%
+% (c) The University of Glasgow 2006
% (c) The GRASP/AQUA Project, Glasgow University, 1998
%
\section[DataCon]{@DataCon@: Data Constructors}
\begin{code}
module DataCon (
+ -- * Main data types
DataCon, DataConIds(..),
- ConTag, fIRST_TAG,
- mkDataCon,
- dataConRepType, dataConSig, dataConName, dataConTag, dataConTyCon,
- dataConTyVars, dataConResTys,
- dataConStupidTheta,
- dataConInstArgTys, dataConOrigArgTys, dataConInstResTy,
+ ConTag,
+
+ -- ** Type construction
+ mkDataCon, fIRST_TAG,
+
+ -- ** Type deconstruction
+ dataConRepType, dataConSig, dataConFullSig,
+ dataConName, dataConIdentity, dataConTag, dataConTyCon,
+ dataConOrigTyCon, dataConUserType,
+ dataConUnivTyVars, dataConExTyVars, dataConAllTyVars,
+ dataConEqSpec, eqSpecPreds, dataConTheta,
+ dataConStupidTheta,
+ dataConInstArgTys, dataConOrigArgTys, dataConOrigResTy,
dataConInstOrigArgTys, dataConRepArgTys,
dataConFieldLabels, dataConFieldType,
dataConStrictMarks, dataConExStricts,
dataConIsInfix,
dataConWorkId, dataConWrapId, dataConWrapId_maybe, dataConImplicitIds,
dataConRepStrictness,
+
+ -- ** Predicates on DataCons
isNullarySrcDataCon, isNullaryRepDataCon, isTupleCon, isUnboxedTupleCon,
- isVanillaDataCon, classDataCon,
+ isVanillaDataCon, classDataCon, dataConCannotMatch,
- splitProductType_maybe, splitProductType,
+ -- * Splitting product types
+ splitProductType_maybe, splitProductType, deepSplitProductType,
+ deepSplitProductType_maybe
) where
#include "HsVersions.h"
-import Type ( Type, ThetaType, substTyWith, substTy, zipOpenTvSubst,
- mkForAllTys, mkFunTys, mkTyConApp,
- splitTyConApp_maybe,
- mkPredTys, isStrictPred, pprType
- )
-import TyCon ( TyCon, FieldLabel, tyConDataCons,
- isProductTyCon, isTupleTyCon, isUnboxedTupleTyCon )
-import Class ( Class, classTyCon )
-import Name ( Name, NamedThing(..), nameUnique )
-import Var ( TyVar, Id )
-import BasicTypes ( Arity, StrictnessMark(..) )
+import Type
+import Unify
+import Coercion
+import TyCon
+import Class
+import Name
+import Var
+import BasicTypes
import Outputable
-import Unique ( Unique, Uniquable(..) )
-import ListSetOps ( assoc )
-import Util ( zipEqual, zipWithEqual )
-import Maybes ( expectJust )
+import Unique
+import ListSetOps
+import Util
+import FastString
+import Module
+
+import qualified Data.Data as Data
+import Data.Char
+import Data.Word
\end{code}
Note [Data Constructor Naming]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-Each data constructor C has two, and possibly three, Names associated with it:
-
- OccName Name space Used for
- ---------------------------------------------------------------------------
- * The "source data con" C DataName The DataCon itself
- * The "real data con" C VarName Its worker Id
- * The "wrapper data con" $WC VarName Wrapper Id (optional)
-
-Each of these three has a distinct Unique. The "source data con" name
+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.
- Its type may be different to the Haskell source constructor
- because:
- - useless dict args are dropped
- - strict args may be flattened
- The worker is very like a primop, in that it has no binding.
+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
- Newtypes have no worker Id
+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
- The "wrapper Id", $WC, whose 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.
+* Equality constraints for GADTs
+ data T a where { MkT :: a -> T [a] }
- The wrapper Id isn't generated for a data type if the worker
- and wrapper are identical. It's always generated for a newtype.
+ 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 coerion
+ [a] :: [a]~[a]
+
+INVARIANT: the dictionary constructor for a class
+ never has a wrapper.
A note about the stupid context
%************************************************************************
\begin{code}
+-- | A data constructor
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,
+ dcTag :: ConTag, -- ^ Tag, used for ordering 'DataCon's
-- Running example:
--
- -- data Eq a => T a = forall b. Ord b => MkT a [b]
+ -- *** 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.
--
- -- dcTyVars = [a,b]
- -- dcStupidTheta = [Eq a]
- -- dcTheta = [Ord b]
+ -- dcUnivTyVars = [a]
+ -- dcExTyVars = [x,y]
+ -- dcEqSpec = [a~(x,y)]
+ -- dcOtherTheta = [x~y, Ord x]
-- dcOrigArgTys = [a,List b]
- -- dcTyCon = T
- -- dcTyArgs = [a,b]
+ -- 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 GADTs, nothing.
- --
- -- NB1: the order of the forall'd variables does matter;
- -- for a vanilla constructor, we assume that if the result
- -- type is (T t1 ... tn) then we can instantiate the constr
- -- at types [t1, ..., tn]
- --
- -- NB2: a vanilla constructor can still be declared in GADT-style
- -- syntax, provided its type looks like the above.
-
- dcTyVars :: [TyVar], -- Universally-quantified type vars
- -- for the data constructor.
- -- See NB1 on dcVanilla for the conneciton between dcTyVars and dcResTys
- --
- -- In general, the dcTyVars are NOT NECESSARILY THE SAME AS THE TYVARS
+ -- 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)
+
+ 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.]
- dcStupidTheta :: ThetaType, -- This is a "thinned" version of
- -- the context of the data decl.
+ -- INVARIANT: the UnivTyVars and ExTyVars all have distinct OccNames
+ -- Reason: less confusing, and easier to generate IfaceSyn
+
+ dcEqSpec :: [(TyVar,Type)], -- 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
--
- -- "Stupid", because the dictionaries aren't used for anything.
+ -- INVARIANT: the free tyvars of dcStupidTheta are a subset of dcUnivTyVars
+ -- Reason: dcStupidTeta is gotten by thinning the stupid theta from the tycon
--
- -- 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.
- --
- -- Fact: the free tyvars of dcStupidTheta are a subset of
- -- the free tyvars of dcResTys
- -- Reason: dcStupidTeta is gotten by instantiating the
- -- stupid theta from the tycon (see BuildTyCl.mkDataConStupidTheta)
+ -- "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.
- dcTheta :: ThetaType, -- The existentially quantified stuff
-
dcOrigArgTys :: [Type], -- Original argument types
- -- (before unboxing and flattening of
- -- strict fields)
-
- -- Result type of constructor is T t1..tn
- dcTyCon :: TyCon, -- Result tycon, T
- dcResTys :: [Type], -- Result type args, t1..tn
+ -- (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
- dcStrictMarks :: [StrictnessMark],
+ dcStrictMarks :: [HsBang],
-- Strictness annotations as decided by the compiler.
-- Does *not* include the existential dictionaries
-- length = dataConSourceArity dataCon
dcFields :: [FieldLabel],
-- Field labels for this constructor, in the
- -- same order as the argument types;
+ -- same order as the dcOrigArgTys;
-- length = 0 (if not a record) or dataConSourceArity.
-- Constructor representation
- dcRepArgTys :: [Type], -- Final, representation argument types,
- -- after unboxing and flattening,
- -- and *including* existential dictionaries
+ dcRepArgTys :: [Type], -- Final, representation argument types,
+ -- after unboxing and flattening,
+ -- and *including* all existential evidence args
- dcRepStrictness :: [StrictnessMark], -- One for each *representation* argument
+ dcRepStrictness :: [StrictnessMark],
+ -- One for each *representation* *value* argument
+ -- See also Note [Data-con worker strictness] in MkId.lhs
+
+ -- Result type of constructor is T t1..tn
+ dcRepTyCon :: TyCon, -- Result tycon, T
dcRepType :: Type, -- Type of the constructor
- -- forall a b . Ord b => a -> [b] -> MkT a
+ -- forall a x y. (a~(x,y), x~y, Ord x) =>
+ -- x -> y -> T a
-- (this is *not* of the constructor wrapper Id:
- -- see notes after this data type declaration)
- --
+ -- 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 b (d:Ord b) (x:t) (xs:[b]) -> ... }
+ -- 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 b. Ord b => ...
+ -- 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
- -- use in CoreLint.
+ -- used in CoreLint.
- -- Finally, the curried worker function that corresponds to the constructor
+ -- 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.
--
-- The actual fixity is stored elsewhere
}
+-- | Contains the Ids of the data constructor functions
data DataConIds
- = NewDC Id -- Newtypes have only a wrapper, but no worker
- | AlgDC (Maybe Id) Id -- Algebraic data types always have a worker, and
+ = DCIds (Maybe Id) Id -- Algebraic data types always have a worker, and
-- may or may not have a wrapper, depending on whether
- -- the wrapper does anything.
+ -- the wrapper does anything. Newtypes just have a worker
-- _Neither_ the worker _nor_ the wrapper take the dcStupidTheta dicts as arguments
-- The worker takes dcRepArgTys as its arguments
-- If the worker is absent, dcRepArgTys is the same as dcOrigArgTys
- -- The 'Nothing' case of AlgDC is important
+ -- The 'Nothing' case of DCIds is important
-- Not only is this efficient,
-- but it also ensures that the wrapper is replaced
- -- by the worker (becuase it *is* the wroker)
+ -- by the worker (because it *is* the worker)
-- even when there are no args. E.g. in
-- f (:) x
-- the (:) *is* the worker.
-- but that makes it less likely that rules will match
-- when we bring bits of unfoldings together.)
+-- | Type of the tags associated with each constructor possibility
type ConTag = Int
fIRST_TAG :: ConTag
-fIRST_TAG = 1 -- Tags allocated from here for real constructors
+-- ^ Tags are allocated from here for real constructors
+fIRST_TAG = 1
\end{code}
+Note [Data con representation]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The dcRepType field contains the type of the representation of a contructor
This may differ from the type of the contructor *Id* (built
by MkId.mkDataConId) for two reasons:
instance Show DataCon where
showsPrec p con = showsPrecSDoc p (ppr con)
+
+instance Data.Typeable DataCon where
+ typeOf _ = Data.mkTyConApp (Data.mkTyCon "DataCon") []
+
+instance Data.Data DataCon where
+ -- don't traverse?
+ toConstr _ = abstractConstr "DataCon"
+ gunfold _ _ = error "gunfold"
+ dataTypeOf _ = mkNoRepType "DataCon"
\end{code}
%************************************************************************
\begin{code}
+-- | Build a new data constructor
mkDataCon :: Name
- -> Bool -- Declared infix
- -> Bool -- Vanilla (see notes with dcVanilla)
- -> [StrictnessMark] -> [FieldLabel]
- -> [TyVar] -> ThetaType -> ThetaType
- -> [Type] -> TyCon -> [Type]
- -> DataConIds
+ -> Bool -- ^ Is the constructor declared infix?
+ -> [HsBang] -- ^ Strictness annotations written in the source file
+ -> [FieldLabel] -- ^ Field labels for the constructor, if it is a record,
+ -- otherwise empty
+ -> [TyVar] -- ^ Universally quantified type variables
+ -> [TyVar] -- ^ Existentially quantified type variables
+ -> [(TyVar,Type)] -- ^ GADT equalities
+ -> ThetaType -- ^ Theta-type occuring before the arguments proper
+ -> [Type] -- ^ Original argument types
+ -> Type -- ^ Original result type
+ -> TyCon -- ^ Representation type constructor
+ -> ThetaType -- ^ The "stupid theta", context of the data declaration
+ -- e.g. @data Eq a => T a ...@
+ -> DataConIds -- ^ The Ids of the actual builder functions
-> DataCon
-- Can get the tag from the TyCon
-mkDataCon name declared_infix vanilla
+mkDataCon name declared_infix
arg_stricts -- Must match orig_arg_tys 1-1
fields
- tyvars stupid_theta theta orig_arg_tys tycon res_tys
- ids
- = con
+ univ_tvs ex_tvs
+ eq_spec theta
+ orig_arg_tys orig_res_ty rep_tycon
+ stupid_theta ids
+-- 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.
+
+ = -- ASSERT( not (any isEqPred theta) )
+ -- We don't currently allow any equality predicates on
+ -- a data constructor (apart from the GADT ones in eq_spec)
+ con
where
- con = MkData {dcName = name,
- dcUnique = nameUnique name, dcVanilla = vanilla,
- dcTyVars = tyvars, dcStupidTheta = stupid_theta, dcTheta = theta,
- dcOrigArgTys = orig_arg_tys, dcTyCon = tycon, dcResTys = res_tys,
+ 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, dcExTyVars = ex_tvs,
+ dcEqSpec = eq_spec,
+ dcOtherTheta = theta,
+ dcStupidTheta = stupid_theta,
+ dcOrigArgTys = orig_arg_tys, dcOrigResTy = orig_res_ty,
+ dcRepTyCon = rep_tycon,
dcRepArgTys = rep_arg_tys,
- dcStrictMarks = arg_stricts, dcRepStrictness = rep_arg_stricts,
+ dcStrictMarks = arg_stricts,
+ dcRepStrictness = rep_arg_stricts,
dcFields = fields, dcTag = tag, dcRepType = ty,
- dcIds = ids, dcInfix = declared_infix}
+ dcIds = ids }
-- Strictness marks for source-args
-- *after unboxing choices*,
-- The 'arg_stricts' passed to mkDataCon are simply those for the
-- source-language arguments. We add extra ones for the
-- dictionary arguments right here.
- dict_tys = mkPredTys theta
- real_arg_tys = dict_tys ++ orig_arg_tys
- real_stricts = map mk_dict_strict_mark theta ++ arg_stricts
+ full_theta = eqSpecPreds eq_spec ++ theta
+ real_arg_tys = mkPredTys full_theta ++ orig_arg_tys
+ real_stricts = map mk_dict_strict_mark full_theta ++ arg_stricts
-- Representation arguments and demands
+ -- To do: eliminate duplication with MkId
(rep_arg_stricts, rep_arg_tys) = computeRep real_stricts real_arg_tys
- tag = assoc "mkDataCon" (tyConDataCons tycon `zip` [fIRST_TAG..]) con
- ty = mkForAllTys tyvars (mkFunTys rep_arg_tys result_ty)
- -- NB: the existential dict args are already in rep_arg_tys
+ tag = assoc "mkDataCon" (tyConDataCons rep_tycon `zip` [fIRST_TAG..]) con
+ ty = mkForAllTys univ_tvs $ mkForAllTys ex_tvs $
+ mkFunTys rep_arg_tys $
+ mkTyConApp rep_tycon (mkTyVarTys univ_tvs)
- result_ty = mkTyConApp tycon res_tys
+eqSpecPreds :: [(TyVar,Type)] -> ThetaType
+eqSpecPreds spec = [ mkEqPred (mkTyVarTy tv, ty) | (tv,ty) <- spec ]
-mk_dict_strict_mark pred | isStrictPred pred = MarkedStrict
- | otherwise = NotMarkedStrict
+mk_dict_strict_mark :: PredType -> HsBang
+mk_dict_strict_mark pred | isStrictPred pred = HsStrict
+ | otherwise = HsNoBang
\end{code}
\begin{code}
+-- | 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 = dcTyCon
-
+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
-dataConTyVars :: DataCon -> [TyVar]
-dataConTyVars = dcTyVars
-
+-- | The universally-quantified type variables of the constructor
+dataConUnivTyVars :: DataCon -> [TyVar]
+dataConUnivTyVars = dcUnivTyVars
+
+-- | The existentially-quantified type variables of the constructor
+dataConExTyVars :: DataCon -> [TyVar]
+dataConExTyVars = dcExTyVars
+
+-- | 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
+dataConEqSpec :: DataCon -> [(TyVar,Type)]
+dataConEqSpec = dcEqSpec
+
+-- | 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 = case dcIds dc of
- AlgDC _ wrk_id -> wrk_id
- NewDC _ -> pprPanic "dataConWorkId" (ppr dc)
+ DCIds _ wrk_id -> wrk_id
+-- | 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 dcIds dc of
- AlgDC mb_wrap _ -> mb_wrap
- NewDC wrap -> Just wrap
+ DCIds mb_wrap _ -> mb_wrap
+-- | 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
--- Returns an Id which looks like the Haskell-source constructor
dataConWrapId dc = case dcIds dc of
- AlgDC (Just wrap) _ -> wrap
- AlgDC Nothing wrk -> wrk -- worker=wrapper
- NewDC wrap -> wrap
+ DCIds (Just wrap) _ -> wrap
+ DCIds Nothing wrk -> wrk -- worker=wrapper
+-- | Find all the 'Id's implicitly brought into scope by the data constructor. Currently,
+-- the union of the 'dataConWorkId' and the 'dataConWrapId'
dataConImplicitIds :: DataCon -> [Id]
dataConImplicitIds dc = case dcIds dc of
- AlgDC (Just wrap) work -> [wrap,work]
- AlgDC Nothing work -> [work]
- NewDC wrap -> [wrap]
+ DCIds (Just wrap) work -> [wrap,work]
+ DCIds Nothing work -> [work]
+-- | 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 -> FieldLabel -> Type
-dataConFieldType con label = expectJust "unexpected label" $
- lookup label (dcFields con `zip` dcOrigArgTys con)
-
-dataConStrictMarks :: DataCon -> [StrictnessMark]
+dataConFieldType con label
+ = case lookup label (dcFields con `zip` dcOrigArgTys con) of
+ Just ty -> ty
+ Nothing -> pprPanic "dataConFieldType" (ppr con <+> ppr label)
+
+-- | The strictness markings decided on by the compiler. Does not include those for
+-- existential dictionaries. The list is in one-to-one correspondence with the arity of the 'DataCon'
+dataConStrictMarks :: DataCon -> [HsBang]
dataConStrictMarks = dcStrictMarks
-dataConExStricts :: DataCon -> [StrictnessMark]
--- Strictness of *existential* arguments only
+-- | Strictness of evidence arguments to the wrapper function
+dataConExStricts :: DataCon -> [HsBang]
-- Usually empty, so we don't bother to cache this
-dataConExStricts dc = map mk_dict_strict_mark (dcTheta dc)
+dataConExStricts dc = map mk_dict_strict_mark $ (dataConTheta dc)
+-- | Source-level arity of the data constructor
dataConSourceArity :: DataCon -> Arity
- -- Source-level arity of the data constructor
dataConSourceArity dc = length (dcOrigArgTys dc)
--- dataConRepArity gives the number of actual fields in the
--- {\em representation} of the data constructor. This may be more than appear
--- in the source code; the extra ones are the existentially quantified
--- dictionaries
+-- | 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 -> Int
dataConRepArity (MkData {dcRepArgTys = arg_tys}) = length arg_tys
-isNullarySrcDataCon, isNullaryRepDataCon :: DataCon -> Bool
+-- | 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 = null (dcRepArgTys dc)
dataConRepStrictness :: DataCon -> [StrictnessMark]
- -- Give the demands on the arguments of a
- -- Core constructor application (Con dc args)
+-- ^ Give the demands on the arguments of a
+-- Core constructor application (Con dc args)
dataConRepStrictness dc = dcRepStrictness dc
-dataConSig :: DataCon -> ([TyVar], ThetaType,
- [Type], TyCon, [Type])
-
-dataConSig (MkData {dcTyVars = tyvars, dcTheta = theta,
- dcOrigArgTys = arg_tys, dcTyCon = tycon, dcResTys = res_tys})
- = (tyvars, theta, arg_tys, tycon, res_tys)
-
+-- | 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 (MkData {dcUnivTyVars = univ_tvs, dcExTyVars = ex_tvs,
+ dcEqSpec = eq_spec, dcOtherTheta = theta,
+ dcOrigArgTys = arg_tys, dcOrigResTy = res_ty})
+ = (univ_tvs ++ ex_tvs, eqSpecPreds eq_spec ++ theta, arg_tys, res_ty)
+
+-- | The \"full signature\" of the 'DataCon' returns, in order:
+--
+-- 1) The result of 'dataConUnivTyVars'
+--
+-- 2) The result of 'dataConExTyVars'
+--
+-- 3) The result of 'dataConEqSpec'
+--
+-- 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], [(TyVar,Type)], 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
-dataConResTys :: DataCon -> [Type]
-dataConResTys dc = dcResTys dc
-
-dataConInstArgTys :: DataCon
- -> [Type] -- Instantiated at these types
- -- NB: these INCLUDE the existentially quantified arg types
- -> [Type] -- Needs arguments of these types
- -- NB: these INCLUDE the existentially quantified dict args
- -- but EXCLUDE the data-decl context which is discarded
- -- It's all post-flattening etc; this is a representation type
-dataConInstArgTys (MkData {dcRepArgTys = arg_tys, dcTyVars = tyvars}) inst_tys
- = ASSERT( length tyvars == length inst_tys )
- map (substTyWith tyvars inst_tys) arg_tys
-
-dataConInstResTy :: DataCon -> [Type] -> Type
-dataConInstResTy (MkData {dcTyVars = tyvars, dcTyCon = tc, dcResTys = res_tys}) inst_tys
- = ASSERT( length tyvars == length inst_tys )
- substTy (zipOpenTvSubst tyvars inst_tys) (mkTyConApp tc res_tys)
- -- res_tys can't currently contain any foralls,
- -- but might in future; hence zipOpenTvSubst
-
--- And the same deal for the original arg tys
-dataConInstOrigArgTys :: DataCon -> [Type] -> [Type]
-dataConInstOrigArgTys (MkData {dcOrigArgTys = arg_tys, dcTyVars = tyvars}) inst_tys
- = ASSERT( length tyvars == length inst_tys )
- map (substTyWith tyvars inst_tys) arg_tys
+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 { dcUnivTyVars = univ_tvs,
+ dcExTyVars = ex_tvs, dcEqSpec = eq_spec,
+ dcOtherTheta = theta, dcOrigArgTys = arg_tys,
+ dcOrigResTy = res_ty })
+ = mkForAllTys ((univ_tvs `minusList` map fst eq_spec) ++ ex_tvs) $
+ mkFunTys (mkPredTys theta) $
+ mkFunTys arg_tys $
+ res_ty
+
+-- | 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 {dcRepArgTys = rep_arg_tys,
+ dcUnivTyVars = univ_tvs, dcEqSpec = eq_spec,
+ dcExTyVars = ex_tvs}) inst_tys
+ = ASSERT2 ( length univ_tvs == length inst_tys
+ , ptext (sLit "dataConInstArgTys") <+> ppr dc $$ ppr univ_tvs $$ ppr inst_tys)
+ ASSERT2 ( null ex_tvs && null eq_spec, ppr dc )
+ map (substTyWith univ_tvs inst_tys) rep_arg_tys
+
+-- | 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
+ , ptext (sLit "dataConInstOrigArgTys") <+> ppr dc $$ ppr tyvars $$ ppr inst_tys )
+ map (substTyWith tyvars inst_tys) arg_tys
+ where
+ tyvars = univ_tvs ++ ex_tvs
\end{code}
-These two functions get the real argument types of the constructor,
-without substituting for any type variables.
-
-dataConOrigArgTys returns the arg types of the wrapper, excluding all dictionary args.
-
-dataConRepArgTys retuns the arg types of the worker, including all dictionaries, and
-after any flattening has been done.
-
\begin{code}
+-- | 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 dictionaries, after any
+-- flattening has been done and without substituting for any type variables
dataConRepArgTys :: DataCon -> [Type]
dataConRepArgTys dc = dcRepArgTys dc
\end{code}
+\begin{code}
+-- | 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 (packageIdFS (modulePackageId mod)) ++
+ fromIntegral (ord ':') : bytesFS (moduleNameFS (moduleName mod)) ++
+ fromIntegral (ord '.') : bytesFS (occNameFS (nameOccName name))
+ where name = dataConName dc
+ mod = ASSERT( isExternalName name ) nameModule name
+\end{code}
\begin{code}
isTupleCon :: DataCon -> Bool
-isTupleCon (MkData {dcTyCon = tc}) = isTupleTyCon tc
+isTupleCon (MkData {dcRepTyCon = tc}) = isTupleTyCon tc
isUnboxedTupleCon :: DataCon -> Bool
-isUnboxedTupleCon (MkData {dcTyCon = tc}) = isUnboxedTupleTyCon tc
+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
\end{code}
-
\begin{code}
classDataCon :: Class -> DataCon
classDataCon clas = case tyConDataCons (classTyCon clas) of
(dict_constr:no_more) -> ASSERT( null no_more ) dict_constr
+ [] -> panic "classDataCon"
+\end{code}
+
+\begin{code}
+dataConCannotMatch :: [Type] -> DataCon -> Bool
+-- Returns True iff the data con *definitely cannot* match a
+-- scrutinee of type (T tys)
+-- where T is the type constructor for the data con
+-- NB: look at *all* equality constraints, not only those
+-- in dataConEqSpec; see Trac #5168
+dataConCannotMatch tys con
+ | null theta = False -- Common
+ | all isTyVarTy tys = False -- Also common
+ | otherwise
+ = typesCantMatch [(Type.substTy subst ty1, Type.substTy subst ty2)
+ | EqPred ty1 ty2 <- theta ]
+ where
+ dc_tvs = dataConUnivTyVars con
+ theta = dataConTheta con
+ subst = zipTopTvSubst dc_tvs tys
\end{code}
%************************************************************************
%************************************************************************
\begin{code}
+-- | 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@
splitProductType_maybe
- :: Type -- A product type, perhaps
+ :: 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
+ [Type]) -- Its /representation/ arg types
- -- Returns (Just ...) for any
- -- concrete (i.e. constructors visible)
- -- single-constructor
- -- not existentially quantified
- -- type whether a data type or a new type
- --
-- Rejecing 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.
-- and for constructors visible
-> Just (tycon, ty_args, data_con, dataConInstArgTys data_con ty_args)
where
- data_con = head (tyConDataCons tycon)
- other -> Nothing
+ data_con = ASSERT( not (null (tyConDataCons tycon)) )
+ head (tyConDataCons tycon)
+ _other -> Nothing
+-- | As 'splitProductType_maybe', but panics if the 'Type' is not a product type
+splitProductType :: String -> Type -> (TyCon, [Type], DataCon, [Type])
splitProductType str ty
= case splitProductType_maybe ty of
Just stuff -> stuff
Nothing -> pprPanic (str ++ ": not a product") (pprType ty)
-computeRep :: [StrictnessMark] -- Original arg strictness
- -> [Type] -- and types
+-- | As 'splitProductType_maybe', but in turn instantiates the 'TyCon' returned
+-- and hence recursively tries to unpack it as far as it able to
+deepSplitProductType_maybe :: Type -> Maybe (TyCon, [Type], DataCon, [Type])
+deepSplitProductType_maybe ty
+ = do { (res@(tycon, tycon_args, _, _)) <- splitProductType_maybe ty
+ ; let {result
+ | Just (ty', _co) <- instNewTyCon_maybe tycon tycon_args
+ , not (isRecursiveTyCon tycon)
+ = deepSplitProductType_maybe ty' -- Ignore the coercion?
+ | isNewTyCon tycon = Nothing -- cannot unbox through recursive
+ -- newtypes nor through families
+ | otherwise = Just res}
+ ; result
+ }
+
+-- | As 'deepSplitProductType_maybe', but panics if the 'Type' is not a product type
+deepSplitProductType :: String -> Type -> (TyCon, [Type], DataCon, [Type])
+deepSplitProductType str ty
+ = case deepSplitProductType_maybe ty of
+ Just stuff -> stuff
+ Nothing -> pprPanic (str ++ ": not a product") (pprType ty)
+
+-- | Compute the representation type strictness and type suitable for a 'DataCon'
+computeRep :: [HsBang] -- ^ Original argument strictness
+ -> [Type] -- ^ Original argument types
-> ([StrictnessMark], -- Representation arg strictness
[Type]) -- And type
computeRep stricts tys
= unzip $ concat $ zipWithEqual "computeRep" unbox stricts tys
where
- unbox NotMarkedStrict ty = [(NotMarkedStrict, ty)]
- unbox MarkedStrict ty = [(MarkedStrict, ty)]
- unbox MarkedUnboxed ty = zipEqual "computeRep" (dataConRepStrictness arg_dc) arg_tys
- where
- (_, _, arg_dc, arg_tys) = splitProductType "unbox_strict_arg_ty" ty
+ unbox HsNoBang ty = [(NotMarkedStrict, ty)]
+ unbox HsStrict ty = [(MarkedStrict, ty)]
+ unbox HsUnpackFailed ty = [(MarkedStrict, ty)]
+ unbox HsUnpack ty = zipEqual "computeRep" (dataConRepStrictness arg_dc) arg_tys
+ where
+ (_tycon, _tycon_args, arg_dc, arg_tys)
+ = deepSplitProductType "unbox_strict_arg_ty" ty
\end{code}
projects / ghc-hetmet.git / blobdiff