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,
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, zipFunTys )
34 import Variance ( calcTyConArgVrcs )
35 import Class ( Class, mkClass, classTyCon )
36 import TyCon ( TyCon, tyConKind, ArgVrcs, AlgTyConFlavour(..),
37 mkSynTyCon, mkAlgTyCon, mkClassTyCon )
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 (tcdTyVars 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 decl@(TyData {tcdND = new_or_data, tcdCtxt = context, tcdCons = con_decls})
246 = kcTyClDeclBody decl $ \ result_kind ->
247 kcHsContext context `thenTc_`
248 mapTc_ kc_con_decl con_decls
250 kc_con_decl (ConDecl _ _ ex_tvs ex_ctxt details loc)
251 = kcHsTyVars ex_tvs `thenNF_Tc` \ kind_env ->
252 tcExtendKindEnv kind_env $
253 kcConDetails new_or_data ex_ctxt details
255 kcTyClDecl decl@(ClassDecl {tcdCtxt = context, tcdSigs = class_sigs})
256 = kcTyClDeclBody decl $ \ result_kind ->
257 kcHsContext context `thenTc_`
258 mapTc_ kc_sig (filter isClassOpSig class_sigs)
260 kc_sig (ClassOpSig _ _ op_ty loc) = kcHsLiftedSigType op_ty
262 kcTyClDeclBody :: RenamedTyClDecl -> (Kind -> TcM a) -> TcM a
263 -- Extend the env with bindings for the tyvars, taken from
264 -- the kind of the tycon/class. Give it to the thing inside, and
265 -- check the result kind matches
266 kcTyClDeclBody decl thing_inside
267 = tcAddDeclCtxt decl $
268 tcLookup (tcdName decl) `thenNF_Tc` \ thing ->
271 AGlobal (ATyCon tc) -> tyConKind tc
272 AGlobal (AClass cl) -> tyConKind (classTyCon cl)
274 -- For some odd reason, a class doesn't include its kind
276 (tyvars_w_kinds, result_kind) = zipFunTys (hsTyVarNames (tcdTyVars decl)) kind
278 tcExtendKindEnv tyvars_w_kinds (thing_inside result_kind)
282 %************************************************************************
284 \subsection{Step 4: Building the tycon/class}
286 %************************************************************************
291 -> RecFlag -> NameEnv Kind
292 -> FiniteMap TyCon ArgVrcs -> NameEnv TyThingDetails
293 -> RenamedTyClDecl -> TyThing
295 buildTyConOrClass dflags is_rec kenv rec_vrcs rec_details
296 (TySynonym {tcdName = tycon_name, tcdTyVars = tyvar_names})
299 tycon = mkSynTyCon tycon_name tycon_kind arity tyvars rhs_ty argvrcs
300 tycon_kind = lookupNameEnv_NF kenv tycon_name
301 arity = length tyvar_names
302 tyvars = mkTyClTyVars tycon_kind tyvar_names
303 SynTyDetails rhs_ty = lookupNameEnv_NF rec_details tycon_name
304 argvrcs = lookupWithDefaultFM rec_vrcs bogusVrcs tycon
306 buildTyConOrClass dflags is_rec kenv rec_vrcs rec_details
307 (TyData {tcdND = data_or_new, tcdName = tycon_name, tcdTyVars = tyvar_names,
308 tcdNCons = nconstrs, tcdSysNames = sys_names})
311 tycon = mkAlgTyCon tycon_name tycon_kind tyvars ctxt argvrcs
312 data_cons nconstrs sel_ids
313 flavour is_rec gen_info
315 gen_info | not (dopt Opt_Generics dflags) = Nothing
316 | otherwise = mkTyConGenInfo tycon sys_names
318 DataTyDetails ctxt data_cons sel_ids = lookupNameEnv_NF rec_details tycon_name
320 tycon_kind = lookupNameEnv_NF kenv tycon_name
321 tyvars = mkTyClTyVars tycon_kind tyvar_names
322 argvrcs = lookupWithDefaultFM rec_vrcs bogusVrcs tycon
324 flavour = case data_or_new of
325 NewType -> NewTyCon (mkNewTyConRep tycon)
326 DataType | all isNullaryDataCon data_cons -> EnumTyCon
327 | otherwise -> DataTyCon
329 buildTyConOrClass dflags is_rec kenv rec_vrcs rec_details
330 (ClassDecl {tcdName = class_name, tcdTyVars = tyvar_names,
331 tcdFDs = fundeps, tcdSysNames = name_list} )
334 (tycon_name, _, _, _) = getClassDeclSysNames name_list
335 clas = mkClass class_name tyvars fds
336 sc_theta sc_sel_ids op_items
339 tycon = mkClassTyCon tycon_name class_kind tyvars
341 clas -- Yes! It's a dictionary
344 ClassDetails sc_theta sc_sel_ids op_items dict_con = lookupNameEnv_NF rec_details class_name
346 class_kind = lookupNameEnv_NF kenv class_name
347 tyvars = mkTyClTyVars class_kind tyvar_names
348 argvrcs = lookupWithDefaultFM rec_vrcs bogusVrcs tycon
349 n_fields = length sc_sel_ids + length op_items
351 flavour | n_fields == 1 = NewTyCon (mkNewTyConRep tycon)
352 | otherwise = DataTyCon
354 -- We can find the functional dependencies right away,
355 -- and it is vital to do so. Why? Because in the next pass
356 -- we check for ambiguity in all the type signatures, and we
357 -- need the functional dependcies to be done by then
358 fds = [(map lookup xs, map lookup ys) | (xs,ys) <- fundeps]
359 tyvar_env = mkNameEnv [(varName tv, tv) | tv <- tyvars]
360 lookup = lookupNameEnv_NF tyvar_env
362 bogusVrcs = panic "Bogus tycon arg variances"
366 %************************************************************************
368 \subsection{Dependency analysis}
370 %************************************************************************
375 sortByDependency :: [RenamedTyClDecl] -> TcM [SCC RenamedTyClDecl]
376 sortByDependency decls
377 = let -- CHECK FOR CLASS CYCLES
378 cls_sccs = stronglyConnComp (mapMaybe mkClassEdges tycl_decls)
379 cls_cycles = [ decls | CyclicSCC decls <- cls_sccs]
381 checkTc (null cls_cycles) (classCycleErr cls_cycles) `thenTc_`
383 let -- CHECK FOR SYNONYM CYCLES
384 syn_sccs = stronglyConnComp (filter is_syn_decl edges)
385 syn_cycles = [ decls | CyclicSCC decls <- syn_sccs]
388 checkTc (null syn_cycles) (typeCycleErr syn_cycles) `thenTc_`
390 -- DO THE MAIN DEPENDENCY ANALYSIS
392 decl_sccs = stronglyConnComp edges
396 tycl_decls = filter (not . isIfaceSigDecl) decls
397 edges = map mkEdges tycl_decls
399 is_syn_decl (d, _, _) = isSynDecl d
402 Edges in Type/Class decls
403 ~~~~~~~~~~~~~~~~~~~~~~~~~
406 tyClDeclFTVs :: RenamedTyClDecl -> [Name]
407 -- Find the free non-tyvar vars
408 tyClDeclFTVs d = foldNameSet add [] (tyClDeclFVs d)
410 add n fvs | isTyVarName n = fvs
411 | otherwise = n : fvs
413 ----------------------------------------------------
414 -- mk_cls_edges looks only at the context of class decls
415 -- Its used when we are figuring out if there's a cycle in the
416 -- superclass hierarchy
418 mkClassEdges :: RenamedTyClDecl -> Maybe (RenamedTyClDecl, Name, [Name])
420 mkClassEdges decl@(ClassDecl {tcdCtxt = ctxt, tcdName = name}) = Just (decl, name, [c | HsClassP c _ <- ctxt])
421 mkClassEdges other_decl = Nothing
423 mkEdges :: RenamedTyClDecl -> (RenamedTyClDecl, Name, [Name])
424 mkEdges decl = (decl, tyClDeclName decl, tyClDeclFTVs decl)
428 %************************************************************************
430 \subsection{Error management
432 %************************************************************************
435 typeCycleErr, classCycleErr :: [[RenamedTyClDecl]] -> Message
437 typeCycleErr syn_cycles
438 = vcat (map (pp_cycle "Cycle in type declarations:") syn_cycles)
440 classCycleErr cls_cycles
441 = vcat (map (pp_cycle "Cycle in class declarations:") cls_cycles)
445 4 (vcat (map pp_decl decls))
448 = hsep [quotes (ppr name), ptext SLIT("at"), ppr (getSrcLoc name)]
450 name = tyClDeclName decl