isSingleton orig_arg_tys )
-- No existentials on a newtype, but it can have a context
-- e.g. newtype Eq a => T a = MkT (...)
- mkTopUnfolding $ Note InlineMe $
+ mkCompulsoryUnfolding $
mkLams tyvars $ Lam id_arg1 $
mkNewTypeBody tycon result_ty (Var id_arg1)