-- We don't have to do this for givens, as we fully know the evidence for them.
; rec_ev_ok <-
case (cc_flavor inert, cc_flavor workitem) of
- (Wanted loc, Derived {}) -> isGoodRecEv work_ev (WantedEvVar inert_ev loc)
- (Derived {}, Wanted loc) -> isGoodRecEv inert_ev (WantedEvVar work_ev loc)
- _ -> return True
+ (Wanted {}, Derived {}) -> isGoodRecEv work_ev inert_ev
+ (Derived {}, Wanted {}) -> isGoodRecEv inert_ev work_ev
+ _ -> return True
; if is_allowed && rec_ev_ok then
doInteractWithInert fdimprs inert workitem
\begin{code}
-isGoodRecEv :: EvVar -> WantedEvVar -> TcS Bool
+isGoodRecEv :: EvVar -> EvVar -> TcS Bool
-- In a call (isGoodRecEv ev wv), we are considering solving wv
-- using some term that involves ev, such as:
-- by setting wv = ev
-- call (constructor) and -1 for every superclass selection (destructor).
--
-- See Note [Superclasses and recursive dictionaries] in TcInteract
-isGoodRecEv ev_var (WantedEvVar wv _)
+isGoodRecEv ev_var wv
= do { tc_evbinds <- getTcEvBindsBag
; mb <- chase_ev_var tc_evbinds wv 0 [] ev_var
; return $ case mb of
| Just (EvBind _ ev_trm) <- lookupEvBind assocs orig
= chase_ev assocs trg curr_grav (orig:visited) ev_trm
-{- No longer needed: evidence is in the EvBinds
- | isTcTyVar orig && isMetaTyVar orig
- = do { meta_details <- wrapTcS $ TcM.readWantedCoVar orig
- ; case meta_details of
- Flexi -> return Nothing
- Indirect tyco -> chase_ev assocs trg curr_grav
- (orig:visited) (EvCoercion tyco)
- }
--}
- | otherwise = return Nothing
+ | otherwise = return Nothing
chase_ev assocs trg curr_grav visited (EvId v)
= chase_ev_var assocs trg curr_grav visited v