--
normaliseEqs :: [Inst] -> TcM EqConfig
normaliseEqs eqs
- = do { (eqss, skolemss) <- mapAndUnzipM normEqInst eqs
+ = do { ASSERTM2( allM isValidWantedEqInst eqs, ppr eqs )
+ ; traceTc $ ptext (sLit "normaliseEqs")
+
+ ; (eqss, skolemss) <- mapAndUnzipM normEqInst eqs
; return $ emptyEqConfig { eqs = concat eqss
, skolems = unionVarSets skolemss
}
--
normaliseDicts :: Bool -> [Inst] -> TcM EqConfig
normaliseDicts isWanted insts
- = do { (insts', eqss, bindss, skolemss) <- mapAndUnzip4M (normDict isWanted)
+ = do { traceTc $ ptext (sLit "normaliseDicts") <+>
+ ptext (if isWanted then sLit "[Wanted]" else sLit "[Local]")
+ ; (insts', eqss, bindss, skolemss) <- mapAndUnzip4M (normDict isWanted)
insts
; return $ emptyEqConfig { eqs = concat eqss
, locals = if isWanted then [] else insts'
--
propagateEqs :: EqConfig -> TcM EqConfig
propagateEqs eqCfg@(EqConfig {eqs = todoEqs})
- = propagate todoEqs (eqCfg {eqs = []})
+ = do { traceTc $ ptext (sLit "propagateEqs")
+ ; propagate todoEqs (eqCfg {eqs = []})
+ }
-- |Finalise a set of equalities and associated dictionaries after
-- propagation. The returned Boolean value is `True' iff any flexible
, wanteds = wanteds
, binds = binds
})
- = do { (eqs', subst_binds, locals', wanteds') <- substitute eqs locals wanteds
+ = do { traceTc $ ptext (sLit "finaliseEqsAndDicts")
+ ; (eqs', subst_binds, locals', wanteds') <- substitute eqs locals wanteds
; (eqs'', improved) <- instantiateAndExtract eqs'
; final_binds <- filterM nonTrivialDictBind $
bagToList (subst_binds `unionBags` binds)
+
+ ; ASSERTM2( allM isValidWantedEqInst eqs'', ppr eqs'' )
; return (locals', eqs'' ++ wanteds', listToBag final_binds, improved)
}
where
\begin{code}
data RewriteInst
= RewriteVar -- Form (2) above
- { rwi_var :: TyVar -- may be rigid or flexible
- , rwi_right :: TcType -- contains no synonym family applications
- , rwi_co :: EqInstCo -- the wanted or given coercion
- , rwi_loc :: InstLoc
- , rwi_name :: Name -- no semantic significance (cf. TcRnTypes.EqInst)
+ { rwi_var :: TyVar -- may be rigid or flexible
+ , rwi_right :: TcType -- contains no synonym family applications
+ , rwi_co :: EqInstCo -- the wanted or given coercion
+ , rwi_loc :: InstLoc
+ , rwi_name :: Name -- no semantic significance (cf. TcRnTypes.EqInst)
+ , rwi_swapped :: Bool -- swapped orientation of original EqInst
}
| RewriteFam -- Forms (1) above
- { rwi_fam :: TyCon -- synonym family tycon
- , rwi_args :: [Type] -- contain no synonym family applications
- , rwi_right :: TcType -- contains no synonym family applications
- , rwi_co :: EqInstCo -- the wanted or given coercion
- , rwi_loc :: InstLoc
- , rwi_name :: Name -- no semantic significance (cf. TcRnTypes.EqInst)
+ { rwi_fam :: TyCon -- synonym family tycon
+ , rwi_args :: [Type] -- contain no synonym family applications
+ , rwi_right :: TcType -- contains no synonym family applications
+ , rwi_co :: EqInstCo -- the wanted or given coercion
+ , rwi_loc :: InstLoc
+ , rwi_name :: Name -- no semantic significance (cf. TcRnTypes.EqInst)
+ , rwi_swapped :: Bool -- swapped orientation of original EqInst
}
isWantedRewriteInst :: RewriteInst -> Bool
isWantedRewriteInst = isWantedCo . rwi_co
-rewriteInstToInst :: RewriteInst -> Inst
+rewriteInstToInst :: RewriteInst -> TcM Inst
rewriteInstToInst eq@(RewriteVar {rwi_var = tv})
- = EqInst
- { tci_left = mkTyVarTy tv
- , tci_right = rwi_right eq
- , tci_co = rwi_co eq
- , tci_loc = rwi_loc eq
- , tci_name = rwi_name eq
- }
+ = deriveEqInst eq (mkTyVarTy tv) (rwi_right eq) (rwi_co eq)
rewriteInstToInst eq@(RewriteFam {rwi_fam = fam, rwi_args = args})
- = EqInst
- { tci_left = mkTyConApp fam args
- , tci_right = rwi_right eq
- , tci_co = rwi_co eq
- , tci_loc = rwi_loc eq
- , tci_name = rwi_name eq
- }
+ = deriveEqInst eq (mkTyConApp fam args) (rwi_right eq) (rwi_co eq)
+
+-- Derive an EqInst based from a RewriteInst, possibly swapping the types
+-- around.
+--
+deriveEqInst :: RewriteInst -> TcType -> TcType -> EqInstCo -> TcM Inst
+deriveEqInst rewrite ty1 ty2 co
+ = do { co_adjusted <- if not swapped then return co
+ else mkSymEqInstCo co (ty2, ty1)
+ ; return $ EqInst
+ { tci_left = left
+ , tci_right = right
+ , tci_co = co_adjusted
+ , tci_loc = rwi_loc rewrite
+ , tci_name = rwi_name rewrite
+ }
+ }
+ where
+ swapped = rwi_swapped rewrite
+ (left, right) = if not swapped then (ty1, ty2) else (ty2, ty1)
\end{code}
The following functions turn an arbitrary equality into a set of normal
-- left-to-right rule with type family head
go (TyConApp con args) ty2 co
| isOpenSynTyCon con
- = mkRewriteFam con args ty2 co
+ = mkRewriteFam False con args ty2 co
-- right-to-left rule with type family head
go ty1 ty2@(TyConApp con args) co
| isOpenSynTyCon con
= do { co' <- mkSymEqInstCo co (ty2, ty1)
- ; mkRewriteFam con args ty1 co'
+ ; mkRewriteFam True con args ty1 co'
}
-- no outermost family
ty1_skolems `unionVarSet` ty2_skolems)
}
- mkRewriteFam con args ty2 co
+ mkRewriteFam swapped con args ty2 co
= do { (args', cargs, args_eqss, args_skolemss)
<- mapAndUnzip4M (flattenType inst) args
; (ty2', co2, ty2_eqs, ty2_skolems) <- flattenType inst ty2
eqTys = (mkTyConApp con args', ty2')
; (co', all_eqs') <- adjustCoercions co rewriteCo eqTys all_eqs
; let thisRewriteFam = RewriteFam
- { rwi_fam = con
- , rwi_args = args'
- , rwi_right = ty2'
- , rwi_co = co'
- , rwi_loc = tci_loc inst
- , rwi_name = tci_name inst
+ { rwi_fam = con
+ , rwi_args = args'
+ , rwi_right = ty2'
+ , rwi_co = co'
+ , rwi_loc = tci_loc inst
+ , rwi_name = tci_name inst
+ , rwi_swapped = swapped
}
; return $ (thisRewriteFam : all_eqs',
unionVarSets (ty2_skolems:args_skolemss))
-- two tvs, left greater => unchanged
go ty1@(TyVarTy tv1) ty2@(TyVarTy tv2)
| tv1 > tv2
- = mkRewriteVar tv1 ty2 co
+ = mkRewriteVar False tv1 ty2 co
-- two tvs, right greater => swap
| otherwise
= do { co' <- mkSymEqInstCo co (ty2, ty1)
- ; mkRewriteVar tv2 ty1 co'
+ ; mkRewriteVar True tv2 ty1 co'
}
-- only lhs is a tv => unchanged
| ty1 `tcPartOfType` ty2 -- occurs check!
= occurCheckErr ty1 ty2
| otherwise
- = mkRewriteVar tv1 ty2 co
+ = mkRewriteVar False tv1 ty2 co
-- only rhs is a tv => swap
go ty1 ty2@(TyVarTy tv2)
= occurCheckErr ty2 ty1
| otherwise
= do { co' <- mkSymEqInstCo co (ty2, ty1)
- ; mkRewriteVar tv2 ty1 co'
+ ; mkRewriteVar True tv2 ty1 co'
}
-- type applications => decompose
= ASSERT( (not . isForAllTy $ ty1) && (not . isForAllTy $ ty2) )
eqInstMisMatch inst
- mkRewriteVar tv ty co = return [RewriteVar
- { rwi_var = tv
- , rwi_right = ty
- , rwi_co = co
- , rwi_loc = tci_loc inst
- , rwi_name = tci_name inst
- }]
+ mkRewriteVar swapped tv ty co = return [RewriteVar
+ { rwi_var = tv
+ , rwi_right = ty
+ , rwi_co = co
+ , rwi_loc = tci_loc inst
+ , rwi_name = tci_name inst
+ , rwi_swapped = swapped
+ }]
flattenType :: Inst -- context to get location & name
-> Type -- the type to flatten
-- look through synonyms
go ty | Just ty' <- tcView ty = go ty'
+ -- type variable => nothing to do
+ go ty@(TyVarTy _)
+ = return (ty, ty, [] , emptyVarSet)
+
-- type family application
-- => flatten to "gamma :: F t1'..tn' ~ alpha" (alpha & gamma fresh)
go ty@(TyConApp con args)
; let alphaTy = mkTyVarTy alpha
; cotv <- newMetaCoVar (mkTyConApp con args') alphaTy
; let thisRewriteFam = RewriteFam
- { rwi_fam = con
- , rwi_args = args'
- , rwi_right = alphaTy
- , rwi_co = mkWantedCo cotv
- , rwi_loc = tci_loc inst
- , rwi_name = tci_name inst
+ { rwi_fam = con
+ , rwi_args = args'
+ , rwi_right = alphaTy
+ , rwi_co = mkWantedCo cotv
+ , rwi_loc = tci_loc inst
+ , rwi_name = tci_name inst
+ , rwi_swapped = True
}
; return (alphaTy,
mkTyConApp con cargs `mkTransCoercion` mkTyVarTy cotv,
skolems_l `unionVarSet` skolems_r)
}
- -- free of type families => leave as is
- go ty
- = ASSERT( not . isForAllTy $ ty )
- return (ty, ty, [] , emptyVarSet)
+ -- forall type => panic if the body contains a type family
+ -- !!!TODO: As long as the family does not contain a quantified variable
+ -- we might pull it out, but what if it does contain a quantified
+ -- variable???
+ go ty@(ForAllTy _ body)
+ | null (tyFamInsts body)
+ = return (ty, ty, [] , emptyVarSet)
+ | otherwise
+ = panic "TcTyFuns.flattenType: synonym family in a rank-n type"
+
+ -- we should never see a predicate type
+ go (PredTy _)
+ = panic "TcTyFuns.flattenType: unexpected PredType"
adjustCoercions :: EqInstCo -- coercion of original equality
-> Coercion -- coercion witnessing the rewrite
Nothing -> return Nothing
Just (lhs, rewrite_co)
-> do { co' <- mkRightTransEqInstCo co rewrite_co (lhs, rhs)
- ; let eq' = EqInst
- { tci_left = lhs
- , tci_right = rhs
- , tci_co = co'
- , tci_loc = rwi_loc eq
- , tci_name = rwi_name eq
- }
+ ; eq' <- deriveEqInst eq lhs rhs co'
; liftM Just $ normEqInst eq'
}
}
-- !!!Check whether anything breaks by making tcEqTypes look through synonyms.
-- !!!Should be ok and we don't want three type equalities.
= do { co2' <- mkRightTransEqInstCo co2 co1 (lhs, rhs)
- ; let eq2' = EqInst
- { tci_left = lhs
- , tci_right = rhs
- , tci_co = co2'
- , tci_loc = rwi_loc eq2
- , tci_name = rwi_name eq2
- }
+ ; eq2' <- deriveEqInst eq2 lhs rhs co2'
; liftM Just $ normEqInst eq2'
}
where
| tv1 == tv2 &&
(isWantedRewriteInst eq2 || not (isWantedRewriteInst eq1))
= do { co2' <- mkRightTransEqInstCo co2 co1 (lhs, rhs)
- ; let eq2' = EqInst
- { tci_left = lhs
- , tci_right = rhs
- , tci_co = co2'
- , tci_loc = rwi_loc eq2
- , tci_name = rwi_name eq2
- }
+ ; eq2' <- deriveEqInst eq2 lhs rhs co2'
; liftM Just $ normEqInst eq2'
}
where
; wanteds' <- mapM inst wanteds
; let residuals = catMaybes wanteds'
improved = length wanteds /= length residuals
- ; return (map rewriteInstToInst residuals, improved)
+ ; residuals' <- mapM rewriteInstToInst residuals
+ ; return (residuals', improved)
}
where
inst eq@(RewriteVar {rwi_var = tv1, rwi_right = ty2, rwi_co = co})
-- co :: alpha ~ t
| isMetaTyVar tv1
- = doInst tv1 ty2 co eq
+ = doInst (rwi_swapped eq) tv1 ty2 co eq
-- co :: a ~ alpha
| Just tv2 <- tcGetTyVar_maybe ty2
, isMetaTyVar tv2
- = doInst tv2 (mkTyVarTy tv1) co eq
+ = doInst (not $ rwi_swapped eq) tv2 (mkTyVarTy tv1) co eq
inst eq = return $ Just eq
- doInst _ _ (Right ty) _eq = pprPanic "TcTyFuns.doInst: local eq: "
- (ppr ty)
- doInst tv ty (Left cotv) eq = do { lookupTV <- lookupTcTyVar tv
- ; uMeta False tv lookupTV ty cotv
- }
+ doInst _swapped _tv _ty (Right ty) _eq
+ = pprPanic "TcTyFuns.doInst: local eq: " (ppr ty)
+ doInst swapped tv ty (Left cotv) eq
+ = do { lookupTV <- lookupTcTyVar tv
+ ; uMeta swapped tv lookupTV ty cotv
+ }
where
-- meta variable has been filled already
-- => ignore (must be a skolem that was introduced by flattening locals)
projects / ghc-hetmet.git / commitdiff