{-# LANGUAGE CPP #-}
{-# LANGUAGE DeriveFunctor #-}
{-# LANGUAGE DerivingStrategies #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE MultiWayIf #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE ViewPatterns #-}

{-# OPTIONS_GHC -Wno-incomplete-record-updates -Wno-orphans #-}

-- | Monadic definitions for the constraint solver
module GHC.Tc.Solver.Monad (

    -- The TcS monad
    TcS, runTcS, runTcSEarlyAbort, runTcSWithEvBinds, runTcSInerts,
    failTcS, warnTcS, addErrTcS, wrapTcS,
    runTcSEqualities,
    nestTcS, nestImplicTcS, setEvBindsTcS,
    emitImplicationTcS, emitTvImplicationTcS,

    selectNextWorkItem,
    getWorkList,
    updWorkListTcS,
    pushLevelNoWorkList,

    runTcPluginTcS, addUsedGRE, addUsedGREs, keepAlive,
    matchGlobalInst, TcM.ClsInstResult(..),

    QCInst(..),

    -- Tracing etc
    panicTcS, traceTcS,
    traceFireTcS, bumpStepCountTcS, csTraceTcS,
    wrapErrTcS, wrapWarnTcS,
    resetUnificationFlag, setUnificationFlag,

    -- Evidence creation and transformation
    MaybeNew(..), freshGoals, isFresh, getEvExpr,

    newTcEvBinds, newNoTcEvBinds,
    newWantedEq, emitNewWantedEq,
    newWanted,
    newWantedNC, newWantedEvVarNC,
    newBoundEvVarId,
    unifyTyVar, reportUnifications, touchabilityTest, TouchabilityTestResult(..),
    setEvBind, setWantedEq,
    setWantedEvTerm, setEvBindIfWanted,
    newEvVar, newGivenEvVar, newGivenEvVars,
    checkReductionDepth,
    getSolvedDicts, setSolvedDicts,

    getInstEnvs, getFamInstEnvs,                -- Getting the environments
    getTopEnv, getGblEnv, getLclEnv, setLclEnv,
    getTcEvBindsVar, getTcLevel,
    getTcEvTyCoVars, getTcEvBindsMap, setTcEvBindsMap,
    tcLookupClass, tcLookupId,

    -- Inerts
    updInertTcS, updInertCans, updInertDicts, updInertIrreds,
    getHasGivenEqs, setInertCans,
    getInertEqs, getInertCans, getInertGivens,
    getInertInsols, getInnermostGivenEqLevel,
    getTcSInerts, setTcSInerts,
    getUnsolvedInerts,
    removeInertCts, getPendingGivenScs,
    addInertCan, insertFunEq, addInertForAll,
    emitWorkNC, emitWork,
    lookupInertDict,

    -- The Model
    kickOutAfterUnification,

    -- Inert Safe Haskell safe-overlap failures
    addInertSafehask, insertSafeOverlapFailureTcS, updInertSafehask,
    getSafeOverlapFailures,

    -- Inert solved dictionaries
    addSolvedDict, lookupSolvedDict,

    -- Irreds
    foldIrreds,

    -- The family application cache
    lookupFamAppInert, lookupFamAppCache, extendFamAppCache,
    pprKicked,

    instDFunType,                              -- Instantiation

    -- MetaTyVars
    newFlexiTcSTy, instFlexi, instFlexiX,
    cloneMetaTyVar,
    tcInstSkolTyVarsX,

    TcLevel,
    isFilledMetaTyVar_maybe, isFilledMetaTyVar,
    zonkTyCoVarsAndFV, zonkTcType, zonkTcTypes, zonkTcTyVar, zonkCo,
    zonkTyCoVarsAndFVList,
    zonkSimples, zonkWC,
    zonkTyCoVarKind,

    -- References
    newTcRef, readTcRef, writeTcRef, updTcRef,

    -- Misc
    getDefaultInfo, getDynFlags, getGlobalRdrEnvTcS,
    matchFam, matchFamTcM,
    checkWellStagedDFun,
    pprEq,                                   -- Smaller utils, re-exported from TcM
                                             -- TODO (DV): these are only really used in the
                                             -- instance matcher in GHC.Tc.Solver. I am wondering
                                             -- if the whole instance matcher simply belongs
                                             -- here

    breakTyEqCycle_maybe, rewriterView
) where

import GHC.Prelude

import GHC.Driver.Env

import qualified GHC.Tc.Utils.Instantiate as TcM
import GHC.Core.InstEnv
import GHC.Tc.Instance.Family as FamInst
import GHC.Core.FamInstEnv

import qualified GHC.Tc.Utils.Monad    as TcM
import qualified GHC.Tc.Utils.TcMType  as TcM
import qualified GHC.Tc.Instance.Class as TcM( matchGlobalInst, ClsInstResult(..) )
import qualified GHC.Tc.Utils.Env      as TcM
       ( checkWellStaged, tcGetDefaultTys, tcLookupClass, tcLookupId, topIdLvl
       , tcInitTidyEnv )
import GHC.Tc.Instance.Class( InstanceWhat(..), safeOverlap, instanceReturnsDictCon )
import GHC.Tc.Utils.TcType
import GHC.Driver.Session
import GHC.Core.Type
import qualified GHC.Core.TyCo.Rep as Rep  -- this needs to be used only very locally
import GHC.Core.Coercion
import GHC.Core.Reduction

import GHC.Tc.Solver.Types
import GHC.Tc.Solver.InertSet

import GHC.Tc.Types.Evidence
import GHC.Core.Class
import GHC.Core.TyCon
import GHC.Tc.Errors.Types
import GHC.Types.Error ( mkPlainError, noHints )

import GHC.Types.Name
import GHC.Types.TyThing
import GHC.Unit.Module ( HasModule, getModule, extractModule )
import GHC.Types.Name.Reader ( GlobalRdrEnv, GlobalRdrElt )
import qualified GHC.Rename.Env as TcM
import GHC.Types.Var
import GHC.Types.Var.Env
import GHC.Types.Var.Set
import GHC.Utils.Outputable
import GHC.Utils.Panic
import GHC.Utils.Logger
import GHC.Utils.Misc (HasDebugCallStack)
import GHC.Data.Bag as Bag
import GHC.Types.Unique.Supply
import GHC.Tc.Types
import GHC.Tc.Types.Origin
import GHC.Tc.Types.Constraint
import GHC.Tc.Utils.Unify
import GHC.Core.Predicate
import GHC.Types.Unique.Set (nonDetEltsUniqSet)

import Control.Monad
import GHC.Utils.Monad
import Data.IORef
import GHC.Exts (oneShot)
import Data.List ( mapAccumL, partition, find )

#if defined(DEBUG)
import GHC.Data.Graph.Directed
#endif

{- *********************************************************************
*                                                                      *
                   Inert instances: inert_insts
*                                                                      *
********************************************************************* -}

addInertForAll :: QCInst -> TcS ()
-- Add a local Given instance, typically arising from a type signature
addInertForAll :: QCInst -> TcS ()
addInertForAll QCInst
new_qci
  = do { InertCans
ics  <- TcS InertCans
getInertCans
       ; InertCans
ics1 <- InertCans -> TcS InertCans
add_qci InertCans
ics

       -- Update given equalities. C.f updateGivenEqs
       ; TcLevel
tclvl <- TcS TcLevel
getTcLevel
       ; let pred :: Type
pred         = QCInst -> Type
qci_pred QCInst
new_qci
             not_equality :: Bool
not_equality = Type -> Bool
isClassPred Type
pred Bool -> Bool -> Bool
&& Bool -> Bool
not (Type -> Bool
isEqPred Type
pred)
                  -- True <=> definitely not an equality
                  -- A qci_pred like (f a) might be an equality

             ics2 :: InertCans
ics2 | Bool
not_equality = InertCans
ics1
                  | Bool
otherwise    = InertCans
ics1 { inert_given_eq_lvl :: TcLevel
inert_given_eq_lvl = TcLevel
tclvl
                                        , inert_given_eqs :: Bool
inert_given_eqs    = Bool
True }

       ; InertCans -> TcS ()
setInertCans InertCans
ics2 }
  where
    add_qci :: InertCans -> TcS InertCans
    -- See Note [Do not add duplicate quantified instances]
    add_qci :: InertCans -> TcS InertCans
add_qci ics :: InertCans
ics@(IC { inert_insts :: InertCans -> [QCInst]
inert_insts = [QCInst]
qcis })
      | (QCInst -> Bool) -> [QCInst] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
any QCInst -> Bool
same_qci [QCInst]
qcis
      = do { String -> SDoc -> TcS ()
traceTcS String
"skipping duplicate quantified instance" (QCInst -> SDoc
forall a. Outputable a => a -> SDoc
ppr QCInst
new_qci)
           ; InertCans -> TcS InertCans
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return InertCans
ics }

      | Bool
otherwise
      = do { String -> SDoc -> TcS ()
traceTcS String
"adding new inert quantified instance" (QCInst -> SDoc
forall a. Outputable a => a -> SDoc
ppr QCInst
new_qci)
           ; InertCans -> TcS InertCans
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (InertCans
ics { inert_insts :: [QCInst]
inert_insts = QCInst
new_qci QCInst -> [QCInst] -> [QCInst]
forall a. a -> [a] -> [a]
: [QCInst]
qcis }) }

    same_qci :: QCInst -> Bool
same_qci QCInst
old_qci = (() :: Constraint) => Type -> Type -> Bool
Type -> Type -> Bool
tcEqType (CtEvidence -> Type
ctEvPred (QCInst -> CtEvidence
qci_ev QCInst
old_qci))
                                (CtEvidence -> Type
ctEvPred (QCInst -> CtEvidence
qci_ev QCInst
new_qci))

{- Note [Do not add duplicate quantified instances]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider this (#15244):

  f :: (C g, D g) => ....
  class S g => C g where ...
  class S g => D g where ...
  class (forall a. Eq a => Eq (g a)) => S g where ...

Then in f's RHS there are two identical quantified constraints
available, one via the superclasses of C and one via the superclasses
of D.  The two are identical, and it seems wrong to reject the program
because of that. But without doing duplicate-elimination we will have
two matching QCInsts when we try to solve constraints arising from f's
RHS.

The simplest thing is simply to eliminate duplicates, which we do here.
-}

{- *********************************************************************
*                                                                      *
                  Adding an inert
*                                                                      *
************************************************************************

Note [Adding an equality to the InertCans]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When adding an equality to the inerts:

* Kick out any constraints that can be rewritten by the thing
  we are adding.  Done by kickOutRewritable.

* Note that unifying a:=ty, is like adding [G] a~ty; just use
  kickOutRewritable with Nominal, Given.  See kickOutAfterUnification.

Note [Kick out existing binding for implicit parameter]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Suppose we have (typecheck/should_compile/ImplicitParamFDs)
  flub :: (?x :: Int) => (Int, Integer)
  flub = (?x, let ?x = 5 in ?x)
When we are checking the last ?x occurrence, we guess its type
to be a fresh unification variable alpha and emit an (IP "x" alpha)
constraint. But the given (?x :: Int) has been translated to an
IP "x" Int constraint, which has a functional dependency from the
name to the type. So fundep interaction tells us that alpha ~ Int,
and we get a type error. This is bad.

Instead, we wish to excise any old given for an IP when adding a
new one. We also must make sure not to float out
any IP constraints outside an implication that binds an IP of
the same name; see GHC.Tc.Solver.floatConstraints.
-}

addInertCan :: Ct -> TcS ()
-- Precondition: item /is/ canonical
-- See Note [Adding an equality to the InertCans]
addInertCan :: Ct -> TcS ()
addInertCan Ct
ct =
    do { String -> SDoc -> TcS ()
traceTcS String
"addInertCan {" (SDoc -> TcS ()) -> SDoc -> TcS ()
forall a b. (a -> b) -> a -> b
$
         String -> SDoc
text String
"Trying to insert new inert item:" SDoc -> SDoc -> SDoc
<+> Ct -> SDoc
forall a. Outputable a => a -> SDoc
ppr Ct
ct
       ; (TcSEnv -> TcM ()) -> TcS ()
forall a. (TcSEnv -> TcM a) -> TcS a
mkTcS (\TcSEnv{tcs_abort_on_insoluble :: TcSEnv -> Bool
tcs_abort_on_insoluble=Bool
abort_flag} ->
                 Bool -> TcM () -> TcM ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (Bool
abort_flag Bool -> Bool -> Bool
&& Ct -> Bool
insolubleEqCt Ct
ct) TcM ()
forall env a. IOEnv env a
TcM.failM)
       ; InertCans
ics <- TcS InertCans
getInertCans
       ; InertCans
ics <- InertCans -> Ct -> TcS InertCans
maybeKickOut InertCans
ics Ct
ct
       ; TcLevel
tclvl <- TcS TcLevel
getTcLevel
       ; InertCans -> TcS ()
setInertCans (TcLevel -> InertCans -> Ct -> InertCans
addInertItem TcLevel
tclvl InertCans
ics Ct
ct)

       ; String -> SDoc -> TcS ()
traceTcS String
"addInertCan }" (SDoc -> TcS ()) -> SDoc -> TcS ()
forall a b. (a -> b) -> a -> b
$ SDoc
empty }

maybeKickOut :: InertCans -> Ct -> TcS InertCans
-- For a CEqCan, kick out any inert that can be rewritten by the CEqCan
maybeKickOut :: InertCans -> Ct -> TcS InertCans
maybeKickOut InertCans
ics Ct
ct
  | CEqCan { cc_lhs :: Ct -> CanEqLHS
cc_lhs = CanEqLHS
lhs, cc_ev :: Ct -> CtEvidence
cc_ev = CtEvidence
ev, cc_eq_rel :: Ct -> EqRel
cc_eq_rel = EqRel
eq_rel } <- Ct
ct
  = do { (Int
_, InertCans
ics') <- CtFlavourRole -> CanEqLHS -> InertCans -> TcS (Int, InertCans)
kickOutRewritable (CtEvidence -> CtFlavour
ctEvFlavour CtEvidence
ev, EqRel
eq_rel) CanEqLHS
lhs InertCans
ics
       ; InertCans -> TcS InertCans
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return InertCans
ics' }

     -- See [Kick out existing binding for implicit parameter]
  | Ct -> Bool
isGivenCt Ct
ct
  , CDictCan { cc_class :: Ct -> Class
cc_class = Class
cls, cc_tyargs :: Ct -> [Type]
cc_tyargs = [Type
ip_name_strty, Type
_ip_ty] } <- Ct
ct
  , Class -> Bool
isIPClass Class
cls
  , Just FastString
ip_name <- Type -> Maybe FastString
isStrLitTy Type
ip_name_strty
     -- Would this be more efficient if we used findDictsByClass and then delDict?
  = let dict_map :: DictMap Ct
dict_map = InertCans -> DictMap Ct
inert_dicts InertCans
ics
        dict_map' :: DictMap Ct
dict_map' = (Ct -> Bool) -> DictMap Ct -> DictMap Ct
filterDicts Ct -> Bool
doesn't_match_ip_name DictMap Ct
dict_map

        doesn't_match_ip_name :: Ct -> Bool
        doesn't_match_ip_name :: Ct -> Bool
doesn't_match_ip_name Ct
ct
          | Just (FastString
inert_ip_name, Type
_inert_ip_ty) <- Type -> Maybe (FastString, Type)
isIPPred_maybe (Ct -> Type
ctPred Ct
ct)
          = FastString
inert_ip_name FastString -> FastString -> Bool
forall a. Eq a => a -> a -> Bool
/= FastString
ip_name

          | Bool
otherwise
          = Bool
True

    in
    InertCans -> TcS InertCans
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (InertCans
ics { inert_dicts :: DictMap Ct
inert_dicts = DictMap Ct
dict_map' })

  | Bool
otherwise
  = InertCans -> TcS InertCans
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return InertCans
ics

-----------------------------------------
kickOutRewritable  :: CtFlavourRole  -- Flavour/role of the equality that
                                      -- is being added to the inert set
                   -> CanEqLHS        -- The new equality is lhs ~ ty
                   -> InertCans
                   -> TcS (Int, InertCans)
kickOutRewritable :: CtFlavourRole -> CanEqLHS -> InertCans -> TcS (Int, InertCans)
kickOutRewritable CtFlavourRole
new_fr CanEqLHS
new_lhs InertCans
ics
  = do { let (WorkList
kicked_out, InertCans
ics') = CtFlavourRole -> CanEqLHS -> InertCans -> (WorkList, InertCans)
kickOutRewritableLHS CtFlavourRole
new_fr CanEqLHS
new_lhs InertCans
ics
             n_kicked :: Int
n_kicked = WorkList -> Int
workListSize WorkList
kicked_out

       ; Bool -> TcS () -> TcS ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
unless (Int
n_kicked Int -> Int -> Bool
forall a. Eq a => a -> a -> Bool
== Int
0) (TcS () -> TcS ()) -> TcS () -> TcS ()
forall a b. (a -> b) -> a -> b
$
         do { (WorkList -> WorkList) -> TcS ()
updWorkListTcS (WorkList -> WorkList -> WorkList
appendWorkList WorkList
kicked_out)

              -- The famapp-cache contains Given evidence from the inert set.
              -- If we're kicking out Givens, we need to remove this evidence
              -- from the cache, too.
            ; let kicked_given_ev_vars :: [TcTyVar]
kicked_given_ev_vars =
                    [ TcTyVar
ev_var | Ct
ct <- WorkList -> [Ct]
wl_eqs WorkList
kicked_out
                             , CtGiven { ctev_evar :: CtEvidence -> TcTyVar
ctev_evar = TcTyVar
ev_var } <- [Ct -> CtEvidence
ctEvidence Ct
ct] ]
            ; Bool -> TcS () -> TcS ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (CtFlavourRole
new_fr CtFlavourRole -> CtFlavourRole -> Bool
`eqCanRewriteFR` (CtFlavour
Given, EqRel
NomEq) Bool -> Bool -> Bool
&&
                   -- if this isn't true, no use looking through the constraints
                    Bool -> Bool
not ([TcTyVar] -> Bool
forall a. [a] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [TcTyVar]
kicked_given_ev_vars)) (TcS () -> TcS ()) -> TcS () -> TcS ()
forall a b. (a -> b) -> a -> b
$
              do { String -> SDoc -> TcS ()
traceTcS String
"Given(s) have been kicked out; drop from famapp-cache"
                            ([TcTyVar] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TcTyVar]
kicked_given_ev_vars)
                 ; VarSet -> TcS ()
dropFromFamAppCache ([TcTyVar] -> VarSet
mkVarSet [TcTyVar]
kicked_given_ev_vars) }

            ; SDoc -> TcS ()
csTraceTcS (SDoc -> TcS ()) -> SDoc -> TcS ()
forall a b. (a -> b) -> a -> b
$
              SDoc -> Int -> SDoc -> SDoc
hang (String -> SDoc
text String
"Kick out, lhs =" SDoc -> SDoc -> SDoc
<+> CanEqLHS -> SDoc
forall a. Outputable a => a -> SDoc
ppr CanEqLHS
new_lhs)
                 Int
2 ([SDoc] -> SDoc
vcat [ String -> SDoc
text String
"n-kicked =" SDoc -> SDoc -> SDoc
<+> Int -> SDoc
int Int
n_kicked
                         , String -> SDoc
text String
"kicked_out =" SDoc -> SDoc -> SDoc
<+> WorkList -> SDoc
forall a. Outputable a => a -> SDoc
ppr WorkList
kicked_out
                         , String -> SDoc
text String
"Residual inerts =" SDoc -> SDoc -> SDoc
<+> InertCans -> SDoc
forall a. Outputable a => a -> SDoc
ppr InertCans
ics' ]) }

       ; (Int, InertCans) -> TcS (Int, InertCans)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (Int
n_kicked, InertCans
ics') }

kickOutAfterUnification :: TcTyVar -> TcS Int
kickOutAfterUnification :: TcTyVar -> TcS Int
kickOutAfterUnification TcTyVar
new_tv
  = do { InertCans
ics <- TcS InertCans
getInertCans
       ; (Int
n_kicked, InertCans
ics2) <- CtFlavourRole -> CanEqLHS -> InertCans -> TcS (Int, InertCans)
kickOutRewritable (CtFlavour
Given,EqRel
NomEq)
                                                 (TcTyVar -> CanEqLHS
TyVarLHS TcTyVar
new_tv) InertCans
ics
                     -- Given because the tv := xi is given; NomEq because
                     -- only nominal equalities are solved by unification

       ; InertCans -> TcS ()
setInertCans InertCans
ics2
       ; Int -> TcS Int
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return Int
n_kicked }

-- See Wrinkle (2) in Note [Equalities with incompatible kinds] in GHC.Tc.Solver.Canonical
-- It's possible that this could just go ahead and unify, but could there be occurs-check
-- problems? Seems simpler just to kick out.
kickOutAfterFillingCoercionHole :: CoercionHole -> TcS ()
kickOutAfterFillingCoercionHole :: CoercionHole -> TcS ()
kickOutAfterFillingCoercionHole CoercionHole
hole
  = do { InertCans
ics <- TcS InertCans
getInertCans
       ; let (WorkList
kicked_out, InertCans
ics') = InertCans -> (WorkList, InertCans)
kick_out InertCans
ics
             n_kicked :: Int
n_kicked           = WorkList -> Int
workListSize WorkList
kicked_out

       ; Bool -> TcS () -> TcS ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
unless (Int
n_kicked Int -> Int -> Bool
forall a. Eq a => a -> a -> Bool
== Int
0) (TcS () -> TcS ()) -> TcS () -> TcS ()
forall a b. (a -> b) -> a -> b
$
         do { (WorkList -> WorkList) -> TcS ()
updWorkListTcS (WorkList -> WorkList -> WorkList
appendWorkList WorkList
kicked_out)
            ; SDoc -> TcS ()
csTraceTcS (SDoc -> TcS ()) -> SDoc -> TcS ()
forall a b. (a -> b) -> a -> b
$
              SDoc -> Int -> SDoc -> SDoc
hang (String -> SDoc
text String
"Kick out, hole =" SDoc -> SDoc -> SDoc
<+> CoercionHole -> SDoc
forall a. Outputable a => a -> SDoc
ppr CoercionHole
hole)
                 Int
2 ([SDoc] -> SDoc
vcat [ String -> SDoc
text String
"n-kicked =" SDoc -> SDoc -> SDoc
<+> Int -> SDoc
int Int
n_kicked
                         , String -> SDoc
text String
"kicked_out =" SDoc -> SDoc -> SDoc
<+> WorkList -> SDoc
forall a. Outputable a => a -> SDoc
ppr WorkList
kicked_out
                         , String -> SDoc
text String
"Residual inerts =" SDoc -> SDoc -> SDoc
<+> InertCans -> SDoc
forall a. Outputable a => a -> SDoc
ppr InertCans
ics' ]) }

       ; InertCans -> TcS ()
setInertCans InertCans
ics' }
  where
    kick_out :: InertCans -> (WorkList, InertCans)
    kick_out :: InertCans -> (WorkList, InertCans)
kick_out ics :: InertCans
ics@(IC { inert_eqs :: InertCans -> InertEqs
inert_eqs = InertEqs
eqs, inert_funeqs :: InertCans -> FunEqMap [Ct]
inert_funeqs = FunEqMap [Ct]
funeqs })
      = (WorkList
kicked_out, InertCans
ics { inert_eqs :: InertEqs
inert_eqs = InertEqs
eqs_to_keep, inert_funeqs :: FunEqMap [Ct]
inert_funeqs = FunEqMap [Ct]
funeqs_to_keep })
      where
        ([Ct]
eqs_to_kick, InertEqs
eqs_to_keep)       = (Ct -> Bool) -> InertEqs -> ([Ct], InertEqs)
partitionInertEqs Ct -> Bool
kick_ct InertEqs
eqs
        ([Ct]
funeqs_to_kick, FunEqMap [Ct]
funeqs_to_keep) = (Ct -> Bool) -> FunEqMap [Ct] -> ([Ct], FunEqMap [Ct])
partitionFunEqs Ct -> Bool
kick_ct FunEqMap [Ct]
funeqs
        kicked_out :: WorkList
kicked_out = [Ct] -> WorkList -> WorkList
extendWorkListCts ([Ct]
eqs_to_kick [Ct] -> [Ct] -> [Ct]
forall a. [a] -> [a] -> [a]
++ [Ct]
funeqs_to_kick) WorkList
emptyWorkList

    kick_ct :: Ct -> Bool
         -- True: kick out; False: keep.
    kick_ct :: Ct -> Bool
kick_ct (CEqCan { cc_rhs :: Ct -> Type
cc_rhs = Type
rhs, cc_ev :: Ct -> CtEvidence
cc_ev = CtEvidence
ctev })
      = CtEvidence -> Bool
isWanted CtEvidence
ctev Bool -> Bool -> Bool
&&    -- optimisation: givens don't have coercion holes anyway
        Type
rhs Type -> CoercionHole -> Bool
`hasThisCoercionHoleTy` CoercionHole
hole
    kick_ct Ct
other = String -> SDoc -> Bool
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"kick_ct (coercion hole)" (Ct -> SDoc
forall a. Outputable a => a -> SDoc
ppr Ct
other)

--------------
addInertSafehask :: InertCans -> Ct -> InertCans
addInertSafehask :: InertCans -> Ct -> InertCans
addInertSafehask InertCans
ics item :: Ct
item@(CDictCan { cc_class :: Ct -> Class
cc_class = Class
cls, cc_tyargs :: Ct -> [Type]
cc_tyargs = [Type]
tys })
  = InertCans
ics { inert_safehask :: DictMap Ct
inert_safehask = DictMap Ct -> Class -> [Type] -> Ct -> DictMap Ct
forall a. DictMap a -> Class -> [Type] -> a -> DictMap a
addDict (InertCans -> DictMap Ct
inert_dicts InertCans
ics) Class
cls [Type]
tys Ct
item }

addInertSafehask InertCans
_ Ct
item
  = String -> SDoc -> InertCans
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"addInertSafehask: can't happen! Inserting " (SDoc -> InertCans) -> SDoc -> InertCans
forall a b. (a -> b) -> a -> b
$ Ct -> SDoc
forall a. Outputable a => a -> SDoc
ppr Ct
item

insertSafeOverlapFailureTcS :: InstanceWhat -> Ct -> TcS ()
-- See Note [Safe Haskell Overlapping Instances Implementation] in GHC.Tc.Solver
insertSafeOverlapFailureTcS :: InstanceWhat -> Ct -> TcS ()
insertSafeOverlapFailureTcS InstanceWhat
what Ct
item
  | InstanceWhat -> Bool
safeOverlap InstanceWhat
what = () -> TcS ()
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return ()
  | Bool
otherwise        = (InertCans -> InertCans) -> TcS ()
updInertCans (\InertCans
ics -> InertCans -> Ct -> InertCans
addInertSafehask InertCans
ics Ct
item)

getSafeOverlapFailures :: TcS Cts
-- See Note [Safe Haskell Overlapping Instances Implementation] in GHC.Tc.Solver
getSafeOverlapFailures :: TcS Cts
getSafeOverlapFailures
 = do { IC { inert_safehask :: InertCans -> DictMap Ct
inert_safehask = DictMap Ct
safehask } <- TcS InertCans
getInertCans
      ; Cts -> TcS Cts
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (Cts -> TcS Cts) -> Cts -> TcS Cts
forall a b. (a -> b) -> a -> b
$ (Ct -> Cts -> Cts) -> DictMap Ct -> Cts -> Cts
forall a b. (a -> b -> b) -> DictMap a -> b -> b
foldDicts Ct -> Cts -> Cts
consCts DictMap Ct
safehask Cts
emptyCts }

--------------
addSolvedDict :: InstanceWhat -> CtEvidence -> Class -> [Type] -> TcS ()
-- Conditionally add a new item in the solved set of the monad
-- See Note [Solved dictionaries] in GHC.Tc.Solver.InertSet
addSolvedDict :: InstanceWhat -> CtEvidence -> Class -> [Type] -> TcS ()
addSolvedDict InstanceWhat
what CtEvidence
item Class
cls [Type]
tys
  | CtEvidence -> Bool
isWanted CtEvidence
item
  , InstanceWhat -> Bool
instanceReturnsDictCon InstanceWhat
what
  = do { String -> SDoc -> TcS ()
traceTcS String
"updSolvedSetTcs:" (SDoc -> TcS ()) -> SDoc -> TcS ()
forall a b. (a -> b) -> a -> b
$ CtEvidence -> SDoc
forall a. Outputable a => a -> SDoc
ppr CtEvidence
item
       ; (InertSet -> InertSet) -> TcS ()
updInertTcS ((InertSet -> InertSet) -> TcS ())
-> (InertSet -> InertSet) -> TcS ()
forall a b. (a -> b) -> a -> b
$ \ InertSet
ics ->
             InertSet
ics { inert_solved_dicts :: DictMap CtEvidence
inert_solved_dicts = DictMap CtEvidence
-> Class -> [Type] -> CtEvidence -> DictMap CtEvidence
forall a. DictMap a -> Class -> [Type] -> a -> DictMap a
addDict (InertSet -> DictMap CtEvidence
inert_solved_dicts InertSet
ics) Class
cls [Type]
tys CtEvidence
item } }
  | Bool
otherwise
  = () -> TcS ()
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return ()

getSolvedDicts :: TcS (DictMap CtEvidence)
getSolvedDicts :: TcS (DictMap CtEvidence)
getSolvedDicts = do { InertSet
ics <- TcS InertSet
getTcSInerts; DictMap CtEvidence -> TcS (DictMap CtEvidence)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (InertSet -> DictMap CtEvidence
inert_solved_dicts InertSet
ics) }

setSolvedDicts :: DictMap CtEvidence -> TcS ()
setSolvedDicts :: DictMap CtEvidence -> TcS ()
setSolvedDicts DictMap CtEvidence
solved_dicts
  = (InertSet -> InertSet) -> TcS ()
updInertTcS ((InertSet -> InertSet) -> TcS ())
-> (InertSet -> InertSet) -> TcS ()
forall a b. (a -> b) -> a -> b
$ \ InertSet
ics ->
    InertSet
ics { inert_solved_dicts :: DictMap CtEvidence
inert_solved_dicts = DictMap CtEvidence
solved_dicts }

{- *********************************************************************
*                                                                      *
                  Other inert-set operations
*                                                                      *
********************************************************************* -}

updInertTcS :: (InertSet -> InertSet) -> TcS ()
-- Modify the inert set with the supplied function
updInertTcS :: (InertSet -> InertSet) -> TcS ()
updInertTcS InertSet -> InertSet
upd_fn
  = do { IORef InertSet
is_var <- TcS (IORef InertSet)
getTcSInertsRef
       ; TcM () -> TcS ()
forall a. TcM a -> TcS a
wrapTcS (do { InertSet
curr_inert <- IORef InertSet -> TcRnIf TcGblEnv TcLclEnv InertSet
forall a gbl lcl. TcRef a -> TcRnIf gbl lcl a
TcM.readTcRef IORef InertSet
is_var
                     ; IORef InertSet -> InertSet -> TcM ()
forall a gbl lcl. TcRef a -> a -> TcRnIf gbl lcl ()
TcM.writeTcRef IORef InertSet
is_var (InertSet -> InertSet
upd_fn InertSet
curr_inert) }) }

getInertCans :: TcS InertCans
getInertCans :: TcS InertCans
getInertCans = do { InertSet
inerts <- TcS InertSet
getTcSInerts; InertCans -> TcS InertCans
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (InertSet -> InertCans
inert_cans InertSet
inerts) }

setInertCans :: InertCans -> TcS ()
setInertCans :: InertCans -> TcS ()
setInertCans InertCans
ics = (InertSet -> InertSet) -> TcS ()
updInertTcS ((InertSet -> InertSet) -> TcS ())
-> (InertSet -> InertSet) -> TcS ()
forall a b. (a -> b) -> a -> b
$ \ InertSet
inerts -> InertSet
inerts { inert_cans :: InertCans
inert_cans = InertCans
ics }

updRetInertCans :: (InertCans -> (a, InertCans)) -> TcS a
-- Modify the inert set with the supplied function
updRetInertCans :: forall a. (InertCans -> (a, InertCans)) -> TcS a
updRetInertCans InertCans -> (a, InertCans)
upd_fn
  = do { IORef InertSet
is_var <- TcS (IORef InertSet)
getTcSInertsRef
       ; TcM a -> TcS a
forall a. TcM a -> TcS a
wrapTcS (do { InertSet
inerts <- IORef InertSet -> TcRnIf TcGblEnv TcLclEnv InertSet
forall a gbl lcl. TcRef a -> TcRnIf gbl lcl a
TcM.readTcRef IORef InertSet
is_var
                     ; let (a
res, InertCans
cans') = InertCans -> (a, InertCans)
upd_fn (InertSet -> InertCans
inert_cans InertSet
inerts)
                     ; IORef InertSet -> InertSet -> TcM ()
forall a gbl lcl. TcRef a -> a -> TcRnIf gbl lcl ()
TcM.writeTcRef IORef InertSet
is_var (InertSet
inerts { inert_cans :: InertCans
inert_cans = InertCans
cans' })
                     ; a -> TcM a
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return a
res }) }

updInertCans :: (InertCans -> InertCans) -> TcS ()
-- Modify the inert set with the supplied function
updInertCans :: (InertCans -> InertCans) -> TcS ()
updInertCans InertCans -> InertCans
upd_fn
  = (InertSet -> InertSet) -> TcS ()
updInertTcS ((InertSet -> InertSet) -> TcS ())
-> (InertSet -> InertSet) -> TcS ()
forall a b. (a -> b) -> a -> b
$ \ InertSet
inerts -> InertSet
inerts { inert_cans :: InertCans
inert_cans = InertCans -> InertCans
upd_fn (InertSet -> InertCans
inert_cans InertSet
inerts) }

updInertDicts :: (DictMap Ct -> DictMap Ct) -> TcS ()
-- Modify the inert set with the supplied function
updInertDicts :: (DictMap Ct -> DictMap Ct) -> TcS ()
updInertDicts DictMap Ct -> DictMap Ct
upd_fn
  = (InertCans -> InertCans) -> TcS ()
updInertCans ((InertCans -> InertCans) -> TcS ())
-> (InertCans -> InertCans) -> TcS ()
forall a b. (a -> b) -> a -> b
$ \ InertCans
ics -> InertCans
ics { inert_dicts :: DictMap Ct
inert_dicts = DictMap Ct -> DictMap Ct
upd_fn (InertCans -> DictMap Ct
inert_dicts InertCans
ics) }

updInertSafehask :: (DictMap Ct -> DictMap Ct) -> TcS ()
-- Modify the inert set with the supplied function
updInertSafehask :: (DictMap Ct -> DictMap Ct) -> TcS ()
updInertSafehask DictMap Ct -> DictMap Ct
upd_fn
  = (InertCans -> InertCans) -> TcS ()
updInertCans ((InertCans -> InertCans) -> TcS ())
-> (InertCans -> InertCans) -> TcS ()
forall a b. (a -> b) -> a -> b
$ \ InertCans
ics -> InertCans
ics { inert_safehask :: DictMap Ct
inert_safehask = DictMap Ct -> DictMap Ct
upd_fn (InertCans -> DictMap Ct
inert_safehask InertCans
ics) }

updInertIrreds :: (Cts -> Cts) -> TcS ()
-- Modify the inert set with the supplied function
updInertIrreds :: (Cts -> Cts) -> TcS ()
updInertIrreds Cts -> Cts
upd_fn
  = (InertCans -> InertCans) -> TcS ()
updInertCans ((InertCans -> InertCans) -> TcS ())
-> (InertCans -> InertCans) -> TcS ()
forall a b. (a -> b) -> a -> b
$ \ InertCans
ics -> InertCans
ics { inert_irreds :: Cts
inert_irreds = Cts -> Cts
upd_fn (InertCans -> Cts
inert_irreds InertCans
ics) }

getInertEqs :: TcS InertEqs
getInertEqs :: TcS InertEqs
getInertEqs = do { InertCans
inert <- TcS InertCans
getInertCans; InertEqs -> TcS InertEqs
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (InertCans -> InertEqs
inert_eqs InertCans
inert) }

getInnermostGivenEqLevel :: TcS TcLevel
getInnermostGivenEqLevel :: TcS TcLevel
getInnermostGivenEqLevel = do { InertCans
inert <- TcS InertCans
getInertCans
                              ; TcLevel -> TcS TcLevel
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (InertCans -> TcLevel
inert_given_eq_lvl InertCans
inert) }

getInertInsols :: TcS Cts
-- Returns insoluble equality constraints and TypeError constraints,
-- specifically including Givens.
--
-- Note that this function only inspects irreducible constraints;
-- a DictCan constraint such as 'Eq (TypeError msg)' is not
-- considered to be an insoluble constraint by this function.
--
-- See Note [Pattern match warnings with insoluble Givens] in GHC.Tc.Solver.
getInertInsols :: TcS Cts
getInertInsols = do { InertCans
inert <- TcS InertCans
getInertCans
                    ; Cts -> TcS Cts
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (Cts -> TcS Cts) -> Cts -> TcS Cts
forall a b. (a -> b) -> a -> b
$ (Ct -> Bool) -> Cts -> Cts
forall a. (a -> Bool) -> Bag a -> Bag a
filterBag Ct -> Bool
insolubleCt (InertCans -> Cts
inert_irreds InertCans
inert) }

getInertGivens :: TcS [Ct]
-- Returns the Given constraints in the inert set
getInertGivens :: TcS [Ct]
getInertGivens
  = do { InertCans
inerts <- TcS InertCans
getInertCans
       ; let all_cts :: [Ct]
all_cts = (Ct -> [Ct] -> [Ct]) -> Cts -> [Ct] -> [Ct]
forall b. (Ct -> b -> b) -> Cts -> b -> b
foldIrreds (:) (InertCans -> Cts
inert_irreds InertCans
inerts)
                     ([Ct] -> [Ct]) -> [Ct] -> [Ct]
forall a b. (a -> b) -> a -> b
$ (Ct -> [Ct] -> [Ct]) -> DictMap Ct -> [Ct] -> [Ct]
forall a b. (a -> b -> b) -> DictMap a -> b -> b
foldDicts (:) (InertCans -> DictMap Ct
inert_dicts InertCans
inerts)
                     ([Ct] -> [Ct]) -> [Ct] -> [Ct]
forall a b. (a -> b) -> a -> b
$ ([Ct] -> [Ct] -> [Ct]) -> FunEqMap [Ct] -> [Ct] -> [Ct]
forall a b. (a -> b -> b) -> DictMap a -> b -> b
foldFunEqs [Ct] -> [Ct] -> [Ct]
forall a. [a] -> [a] -> [a]
(++) (InertCans -> FunEqMap [Ct]
inert_funeqs InertCans
inerts)
                     ([Ct] -> [Ct]) -> [Ct] -> [Ct]
forall a b. (a -> b) -> a -> b
$ ([Ct] -> [Ct] -> [Ct]) -> [Ct] -> InertEqs -> [Ct]
forall a b. (a -> b -> b) -> b -> DVarEnv a -> b
foldDVarEnv [Ct] -> [Ct] -> [Ct]
forall a. [a] -> [a] -> [a]
(++) [] (InertCans -> InertEqs
inert_eqs InertCans
inerts)
       ; [Ct] -> TcS [Ct]
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return ((Ct -> Bool) -> [Ct] -> [Ct]
forall a. (a -> Bool) -> [a] -> [a]
filter Ct -> Bool
isGivenCt [Ct]
all_cts) }

getPendingGivenScs :: TcS [Ct]
-- Find all inert Given dictionaries, or quantified constraints,
--     whose cc_pend_sc flag is True
--     and that belong to the current level
-- Set their cc_pend_sc flag to False in the inert set, and return that Ct
getPendingGivenScs :: TcS [Ct]
getPendingGivenScs = do { TcLevel
lvl <- TcS TcLevel
getTcLevel
                        ; (InertCans -> ([Ct], InertCans)) -> TcS [Ct]
forall a. (InertCans -> (a, InertCans)) -> TcS a
updRetInertCans (TcLevel -> InertCans -> ([Ct], InertCans)
get_sc_pending TcLevel
lvl) }

get_sc_pending :: TcLevel -> InertCans -> ([Ct], InertCans)
get_sc_pending :: TcLevel -> InertCans -> ([Ct], InertCans)
get_sc_pending TcLevel
this_lvl ic :: InertCans
ic@(IC { inert_dicts :: InertCans -> DictMap Ct
inert_dicts = DictMap Ct
dicts, inert_insts :: InertCans -> [QCInst]
inert_insts = [QCInst]
insts })
  = Bool -> SDoc -> ([Ct], InertCans) -> ([Ct], InertCans)
forall a. HasCallStack => Bool -> SDoc -> a -> a
assertPpr ((Ct -> Bool) -> [Ct] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
all Ct -> Bool
isGivenCt [Ct]
sc_pending) ([Ct] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Ct]
sc_pending)
       -- When getPendingScDics is called,
       -- there are never any Wanteds in the inert set
    ([Ct]
sc_pending, InertCans
ic { inert_dicts :: DictMap Ct
inert_dicts = DictMap Ct
dicts', inert_insts :: [QCInst]
inert_insts = [QCInst]
insts' })
  where
    sc_pending :: [Ct]
sc_pending = [Ct]
sc_pend_insts [Ct] -> [Ct] -> [Ct]
forall a. [a] -> [a] -> [a]
++ [Ct]
sc_pend_dicts

    sc_pend_dicts :: [Ct]
sc_pend_dicts = (Ct -> [Ct] -> [Ct]) -> DictMap Ct -> [Ct] -> [Ct]
forall a b. (a -> b -> b) -> DictMap a -> b -> b
foldDicts Ct -> [Ct] -> [Ct]
get_pending DictMap Ct
dicts []
    dicts' :: DictMap Ct
dicts' = (Ct -> DictMap Ct -> DictMap Ct)
-> DictMap Ct -> [Ct] -> DictMap Ct
forall a b. (a -> b -> b) -> b -> [a] -> b
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr Ct -> DictMap Ct -> DictMap Ct
add DictMap Ct
dicts [Ct]
sc_pend_dicts

    ([Ct]
sc_pend_insts, [QCInst]
insts') = ([Ct] -> QCInst -> ([Ct], QCInst))
-> [Ct] -> [QCInst] -> ([Ct], [QCInst])
forall (t :: * -> *) s a b.
Traversable t =>
(s -> a -> (s, b)) -> s -> t a -> (s, t b)
mapAccumL [Ct] -> QCInst -> ([Ct], QCInst)
get_pending_inst [] [QCInst]
insts

    get_pending :: Ct -> [Ct] -> [Ct]  -- Get dicts with cc_pend_sc = True
                                       -- but flipping the flag
    get_pending :: Ct -> [Ct] -> [Ct]
get_pending Ct
dict [Ct]
dicts
        | Just Ct
dict' <- Ct -> Maybe Ct
pendingScDict_maybe Ct
dict
        , CtEvidence -> Bool
belongs_to_this_level (Ct -> CtEvidence
ctEvidence Ct
dict)
        = Ct
dict' Ct -> [Ct] -> [Ct]
forall a. a -> [a] -> [a]
: [Ct]
dicts
        | Bool
otherwise
        = [Ct]
dicts

    add :: Ct -> DictMap Ct -> DictMap Ct
    add :: Ct -> DictMap Ct -> DictMap Ct
add ct :: Ct
ct@(CDictCan { cc_class :: Ct -> Class
cc_class = Class
cls, cc_tyargs :: Ct -> [Type]
cc_tyargs = [Type]
tys }) DictMap Ct
dicts
        = DictMap Ct -> Class -> [Type] -> Ct -> DictMap Ct
forall a. DictMap a -> Class -> [Type] -> a -> DictMap a
addDict DictMap Ct
dicts Class
cls [Type]
tys Ct
ct
    add Ct
ct DictMap Ct
_ = String -> SDoc -> DictMap Ct
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"getPendingScDicts" (Ct -> SDoc
forall a. Outputable a => a -> SDoc
ppr Ct
ct)

    get_pending_inst :: [Ct] -> QCInst -> ([Ct], QCInst)
    get_pending_inst :: [Ct] -> QCInst -> ([Ct], QCInst)
get_pending_inst [Ct]
cts qci :: QCInst
qci@(QCI { qci_ev :: QCInst -> CtEvidence
qci_ev = CtEvidence
ev })
       | Just QCInst
qci' <- QCInst -> Maybe QCInst
pendingScInst_maybe QCInst
qci
       , CtEvidence -> Bool
belongs_to_this_level CtEvidence
ev
       = (QCInst -> Ct
CQuantCan QCInst
qci' Ct -> [Ct] -> [Ct]
forall a. a -> [a] -> [a]
: [Ct]
cts, QCInst
qci')
       | Bool
otherwise
       = ([Ct]
cts, QCInst
qci)

    belongs_to_this_level :: CtEvidence -> Bool
belongs_to_this_level CtEvidence
ev = CtLoc -> TcLevel
ctLocLevel (CtEvidence -> CtLoc
ctEvLoc CtEvidence
ev) TcLevel -> TcLevel -> Bool
forall a. Eq a => a -> a -> Bool
== TcLevel
this_lvl
    -- We only want Givens from this level; see (3a) in
    -- Note [The superclass story] in GHC.Tc.Solver.Canonical

getUnsolvedInerts :: TcS ( Bag Implication
                         , Cts )   -- All simple constraints
-- Return all the unsolved [Wanted] constraints
--
-- Post-condition: the returned simple constraints are all fully zonked
--                     (because they come from the inert set)
--                 the unsolved implics may not be
getUnsolvedInerts :: TcS (Bag Implication, Cts)
getUnsolvedInerts
 = do { IC { inert_eqs :: InertCans -> InertEqs
inert_eqs     = InertEqs
tv_eqs
           , inert_funeqs :: InertCans -> FunEqMap [Ct]
inert_funeqs  = FunEqMap [Ct]
fun_eqs
           , inert_irreds :: InertCans -> Cts
inert_irreds  = Cts
irreds
           , inert_dicts :: InertCans -> DictMap Ct
inert_dicts   = DictMap Ct
idicts
           } <- TcS InertCans
getInertCans

      ; let unsolved_tv_eqs :: Cts
unsolved_tv_eqs  = (Ct -> Cts -> Cts) -> InertEqs -> Cts -> Cts
forall b. (Ct -> b -> b) -> InertEqs -> b -> b
foldTyEqs Ct -> Cts -> Cts
add_if_unsolved InertEqs
tv_eqs Cts
emptyCts
            unsolved_fun_eqs :: Cts
unsolved_fun_eqs = ([Ct] -> Cts -> Cts) -> FunEqMap [Ct] -> Cts -> Cts
forall a b. (a -> b -> b) -> DictMap a -> b -> b
foldFunEqs [Ct] -> Cts -> Cts
add_if_unsolveds FunEqMap [Ct]
fun_eqs Cts
emptyCts
            unsolved_irreds :: Cts
unsolved_irreds  = (Ct -> Bool) -> Cts -> Cts
forall a. (a -> Bool) -> Bag a -> Bag a
Bag.filterBag Ct -> Bool
isWantedCt Cts
irreds
            unsolved_dicts :: Cts
unsolved_dicts   = (Ct -> Cts -> Cts) -> DictMap Ct -> Cts -> Cts
forall a b. (a -> b -> b) -> DictMap a -> b -> b
foldDicts Ct -> Cts -> Cts
add_if_unsolved DictMap Ct
idicts Cts
emptyCts
            unsolved_others :: Cts
unsolved_others  = [Cts] -> Cts
forall a. [Bag a] -> Bag a
unionManyBags [ Cts
unsolved_irreds
                                             , Cts
unsolved_dicts ]

      ; Bag Implication
implics <- TcS (Bag Implication)
getWorkListImplics

      ; String -> SDoc -> TcS ()
traceTcS String
"getUnsolvedInerts" (SDoc -> TcS ()) -> SDoc -> TcS ()
forall a b. (a -> b) -> a -> b
$
        [SDoc] -> SDoc
vcat [ String -> SDoc
text String
" tv eqs =" SDoc -> SDoc -> SDoc
<+> Cts -> SDoc
forall a. Outputable a => a -> SDoc
ppr Cts
unsolved_tv_eqs
             , String -> SDoc
text String
"fun eqs =" SDoc -> SDoc -> SDoc
<+> Cts -> SDoc
forall a. Outputable a => a -> SDoc
ppr Cts
unsolved_fun_eqs
             , String -> SDoc
text String
"others =" SDoc -> SDoc -> SDoc
<+> Cts -> SDoc
forall a. Outputable a => a -> SDoc
ppr Cts
unsolved_others
             , String -> SDoc
text String
"implics =" SDoc -> SDoc -> SDoc
<+> Bag Implication -> SDoc
forall a. Outputable a => a -> SDoc
ppr Bag Implication
implics ]

      ; (Bag Implication, Cts) -> TcS (Bag Implication, Cts)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return ( Bag Implication
implics, Cts
unsolved_tv_eqs Cts -> Cts -> Cts
forall a. Bag a -> Bag a -> Bag a
`unionBags`
                          Cts
unsolved_fun_eqs Cts -> Cts -> Cts
forall a. Bag a -> Bag a -> Bag a
`unionBags`
                          Cts
unsolved_others) }
  where
    add_if_unsolved :: Ct -> Cts -> Cts
    add_if_unsolved :: Ct -> Cts -> Cts
add_if_unsolved Ct
ct Cts
cts | Ct -> Bool
isWantedCt Ct
ct = Ct
ct Ct -> Cts -> Cts
`consCts` Cts
cts
                           | Bool
otherwise     = Cts
cts

    add_if_unsolveds :: EqualCtList -> Cts -> Cts
    add_if_unsolveds :: [Ct] -> Cts -> Cts
add_if_unsolveds [Ct]
new_cts Cts
old_cts = (Ct -> Cts -> Cts) -> Cts -> [Ct] -> Cts
forall a b. (a -> b -> b) -> b -> [a] -> b
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr Ct -> Cts -> Cts
add_if_unsolved Cts
old_cts [Ct]
new_cts

getHasGivenEqs :: TcLevel           -- TcLevel of this implication
               -> TcS ( HasGivenEqs -- are there Given equalities?
                      , Cts )       -- Insoluble equalities arising from givens
-- See Note [Tracking Given equalities] in GHC.Tc.Solver.InertSet
getHasGivenEqs :: TcLevel -> TcS (HasGivenEqs, Cts)
getHasGivenEqs TcLevel
tclvl
  = do { inerts :: InertCans
inerts@(IC { inert_irreds :: InertCans -> Cts
inert_irreds       = Cts
irreds
                    , inert_given_eqs :: InertCans -> Bool
inert_given_eqs    = Bool
given_eqs
                    , inert_given_eq_lvl :: InertCans -> TcLevel
inert_given_eq_lvl = TcLevel
ge_lvl })
              <- TcS InertCans
getInertCans
       ; let given_insols :: Cts
given_insols = (Ct -> Bool) -> Cts -> Cts
forall a. (a -> Bool) -> Bag a -> Bag a
filterBag Ct -> Bool
insoluble_given_equality Cts
irreds
                      -- Specifically includes ones that originated in some
                      -- outer context but were refined to an insoluble by
                      -- a local equality; so no level-check needed

             -- See Note [HasGivenEqs] in GHC.Tc.Types.Constraint, and
             -- Note [Tracking Given equalities] in GHC.Tc.Solver.InertSet
             has_ge :: HasGivenEqs
has_ge | TcLevel
ge_lvl TcLevel -> TcLevel -> Bool
forall a. Eq a => a -> a -> Bool
== TcLevel
tclvl = HasGivenEqs
MaybeGivenEqs
                    | Bool
given_eqs       = HasGivenEqs
LocalGivenEqs
                    | Bool
otherwise       = HasGivenEqs
NoGivenEqs

       ; String -> SDoc -> TcS ()
traceTcS String
"getHasGivenEqs" (SDoc -> TcS ()) -> SDoc -> TcS ()
forall a b. (a -> b) -> a -> b
$
         [SDoc] -> SDoc
vcat [ String -> SDoc
text String
"given_eqs:" SDoc -> SDoc -> SDoc
<+> Bool -> SDoc
forall a. Outputable a => a -> SDoc
ppr Bool
given_eqs
              , String -> SDoc
text String
"ge_lvl:" SDoc -> SDoc -> SDoc
<+> TcLevel -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcLevel
ge_lvl
              , String -> SDoc
text String
"ambient level:" SDoc -> SDoc -> SDoc
<+> TcLevel -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcLevel
tclvl
              , String -> SDoc
text String
"Inerts:" SDoc -> SDoc -> SDoc
<+> InertCans -> SDoc
forall a. Outputable a => a -> SDoc
ppr InertCans
inerts
              , String -> SDoc
text String
"Insols:" SDoc -> SDoc -> SDoc
<+> Cts -> SDoc
forall a. Outputable a => a -> SDoc
ppr Cts
given_insols]
       ; (HasGivenEqs, Cts) -> TcS (HasGivenEqs, Cts)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (HasGivenEqs
has_ge, Cts
given_insols) }
  where
    insoluble_given_equality :: Ct -> Bool
insoluble_given_equality Ct
ct
       = Ct -> Bool
insolubleEqCt Ct
ct Bool -> Bool -> Bool
&& Ct -> Bool
isGivenCt Ct
ct

removeInertCts :: [Ct] -> InertCans -> InertCans
-- ^ Remove inert constraints from the 'InertCans', for use when a
-- typechecker plugin wishes to discard a given.
removeInertCts :: [Ct] -> InertCans -> InertCans
removeInertCts [Ct]
cts InertCans
icans = (InertCans -> Ct -> InertCans) -> InertCans -> [Ct] -> InertCans
forall b a. (b -> a -> b) -> b -> [a] -> b
forall (t :: * -> *) b a.
Foldable t =>
(b -> a -> b) -> b -> t a -> b
foldl' InertCans -> Ct -> InertCans
removeInertCt InertCans
icans [Ct]
cts

removeInertCt :: InertCans -> Ct -> InertCans
removeInertCt :: InertCans -> Ct -> InertCans
removeInertCt InertCans
is Ct
ct =
  case Ct
ct of

    CDictCan  { cc_class :: Ct -> Class
cc_class = Class
cl, cc_tyargs :: Ct -> [Type]
cc_tyargs = [Type]
tys } ->
      InertCans
is { inert_dicts :: DictMap Ct
inert_dicts = DictMap Ct -> Class -> [Type] -> DictMap Ct
forall a. DictMap a -> Class -> [Type] -> DictMap a
delDict (InertCans -> DictMap Ct
inert_dicts InertCans
is) Class
cl [Type]
tys }

    CEqCan    { cc_lhs :: Ct -> CanEqLHS
cc_lhs  = CanEqLHS
lhs, cc_rhs :: Ct -> Type
cc_rhs = Type
rhs } -> InertCans -> CanEqLHS -> Type -> InertCans
delEq InertCans
is CanEqLHS
lhs Type
rhs

    CIrredCan {}     -> InertCans
is { inert_irreds :: Cts
inert_irreds = (Ct -> Bool) -> Cts -> Cts
forall a. (a -> Bool) -> Bag a -> Bag a
filterBag (Bool -> Bool
not (Bool -> Bool) -> (Ct -> Bool) -> Ct -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Ct -> Ct -> Bool
eqCt Ct
ct) (Cts -> Cts) -> Cts -> Cts
forall a b. (a -> b) -> a -> b
$ InertCans -> Cts
inert_irreds InertCans
is }

    CQuantCan {}     -> String -> InertCans
forall a. String -> a
panic String
"removeInertCt: CQuantCan"
    CNonCanonical {} -> String -> InertCans
forall a. String -> a
panic String
"removeInertCt: CNonCanonical"

eqCt :: Ct -> Ct -> Bool
-- Equality via ctEvId
eqCt :: Ct -> Ct -> Bool
eqCt Ct
c Ct
c' = (() :: Constraint) => Ct -> TcTyVar
Ct -> TcTyVar
ctEvId Ct
c TcTyVar -> TcTyVar -> Bool
forall a. Eq a => a -> a -> Bool
== (() :: Constraint) => Ct -> TcTyVar
Ct -> TcTyVar
ctEvId Ct
c'

-- | Looks up a family application in the inerts.
lookupFamAppInert :: (CtFlavourRole -> Bool)  -- can it rewrite the target?
                  -> TyCon -> [Type] -> TcS (Maybe (Reduction, CtFlavourRole))
lookupFamAppInert :: (CtFlavourRole -> Bool)
-> TyCon -> [Type] -> TcS (Maybe (Reduction, CtFlavourRole))
lookupFamAppInert CtFlavourRole -> Bool
rewrite_pred TyCon
fam_tc [Type]
tys
  = do { IS { inert_cans :: InertSet -> InertCans
inert_cans = IC { inert_funeqs :: InertCans -> FunEqMap [Ct]
inert_funeqs = FunEqMap [Ct]
inert_funeqs } } <- TcS InertSet
getTcSInerts
       ; Maybe (Reduction, CtFlavourRole)
-> TcS (Maybe (Reduction, CtFlavourRole))
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (FunEqMap [Ct] -> Maybe (Reduction, CtFlavourRole)
lookup_inerts FunEqMap [Ct]
inert_funeqs) }
  where
    lookup_inerts :: FunEqMap [Ct] -> Maybe (Reduction, CtFlavourRole)
lookup_inerts FunEqMap [Ct]
inert_funeqs
      | Just [Ct]
ecl <- FunEqMap [Ct] -> TyCon -> [Type] -> Maybe [Ct]
forall a. FunEqMap a -> TyCon -> [Type] -> Maybe a
findFunEq FunEqMap [Ct]
inert_funeqs TyCon
fam_tc [Type]
tys
      , Just (CEqCan { cc_ev :: Ct -> CtEvidence
cc_ev = CtEvidence
ctev, cc_rhs :: Ct -> Type
cc_rhs = Type
rhs })
          <- (Ct -> Bool) -> [Ct] -> Maybe Ct
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Maybe a
find (CtFlavourRole -> Bool
rewrite_pred (CtFlavourRole -> Bool) -> (Ct -> CtFlavourRole) -> Ct -> Bool
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Ct -> CtFlavourRole
ctFlavourRole) [Ct]
ecl
      = (Reduction, CtFlavourRole) -> Maybe (Reduction, CtFlavourRole)
forall a. a -> Maybe a
Just (Coercion -> Type -> Reduction
mkReduction ((() :: Constraint) => CtEvidence -> Coercion
CtEvidence -> Coercion
ctEvCoercion CtEvidence
ctev) Type
rhs, CtEvidence -> CtFlavourRole
ctEvFlavourRole CtEvidence
ctev)
      | Bool
otherwise = Maybe (Reduction, CtFlavourRole)
forall a. Maybe a
Nothing

lookupInInerts :: CtLoc -> TcPredType -> TcS (Maybe CtEvidence)
-- Is this exact predicate type cached in the solved or canonicals of the InertSet?
lookupInInerts :: CtLoc -> Type -> TcS (Maybe CtEvidence)
lookupInInerts CtLoc
loc Type
pty
  | ClassPred Class
cls [Type]
tys <- Type -> Pred
classifyPredType Type
pty
  = do { InertSet
inerts <- TcS InertSet
getTcSInerts
       ; Maybe CtEvidence -> TcS (Maybe CtEvidence)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (InertSet -> CtLoc -> Class -> [Type] -> Maybe CtEvidence
lookupSolvedDict InertSet
inerts CtLoc
loc Class
cls [Type]
tys Maybe CtEvidence -> Maybe CtEvidence -> Maybe CtEvidence
forall a. Maybe a -> Maybe a -> Maybe a
forall (m :: * -> *) a. MonadPlus m => m a -> m a -> m a
`mplus`
                 (Ct -> CtEvidence) -> Maybe Ct -> Maybe CtEvidence
forall a b. (a -> b) -> Maybe a -> Maybe b
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
fmap Ct -> CtEvidence
ctEvidence (InertCans -> CtLoc -> Class -> [Type] -> Maybe Ct
lookupInertDict (InertSet -> InertCans
inert_cans InertSet
inerts) CtLoc
loc Class
cls [Type]
tys)) }
  | Bool
otherwise -- NB: No caching for equalities, IPs, holes, or errors
  = Maybe CtEvidence -> TcS (Maybe CtEvidence)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe CtEvidence
forall a. Maybe a
Nothing

-- | Look up a dictionary inert.
lookupInertDict :: InertCans -> CtLoc -> Class -> [Type] -> Maybe Ct
lookupInertDict :: InertCans -> CtLoc -> Class -> [Type] -> Maybe Ct
lookupInertDict (IC { inert_dicts :: InertCans -> DictMap Ct
inert_dicts = DictMap Ct
dicts }) CtLoc
loc Class
cls [Type]
tys
  = case DictMap Ct -> CtLoc -> Class -> [Type] -> Maybe Ct
forall a. DictMap a -> CtLoc -> Class -> [Type] -> Maybe a
findDict DictMap Ct
dicts CtLoc
loc Class
cls [Type]
tys of
      Just Ct
ct -> Ct -> Maybe Ct
forall a. a -> Maybe a
Just Ct
ct
      Maybe Ct
_       -> Maybe Ct
forall a. Maybe a
Nothing

-- | Look up a solved inert.
lookupSolvedDict :: InertSet -> CtLoc -> Class -> [Type] -> Maybe CtEvidence
-- Returns just if exactly this predicate type exists in the solved.
lookupSolvedDict :: InertSet -> CtLoc -> Class -> [Type] -> Maybe CtEvidence
lookupSolvedDict (IS { inert_solved_dicts :: InertSet -> DictMap CtEvidence
inert_solved_dicts = DictMap CtEvidence
solved }) CtLoc
loc Class
cls [Type]
tys
  = case DictMap CtEvidence -> CtLoc -> Class -> [Type] -> Maybe CtEvidence
forall a. DictMap a -> CtLoc -> Class -> [Type] -> Maybe a
findDict DictMap CtEvidence
solved CtLoc
loc Class
cls [Type]
tys of
      Just CtEvidence
ev -> CtEvidence -> Maybe CtEvidence
forall a. a -> Maybe a
Just CtEvidence
ev
      Maybe CtEvidence
_       -> Maybe CtEvidence
forall a. Maybe a
Nothing

---------------------------
lookupFamAppCache :: TyCon -> [Type] -> TcS (Maybe Reduction)
lookupFamAppCache :: TyCon -> [Type] -> TcS (Maybe Reduction)
lookupFamAppCache TyCon
fam_tc [Type]
tys
  = do { IS { inert_famapp_cache :: InertSet -> FunEqMap Reduction
inert_famapp_cache = FunEqMap Reduction
famapp_cache } <- TcS InertSet
getTcSInerts
       ; case FunEqMap Reduction -> TyCon -> [Type] -> Maybe Reduction
forall a. FunEqMap a -> TyCon -> [Type] -> Maybe a
findFunEq FunEqMap Reduction
famapp_cache TyCon
fam_tc [Type]
tys of
           result :: Maybe Reduction
result@(Just Reduction
redn) ->
             do { String -> SDoc -> TcS ()
traceTcS String
"famapp_cache hit" ([SDoc] -> SDoc
vcat [ Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TyCon -> [Type] -> Type
mkTyConApp TyCon
fam_tc [Type]
tys)
                                                    , Reduction -> SDoc
forall a. Outputable a => a -> SDoc
ppr Reduction
redn ])
                ; Maybe Reduction -> TcS (Maybe Reduction)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe Reduction
result }
           Maybe Reduction
Nothing -> Maybe Reduction -> TcS (Maybe Reduction)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe Reduction
forall a. Maybe a
Nothing }

extendFamAppCache :: TyCon -> [Type] -> Reduction -> TcS ()
-- NB: co :: rhs ~ F tys, to match expectations of rewriter
extendFamAppCache :: TyCon -> [Type] -> Reduction -> TcS ()
extendFamAppCache TyCon
tc [Type]
xi_args stuff :: Reduction
stuff@(Reduction Coercion
_ Type
ty)
  = do { DynFlags
dflags <- TcS DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
       ; Bool -> TcS () -> TcS ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (GeneralFlag -> DynFlags -> Bool
gopt GeneralFlag
Opt_FamAppCache DynFlags
dflags) (TcS () -> TcS ()) -> TcS () -> TcS ()
forall a b. (a -> b) -> a -> b
$
    do { String -> SDoc -> TcS ()
traceTcS String
"extendFamAppCache" ([SDoc] -> SDoc
vcat [ TyCon -> SDoc
forall a. Outputable a => a -> SDoc
ppr TyCon
tc SDoc -> SDoc -> SDoc
<+> [Type] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Type]
xi_args
                                            , Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
ty ])
       ; (InertSet -> InertSet) -> TcS ()
updInertTcS ((InertSet -> InertSet) -> TcS ())
-> (InertSet -> InertSet) -> TcS ()
forall a b. (a -> b) -> a -> b
$ \ is :: InertSet
is@(IS { inert_famapp_cache :: InertSet -> FunEqMap Reduction
inert_famapp_cache = FunEqMap Reduction
fc }) ->
            InertSet
is { inert_famapp_cache :: FunEqMap Reduction
inert_famapp_cache = FunEqMap Reduction
-> TyCon -> [Type] -> Reduction -> FunEqMap Reduction
forall a. FunEqMap a -> TyCon -> [Type] -> a -> FunEqMap a
insertFunEq FunEqMap Reduction
fc TyCon
tc [Type]
xi_args Reduction
stuff } } }

-- Remove entries from the cache whose evidence mentions variables in the
-- supplied set
dropFromFamAppCache :: VarSet -> TcS ()
dropFromFamAppCache :: VarSet -> TcS ()
dropFromFamAppCache VarSet
varset
  = do { inerts :: InertSet
inerts@(IS { inert_famapp_cache :: InertSet -> FunEqMap Reduction
inert_famapp_cache = FunEqMap Reduction
famapp_cache }) <- TcS InertSet
getTcSInerts
       ; let filtered :: FunEqMap Reduction
filtered = (Reduction -> Bool) -> FunEqMap Reduction -> FunEqMap Reduction
forall a. (a -> Bool) -> TcAppMap a -> TcAppMap a
filterTcAppMap Reduction -> Bool
check FunEqMap Reduction
famapp_cache
       ; InertSet -> TcS ()
setTcSInerts (InertSet -> TcS ()) -> InertSet -> TcS ()
forall a b. (a -> b) -> a -> b
$ InertSet
inerts { inert_famapp_cache :: FunEqMap Reduction
inert_famapp_cache = FunEqMap Reduction
filtered } }
  where
    check :: Reduction -> Bool
    check :: Reduction -> Bool
check Reduction
redn
      = Bool -> Bool
not ((TcTyVar -> Bool) -> Coercion -> Bool
anyFreeVarsOfCo (TcTyVar -> VarSet -> Bool
`elemVarSet` VarSet
varset) (Coercion -> Bool) -> Coercion -> Bool
forall a b. (a -> b) -> a -> b
$ Reduction -> Coercion
reductionCoercion Reduction
redn)

{- *********************************************************************
*                                                                      *
                   Irreds
*                                                                      *
********************************************************************* -}

foldIrreds :: (Ct -> b -> b) -> Cts -> b -> b
foldIrreds :: forall b. (Ct -> b -> b) -> Cts -> b -> b
foldIrreds Ct -> b -> b
k Cts
irreds b
z = (Ct -> b -> b) -> b -> Cts -> b
forall a b. (a -> b -> b) -> b -> Bag a -> b
forall (t :: * -> *) a b.
Foldable t =>
(a -> b -> b) -> b -> t a -> b
foldr Ct -> b -> b
k b
z Cts
irreds

{-
************************************************************************
*                                                                      *
*              The TcS solver monad                                    *
*                                                                      *
************************************************************************

Note [The TcS monad]
~~~~~~~~~~~~~~~~~~~~
The TcS monad is a weak form of the main Tc monad

All you can do is
    * fail
    * allocate new variables
    * fill in evidence variables

Filling in a dictionary evidence variable means to create a binding
for it, so TcS carries a mutable location where the binding can be
added.  This is initialised from the innermost implication constraint.
-}

data TcSEnv
  = TcSEnv {
      TcSEnv -> EvBindsVar
tcs_ev_binds    :: EvBindsVar,

      TcSEnv -> IORef Int
tcs_unified     :: IORef Int,
         -- The number of unification variables we have filled
         -- The important thing is whether it is non-zero

      TcSEnv -> IORef (Maybe TcLevel)
tcs_unif_lvl  :: IORef (Maybe TcLevel),
         -- The Unification Level Flag
         -- Outermost level at which we have unified a meta tyvar
         -- Starts at Nothing, then (Just i), then (Just j) where j<i
         -- See Note [The Unification Level Flag]

      TcSEnv -> IORef Int
tcs_count     :: IORef Int, -- Global step count

      TcSEnv -> IORef InertSet
tcs_inerts    :: IORef InertSet, -- Current inert set

      -- Whether to throw an exception if we come across an insoluble constraint.
      -- Used to fail-fast when checking for hole-fits. See Note [Speeding up
      -- valid hole-fits].
      TcSEnv -> Bool
tcs_abort_on_insoluble :: Bool,

      -- See Note [WorkList priorities] in GHC.Tc.Solver.InertSet
      TcSEnv -> IORef WorkList
tcs_worklist  :: IORef WorkList -- Current worklist
    }

---------------
newtype TcS a = TcS { forall a. TcS a -> TcSEnv -> TcM a
unTcS :: TcSEnv -> TcM a } deriving ((forall a b. (a -> b) -> TcS a -> TcS b)
-> (forall a b. a -> TcS b -> TcS a) -> Functor TcS
forall a b. a -> TcS b -> TcS a
forall a b. (a -> b) -> TcS a -> TcS b
forall (f :: * -> *).
(forall a b. (a -> b) -> f a -> f b)
-> (forall a b. a -> f b -> f a) -> Functor f
$cfmap :: forall a b. (a -> b) -> TcS a -> TcS b
fmap :: forall a b. (a -> b) -> TcS a -> TcS b
$c<$ :: forall a b. a -> TcS b -> TcS a
<$ :: forall a b. a -> TcS b -> TcS a
Functor)

-- | Smart constructor for 'TcS', as describe in Note [The one-shot state
-- monad trick] in "GHC.Utils.Monad".
mkTcS :: (TcSEnv -> TcM a) -> TcS a
mkTcS :: forall a. (TcSEnv -> TcM a) -> TcS a
mkTcS TcSEnv -> TcM a
f = (TcSEnv -> TcM a) -> TcS a
forall a. (TcSEnv -> TcM a) -> TcS a
TcS ((TcSEnv -> TcM a) -> TcSEnv -> TcM a
forall a b. (a -> b) -> a -> b
oneShot TcSEnv -> TcM a
f)

instance Applicative TcS where
  pure :: forall a. a -> TcS a
pure a
x = (TcSEnv -> TcM a) -> TcS a
forall a. (TcSEnv -> TcM a) -> TcS a
mkTcS ((TcSEnv -> TcM a) -> TcS a) -> (TcSEnv -> TcM a) -> TcS a
forall a b. (a -> b) -> a -> b
$ \TcSEnv
_ -> a -> TcM a
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return a
x
  <*> :: forall a b. TcS (a -> b) -> TcS a -> TcS b
(<*>) = TcS (a -> b) -> TcS a -> TcS b
forall (m :: * -> *) a b. Monad m => m (a -> b) -> m a -> m b
ap

instance Monad TcS where
  TcS a
m >>= :: forall a b. TcS a -> (a -> TcS b) -> TcS b
>>= a -> TcS b
k   = (TcSEnv -> TcM b) -> TcS b
forall a. (TcSEnv -> TcM a) -> TcS a
mkTcS ((TcSEnv -> TcM b) -> TcS b) -> (TcSEnv -> TcM b) -> TcS b
forall a b. (a -> b) -> a -> b
$ \TcSEnv
ebs -> do
    TcS a -> TcSEnv -> TcM a
forall a. TcS a -> TcSEnv -> TcM a
unTcS TcS a
m TcSEnv
ebs TcM a -> (a -> TcM b) -> TcM b
forall a b.
IOEnv (Env TcGblEnv TcLclEnv) a
-> (a -> IOEnv (Env TcGblEnv TcLclEnv) b)
-> IOEnv (Env TcGblEnv TcLclEnv) b
forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b
>>= (\a
r -> TcS b -> TcSEnv -> TcM b
forall a. TcS a -> TcSEnv -> TcM a
unTcS (a -> TcS b
k a
r) TcSEnv
ebs)

instance MonadIO TcS where
  liftIO :: forall a. IO a -> TcS a
liftIO IO a
act = (TcSEnv -> TcM a) -> TcS a
forall a. (TcSEnv -> TcM a) -> TcS a
TcS ((TcSEnv -> TcM a) -> TcS a) -> (TcSEnv -> TcM a) -> TcS a
forall a b. (a -> b) -> a -> b
$ \TcSEnv
_env -> IO a -> TcM a
forall a. IO a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. MonadIO m => IO a -> m a
liftIO IO a
act

instance MonadFail TcS where
  fail :: forall a. String -> TcS a
fail String
err  = (TcSEnv -> TcM a) -> TcS a
forall a. (TcSEnv -> TcM a) -> TcS a
mkTcS ((TcSEnv -> TcM a) -> TcS a) -> (TcSEnv -> TcM a) -> TcS a
forall a b. (a -> b) -> a -> b
$ \TcSEnv
_ -> String -> TcM a
forall a. String -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. MonadFail m => String -> m a
fail String
err

instance MonadUnique TcS where
   getUniqueSupplyM :: TcS UniqSupply
getUniqueSupplyM = TcM UniqSupply -> TcS UniqSupply
forall a. TcM a -> TcS a
wrapTcS TcM UniqSupply
forall (m :: * -> *). MonadUnique m => m UniqSupply
getUniqueSupplyM

instance HasModule TcS where
   getModule :: TcS Module
getModule = TcM Module -> TcS Module
forall a. TcM a -> TcS a
wrapTcS TcM Module
forall (m :: * -> *). HasModule m => m Module
getModule

instance MonadThings TcS where
   lookupThing :: Name -> TcS TyThing
lookupThing Name
n = TcM TyThing -> TcS TyThing
forall a. TcM a -> TcS a
wrapTcS (Name -> TcM TyThing
forall (m :: * -> *). MonadThings m => Name -> m TyThing
lookupThing Name
n)

-- Basic functionality
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
wrapTcS :: TcM a -> TcS a
-- Do not export wrapTcS, because it promotes an arbitrary TcM to TcS,
-- and TcS is supposed to have limited functionality
wrapTcS :: forall a. TcM a -> TcS a
wrapTcS TcM a
action = (TcSEnv -> TcM a) -> TcS a
forall a. (TcSEnv -> TcM a) -> TcS a
mkTcS ((TcSEnv -> TcM a) -> TcS a) -> (TcSEnv -> TcM a) -> TcS a
forall a b. (a -> b) -> a -> b
$ \TcSEnv
_env -> TcM a
action -- a TcM action will not use the TcEvBinds

wrap2TcS :: (TcM a -> TcM a) -> TcS a -> TcS a
wrap2TcS :: forall a. (TcM a -> TcM a) -> TcS a -> TcS a
wrap2TcS TcM a -> TcM a
fn (TcS TcSEnv -> TcM a
thing) = (TcSEnv -> TcM a) -> TcS a
forall a. (TcSEnv -> TcM a) -> TcS a
mkTcS ((TcSEnv -> TcM a) -> TcS a) -> (TcSEnv -> TcM a) -> TcS a
forall a b. (a -> b) -> a -> b
$ \TcSEnv
env -> TcM a -> TcM a
fn (TcSEnv -> TcM a
thing TcSEnv
env)

wrapErrTcS :: TcM a -> TcS a
-- The thing wrapped should just fail
-- There's no static check; it's up to the user
-- Having a variant for each error message is too painful
wrapErrTcS :: forall a. TcM a -> TcS a
wrapErrTcS = TcM a -> TcS a
forall a. TcM a -> TcS a
wrapTcS

wrapWarnTcS :: TcM a -> TcS a
-- The thing wrapped should just add a warning, or no-op
-- There's no static check; it's up to the user
wrapWarnTcS :: forall a. TcM a -> TcS a
wrapWarnTcS = TcM a -> TcS a
forall a. TcM a -> TcS a
wrapTcS

panicTcS  :: SDoc -> TcS a
failTcS   :: TcRnMessage -> TcS a
warnTcS, addErrTcS :: TcRnMessage -> TcS ()
failTcS :: forall a. TcRnMessage -> TcS a
failTcS      = TcM a -> TcS a
forall a. TcM a -> TcS a
wrapTcS (TcM a -> TcS a) -> (TcRnMessage -> TcM a) -> TcRnMessage -> TcS a
forall b c a. (b -> c) -> (a -> b) -> a -> c
. TcRnMessage -> TcM a
forall a. TcRnMessage -> TcRn a
TcM.failWith
warnTcS :: TcRnMessage -> TcS ()
warnTcS TcRnMessage
msg  = TcM () -> TcS ()
forall a. TcM a -> TcS a
wrapTcS (TcRnMessage -> TcM ()
TcM.addDiagnostic TcRnMessage
msg)
addErrTcS :: TcRnMessage -> TcS ()
addErrTcS    = TcM () -> TcS ()
forall a. TcM a -> TcS a
wrapTcS (TcM () -> TcS ())
-> (TcRnMessage -> TcM ()) -> TcRnMessage -> TcS ()
forall b c a. (b -> c) -> (a -> b) -> a -> c
. TcRnMessage -> TcM ()
TcM.addErr
panicTcS :: forall a. SDoc -> TcS a
panicTcS SDoc
doc = String -> SDoc -> TcS a
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"GHC.Tc.Solver.Canonical" SDoc
doc

traceTcS :: String -> SDoc -> TcS ()
traceTcS :: String -> SDoc -> TcS ()
traceTcS String
herald SDoc
doc = TcM () -> TcS ()
forall a. TcM a -> TcS a
wrapTcS (String -> SDoc -> TcM ()
TcM.traceTc String
herald SDoc
doc)
{-# INLINE traceTcS #-}  -- see Note [INLINE conditional tracing utilities]

runTcPluginTcS :: TcPluginM a -> TcS a
runTcPluginTcS :: forall a. TcPluginM a -> TcS a
runTcPluginTcS = TcM a -> TcS a
forall a. TcM a -> TcS a
wrapTcS (TcM a -> TcS a) -> (TcPluginM a -> TcM a) -> TcPluginM a -> TcS a
forall b c a. (b -> c) -> (a -> b) -> a -> c
. TcPluginM a -> TcM a
forall a. TcPluginM a -> TcM a
runTcPluginM

instance HasDynFlags TcS where
    getDynFlags :: TcS DynFlags
getDynFlags = TcM DynFlags -> TcS DynFlags
forall a. TcM a -> TcS a
wrapTcS TcM DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags

getGlobalRdrEnvTcS :: TcS GlobalRdrEnv
getGlobalRdrEnvTcS :: TcS GlobalRdrEnv
getGlobalRdrEnvTcS = TcM GlobalRdrEnv -> TcS GlobalRdrEnv
forall a. TcM a -> TcS a
wrapTcS TcM GlobalRdrEnv
TcM.getGlobalRdrEnv

bumpStepCountTcS :: TcS ()
bumpStepCountTcS :: TcS ()
bumpStepCountTcS = (TcSEnv -> TcM ()) -> TcS ()
forall a. (TcSEnv -> TcM a) -> TcS a
mkTcS ((TcSEnv -> TcM ()) -> TcS ()) -> (TcSEnv -> TcM ()) -> TcS ()
forall a b. (a -> b) -> a -> b
$ \TcSEnv
env ->
  do { let ref :: IORef Int
ref = TcSEnv -> IORef Int
tcs_count TcSEnv
env
     ; Int
n <- IORef Int -> TcRnIf TcGblEnv TcLclEnv Int
forall a gbl lcl. TcRef a -> TcRnIf gbl lcl a
TcM.readTcRef IORef Int
ref
     ; IORef Int -> Int -> TcM ()
forall a gbl lcl. TcRef a -> a -> TcRnIf gbl lcl ()
TcM.writeTcRef IORef Int
ref (Int
nInt -> Int -> Int
forall a. Num a => a -> a -> a
+Int
1) }

csTraceTcS :: SDoc -> TcS ()
csTraceTcS :: SDoc -> TcS ()
csTraceTcS SDoc
doc
  = TcM () -> TcS ()
forall a. TcM a -> TcS a
wrapTcS (TcM () -> TcS ()) -> TcM () -> TcS ()
forall a b. (a -> b) -> a -> b
$ TcM SDoc -> TcM ()
csTraceTcM (SDoc -> TcM SDoc
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return SDoc
doc)
{-# INLINE csTraceTcS #-}  -- see Note [INLINE conditional tracing utilities]

traceFireTcS :: CtEvidence -> SDoc -> TcS ()
-- Dump a rule-firing trace
traceFireTcS :: CtEvidence -> SDoc -> TcS ()
traceFireTcS CtEvidence
ev SDoc
doc
  = (TcSEnv -> TcM ()) -> TcS ()
forall a. (TcSEnv -> TcM a) -> TcS a
mkTcS ((TcSEnv -> TcM ()) -> TcS ()) -> (TcSEnv -> TcM ()) -> TcS ()
forall a b. (a -> b) -> a -> b
$ \TcSEnv
env -> TcM SDoc -> TcM ()
csTraceTcM (TcM SDoc -> TcM ()) -> TcM SDoc -> TcM ()
forall a b. (a -> b) -> a -> b
$
    do { Int
n <- IORef Int -> TcRnIf TcGblEnv TcLclEnv Int
forall a gbl lcl. TcRef a -> TcRnIf gbl lcl a
TcM.readTcRef (TcSEnv -> IORef Int
tcs_count TcSEnv
env)
       ; TcLevel
tclvl <- TcM TcLevel
TcM.getTcLevel
       ; SDoc -> TcM SDoc
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (SDoc -> Int -> SDoc -> SDoc
hang (String -> SDoc
text String
"Step" SDoc -> SDoc -> SDoc
<+> Int -> SDoc
int Int
n
                       SDoc -> SDoc -> SDoc
<> SDoc -> SDoc
brackets (String -> SDoc
text String
"l:" SDoc -> SDoc -> SDoc
<> TcLevel -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcLevel
tclvl SDoc -> SDoc -> SDoc
<> SDoc
comma SDoc -> SDoc -> SDoc
<>
                                    String -> SDoc
text String
"d:" SDoc -> SDoc -> SDoc
<> SubGoalDepth -> SDoc
forall a. Outputable a => a -> SDoc
ppr (CtLoc -> SubGoalDepth
ctLocDepth (CtEvidence -> CtLoc
ctEvLoc CtEvidence
ev)))
                       SDoc -> SDoc -> SDoc
<+> SDoc
doc SDoc -> SDoc -> SDoc
<> SDoc
colon)
                     Int
4 (CtEvidence -> SDoc
forall a. Outputable a => a -> SDoc
ppr CtEvidence
ev)) }
{-# INLINE traceFireTcS #-}  -- see Note [INLINE conditional tracing utilities]

csTraceTcM :: TcM SDoc -> TcM ()
-- Constraint-solver tracing, -ddump-cs-trace
csTraceTcM :: TcM SDoc -> TcM ()
csTraceTcM TcM SDoc
mk_doc
  = do { Logger
logger <- IOEnv (Env TcGblEnv TcLclEnv) Logger
forall (m :: * -> *). HasLogger m => m Logger
getLogger
       ; Bool -> TcM () -> TcM ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (  Logger -> DumpFlag -> Bool
logHasDumpFlag Logger
logger DumpFlag
Opt_D_dump_cs_trace
                  Bool -> Bool -> Bool
|| Logger -> DumpFlag -> Bool
logHasDumpFlag Logger
logger DumpFlag
Opt_D_dump_tc_trace)
              ( do { SDoc
msg <- TcM SDoc
mk_doc
                   ; Bool -> DumpFlag -> String -> DumpFormat -> SDoc -> TcM ()
TcM.dumpTcRn Bool
False
                       DumpFlag
Opt_D_dump_cs_trace
                       String
"" DumpFormat
FormatText
                       SDoc
msg }) }
{-# INLINE csTraceTcM #-}  -- see Note [INLINE conditional tracing utilities]

runTcS :: TcS a                -- What to run
       -> TcM (a, EvBindMap)
runTcS :: forall a. TcS a -> TcM (a, EvBindMap)
runTcS TcS a
tcs
  = do { EvBindsVar
ev_binds_var <- TcM EvBindsVar
TcM.newTcEvBinds
       ; a
res <- EvBindsVar -> TcS a -> TcM a
forall a. EvBindsVar -> TcS a -> TcM a
runTcSWithEvBinds EvBindsVar
ev_binds_var TcS a
tcs
       ; EvBindMap
ev_binds <- EvBindsVar -> TcM EvBindMap
TcM.getTcEvBindsMap EvBindsVar
ev_binds_var
       ; (a, EvBindMap) -> TcM (a, EvBindMap)
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (a
res, EvBindMap
ev_binds) }

-- | This variant of 'runTcS' will immediatley fail upon encountering an
-- insoluble ct. See Note [Speeding up valid hole-fits]. Its one usage
-- site does not need the ev_binds, so we do not return them.
runTcSEarlyAbort :: TcS a -> TcM a
runTcSEarlyAbort :: forall a. TcS a -> TcM a
runTcSEarlyAbort TcS a
tcs
  = do { EvBindsVar
ev_binds_var <- TcM EvBindsVar
TcM.newTcEvBinds
       ; Bool -> Bool -> EvBindsVar -> TcS a -> TcM a
forall a. Bool -> Bool -> EvBindsVar -> TcS a -> TcM a
runTcSWithEvBinds' Bool
True Bool
True EvBindsVar
ev_binds_var TcS a
tcs }

-- | This can deal only with equality constraints.
runTcSEqualities :: TcS a -> TcM a
runTcSEqualities :: forall a. TcS a -> TcM a
runTcSEqualities TcS a
thing_inside
  = do { EvBindsVar
ev_binds_var <- TcM EvBindsVar
TcM.newNoTcEvBinds
       ; EvBindsVar -> TcS a -> TcM a
forall a. EvBindsVar -> TcS a -> TcM a
runTcSWithEvBinds EvBindsVar
ev_binds_var TcS a
thing_inside }

-- | A variant of 'runTcS' that takes and returns an 'InertSet' for
-- later resumption of the 'TcS' session.
runTcSInerts :: InertSet -> TcS a -> TcM (a, InertSet)
runTcSInerts :: forall a. InertSet -> TcS a -> TcM (a, InertSet)
runTcSInerts InertSet
inerts TcS a
tcs = do
  EvBindsVar
ev_binds_var <- TcM EvBindsVar
TcM.newTcEvBinds
  Bool
-> Bool -> EvBindsVar -> TcS (a, InertSet) -> TcM (a, InertSet)
forall a. Bool -> Bool -> EvBindsVar -> TcS a -> TcM a
runTcSWithEvBinds' Bool
False Bool
False EvBindsVar
ev_binds_var (TcS (a, InertSet) -> TcM (a, InertSet))
-> TcS (a, InertSet) -> TcM (a, InertSet)
forall a b. (a -> b) -> a -> b
$ do
    InertSet -> TcS ()
setTcSInerts InertSet
inerts
    a
a <- TcS a
tcs
    InertSet
new_inerts <- TcS InertSet
getTcSInerts
    (a, InertSet) -> TcS (a, InertSet)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (a
a, InertSet
new_inerts)

runTcSWithEvBinds :: EvBindsVar
                  -> TcS a
                  -> TcM a
runTcSWithEvBinds :: forall a. EvBindsVar -> TcS a -> TcM a
runTcSWithEvBinds = Bool -> Bool -> EvBindsVar -> TcS a -> TcM a
forall a. Bool -> Bool -> EvBindsVar -> TcS a -> TcM a
runTcSWithEvBinds' Bool
True Bool
False

runTcSWithEvBinds' :: Bool -- ^ Restore type variable cycles afterwards?
                           -- Don't if you want to reuse the InertSet.
                           -- See also Note [Type equality cycles]
                           -- in GHC.Tc.Solver.Canonical
                   -> Bool
                   -> EvBindsVar
                   -> TcS a
                   -> TcM a
runTcSWithEvBinds' :: forall a. Bool -> Bool -> EvBindsVar -> TcS a -> TcM a
runTcSWithEvBinds' Bool
restore_cycles Bool
abort_on_insoluble EvBindsVar
ev_binds_var TcS a
tcs
  = do { IORef Int
unified_var <- Int -> TcRnIf TcGblEnv TcLclEnv (IORef Int)
forall a gbl lcl. a -> TcRnIf gbl lcl (TcRef a)
TcM.newTcRef Int
0
       ; IORef Int
step_count <- Int -> TcRnIf TcGblEnv TcLclEnv (IORef Int)
forall a gbl lcl. a -> TcRnIf gbl lcl (TcRef a)
TcM.newTcRef Int
0
       ; IORef InertSet
inert_var <- InertSet -> TcRnIf TcGblEnv TcLclEnv (IORef InertSet)
forall a gbl lcl. a -> TcRnIf gbl lcl (TcRef a)
TcM.newTcRef InertSet
emptyInert
       ; IORef WorkList
wl_var <- WorkList -> TcRnIf TcGblEnv TcLclEnv (IORef WorkList)
forall a gbl lcl. a -> TcRnIf gbl lcl (TcRef a)
TcM.newTcRef WorkList
emptyWorkList
       ; IORef (Maybe TcLevel)
unif_lvl_var <- Maybe TcLevel -> TcRnIf TcGblEnv TcLclEnv (IORef (Maybe TcLevel))
forall a gbl lcl. a -> TcRnIf gbl lcl (TcRef a)
TcM.newTcRef Maybe TcLevel
forall a. Maybe a
Nothing
       ; let env :: TcSEnv
env = TcSEnv { tcs_ev_binds :: EvBindsVar
tcs_ev_binds           = EvBindsVar
ev_binds_var
                          , tcs_unified :: IORef Int
tcs_unified            = IORef Int
unified_var
                          , tcs_unif_lvl :: IORef (Maybe TcLevel)
tcs_unif_lvl           = IORef (Maybe TcLevel)
unif_lvl_var
                          , tcs_count :: IORef Int
tcs_count              = IORef Int
step_count
                          , tcs_inerts :: IORef InertSet
tcs_inerts             = IORef InertSet
inert_var
                          , tcs_abort_on_insoluble :: Bool
tcs_abort_on_insoluble = Bool
abort_on_insoluble
                          , tcs_worklist :: IORef WorkList
tcs_worklist           = IORef WorkList
wl_var }

             -- Run the computation
       ; a
res <- TcS a -> TcSEnv -> TcM a
forall a. TcS a -> TcSEnv -> TcM a
unTcS TcS a
tcs TcSEnv
env

       ; Int
count <- IORef Int -> TcRnIf TcGblEnv TcLclEnv Int
forall a gbl lcl. TcRef a -> TcRnIf gbl lcl a
TcM.readTcRef IORef Int
step_count
       ; Bool -> TcM () -> TcM ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (Int
count Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
> Int
0) (TcM () -> TcM ()) -> TcM () -> TcM ()
forall a b. (a -> b) -> a -> b
$
         TcM SDoc -> TcM ()
csTraceTcM (TcM SDoc -> TcM ()) -> TcM SDoc -> TcM ()
forall a b. (a -> b) -> a -> b
$ SDoc -> TcM SDoc
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (String -> SDoc
text String
"Constraint solver steps =" SDoc -> SDoc -> SDoc
<+> Int -> SDoc
int Int
count)

       ; Bool -> TcM () -> TcM ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when Bool
restore_cycles (TcM () -> TcM ()) -> TcM () -> TcM ()
forall a b. (a -> b) -> a -> b
$
         do { InertSet
inert_set <- IORef InertSet -> TcRnIf TcGblEnv TcLclEnv InertSet
forall a gbl lcl. TcRef a -> TcRnIf gbl lcl a
TcM.readTcRef IORef InertSet
inert_var
            ; InertSet -> TcM ()
restoreTyVarCycles InertSet
inert_set }

#if defined(DEBUG)
       ; ev_binds <- TcM.getTcEvBindsMap ev_binds_var
       ; checkForCyclicBinds ev_binds
#endif

       ; a -> TcM a
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return a
res }

----------------------------
#if defined(DEBUG)
checkForCyclicBinds :: EvBindMap -> TcM ()
checkForCyclicBinds ev_binds_map
  | null cycles
  = return ()
  | null coercion_cycles
  = TcM.traceTc "Cycle in evidence binds" $ ppr cycles
  | otherwise
  = pprPanic "Cycle in coercion bindings" $ ppr coercion_cycles
  where
    ev_binds = evBindMapBinds ev_binds_map

    cycles :: [[EvBind]]
    cycles = [c | CyclicSCC c <- stronglyConnCompFromEdgedVerticesUniq edges]

    coercion_cycles = [c | c <- cycles, any is_co_bind c]
    is_co_bind (EvBind { eb_lhs = b }) = isEqPrimPred (varType b)

    edges :: [ Node EvVar EvBind ]
    edges = [ DigraphNode bind bndr (nonDetEltsUniqSet (evVarsOfTerm rhs))
            | bind@(EvBind { eb_lhs = bndr, eb_rhs = rhs}) <- bagToList ev_binds ]
            -- It's OK to use nonDetEltsUFM here as
            -- stronglyConnCompFromEdgedVertices is still deterministic even
            -- if the edges are in nondeterministic order as explained in
            -- Note [Deterministic SCC] in GHC.Data.Graph.Directed.
#endif

----------------------------
setEvBindsTcS :: EvBindsVar -> TcS a -> TcS a
setEvBindsTcS :: forall a. EvBindsVar -> TcS a -> TcS a
setEvBindsTcS EvBindsVar
ref (TcS TcSEnv -> TcM a
thing_inside)
 = (TcSEnv -> TcM a) -> TcS a
forall a. (TcSEnv -> TcM a) -> TcS a
TcS ((TcSEnv -> TcM a) -> TcS a) -> (TcSEnv -> TcM a) -> TcS a
forall a b. (a -> b) -> a -> b
$ \ TcSEnv
env -> TcSEnv -> TcM a
thing_inside (TcSEnv
env { tcs_ev_binds :: EvBindsVar
tcs_ev_binds = EvBindsVar
ref })

nestImplicTcS :: EvBindsVar
              -> TcLevel -> TcS a
              -> TcS a
nestImplicTcS :: forall a. EvBindsVar -> TcLevel -> TcS a -> TcS a
nestImplicTcS EvBindsVar
ref TcLevel
inner_tclvl (TcS TcSEnv -> TcM a
thing_inside)
  = (TcSEnv -> TcM a) -> TcS a
forall a. (TcSEnv -> TcM a) -> TcS a
TcS ((TcSEnv -> TcM a) -> TcS a) -> (TcSEnv -> TcM a) -> TcS a
forall a b. (a -> b) -> a -> b
$ \ TcSEnv { tcs_unified :: TcSEnv -> IORef Int
tcs_unified            = IORef Int
unified_var
                   , tcs_inerts :: TcSEnv -> IORef InertSet
tcs_inerts             = IORef InertSet
old_inert_var
                   , tcs_count :: TcSEnv -> IORef Int
tcs_count              = IORef Int
count
                   , tcs_unif_lvl :: TcSEnv -> IORef (Maybe TcLevel)
tcs_unif_lvl           = IORef (Maybe TcLevel)
unif_lvl
                   , tcs_abort_on_insoluble :: TcSEnv -> Bool
tcs_abort_on_insoluble = Bool
abort_on_insoluble
                   } ->
    do { InertSet
inerts <- IORef InertSet -> TcRnIf TcGblEnv TcLclEnv InertSet
forall a gbl lcl. TcRef a -> TcRnIf gbl lcl a
TcM.readTcRef IORef InertSet
old_inert_var
       ; let nest_inert :: InertSet
nest_inert = InertSet
inerts { inert_cycle_breakers :: CycleBreakerVarStack
inert_cycle_breakers = CycleBreakerVarStack -> CycleBreakerVarStack
pushCycleBreakerVarStack
                                                            (InertSet -> CycleBreakerVarStack
inert_cycle_breakers InertSet
inerts)
                                 , inert_cans :: InertCans
inert_cans = (InertSet -> InertCans
inert_cans InertSet
inerts)
                                                   { inert_given_eqs :: Bool
inert_given_eqs = Bool
False } }
                 -- All other InertSet fields are inherited
       ; IORef InertSet
new_inert_var <- InertSet -> TcRnIf TcGblEnv TcLclEnv (IORef InertSet)
forall a gbl lcl. a -> TcRnIf gbl lcl (TcRef a)
TcM.newTcRef InertSet
nest_inert
       ; IORef WorkList
new_wl_var    <- WorkList -> TcRnIf TcGblEnv TcLclEnv (IORef WorkList)
forall a gbl lcl. a -> TcRnIf gbl lcl (TcRef a)
TcM.newTcRef WorkList
emptyWorkList
       ; let nest_env :: TcSEnv
nest_env = TcSEnv { tcs_count :: IORef Int
tcs_count              = IORef Int
count     -- Inherited
                               , tcs_unif_lvl :: IORef (Maybe TcLevel)
tcs_unif_lvl           = IORef (Maybe TcLevel)
unif_lvl  -- Inherited
                               , tcs_ev_binds :: EvBindsVar
tcs_ev_binds           = EvBindsVar
ref
                               , tcs_unified :: IORef Int
tcs_unified            = IORef Int
unified_var
                               , tcs_inerts :: IORef InertSet
tcs_inerts             = IORef InertSet
new_inert_var
                               , tcs_abort_on_insoluble :: Bool
tcs_abort_on_insoluble = Bool
abort_on_insoluble
                               , tcs_worklist :: IORef WorkList
tcs_worklist           = IORef WorkList
new_wl_var }
       ; a
res <- TcLevel -> TcM a -> TcM a
forall a. TcLevel -> TcM a -> TcM a
TcM.setTcLevel TcLevel
inner_tclvl (TcM a -> TcM a) -> TcM a -> TcM a
forall a b. (a -> b) -> a -> b
$
                TcSEnv -> TcM a
thing_inside TcSEnv
nest_env

       ; InertSet
out_inert_set <- IORef InertSet -> TcRnIf TcGblEnv TcLclEnv InertSet
forall a gbl lcl. TcRef a -> TcRnIf gbl lcl a
TcM.readTcRef IORef InertSet
new_inert_var
       ; InertSet -> TcM ()
restoreTyVarCycles InertSet
out_inert_set

#if defined(DEBUG)
       -- Perform a check that the thing_inside did not cause cycles
       ; ev_binds <- TcM.getTcEvBindsMap ref
       ; checkForCyclicBinds ev_binds
#endif
       ; a -> TcM a
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return a
res }

nestTcS ::  TcS a -> TcS a
-- Use the current untouchables, augmenting the current
-- evidence bindings, and solved dictionaries
-- But have no effect on the InertCans, or on the inert_famapp_cache
-- (we want to inherit the latter from processing the Givens)
nestTcS :: forall a. TcS a -> TcS a
nestTcS (TcS TcSEnv -> TcM a
thing_inside)
  = (TcSEnv -> TcM a) -> TcS a
forall a. (TcSEnv -> TcM a) -> TcS a
TcS ((TcSEnv -> TcM a) -> TcS a) -> (TcSEnv -> TcM a) -> TcS a
forall a b. (a -> b) -> a -> b
$ \ env :: TcSEnv
env@(TcSEnv { tcs_inerts :: TcSEnv -> IORef InertSet
tcs_inerts = IORef InertSet
inerts_var }) ->
    do { InertSet
inerts <- IORef InertSet -> TcRnIf TcGblEnv TcLclEnv InertSet
forall a gbl lcl. TcRef a -> TcRnIf gbl lcl a
TcM.readTcRef IORef InertSet
inerts_var
       ; IORef InertSet
new_inert_var <- InertSet -> TcRnIf TcGblEnv TcLclEnv (IORef InertSet)
forall a gbl lcl. a -> TcRnIf gbl lcl (TcRef a)
TcM.newTcRef InertSet
inerts
       ; IORef WorkList
new_wl_var    <- WorkList -> TcRnIf TcGblEnv TcLclEnv (IORef WorkList)
forall a gbl lcl. a -> TcRnIf gbl lcl (TcRef a)
TcM.newTcRef WorkList
emptyWorkList
       ; let nest_env :: TcSEnv
nest_env = TcSEnv
env { tcs_inerts :: IORef InertSet
tcs_inerts   = IORef InertSet
new_inert_var
                            , tcs_worklist :: IORef WorkList
tcs_worklist = IORef WorkList
new_wl_var }

       ; a
res <- TcSEnv -> TcM a
thing_inside TcSEnv
nest_env

       ; InertSet
new_inerts <- IORef InertSet -> TcRnIf TcGblEnv TcLclEnv InertSet
forall a gbl lcl. TcRef a -> TcRnIf gbl lcl a
TcM.readTcRef IORef InertSet
new_inert_var

       -- we want to propagate the safe haskell failures
       ; let old_ic :: InertCans
old_ic = InertSet -> InertCans
inert_cans InertSet
inerts
             new_ic :: InertCans
new_ic = InertSet -> InertCans
inert_cans InertSet
new_inerts
             nxt_ic :: InertCans
nxt_ic = InertCans
old_ic { inert_safehask :: DictMap Ct
inert_safehask = InertCans -> DictMap Ct
inert_safehask InertCans
new_ic }

       ; IORef InertSet -> InertSet -> TcM ()
forall a gbl lcl. TcRef a -> a -> TcRnIf gbl lcl ()
TcM.writeTcRef IORef InertSet
inerts_var  -- See Note [Propagate the solved dictionaries]
                        (InertSet
inerts { inert_solved_dicts :: DictMap CtEvidence
inert_solved_dicts = InertSet -> DictMap CtEvidence
inert_solved_dicts InertSet
new_inerts
                                , inert_cans :: InertCans
inert_cans = InertCans
nxt_ic })

       ; a -> TcM a
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return a
res }

emitImplicationTcS :: TcLevel -> SkolemInfoAnon
                   -> [TcTyVar]        -- Skolems
                   -> [EvVar]          -- Givens
                   -> Cts              -- Wanteds
                   -> TcS TcEvBinds
-- Add an implication to the TcS monad work-list
emitImplicationTcS :: TcLevel
-> SkolemInfoAnon -> [TcTyVar] -> [TcTyVar] -> Cts -> TcS TcEvBinds
emitImplicationTcS TcLevel
new_tclvl SkolemInfoAnon
skol_info [TcTyVar]
skol_tvs [TcTyVar]
givens Cts
wanteds
  = do { let wc :: WantedConstraints
wc = WantedConstraints
emptyWC { wc_simple :: Cts
wc_simple = Cts
wanteds }
       ; Implication
imp <- TcM Implication -> TcS Implication
forall a. TcM a -> TcS a
wrapTcS (TcM Implication -> TcS Implication)
-> TcM Implication -> TcS Implication
forall a b. (a -> b) -> a -> b
$
                do { EvBindsVar
ev_binds_var <- TcM EvBindsVar
TcM.newTcEvBinds
                   ; Implication
imp <- TcM Implication
TcM.newImplication
                   ; Implication -> TcM Implication
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (Implication
imp { ic_tclvl :: TcLevel
ic_tclvl  = TcLevel
new_tclvl
                                 , ic_skols :: [TcTyVar]
ic_skols  = [TcTyVar]
skol_tvs
                                 , ic_given :: [TcTyVar]
ic_given  = [TcTyVar]
givens
                                 , ic_wanted :: WantedConstraints
ic_wanted = WantedConstraints
wc
                                 , ic_binds :: EvBindsVar
ic_binds  = EvBindsVar
ev_binds_var
                                 , ic_info :: SkolemInfoAnon
ic_info   = SkolemInfoAnon
skol_info }) }

       ; Implication -> TcS ()
emitImplication Implication
imp
       ; TcEvBinds -> TcS TcEvBinds
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (EvBindsVar -> TcEvBinds
TcEvBinds (Implication -> EvBindsVar
ic_binds Implication
imp)) }

emitTvImplicationTcS :: TcLevel -> SkolemInfoAnon
                     -> [TcTyVar]        -- Skolems
                     -> Cts              -- Wanteds
                     -> TcS ()
-- Just like emitImplicationTcS but no givens and no bindings
emitTvImplicationTcS :: TcLevel -> SkolemInfoAnon -> [TcTyVar] -> Cts -> TcS ()
emitTvImplicationTcS TcLevel
new_tclvl SkolemInfoAnon
skol_info [TcTyVar]
skol_tvs Cts
wanteds
  = do { let wc :: WantedConstraints
wc = WantedConstraints
emptyWC { wc_simple :: Cts
wc_simple = Cts
wanteds }
       ; Implication
imp <- TcM Implication -> TcS Implication
forall a. TcM a -> TcS a
wrapTcS (TcM Implication -> TcS Implication)
-> TcM Implication -> TcS Implication
forall a b. (a -> b) -> a -> b
$
                do { EvBindsVar
ev_binds_var <- TcM EvBindsVar
TcM.newNoTcEvBinds
                   ; Implication
imp <- TcM Implication
TcM.newImplication
                   ; Implication -> TcM Implication
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (Implication
imp { ic_tclvl :: TcLevel
ic_tclvl  = TcLevel
new_tclvl
                                 , ic_skols :: [TcTyVar]
ic_skols  = [TcTyVar]
skol_tvs
                                 , ic_wanted :: WantedConstraints
ic_wanted = WantedConstraints
wc
                                 , ic_binds :: EvBindsVar
ic_binds  = EvBindsVar
ev_binds_var
                                 , ic_info :: SkolemInfoAnon
ic_info   = SkolemInfoAnon
skol_info }) }

       ; Implication -> TcS ()
emitImplication Implication
imp }


{- Note [Propagate the solved dictionaries]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
It's really quite important that nestTcS does not discard the solved
dictionaries from the thing_inside.
Consider
   Eq [a]
   forall b. empty =>  Eq [a]
We solve the simple (Eq [a]), under nestTcS, and then turn our attention to
the implications.  It's definitely fine to use the solved dictionaries on
the inner implications, and it can make a significant performance difference
if you do so.
-}

-- Getters and setters of GHC.Tc.Utils.Env fields
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

-- Getter of inerts and worklist
getTcSInertsRef :: TcS (IORef InertSet)
getTcSInertsRef :: TcS (IORef InertSet)
getTcSInertsRef = (TcSEnv -> TcRnIf TcGblEnv TcLclEnv (IORef InertSet))
-> TcS (IORef InertSet)
forall a. (TcSEnv -> TcM a) -> TcS a
TcS (IORef InertSet -> TcRnIf TcGblEnv TcLclEnv (IORef InertSet)
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (IORef InertSet -> TcRnIf TcGblEnv TcLclEnv (IORef InertSet))
-> (TcSEnv -> IORef InertSet)
-> TcSEnv
-> TcRnIf TcGblEnv TcLclEnv (IORef InertSet)
forall b c a. (b -> c) -> (a -> b) -> a -> c
. TcSEnv -> IORef InertSet
tcs_inerts)

getTcSWorkListRef :: TcS (IORef WorkList)
getTcSWorkListRef :: TcS (IORef WorkList)
getTcSWorkListRef = (TcSEnv -> TcRnIf TcGblEnv TcLclEnv (IORef WorkList))
-> TcS (IORef WorkList)
forall a. (TcSEnv -> TcM a) -> TcS a
TcS (IORef WorkList -> TcRnIf TcGblEnv TcLclEnv (IORef WorkList)
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (IORef WorkList -> TcRnIf TcGblEnv TcLclEnv (IORef WorkList))
-> (TcSEnv -> IORef WorkList)
-> TcSEnv
-> TcRnIf TcGblEnv TcLclEnv (IORef WorkList)
forall b c a. (b -> c) -> (a -> b) -> a -> c
. TcSEnv -> IORef WorkList
tcs_worklist)

getTcSInerts :: TcS InertSet
getTcSInerts :: TcS InertSet
getTcSInerts = TcS (IORef InertSet)
getTcSInertsRef TcS (IORef InertSet)
-> (IORef InertSet -> TcS InertSet) -> TcS InertSet
forall a b. TcS a -> (a -> TcS b) -> TcS b
forall (m :: * -> *) a b. Monad m => m a -> (a -> m b) -> m b
>>= IORef InertSet -> TcS InertSet
forall a. TcRef a -> TcS a
readTcRef

setTcSInerts :: InertSet -> TcS ()
setTcSInerts :: InertSet -> TcS ()
setTcSInerts InertSet
ics = do { IORef InertSet
r <- TcS (IORef InertSet)
getTcSInertsRef; IORef InertSet -> InertSet -> TcS ()
forall a. TcRef a -> a -> TcS ()
writeTcRef IORef InertSet
r InertSet
ics }

getWorkListImplics :: TcS (Bag Implication)
getWorkListImplics :: TcS (Bag Implication)
getWorkListImplics
  = do { IORef WorkList
wl_var <- TcS (IORef WorkList)
getTcSWorkListRef
       ; WorkList
wl_curr <- IORef WorkList -> TcS WorkList
forall a. TcRef a -> TcS a
readTcRef IORef WorkList
wl_var
       ; Bag Implication -> TcS (Bag Implication)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (WorkList -> Bag Implication
wl_implics WorkList
wl_curr) }

pushLevelNoWorkList :: SDoc -> TcS a -> TcS (TcLevel, a)
-- Push the level and run thing_inside
-- However, thing_inside should not generate any work items
#if defined(DEBUG)
pushLevelNoWorkList err_doc (TcS thing_inside)
  = TcS (\env -> TcM.pushTcLevelM $
                 thing_inside (env { tcs_worklist = wl_panic })
        )
  where
    wl_panic  = pprPanic "GHC.Tc.Solver.Monad.buildImplication" err_doc
                         -- This panic checks that the thing-inside
                         -- does not emit any work-list constraints
#else
pushLevelNoWorkList :: forall a. SDoc -> TcS a -> TcS (TcLevel, a)
pushLevelNoWorkList SDoc
_ (TcS TcSEnv -> TcM a
thing_inside)
  = (TcSEnv -> TcM (TcLevel, a)) -> TcS (TcLevel, a)
forall a. (TcSEnv -> TcM a) -> TcS a
TcS (\TcSEnv
env -> TcM a -> TcM (TcLevel, a)
forall a. TcM a -> TcM (TcLevel, a)
TcM.pushTcLevelM (TcSEnv -> TcM a
thing_inside TcSEnv
env))  -- Don't check
#endif

updWorkListTcS :: (WorkList -> WorkList) -> TcS ()
updWorkListTcS :: (WorkList -> WorkList) -> TcS ()
updWorkListTcS WorkList -> WorkList
f
  = do { IORef WorkList
wl_var <- TcS (IORef WorkList)
getTcSWorkListRef
       ; IORef WorkList -> (WorkList -> WorkList) -> TcS ()
forall a. TcRef a -> (a -> a) -> TcS ()
updTcRef IORef WorkList
wl_var WorkList -> WorkList
f }

emitWorkNC :: [CtEvidence] -> TcS ()
emitWorkNC :: [CtEvidence] -> TcS ()
emitWorkNC [CtEvidence]
evs
  | [CtEvidence] -> Bool
forall a. [a] -> Bool
forall (t :: * -> *) a. Foldable t => t a -> Bool
null [CtEvidence]
evs
  = () -> TcS ()
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return ()
  | Bool
otherwise
  = [Ct] -> TcS ()
emitWork ((CtEvidence -> Ct) -> [CtEvidence] -> [Ct]
forall a b. (a -> b) -> [a] -> [b]
map CtEvidence -> Ct
mkNonCanonical [CtEvidence]
evs)

emitWork :: [Ct] -> TcS ()
emitWork :: [Ct] -> TcS ()
emitWork [] = () -> TcS ()
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return ()   -- avoid printing, among other work
emitWork [Ct]
cts
  = do { String -> SDoc -> TcS ()
traceTcS String
"Emitting fresh work" ([SDoc] -> SDoc
vcat ((Ct -> SDoc) -> [Ct] -> [SDoc]
forall a b. (a -> b) -> [a] -> [b]
map Ct -> SDoc
forall a. Outputable a => a -> SDoc
ppr [Ct]
cts))
       ; (WorkList -> WorkList) -> TcS ()
updWorkListTcS ([Ct] -> WorkList -> WorkList
extendWorkListCts [Ct]
cts) }

emitImplication :: Implication -> TcS ()
emitImplication :: Implication -> TcS ()
emitImplication Implication
implic
  = (WorkList -> WorkList) -> TcS ()
updWorkListTcS (Implication -> WorkList -> WorkList
extendWorkListImplic Implication
implic)

newTcRef :: a -> TcS (TcRef a)
newTcRef :: forall a. a -> TcS (TcRef a)
newTcRef a
x = TcM (TcRef a) -> TcS (TcRef a)
forall a. TcM a -> TcS a
wrapTcS (a -> TcM (TcRef a)
forall a gbl lcl. a -> TcRnIf gbl lcl (TcRef a)
TcM.newTcRef a
x)

readTcRef :: TcRef a -> TcS a
readTcRef :: forall a. TcRef a -> TcS a
readTcRef TcRef a
ref = TcM a -> TcS a
forall a. TcM a -> TcS a
wrapTcS (TcRef a -> TcM a
forall a gbl lcl. TcRef a -> TcRnIf gbl lcl a
TcM.readTcRef TcRef a
ref)

writeTcRef :: TcRef a -> a -> TcS ()
writeTcRef :: forall a. TcRef a -> a -> TcS ()
writeTcRef TcRef a
ref a
val = TcM () -> TcS ()
forall a. TcM a -> TcS a
wrapTcS (TcRef a -> a -> TcM ()
forall a gbl lcl. TcRef a -> a -> TcRnIf gbl lcl ()
TcM.writeTcRef TcRef a
ref a
val)

updTcRef :: TcRef a -> (a->a) -> TcS ()
updTcRef :: forall a. TcRef a -> (a -> a) -> TcS ()
updTcRef TcRef a
ref a -> a
upd_fn = TcM () -> TcS ()
forall a. TcM a -> TcS a
wrapTcS (TcRef a -> (a -> a) -> TcM ()
forall a gbl lcl. TcRef a -> (a -> a) -> TcRnIf gbl lcl ()
TcM.updTcRef TcRef a
ref a -> a
upd_fn)

getTcEvBindsVar :: TcS EvBindsVar
getTcEvBindsVar :: TcS EvBindsVar
getTcEvBindsVar = (TcSEnv -> TcM EvBindsVar) -> TcS EvBindsVar
forall a. (TcSEnv -> TcM a) -> TcS a
TcS (EvBindsVar -> TcM EvBindsVar
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (EvBindsVar -> TcM EvBindsVar)
-> (TcSEnv -> EvBindsVar) -> TcSEnv -> TcM EvBindsVar
forall b c a. (b -> c) -> (a -> b) -> a -> c
. TcSEnv -> EvBindsVar
tcs_ev_binds)

getTcLevel :: TcS TcLevel
getTcLevel :: TcS TcLevel
getTcLevel = TcM TcLevel -> TcS TcLevel
forall a. TcM a -> TcS a
wrapTcS TcM TcLevel
TcM.getTcLevel

getTcEvTyCoVars :: EvBindsVar -> TcS TyCoVarSet
getTcEvTyCoVars :: EvBindsVar -> TcS VarSet
getTcEvTyCoVars EvBindsVar
ev_binds_var
  = TcM VarSet -> TcS VarSet
forall a. TcM a -> TcS a
wrapTcS (TcM VarSet -> TcS VarSet) -> TcM VarSet -> TcS VarSet
forall a b. (a -> b) -> a -> b
$ EvBindsVar -> TcM VarSet
TcM.getTcEvTyCoVars EvBindsVar
ev_binds_var

getTcEvBindsMap :: EvBindsVar -> TcS EvBindMap
getTcEvBindsMap :: EvBindsVar -> TcS EvBindMap
getTcEvBindsMap EvBindsVar
ev_binds_var
  = TcM EvBindMap -> TcS EvBindMap
forall a. TcM a -> TcS a
wrapTcS (TcM EvBindMap -> TcS EvBindMap) -> TcM EvBindMap -> TcS EvBindMap
forall a b. (a -> b) -> a -> b
$ EvBindsVar -> TcM EvBindMap
TcM.getTcEvBindsMap EvBindsVar
ev_binds_var

setTcEvBindsMap :: EvBindsVar -> EvBindMap -> TcS ()
setTcEvBindsMap :: EvBindsVar -> EvBindMap -> TcS ()
setTcEvBindsMap EvBindsVar
ev_binds_var EvBindMap
binds
  = TcM () -> TcS ()
forall a. TcM a -> TcS a
wrapTcS (TcM () -> TcS ()) -> TcM () -> TcS ()
forall a b. (a -> b) -> a -> b
$ EvBindsVar -> EvBindMap -> TcM ()
TcM.setTcEvBindsMap EvBindsVar
ev_binds_var EvBindMap
binds

unifyTyVar :: TcTyVar -> TcType -> TcS ()
-- Unify a meta-tyvar with a type
-- We keep track of how many unifications have happened in tcs_unified,
--
-- We should never unify the same variable twice!
unifyTyVar :: TcTyVar -> Type -> TcS ()
unifyTyVar TcTyVar
tv Type
ty
  = Bool -> SDoc -> TcS () -> TcS ()
forall a. HasCallStack => Bool -> SDoc -> a -> a
assertPpr (TcTyVar -> Bool
isMetaTyVar TcTyVar
tv) (TcTyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcTyVar
tv) (TcS () -> TcS ()) -> TcS () -> TcS ()
forall a b. (a -> b) -> a -> b
$
    (TcSEnv -> TcM ()) -> TcS ()
forall a. (TcSEnv -> TcM a) -> TcS a
TcS ((TcSEnv -> TcM ()) -> TcS ()) -> (TcSEnv -> TcM ()) -> TcS ()
forall a b. (a -> b) -> a -> b
$ \ TcSEnv
env ->
    do { String -> SDoc -> TcM ()
TcM.traceTc String
"unifyTyVar" (TcTyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcTyVar
tv SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
":=" SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
ty)
       ; (() :: Constraint) => TcTyVar -> Type -> TcM ()
TcTyVar -> Type -> TcM ()
TcM.writeMetaTyVar TcTyVar
tv Type
ty
       ; IORef Int -> (Int -> Int) -> TcM ()
forall a gbl lcl. TcRef a -> (a -> a) -> TcRnIf gbl lcl ()
TcM.updTcRef (TcSEnv -> IORef Int
tcs_unified TcSEnv
env) (Int -> Int -> Int
forall a. Num a => a -> a -> a
+Int
1) }

reportUnifications :: TcS a -> TcS (Int, a)
reportUnifications :: forall a. TcS a -> TcS (Int, a)
reportUnifications (TcS TcSEnv -> TcM a
thing_inside)
  = (TcSEnv -> TcM (Int, a)) -> TcS (Int, a)
forall a. (TcSEnv -> TcM a) -> TcS a
TcS ((TcSEnv -> TcM (Int, a)) -> TcS (Int, a))
-> (TcSEnv -> TcM (Int, a)) -> TcS (Int, a)
forall a b. (a -> b) -> a -> b
$ \ TcSEnv
env ->
    do { IORef Int
inner_unified <- Int -> TcRnIf TcGblEnv TcLclEnv (IORef Int)
forall a gbl lcl. a -> TcRnIf gbl lcl (TcRef a)
TcM.newTcRef Int
0
       ; a
res <- TcSEnv -> TcM a
thing_inside (TcSEnv
env { tcs_unified :: IORef Int
tcs_unified = IORef Int
inner_unified })
       ; Int
n_unifs <- IORef Int -> TcRnIf TcGblEnv TcLclEnv Int
forall a gbl lcl. TcRef a -> TcRnIf gbl lcl a
TcM.readTcRef IORef Int
inner_unified
       ; IORef Int -> (Int -> Int) -> TcM ()
forall a gbl lcl. TcRef a -> (a -> a) -> TcRnIf gbl lcl ()
TcM.updTcRef (TcSEnv -> IORef Int
tcs_unified TcSEnv
env) (Int -> Int -> Int
forall a. Num a => a -> a -> a
+ Int
n_unifs)
       ; (Int, a) -> TcM (Int, a)
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (Int
n_unifs, a
res) }

data TouchabilityTestResult
  -- See Note [Solve by unification] in GHC.Tc.Solver.Interact
  -- which points out that having TouchableSameLevel is just an optimisation;
  -- we could manage with TouchableOuterLevel alone (suitably renamed)
  = TouchableSameLevel
  | TouchableOuterLevel [TcTyVar]   -- Promote these
                        TcLevel     -- ..to this level
  | Untouchable

instance Outputable TouchabilityTestResult where
  ppr :: TouchabilityTestResult -> SDoc
ppr TouchabilityTestResult
TouchableSameLevel            = String -> SDoc
text String
"TouchableSameLevel"
  ppr (TouchableOuterLevel [TcTyVar]
tvs TcLevel
lvl) = String -> SDoc
text String
"TouchableOuterLevel" SDoc -> SDoc -> SDoc
<> SDoc -> SDoc
parens (TcLevel -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcLevel
lvl SDoc -> SDoc -> SDoc
<+> [TcTyVar] -> SDoc
forall a. Outputable a => a -> SDoc
ppr [TcTyVar]
tvs)
  ppr TouchabilityTestResult
Untouchable                   = String -> SDoc
text String
"Untouchable"

touchabilityTest :: CtFlavour -> TcTyVar -> TcType -> TcS (TouchabilityTestResult, TcType)
-- ^ This is the key test for untouchability:
-- See Note [Unification preconditions] in GHC.Tc.Utils.Unify
-- and Note [Solve by unification] in GHC.Tc.Solver.Interact
--
-- Returns a new rhs type, as this function can turn make some metavariables concrete.
touchabilityTest :: CtFlavour -> TcTyVar -> Type -> TcS (TouchabilityTestResult, Type)
touchabilityTest CtFlavour
flav TcTyVar
tv1 Type
rhs
  | CtFlavour
flav CtFlavour -> CtFlavour -> Bool
forall a. Eq a => a -> a -> Bool
/= CtFlavour
Given  -- See Note [Do not unify Givens]
  , MetaTv { mtv_tclvl :: TcTyVarDetails -> TcLevel
mtv_tclvl = TcLevel
tv_lvl, mtv_info :: TcTyVarDetails -> MetaInfo
mtv_info = MetaInfo
info } <- TcTyVar -> TcTyVarDetails
tcTyVarDetails TcTyVar
tv1
  = do { Maybe Type
continue_solving <- TcM (Maybe Type) -> TcS (Maybe Type)
forall a. TcM a -> TcS a
wrapTcS (TcM (Maybe Type) -> TcS (Maybe Type))
-> TcM (Maybe Type) -> TcS (Maybe Type)
forall a b. (a -> b) -> a -> b
$ MetaInfo -> Type -> TcM (Maybe Type)
startSolvingByUnification MetaInfo
info Type
rhs
       ; case Maybe Type
continue_solving of
       { Maybe Type
Nothing -> (TouchabilityTestResult, Type)
-> TcS (TouchabilityTestResult, Type)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (TouchabilityTestResult
Untouchable, Type
rhs)
       ; Just Type
rhs ->
    do { let ([TcTyVar]
free_metas, [TcTyVar]
free_skols) = (TcTyVar -> Bool) -> [TcTyVar] -> ([TcTyVar], [TcTyVar])
forall a. (a -> Bool) -> [a] -> ([a], [a])
partition TcTyVar -> Bool
isPromotableMetaTyVar ([TcTyVar] -> ([TcTyVar], [TcTyVar]))
-> [TcTyVar] -> ([TcTyVar], [TcTyVar])
forall a b. (a -> b) -> a -> b
$
                                        VarSet -> [TcTyVar]
forall elt. UniqSet elt -> [elt]
nonDetEltsUniqSet               (VarSet -> [TcTyVar]) -> VarSet -> [TcTyVar]
forall a b. (a -> b) -> a -> b
$
                                        Type -> VarSet
tyCoVarsOfType Type
rhs
       ; TcLevel
ambient_lvl  <- TcS TcLevel
getTcLevel
       ; TcLevel
given_eq_lvl <- TcS TcLevel
getInnermostGivenEqLevel

       ; if | TcLevel
tv_lvl TcLevel -> TcLevel -> Bool
`sameDepthAs` TcLevel
ambient_lvl
            -> (TouchabilityTestResult, Type)
-> TcS (TouchabilityTestResult, Type)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (TouchabilityTestResult
TouchableSameLevel, Type
rhs)

            | TcLevel
tv_lvl TcLevel -> TcLevel -> Bool
`deeperThanOrSame` TcLevel
given_eq_lvl   -- No intervening given equalities
            , (TcTyVar -> Bool) -> [TcTyVar] -> Bool
forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
all (TcLevel -> TcTyVar -> Bool
does_not_escape TcLevel
tv_lvl) [TcTyVar]
free_skols  -- No skolem escapes
            -> (TouchabilityTestResult, Type)
-> TcS (TouchabilityTestResult, Type)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return ([TcTyVar] -> TcLevel -> TouchabilityTestResult
TouchableOuterLevel [TcTyVar]
free_metas TcLevel
tv_lvl, Type
rhs)

            | Bool
otherwise
            -> (TouchabilityTestResult, Type)
-> TcS (TouchabilityTestResult, Type)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (TouchabilityTestResult
Untouchable, Type
rhs) } } }
  | Bool
otherwise
  = (TouchabilityTestResult, Type)
-> TcS (TouchabilityTestResult, Type)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (TouchabilityTestResult
Untouchable, Type
rhs)
  where

     does_not_escape :: TcLevel -> TcTyVar -> Bool
does_not_escape TcLevel
tv_lvl TcTyVar
fv
       | TcTyVar -> Bool
isTyVar TcTyVar
fv = TcLevel
tv_lvl TcLevel -> TcLevel -> Bool
`deeperThanOrSame` TcTyVar -> TcLevel
tcTyVarLevel TcTyVar
fv
       | Bool
otherwise  = Bool
True
       -- Coercion variables are not an escape risk
       -- If an implication binds a coercion variable, it'll have equalities,
       -- so the "intervening given equalities" test above will catch it
       -- Coercion holes get filled with coercions, so again no problem.

{- Note [Do not unify Givens]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider this GADT match
   data T a where
      T1 :: T Int
      ...

   f x = case x of
           T1 -> True
           ...

So we get f :: T alpha[1] -> beta[1]
          x :: T alpha[1]
and from the T1 branch we get the implication
   forall[2] (alpha[1] ~ Int) => beta[1] ~ Bool

Now, clearly we don't want to unify alpha:=Int!  Yet at the moment we
process [G] alpha[1] ~ Int, we don't have any given-equalities in the
inert set, and hence there are no given equalities to make alpha untouchable.

NB: if it were alpha[2] ~ Int, this argument wouldn't hold.  But that
never happens: invariant (GivenInv) in Note [TcLevel invariants]
in GHC.Tc.Utils.TcType.

Simple solution: never unify in Givens!
-}

getDefaultInfo ::  TcS ([Type], (Bool, Bool))
getDefaultInfo :: TcS ([Type], (Bool, Bool))
getDefaultInfo = TcM ([Type], (Bool, Bool)) -> TcS ([Type], (Bool, Bool))
forall a. TcM a -> TcS a
wrapTcS TcM ([Type], (Bool, Bool))
TcM.tcGetDefaultTys

getWorkList :: TcS WorkList
getWorkList :: TcS WorkList
getWorkList = do { IORef WorkList
wl_var <- TcS (IORef WorkList)
getTcSWorkListRef
                 ; TcM WorkList -> TcS WorkList
forall a. TcM a -> TcS a
wrapTcS (IORef WorkList -> TcM WorkList
forall a gbl lcl. TcRef a -> TcRnIf gbl lcl a
TcM.readTcRef IORef WorkList
wl_var) }

selectNextWorkItem :: TcS (Maybe Ct)
-- Pick which work item to do next
-- See Note [Prioritise equalities]
selectNextWorkItem :: TcS (Maybe Ct)
selectNextWorkItem
  = do { IORef WorkList
wl_var <- TcS (IORef WorkList)
getTcSWorkListRef
       ; WorkList
wl <- IORef WorkList -> TcS WorkList
forall a. TcRef a -> TcS a
readTcRef IORef WorkList
wl_var
       ; case WorkList -> Maybe (Ct, WorkList)
selectWorkItem WorkList
wl of {
           Maybe (Ct, WorkList)
Nothing -> Maybe Ct -> TcS (Maybe Ct)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe Ct
forall a. Maybe a
Nothing ;
           Just (Ct
ct, WorkList
new_wl) ->
    do { -- checkReductionDepth (ctLoc ct) (ctPred ct)
         -- This is done by GHC.Tc.Solver.Interact.chooseInstance
       ; IORef WorkList -> WorkList -> TcS ()
forall a. TcRef a -> a -> TcS ()
writeTcRef IORef WorkList
wl_var WorkList
new_wl
       ; Maybe Ct -> TcS (Maybe Ct)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (Ct -> Maybe Ct
forall a. a -> Maybe a
Just Ct
ct) } } }

-- Just get some environments needed for instance looking up and matching
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

getInstEnvs :: TcS InstEnvs
getInstEnvs :: TcS InstEnvs
getInstEnvs = TcM InstEnvs -> TcS InstEnvs
forall a. TcM a -> TcS a
wrapTcS (TcM InstEnvs -> TcS InstEnvs) -> TcM InstEnvs -> TcS InstEnvs
forall a b. (a -> b) -> a -> b
$ TcM InstEnvs
TcM.tcGetInstEnvs

getFamInstEnvs :: TcS (FamInstEnv, FamInstEnv)
getFamInstEnvs :: TcS (FamInstEnv, FamInstEnv)
getFamInstEnvs = TcM (FamInstEnv, FamInstEnv) -> TcS (FamInstEnv, FamInstEnv)
forall a. TcM a -> TcS a
wrapTcS (TcM (FamInstEnv, FamInstEnv) -> TcS (FamInstEnv, FamInstEnv))
-> TcM (FamInstEnv, FamInstEnv) -> TcS (FamInstEnv, FamInstEnv)
forall a b. (a -> b) -> a -> b
$ TcM (FamInstEnv, FamInstEnv)
FamInst.tcGetFamInstEnvs

getTopEnv :: TcS HscEnv
getTopEnv :: TcS HscEnv
getTopEnv = TcM HscEnv -> TcS HscEnv
forall a. TcM a -> TcS a
wrapTcS (TcM HscEnv -> TcS HscEnv) -> TcM HscEnv -> TcS HscEnv
forall a b. (a -> b) -> a -> b
$ TcM HscEnv
forall gbl lcl. TcRnIf gbl lcl HscEnv
TcM.getTopEnv

getGblEnv :: TcS TcGblEnv
getGblEnv :: TcS TcGblEnv
getGblEnv = TcM TcGblEnv -> TcS TcGblEnv
forall a. TcM a -> TcS a
wrapTcS (TcM TcGblEnv -> TcS TcGblEnv) -> TcM TcGblEnv -> TcS TcGblEnv
forall a b. (a -> b) -> a -> b
$ TcM TcGblEnv
forall gbl lcl. TcRnIf gbl lcl gbl
TcM.getGblEnv

getLclEnv :: TcS TcLclEnv
getLclEnv :: TcS TcLclEnv
getLclEnv = TcM TcLclEnv -> TcS TcLclEnv
forall a. TcM a -> TcS a
wrapTcS (TcM TcLclEnv -> TcS TcLclEnv) -> TcM TcLclEnv -> TcS TcLclEnv
forall a b. (a -> b) -> a -> b
$ TcM TcLclEnv
forall gbl lcl. TcRnIf gbl lcl lcl
TcM.getLclEnv

setLclEnv :: TcLclEnv -> TcS a -> TcS a
setLclEnv :: forall a. TcLclEnv -> TcS a -> TcS a
setLclEnv TcLclEnv
env = (TcM a -> TcM a) -> TcS a -> TcS a
forall a. (TcM a -> TcM a) -> TcS a -> TcS a
wrap2TcS (TcLclEnv -> TcM a -> TcM a
forall lcl' gbl a lcl.
lcl' -> TcRnIf gbl lcl' a -> TcRnIf gbl lcl a
TcM.setLclEnv TcLclEnv
env)

tcLookupClass :: Name -> TcS Class
tcLookupClass :: Name -> TcS Class
tcLookupClass Name
c = TcM Class -> TcS Class
forall a. TcM a -> TcS a
wrapTcS (TcM Class -> TcS Class) -> TcM Class -> TcS Class
forall a b. (a -> b) -> a -> b
$ Name -> TcM Class
TcM.tcLookupClass Name
c

tcLookupId :: Name -> TcS Id
tcLookupId :: Name -> TcS TcTyVar
tcLookupId Name
n = TcM TcTyVar -> TcS TcTyVar
forall a. TcM a -> TcS a
wrapTcS (TcM TcTyVar -> TcS TcTyVar) -> TcM TcTyVar -> TcS TcTyVar
forall a b. (a -> b) -> a -> b
$ Name -> TcM TcTyVar
TcM.tcLookupId Name
n

-- Setting names as used (used in the deriving of Coercible evidence)
-- Too hackish to expose it to TcS? In that case somehow extract the used
-- constructors from the result of solveInteract
addUsedGREs :: [GlobalRdrElt] -> TcS ()
addUsedGREs :: [GlobalRdrElt] -> TcS ()
addUsedGREs [GlobalRdrElt]
gres = TcM () -> TcS ()
forall a. TcM a -> TcS a
wrapTcS  (TcM () -> TcS ()) -> TcM () -> TcS ()
forall a b. (a -> b) -> a -> b
$ [GlobalRdrElt] -> TcM ()
TcM.addUsedGREs [GlobalRdrElt]
gres

addUsedGRE :: Bool -> GlobalRdrElt -> TcS ()
addUsedGRE :: Bool -> GlobalRdrElt -> TcS ()
addUsedGRE Bool
warn_if_deprec GlobalRdrElt
gre = TcM () -> TcS ()
forall a. TcM a -> TcS a
wrapTcS (TcM () -> TcS ()) -> TcM () -> TcS ()
forall a b. (a -> b) -> a -> b
$ Bool -> GlobalRdrElt -> TcM ()
TcM.addUsedGRE Bool
warn_if_deprec GlobalRdrElt
gre

keepAlive :: Name -> TcS ()
keepAlive :: Name -> TcS ()
keepAlive = TcM () -> TcS ()
forall a. TcM a -> TcS a
wrapTcS (TcM () -> TcS ()) -> (Name -> TcM ()) -> Name -> TcS ()
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Name -> TcM ()
TcM.keepAlive

-- Various smaller utilities [TODO, maybe will be absorbed in the instance matcher]
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

checkWellStagedDFun :: CtLoc -> InstanceWhat -> PredType -> TcS ()
-- Check that we do not try to use an instance before it is available.  E.g.
--    instance Eq T where ...
--    f x = $( ... (\(p::T) -> p == p)... )
-- Here we can't use the equality function from the instance in the splice

checkWellStagedDFun :: CtLoc -> InstanceWhat -> Type -> TcS ()
checkWellStagedDFun CtLoc
loc InstanceWhat
what Type
pred
  = do
      Maybe Int
mbind_lvl <- InstanceWhat -> TcS (Maybe Int)
checkWellStagedInstanceWhat InstanceWhat
what
      case Maybe Int
mbind_lvl of
        Just Int
bind_lvl | Int
bind_lvl Int -> Int -> Bool
forall a. Ord a => a -> a -> Bool
> Int
impLevel ->
          TcM () -> TcS ()
forall a. TcM a -> TcS a
wrapTcS (TcM () -> TcS ()) -> TcM () -> TcS ()
forall a b. (a -> b) -> a -> b
$ CtLoc -> TcM () -> TcM ()
forall a. CtLoc -> TcM a -> TcM a
TcM.setCtLocM CtLoc
loc (TcM () -> TcM ()) -> TcM () -> TcM ()
forall a b. (a -> b) -> a -> b
$ do
              { ThStage
use_stage <- TcM ThStage
TcM.getStage
              ; SDoc -> Int -> Int -> TcM ()
TcM.checkWellStaged SDoc
pp_thing Int
bind_lvl (ThStage -> Int
thLevel ThStage
use_stage) }
        Maybe Int
_ ->
          () -> TcS ()
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return ()
  where
    pp_thing :: SDoc
pp_thing = String -> SDoc
text String
"instance for" SDoc -> SDoc -> SDoc
<+> SDoc -> SDoc
quotes (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
pred)

-- | Returns the ThLevel of evidence for the solved constraint (if it has evidence)
-- See Note [Well-staged instance evidence]
checkWellStagedInstanceWhat :: InstanceWhat -> TcS (Maybe ThLevel)
checkWellStagedInstanceWhat :: InstanceWhat -> TcS (Maybe Int)
checkWellStagedInstanceWhat InstanceWhat
what
  | TopLevInstance { iw_dfun_id :: InstanceWhat -> TcTyVar
iw_dfun_id = TcTyVar
dfun_id } <- InstanceWhat
what
    = Maybe Int -> TcS (Maybe Int)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (Maybe Int -> TcS (Maybe Int)) -> Maybe Int -> TcS (Maybe Int)
forall a b. (a -> b) -> a -> b
$ Int -> Maybe Int
forall a. a -> Maybe a
Just (TcTyVar -> Int
TcM.topIdLvl TcTyVar
dfun_id)
  | BuiltinTypeableInstance TyCon
tc <- InstanceWhat
what
    = do
        Module
cur_mod <- TcGblEnv -> Module
forall t. ContainsModule t => t -> Module
extractModule (TcGblEnv -> Module) -> TcS TcGblEnv -> TcS Module
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> TcS TcGblEnv
getGblEnv
        Maybe Int -> TcS (Maybe Int)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (Maybe Int -> TcS (Maybe Int)) -> Maybe Int -> TcS (Maybe Int)
forall a b. (a -> b) -> a -> b
$ Int -> Maybe Int
forall a. a -> Maybe a
Just (if Module -> Name -> Bool
nameIsLocalOrFrom Module
cur_mod (TyCon -> Name
tyConName TyCon
tc)
                        then Int
outerLevel
                        else Int
impLevel)
  | Bool
otherwise = Maybe Int -> TcS (Maybe Int)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe Int
forall a. Maybe a
Nothing

{-
Note [Well-staged instance evidence]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Evidence for instances must obey the same level restrictions as normal bindings.
In particular, it is forbidden to use an instance in a top-level splice in the
module which the instance is defined. This is because the evidence is bound at
the top-level and top-level definitions are forbidden from being using in top-level splices in
the same module.

For example, suppose you have a function..  foo :: Show a => Code Q a -> Code Q ()
then the following program is disallowed,

```
data T a = T a deriving (Show)

main :: IO ()
main =
  let x = $$(foo [|| T () ||])
  in return ()
```

because the `foo` function (used in a top-level splice) requires `Show T` evidence,
which is defined at the top-level and therefore fails with an error that we have violated
the stage restriction.

```
Main.hs:12:14: error:
    • GHC stage restriction:
        instance for ‘Show
                        (T ())’ is used in a top-level splice, quasi-quote, or annotation,
        and must be imported, not defined locally
    • In the expression: foo [|| T () ||]
      In the Template Haskell splice $$(foo [|| T () ||])
      In the expression: $$(foo [|| T () ||])
   |
12 |   let x = $$(foo [|| T () ||])
   |
```

Solving a `Typeable (T t1 ...tn)` constraint generates code that relies on
`$tcT`, the `TypeRep` for `T`; and we must check that this reference to `$tcT`
is well staged.  It's easy to know the stage of `$tcT`: for imported TyCons it
will be `impLevel`, and for local TyCons it will be `toplevel`.

Therefore the `InstanceWhat` type had to be extended with
a special case for `Typeable`, which recorded the TyCon the evidence was for and
could them be used to check that we were not attempting to evidence in a stage incorrect
manner.

-}

pprEq :: TcType -> TcType -> SDoc
pprEq :: Type -> Type -> SDoc
pprEq Type
ty1 Type
ty2 = Type -> SDoc
pprParendType Type
ty1 SDoc -> SDoc -> SDoc
<+> Char -> SDoc
char Char
'~' SDoc -> SDoc -> SDoc
<+> Type -> SDoc
pprParendType Type
ty2

isFilledMetaTyVar_maybe :: TcTyVar -> TcS (Maybe Type)
isFilledMetaTyVar_maybe :: TcTyVar -> TcS (Maybe Type)
isFilledMetaTyVar_maybe TcTyVar
tv = TcM (Maybe Type) -> TcS (Maybe Type)
forall a. TcM a -> TcS a
wrapTcS (TcTyVar -> TcM (Maybe Type)
TcM.isFilledMetaTyVar_maybe TcTyVar
tv)

isFilledMetaTyVar :: TcTyVar -> TcS Bool
isFilledMetaTyVar :: TcTyVar -> TcS Bool
isFilledMetaTyVar TcTyVar
tv = TcM Bool -> TcS Bool
forall a. TcM a -> TcS a
wrapTcS (TcTyVar -> TcM Bool
TcM.isFilledMetaTyVar TcTyVar
tv)

zonkTyCoVarsAndFV :: TcTyCoVarSet -> TcS TcTyCoVarSet
zonkTyCoVarsAndFV :: VarSet -> TcS VarSet
zonkTyCoVarsAndFV VarSet
tvs = TcM VarSet -> TcS VarSet
forall a. TcM a -> TcS a
wrapTcS (VarSet -> TcM VarSet
TcM.zonkTyCoVarsAndFV VarSet
tvs)

zonkTyCoVarsAndFVList :: [TcTyCoVar] -> TcS [TcTyCoVar]
zonkTyCoVarsAndFVList :: [TcTyVar] -> TcS [TcTyVar]
zonkTyCoVarsAndFVList [TcTyVar]
tvs = TcM [TcTyVar] -> TcS [TcTyVar]
forall a. TcM a -> TcS a
wrapTcS ([TcTyVar] -> TcM [TcTyVar]
TcM.zonkTyCoVarsAndFVList [TcTyVar]
tvs)

zonkCo :: Coercion -> TcS Coercion
zonkCo :: Coercion -> TcS Coercion
zonkCo = TcM Coercion -> TcS Coercion
forall a. TcM a -> TcS a
wrapTcS (TcM Coercion -> TcS Coercion)
-> (Coercion -> TcM Coercion) -> Coercion -> TcS Coercion
forall b c a. (b -> c) -> (a -> b) -> a -> c
. Coercion -> TcM Coercion
TcM.zonkCo

zonkTcType :: TcType -> TcS TcType
zonkTcType :: Type -> TcS Type
zonkTcType Type
ty = TcM Type -> TcS Type
forall a. TcM a -> TcS a
wrapTcS (Type -> TcM Type
TcM.zonkTcType Type
ty)

zonkTcTypes :: [TcType] -> TcS [TcType]
zonkTcTypes :: [Type] -> TcS [Type]
zonkTcTypes [Type]
tys = TcM [Type] -> TcS [Type]
forall a. TcM a -> TcS a
wrapTcS ([Type] -> TcM [Type]
TcM.zonkTcTypes [Type]
tys)

zonkTcTyVar :: TcTyVar -> TcS TcType
zonkTcTyVar :: TcTyVar -> TcS Type
zonkTcTyVar TcTyVar
tv = TcM Type -> TcS Type
forall a. TcM a -> TcS a
wrapTcS (TcTyVar -> TcM Type
TcM.zonkTcTyVar TcTyVar
tv)

zonkSimples :: Cts -> TcS Cts
zonkSimples :: Cts -> TcS Cts
zonkSimples Cts
cts = TcM Cts -> TcS Cts
forall a. TcM a -> TcS a
wrapTcS (Cts -> TcM Cts
TcM.zonkSimples Cts
cts)

zonkWC :: WantedConstraints -> TcS WantedConstraints
zonkWC :: WantedConstraints -> TcS WantedConstraints
zonkWC WantedConstraints
wc = TcM WantedConstraints -> TcS WantedConstraints
forall a. TcM a -> TcS a
wrapTcS (WantedConstraints -> TcM WantedConstraints
TcM.zonkWC WantedConstraints
wc)

zonkTyCoVarKind :: TcTyCoVar -> TcS TcTyCoVar
zonkTyCoVarKind :: TcTyVar -> TcS TcTyVar
zonkTyCoVarKind TcTyVar
tv = TcM TcTyVar -> TcS TcTyVar
forall a. TcM a -> TcS a
wrapTcS (TcTyVar -> TcM TcTyVar
TcM.zonkTyCoVarKind TcTyVar
tv)

----------------------------
pprKicked :: Int -> SDoc
pprKicked :: Int -> SDoc
pprKicked Int
0 = SDoc
empty
pprKicked Int
n = SDoc -> SDoc
parens (Int -> SDoc
int Int
n SDoc -> SDoc -> SDoc
<+> String -> SDoc
text String
"kicked out")

{- *********************************************************************
*                                                                      *
*              The Unification Level Flag                              *
*                                                                      *
********************************************************************* -}

{- Note [The Unification Level Flag]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider a deep tree of implication constraints
   forall[1] a.                              -- Outer-implic
      C alpha[1]                               -- Simple
      forall[2] c. ....(C alpha[1])....        -- Implic-1
      forall[2] b. ....(alpha[1] ~ Int)....    -- Implic-2

The (C alpha) is insoluble until we know alpha.  We solve alpha
by unifying alpha:=Int somewhere deep inside Implic-2. But then we
must try to solve the Outer-implic all over again. This time we can
solve (C alpha) both in Outer-implic, and nested inside Implic-1.

When should we iterate solving a level-n implication?
Answer: if any unification of a tyvar at level n takes place
        in the ic_implics of that implication.

* What if a unification takes place at level n-1? Then don't iterate
  level n, because we'll iterate level n-1, and that will in turn iterate
  level n.

* What if a unification takes place at level n, in the ic_simples of
  level n?  No need to track this, because the kick-out mechanism deals
  with it.  (We can't drop kick-out in favour of iteration, because kick-out
  works for skolem-equalities, not just unifications.)

So the monad-global Unification Level Flag, kept in tcs_unif_lvl keeps
track of
  - Whether any unifications at all have taken place (Nothing => no unifications)
  - If so, what is the outermost level that has seen a unification (Just lvl)

The iteration done in the simplify_loop/maybe_simplify_again loop in GHC.Tc.Solver.

It helpful not to iterate unless there is a chance of progress.  #8474 is
an example:

  * There's a deeply-nested chain of implication constraints.
       ?x:alpha => ?y1:beta1 => ... ?yn:betan => [W] ?x:Int

  * From the innermost one we get a [W] alpha[1] ~ Int,
    so we can unify.

  * It's better not to iterate the inner implications, but go all the
    way out to level 1 before iterating -- because iterating level 1
    will iterate the inner levels anyway.

(In the olden days when we "floated" thse Derived constraints, this was
much, much more important -- we got exponential behaviour, as each iteration
produced the same Derived constraint.)
-}


resetUnificationFlag :: TcS Bool
-- We are at ambient level i
-- If the unification flag = Just i, reset it to Nothing and return True
-- Otherwise leave it unchanged and return False
resetUnificationFlag :: TcS Bool
resetUnificationFlag
  = (TcSEnv -> TcM Bool) -> TcS Bool
forall a. (TcSEnv -> TcM a) -> TcS a
TcS ((TcSEnv -> TcM Bool) -> TcS Bool)
-> (TcSEnv -> TcM Bool) -> TcS Bool
forall a b. (a -> b) -> a -> b
$ \TcSEnv
env ->
    do { let ref :: IORef (Maybe TcLevel)
ref = TcSEnv -> IORef (Maybe TcLevel)
tcs_unif_lvl TcSEnv
env
       ; TcLevel
ambient_lvl <- TcM TcLevel
TcM.getTcLevel
       ; Maybe TcLevel
mb_lvl <- IORef (Maybe TcLevel) -> TcRnIf TcGblEnv TcLclEnv (Maybe TcLevel)
forall a gbl lcl. TcRef a -> TcRnIf gbl lcl a
TcM.readTcRef IORef (Maybe TcLevel)
ref
       ; String -> SDoc -> TcM ()
TcM.traceTc String
"resetUnificationFlag" (SDoc -> TcM ()) -> SDoc -> TcM ()
forall a b. (a -> b) -> a -> b
$
         [SDoc] -> SDoc
vcat [ String -> SDoc
text String
"ambient:" SDoc -> SDoc -> SDoc
<+> TcLevel -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcLevel
ambient_lvl
              , String -> SDoc
text String
"unif_lvl:" SDoc -> SDoc -> SDoc
<+> Maybe TcLevel -> SDoc
forall a. Outputable a => a -> SDoc
ppr Maybe TcLevel
mb_lvl ]
       ; case Maybe TcLevel
mb_lvl of
           Maybe TcLevel
Nothing       -> Bool -> TcM Bool
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return Bool
False
           Just TcLevel
unif_lvl | TcLevel
ambient_lvl TcLevel -> TcLevel -> Bool
`strictlyDeeperThan` TcLevel
unif_lvl
                         -> Bool -> TcM Bool
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return Bool
False
                         | Bool
otherwise
                         -> do { IORef (Maybe TcLevel) -> Maybe TcLevel -> TcM ()
forall a gbl lcl. TcRef a -> a -> TcRnIf gbl lcl ()
TcM.writeTcRef IORef (Maybe TcLevel)
ref Maybe TcLevel
forall a. Maybe a
Nothing
                               ; Bool -> TcM Bool
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return Bool
True } }

setUnificationFlag :: TcLevel -> TcS ()
-- (setUnificationFlag i) sets the unification level to (Just i)
-- unless it already is (Just j) where j <= i
setUnificationFlag :: TcLevel -> TcS ()
setUnificationFlag TcLevel
lvl
  = (TcSEnv -> TcM ()) -> TcS ()
forall a. (TcSEnv -> TcM a) -> TcS a
TcS ((TcSEnv -> TcM ()) -> TcS ()) -> (TcSEnv -> TcM ()) -> TcS ()
forall a b. (a -> b) -> a -> b
$ \TcSEnv
env ->
    do { let ref :: IORef (Maybe TcLevel)
ref = TcSEnv -> IORef (Maybe TcLevel)
tcs_unif_lvl TcSEnv
env
       ; Maybe TcLevel
mb_lvl <- IORef (Maybe TcLevel) -> TcRnIf TcGblEnv TcLclEnv (Maybe TcLevel)
forall a gbl lcl. TcRef a -> TcRnIf gbl lcl a
TcM.readTcRef IORef (Maybe TcLevel)
ref
       ; case Maybe TcLevel
mb_lvl of
           Just TcLevel
unif_lvl | TcLevel
lvl TcLevel -> TcLevel -> Bool
`deeperThanOrSame` TcLevel
unif_lvl
                         -> () -> TcM ()
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return ()
           Maybe TcLevel
_ -> IORef (Maybe TcLevel) -> Maybe TcLevel -> TcM ()
forall a gbl lcl. TcRef a -> a -> TcRnIf gbl lcl ()
TcM.writeTcRef IORef (Maybe TcLevel)
ref (TcLevel -> Maybe TcLevel
forall a. a -> Maybe a
Just TcLevel
lvl) }


{- *********************************************************************
*                                                                      *
*                Instantiation etc.
*                                                                      *
********************************************************************* -}

-- Instantiations
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

instDFunType :: DFunId -> [DFunInstType] -> TcS ([TcType], TcThetaType)
instDFunType :: TcTyVar -> [Maybe Type] -> TcS ([Type], [Type])
instDFunType TcTyVar
dfun_id [Maybe Type]
inst_tys
  = TcM ([Type], [Type]) -> TcS ([Type], [Type])
forall a. TcM a -> TcS a
wrapTcS (TcM ([Type], [Type]) -> TcS ([Type], [Type]))
-> TcM ([Type], [Type]) -> TcS ([Type], [Type])
forall a b. (a -> b) -> a -> b
$ TcTyVar -> [Maybe Type] -> TcM ([Type], [Type])
TcM.instDFunType TcTyVar
dfun_id [Maybe Type]
inst_tys

newFlexiTcSTy :: Kind -> TcS TcType
newFlexiTcSTy :: Type -> TcS Type
newFlexiTcSTy Type
knd = TcM Type -> TcS Type
forall a. TcM a -> TcS a
wrapTcS (Type -> TcM Type
TcM.newFlexiTyVarTy Type
knd)

cloneMetaTyVar :: TcTyVar -> TcS TcTyVar
cloneMetaTyVar :: TcTyVar -> TcS TcTyVar
cloneMetaTyVar TcTyVar
tv = TcM TcTyVar -> TcS TcTyVar
forall a. TcM a -> TcS a
wrapTcS (TcTyVar -> TcM TcTyVar
TcM.cloneMetaTyVar TcTyVar
tv)

instFlexi :: [TKVar] -> TcS TCvSubst
instFlexi :: [TcTyVar] -> TcS TCvSubst
instFlexi = TCvSubst -> [TcTyVar] -> TcS TCvSubst
instFlexiX TCvSubst
emptyTCvSubst

instFlexiX :: TCvSubst -> [TKVar] -> TcS TCvSubst
instFlexiX :: TCvSubst -> [TcTyVar] -> TcS TCvSubst
instFlexiX TCvSubst
subst [TcTyVar]
tvs
  = TcM TCvSubst -> TcS TCvSubst
forall a. TcM a -> TcS a
wrapTcS ((TCvSubst -> TcTyVar -> TcM TCvSubst)
-> TCvSubst -> [TcTyVar] -> TcM TCvSubst
forall (t :: * -> *) (m :: * -> *) b a.
(Foldable t, Monad m) =>
(b -> a -> m b) -> b -> t a -> m b
foldlM TCvSubst -> TcTyVar -> TcM TCvSubst
instFlexiHelper TCvSubst
subst [TcTyVar]
tvs)

instFlexiHelper :: TCvSubst -> TKVar -> TcM TCvSubst
instFlexiHelper :: TCvSubst -> TcTyVar -> TcM TCvSubst
instFlexiHelper TCvSubst
subst TcTyVar
tv
  = do { Unique
uniq <- TcRnIf TcGblEnv TcLclEnv Unique
forall gbl lcl. TcRnIf gbl lcl Unique
TcM.newUnique
       ; TcTyVarDetails
details <- MetaInfo -> TcM TcTyVarDetails
TcM.newMetaDetails MetaInfo
TauTv
       ; let name :: Name
name = Name -> Unique -> Name
setNameUnique (TcTyVar -> Name
tyVarName TcTyVar
tv) Unique
uniq
             kind :: Type
kind = TCvSubst -> Type -> Type
substTyUnchecked TCvSubst
subst (TcTyVar -> Type
tyVarKind TcTyVar
tv)
             ty' :: Type
ty'  = TcTyVar -> Type
mkTyVarTy (Name -> Type -> TcTyVarDetails -> TcTyVar
mkTcTyVar Name
name Type
kind TcTyVarDetails
details)
       ; String -> SDoc -> TcM ()
TcM.traceTc String
"instFlexi" (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
ty')
       ; TCvSubst -> TcM TCvSubst
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return (TCvSubst -> TcTyVar -> Type -> TCvSubst
extendTvSubst TCvSubst
subst TcTyVar
tv Type
ty') }

matchGlobalInst :: DynFlags
                -> Bool      -- True <=> caller is the short-cut solver
                             -- See Note [Shortcut solving: overlap]
                -> Class -> [Type] -> TcS TcM.ClsInstResult
matchGlobalInst :: DynFlags -> Bool -> Class -> [Type] -> TcS ClsInstResult
matchGlobalInst DynFlags
dflags Bool
short_cut Class
cls [Type]
tys
  = TcM ClsInstResult -> TcS ClsInstResult
forall a. TcM a -> TcS a
wrapTcS (DynFlags -> Bool -> Class -> [Type] -> TcM ClsInstResult
TcM.matchGlobalInst DynFlags
dflags Bool
short_cut Class
cls [Type]
tys)

tcInstSkolTyVarsX :: SkolemInfo -> TCvSubst -> [TyVar] -> TcS (TCvSubst, [TcTyVar])
tcInstSkolTyVarsX :: SkolemInfo -> TCvSubst -> [TcTyVar] -> TcS (TCvSubst, [TcTyVar])
tcInstSkolTyVarsX SkolemInfo
skol_info TCvSubst
subst [TcTyVar]
tvs = TcM (TCvSubst, [TcTyVar]) -> TcS (TCvSubst, [TcTyVar])
forall a. TcM a -> TcS a
wrapTcS (TcM (TCvSubst, [TcTyVar]) -> TcS (TCvSubst, [TcTyVar]))
-> TcM (TCvSubst, [TcTyVar]) -> TcS (TCvSubst, [TcTyVar])
forall a b. (a -> b) -> a -> b
$ SkolemInfo -> TCvSubst -> [TcTyVar] -> TcM (TCvSubst, [TcTyVar])
TcM.tcInstSkolTyVarsX SkolemInfo
skol_info TCvSubst
subst [TcTyVar]
tvs

-- Creating and setting evidence variables and CtFlavors
-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

data MaybeNew = Fresh CtEvidence | Cached EvExpr

isFresh :: MaybeNew -> Bool
isFresh :: MaybeNew -> Bool
isFresh (Fresh {})  = Bool
True
isFresh (Cached {}) = Bool
False

freshGoals :: [MaybeNew] -> [CtEvidence]
freshGoals :: [MaybeNew] -> [CtEvidence]
freshGoals [MaybeNew]
mns = [ CtEvidence
ctev | Fresh CtEvidence
ctev <- [MaybeNew]
mns ]

getEvExpr :: MaybeNew -> EvExpr
getEvExpr :: MaybeNew -> EvExpr
getEvExpr (Fresh CtEvidence
ctev) = (() :: Constraint) => CtEvidence -> EvExpr
CtEvidence -> EvExpr
ctEvExpr CtEvidence
ctev
getEvExpr (Cached EvExpr
evt) = EvExpr
evt

setEvBind :: EvBind -> TcS ()
setEvBind :: EvBind -> TcS ()
setEvBind EvBind
ev_bind
  = do { EvBindsVar
evb <- TcS EvBindsVar
getTcEvBindsVar
       ; TcM () -> TcS ()
forall a. TcM a -> TcS a
wrapTcS (TcM () -> TcS ()) -> TcM () -> TcS ()
forall a b. (a -> b) -> a -> b
$ EvBindsVar -> EvBind -> TcM ()
TcM.addTcEvBind EvBindsVar
evb EvBind
ev_bind }

-- | Mark variables as used filling a coercion hole
useVars :: CoVarSet -> TcS ()
useVars :: VarSet -> TcS ()
useVars VarSet
co_vars
  = do { EvBindsVar
ev_binds_var <- TcS EvBindsVar
getTcEvBindsVar
       ; let ref :: IORef VarSet
ref = EvBindsVar -> IORef VarSet
ebv_tcvs EvBindsVar
ev_binds_var
       ; TcM () -> TcS ()
forall a. TcM a -> TcS a
wrapTcS (TcM () -> TcS ()) -> TcM () -> TcS ()
forall a b. (a -> b) -> a -> b
$
         do { VarSet
tcvs <- IORef VarSet -> TcM VarSet
forall a gbl lcl. TcRef a -> TcRnIf gbl lcl a
TcM.readTcRef IORef VarSet
ref
            ; let tcvs' :: VarSet
tcvs' = VarSet
tcvs VarSet -> VarSet -> VarSet
`unionVarSet` VarSet
co_vars
            ; IORef VarSet -> VarSet -> TcM ()
forall a gbl lcl. TcRef a -> a -> TcRnIf gbl lcl ()
TcM.writeTcRef IORef VarSet
ref VarSet
tcvs' } }

-- | Equalities only
setWantedEq :: HasDebugCallStack => TcEvDest -> Coercion -> TcS ()
setWantedEq :: (() :: Constraint) => TcEvDest -> Coercion -> TcS ()
setWantedEq (HoleDest CoercionHole
hole) Coercion
co
  = do { VarSet -> TcS ()
useVars (Coercion -> VarSet
coVarsOfCo Coercion
co)
       ; CoercionHole -> Coercion -> TcS ()
fillCoercionHole CoercionHole
hole Coercion
co }
setWantedEq (EvVarDest TcTyVar
ev) Coercion
_ = String -> SDoc -> TcS ()
forall a. HasCallStack => String -> SDoc -> a
pprPanic String
"setWantedEq: EvVarDest" (TcTyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcTyVar
ev)

-- | Good for both equalities and non-equalities
setWantedEvTerm :: TcEvDest -> EvTerm -> TcS ()
setWantedEvTerm :: TcEvDest -> EvTerm -> TcS ()
setWantedEvTerm (HoleDest CoercionHole
hole) EvTerm
tm
  | Just Coercion
co <- EvTerm -> Maybe Coercion
evTermCoercion_maybe EvTerm
tm
  = do { VarSet -> TcS ()
useVars (Coercion -> VarSet
coVarsOfCo Coercion
co)
       ; CoercionHole -> Coercion -> TcS ()
fillCoercionHole CoercionHole
hole Coercion
co }
  | Bool
otherwise
  = -- See Note [Yukky eq_sel for a HoleDest]
    do { let co_var :: TcTyVar
co_var = CoercionHole -> TcTyVar
coHoleCoVar CoercionHole
hole
       ; EvBind -> TcS ()
setEvBind (TcTyVar -> EvTerm -> EvBind
mkWantedEvBind TcTyVar
co_var EvTerm
tm)
       ; CoercionHole -> Coercion -> TcS ()
fillCoercionHole CoercionHole
hole (TcTyVar -> Coercion
mkTcCoVarCo TcTyVar
co_var) }

setWantedEvTerm (EvVarDest TcTyVar
ev_id) EvTerm
tm
  = EvBind -> TcS ()
setEvBind (TcTyVar -> EvTerm -> EvBind
mkWantedEvBind TcTyVar
ev_id EvTerm
tm)

{- Note [Yukky eq_sel for a HoleDest]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
How can it be that a Wanted with HoleDest gets evidence that isn't
just a coercion? i.e. evTermCoercion_maybe returns Nothing.

Consider [G] forall a. blah => a ~ T
         [W] S ~# T

Then doTopReactEqPred carefully looks up the (boxed) constraint (S ~ T)
in the quantified constraints, and wraps the (boxed) evidence it
gets back in an eq_sel to extract the unboxed (S ~# T).  We can't put
that term into a coercion, so we add a value binding
    h = eq_sel (...)
and the coercion variable h to fill the coercion hole.
We even re-use the CoHole's Id for this binding!

Yuk!
-}

fillCoercionHole :: CoercionHole -> Coercion -> TcS ()
fillCoercionHole :: CoercionHole -> Coercion -> TcS ()
fillCoercionHole CoercionHole
hole Coercion
co
  = do { TcM () -> TcS ()
forall a. TcM a -> TcS a
wrapTcS (TcM () -> TcS ()) -> TcM () -> TcS ()
forall a b. (a -> b) -> a -> b
$ CoercionHole -> Coercion -> TcM ()
TcM.fillCoercionHole CoercionHole
hole Coercion
co
       ; CoercionHole -> TcS ()
kickOutAfterFillingCoercionHole CoercionHole
hole }

setEvBindIfWanted :: CtEvidence -> EvTerm -> TcS ()
setEvBindIfWanted :: CtEvidence -> EvTerm -> TcS ()
setEvBindIfWanted CtEvidence
ev EvTerm
tm
  = case CtEvidence
ev of
      CtWanted { ctev_dest :: CtEvidence -> TcEvDest
ctev_dest = TcEvDest
dest } -> TcEvDest -> EvTerm -> TcS ()
setWantedEvTerm TcEvDest
dest EvTerm
tm
      CtEvidence
_                             -> () -> TcS ()
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return ()

newTcEvBinds :: TcS EvBindsVar
newTcEvBinds :: TcS EvBindsVar
newTcEvBinds = TcM EvBindsVar -> TcS EvBindsVar
forall a. TcM a -> TcS a
wrapTcS TcM EvBindsVar
TcM.newTcEvBinds

newNoTcEvBinds :: TcS EvBindsVar
newNoTcEvBinds :: TcS EvBindsVar
newNoTcEvBinds = TcM EvBindsVar -> TcS EvBindsVar
forall a. TcM a -> TcS a
wrapTcS TcM EvBindsVar
TcM.newNoTcEvBinds

newEvVar :: TcPredType -> TcS EvVar
newEvVar :: Type -> TcS TcTyVar
newEvVar Type
pred = TcM TcTyVar -> TcS TcTyVar
forall a. TcM a -> TcS a
wrapTcS (Type -> TcM TcTyVar
forall gbl lcl. Type -> TcRnIf gbl lcl TcTyVar
TcM.newEvVar Type
pred)

newGivenEvVar :: CtLoc -> (TcPredType, EvTerm) -> TcS CtEvidence
-- Make a new variable of the given PredType,
-- immediately bind it to the given term
-- and return its CtEvidence
-- See Note [Bind new Givens immediately] in GHC.Tc.Types.Constraint
newGivenEvVar :: CtLoc -> (Type, EvTerm) -> TcS CtEvidence
newGivenEvVar CtLoc
loc (Type
pred, EvTerm
rhs)
  = do { TcTyVar
new_ev <- Type -> EvTerm -> TcS TcTyVar
newBoundEvVarId Type
pred EvTerm
rhs
       ; CtEvidence -> TcS CtEvidence
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (CtGiven { ctev_pred :: Type
ctev_pred = Type
pred, ctev_evar :: TcTyVar
ctev_evar = TcTyVar
new_ev, ctev_loc :: CtLoc
ctev_loc = CtLoc
loc }) }

-- | Make a new 'Id' of the given type, bound (in the monad's EvBinds) to the
-- given term
newBoundEvVarId :: TcPredType -> EvTerm -> TcS EvVar
newBoundEvVarId :: Type -> EvTerm -> TcS TcTyVar
newBoundEvVarId Type
pred EvTerm
rhs
  = do { TcTyVar
new_ev <- Type -> TcS TcTyVar
newEvVar Type
pred
       ; EvBind -> TcS ()
setEvBind (TcTyVar -> EvTerm -> EvBind
mkGivenEvBind TcTyVar
new_ev EvTerm
rhs)
       ; TcTyVar -> TcS TcTyVar
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return TcTyVar
new_ev }

newGivenEvVars :: CtLoc -> [(TcPredType, EvTerm)] -> TcS [CtEvidence]
newGivenEvVars :: CtLoc -> [(Type, EvTerm)] -> TcS [CtEvidence]
newGivenEvVars CtLoc
loc [(Type, EvTerm)]
pts = ((Type, EvTerm) -> TcS CtEvidence)
-> [(Type, EvTerm)] -> TcS [CtEvidence]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
forall (m :: * -> *) a b. Monad m => (a -> m b) -> [a] -> m [b]
mapM (CtLoc -> (Type, EvTerm) -> TcS CtEvidence
newGivenEvVar CtLoc
loc) [(Type, EvTerm)]
pts

emitNewWantedEq :: CtLoc -> RewriterSet -> Role -> TcType -> TcType -> TcS Coercion
-- | Emit a new Wanted equality into the work-list
emitNewWantedEq :: CtLoc -> RewriterSet -> Role -> Type -> Type -> TcS Coercion
emitNewWantedEq CtLoc
loc RewriterSet
rewriters Role
role Type
ty1 Type
ty2
  = do { (CtEvidence
ev, Coercion
co) <- CtLoc
-> RewriterSet
-> Role
-> Type
-> Type
-> TcS (CtEvidence, Coercion)
newWantedEq CtLoc
loc RewriterSet
rewriters Role
role Type
ty1 Type
ty2
       ; (WorkList -> WorkList) -> TcS ()
updWorkListTcS (Ct -> WorkList -> WorkList
extendWorkListEq (CtEvidence -> Ct
mkNonCanonical CtEvidence
ev))
       ; Coercion -> TcS Coercion
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return Coercion
co }

-- | Create a new Wanted constraint holding a coercion hole
-- for an equality between the two types at the given 'Role'.
newWantedEq :: CtLoc -> RewriterSet -> Role -> TcType -> TcType
            -> TcS (CtEvidence, Coercion)
newWantedEq :: CtLoc
-> RewriterSet
-> Role
-> Type
-> Type
-> TcS (CtEvidence, Coercion)
newWantedEq CtLoc
loc RewriterSet
rewriters Role
role Type
ty1 Type
ty2
  = do { CoercionHole
hole <- TcM CoercionHole -> TcS CoercionHole
forall a. TcM a -> TcS a
wrapTcS (TcM CoercionHole -> TcS CoercionHole)
-> TcM CoercionHole -> TcS CoercionHole
forall a b. (a -> b) -> a -> b
$ Type -> TcM CoercionHole
TcM.newCoercionHole Type
pty
       ; String -> SDoc -> TcS ()
traceTcS String
"Emitting new coercion hole" (CoercionHole -> SDoc
forall a. Outputable a => a -> SDoc
ppr CoercionHole
hole SDoc -> SDoc -> SDoc
<+> SDoc
dcolon SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
pty)
       ; (CtEvidence, Coercion) -> TcS (CtEvidence, Coercion)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return ( CtWanted { ctev_pred :: Type
ctev_pred      = Type
pty
                           , ctev_dest :: TcEvDest
ctev_dest      = CoercionHole -> TcEvDest
HoleDest CoercionHole
hole
                           , ctev_loc :: CtLoc
ctev_loc       = CtLoc
loc
                           , ctev_rewriters :: RewriterSet
ctev_rewriters = RewriterSet
rewriters }
                , CoercionHole -> Coercion
mkHoleCo CoercionHole
hole ) }
  where
    pty :: Type
pty = Role -> Type -> Type -> Type
mkPrimEqPredRole Role
role Type
ty1 Type
ty2

-- | Create a new Wanted constraint holding an evidence variable.
--
-- Don't use this for equality constraints: use 'newWantedEq' instead.
newWantedEvVarNC :: CtLoc -> RewriterSet
                 -> TcPredType -> TcS CtEvidence
-- Don't look up in the solved/inerts; we know it's not there
newWantedEvVarNC :: CtLoc -> RewriterSet -> Type -> TcS CtEvidence
newWantedEvVarNC CtLoc
loc RewriterSet
rewriters Type
pty
  = do { TcTyVar
new_ev <- Type -> TcS TcTyVar
newEvVar Type
pty
       ; String -> SDoc -> TcS ()
traceTcS String
"Emitting new wanted" (TcTyVar -> SDoc
forall a. Outputable a => a -> SDoc
ppr TcTyVar
new_ev SDoc -> SDoc -> SDoc
<+> SDoc
dcolon SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
pty SDoc -> SDoc -> SDoc
$$
                                         CtLoc -> SDoc
pprCtLoc CtLoc
loc)
       ; CtEvidence -> TcS CtEvidence
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (CtWanted { ctev_pred :: Type
ctev_pred      = Type
pty
                          , ctev_dest :: TcEvDest
ctev_dest      = TcTyVar -> TcEvDest
EvVarDest TcTyVar
new_ev
                          , ctev_loc :: CtLoc
ctev_loc       = CtLoc
loc
                          , ctev_rewriters :: RewriterSet
ctev_rewriters = RewriterSet
rewriters })}

-- | Like 'newWantedEvVarNC', except it might look up in the inert set
-- to see if an inert already exists, and uses that instead of creating
-- a new Wanted constraint.
--
-- Don't use this for equality constraints: this function is only for
-- constraints with 'EvVarDest'.
newWantedEvVar :: CtLoc -> RewriterSet
               -> TcPredType -> TcS MaybeNew
-- For anything except ClassPred, this is the same as newWantedEvVarNC
newWantedEvVar :: CtLoc -> RewriterSet -> Type -> TcS MaybeNew
newWantedEvVar CtLoc
loc RewriterSet
rewriters Type
pty
  = Bool -> SDoc -> TcS MaybeNew -> TcS MaybeNew
forall a. HasCallStack => Bool -> SDoc -> a -> a
assertPpr (Bool -> Bool
not (Type -> Bool
isEqPrimPred Type
pty))
      ([SDoc] -> SDoc
vcat [ String -> SDoc
text String
"newWantedEvVar: HoleDestPred"
            , String -> SDoc
text String
"pty:" SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
pty ]) (TcS MaybeNew -> TcS MaybeNew) -> TcS MaybeNew -> TcS MaybeNew
forall a b. (a -> b) -> a -> b
$
    do { Maybe CtEvidence
mb_ct <- CtLoc -> Type -> TcS (Maybe CtEvidence)
lookupInInerts CtLoc
loc Type
pty
       ; case Maybe CtEvidence
mb_ct of
            Just CtEvidence
ctev
              -> do { String -> SDoc -> TcS ()
traceTcS String
"newWantedEvVar/cache hit" (SDoc -> TcS ()) -> SDoc -> TcS ()
forall a b. (a -> b) -> a -> b
$ CtEvidence -> SDoc
forall a. Outputable a => a -> SDoc
ppr CtEvidence
ctev
                    ; MaybeNew -> TcS MaybeNew
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (MaybeNew -> TcS MaybeNew) -> MaybeNew -> TcS MaybeNew
forall a b. (a -> b) -> a -> b
$ EvExpr -> MaybeNew
Cached ((() :: Constraint) => CtEvidence -> EvExpr
CtEvidence -> EvExpr
ctEvExpr CtEvidence
ctev) }
            Maybe CtEvidence
_ -> do { CtEvidence
ctev <- CtLoc -> RewriterSet -> Type -> TcS CtEvidence
newWantedEvVarNC CtLoc
loc RewriterSet
rewriters Type
pty
                    ; MaybeNew -> TcS MaybeNew
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (CtEvidence -> MaybeNew
Fresh CtEvidence
ctev) } }

-- | Create a new Wanted constraint, potentially looking up
-- non-equality constraints in the cache instead of creating
-- a new one from scratch.
--
-- Deals with both equality and non-equality constraints.
newWanted :: CtLoc -> RewriterSet -> PredType -> TcS MaybeNew
newWanted :: CtLoc -> RewriterSet -> Type -> TcS MaybeNew
newWanted CtLoc
loc RewriterSet
rewriters Type
pty
  | Just (Role
role, Type
ty1, Type
ty2) <- Type -> Maybe (Role, Type, Type)
getEqPredTys_maybe Type
pty
  = CtEvidence -> MaybeNew
Fresh (CtEvidence -> MaybeNew)
-> ((CtEvidence, Coercion) -> CtEvidence)
-> (CtEvidence, Coercion)
-> MaybeNew
forall b c a. (b -> c) -> (a -> b) -> a -> c
. (CtEvidence, Coercion) -> CtEvidence
forall a b. (a, b) -> a
fst ((CtEvidence, Coercion) -> MaybeNew)
-> TcS (CtEvidence, Coercion) -> TcS MaybeNew
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> CtLoc
-> RewriterSet
-> Role
-> Type
-> Type
-> TcS (CtEvidence, Coercion)
newWantedEq CtLoc
loc RewriterSet
rewriters Role
role Type
ty1 Type
ty2
  | Bool
otherwise
  = CtLoc -> RewriterSet -> Type -> TcS MaybeNew
newWantedEvVar CtLoc
loc RewriterSet
rewriters Type
pty

-- | Create a new Wanted constraint.
--
-- Deals with both equality and non-equality constraints.
--
-- Does not attempt to re-use non-equality constraints that already
-- exist in the inert set.
newWantedNC :: CtLoc -> RewriterSet -> PredType -> TcS CtEvidence
newWantedNC :: CtLoc -> RewriterSet -> Type -> TcS CtEvidence
newWantedNC CtLoc
loc RewriterSet
rewriters Type
pty
  | Just (Role
role, Type
ty1, Type
ty2) <- Type -> Maybe (Role, Type, Type)
getEqPredTys_maybe Type
pty
  = (CtEvidence, Coercion) -> CtEvidence
forall a b. (a, b) -> a
fst ((CtEvidence, Coercion) -> CtEvidence)
-> TcS (CtEvidence, Coercion) -> TcS CtEvidence
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> CtLoc
-> RewriterSet
-> Role
-> Type
-> Type
-> TcS (CtEvidence, Coercion)
newWantedEq CtLoc
loc RewriterSet
rewriters Role
role Type
ty1 Type
ty2
  | Bool
otherwise
  = CtLoc -> RewriterSet -> Type -> TcS CtEvidence
newWantedEvVarNC CtLoc
loc RewriterSet
rewriters Type
pty

-- --------- Check done in GHC.Tc.Solver.Interact.selectNewWorkItem???? ---------
-- | Checks if the depth of the given location is too much. Fails if
-- it's too big, with an appropriate error message.
checkReductionDepth :: CtLoc -> TcType   -- ^ type being reduced
                    -> TcS ()
checkReductionDepth :: CtLoc -> Type -> TcS ()
checkReductionDepth CtLoc
loc Type
ty
  = do { DynFlags
dflags <- TcS DynFlags
forall (m :: * -> *). HasDynFlags m => m DynFlags
getDynFlags
       ; Bool -> TcS () -> TcS ()
forall (f :: * -> *). Applicative f => Bool -> f () -> f ()
when (DynFlags -> SubGoalDepth -> Bool
subGoalDepthExceeded DynFlags
dflags (CtLoc -> SubGoalDepth
ctLocDepth CtLoc
loc)) (TcS () -> TcS ()) -> TcS () -> TcS ()
forall a b. (a -> b) -> a -> b
$
         TcM () -> TcS ()
forall a. TcM a -> TcS a
wrapErrTcS (TcM () -> TcS ()) -> TcM () -> TcS ()
forall a b. (a -> b) -> a -> b
$ CtLoc -> Type -> TcM ()
forall a. CtLoc -> Type -> TcM a
solverDepthError CtLoc
loc Type
ty }

matchFam :: TyCon -> [Type] -> TcS (Maybe ReductionN)
matchFam :: TyCon -> [Type] -> TcS (Maybe Reduction)
matchFam TyCon
tycon [Type]
args = TcM (Maybe Reduction) -> TcS (Maybe Reduction)
forall a. TcM a -> TcS a
wrapTcS (TcM (Maybe Reduction) -> TcS (Maybe Reduction))
-> TcM (Maybe Reduction) -> TcS (Maybe Reduction)
forall a b. (a -> b) -> a -> b
$ TyCon -> [Type] -> TcM (Maybe Reduction)
matchFamTcM TyCon
tycon [Type]
args

matchFamTcM :: TyCon -> [Type] -> TcM (Maybe ReductionN)
-- Given (F tys) return (ty, co), where co :: F tys ~N ty
matchFamTcM :: TyCon -> [Type] -> TcM (Maybe Reduction)
matchFamTcM TyCon
tycon [Type]
args
  = do { (FamInstEnv, FamInstEnv)
fam_envs <- TcM (FamInstEnv, FamInstEnv)
FamInst.tcGetFamInstEnvs
       ; let match_fam_result :: Maybe Reduction
match_fam_result
              = (FamInstEnv, FamInstEnv)
-> Role -> TyCon -> [Type] -> Maybe Reduction
reduceTyFamApp_maybe (FamInstEnv, FamInstEnv)
fam_envs Role
Nominal TyCon
tycon [Type]
args
       ; String -> SDoc -> TcM ()
TcM.traceTc String
"matchFamTcM" (SDoc -> TcM ()) -> SDoc -> TcM ()
forall a b. (a -> b) -> a -> b
$
         [SDoc] -> SDoc
vcat [ String -> SDoc
text String
"Matching:" SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr (TyCon -> [Type] -> Type
mkTyConApp TyCon
tycon [Type]
args)
              , Maybe Reduction -> SDoc
ppr_res Maybe Reduction
match_fam_result ]
       ; Maybe Reduction -> TcM (Maybe Reduction)
forall a. a -> IOEnv (Env TcGblEnv TcLclEnv) a
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe Reduction
match_fam_result }
  where
    ppr_res :: Maybe Reduction -> SDoc
ppr_res Maybe Reduction
Nothing = String -> SDoc
text String
"Match failed"
    ppr_res (Just (Reduction Coercion
co Type
ty))
      = SDoc -> Int -> SDoc -> SDoc
hang (String -> SDoc
text String
"Match succeeded:")
          Int
2 ([SDoc] -> SDoc
vcat [ String -> SDoc
text String
"Rewrites to:" SDoc -> SDoc -> SDoc
<+> Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
ty
                  , String -> SDoc
text String
"Coercion:" SDoc -> SDoc -> SDoc
<+> Coercion -> SDoc
forall a. Outputable a => a -> SDoc
ppr Coercion
co ])

solverDepthError :: CtLoc -> TcType -> TcM a
solverDepthError :: forall a. CtLoc -> Type -> TcM a
solverDepthError CtLoc
loc Type
ty
  = CtLoc -> TcM a -> TcM a
forall a. CtLoc -> TcM a -> TcM a
TcM.setCtLocM CtLoc
loc (TcM a -> TcM a) -> TcM a -> TcM a
forall a b. (a -> b) -> a -> b
$
    do { Type
ty <- Type -> TcM Type
TcM.zonkTcType Type
ty
       ; TidyEnv
env0 <- TcM TidyEnv
TcM.tcInitTidyEnv
       ; let tidy_env :: TidyEnv
tidy_env     = TidyEnv -> [TcTyVar] -> TidyEnv
tidyFreeTyCoVars TidyEnv
env0 (Type -> [TcTyVar]
tyCoVarsOfTypeList Type
ty)
             tidy_ty :: Type
tidy_ty      = TidyEnv -> Type -> Type
tidyType TidyEnv
tidy_env Type
ty
             msg :: TcRnMessage
msg = DiagnosticMessage -> TcRnMessage
forall a. (Diagnostic a, Typeable a) => a -> TcRnMessage
TcRnUnknownMessage (DiagnosticMessage -> TcRnMessage)
-> DiagnosticMessage -> TcRnMessage
forall a b. (a -> b) -> a -> b
$ [GhcHint] -> SDoc -> DiagnosticMessage
mkPlainError [GhcHint]
noHints (SDoc -> DiagnosticMessage) -> SDoc -> DiagnosticMessage
forall a b. (a -> b) -> a -> b
$
               [SDoc] -> SDoc
vcat [ String -> SDoc
text String
"Reduction stack overflow; size =" SDoc -> SDoc -> SDoc
<+> SubGoalDepth -> SDoc
forall a. Outputable a => a -> SDoc
ppr SubGoalDepth
depth
                      , SDoc -> Int -> SDoc -> SDoc
hang (String -> SDoc
text String
"When simplifying the following type:")
                           Int
2 (Type -> SDoc
forall a. Outputable a => a -> SDoc
ppr Type
tidy_ty)
                      , SDoc
note ]
       ; (TidyEnv, TcRnMessage) -> TcM a
forall a. (TidyEnv, TcRnMessage) -> TcM a
TcM.failWithTcM (TidyEnv
tidy_env, TcRnMessage
msg) }
  where
    depth :: SubGoalDepth
depth = CtLoc -> SubGoalDepth
ctLocDepth CtLoc
loc
    note :: SDoc
note = [SDoc] -> SDoc
vcat
      [ String -> SDoc
text String
"Use -freduction-depth=0 to disable this check"
      , String -> SDoc
text String
"(any upper bound you could choose might fail unpredictably with"
      , String -> SDoc
text String
" minor updates to GHC, so disabling the check is recommended if"
      , String -> SDoc
text String
" you're sure that type checking should terminate)" ]


{-
************************************************************************
*                                                                      *
              Breaking type variable cycles
*                                                                      *
************************************************************************
-}

-- | Conditionally replace all type family applications in the RHS with fresh
-- variables, emitting givens that relate the type family application to the
-- variable. See Note [Type equality cycles] in GHC.Tc.Solver.Canonical.
-- This only works under conditions as described in the Note; otherwise, returns
-- Nothing.
breakTyEqCycle_maybe :: CtEvidence
                     -> CheckTyEqResult   -- result of checkTypeEq
                     -> CanEqLHS
                     -> TcType     -- RHS
                     -> TcS (Maybe ReductionN)
                         -- new RHS that doesn't have any type families
breakTyEqCycle_maybe :: CtEvidence
-> CheckTyEqResult -> CanEqLHS -> Type -> TcS (Maybe Reduction)
breakTyEqCycle_maybe (CtLoc -> CtOrigin
ctLocOrigin (CtLoc -> CtOrigin)
-> (CtEvidence -> CtLoc) -> CtEvidence -> CtOrigin
forall b c a. (b -> c) -> (a -> b) -> a -> c
. CtEvidence -> CtLoc
ctEvLoc -> CycleBreakerOrigin CtOrigin
_) CheckTyEqResult
_ CanEqLHS
_ Type
_
  -- see Detail (7) of Note
  = Maybe Reduction -> TcS (Maybe Reduction)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe Reduction
forall a. Maybe a
Nothing

breakTyEqCycle_maybe CtEvidence
ev CheckTyEqResult
cte_result CanEqLHS
lhs Type
rhs
  | EqRel
NomEq <- EqRel
eq_rel

  , CheckTyEqResult
cte_result CheckTyEqResult -> CheckTyEqProblem -> Bool
`cterHasOnlyProblem` CheckTyEqProblem
cteSolubleOccurs
     -- only do this if the only problem is a soluble occurs-check
     -- See Detail (8) of the Note.

  = do { Maybe Type
should_break <- TcS (Maybe Type)
final_check
       ; (Type -> TcS Reduction) -> Maybe Type -> TcS (Maybe Reduction)
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
forall (m :: * -> *) a b.
Monad m =>
(a -> m b) -> Maybe a -> m (Maybe b)
mapM Type -> TcS Reduction
go Maybe Type
should_break }
  where
    flavour :: CtFlavour
flavour = CtEvidence -> CtFlavour
ctEvFlavour CtEvidence
ev
    eq_rel :: EqRel
eq_rel  = CtEvidence -> EqRel
ctEvEqRel CtEvidence
ev

    final_check :: TcS (Maybe Type)
final_check = case CtFlavour
flavour of
      CtFlavour
Given  -> Maybe Type -> TcS (Maybe Type)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (Maybe Type -> TcS (Maybe Type)) -> Maybe Type -> TcS (Maybe Type)
forall a b. (a -> b) -> a -> b
$ Type -> Maybe Type
forall a. a -> Maybe a
Just Type
rhs
      CtFlavour
Wanted    -- Wanteds work only with a touchable tyvar on the left
                -- See "Wanted" section of the Note.
        | TyVarLHS TcTyVar
lhs_tv <- CanEqLHS
lhs ->
          do { (TouchabilityTestResult
result, Type
rhs) <- CtFlavour -> TcTyVar -> Type -> TcS (TouchabilityTestResult, Type)
touchabilityTest CtFlavour
Wanted TcTyVar
lhs_tv Type
rhs
             ; Maybe Type -> TcS (Maybe Type)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (Maybe Type -> TcS (Maybe Type)) -> Maybe Type -> TcS (Maybe Type)
forall a b. (a -> b) -> a -> b
$ case TouchabilityTestResult
result of
                          TouchabilityTestResult
Untouchable -> Maybe Type
forall a. Maybe a
Nothing
                          TouchabilityTestResult
_           -> Type -> Maybe Type
forall a. a -> Maybe a
Just Type
rhs }
        | Bool
otherwise -> Maybe Type -> TcS (Maybe Type)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe Type
forall a. Maybe a
Nothing

    -- This could be considerably more efficient. See Detail (5) of Note.
    go :: TcType -> TcS ReductionN
    go :: Type -> TcS Reduction
go Type
ty | Just Type
ty' <- Type -> Maybe Type
rewriterView Type
ty = Type -> TcS Reduction
go Type
ty'
    go (Rep.TyConApp TyCon
tc [Type]
tys)
      | TyCon -> Bool
isTypeFamilyTyCon TyCon
tc  -- worried about whether this type family is not actually
                              -- causing trouble? See Detail (5) of Note.
      = do { let ([Type]
fun_args, [Type]
extra_args) = Int -> [Type] -> ([Type], [Type])
forall a. Int -> [a] -> ([a], [a])
splitAt (TyCon -> Int
tyConArity TyCon
tc) [Type]
tys
                 fun_app :: Type
fun_app                = TyCon -> [Type] -> Type
mkTyConApp TyCon
tc [Type]
fun_args
                 fun_app_kind :: Type
fun_app_kind           = (() :: Constraint) => Type -> Type
Type -> Type
tcTypeKind Type
fun_app
           ; Reduction
fun_redn <- Type -> Type -> TcS Reduction
emit_work Type
fun_app_kind Type
fun_app
           ; Reductions
arg_redns <- [Reduction] -> Reductions
unzipRedns ([Reduction] -> Reductions) -> TcS [Reduction] -> TcS Reductions
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> (Type -> TcS Reduction) -> [Type] -> TcS [Reduction]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
forall (m :: * -> *) a b. Monad m => (a -> m b) -> [a] -> m [b]
mapM Type -> TcS Reduction
go [Type]
extra_args
           ; Reduction -> TcS Reduction
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (Reduction -> TcS Reduction) -> Reduction -> TcS Reduction
forall a b. (a -> b) -> a -> b
$ Reduction -> Reductions -> Reduction
mkAppRedns Reduction
fun_redn Reductions
arg_redns }
              -- Worried that this substitution will change kinds?
              -- See Detail (3) of Note

      | Bool
otherwise
      = do { Reductions
arg_redns <- [Reduction] -> Reductions
unzipRedns ([Reduction] -> Reductions) -> TcS [Reduction] -> TcS Reductions
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> (Type -> TcS Reduction) -> [Type] -> TcS [Reduction]
forall (t :: * -> *) (m :: * -> *) a b.
(Traversable t, Monad m) =>
(a -> m b) -> t a -> m (t b)
forall (m :: * -> *) a b. Monad m => (a -> m b) -> [a] -> m [b]
mapM Type -> TcS Reduction
go [Type]
tys
           ; Reduction -> TcS Reduction
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (Reduction -> TcS Reduction) -> Reduction -> TcS Reduction
forall a b. (a -> b) -> a -> b
$ Role -> TyCon -> Reductions -> Reduction
mkTyConAppRedn Role
Nominal TyCon
tc Reductions
arg_redns }

    go (Rep.AppTy Type
ty1 Type
ty2)
      = Reduction -> Reduction -> Reduction
mkAppRedn (Reduction -> Reduction -> Reduction)
-> TcS Reduction -> TcS (Reduction -> Reduction)
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> Type -> TcS Reduction
go Type
ty1 TcS (Reduction -> Reduction) -> TcS Reduction -> TcS Reduction
forall a b. TcS (a -> b) -> TcS a -> TcS b
forall (f :: * -> *) a b. Applicative f => f (a -> b) -> f a -> f b
<*> Type -> TcS Reduction
go Type
ty2
    go (Rep.FunTy AnonArgFlag
vis Type
w Type
arg Type
res)
      = Role
-> AnonArgFlag -> Reduction -> Reduction -> Reduction -> Reduction
mkFunRedn Role
Nominal AnonArgFlag
vis (Reduction -> Reduction -> Reduction -> Reduction)
-> TcS Reduction -> TcS (Reduction -> Reduction -> Reduction)
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> Type -> TcS Reduction
go Type
w TcS (Reduction -> Reduction -> Reduction)
-> TcS Reduction -> TcS (Reduction -> Reduction)
forall a b. TcS (a -> b) -> TcS a -> TcS b
forall (f :: * -> *) a b. Applicative f => f (a -> b) -> f a -> f b
<*> Type -> TcS Reduction
go Type
arg TcS (Reduction -> Reduction) -> TcS Reduction -> TcS Reduction
forall a b. TcS (a -> b) -> TcS a -> TcS b
forall (f :: * -> *) a b. Applicative f => f (a -> b) -> f a -> f b
<*> Type -> TcS Reduction
go Type
res
    go (Rep.CastTy Type
ty Coercion
cast_co)
      = Role -> Type -> Coercion -> Reduction -> Reduction
mkCastRedn1 Role
Nominal Type
ty Coercion
cast_co (Reduction -> Reduction) -> TcS Reduction -> TcS Reduction
forall (f :: * -> *) a b. Functor f => (a -> b) -> f a -> f b
<$> Type -> TcS Reduction
go Type
ty
    go ty :: Type
ty@(Rep.TyVarTy {})    = Type -> TcS Reduction
forall {m :: * -> *}. Monad m => Type -> m Reduction
skip Type
ty
    go ty :: Type
ty@(Rep.LitTy {})      = Type -> TcS Reduction
forall {m :: * -> *}. Monad m => Type -> m Reduction
skip Type
ty
    go ty :: Type
ty@(Rep.ForAllTy {})   = Type -> TcS Reduction
forall {m :: * -> *}. Monad m => Type -> m Reduction
skip Type
ty  -- See Detail (1) of Note
    go ty :: Type
ty@(Rep.CoercionTy {}) = Type -> TcS Reduction
forall {m :: * -> *}. Monad m => Type -> m Reduction
skip Type
ty  -- See Detail (2) of Note

    skip :: Type -> m Reduction
skip Type
ty = Reduction -> m Reduction
forall a. a -> m a
forall (m :: * -> *) a. Monad m => a -> m a
return (Reduction -> m Reduction) -> Reduction -> m Reduction
forall a b. (a -> b) -> a -> b
$ Role -> Type -> Reduction
mkReflRedn Role
Nominal Type
ty

    emit_work :: TcKind         -- of the function application
              -> TcType         -- original function application
              -> TcS ReductionN -- rewritten type (the fresh tyvar)
    emit_work :: Type -> Type -> TcS Reduction
emit_work Type
fun_app_kind Type
fun_app = case CtFlavour
flavour of
      CtFlavour
Given ->
        do { TcTyVar
new_tv <- TcM TcTyVar -> TcS TcTyVar
forall a. TcM a -> TcS a
wrapTcS (Type -> TcM TcTyVar
TcM.newCycleBreakerTyVar Type
fun_app_kind)
           ; let new_ty :: Type
new_ty     = TcTyVar -> Type
mkTyVarTy TcTyVar
new_tv
                 given_pred :: Type
given_pred = Type -> Type -> Type -> Type -> Type
mkHeteroPrimEqPred Type
fun_app_kind Type
fun_app_kind
                                                 Type
fun_app Type
new_ty
                 given_term :: EvTerm
given_term = Coercion -> EvTerm
evCoercion (Coercion -> EvTerm) -> Coercion -> EvTerm
forall a b. (a -> b) -> a -> b
$ Type -> Coercion
mkNomReflCo Type
new_ty  -- See Detail (4) of Note
           ; CtEvidence
new_given <- CtLoc -> (Type, EvTerm) -> TcS CtEvidence
newGivenEvVar CtLoc
new_loc (Type
given_pred, EvTerm
given_term)
           ; String -> SDoc -> TcS ()
traceTcS String
"breakTyEqCycle replacing type family in Given" (CtEvidence -> SDoc
forall a. Outputable a => a -> SDoc
ppr CtEvidence
new_given)
           ; [CtEvidence] -> TcS ()
emitWorkNC [CtEvidence
new_given]
           ; (InertSet -> InertSet) -> TcS ()
updInertTcS ((InertSet -> InertSet) -> TcS ())
-> (InertSet -> InertSet) -> TcS ()
forall a b. (a -> b) -> a -> b
$ \InertSet
is ->
               InertSet
is { inert_cycle_breakers :: CycleBreakerVarStack
inert_cycle_breakers = TcTyVar -> Type -> CycleBreakerVarStack -> CycleBreakerVarStack
insertCycleBreakerBinding TcTyVar
new_tv Type
fun_app
                                             (InertSet -> CycleBreakerVarStack
inert_cycle_breakers InertSet
is) }
           ; Reduction -> TcS Reduction
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (Reduction -> TcS Reduction) -> Reduction -> TcS Reduction
forall a b. (a -> b) -> a -> b
$ Role -> Type -> Reduction
mkReflRedn Role
Nominal Type
new_ty }
                -- Why reflexive? See Detail (4) of the Note

      CtFlavour
Wanted ->
        do { TcTyVar
new_tv <- TcM TcTyVar -> TcS TcTyVar
forall a. TcM a -> TcS a
wrapTcS (Type -> TcM TcTyVar
TcM.newFlexiTyVar Type
fun_app_kind)
           ; let new_ty :: Type
new_ty = TcTyVar -> Type
mkTyVarTy TcTyVar
new_tv
           ; Coercion
co <- CtLoc -> RewriterSet -> Role -> Type -> Type -> TcS Coercion
emitNewWantedEq CtLoc
new_loc (CtEvidence -> RewriterSet
ctEvRewriters CtEvidence
ev) Role
Nominal Type
new_ty Type
fun_app
           ; Reduction -> TcS Reduction
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return (Reduction -> TcS Reduction) -> Reduction -> TcS Reduction
forall a b. (a -> b) -> a -> b
$ Coercion -> Type -> Reduction
mkReduction (Coercion -> Coercion
mkSymCo Coercion
co) Type
new_ty }

      -- See Detail (7) of the Note
    new_loc :: CtLoc
new_loc = CtLoc -> (CtOrigin -> CtOrigin) -> CtLoc
updateCtLocOrigin (CtEvidence -> CtLoc
ctEvLoc CtEvidence
ev) CtOrigin -> CtOrigin
CycleBreakerOrigin

-- does not fit scenario from Note
breakTyEqCycle_maybe CtEvidence
_ CheckTyEqResult
_ CanEqLHS
_ Type
_ = Maybe Reduction -> TcS (Maybe Reduction)
forall a. a -> TcS a
forall (m :: * -> *) a. Monad m => a -> m a
return Maybe Reduction
forall a. Maybe a
Nothing

-- | Fill in CycleBreakerTvs with the variables they stand for.
-- See Note [Type equality cycles] in GHC.Tc.Solver.Canonical.
restoreTyVarCycles :: InertSet -> TcM ()
restoreTyVarCycles :: InertSet -> TcM ()
restoreTyVarCycles InertSet
is
  = CycleBreakerVarStack -> (TcTyVar -> Type -> TcM ()) -> TcM ()
forall (m :: * -> *).
Monad m =>
CycleBreakerVarStack -> (TcTyVar -> Type -> m ()) -> m ()
forAllCycleBreakerBindings_ (InertSet -> CycleBreakerVarStack
inert_cycle_breakers InertSet
is) (() :: Constraint) => TcTyVar -> Type -> TcM ()
TcTyVar -> Type -> TcM ()
TcM.writeMetaTyVar
{-# SPECIALISE forAllCycleBreakerBindings_ ::
      CycleBreakerVarStack -> (TcTyVar -> TcType -> TcM ()) -> TcM () #-}

-- Unwrap a type synonym only when either:
--   The type synonym is forgetful, or
--   the type synonym mentions a type family in its expansion
-- See Note [Rewriting synonyms] in GHC.Tc.Solver.Rewrite.
rewriterView :: TcType -> Maybe TcType
rewriterView :: Type -> Maybe Type
rewriterView ty :: Type
ty@(Rep.TyConApp TyCon
tc [Type]
_)
  | TyCon -> Bool
isForgetfulSynTyCon TyCon
tc Bool -> Bool -> Bool
|| (TyCon -> Bool
isTypeSynonymTyCon TyCon
tc Bool -> Bool -> Bool
&& Bool -> Bool
not (TyCon -> Bool
isFamFreeTyCon TyCon
tc))
  = Type -> Maybe Type
tcView Type
ty
rewriterView Type
_other = Maybe Type
forall a. Maybe a
Nothing