{-# Language CPP, DeriveDataTypeable, ScopedTypeVariables, TupleSections #-} #if MIN_VERSION_base(4,4,0) #define HAS_GENERICS {-# Language DeriveGeneric #-} #endif #if MIN_VERSION_template_haskell(2,12,0) {-# Language Safe #-} #elif __GLASGOW_HASKELL__ >= 702 {-# Language Trustworthy #-} #endif {-| Module : Language.Haskell.TH.Datatype Description : Backwards-compatible interface to reified information about datatypes. Copyright : Eric Mertens 2017-2020 License : ISC Maintainer : emertens@gmail.com This module provides a flattened view of information about data types and newtypes that can be supported uniformly across multiple versions of the @template-haskell@ package. Sample output for @'reifyDatatype' ''Maybe@ @ 'DatatypeInfo' { 'datatypeContext' = [] , 'datatypeName' = GHC.Base.Maybe , 'datatypeVars' = [ 'KindedTV' a_3530822107858468866 () 'StarT' ] , 'datatypeInstTypes' = [ 'SigT' ('VarT' a_3530822107858468866) 'StarT' ] , 'datatypeVariant' = 'Datatype' , 'datatypeReturnKind' = 'StarT' , 'datatypeCons' = [ 'ConstructorInfo' { 'constructorName' = GHC.Base.Nothing , 'constructorVars' = [] , 'constructorContext' = [] , 'constructorFields' = [] , 'constructorStrictness' = [] , 'constructorVariant' = 'NormalConstructor' } , 'ConstructorInfo' { 'constructorName' = GHC.Base.Just , 'constructorVars' = [] , 'constructorContext' = [] , 'constructorFields' = [ 'VarT' a_3530822107858468866 ] , 'constructorStrictness' = [ 'FieldStrictness' 'UnspecifiedUnpackedness' 'Lazy' ] , 'constructorVariant' = 'NormalConstructor' } ] } @ Datatypes declared with GADT syntax are normalized to constructors with existentially quantified type variables and equality constraints. -} module Language.Haskell.TH.Datatype ( -- * Types DatatypeInfo(..) , ConstructorInfo(..) , DatatypeVariant(..) , ConstructorVariant(..) , FieldStrictness(..) , Unpackedness(..) , Strictness(..) -- * Normalization functions , reifyDatatype , reifyConstructor , reifyRecord , normalizeInfo , normalizeDec , normalizeCon -- * 'DatatypeInfo' lookup functions , lookupByConstructorName , lookupByRecordName -- * Type variable manipulation , TypeSubstitution(..) , quantifyType , freeVariablesWellScoped , freshenFreeVariables -- * 'Pred' functions , equalPred , classPred , asEqualPred , asClassPred -- * Backward compatible data definitions , dataDCompat , newtypeDCompat , tySynInstDCompat , pragLineDCompat , arrowKCompat -- * Strictness annotations , isStrictAnnot , notStrictAnnot , unpackedAnnot -- * Type simplification , resolveTypeSynonyms , resolveKindSynonyms , resolvePredSynonyms , resolveInfixT -- * Fixities , reifyFixityCompat , showFixity , showFixityDirection -- * Convenience functions , unifyTypes , tvName , tvKind , datatypeType ) where import Data.Data (Typeable, Data) import Data.Foldable (foldMap, foldl') import Data.List (mapAccumL, nub, find, union, (\\)) import Data.Map (Map) import qualified Data.Map as Map import Data.Maybe import qualified Data.Set as Set import Data.Set (Set) import qualified Data.Traversable as T import Control.Monad import Language.Haskell.TH #if MIN_VERSION_template_haskell(2,11,0) hiding (Extension(..)) #endif import Language.Haskell.TH.Datatype.Internal import Language.Haskell.TH.Datatype.TyVarBndr import Language.Haskell.TH.Lib (arrowK, starK) -- needed for th-2.4 #ifdef HAS_GENERICS import GHC.Generics (Generic) #endif #if !MIN_VERSION_base(4,8,0) import Control.Applicative (Applicative(..), (<$>)) import Data.Monoid (Monoid(..)) #endif -- | Normalized information about newtypes and data types. -- -- 'DatatypeInfo' contains two fields, 'datatypeVars' and 'datatypeInstTypes', -- which encode information about the argument types. The simplest explanation -- is that 'datatypeVars' contains all the type /variables/ bound by the data -- type constructor, while 'datatypeInstTypes' contains the type /arguments/ -- to the data type constructor. To be more precise: -- -- * For ADTs declared with @data@ and @newtype@, it will likely be the case -- that 'datatypeVars' and 'datatypeInstTypes' coincide. For instance, given -- @newtype Id a = MkId a@, in the 'DatatypeInfo' for @Id@ we would -- have @'datatypeVars' = ['KindedTV' a () 'StarT']@ and -- @'datatypeInstVars' = ['SigT' ('VarT' a) 'StarT']@. -- -- ADTs that leverage @PolyKinds@ may have more 'datatypeVars' than -- 'datatypeInstTypes'. For instance, given @data Proxy (a :: k) = MkProxy@, -- in the 'DatatypeInfo' for @Proxy@ we would have -- @'datatypeVars' = ['KindedTV' k () 'StarT', 'KindedTV' a () ('VarT' k)]@ -- (since there are two variables, @k@ and @a@), whereas -- @'datatypeInstTypes' = ['SigT' ('VarT' a) ('VarT' k)]@, since there is -- only one explicit type argument to @Proxy@. -- -- The same outcome would occur if @Proxy@ were declared using -- @TypeAbstractions@, i.e., if it were declared as -- @data Proxy \@k (a :: k) = MkProxy@. The 'datatypeInstTypes' would /not/ -- include a separate type for @\@k@. -- -- * For @data instance@s and @newtype instance@s of data families, -- 'datatypeVars' and 'datatypeInstTypes' can be quite different. Here is -- an example to illustrate the difference: -- -- @ -- data family F a b -- data instance F (Maybe c) (f x) = MkF c (f x) -- @ -- -- Then in the 'DatatypeInfo' for @F@'s data instance, we would have: -- -- @ -- 'datatypeVars' = [ 'KindedTV' c () 'StarT' -- , 'KindedTV' f () 'StarT' -- , 'KindedTV' x () 'StarT' ] -- 'datatypeInstTypes' = [ 'AppT' ('ConT' ''Maybe) ('VarT' c) -- , 'AppT' ('VarT' f) ('VarT' x) ] -- @ data DatatypeInfo = DatatypeInfo { datatypeContext :: Cxt -- ^ Data type context (deprecated) , datatypeName :: Name -- ^ Type constructor , datatypeVars :: [TyVarBndrUnit] -- ^ Type parameters , datatypeInstTypes :: [Type] -- ^ Argument types , datatypeVariant :: DatatypeVariant -- ^ Extra information , datatypeReturnKind:: Kind -- ^ Return 'Kind' of the type. -- -- If normalization is unable to determine the return kind, -- then this is conservatively set to @StarT@. , datatypeCons :: [ConstructorInfo] -- ^ Normalize constructor information } deriving (Show, Eq, Typeable, Data #ifdef HAS_GENERICS ,Generic #endif ) -- | Possible variants of data type declarations. data DatatypeVariant = Datatype -- ^ Type declared with @data@ or a primitive datatype. | Newtype -- ^ Type declared with @newtype@. -- -- A 'DatatypeInfo' that uses 'Newtype' will uphold the -- invariant that there will be exactly one -- 'ConstructorInfo' in the 'datatypeCons'. | DataInstance -- ^ Type declared with @data instance@. | NewtypeInstance -- ^ Type declared with @newtype instance@. -- -- A 'DatatypeInfo' that uses 'NewtypeInstance' will -- uphold the invariant that there will be exactly one -- 'ConstructorInfo' in the 'datatypeCons'. | TypeData -- ^ Type declared with @type data@. -- -- A 'DatatypeInfo' that uses 'TypeData' will uphold the -- following invariants: -- -- * The 'datatypeContext' will be empty. -- -- * None of the 'constructorVariant's in any of the -- 'datatypeCons' will be 'RecordConstructor'. -- -- * Each of the 'constructorStrictness' values in each -- of the 'datatypeCons' will be equal to -- 'notStrictAnnot'. deriving (Show, Read, Eq, Ord, Typeable, Data #ifdef HAS_GENERICS ,Generic #endif ) -- | Normalized information about constructors associated with newtypes and -- data types. data ConstructorInfo = ConstructorInfo { constructorName :: Name -- ^ Constructor name , constructorVars :: [TyVarBndrUnit] -- ^ Constructor type parameters , constructorContext :: Cxt -- ^ Constructor constraints , constructorFields :: [Type] -- ^ Constructor fields , constructorStrictness :: [FieldStrictness] -- ^ Constructor fields' strictness -- (Invariant: has the same length -- as constructorFields) , constructorVariant :: ConstructorVariant -- ^ Extra information } deriving (Show, Eq, Typeable, Data #ifdef HAS_GENERICS ,Generic #endif ) -- | Possible variants of data constructors. data ConstructorVariant = NormalConstructor -- ^ Constructor without field names | InfixConstructor -- ^ Constructor without field names that is -- declared infix | RecordConstructor [Name] -- ^ Constructor with field names deriving (Show, Eq, Ord, Typeable, Data #ifdef HAS_GENERICS ,Generic #endif ) -- | Normalized information about a constructor field's @UNPACK@ and -- strictness annotations. -- -- Note that the interface for reifying strictness in Template Haskell changed -- considerably in GHC 8.0. The presentation in this library mirrors that which -- can be found in GHC 8.0 or later, whereas previously, unpackedness and -- strictness were represented with a single data type: -- -- @ -- data Strict -- = IsStrict -- | NotStrict -- | Unpacked -- On GHC 7.4 or later -- @ -- -- For backwards compatibility, we retrofit these constructors onto the -- following three values, respectively: -- -- @ -- 'isStrictAnnot' = 'FieldStrictness' 'UnspecifiedUnpackedness' 'Strict' -- 'notStrictAnnot' = 'FieldStrictness' 'UnspecifiedUnpackedness' 'UnspecifiedStrictness' -- 'unpackedAnnot' = 'FieldStrictness' 'Unpack' 'Strict' -- @ data FieldStrictness = FieldStrictness { fieldUnpackedness :: Unpackedness , fieldStrictness :: Strictness } deriving (Show, Eq, Ord, Typeable, Data #ifdef HAS_GENERICS ,Generic #endif ) -- | Information about a constructor field's unpackedness annotation. data Unpackedness = UnspecifiedUnpackedness -- ^ No annotation whatsoever | NoUnpack -- ^ Annotated with @{\-\# NOUNPACK \#-\}@ | Unpack -- ^ Annotated with @{\-\# UNPACK \#-\}@ deriving (Show, Eq, Ord, Typeable, Data #ifdef HAS_GENERICS ,Generic #endif ) -- | Information about a constructor field's strictness annotation. data Strictness = UnspecifiedStrictness -- ^ No annotation whatsoever | Lazy -- ^ Annotated with @~@ | Strict -- ^ Annotated with @!@ deriving (Show, Eq, Ord, Typeable, Data #ifdef HAS_GENERICS ,Generic #endif ) isStrictAnnot, notStrictAnnot, unpackedAnnot :: FieldStrictness isStrictAnnot = FieldStrictness UnspecifiedUnpackedness Strict notStrictAnnot = FieldStrictness UnspecifiedUnpackedness UnspecifiedStrictness unpackedAnnot = FieldStrictness Unpack Strict -- | Construct a Type using the datatype's type constructor and type -- parameters. Kind signatures are removed. datatypeType :: DatatypeInfo -> Type datatypeType di = foldl AppT (ConT (datatypeName di)) $ map stripSigT $ datatypeInstTypes di -- | Compute a normalized view of the metadata about a data type or newtype -- given a constructor. -- -- This function will accept any constructor (value or type) for a type -- declared with newtype or data. Value constructors must be used to -- lookup datatype information about /data instances/ and /newtype instances/, -- as giving the type constructor of a data family is often not enough to -- determine a particular data family instance. -- -- In addition, this function will also accept a record selector for a -- data type with a constructor which uses that record. -- -- GADT constructors are normalized into datatypes with explicit equality -- constraints. Note that no effort is made to distinguish between equalities of -- the same (homogeneous) kind and equalities between different (heterogeneous) -- kinds. For instance, the following GADT's constructors: -- -- @ -- data T (a :: k -> *) where -- MkT1 :: T Proxy -- MkT2 :: T Maybe -- @ -- -- will be normalized to the following equality constraints: -- -- @ -- AppT (AppT EqualityT (VarT a)) (ConT Proxy) -- MkT1 -- AppT (AppT EqualityT (VarT a)) (ConT Maybe) -- MkT2 -- @ -- -- But only the first equality constraint is well kinded, since in the second -- constraint, the kinds of @(a :: k -> *)@ and @(Maybe :: * -> *)@ are different. -- Trying to categorize which constraints need homogeneous or heterogeneous -- equality is tricky, so we leave that task to users of this library. -- -- Primitive types (other than unboxed sums and tuples) will have -- no @datatypeCons@ in their normalization. -- -- This function will apply various bug-fixes to the output of the underlying -- @template-haskell@ library in order to provide a view of datatypes in -- as uniform a way as possible. reifyDatatype :: Name {- ^ data type or constructor name -} -> Q DatatypeInfo reifyDatatype n = normalizeInfo' "reifyDatatype" isReified =<< reify n -- | Compute a normalized view of the metadata about a constructor given its -- 'Name'. This is useful for scenarios when you don't care about the info for -- the enclosing data type. reifyConstructor :: Name {- ^ constructor name -} -> Q ConstructorInfo reifyConstructor conName = do dataInfo <- reifyDatatype conName return $ lookupByConstructorName conName dataInfo -- | Compute a normalized view of the metadata about a constructor given the -- 'Name' of one of its record selectors. This is useful for scenarios when you -- don't care about the info for the enclosing data type. reifyRecord :: Name {- ^ record name -} -> Q ConstructorInfo reifyRecord recordName = do dataInfo <- reifyDatatype recordName return $ lookupByRecordName recordName dataInfo -- | Given a 'DatatypeInfo', find the 'ConstructorInfo' corresponding to the -- 'Name' of one of its constructors. lookupByConstructorName :: Name {- ^ constructor name -} -> DatatypeInfo {- ^ info for the datatype which has that constructor -} -> ConstructorInfo lookupByConstructorName conName dataInfo = case find ((== conName) . constructorName) (datatypeCons dataInfo) of Just conInfo -> conInfo Nothing -> error $ "Datatype " ++ nameBase (datatypeName dataInfo) ++ " does not have a constructor named " ++ nameBase conName -- | Given a 'DatatypeInfo', find the 'ConstructorInfo' corresponding to the -- 'Name' of one of its constructors. lookupByRecordName :: Name {- ^ record name -} -> DatatypeInfo {- ^ info for the datatype which has that constructor -} -> ConstructorInfo lookupByRecordName recordName dataInfo = case find (conHasRecord recordName) (datatypeCons dataInfo) of Just conInfo -> conInfo Nothing -> error $ "Datatype " ++ nameBase (datatypeName dataInfo) ++ " does not have any constructors with a " ++ "record selector named " ++ nameBase recordName -- | Normalize 'Info' for a newtype or datatype into a 'DatatypeInfo'. -- Fail in 'Q' otherwise. normalizeInfo :: Info -> Q DatatypeInfo normalizeInfo = normalizeInfo' "normalizeInfo" isn'tReified normalizeInfo' :: String -> IsReifiedDec -> Info -> Q DatatypeInfo normalizeInfo' entry reifiedDec i = case i of (PrimTyConI name arity unlifted) -> do #if MIN_VERSION_template_haskell(2,16,0) -- We provide a minimal @DataD@ because, since TH 2.16, -- we can rely on the call to @reifyType@ in -- @normalizeDecFor@ to fill in the missing details. normalizeDecFor reifiedDec $ DataD [] name [] Nothing [] [] #else -- On older versions, we are very limited in what we can deduce. -- All we know is the appropriate amount of type constructors. -- Note that this will default all kinds to @Type@, which is all -- that is available anyway. args <- replicateM arity (newName "x") dec <- dataDCompat (return []) name (map plainTV args) [] [] normalizeDecFor reifiedDec dec #endif ClassI{} -> bad "Class not supported" #if MIN_VERSION_template_haskell(2,11,0) FamilyI DataFamilyD{} _ -> #elif MIN_VERSION_template_haskell(2,7,0) FamilyI (FamilyD DataFam _ _ _) _ -> #else TyConI (FamilyD DataFam _ _ _) -> #endif bad "Use a value constructor to reify a data family instance" #if MIN_VERSION_template_haskell(2,7,0) FamilyI _ _ -> bad "Type families not supported" #endif TyConI dec -> normalizeDecFor reifiedDec dec #if MIN_VERSION_template_haskell(2,11,0) DataConI name _ parent -> reifyParent name parent -- NB: We do not pass the IsReifiedDec information here -- because there's no point. We have no choice but to -- call reify here, since we need to determine the -- parent data type/family. #else DataConI name _ parent _ -> reifyParent name parent #endif #if MIN_VERSION_template_haskell(2,11,0) VarI recName recTy _ -> reifyRecordType recName recTy -- NB: Similarly, we do not pass the IsReifiedDec -- information here. #else VarI recName recTy _ _ -> reifyRecordType recName recTy #endif _ -> bad "Expected a type constructor" where bad msg = fail (entry ++ ": " ++ msg) reifyParent :: Name -> Name -> Q DatatypeInfo reifyParent con = reifyParentWith "reifyParent" p where p :: DatatypeInfo -> Bool p info = con `elem` map constructorName (datatypeCons info) reifyRecordType :: Name -> Type -> Q DatatypeInfo reifyRecordType recName recTy = let (_, _, argTys :|- _) = uncurryType recTy in case argTys of dataTy:_ -> decomposeDataType dataTy _ -> notRecSelFailure where decomposeDataType :: Type -> Q DatatypeInfo decomposeDataType ty = do case decomposeType ty of ConT parent :| _ -> reifyParentWith "reifyRecordType" p parent _ -> notRecSelFailure notRecSelFailure :: Q a notRecSelFailure = fail $ "reifyRecordType: Not a record selector type: " ++ nameBase recName ++ " :: " ++ show recTy p :: DatatypeInfo -> Bool p info = any (conHasRecord recName) (datatypeCons info) reifyParentWith :: String {- ^ prefix for error messages -} -> (DatatypeInfo -> Bool) {- ^ predicate for finding the right data family instance -} -> Name {- ^ parent data type name -} -> Q DatatypeInfo reifyParentWith prefix p n = do info <- reify n case info of #if !(MIN_VERSION_template_haskell(2,11,0)) -- This unusual combination of Info and Dec is only possible to reify on -- GHC 7.0 and 7.2, when you try to reify a data family. Because there's -- no way to reify the data family *instances* on these versions of GHC, -- we have no choice but to fail. TyConI FamilyD{} -> dataFamiliesOnOldGHCsError #endif TyConI dec -> normalizeDecFor isReified dec #if MIN_VERSION_template_haskell(2,7,0) FamilyI dec instances -> do instances1 <- mapM (repairDataFam dec) instances instances2 <- mapM (normalizeDecFor isReified) instances1 case find p instances2 of Just inst -> return inst Nothing -> panic "lost the instance" #endif _ -> panic "unexpected parent" where dataFamiliesOnOldGHCsError :: Q a dataFamiliesOnOldGHCsError = fail $ prefix ++ ": Data family instances can only be reified with GHC 7.4 or later" panic :: String -> Q a panic message = fail $ "PANIC: " ++ prefix ++ " " ++ message #if MIN_VERSION_template_haskell(2,8,0) && (!MIN_VERSION_template_haskell(2,10,0)) -- A GHC 7.6-specific bug requires us to replace all occurrences of -- (ConT GHC.Prim.*) with StarT, or else Template Haskell will reject it. -- Luckily, (ConT GHC.Prim.*) only seems to occur in this one spot. sanitizeStars :: Kind -> Kind sanitizeStars = go where go :: Kind -> Kind go (AppT t1 t2) = AppT (go t1) (go t2) go (SigT t k) = SigT (go t) (go k) go (ConT n) | n == starKindName = StarT go t = t -- A version of repairVarKindsWith that does much more extra work to -- (1) eta-expand missing type patterns, and (2) ensure that the kind -- signatures for these new type patterns match accordingly. repairVarKindsWith' :: [TyVarBndrUnit] -> Maybe Kind -> [Type] -> Q [Type] repairVarKindsWith' dvars dkind ts = let kindVars = freeVariables . map kindPart kindPart (KindedTV _ k) = [k] kindPart (PlainTV _ ) = [] nparams = length dvars kparams = kindVars dvars (tsKinds,tsNoKinds) = splitAt (length kparams) ts tsKinds' = map sanitizeStars tsKinds extraTys = drop (length tsNoKinds) (bndrParams dvars) ts' = tsNoKinds ++ extraTys -- eta-expand in fmap (applySubstitution (Map.fromList (zip kparams tsKinds'))) $ repairVarKindsWith dvars dkind ts' -- Sadly, Template Haskell's treatment of data family instances leaves much -- to be desired. Here are some problems that we have to work around: -- -- 1. On all versions of GHC, TH leaves off the kind signatures on the -- type patterns of data family instances where a kind signature isn't -- specified explicitly. Here, we can use the parent data family's -- type variable binders to reconstruct the kind signatures if they -- are missing. -- 2. On GHC 7.6 and 7.8, TH will eta-reduce data instances. We can find -- the missing type variables on the data constructor. -- -- We opt to avoid propagating these new type variables through to the -- constructor now, but we will return to this task in normalizeCon. repairDataFam :: Dec {- ^ family declaration -} -> Dec {- ^ instance declaration -} -> Q Dec {- ^ instance declaration -} repairDataFam (FamilyD _ _ dvars dk) (NewtypeInstD cx n ts con deriv) = do ts' <- repairVarKindsWith' dvars dk ts return $ NewtypeInstD cx n ts' con deriv repairDataFam (FamilyD _ _ dvars dk) (DataInstD cx n ts cons deriv) = do ts' <- repairVarKindsWith' dvars dk ts return $ DataInstD cx n ts' cons deriv #else repairDataFam famD instD # if MIN_VERSION_template_haskell(2,15,0) | DataFamilyD _ dvars dk <- famD , NewtypeInstD cx mbInstVars nts k c deriv <- instD , con :| ts <- decomposeType nts = do ts' <- repairVarKindsWith dvars dk ts return $ NewtypeInstD cx mbInstVars (foldl' AppT con ts') k c deriv | DataFamilyD _ dvars dk <- famD , DataInstD cx mbInstVars nts k c deriv <- instD , con :| ts <- decomposeType nts = do ts' <- repairVarKindsWith dvars dk ts return $ DataInstD cx mbInstVars (foldl' AppT con ts') k c deriv # elif MIN_VERSION_template_haskell(2,11,0) | DataFamilyD _ dvars dk <- famD , NewtypeInstD cx n ts k c deriv <- instD = do ts' <- repairVarKindsWith dvars dk ts return $ NewtypeInstD cx n ts' k c deriv | DataFamilyD _ dvars dk <- famD , DataInstD cx n ts k c deriv <- instD = do ts' <- repairVarKindsWith dvars dk ts return $ DataInstD cx n ts' k c deriv # else | FamilyD _ _ dvars dk <- famD , NewtypeInstD cx n ts c deriv <- instD = do ts' <- repairVarKindsWith dvars dk ts return $ NewtypeInstD cx n ts' c deriv | FamilyD _ _ dvars dk <- famD , DataInstD cx n ts c deriv <- instD = do ts' <- repairVarKindsWith dvars dk ts return $ DataInstD cx n ts' c deriv # endif #endif repairDataFam _ instD = return instD -- | @'repairVarKindsWith' tvbs mbKind ts@ returns @ts@, but where each element -- has an explicit kind signature taken from a 'TyVarBndr' in the corresponding -- position in @tvbs@, or from the corresponding kind argument in 'mbKind' if -- there aren't enough 'TyVarBndr's available. An example where @tvbs@ can be -- shorter than @ts@ can be found in this example from #95: -- -- @ -- data family F :: Type -> Type -- data instance F a = C -- @ -- -- The @F@ has no type variable binders in its @data family@ declaration, and -- it has a return kind of @Type -> Type@. As a result, we pair up @Type@ with -- @VarT a@ to get @SigT a (ConT ''Type)@. repairVarKindsWith :: [TyVarBndrVis] -> Maybe Kind -> [Type] -> Q [Type] repairVarKindsWith tvbs mbKind ts = do extra_tvbs <- mkExtraKindBinders $ fromMaybe starK mbKind -- This list should be the same length as @ts@. If it isn't, something has -- gone terribly wrong. let tvbs' = changeTVFlags () tvbs ++ extra_tvbs return $ zipWith stealKindForType tvbs' ts -- If a VarT is missing an explicit kind signature, steal it from a TyVarBndr. stealKindForType :: TyVarBndr_ flag -> Type -> Type stealKindForType tvb t@VarT{} = SigT t (tvKind tvb) stealKindForType _ t = t -- | Normalize 'Dec' for a newtype or datatype into a 'DatatypeInfo'. -- Fail in 'Q' otherwise. -- -- Beware: 'normalizeDec' can have surprising behavior when it comes to fixity. -- For instance, if you have this quasiquoted data declaration: -- -- @ -- [d| infix 5 :^^: -- data Foo where -- (:^^:) :: Int -> Int -> Foo |] -- @ -- -- Then if you pass the 'Dec' for @Foo@ to 'normalizeDec' without splicing it -- in a previous Template Haskell splice, then @(:^^:)@ will be labeled a 'NormalConstructor' -- instead of an 'InfixConstructor'. This is because Template Haskell has no way to -- reify the fixity declaration for @(:^^:)@, so it must assume there isn't one. To -- work around this behavior, use 'reifyDatatype' instead. normalizeDec :: Dec -> Q DatatypeInfo normalizeDec = normalizeDecFor isn'tReified normalizeDecFor :: IsReifiedDec -> Dec -> Q DatatypeInfo normalizeDecFor isReified dec = case dec of #if MIN_VERSION_template_haskell(2,20,0) TypeDataD name tyvars mbKind cons -> normalizeDataD [] name tyvars mbKind cons TypeData #endif #if MIN_VERSION_template_haskell(2,12,0) NewtypeD context name tyvars mbKind con _derives -> normalizeDataD context name tyvars mbKind [con] Newtype DataD context name tyvars mbKind cons _derives -> normalizeDataD context name tyvars mbKind cons Datatype # if MIN_VERSION_template_haskell(2,15,0) NewtypeInstD context mbTyvars nameInstTys mbKind con _derives -> normalizeDataInstDPostTH2'15 "newtype" context mbTyvars nameInstTys mbKind [con] NewtypeInstance DataInstD context mbTyvars nameInstTys mbKind cons _derives -> normalizeDataInstDPostTH2'15 "data" context mbTyvars nameInstTys mbKind cons DataInstance # else NewtypeInstD context name instTys mbKind con _derives -> normalizeDataInstDPreTH2'15 context name instTys mbKind [con] NewtypeInstance DataInstD context name instTys mbKind cons _derives -> normalizeDataInstDPreTH2'15 context name instTys mbKind cons DataInstance # endif #elif MIN_VERSION_template_haskell(2,11,0) NewtypeD context name tyvars mbKind con _derives -> normalizeDataD context name tyvars mbKind [con] Newtype DataD context name tyvars mbKind cons _derives -> normalizeDataD context name tyvars mbKind cons Datatype NewtypeInstD context name instTys mbKind con _derives -> normalizeDataInstDPreTH2'15 context name instTys mbKind [con] NewtypeInstance DataInstD context name instTys mbKind cons _derives -> normalizeDataInstDPreTH2'15 context name instTys mbKind cons DataInstance #else NewtypeD context name tyvars con _derives -> normalizeDataD context name tyvars Nothing [con] Newtype DataD context name tyvars cons _derives -> normalizeDataD context name tyvars Nothing cons Datatype NewtypeInstD context name instTys con _derives -> normalizeDataInstDPreTH2'15 context name instTys Nothing [con] NewtypeInstance DataInstD context name instTys cons _derives -> normalizeDataInstDPreTH2'15 context name instTys Nothing cons DataInstance #endif _ -> fail "normalizeDecFor: DataD or NewtypeD required" where -- We only need to repair reified declarations for data family instances. repair13618' :: DatatypeInfo -> Q DatatypeInfo repair13618' di@DatatypeInfo{datatypeVariant = variant} | isReified && isFamInstVariant variant = repair13618 di | otherwise = return di -- If a data type lacks an explicit return kind, use `reifyType` to compute -- it, as described in step (1) of Note [Tricky result kinds]. normalizeMbKind :: Name -> [Type] -> Maybe Kind -> Q (Maybe Kind) normalizeMbKind _name _instTys mbKind@(Just _) = return mbKind normalizeMbKind name instTys Nothing = do #if MIN_VERSION_template_haskell(2,16,0) mbReifiedKind <- return Nothing `recover` fmap Just (reifyType name) T.mapM normalizeKind mbReifiedKind where normalizeKind :: Kind -> Q Kind normalizeKind k = do k' <- resolveKindSynonyms k -- Step (1) in Note [Tricky result kinds] -- (Wrinkle: normalizeMbKind argument unification). let (args, res) = unravelKindUpTo instTys k' -- Step (2) in Note [Tricky result kinds] -- (Wrinkle: normalizeMbKind argument unification). (instTys', args') = unzip $ mapMaybe (\(instTy, arg) -> case arg of VisFADep tvb -> Just (instTy, bndrParam tvb) VisFAAnon k -> (, k) <$> sigTMaybeKind instTy) args (subst, _) = mergeArguments args' instTys' -- Step (3) in Note [Tricky result kinds] -- (Wrinkle: normalizeMbKind argument unification). pure $ applySubstitution (VarT <$> subst) res #else return Nothing #endif -- Given a data type declaration's binders, as well as the arguments and -- result of its explicit return kind, compute the free type variables. -- For example, this: -- -- @ -- data T (a :: j) :: forall k. Maybe k -> Type -- @ -- -- Would yield: -- -- @ -- [j, (a :: j), k, (b :: k)] -- @ -- -- Where @b@ is a fresh name that is generated in 'mkExtraFunArgForalls'. datatypeFreeVars :: [TyVarBndr_ flag] -> FunArgs -> Kind -> [TyVarBndrUnit] datatypeFreeVars declBndrs kindArgs kindRes = freeVariablesWellScoped $ bndrParams declBndrs ++ #if MIN_VERSION_template_haskell(2,8,0) funArgTys kindArgs ++ [kindRes] #else [] -- No kind variables #endif normalizeDataD :: Cxt -> Name -> [TyVarBndrVis] -> Maybe Kind -> [Con] -> DatatypeVariant -> Q DatatypeInfo normalizeDataD context name tyvars mbKind cons variant = do -- NB: use `filter isRequiredTvb tyvars` here. It is possible for some of -- the `tyvars` to be `BndrInvis` if the data type is quoted, e.g., -- -- data D @k (a :: k) -- -- th-abstraction adopts the convention that all binders in the -- 'datatypeInstTypes' are required, so we want to filter out the `@k`. let tys = bndrParams $ filter isRequiredTvb tyvars mbKind' <- normalizeMbKind name tys mbKind normalize' context name tyvars tys mbKind' cons variant normalizeDataInstDPostTH2'15 :: String -> Cxt -> Maybe [TyVarBndrUnit] -> Type -> Maybe Kind -> [Con] -> DatatypeVariant -> Q DatatypeInfo normalizeDataInstDPostTH2'15 what context mbTyvars nameInstTys mbKind cons variant = case decomposeType nameInstTys of ConT name :| instTys -> do mbKind' <- normalizeMbKind name instTys mbKind normalize' context name (fromMaybe (freeVariablesWellScoped instTys) mbTyvars) instTys mbKind' cons variant _ -> fail $ "Unexpected " ++ what ++ " instance head: " ++ pprint nameInstTys normalizeDataInstDPreTH2'15 :: Cxt -> Name -> [Type] -> Maybe Kind -> [Con] -> DatatypeVariant -> Q DatatypeInfo normalizeDataInstDPreTH2'15 context name instTys mbKind cons variant = do mbKind' <- normalizeMbKind name instTys mbKind normalize' context name (freeVariablesWellScoped instTys) instTys mbKind' cons variant -- The main worker of this function. normalize' :: Cxt -> Name -> [TyVarBndr_ flag] -> [Type] -> Maybe Kind -> [Con] -> DatatypeVariant -> Q DatatypeInfo normalize' context name tvbs instTys mbKind cons variant = do -- If `mbKind` is *still* Nothing after all of the work done in -- normalizeMbKind, then conservatively assume that the return kind is -- `Type`. See step (1) of Note [Tricky result kinds]. let kind = fromMaybe starK mbKind kind' <- resolveKindSynonyms kind let (kindArgs, kindRes) = unravelKind kind' (extra_vis_tvbs, kindArgs') <- mkExtraFunArgForalls kindArgs let tvbs' = datatypeFreeVars tvbs kindArgs' kindRes instTys' = instTys ++ bndrParams extra_vis_tvbs dec <- normalizeDec' isReified context name tvbs' instTys' kindRes cons variant repair13618' $ giveDIVarsStarKinds isReified dec {- Note [Tricky result kinds] ~~~~~~~~~~~~~~~~~~~~~~~~~~ Consider this example, which uses UnliftedNewtypes: type T :: TYPE r newtype T where MkT :: forall r. Any @(TYPE r) -> T @r This has one universally quantified type variable `r`, but making `reifyDatatype ''T` realize this is surprisingly tricky. There root of the trickiness is the fact that `Language.Haskell.TH.reify ''T` will yield this: newtype T where MkT :: forall r. (Any :: TYPE r) -> (T :: TYPE r) In particular, note that: 1. `reify` does not give `T` an explicit return kind of `TYPE r`. This is bad, because without this, we cannot conclude that `r` is universally quantified. 2. The reified type of the `MkT` constructor uses explicit kind annotations instead of visible kind applications. That is, the return type is `T :: TYPE r` instead of `T @r`. This makes it even trickier to figure out that `r` is universally quantified, as `r` does not appear directly underneath an application of `T`. We resolve each of these issues as follows: 1. In `normalizeDecFor.normalizeMbKind`, we attempt to use `reifyType` to look up the return kind of the data type. In the `T` example above, this suffices to conclude that `T :: TYPE r`. `reifyType` won't always work (e.g., when using `normalizeDec` on a data type without an explicit return kind), so for those situations, we conservatively assume that the data type has return kind `Type`. The implementation of `normalizeMbKind` is somewhat involved. See "Wrinkle: normalizeMbKind argument unification" below for more details. 2. After determining the result kind `K1`, we pass `K1` through to `normalizeGadtC`. In that function, we check if the return type of the data constructor is of the form `Ty :: K2`, and if so, we attempt to unify `K1` and `K2` by passing through to `mergeArguments`. In the example above, this lets us conclude that the `r` in the data type return kind is the same `r` as in the data constructor. =================================================== == Wrinkle: normalizeMbKind argument unification == =================================================== Here is a slightly more involved example: type T2 :: TYPE r1 -> TYPE r1 newtype T2 (a :: TYPE r2) = MkT2 a Here, we must use `reifyType` in `normalizeMbKind` to determine that the return kind is `TYPE r1`. But we must be careful here: `r1` is actually the same type variable as `r2`! We don't want to accidentally end up quantifying over the two variables separately in `datatypeInstVars`, since they're really one and the same. We accomplish this by doing the following: 1. After calling `reifyKind` in `normalizeMbKind`, split the result kind into as many arguments as there are visible binders in the data type declaration. In the `T2` example above, there is exactly one visible binder in `newtype T2 a`, so we split the kind `TYPE r1 -> TYPE r1` by one argument to get ([TYPE r1], TYPE r1). See `unravelKindUpTo` for how this splitting logic is implemented. 2. We then unify the argument kinds resuling from the splitting in the previous step with the corresponding kinds from the data type declaration. In the example above, the split argument kind is `TYPE r1`, and the binder in the declaration has kind `TYPE r2`, so we unify `TYPE r1` with `TYPE r2` using `mergeArgumentKinds` to get a substitution [r1 :-> r2]. 3. We then apply the substitution from the previous step to the rest of the kind. In the example above, that means we apply the [r1 :-> r2] substitution to `TYPE r1` to obtain `TYPE r2`. The payoff is that everything consistently refers to `r2`, rather than the mix of `r1` and `r2` as before. -} -- | Create new kind variable binder names corresponding to the return kind of -- a data type. This is useful when you have a data type like: -- -- @ -- data Foo :: forall k. k -> Type -> Type where ... -- @ -- -- But you want to be able to refer to the type @Foo a b@. -- 'mkExtraKindBinders' will take the kind @forall k. k -> Type -> Type@, -- discover that is has two visible argument kinds, and return as a result -- two new kind variable binders @[a :: k, b :: Type]@, where @a@ and @b@ -- are fresh type variable names. -- -- This expands kind synonyms if necessary. mkExtraKindBinders :: Kind -> Q [TyVarBndrUnit] mkExtraKindBinders kind = do kind' <- resolveKindSynonyms kind let (args, _) = unravelKind kind' (extra_kvbs, _) <- mkExtraFunArgForalls args return extra_kvbs -- | Take the supplied function kind arguments ('FunArgs') and do two things: -- -- 1. For each 'FAAnon' with kind @k@, generate a fresh name @a@ and return -- the 'TyVarBndr' @a :: k@. Also return each visible @forall@ in an -- 'FAForalls' as a 'TyVarBndr'. (This is what the list of 'TyVarBndrUnit's -- in the return type consists of.) -- -- 2. Return a new 'FunArgs' value where each 'FAAnon' has been replaced with -- @'FAForalls' ('ForallVis' [a :: k])@, where @a :: k@ the corresponding -- 'TyVarBndr' computed in step (1). -- -- As an example, consider this function kind: -- -- @ -- forall k. k -> Type -> Type -- @ -- -- After splitting this kind into its 'FunArgs': -- -- @ -- ['FAForalls' ('ForallInvis' [k]), 'FAAnon' k, 'FAAnon' Type] -- @ -- -- Calling 'mkExtraFunArgForalls' on this 'FunArgs' value would return: -- -- @ -- ( [a :: k, b :: Type] -- , [ 'FAForalls' ('ForallInvis' [k]) -- , 'FAForalls' ('ForallVis' [a :: k]) -- , 'FAForalls' ('ForallVis' [b :: Type]) -- ] -- ) -- @ -- -- Where @a@ and @b@ are fresh. -- -- This function is used in two places: -- -- 1. As the workhorse for 'mkExtraKindBinders'. -- -- 2. In 'normalizeDecFor', as part of computing the 'datatypeInstVars' and as -- part of eta expanding the explicit return kind. mkExtraFunArgForalls :: FunArgs -> Q ([TyVarBndrUnit], FunArgs) mkExtraFunArgForalls FANil = return ([], FANil) mkExtraFunArgForalls (FAForalls tele args) = do (extra_vis_tvbs', args') <- mkExtraFunArgForalls args case tele of ForallVis tvbs -> return ( tvbs ++ extra_vis_tvbs' , FAForalls (ForallVis tvbs) args' ) ForallInvis tvbs -> return ( extra_vis_tvbs' , FAForalls (ForallInvis tvbs) args' ) mkExtraFunArgForalls (FACxt ctxt args) = do (extra_vis_tvbs', args') <- mkExtraFunArgForalls args return (extra_vis_tvbs', FACxt ctxt args') mkExtraFunArgForalls (FAAnon anon args) = do name <- newName "x" let tvb = kindedTV name anon (extra_vis_tvbs', args') <- mkExtraFunArgForalls args return ( tvb : extra_vis_tvbs' , FAForalls (ForallVis [tvb]) args' ) -- | Is a declaration for a @data instance@ or @newtype instance@? isFamInstVariant :: DatatypeVariant -> Bool isFamInstVariant dv = case dv of Datatype -> False Newtype -> False DataInstance -> True NewtypeInstance -> True TypeData -> False bndrParams :: [TyVarBndr_ flag] -> [Type] bndrParams = map bndrParam bndrParam :: TyVarBndr_ flag -> Type bndrParam = elimTV VarT (\n k -> SigT (VarT n) k) -- | Returns 'True' if the flag of the supplied 'TyVarBndrVis' is 'BndrReq'. isRequiredTvb :: TyVarBndrVis -> Bool #if __GLASGOW_HASKELL__ >= 708 isRequiredTvb tvb = tvFlag tvb == BndrReq #else isRequiredTvb _ = True #endif -- | Remove the outermost 'SigT'. stripSigT :: Type -> Type stripSigT (SigT t _) = t stripSigT t = t -- | If the supplied 'Type' is a @'SigT' _ k@, return @'Just' k@. Otherwise, -- return 'Nothing'. sigTMaybeKind :: Type -> Maybe Kind sigTMaybeKind (SigT _ k) = Just k sigTMaybeKind _ = Nothing normalizeDec' :: IsReifiedDec {- ^ Is this a reified 'Dec'? -} -> Cxt {- ^ Datatype context -} -> Name {- ^ Type constructor -} -> [TyVarBndrUnit] {- ^ Type parameters -} -> [Type] {- ^ Argument types -} -> Kind {- ^ Result kind -} -> [Con] {- ^ Constructors -} -> DatatypeVariant {- ^ Extra information -} -> Q DatatypeInfo normalizeDec' reifiedDec context name params instTys resKind cons variant = do cons' <- concat <$> mapM (normalizeConFor reifiedDec name params instTys resKind variant) cons return DatatypeInfo { datatypeContext = context , datatypeName = name , datatypeVars = params , datatypeInstTypes = instTys , datatypeCons = cons' , datatypeReturnKind = resKind , datatypeVariant = variant } -- | Normalize a 'Con' into a 'ConstructorInfo'. This requires knowledge of -- the type and parameters of the constructor, as well as whether the constructor -- is for a data family instance, as extracted from the outer -- 'Dec'. normalizeCon :: Name {- ^ Type constructor -} -> [TyVarBndrUnit] {- ^ Type parameters -} -> [Type] {- ^ Argument types -} -> Kind {- ^ Result kind -} -> DatatypeVariant {- ^ Extra information -} -> Con {- ^ Constructor -} -> Q [ConstructorInfo] normalizeCon = normalizeConFor isn'tReified normalizeConFor :: IsReifiedDec {- ^ Is this a reified 'Dec'? -} -> Name {- ^ Type constructor -} -> [TyVarBndrUnit] {- ^ Type parameters -} -> [Type] {- ^ Argument types -} -> Kind {- ^ Result kind -} -> DatatypeVariant {- ^ Extra information -} -> Con {- ^ Constructor -} -> Q [ConstructorInfo] normalizeConFor reifiedDec typename params instTys resKind variant = fmap (map (giveCIVarsStarKinds reifiedDec)) . dispatch where -- A GADT constructor is declared infix when: -- -- 1. Its name uses operator syntax (e.g., (:*:)) -- 2. It has exactly two fields -- 3. It has a programmer-supplied fixity declaration checkGadtFixity :: [Type] -> Name -> Q ConstructorVariant checkGadtFixity ts n = do #if MIN_VERSION_template_haskell(2,11,0) -- Don't call reifyFixityCompat here! We need to be able to distinguish -- between a default fixity and an explicit @infixl 9@. mbFi <- return Nothing `recover` reifyFixity n let userSuppliedFixity = isJust mbFi #else -- On old GHCs, there is a bug where infix GADT constructors will -- mistakenly be marked as (ForallC (NormalC ...)) instead of -- (ForallC (InfixC ...)). This is especially annoying since on these -- versions of GHC, Template Haskell doesn't grant the ability to query -- whether a constructor was given a user-supplied fixity declaration. -- Rather, you can only check the fixity that GHC ultimately decides on -- for a constructor, regardless of whether it was a default fixity or -- it was user-supplied. -- -- We can approximate whether a fixity was user-supplied by checking if -- it is not equal to defaultFixity (infixl 9). Unfortunately, -- there is no way to distinguish between a user-supplied fixity of -- infixl 9 and the fixity that GHC defaults to, so we cannot properly -- handle that case. mbFi <- reifyFixityCompat n let userSuppliedFixity = isJust mbFi && mbFi /= Just defaultFixity #endif return $ if isInfixDataCon (nameBase n) && length ts == 2 && userSuppliedFixity then InfixConstructor else NormalConstructor -- Checks if a String names a valid Haskell infix data -- constructor (i.e., does it begin with a colon?). isInfixDataCon :: String -> Bool isInfixDataCon (':':_) = True isInfixDataCon _ = False dispatch :: Con -> Q [ConstructorInfo] dispatch = let defaultCase :: Con -> Q [ConstructorInfo] defaultCase = go [] [] False where go :: [TyVarBndrUnit] -> Cxt -> Bool -- Is this a GADT? (see the documentation for -- for checkGadtFixity) -> Con -> Q [ConstructorInfo] go tyvars context gadt c = case c of NormalC n xs -> do let (bangs, ts) = unzip xs stricts = map normalizeStrictness bangs fi <- if gadt then checkGadtFixity ts n else return NormalConstructor return [ConstructorInfo n tyvars context ts stricts fi] InfixC l n r -> let (bangs, ts) = unzip [l,r] stricts = map normalizeStrictness bangs in return [ConstructorInfo n tyvars context ts stricts InfixConstructor] RecC n xs -> let fns = takeFieldNames xs stricts = takeFieldStrictness xs in return [ConstructorInfo n tyvars context (takeFieldTypes xs) stricts (RecordConstructor fns)] ForallC tyvars' context' c' -> go (changeTVFlags () tyvars'++tyvars) (context'++context) True c' #if MIN_VERSION_template_haskell(2,11,0) GadtC ns xs innerType -> let (bangs, ts) = unzip xs stricts = map normalizeStrictness bangs in gadtCase ns innerType ts stricts (checkGadtFixity ts) RecGadtC ns xs innerType -> let fns = takeFieldNames xs stricts = takeFieldStrictness xs in gadtCase ns innerType (takeFieldTypes xs) stricts (const $ return $ RecordConstructor fns) where gadtCase = normalizeGadtC typename params instTys resKind tyvars context #endif #if MIN_VERSION_template_haskell(2,8,0) && (!MIN_VERSION_template_haskell(2,10,0)) dataFamCompatCase :: Con -> Q [ConstructorInfo] dataFamCompatCase = go [] where go tyvars c = case c of NormalC n xs -> let stricts = map (normalizeStrictness . fst) xs in dataFamCase' n stricts NormalConstructor InfixC l n r -> let stricts = map (normalizeStrictness . fst) [l,r] in dataFamCase' n stricts InfixConstructor RecC n xs -> let stricts = takeFieldStrictness xs in dataFamCase' n stricts (RecordConstructor (takeFieldNames xs)) ForallC tyvars' context' c' -> go (tyvars'++tyvars) c' dataFamCase' :: Name -> [FieldStrictness] -> ConstructorVariant -> Q [ConstructorInfo] dataFamCase' n stricts variant = do mbInfo <- reifyMaybe n case mbInfo of Just (DataConI _ ty _ _) -> do let (tyvars, context, argTys :|- returnTy) = uncurryType ty returnTy' <- resolveTypeSynonyms returnTy -- Notice that we've ignored the TyVarBndrs, Cxt and argument -- Types from the Con argument above, as they might be scoped -- over eta-reduced variables. Instead of trying to figure out -- what the eta-reduced variables should be substituted with -- post facto, we opt for the simpler approach of using the -- context and argument types from the reified constructor -- Info, which will at least be correctly scoped. This will -- make the task of substituting those types with the variables -- we put in place of the eta-reduced variables -- (in normalizeDec) much easier. normalizeGadtC typename params instTys resKind tyvars context [n] returnTy' argTys stricts (const $ return variant) _ -> fail $ unlines [ "normalizeCon: Cannot reify constructor " ++ nameBase n , "You are likely calling normalizeDec on GHC 7.6 or 7.8 on a data family" , "whose type variables have been eta-reduced due to GHC Trac #9692." , "Unfortunately, without being able to reify the constructor's type," , "there is no way to recover the eta-reduced type variables in general." , "A recommended workaround is to use reifyDatatype instead." ] -- A very ad hoc way of determining if we need to perform some extra passes -- to repair an eta-reduction bug for data family instances that only occurs -- with GHC 7.6 and 7.8. We want to avoid doing these passes if at all possible, -- since they require reifying extra information, and reifying during -- normalization can be problematic for locally declared Template Haskell -- splices (see ##22). mightHaveBeenEtaReduced :: [Type] -> Bool mightHaveBeenEtaReduced ts = case unsnoc ts of Nothing -> False Just (initTs :|- lastT) -> case varTName lastT of Nothing -> False Just n -> not (n `elem` freeVariables initTs) -- If the list is empty returns 'Nothing', otherwise returns the -- 'init' and the 'last'. unsnoc :: [a] -> Maybe (NonEmptySnoc a) unsnoc [] = Nothing unsnoc (x:xs) = case unsnoc xs of Just (a :|- b) -> Just ((x:a) :|- b) Nothing -> Just ([] :|- x) -- If a Type is a VarT, find Just its Name. Otherwise, return Nothing. varTName :: Type -> Maybe Name varTName (SigT t _) = varTName t varTName (VarT n) = Just n varTName _ = Nothing in case variant of -- On GHC 7.6 and 7.8, there's quite a bit of post-processing that -- needs to be performed to work around an old bug that eta-reduces the -- type patterns of data families (but only for reified data family instances). DataInstance | reifiedDec, mightHaveBeenEtaReduced instTys -> dataFamCompatCase NewtypeInstance | reifiedDec, mightHaveBeenEtaReduced instTys -> dataFamCompatCase _ -> defaultCase #else in defaultCase #endif #if MIN_VERSION_template_haskell(2,11,0) normalizeStrictness :: Bang -> FieldStrictness normalizeStrictness (Bang upk str) = FieldStrictness (normalizeSourceUnpackedness upk) (normalizeSourceStrictness str) where normalizeSourceUnpackedness :: SourceUnpackedness -> Unpackedness normalizeSourceUnpackedness NoSourceUnpackedness = UnspecifiedUnpackedness normalizeSourceUnpackedness SourceNoUnpack = NoUnpack normalizeSourceUnpackedness SourceUnpack = Unpack normalizeSourceStrictness :: SourceStrictness -> Strictness normalizeSourceStrictness NoSourceStrictness = UnspecifiedStrictness normalizeSourceStrictness SourceLazy = Lazy normalizeSourceStrictness SourceStrict = Strict #else normalizeStrictness :: Strict -> FieldStrictness normalizeStrictness IsStrict = isStrictAnnot normalizeStrictness NotStrict = notStrictAnnot # if MIN_VERSION_template_haskell(2,7,0) normalizeStrictness Unpacked = unpackedAnnot # endif #endif normalizeGadtC :: Name {- ^ Type constructor -} -> [TyVarBndrUnit] {- ^ Type parameters -} -> [Type] {- ^ Argument types -} -> Kind {- ^ Result kind -} -> [TyVarBndrUnit] {- ^ Constructor parameters -} -> Cxt {- ^ Constructor context -} -> [Name] {- ^ Constructor names -} -> Type {- ^ Declared type of constructor -} -> [Type] {- ^ Constructor field types -} -> [FieldStrictness] {- ^ Constructor field strictness -} -> (Name -> Q ConstructorVariant) {- ^ Determine a constructor variant from its 'Name' -} -> Q [ConstructorInfo] normalizeGadtC typename params instTys resKind tyvars context names innerType fields stricts getVariant = do -- It's possible that the constructor has implicitly quantified type -- variables, such as in the following example (from #58): -- -- [d| data Foo where -- MkFoo :: a -> Foo |] -- -- normalizeGadtC assumes that all type variables have binders, however, -- so we use freeVariablesWellScoped to obtain the implicit type -- variables' binders before proceeding. let implicitTyvars = freeVariablesWellScoped [curryType (changeTVFlags SpecifiedSpec tyvars) context fields innerType] allTyvars = implicitTyvars ++ tyvars -- Due to GHC Trac #13885, it's possible that the type variables bound by -- a GADT constructor will shadow those that are bound by the data type. -- This function assumes this isn't the case in certain parts (e.g., when -- mergeArguments is invoked), so we do an alpha-renaming of the -- constructor-bound variables before proceeding. See #36 for an example -- of what can go wrong if this isn't done. let conBoundNames = concatMap (\tvb -> tvName tvb:freeVariables (tvKind tvb)) allTyvars conSubst <- T.sequence $ Map.fromList [ (n, newName (nameBase n)) | n <- conBoundNames ] let conSubst' = fmap VarT conSubst renamedTyvars = map (elimTV (\n -> plainTV (conSubst Map.! n)) (\n k -> kindedTV (conSubst Map.! n) (applySubstitution conSubst' k))) allTyvars renamedContext = applySubstitution conSubst' context renamedInnerType = applySubstitution conSubst' innerType renamedFields = applySubstitution conSubst' fields innerType' <- resolveTypeSynonyms renamedInnerType -- If the return type in the data constructor is of the form `T :: K`, then -- return (T, Just K, Just resKind), where `resKind` is the result kind of -- the parent data type. Otherwise, return (T :: K, Nothing, Nothing). The -- two `Maybe` values are passed below to `mergeArgumentKinds` such that if -- they are both `Just`, then we will attempt to unify `K` and `resKind`. -- See step (2) of Note [Tricky result kinds]. let (innerType'', mbInnerResKind, mbResKind) = case innerType' of SigT t innerResKind -> (t, Just innerResKind, Just resKind) _ -> (innerType', Nothing, Nothing) case decomposeType innerType'' of ConT innerTyCon :| ts | typename == innerTyCon -> let -- See step (2) of Note [Tricky result kinds]. #if MIN_VERSION_template_haskell(2,8,0) instTys' = maybeToList mbResKind ++ instTys ts' = maybeToList mbInnerResKind ++ ts #else instTys' = instTys ts' = ts #endif (substName, context1) = closeOverKinds (kindsOfFVsOfTvbs renamedTyvars) (kindsOfFVsOfTvbs params) (mergeArguments instTys' ts') subst = VarT <$> substName exTyvars = [ tv | tv <- renamedTyvars, Map.notMember (tvName tv) subst ] -- The use of substTyVarBndrKinds below will never capture, as the -- range of the substitution will always use distinct names from -- exTyvars due to the alpha-renaming pass above. exTyvars' = substTyVarBndrKinds subst exTyvars context2 = applySubstitution subst (context1 ++ renamedContext) fields' = applySubstitution subst renamedFields in sequence [ ConstructorInfo name exTyvars' context2 fields' stricts <$> variantQ | name <- names , let variantQ = getVariant name ] _ -> fail "normalizeGadtC: Expected type constructor application" {- Extend a type variable renaming subtitution and a list of equality predicates by looking into kind information as much as possible. Why is this necessary? Consider the following example: data (a1 :: k1) :~: (b1 :: k1) where Refl :: forall k2 (a2 :: k2). a2 :~: a2 After an initial call to mergeArguments, we will have the following substitution and context: * Substitution: [a2 :-> a1] * Context: (a2 ~ b1) We shouldn't stop there, however! We determine the existentially quantified type variables of a constructor by filtering out those constructor-bound variables which do not appear in the substitution that mergeArguments returns. In this example, Refl's bound variables are k2 and a2. a2 appears in the returned substitution, but k2 does not, which means that we would mistakenly conclude that k2 is existential! Although we don't have the full power of kind inference to guide us here, we can at least do the next best thing. Generally, the datatype-bound type variables and the constructor type variable binders contain all of the kind information we need, so we proceed as follows: 1. Construct a map from each constructor-bound variable to its kind. (Do the same for each datatype-bound variable). These maps are the first and second arguments to closeOverKinds, respectively. 2. Call mergeArguments once on the GADT return type and datatype-bound types, and pass that in as the third argument to closeOverKinds. 3. For each name-name pair in the supplied substitution, check if the first and second names map to kinds in the first and second kind maps in closeOverKinds, respectively. If so, associate the first kind with the second kind. 4. For each kind association discovered in part (3), call mergeArguments on the lists of kinds. This will yield a kind substitution and kind equality context. 5. If the kind substitution is non-empty, then go back to step (3) and repeat the process on the new kind substitution and context. Otherwise, if the kind substitution is empty, then we have reached a fixed- point (i.e., we have closed over the kinds), so proceed. 6. Union up all of the substitutions and contexts, and return those. This algorithm is not perfect, as it will only catch everything if all of the kinds are explicitly mentioned somewhere (and not left quantified implicitly). Thankfully, reifying data types via Template Haskell tends to yield a healthy amount of kind signatures, so this works quite well in practice. -} closeOverKinds :: Map Name Kind -> Map Name Kind -> (Map Name Name, Cxt) -> (Map Name Name, Cxt) closeOverKinds domainFVKinds rangeFVKinds = go where go :: (Map Name Name, Cxt) -> (Map Name Name, Cxt) go (subst, context) = let substList = Map.toList subst (kindsInner, kindsOuter) = unzip $ mapMaybe (\(d, r) -> do d' <- Map.lookup d domainFVKinds r' <- Map.lookup r rangeFVKinds return (d', r')) substList (kindSubst, kindContext) = mergeArgumentKinds kindsOuter kindsInner (restSubst, restContext) = if Map.null kindSubst -- Fixed-point calculation then (Map.empty, []) else go (kindSubst, kindContext) finalSubst = Map.unions [subst, kindSubst, restSubst] finalContext = nub $ concat [context, kindContext, restContext] -- Use `nub` here in an effort to minimize the number of -- redundant equality constraints in the returned context. in (finalSubst, finalContext) -- Look into a list of types and map each free variable name to its kind. kindsOfFVsOfTypes :: [Type] -> Map Name Kind kindsOfFVsOfTypes = foldMap go where go :: Type -> Map Name Kind go (AppT t1 t2) = go t1 `Map.union` go t2 go (SigT t k) = let kSigs = #if MIN_VERSION_template_haskell(2,8,0) go k #else Map.empty #endif in case t of VarT n -> Map.insert n k kSigs _ -> go t `Map.union` kSigs go (ForallT {}) = forallError #if MIN_VERSION_template_haskell(2,16,0) go (ForallVisT {}) = forallError #endif go _ = Map.empty forallError :: a forallError = error "`forall` type used in data family pattern" -- Look into a list of type variable binder and map each free variable name -- to its kind (also map the names that KindedTVs bind to their respective -- kinds). This function considers the kind of a PlainTV to be *. kindsOfFVsOfTvbs :: [TyVarBndr_ flag] -> Map Name Kind kindsOfFVsOfTvbs = foldMap go where go :: TyVarBndr_ flag -> Map Name Kind go = elimTV (\n -> Map.singleton n starK) (\n k -> let kSigs = #if MIN_VERSION_template_haskell(2,8,0) kindsOfFVsOfTypes [k] #else Map.empty #endif in Map.insert n k kSigs) mergeArguments :: [Type] {- ^ outer parameters -} -> [Type] {- ^ inner parameters (specializations ) -} -> (Map Name Name, Cxt) mergeArguments ns ts = foldr aux (Map.empty, []) (zip ns ts) where aux (f `AppT` x, g `AppT` y) sc = aux (x,y) (aux (f,g) sc) aux (VarT n,p) (subst, context) = case p of VarT m | m == n -> (subst, context) -- If the two variables are the same, don't bother extending -- the substitution. (This is purely an optimization.) | Just n' <- Map.lookup m subst , n == n' -> (subst, context) -- If a variable is already in a substitution and it maps -- to the variable that we are trying to unify with, then -- leave the context alone. (Not doing so caused #46.) | Map.notMember m subst -> (Map.insert m n subst, context) _ -> (subst, equalPred (VarT n) p : context) aux (SigT x _, y) sc = aux (x,y) sc -- learn about kinds?? -- This matches *after* VarT so that we can compute a substitution -- that includes the kind signature. aux (x, SigT y _) sc = aux (x,y) sc aux _ sc = sc -- | A specialization of 'mergeArguments' to 'Kind'. -- Needed only for backwards compatibility with older versions of -- @template-haskell@. mergeArgumentKinds :: [Kind] -> [Kind] -> (Map Name Name, Cxt) #if MIN_VERSION_template_haskell(2,8,0) mergeArgumentKinds = mergeArguments #else mergeArgumentKinds _ _ = (Map.empty, []) #endif -- | Expand all of the type synonyms in a type. -- -- Note that this function will drop parentheses as a side effect. resolveTypeSynonyms :: Type -> Q Type resolveTypeSynonyms t = let (f, xs) = decomposeTypeArgs t normal_xs = filterTANormals xs -- Either the type is not headed by a type synonym, or it is headed by a -- type synonym that is not applied to enough arguments. Leave the type -- alone and only expand its arguments. defaultCase :: Type -> Q Type defaultCase ty = foldl appTypeArg ty <$> mapM resolveTypeArgSynonyms xs expandCon :: Name -- The Name to check whether it is a type synonym or not -> Type -- The argument type to fall back on if the supplied -- Name isn't a type synonym -> Q Type expandCon n ty = do mbInfo <- reifyMaybe n case mbInfo of Just (TyConI (TySynD _ synvars def)) | length normal_xs >= length synvars -- Don't expand undersaturated type synonyms (#88) -> resolveTypeSynonyms $ expandSynonymRHS synvars normal_xs def _ -> defaultCase ty in case f of ForallT tvbs ctxt body -> ForallT `fmap` mapM resolve_tvb_syns tvbs `ap` mapM resolvePredSynonyms ctxt `ap` resolveTypeSynonyms body SigT ty ki -> do ty' <- resolveTypeSynonyms ty ki' <- resolveKindSynonyms ki defaultCase $ SigT ty' ki' ConT n -> expandCon n f #if MIN_VERSION_template_haskell(2,11,0) InfixT t1 n t2 -> do t1' <- resolveTypeSynonyms t1 t2' <- resolveTypeSynonyms t2 expandCon n (InfixT t1' n t2') UInfixT t1 n t2 -> do t1' <- resolveTypeSynonyms t1 t2' <- resolveTypeSynonyms t2 expandCon n (UInfixT t1' n t2') #endif #if MIN_VERSION_template_haskell(2,15,0) ImplicitParamT n t -> do ImplicitParamT n <$> resolveTypeSynonyms t #endif #if MIN_VERSION_template_haskell(2,16,0) ForallVisT tvbs body -> ForallVisT `fmap` mapM resolve_tvb_syns tvbs `ap` resolveTypeSynonyms body #endif #if MIN_VERSION_template_haskell(2,19,0) PromotedInfixT t1 n t2 -> do t1' <- resolveTypeSynonyms t1 t2' <- resolveTypeSynonyms t2 return $ PromotedInfixT t1' n t2' PromotedUInfixT t1 n t2 -> do t1' <- resolveTypeSynonyms t1 t2' <- resolveTypeSynonyms t2 return $ PromotedUInfixT t1' n t2' #endif _ -> defaultCase f -- | Expand all of the type synonyms in a 'TypeArg'. resolveTypeArgSynonyms :: TypeArg -> Q TypeArg resolveTypeArgSynonyms (TANormal t) = TANormal <$> resolveTypeSynonyms t resolveTypeArgSynonyms (TyArg k) = TyArg <$> resolveKindSynonyms k -- | Expand all of the type synonyms in a 'Kind'. resolveKindSynonyms :: Kind -> Q Kind #if MIN_VERSION_template_haskell(2,8,0) resolveKindSynonyms = resolveTypeSynonyms #else resolveKindSynonyms = return -- One simply couldn't put type synonyms into -- kinds on old versions of GHC. #endif -- | Expand all of the type synonyms in a the kind of a 'TyVarBndr'. resolve_tvb_syns :: TyVarBndr_ flag -> Q (TyVarBndr_ flag) resolve_tvb_syns = mapMTVKind resolveKindSynonyms expandSynonymRHS :: [TyVarBndr_ flag] {- ^ Substitute these variables... -} -> [Type] {- ^ ...with these types... -} -> Type {- ^ ...inside of this type. -} -> Type expandSynonymRHS synvars ts def = let argNames = map tvName synvars (args,rest) = splitAt (length argNames) ts subst = Map.fromList (zip argNames args) in foldl AppT (applySubstitution subst def) rest -- | Expand all of the type synonyms in a 'Pred'. resolvePredSynonyms :: Pred -> Q Pred #if MIN_VERSION_template_haskell(2,10,0) resolvePredSynonyms = resolveTypeSynonyms #else resolvePredSynonyms (ClassP n ts) = do mbInfo <- reifyMaybe n case mbInfo of Just (TyConI (TySynD _ synvars def)) | length ts >= length synvars -- Don't expand undersaturated type synonyms (#88) -> resolvePredSynonyms $ typeToPred $ expandSynonymRHS synvars ts def _ -> ClassP n <$> mapM resolveTypeSynonyms ts resolvePredSynonyms (EqualP t1 t2) = do t1' <- resolveTypeSynonyms t1 t2' <- resolveTypeSynonyms t2 return (EqualP t1' t2') typeToPred :: Type -> Pred typeToPred t = let f :| xs = decomposeType t in case f of ConT n | n == eqTypeName # if __GLASGOW_HASKELL__ == 704 -- There's an unfortunate bug in GHC 7.4 where the (~) type is reified -- with an explicit kind argument. To work around this, we ignore it. , [_,t1,t2] <- xs # else , [t1,t2] <- xs # endif -> EqualP t1 t2 | otherwise -> ClassP n xs _ -> error $ "typeToPred: Can't handle type " ++ show t #endif -- | Decompose a type into a list of it's outermost applications. This process -- forgets about infix application, explicit parentheses, and visible kind -- applications. -- -- This operation should be used after all 'UInfixT' cases have been resolved -- by 'resolveFixities' if the argument is being user generated. -- -- > t ~= foldl1 AppT (decomposeType t) decomposeType :: Type -> NonEmpty Type decomposeType t = case decomposeTypeArgs t of (f, x) -> f :| filterTANormals x -- | A variant of 'decomposeType' that preserves information about visible kind -- applications by returning a 'NonEmpty' list of 'TypeArg's. decomposeTypeArgs :: Type -> (Type, [TypeArg]) decomposeTypeArgs = go [] where go :: [TypeArg] -> Type -> (Type, [TypeArg]) go args (AppT f x) = go (TANormal x:args) f #if MIN_VERSION_template_haskell(2,11,0) go args (ParensT t) = go args t #endif #if MIN_VERSION_template_haskell(2,15,0) go args (AppKindT f x) = go (TyArg x:args) f #endif go args t = (t, args) -- | An argument to a type, either a normal type ('TANormal') or a visible -- kind application ('TyArg'). data TypeArg = TANormal Type | TyArg Kind -- | Apply a 'Type' to a 'TypeArg'. appTypeArg :: Type -> TypeArg -> Type appTypeArg f (TANormal x) = f `AppT` x appTypeArg f (TyArg _k) = #if MIN_VERSION_template_haskell(2,15,0) f `AppKindT` _k #else f -- VKA isn't supported, so conservatively drop the argument #endif -- | Filter out all of the normal type arguments from a list of 'TypeArg's. filterTANormals :: [TypeArg] -> [Type] filterTANormals = mapMaybe f where f :: TypeArg -> Maybe Type f (TANormal t) = Just t f (TyArg {}) = Nothing -- 'NonEmpty' didn't move into base until recently. Reimplementing it locally -- saves dependencies for supporting older GHCs data NonEmpty a = a :| [a] data NonEmptySnoc a = [a] :|- a -- Decompose a function type into its context, argument types, -- and return type. For instance, this -- -- forall a b. (Show a, b ~ Int) => (a -> b) -> Char -> Int -- -- becomes -- -- ([a, b], [Show a, b ~ Int], [a -> b, Char] :|- Int) uncurryType :: Type -> ([TyVarBndrSpec], Cxt, NonEmptySnoc Type) uncurryType = go [] [] [] where go tvbs ctxt args (AppT (AppT ArrowT t1) t2) = go tvbs ctxt (t1:args) t2 go tvbs ctxt args (ForallT tvbs' ctxt' t) = go (tvbs++tvbs') (ctxt++ctxt') args t go tvbs ctxt args t = (tvbs, ctxt, reverse args :|- t) -- Reconstruct a function type from its type variable binders, context, -- argument types and return type. curryType :: [TyVarBndrSpec] -> Cxt -> [Type] -> Type -> Type curryType tvbs ctxt args res = ForallT tvbs ctxt $ foldr (\arg t -> ArrowT `AppT` arg `AppT` t) res args -- All of the code from @ForallTelescope@ through @unravelType@ is taken from -- the @th-desugar@ library, which is licensed under a 3-Clause BSD license. -- | The type variable binders in a @forall@. This is not used by the TH AST -- itself, but this is used as an intermediate data type in 'FAForalls'. data ForallTelescope = ForallVis [TyVarBndrUnit] -- ^ A visible @forall@ (e.g., @forall a -> {...}@). -- These do not have any notion of specificity, so we use -- '()' as a placeholder value in the 'TyVarBndr's. | ForallInvis [TyVarBndrSpec] -- ^ An invisible @forall@ (e.g., @forall a {b} c -> {...}@), -- where each binder has a 'Specificity'. -- | The list of arguments in a function 'Type'. data FunArgs = FANil -- ^ No more arguments. | FAForalls ForallTelescope FunArgs -- ^ A series of @forall@ed type variables followed by a dot (if -- 'ForallInvis') or an arrow (if 'ForallVis'). For example, -- the type variables @a1 ... an@ in @forall a1 ... an. r@. | FACxt Cxt FunArgs -- ^ A series of constraint arguments followed by @=>@. For example, -- the @(c1, ..., cn)@ in @(c1, ..., cn) => r@. | FAAnon Kind FunArgs -- ^ An anonymous argument followed by an arrow. For example, the @a@ -- in @a -> r@. -- | A /visible/ function argument type (i.e., one that must be supplied -- explicitly in the source code). This is in contrast to /invisible/ -- arguments (e.g., the @c@ in @c => r@), which are instantiated without -- the need for explicit user input. data VisFunArg = VisFADep TyVarBndrUnit -- ^ A visible @forall@ (e.g., @forall a -> a@). | VisFAAnon Kind -- ^ An anonymous argument followed by an arrow (e.g., @a -> r@). #if MIN_VERSION_template_haskell(2,8,0) -- | Decompose a function 'Type' into its arguments (the 'FunArgs') and its -- result type (the 'Type). unravelType :: Type -> (FunArgs, Type) unravelType (ForallT tvbs cxt ty) = let (args, res) = unravelType ty in (FAForalls (ForallInvis tvbs) (FACxt cxt args), res) unravelType (AppT (AppT ArrowT t1) t2) = let (args, res) = unravelType t2 in (FAAnon t1 args, res) # if __GLASGOW_HASKELL__ >= 809 unravelType (ForallVisT tvbs ty) = let (args, res) = unravelType ty in (FAForalls (ForallVis tvbs) args, res) # endif unravelType t = (FANil, t) -- | Reconstruct an arrow 'Type' from its argument and result types. ravelType :: FunArgs -> Type -> Type ravelType FANil res = res -- We need a special case for FAForalls ForallInvis followed by FACxt so that we may -- collapse them into a single ForallT when raveling. ravelType (FAForalls (ForallInvis tvbs) (FACxt p args)) res = ForallT tvbs p (ravelType args res) ravelType (FAForalls (ForallInvis tvbs) args) res = ForallT tvbs [] (ravelType args res) ravelType (FAForalls (ForallVis _tvbs) _args) _res = #if __GLASGOW_HASKELL__ >= 809 ForallVisT _tvbs (ravelType _args _res) #else error "Visible dependent quantification supported only on GHC 8.10+" #endif ravelType (FACxt cxt args) res = ForallT [] cxt (ravelType args res) ravelType (FAAnon t args) res = AppT (AppT ArrowT t) (ravelType args res) -- | Convert a 'FunArg's value into the list of 'Type's that it contains. -- For example, given this function type: -- -- @ -- forall k (a :: k). Proxy a -> forall b. Maybe b -- @ -- -- Then calling @funArgTys@ on the arguments would yield: -- -- @ -- [k, (a :: k), Proxy a, b, Maybe b] -- @ -- -- This is primarily used for the purposes of computing all of the type -- variables that appear in a 'FunArgs' value. funArgTys :: FunArgs -> [Type] funArgTys FANil = [] funArgTys (FAForalls tele args) = forallTelescopeTys tele ++ funArgTys args # if __GLASGOW_HASKELL__ >= 800 funArgTys (FACxt ctxt args) = ctxt ++ funArgTys args # else funArgTys (FACxt {}) = error "Constraints in kinds not supported prior to GHC 8.0" # endif funArgTys (FAAnon anon args) = anon : funArgTys args -- | Convert a 'ForallTelescope' value into the list of 'Type's that it -- contains. See the Haddocks for 'funArgTys' for an example of what this does. forallTelescopeTys :: ForallTelescope -> [Type] forallTelescopeTys (ForallVis tvbs) = bndrParams tvbs forallTelescopeTys (ForallInvis tvbs) = bndrParams tvbs #endif -- | Reconstruct an arrow 'Kind' from its argument and result kinds. ravelKind :: FunArgs -> Kind -> Kind #if MIN_VERSION_template_haskell(2,8,0) ravelKind = ravelType #else ravelKind FANil res = res ravelKind (FAAnon k args) res = ArrowK k (ravelKind args res) ravelKind (FAForalls {}) _res = error "TH doesn't support `forall`s in kinds prior to template-haskell-2.8.0.0" ravelKind (FACxt {}) _res = error "TH doesn't support contexts in kinds prior to template-haskell-2.8.0.0" #endif -- | Decompose a function 'Kind' into its arguments (the 'FunArgs') and its -- result type (the 'Kind). unravelKind :: Kind -> (FunArgs, Kind) #if MIN_VERSION_template_haskell(2,8,0) unravelKind = unravelType #else unravelKind (ArrowK k1 k2) = let (args, res) = unravelKind k2 in (FAAnon k1 args, res) unravelKind StarK = (FANil, StarK) #endif -- | @'filterVisFunArgsUpTo' xs args@ will split @args@ into 'VisFunArg's as -- many times as there are elements in @xs@, pairing up each entry in @xs@ with -- the corresponding 'VisFunArg' in the process. This will stop after the last -- entry in @xs@ has been paired up. -- -- For example, this: -- -- @ -- 'filterVisFunArgsUpTo' -- [Bool, True] -- [ FAForalls (ForallVis [j]) -- , FAAnon j -- , FAForalls (ForallInvis [k]) -- , FAAnon k -- ] -- @ -- -- Will yield: -- -- @ -- ( [(Bool, VisFADep j), (True, VisFAAnon j)] -- , [FAForalls (ForallInvis [k]), FAAnon k] -- ) -- @ -- -- This function assumes the precondition that there are at least as many -- visible function arguments in @args@ as there are elements in @xs@. If this -- is not the case, this function will raise an error. filterVisFunArgsUpTo :: forall a. [a] -> FunArgs -> ([(a, VisFunArg)], FunArgs) filterVisFunArgsUpTo = go_fun_args where go_fun_args :: [a] -> FunArgs -> ([(a, VisFunArg)], FunArgs) go_fun_args [] args = ([], args) go_fun_args (_:_) FANil = error "filterVisFunArgsUpTo.go_fun_args: Too few FunArgs" go_fun_args xs (FACxt _ args) = go_fun_args xs args go_fun_args (x:xs) (FAAnon t args) = let (xs', args') = go_fun_args xs args in ((x, VisFAAnon t):xs', args') go_fun_args xs (FAForalls tele args) = case tele of ForallVis tvbs -> go_vis_tvbs tvbs xs args ForallInvis _ -> go_fun_args xs args go_vis_tvbs :: [TyVarBndrUnit] -> [a] -> FunArgs -> ([(a, VisFunArg)], FunArgs) go_vis_tvbs [] xs args = go_fun_args xs args go_vis_tvbs (tvb:tvbs) (x:xs) args = let (xs', args') = go_vis_tvbs tvbs xs args in ((x, VisFADep tvb):xs', args') go_vis_tvbs tvbs [] args = ([], FAForalls (ForallVis tvbs) args) -- | @'unravelKindUpTo' xs k@ will split the function kind @k@ into its argument -- kinds @args@ and result kind @res@, and then it will call -- @'filterVisFunArgsUpTo' xs args@. The leftover arguments that were not split -- apart by 'filterVisFunArgsUpTo' are then raveled back into @res@. -- -- For example, this: -- -- @ -- 'filterVisFunArgsUpTo' -- [Bool, True] -- (forall j -> j -> forall k. k -> Type) -- @ -- -- Will yield: -- -- @ -- ( [(Bool, VisFADep j), (True, VisFAAnon j)] -- , forall k. k -> Type -- ) -- @ -- -- This function assumes the precondition that there are at least as many -- visible function arguments in @args@ as there are elements in @xs@. If this -- is not the case, this function will raise an error. unravelKindUpTo :: [a] -> Kind -> ([(a, VisFunArg)], Kind) unravelKindUpTo xs k = (xs', ravelKind args' res) where (args, res) = unravelKind k (xs', args') = filterVisFunArgsUpTo xs args -- | Resolve any infix type application in a type using the fixities that -- are currently available. Starting in `template-haskell-2.11` types could -- contain unresolved infix applications. resolveInfixT :: Type -> Q Type #if MIN_VERSION_template_haskell(2,11,0) resolveInfixT (ForallT vs cx t) = ForallT <$> traverse (traverseTVKind resolveInfixT) vs <*> mapM resolveInfixT cx <*> resolveInfixT t resolveInfixT (f `AppT` x) = resolveInfixT f `appT` resolveInfixT x resolveInfixT (ParensT t) = resolveInfixT t resolveInfixT (InfixT l o r) = conT o `appT` resolveInfixT l `appT` resolveInfixT r resolveInfixT (SigT t k) = SigT <$> resolveInfixT t <*> resolveInfixT k resolveInfixT t@UInfixT{} = resolveInfixT =<< resolveInfixT1 (gatherUInfixT t) # if MIN_VERSION_template_haskell(2,15,0) resolveInfixT (f `AppKindT` x) = appKindT (resolveInfixT f) (resolveInfixT x) resolveInfixT (ImplicitParamT n t) = implicitParamT n $ resolveInfixT t # endif # if MIN_VERSION_template_haskell(2,16,0) resolveInfixT (ForallVisT vs t) = ForallVisT <$> traverse (traverseTVKind resolveInfixT) vs <*> resolveInfixT t # endif # if MIN_VERSION_template_haskell(2,19,0) resolveInfixT (PromotedInfixT l o r) = promotedT o `appT` resolveInfixT l `appT` resolveInfixT r resolveInfixT t@PromotedUInfixT{} = resolveInfixT =<< resolveInfixT1 (gatherUInfixT t) # endif resolveInfixT t = return t gatherUInfixT :: Type -> InfixList gatherUInfixT (UInfixT l o r) = ilAppend (gatherUInfixT l) o False (gatherUInfixT r) # if MIN_VERSION_template_haskell(2,19,0) gatherUInfixT (PromotedUInfixT l o r) = ilAppend (gatherUInfixT l) o True (gatherUInfixT r) # endif gatherUInfixT t = ILNil t -- This can fail due to incompatible fixities resolveInfixT1 :: InfixList -> TypeQ resolveInfixT1 = go [] where go :: [(Type,Name,Bool,Fixity)] -> InfixList -> TypeQ go ts (ILNil u) = return (foldl (\acc (l,o,p,_) -> mkConT p o `AppT` l `AppT` acc) u ts) go ts (ILCons l o p r) = do ofx <- fromMaybe defaultFixity <$> reifyFixityCompat o let push = go ((l,o,p,ofx):ts) r case ts of (l1,o1,p1,o1fx):ts' -> case compareFixity o1fx ofx of Just True -> go ((mkConT p1 o1 `AppT` l1 `AppT` l, o, p, ofx):ts') r Just False -> push Nothing -> fail (precedenceError o1 o1fx o ofx) _ -> push mkConT :: Bool -> Name -> Type mkConT promoted = if promoted then PromotedT else ConT compareFixity :: Fixity -> Fixity -> Maybe Bool compareFixity (Fixity n1 InfixL) (Fixity n2 InfixL) = Just (n1 >= n2) compareFixity (Fixity n1 InfixR) (Fixity n2 InfixR) = Just (n1 > n2) compareFixity (Fixity n1 _ ) (Fixity n2 _ ) = case compare n1 n2 of GT -> Just True LT -> Just False EQ -> Nothing precedenceError :: Name -> Fixity -> Name -> Fixity -> String precedenceError o1 ofx1 o2 ofx2 = "Precedence parsing error: cannot mix ‘" ++ nameBase o1 ++ "’ [" ++ showFixity ofx1 ++ "] and ‘" ++ nameBase o2 ++ "’ [" ++ showFixity ofx2 ++ "] in the same infix type expression" data InfixList = ILCons Type -- The first argument to the type operator Name -- The name of the infix type operator Bool -- 'True' if this is a promoted infix data constructor, -- 'False' otherwise InfixList -- The rest of the infix applications to resolve | ILNil Type ilAppend :: InfixList -> Name -> Bool -> InfixList -> InfixList ilAppend (ILNil l) o p r = ILCons l o p r ilAppend (ILCons l1 o1 p1 r1) o p r = ILCons l1 o1 p1 (ilAppend r1 o p r) #else -- older template-haskell packages don't have UInfixT resolveInfixT = return #endif -- | Render a 'Fixity' as it would appear in Haskell source. -- -- Example: @infixl 5@ showFixity :: Fixity -> String showFixity (Fixity n d) = showFixityDirection d ++ " " ++ show n -- | Render a 'FixityDirection' like it would appear in Haskell source. -- -- Examples: @infixl@ @infixr@ @infix@ showFixityDirection :: FixityDirection -> String showFixityDirection InfixL = "infixl" showFixityDirection InfixR = "infixr" showFixityDirection InfixN = "infix" takeFieldNames :: [(Name,a,b)] -> [Name] takeFieldNames xs = [a | (a,_,_) <- xs] #if MIN_VERSION_template_haskell(2,11,0) takeFieldStrictness :: [(a,Bang,b)] -> [FieldStrictness] #else takeFieldStrictness :: [(a,Strict,b)] -> [FieldStrictness] #endif takeFieldStrictness xs = [normalizeStrictness a | (_,a,_) <- xs] takeFieldTypes :: [(a,b,Type)] -> [Type] takeFieldTypes xs = [a | (_,_,a) <- xs] conHasRecord :: Name -> ConstructorInfo -> Bool conHasRecord recName info = case constructorVariant info of NormalConstructor -> False InfixConstructor -> False RecordConstructor fields -> recName `elem` fields ------------------------------------------------------------------------ -- | 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 signature. (In -- contrast with being dependent upon the Ord instance for 'Name') quantifyType :: Type -> Type quantifyType t | null tvbs = t | ForallT tvbs' ctxt' t' <- t -- Collapse two consecutive foralls (#63) = ForallT (tvbs ++ tvbs') ctxt' t' | otherwise = ForallT tvbs [] t where tvbs = changeTVFlags SpecifiedSpec $ freeVariablesWellScoped [t] -- | Take a list of 'Type's, find their free variables, and sort them -- according to dependency order. -- -- As an example of how this function works, consider the following type: -- -- @ -- Proxy (a :: k) -- @ -- -- Calling 'freeVariables' on this type would yield @[a, k]@, since that is -- the order in which those variables appear in a left-to-right fashion. But -- this order does not preserve the fact that @k@ is the kind of @a@. Moreover, -- if you tried writing the type @forall a k. Proxy (a :: k)@, GHC would reject -- this, since GHC would demand that @k@ come before @a@. -- -- 'freeVariablesWellScoped' orders the free variables of a type in a way that -- preserves this dependency ordering. If one were to call -- 'freeVariablesWellScoped' on the type above, it would return -- @[k, (a :: k)]@. (This is why 'freeVariablesWellScoped' returns a list of -- 'TyVarBndr's instead of 'Name's, since it must make it explicit that @k@ -- is the kind of @a@.) -- -- 'freeVariablesWellScoped' guarantees the free variables returned will be -- ordered such that: -- -- 1. Whenever an explicit kind signature of the form @(A :: K)@ is -- encountered, the free variables of @K@ will always appear to the left of -- the free variables of @A@ in the returned result. -- -- 2. The constraint in (1) notwithstanding, free variables will appear in -- left-to-right order of their original appearance. -- -- On older GHCs, this takes measures to avoid returning explicitly bound -- kind variables, which was not possible before @TypeInType@. freeVariablesWellScoped :: [Type] -> [TyVarBndrUnit] freeVariablesWellScoped tys = let fvs :: [Name] fvs = freeVariables tys varKindSigs :: Map Name Kind varKindSigs = foldMap go_ty tys where go_ty :: Type -> Map Name Kind go_ty (ForallT tvbs ctxt t) = foldr (\tvb -> Map.delete (tvName tvb)) (foldMap go_pred ctxt `mappend` go_ty t) tvbs go_ty (AppT t1 t2) = go_ty t1 `mappend` go_ty t2 go_ty (SigT t k) = let kSigs = #if MIN_VERSION_template_haskell(2,8,0) go_ty k #else mempty #endif in case t of VarT n -> Map.insert n k kSigs _ -> go_ty t `mappend` kSigs #if MIN_VERSION_template_haskell(2,15,0) go_ty (AppKindT t k) = go_ty t `mappend` go_ty k go_ty (ImplicitParamT _ t) = go_ty t #endif #if MIN_VERSION_template_haskell(2,16,0) go_ty (ForallVisT tvbs t) = foldr (\tvb -> Map.delete (tvName tvb)) (go_ty t) tvbs #endif go_ty _ = mempty go_pred :: Pred -> Map Name Kind #if MIN_VERSION_template_haskell(2,10,0) go_pred = go_ty #else go_pred (ClassP _ ts) = foldMap go_ty ts go_pred (EqualP t1 t2) = go_ty t1 `mappend` go_ty t2 #endif -- | Do a topological sort on a list of tyvars, -- so that binders occur before occurrences -- E.g. given [ a::k, k::*, b::k ] -- it'll return a well-scoped list [ k::*, a::k, b::k ] -- -- This is a deterministic sorting operation -- (that is, doesn't depend on Uniques). -- -- It is also meant to be stable: that is, variables should not -- be reordered unnecessarily. scopedSort :: [Name] -> [Name] scopedSort = go [] [] go :: [Name] -- already sorted, in reverse order -> [Set Name] -- each set contains all the variables which must be placed -- before the tv corresponding to the set; they are accumulations -- of the fvs in the sorted tvs' kinds -- This list is in 1-to-1 correspondence with the sorted tyvars -- INVARIANT: -- all (\tl -> all (`isSubsetOf` head tl) (tail tl)) (tails fv_list) -- That is, each set in the list is a superset of all later sets. -> [Name] -- yet to be sorted -> [Name] go acc _fv_list [] = reverse acc go acc fv_list (tv:tvs) = go acc' fv_list' tvs where (acc', fv_list') = insert tv acc fv_list insert :: Name -- var to insert -> [Name] -- sorted list, in reverse order -> [Set Name] -- list of fvs, as above -> ([Name], [Set Name]) -- augmented lists insert tv [] [] = ([tv], [kindFVSet tv]) insert tv (a:as) (fvs:fvss) | tv `Set.member` fvs , (as', fvss') <- insert tv as fvss = (a:as', fvs `Set.union` fv_tv : fvss') | otherwise = (tv:a:as, fvs `Set.union` fv_tv : fvs : fvss) where fv_tv = kindFVSet tv -- lists not in correspondence insert _ _ _ = error "scopedSort" kindFVSet n = maybe Set.empty (Set.fromList . freeVariables) (Map.lookup n varKindSigs) ascribeWithKind n = maybe (plainTV n) (kindedTV n) (Map.lookup n varKindSigs) -- An annoying wrinkle: GHCs before 8.0 don't support explicitly -- quantifying kinds, so something like @forall k (a :: k)@ would be -- rejected. To work around this, we filter out any binders whose names -- also appear in a kind on old GHCs. isKindBinderOnOldGHCs #if __GLASGOW_HASKELL__ >= 800 = const False #else = (`elem` kindVars) where kindVars = freeVariables $ Map.elems varKindSigs #endif in map ascribeWithKind $ filter (not . isKindBinderOnOldGHCs) $ scopedSort fvs -- | Substitute all of the free variables in a type with fresh ones freshenFreeVariables :: Type -> Q Type freshenFreeVariables t = do let xs = [ (n, VarT <$> newName (nameBase n)) | n <- freeVariables t] subst <- T.sequence (Map.fromList xs) return (applySubstitution subst t) -- | Class for types that support type variable substitution. class TypeSubstitution a where -- | Apply a type variable substitution. applySubstitution :: Map Name Type -> a -> a -- | Compute the free type variables freeVariables :: a -> [Name] instance TypeSubstitution a => TypeSubstitution [a] where freeVariables = nub . concat . map freeVariables applySubstitution = fmap . applySubstitution instance TypeSubstitution Type where applySubstitution subst = go where go (ForallT tvs context t) = let (subst', tvs') = substTyVarBndrs subst tvs in ForallT tvs' (applySubstitution subst' context) (applySubstitution subst' t) go (AppT f x) = AppT (go f) (go x) go (SigT t k) = SigT (go t) (applySubstitution subst k) -- k could be Kind go (VarT v) = Map.findWithDefault (VarT v) v subst #if MIN_VERSION_template_haskell(2,11,0) go (InfixT l c r) = InfixT (go l) c (go r) go (UInfixT l c r) = UInfixT (go l) c (go r) go (ParensT t) = ParensT (go t) #endif #if MIN_VERSION_template_haskell(2,15,0) go (AppKindT t k) = AppKindT (go t) (go k) go (ImplicitParamT n t) = ImplicitParamT n (go t) #endif #if MIN_VERSION_template_haskell(2,16,0) go (ForallVisT tvs t) = let (subst', tvs') = substTyVarBndrs subst tvs in ForallVisT tvs' (applySubstitution subst' t) #endif #if MIN_VERSION_template_haskell(2,19,0) go (PromotedInfixT l c r) = PromotedInfixT (go l) c (go r) go (PromotedUInfixT l c r) = PromotedUInfixT (go l) c (go r) #endif go t = t subst_tvbs :: [TyVarBndr_ flag] -> (Map Name Type -> a) -> a subst_tvbs tvs k = k $ foldl' (flip Map.delete) subst (map tvName tvs) freeVariables t = case t of ForallT tvs context t' -> fvs_under_forall tvs (freeVariables context `union` freeVariables t') AppT f x -> freeVariables f `union` freeVariables x SigT t' k -> freeVariables t' `union` freeVariables k VarT v -> [v] #if MIN_VERSION_template_haskell(2,11,0) InfixT l _ r -> freeVariables l `union` freeVariables r UInfixT l _ r -> freeVariables l `union` freeVariables r ParensT t' -> freeVariables t' #endif #if MIN_VERSION_template_haskell(2,15,0) AppKindT t k -> freeVariables t `union` freeVariables k ImplicitParamT _ t -> freeVariables t #endif #if MIN_VERSION_template_haskell(2,16,0) ForallVisT tvs t' -> fvs_under_forall tvs (freeVariables t') #endif #if MIN_VERSION_template_haskell(2,19,0) PromotedInfixT l _ r -> freeVariables l `union` freeVariables r PromotedUInfixT l _ r -> freeVariables l `union` freeVariables r #endif _ -> [] where fvs_under_forall :: [TyVarBndr_ flag] -> [Name] -> [Name] fvs_under_forall tvs fvs = (freeVariables (map tvKind tvs) `union` fvs) \\ map tvName tvs instance TypeSubstitution ConstructorInfo where freeVariables ci = (freeVariables (map tvKind (constructorVars ci)) `union` freeVariables (constructorContext ci) `union` freeVariables (constructorFields ci)) \\ (tvName <$> constructorVars ci) applySubstitution subst ci = let subst' = foldl' (flip Map.delete) subst (map tvName (constructorVars ci)) in ci { constructorVars = map (mapTVKind (applySubstitution subst')) (constructorVars ci) , constructorContext = applySubstitution subst' (constructorContext ci) , constructorFields = applySubstitution subst' (constructorFields ci) } -- 'Pred' became a type synonym for 'Type' #if !MIN_VERSION_template_haskell(2,10,0) instance TypeSubstitution Pred where freeVariables (ClassP _ xs) = freeVariables xs freeVariables (EqualP x y) = freeVariables x `union` freeVariables y applySubstitution p (ClassP n xs) = ClassP n (applySubstitution p xs) applySubstitution p (EqualP x y) = EqualP (applySubstitution p x) (applySubstitution p y) #endif -- 'Kind' became a type synonym for 'Type'. Previously there were no kind variables #if !MIN_VERSION_template_haskell(2,8,0) instance TypeSubstitution Kind where freeVariables _ = [] applySubstitution _ k = k #endif -- | Substitutes into the kinds of type variable binders. This makes an effort -- to avoid capturing the 'TyVarBndr' names during substitution by -- alpha-renaming names if absolutely necessary. For a version of this function -- which does /not/ avoid capture, see 'substTyVarBndrKinds'. substTyVarBndrs :: Map Name Type -> [TyVarBndr_ flag] -> (Map Name Type, [TyVarBndr_ flag]) substTyVarBndrs = mapAccumL substTyVarBndr -- | The workhorse for 'substTyVarBndrs'. substTyVarBndr :: Map Name Type -> TyVarBndr_ flag -> (Map Name Type, TyVarBndr_ flag) substTyVarBndr subst tvb | tvbName `Map.member` subst = (Map.delete tvbName subst, mapTVKind (applySubstitution subst) tvb) | tvbName `Set.notMember` substRangeFVs = (subst, mapTVKind (applySubstitution subst) tvb) | otherwise = let tvbName' = evade tvbName in ( Map.insert tvbName (VarT tvbName') subst , mapTV (\_ -> tvbName') id (applySubstitution subst) tvb ) where tvbName :: Name tvbName = tvName tvb substRangeFVs :: Set Name substRangeFVs = Set.fromList $ freeVariables $ Map.elems subst evade :: Name -> Name evade n | n `Set.member` substRangeFVs = evade $ bump n | otherwise = n -- An improvement would be to try a variety of different characters instead -- of prepending the same character repeatedly. Let's wait to see if -- someone complains about this before making this more complicated, -- however. bump :: Name -> Name bump n = mkName $ 'f':nameBase n -- | Substitutes into the kinds of type variable binders. This is slightly more -- efficient than 'substTyVarBndrs', but at the expense of not avoiding -- capture. Only use this function in situations where you know that none of -- the 'TyVarBndr' names are contained in the range of the substitution. substTyVarBndrKinds :: Map Name Type -> [TyVarBndr_ flag] -> [TyVarBndr_ flag] substTyVarBndrKinds subst = map (substTyVarBndrKind subst) -- | The workhorse for 'substTyVarBndrKinds'. substTyVarBndrKind :: Map Name Type -> TyVarBndr_ flag -> TyVarBndr_ flag substTyVarBndrKind subst = mapTVKind (applySubstitution subst) ------------------------------------------------------------------------ combineSubstitutions :: Map Name Type -> Map Name Type -> Map Name Type combineSubstitutions x y = Map.union (fmap (applySubstitution y) x) y -- | Compute the type variable substitution that unifies a list of types, -- or fail in 'Q'. -- -- All infix issue should be resolved before using 'unifyTypes' -- -- Alpha equivalent quantified types are not unified. unifyTypes :: [Type] -> Q (Map Name Type) unifyTypes [] = return Map.empty unifyTypes (t:ts) = do t':ts' <- mapM resolveTypeSynonyms (t:ts) let aux sub u = do sub' <- unify' (applySubstitution sub t') (applySubstitution sub u) return (combineSubstitutions sub sub') case foldM aux Map.empty ts' of Right m -> return m Left (x,y) -> fail $ showString "Unable to unify types " . showsPrec 11 x . showString " and " . showsPrec 11 y $ "" unify' :: Type -> Type -> Either (Type,Type) (Map Name Type) unify' (VarT n) (VarT m) | n == m = pure Map.empty unify' (VarT n) t | n `elem` freeVariables t = Left (VarT n, t) | otherwise = Right (Map.singleton n t) unify' t (VarT n) | n `elem` freeVariables t = Left (VarT n, t) | otherwise = Right (Map.singleton n t) unify' (AppT f1 x1) (AppT f2 x2) = do sub1 <- unify' f1 f2 sub2 <- unify' (applySubstitution sub1 x1) (applySubstitution sub1 x2) Right (combineSubstitutions sub1 sub2) -- Doesn't unify kind signatures unify' (SigT t _) u = unify' t u unify' t (SigT u _) = unify' t u -- only non-recursive cases should remain at this point unify' t u | t == u = Right Map.empty | otherwise = Left (t,u) -- | Construct an equality constraint. The implementation of 'Pred' varies -- across versions of Template Haskell. equalPred :: Type -> Type -> Pred equalPred x y = #if MIN_VERSION_template_haskell(2,10,0) AppT (AppT EqualityT x) y #else EqualP x y #endif -- | Construct a typeclass constraint. The implementation of 'Pred' varies -- across versions of Template Haskell. classPred :: Name {- ^ class -} -> [Type] {- ^ parameters -} -> Pred classPred = #if MIN_VERSION_template_haskell(2,10,0) foldl AppT . ConT #else ClassP #endif -- | Match a 'Pred' representing an equality constraint. Returns -- arguments to the equality constraint if successful. asEqualPred :: Pred -> Maybe (Type,Type) #if MIN_VERSION_template_haskell(2,10,0) asEqualPred (EqualityT `AppT` x `AppT` y) = Just (x,y) asEqualPred (ConT eq `AppT` x `AppT` y) | eq == eqTypeName = Just (x,y) #else asEqualPred (EqualP x y) = Just (x,y) #endif asEqualPred _ = Nothing -- | Match a 'Pred' representing a class constraint. -- Returns the classname and parameters if successful. asClassPred :: Pred -> Maybe (Name, [Type]) #if MIN_VERSION_template_haskell(2,10,0) asClassPred t = case decomposeType t of ConT f :| xs | f /= eqTypeName -> Just (f,xs) _ -> Nothing #else asClassPred (ClassP f xs) = Just (f,xs) asClassPred _ = Nothing #endif ------------------------------------------------------------------------ -- | If we are working with a 'Dec' obtained via 'reify' (as opposed to one -- created from, say, [d| ... |] quotes), then we need to apply more hacks than -- we otherwise would to sanitize the 'Dec'. See #28. type IsReifiedDec = Bool isReified, isn'tReified :: IsReifiedDec isReified = True isn'tReified = False -- On old versions of GHC, reify would not give you kind signatures for -- GADT type variables of kind *. To work around this, we insert the kinds -- manually on any reified type variable binders without a signature. However, -- don't do this for quoted type variable binders (#84). giveDIVarsStarKinds :: IsReifiedDec -> DatatypeInfo -> DatatypeInfo giveDIVarsStarKinds isReified info = info { datatypeVars = map (giveTyVarBndrStarKind isReified) (datatypeVars info) , datatypeInstTypes = map (giveTypeStarKind isReified) (datatypeInstTypes info) } giveCIVarsStarKinds :: IsReifiedDec -> ConstructorInfo -> ConstructorInfo giveCIVarsStarKinds isReified info = info { constructorVars = map (giveTyVarBndrStarKind isReified) (constructorVars info) } giveTyVarBndrStarKind :: IsReifiedDec -> TyVarBndrUnit -> TyVarBndrUnit giveTyVarBndrStarKind isReified tvb | isReified = elimTV (\n -> kindedTV n starK) (\_ _ -> tvb) tvb | otherwise = tvb giveTypeStarKind :: IsReifiedDec -> Type -> Type giveTypeStarKind isReified t | isReified = case t of VarT n -> SigT t starK _ -> t | otherwise = t -- | Prior to GHC 8.2.1, reify was broken for data instances and newtype -- instances. This code attempts to detect the problem and repair it if -- possible. -- -- The particular problem is that the type variables used in the patterns -- while defining a data family instance do not completely match those -- used when defining the fields of the value constructors beyond the -- base names. This code attempts to recover the relationship between the -- type variables. -- -- It is possible, however, to generate these kinds of declarations by -- means other than reify. In these cases the name bases might not be -- unique and the declarations might be well formed. In such a case this -- code attempts to avoid altering the declaration. -- -- https://ghc.haskell.org/trac/ghc/ticket/13618 repair13618 :: DatatypeInfo -> Q DatatypeInfo repair13618 info = do s <- T.sequence (Map.fromList substList) return info { datatypeCons = applySubstitution s (datatypeCons info) } where used = freeVariables (datatypeCons info) bound = map tvName (datatypeVars info) free = used \\ bound substList = [ (u, substEntry u vs) | u <- free , let vs = [v | v <- bound, nameBase v == nameBase u] ] substEntry _ [v] = varT v substEntry u [] = fail ("Impossible free variable: " ++ show u) substEntry u _ = fail ("Ambiguous free variable: " ++ show u) ------------------------------------------------------------------------ -- | Backward compatible version of 'dataD' dataDCompat :: CxtQ {- ^ context -} -> Name {- ^ type constructor -} -> [TyVarBndrVis] {- ^ type parameters -} -> [ConQ] {- ^ constructor definitions -} -> [Name] {- ^ derived class names -} -> DecQ #if MIN_VERSION_template_haskell(2,12,0) dataDCompat c n ts cs ds = dataD c n ts Nothing cs (if null ds then [] else [derivClause Nothing (map conT ds)]) #elif MIN_VERSION_template_haskell(2,11,0) dataDCompat c n ts cs ds = dataD c n ts Nothing cs (return (map ConT ds)) #else dataDCompat = dataD #endif -- | Backward compatible version of 'newtypeD' newtypeDCompat :: CxtQ {- ^ context -} -> Name {- ^ type constructor -} -> [TyVarBndrVis] {- ^ type parameters -} -> ConQ {- ^ constructor definition -} -> [Name] {- ^ derived class names -} -> DecQ #if MIN_VERSION_template_haskell(2,12,0) newtypeDCompat c n ts cs ds = newtypeD c n ts Nothing cs (if null ds then [] else [derivClause Nothing (map conT ds)]) #elif MIN_VERSION_template_haskell(2,11,0) newtypeDCompat c n ts cs ds = newtypeD c n ts Nothing cs (return (map ConT ds)) #else newtypeDCompat = newtypeD #endif -- | Backward compatible version of 'tySynInstD' tySynInstDCompat :: Name {- ^ type family name -} -> Maybe [Q TyVarBndrUnit] {- ^ type variable binders -} -> [TypeQ] {- ^ instance parameters -} -> TypeQ {- ^ instance result -} -> DecQ #if MIN_VERSION_template_haskell(2,15,0) tySynInstDCompat n mtvbs ps r = TySynInstD <$> (TySynEqn <$> mapM sequence mtvbs <*> foldl' appT (conT n) ps <*> r) #elif MIN_VERSION_template_haskell(2,9,0) tySynInstDCompat n _ ps r = TySynInstD n <$> (TySynEqn <$> sequence ps <*> r) #else tySynInstDCompat n _ = tySynInstD n #endif -- | Backward compatible version of 'pragLineD'. Returns -- 'Nothing' if line pragmas are not suported. pragLineDCompat :: Int {- ^ line number -} -> String {- ^ file name -} -> Maybe DecQ #if MIN_VERSION_template_haskell(2,10,0) pragLineDCompat ln fn = Just (pragLineD ln fn) #else pragLineDCompat _ _ = Nothing #endif arrowKCompat :: Kind -> Kind -> Kind #if MIN_VERSION_template_haskell(2,8,0) arrowKCompat x y = arrowK `appK` x `appK` y #else arrowKCompat = arrowK #endif ------------------------------------------------------------------------ -- | Backwards compatibility wrapper for 'Fixity' lookup. -- -- In @template-haskell-2.11.0.0@ and later, the answer will always -- be 'Just' of a fixity. -- -- Before @template-haskell-2.11.0.0@ it was only possible to determine -- fixity information for variables, class methods, and data constructors. -- In this case for type operators the answer could be 'Nothing', which -- indicates that the answer is unavailable. reifyFixityCompat :: Name -> Q (Maybe Fixity) #if MIN_VERSION_template_haskell(2,11,0) reifyFixityCompat n = recover (return Nothing) ((`mplus` Just defaultFixity) <$> reifyFixity n) #else reifyFixityCompat n = recover (return Nothing) $ do info <- reify n return $! case info of ClassOpI _ _ _ fixity -> Just fixity DataConI _ _ _ fixity -> Just fixity VarI _ _ _ fixity -> Just fixity _ -> Nothing #endif -- | Call 'reify' and return @'Just' info@ if successful or 'Nothing' if -- reification failed. reifyMaybe :: Name -> Q (Maybe Info) reifyMaybe n = return Nothing `recover` fmap Just (reify n)