-- Canonical constraints
CanonicalCts, emptyCCan, andCCan, andCCans,
- singleCCan, extendCCans, isEmptyCCan,
- CanonicalCt(..), Xi, tyVarsOfCanonical, tyVarsOfCanonicals,
+ singleCCan, extendCCans, isEmptyCCan, isTyEqCCan,
+ CanonicalCt(..), Xi, tyVarsOfCanonical, tyVarsOfCanonicals, tyVarsOfCDicts,
mkWantedConstraints, deCanonicaliseWanted,
- makeGivens, makeSolved,
+ makeGivens, makeSolvedByInst,
- CtFlavor (..), isWanted, isGiven, isDerived, canRewrite,
- joinFlavors, mkGivenFlavor,
+ CtFlavor (..), isWanted, isGiven, isDerived, isDerivedSC, isDerivedByInst,
+ DerivedOrig (..),
+ canRewrite, canSolve,
+ combineCtLoc, mkGivenFlavor,
TcS, runTcS, failTcS, panicTcS, traceTcS, traceTcS0, -- Basic functionality
- tryTcS, nestImplicTcS, wrapErrTcS, wrapWarnTcS,
+ tryTcS, nestImplicTcS, recoverTcS, wrapErrTcS, wrapWarnTcS,
SimplContext(..), isInteractive, simplEqsOnly, performDefaulting,
-- Creation of evidence variables
newTcEvBindsTcS,
getInstEnvs, getFamInstEnvs, -- Getting the environments
- getTopEnv, getGblEnv, getTcEvBinds, getUntouchablesTcS,
- getTcEvBindsBag, getTcSContext, getTcSTyBinds,
+ getTopEnv, getGblEnv, getTcEvBinds, getUntouchables,
+ getTcEvBindsBag, getTcSContext, getTcSTyBinds, getTcSTyBindsMap,
newFlattenSkolemTy, -- Flatten skolems
+
instDFunTypes, -- Instantiation
instDFunConstraints,
isGoodRecEv,
+ zonkTcTypeTcS, -- Zonk through the TyBinds of the Tcs Monad
+ compatKind,
+
+
isTouchableMetaTyVar,
+ isTouchableMetaTyVar_InRange,
getDefaultInfo, getDynFlags,
import HscTypes
import BasicTypes
-import Type
import Inst
import InstEnv
import Coercion
import Class
import TyCon
+import TypeRep
+
import Name
import Var
+import VarEnv
import Outputable
import Bag
import MonadUtils
import TcRnTypes
-import Control.Monad
import Data.IORef
\end{code}
| CTyEqCan { -- tv ~ xi (recall xi means function free)
-- Invariant:
-- * tv not in tvs(xi) (occurs check)
- -- * If tv is a MetaTyVar, then typeKind xi <: typeKind tv
- -- a skolem, then typeKind xi = typeKind tv
+ -- * If constraint is given then typeKind xi `compatKind` typeKind tv
+ -- See Note [Spontaneous solving and kind compatibility]
+ -- * if xi is a flatten skolem then tv must be a flatten skolem
+ -- i.e. equalities prefer flatten skolems in their LHS.
+ -- See Note [Loopy Spontaneous Solving, Example 4]
+ -- Also related to [Flatten Skolem Equivalence Classes]
cc_id :: EvVar,
cc_flavor :: CtFlavor,
- cc_tyvar :: TcTyVar,
- cc_rhs :: Xi
+ cc_tyvar :: TcTyVar,
+ cc_rhs :: Xi
}
| CFunEqCan { -- F xis ~ xi
-- Invariant: * isSynFamilyTyCon cc_fun
-- * cc_rhs is not a touchable unification variable
-- See Note [No touchables as FunEq RHS]
- -- * typeKind (TyConApp cc_fun cc_tyargs) == typeKind cc_rhs
+ -- * If constraint is given then
+ -- typeKind (TyConApp cc_fun cc_tyargs) `compatKind` typeKind cc_rhs
cc_id :: EvVar,
cc_flavor :: CtFlavor,
cc_fun :: TyCon, -- A type function
}
+compatKind :: Kind -> Kind -> Bool
+compatKind k1 k2 = k1 `isSubKind` k2 || k2 `isSubKind` k1
+
makeGivens :: CanonicalCts -> CanonicalCts
makeGivens = mapBag (\ct -> ct { cc_flavor = mkGivenFlavor (cc_flavor ct) UnkSkol })
-- The UnkSkol doesn't matter because these givens are
-- not contradictory (else we'd have rejected them already)
-makeSolved :: CanonicalCt -> CanonicalCt
+makeSolvedByInst :: CanonicalCt -> CanonicalCt
-- Record that a constraint is now solved
-- Wanted -> Derived
-- Given, Derived -> no-op
-makeSolved ct
- | Wanted loc <- cc_flavor ct = ct { cc_flavor = Derived loc }
+makeSolvedByInst ct
+ | Wanted loc <- cc_flavor ct = ct { cc_flavor = Derived loc DerInst }
| otherwise = ct
mkWantedConstraints :: CanonicalCts -> Bag Implication -> WantedConstraints
tyVarsOfCanonical (CDictCan { cc_tyargs = tys }) = tyVarsOfTypes tys
tyVarsOfCanonical (CIPCan { cc_ip_ty = ty }) = tyVarsOfType ty
+tyVarsOfCDict :: CanonicalCt -> TcTyVarSet
+tyVarsOfCDict (CDictCan { cc_tyargs = tys }) = tyVarsOfTypes tys
+tyVarsOfCDict _ct = emptyVarSet
+
+tyVarsOfCDicts :: CanonicalCts -> TcTyVarSet
+tyVarsOfCDicts = foldrBag (unionVarSet . tyVarsOfCDict) emptyVarSet
+
tyVarsOfCanonicals :: CanonicalCts -> TcTyVarSet
tyVarsOfCanonicals = foldrBag (unionVarSet . tyVarsOfCanonical) emptyVarSet
Hence the invariant.
+The invariant is
+
Note [Canonical implicit parameter constraints]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The type in a canonical implicit parameter constraint doesn't need to
isEmptyCCan :: CanonicalCts -> Bool
isEmptyCCan = isEmptyBag
+
+isTyEqCCan :: CanonicalCt -> Bool
+isTyEqCCan (CTyEqCan {}) = True
+isTyEqCCan (CFunEqCan {}) = False
+isTyEqCCan _ = False
+
\end{code}
%************************************************************************
\begin{code}
data CtFlavor
= Given GivenLoc -- We have evidence for this constraint in TcEvBinds
- | Derived WantedLoc -- We have evidence for this constraint in TcEvBinds;
+ | Derived WantedLoc DerivedOrig
+ -- We have evidence for this constraint in TcEvBinds;
-- *however* this evidence can contain wanteds, so
-- it's valid only provisionally to the solution of
-- these wanteds
| Wanted WantedLoc -- We have no evidence bindings for this constraint.
+data DerivedOrig = DerSC | DerInst
+-- Deriveds are either superclasses of other wanteds or deriveds, or partially
+-- solved wanteds from instances.
+
instance Outputable CtFlavor where
- ppr (Given _) = ptext (sLit "[Given]")
- ppr (Wanted _) = ptext (sLit "[Wanted]")
- ppr (Derived _) = ptext (sLit "[Derived]")
+ ppr (Given _) = ptext (sLit "[Given]")
+ ppr (Wanted _) = ptext (sLit "[Wanted]")
+ ppr (Derived {}) = ptext (sLit "[Derived]")
isWanted :: CtFlavor -> Bool
isWanted (Wanted {}) = True
isGiven _ = False
isDerived :: CtFlavor -> Bool
-isDerived ctid = not $ isGiven ctid || isWanted ctid
+isDerived (Derived {}) = True
+isDerived _ = False
+
+isDerivedSC :: CtFlavor -> Bool
+isDerivedSC (Derived _ DerSC) = True
+isDerivedSC _ = False
+
+isDerivedByInst :: CtFlavor -> Bool
+isDerivedByInst (Derived _ DerInst) = True
+isDerivedByInst _ = False
+
+canSolve :: CtFlavor -> CtFlavor -> Bool
+-- canSolve ctid1 ctid2
+-- The constraint ctid1 can be used to solve ctid2
+-- "to solve" means a reaction where the active parts of the two constraints match.
+-- active(F xis ~ xi) = F xis
+-- active(tv ~ xi) = tv
+-- active(D xis) = D xis
+-- active(IP nm ty) = nm
+-----------------------------------------
+canSolve (Given {}) _ = True
+canSolve (Derived {}) (Wanted {}) = True
+canSolve (Derived {}) (Derived {}) = True
+canSolve (Wanted {}) (Wanted {}) = True
+canSolve _ _ = False
canRewrite :: CtFlavor -> CtFlavor -> Bool
-- canRewrite ctid1 ctid2
--- The constraint ctid1 can be used to rewrite ctid2
-canRewrite (Given {}) _ = True
-canRewrite (Derived {}) (Wanted {}) = True
-canRewrite (Derived {}) (Derived {}) = True
-canRewrite (Wanted {}) (Wanted {}) = True
-canRewrite _ _ = False
-
-joinFlavors :: CtFlavor -> CtFlavor -> CtFlavor
-joinFlavors (Wanted loc) _ = Wanted loc
-joinFlavors _ (Wanted loc) = Wanted loc
-joinFlavors (Derived loc) _ = Derived loc
-joinFlavors _ (Derived loc) = Derived loc
-joinFlavors (Given loc) _ = Given loc
+-- The *equality_constraint* ctid1 can be used to rewrite inside ctid2
+canRewrite = canSolve
+
+combineCtLoc :: CtFlavor -> CtFlavor -> WantedLoc
+-- Precondition: At least one of them should be wanted
+combineCtLoc (Wanted loc) _ = loc
+combineCtLoc _ (Wanted loc) = loc
+combineCtLoc (Derived loc _) _ = loc
+combineCtLoc _ (Derived loc _) = loc
+combineCtLoc _ _ = panic "combineCtLoc: both given"
mkGivenFlavor :: CtFlavor -> SkolemInfo -> CtFlavor
-mkGivenFlavor (Wanted loc) sk = Given (setCtLocOrigin loc sk)
-mkGivenFlavor (Derived loc) sk = Given (setCtLocOrigin loc sk)
-mkGivenFlavor (Given loc) sk = Given (setCtLocOrigin loc sk)
+mkGivenFlavor (Wanted loc) sk = Given (setCtLocOrigin loc sk)
+mkGivenFlavor (Derived loc _) sk = Given (setCtLocOrigin loc sk)
+mkGivenFlavor (Given loc) sk = Given (setCtLocOrigin loc sk)
\end{code}
tcs_ev_binds :: EvBindsVar,
-- Evidence bindings
- tcs_ty_binds :: IORef (Bag (TcTyVar, TcType)),
+ tcs_ty_binds :: IORef (TyVarEnv (TcTyVar, TcType)),
-- Global type bindings
- tcs_context :: SimplContext
+ tcs_context :: SimplContext,
+
+ tcs_untch :: Untouchables
}
data SimplContext
traceTcS0 herald doc = TcS $ \_env -> TcM.traceTcN 0 herald doc
runTcS :: SimplContext
- -> TcTyVarSet -- Untouchables
+ -> Untouchables -- Untouchables
-> TcS a -- What to run
-> TcM (a, Bag EvBind)
runTcS context untouch tcs
- = do { ty_binds_var <- TcM.newTcRef emptyBag
+ = do { ty_binds_var <- TcM.newTcRef emptyVarEnv
; ev_binds_var@(EvBindsVar evb_ref _) <- TcM.newTcEvBinds
; let env = TcSEnv { tcs_ev_binds = ev_binds_var
, tcs_ty_binds = ty_binds_var
- , tcs_context = context }
+ , tcs_context = context
+ , tcs_untch = untouch }
-- Run the computation
- ; res <- TcM.setUntouchables untouch (unTcS tcs env)
+ ; res <- unTcS tcs env
-- Perform the type unifications required
; ty_binds <- TcM.readTcRef ty_binds_var
- ; mapBagM_ do_unification ty_binds
+ ; mapM_ do_unification (varEnvElts ty_binds)
-- And return
; ev_binds <- TcM.readTcRef evb_ref
; return (res, evBindMapBinds ev_binds) }
where
do_unification (tv,ty) = TcM.writeMetaTyVar tv ty
+
-nestImplicTcS :: EvBindsVar -> TcTyVarSet -> TcS a -> TcS a
-nestImplicTcS ref untouch tcs
+nestImplicTcS :: EvBindsVar -> Untouchables -> TcS a -> TcS a
+nestImplicTcS ref untch (TcS thing_inside)
= TcS $ \ TcSEnv { tcs_ty_binds = ty_binds, tcs_context = ctxt } ->
let
nest_env = TcSEnv { tcs_ev_binds = ref
, tcs_ty_binds = ty_binds
- , tcs_context = ctxtUnderImplic ctxt }
+ , tcs_untch = untch
+ , tcs_context = ctxtUnderImplic ctxt }
in
- TcM.setUntouchables untouch (unTcS tcs nest_env)
+ thing_inside nest_env
+
+recoverTcS :: TcS a -> TcS a -> TcS a
+recoverTcS (TcS recovery_code) (TcS thing_inside)
+ = TcS $ \ env ->
+ TcM.recoverM (recovery_code env) (thing_inside env)
ctxtUnderImplic :: SimplContext -> SimplContext
-- See Note [Simplifying RULE lhs constraints] in TcSimplify
ctxtUnderImplic SimplRuleLhs = SimplCheck
ctxtUnderImplic ctxt = ctxt
-tryTcS :: TcTyVarSet -> TcS a -> TcS a
+tryTcS :: TcS a -> TcS a
-- Like runTcS, but from within the TcS monad
-- Ignore all the evidence generated, and do not affect caller's evidence!
-tryTcS untch tcs
- = TcS (\env -> do { ty_binds_var <- TcM.newTcRef emptyBag
+tryTcS tcs
+ = TcS (\env -> do { ty_binds_var <- TcM.newTcRef emptyVarEnv
; ev_binds_var <- TcM.newTcEvBinds
; let env1 = env { tcs_ev_binds = ev_binds_var
, tcs_ty_binds = ty_binds_var }
- ; TcM.setUntouchables untch (unTcS tcs env1) })
+ ; unTcS tcs env1 })
-- Update TcEvBinds
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
getTcEvBinds :: TcS EvBindsVar
getTcEvBinds = TcS (return . tcs_ev_binds)
-getTcSTyBinds :: TcS (IORef (Bag (TcTyVar, TcType)))
+getUntouchables :: TcS Untouchables
+getUntouchables = TcS (return . tcs_untch)
+
+getTcSTyBinds :: TcS (IORef (TyVarEnv (TcTyVar, TcType)))
getTcSTyBinds = TcS (return . tcs_ty_binds)
+getTcSTyBindsMap :: TcS (TyVarEnv (TcTyVar, TcType))
+getTcSTyBindsMap = getTcSTyBinds >>= wrapTcS . (TcM.readTcRef)
+
+
getTcEvBindsBag :: TcS EvBindMap
getTcEvBindsBag
= do { EvBindsVar ev_ref _ <- getTcEvBinds
= do { ref <- getTcSTyBinds
; wrapTcS $
do { ty_binds <- TcM.readTcRef ref
- ; TcM.writeTcRef ref (ty_binds `snocBag` (tv,ty)) } }
+ ; TcM.writeTcRef ref (extendVarEnv ty_binds tv (tv,ty)) } }
setIPBind :: EvVar -> EvTerm -> TcS ()
setIPBind = setEvBind
getGblEnv :: TcS TcGblEnv
getGblEnv = wrapTcS $ TcM.getGblEnv
-getUntouchablesTcS :: TcS TcTyVarSet
-getUntouchablesTcS = wrapTcS $ TcM.getUntouchables
-
-- Various smaller utilities [TODO, maybe will be absorbed in the instance matcher]
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
pprEq ty1 ty2 = pprPred $ mkEqPred (ty1,ty2)
isTouchableMetaTyVar :: TcTyVar -> TcS Bool
--- is touchable variable!
-isTouchableMetaTyVar v
- | isMetaTyVar v = wrapTcS $ do { untch <- TcM.isUntouchable v;
- ; return (not untch) }
- | otherwise = return False
+isTouchableMetaTyVar tv
+ = do { untch <- getUntouchables
+ ; return $ isTouchableMetaTyVar_InRange untch tv }
+
+isTouchableMetaTyVar_InRange :: Untouchables -> TcTyVar -> Bool
+isTouchableMetaTyVar_InRange untch tv
+ = case tcTyVarDetails tv of
+ MetaTv TcsTv _ -> True -- See Note [Touchable meta type variables]
+ MetaTv {} -> inTouchableRange untch tv
+ _ -> False
+
+
+\end{code}
+Note [Touchable meta type variables]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Meta type variables allocated *by the constraint solver itself* are always
+touchable. Example:
+ instance C a b => D [a] where...
+if we use this instance declaration we "make up" a fresh meta type
+variable for 'b', which we must later guess. (Perhaps C has a
+functional dependency.) But since we aren't in the constraint *generator*
+we can't allocate a Unique in the touchable range for this implication
+constraint. Instead, we mark it as a "TcsTv", which makes it always-touchable.
+
+
+\begin{code}
-- Flatten skolems
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
newFlattenSkolemTy :: TcType -> TcS TcType
newFlattenSkolemTy ty = mkTyVarTy <$> newFlattenSkolemTyVar ty
- where newFlattenSkolemTyVar :: TcType -> TcS TcTyVar
- newFlattenSkolemTyVar ty
- = wrapTcS $ do { uniq <- TcM.newUnique
- ; let name = mkSysTvName uniq (fsLit "f")
- ; return $ mkTcTyVar name (typeKind ty) (FlatSkol ty)
- }
+
+newFlattenSkolemTyVar :: TcType -> TcS TcTyVar
+newFlattenSkolemTyVar ty
+ = wrapTcS $ do { uniq <- TcM.newUnique
+ ; let name = mkSysTvName uniq (fsLit "f")
+ ; return $ mkTcTyVar name (typeKind ty) (FlatSkol ty) }
-- Instantiations
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
instDFunTypes :: [Either TyVar TcType] -> TcS [TcType]
-instDFunTypes mb_inst_tys =
- let inst_tv :: Either TyVar TcType -> TcS Type
- inst_tv (Left tv) = wrapTcS $ TcM.tcInstTyVar tv >>= return . mkTyVarTy
- inst_tv (Right ty) = return ty
- in mapM inst_tv mb_inst_tys
-
+instDFunTypes mb_inst_tys
+ = mapM inst_tv mb_inst_tys
+ where
+ inst_tv :: Either TyVar TcType -> TcS Type
+ inst_tv (Left tv) = mkTyVarTy <$> newFlexiTcS tv
+ inst_tv (Right ty) = return ty
instDFunConstraints :: TcThetaType -> TcS [EvVar]
instDFunConstraints preds = wrapTcS $ TcM.newWantedEvVars preds
+-- newFlexiTcS :: TyVar -> TcS TcTyVar
+-- -- Make a TcsTv meta tyvar; it is always touchable,
+-- -- but we are supposed to guess its instantiation
+-- -- See Note [Touchable meta type variables]
+-- newFlexiTcS tv = wrapTcS $ TcM.instMetaTyVar TcsTv tv
+
+newFlexiTcS :: TyVar -> TcS TcTyVar
+-- Like TcM.instMetaTyVar but the variable that is created is always
+-- touchable; we are supposed to guess its instantiation.
+-- See Note [Touchable meta type variables]
+newFlexiTcS tv = newFlexiTcSHelper (tyVarName tv) (tyVarKind tv)
+
+newKindConstraint :: TcTyVar -> Kind -> TcS (CoVar, Type)
+-- Create new wanted CoVar that constrains the type to have the specified kind.
+newKindConstraint tv knd
+ = do { tv_k <- newFlexiTcSHelper (tyVarName tv) knd
+ ; let ty_k = mkTyVarTy tv_k
+ ; co_var <- newWantedCoVar (mkTyVarTy tv) ty_k
+ ; return (co_var, ty_k) }
+
+newFlexiTcSHelper :: Name -> Kind -> TcS TcTyVar
+newFlexiTcSHelper tvname tvkind
+ = wrapTcS $
+ do { uniq <- TcM.newUnique
+ ; ref <- TcM.newMutVar Flexi
+ ; let name = setNameUnique tvname uniq
+ kind = tvkind
+ ; return (mkTcTyVar name kind (MetaTv TcsTv ref)) }
+
-- Superclasses and recursive dictionaries
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
newWantedCoVar :: TcType -> TcType -> TcS EvVar
newWantedCoVar ty1 ty2 = wrapTcS $ TcM.newWantedCoVar ty1 ty2
-newKindConstraint :: TcType -> Kind -> TcS (CoVar, TcType)
-newKindConstraint ty kind = wrapTcS $ TcM.newKindConstraint ty kind
newCoVar :: TcType -> TcType -> TcS EvVar
newCoVar ty1 ty2 = wrapTcS $ TcM.newCoVar ty1 ty2
}
+zonkTcTypeTcS :: TcType -> TcS TcType
+-- Zonk through the TyBinds of the Tcs Monad
+zonkTcTypeTcS ty
+ = do { subst <- getTcSTyBindsMap >>= return . varEnvElts
+ ; let (dom,rng) = unzip subst
+ apply_once = substTyWith dom rng
+ ; let rng_idemp = [ substTyWith dom rng_idemp (apply_once t) | t <- rng ]
+ ; return (substTyWith dom rng_idemp ty) }
+
+
+
+
+
+
-- Functional dependencies, instantiation of equations
-------------------------------------------------------
where
to_work_item :: (Equation, (PredType,SDoc), (PredType,SDoc)) -> TcS [WantedEvVar]
to_work_item ((qtvs, pairs), _, _)
- = do { (_, _, tenv) <- wrapTcS $ TcM.tcInstTyVars (varSetElems qtvs)
- ; mapM (do_one tenv) pairs }
+ = do { let tvs = varSetElems qtvs
+ ; tvs' <- mapM newFlexiTcS tvs
+ ; let subst = zipTopTvSubst tvs (mkTyVarTys tvs')
+ ; mapM (do_one subst) pairs }
- do_one tenv (ty1, ty2) = do { let sty1 = substTy tenv ty1
- sty2 = substTy tenv ty2
+ do_one subst (ty1, ty2) = do { let sty1 = substTy subst ty1
+ sty2 = substTy subst ty2
; ev <- newWantedCoVar sty1 sty2
; return (WantedEvVar ev loc) }
projects / ghc-hetmet.git / blobdiff