\begin{code}
module DataCon (
- DataCon,
+ DataCon, DataConIds(..),
ConTag, fIRST_TAG,
mkDataCon,
dataConRepType, dataConSig, dataConName, dataConTag, dataConTyCon,
- dataConArgTys, dataConOrigArgTys, dataConInstOrigArgTys,
- dataConRepArgTys, dataConTheta,
- dataConFieldLabels, dataConStrictMarks,
+ dataConTyVars, dataConResTys,
+ dataConStupidTheta,
+ dataConInstArgTys, dataConOrigArgTys, dataConInstResTy,
+ dataConInstOrigArgTys, dataConRepArgTys,
+ dataConFieldLabels, dataConFieldType,
+ dataConStrictMarks, dataConExStricts,
dataConSourceArity, dataConRepArity,
- dataConNumInstArgs,
- dataConWorkId, dataConWrapId, dataConWrapId_maybe,
+ dataConIsInfix,
+ dataConWorkId, dataConWrapId, dataConWrapId_maybe, dataConImplicitIds,
dataConRepStrictness,
- isNullaryDataCon, isTupleCon, isUnboxedTupleCon,
- isExistentialDataCon, classDataCon, dataConExistentialTyVars,
+ isNullarySrcDataCon, isNullaryRepDataCon, isTupleCon, isUnboxedTupleCon,
+ isVanillaDataCon, classDataCon,
splitProductType_maybe, splitProductType,
) where
#include "HsVersions.h"
-import {-# SOURCE #-} Subst( substTyWith )
-import {-# SOURCE #-} PprType( pprType )
-
-import Type ( Type, ThetaType,
+import Type ( Type, ThetaType, substTyWith, substTy, zipOpenTvSubst,
mkForAllTys, mkFunTys, mkTyConApp,
- mkTyVarTys, splitTyConApp_maybe, repType,
- mkPredTys, isStrictType
+ splitTyConApp_maybe,
+ mkPredTys, isStrictPred, pprType
)
-import TyCon ( TyCon, tyConDataCons, tyConDataCons, isProductTyCon,
- isTupleTyCon, isUnboxedTupleTyCon, isRecursiveTyCon )
+import TyCon ( TyCon, FieldLabel, tyConDataCons,
+ isProductTyCon, isTupleTyCon, isUnboxedTupleTyCon )
import Class ( Class, classTyCon )
import Name ( Name, NamedThing(..), nameUnique )
import Var ( TyVar, Id )
-import FieldLabel ( FieldLabel )
import BasicTypes ( Arity, StrictnessMark(..) )
import Outputable
import Unique ( Unique, Uniquable(..) )
-import CmdLineOpts ( opt_UnboxStrictFields )
-import Maybes ( orElse )
import ListSetOps ( assoc )
-import Util ( zipEqual, zipWithEqual, equalLength, notNull )
+import Util ( zipEqual, zipWithEqual )
+import Maybes ( expectJust )
\end{code}
---------------------------------------------------------------------------
* 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)
+ * 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
- strict args may be flattened
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.
+ Newtypes have no worker Id
- The "wrapper Id", $wC, whose type is exactly what it looks like
+ 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.
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).
+ 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.
-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.
%************************************************************************
%* *
\begin{code}
data DataCon
- = MkData { -- Used for data constructors only;
- -- there *is* no constructor for a newtype
- dcName :: Name,
-
- dcUnique :: Unique, -- Cached from Name
+ = 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,
-- Running example:
--
-- data Eq a => T a = forall b. Ord b => MkT a [b]
- dcRepType :: Type, -- Type of the constructor
- -- 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.
--
- -- dcTyVars = [a]
- -- dcTheta = [Eq a]
- -- dcExTyVars = [b]
- -- dcExTheta = [Ord b]
- -- dcOrigArgTys = [a,List b]
- -- dcTyCon = T
-
- 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
-
- dcStupidTheta :: ThetaType, -- This is a "thinned" version of the context of
- -- the data decl.
+ -- dcTyVars = [a,b]
+ -- dcStupidTheta = [Eq a]
+ -- dcTheta = [Ord b]
+ -- dcOrigArgTys = [a,List b]
+ -- dcTyCon = T
+ -- dcTyArgs = [a,b]
+
+ 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
+ -- 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.
-- "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
+ -- 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)
- dcExTyVars :: [TyVar], -- Ditto for the context of the constructor,
- dcExTheta :: ThetaType, -- the existentially quantified stuff
+ dcTheta :: ThetaType, -- The existentially quantified stuff
dcOrigArgTys :: [Type], -- Original argument types
-- (before unboxing and flattening of
-- strict fields)
- dcRepArgTys :: [Type], -- Final, representation argument types, after unboxing and flattening,
- -- and including existential dictionaries
-
- dcRepStrictness :: [StrictnessMark], -- One for each representation argument
-
- dcTyCon :: TyCon, -- Result tycon
+ -- Result type of constructor is T t1..tn
+ dcTyCon :: TyCon, -- Result tycon, T
+ dcResTys :: [Type], -- Result type args, t1..tn
-- Now the strictness annotations and field labels of the constructor
dcStrictMarks :: [StrictnessMark],
- -- Strictness annotations as deduced by the compiler.
- -- Has no MarkedUserStrict; they have been changed to MarkedStrict
- -- or MarkedUnboxed by the compiler.
- -- *Includes the existential dictionaries*
- -- length = length dcExTheta + dataConSourceArity dataCon
+ -- 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;
-- length = 0 (if not a record) or dataConSourceArity.
+ -- Constructor representation
+ dcRepArgTys :: [Type], -- Final, representation argument types,
+ -- after unboxing and flattening,
+ -- and *including* existential dictionaries
+
+ dcRepStrictness :: [StrictnessMark], -- One for each *representation* argument
+
+ dcRepType :: Type, -- Type of the constructor
+ -- 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.
+
+
-- Finally, 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.
--
-- An entirely separate wrapper function is built in TcTyDecls
+ dcIds :: DataConIds,
- dcWorkId :: Id, -- The corresponding worker Id
- -- Takes dcRepArgTys as its arguments
- -- Perhaps this should be a 'Maybe'; not reqd for newtype constructors
-
- dcWrapId :: Maybe Id -- The wrapper Id, if it's necessary
- -- It's deemed unnecessary if it performs the
- -- identity function
+ dcInfix :: Bool -- True <=> declared infix
+ -- Used for Template Haskell and 'deriving' only
+ -- The actual fixity is stored elsewhere
}
+data DataConIds
+ = NewDC Id -- Newtypes have only a wrapper, but no worker
+ | AlgDC (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.
+
+ -- _Neither_ the worker _nor_ the wrapper take the dcStupidTheta dicts as arguments
+
+ -- The wrapper takes dcOrigArgTys as its 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
+ -- Not only is this efficient,
+ -- but it also ensures that the wrapper is replaced
+ -- by the worker (becuase it *is* the wroker)
+ -- 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.)
+
type ConTag = Int
fIRST_TAG :: ConTag
\begin{code}
mkDataCon :: Name
+ -> Bool -- Declared infix
+ -> Bool -- Vanilla (see notes with dcVanilla)
-> [StrictnessMark] -> [FieldLabel]
- -> [TyVar] -> ThetaType
- -> [TyVar] -> ThetaType
- -> [Type] -> TyCon
- -> Id -> Maybe Id -- Worker and possible wrapper
+ -> [TyVar] -> ThetaType -> ThetaType
+ -> [Type] -> TyCon -> [Type]
+ -> DataConIds
-> DataCon
-- Can get the tag from the TyCon
-mkDataCon name
- arg_stricts -- Use [] to mean 'all non-strict'
+mkDataCon name declared_infix vanilla
+ arg_stricts -- Must match orig_arg_tys 1-1
fields
- tyvars theta ex_tyvars ex_theta orig_arg_tys tycon
- work_id wrap_id
+ tyvars stupid_theta theta orig_arg_tys tycon res_tys
+ ids
= con
where
con = MkData {dcName = name,
- dcUnique = nameUnique name,
- dcTyVars = tyvars, dcStupidTheta = theta,
- dcOrigArgTys = orig_arg_tys,
+ dcUnique = nameUnique name, dcVanilla = vanilla,
+ dcTyVars = tyvars, dcStupidTheta = stupid_theta, dcTheta = theta,
+ dcOrigArgTys = orig_arg_tys, dcTyCon = tycon, dcResTys = res_tys,
dcRepArgTys = rep_arg_tys,
- dcExTyVars = ex_tyvars, dcExTheta = ex_theta,
- dcStrictMarks = real_stricts, dcRepStrictness = rep_arg_stricts,
- dcFields = fields, dcTag = tag, dcTyCon = tycon, dcRepType = ty,
- dcWorkId = work_id, dcWrapId = wrap_id}
+ dcStrictMarks = arg_stricts, dcRepStrictness = rep_arg_stricts,
+ dcFields = fields, dcTag = tag, dcRepType = ty,
+ dcIds = ids, dcInfix = declared_infix}
-- 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.
- 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
+ dict_tys = mkPredTys theta
+ real_arg_tys = dict_tys ++ orig_arg_tys
+ real_stricts = map mk_dict_strict_mark theta ++ arg_stricts
-- Representation arguments and demands
(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)
- (mkFunTys rep_arg_tys result_ty)
+ ty = mkForAllTys tyvars (mkFunTys rep_arg_tys result_ty)
-- NB: the existential dict args are already in rep_arg_tys
- result_ty = mkTyConApp tycon (mkTyVarTys tyvars)
+ result_ty = mkTyConApp tycon res_tys
-mk_dict_strict_mark ty | isStrictType ty = MarkedStrict
- | otherwise = NotMarkedStrict
+mk_dict_strict_mark pred | isStrictPred pred = MarkedStrict
+ | otherwise = NotMarkedStrict
\end{code}
\begin{code}
dataConRepType :: DataCon -> Type
dataConRepType = dcRepType
+dataConIsInfix :: DataCon -> Bool
+dataConIsInfix = dcInfix
+
+dataConTyVars :: DataCon -> [TyVar]
+dataConTyVars = dcTyVars
+
dataConWorkId :: DataCon -> Id
-dataConWorkId = dcWorkId
+dataConWorkId dc = case dcIds dc of
+ AlgDC _ wrk_id -> wrk_id
+ NewDC _ -> pprPanic "dataConWorkId" (ppr dc)
dataConWrapId_maybe :: DataCon -> Maybe Id
-dataConWrapId_maybe = dcWrapId
+dataConWrapId_maybe dc = case dcIds dc of
+ AlgDC mb_wrap _ -> mb_wrap
+ NewDC wrap -> Just wrap
dataConWrapId :: DataCon -> Id
-- 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
+dataConWrapId dc = case dcIds dc of
+ AlgDC (Just wrap) _ -> wrap
+ AlgDC Nothing wrk -> wrk -- worker=wrapper
+ NewDC wrap -> wrap
+
+dataConImplicitIds :: DataCon -> [Id]
+dataConImplicitIds dc = case dcIds dc of
+ AlgDC (Just wrap) work -> [wrap,work]
+ AlgDC Nothing work -> [work]
+ NewDC wrap -> [wrap]
dataConFieldLabels :: DataCon -> [FieldLabel]
dataConFieldLabels = dcFields
+dataConFieldType :: DataCon -> FieldLabel -> Type
+dataConFieldType con label = expectJust "unexpected label" $
+ lookup label (dcFields con `zip` dcOrigArgTys con)
+
dataConStrictMarks :: DataCon -> [StrictnessMark]
dataConStrictMarks = dcStrictMarks
--- Number of type-instantiation arguments
--- All the remaining arguments of the DataCon are (notionally)
--- stored in the DataCon, and are matched in a case expression
-dataConNumInstArgs (MkData {dcTyVars = tyvars}) = length tyvars
+dataConExStricts :: DataCon -> [StrictnessMark]
+-- Strictness of *existential* arguments only
+-- Usually empty, so we don't bother to cache this
+dataConExStricts dc = map mk_dict_strict_mark (dcTheta dc)
dataConSourceArity :: DataCon -> Arity
-- Source-level arity of the data constructor
-- dictionaries
dataConRepArity (MkData {dcRepArgTys = arg_tys}) = length arg_tys
-isNullaryDataCon con = dataConRepArity con == 0
+isNullarySrcDataCon, isNullaryRepDataCon :: DataCon -> Bool
+isNullarySrcDataCon dc = null (dcOrigArgTys dc)
+isNullaryRepDataCon dc = null (dcRepArgTys dc)
dataConRepStrictness :: DataCon -> [StrictnessMark]
-- Give the demands on the arguments of a
dataConRepStrictness dc = dcRepStrictness dc
dataConSig :: DataCon -> ([TyVar], ThetaType,
- [TyVar], ThetaType,
- [Type], TyCon)
-
-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)
-
-dataConArgTys :: 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
-
-dataConArgTys (MkData {dcRepArgTys = arg_tys, dcTyVars = tyvars,
- dcExTyVars = ex_tyvars}) inst_tys
- = map (substTyWith (tyvars ++ ex_tyvars) inst_tys) arg_tys
+ [Type], TyCon, [Type])
-dataConTheta :: DataCon -> ThetaType
-dataConTheta dc = dcStupidTheta dc
+dataConSig (MkData {dcTyVars = tyvars, dcTheta = theta,
+ dcOrigArgTys = arg_tys, dcTyCon = tycon, dcResTys = res_tys})
+ = (tyvars, theta, arg_tys, tycon, res_tys)
-dataConExistentialTyVars :: DataCon -> [TyVar]
-dataConExistentialTyVars dc = dcExTyVars dc
+dataConStupidTheta :: DataCon -> ThetaType
+dataConStupidTheta dc = dcStupidTheta dc
--- And the same deal for the original arg tys:
+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,
- dcExTyVars = ex_tyvars}) inst_tys
- = map (substTyWith (tyvars ++ ex_tyvars) inst_tys) arg_tys
+dataConInstOrigArgTys (MkData {dcOrigArgTys = arg_tys, dcTyVars = tyvars}) inst_tys
+ = ASSERT( length tyvars == length inst_tys )
+ map (substTyWith tyvars inst_tys) arg_tys
\end{code}
These two functions get the real argument types of the constructor,
isUnboxedTupleCon :: DataCon -> Bool
isUnboxedTupleCon (MkData {dcTyCon = tc}) = isUnboxedTupleTyCon tc
-isExistentialDataCon :: DataCon -> Bool
-isExistentialDataCon (MkData {dcExTyVars = tvs}) = notNull tvs
+isVanillaDataCon :: DataCon -> Bool
+isVanillaDataCon dc = dcVanilla dc
\end{code}
Just (tycon,ty_args)
| isProductTyCon tycon -- Includes check for non-existential,
-- and for constructors visible
- -> Just (tycon, ty_args, data_con, dataConArgTys data_con ty_args)
+ -> Just (tycon, ty_args, data_con, dataConInstArgTys data_con ty_args)
where
data_con = head (tyConDataCons tycon)
other -> Nothing
Just stuff -> stuff
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
--- (ii) The tycon is defined in this module, the field is marked '!',
--- and the -funbox-strict-fields flag is on.
---
--- This ensures that if we compile some modules with -funbox-strict-fields and
--- some without, the compiler doesn't get confused about the constructor
--- representations.
-
-chooseBoxingStrategy :: TyCon -> Type -> StrictnessMark -> StrictnessMark
- -- Transforms any MarkedUserStricts into MarkUnboxed or MarkedStrict
-chooseBoxingStrategy tycon arg_ty strict
- = case strict of
- MarkedUserStrict
- | opt_UnboxStrictFields
- && unbox arg_ty -> MarkedUnboxed
- | otherwise -> MarkedStrict
- other -> strict
- where
- -- beware: repType will go into a loop if we try this on a recursive
- -- type (for reasons unknown...), hence the check for recursion below.
- unbox ty =
- case splitTyConApp_maybe ty of
- Nothing -> False
- Just (arg_tycon, _)
- | isRecursiveTyCon arg_tycon -> False
- | otherwise ->
- case splitTyConApp_maybe (repType ty) of
- Nothing -> False
- Just (arg_tycon, _) -> isProductTyCon arg_tycon
computeRep :: [StrictnessMark] -- Original arg strictness
- -- [after strategy choice; can't be MarkedUserStrict]
-> [Type] -- and types
-> ([StrictnessMark], -- Representation arg strictness
[Type]) -- And type
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)
+ (_, _, arg_dc, arg_tys) = splitProductType "unbox_strict_arg_ty" ty
\end{code}
projects / ghc-hetmet.git / blobdiff