Language.Haskell.TH.Datatype

This module provides a flattened view of information about data types and newtypes that can be supported uniformly across multiple verisons of the template-haskell package.

Sample output for reifyDatatype ''Maybe

DatatypeInfo
 { datatypeContext = []
 , datatypeName = GHC.Base.Maybe
 , datatypeVars = [ VarT a_3530822107858468866 ]
 , datatypeVariant = Datatype
 , datatypeCons =
     [ ConstructorInfo
         { constructorName = GHC.Base.Nothing
         , constructorVars = []
         , constructorContext = []
         , constructorFields = []
         , constructorVariant = NormalConstructor
         }
     , ConstructorInfo
         { constructorName = GHC.Base.Just
         , constructorVars = []
         , constructorContext = []
         , constructorFields = [ VarT a_3530822107858468866 ]
         , constructorVariant = NormalConstructor
         }
     ]
 }

Datatypes declared with GADT syntax are normalized to constructors with existentially quantified type variables and equality constraints.

Types

data DatatypeInfo

Normalized information about newtypes and data types.

Constructors

DatatypeInfo

Fields

• datatypeContext :: Cxt

  Data type context (deprecated)

• datatypeName :: Name

  Type constructor

• datatypeVars :: [Type]

  Type parameters

• datatypeVariant :: DatatypeVariant

  Extra information

• datatypeCons :: [ConstructorInfo]

  Normalize constructor information

Instances

Eq DatatypeInfo

Methods

(==) :: DatatypeInfo -> DatatypeInfo -> Bool

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

Data DatatypeInfo

Methods

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

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

toConstr :: DatatypeInfo -> Constr

dataTypeOf :: DatatypeInfo -> DataType

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

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

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

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

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

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

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

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

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

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

Show DatatypeInfo

Methods

showsPrec :: Int -> DatatypeInfo -> ShowS

show :: DatatypeInfo -> String

showList :: [DatatypeInfo] -> ShowS

Generic DatatypeInfo

Associated Types

type Rep DatatypeInfo :: * -> *

Methods

from :: DatatypeInfo -> Rep DatatypeInfo x

to :: Rep DatatypeInfo x -> DatatypeInfo

type Rep DatatypeInfo

type Rep DatatypeInfo = D1 (MetaData "DatatypeInfo" "Language.Haskell.TH.Datatype" "th-abstraction-0.1.0.0-2XiZxdVTYK6B4lHXVGoWsL" False) (C1 (MetaCons "DatatypeInfo" PrefixI True) ((:*:) ((:*:) (S1 (MetaSel (Just Symbol "datatypeContext") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 Cxt)) (S1 (MetaSel (Just Symbol "datatypeName") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 Name))) ((:*:) (S1 (MetaSel (Just Symbol "datatypeVars") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 [Type])) ((:*:) (S1 (MetaSel (Just Symbol "datatypeVariant") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 DatatypeVariant)) (S1 (MetaSel (Just Symbol "datatypeCons") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 [ConstructorInfo]))))))

data ConstructorInfo

Normalized information about constructors associated with newtypes and data types.

Constructors

ConstructorInfo

Fields

• constructorName :: Name

  Constructor name

• constructorVars :: [TyVarBndr]

  Constructor type parameters

• constructorContext :: Cxt

  Constructor constraints

• constructorFields :: [Type]

  Constructor fields

• constructorVariant :: ConstructorVariant

  Extra information

Instances

Eq ConstructorInfo

Methods

(==) :: ConstructorInfo -> ConstructorInfo -> Bool

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

Data ConstructorInfo

Methods

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

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

toConstr :: ConstructorInfo -> Constr

dataTypeOf :: ConstructorInfo -> DataType

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

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

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

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

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

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

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

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

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

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

Show ConstructorInfo

Methods

showsPrec :: Int -> ConstructorInfo -> ShowS

show :: ConstructorInfo -> String

showList :: [ConstructorInfo] -> ShowS

Generic ConstructorInfo

Associated Types

type Rep ConstructorInfo :: * -> *

Methods

from :: ConstructorInfo -> Rep ConstructorInfo x

to :: Rep ConstructorInfo x -> ConstructorInfo

TypeSubstitution ConstructorInfo

Methods

applySubstitution :: Map Name Type -> ConstructorInfo -> ConstructorInfo

freeVariables :: ConstructorInfo -> [Name]

type Rep ConstructorInfo

type Rep ConstructorInfo = D1 (MetaData "ConstructorInfo" "Language.Haskell.TH.Datatype" "th-abstraction-0.1.0.0-2XiZxdVTYK6B4lHXVGoWsL" False) (C1 (MetaCons "ConstructorInfo" PrefixI True) ((:*:) ((:*:) (S1 (MetaSel (Just Symbol "constructorName") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 Name)) (S1 (MetaSel (Just Symbol "constructorVars") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 [TyVarBndr]))) ((:*:) (S1 (MetaSel (Just Symbol "constructorContext") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 Cxt)) ((:*:) (S1 (MetaSel (Just Symbol "constructorFields") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 [Type])) (S1 (MetaSel (Just Symbol "constructorVariant") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 ConstructorVariant))))))

data DatatypeVariant

Possible variants of data type declarations.

Constructors

Datatype

Type declared with data

Newtype

Type declared with newtype

DataInstance

Type declared with data instance

NewtypeInstance

Type declared with newtype instance

Instances

Eq DatatypeVariant

Methods

(==) :: DatatypeVariant -> DatatypeVariant -> Bool

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

Data DatatypeVariant

Methods

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

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

toConstr :: DatatypeVariant -> Constr

dataTypeOf :: DatatypeVariant -> DataType

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

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

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

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

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

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

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

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

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

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

Ord DatatypeVariant

Methods

compare :: DatatypeVariant -> DatatypeVariant -> Ordering

(<) :: DatatypeVariant -> DatatypeVariant -> Bool

(<=) :: DatatypeVariant -> DatatypeVariant -> Bool

(>) :: DatatypeVariant -> DatatypeVariant -> Bool

(>=) :: DatatypeVariant -> DatatypeVariant -> Bool

max :: DatatypeVariant -> DatatypeVariant -> DatatypeVariant

min :: DatatypeVariant -> DatatypeVariant -> DatatypeVariant

Read DatatypeVariant

Methods

readsPrec :: Int -> ReadS DatatypeVariant

readList :: ReadS [DatatypeVariant]

readPrec :: ReadPrec DatatypeVariant

readListPrec :: ReadPrec [DatatypeVariant]

Show DatatypeVariant

Methods

showsPrec :: Int -> DatatypeVariant -> ShowS

show :: DatatypeVariant -> String

showList :: [DatatypeVariant] -> ShowS

Generic DatatypeVariant

Associated Types

type Rep DatatypeVariant :: * -> *

Methods

from :: DatatypeVariant -> Rep DatatypeVariant x

to :: Rep DatatypeVariant x -> DatatypeVariant

type Rep DatatypeVariant

type Rep DatatypeVariant = D1 (MetaData "DatatypeVariant" "Language.Haskell.TH.Datatype" "th-abstraction-0.1.0.0-2XiZxdVTYK6B4lHXVGoWsL" False) ((:+:) ((:+:) (C1 (MetaCons "Datatype" PrefixI False) U1) (C1 (MetaCons "Newtype" PrefixI False) U1)) ((:+:) (C1 (MetaCons "DataInstance" PrefixI False) U1) (C1 (MetaCons "NewtypeInstance" PrefixI False) U1)))

data ConstructorVariant

Possible variants of data constructors.

Constructors

NormalConstructor

Constructor without field names

RecordConstructor [Name]

Constructor with field names

Instances

Eq ConstructorVariant

Methods

(==) :: ConstructorVariant -> ConstructorVariant -> Bool

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

Data ConstructorVariant

Methods

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

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

toConstr :: ConstructorVariant -> Constr

dataTypeOf :: ConstructorVariant -> DataType

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

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

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

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

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

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

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

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

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

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

Ord ConstructorVariant

Methods

compare :: ConstructorVariant -> ConstructorVariant -> Ordering

(<) :: ConstructorVariant -> ConstructorVariant -> Bool

(<=) :: ConstructorVariant -> ConstructorVariant -> Bool

(>) :: ConstructorVariant -> ConstructorVariant -> Bool

(>=) :: ConstructorVariant -> ConstructorVariant -> Bool

max :: ConstructorVariant -> ConstructorVariant -> ConstructorVariant

min :: ConstructorVariant -> ConstructorVariant -> ConstructorVariant

Show ConstructorVariant

Methods

showsPrec :: Int -> ConstructorVariant -> ShowS

show :: ConstructorVariant -> String

showList :: [ConstructorVariant] -> ShowS

Generic ConstructorVariant

Associated Types

type Rep ConstructorVariant :: * -> *

Methods

from :: ConstructorVariant -> Rep ConstructorVariant x

to :: Rep ConstructorVariant x -> ConstructorVariant

type Rep ConstructorVariant

type Rep ConstructorVariant = D1 (MetaData "ConstructorVariant" "Language.Haskell.TH.Datatype" "th-abstraction-0.1.0.0-2XiZxdVTYK6B4lHXVGoWsL" False) ((:+:) (C1 (MetaCons "NormalConstructor" PrefixI False) U1) (C1 (MetaCons "RecordConstructor" PrefixI False) (S1 (MetaSel (Nothing Symbol) NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 [Name]))))

Normalization functions

reifyDatatype

Arguments

:: Name

type constructor

-> Q DatatypeInfo

Compute a normalized view of the metadata about a data type or newtype given a type constructor.

normalizeInfo :: Info -> Q DatatypeInfo

Normalize Info for a newtype or datatype into a DatatypeInfo. Fail in Q otherwise.

normalizeDec :: Dec -> Q DatatypeInfo

Normalize Dec for a newtype or datatype into a DatatypeInfo. Fail in Q otherwise.

normalizeCon

Arguments

:: Name

Type constructor

-> [Name]

Type parameters

-> Con

Constructor

-> Q [ConstructorInfo]

Normalize a Con into a ConstructorInfo. This requires knowledge of the type and parameters of the constructor as extracted from the outer Dec.

Type variable manipulation

class TypeSubstitution a where

Class for types that support type variable substitution.

Minimal complete definition

applySubstitution, freeVariables

Methods

applySubstitution :: Map Name Type -> a -> a

Apply a type variable substitution

freeVariables :: a -> [Name]

Compute the free type variables

Instances

TypeSubstitution Type

Methods

applySubstitution :: Map Name Type -> Type -> Type

freeVariables :: Type -> [Name]

TypeSubstitution ConstructorInfo

Methods

applySubstitution :: Map Name Type -> ConstructorInfo -> ConstructorInfo

freeVariables :: ConstructorInfo -> [Name]

TypeSubstitution a => TypeSubstitution [a]

Methods

applySubstitution :: Map Name Type -> [a] -> [a]

freeVariables :: [a] -> [Name]

quantifyType :: Type -> Type

Add universal quantifier for all free variables in the type. This is useful when constructing a type signature for a declaration. This code is careful to ensure that the order of the variables quantified is determined by their order of appearance in the type singnature. (In contrast with being dependent upon the Ord instance for Name)

freshenFreeVariables :: Type -> Q Type

Substitute all of the free variables in a type with fresh ones

Pred functions

equalPred :: Type -> Type -> Pred

Construct an equality constraint. The implementation of Pred varies across versions of Template Haskell.

classPred

Arguments

:: Name

class

-> [Type]

parameters

-> Pred

Construct a typeclass constraint. The implementation of Pred varies across versions of Template Haskell.

Convenience functions

resolveTypeSynonyms :: Type -> Q Type

Expand all of the type synonyms in a type.

unifyTypes :: [Type] -> Q (Map Name Type)

Compute the type variable substitution that unifies a list of types, or fail in Q.

tvName :: TyVarBndr -> Name

Extract the type variable name from a TyVarBndr ignoring the kind signature if one exists.

datatypeType :: DatatypeInfo -> Type

Construct a Type using the datatype's type constructor and type parameteters.