%
-% (c) The AQUA Project, Glasgow University, 1996
+% (c) The AQUA Project, Glasgow University, 1996-1998
%
\section[TcTyClsDecls]{Typecheck type and class declarations}
\begin{code}
-#include "HsVersions.h"
-
module TcTyClsDecls (
- tcTyAndClassDecls1
+ tcTyAndClassDecls
) where
-IMP_Ubiq(){-uitous-}
+#include "HsVersions.h"
-import HsSyn ( HsDecl(..), TyDecl(..), ConDecl(..), ConDetails(..), BangType(..),
- ClassDecl(..), HsType(..), HsTyVar, DefaultDecl, InstDecl,
- IfaceSig, Sig(..), MonoBinds, Fake, InPat, HsBinds(..), HsExpr, NewOrData,
- hsDeclName
+import HsSyn ( TyClDecl(..),
+ ConDecl(..), Sig(..), HsPred(..),
+ tyClDeclName, hsTyVarNames, tyClDeclTyVars,
+ isTypeOrClassDecl, isClassDecl, isSynDecl, isClassOpSig
)
-import RnHsSyn ( RenamedTyDecl(..), RenamedClassDecl(..), SYN_IE(RenamedHsDecl)
- )
-import TcHsSyn ( SYN_IE(TcHsBinds), TcIdOcc(..) )
-
-import TcMonad
-import Inst ( SYN_IE(InstanceMapper) )
+import RnHsSyn ( RenamedTyClDecl, tyClDeclFVs )
+import BasicTypes ( RecFlag(..), NewOrData(..) )
+import HscTypes ( implicitTyThings )
+
+import TcRnMonad
+import TcEnv ( TcTyThing(..), TyThing(..), TyThingDetails(..),
+ tcExtendKindEnv, tcLookup, tcLookupGlobal, tcExtendGlobalEnv,
+ isLocalThing )
+import TcTyDecls ( tcTyDecl, kcConDetails )
import TcClassDcl ( tcClassDecl1 )
-import TcEnv ( tcExtendTyConEnv, tcExtendClassEnv )
-import SpecEnv ( SpecEnv )
-import TcKind ( TcKind, newKindVars )
-import TcTyDecls ( tcTyDecl, mkDataBinds )
-import TcMonoType ( tcTyVarScope )
-
-import Bag
-import Class ( SYN_IE(Class) )
+import TcInstDcls ( tcAddDeclCtxt )
+import TcMonoType ( kcHsTyVars, kcHsType, kcHsLiftedSigType, kcHsContext, mkTyClTyVars )
+import TcMType ( newKindVar, zonkKindEnv, checkValidTyCon, checkValidClass )
+import TcUnify ( unifyKind )
+import TcType ( Type, Kind, TcKind, mkArrowKind, liftedTypeKind, zipFunTys )
+import Type ( splitTyConApp_maybe )
+import Variance ( calcTyConArgVrcs )
+import Class ( Class, mkClass, classTyCon )
+import TyCon ( TyCon, ArgVrcs, AlgTyConFlavour(..), DataConDetails(..), visibleDataCons,
+ tyConKind, tyConTyVars, tyConDataCons, isNewTyCon,
+ mkSynTyCon, mkAlgTyCon, mkClassTyCon, mkForeignTyCon
+ )
+import TysWiredIn ( unitTy )
+import Subst ( substTyWith )
+import DataCon ( dataConOrigArgTys )
+import Var ( varName )
+import FiniteMap
import Digraph ( stronglyConnComp, SCC(..) )
-import Name ( Name, getSrcLoc, isTvOcc, nameOccName )
+import Name ( Name )
+import NameEnv
+import NameSet
import Outputable
-import Pretty
import Maybes ( mapMaybe )
-import UniqSet ( SYN_IE(UniqSet), emptyUniqSet,
- unitUniqSet, unionUniqSets,
- unionManyUniqSets, uniqSetToList )
-import SrcLoc ( SrcLoc )
-import TyCon ( TyCon, SYN_IE(Arity) )
-import Unique ( Unique, Uniquable(..) )
-import Util ( panic{-, pprTrace-} )
-
\end{code}
+
+%************************************************************************
+%* *
+\subsection{Type checking for type and class declarations}
+%* *
+%************************************************************************
+
The main function
~~~~~~~~~~~~~~~~~
\begin{code}
-tcTyAndClassDecls1 :: TcEnv s -> InstanceMapper -- Knot tying stuff
- -> [RenamedHsDecl]
- -> TcM s (TcEnv s)
+tcTyAndClassDecls :: [RenamedTyClDecl]
+ -> TcM TcGblEnv -- Returns extended environment
-tcTyAndClassDecls1 unf_env inst_mapper decls
- = sortByDependency decls `thenTc` \ groups ->
- tcGroups unf_env inst_mapper groups
-
-tcGroups unf_env inst_mapper []
- = tcGetEnv `thenNF_Tc` \ env ->
- returnTc env
-
-tcGroups unf_env inst_mapper (group:groups)
- = tcGroup unf_env inst_mapper group `thenTc` \ new_env ->
+tcTyAndClassDecls decls
+ = tcGroups (stronglyConnComp edges)
+ where
+ edges = map mkEdges (filter isTypeOrClassDecl decls)
- -- Extend the environment using the new tycons and classes
- tcSetEnv new_env $
+tcGroups [] = getGblEnv
- -- Do the remaining groups
- tcGroups unf_env inst_mapper groups
+tcGroups (group:groups)
+ = tcGroup group `thenM` \ env ->
+ setGblEnv env $
+ tcGroups groups
\end{code}
Dealing with a group
~~~~~~~~~~~~~~~~~~~~
-\begin{code}
-tcGroup :: TcEnv s -> InstanceMapper -> Bag RenamedHsDecl -> TcM s (TcEnv s)
-tcGroup unf_env inst_mapper decls
- = -- TIE THE KNOT
- fixTc ( \ ~(tycons,classes,_) ->
-
- -- EXTEND TYPE AND CLASS ENVIRONMENTS
- -- NB: it's important that the tycons and classes come back in just
- -- the same order from this fix as from get_binders, so that these
- -- extend-env things work properly. A bit UGH-ish.
- tcExtendTyConEnv tycon_names_w_arities tycons $
- tcExtendClassEnv class_names classes $
-
- -- DEAL WITH TYPE VARIABLES
- tcTyVarScope tyvar_names ( \ tyvars ->
-
- -- DEAL WITH THE DEFINITIONS THEMSELVES
- foldBag combine (tcDecl unf_env inst_mapper)
- (returnTc (emptyBag, emptyBag))
- decls
- ) `thenTc` \ (tycon_bag,class_bag) ->
- let
- tycons = bagToList tycon_bag
- classes = bagToList class_bag
- in
-
- -- SNAFFLE ENV TO RETURN
- tcGetEnv `thenNF_Tc` \ final_env ->
-
- returnTc (tycons, classes, final_env)
- ) `thenTc` \ (_, _, final_env) ->
-
- returnTc final_env
+Consider a mutually-recursive group, binding
+a type constructor T and a class C.
- where
- (tyvar_names, tycon_names_w_arities, class_names) = get_binders decls
+Step 1: getInitialKind
+ Construct a KindEnv by binding T and C to a kind variable
- combine do_a do_b
- = do_a `thenTc` \ (a1,a2) ->
- do_b `thenTc` \ (b1,b2) ->
- returnTc (a1 `unionBags` b1, a2 `unionBags` b2)
-\end{code}
+Step 2: kcTyClDecl
+ In that environment, do a kind check
-Dealing with one decl
-~~~~~~~~~~~~~~~~~~~~~
-\begin{code}
-tcDecl :: TcEnv s -> InstanceMapper
- -> RenamedHsDecl
- -> TcM s (Bag TyCon, Bag Class)
+Step 3: Zonk the kinds
-tcDecl unf_env inst_mapper (TyD decl)
- = tcTyDecl decl `thenTc` \ tycon ->
- returnTc (unitBag tycon, emptyBag)
+Step 4: buildTyConOrClass
+ Construct an environment binding T to a TyCon and C to a Class.
+ a) Their kinds comes from zonking the relevant kind variable
+ b) Their arity (for synonyms) comes direct from the decl
+ c) The funcional dependencies come from the decl
+ d) The rest comes a knot-tied binding of T and C, returned from Step 4
+ e) The variances of the tycons in the group is calculated from
+ the knot-tied stuff
-tcDecl unf_env inst_mapper (ClD decl)
- = tcClassDecl1 unf_env inst_mapper decl `thenTc` \ clas ->
- returnTc (emptyBag, unitBag clas)
-\end{code}
+Step 5: tcTyClDecl1
+ In this environment, walk over the decls, constructing the TyCons and Classes.
+ This uses in a strict way items (a)-(c) above, which is why they must
+ be constructed in Step 4. Feed the results back to Step 4.
+ For this step, pass the is-recursive flag as the wimp-out flag
+ to tcTyClDecl1.
+
-Dependency analysis
-~~~~~~~~~~~~~~~~~~~
-\begin{code}
-sortByDependency :: [RenamedHsDecl] -> TcM s [Bag RenamedHsDecl]
-sortByDependency decls
- = let -- CHECK FOR SYNONYM CYCLES
- syn_sccs = stronglyConnComp (filter is_syn_decl edges)
- syn_cycles = [ decls | CyclicSCC decls <- syn_sccs]
+Step 6: Extend environment
+ We extend the type environment with bindings not only for the TyCons and Classes,
+ but also for their "implicit Ids" like data constructors and class selectors
- in
- checkTc (null syn_cycles) (typeCycleErr syn_cycles) `thenTc_`
+Step 7: checkValidTyCl
+ For a recursive group only, check all the decls again, just
+ to check all the side conditions on validity. We could not
+ do this before because we were in a mutually recursive knot.
- let -- CHECK FOR CLASS CYCLES
- cls_sccs = stronglyConnComp (filter is_cls_decl edges)
- cls_cycles = [ decls | CyclicSCC decls <- cls_sccs]
- in
- checkTc (null cls_cycles) (classCycleErr cls_cycles) `thenTc_`
+The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to
+@TyThing@s. @rec_vrcs@ is a finite map from @Name@s to @ArgVrcs@s.
- -- DO THE MAIN DEPENDENCY ANALYSIS
- let
- decl_sccs = stronglyConnComp (filter is_ty_cls_decl edges)
- scc_bags = map bag_acyclic decl_sccs
+\begin{code}
+tcGroup :: SCC RenamedTyClDecl
+ -> TcM TcGblEnv -- Input env extended by types and classes
+ -- and their implicit Ids,DataCons
+
+tcGroup scc
+ = -- Step 1
+ mappM getInitialKind decls `thenM` \ initial_kinds ->
+
+ -- Step 2
+ tcExtendKindEnv initial_kinds (mappM kcTyClDecl decls) `thenM_`
+
+ -- Step 3
+ zonkKindEnv initial_kinds `thenM` \ final_kinds ->
+
+ -- Check for loops; if any are found, bale out now
+ -- because the compiler itself will loop otherwise!
+ checkNoErrs (checkLoops scc) `thenM` \ is_rec_tycon ->
+
+ -- Tie the knot
+ traceTc (text "starting" <+> ppr final_kinds) `thenM_`
+ fixM ( \ ~(rec_details_list, _, rec_all_tyclss) ->
+ -- Step 4
+ let
+ kind_env = mkNameEnv final_kinds
+ rec_details = mkNameEnv rec_details_list
+
+ -- Calculate variances, and feed into buildTyConOrClass
+ rec_vrcs = calcTyConArgVrcs [tc | ATyCon tc <- rec_all_tyclss]
+
+ build_one = buildTyConOrClass is_rec_tycon kind_env
+ rec_vrcs rec_details
+ tyclss = map build_one decls
+
+ in
+ -- Step 5
+ -- Extend the environment with the final
+ -- TyCons/Classes and check the decls
+ tcExtendGlobalEnv tyclss $
+ mappM tcTyClDecl1 decls `thenM` \ tycls_details ->
+
+ -- Return results
+ getGblEnv `thenM` \ env ->
+ returnM (tycls_details, env, tyclss)
+ ) `thenM` \ (_, env, tyclss) ->
+
+ -- Step 7: Check validity
+ setGblEnv env $
+
+ traceTc (text "ready for validity check") `thenM_`
+ getModule `thenM` \ mod ->
+ mappM_ (checkValidTyCl mod) decls `thenM_`
+ traceTc (text "done") `thenM_`
+
+ let -- Add the tycons that come from the classes
+ -- We want them in the environment because
+ -- they are mentioned in interface files
+ implicit_things = implicitTyThings tyclss
in
- returnTc (scc_bags)
+ traceTc ((text "Adding" <+> ppr tyclss) $$ (text "and" <+> ppr implicit_things)) `thenM_`
+ tcExtendGlobalEnv implicit_things getGblEnv
where
- edges = mapMaybe mk_edges decls
-
-bag_acyclic (AcyclicSCC scc) = unitBag scc
-bag_acyclic (CyclicSCC sccs) = listToBag sccs
-
-is_syn_decl (TyD (TySynonym _ _ _ _), _, _) = True
-is_syn_decl _ = False
-
-is_ty_cls_decl (TyD _, _, _) = True
-is_ty_cls_decl (ClD _, _, _) = True
-is_ty_cls_decl other = False
-
-is_cls_decl (ClD _, _, _) = True
-is_cls_decl other = False
+ decls = case scc of
+ AcyclicSCC decl -> [decl]
+ CyclicSCC decls -> decls
+
+tcTyClDecl1 decl
+ | isClassDecl decl = tcAddDeclCtxt decl (tcClassDecl1 decl)
+ | otherwise = tcAddDeclCtxt decl (tcTyDecl decl)
+
+-- We do the validity check over declarations, rather than TyThings
+-- only so that we can add a nice context with tcAddDeclCtxt
+checkValidTyCl this_mod decl
+ = tcLookupGlobal (tcdName decl) `thenM` \ thing ->
+ if not (isLocalThing this_mod thing) then
+ -- Don't bother to check validity for non-local things
+ returnM ()
+ else
+ tcAddDeclCtxt decl $
+ case thing of
+ ATyCon tc -> checkValidTyCon tc
+ AClass cl -> checkValidClass cl
\end{code}
-Edges in Type/Class decls
-~~~~~~~~~~~~~~~~~~~~~~~~~
-\begin{code}
-mk_edges decl@(TyD (TyData _ ctxt name _ condecls derivs _ _))
- = Just (decl, uniqueOf name, uniqSetToList (get_ctxt ctxt `unionUniqSets`
- get_cons condecls `unionUniqSets`
- get_deriv derivs))
-mk_edges decl@(TyD (TySynonym name _ rhs _))
- = Just (decl, uniqueOf name, uniqSetToList (get_ty rhs))
+%************************************************************************
+%* *
+\subsection{Step 1: Initial environment}
+%* *
+%************************************************************************
-mk_edges decl@(ClD (ClassDecl ctxt name _ sigs _ _ _))
- = Just (decl, uniqueOf name, uniqSetToList (get_ctxt ctxt `unionUniqSets`
- get_sigs sigs))
+\begin{code}
+getInitialKind :: RenamedTyClDecl -> TcM (Name, TcKind)
+getInitialKind decl
+ = kcHsTyVars (tyClDeclTyVars decl) `thenM` \ arg_kinds ->
+ newKindVar `thenM` \ result_kind ->
+ returnM (tcdName decl, mk_kind arg_kinds result_kind)
-mk_edges other_decl = Nothing
+mk_kind tvs_w_kinds res_kind = foldr (mkArrowKind . snd) res_kind tvs_w_kinds
+\end{code}
-get_ctxt ctxt = unionManyUniqSets (map (set_name.fst) ctxt)
-get_deriv Nothing = emptyUniqSet
-get_deriv (Just clss) = unionManyUniqSets (map set_name clss)
+%************************************************************************
+%* *
+\subsection{Step 2: Kind checking}
+%* *
+%************************************************************************
-get_cons cons = unionManyUniqSets (map get_con cons)
+We need to kind check all types in the mutually recursive group
+before we know the kind of the type variables. For example:
-get_con (ConDecl _ ctxt details _)
- = get_ctxt ctxt `unionUniqSets` get_con_details details
+class C a where
+ op :: D b => a -> b -> b
-get_con_details (VanillaCon btys) = unionManyUniqSets (map get_bty btys)
-get_con_details (InfixCon bty1 bty2) = unionUniqSets (get_bty bty1) (get_bty bty2)
-get_con_details (NewCon ty) = get_ty ty
-get_con_details (RecCon nbtys) = unionManyUniqSets (map (get_bty.snd) nbtys)
+class D c where
+ bop :: (Monad c) => ...
-get_bty (Banged ty) = get_ty ty
-get_bty (Unbanged ty) = get_ty ty
+Here, the kind of the locally-polymorphic type variable "b"
+depends on *all the uses of class D*. For example, the use of
+Monad c in bop's type signature means that D must have kind Type->Type.
-get_ty (MonoTyVar name)
- = if isTvOcc (nameOccName name) then emptyUniqSet else set_name name
-get_ty (MonoTyApp ty1 ty2)
- = unionUniqSets (get_ty ty1) (get_ty ty2)
-get_ty (MonoFunTy ty1 ty2)
- = unionUniqSets (get_ty ty1) (get_ty ty2)
-get_ty (MonoListTy tc ty)
- = set_name tc `unionUniqSets` get_ty ty
-get_ty (MonoTupleTy tc tys)
- = set_name tc `unionUniqSets` get_tys tys
-get_ty (HsForAllTy _ ctxt mty)
- = get_ctxt ctxt `unionUniqSets` get_ty mty
-get_ty other = panic "TcTyClsDecls:get_ty"
+\begin{code}
+kcTyClDecl :: RenamedTyClDecl -> TcM ()
-get_tys tys
- = unionManyUniqSets (map get_ty tys)
+kcTyClDecl decl@(TySynonym {tcdSynRhs = rhs})
+ = kcTyClDeclBody decl $ \ result_kind ->
+ kcHsType rhs `thenM` \ rhs_kind ->
+ unifyKind result_kind rhs_kind
-get_sigs sigs
- = unionManyUniqSets (map get_sig sigs)
- where
- get_sig (ClassOpSig _ _ ty _) = get_ty ty
- get_sig other = panic "TcTyClsDecls:get_sig"
+kcTyClDecl (ForeignType {}) = returnM ()
-set_name name = unitUniqSet (uniqueOf name)
+kcTyClDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = context, tcdCons = con_decls})
+ = kcTyClDeclBody decl $ \ result_kind ->
+ kcHsContext context `thenM_`
+ mappM_ kc_con_decl (visibleDataCons con_decls)
+ where
+ kc_con_decl (ConDecl _ ex_tvs ex_ctxt details loc)
+ = kcHsTyVars ex_tvs `thenM` \ kind_env ->
+ tcExtendKindEnv kind_env $
+ kcConDetails new_or_data ex_ctxt details
+
+kcTyClDecl decl@(ClassDecl {tcdCtxt = context, tcdSigs = class_sigs})
+ = kcTyClDeclBody decl $ \ result_kind ->
+ kcHsContext context `thenM_`
+ mappM_ kc_sig (filter isClassOpSig class_sigs)
+ where
+ kc_sig (ClassOpSig _ _ op_ty loc) = kcHsLiftedSigType op_ty
+
+kcTyClDeclBody :: RenamedTyClDecl -> (Kind -> TcM a) -> TcM a
+-- Extend the env with bindings for the tyvars, taken from
+-- the kind of the tycon/class. Give it to the thing inside, and
+-- check the result kind matches
+kcTyClDeclBody decl thing_inside
+ = tcAddDeclCtxt decl $
+ tcLookup (tcdName decl) `thenM` \ thing ->
+ let
+ kind = case thing of
+ AGlobal (ATyCon tc) -> tyConKind tc
+ AGlobal (AClass cl) -> tyConKind (classTyCon cl)
+ AThing kind -> kind
+ -- For some odd reason, a class doesn't include its kind
-set_to_bag set = listToBag (uniqSetToList set)
+ (tyvars_w_kinds, result_kind) = zipFunTys (hsTyVarNames (tyClDeclTyVars decl)) kind
+ in
+ tcExtendKindEnv tyvars_w_kinds (thing_inside result_kind)
\end{code}
-get_binders
-~~~~~~~~~~~
-Extract *binding* names from type and class decls. Type variables are
-bound in type, data, newtype and class declarations and the polytypes
-in the class op sigs.
-Why do we need to grab all these type variables at once, including
-those locally-quantified type variables in class op signatures?
-Because we can only commit to the final kind of a type variable when
-we've completed the mutually recursive group. For example:
+%************************************************************************
+%* *
+\subsection{Step 4: Building the tycon/class}
+%* *
+%************************************************************************
-class C a where
- op :: D b => a -> b -> b
-
-class D c where
- bop :: (Monad c) => ...
+\begin{code}
+buildTyConOrClass
+ :: (Name -> AlgTyConFlavour -> RecFlag) -- Whether it's recursive
+ -> NameEnv Kind
+ -> FiniteMap TyCon ArgVrcs -> NameEnv TyThingDetails
+ -> RenamedTyClDecl -> TyThing
+
+buildTyConOrClass rec_tycon kenv rec_vrcs rec_details
+ (TySynonym {tcdName = tycon_name, tcdTyVars = tyvar_names})
+ = ATyCon tycon
+ where
+ tycon = mkSynTyCon tycon_name tycon_kind arity tyvars rhs_ty argvrcs
+ tycon_kind = lookupNameEnv_NF kenv tycon_name
+ arity = length tyvar_names
+ tyvars = mkTyClTyVars tycon_kind tyvar_names
+ SynTyDetails rhs_ty = lookupNameEnv_NF rec_details tycon_name
+ argvrcs = lookupWithDefaultFM rec_vrcs bogusVrcs tycon
+
+buildTyConOrClass rec_tycon kenv rec_vrcs rec_details
+ (TyData {tcdND = data_or_new, tcdName = tycon_name,
+ tcdTyVars = tyvar_names})
+ = ATyCon tycon
+ where
+ tycon = mkAlgTyCon tycon_name tycon_kind tyvars ctxt argvrcs
+ data_cons sel_ids flavour
+ (rec_tycon tycon_name flavour) gen_info
+
+ DataTyDetails ctxt data_cons sel_ids gen_info = lookupNameEnv_NF rec_details tycon_name
+
+ tycon_kind = lookupNameEnv_NF kenv tycon_name
+ tyvars = mkTyClTyVars tycon_kind tyvar_names
+ argvrcs = lookupWithDefaultFM rec_vrcs bogusVrcs tycon
+
+ -- Watch out! mkTyConApp asks whether the tycon is a NewType,
+ -- so flavour has to be able to answer this question without consulting rec_details
+ flavour = case data_or_new of
+ NewType -> NewTyCon (mkNewTyConRep tycon)
+ DataType | all_nullary data_cons -> EnumTyCon
+ | otherwise -> DataTyCon
+
+ all_nullary (DataCons cons) = all (null . dataConOrigArgTys) cons
+ all_nullary other = False -- Safe choice for unknown data types
+ -- NB (null . dataConOrigArgTys). It used to say isNullaryDataCon
+ -- but that looks at the *representation* arity, and that in turn
+ -- depends on deciding whether to unpack the args, and that
+ -- depends on whether it's a data type or a newtype --- so
+ -- in the recursive case we can get a loop. This version is simple!
+
+buildTyConOrClass rec_tycon kenv rec_vrcs rec_details
+ (ForeignType {tcdName = tycon_name, tcdExtName = tycon_ext_name})
+ = ATyCon (mkForeignTyCon tycon_name tycon_ext_name liftedTypeKind 0 [])
+
+buildTyConOrClass rec_tycon kenv rec_vrcs rec_details
+ (ClassDecl {tcdName = class_name, tcdTyVars = tyvar_names, tcdFDs = fundeps} )
+ = AClass clas
+ where
+ clas = mkClass class_name tyvars fds
+ sc_theta sc_sel_ids op_items
+ tycon
+
+ tycon = mkClassTyCon tycon_name class_kind tyvars
+ argvrcs dict_con
+ clas -- Yes! It's a dictionary
+ flavour
+ (rec_tycon class_name flavour)
+ -- 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 toan inifinite type
+
+ ClassDetails sc_theta sc_sel_ids op_items dict_con tycon_name
+ = lookupNameEnv_NF rec_details class_name
+
+ class_kind = lookupNameEnv_NF kenv class_name
+ tyvars = mkTyClTyVars class_kind tyvar_names
+ argvrcs = lookupWithDefaultFM rec_vrcs bogusVrcs tycon
+
+ flavour = case dataConOrigArgTys dict_con of
+ -- The tyvars in the datacon are the same as in the class
+ [rep_ty] -> NewTyCon rep_ty
+ other -> DataTyCon
+
+ -- We can find the functional dependencies right away,
+ -- and it is vital to do so. Why? Because in the next pass
+ -- we check for ambiguity in all the type signatures, and we
+ -- need the functional dependcies to be done by then
+ fds = [(map lookup xs, map lookup ys) | (xs,ys) <- fundeps]
+ tyvar_env = mkNameEnv [(varName tv, tv) | tv <- tyvars]
+ lookup = lookupNameEnv_NF tyvar_env
+
+bogusVrcs = panic "Bogus tycon arg variances"
+\end{code}
-Here, the kind of the locally-polymorphic type variable "b"
-depends on *all the uses of class D*. For example, the use of
-Monad c in bop's type signature means that D must have kind Type->Type.
+\begin{code}
+mkNewTyConRep :: TyCon -- The original type constructor
+ -> Type -- Chosen representation type
+ -- (guaranteed not to be another newtype)
+
+-- Find the representation type for this newtype TyCon
+-- Remember that the representation type is the ultimate representation
+-- type, looking through other newtypes.
+--
+-- The non-recursive newtypes are easy, because they look transparent
+-- to splitTyConApp_maybe, but recursive ones really are represented as
+-- TyConApps (see TypeRep).
+--
+-- The trick is to to deal correctly with recursive newtypes
+-- such as newtype T = MkT T
+
+mkNewTyConRep tc
+ = go [] tc
+ where
+ -- Invariant: tc is a NewTyCon
+ -- tcs have been seen before
+ go tcs tc
+ | tc `elem` tcs = unitTy
+ | otherwise
+ = let
+ rep_ty = head (dataConOrigArgTys (head (tyConDataCons tc)))
+ in
+ case splitTyConApp_maybe rep_ty of
+ Nothing -> rep_ty
+ Just (tc', tys) | not (isNewTyCon tc') -> rep_ty
+ | otherwise -> go1 (tc:tcs) tc' tys
+
+ go1 tcs tc tys = substTyWith (tyConTyVars tc) tys (go tcs tc)
+\end{code}
+%************************************************************************
+%* *
+\subsection{Dependency analysis}
+%* *
+%************************************************************************
+Dependency analysis
+~~~~~~~~~~~~~~~~~~~
\begin{code}
-get_binders :: Bag RenamedHsDecl
- -> ([HsTyVar Name], -- TyVars; no dups
- [(Name, Maybe Arity)], -- Tycons; no dups; arities for synonyms
- [Name]) -- Classes; no dups
+checkLoops :: SCC RenamedTyClDecl
+ -> TcM (Name -> AlgTyConFlavour -> RecFlag)
+-- Check for illegal loops,
+-- a) type synonyms
+-- b) superclass hierarchy
+--
+-- Also return a function that says which tycons are recursive.
+-- Remember:
+-- a newtype is recursive if it is part of a recursive
+-- group consisting only of newtype and synonyms
+
+checkLoops (AcyclicSCC _)
+ = returnM (\ _ _ -> NonRecursive)
+
+checkLoops (CyclicSCC decls)
+ = let -- CHECK FOR CLASS CYCLES
+ cls_edges = mapMaybe mkClassEdges decls
+ cls_cycles = findCycles cls_edges
+ in
+ mapM_ (cycleErr "class") cls_cycles `thenM_`
-get_binders decls = (bagToList tyvars, bagToList tycons, bagToList classes)
- where
- (tyvars, tycons, classes) = foldBag union3 get_binders1
- (emptyBag,emptyBag,emptyBag)
- decls
-
- union3 (a1,a2,a3) (b1,b2,b3)
- = (a1 `unionBags` b1, a2 `unionBags` b2, a3 `unionBags` b3)
-
-get_binders1 (TyD (TyData _ _ name tyvars _ _ _ _))
- = (listToBag tyvars, unitBag (name,Nothing), emptyBag)
-get_binders1 (TyD (TySynonym name tyvars _ _))
- = (listToBag tyvars, unitBag (name, Just (length tyvars)), emptyBag)
-get_binders1 (ClD (ClassDecl _ name tyvar sigs _ _ _))
- = (unitBag tyvar `unionBags` sigs_tvs sigs,
- emptyBag, unitBag name)
-
-sigs_tvs sigs = unionManyBags (map sig_tvs sigs)
- where
- sig_tvs (ClassOpSig _ _ ty _) = pty_tvs ty
- pty_tvs (HsForAllTy tvs _ _) = listToBag tvs -- tvs doesn't include the class tyvar
- pty_tvs other = emptyBag
+ let -- CHECK FOR SYNONYM CYCLES
+ syn_edges = map mkEdges (filter isSynDecl decls)
+ syn_cycles = findCycles syn_edges
+ in
+ mapM_ (cycleErr "type synonym") syn_cycles `thenM_`
+
+ let -- CHECK FOR NEWTYPE CYCLES
+ newtype_edges = map mkEdges (filter is_nt_cycle_decl decls)
+ newtype_cycles = findCycles newtype_edges
+ rec_newtypes = mkNameSet [tcdName d | ds <- newtype_cycles, d <- ds]
+
+ rec_tycon name (NewTyCon _)
+ | name `elemNameSet` rec_newtypes = Recursive
+ | otherwise = NonRecursive
+ rec_tycon name other_flavour = Recursive
+ in
+ returnM rec_tycon
+
+----------------------------------------------------
+-- A class with one op and no superclasses, or vice versa,
+-- is treated just like a newtype.
+-- It's a bit unclean that this test is repeated in buildTyConOrClass
+is_nt_cycle_decl (TySynonym {}) = True
+is_nt_cycle_decl (TyData {tcdND = NewType}) = True
+is_nt_cycle_decl (ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs}) = length ctxt + length sigs == 1
+is_nt_cycle_decl other = False
+
+----------------------------------------------------
+findCycles edges = [ ds | CyclicSCC ds <- stronglyConnComp edges]
+
+----------------------------------------------------
+mkEdges :: RenamedTyClDecl -> (RenamedTyClDecl, Name, [Name])
+mkEdges decl = (decl, tyClDeclName decl, nameSetToList (tyClDeclFVs decl))
+
+----------------------------------------------------
+-- mk_cls_edges looks only at the context of class decls
+-- Its used when we are figuring out if there's a cycle in the
+-- superclass hierarchy
+
+mkClassEdges :: RenamedTyClDecl -> Maybe (RenamedTyClDecl, Name, [Name])
+mkClassEdges decl@(ClassDecl {tcdCtxt = ctxt, tcdName = name}) = Just (decl, name, [c | HsClassP c _ <- ctxt])
+mkClassEdges other_decl = Nothing
\end{code}
+%************************************************************************
+%* *
+\subsection{Error management
+%* *
+%************************************************************************
+
\begin{code}
-typeCycleErr syn_cycles sty
- = vcat (map (pp_cycle sty "Cycle in type declarations ...") syn_cycles)
+cycleErr :: String -> [RenamedTyClDecl] -> TcM ()
-classCycleErr cls_cycles sty
- = vcat (map (pp_cycle sty "Cycle in class declarations ...") cls_cycles)
+cycleErr kind_of_decl decls
+ = addErrAt loc (ppr_cycle kind_of_decl decls)
+ where
+ loc = tcdLoc (head decls)
-pp_cycle sty str decls
- = hang (text str)
+ppr_cycle kind_of_decl decls
+ = hang (ptext SLIT("Cycle in") <+> text kind_of_decl <+> ptext SLIT("declarations:"))
4 (vcat (map pp_decl decls))
where
- pp_decl decl
- = hsep [ppr sty name, ppr sty (getSrcLoc name)]
- where
- name = hsDeclName decl
+ pp_decl decl = hsep [quotes (ppr (tcdName decl)),
+ ptext SLIT("at"), ppr (tcdLoc decl)]
\end{code}
projects / ghc-hetmet.git / blobdiff