private static bool CheckFieldName(IFieldSymbol fieldSymbol) { if (!fieldSymbol.ContainingType.IsTupleType()) { return(false); } // check if this already is a proper tuple field name if (!Equals(fieldSymbol.CorrespondingTupleField(), fieldSymbol)) { return(false); } // check if there is a tuple field name declared. return(fieldSymbol.ContainingType.GetMembers().OfType <IFieldSymbol>().Count(fs => Equals(fs.CorrespondingTupleField(), fieldSymbol)) > 1); }