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,
16 LTyClDecl, tcdName, LHsTyVarBndr
18 import HsTypes ( HsBang(..), getBangStrictness )
19 import BasicTypes ( RecFlag(..), StrictnessMark(..) )
20 import HscTypes ( implicitTyThings, ModDetails )
21 import BuildTyCl ( buildClass, buildAlgTyCon, buildSynTyCon, buildDataCon,
22 mkDataTyConRhs, mkNewTyConRhs )
24 import TcEnv ( 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, tcDataKindSig )
33 import TcMType ( newKindVar, checkValidTheta, checkValidType, checkFreeness,
34 UserTypeCtxt(..), SourceTyCtxt(..) )
35 import TcUnify ( unifyKind )
36 import TcType ( TcKind, 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, AlgTyConRhs( AbstractTyCon ),
43 tyConDataCons, mkForeignTyCon, isProductTyCon, isRecursiveTyCon,
44 tyConStupidTheta, getSynTyConDefn, 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 DynFlags ( DynFlag( Opt_GlasgowExts, Opt_Generics,
58 Opt_UnboxStrictFields ) )
62 %************************************************************************
64 \subsection{Type checking for type and class declarations}
66 %************************************************************************
70 Consider a mutually-recursive group, binding
71 a type constructor T and a class C.
73 Step 1: getInitialKind
74 Construct a KindEnv by binding T and C to a kind variable
77 In that environment, do a kind check
79 Step 3: Zonk the kinds
81 Step 4: buildTyConOrClass
82 Construct an environment binding T to a TyCon and C to a Class.
83 a) Their kinds comes from zonking the relevant kind variable
84 b) Their arity (for synonyms) comes direct from the decl
85 c) The funcional dependencies come from the decl
86 d) The rest comes a knot-tied binding of T and C, returned from Step 4
87 e) The variances of the tycons in the group is calculated from
91 In this environment, walk over the decls, constructing the TyCons and Classes.
92 This uses in a strict way items (a)-(c) above, which is why they must
93 be constructed in Step 4. Feed the results back to Step 4.
94 For this step, pass the is-recursive flag as the wimp-out flag
98 Step 6: Extend environment
99 We extend the type environment with bindings not only for the TyCons and Classes,
100 but also for their "implicit Ids" like data constructors and class selectors
102 Step 7: checkValidTyCl
103 For a recursive group only, check all the decls again, just
104 to check all the side conditions on validity. We could not
105 do this before because we were in a mutually recursive knot.
108 The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to
109 @TyThing@s. @rec_vrcs@ is a finite map from @Name@s to @ArgVrcs@s.
112 tcTyAndClassDecls :: ModDetails -> [LTyClDecl Name]
113 -> TcM TcGblEnv -- Input env extended by types and classes
114 -- and their implicit Ids,DataCons
115 tcTyAndClassDecls boot_details decls
116 = do { -- First check for cyclic type synonysm or classes
117 -- See notes with checkCycleErrs
120 ; traceTc (text "tcTyAndCl" <+> ppr mod)
121 ; (syn_tycons, alg_tyclss) <- fixM (\ ~(rec_syn_tycons, rec_alg_tyclss) ->
122 do { let { -- Calculate variances and rec-flag
123 ; (syn_decls, alg_decls) = partition (isSynDecl . unLoc) decls }
125 -- Extend the global env with the knot-tied results
126 -- for data types and classes
128 -- We must populate the environment with the loop-tied T's right
129 -- away, because the kind checker may "fault in" some type
130 -- constructors that recursively mention T
131 ; let { gbl_things = mkGlobalThings alg_decls rec_alg_tyclss }
132 ; tcExtendRecEnv gbl_things $ do
134 -- Kind-check the declarations
135 { (kc_syn_decls, kc_alg_decls) <- kcTyClDecls syn_decls alg_decls
137 ; let { calc_vrcs = calcTyConArgVrcs (rec_syn_tycons ++ rec_alg_tyclss)
138 ; calc_rec = calcRecFlags boot_details rec_alg_tyclss
139 ; tc_decl = addLocM (tcTyClDecl calc_vrcs calc_rec) }
140 -- Type-check the type synonyms, and extend the envt
141 ; syn_tycons <- tcSynDecls calc_vrcs kc_syn_decls
142 ; tcExtendGlobalEnv syn_tycons $ do
144 -- Type-check the data types and classes
145 { alg_tyclss <- mappM tc_decl kc_alg_decls
146 ; return (syn_tycons, alg_tyclss)
148 -- Finished with knot-tying now
149 -- Extend the environment with the finished things
150 ; tcExtendGlobalEnv (syn_tycons ++ alg_tyclss) $ do
152 -- Perform the validity check
153 { traceTc (text "ready for validity check")
154 ; mappM_ (addLocM checkValidTyCl) decls
155 ; traceTc (text "done")
157 -- Add the implicit things;
158 -- we want them in the environment because
159 -- they may be mentioned in interface files
160 ; let { implicit_things = concatMap implicitTyThings alg_tyclss }
161 ; traceTc ((text "Adding" <+> ppr alg_tyclss) $$ (text "and" <+> ppr implicit_things))
162 ; tcExtendGlobalEnv implicit_things getGblEnv
165 mkGlobalThings :: [LTyClDecl Name] -- The decls
166 -> [TyThing] -- Knot-tied, in 1-1 correspondence with the decls
168 -- Driven by the Decls, and treating the TyThings lazily
169 -- make a TypeEnv for the new things
170 mkGlobalThings decls things
171 = map mk_thing (decls `zipLazy` things)
173 mk_thing (L _ (ClassDecl {tcdLName = L _ name}), ~(AClass cl))
175 mk_thing (L _ decl, ~(ATyCon tc))
176 = (tcdName decl, ATyCon tc)
180 %************************************************************************
184 %************************************************************************
186 We need to kind check all types in the mutually recursive group
187 before we know the kind of the type variables. For example:
190 op :: D b => a -> b -> b
193 bop :: (Monad c) => ...
195 Here, the kind of the locally-polymorphic type variable "b"
196 depends on *all the uses of class D*. For example, the use of
197 Monad c in bop's type signature means that D must have kind Type->Type.
199 However type synonyms work differently. They can have kinds which don't
200 just involve (->) and *:
201 type R = Int# -- Kind #
202 type S a = Array# a -- Kind * -> #
203 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
204 So we must infer their kinds from their right-hand sides *first* and then
205 use them, whereas for the mutually recursive data types D we bring into
206 scope kind bindings D -> k, where k is a kind variable, and do inference.
209 kcTyClDecls syn_decls alg_decls
210 = do { -- First extend the kind env with each data
211 -- type and class, mapping them to a type variable
212 alg_kinds <- mappM getInitialKind alg_decls
213 ; tcExtendKindEnv alg_kinds $ do
215 -- Now kind-check the type synonyms, in dependency order
216 -- We do these differently to data type and classes,
217 -- because a type synonym can be an unboxed type
219 -- and a kind variable can't unify with UnboxedTypeKind
220 -- So we infer their kinds in dependency order
221 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
222 ; tcExtendKindEnv syn_kinds $ do
224 -- Now kind-check the data type and class declarations,
225 -- returning kind-annotated decls
226 { kc_alg_decls <- mappM (wrapLocM kcTyClDecl) alg_decls
228 ; return (kc_syn_decls, kc_alg_decls) }}}
230 ------------------------------------------------------------------------
231 getInitialKind :: LTyClDecl Name -> TcM (Name, TcKind)
234 = newKindVar `thenM` \ kind ->
235 returnM (unLoc (tcdLName (unLoc decl)), kind)
238 kcSynDecls :: [SCC (LTyClDecl Name)]
239 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
240 [(Name,TcKind)]) -- Kind bindings
243 kcSynDecls (group : groups)
244 = do { (decl, nk) <- kcSynDecl group
245 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
246 ; return (decl:decls, nk:nks) }
249 kcSynDecl :: SCC (LTyClDecl Name)
250 -> TcM (LTyClDecl Name, -- Kind-annotated decls
251 (Name,TcKind)) -- Kind bindings
252 kcSynDecl (AcyclicSCC ldecl@(L loc decl))
253 = tcAddDeclCtxt decl $
254 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
255 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
256 <+> brackets (ppr k_tvs))
257 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
258 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
259 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
260 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
261 (unLoc (tcdLName decl), tc_kind)) })
263 kcSynDecl (CyclicSCC decls)
264 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
265 -- of out-of-scope tycons
267 ------------------------------------------------------------------------
268 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
269 -- Not used for type synonyms (see kcSynDecl)
271 kcTyClDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
272 = kcTyClDeclBody decl $ \ tvs' ->
273 do { ctxt' <- kcHsContext ctxt
274 ; cons' <- mappM (wrapLocM kc_con_decl) cons
275 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdCons = cons'}) }
277 kc_con_decl (ConDecl name ex_tvs ex_ctxt details)
278 = kcHsTyVars ex_tvs $ \ ex_tvs' ->
279 do { ex_ctxt' <- kcHsContext ex_ctxt
280 ; details' <- kc_con_details details
281 ; return (ConDecl name ex_tvs' ex_ctxt' details')}
282 kc_con_decl (GadtDecl name ty)
283 = do { ty' <- kcHsSigType ty
284 ; traceTc (text "kc_con_decl" <+> ppr name <+> ppr ty')
285 ; return (GadtDecl name ty') }
287 kc_con_details (PrefixCon btys)
288 = do { btys' <- mappM kc_larg_ty btys ; return (PrefixCon btys') }
289 kc_con_details (InfixCon bty1 bty2)
290 = do { bty1' <- kc_larg_ty bty1; bty2' <- kc_larg_ty bty2; return (InfixCon bty1' bty2') }
291 kc_con_details (RecCon fields)
292 = do { fields' <- mappM kc_field fields; return (RecCon fields') }
294 kc_field (fld, bty) = do { bty' <- kc_larg_ty bty ; return (fld, bty') }
296 kc_larg_ty bty = case new_or_data of
297 DataType -> kcHsSigType bty
298 NewType -> kcHsLiftedSigType bty
299 -- Can't allow an unlifted type for newtypes, because we're effectively
300 -- going to remove the constructor while coercing it to a lifted type.
301 -- And newtypes can't be bang'd
303 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs})
304 = kcTyClDeclBody decl $ \ tvs' ->
305 do { ctxt' <- kcHsContext ctxt
306 ; sigs' <- mappM (wrapLocM kc_sig) sigs
307 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs'}) }
309 kc_sig (Sig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
310 ; return (Sig nm op_ty') }
311 kc_sig other_sig = return other_sig
313 kcTyClDecl decl@(ForeignType {})
316 kcTyClDeclBody :: TyClDecl Name
317 -> ([LHsTyVarBndr Name] -> TcM a)
319 -- Extend the env with bindings for the tyvars, taken from
320 -- the kind of the tycon/class. Give it to the thing inside, and
321 -- check the result kind matches
322 kcTyClDeclBody decl thing_inside
323 = tcAddDeclCtxt decl $
324 kcHsTyVars (tyClDeclTyVars decl) $ \ kinded_tvs ->
325 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
326 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
328 ; traceTc (text "kcbody" <+> ppr decl <+> ppr tc_kind <+> ppr (map kindedTyVarKind kinded_tvs) <+> ppr (result_kind decl))
329 ; unifyKind tc_kind (foldr (mkArrowKind . kindedTyVarKind)
332 ; thing_inside kinded_tvs }
334 result_kind (TyData { tcdKindSig = Just kind }) = kind
335 result_kind other = liftedTypeKind
336 -- On GADT-style declarations we allow a kind signature
337 -- data T :: *->* where { ... }
339 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
343 %************************************************************************
345 \subsection{Type checking}
347 %************************************************************************
350 tcSynDecls :: (Name -> ArgVrcs) -> [LTyClDecl Name] -> TcM [TyThing]
351 tcSynDecls calc_vrcs [] = return []
352 tcSynDecls calc_vrcs (decl : decls)
353 = do { syn_tc <- addLocM (tcSynDecl calc_vrcs) decl
354 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls calc_vrcs decls)
355 ; return (syn_tc : syn_tcs) }
358 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
359 = tcTyVarBndrs tvs $ \ tvs' -> do
360 { traceTc (text "tcd1" <+> ppr tc_name)
361 ; rhs_ty' <- tcHsKindedType rhs_ty
362 ; return (ATyCon (buildSynTyCon tc_name tvs' rhs_ty' (calc_vrcs tc_name))) }
365 tcTyClDecl :: (Name -> ArgVrcs) -> (Name -> RecFlag)
366 -> TyClDecl Name -> TcM TyThing
368 tcTyClDecl calc_vrcs calc_isrec decl
369 = tcAddDeclCtxt decl (tcTyClDecl1 calc_vrcs calc_isrec decl)
371 tcTyClDecl1 calc_vrcs calc_isrec
372 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
373 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
374 = tcTyVarBndrs tvs $ \ tvs' -> do
375 { extra_tvs <- tcDataKindSig mb_ksig
376 ; let final_tvs = tvs' ++ extra_tvs
377 ; stupid_theta <- tcHsKindedContext ctxt
378 ; want_generic <- doptM Opt_Generics
379 ; unbox_strict <- doptM Opt_UnboxStrictFields
380 ; gla_exts <- doptM Opt_GlasgowExts
381 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
383 -- Check that we don't use GADT syntax in H98 world
384 ; checkTc (gla_exts || h98_syntax) (badGadtDecl tc_name)
386 -- Check that there's at least one condecl,
387 -- or else we're reading an interface file, or -fglasgow-exts
388 ; checkTc (not (null cons) || gla_exts || is_boot)
389 (emptyConDeclsErr tc_name)
391 ; tycon <- fixM (\ tycon -> do
392 { data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data
396 | null cons && is_boot -- In a hs-boot file, empty cons means
397 = AbstractTyCon -- "don't know"; hence Abstract
399 = case new_or_data of
400 DataType -> mkDataTyConRhs data_cons
401 NewType -> ASSERT( isSingleton data_cons )
402 mkNewTyConRhs tycon (head data_cons)
403 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs arg_vrcs is_rec
404 (want_generic && canDoGenerics data_cons)
406 ; return (ATyCon tycon)
409 arg_vrcs = calc_vrcs tc_name
410 is_rec = calc_isrec tc_name
411 h98_syntax = case cons of -- All constructors have same shape
412 L _ (GadtDecl {}) : _ -> False
415 tcTyClDecl1 calc_vrcs calc_isrec
416 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
417 tcdCtxt = ctxt, tcdMeths = meths,
418 tcdFDs = fundeps, tcdSigs = sigs} )
419 = tcTyVarBndrs tvs $ \ tvs' -> do
420 { ctxt' <- tcHsKindedContext ctxt
421 ; fds' <- mappM (addLocM tc_fundep) fundeps
422 ; sig_stuff <- tcClassSigs class_name sigs meths
423 ; clas <- fixM (\ clas ->
424 let -- This little knot is just so we can get
425 -- hold of the name of the class TyCon, which we
426 -- need to look up its recursiveness and variance
427 tycon_name = tyConName (classTyCon clas)
428 tc_isrec = calc_isrec tycon_name
429 tc_vrcs = calc_vrcs tycon_name
431 buildClass class_name tvs' ctxt' fds'
432 sig_stuff tc_isrec tc_vrcs)
433 ; return (AClass clas) }
435 tc_fundep (tvs1, tvs2) = do { tvs1' <- mappM tcLookupTyVar tvs1 ;
436 ; tvs2' <- mappM tcLookupTyVar tvs2 ;
437 ; return (tvs1', tvs2') }
440 tcTyClDecl1 calc_vrcs calc_isrec
441 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
442 = returnM (ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0 []))
444 -----------------------------------
445 tcConDecl :: Bool -- True <=> -funbox-strict_fields
446 -> NewOrData -> TyCon -> [TyVar]
447 -> ConDecl Name -> TcM DataCon
449 tcConDecl unbox_strict NewType tycon tc_tvs -- Newtypes
450 (ConDecl name ex_tvs ex_ctxt details)
451 = ASSERT( null ex_tvs && null (unLoc ex_ctxt) )
452 do { let tc_datacon field_lbls arg_ty
453 = do { arg_ty' <- tcHsKindedType arg_ty -- No bang on newtype
454 ; buildDataCon (unLoc name) False {- Prefix -}
455 True {- Vanilla -} [NotMarkedStrict]
456 (map unLoc field_lbls)
458 tycon (mkTyVarTys tc_tvs) }
460 PrefixCon [arg_ty] -> tc_datacon [] arg_ty
461 RecCon [(field_lbl, arg_ty)] -> tc_datacon [field_lbl] arg_ty }
463 tcConDecl unbox_strict DataType tycon tc_tvs -- Ordinary data types
464 (ConDecl name ex_tvs ex_ctxt details)
465 = tcTyVarBndrs ex_tvs $ \ ex_tvs' -> do
466 { ex_ctxt' <- tcHsKindedContext ex_ctxt
468 is_vanilla = null ex_tvs && null (unLoc ex_ctxt)
469 -- Vanilla iff no ex_tvs and no context
470 -- Must check the context too because of
471 -- implicit params; e.g.
472 -- data T = (?x::Int) => MkT Int
474 tc_datacon is_infix field_lbls btys
475 = do { let { bangs = map getBangStrictness btys }
476 ; arg_tys <- mappM tcHsBangType btys
477 ; buildDataCon (unLoc name) is_infix is_vanilla
478 (argStrictness unbox_strict tycon bangs arg_tys)
479 (map unLoc field_lbls)
483 tycon (mkTyVarTys tc_tvs) }
485 PrefixCon btys -> tc_datacon False [] btys
486 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
487 RecCon fields -> do { checkTc (null ex_tvs) (exRecConErr name)
488 -- It's ok to have an implicit-parameter context
489 -- for the data constructor, provided it binds
491 ; let { (field_names, btys) = unzip fields }
492 ; tc_datacon False field_names btys } }
494 tcConDecl unbox_strict DataType tycon tc_tvs -- GADTs
495 decl@(GadtDecl name con_ty)
496 = do { traceTc (text "tcConDecl" <+> ppr name)
497 ; (tvs, theta, bangs, arg_tys, data_tc, res_tys) <- tcLHsConSig con_ty
499 ; traceTc (text "tcConDecl1" <+> ppr name)
500 ; let -- Now dis-assemble the type, and check its form
501 is_vanilla = null theta && mkTyVarTys tvs `tcEqTypes` res_tys
503 -- Vanilla datacons guarantee to use the same
504 -- type variables as the parent tycon
505 (tvs', arg_tys', res_tys')
506 | is_vanilla = (tc_tvs, substTys subst arg_tys, substTys subst res_tys)
507 | otherwise = (tvs, arg_tys, res_tys)
508 subst = zipTopTvSubst tvs (mkTyVarTys tc_tvs)
510 ; traceTc (text "tcConDecl3" <+> ppr name)
511 ; buildDataCon (unLoc name) False {- Not infix -} is_vanilla
512 (argStrictness unbox_strict tycon bangs arg_tys)
513 [{- No field labels -}]
514 tvs' theta arg_tys' data_tc res_tys' }
515 -- NB: we put data_tc, the type constructor gotten from the constructor
516 -- type signature into the data constructor; that way checkValidDataCon
517 -- can complain if it's wrong.
520 argStrictness :: Bool -- True <=> -funbox-strict_fields
522 -> [TcType] -> [StrictnessMark]
523 argStrictness unbox_strict tycon bangs arg_tys
524 = ASSERT( length bangs == length arg_tys )
525 zipWith (chooseBoxingStrategy unbox_strict tycon) arg_tys bangs
527 -- We attempt to unbox/unpack a strict field when either:
528 -- (i) The field is marked '!!', or
529 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
531 chooseBoxingStrategy :: Bool -> TyCon -> TcType -> HsBang -> StrictnessMark
532 chooseBoxingStrategy unbox_strict_fields tycon arg_ty bang
534 HsNoBang -> NotMarkedStrict
535 HsStrict | unbox_strict_fields && can_unbox -> MarkedUnboxed
536 HsUnbox | can_unbox -> MarkedUnboxed
537 other -> MarkedStrict
539 can_unbox = case splitTyConApp_maybe arg_ty of
541 Just (arg_tycon, _) -> not (isRecursiveTyCon tycon) &&
542 isProductTyCon arg_tycon
545 %************************************************************************
547 \subsection{Dependency analysis}
549 %************************************************************************
551 Validity checking is done once the mutually-recursive knot has been
552 tied, so we can look at things freely.
555 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
556 checkCycleErrs tyclss
560 = do { mappM_ recClsErr cls_cycles
561 ; failM } -- Give up now, because later checkValidTyCl
562 -- will loop if the synonym is recursive
564 cls_cycles = calcClassCycles tyclss
566 checkValidTyCl :: TyClDecl Name -> TcM ()
567 -- We do the validity check over declarations, rather than TyThings
568 -- only so that we can add a nice context with tcAddDeclCtxt
570 = tcAddDeclCtxt decl $
571 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
572 ; traceTc (text "Validity of" <+> ppr thing)
574 ATyCon tc -> checkValidTyCon tc
575 AClass cl -> checkValidClass cl
576 ; traceTc (text "Done validity of" <+> ppr thing)
579 -------------------------
580 checkValidTyCon :: TyCon -> TcM ()
583 = checkValidType syn_ctxt syn_rhs
585 = -- Check the context on the data decl
586 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
588 -- Check arg types of data constructors
589 mappM_ (checkValidDataCon tc) data_cons `thenM_`
591 -- Check that fields with the same name share a type
592 mappM_ check_fields groups
595 syn_ctxt = TySynCtxt name
597 (_, syn_rhs) = getSynTyConDefn tc
598 data_cons = tyConDataCons tc
600 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
601 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
602 get_fields con = dataConFieldLabels con `zip` dataConOrigArgTys con
603 -- dataConFieldLabels may return the empty list, which is fine
605 check_fields fields@((first_field_label, field_ty) : other_fields)
606 -- These fields all have the same name, but are from
607 -- different constructors in the data type
608 = -- Check that all the fields in the group have the same type
609 -- NB: this check assumes that all the constructors of a given
610 -- data type use the same type variables
611 checkTc (all (tcEqType field_ty . snd) other_fields)
612 (fieldTypeMisMatch first_field_label)
614 -------------------------------
615 checkValidDataCon :: TyCon -> DataCon -> TcM ()
616 checkValidDataCon tc con
617 = addErrCtxt (dataConCtxt con) $
618 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
619 ; checkValidType ctxt (idType (dataConWrapId con)) }
621 -- This checks the argument types and
622 -- ambiguity of the existential context (if any)
624 -- Note [Sept 04] Now that tvs is all the tvs, this
625 -- test doesn't actually check anything
626 -- ; checkFreeness tvs ex_theta }
628 ctxt = ConArgCtxt (dataConName con)
629 -- (tvs, ex_theta, _, _, _) = dataConSig con
632 -------------------------------
633 checkValidClass :: Class -> TcM ()
635 = do { -- CHECK ARITY 1 FOR HASKELL 1.4
636 gla_exts <- doptM Opt_GlasgowExts
638 -- Check that the class is unary, unless GlaExs
639 ; checkTc (notNull tyvars) (nullaryClassErr cls)
640 ; checkTc (gla_exts || unary) (classArityErr cls)
642 -- Check the super-classes
643 ; checkValidTheta (ClassSCCtxt (className cls)) theta
645 -- Check the class operations
646 ; mappM_ check_op op_stuff
648 -- Check that if the class has generic methods, then the
649 -- class has only one parameter. We can't do generic
650 -- multi-parameter type classes!
651 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
654 (tyvars, theta, _, op_stuff) = classBigSig cls
655 unary = isSingleton tyvars
656 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
658 check_op (sel_id, dm)
659 = addErrCtxt (classOpCtxt sel_id tau) $ do
660 { checkValidTheta SigmaCtxt (tail theta)
661 -- The 'tail' removes the initial (C a) from the
662 -- class itself, leaving just the method type
664 ; checkValidType (FunSigCtxt op_name) tau
666 -- Check that the type mentions at least one of
667 -- the class type variables
668 ; checkTc (any (`elemVarSet` tyVarsOfType tau) tyvars)
669 (noClassTyVarErr cls sel_id)
671 -- Check that for a generic method, the type of
672 -- the method is sufficiently simple
673 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
674 (badGenericMethodType op_name op_ty)
677 op_name = idName sel_id
678 op_ty = idType sel_id
679 (_,theta,tau) = tcSplitSigmaTy op_ty
683 ---------------------------------------------------------------------
684 fieldTypeMisMatch field_name
685 = sep [ptext SLIT("Different constructors give different types for field"), quotes (ppr field_name)]
687 dataConCtxt con = sep [ptext SLIT("When checking the data constructor:"),
688 nest 2 (ex_part <+> pprThetaArrow ex_theta <+> ppr con <+> arg_part)]
690 (ex_tvs, ex_theta, arg_tys, _, _) = dataConSig con
691 ex_part | null ex_tvs = empty
692 | otherwise = ptext SLIT("forall") <+> hsep (map ppr ex_tvs) <> dot
693 -- The 'ex_theta' part could be non-empty, if the user (bogusly) wrote
694 -- data T a = Eq a => T a a
695 -- So we make sure to print it
697 fields = dataConFieldLabels con
698 arg_part | null fields = sep (map pprParendType arg_tys)
699 | otherwise = braces (sep (punctuate comma
700 [ ppr n <+> dcolon <+> ppr ty
701 | (n,ty) <- fields `zip` arg_tys]))
703 classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
704 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
707 = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
710 = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
711 parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
713 noClassTyVarErr clas op
714 = sep [ptext SLIT("The class method") <+> quotes (ppr op),
715 ptext SLIT("mentions none of the type variables of the class") <+>
716 ppr clas <+> hsep (map ppr (classTyVars clas))]
718 genericMultiParamErr clas
719 = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
720 ptext SLIT("cannot have generic methods")
722 badGenericMethodType op op_ty
723 = hang (ptext SLIT("Generic method type is too complex"))
724 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
725 ptext SLIT("You can only use type variables, arrows, lists, and tuples")])
728 = setSrcSpan (getLoc (head sorted_decls)) $
729 addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
730 nest 2 (vcat (map ppr_decl sorted_decls))])
732 sorted_decls = sortLocated syn_decls
733 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
736 = setSrcSpan (getLoc (head sorted_decls)) $
737 addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
738 nest 2 (vcat (map ppr_decl sorted_decls))])
740 sorted_decls = sortLocated cls_decls
741 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
743 sortLocated :: [Located a] -> [Located a]
744 sortLocated things = sortLe le things
746 le (L l1 _) (L l2 _) = l1 <= l2
749 = ptext SLIT("Can't combine named fields with locally-quantified type variables or context")
751 (ptext SLIT("In the declaration of data constructor") <+> ppr name)
753 badDataConTyCon data_con
754 = hang (ptext SLIT("Data constructor") <+> quotes (ppr data_con) <+>
755 ptext SLIT("returns type") <+> quotes (ppr (dataConTyCon data_con)))
756 2 (ptext SLIT("instead of its parent type"))
759 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
760 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow GADTs")) ]
762 emptyConDeclsErr tycon
763 = sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
764 nest 4 (ptext SLIT("(-fglasgow-exts permits this)"))]