InstEnv

Documentation

type DFunId = Id

Dictionary Function Identifier

type InstMatch = (ClsInst, [DFunInstType])

type ClsInstLookupResult = ([InstMatch], [ClsInst], [InstMatch])

data OverlapFlag

The semantics allowed for overlapping instances for a particular instance. See Note [Safe Haskell isSafeOverlap] (in hs) for a explanation of the isSafeOverlap field.

• AnnKeywordId : AnnOpen '{-# OVERLAPPABLE' or '{-# OVERLAPPING' or '{-# OVERLAPS' or '{-# INCOHERENT', AnnClose `#-}`,

Constructors

OverlapFlag

Fields

• overlapMode :: OverlapMode
• isSafeOverlap :: Bool

Instances

Eq OverlapFlag

Methods

(==) :: OverlapFlag -> OverlapFlag -> Bool

(/=) :: OverlapFlag -> OverlapFlag -> Bool

Data OverlapFlag

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> OverlapFlag -> c OverlapFlag

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c OverlapFlag

toConstr :: OverlapFlag -> Constr

dataTypeOf :: OverlapFlag -> DataType

dataCast1 :: Typeable (* -> *) t => (forall d. Data d => c (t d)) -> Maybe (c OverlapFlag)

dataCast2 :: Typeable (* -> * -> *) t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c OverlapFlag)

gmapT :: (forall b. Data b => b -> b) -> OverlapFlag -> OverlapFlag

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> OverlapFlag -> r

gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> OverlapFlag -> r

gmapQ :: (forall d. Data d => d -> u) -> OverlapFlag -> [u]

gmapQi :: Int -> (forall d. Data d => d -> u) -> OverlapFlag -> u

gmapM :: Monad m => (forall d. Data d => d -> m d) -> OverlapFlag -> m OverlapFlag

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> OverlapFlag -> m OverlapFlag

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> OverlapFlag -> m OverlapFlag

Outputable OverlapFlag

Methods

ppr :: OverlapFlag -> SDoc

pprPrec :: Rational -> OverlapFlag -> SDoc

Binary OverlapFlag

Methods

put_ :: BinHandle -> OverlapFlag -> IO ()

put :: BinHandle -> OverlapFlag -> IO (Bin * OverlapFlag)

get :: BinHandle -> IO OverlapFlag

data OverlapMode

Constructors

NoOverlap SourceText

This instance must not overlap another NoOverlap instance. However, it may be overlapped by Overlapping instances, and it may overlap Overlappable instances.

Overlappable SourceText

Silently ignore this instance if you find a more specific one that matches the constraint you are trying to resolve

Example: constraint (Foo [Int]) instance Foo [Int] instance {--} Foo [a]

Since the second instance has the Overlappable flag, the first instance will be chosen (otherwise its ambiguous which to choose)

Overlapping SourceText

Silently ignore any more general instances that may be used to solve the constraint.

Example: constraint (Foo [Int]) instance {--} Foo [Int] instance Foo [a]

Since the first instance has the Overlapping flag, the second---more general---instance will be ignored (otherwise it is ambiguous which to choose)

Overlaps SourceText

Equivalent to having both Overlapping and Overlappable flags.

Incoherent SourceText

Behave like Overlappable and Overlapping, and in addition pick an an arbitrary one if there are multiple matching candidates, and don't worry about later instantiation

Example: constraint (Foo [b]) instance {-# INCOHERENT -} Foo [Int] instance Foo [a] Without the Incoherent flag, we'd complain that instantiating b would change which instance was chosen. See also note [Incoherent instances] in InstEnv

Instances

Eq OverlapMode

Methods

(==) :: OverlapMode -> OverlapMode -> Bool

(/=) :: OverlapMode -> OverlapMode -> Bool

Data OverlapMode

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> OverlapMode -> c OverlapMode

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c OverlapMode

toConstr :: OverlapMode -> Constr

dataTypeOf :: OverlapMode -> DataType

dataCast1 :: Typeable (* -> *) t => (forall d. Data d => c (t d)) -> Maybe (c OverlapMode)

dataCast2 :: Typeable (* -> * -> *) t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c OverlapMode)

gmapT :: (forall b. Data b => b -> b) -> OverlapMode -> OverlapMode

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> OverlapMode -> r

gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> OverlapMode -> r

gmapQ :: (forall d. Data d => d -> u) -> OverlapMode -> [u]

gmapQi :: Int -> (forall d. Data d => d -> u) -> OverlapMode -> u

gmapM :: Monad m => (forall d. Data d => d -> m d) -> OverlapMode -> m OverlapMode

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> OverlapMode -> m OverlapMode

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> OverlapMode -> m OverlapMode

Outputable OverlapMode

Methods

ppr :: OverlapMode -> SDoc

pprPrec :: Rational -> OverlapMode -> SDoc

Binary OverlapMode

Methods

put_ :: BinHandle -> OverlapMode -> IO ()

put :: BinHandle -> OverlapMode -> IO (Bin * OverlapMode)

get :: BinHandle -> IO OverlapMode

setOverlapModeMaybe :: OverlapFlag -> Maybe OverlapMode -> OverlapFlag

data ClsInst

A type-class instance. Note that there is some tricky laziness at work here. See Note [ClsInst laziness and the rough-match fields] for more details.

Constructors

ClsInst

Fields

• is_cls_nm :: Name

  Class name

• is_tcs :: [Maybe Name]

  Top of type args

• is_dfun_name :: Name

  is_dfun_name = idName . is_dfun.

  We use is_dfun_name for the visibility check, instIsVisible, which needs to know the Module which the dictionary is defined in. However, we cannot use the Module attached to is_dfun since doing so would mean we would potentially pull in an entire interface file unnecessarily. This was the cause of #12367.

• is_tvs :: [TyVar]
• is_cls :: Class
• is_tys :: [Type]
• is_dfun :: DFunId
• is_flag :: OverlapFlag
• is_orphan :: IsOrphan

Instances

Data ClsInst

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> ClsInst -> c ClsInst

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c ClsInst

toConstr :: ClsInst -> Constr

dataTypeOf :: ClsInst -> DataType

dataCast1 :: Typeable (* -> *) t => (forall d. Data d => c (t d)) -> Maybe (c ClsInst)

dataCast2 :: Typeable (* -> * -> *) t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c ClsInst)

gmapT :: (forall b. Data b => b -> b) -> ClsInst -> ClsInst

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> ClsInst -> r

gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> ClsInst -> r

gmapQ :: (forall d. Data d => d -> u) -> ClsInst -> [u]

gmapQi :: Int -> (forall d. Data d => d -> u) -> ClsInst -> u

gmapM :: Monad m => (forall d. Data d => d -> m d) -> ClsInst -> m ClsInst

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> ClsInst -> m ClsInst

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> ClsInst -> m ClsInst

Outputable ClsInst

Methods

ppr :: ClsInst -> SDoc

pprPrec :: Rational -> ClsInst -> SDoc

NamedThing ClsInst

Methods

getOccName :: ClsInst -> OccName

getName :: ClsInst -> Name

type DFunInstType = Maybe Type

pprInstance :: ClsInst -> SDoc

pprInstanceHdr :: ClsInst -> SDoc

pprInstances :: [ClsInst] -> SDoc

instanceHead :: ClsInst -> ([TyVar], Class, [Type])

instanceSig :: ClsInst -> ([TyVar], [Type], Class, [Type])

mkLocalInstance :: DFunId -> OverlapFlag -> [TyVar] -> Class -> [Type] -> ClsInst

mkImportedInstance

Arguments

:: Name

the name of the class

-> [Maybe Name]

the types which the class was applied to

-> Name

the Name of the dictionary binding

-> DFunId

the Id of the dictionary.

-> OverlapFlag

may this instance overlap?

-> IsOrphan

is this instance an orphan?

-> ClsInst

instanceDFunId :: ClsInst -> DFunId

tidyClsInstDFun :: (DFunId -> DFunId) -> ClsInst -> ClsInst

instanceRoughTcs :: ClsInst -> [Maybe Name]

fuzzyClsInstCmp :: ClsInst -> ClsInst -> Ordering

A fuzzy comparison function for class instances, intended for sorting instances before displaying them to the user.

orphNamesOfClsInst :: ClsInst -> NameSet

Collects the names of concrete types and type constructors that make up the head of a class instance. For instance, given `class Foo a b`:

`instance Foo (Either (Maybe Int) a) Bool` would yield [Either, Maybe, Int, Bool]

Used in the implementation of ":info" in GHCi.

The tcSplitSigmaTy is because of instance Foo a => Baz T where ... The decl is an orphan if Baz and T are both not locally defined, even if Foo *is* locally defined

data InstEnvs

InstEnvs represents the combination of the global type class instance environment, the local type class instance environment, and the set of transitively reachable orphan modules (according to what modules have been directly imported) used to test orphan instance visibility.

Constructors

InstEnvs

Fields

• ie_global :: InstEnv
• ie_local :: InstEnv
• ie_visible :: VisibleOrphanModules

type VisibleOrphanModules = ModuleSet

Set of visible orphan modules, according to what modules have been directly imported. This is based off of the dep_orphs field, which records transitively reachable orphan modules (modules that define orphan instances).

type InstEnv = UniqDFM ClsInstEnv

emptyInstEnv :: InstEnv

extendInstEnv :: InstEnv -> ClsInst -> InstEnv

deleteFromInstEnv :: InstEnv -> ClsInst -> InstEnv

identicalClsInstHead :: ClsInst -> ClsInst -> Bool

True when when the instance heads are the same e.g. both are Eq [(a,b)] Used for overriding in GHCi Obviously should be insenstive to alpha-renaming

extendInstEnvList :: InstEnv -> [ClsInst] -> InstEnv

lookupUniqueInstEnv :: InstEnvs -> Class -> [Type] -> Either MsgDoc (ClsInst, [Type])

Look up an instance in the given instance environment. The given class application must match exactly one instance and the match may not contain any flexi type variables. If the lookup is unsuccessful, yield 'Left errorMessage'.

lookupInstEnv :: Bool -> InstEnvs -> Class -> [Type] -> ClsInstLookupResult

See Note [Rules for instance lookup] ^ See Note [Safe Haskell Overlapping Instances] in TcSimplify ^ See Note [Safe Haskell Overlapping Instances Implementation] in TcSimplify

instEnvElts :: InstEnv -> [ClsInst]

memberInstEnv :: InstEnv -> ClsInst -> Bool

Checks for an exact match of ClsInst in the instance environment. We use this when we do signature checking in TcRnDriver

instIsVisible :: VisibleOrphanModules -> ClsInst -> Bool

Test if an instance is visible, by checking that its origin module is in VisibleOrphanModules. See Note [Instance lookup and orphan instances]

classInstances :: InstEnvs -> Class -> [ClsInst]

instanceBindFun :: TyCoVar -> BindFlag

instanceCantMatch :: [Maybe Name] -> [Maybe Name] -> Bool

roughMatchTcs :: [Type] -> [Maybe Name]

isOverlappable :: ClsInst -> Bool

isOverlapping :: ClsInst -> Bool

isIncoherent :: ClsInst -> Bool