-- Canonical constraints
CanonicalCts, emptyCCan, andCCan, andCCans,
singleCCan, extendCCans, isEmptyCCan, isCTyEqCan,
- isCDictCan_Maybe, isCIPCan_Maybe, isCFunEqCan_Maybe,
+ isCDictCan_Maybe, isCIPCan_Maybe, isCFunEqCan_Maybe,
+ isCFrozenErr,
+
+ WorkList, unionWorkList, unionWorkLists, isEmptyWorkList, emptyWorkList,
+ workListFromEq, workListFromNonEq,
+ workListFromEqs, workListFromNonEqs, foldrWorkListM,
CanonicalCt(..), Xi, tyVarsOfCanonical, tyVarsOfCanonicals, tyVarsOfCDicts,
- mkWantedConstraints, deCanonicaliseWanted,
- makeGivens, makeSolvedByInst,
+ deCanonicalise, mkFrozenError,
- CtFlavor (..), isWanted, isGiven, isDerived,
- isGivenCt, isWantedCt, pprFlavorArising,
+ isWanted, isGiven, isDerived,
+ isGivenCt, isWantedCt, isDerivedCt, pprFlavorArising,
isFlexiTcsTv,
- DerivedOrig (..),
canRewrite, canSolve,
combineCtLoc, mkGivenFlavor, mkWantedFlavor,
getWantedLoc,
- TcS, runTcS, failTcS, panicTcS, traceTcS, traceTcS0, -- Basic functionality
+ TcS, runTcS, failTcS, panicTcS, traceTcS, -- Basic functionality
+ traceFireTcS, bumpStepCountTcS,
tryTcS, nestImplicTcS, recoverTcS, wrapErrTcS, wrapWarnTcS,
SimplContext(..), isInteractive, simplEqsOnly, performDefaulting,
-
- -- Creation of evidence variables
- newWantedCoVar, newGivOrDerCoVar, newGivOrDerEvVar,
+ -- Creation of evidence variables
+ newEvVar, newCoVar, newGivenCoVar,
+ newDerivedId,
newIPVar, newDictVar, newKindConstraint,
-- Setting evidence variables
- setWantedCoBind, setDerivedCoBind,
- setIPBind, setDictBind, setEvBind,
+ setCoBind, setIPBind, setDictBind, setEvBind,
setWantedTyBind,
- newTcEvBindsTcS,
-
- getInstEnvs, getFamInstEnvs, -- Getting the environments
+ getInstEnvs, getFamInstEnvs, -- Getting the environments
getTopEnv, getGblEnv, getTcEvBinds, getUntouchables,
- getTcEvBindsBag, getTcSContext, getTcSTyBinds, getTcSTyBindsMap, getTcSErrors,
- getTcSErrorsBag, FrozenError (..),
- addErrorTcS,
- ErrorKind(..),
+ getTcEvBindsBag, getTcSContext, getTcSTyBinds, getTcSTyBindsMap,
newFlattenSkolemTy, -- Flatten skolems
instDFunTypes, -- Instantiation
instDFunConstraints,
- newFlexiTcSTy,
-
- isGoodRecEv,
+ newFlexiTcSTy, instFlexiTcS,
compatKind,
-
TcsUntouchables,
isTouchableMetaTyVar,
isTouchableMetaTyVar_InRange,
matchClass, matchFam, MatchInstResult (..),
checkWellStagedDFun,
warnTcS,
- pprEq, -- Smaller utils, re-exported from TcM
+ pprEq -- Smaller utils, re-exported from TcM
-- TODO (DV): these are only really used in the
-- instance matcher in TcSimplify. I am wondering
-- if the whole instance matcher simply belongs
-- here
-
-
- mkWantedFunDepEqns -- Instantiation of 'Equations' from FunDeps
-
) where
#include "HsVersions.h"
import qualified TcMType as TcM
import qualified TcEnv as TcM
( checkWellStaged, topIdLvl, tcLookupFamInst, tcGetDefaultTys )
+import Kind
import TcType
import DynFlags
import Bag
import MonadUtils
import VarSet
+import Pair
import FastString
import HsBinds -- for TcEvBinds stuff
import Id
-import FunDeps
-
import TcRnTypes
-
-import Control.Monad
import Data.IORef
+
+#ifdef DEBUG
+import StaticFlags( opt_PprStyle_Debug )
+import Control.Monad( when )
+#endif
\end{code}
| CTyEqCan { -- tv ~ xi (recall xi means function free)
-- Invariant:
-- * tv not in tvs(xi) (occurs check)
- -- * If constraint is given then typeKind xi `compatKind` typeKind tv
- -- See Note [Spontaneous solving and kind compatibility]
+ -- * typeKind xi `compatKind` typeKind tv
+ -- See Note [Spontaneous solving and kind compatibility]
-- * We prefer unification variables on the left *JUST* for efficiency
cc_id :: EvVar,
cc_flavor :: CtFlavor,
| CFunEqCan { -- F xis ~ xi
-- Invariant: * isSynFamilyTyCon cc_fun
- -- * If constraint is given then
- -- typeKind (F xis) `compatKind` typeKind xi
+ -- * typeKind (F xis) `compatKind` typeKind xi
cc_id :: EvVar,
cc_flavor :: CtFlavor,
cc_fun :: TyCon, -- A type function
}
-compatKind :: Kind -> Kind -> Bool
+ | CFrozenErr { -- A "frozen error" does not interact with anything
+ -- See Note [Frozen Errors]
+ cc_id :: EvVar,
+ cc_flavor :: CtFlavor
+ }
+
+mkFrozenError :: CtFlavor -> EvVar -> CanonicalCt
+mkFrozenError fl ev = CFrozenErr { cc_id = ev, cc_flavor = fl }
+
+compatKind :: Kind -> Kind -> Bool
compatKind k1 k2 = k1 `isSubKind` k2 || k2 `isSubKind` k1
-makeGivens :: Bag WantedEvVar -> Bag (CtFlavor,EvVar)
-makeGivens = mapBag (\(WantedEvVar ev wloc) -> (mkGivenFlavor (Wanted wloc) UnkSkol, ev))
--- 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)
-
-makeSolvedByInst :: CanonicalCt -> CanonicalCt
--- Record that a constraint is now solved
--- Wanted -> Derived
--- Given, Derived -> no-op
-makeSolvedByInst ct
- | Wanted loc <- cc_flavor ct = ct { cc_flavor = Derived loc DerInst }
- | otherwise = ct
-
-mkWantedConstraints :: CanonicalCts -> Bag Implication -> WantedConstraints
-mkWantedConstraints flats implics
- = mapBag (WcEvVar . deCanonicaliseWanted) flats `unionBags` mapBag WcImplic implics
-
-deCanonicaliseWanted :: CanonicalCt -> WantedEvVar
-deCanonicaliseWanted ct
- = WARN( not (isWanted $ cc_flavor ct), ppr ct )
- let Wanted loc = cc_flavor ct
- in WantedEvVar (cc_id ct) loc
+deCanonicalise :: CanonicalCt -> FlavoredEvVar
+deCanonicalise ct = mkEvVarX (cc_id ct) (cc_flavor ct)
tyVarsOfCanonical :: CanonicalCt -> TcTyVarSet
tyVarsOfCanonical (CTyEqCan { cc_tyvar = tv, cc_rhs = xi }) = extendVarSet (tyVarsOfType xi) tv
tyVarsOfCanonical (CFunEqCan { cc_tyargs = tys, cc_rhs = xi }) = tyVarsOfTypes (xi:tys)
tyVarsOfCanonical (CDictCan { cc_tyargs = tys }) = tyVarsOfTypes tys
-tyVarsOfCanonical (CIPCan { cc_ip_ty = ty }) = tyVarsOfType ty
+tyVarsOfCanonical (CIPCan { cc_ip_ty = ty }) = tyVarsOfType ty
+tyVarsOfCanonical (CFrozenErr { cc_id = ev }) = tyVarsOfEvVar ev
tyVarsOfCDict :: CanonicalCt -> TcTyVarSet
tyVarsOfCDict (CDictCan { cc_tyargs = tys }) = tyVarsOfTypes tys
ppr (CIPCan ip fl ip_nm ty)
= ppr fl <+> ppr ip <+> dcolon <+> parens (ppr ip_nm <> dcolon <> ppr ty)
ppr (CTyEqCan co fl tv ty)
- = ppr fl <+> ppr co <+> dcolon <+> pprEqPred (mkTyVarTy tv, ty)
+ = ppr fl <+> ppr co <+> dcolon <+> pprEqPred (Pair (mkTyVarTy tv) ty)
ppr (CFunEqCan co fl tc tys ty)
- = ppr fl <+> ppr co <+> dcolon <+> pprEqPred (mkTyConApp tc tys, ty)
+ = ppr fl <+> ppr co <+> dcolon <+> pprEqPred (Pair (mkTyConApp tc tys) ty)
+ ppr (CFrozenErr co fl)
+ = ppr fl <+> pprEvVarWithType co
\end{code}
Note [Canonical implicit parameter constraints]
isCFunEqCan_Maybe (CFunEqCan { cc_fun = tc }) = Just tc
isCFunEqCan_Maybe _ = Nothing
+isCFrozenErr :: CanonicalCt -> Bool
+isCFrozenErr (CFrozenErr {}) = True
+isCFrozenErr _ = False
+
+
+-- A mixture of Given, Wanted, and Derived constraints.
+-- We split between equalities and the rest to process equalities first.
+data WorkList = WorkList { weqs :: CanonicalCts
+ -- NB: weqs includes equalities /and/ family equalities
+ , wrest :: CanonicalCts }
+
+unionWorkList :: WorkList -> WorkList -> WorkList
+unionWorkList wl1 wl2
+ = WorkList { weqs = weqs wl1 `andCCan` weqs wl2
+ , wrest = wrest wl1 `andCCan` wrest wl2 }
+
+unionWorkLists :: [WorkList] -> WorkList
+unionWorkLists = foldr unionWorkList emptyWorkList
+
+isEmptyWorkList :: WorkList -> Bool
+isEmptyWorkList wl = isEmptyCCan (weqs wl) && isEmptyCCan (wrest wl)
+
+emptyWorkList :: WorkList
+emptyWorkList
+ = WorkList { weqs = emptyBag, wrest = emptyBag }
+
+workListFromEq :: CanonicalCt -> WorkList
+workListFromEq = workListFromEqs . singleCCan
+
+workListFromNonEq :: CanonicalCt -> WorkList
+workListFromNonEq = workListFromNonEqs . singleCCan
+
+workListFromNonEqs :: CanonicalCts -> WorkList
+workListFromNonEqs cts
+ = WorkList { weqs = emptyCCan, wrest = cts }
+
+workListFromEqs :: CanonicalCts -> WorkList
+workListFromEqs cts
+ = WorkList { weqs = cts, wrest = emptyCCan }
+
+foldrWorkListM :: (Monad m) => (CanonicalCt -> r -> m r)
+ -> r -> WorkList -> m r
+-- Prioritizes equalities
+foldrWorkListM on_ct r (WorkList {weqs = eqs, wrest = rest })
+ = do { r1 <- foldrBagM on_ct r eqs
+ ; foldrBagM on_ct r1 rest }
+
+instance Outputable WorkList where
+ ppr wl = vcat [ text "WorkList (Equalities) = " <+> ppr (weqs wl)
+ , text "WorkList (Other) = " <+> ppr (wrest wl) ]
+
\end{code}
+
+
%************************************************************************
%* *
CtFlavor
%************************************************************************
\begin{code}
-data CtFlavor
- = Given GivenLoc -- 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 | DerSelf
--- Deriveds are either superclasses of other wanteds or deriveds, or partially
--- solved wanteds from instances, or 'self' dictionaries containing yet wanted
--- superclasses.
-
-instance Outputable CtFlavor where
- ppr (Given _) = ptext (sLit "[Given]")
- ppr (Wanted _) = ptext (sLit "[Wanted]")
- ppr (Derived {}) = ptext (sLit "[Derived]")
-
-isWanted :: CtFlavor -> Bool
-isWanted (Wanted {}) = True
-isWanted _ = False
-
-isGiven :: CtFlavor -> Bool
-isGiven (Given {}) = True
-isGiven _ = False
-
-isDerived :: CtFlavor -> Bool
-isDerived (Derived {}) = True
-isDerived _ = False
-
-pprFlavorArising :: CtFlavor -> SDoc
-pprFlavorArising (Derived wl _) = pprArisingAt wl
-pprFlavorArising (Wanted wl) = pprArisingAt wl
-pprFlavorArising (Given gl) = pprArisingAt gl
-
getWantedLoc :: CanonicalCt -> WantedLoc
getWantedLoc ct
= ASSERT (isWanted (cc_flavor ct))
Wanted wl -> wl
_ -> pprPanic "Can't get WantedLoc of non-wanted constraint!" empty
-
-isWantedCt :: CanonicalCt -> Bool
+isWantedCt :: CanonicalCt -> Bool
isWantedCt ct = isWanted (cc_flavor ct)
-isGivenCt :: CanonicalCt -> Bool
-isGivenCt ct = isGiven (cc_flavor ct)
+isGivenCt :: CanonicalCt -> Bool
+isGivenCt ct = isGiven (cc_flavor ct)
+isDerivedCt :: CanonicalCt -> Bool
+isDerivedCt ct = isDerived (cc_flavor ct)
canSolve :: CtFlavor -> CtFlavor -> Bool
-- canSolve ctid1 ctid2
-- active(tv ~ xi) = tv
-- active(D xis) = D xis
-- active(IP nm ty) = nm
+--
+-- NB: either (a `canSolve` b) or (b `canSolve` a) must hold
-----------------------------------------
canSolve (Given {}) _ = True
-canSolve (Derived {}) (Wanted {}) = True
-canSolve (Derived {}) (Derived {}) = True
+canSolve (Wanted {}) (Derived {}) = True
canSolve (Wanted {}) (Wanted {}) = True
-canSolve _ _ = False
+canSolve (Derived {}) (Derived {}) = True -- Important: derived can't solve wanted/given
+canSolve _ _ = False -- (There is no *evidence* for a derived.)
canRewrite :: CtFlavor -> CtFlavor -> Bool
-- canRewrite ctid1 ctid2
-- 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 (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)
+
mkWantedFlavor :: CtFlavor -> CtFlavor
-mkWantedFlavor (Wanted loc) = Wanted loc
-mkWantedFlavor (Derived loc _) = Wanted loc
-mkWantedFlavor fl@(Given {}) = pprPanic "mkWantedFlavour" (ppr fl)
+mkWantedFlavor (Wanted loc) = Wanted loc
+mkWantedFlavor (Derived loc) = Wanted loc
+mkWantedFlavor fl@(Given {}) = pprPanic "mkWantedFlavour" (ppr fl)
\end{code}
-
%************************************************************************
%* *
%* The TcS solver monad *
tcs_context :: SimplContext,
- tcs_errors :: IORef (Bag FrozenError),
- -- Frozen errors that we defer reporting as much as possible, in order to
- -- make them as informative as possible. See Note [Frozen Errors]
+ tcs_untch :: TcsUntouchables,
- tcs_untch :: TcsUntouchables
+ tcs_ic_depth :: Int, -- Implication nesting depth
+ tcs_count :: IORef Int -- Global step count
}
type TcsUntouchables = (Untouchables,TcTyVarSet)
-- Like the TcM Untouchables,
-- but records extra TcsTv variables generated during simplification
-- See Note [Extra TcsTv untouchables] in TcSimplify
-
-data FrozenError
- = FrozenError ErrorKind CtFlavor TcType TcType
-
-data ErrorKind
- = MisMatchError | OccCheckError | KindError
-
-instance Outputable FrozenError where
- ppr (FrozenError _frknd fl ty1 ty2) = ppr fl <+> pprEq ty1 ty2 <+> text "(frozen)"
-
\end{code}
-Note [Frozen Errors]
-~~~~~~~~~~~~~~~~~~~~
-Some of the errors that we get during canonicalization are best reported when all constraints
-have been simplified as much as possible. For instance, assume that during simplification
-the following constraints arise:
-
- [Wanted] F alpha ~ uf1
- [Wanted] beta ~ uf1 beta
-
-When canonicalizing the wanted (beta ~ uf1 beta), if we eagerly fail we will simply
-see a message:
- 'Can't construct the infinite type beta ~ uf1 beta'
-and the user has no idea what the uf1 variable is.
-
-Instead our plan is that we will NOT fail immediately, but:
- (1) Record the "frozen" error in the tcs_errors field
- (2) Isolate the offending constraint from the rest of the inerts
- (3) Keep on simplifying/canonicalizing
-
-At the end, we will hopefully have substituted uf1 := F alpha, and we will be able to
-report a more informative error:
- 'Can't construct the infinite type beta ~ F alpha beta'
\begin{code}
-
data SimplContext
- = SimplInfer -- Inferring type of a let-bound thing
- | SimplRuleLhs -- Inferring type of a RULE lhs
- | SimplInteractive -- Inferring type at GHCi prompt
- | SimplCheck -- Checking a type signature or RULE rhs
- deriving Eq
+ = SimplInfer SDoc -- Inferring type of a let-bound thing
+ | SimplRuleLhs RuleName -- Inferring type of a RULE lhs
+ | SimplInteractive -- Inferring type at GHCi prompt
+ | SimplCheck SDoc -- Checking a type signature or RULE rhs
instance Outputable SimplContext where
- ppr SimplInfer = ptext (sLit "SimplInfer")
- ppr SimplRuleLhs = ptext (sLit "SimplRuleLhs")
+ ppr (SimplInfer d) = ptext (sLit "SimplInfer") <+> d
+ ppr (SimplCheck d) = ptext (sLit "SimplCheck") <+> d
+ ppr (SimplRuleLhs n) = ptext (sLit "SimplRuleLhs") <+> doubleQuotes (ftext n)
ppr SimplInteractive = ptext (sLit "SimplInteractive")
- ppr SimplCheck = ptext (sLit "SimplCheck")
isInteractive :: SimplContext -> Bool
isInteractive SimplInteractive = True
-- Simplify equalities only, not dictionaries
-- This is used for the LHS of rules; ee
-- Note [Simplifying RULE lhs constraints] in TcSimplify
-simplEqsOnly SimplRuleLhs = True
-simplEqsOnly _ = False
+simplEqsOnly (SimplRuleLhs {}) = True
+simplEqsOnly _ = False
performDefaulting :: SimplContext -> Bool
-performDefaulting SimplInfer = False
-performDefaulting SimplRuleLhs = False
-performDefaulting SimplInteractive = True
-performDefaulting SimplCheck = True
+performDefaulting (SimplInfer {}) = False
+performDefaulting (SimplRuleLhs {}) = False
+performDefaulting SimplInteractive = True
+performDefaulting (SimplCheck {}) = True
---------------
newtype TcS a = TcS { unTcS :: TcSEnv -> TcM a }
traceTcS :: String -> SDoc -> TcS ()
traceTcS herald doc = TcS $ \_env -> TcM.traceTc herald doc
-traceTcS0 :: String -> SDoc -> TcS ()
-traceTcS0 herald doc = TcS $ \_env -> TcM.traceTcN 0 herald doc
+bumpStepCountTcS :: TcS ()
+bumpStepCountTcS = TcS $ \env -> do { let ref = tcs_count env
+ ; n <- TcM.readTcRef ref
+ ; TcM.writeTcRef ref (n+1) }
+
+traceFireTcS :: Int -> SDoc -> TcS ()
+-- Dump a rule-firing trace
+traceFireTcS depth doc
+ = TcS $ \env ->
+ TcM.ifDOptM Opt_D_dump_cs_trace $
+ do { n <- TcM.readTcRef (tcs_count env)
+ ; let msg = int n
+ <> text (replicate (tcs_ic_depth env) '>')
+ <> brackets (int depth) <+> doc
+ ; TcM.dumpTcRn msg }
runTcS :: SimplContext
-> Untouchables -- Untouchables
-> TcS a -- What to run
- -> TcM (a, Bag FrozenError, Bag EvBind)
+ -> TcM (a, Bag EvBind)
runTcS context untouch tcs
= do { ty_binds_var <- TcM.newTcRef emptyVarEnv
; ev_binds_var@(EvBindsVar evb_ref _) <- TcM.newTcEvBinds
- ; err_ref <- TcM.newTcRef emptyBag
+ ; step_count <- TcM.newTcRef 0
; let env = TcSEnv { tcs_ev_binds = ev_binds_var
, tcs_ty_binds = ty_binds_var
, tcs_context = context
, tcs_untch = (untouch, emptyVarSet) -- No Tcs untouchables yet
- , tcs_errors = err_ref
+ , tcs_count = step_count
+ , tcs_ic_depth = 0
}
-- Run the computation
; ty_binds <- TcM.readTcRef ty_binds_var
; mapM_ do_unification (varEnvElts ty_binds)
+#ifdef DEBUG
+ ; count <- TcM.readTcRef step_count
+ ; when (opt_PprStyle_Debug && count > 0) $
+ TcM.debugDumpTcRn (ptext (sLit "Constraint solver steps =")
+ <+> int count <+> ppr context)
+#endif
-- And return
- ; frozen_errors <- TcM.readTcRef err_ref
; ev_binds <- TcM.readTcRef evb_ref
- ; return (res, frozen_errors, evBindMapBinds ev_binds) }
+ ; return (res, evBindMapBinds ev_binds) }
where
do_unification (tv,ty) = TcM.writeMetaTyVar tv ty
nestImplicTcS :: EvBindsVar -> TcsUntouchables -> TcS a -> TcS a
-nestImplicTcS ref untch (TcS thing_inside)
- = TcS $ \ TcSEnv { tcs_ty_binds = ty_binds,
- tcs_context = ctxt,
- tcs_errors = err_ref } ->
+nestImplicTcS ref (inner_range, inner_tcs) (TcS thing_inside)
+ = TcS $ \ TcSEnv { tcs_ty_binds = ty_binds
+ , tcs_untch = (_outer_range, outer_tcs)
+ , tcs_count = count
+ , tcs_ic_depth = idepth
+ , tcs_context = ctxt } ->
let
+ inner_untch = (inner_range, outer_tcs `unionVarSet` inner_tcs)
+ -- The inner_range should be narrower than the outer one
+ -- (thus increasing the set of untouchables) but
+ -- the inner Tcs-untouchables must be unioned with the
+ -- outer ones!
nest_env = TcSEnv { tcs_ev_binds = ref
, tcs_ty_binds = ty_binds
- , tcs_untch = untch
- , tcs_context = ctxtUnderImplic ctxt
- , tcs_errors = err_ref }
+ , tcs_untch = inner_untch
+ , tcs_count = count
+ , tcs_ic_depth = idepth+1
+ , tcs_context = ctxtUnderImplic ctxt }
in
thing_inside nest_env
ctxtUnderImplic :: SimplContext -> SimplContext
-- See Note [Simplifying RULE lhs constraints] in TcSimplify
-ctxtUnderImplic SimplRuleLhs = SimplCheck
-ctxtUnderImplic ctxt = ctxt
+ctxtUnderImplic (SimplRuleLhs n) = SimplCheck (ptext (sLit "lhs of rule")
+ <+> doubleQuotes (ftext n))
+ctxtUnderImplic ctxt = ctxt
tryTcS :: TcS a -> TcS a
-- Like runTcS, but from within the TcS monad
tryTcS tcs
= TcS (\env -> do { ty_binds_var <- TcM.newTcRef emptyVarEnv
; ev_binds_var <- TcM.newTcEvBinds
- ; err_ref <- TcM.newTcRef emptyBag
; let env1 = env { tcs_ev_binds = ev_binds_var
- , tcs_ty_binds = ty_binds_var
- , tcs_errors = err_ref }
+ , tcs_ty_binds = ty_binds_var }
; unTcS tcs env1 })
-- Update TcEvBinds
getTcSTyBinds :: TcS (IORef (TyVarEnv (TcTyVar, TcType)))
getTcSTyBinds = TcS (return . tcs_ty_binds)
-getTcSErrors :: TcS (IORef (Bag FrozenError))
-getTcSErrors = TcS (return . tcs_errors)
-
-getTcSErrorsBag :: TcS (Bag FrozenError)
-getTcSErrorsBag = do { err_ref <- getTcSErrors
- ; wrapTcS $ TcM.readTcRef err_ref }
-
-getTcSTyBindsMap :: TcS (TyVarEnv (TcTyVar, TcType))
+getTcSTyBindsMap :: TcS (TyVarEnv (TcTyVar, TcType))
getTcSTyBindsMap = getTcSTyBinds >>= wrapTcS . (TcM.readTcRef)
= do { EvBindsVar ev_ref _ <- getTcEvBinds
; wrapTcS $ TcM.readTcRef ev_ref }
-setWantedCoBind :: CoVar -> Coercion -> TcS ()
-setWantedCoBind cv co
- = setEvBind cv (EvCoercion co)
- -- Was: wrapTcS $ TcM.writeWantedCoVar cv co
-
-setDerivedCoBind :: CoVar -> Coercion -> TcS ()
-setDerivedCoBind cv co
- = setEvBind cv (EvCoercion co)
+setCoBind :: CoVar -> Coercion -> TcS ()
+setCoBind cv co = setEvBind cv (EvCoercion co)
setWantedTyBind :: TcTyVar -> TcType -> TcS ()
-- Add a type binding
setEvBind :: EvVar -> EvTerm -> TcS ()
-- Internal
setEvBind ev rhs
- = do { tc_evbinds <- getTcEvBinds
+ = do { tc_evbinds <- getTcEvBinds
; wrapTcS (TcM.addTcEvBind tc_evbinds ev rhs) }
-newTcEvBindsTcS :: TcS EvBindsVar
-newTcEvBindsTcS = wrapTcS (TcM.newTcEvBinds)
-
warnTcS :: CtLoc orig -> Bool -> SDoc -> TcS ()
warnTcS loc warn_if doc
| warn_if = wrapTcS $ TcM.setCtLoc loc $ TcM.addWarnTc doc
; (tys, flags) <- wrapTcS (TcM.tcGetDefaultTys (isInteractive ctxt))
; return (ctxt, tys, flags) }
-
-
--- Recording errors in the TcS monad
--- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-addErrorTcS :: ErrorKind -> CtFlavor -> TcType -> TcType -> TcS ()
-addErrorTcS frknd fl ty1 ty2
- = do { err_ref <- getTcSErrors
- ; wrapTcS $ do
- { TcM.updTcRef err_ref $ \ errs ->
- consBag (FrozenError frknd fl ty1 ty2) errs
-
- -- If there's an error in the *given* constraints,
- -- stop right now, to avoid a cascade of errors
- -- in the wanteds
- ; when (isGiven fl) TcM.failM
-
- ; return () } }
-
-- Just get some environments needed for instance looking up and matching
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
bind_lvl = TcM.topIdLvl dfun_id
pprEq :: TcType -> TcType -> SDoc
-pprEq ty1 ty2 = pprPred $ mkEqPred (ty1,ty2)
+pprEq ty1 ty2 = pprPredTy $ mkEqPred (ty1,ty2)
isTouchableMetaTyVar :: TcTyVar -> TcS Bool
isTouchableMetaTyVar tv
newFlattenSkolemTyVar :: TcType -> TcS TcTyVar
newFlattenSkolemTyVar ty
= do { tv <- wrapTcS $ do { uniq <- TcM.newUnique
- ; let name = mkSysTvName uniq (fsLit "f")
+ ; let name = TcM.mkTcTyVarName uniq (fsLit "f")
; return $ mkTcTyVar name (typeKind ty) (FlatSkol ty) }
; traceTcS "New Flatten Skolem Born" $
(ppr tv <+> text "[:= " <+> ppr ty <+> text "]")
= wrapTcS $
do { uniq <- TcM.newUnique
; ref <- TcM.newMutVar Flexi
- ; let name = mkSysTvName uniq (fsLit "uf")
+ ; let name = TcM.mkTcTyVarName uniq (fsLit "uf")
; return $ mkTyVarTy (mkTcTyVar name knd (MetaTv TcsTv ref)) }
isFlexiTcsTv :: TyVar -> Bool
newKindConstraint tv knd
= do { tv_k <- instFlexiTcSHelper (tyVarName tv) knd
; let ty_k = mkTyVarTy tv_k
- ; co_var <- newWantedCoVar (mkTyVarTy tv) ty_k
+ ; co_var <- newCoVar (mkTyVarTy tv) ty_k
; return co_var }
instFlexiTcSHelper :: Name -> Kind -> TcS TcTyVar
-- Superclasses and recursive dictionaries
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-newGivOrDerEvVar :: TcPredType -> EvTerm -> TcS EvVar
-newGivOrDerEvVar pty evtrm
- = do { ev <- wrapTcS $ TcM.newEvVar pty
- ; setEvBind ev evtrm
- ; return ev }
+newEvVar :: TcPredType -> TcS EvVar
+newEvVar pty = wrapTcS $ TcM.newEvVar pty
+
+newDerivedId :: TcPredType -> TcS EvVar
+newDerivedId pty = wrapTcS $ TcM.newEvVar pty
-newGivOrDerCoVar :: TcType -> TcType -> Coercion -> TcS EvVar
+newGivenCoVar :: TcType -> TcType -> Coercion -> TcS EvVar
-- Note we create immutable variables for given or derived, since we
-- must bind them to TcEvBinds (because their evidence may involve
-- superclasses). However we should be able to override existing
-- 'derived' evidence, even in TcEvBinds
-newGivOrDerCoVar ty1 ty2 co
+newGivenCoVar ty1 ty2 co
= do { cv <- newCoVar ty1 ty2
; setEvBind cv (EvCoercion co)
; return cv }
-newWantedCoVar :: TcType -> TcType -> TcS EvVar
-newWantedCoVar ty1 ty2 = wrapTcS $ TcM.newWantedCoVar ty1 ty2
-
-
-newCoVar :: TcType -> TcType -> TcS EvVar
+newCoVar :: TcType -> TcType -> TcS EvVar
newCoVar ty1 ty2 = wrapTcS $ TcM.newCoVar ty1 ty2
newIPVar :: IPName Name -> TcType -> TcS EvVar
\begin{code}
-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
--- or wv = EvCast x |> ev
--- etc.
--- But that would be Very Bad if the evidence for 'ev' mentions 'wv',
--- in an "unguarded" way. So isGoodRecEv looks at the evidence ev
--- recursively through the evidence binds, to see if uses of 'wv' are guarded.
---
--- Guarded means: more instance calls than superclass selections. We
--- compute this by chasing the evidence, adding +1 for every instance
--- call (constructor) and -1 for every superclass selection (destructor).
---
--- See Note [Superclasses and recursive dictionaries] in TcInteract
-isGoodRecEv ev_var wv
- = do { tc_evbinds <- getTcEvBindsBag
- ; mb <- chase_ev_var tc_evbinds wv 0 [] ev_var
- ; return $ case mb of
- Nothing -> True
- Just min_guardedness -> min_guardedness > 0
- }
-
- where chase_ev_var :: EvBindMap -- Evidence binds
- -> EvVar -- Target variable whose gravity we want to return
- -> Int -- Current gravity
- -> [EvVar] -- Visited nodes
- -> EvVar -- Current node
- -> TcS (Maybe Int)
- chase_ev_var assocs trg curr_grav visited orig
- | trg == orig = return $ Just curr_grav
- | orig `elem` visited = return $ Nothing
- | Just (EvBind _ ev_trm) <- lookupEvBind assocs orig
- = chase_ev assocs trg curr_grav (orig:visited) ev_trm
-
- | otherwise = return Nothing
-
- chase_ev assocs trg curr_grav visited (EvId v)
- = chase_ev_var assocs trg curr_grav visited v
- chase_ev assocs trg curr_grav visited (EvSuperClass d_id _)
- = chase_ev_var assocs trg (curr_grav-1) visited d_id
- chase_ev assocs trg curr_grav visited (EvCast v co)
- = do { m1 <- chase_ev_var assocs trg curr_grav visited v
- ; m2 <- chase_co assocs trg curr_grav visited co
- ; return (comb_chase_res Nothing [m1,m2]) }
-
- chase_ev assocs trg curr_grav visited (EvCoercion co)
- = chase_co assocs trg curr_grav visited co
- chase_ev assocs trg curr_grav visited (EvDFunApp _ _ ev_deps)
- = do { chase_results <- mapM (chase_ev_var assocs trg (curr_grav+1) visited) ev_deps
- ; return (comb_chase_res Nothing chase_results) }
-
- chase_co assocs trg curr_grav visited co
- = -- Look for all the coercion variables in the coercion
- -- chase them, and combine the results. This is OK since the
- -- coercion will not contain any superclass terms -- anything
- -- that involves dictionaries will be bound in assocs.
- let co_vars = foldVarSet (\v vrs -> if isCoVar v then (v:vrs) else vrs) []
- (tyVarsOfType co)
- in do { chase_results <- mapM (chase_ev_var assocs trg curr_grav visited) co_vars
- ; return (comb_chase_res Nothing chase_results) }
-
- comb_chase_res f [] = f
- comb_chase_res f (Nothing:rest) = comb_chase_res f rest
- comb_chase_res Nothing (Just n:rest) = comb_chase_res (Just n) rest
- comb_chase_res (Just m) (Just n:rest) = comb_chase_res (Just (min n m)) rest
-
-
-- Matching and looking up classes and family instances
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
; traceTcS "matchClass success"
(vcat [text "dict" <+> ppr pred,
text "witness" <+> ppr dfun_id
- <+> ppr (idType dfun_id), ppr instEnvs ])
+ <+> ppr (idType dfun_id) ])
-- Record that this dfun is needed
; return $ MatchInstSingle (dfun_id, inst_tys)
} ;
-- DV: We never return MatchInstMany, since tcLookupFamInst never returns
-- multiple matches. Check.
}
-
-
--- Functional dependencies, instantiation of equations
--------------------------------------------------------
-
-mkWantedFunDepEqns :: WantedLoc
- -> [(Equation, (PredType, SDoc), (PredType, SDoc))]
- -> TcS [WantedEvVar]
-mkWantedFunDepEqns _ [] = return []
-mkWantedFunDepEqns loc eqns
- = do { traceTcS "Improve:" (vcat (map pprEquationDoc eqns))
- ; wevvars <- mapM to_work_item eqns
- ; return $ concat wevvars }
- where
- to_work_item :: (Equation, (PredType,SDoc), (PredType,SDoc)) -> TcS [WantedEvVar]
- to_work_item ((qtvs, pairs), d1, d2)
- = do { let tvs = varSetElems qtvs
- ; tvs' <- mapM instFlexiTcS tvs
- ; let subst = zipTopTvSubst tvs (mkTyVarTys tvs')
- loc' = pushErrCtxt FunDepOrigin (False, mkEqnMsg d1 d2) loc
- ; mapM (do_one subst loc') pairs }
-
- do_one subst loc' (ty1, ty2)
- = do { let sty1 = substTy subst ty1
- sty2 = substTy subst ty2
- ; ev <- newWantedCoVar sty1 sty2
- ; return (WantedEvVar ev loc') }
-
-pprEquationDoc :: (Equation, (PredType, SDoc), (PredType, SDoc)) -> SDoc
-pprEquationDoc (eqn, (p1, _), (p2, _))
- = vcat [pprEquation eqn, nest 2 (ppr p1), nest 2 (ppr p2)]
-
-mkEqnMsg :: (TcPredType, SDoc) -> (TcPredType, SDoc) -> TidyEnv
- -> TcM (TidyEnv, SDoc)
-mkEqnMsg (pred1,from1) (pred2,from2) tidy_env
- = do { pred1' <- TcM.zonkTcPredType pred1
- ; pred2' <- TcM.zonkTcPredType pred2
- ; let { pred1'' = tidyPred tidy_env pred1'
- ; pred2'' = tidyPred tidy_env pred2' }
- ; let msg = vcat [ptext (sLit "When using functional dependencies to combine"),
- nest 2 (sep [ppr pred1'' <> comma, nest 2 from1]),
- nest 2 (sep [ppr pred2'' <> comma, nest 2 from2])]
- ; return (tidy_env, msg) }
\end{code}
projects / ghc-hetmet.git / blobdiff