(kvp.Value.UntargettedExitCount == 0)
)
{
kvp.Value.DirectExitLabel = targetLabels[0];
}
else
{
kvp.Value.DirectExitLabel = null;
}
}
// Scan all the labels again to determine their recursive exit label
foreach (var kvp in data)
{
var rel = kvp.Value.RecursiveExitLabel = ComputeRecursiveExitLabel(data, kvp.Key);
if (rel != null)
{
data[rel].TimesUsedAsRecursiveExitTarget += 1;
}
}
// If we have one label that is the recursive exit target for all other labels, we can turn it into the exit label
var recursiveExitTargets = data.Where(
(kvp) => kvp.Value.TimesUsedAsRecursiveExitTarget > 0
).ToArray();
if (recursiveExitTargets.Length == 1)
{
var onlyRecursiveExitTarget = recursiveExitTargets[0].Key;
var exitLabel = lgs.ExitLabel;
var newExitLabel = lgs.Labels[onlyRecursiveExitTarget];
var newExitLabelData = data[newExitLabel.Label];
if (
(newExitLabelData.ExitTargetLabels.Count == 0) &&
(newExitLabelData.UntargettedExitCount == 0) &&
(newExitLabel != lgs.Labels.LastOrDefault().Value)
)
{
if (TraceLevel >= 1)
{
Console.WriteLine("// Cannot mark label '{0}' as exit label because it falls through and is not the last label", onlyRecursiveExitTarget);
}
}
else if (exitLabel != null)
{
if (exitLabel != newExitLabel)
{
if (TraceLevel >= 1)
{
Console.WriteLine("// Cannot mark label '{0}' as exit label because this labelgroup already has one", onlyRecursiveExitTarget);
}
}
}
else
{
if (TraceLevel >= 1)
{
Console.WriteLine("// Marking label '{0}' as exit label", onlyRecursiveExitTarget);
}
lgs.ExitLabel = newExitLabel;
MadeChanges = true;
}
}
if ((lgs.ExitLabel != null) && (lgs.Labels.Count > 1))
{
ExtractExitLabel(lgs);
}
LabelGroupStack.Pop();
}
