void FindStartEndPos(out int? startPos, out int? endPos)
{
startPos = null;
endPos = null;
for (var i = this.programCounter; i >= 0; i--) {
var instruction = this.bytecode [i];
if (instruction.StartPos != null && instruction.EndPos != null) {
startPos = instruction.StartPos;
endPos = instruction.EndPos;
return;
}
}
}