internal LabelInfo(ILGen il, LabelTarget node, bool canReturn)
{
_ilg = il;
Node = node;
Label = il.DefineLabel();
_canReturn = canReturn;
if (node != null && node.Type != typeof(void))
{
Value = il.DeclareLocal(node.Type);
}
// Until we have more information, default to a leave instruction, which always works
_opCode = OpCodes.Leave;
}
// Returns true if the label was successfully defined
// or false if the label is now ambiguous
internal void Define(ILGen il, LabelBlockInfo block)
{
// Prevent the label from being shadowed, which enforces cleaner
// trees. Also we depend on this for simplicity (keeping only one
// active IL Label per LabelInfo)
for (LabelBlockInfo j = block; j != null; j = j.Parent)
{
if (j.ContainsTarget(Node))
{
throw Error.LabelTargetAlreadyDefined(Node.Name);
}
}
Definitions.Add(block);
block.AddLabelInfo(Node, this);
// Once defined, validate all jumps
if (Definitions.Count == 1)
{
foreach (var r in References)
{
ValidateJump(r);
}
}
else
{
// Was just redefined, if we had any across block jumps, they're
// now invalid
if (_acrossBlockJump)
{
throw Error.AmbiguousJump(Node.Name);
}
// For local jumps, we need a new IL label
// This is okay because:
// 1. no across block jumps have been made or will be made
// 2. we don't allow the label to be shadowed
Label = il.DefineLabel();
}
}
