{- (c) The University of Glasgow 2006 (c) The GRASP/AQUA Project, Glasgow University, 1998 \section[DataCon]{@DataCon@: Data Constructors} -} {-# LANGUAGE CPP, DeriveDataTypeable #-} module DataCon ( -- * Main data types DataCon, DataConRep(..), SrcStrictness(..), SrcUnpackedness(..), HsSrcBang(..), HsImplBang(..), StrictnessMark(..), ConTag, -- ** Equality specs EqSpec, mkEqSpec, eqSpecTyVar, eqSpecType, eqSpecPair, eqSpecPreds, substEqSpec, filterEqSpec, -- ** Field labels FieldLbl(..), FieldLabel, FieldLabelString, -- ** Type construction mkDataCon, buildAlgTyCon, fIRST_TAG, -- ** Type deconstruction dataConRepType, dataConSig, dataConInstSig, dataConFullSig, dataConName, dataConIdentity, dataConTag, dataConTyCon, dataConOrigTyCon, dataConUserType, dataConUnivTyVars, dataConUnivTyBinders, dataConExTyVars, dataConExTyBinders, dataConAllTyVars, dataConEqSpec, dataConTheta, dataConStupidTheta, dataConInstArgTys, dataConOrigArgTys, dataConOrigResTy, dataConInstOrigArgTys, dataConRepArgTys, dataConFieldLabels, dataConFieldType, dataConSrcBangs, dataConSourceArity, dataConRepArity, dataConRepRepArity, dataConIsInfix, dataConWorkId, dataConWrapId, dataConWrapId_maybe, dataConImplicitTyThings, dataConRepStrictness, dataConImplBangs, dataConBoxer, splitDataProductType_maybe, -- ** Predicates on DataCons isNullarySrcDataCon, isNullaryRepDataCon, isTupleDataCon, isUnboxedTupleCon, isVanillaDataCon, classDataCon, dataConCannotMatch, isBanged, isMarkedStrict, eqHsBang, isSrcStrict, isSrcUnpacked, specialPromotedDc, isLegacyPromotableDataCon, isLegacyPromotableTyCon, -- ** Promotion related functions promoteDataCon ) where #include "HsVersions.h" import {-# SOURCE #-} MkId( DataConBoxer ) import Type import ForeignCall ( CType ) import Coercion import Unify import TyCon import FieldLabel import Class import Name import PrelNames import NameEnv import Var import Outputable import ListSetOps import Util import BasicTypes import FastString import Module import Binary import qualified Data.Data as Data import qualified Data.Typeable import Data.Char import Data.Word import Data.List( mapAccumL, find ) {- Data constructor representation ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Consider the following Haskell data type declaration data T = T !Int ![Int] Using the strictness annotations, GHC will represent this as data T = T Int# [Int] That is, the Int has been unboxed. Furthermore, the Haskell source construction T e1 e2 is translated to case e1 of { I# x -> case e2 of { r -> T x r }} That is, the first argument is unboxed, and the second is evaluated. Finally, pattern matching is translated too: case e of { T a b -> ... } becomes case e of { T a' b -> let a = I# a' in ... } To keep ourselves sane, we name the different versions of the data constructor differently, as follows. Note [Data Constructor Naming] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Each data constructor C has two, and possibly up to four, Names associated with it: OccName Name space Name of Notes --------------------------------------------------------------------------- The "data con itself" C DataName DataCon In dom( GlobalRdrEnv ) The "worker data con" C VarName Id The worker The "wrapper data con" $WC VarName Id The wrapper The "newtype coercion" :CoT TcClsName TyCon EVERY data constructor (incl for newtypes) has the former two (the data con itself, and its worker. But only some data constructors have a wrapper (see Note [The need for a wrapper]). Each of these three has a distinct Unique. The "data con itself" name appears in the output of the renamer, and names the Haskell-source data constructor. The type checker translates it into either the wrapper Id (if it exists) or worker Id (otherwise). The data con has one or two Ids associated with it: The "worker Id", is the actual data constructor. * Every data constructor (newtype or data type) has a worker * The worker is very like a primop, in that it has no binding. * For a *data* type, the worker *is* the data constructor; it has no unfolding * For a *newtype*, the worker has a compulsory unfolding which does a cast, e.g. newtype T = MkT Int The worker for MkT has unfolding \\(x:Int). x `cast` sym CoT Here CoT is the type constructor, witnessing the FC axiom axiom CoT : T = Int The "wrapper Id", \$WC, goes as follows * Its type is exactly what it looks like in the source program. * It is an ordinary function, and it gets a top-level binding like any other function. * The wrapper Id isn't generated for a data type if there is nothing for the wrapper to do. That is, if its defn would be \$wC = C Note [The need for a wrapper] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Why might the wrapper have anything to do? Two reasons: * Unboxing strict fields (with -funbox-strict-fields) data T = MkT !(Int,Int) \$wMkT :: (Int,Int) -> T \$wMkT (x,y) = MkT x y Notice that the worker has two fields where the wapper has just one. That is, the worker has type MkT :: Int -> Int -> T * Equality constraints for GADTs data T a where { MkT :: a -> T [a] } The worker gets a type with explicit equality constraints, thus: MkT :: forall a b. (a=[b]) => b -> T a The wrapper has the programmer-specified type: \$wMkT :: a -> T [a] \$wMkT a x = MkT [a] a [a] x The third argument is a coercion [a] :: [a]~[a] INVARIANT: the dictionary constructor for a class never has a wrapper. A note about the stupid context ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Data types can have a context: data (Eq a, Ord b) => T a b = T1 a b | T2 a and that makes the constructors have a context too (notice that T2's context is "thinned"): T1 :: (Eq a, Ord b) => a -> b -> T a b T2 :: (Eq a) => a -> T a b Furthermore, this context pops up when pattern matching (though GHC hasn't implemented this, but it is in H98, and I've fixed GHC so that it now does): f (T2 x) = x gets inferred type f :: Eq a => T a b -> a I say the context is "stupid" because the dictionaries passed are immediately discarded -- they do nothing and have no benefit. It's a flaw in the language. Up to now [March 2002] I have put this stupid context into the type of the "wrapper" constructors functions, T1 and T2, but that turned out to be jolly inconvenient for generics, and record update, and other functions that build values of type T (because they don't have suitable dictionaries available). So now I've taken the stupid context out. I simply deal with it separately in the type checker on occurrences of a constructor, either in an expression or in a pattern. [May 2003: actually I think this decision could evasily be reversed now, and probably should be. Generics could be disabled for types with a stupid context; record updates now (H98) needs the context too; etc. It's an unforced change, so I'm leaving it for now --- but it does seem odd that the wrapper doesn't include the stupid context.] [July 04] With the advent of generalised data types, it's less obvious what the "stupid context" is. Consider C :: forall a. Ord a => a -> a -> T (Foo a) Does the C constructor in Core contain the Ord dictionary? Yes, it must: f :: T b -> Ordering f = /\b. \x:T b. case x of C a (d:Ord a) (p:a) (q:a) -> compare d p q Note that (Foo a) might not be an instance of Ord. ************************************************************************ * * \subsection{Data constructors} * * ************************************************************************ -} -- | A data constructor -- -- - 'ApiAnnotation.AnnKeywordId' : 'ApiAnnotation.AnnOpen', -- 'ApiAnnotation.AnnClose','ApiAnnotation.AnnComma' -- For details on above see note [Api annotations] in ApiAnnotation data DataCon = MkData { dcName :: Name, -- This is the name of the *source data con* -- (see "Note [Data Constructor Naming]" above) dcUnique :: Unique, -- Cached from Name dcTag :: ConTag, -- ^ Tag, used for ordering 'DataCon's -- Running example: -- -- *** As declared by the user -- data T a where -- MkT :: forall x y. (x~y,Ord x) => x -> y -> T (x,y) -- *** As represented internally -- data T a where -- MkT :: forall a. forall x y. (a~(x,y),x~y,Ord x) => x -> y -> T a -- -- The next six fields express the type of the constructor, in pieces -- e.g. -- -- dcUnivTyVars = [a] -- dcExTyVars = [x,y] -- dcEqSpec = [a~(x,y)] -- dcOtherTheta = [x~y, Ord x] -- dcOrigArgTys = [x,y] -- dcRepTyCon = T dcVanilla :: Bool, -- True <=> This is a vanilla Haskell 98 data constructor -- Its type is of form -- forall a1..an . t1 -> ... tm -> T a1..an -- No existentials, no coercions, nothing. -- That is: dcExTyVars = dcEqSpec = dcOtherTheta = [] -- NB 1: newtypes always have a vanilla data con -- NB 2: a vanilla constructor can still be declared in GADT-style -- syntax, provided its type looks like the above. -- The declaration format is held in the TyCon (algTcGadtSyntax) dcUnivTyVars :: [TyVar], -- Universally-quantified type vars [a,b,c] -- INVARIANT: length matches arity of the dcRepTyCon --- result type of (rep) data con is exactly (T a b c) dcUnivTyBinders :: [TyBinder], -- Binders for universal tyvars. These will all -- be Named, and all be Invisible or Specified. -- Storing these separately from dcUnivTyVars -- is solely because we usually don't need the -- binders, and the extraction of the tyvars is -- unnecessary work. See also -- Note [TyBinders in DataCons] dcExTyVars :: [TyVar], -- Existentially-quantified type vars -- In general, the dcUnivTyVars are NOT NECESSARILY THE SAME AS THE TYVARS -- FOR THE PARENT TyCon. With GADTs the data con might not even have -- the same number of type variables. -- [This is a change (Oct05): previously, vanilla datacons guaranteed to -- have the same type variables as their parent TyCon, but that seems ugly.] dcExTyBinders :: [TyBinder], -- see dcUnivTyBinders -- INVARIANT: the UnivTyVars and ExTyVars all have distinct OccNames -- Reason: less confusing, and easier to generate IfaceSyn dcEqSpec :: [EqSpec], -- Equalities derived from the result type, -- _as written by the programmer_ -- This field allows us to move conveniently between the two ways -- of representing a GADT constructor's type: -- MkT :: forall a b. (a ~ [b]) => b -> T a -- MkT :: forall b. b -> T [b] -- Each equality is of the form (a ~ ty), where 'a' is one of -- the universally quantified type variables -- The next two fields give the type context of the data constructor -- (aside from the GADT constraints, -- which are given by the dcExpSpec) -- In GADT form, this is *exactly* what the programmer writes, even if -- the context constrains only universally quantified variables -- MkT :: forall a b. (a ~ b, Ord b) => a -> T a b dcOtherTheta :: ThetaType, -- The other constraints in the data con's type -- other than those in the dcEqSpec dcStupidTheta :: ThetaType, -- The context of the data type declaration -- data Eq a => T a = ... -- or, rather, a "thinned" version thereof -- "Thinned", because the Report says -- to eliminate any constraints that don't mention -- tyvars free in the arg types for this constructor -- -- INVARIANT: the free tyvars of dcStupidTheta are a subset of dcUnivTyVars -- Reason: dcStupidTeta is gotten by thinning the stupid theta from the tycon -- -- "Stupid", because the dictionaries aren't used for anything. -- Indeed, [as of March 02] they are no longer in the type of -- the wrapper Id, because that makes it harder to use the wrap-id -- to rebuild values after record selection or in generics. dcOrigArgTys :: [Type], -- Original argument types -- (before unboxing and flattening of strict fields) dcOrigResTy :: Type, -- Original result type, as seen by the user -- NB: for a data instance, the original user result type may -- differ from the DataCon's representation TyCon. Example -- data instance T [a] where MkT :: a -> T [a] -- The OrigResTy is T [a], but the dcRepTyCon might be :T123 -- Now the strictness annotations and field labels of the constructor dcSrcBangs :: [HsSrcBang], -- See Note [Bangs on data constructor arguments] -- -- The [HsSrcBang] as written by the programmer. -- -- Matches 1-1 with dcOrigArgTys -- Hence length = dataConSourceArity dataCon dcFields :: [FieldLabel], -- Field labels for this constructor, in the -- same order as the dcOrigArgTys; -- length = 0 (if not a record) or dataConSourceArity. -- The curried worker function that corresponds to the constructor: -- It doesn't have an unfolding; the code generator saturates these Ids -- and allocates a real constructor when it finds one. dcWorkId :: Id, -- Constructor representation dcRep :: DataConRep, -- Cached -- dcRepArity == length dataConRepArgTys dcRepArity :: Arity, -- dcSourceArity == length dcOrigArgTys dcSourceArity :: Arity, -- Result type of constructor is T t1..tn dcRepTyCon :: TyCon, -- Result tycon, T dcRepType :: Type, -- Type of the constructor -- forall a x y. (a~(x,y), x~y, Ord x) => -- x -> y -> T a -- (this is *not* of the constructor wrapper Id: -- see Note [Data con representation] below) -- Notice that the existential type parameters come *second*. -- Reason: in a case expression we may find: -- case (e :: T t) of -- MkT x y co1 co2 (d:Ord x) (v:r) (w:F s) -> ... -- It's convenient to apply the rep-type of MkT to 't', to get -- forall x y. (t~(x,y), x~y, Ord x) => x -> y -> T t -- and use that to check the pattern. Mind you, this is really only -- used in CoreLint. dcInfix :: Bool, -- True <=> declared infix -- Used for Template Haskell and 'deriving' only -- The actual fixity is stored elsewhere dcPromoted :: TyCon -- The promoted TyCon -- See Note [Promoted data constructors] in TyCon } deriving Data.Typeable.Typeable data DataConRep = NoDataConRep -- No wrapper | DCR { dcr_wrap_id :: Id -- Takes src args, unboxes/flattens, -- and constructs the representation , dcr_boxer :: DataConBoxer , dcr_arg_tys :: [Type] -- Final, representation argument types, -- after unboxing and flattening, -- and *including* all evidence args , dcr_stricts :: [StrictnessMark] -- 1-1 with dcr_arg_tys -- See also Note [Data-con worker strictness] in MkId.hs , dcr_bangs :: [HsImplBang] -- The actual decisions made (including failures) -- about the original arguments; 1-1 with orig_arg_tys -- See Note [Bangs on data constructor arguments] } -- Algebraic data types always have a worker, and -- may or may not have a wrapper, depending on whether -- the wrapper does anything. -- -- Data types have a worker with no unfolding -- Newtypes just have a worker, which has a compulsory unfolding (just a cast) -- _Neither_ the worker _nor_ the wrapper take the dcStupidTheta dicts as arguments -- The wrapper (if it exists) takes dcOrigArgTys as its arguments -- The worker takes dataConRepArgTys as its arguments -- If the worker is absent, dataConRepArgTys is the same as dcOrigArgTys -- The 'NoDataConRep' case is important -- Not only is this efficient, -- but it also ensures that the wrapper is replaced -- by the worker (because it *is* the worker) -- even when there are no args. E.g. in -- f (:) x -- the (:) *is* the worker. -- This is really important in rule matching, -- (We could match on the wrappers, -- but that makes it less likely that rules will match -- when we bring bits of unfoldings together.) ------------------------- -- | Bangs on data constructor arguments as the user wrote them in the -- source code. -- -- (HsSrcBang _ SrcUnpack SrcLazy) and -- (HsSrcBang _ SrcUnpack NoSrcStrict) (without StrictData) makes no sense, we -- emit a warning (in checkValidDataCon) and treat it like -- (HsSrcBang _ NoSrcUnpack SrcLazy) data HsSrcBang = HsSrcBang (Maybe SourceText) -- Note [Pragma source text] in BasicTypes SrcUnpackedness SrcStrictness deriving (Data.Data, Data.Typeable) -- | Bangs of data constructor arguments as generated by the compiler -- after consulting HsSrcBang, flags, etc. data HsImplBang = HsLazy -- ^ Lazy field | HsStrict -- ^ Strict but not unpacked field | HsUnpack (Maybe Coercion) -- ^ Strict and unpacked field -- co :: arg-ty ~ product-ty HsBang deriving (Data.Data, Data.Typeable) -- | What strictness annotation the user wrote data SrcStrictness = SrcLazy -- ^ Lazy, ie '~' | SrcStrict -- ^ Strict, ie '!' | NoSrcStrict -- ^ no strictness annotation deriving (Eq, Data.Data, Data.Typeable) -- | What unpackedness the user requested data SrcUnpackedness = SrcUnpack -- ^ {-# UNPACK #-} specified | SrcNoUnpack -- ^ {-# NOUNPACK #-} specified | NoSrcUnpack -- ^ no unpack pragma deriving (Eq, Data.Data, Data.Typeable) ------------------------- -- StrictnessMark is internal only, used to indicate strictness -- of the DataCon *worker* fields data StrictnessMark = MarkedStrict | NotMarkedStrict -- | An 'EqSpec' is a tyvar/type pair representing an equality made in -- rejigging a GADT constructor data EqSpec = EqSpec TyVar Type -- | Make an 'EqSpec' mkEqSpec :: TyVar -> Type -> EqSpec mkEqSpec tv ty = EqSpec tv ty eqSpecTyVar :: EqSpec -> TyVar eqSpecTyVar (EqSpec tv _) = tv eqSpecType :: EqSpec -> Type eqSpecType (EqSpec _ ty) = ty eqSpecPair :: EqSpec -> (TyVar, Type) eqSpecPair (EqSpec tv ty) = (tv, ty) eqSpecPreds :: [EqSpec] -> ThetaType eqSpecPreds spec = [ mkPrimEqPred (mkTyVarTy tv) ty | EqSpec tv ty <- spec ] -- | Substitute in an 'EqSpec'. Precondition: if the LHS of the EqSpec -- is mapped in the substitution, it is mapped to a type variable, not -- a full type. substEqSpec :: TCvSubst -> EqSpec -> EqSpec substEqSpec subst (EqSpec tv ty) = EqSpec tv' (substTy subst ty) where tv' = getTyVar "substEqSpec" (substTyVar subst tv) -- | Filter out any TyBinders mentioned in an EqSpec filterEqSpec :: [EqSpec] -> [TyBinder] -> [TyBinder] filterEqSpec eq_spec = filter not_in_eq_spec where not_in_eq_spec bndr = let var = binderVar "filterEqSpec" bndr in all (not . (== var) . eqSpecTyVar) eq_spec instance Outputable EqSpec where ppr (EqSpec tv ty) = ppr (tv, ty) {- Note [Bangs on data constructor arguments] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Consider data T = MkT !Int {-# UNPACK #-} !Int Bool When compiling the module, GHC will decide how to represent MkT, depending on the optimisation level, and settings of flags like -funbox-small-strict-fields. Terminology: * HsSrcBang: What the user wrote Constructors: HsSrcBang * HsImplBang: What GHC decided Constructors: HsLazy, HsStrict, HsUnpack * If T was defined in this module, MkT's dcSrcBangs field records the [HsSrcBang] of what the user wrote; in the example [ HsSrcBang _ NoSrcUnpack SrcStrict , HsSrcBang _ SrcUnpack SrcStrict , HsSrcBang _ NoSrcUnpack NoSrcStrictness] * However, if T was defined in an imported module, the importing module must follow the decisions made in the original module, regardless of the flag settings in the importing module. Also see Note [Bangs on imported data constructors] in MkId * The dcr_bangs field of the dcRep field records the [HsImplBang] If T was defined in this module, Without -O the dcr_bangs might be [HsStrict, HsStrict, HsLazy] With -O it might be [HsStrict, HsUnpack _, HsLazy] With -funbox-small-strict-fields it might be [HsUnpack, HsUnpack _, HsLazy] With -XStrictData it might be [HsStrict, HsUnpack _, HsStrict] Note [Data con representation] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The dcRepType field contains the type of the representation of a contructor This may differ from the type of the constructor *Id* (built by MkId.mkDataConId) for two reasons: a) the constructor Id may be overloaded, but the dictionary isn't stored e.g. data Eq a => T a = MkT a a b) the constructor may store an unboxed version of a strict field. Here's an example illustrating both: data Ord a => T a = MkT Int! a Here T :: Ord a => Int -> a -> T a but the rep type is Trep :: Int# -> a -> T a Actually, the unboxed part isn't implemented yet! ************************************************************************ * * \subsection{Instances} * * ************************************************************************ -} instance Eq DataCon where a == b = getUnique a == getUnique b a /= b = getUnique a /= getUnique b instance Ord DataCon where a <= b = getUnique a <= getUnique b a < b = getUnique a < getUnique b a >= b = getUnique a >= getUnique b a > b = getUnique a > getUnique b compare a b = getUnique a `compare` getUnique b instance Uniquable DataCon where getUnique = dcUnique instance NamedThing DataCon where getName = dcName instance Outputable DataCon where ppr con = ppr (dataConName con) instance OutputableBndr DataCon where pprInfixOcc con = pprInfixName (dataConName con) pprPrefixOcc con = pprPrefixName (dataConName con) instance Data.Data DataCon where -- don't traverse? toConstr _ = abstractConstr "DataCon" gunfold _ _ = error "gunfold" dataTypeOf _ = mkNoRepType "DataCon" instance Outputable HsSrcBang where ppr (HsSrcBang _ prag mark) = ppr prag <+> ppr mark instance Outputable HsImplBang where ppr HsLazy = text "Lazy" ppr (HsUnpack Nothing) = text "Unpacked" ppr (HsUnpack (Just co)) = text "Unpacked" <> parens (ppr co) ppr HsStrict = text "StrictNotUnpacked" instance Outputable SrcStrictness where ppr SrcLazy = char '~' ppr SrcStrict = char '!' ppr NoSrcStrict = empty instance Outputable SrcUnpackedness where ppr SrcUnpack = text "{-# UNPACK #-}" ppr SrcNoUnpack = text "{-# NOUNPACK #-}" ppr NoSrcUnpack = empty instance Outputable StrictnessMark where ppr MarkedStrict = text "!" ppr NotMarkedStrict = empty instance Binary SrcStrictness where put_ bh SrcLazy = putByte bh 0 put_ bh SrcStrict = putByte bh 1 put_ bh NoSrcStrict = putByte bh 2 get bh = do h <- getByte bh case h of 0 -> return SrcLazy 1 -> return SrcLazy _ -> return NoSrcStrict instance Binary SrcUnpackedness where put_ bh SrcNoUnpack = putByte bh 0 put_ bh SrcUnpack = putByte bh 1 put_ bh NoSrcUnpack = putByte bh 2 get bh = do h <- getByte bh case h of 0 -> return SrcNoUnpack 1 -> return SrcUnpack _ -> return NoSrcUnpack -- | Compare strictness annotations eqHsBang :: HsImplBang -> HsImplBang -> Bool eqHsBang HsLazy HsLazy = True eqHsBang HsStrict HsStrict = True eqHsBang (HsUnpack Nothing) (HsUnpack Nothing) = True eqHsBang (HsUnpack (Just c1)) (HsUnpack (Just c2)) = eqType (coercionType c1) (coercionType c2) eqHsBang _ _ = False isBanged :: HsImplBang -> Bool isBanged (HsUnpack {}) = True isBanged (HsStrict {}) = True isBanged HsLazy = False isSrcStrict :: SrcStrictness -> Bool isSrcStrict SrcStrict = True isSrcStrict _ = False isSrcUnpacked :: SrcUnpackedness -> Bool isSrcUnpacked SrcUnpack = True isSrcUnpacked _ = False isMarkedStrict :: StrictnessMark -> Bool isMarkedStrict NotMarkedStrict = False isMarkedStrict _ = True -- All others are strict {- ************************************************************************ * * \subsection{Construction} * * ************************************************************************ Note [TyBinders in DataCons] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ A DataCon needs to keep track of the visibility of its universals and existentials, so that visible type application can work properly. This is done by storing the universal and existential TyBinders, along with the TyVars. These TyBinders should all be Named and should all be Invisible or Specified; we don't have Visible or Anon type arguments. During construction of a DataCon, we often have the TyBinders of the parent TyCon. But those TyBinders are *different* than those of the DataCon. Here is an example: data Proxy a = P The TyCon has these TyBinders: [ Named (k :: *) Invisible, Anon k ] Note that Proxy's kind is forall k. k -> *. But the DataCon P should have (universal) TyBinders [ Named (k :: *) Invisible, Named (a :: k) Specified ] So we want to take the TyCon's TyBinders and the TyCon's TyVars and merge them, pulling variable names from the TyVars but visibilities from the TyBinders, perserving Invisible but changing Visible to Specified. (The `a` in Proxy is indeed Visible, but the `a` in P should be Specified.) This merging operation is done in buildDataCon. In contrast, the TyBinders passed to mkDataCon are the real TyBinders stored in the DataCon. Note that passing the TyVars into mkDataCon is redundant, but convenient for both caller and the function's implementation. In most places in GHC, it's just the TyVars that are needed, so that's what's returned from, say, dataConFullSig. -} -- | Build a new data constructor mkDataCon :: Name -> Bool -- ^ Is the constructor declared infix? -> TyConRepName -- ^ TyConRepName for the promoted TyCon -> [HsSrcBang] -- ^ Strictness/unpack annotations, from user -> [FieldLabel] -- ^ Field labels for the constructor, -- if it is a record, otherwise empty -> [TyVar] -> [TyBinder] -- ^ Universals. See Note [TyBinders in DataCons] -> [TyVar] -> [TyBinder] -- ^ Existentials. -- (These last two must be Named and Invisible/Specified) -> [EqSpec] -- ^ GADT equalities -> ThetaType -- ^ Theta-type occuring before the arguments proper -> [Type] -- ^ Original argument types -> Type -- ^ Original result type -> RuntimeRepInfo -- ^ See comments on 'TyCon.RuntimeRepInfo' -> TyCon -- ^ Representation type constructor -> ThetaType -- ^ The "stupid theta", context of the data -- declaration e.g. @data Eq a => T a ...@ -> Id -- ^ Worker Id -> DataConRep -- ^ Representation -> DataCon -- Can get the tag from the TyCon mkDataCon name declared_infix prom_info arg_stricts -- Must match orig_arg_tys 1-1 fields univ_tvs univ_bndrs ex_tvs ex_bndrs eq_spec theta orig_arg_tys orig_res_ty rep_info rep_tycon stupid_theta work_id rep -- Warning: mkDataCon is not a good place to check invariants. -- If the programmer writes the wrong result type in the decl, thus: -- data T a where { MkT :: S } -- then it's possible that the univ_tvs may hit an assertion failure -- if you pull on univ_tvs. This case is checked by checkValidDataCon, -- so the error is detected properly... it's just that asaertions here -- are a little dodgy. = con where is_vanilla = null ex_tvs && null eq_spec && null theta con = MkData {dcName = name, dcUnique = nameUnique name, dcVanilla = is_vanilla, dcInfix = declared_infix, dcUnivTyVars = univ_tvs, dcUnivTyBinders = univ_bndrs, dcExTyVars = ex_tvs, dcExTyBinders = ex_bndrs, dcEqSpec = eq_spec, dcOtherTheta = theta, dcStupidTheta = stupid_theta, dcOrigArgTys = orig_arg_tys, dcOrigResTy = orig_res_ty, dcRepTyCon = rep_tycon, dcSrcBangs = arg_stricts, dcFields = fields, dcTag = tag, dcRepType = rep_ty, dcWorkId = work_id, dcRep = rep, dcSourceArity = length orig_arg_tys, dcRepArity = length rep_arg_tys, dcPromoted = promoted } -- The 'arg_stricts' passed to mkDataCon are simply those for the -- source-language arguments. We add extra ones for the -- dictionary arguments right here. tag = assoc "mkDataCon" (tyConDataCons rep_tycon `zip` [fIRST_TAG..]) con rep_arg_tys = dataConRepArgTys con rep_ty = mkForAllTys univ_bndrs $ mkForAllTys ex_bndrs $ mkFunTys rep_arg_tys $ mkTyConApp rep_tycon (mkTyVarTys univ_tvs) -- See Note [Promoted data constructors] in TyCon prom_binders = filterEqSpec eq_spec univ_bndrs ++ ex_bndrs ++ map mkAnonBinder theta ++ map mkAnonBinder orig_arg_tys prom_res_kind = orig_res_ty promoted = mkPromotedDataCon con name prom_info prom_binders prom_res_kind roles rep_info roles = map (const Nominal) (univ_tvs ++ ex_tvs) ++ map (const Representational) orig_arg_tys -- | The 'Name' of the 'DataCon', giving it a unique, rooted identification dataConName :: DataCon -> Name dataConName = dcName -- | The tag used for ordering 'DataCon's dataConTag :: DataCon -> ConTag dataConTag = dcTag -- | The type constructor that we are building via this data constructor dataConTyCon :: DataCon -> TyCon dataConTyCon = dcRepTyCon -- | The original type constructor used in the definition of this data -- constructor. In case of a data family instance, that will be the family -- type constructor. dataConOrigTyCon :: DataCon -> TyCon dataConOrigTyCon dc | Just (tc, _) <- tyConFamInst_maybe (dcRepTyCon dc) = tc | otherwise = dcRepTyCon dc -- | The representation type of the data constructor, i.e. the sort -- type that will represent values of this type at runtime dataConRepType :: DataCon -> Type dataConRepType = dcRepType -- | Should the 'DataCon' be presented infix? dataConIsInfix :: DataCon -> Bool dataConIsInfix = dcInfix -- | The universally-quantified type variables of the constructor dataConUnivTyVars :: DataCon -> [TyVar] dataConUnivTyVars = dcUnivTyVars -- | 'TyBinder's for the universally-quantified type variables dataConUnivTyBinders :: DataCon -> [TyBinder] dataConUnivTyBinders = dcUnivTyBinders -- | The existentially-quantified type variables of the constructor dataConExTyVars :: DataCon -> [TyVar] dataConExTyVars = dcExTyVars -- | 'TyBinder's for the existentially-quantified type variables dataConExTyBinders :: DataCon -> [TyBinder] dataConExTyBinders = dcExTyBinders -- | Both the universal and existentiatial type variables of the constructor dataConAllTyVars :: DataCon -> [TyVar] dataConAllTyVars (MkData { dcUnivTyVars = univ_tvs, dcExTyVars = ex_tvs }) = univ_tvs ++ ex_tvs -- | Equalities derived from the result type of the data constructor, as written -- by the programmer in any GADT declaration. This includes *all* GADT-like -- equalities, including those written in by hand by the programmer. dataConEqSpec :: DataCon -> [EqSpec] dataConEqSpec (MkData { dcEqSpec = eq_spec, dcOtherTheta = theta }) = eq_spec ++ [ spec -- heterogeneous equality | Just (tc, [_k1, _k2, ty1, ty2]) <- map splitTyConApp_maybe theta , tc `hasKey` heqTyConKey , spec <- case (getTyVar_maybe ty1, getTyVar_maybe ty2) of (Just tv1, _) -> [mkEqSpec tv1 ty2] (_, Just tv2) -> [mkEqSpec tv2 ty1] _ -> [] ] ++ [ spec -- homogeneous equality | Just (tc, [_k, ty1, ty2]) <- map splitTyConApp_maybe theta , tc `hasKey` eqTyConKey , spec <- case (getTyVar_maybe ty1, getTyVar_maybe ty2) of (Just tv1, _) -> [mkEqSpec tv1 ty2] (_, Just tv2) -> [mkEqSpec tv2 ty1] _ -> [] ] -- | The *full* constraints on the constructor type. dataConTheta :: DataCon -> ThetaType dataConTheta (MkData { dcEqSpec = eq_spec, dcOtherTheta = theta }) = eqSpecPreds eq_spec ++ theta -- | Get the Id of the 'DataCon' worker: a function that is the "actual" -- constructor and has no top level binding in the program. The type may -- be different from the obvious one written in the source program. Panics -- if there is no such 'Id' for this 'DataCon' dataConWorkId :: DataCon -> Id dataConWorkId dc = dcWorkId dc -- | Get the Id of the 'DataCon' wrapper: a function that wraps the "actual" -- constructor so it has the type visible in the source program: c.f. 'dataConWorkId'. -- Returns Nothing if there is no wrapper, which occurs for an algebraic data constructor -- and also for a newtype (whose constructor is inlined compulsorily) dataConWrapId_maybe :: DataCon -> Maybe Id dataConWrapId_maybe dc = case dcRep dc of NoDataConRep -> Nothing DCR { dcr_wrap_id = wrap_id } -> Just wrap_id -- | Returns an Id which looks like the Haskell-source constructor by using -- the wrapper if it exists (see 'dataConWrapId_maybe') and failing over to -- the worker (see 'dataConWorkId') dataConWrapId :: DataCon -> Id dataConWrapId dc = case dcRep dc of NoDataConRep-> dcWorkId dc -- worker=wrapper DCR { dcr_wrap_id = wrap_id } -> wrap_id -- | Find all the 'Id's implicitly brought into scope by the data constructor. Currently, -- the union of the 'dataConWorkId' and the 'dataConWrapId' dataConImplicitTyThings :: DataCon -> [TyThing] dataConImplicitTyThings (MkData { dcWorkId = work, dcRep = rep }) = [AnId work] ++ wrap_ids where wrap_ids = case rep of NoDataConRep -> [] DCR { dcr_wrap_id = wrap } -> [AnId wrap] -- | The labels for the fields of this particular 'DataCon' dataConFieldLabels :: DataCon -> [FieldLabel] dataConFieldLabels = dcFields -- | Extract the type for any given labelled field of the 'DataCon' dataConFieldType :: DataCon -> FieldLabelString -> Type dataConFieldType con label = case find ((== label) . flLabel . fst) (dcFields con `zip` dcOrigArgTys con) of Just (_, ty) -> ty Nothing -> pprPanic "dataConFieldType" (ppr con <+> ppr label) -- | Strictness/unpack annotations, from user; or, for imported -- DataCons, from the interface file -- The list is in one-to-one correspondence with the arity of the 'DataCon' dataConSrcBangs :: DataCon -> [HsSrcBang] dataConSrcBangs = dcSrcBangs -- | Source-level arity of the data constructor dataConSourceArity :: DataCon -> Arity dataConSourceArity (MkData { dcSourceArity = arity }) = arity -- | Gives the number of actual fields in the /representation/ of the -- data constructor. This may be more than appear in the source code; -- the extra ones are the existentially quantified dictionaries dataConRepArity :: DataCon -> Arity dataConRepArity (MkData { dcRepArity = arity }) = arity -- | The number of fields in the /representation/ of the constructor -- AFTER taking into account the unpacking of any unboxed tuple fields dataConRepRepArity :: DataCon -> RepArity dataConRepRepArity dc = typeRepArity (dataConRepArity dc) (dataConRepType dc) -- | Return whether there are any argument types for this 'DataCon's original source type isNullarySrcDataCon :: DataCon -> Bool isNullarySrcDataCon dc = null (dcOrigArgTys dc) -- | Return whether there are any argument types for this 'DataCon's runtime representation type isNullaryRepDataCon :: DataCon -> Bool isNullaryRepDataCon dc = dataConRepArity dc == 0 dataConRepStrictness :: DataCon -> [StrictnessMark] -- ^ Give the demands on the arguments of a -- Core constructor application (Con dc args) dataConRepStrictness dc = case dcRep dc of NoDataConRep -> [NotMarkedStrict | _ <- dataConRepArgTys dc] DCR { dcr_stricts = strs } -> strs dataConImplBangs :: DataCon -> [HsImplBang] -- The implementation decisions about the strictness/unpack of each -- source program argument to the data constructor dataConImplBangs dc = case dcRep dc of NoDataConRep -> replicate (dcSourceArity dc) HsLazy DCR { dcr_bangs = bangs } -> bangs dataConBoxer :: DataCon -> Maybe DataConBoxer dataConBoxer (MkData { dcRep = DCR { dcr_boxer = boxer } }) = Just boxer dataConBoxer _ = Nothing -- | The \"signature\" of the 'DataCon' returns, in order: -- -- 1) The result of 'dataConAllTyVars', -- -- 2) All the 'ThetaType's relating to the 'DataCon' (coercion, dictionary, implicit -- parameter - whatever) -- -- 3) The type arguments to the constructor -- -- 4) The /original/ result type of the 'DataCon' dataConSig :: DataCon -> ([TyVar], ThetaType, [Type], Type) dataConSig con@(MkData {dcUnivTyVars = univ_tvs, dcExTyVars = ex_tvs, dcOrigArgTys = arg_tys, dcOrigResTy = res_ty}) = (univ_tvs ++ ex_tvs, dataConTheta con, arg_tys, res_ty) dataConInstSig :: DataCon -> [Type] -- Instantiate the *universal* tyvars with these types -> ([TyVar], ThetaType, [Type]) -- Return instantiated existentials -- theta and arg tys -- ^ Instantantiate the universal tyvars of a data con, -- returning the instantiated existentials, constraints, and args dataConInstSig (MkData { dcUnivTyVars = univ_tvs, dcExTyVars = ex_tvs , dcEqSpec = eq_spec, dcOtherTheta = theta , dcOrigArgTys = arg_tys }) univ_tys = (ex_tvs' , substTheta subst (eqSpecPreds eq_spec ++ theta) , substTys subst arg_tys) where univ_subst = zipTvSubst univ_tvs univ_tys (subst, ex_tvs') = mapAccumL Type.substTyVarBndr univ_subst ex_tvs -- | The \"full signature\" of the 'DataCon' returns, in order: -- -- 1) The result of 'dataConUnivTyVars' -- -- 2) The result of 'dataConExTyVars' -- -- 3) The GADT equalities -- -- 4) The result of 'dataConDictTheta' -- -- 5) The original argument types to the 'DataCon' (i.e. before -- any change of the representation of the type) -- -- 6) The original result type of the 'DataCon' dataConFullSig :: DataCon -> ([TyVar], [TyVar], [EqSpec], ThetaType, [Type], Type) dataConFullSig (MkData {dcUnivTyVars = univ_tvs, dcExTyVars = ex_tvs, dcEqSpec = eq_spec, dcOtherTheta = theta, dcOrigArgTys = arg_tys, dcOrigResTy = res_ty}) = (univ_tvs, ex_tvs, eq_spec, theta, arg_tys, res_ty) dataConOrigResTy :: DataCon -> Type dataConOrigResTy dc = dcOrigResTy dc -- | The \"stupid theta\" of the 'DataCon', such as @data Eq a@ in: -- -- > data Eq a => T a = ... dataConStupidTheta :: DataCon -> ThetaType dataConStupidTheta dc = dcStupidTheta dc dataConUserType :: DataCon -> Type -- ^ The user-declared type of the data constructor -- in the nice-to-read form: -- -- > T :: forall a b. a -> b -> T [a] -- -- rather than: -- -- > T :: forall a c. forall b. (c~[a]) => a -> b -> T c -- -- NB: If the constructor is part of a data instance, the result type -- mentions the family tycon, not the internal one. dataConUserType (MkData { dcUnivTyBinders = univ_bndrs, dcExTyBinders = ex_bndrs, dcEqSpec = eq_spec, dcOtherTheta = theta, dcOrigArgTys = arg_tys, dcOrigResTy = res_ty }) = mkForAllTys (filterEqSpec eq_spec univ_bndrs) $ mkForAllTys ex_bndrs $ mkFunTys theta $ mkFunTys arg_tys $ res_ty where -- | Finds the instantiated types of the arguments required to construct a 'DataCon' representation -- NB: these INCLUDE any dictionary args -- but EXCLUDE the data-declaration context, which is discarded -- It's all post-flattening etc; this is a representation type dataConInstArgTys :: DataCon -- ^ A datacon with no existentials or equality constraints -- However, it can have a dcTheta (notably it can be a -- class dictionary, with superclasses) -> [Type] -- ^ Instantiated at these types -> [Type] dataConInstArgTys dc@(MkData {dcUnivTyVars = univ_tvs, dcExTyVars = ex_tvs}) inst_tys = ASSERT2( length univ_tvs == length inst_tys , text "dataConInstArgTys" <+> ppr dc $$ ppr univ_tvs $$ ppr inst_tys) ASSERT2( null ex_tvs, ppr dc ) map (substTyWith univ_tvs inst_tys) (dataConRepArgTys dc) -- | Returns just the instantiated /value/ argument types of a 'DataCon', -- (excluding dictionary args) dataConInstOrigArgTys :: DataCon -- Works for any DataCon -> [Type] -- Includes existential tyvar args, but NOT -- equality constraints or dicts -> [Type] -- For vanilla datacons, it's all quite straightforward -- But for the call in MatchCon, we really do want just the value args dataConInstOrigArgTys dc@(MkData {dcOrigArgTys = arg_tys, dcUnivTyVars = univ_tvs, dcExTyVars = ex_tvs}) inst_tys = ASSERT2( length tyvars == length inst_tys , text "dataConInstOrigArgTys" <+> ppr dc $$ ppr tyvars $$ ppr inst_tys ) map (substTyWith tyvars inst_tys) arg_tys where tyvars = univ_tvs ++ ex_tvs -- | Returns the argument types of the wrapper, excluding all dictionary arguments -- and without substituting for any type variables dataConOrigArgTys :: DataCon -> [Type] dataConOrigArgTys dc = dcOrigArgTys dc -- | Returns the arg types of the worker, including *all* -- evidence, after any flattening has been done and without substituting for -- any type variables dataConRepArgTys :: DataCon -> [Type] dataConRepArgTys (MkData { dcRep = rep , dcEqSpec = eq_spec , dcOtherTheta = theta , dcOrigArgTys = orig_arg_tys }) = case rep of NoDataConRep -> ASSERT( null eq_spec ) theta ++ orig_arg_tys DCR { dcr_arg_tys = arg_tys } -> arg_tys -- | The string @package:module.name@ identifying a constructor, which is attached -- to its info table and used by the GHCi debugger and the heap profiler dataConIdentity :: DataCon -> [Word8] -- We want this string to be UTF-8, so we get the bytes directly from the FastStrings. dataConIdentity dc = bytesFS (unitIdFS (moduleUnitId mod)) ++ fromIntegral (ord ':') : bytesFS (moduleNameFS (moduleName mod)) ++ fromIntegral (ord '.') : bytesFS (occNameFS (nameOccName name)) where name = dataConName dc mod = ASSERT( isExternalName name ) nameModule name isTupleDataCon :: DataCon -> Bool isTupleDataCon (MkData {dcRepTyCon = tc}) = isTupleTyCon tc isUnboxedTupleCon :: DataCon -> Bool isUnboxedTupleCon (MkData {dcRepTyCon = tc}) = isUnboxedTupleTyCon tc -- | Vanilla 'DataCon's are those that are nice boring Haskell 98 constructors isVanillaDataCon :: DataCon -> Bool isVanillaDataCon dc = dcVanilla dc -- | Should this DataCon be allowed in a type even without -XDataKinds? -- Currently, only Lifted & Unlifted specialPromotedDc :: DataCon -> Bool specialPromotedDc = isKindTyCon . dataConTyCon -- | Was this datacon promotable before GHC 8.0? That is, is it promotable -- without -XTypeInType isLegacyPromotableDataCon :: DataCon -> Bool isLegacyPromotableDataCon dc = null (dataConEqSpec dc) -- no GADTs && null (dataConTheta dc) -- no context && not (isFamInstTyCon (dataConTyCon dc)) -- no data instance constructors && all isLegacyPromotableTyCon (nameEnvElts $ tyConsOfType (dataConUserType dc)) -- | Was this tycon promotable before GHC 8.0? That is, is it promotable -- without -XTypeInType isLegacyPromotableTyCon :: TyCon -> Bool isLegacyPromotableTyCon tc = isVanillaAlgTyCon tc || -- This returns True more often than it should, but it's quite painful -- to make this fully accurate. And no harm is caused; we just don't -- require -XTypeInType every time we need to. (We'll always require -- -XDataKinds, though, so there's no standards-compliance issue.) isFunTyCon tc || isKindTyCon tc classDataCon :: Class -> DataCon classDataCon clas = case tyConDataCons (classTyCon clas) of (dict_constr:no_more) -> ASSERT( null no_more ) dict_constr [] -> panic "classDataCon" dataConCannotMatch :: [Type] -> DataCon -> Bool -- Returns True iff the data con *definitely cannot* match a -- scrutinee of type (T tys) -- where T is the dcRepTyCon for the data con dataConCannotMatch tys con | null inst_theta = False -- Common | all isTyVarTy tys = False -- Also common | otherwise = typesCantMatch (concatMap predEqs inst_theta) where (_, inst_theta, _) = dataConInstSig con tys -- TODO: could gather equalities from superclasses too predEqs pred = case classifyPredType pred of EqPred NomEq ty1 ty2 -> [(ty1, ty2)] ClassPred eq [_, ty1, ty2] | eq `hasKey` eqTyConKey -> [(ty1, ty2)] _ -> [] {- %************************************************************************ %* * Promoting of data types to the kind level * * ************************************************************************ -} promoteDataCon :: DataCon -> TyCon promoteDataCon (MkData { dcPromoted = tc }) = tc {- ************************************************************************ * * \subsection{Splitting products} * * ************************************************************************ -} -- | Extract the type constructor, type argument, data constructor and it's -- /representation/ argument types from a type if it is a product type. -- -- Precisely, we return @Just@ for any type that is all of: -- -- * Concrete (i.e. constructors visible) -- -- * Single-constructor -- -- * Not existentially quantified -- -- Whether the type is a @data@ type or a @newtype@ splitDataProductType_maybe :: Type -- ^ A product type, perhaps -> Maybe (TyCon, -- The type constructor [Type], -- Type args of the tycon DataCon, -- The data constructor [Type]) -- Its /representation/ arg types -- Rejecting existentials is conservative. Maybe some things -- could be made to work with them, but I'm not going to sweat -- it through till someone finds it's important. splitDataProductType_maybe ty | Just (tycon, ty_args) <- splitTyConApp_maybe ty , Just con <- isDataProductTyCon_maybe tycon = Just (tycon, ty_args, con, dataConInstArgTys con ty_args) | otherwise = Nothing {- ************************************************************************ * * Building an algebraic data type * * ************************************************************************ buildAlgTyCon is here because it is called from TysWiredIn, which can depend on this module, but not on BuildTyCl. -} buildAlgTyCon :: Name -> [TyVar] -- ^ Kind variables and type variables -> [Role] -> Maybe CType -> ThetaType -- ^ Stupid theta -> AlgTyConRhs -> RecFlag -> Bool -- ^ True <=> was declared in GADT syntax -> AlgTyConFlav -> TyCon buildAlgTyCon tc_name ktvs roles cType stupid_theta rhs is_rec gadt_syn parent = mkAlgTyCon tc_name binders liftedTypeKind ktvs roles cType stupid_theta rhs parent is_rec gadt_syn where binders = mkTyBindersPreferAnon ktvs liftedTypeKind