GHC.Tc.Solver.InertSet

The work list

data WorkList

Constructors

WL

Fields

• wl_eqs :: [Ct]
• wl_rest :: [Ct]
• wl_implics :: Bag Implication

Instances

Outputable WorkList

Defined in GHC.Tc.Solver.InertSet

Methods

ppr :: WorkList -> SDoc

isEmptyWorkList :: WorkList -> Bool

emptyWorkList :: WorkList

extendWorkListNonEq :: Ct -> WorkList -> WorkList

extendWorkListCt :: Ct -> WorkList -> WorkList

extendWorkListCts :: [Ct] -> WorkList -> WorkList

extendWorkListEq :: Ct -> WorkList -> WorkList

appendWorkList :: WorkList -> WorkList -> WorkList

extendWorkListImplic :: Implication -> WorkList -> WorkList

workListSize :: WorkList -> Int

selectWorkItem :: WorkList -> Maybe (Ct, WorkList)

The inert set

data InertSet

Constructors

IS

Fields

• inert_cans :: InertCans
• inert_cycle_breakers :: CycleBreakerVarStack
• inert_famapp_cache :: FunEqMap Reduction
• inert_solved_dicts :: DictMap CtEvidence

Instances

Outputable InertSet

Defined in GHC.Tc.Solver.InertSet

Methods

ppr :: InertSet -> SDoc

data InertCans

Constructors

IC

Fields

• inert_eqs :: InertEqs
• inert_funeqs :: FunEqMap EqualCtList
• inert_dicts :: DictMap Ct
• inert_insts :: [QCInst]
• inert_safehask :: DictMap Ct

  See Note [Safe Haskell Overlapping Instances Implementation] in GHC.Tc.Solver

• inert_irreds :: Cts
• inert_given_eq_lvl :: TcLevel
• inert_given_eqs :: Bool

Instances

Outputable InertCans

Defined in GHC.Tc.Solver.InertSet

Methods

ppr :: InertCans -> SDoc

type InertEqs = DTyVarEnv EqualCtList

emptyInert :: InertSet

addInertItem :: TcLevel -> InertCans -> Ct -> InertCans

noMatchableGivenDicts :: InertSet -> CtLoc -> Class -> [TcType] -> Bool

Returns True iff there are no Given constraints that might, potentially, match the given class consraint. This is used when checking to see if a Given might overlap with an instance. See Note [Instance and Given overlap] in GHC.Tc.Solver.Interact

noGivenNewtypeReprEqs :: TyCon -> InertSet -> Bool

mightEqualLater :: InertSet -> TcPredType -> CtLoc -> TcPredType -> CtLoc -> Maybe Subst

prohibitedSuperClassSolve

Arguments

:: CtLoc

is it loopy to use this one ...

-> CtLoc

... to solve this one?

-> Bool

True ==> don't solve it

Is it (potentially) loopy to use the first ct1 to solve ct2?

Necessary (but not sufficient) conditions for this function to return True:

• ct1 and ct2 both arise from superclass expansion,
• ct1 is a Given and ct2 is a Wanted.

See Note [Solving superclass constraints] in GHC.Tc.TyCl.Instance, (sc2).

Inert equalities

foldTyEqs :: (Ct -> b -> b) -> InertEqs -> b -> b

delEq :: InertCans -> CanEqLHS -> TcType -> InertCans

findEq :: InertCans -> CanEqLHS -> [Ct]

partitionInertEqs :: (Ct -> Bool) -> InertEqs -> ([Ct], InertEqs)

partitionFunEqs :: (Ct -> Bool) -> FunEqMap EqualCtList -> ([Ct], FunEqMap EqualCtList)

Kick-out

kickOutRewritableLHS :: CtFlavourRole -> CanEqLHS -> InertCans -> (WorkList, InertCans)

Cycle breaker vars

type CycleBreakerVarStack

Arguments

 = NonEmpty [(TcTyVar, TcType)]

a stack of (CycleBreakerTv, original family applications) lists first element in the stack corresponds to current implication; later elements correspond to outer implications used to undo the cycle-breaking needed to handle Note [Type equality cycles] in GHC.Tc.Solver.Canonical Why store the outer implications? For the use in mightEqualLater (only)

pushCycleBreakerVarStack :: CycleBreakerVarStack -> CycleBreakerVarStack

Push a fresh environment onto the cycle-breaker var stack. Useful when entering a nested implication.

insertCycleBreakerBinding

Arguments

:: TcTyVar

cbv, must be a CycleBreakerTv

-> TcType

cbv's expansion

-> CycleBreakerVarStack

-> CycleBreakerVarStack

Add a new cycle-breaker binding to the top environment on the stack.

forAllCycleBreakerBindings_ :: Monad m => CycleBreakerVarStack -> (TcTyVar -> TcType -> m ()) -> m ()

Perform a monadic operation on all pairs in the top environment in the stack.