-- ^ Used to create the view /Core/ has on 'TyCon's. We expand not only closed synonyms like 'tcExpandTyCon_maybe',
-- but also non-recursive @newtype@s
-coreExpandTyCon_maybe (AlgTyCon {algTcRec = NonRecursive, -- Not recursive
+coreExpandTyCon_maybe (AlgTyCon {
algTcRhs = NewTyCon { nt_etad_rhs = etad_rhs, nt_co = Nothing }}) tys
= case etad_rhs of -- Don't do this in the pattern match, lest we accidentally
-- match the etad_rhs of a *recursive* newtype