make_coercion cls_tycon initial_cls_inst_tys nt_tycon tc_args
| Just co_con <- newTyConCo_maybe nt_tycon
, let co = mkSymCoercion (mkTyConApp co_con tc_args)
- = WpCo (mkTyConApp cls_tycon (initial_cls_inst_tys ++ [co]))
+ = WpCast (mkTyConApp cls_tycon (initial_cls_inst_tys ++ [co]))
| otherwise -- The newtype is transparent; no need for a cast
= idHsWrapper