%
+% (c) The University of Glasgow 2006
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
module BuildTyCl (
buildSynTyCon, buildAlgTyCon, buildDataCon,
buildClass,
- mkAbstractTyConRhs, mkOpenDataTyConRhs, mkOpenNewTyConRhs,
- mkNewTyConRhs, mkDataTyConRhs
+ mkAbstractTyConRhs, mkOpenDataTyConRhs,
+ mkNewTyConRhs, mkDataTyConRhs, setAssocFamilyPermutation
) where
#include "HsVersions.h"
-import IfaceEnv ( newImplicitBinder )
-import TcRnMonad
+import IfaceEnv
-import DataCon ( DataCon, isNullarySrcDataCon, dataConUnivTyVars,
- mkDataCon, dataConFieldLabels, dataConInstOrigArgTys,
- dataConTyCon )
-import Var ( tyVarKind, TyVar, Id )
-import VarSet ( isEmptyVarSet, intersectVarSet, elemVarSet )
-import TysWiredIn ( unitTy )
-import BasicTypes ( RecFlag, StrictnessMark(..) )
-import Name ( Name )
-import OccName ( mkDataConWrapperOcc, mkDataConWorkerOcc, mkClassTyConOcc,
- mkClassDataConOcc, mkSuperDictSelOcc, mkNewTyCoOcc )
-import MkId ( mkDataConIds, mkRecordSelId, mkDictSelId )
-import Class ( mkClass, Class( classTyCon), FunDep, DefMeth(..) )
-import TyCon ( mkSynTyCon, mkAlgTyCon, visibleDataCons,
- tyConStupidTheta, tyConDataCons, isNewTyCon,
- mkClassTyCon, TyCon( tyConTyVars ),
- isRecursiveTyCon, tyConArity, AlgTyConRhs(..),
- SynTyConRhs(..), newTyConRhs )
-import Type ( mkArrowKinds, liftedTypeKind, typeKind,
- tyVarsOfType, tyVarsOfTypes, tyVarsOfPred,
- splitTyConApp_maybe, splitAppTy_maybe,
- getTyVar_maybe,
- mkPredTys, mkTyVarTys, ThetaType, Type, Kind,
- substTyWith, zipTopTvSubst, substTheta, mkForAllTys,
- mkTyConApp, mkTyVarTy )
-import Coercion ( mkNewTypeCoercion )
-import Outputable
-import List ( nub )
+import DataCon
+import Var
+import VarSet
+import BasicTypes
+import Name
+import MkId
+import Class
+import TyCon
+import Type
+import Coercion
+import TcRnMonad
+import Util ( count )
+import Outputable
\end{code}
\begin{code}
------------------------------------------------------
-buildSynTyCon :: Name -> [TyVar] -> SynTyConRhs -> TyCon
-buildSynTyCon name tvs rhs@(OpenSynTyCon rhs_ki)
- = mkSynTyCon name kind tvs rhs
- where
- kind = mkArrowKinds (map tyVarKind tvs) rhs_ki
-buildSynTyCon name tvs rhs@(SynonymTyCon rhs_ty)
- = mkSynTyCon name kind tvs rhs
- where
- kind = mkArrowKinds (map tyVarKind tvs) (typeKind rhs_ty)
-
+buildSynTyCon :: Name -> [TyVar]
+ -> SynTyConRhs
+ -> Kind -- Kind of the RHS
+ -> Maybe (TyCon, [Type]) -- family instance if applicable
+ -> TcRnIf m n TyCon
+
+buildSynTyCon tc_name tvs rhs@(OpenSynTyCon {}) rhs_kind _
+ = let
+ kind = mkArrowKinds (map tyVarKind tvs) rhs_kind
+ in
+ return $ mkSynTyCon tc_name kind tvs rhs NoParentTyCon
+
+buildSynTyCon tc_name tvs rhs@(SynonymTyCon {}) rhs_kind mb_family
+ = do { -- We need to tie a knot as the coercion of a data instance depends
+ -- on the instance representation tycon and vice versa.
+ ; tycon <- fixM (\ tycon_rec -> do
+ { parent <- mkParentInfo mb_family tc_name tvs tycon_rec
+ ; let { tycon = mkSynTyCon tc_name kind tvs rhs parent
+ ; kind = mkArrowKinds (map tyVarKind tvs) rhs_kind
+ }
+ ; return tycon
+ })
+ ; return tycon
+ }
------------------------------------------------------
buildAlgTyCon :: Name -> [TyVar]
-> RecFlag
-> Bool -- True <=> want generics functions
-> Bool -- True <=> was declared in GADT syntax
+ -> Maybe (TyCon, [Type]) -- family instance if applicable
-> TcRnIf m n TyCon
buildAlgTyCon tc_name tvs stupid_theta rhs is_rec want_generics gadt_syn
- = do { let { tycon = mkAlgTyCon tc_name kind tvs stupid_theta
- rhs fields is_rec want_generics gadt_syn
- ; kind = mkArrowKinds (map tyVarKind tvs) liftedTypeKind
- ; fields = mkTyConSelIds tycon rhs
- }
- ; return tycon }
-
+ mb_family
+ = do { -- We need to tie a knot as the coercion of a data instance depends
+ -- on the instance representation tycon and vice versa.
+ ; tycon <- fixM (\ tycon_rec -> do
+ { parent <- mkParentInfo mb_family tc_name tvs tycon_rec
+ ; let { tycon = mkAlgTyCon tc_name kind tvs stupid_theta rhs
+ parent is_rec want_generics gadt_syn
+ ; kind = mkArrowKinds (map tyVarKind tvs) liftedTypeKind
+ }
+ ; return tycon
+ })
+ ; return tycon
+ }
+
+-- If a family tycon with instance types is given, the current tycon is an
+-- instance of that family and we need to
+--
+-- (1) create a coercion that identifies the family instance type and the
+-- representation type from Step (1); ie, it is of the form
+-- `Co tvs :: F ts ~ R tvs', where `Co' is the name of the coercion,
+-- `F' the family tycon and `R' the (derived) representation tycon,
+-- and
+-- (2) produce a `TyConParent' value containing the parent and coercion
+-- information.
+--
+mkParentInfo :: Maybe (TyCon, [Type])
+ -> Name -> [TyVar]
+ -> TyCon
+ -> TcRnIf m n TyConParent
+mkParentInfo Nothing _ _ _ =
+ return NoParentTyCon
+mkParentInfo (Just (family, instTys)) tc_name tvs rep_tycon =
+ do { -- Create the coercion
+ ; co_tycon_name <- newImplicitBinder tc_name mkInstTyCoOcc
+ ; let co_tycon = mkFamInstCoercion co_tycon_name tvs
+ family instTys rep_tycon
+ ; return $ FamilyTyCon family instTys co_tycon
+ }
+
------------------------------------------------------
mkAbstractTyConRhs :: AlgTyConRhs
mkAbstractTyConRhs = AbstractTyCon
mkOpenDataTyConRhs :: AlgTyConRhs
-mkOpenDataTyConRhs = OpenDataTyCon
-
-mkOpenNewTyConRhs :: AlgTyConRhs
-mkOpenNewTyConRhs = OpenNewTyCon
+mkOpenDataTyConRhs = OpenTyCon Nothing
mkDataTyConRhs :: [DataCon] -> AlgTyConRhs
mkDataTyConRhs cons
- = DataTyCon { data_cons = cons, is_enum = all isNullarySrcDataCon cons }
+ = DataTyCon {
+ data_cons = cons,
+ is_enum = -- We define datatypes with no constructors to not be
+ -- enumerations; this fixes trac #2578, Otherwise we
+ -- end up generating an empty table for
+ -- <mod>_<type>_closure_tbl
+ -- which is used by tagToEnum# to map Int# to constructors
+ -- in an enumeration. The empty table apparently upset
+ -- the linker.
+ not (null cons) &&
+ all isNullarySrcDataCon cons
+ }
mkNewTyConRhs :: Name -> TyCon -> DataCon -> TcRnIf m n AlgTyConRhs
-- Monadic because it makes a Name for the coercion TyCon
-- because the latter is part of a knot, whereas the former is not.
mkNewTyConRhs tycon_name tycon con
= do { co_tycon_name <- newImplicitBinder tycon_name mkNewTyCoOcc
- ; let co_tycon = mkNewTypeCoercion co_tycon_name tycon tvs rhs_ty
- cocon_maybe
- | all_coercions || isRecursiveTyCon tycon
- = Just co_tycon
- | otherwise
- = Nothing
- ; return (NewTyCon { data_con = con,
- nt_co = cocon_maybe,
+ ; let co_tycon = mkNewTypeCoercion co_tycon_name tycon etad_tvs etad_rhs
+ cocon_maybe | all_coercions || isRecursiveTyCon tycon
+ = Just co_tycon
+ | otherwise
+ = Nothing
+ ; traceIf (text "mkNewTyConRhs" <+> ppr cocon_maybe)
+ ; return (NewTyCon { data_con = con,
+ nt_rhs = rhs_ty,
+ nt_etad_rhs = (etad_tvs, etad_rhs),
+ nt_co = cocon_maybe } ) }
-- Coreview looks through newtypes with a Nothing
-- for nt_co, or uses explicit coercions otherwise
- nt_rhs = rhs_ty,
- nt_etad_rhs = eta_reduce tvs rhs_ty,
- nt_rep = mkNewTyConRep tycon rhs_ty }) }
where
- -- if all_coercions is True then we use coercions for all newtypes
+ -- If all_coercions is True then we use coercions for all newtypes
-- otherwise we use coercions for recursive newtypes and look through
-- non-recursive newtypes
all_coercions = True
tvs = tyConTyVars tycon
- rhs_ty = head (dataConInstOrigArgTys con (mkTyVarTys tvs))
+ inst_con_ty = applyTys (dataConUserType con) (mkTyVarTys tvs)
+ rhs_ty = ASSERT( isFunTy inst_con_ty ) funArgTy inst_con_ty
-- Instantiate the data con with the
-- type variables from the tycon
-
- eta_reduce [] ty = ([], ty)
- eta_reduce (a:as) ty | null as',
- Just (fun, arg) <- splitAppTy_maybe ty',
+ -- NB: a newtype DataCon has a type that must look like
+ -- forall tvs. <arg-ty> -> T tvs
+ -- Note that we *can't* use dataConInstOrigArgTys here because
+ -- the newtype arising from class Foo a => Bar a where {}
+ -- has a single argument (Foo a) that is a *type class*, so
+ -- dataConInstOrigArgTys returns [].
+
+ etad_tvs :: [TyVar] -- Matched lazily, so that mkNewTypeCoercion can
+ etad_rhs :: Type -- return a TyCon without pulling on rhs_ty
+ -- See Note [Tricky iface loop] in LoadIface
+ (etad_tvs, etad_rhs) = eta_reduce (reverse tvs) rhs_ty
+
+ eta_reduce :: [TyVar] -- Reversed
+ -> Type -- Rhs type
+ -> ([TyVar], Type) -- Eta-reduced version (tyvars in normal order)
+ eta_reduce (a:as) ty | Just (fun, arg) <- splitAppTy_maybe ty,
Just tv <- getTyVar_maybe arg,
tv == a,
not (a `elemVarSet` tyVarsOfType fun)
- = ([], fun) -- Successful eta reduction
- | otherwise
- = (a:as', ty')
- where
- (as', ty') = eta_reduce as ty
+ = eta_reduce as fun
+ eta_reduce tvs ty = (reverse tvs, ty)
-mkNewTyConRep :: TyCon -- The original type constructor
- -> Type -- The arg type of its constructor
- -> Type -- Chosen representation type
--- The "representation type" is guaranteed not to be another newtype
--- at the outermost level; but it might have newtypes in type arguments
-
--- Find the representation type for this newtype TyCon
--- Remember that the representation type is the *ultimate* representation
--- type, looking through other newtypes.
---
--- splitTyConApp_maybe no longer looks through newtypes, so we must
--- deal explicitly with this case
---
--- The trick is to to deal correctly with recursive newtypes
--- such as newtype T = MkT T
-
-mkNewTyConRep tc rhs_ty
- | null (tyConDataCons tc) = unitTy
- -- External Core programs can have newtypes with no data constructors
- | otherwise = go [tc] rhs_ty
- where
- -- Invariant: tcs have been seen before
- go tcs rep_ty
- = case splitTyConApp_maybe rep_ty of
- Just (tc, tys)
- | tc `elem` tcs -> unitTy -- Recursive loop
- | isNewTyCon tc ->
- if isRecursiveTyCon tc then
- go (tc:tcs) (substTyWith tvs tys rhs_ty)
- else
- substTyWith tvs tys rhs_ty
- where
- (tvs, rhs_ty) = newTyConRhs tc
-
- other -> rep_ty
+
+setAssocFamilyPermutation :: [TyVar] -> TyThing -> TyThing
+setAssocFamilyPermutation clas_tvs (ATyCon tc)
+ = ATyCon (setTyConArgPoss clas_tvs tc)
+setAssocFamilyPermutation _clas_tvs other
+ = pprPanic "setAssocFamilyPermutation" (ppr other)
+
------------------------------------------------------
buildDataCon :: Name -> Bool
- -> [StrictnessMark]
+ -> [HsBang]
-> [Name] -- Field labels
-> [TyVar] -> [TyVar] -- Univ and ext
-> [(TyVar,Type)] -- Equality spec
-> ThetaType -- Does not include the "stupid theta"
-- or the GADT equalities
- -> [Type] -> TyCon
+ -> [Type] -> Type -- Argument and result types
+ -> TyCon -- Rep tycon
-> TcRnIf m n DataCon
-- A wrapper for DataCon.mkDataCon that
-- a) makes the worker Id
-- b) makes the wrapper Id if necessary, including
-- allocating its unique (hence monadic)
buildDataCon src_name declared_infix arg_stricts field_lbls
- univ_tvs ex_tvs eq_spec ctxt arg_tys tycon
+ univ_tvs ex_tvs eq_spec ctxt arg_tys res_ty rep_tycon
= do { wrap_name <- newImplicitBinder src_name mkDataConWrapperOcc
; work_name <- newImplicitBinder src_name mkDataConWorkerOcc
-- This last one takes the name of the data constructor in the source
-- space, and puts it into the VarName name space
; let
- stupid_ctxt = mkDataConStupidTheta tycon arg_tys univ_tvs
+ stupid_ctxt = mkDataConStupidTheta rep_tycon arg_tys univ_tvs
data_con = mkDataCon src_name declared_infix
arg_stricts field_lbls
univ_tvs ex_tvs eq_spec ctxt
- arg_tys tycon stupid_ctxt dc_ids
+ arg_tys res_ty rep_tycon
+ stupid_ctxt dc_ids
dc_ids = mkDataConIds wrap_name work_name data_con
- ; returnM data_con }
+ ; return data_con }
-- The stupid context for a data constructor should be limited to
-- the type variables mentioned in the arg_tys
-- ToDo: Or functionally dependent on?
-- This whole stupid theta thing is, well, stupid.
+mkDataConStupidTheta :: TyCon -> [Type] -> [TyVar] -> [PredType]
mkDataConStupidTheta tycon arg_tys univ_tvs
| null stupid_theta = [] -- The common case
| otherwise = filter in_arg_tys stupid_theta
arg_tyvars = tyVarsOfTypes arg_tys
in_arg_tys pred = not $ isEmptyVarSet $
tyVarsOfPred pred `intersectVarSet` arg_tyvars
-
-------------------------------------------------------
-mkTyConSelIds :: TyCon -> AlgTyConRhs -> [Id]
-mkTyConSelIds tycon rhs
- = [ mkRecordSelId tycon fld
- | fld <- nub (concatMap dataConFieldLabels (visibleDataCons rhs)) ]
- -- We'll check later that fields with the same name
- -- from different constructors have the same type.
\end{code}
------------------------------------------------------
\begin{code}
-buildClass :: Name -> [TyVar] -> ThetaType
+buildClass :: Bool -- True <=> do not include unfoldings
+ -- on dict selectors
+ -- Used when importing a class without -O
+ -> Name -> [TyVar] -> ThetaType
-> [FunDep TyVar] -- Functional dependencies
+ -> [TyThing] -- Associated types
-> [(Name, DefMeth, Type)] -- Method info
-> RecFlag -- Info for type constructor
-> TcRnIf m n Class
-buildClass class_name tvs sc_theta fds sig_stuff tc_isrec
- = do { tycon_name <- newImplicitBinder class_name mkClassTyConOcc
+buildClass no_unf class_name tvs sc_theta fds ats sig_stuff tc_isrec
+ = do { traceIf (text "buildClass")
+ ; tycon_name <- newImplicitBinder class_name mkClassTyConOcc
; datacon_name <- newImplicitBinder class_name mkClassDataConOcc
-- The class name is the 'parent' for this datacon, not its tycon,
-- because one should import the class to get the binding for
-- the datacon
- ; sc_sel_names <- mapM (newImplicitBinder class_name . mkSuperDictSelOcc)
- [1..length sc_theta]
- -- We number off the superclass selectors, 1, 2, 3 etc so that we
- -- can construct names for the selectors. Thus
+
+ ; fixM (\ rec_clas -> do { -- Only name generation inside loop
+
+ let { rec_tycon = classTyCon rec_clas
+ ; op_tys = [ty | (_,_,ty) <- sig_stuff]
+ ; op_names = [op | (op,_,_) <- sig_stuff]
+ ; op_items = [ (mkDictSelId no_unf op_name rec_clas, dm_info)
+ | (op_name, dm_info, _) <- sig_stuff ] }
+ -- Build the selector id and default method id
+
+ ; let n_value_preds = count (not . isEqPred) sc_theta
+ all_value_preds = n_value_preds == length sc_theta
+ -- We only make selectors for the *value* superclasses,
+ -- not equality predicates
+
+ ; sc_sel_names <- mapM (newImplicitBinder class_name . mkSuperDictSelOcc)
+ [1..n_value_preds]
+ ; let sc_sel_ids = [mkDictSelId no_unf sc_name rec_clas | sc_name <- sc_sel_names]
+ -- We number off the Dict superclass selectors, 1, 2, 3 etc so that we
+ -- can construct names for the selectors. Thus
-- class (C a, C b) => D a b where ...
-- gives superclass selectors
-- D_sc1, D_sc2
-- (We used to call them D_C, but now we can have two different
-- superclasses both called C!)
-
- ; fixM (\ rec_clas -> do { -- Only name generation inside loop
-
- let { rec_tycon = classTyCon rec_clas
- ; op_tys = [ty | (_,_,ty) <- sig_stuff]
- ; sc_tys = mkPredTys sc_theta
- ; dict_component_tys = sc_tys ++ op_tys
- ; sc_sel_ids = [mkDictSelId sc_name rec_clas | sc_name <- sc_sel_names]
- ; op_items = [ (mkDictSelId op_name rec_clas, dm_info)
- | (op_name, dm_info, _) <- sig_stuff ] }
- -- Build the selector id and default method id
+ --
+
+ ; let use_newtype = (n_value_preds + length sig_stuff == 1) && all_value_preds
+ -- Use a newtype if the data constructor has
+ -- (a) exactly one value field
+ -- (b) no existential or equality-predicate fields
+ -- i.e. exactly one operation or superclass taken together
+ -- See note [Class newtypes and equality predicates]
+
+ -- We play a bit fast and loose by treating the superclasses
+ -- as ordinary arguments. That means that in the case of
+ -- class C a => D a
+ -- we don't get a newtype with no arguments!
+ args = sc_sel_names ++ op_names
+ arg_tys = map mkPredTy sc_theta ++ op_tys
; dict_con <- buildDataCon datacon_name
False -- Not declared infix
- (map (const NotMarkedStrict) dict_component_tys)
- [{- No labelled fields -}]
+ (map (const HsNoBang) args)
+ [{- No fields -}]
tvs [{- no existentials -}]
- [{- No equalities -}] [{-No context-}]
- dict_component_tys
+ [{- No GADT equalities -}] [{- No theta -}]
+ arg_tys
+ (mkTyConApp rec_tycon (mkTyVarTys tvs))
rec_tycon
- ; rhs <- case dict_component_tys of
- [rep_ty] -> mkNewTyConRhs tycon_name rec_tycon dict_con
- other -> return (mkDataTyConRhs [dict_con])
+ ; rhs <- if use_newtype
+ then mkNewTyConRhs tycon_name rec_tycon dict_con
+ else return (mkDataTyConRhs [dict_con])
; let { clas_kind = mkArrowKinds (map tyVarKind tvs) liftedTypeKind
; tycon = mkClassTyCon tycon_name clas_kind tvs
- rhs rec_clas tc_isrec
+ rhs rec_clas tc_isrec
-- A class can be recursive, and in the case of newtypes
-- this matters. For example
-- class C a where { op :: C b => a -> b -> Int }
-- Because C has only one operation, it is represented by
-- a newtype, and it should be a *recursive* newtype.
-- [If we don't make it a recursive newtype, we'll expand the
- -- newtype like a synonym, but that will lead to an infinite type]
+ -- newtype like a synonym, but that will lead to an infinite
+ -- type]
+ ; atTyCons = [tycon | ATyCon tycon <- ats]
+
+ ; result = mkClass class_name tvs fds
+ sc_theta sc_sel_ids atTyCons
+ op_items tycon
}
- ; return (mkClass class_name tvs fds
- sc_theta sc_sel_ids op_items
- tycon)
+ ; traceIf (text "buildClass" <+> ppr tycon)
+ ; return result
})}
\end{code}
+Note [Class newtypes and equality predicates]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Consider
+ class (a ~ F b) => C a b where
+ op :: a -> b
+
+We cannot represent this by a newtype, even though it's not
+existential, and there's only one value field, because we do
+capture an equality predicate:
+
+ data C a b where
+ MkC :: forall a b. (a ~ F b) => (a->b) -> C a b
+
+We need to access this equality predicate when we get passes a C
+dictionary. See Trac #2238
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