protected override void GenerateFields()
{
// Add a field: T current
currentField = F.SynthesizeField(elementType, GeneratedNames.MakeIteratorCurrentBackingFieldName());
// if it is an iterable, add a field: int initialThreadId
var threadType = F.Compilation.GetWellKnownType(WellKnownType.System_Threading_Thread);
initialThreadIdField = isEnumerable && (object)threadType != null && !threadType.IsErrorType()
? F.SynthesizeField(F.SpecialType(SpecialType.System_Int32), GeneratedNames.MakeIteratorCurrentThreadIdName())
: null;
}