2 % (c) The AQUA Project, Glasgow University, 1996-1998
4 \section[TcTyClsDecls]{Typecheck type and class declarations}
11 #include "HsVersions.h"
13 import CmdLineOpts ( DynFlags, DynFlag(..), dopt )
14 import HsSyn ( TyClDecl(..),
15 ConDecl(..), Sig(..), HsPred(..),
16 tyClDeclName, hsTyVarNames, tyClDeclTyVars,
17 isIfaceSigDecl, isClassDecl, isSynDecl, isClassOpSig
19 import RnHsSyn ( RenamedTyClDecl, tyClDeclFVs )
20 import BasicTypes ( RecFlag(..), NewOrData(..), isRec )
21 import HscTypes ( implicitTyThingIds )
24 import TcEnv ( TcEnv, RecTcEnv, TcTyThing(..), TyThing(..), TyThingDetails(..),
25 tcExtendKindEnv, tcLookup, tcExtendGlobalEnv, tcExtendGlobalValEnv )
26 import TcTyDecls ( tcTyDecl1, kcConDetails, mkNewTyConRep )
27 import TcClassDcl ( tcClassDecl1 )
28 import TcMonoType ( kcHsTyVars, kcHsType, kcHsLiftedSigType, kcHsContext, mkTyClTyVars )
29 import TcType ( TcKind, newKindVar, zonkKindEnv )
31 import TcUnify ( unifyKind )
32 import TcInstDcls ( tcAddDeclCtxt )
33 import Type ( Kind, mkArrowKind, liftedTypeKind, zipFunTys )
34 import Variance ( calcTyConArgVrcs )
35 import Class ( Class, mkClass, classTyCon )
36 import TyCon ( TyCon, tyConKind, ArgVrcs, AlgTyConFlavour(..),
37 mkSynTyCon, mkAlgTyCon, mkClassTyCon, mkForeignTyCon )
38 import DataCon ( isNullaryDataCon )
39 import Var ( varName )
41 import Digraph ( stronglyConnComp, SCC(..) )
42 import Name ( Name, getSrcLoc, isTyVarName )
43 import NameEnv ( NameEnv, mkNameEnv, lookupNameEnv_NF )
46 import Maybes ( mapMaybe )
47 import ErrUtils ( Message )
48 import HsDecls ( getClassDeclSysNames )
49 import Generics ( mkTyConGenInfo )
53 %************************************************************************
55 \subsection{Type checking for type and class declarations}
57 %************************************************************************
62 tcTyAndClassDecls :: RecTcEnv -- Knot tying stuff
66 tcTyAndClassDecls unf_env decls
67 = sortByDependency decls `thenTc` \ groups ->
68 tcGroups unf_env groups
71 = tcGetEnv `thenNF_Tc` \ env ->
74 tcGroups unf_env (group:groups)
75 = tcGroup unf_env group `thenTc` \ env ->
77 tcGroups unf_env groups
82 Consider a mutually-recursive group, binding
83 a type constructor T and a class C.
85 Step 1: getInitialKind
86 Construct a KindEnv by binding T and C to a kind variable
89 In that environment, do a kind check
91 Step 3: Zonk the kinds
93 Step 4: buildTyConOrClass
94 Construct an environment binding T to a TyCon and C to a Class.
95 a) Their kinds comes from zonking the relevant kind variable
96 b) Their arity (for synonyms) comes direct from the decl
97 c) The funcional dependencies come from the decl
98 d) The rest comes a knot-tied binding of T and C, returned from Step 4
99 e) The variances of the tycons in the group is calculated from
103 In this environment, walk over the decls, constructing the TyCons and Classes.
104 This uses in a strict way items (a)-(c) above, which is why they must
105 be constructed in Step 4. Feed the results back to Step 4.
106 For this step, pass the is-recursive flag as the wimp-out flag
110 Step 6: tcTyClDecl1 again
111 For a recursive group only, check all the decls again, just
112 but this time with the wimp flag off. Now we can check things
113 like whether a function argument is an unlifted tuple, looking
114 through type synonyms properly. We can't do that in Step 5.
116 Step 7: Extend environment
117 We extend the type environment with bindings not only for the TyCons and Classes,
118 but also for their "implicit Ids" like data constructors and class selectors
120 The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to
121 @TyThing@s. @rec_vrcs@ is a finite map from @Name@s to @ArgVrcs@s.
124 tcGroup :: RecTcEnv -> SCC RenamedTyClDecl -> TcM TcEnv
126 = getDOptsTc `thenTc` \ dflags ->
128 mapNF_Tc getInitialKind decls `thenNF_Tc` \ initial_kinds ->
131 tcExtendKindEnv initial_kinds (mapTc kcTyClDecl decls) `thenTc_`
134 zonkKindEnv initial_kinds `thenNF_Tc` \ final_kinds ->
137 traceTc (text "starting" <+> ppr final_kinds) `thenTc_`
138 fixTc ( \ ~(rec_details_list, _, _) ->
141 kind_env = mkNameEnv final_kinds
142 rec_details = mkNameEnv rec_details_list
144 tyclss, all_tyclss :: [TyThing]
145 tyclss = map (buildTyConOrClass dflags is_rec kind_env
146 rec_vrcs rec_details) decls
148 -- Add the tycons that come from the classes
149 -- We want them in the environment because
150 -- they are mentioned in interface files
151 all_tyclss = [ ATyCon (classTyCon clas) | AClass clas <- tyclss]
154 -- Calculate variances, and (yes!) feed back into buildTyConOrClass.
155 rec_vrcs = calcTyConArgVrcs [tc | ATyCon tc <- all_tyclss]
158 tcExtendGlobalEnv all_tyclss $
159 mapTc (tcTyClDecl1 is_rec unf_env) decls `thenTc` \ tycls_details ->
162 tcGetEnv `thenNF_Tc` \ env ->
163 returnTc (tycls_details, all_tyclss, env)
164 ) `thenTc` \ (_, all_tyclss, env) ->
168 traceTc (text "ready for pass 2" <+> ppr (isRec is_rec)) `thenTc_`
171 -- For a recursive group, check all the types again,
172 -- this time with the wimp flag off
173 (if isRec is_rec then
174 mapTc_ (tcTyClDecl1 NonRecursive unf_env) decls
179 traceTc (text "done") `thenTc_`
182 -- Extend the environment with the final TyCons/Classes
183 -- and their implicit Ids
184 tcExtendGlobalValEnv (implicitTyThingIds all_tyclss) tcGetEnv
188 AcyclicSCC _ -> NonRecursive
189 CyclicSCC _ -> Recursive
192 AcyclicSCC decl -> [decl]
193 CyclicSCC decls -> decls
195 tcTyClDecl1 is_rec unf_env decl
196 | isClassDecl decl = tcAddDeclCtxt decl (tcClassDecl1 is_rec unf_env decl)
197 | otherwise = tcAddDeclCtxt decl (tcTyDecl1 is_rec unf_env decl)
201 %************************************************************************
203 \subsection{Step 1: Initial environment}
205 %************************************************************************
208 getInitialKind :: RenamedTyClDecl -> NF_TcM (Name, TcKind)
210 = kcHsTyVars (tyClDeclTyVars decl) `thenNF_Tc` \ arg_kinds ->
211 newKindVar `thenNF_Tc` \ result_kind ->
212 returnNF_Tc (tcdName decl, mk_kind arg_kinds result_kind)
214 mk_kind tvs_w_kinds res_kind = foldr (mkArrowKind . snd) res_kind tvs_w_kinds
218 %************************************************************************
220 \subsection{Step 2: Kind checking}
222 %************************************************************************
224 We need to kind check all types in the mutually recursive group
225 before we know the kind of the type variables. For example:
228 op :: D b => a -> b -> b
231 bop :: (Monad c) => ...
233 Here, the kind of the locally-polymorphic type variable "b"
234 depends on *all the uses of class D*. For example, the use of
235 Monad c in bop's type signature means that D must have kind Type->Type.
238 kcTyClDecl :: RenamedTyClDecl -> TcM ()
240 kcTyClDecl decl@(TySynonym {tcdSynRhs = rhs})
241 = kcTyClDeclBody decl $ \ result_kind ->
242 kcHsType rhs `thenTc` \ rhs_kind ->
243 unifyKind result_kind rhs_kind
245 kcTyClDecl (ForeignType {}) = returnTc ()
247 kcTyClDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = context, tcdCons = con_decls})
248 = kcTyClDeclBody decl $ \ result_kind ->
249 kcHsContext context `thenTc_`
250 mapTc_ kc_con_decl con_decls
252 kc_con_decl (ConDecl _ _ ex_tvs ex_ctxt details loc)
253 = kcHsTyVars ex_tvs `thenNF_Tc` \ kind_env ->
254 tcExtendKindEnv kind_env $
255 kcConDetails new_or_data ex_ctxt details
257 kcTyClDecl decl@(ClassDecl {tcdCtxt = context, tcdSigs = class_sigs})
258 = kcTyClDeclBody decl $ \ result_kind ->
259 kcHsContext context `thenTc_`
260 mapTc_ kc_sig (filter isClassOpSig class_sigs)
262 kc_sig (ClassOpSig _ _ op_ty loc) = kcHsLiftedSigType op_ty
264 kcTyClDeclBody :: RenamedTyClDecl -> (Kind -> TcM a) -> TcM a
265 -- Extend the env with bindings for the tyvars, taken from
266 -- the kind of the tycon/class. Give it to the thing inside, and
267 -- check the result kind matches
268 kcTyClDeclBody decl thing_inside
269 = tcAddDeclCtxt decl $
270 tcLookup (tcdName decl) `thenNF_Tc` \ thing ->
273 AGlobal (ATyCon tc) -> tyConKind tc
274 AGlobal (AClass cl) -> tyConKind (classTyCon cl)
276 -- For some odd reason, a class doesn't include its kind
278 (tyvars_w_kinds, result_kind) = zipFunTys (hsTyVarNames (tyClDeclTyVars decl)) kind
280 tcExtendKindEnv tyvars_w_kinds (thing_inside result_kind)
284 %************************************************************************
286 \subsection{Step 4: Building the tycon/class}
288 %************************************************************************
293 -> RecFlag -> NameEnv Kind
294 -> FiniteMap TyCon ArgVrcs -> NameEnv TyThingDetails
295 -> RenamedTyClDecl -> TyThing
297 buildTyConOrClass dflags is_rec kenv rec_vrcs rec_details
298 (TySynonym {tcdName = tycon_name, tcdTyVars = tyvar_names})
301 tycon = mkSynTyCon tycon_name tycon_kind arity tyvars rhs_ty argvrcs
302 tycon_kind = lookupNameEnv_NF kenv tycon_name
303 arity = length tyvar_names
304 tyvars = mkTyClTyVars tycon_kind tyvar_names
305 SynTyDetails rhs_ty = lookupNameEnv_NF rec_details tycon_name
306 argvrcs = lookupWithDefaultFM rec_vrcs bogusVrcs tycon
308 buildTyConOrClass dflags is_rec kenv rec_vrcs rec_details
309 (TyData {tcdND = data_or_new, tcdName = tycon_name, tcdTyVars = tyvar_names,
310 tcdNCons = nconstrs, tcdSysNames = sys_names})
313 tycon = mkAlgTyCon tycon_name tycon_kind tyvars ctxt argvrcs
314 data_cons nconstrs sel_ids
315 flavour is_rec gen_info
317 gen_info | not (dopt Opt_Generics dflags) = Nothing
318 | otherwise = mkTyConGenInfo tycon sys_names
320 DataTyDetails ctxt data_cons sel_ids = lookupNameEnv_NF rec_details tycon_name
322 tycon_kind = lookupNameEnv_NF kenv tycon_name
323 tyvars = mkTyClTyVars tycon_kind tyvar_names
324 argvrcs = lookupWithDefaultFM rec_vrcs bogusVrcs tycon
326 flavour = case data_or_new of
327 NewType -> NewTyCon (mkNewTyConRep tycon)
328 DataType | all isNullaryDataCon data_cons -> EnumTyCon
329 | otherwise -> DataTyCon
331 buildTyConOrClass dflags is_rec kenv rec_vrcs rec_details
332 (ForeignType {tcdName = tycon_name})
333 = ATyCon (mkForeignTyCon tycon_name liftedTypeKind 0 [])
335 buildTyConOrClass dflags is_rec kenv rec_vrcs rec_details
336 (ClassDecl {tcdName = class_name, tcdTyVars = tyvar_names,
337 tcdFDs = fundeps, tcdSysNames = name_list} )
340 (tycon_name, _, _, _) = getClassDeclSysNames name_list
341 clas = mkClass class_name tyvars fds
342 sc_theta sc_sel_ids op_items
345 tycon = mkClassTyCon tycon_name class_kind tyvars
347 clas -- Yes! It's a dictionary
350 ClassDetails sc_theta sc_sel_ids op_items dict_con = lookupNameEnv_NF rec_details class_name
352 class_kind = lookupNameEnv_NF kenv class_name
353 tyvars = mkTyClTyVars class_kind tyvar_names
354 argvrcs = lookupWithDefaultFM rec_vrcs bogusVrcs tycon
355 n_fields = length sc_sel_ids + length op_items
357 flavour | n_fields == 1 = NewTyCon (mkNewTyConRep tycon)
358 | otherwise = DataTyCon
360 -- We can find the functional dependencies right away,
361 -- and it is vital to do so. Why? Because in the next pass
362 -- we check for ambiguity in all the type signatures, and we
363 -- need the functional dependcies to be done by then
364 fds = [(map lookup xs, map lookup ys) | (xs,ys) <- fundeps]
365 tyvar_env = mkNameEnv [(varName tv, tv) | tv <- tyvars]
366 lookup = lookupNameEnv_NF tyvar_env
368 bogusVrcs = panic "Bogus tycon arg variances"
372 %************************************************************************
374 \subsection{Dependency analysis}
376 %************************************************************************
381 sortByDependency :: [RenamedTyClDecl] -> TcM [SCC RenamedTyClDecl]
382 sortByDependency decls
383 = let -- CHECK FOR CLASS CYCLES
384 cls_sccs = stronglyConnComp (mapMaybe mkClassEdges tycl_decls)
385 cls_cycles = [ decls | CyclicSCC decls <- cls_sccs]
387 checkTc (null cls_cycles) (classCycleErr cls_cycles) `thenTc_`
389 let -- CHECK FOR SYNONYM CYCLES
390 syn_sccs = stronglyConnComp (filter is_syn_decl edges)
391 syn_cycles = [ decls | CyclicSCC decls <- syn_sccs]
394 checkTc (null syn_cycles) (typeCycleErr syn_cycles) `thenTc_`
396 -- DO THE MAIN DEPENDENCY ANALYSIS
398 decl_sccs = stronglyConnComp edges
402 tycl_decls = filter (not . isIfaceSigDecl) decls
403 edges = map mkEdges tycl_decls
405 is_syn_decl (d, _, _) = isSynDecl d
408 Edges in Type/Class decls
409 ~~~~~~~~~~~~~~~~~~~~~~~~~
412 tyClDeclFTVs :: RenamedTyClDecl -> [Name]
413 -- Find the free non-tyvar vars
414 tyClDeclFTVs d = foldNameSet add [] (tyClDeclFVs d)
416 add n fvs | isTyVarName n = fvs
417 | otherwise = n : fvs
419 ----------------------------------------------------
420 -- mk_cls_edges looks only at the context of class decls
421 -- Its used when we are figuring out if there's a cycle in the
422 -- superclass hierarchy
424 mkClassEdges :: RenamedTyClDecl -> Maybe (RenamedTyClDecl, Name, [Name])
426 mkClassEdges decl@(ClassDecl {tcdCtxt = ctxt, tcdName = name}) = Just (decl, name, [c | HsClassP c _ <- ctxt])
427 mkClassEdges other_decl = Nothing
429 mkEdges :: RenamedTyClDecl -> (RenamedTyClDecl, Name, [Name])
430 mkEdges decl = (decl, tyClDeclName decl, tyClDeclFTVs decl)
434 %************************************************************************
436 \subsection{Error management
438 %************************************************************************
441 typeCycleErr, classCycleErr :: [[RenamedTyClDecl]] -> Message
443 typeCycleErr syn_cycles
444 = vcat (map (pp_cycle "Cycle in type declarations:") syn_cycles)
446 classCycleErr cls_cycles
447 = vcat (map (pp_cycle "Cycle in class declarations:") cls_cycles)
451 4 (vcat (map pp_decl decls))
454 = hsep [quotes (ppr name), ptext SLIT("at"), ppr (getSrcLoc name)]
456 name = tyClDeclName decl