%
-% (c) The AQUA Project, Glasgow University, 1996
+% (c) The AQUA Project, Glasgow University, 1996-1998
%
\section[TcTyClsDecls]{Typecheck type and class declarations}
\begin{code}
module TcTyClsDecls (
- tcTyAndClassDecls1
+ tcTyAndClassDecls
) where
#include "HsVersions.h"
-import HsSyn ( HsDecl(..), TyDecl(..), ClassDecl(..),
- HsType(..), HsTyVar,
- ConDecl(..), ConDetails(..), BangType(..),
- Sig(..),
- hsDeclName
+import CmdLineOpts ( DynFlags, DynFlag(..), dopt )
+import HsSyn ( TyClDecl(..),
+ ConDecl(..), Sig(..), HsPred(..),
+ tyClDeclName, hsTyVarNames,
+ isIfaceSigDecl, isClassDecl, isSynDecl, isClassOpSig
)
-import RnHsSyn ( RenamedTyDecl(..), RenamedClassDecl(..), RenamedHsDecl )
-import TcHsSyn ( TcHsBinds )
-import BasicTypes ( RecFlag(..) )
+import RnHsSyn ( RenamedTyClDecl, tyClDeclFVs )
+import BasicTypes ( RecFlag(..), NewOrData(..), isRec )
+import HscTypes ( implicitTyThingIds )
import TcMonad
-import Inst ( InstanceMapper )
+import TcEnv ( TcEnv, RecTcEnv, TcTyThing(..), TyThing(..), TyThingDetails(..),
+ tcExtendKindEnv, tcLookup, tcExtendGlobalEnv, tcExtendGlobalValEnv )
+import TcTyDecls ( tcTyDecl1, kcConDetails, mkNewTyConRep )
import TcClassDcl ( tcClassDecl1 )
-import TcEnv ( TcIdOcc(..), GlobalValueEnv, tcExtendTyConEnv, tcExtendClassEnv )
-import TcKind ( TcKind, newKindVar, newKindVars, tcDefaultKind, kindToTcKind )
-import TcTyDecls ( tcTyDecl, mkDataBinds )
-import TcMonoType ( tcTyVarScope )
-
-import TyCon ( tyConKind, tyConArity, isSynTyCon )
-import Class ( Class, classBigSig )
-import TyVar ( tyVarKind )
-import Bag
+import TcMonoType ( kcHsTyVars, kcHsType, kcHsBoxedSigType, kcHsContext, mkTyClTyVars )
+import TcType ( TcKind, newKindVar, zonkKindEnv )
+
+import TcUnify ( unifyKind )
+import TcInstDcls ( tcAddDeclCtxt )
+import Type ( Kind, mkArrowKind, zipFunTys )
+import Variance ( calcTyConArgVrcs )
+import Class ( Class, mkClass, classTyCon )
+import TyCon ( TyCon, tyConKind, ArgVrcs, AlgTyConFlavour(..),
+ mkSynTyCon, mkAlgTyCon, mkClassTyCon )
+import DataCon ( isNullaryDataCon )
+import Var ( varName )
+import FiniteMap
import Digraph ( stronglyConnComp, SCC(..) )
-import Name ( Name, NamedThing(..), getSrcLoc, isTvOcc, nameOccName )
+import Name ( Name, getSrcLoc, isTyVarName )
+import Name ( NameEnv, mkNameEnv, lookupNameEnv_NF )
+import NameSet
import Outputable
import Maybes ( mapMaybe )
-import UniqSet ( UniqSet, emptyUniqSet,
- unitUniqSet, unionUniqSets,
- unionManyUniqSets, uniqSetToList )
-import SrcLoc ( SrcLoc )
-import TyCon ( TyCon, Arity )
-import Unique ( Unique, Uniquable(..) )
-import Util ( panic{-, pprTrace-} )
-
+import ErrUtils ( Message )
+import HsDecls ( getClassDeclSysNames )
+import Generics ( mkTyConGenInfo )
\end{code}
+
+%************************************************************************
+%* *
+\subsection{Type checking for type and class declarations}
+%* *
+%************************************************************************
+
The main function
~~~~~~~~~~~~~~~~~
\begin{code}
-tcTyAndClassDecls1 :: GlobalValueEnv -> InstanceMapper -- Knot tying stuff
- -> [RenamedHsDecl]
- -> TcM s (TcEnv s)
+tcTyAndClassDecls :: RecTcEnv -- Knot tying stuff
+ -> [RenamedTyClDecl]
+ -> TcM TcEnv
-tcTyAndClassDecls1 unf_env inst_mapper decls
+tcTyAndClassDecls unf_env decls
= sortByDependency decls `thenTc` \ groups ->
- tcGroups unf_env inst_mapper groups
+ tcGroups unf_env groups
-tcGroups unf_env inst_mapper []
+tcGroups unf_env []
= tcGetEnv `thenNF_Tc` \ env ->
returnTc env
-tcGroups unf_env inst_mapper (group:groups)
- = tcGroup unf_env inst_mapper group `thenTc` \ (group_tycons, group_classes) ->
-
- -- Extend the environment using the new tycons and classes
- tcExtendTyConEnv [(getName tycon, (kindToTcKind (tyConKind tycon),
- if isSynTyCon tycon then Just (tyConArity tycon) else Nothing,
- tycon))
- | tycon <- group_tycons] $
-
- tcExtendClassEnv [(getName clas, (classKind clas, clas))
- | clas <- group_classes] $
-
-
- -- Do the remaining groups
- tcGroups unf_env inst_mapper groups
- where
- classKind clas = map (kindToTcKind . tyVarKind) tyvars
- where
- (tyvars, _, _, _, _) = classBigSig clas
+tcGroups unf_env (group:groups)
+ = tcGroup unf_env group `thenTc` \ env ->
+ tcSetEnv env $
+ tcGroups unf_env groups
\end{code}
Dealing with a group
~~~~~~~~~~~~~~~~~~~~
+Consider a mutually-recursive group, binding
+a type constructor T and a class C.
+
+Step 1: getInitialKind
+ Construct a KindEnv by binding T and C to a kind variable
+
+Step 2: kcTyClDecl
+ In that environment, do a kind check
+
+Step 3: Zonk the kinds
+
+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
+
+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.
+
+
+Step 6: tcTyClDecl1 again
+ For a recursive group only, check all the decls again, just
+ but this time with the wimp flag off. Now we can check things
+ like whether a function argument is an unboxed tuple, looking
+ through type synonyms properly. We can't do that in Step 5.
+
+Step 7: 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
+
+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.
-Notice the uses of @zipLazy@, which makes sure
-that the knot-tied TyVars, TyCons and Classes aren't looked at too early.
-
-
\begin{code}
-tcGroup :: GlobalValueEnv -> InstanceMapper -> SCC RenamedHsDecl -> TcM s ([TyCon], [Class])
-tcGroup unf_env inst_mapper scc
- = -- TIE THE KNOT
- fixTc ( \ ~(rec_tycons, rec_classes) ->
-
- -- EXTEND TYPE AND CLASS ENVIRONMENTS
- let
- mk_tycon_bind (name, arity) = newKindVar `thenNF_Tc` \ kind ->
- returnNF_Tc (name, (kind, arity, find name rec_tycons))
-
- mk_class_bind (name, arity) = newKindVars arity `thenNF_Tc` \ kinds ->
- returnNF_Tc (name, (kinds, find name rec_classes))
-
- find name [] = pprPanic "tcGroup" (ppr name)
- find name (thing:things) | name == getName thing = thing
- | otherwise = find name things
-
- in
- mapNF_Tc mk_tycon_bind tycon_names_w_arities `thenNF_Tc` \ tycon_binds ->
- mapNF_Tc mk_class_bind class_names_w_arities `thenNF_Tc` \ class_binds ->
- tcExtendTyConEnv tycon_binds $
- tcExtendClassEnv class_binds $
-
- -- DEAL WITH TYPE VARIABLES
- tcTyVarScope tyvar_names ( \ tyvars ->
-
- -- DEAL WITH THE DEFINITIONS THEMSELVES
- foldlTc (tcDecl is_rec_group unf_env inst_mapper) ([], []) decls
- ) `thenTc` \ (tycons, classes) ->
-
- returnTc (tycons, classes)
- )
+tcGroup :: RecTcEnv -> SCC RenamedTyClDecl -> TcM TcEnv
+tcGroup unf_env scc
+ = getDOptsTc `thenTc` \ dflags ->
+ -- Step 1
+ mapNF_Tc getInitialKind decls `thenNF_Tc` \ initial_kinds ->
+
+ -- Step 2
+ tcExtendKindEnv initial_kinds (mapTc kcTyClDecl decls) `thenTc_`
+
+ -- Step 3
+ zonkKindEnv initial_kinds `thenNF_Tc` \ final_kinds ->
+
+ -- Tie the knot
+ fixTc ( \ ~(rec_details_list, _, _) ->
+ -- Step 4
+ let
+ kind_env = mkNameEnv final_kinds
+ rec_details = mkNameEnv rec_details_list
+
+ tyclss, all_tyclss :: [TyThing]
+ tyclss = map (buildTyConOrClass dflags is_rec kind_env
+ rec_vrcs rec_details) decls
+
+ -- Add the tycons that come from the classes
+ -- We want them in the environment because
+ -- they are mentioned in interface files
+ all_tyclss = [ ATyCon (classTyCon clas) | AClass clas <- tyclss]
+ ++ tyclss
+
+ -- Calculate variances, and (yes!) feed back into buildTyConOrClass.
+ rec_vrcs = calcTyConArgVrcs [tc | ATyCon tc <- all_tyclss]
+ in
+ -- Step 5
+ tcExtendGlobalEnv all_tyclss $
+ mapTc (tcTyClDecl1 is_rec unf_env) decls `thenTc` \ tycls_details ->
+
+ -- Return results
+ tcGetEnv `thenNF_Tc` \ env ->
+ returnTc (tycls_details, all_tyclss, env)
+ ) `thenTc` \ (_, all_tyclss, env) ->
+
+ tcSetEnv env $
+
+ -- Step 6
+ -- For a recursive group, check all the types again,
+ -- this time with the wimp flag off
+ (if isRec is_rec then
+ mapTc_ (tcTyClDecl1 NonRecursive unf_env) decls
+ else
+ returnTc ()
+ ) `thenTc_`
+
+ -- Step 7
+ -- Extend the environment with the final TyCons/Classes
+ -- and their implicit Ids
+ tcExtendGlobalValEnv (implicitTyThingIds all_tyclss) tcGetEnv
+
where
- is_rec_group = case scc of
- AcyclicSCC _ -> NonRecursive
- CyclicSCC _ -> Recursive
+ is_rec = case scc of
+ AcyclicSCC _ -> NonRecursive
+ CyclicSCC _ -> Recursive
decls = case scc of
AcyclicSCC decl -> [decl]
CyclicSCC decls -> decls
- (tyvar_names, tycon_names_w_arities, class_names_w_arities) = get_binders decls
+tcTyClDecl1 is_rec unf_env decl
+ | isClassDecl decl = tcAddDeclCtxt decl (tcClassDecl1 is_rec unf_env decl)
+ | otherwise = tcAddDeclCtxt decl (tcTyDecl1 is_rec unf_env decl)
\end{code}
-Dealing with one decl
-~~~~~~~~~~~~~~~~~~~~~
-\begin{code}
-tcDecl :: RecFlag -- True => recursive group
- -> GlobalValueEnv -> InstanceMapper
- -> ([TyCon], [Class]) -- Accumulating parameter
- -> RenamedHsDecl
- -> TcM s ([TyCon], [Class])
-
-tcDecl is_rec_group unf_env inst_mapper (tycons, classes) (TyD decl)
- = tcTyDecl is_rec_group decl `thenTc` \ tycon ->
- returnTc (tycon:tycons, classes)
-
-tcDecl is_rec_group unf_env inst_mapper (tycons, classes) (ClD decl)
- = tcClassDecl1 unf_env inst_mapper decl `thenTc` \ clas ->
- returnTc (tycons, clas:classes)
-\end{code}
-Dependency analysis
-~~~~~~~~~~~~~~~~~~~
-\begin{code}
-sortByDependency :: [RenamedHsDecl] -> TcM s [SCC RenamedHsDecl]
-sortByDependency decls
- = let -- CHECK FOR SYNONYM CYCLES
- syn_sccs = stronglyConnComp (filter is_syn_decl edges)
- syn_cycles = [ decls | CyclicSCC decls <- syn_sccs]
+%************************************************************************
+%* *
+\subsection{Step 1: Initial environment}
+%* *
+%************************************************************************
- in
- checkTc (null syn_cycles) (typeCycleErr syn_cycles) `thenTc_`
+\begin{code}
+getInitialKind :: RenamedTyClDecl -> NF_TcM (Name, TcKind)
+getInitialKind decl
+ = kcHsTyVars (tcdTyVars decl) `thenNF_Tc` \ arg_kinds ->
+ newKindVar `thenNF_Tc` \ result_kind ->
+ returnNF_Tc (tcdName decl, mk_kind arg_kinds result_kind)
- let -- CHECK FOR CLASS CYCLES
- cls_sccs = stronglyConnComp (filter is_cls_decl edges)
- cls_cycles = [ decls | CyclicSCC decls <- cls_sccs]
+mk_kind tvs_w_kinds res_kind = foldr (mkArrowKind . snd) res_kind tvs_w_kinds
+\end{code}
- in
- checkTc (null cls_cycles) (classCycleErr cls_cycles) `thenTc_`
- -- DO THE MAIN DEPENDENCY ANALYSIS
- let
- decl_sccs = stronglyConnComp (filter is_ty_cls_decl edges)
- in
- returnTc decl_sccs
+%************************************************************************
+%* *
+\subsection{Step 2: Kind checking}
+%* *
+%************************************************************************
- where
- edges = mapMaybe mk_edges decls
-
-bag_acyclic (AcyclicSCC scc) = unitBag scc
-bag_acyclic (CyclicSCC sccs) = listToBag sccs
+We need to kind check all types in the mutually recursive group
+before we know the kind of the type variables. For example:
-is_syn_decl (TyD (TySynonym _ _ _ _), _, _) = True
-is_syn_decl _ = False
+class C a where
+ op :: D b => a -> b -> b
-is_ty_cls_decl (TyD _, _, _) = True
-is_ty_cls_decl (ClD _, _, _) = True
-is_ty_cls_decl other = False
+class D c where
+ bop :: (Monad c) => ...
-is_cls_decl (ClD _, _, _) = True
-is_cls_decl other = False
-\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.
-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))
+kcTyClDecl :: RenamedTyClDecl -> TcM ()
-mk_edges decl@(TyD (TySynonym name _ rhs _))
- = Just (decl, uniqueOf name, uniqSetToList (get_ty rhs))
+kcTyClDecl decl@(TySynonym {tcdSynRhs = rhs})
+ = kcTyClDeclBody decl $ \ result_kind ->
+ kcHsType rhs `thenTc` \ rhs_kind ->
+ unifyKind result_kind rhs_kind
-mk_edges decl@(ClD (ClassDecl ctxt name _ sigs _ _ _ _ _))
- = Just (decl, uniqueOf name, uniqSetToList (get_ctxt ctxt `unionUniqSets`
- get_sigs sigs))
+kcTyClDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = context, tcdCons = con_decls})
+ = kcTyClDeclBody decl $ \ result_kind ->
+ kcHsContext context `thenTc_`
+ mapTc_ kc_con_decl con_decls
+ where
+ kc_con_decl (ConDecl _ _ ex_tvs ex_ctxt details loc)
+ = kcHsTyVars ex_tvs `thenNF_Tc` \ 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 `thenTc_`
+ mapTc_ kc_sig (filter isClassOpSig class_sigs)
+ where
+ kc_sig (ClassOpSig _ _ op_ty loc) = kcHsBoxedSigType 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) `thenNF_Tc` \ 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
-mk_edges other_decl = Nothing
+ (tyvars_w_kinds, result_kind) = zipFunTys (hsTyVarNames (tcdTyVars decl)) kind
+ in
+ tcExtendKindEnv tyvars_w_kinds (thing_inside result_kind)
+\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 4: Building the tycon/class}
+%* *
+%************************************************************************
-get_cons cons = unionManyUniqSets (map get_con cons)
+\begin{code}
+buildTyConOrClass
+ :: DynFlags
+ -> RecFlag -> NameEnv Kind
+ -> FiniteMap TyCon ArgVrcs -> NameEnv TyThingDetails
+ -> RenamedTyClDecl -> TyThing
+
+buildTyConOrClass dflags is_rec 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 dflags is_rec kenv rec_vrcs rec_details
+ (TyData {tcdND = data_or_new, tcdName = tycon_name, tcdTyVars = tyvar_names,
+ tcdNCons = nconstrs, tcdSysNames = sys_names})
+ = ATyCon tycon
+ where
+ tycon = mkAlgTyCon tycon_name tycon_kind tyvars ctxt argvrcs
+ data_cons nconstrs sel_ids
+ flavour is_rec gen_info
-get_con (ConDecl _ ctxt details _)
- = get_ctxt ctxt `unionUniqSets` get_con_details details
+ gen_info | not (dopt Opt_Generics dflags) = Nothing
+ | otherwise = mkTyConGenInfo tycon sys_names
-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)
+ DataTyDetails ctxt data_cons sel_ids = lookupNameEnv_NF rec_details tycon_name
-get_bty (Banged ty) = get_ty ty
-get_bty (Unbanged ty) = get_ty ty
+ tycon_kind = lookupNameEnv_NF kenv tycon_name
+ tyvars = mkTyClTyVars tycon_kind tyvar_names
+ argvrcs = lookupWithDefaultFM rec_vrcs bogusVrcs tycon
-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"
+ flavour = case data_or_new of
+ NewType -> NewTyCon (mkNewTyConRep tycon)
+ DataType | all isNullaryDataCon data_cons -> EnumTyCon
+ | otherwise -> DataTyCon
-get_tys tys
- = unionManyUniqSets (map get_ty tys)
+buildTyConOrClass dflags is_rec kenv rec_vrcs rec_details
+ (ClassDecl {tcdName = class_name, tcdTyVars = tyvar_names,
+ tcdFDs = fundeps, tcdSysNames = name_list} )
+ = AClass clas
+ where
+ (tycon_name, _, _, _) = getClassDeclSysNames name_list
+ 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
+
+ ClassDetails sc_theta sc_sel_ids op_items dict_con = 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
+ n_fields = length sc_sel_ids + length op_items
+
+ flavour | n_fields == 1 = NewTyCon (mkNewTyConRep tycon)
+ | otherwise = 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}
-get_sigs sigs
- = unionManyUniqSets (map get_sig sigs)
- where
- get_sig (ClassOpSig _ _ ty _) = get_ty ty
- get_sig other = panic "TcTyClsDecls:get_sig"
-set_name name = unitUniqSet (uniqueOf name)
+%************************************************************************
+%* *
+\subsection{Dependency analysis}
+%* *
+%************************************************************************
-set_to_bag set = listToBag (uniqSetToList set)
-\end{code}
+Dependency analysis
+~~~~~~~~~~~~~~~~~~~
+\begin{code}
+sortByDependency :: [RenamedTyClDecl] -> TcM [SCC RenamedTyClDecl]
+sortByDependency decls
+ = let -- CHECK FOR CLASS CYCLES
+ cls_sccs = stronglyConnComp (mapMaybe mkClassEdges tycl_decls)
+ cls_cycles = [ decls | CyclicSCC decls <- cls_sccs]
+ in
+ checkTc (null cls_cycles) (classCycleErr cls_cycles) `thenTc_`
+ let -- CHECK FOR SYNONYM CYCLES
+ syn_sccs = stronglyConnComp (filter is_syn_decl edges)
+ syn_cycles = [ decls | CyclicSCC decls <- syn_sccs]
-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.
+ in
+ checkTc (null syn_cycles) (typeCycleErr syn_cycles) `thenTc_`
-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:
+ -- DO THE MAIN DEPENDENCY ANALYSIS
+ let
+ decl_sccs = stronglyConnComp edges
+ in
+ returnTc decl_sccs
+ where
+ tycl_decls = filter (not . isIfaceSigDecl) decls
+ edges = map mkEdges tycl_decls
+
+ is_syn_decl (d, _, _) = isSynDecl d
+\end{code}
-class C a where
- op :: D b => a -> b -> b
+Edges in Type/Class decls
+~~~~~~~~~~~~~~~~~~~~~~~~~
-class D c where
- bop :: (Monad c) => ...
+\begin{code}
+tyClDeclFTVs :: RenamedTyClDecl -> [Name]
+ -- Find the free non-tyvar vars
+tyClDeclFTVs d = foldNameSet add [] (tyClDeclFVs d)
+ where
+ add n fvs | isTyVarName n = fvs
+ | otherwise = n : fvs
-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.
+----------------------------------------------------
+-- 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])
-\begin{code}
-get_binders :: [RenamedHsDecl]
- -> ([HsTyVar Name], -- TyVars; no dups
- [(Name, Maybe Arity)], -- Tycons; no dups; arities for synonyms
- [(Name, Arity)]) -- Classes; no dups; with their arities
+mkClassEdges decl@(ClassDecl {tcdCtxt = ctxt, tcdName = name}) = Just (decl, name, [c | HsPClass c _ <- ctxt])
+mkClassEdges other_decl = Nothing
-get_binders decls = (bagToList tyvars, bagToList tycons, bagToList classes)
- where
- (tyvars, tycons, classes) = foldr (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 tyvars sigs _ _ _ _ _))
- = (listToBag tyvars `unionBags` sigs_tvs sigs,
- emptyBag, unitBag (name, length tyvars))
-
-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
+mkEdges :: RenamedTyClDecl -> (RenamedTyClDecl, Name, [Name])
+mkEdges decl = (decl, tyClDeclName decl, tyClDeclFTVs decl)
\end{code}
+%************************************************************************
+%* *
+\subsection{Error management
+%* *
+%************************************************************************
+
\begin{code}
+typeCycleErr, classCycleErr :: [[RenamedTyClDecl]] -> Message
+
typeCycleErr syn_cycles
= vcat (map (pp_cycle "Cycle in type declarations:") syn_cycles)
pp_decl decl
= hsep [quotes (ppr name), ptext SLIT("at"), ppr (getSrcLoc name)]
where
- name = hsDeclName decl
+ name = tyClDeclName decl
+
\end{code}
projects / ghc-hetmet.git / blobdiff