2 % (c) The AQUA Project, Glasgow University, 1996-1998
4 \section[TcTyClsDecls]{Typecheck type and class declarations}
11 #include "HsVersions.h"
13 import HsSyn ( TyClDecl(..), HsConDetails(..), HsTyVarBndr(..),
14 ConDecl(..), Sig(..), , NewOrData(..),
15 tyClDeclTyVars, isSynDecl, LConDecl,
16 LTyClDecl, tcdName, LHsTyVarBndr, LHsContext
18 import HsTypes ( HsBang(..), getBangStrictness )
19 import BasicTypes ( RecFlag(..), StrictnessMark(..) )
20 import HscTypes ( implicitTyThings )
21 import BuildTyCl ( buildClass, buildAlgTyCon, buildSynTyCon, buildDataCon,
22 mkDataTyConRhs, mkNewTyConRhs )
24 import TcEnv ( TcTyThing(..), TyThing(..),
25 tcLookupLocated, tcLookupLocatedGlobal,
26 tcExtendGlobalEnv, tcExtendKindEnv,
27 tcExtendRecEnv, tcLookupTyVar )
28 import TcTyDecls ( calcTyConArgVrcs, calcRecFlags, calcClassCycles, calcSynCycles )
29 import TcClassDcl ( tcClassSigs, tcAddDeclCtxt )
30 import TcHsType ( kcHsTyVars, kcHsLiftedSigType, kcHsType,
31 kcHsContext, tcTyVarBndrs, tcHsKindedType, tcHsKindedContext,
32 kcHsSigType, tcHsBangType, tcLHsConSig )
33 import TcMType ( newKindVar, checkValidTheta, checkValidType, checkFreeness,
34 UserTypeCtxt(..), SourceTyCtxt(..) )
35 import TcUnify ( unifyKind )
36 import TcType ( TcKind, ThetaType, TcType, tyVarsOfType,
37 mkArrowKind, liftedTypeKind, mkTyVarTys, tcEqTypes,
38 tcSplitSigmaTy, tcEqType )
39 import Type ( splitTyConApp_maybe, pprThetaArrow, pprParendType )
40 import Generics ( validGenericMethodType, canDoGenerics )
41 import Class ( Class, className, classTyCon, DefMeth(..), classBigSig, classTyVars )
42 import TyCon ( TyCon, ArgVrcs,
43 tyConDataCons, mkForeignTyCon, isProductTyCon, isRecursiveTyCon,
44 tyConStupidTheta, getSynTyConDefn, tyConDataCons, isSynTyCon, tyConName )
45 import DataCon ( DataCon, dataConWrapId, dataConName, dataConSig,
46 dataConFieldLabels, dataConOrigArgTys, dataConTyCon )
47 import Type ( zipTopTvSubst, substTys )
48 import Var ( TyVar, idType, idName )
49 import VarSet ( elemVarSet )
52 import Util ( zipLazy, isSingleton, notNull, sortLe )
53 import List ( partition )
54 import SrcLoc ( Located(..), unLoc, getLoc )
55 import ListSetOps ( equivClasses )
56 import Digraph ( SCC(..) )
57 import CmdLineOpts ( DynFlag( Opt_GlasgowExts, Opt_Generics, Opt_UnboxStrictFields ) )
61 %************************************************************************
63 \subsection{Type checking for type and class declarations}
65 %************************************************************************
69 Consider a mutually-recursive group, binding
70 a type constructor T and a class C.
72 Step 1: getInitialKind
73 Construct a KindEnv by binding T and C to a kind variable
76 In that environment, do a kind check
78 Step 3: Zonk the kinds
80 Step 4: buildTyConOrClass
81 Construct an environment binding T to a TyCon and C to a Class.
82 a) Their kinds comes from zonking the relevant kind variable
83 b) Their arity (for synonyms) comes direct from the decl
84 c) The funcional dependencies come from the decl
85 d) The rest comes a knot-tied binding of T and C, returned from Step 4
86 e) The variances of the tycons in the group is calculated from
90 In this environment, walk over the decls, constructing the TyCons and Classes.
91 This uses in a strict way items (a)-(c) above, which is why they must
92 be constructed in Step 4. Feed the results back to Step 4.
93 For this step, pass the is-recursive flag as the wimp-out flag
97 Step 6: Extend environment
98 We extend the type environment with bindings not only for the TyCons and Classes,
99 but also for their "implicit Ids" like data constructors and class selectors
101 Step 7: checkValidTyCl
102 For a recursive group only, check all the decls again, just
103 to check all the side conditions on validity. We could not
104 do this before because we were in a mutually recursive knot.
107 The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to
108 @TyThing@s. @rec_vrcs@ is a finite map from @Name@s to @ArgVrcs@s.
111 tcTyAndClassDecls :: [Name] -> [LTyClDecl Name]
112 -> TcM TcGblEnv -- Input env extended by types and classes
113 -- and their implicit Ids,DataCons
114 tcTyAndClassDecls boot_names decls
115 = do { -- First check for cyclic type synonysm or classes
116 -- See notes with checkCycleErrs
119 ; traceTc (text "tcTyAndCl" <+> ppr mod <+> ppr boot_names)
120 ; (syn_tycons, alg_tyclss) <- fixM (\ ~(rec_syn_tycons, rec_alg_tyclss) ->
121 do { let { -- Calculate variances and rec-flag
122 ; (syn_decls, alg_decls) = partition (isSynDecl . unLoc) decls }
124 -- Extend the global env with the knot-tied results
125 -- for data types and classes
127 -- We must populate the environment with the loop-tied T's right
128 -- away, because the kind checker may "fault in" some type
129 -- constructors that recursively mention T
130 ; let { gbl_things = mkGlobalThings alg_decls rec_alg_tyclss }
131 ; tcExtendRecEnv gbl_things $ do
133 -- Kind-check the declarations
134 { (kc_syn_decls, kc_alg_decls) <- kcTyClDecls syn_decls alg_decls
136 ; let { calc_vrcs = calcTyConArgVrcs (rec_syn_tycons ++ rec_alg_tyclss)
137 ; calc_rec = calcRecFlags boot_names rec_alg_tyclss
138 ; tc_decl = addLocM (tcTyClDecl calc_vrcs calc_rec) }
139 -- Type-check the type synonyms, and extend the envt
140 ; syn_tycons <- tcSynDecls calc_vrcs kc_syn_decls
141 ; tcExtendGlobalEnv syn_tycons $ do
143 -- Type-check the data types and classes
144 { alg_tyclss <- mappM tc_decl kc_alg_decls
145 ; return (syn_tycons, alg_tyclss)
147 -- Finished with knot-tying now
148 -- Extend the environment with the finished things
149 ; tcExtendGlobalEnv (syn_tycons ++ alg_tyclss) $ do
151 -- Perform the validity check
152 { traceTc (text "ready for validity check")
153 ; mappM_ (addLocM checkValidTyCl) decls
154 ; traceTc (text "done")
156 -- Add the implicit things;
157 -- we want them in the environment because
158 -- they may be mentioned in interface files
159 ; let { implicit_things = concatMap implicitTyThings alg_tyclss }
160 ; traceTc ((text "Adding" <+> ppr alg_tyclss) $$ (text "and" <+> ppr implicit_things))
161 ; tcExtendGlobalEnv implicit_things getGblEnv
164 mkGlobalThings :: [LTyClDecl Name] -- The decls
165 -> [TyThing] -- Knot-tied, in 1-1 correspondence with the decls
167 -- Driven by the Decls, and treating the TyThings lazily
168 -- make a TypeEnv for the new things
169 mkGlobalThings decls things
170 = map mk_thing (decls `zipLazy` things)
172 mk_thing (L _ (ClassDecl {tcdLName = L _ name}), ~(AClass cl))
174 mk_thing (L _ decl, ~(ATyCon tc))
175 = (tcdName decl, ATyCon tc)
179 %************************************************************************
183 %************************************************************************
185 We need to kind check all types in the mutually recursive group
186 before we know the kind of the type variables. For example:
189 op :: D b => a -> b -> b
192 bop :: (Monad c) => ...
194 Here, the kind of the locally-polymorphic type variable "b"
195 depends on *all the uses of class D*. For example, the use of
196 Monad c in bop's type signature means that D must have kind Type->Type.
198 However type synonyms work differently. They can have kinds which don't
199 just involve (->) and *:
200 type R = Int# -- Kind #
201 type S a = Array# a -- Kind * -> #
202 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
203 So we must infer their kinds from their right-hand sides *first* and then
204 use them, whereas for the mutually recursive data types D we bring into
205 scope kind bindings D -> k, where k is a kind variable, and do inference.
208 kcTyClDecls syn_decls alg_decls
209 = do { -- First extend the kind env with each data
210 -- type and class, mapping them to a type variable
211 alg_kinds <- mappM getInitialKind alg_decls
212 ; tcExtendKindEnv alg_kinds $ do
214 -- Now kind-check the type synonyms, in dependency order
215 -- We do these differently to data type and classes,
216 -- because a type synonym can be an unboxed type
218 -- and a kind variable can't unify with UnboxedTypeKind
219 -- So we infer their kinds in dependency order
220 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
221 ; tcExtendKindEnv syn_kinds $ do
223 -- Now kind-check the data type and class declarations,
224 -- returning kind-annotated decls
225 { kc_alg_decls <- mappM (wrapLocM kcTyClDecl) alg_decls
227 ; return (kc_syn_decls, kc_alg_decls) }}}
229 ------------------------------------------------------------------------
230 getInitialKind :: LTyClDecl Name -> TcM (Name, TcKind)
233 = newKindVar `thenM` \ kind ->
234 returnM (unLoc (tcdLName (unLoc decl)), kind)
237 kcSynDecls :: [SCC (LTyClDecl Name)]
238 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
239 [(Name,TcKind)]) -- Kind bindings
242 kcSynDecls (group : groups)
243 = do { (decl, nk) <- kcSynDecl group
244 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
245 ; return (decl:decls, nk:nks) }
248 kcSynDecl :: SCC (LTyClDecl Name)
249 -> TcM (LTyClDecl Name, -- Kind-annotated decls
250 (Name,TcKind)) -- Kind bindings
251 kcSynDecl (AcyclicSCC ldecl@(L loc decl))
252 = tcAddDeclCtxt decl $
253 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
254 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
255 <+> brackets (ppr k_tvs))
256 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
257 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
258 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
259 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
260 (unLoc (tcdLName decl), tc_kind)) })
262 kcSynDecl (CyclicSCC decls)
263 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
264 -- of out-of-scope tycons
266 ------------------------------------------------------------------------
267 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
268 -- Not used for type synonyms (see kcSynDecl)
270 kcTyClDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
271 = kcTyClDeclBody decl $ \ tvs' ->
272 do { ctxt' <- kcHsContext ctxt
273 ; cons' <- mappM (wrapLocM kc_con_decl) cons
274 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdCons = cons'}) }
276 kc_con_decl (ConDecl name ex_tvs ex_ctxt details)
277 = kcHsTyVars ex_tvs $ \ ex_tvs' ->
278 do { ex_ctxt' <- kcHsContext ex_ctxt
279 ; details' <- kc_con_details details
280 ; return (ConDecl name ex_tvs' ex_ctxt' details')}
281 kc_con_decl (GadtDecl name ty)
282 = do { ty' <- kcHsSigType ty
283 ; return (GadtDecl name ty') }
285 kc_con_details (PrefixCon btys)
286 = do { btys' <- mappM kc_larg_ty btys ; return (PrefixCon btys') }
287 kc_con_details (InfixCon bty1 bty2)
288 = do { bty1' <- kc_larg_ty bty1; bty2' <- kc_larg_ty bty2; return (InfixCon bty1' bty2') }
289 kc_con_details (RecCon fields)
290 = do { fields' <- mappM kc_field fields; return (RecCon fields') }
292 kc_field (fld, bty) = do { bty' <- kc_larg_ty bty ; return (fld, bty') }
294 kc_larg_ty bty = case new_or_data of
295 DataType -> kcHsSigType bty
296 NewType -> kcHsLiftedSigType bty
297 -- Can't allow an unlifted type for newtypes, because we're effectively
298 -- going to remove the constructor while coercing it to a lifted type.
299 -- And newtypes can't be bang'd
301 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs})
302 = kcTyClDeclBody decl $ \ tvs' ->
303 do { ctxt' <- kcHsContext ctxt
304 ; sigs' <- mappM (wrapLocM kc_sig) sigs
305 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs'}) }
307 kc_sig (Sig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
308 ; return (Sig nm op_ty') }
309 kc_sig other_sig = return other_sig
311 kcTyClDecl decl@(ForeignType {})
314 kcTyClDeclBody :: TyClDecl Name
315 -> ([LHsTyVarBndr Name] -> TcM a)
317 -- Extend the env with bindings for the tyvars, taken from
318 -- the kind of the tycon/class. Give it to the thing inside, and
319 -- check the result kind matches
320 kcTyClDeclBody decl thing_inside
321 = tcAddDeclCtxt decl $
322 kcHsTyVars (tyClDeclTyVars decl) $ \ kinded_tvs ->
323 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
324 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
325 ; unifyKind tc_kind (foldr (mkArrowKind . kindedTyVarKind)
328 ; thing_inside kinded_tvs }
330 result_kind (TyData { tcdKindSig = Just kind }) = kind
331 result_kind other = liftedTypeKind
332 -- On GADT-style declarations we allow a kind signature
333 -- data T :: *->* where { ... }
335 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
339 %************************************************************************
341 \subsection{Type checking}
343 %************************************************************************
346 tcSynDecls :: (Name -> ArgVrcs) -> [LTyClDecl Name] -> TcM [TyThing]
347 tcSynDecls calc_vrcs [] = return []
348 tcSynDecls calc_vrcs (decl : decls)
349 = do { syn_tc <- addLocM (tcSynDecl calc_vrcs) decl
350 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls calc_vrcs decls)
351 ; return (syn_tc : syn_tcs) }
354 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
355 = tcTyVarBndrs tvs $ \ tvs' -> do
356 { traceTc (text "tcd1" <+> ppr tc_name)
357 ; rhs_ty' <- tcHsKindedType rhs_ty
358 ; return (ATyCon (buildSynTyCon tc_name tvs' rhs_ty' (calc_vrcs tc_name))) }
361 tcTyClDecl :: (Name -> ArgVrcs) -> (Name -> RecFlag)
362 -> TyClDecl Name -> TcM TyThing
364 tcTyClDecl calc_vrcs calc_isrec decl
365 = tcAddDeclCtxt decl (tcTyClDecl1 calc_vrcs calc_isrec decl)
367 tcTyClDecl1 calc_vrcs calc_isrec
368 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
369 tcdLName = L _ tc_name, tcdCons = cons})
370 = tcTyVarBndrs tvs $ \ tvs' -> do
371 { stupid_theta <- tcStupidTheta ctxt cons
372 ; want_generic <- doptM Opt_Generics
373 ; tycon <- fixM (\ tycon -> do
374 { unbox_strict <- doptM Opt_UnboxStrictFields
375 ; data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data tycon tvs')) cons
376 ; let tc_rhs = case new_or_data of
377 DataType -> mkDataTyConRhs stupid_theta data_cons
378 NewType -> ASSERT( isSingleton data_cons )
379 mkNewTyConRhs tycon (head data_cons)
380 ; buildAlgTyCon tc_name tvs' tc_rhs arg_vrcs is_rec
381 (want_generic && canDoGenerics data_cons)
383 ; return (ATyCon tycon)
386 arg_vrcs = calc_vrcs tc_name
387 is_rec = calc_isrec tc_name
389 tcTyClDecl1 calc_vrcs calc_isrec
390 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
391 tcdCtxt = ctxt, tcdMeths = meths,
392 tcdFDs = fundeps, tcdSigs = sigs} )
393 = tcTyVarBndrs tvs $ \ tvs' -> do
394 { ctxt' <- tcHsKindedContext ctxt
395 ; fds' <- mappM (addLocM tc_fundep) fundeps
396 ; sig_stuff <- tcClassSigs class_name sigs meths
397 ; clas <- fixM (\ clas ->
398 let -- This little knot is just so we can get
399 -- hold of the name of the class TyCon, which we
400 -- need to look up its recursiveness and variance
401 tycon_name = tyConName (classTyCon clas)
402 tc_isrec = calc_isrec tycon_name
403 tc_vrcs = calc_vrcs tycon_name
405 buildClass class_name tvs' ctxt' fds'
406 sig_stuff tc_isrec tc_vrcs)
407 ; return (AClass clas) }
409 tc_fundep (tvs1, tvs2) = do { tvs1' <- mappM tcLookupTyVar tvs1 ;
410 ; tvs2' <- mappM tcLookupTyVar tvs2 ;
411 ; return (tvs1', tvs2') }
414 tcTyClDecl1 calc_vrcs calc_isrec
415 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
416 = returnM (ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0 []))
418 -----------------------------------
419 tcConDecl :: Bool -- True <=> -funbox-strict_fields
420 -> NewOrData -> TyCon -> [TyVar]
421 -> ConDecl Name -> TcM DataCon
423 tcConDecl unbox_strict NewType tycon tc_tvs -- Newtypes
424 (ConDecl name ex_tvs ex_ctxt details)
425 = ASSERT( null ex_tvs && null (unLoc ex_ctxt) )
426 do { let tc_datacon field_lbls arg_ty
427 = do { arg_ty' <- tcHsKindedType arg_ty -- No bang on newtype
428 ; buildDataCon (unLoc name) False {- Prefix -}
429 True {- Vanilla -} [NotMarkedStrict]
430 (map unLoc field_lbls)
432 tycon (mkTyVarTys tc_tvs) }
434 PrefixCon [arg_ty] -> tc_datacon [] arg_ty
435 RecCon [(field_lbl, arg_ty)] -> tc_datacon [field_lbl] arg_ty }
437 tcConDecl unbox_strict DataType tycon tc_tvs -- Ordinary data types
438 (ConDecl name ex_tvs ex_ctxt details)
439 = tcTyVarBndrs ex_tvs $ \ ex_tvs' -> do
440 { ex_ctxt' <- tcHsKindedContext ex_ctxt
442 is_vanilla = null ex_tvs && null (unLoc ex_ctxt)
443 -- Vanilla iff no ex_tvs and no context
445 tc_datacon is_infix field_lbls btys
446 = do { let { bangs = map getBangStrictness btys }
447 ; arg_tys <- mappM tcHsBangType btys
448 ; buildDataCon (unLoc name) is_infix is_vanilla
449 (argStrictness unbox_strict tycon bangs arg_tys)
450 (map unLoc field_lbls)
454 tycon (mkTyVarTys tc_tvs) }
456 PrefixCon btys -> tc_datacon False [] btys
457 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
458 RecCon fields -> do { checkTc is_vanilla (exRecConErr name)
459 ; let { (field_names, btys) = unzip fields }
460 ; tc_datacon False field_names btys } }
462 tcConDecl unbox_strict DataType tycon tc_tvs -- GADTs
463 decl@(GadtDecl name con_ty)
464 = do { traceTc (text "tcConDecl" <+> ppr name)
465 ; (tvs, theta, bangs, arg_tys, tc, res_tys) <- tcLHsConSig con_ty
467 ; traceTc (text "tcConDecl1" <+> ppr name)
468 ; let -- Now dis-assemble the type, and check its form
469 is_vanilla = null theta && mkTyVarTys tvs `tcEqTypes` res_tys
471 -- Vanilla datacons guarantee to use the same
472 -- type variables as the parent tycon
473 (tvs', arg_tys', res_tys')
474 | is_vanilla = (tc_tvs, substTys subst arg_tys, substTys subst res_tys)
475 | otherwise = (tvs, arg_tys, res_tys)
476 subst = zipTopTvSubst tvs (mkTyVarTys tc_tvs)
478 ; traceTc (text "tcConDecl3" <+> ppr name)
479 ; buildDataCon (unLoc name) False {- Not infix -} is_vanilla
480 (argStrictness unbox_strict tycon bangs arg_tys)
481 [{- No field labels -}]
482 tvs' theta arg_tys' tycon res_tys' }
485 tcStupidTheta :: LHsContext Name -> [LConDecl Name] -> TcM (Maybe ThetaType)
486 -- For GADTs we don't allow a context on the data declaration
487 -- whereas for standard Haskell style data declarations, we do
488 tcStupidTheta ctxt (L _ (ConDecl _ _ _ _) : _)
489 = do { theta <- tcHsKindedContext ctxt; return (Just theta) }
490 tcStupidTheta ctxt other -- Includes an empty constructor list
491 = ASSERT( null (unLoc ctxt) ) return Nothing
494 argStrictness :: Bool -- True <=> -funbox-strict_fields
496 -> [TcType] -> [StrictnessMark]
497 argStrictness unbox_strict tycon bangs arg_tys
498 = ASSERT( length bangs == length arg_tys )
499 zipWith (chooseBoxingStrategy unbox_strict tycon) arg_tys bangs
501 -- We attempt to unbox/unpack a strict field when either:
502 -- (i) The field is marked '!!', or
503 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
505 chooseBoxingStrategy :: Bool -> TyCon -> TcType -> HsBang -> StrictnessMark
506 chooseBoxingStrategy unbox_strict_fields tycon arg_ty bang
508 HsNoBang -> NotMarkedStrict
509 HsStrict | unbox_strict_fields && can_unbox -> MarkedUnboxed
510 HsUnbox | can_unbox -> MarkedUnboxed
511 other -> MarkedStrict
513 can_unbox = case splitTyConApp_maybe arg_ty of
515 Just (arg_tycon, _) -> not (isRecursiveTyCon tycon) &&
516 isProductTyCon arg_tycon
519 %************************************************************************
521 \subsection{Dependency analysis}
523 %************************************************************************
525 Validity checking is done once the mutually-recursive knot has been
526 tied, so we can look at things freely.
529 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
530 checkCycleErrs tyclss
534 = do { mappM_ recClsErr cls_cycles
535 ; failM } -- Give up now, because later checkValidTyCl
536 -- will loop if the synonym is recursive
538 cls_cycles = calcClassCycles tyclss
540 checkValidTyCl :: TyClDecl Name -> TcM ()
541 -- We do the validity check over declarations, rather than TyThings
542 -- only so that we can add a nice context with tcAddDeclCtxt
544 = tcAddDeclCtxt decl $
545 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
546 ; traceTc (text "Validity of" <+> ppr thing)
548 ATyCon tc -> checkValidTyCon tc
549 AClass cl -> checkValidClass cl
550 ; traceTc (text "Done validity of" <+> ppr thing)
553 -------------------------
554 checkValidTyCon :: TyCon -> TcM ()
557 = checkValidType syn_ctxt syn_rhs
559 = -- Check the context on the data decl
560 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
562 -- Check arg types of data constructors
563 mappM_ (checkValidDataCon tc) data_cons `thenM_`
565 -- Check that fields with the same name share a type
566 mappM_ check_fields groups
569 syn_ctxt = TySynCtxt name
571 (_, syn_rhs) = getSynTyConDefn tc
572 data_cons = tyConDataCons tc
574 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
575 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
576 get_fields con = dataConFieldLabels con `zip` dataConOrigArgTys con
577 -- dataConFieldLabels may return the empty list, which is fine
579 check_fields fields@((first_field_label, field_ty) : other_fields)
580 -- These fields all have the same name, but are from
581 -- different constructors in the data type
582 = -- Check that all the fields in the group have the same type
583 -- NB: this check assumes that all the constructors of a given
584 -- data type use the same type variables
585 checkTc (all (tcEqType field_ty . snd) other_fields)
586 (fieldTypeMisMatch first_field_label)
588 -------------------------------
589 checkValidDataCon :: TyCon -> DataCon -> TcM ()
590 checkValidDataCon tc con
591 = addErrCtxt (dataConCtxt con) $
592 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
593 ; checkValidType ctxt (idType (dataConWrapId con)) }
595 -- This checks the argument types and
596 -- ambiguity of the existential context (if any)
598 -- Note [Sept 04] Now that tvs is all the tvs, this
599 -- test doesn't actually check anything
600 -- ; checkFreeness tvs ex_theta }
602 ctxt = ConArgCtxt (dataConName con)
603 (tvs, ex_theta, _, _, _) = dataConSig con
606 -------------------------------
607 checkValidClass :: Class -> TcM ()
609 = do { -- CHECK ARITY 1 FOR HASKELL 1.4
610 gla_exts <- doptM Opt_GlasgowExts
612 -- Check that the class is unary, unless GlaExs
613 ; checkTc (notNull tyvars) (nullaryClassErr cls)
614 ; checkTc (gla_exts || unary) (classArityErr cls)
616 -- Check the super-classes
617 ; checkValidTheta (ClassSCCtxt (className cls)) theta
619 -- Check the class operations
620 ; mappM_ check_op op_stuff
622 -- Check that if the class has generic methods, then the
623 -- class has only one parameter. We can't do generic
624 -- multi-parameter type classes!
625 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
628 (tyvars, theta, _, op_stuff) = classBigSig cls
629 unary = isSingleton tyvars
630 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
632 check_op (sel_id, dm)
633 = addErrCtxt (classOpCtxt sel_id tau) $ do
634 { checkValidTheta SigmaCtxt (tail theta)
635 -- The 'tail' removes the initial (C a) from the
636 -- class itself, leaving just the method type
638 ; checkValidType (FunSigCtxt op_name) tau
640 -- Check that the type mentions at least one of
641 -- the class type variables
642 ; checkTc (any (`elemVarSet` tyVarsOfType tau) tyvars)
643 (noClassTyVarErr cls sel_id)
645 -- Check that for a generic method, the type of
646 -- the method is sufficiently simple
647 ; checkTc (dm /= GenDefMeth || validGenericMethodType op_ty)
648 (badGenericMethodType op_name op_ty)
651 op_name = idName sel_id
652 op_ty = idType sel_id
653 (_,theta,tau) = tcSplitSigmaTy op_ty
657 ---------------------------------------------------------------------
658 fieldTypeMisMatch field_name
659 = sep [ptext SLIT("Different constructors give different types for field"), quotes (ppr field_name)]
661 dataConCtxt con = sep [ptext SLIT("When checking the data constructor:"),
662 nest 2 (ex_part <+> pprThetaArrow ex_theta <+> ppr con <+> arg_part)]
664 (ex_tvs, ex_theta, arg_tys, _, _) = dataConSig con
665 ex_part | null ex_tvs = empty
666 | otherwise = ptext SLIT("forall") <+> hsep (map ppr ex_tvs) <> dot
667 -- The 'ex_theta' part could be non-empty, if the user (bogusly) wrote
668 -- data T a = Eq a => T a a
669 -- So we make sure to print it
671 fields = dataConFieldLabels con
672 arg_part | null fields = sep (map pprParendType arg_tys)
673 | otherwise = braces (sep (punctuate comma
674 [ ppr n <+> dcolon <+> ppr ty
675 | (n,ty) <- fields `zip` arg_tys]))
677 classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
678 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
681 = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
684 = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
685 parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
687 noClassTyVarErr clas op
688 = sep [ptext SLIT("The class method") <+> quotes (ppr op),
689 ptext SLIT("mentions none of the type variables of the class") <+>
690 ppr clas <+> hsep (map ppr (classTyVars clas))]
692 genericMultiParamErr clas
693 = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
694 ptext SLIT("cannot have generic methods")
696 badGenericMethodType op op_ty
697 = hang (ptext SLIT("Generic method type is too complex"))
698 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
699 ptext SLIT("You can only use type variables, arrows, and tuples")])
702 = setSrcSpan (getLoc (head sorted_decls)) $
703 addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
704 nest 2 (vcat (map ppr_decl sorted_decls))])
706 sorted_decls = sortLocated syn_decls
707 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
710 = setSrcSpan (getLoc (head sorted_decls)) $
711 addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
712 nest 2 (vcat (map ppr_decl sorted_decls))])
714 sorted_decls = sortLocated cls_decls
715 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
717 sortLocated :: [Located a] -> [Located a]
718 sortLocated things = sortLe le things
720 le (L l1 _) (L l2 _) = l1 <= l2
723 = ptext SLIT("Can't combine named fields with locally-quantified type variables or context")
725 (ptext SLIT("In the declaration of data constructor") <+> ppr name)
727 badDataConTyCon data_con
728 = hang (ptext SLIT("Data constructor does not return its parent type:"))