+ ; showLIE (text "instance")
+ ; case newTyConCo_maybe (classTyCon clas) of
+ Nothing -- A multi-method class
+ -> return (unitBag (L loc data_bind) `unionBags` arg_binds)
+ where
+ data_dfun_id = dfun_id -- Do not inline; instead give it a magic DFunFunfolding
+ -- See Note [ClassOp/DFun selection]
+ `setIdUnfolding` mkDFunUnfolding dict_constr arg_ids
+ `setInlinePragma` dfunInlinePragma
+
+ data_bind = AbsBinds inst_tyvars' dfun_lam_vars
+ [(inst_tyvars', data_dfun_id, this_dict_id, spec_inst_prags)]
+ (unitBag dict_bind)
+
+ dict_bind = mkVarBind this_dict_id dict_rhs
+ dict_rhs = foldl mk_app inst_constr arg_ids
+ dict_constr = classDataCon clas
+ inst_constr = L loc $ wrapId (mkWpTyApps inst_tys')
+ (dataConWrapId dict_constr)
+ -- We don't produce a binding for the dict_constr; instead we
+ -- rely on the simplifier to unfold this saturated application
+ -- We do this rather than generate an HsCon directly, because
+ -- it means that the special cases (e.g. dictionary with only one
+ -- member) are dealt with by the common MkId.mkDataConWrapId code rather
+ -- than needing to be repeated here.
+
+ mk_app :: LHsExpr Id -> Id -> LHsExpr Id
+ mk_app fun arg_id = L loc (HsApp fun (L loc (wrapId arg_wrapper arg_id)))
+ arg_wrapper = mkWpApps dfun_lam_vars <.> mkWpTyApps (mkTyVarTys inst_tyvars')
+
+ Just the_nt_co -- (Just co) for a single-method class
+ -> return (unitBag (L loc nt_bind) `unionBags` arg_binds)
+ where
+ nt_dfun_id = dfun_id -- Just let the dfun inline; see Note [Single-method classes]
+ `setInlinePragma` alwaysInlinePragma
+
+ local_nt_dfun = setIdType this_dict_id inst_ty -- A bit of a hack, but convenient
+
+ nt_bind = AbsBinds [] []
+ [([], nt_dfun_id, local_nt_dfun, spec_inst_prags)]
+ (unitBag (mkVarBind local_nt_dfun (L loc (wrapId nt_cast the_meth_id))))
+
+ the_meth_id = ASSERT( length arg_ids == 1 ) head arg_ids
+ nt_cast = WpCast $ mkPiTypes (inst_tyvars' ++ dfun_lam_vars) $
+ mkSymCoercion (mkTyConApp the_nt_co inst_tys')
+-}