DataConWorkId dc -> get_main_name (ATyCon (dataConTyCon dc))
DataConWrapId dc -> get_main_name (ATyCon (dataConTyCon dc))
RecordSelId lbl -> get_main_name (ATyCon (fieldLabelTyCon lbl))
+ GenericOpId tc -> get_main_name (ATyCon tc)
+ ClassOpId cl -> className cl
other -> idName id