mkDataCon,
dataConRepType, dataConSig, dataConName, dataConTag, dataConTyCon,
dataConArgTys, dataConOrigArgTys, dataConInstOrigArgTys,
- dataConRepArgTys, dataConTheta,
+ dataConRepArgTys, dataConTheta,
dataConFieldLabels, dataConStrictMarks,
dataConSourceArity, dataConRepArity,
- dataConNumInstArgs, dataConId, dataConWrapId, dataConRepStrictness,
+ dataConNumInstArgs,
+ dataConWorkId, dataConWrapId, dataConWrapId_maybe,
+ dataConRepStrictness,
isNullaryDataCon, isTupleCon, isUnboxedTupleCon,
- isExistentialDataCon, classDataCon,
+ isExistentialDataCon, classDataCon, dataConExistentialTyVars,
splitProductType_maybe, splitProductType,
) where
#include "HsVersions.h"
import {-# SOURCE #-} Subst( substTyWith )
+import {-# SOURCE #-} PprType( pprType )
-import CmdLineOpts ( opt_DictsStrict )
-import Type ( Type, TauType, ThetaType,
+import Type ( Type, ThetaType,
mkForAllTys, mkFunTys, mkTyConApp,
- mkTyVarTys, splitTyConApp_maybe, repType
+ mkTyVarTys, splitTyConApp_maybe, repType,
+ mkPredTys, isStrictType
)
-import TcType ( isStrictPred, mkPredTys )
-import TyCon ( TyCon, tyConDataCons, tyConDataConsIfAvailable, isProductTyCon,
+import TyCon ( TyCon, tyConDataCons, tyConDataCons, isProductTyCon,
isTupleTyCon, isUnboxedTupleTyCon, isRecursiveTyCon )
import Class ( Class, classTyCon )
import Name ( Name, NamedThing(..), nameUnique )
import Var ( TyVar, Id )
import FieldLabel ( FieldLabel )
import BasicTypes ( Arity, StrictnessMark(..) )
-import NewDemand ( Demand, lazyDmd, seqDmd )
import Outputable
import Unique ( Unique, Uniquable(..) )
import CmdLineOpts ( opt_UnboxStrictFields )
-import PprType () -- Instances
-import Maybe
+import Maybes ( orElse )
import ListSetOps ( assoc )
-import Util ( zipEqual, zipWithEqual )
+import Util ( zipEqual, zipWithEqual, notNull )
\end{code}
-Stuff about data constructors
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-Every constructor, C, comes with a
+Data constructor representation
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider the following Haskell data type declaration
- *wrapper*, called C, 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
+ 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 ... }
- *worker*, called $wC, which is the actual data constructor.
- Its type may be different to C, because:
+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 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
+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
- It does not have a binding.
+ The worker is very like a primop, in that it has no binding.
- The worker is very like a primop, in that it has no binding,
+ Newtypes currently do get a worker-Id, but it is never used.
+
+
+ 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.
+
+ The wrapper Id isn't generated for a data type if the worker
+ and wrapper are identical. It's always generated for a newtype.
+
+
+
+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.]
data DataCon
= MkData { -- Used for data constructors only;
-- there *is* no constructor for a newtype
- dcName :: Name,
+
+ dcName :: Name, -- This is the name of the *source data con*
+ -- (see "Note [Data Constructor Naming]" above)
+
dcUnique :: Unique, -- Cached from Name
dcTag :: ConTag,
-- data Eq a => T a = forall b. Ord b => MkT a [b]
dcRepType :: Type, -- Type of the constructor
- -- forall ab . Ord b => a -> [b] -> MkT a
- -- (this is *not* of the constructor Id:
+ -- forall a b . Ord b => a -> [b] -> MkT a
+ -- (this is *not* of the constructor wrapper Id:
-- see notes after this data type declaration)
+ --
+ -- 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]) -> ... }
+ -- It's convenient to apply the rep-type of MkT to 't', to get
+ -- forall b. Ord b => ...
+ -- and use that to check the pattern. Mind you, this is really only
+ -- use in CoreLint.
+
-- The next six fields express the type of the constructor, in pieces
-- e.g.
-- dcOrigArgTys = [a,List b]
-- dcTyCon = T
- dcTyVars :: [TyVar], -- Type vars and context for the data type decl
+ dcTyVars :: [TyVar], -- Type vars for the data type decl
-- These are ALWAYS THE SAME AS THE TYVARS
-- FOR THE PARENT TyCon. We occasionally rely on
-- this just to avoid redundant instantiation
- dcTheta :: ThetaType,
+
+ dcStupidTheta :: ThetaType, -- This is a "thinned" version of the context of
+ -- the data decl.
+ -- "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.
+ --
+ -- Indeed, [as of March 02] they are no
+ -- longer in the type of the dcWrapId, because
+ -- that makes it harder to use the wrap-id to rebuild
+ -- values after record selection or in generics.
dcExTyVars :: [TyVar], -- Ditto for the context of the constructor,
dcExTheta :: ThetaType, -- the existentially quantified stuff
dcRepArgTys :: [Type], -- Final, representation argument types, after unboxing and flattening,
-- and including existential dictionaries
- dcRepStrictness :: [Demand], -- One for each representation argument
+ dcRepStrictness :: [StrictnessMark], -- One for each representation argument
dcTyCon :: TyCon, -- Result tycon
--
-- An entirely separate wrapper function is built in TcTyDecls
- dcId :: Id, -- The corresponding worker Id
+ dcWorkId :: Id, -- The corresponding worker Id
-- Takes dcRepArgTys as its arguments
+ -- Perhaps this should be a 'Maybe'; not reqd for newtype constructors
- dcWrapId :: Id -- The wrapper Id
+ dcWrapId :: Maybe Id -- The wrapper Id, if it's necessary
+ -- It's deemed unnecessary if it performs the
+ -- identity function
}
type ConTag = Int
%************************************************************************
%* *
-\subsection{Consruction}
+\subsection{Construction}
%* *
%************************************************************************
\begin{code}
-mkDataCon :: Name
+mkDataCon :: Name
-> [StrictnessMark] -> [FieldLabel]
-> [TyVar] -> ThetaType
-> [TyVar] -> ThetaType
- -> [TauType] -> TyCon
- -> Id -> Id
+ -> [Type] -> TyCon
+ -> Id -> Maybe Id -- Worker and possible wrapper
-> DataCon
-- Can get the tag from the TyCon
-mkDataCon name arg_stricts fields
+mkDataCon name
+ arg_stricts -- Use [] to mean 'all non-strict'
+ fields
tyvars theta ex_tyvars ex_theta orig_arg_tys tycon
work_id wrap_id
- = ASSERT(length arg_stricts == length orig_arg_tys)
- -- The 'stricts' passed to mkDataCon are simply those for the
- -- source-language arguments. We add extra ones for the
- -- dictionary arguments right here.
- con
+ = con
where
- con = MkData {dcName = name, dcUnique = nameUnique name,
- dcTyVars = tyvars, dcTheta = theta,
+ con = MkData {dcName = name,
+ dcUnique = nameUnique name,
+ dcTyVars = tyvars, dcStupidTheta = theta,
dcOrigArgTys = orig_arg_tys,
dcRepArgTys = rep_arg_tys,
dcExTyVars = ex_tyvars, dcExTheta = ex_theta,
- dcStrictMarks = real_stricts, dcRepStrictness = rep_arg_demands,
+ dcStrictMarks = real_stricts, dcRepStrictness = rep_arg_stricts,
dcFields = fields, dcTag = tag, dcTyCon = tycon, dcRepType = ty,
- dcId = work_id, dcWrapId = wrap_id}
+ dcWorkId = work_id, dcWrapId = wrap_id}
-- Strictness marks for source-args
-- *after unboxing choices*,
-- but *including existential dictionaries*
- real_stricts = (map mk_dict_strict_mark ex_theta) ++
- zipWithEqual "mkDataCon1" (chooseBoxingStrategy tycon)
- orig_arg_tys arg_stricts
+ --
+ -- The 'arg_stricts' passed to mkDataCon are simply those for the
+ -- source-language arguments. We add extra ones for the
+ -- dictionary arguments right here.
+ ex_dict_tys = mkPredTys ex_theta
+ real_stricts = map mk_dict_strict_mark ex_dict_tys ++
+ zipWith (chooseBoxingStrategy tycon)
+ orig_arg_tys
+ (arg_stricts ++ repeat NotMarkedStrict)
+ real_arg_tys = ex_dict_tys ++ orig_arg_tys
-- Representation arguments and demands
- (rep_arg_demands, rep_arg_tys)
- = unzip $ concat $
- zipWithEqual "mkDataCon2" unbox_strict_arg_ty
- real_stricts
- (mkPredTys ex_theta ++ orig_arg_tys)
+ (rep_arg_stricts, rep_arg_tys) = computeRep real_stricts real_arg_tys
tag = assoc "mkDataCon" (tyConDataCons tycon `zip` [fIRST_TAG..]) con
ty = mkForAllTys (tyvars ++ ex_tyvars)
result_ty = mkTyConApp tycon (mkTyVarTys tyvars)
-mk_dict_strict_mark pred | isStrictPred pred = MarkedStrict
- | otherwise = NotMarkedStrict
+mk_dict_strict_mark ty | isStrictType ty = MarkedStrict
+ | otherwise = NotMarkedStrict
\end{code}
\begin{code}
dataConRepType :: DataCon -> Type
dataConRepType = dcRepType
-dataConId :: DataCon -> Id
-dataConId = dcId
+dataConWorkId :: DataCon -> Id
+dataConWorkId = dcWorkId
+
+dataConWrapId_maybe :: DataCon -> Maybe Id
+dataConWrapId_maybe = dcWrapId
dataConWrapId :: DataCon -> Id
-dataConWrapId = dcWrapId
+-- Returns an Id which looks like the Haskell-source constructor
+-- If there is no dcWrapId it's because there is no need for a
+-- wrapper, so the worker is the Right Thing
+dataConWrapId dc = dcWrapId dc `orElse` dcWorkId dc
dataConFieldLabels :: DataCon -> [FieldLabel]
dataConFieldLabels = dcFields
isNullaryDataCon con = dataConRepArity con == 0
-dataConRepStrictness :: DataCon -> [Demand]
+dataConRepStrictness :: DataCon -> [StrictnessMark]
-- Give the demands on the arguments of a
-- Core constructor application (Con dc args)
dataConRepStrictness dc = dcRepStrictness dc
dataConSig :: DataCon -> ([TyVar], ThetaType,
[TyVar], ThetaType,
- [TauType], TyCon)
+ [Type], TyCon)
-dataConSig (MkData {dcTyVars = tyvars, dcTheta = theta,
+dataConSig (MkData {dcTyVars = tyvars, dcStupidTheta = theta,
dcExTyVars = ex_tyvars, dcExTheta = ex_theta,
dcOrigArgTys = arg_tys, dcTyCon = tycon})
= (tyvars, theta, ex_tyvars, ex_theta, arg_tys, tycon)
= map (substTyWith (tyvars ++ ex_tyvars) inst_tys) arg_tys
dataConTheta :: DataCon -> ThetaType
-dataConTheta dc = dcTheta dc
+dataConTheta dc = dcStupidTheta dc
+
+dataConExistentialTyVars :: DataCon -> [TyVar]
+dataConExistentialTyVars dc = dcExTyVars dc
-- And the same deal for the original arg tys:
dataConOrigArgTys :: DataCon -> [Type]
dataConOrigArgTys dc = dcOrigArgTys dc
-dataConRepArgTys :: DataCon -> [TauType]
+dataConRepArgTys :: DataCon -> [Type]
dataConRepArgTys dc = dcRepArgTys dc
\end{code}
isUnboxedTupleCon (MkData {dcTyCon = tc}) = isUnboxedTupleTyCon tc
isExistentialDataCon :: DataCon -> Bool
-isExistentialDataCon (MkData {dcExTyVars = tvs}) = not (null tvs)
+isExistentialDataCon (MkData {dcExTyVars = tvs}) = notNull tvs
\end{code}
-- and for constructors visible
-> Just (tycon, ty_args, data_con, dataConArgTys data_con ty_args)
where
- data_con = head (tyConDataConsIfAvailable tycon)
+ data_con = head (tyConDataCons tycon)
other -> Nothing
splitProductType str ty
= case splitProductType_maybe ty of
Just stuff -> stuff
- Nothing -> pprPanic (str ++ ": not a product") (ppr ty)
+ Nothing -> pprPanic (str ++ ": not a product") (pprType ty)
-- We attempt to unbox/unpack a strict field when either:
-- (i) The tycon is imported, and the field is marked '! !', or
Nothing -> False
Just (arg_tycon, _) -> isProductTyCon arg_tycon
-unbox_strict_arg_ty
- :: StrictnessMark -- After strategy choice; can't be MarkedUserStrict
- -> Type -- Source argument type
- -> [(Demand,Type)] -- Representation argument types and demamds
+computeRep :: [StrictnessMark] -- Original arg strictness
+ -- [after strategy choice; can't be MarkedUserStrict]
+ -> [Type] -- and types
+ -> ([StrictnessMark], -- Representation arg strictness
+ [Type]) -- And type
-unbox_strict_arg_ty NotMarkedStrict ty = [(lazyDmd, ty)]
-unbox_strict_arg_ty MarkedStrict ty = [(seqDmd, ty)]
-unbox_strict_arg_ty MarkedUnboxed ty
- = zipEqual "unbox_strict_arg_ty" (dataConRepStrictness arg_data_con) arg_tys
+computeRep stricts tys
+ = unzip $ concat $ zipWithEqual "computeRep" unbox stricts tys
where
- (_, _, arg_data_con, arg_tys) = splitProductType "unbox_strict_arg_ty" (repType ty)
+ 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" (repType ty)
\end{code}
projects / ghc-hetmet.git / blobdiff