-- standard
import Data.List
-import Control.Monad (liftM)
+import Control.Monad
\end{code}
}
tcGenericNormaliseFamInst fun (NoteTy note ty1)
= do { (coi,nty1) <- tcGenericNormaliseFamInst fun ty1
- ; return (mkNoteTyCoI note coi, NoteTy note nty1)
+ ; return (coi, NoteTy note nty1)
}
tcGenericNormaliseFamInst fun ty@(TyVarTy tv)
| isTcTyVar tv
-- Fals <=> they are given
-> TcM ([Inst],TcDictBinds)
normalise_dicts given_eqs dicts is_wanted
- = do { traceTc $ text "normalise???Dicts <-" <+> ppr dicts <+>
+ = do { traceTc $ let name | is_wanted = "normaliseWantedDicts <-"
+ | otherwise = "normaliseGivenDicts <-"
+ in
+ text name <+> ppr dicts <+>
text "with" <+> ppr given_eqs
; (dicts0, binds0) <- normaliseInsts is_wanted dicts
- ; (dicts1, binds1) <- substEqInDictInsts given_eqs dicts0
+ ; (dicts1, binds1) <- substEqInDictInsts is_wanted given_eqs dicts0
; let binds01 = binds0 `unionBags` binds1
; if isEmptyBag binds1
then return (dicts1, binds01)
- else do { (dicts2, binds2) <- normaliseGivenDicts given_eqs dicts1
+ else do { (dicts2, binds2) <-
+ normalise_dicts given_eqs dicts1 is_wanted
; return (dicts2, binds01 `unionBags` binds2) } }
\end{code}
\begin{code}
trivialRule :: IdemRewriteRule
trivialRule insts
- = liftM catMaybes $ mappM trivial insts
+ = liftM catMaybes $ mapM trivial insts
where
trivial inst
| ASSERT( isEqInst inst )
uMeta _swapped _tv (IndirectTv _) _ty _cotv
= return ([inst], False)
- -- signature skolem meets non-variable type
- -- => cannot update!
- uMeta _swapped _tv (DoneTv (MetaTv (SigTv _) _)) ty _cotv
- | not $ isTyVarTy ty
- = return ([inst], False)
-
-- type variable meets type variable
-- => check that tv2 hasn't been updated yet and choose which to update
uMeta swapped tv1 (DoneTv details1) (TyVarTy tv2) cotv
+ | tv1 == tv2
+ = return ([inst], False) -- The two types are already identical
+
+ | otherwise
= do { lookupTV2 <- lookupTcTyVar tv2
; case lookupTV2 of
- IndirectTv ty -> uMeta swapped tv1 (DoneTv details1) ty cotv
- DoneTv details2 ->
- uMetaVar swapped tv1 details1 tv2 details2 cotv
+ IndirectTv ty -> uMeta swapped tv1 (DoneTv details1) ty cotv
+ DoneTv details2 -> uMetaVar swapped tv1 details1 tv2 details2 cotv
}
+ ------ Beyond this point we know that ty2 is not a type variable
+
+ -- signature skolem meets non-variable type
+ -- => cannot update!
+ uMeta _swapped _tv (DoneTv (MetaTv (SigTv _) _)) _non_tv_ty _cotv
+ = return ([inst], False)
+
-- updatable meta variable meets non-variable type
-- => occurs check, monotype check, and kinds match check, then update
- uMeta swapped tv (DoneTv (MetaTv _ ref)) ty cotv
- = do { mb_ty' <- checkTauTvUpdate tv ty -- occurs + monotype check
+ uMeta swapped tv (DoneTv (MetaTv _ ref)) non_tv_ty cotv
+ = do { mb_ty' <- checkTauTvUpdate tv non_tv_ty -- occurs + monotype check
; case mb_ty' of
Nothing -> return ([inst], False) -- tv occurs in faminst
Just ty' ->
uMeta _ _ _ _ _ = panic "uMeta"
+ -- uMetaVar: unify two type variables
-- meta variable meets skolem
-- => just update
uMetaVar swapped tv1 (MetaTv _ ref) tv2 (SkolemTv _) cotv
where F is a type family.
\begin{code}
-substEqInDictInsts :: [Inst] -- given equalities (used as rewrite rules)
+substEqInDictInsts :: Bool -- whether the *dictionaries* are wanted/given
+ -> [Inst] -- given equalities (used as rewrite rules)
-> [Inst] -- dictinaries to be normalised
-> TcM ([Inst], TcDictBinds)
-substEqInDictInsts eqInsts dictInsts
+substEqInDictInsts isWanted eqInsts dictInsts
= do { traceTc (text "substEqInDictInst <-" <+> ppr dictInsts)
; dictInsts' <-
foldlM rewriteWithOneEquality (dictInsts, emptyBag) eqInsts
tci_right = target})
| isOpenSynTyConApp pattern || isTyVarTy pattern
= do { (dictInsts', moreDictBinds) <-
- genericNormaliseInsts True {- wanted -} applyThisEq dictInsts
+ genericNormaliseInsts isWanted applyThisEq dictInsts
; return (dictInsts', dictBinds `unionBags` moreDictBinds)
}
where
rhs = L (instLocSpan loc) cast_expr
binds = instToDictBind target_dict rhs
-- return the new inst
- ; traceTc $ text "genericNormaliseInst ->" <+> ppr dict'
+ ; traceTc $ let name | isWanted
+ = "genericNormaliseInst (wanted) ->"
+ | otherwise
+ = "genericNormaliseInst (given) ->"
+ in
+ text name <+> ppr dict' <+>
+ text "with" <+> ppr binds
; return (dict', binds)
}
}
-- TOMDO: What do we have to do about ImplicInst, Method, and LitInst??
normaliseOneInst _isWanted _fun inst
= do { inst' <- zonkInst inst
+ ; traceTc $ text "*** TcTyFuns.normaliseOneInst: Skipping" <+>
+ ppr inst
; return (inst', emptyBag)
}
\end{code}