GHC.HsToCore.PmCheck.Oracle

The pattern match oracle. The main export of the module are the functions addTmCt, addVarCoreCt, addRefutableAltCon and addTypeEvidence for adding facts to the oracle, and provideEvidence to turn a Delta into a concrete evidence for an equation.

Documentation

type DsM = TcRnIf DsGblEnv DsLclEnv

tracePm :: String -> SDoc -> DsM ()

mkPmId :: Type -> DsM Id

Generate a fresh Id of a given type

data Delta

Term and type constraints to accompany each value vector abstraction. For efficiency, we store the term oracle state instead of the term constraints.

Instances

Outputable Delta

Defined in GHC.HsToCore.PmCheck.Types

Methods

ppr :: Delta -> SDoc

pprPrec :: Rational -> Delta -> SDoc

initDelta :: Delta

An initial delta that is always satisfiable

lookupRefuts :: Uniquable k => Delta -> k -> [PmAltCon]

lookupSolution :: Delta -> Id -> Maybe (PmAltCon, [Id])

data TmCt

A term constraint. Either equates two variables or a variable with a PmAltCon application.

Constructors

TmVarVar !Id !Id

TmVarCon !Id !PmAltCon ![Id]

TmVarNonVoid !Id

Instances

Outputable TmCt

Defined in GHC.HsToCore.PmCheck.Oracle

Methods

ppr :: TmCt -> SDoc

pprPrec :: Rational -> TmCt -> SDoc

addTypeEvidence :: Delta -> Bag EvVar -> DsM (Maybe Delta)

Add type equalities to Delta.

addRefutableAltCon :: Delta -> Id -> PmAltCon -> DsM (Maybe Delta)

Record that a particular Id can't take the shape of a PmAltCon in the Delta and return Nothing if that leads to a contradiction. See Note [TmState invariants].

addTmCt :: Delta -> TmCt -> DsM (Maybe Delta)

Tries to equate two representatives in Delta. See Note [TmState invariants].

addVarCoreCt :: Delta -> Id -> CoreExpr -> DsM (Maybe Delta)

Records that a variable x is equal to a CoreExpr e.

canDiverge :: Delta -> Id -> Bool

Check whether adding a constraint x ~ BOT to Delta succeeds.

provideEvidence :: [Id] -> Int -> Delta -> DsM [Delta]

provideEvidence vs n delta returns a list of at most n (but perhaps empty) refinements of delta that instantiate vs to compatible constructor applications or wildcards. Negative information is only retained if literals are involved or when for recursive GADTs.