------------------------------
tcSuperClass :: [TyVar] -> [EvVar]
-> EvBind
- -> (Id, PredType) -> TcM (Id, LHsBind Id)
+ -> (Id, PredType) -> TcM (Id, LHsBind Id)
-- Build a top level decl like
-- sc_op = /\a \d. let this = ... in
-- let sc = ... in
-- The "this" part is just-in-case (discarded if not used)
-- See Note [Recursive superclasses]
tcSuperClass tyvars dicts
- self_ev_bind@(EvBind self_dict _)
- (sc_sel, sc_pred)
- = do { (ev_binds, wanted, sc_dict)
- <- newImplication InstSkol tyvars dicts $
- emitWanted ScOrigin sc_pred
-
- ; simplifySuperClass self_dict wanted
- -- We include self_dict in the 'givens'; the simplifier
- -- is clever enough to stop sc_pred geting bound by just
- -- selecting from self_dict!!
+ self_ev_bind
+ (sc_sel, sc_pred)
+ = do { sc_dict <- newWantedEvVar sc_pred
+ ; ev_binds <- simplifySuperClass tyvars dicts sc_dict self_ev_bind
; uniq <- newUnique
; let sc_op_ty = mkForAllTys tyvars $ mkPiTypes dicts (varType sc_dict)
, var_rhs = L noSrcSpan $ wrapId sc_wrapper sc_dict }
sc_wrapper = mkWpTyLams tyvars
<.> mkWpLams dicts
- <.> mkWpLet (EvBinds (unitBag self_ev_bind))
- <.> mkWpLet ev_binds
+ <.> mkWpLet ev_binds
; return (sc_op_id, noLoc sc_op_bind) }
\end{code}