InstEnv

ghc-7.10.3: The GHC API

Safe Haskell | None
Language | Haskell2010

InstEnv

Synopsis

- type DFunId = Id
- type InstMatch = (ClsInst, [DFunInstType])
- type ClsInstLookupResult = ([InstMatch], [ClsInst], Bool)
- data OverlapFlag = OverlapFlag {
  - overlapMode :: OverlapMode
  - isSafeOverlap :: Bool
  }
- data OverlapMode
  - = NoOverlap SourceText
  - | Overlappable SourceText
  - | Overlapping SourceText
  - | Overlaps SourceText
  - | Incoherent SourceText
- setOverlapModeMaybe :: OverlapFlag -> Maybe OverlapMode -> OverlapFlag
- data ClsInst = ClsInst {
  - is_cls_nm :: Name
  - is_tcs :: [Maybe Name]
  - is_tvs :: [TyVar]
  - is_cls :: Class
  - is_tys :: [Type]
  - is_dfun :: DFunId
  - is_flag :: OverlapFlag
  - is_orphan :: IsOrphan
  }
- 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 :: Name -> [Maybe Name] -> DFunId -> OverlapFlag -> IsOrphan -> ClsInst
- instanceDFunId :: ClsInst -> DFunId
- tidyClsInstDFun :: (DFunId -> DFunId) -> ClsInst -> ClsInst
- instanceRoughTcs :: ClsInst -> [Maybe Name]
- fuzzyClsInstCmp :: ClsInst -> ClsInst -> Ordering
- data IsOrphan
  - = IsOrphan
  - | NotOrphan OccName
- isOrphan :: IsOrphan -> Bool
- notOrphan :: IsOrphan -> Bool
- data InstEnvs = InstEnvs {
  - ie_global :: InstEnv
  - ie_local :: InstEnv
  - ie_visible :: VisibleOrphanModules
  }
- type VisibleOrphanModules = ModuleSet
- type InstEnv = UniqFM ClsInstEnv
- emptyInstEnv :: InstEnv
- extendInstEnv :: InstEnv -> ClsInst -> InstEnv
- deleteFromInstEnv :: InstEnv -> ClsInst -> InstEnv
- identicalClsInstHead :: ClsInst -> ClsInst -> Bool
- extendInstEnvList :: InstEnv -> [ClsInst] -> InstEnv
- lookupUniqueInstEnv :: InstEnvs -> Class -> [Type] -> Either MsgDoc (ClsInst, [Type])
- lookupInstEnv' :: InstEnv -> VisibleOrphanModules -> Class -> [Type] -> ([InstMatch], [ClsInst])
- lookupInstEnv :: InstEnvs -> Class -> [Type] -> ClsInstLookupResult
- instEnvElts :: InstEnv -> [ClsInst]
- memberInstEnv :: InstEnv -> ClsInst -> Bool
- instIsVisible :: VisibleOrphanModules -> ClsInst -> Bool
- classInstances :: InstEnvs -> Class -> [ClsInst]
- orphNamesOfClsInst :: ClsInst -> NameSet
- instanceBindFun :: TyVar -> BindFlag
- instanceCantMatch :: [Maybe Name] -> [Maybe Name] -> Bool
- roughMatchTcs :: [Type] -> [Maybe Name]

# Documentation

type DFunId = Id

type InstMatch = (ClsInst, [DFunInstType])

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

data OverlapFlag

The semantics allowed for overlapping instances for a particular instance. See Note [Safe Haskell isSafeOverlap] (in `lhs`) 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 |
Data OverlapFlag |
Outputable OverlapFlag |
Binary 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 |
Data OverlapMode |
Outputable OverlapMode |
Binary OverlapMode |

setOverlapModeMaybe :: OverlapFlag -> Maybe OverlapMode -> OverlapFlag

data ClsInst

Constructors

ClsInst |
Fields is_cls_nm :: Name is_tcs :: [Maybe Name] is_tvs :: [TyVar] is_cls :: Class is_tys :: [Type] is_dfun :: DFunId is_flag :: OverlapFlag is_orphan :: IsOrphan

Instances

Data ClsInst |
Outputable ClsInst |
NamedThing ClsInst |

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 :: Name -> [Maybe Name] -> DFunId -> OverlapFlag -> IsOrphan -> 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.

data IsOrphan

Is this instance an orphan? If it is not an orphan, contains an `OccName` witnessing the instance's non-orphanhood. See Note [Orphans]

Constructors

IsOrphan |
NotOrphan OccName |

Instances

Data IsOrphan |
Binary IsOrphan |

isOrphan :: IsOrphan -> Bool

Returns true if `IsOrphan` is orphan.

notOrphan :: IsOrphan -> Bool

Returns true if `IsOrphan` is not an orphan.

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 = UniqFM 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' :: InstEnv -> VisibleOrphanModules -> Class -> [Type] -> ([InstMatch], [ClsInst])

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

See Note [Rules for instance lookup]

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]

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.

instanceBindFun :: TyVar -> BindFlag

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

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