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GHC 10.0.0.20260917 · lts/ghc-10.0.x · 77a8662 · 2026-10-31

Moduleth-utilities-0.2.5.2Haskell2010

TH.ReifySimple

Utilities for reifying simplified datatype info. It omits details that aren't usually relevant to generating instances that work with the datatype. This makes it easier to use TH to derive instances.

The "Simple" in the module name refers to the simplicity of the datatypes, not the module itself, which exports quite a few things which are useful in some circumstance or another. I anticipate that the most common uses of this will be the following APIs:

Getting info about a data or newtype declaration, via DataType, reifyDataType, and DataCon. This is useful for writing something which generates declarations based on a datatype, one of the most common uses of Template Haskell.
Getting nicely structured info about a named type. See TypeInfo and reifyType. This does not yet support reifying typeclasses, primitive type constructors, or type variables (TyVarI).

Currently, this module supports reifying simplified versions of the following Info constructors:

TyConI with DataD and NewtypeD (becomes a DataType value)
FamilyI becomes a DataFamily or TypeFamily value.
DataConI becomes a DataCon value.

In the future it will hopefully also have support for the remaining Info constructors, ClassI, ClassOpI, PrimTyConI, VarI, and TyVarI.

Contents

Reifying simplified type info
Reifying simplified info for specific declaration varieties
Datatype info
Data constructor info
Data family info
Type family info
Other utilities

Synopsis

data TypeInfo
value reifyType
value infoToType
value reifyTypeNoDataKinds
value infoToTypeNoDataKinds
data DataType
value reifyDataType
value infoToDataType
data DataCon
value reifyDataCon
value infoToDataCon
value typeToDataCon
data DataFamily
data DataInst
value reifyDataFamily
value infoToDataFamily
data TypeFamily
data TypeInst
value reifyTypeFamily
value infoToTypeFamily
value conToDataCons
value reifyDataTypeSubstituted

Packageth-utilities-0.2.5.2
Exports22
LanguageHaskell2010
LicenceMIT
SourceReifySimple.hs

Reifying simplified type info

datadata TypeInfo

valuereifyType :: Name -> Q TypeInfo

Reifies a Name as a TypeInfo, and calls fail if this doesn't work. Use reify with infoToType if you want to handle the failure case more gracefully.

This does not yet support reifying typeclasses, primitive type constructors, or type variables (TyVarI).

valueinfoToType :: Info -> Q (Maybe TypeInfo)

Convert an Info into a TypeInfo if possible, and otherwise yield Nothing. Needs to run in Q so that

valuereifyTypeNoDataKinds :: Name -> Q (Maybe TypeInfo)

Reifies type info, but instead of yielding a LiftedDataConInfo, will instead yield Nothing.

valueinfoToTypeNoDataKinds :: Info -> Maybe TypeInfo

Convert an 'Info into a TypeInfo if possible. If it's a data constructor, instead of yielding LiftedDataConInfo, it will instead yield Nothing.

Reifying simplified info for specific declaration varieties

Datatype info

datadata DataType

Simplified info about a DataD. Omits deriving, strictness, kind info, and whether it's data or newtype.

Constructors

DataType
- dtName :: Name
- dtTvs :: [Name]
- dtCxt :: Cxt
- dtCons :: [DataCon]

Instances6Eq, Data, Ord, Show, Generic, Rep

Eq DataTypeDefined in th-utilities-0.2.5.2 · TH.ReifySimple
Data DataTypeDefined in th-utilities-0.2.5.2 · TH.ReifySimple
Ord DataTypeDefined in th-utilities-0.2.5.2 · TH.ReifySimple
Show DataTypeDefined in th-utilities-0.2.5.2 · TH.ReifySimple
Generic DataTypeDefined in th-utilities-0.2.5.2 · TH.ReifySimple
type Rep DataType = D1 ('MetaData "DataType" "TH.ReifySimple" "th-utilities-0.2.5.2-1G9nzGJ73RB8mzIPvHxUHt" 'False) (C1 ('MetaCons "DataType" 'PrefixI 'True) ((S1 ('MetaSel ('Just "dtName") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 Name) :*: S1 ('MetaSel ('Just "dtTvs") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 [Name])) :*: (S1 ('MetaSel ('Just "dtCxt") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 Cxt) :*: S1 ('MetaSel ('Just "dtCons") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 [DataCon]))))Defined in th-utilities-0.2.5.2 · TH.ReifySimple

valuereifyDataType :: Name -> Q DataType

Reify the given data or newtype declaration, and yields its DataType representation.

valueinfoToDataType :: Info -> Maybe DataType

Data constructor info

datadata DataCon

Simplified info about a Con. Omits deriving, strictness, and kind info. This is much nicer than consuming Con directly, because it unifies all the constructors into one.

Constructors

DataCon
- dcName :: Name
- dcTvs :: [Name]
- dcCxt :: Cxt
- dcFields :: [(Maybe Name, Type)]

Instances6Eq, Data, Ord, Show, Generic, Rep

Eq DataConDefined in th-utilities-0.2.5.2 · TH.ReifySimple
Data DataConDefined in th-utilities-0.2.5.2 · TH.ReifySimple
Ord DataConDefined in th-utilities-0.2.5.2 · TH.ReifySimple
Show DataConDefined in th-utilities-0.2.5.2 · TH.ReifySimple
Generic DataConDefined in th-utilities-0.2.5.2 · TH.ReifySimple
type Rep DataCon = D1 ('MetaData "DataCon" "TH.ReifySimple" "th-utilities-0.2.5.2-1G9nzGJ73RB8mzIPvHxUHt" 'False) (C1 ('MetaCons "DataCon" 'PrefixI 'True) ((S1 ('MetaSel ('Just "dcName") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 Name) :*: S1 ('MetaSel ('Just "dcTvs") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 [Name])) :*: (S1 ('MetaSel ('Just "dcCxt") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 Cxt) :*: S1 ('MetaSel ('Just "dcFields") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 [(Maybe Name, Type)]))))Defined in th-utilities-0.2.5.2 · TH.ReifySimple

valuereifyDataCon :: Name -> Q DataCon

Reify the given data constructor.

valueinfoToDataCon :: Info -> Maybe DataCon

valuetypeToDataCon :: Name -> Type -> DataCon

Creates a DataCon given the Name and Type of a data-constructor. Note that the result the function type is *not* checked to match the provided Name.

Data family info

datadata DataFamily

Simplified info about a data family. Omits deriving, strictness, and kind info.

Constructors

DataFamily
- dfName :: Name
- dfTvs :: [Name]
- dfInsts :: [DataInst]

Instances6Eq, Data, Ord, Show, Generic, Rep

Eq DataFamilyDefined in th-utilities-0.2.5.2 · TH.ReifySimple
Data DataFamilyDefined in th-utilities-0.2.5.2 · TH.ReifySimple
Ord DataFamilyDefined in th-utilities-0.2.5.2 · TH.ReifySimple
Show DataFamilyDefined in th-utilities-0.2.5.2 · TH.ReifySimple
Generic DataFamilyDefined in th-utilities-0.2.5.2 · TH.ReifySimple
type Rep DataFamily = D1 ('MetaData "DataFamily" "TH.ReifySimple" "th-utilities-0.2.5.2-1G9nzGJ73RB8mzIPvHxUHt" 'False) (C1 ('MetaCons "DataFamily" 'PrefixI 'True) (S1 ('MetaSel ('Just "dfName") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 Name) :*: (S1 ('MetaSel ('Just "dfTvs") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 [Name]) :*: S1 ('MetaSel ('Just "dfInsts") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 [DataInst]))))Defined in th-utilities-0.2.5.2 · TH.ReifySimple

datadata DataInst

Simplified info about a data family instance. Omits deriving, strictness, and kind info.

Constructors

DataInst
- diName :: Name
- diCxt :: Cxt
- diParams :: [Type]
- diCons :: [DataCon]

Instances6Eq, Data, Ord, Show, Generic, Rep

Eq DataInstDefined in th-utilities-0.2.5.2 · TH.ReifySimple
Data DataInstDefined in th-utilities-0.2.5.2 · TH.ReifySimple
Ord DataInstDefined in th-utilities-0.2.5.2 · TH.ReifySimple
Show DataInstDefined in th-utilities-0.2.5.2 · TH.ReifySimple
Generic DataInstDefined in th-utilities-0.2.5.2 · TH.ReifySimple
type Rep DataInst = D1 ('MetaData "DataInst" "TH.ReifySimple" "th-utilities-0.2.5.2-1G9nzGJ73RB8mzIPvHxUHt" 'False) (C1 ('MetaCons "DataInst" 'PrefixI 'True) ((S1 ('MetaSel ('Just "diName") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 Name) :*: S1 ('MetaSel ('Just "diCxt") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 Cxt)) :*: (S1 ('MetaSel ('Just "diParams") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 [Type]) :*: S1 ('MetaSel ('Just "diCons") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 [DataCon]))))Defined in th-utilities-0.2.5.2 · TH.ReifySimple

valuereifyDataFamily :: Name -> Q DataFamily

Reify the given data family, and yield its DataFamily representation.

valueinfoToDataFamily :: Info -> Maybe DataFamily

Type family info

datadata TypeFamily

Simplified info about a type family. Omits kind info and injectivity info.

Constructors

TypeFamily
- tfName :: Name
- tfTvs :: [Name]
- tfInsts :: [TypeInst]

Instances6Eq, Data, Ord, Show, Generic, Rep

Eq TypeFamilyDefined in th-utilities-0.2.5.2 · TH.ReifySimple
Data TypeFamilyDefined in th-utilities-0.2.5.2 · TH.ReifySimple
Ord TypeFamilyDefined in th-utilities-0.2.5.2 · TH.ReifySimple
Show TypeFamilyDefined in th-utilities-0.2.5.2 · TH.ReifySimple
Generic TypeFamilyDefined in th-utilities-0.2.5.2 · TH.ReifySimple
type Rep TypeFamily = D1 ('MetaData "TypeFamily" "TH.ReifySimple" "th-utilities-0.2.5.2-1G9nzGJ73RB8mzIPvHxUHt" 'False) (C1 ('MetaCons "TypeFamily" 'PrefixI 'True) (S1 ('MetaSel ('Just "tfName") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 Name) :*: (S1 ('MetaSel ('Just "tfTvs") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 [Name]) :*: S1 ('MetaSel ('Just "tfInsts") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 [TypeInst]))))Defined in th-utilities-0.2.5.2 · TH.ReifySimple

datadata TypeInst

Simplified info about a type family instance. Omits nothing.

Constructors

TypeInst
- tiName :: Name
- tiParams :: [Type]
- tiType :: Type

Instances6Eq, Data, Ord, Show, Generic, Rep

Eq TypeInstDefined in th-utilities-0.2.5.2 · TH.ReifySimple
Data TypeInstDefined in th-utilities-0.2.5.2 · TH.ReifySimple
Ord TypeInstDefined in th-utilities-0.2.5.2 · TH.ReifySimple
Show TypeInstDefined in th-utilities-0.2.5.2 · TH.ReifySimple
Generic TypeInstDefined in th-utilities-0.2.5.2 · TH.ReifySimple
type Rep TypeInst = D1 ('MetaData "TypeInst" "TH.ReifySimple" "th-utilities-0.2.5.2-1G9nzGJ73RB8mzIPvHxUHt" 'False) (C1 ('MetaCons "TypeInst" 'PrefixI 'True) (S1 ('MetaSel ('Just "tiName") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 Name) :*: (S1 ('MetaSel ('Just "tiParams") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 [Type]) :*: S1 ('MetaSel ('Just "tiType") 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 Type))))Defined in th-utilities-0.2.5.2 · TH.ReifySimple

valuereifyTypeFamily :: Name -> Q TypeFamily

Reify the given type family instance declaration, and yields its TypeInst representation.

valueinfoToTypeFamily :: Info -> Maybe TypeFamily

Other utilities

valueconToDataCons :: Con -> [DataCon]

Convert a Con to a list of DataCon. The result is a list because GadtC and RecGadtC can define multiple constructors.

valuereifyDataTypeSubstituted :: Type -> Q DataType

Like reifyDataType, but takes a Type instead of just the Name of the datatype. It expects a normal datatype argument (see typeToNamedCon).