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, 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, 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, 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 <- tcStupidTheta ctxt cons
379 ; want_generic <- doptM Opt_Generics
380 ; unbox_strict <- doptM Opt_UnboxStrictFields
381 ; gla_exts <- doptM Opt_GlasgowExts
382 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
384 -- Check that we don't use GADT syntax in H98 world
385 ; checkTc (gla_exts || h98_syntax) (badGadtDecl tc_name)
387 -- Check that there's at least one condecl,
388 -- or else we're reading an interface file, or -fglasgow-exts
389 ; checkTc (not (null cons) || gla_exts || is_boot)
390 (emptyConDeclsErr tc_name)
392 ; tycon <- fixM (\ tycon -> do
393 { data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data
397 | null cons && is_boot -- In a hs-boot file, empty cons means
398 = AbstractTyCon -- "don't know"; hence Abstract
400 = case new_or_data of
401 DataType -> mkDataTyConRhs stupid_theta data_cons
402 NewType -> ASSERT( isSingleton data_cons )
403 mkNewTyConRhs tycon (head data_cons)
404 ; buildAlgTyCon tc_name final_tvs tc_rhs arg_vrcs is_rec
405 (want_generic && canDoGenerics data_cons)
407 ; return (ATyCon tycon)
410 arg_vrcs = calc_vrcs tc_name
411 is_rec = calc_isrec tc_name
412 h98_syntax = case cons of -- All constructors have same shape
413 L _ (GadtDecl {}) : _ -> False
416 tcTyClDecl1 calc_vrcs calc_isrec
417 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
418 tcdCtxt = ctxt, tcdMeths = meths,
419 tcdFDs = fundeps, tcdSigs = sigs} )
420 = tcTyVarBndrs tvs $ \ tvs' -> do
421 { ctxt' <- tcHsKindedContext ctxt
422 ; fds' <- mappM (addLocM tc_fundep) fundeps
423 ; sig_stuff <- tcClassSigs class_name sigs meths
424 ; clas <- fixM (\ clas ->
425 let -- This little knot is just so we can get
426 -- hold of the name of the class TyCon, which we
427 -- need to look up its recursiveness and variance
428 tycon_name = tyConName (classTyCon clas)
429 tc_isrec = calc_isrec tycon_name
430 tc_vrcs = calc_vrcs tycon_name
432 buildClass class_name tvs' ctxt' fds'
433 sig_stuff tc_isrec tc_vrcs)
434 ; return (AClass clas) }
436 tc_fundep (tvs1, tvs2) = do { tvs1' <- mappM tcLookupTyVar tvs1 ;
437 ; tvs2' <- mappM tcLookupTyVar tvs2 ;
438 ; return (tvs1', tvs2') }
441 tcTyClDecl1 calc_vrcs calc_isrec
442 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
443 = returnM (ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0 []))
445 -----------------------------------
446 tcConDecl :: Bool -- True <=> -funbox-strict_fields
447 -> NewOrData -> TyCon -> [TyVar]
448 -> ConDecl Name -> TcM DataCon
450 tcConDecl unbox_strict NewType tycon tc_tvs -- Newtypes
451 (ConDecl name ex_tvs ex_ctxt details)
452 = ASSERT( null ex_tvs && null (unLoc ex_ctxt) )
453 do { let tc_datacon field_lbls arg_ty
454 = do { arg_ty' <- tcHsKindedType arg_ty -- No bang on newtype
455 ; buildDataCon (unLoc name) False {- Prefix -}
456 True {- Vanilla -} [NotMarkedStrict]
457 (map unLoc field_lbls)
459 tycon (mkTyVarTys tc_tvs) }
461 PrefixCon [arg_ty] -> tc_datacon [] arg_ty
462 RecCon [(field_lbl, arg_ty)] -> tc_datacon [field_lbl] arg_ty }
464 tcConDecl unbox_strict DataType tycon tc_tvs -- Ordinary data types
465 (ConDecl name ex_tvs ex_ctxt details)
466 = tcTyVarBndrs ex_tvs $ \ ex_tvs' -> do
467 { ex_ctxt' <- tcHsKindedContext ex_ctxt
469 is_vanilla = null ex_tvs && null (unLoc ex_ctxt)
470 -- Vanilla iff no ex_tvs and no context
471 -- Must check the context too because of
472 -- implicit params; e.g.
473 -- data T = (?x::Int) => MkT Int
475 tc_datacon is_infix field_lbls btys
476 = do { let { bangs = map getBangStrictness btys }
477 ; arg_tys <- mappM tcHsBangType btys
478 ; buildDataCon (unLoc name) is_infix is_vanilla
479 (argStrictness unbox_strict tycon bangs arg_tys)
480 (map unLoc field_lbls)
484 tycon (mkTyVarTys tc_tvs) }
486 PrefixCon btys -> tc_datacon False [] btys
487 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
488 RecCon fields -> do { checkTc (null ex_tvs) (exRecConErr name)
489 -- It's ok to have an implicit-parameter context
490 -- for the data constructor, provided it binds
492 ; let { (field_names, btys) = unzip fields }
493 ; tc_datacon False field_names btys } }
495 tcConDecl unbox_strict DataType tycon tc_tvs -- GADTs
496 decl@(GadtDecl name con_ty)
497 = do { traceTc (text "tcConDecl" <+> ppr name)
498 ; (tvs, theta, bangs, arg_tys, data_tc, res_tys) <- tcLHsConSig con_ty
500 ; traceTc (text "tcConDecl1" <+> ppr name)
501 ; let -- Now dis-assemble the type, and check its form
502 is_vanilla = null theta && mkTyVarTys tvs `tcEqTypes` res_tys
504 -- Vanilla datacons guarantee to use the same
505 -- type variables as the parent tycon
506 (tvs', arg_tys', res_tys')
507 | is_vanilla = (tc_tvs, substTys subst arg_tys, substTys subst res_tys)
508 | otherwise = (tvs, arg_tys, res_tys)
509 subst = zipTopTvSubst tvs (mkTyVarTys tc_tvs)
511 ; traceTc (text "tcConDecl3" <+> ppr name)
512 ; buildDataCon (unLoc name) False {- Not infix -} is_vanilla
513 (argStrictness unbox_strict tycon bangs arg_tys)
514 [{- No field labels -}]
515 tvs' theta arg_tys' data_tc res_tys' }
516 -- NB: we put data_tc, the type constructor gotten from the constructor
517 -- type signature into the data constructor; that way checkValidDataCon
518 -- can complain if it's wrong.
521 tcStupidTheta :: LHsContext Name -> [LConDecl Name] -> TcM (Maybe ThetaType)
522 -- For GADTs we don't allow a context on the data declaration
523 -- whereas for standard Haskell style data declarations, we do
524 tcStupidTheta ctxt (L _ (ConDecl _ _ _ _) : _)
525 = do { theta <- tcHsKindedContext ctxt; return (Just theta) }
526 tcStupidTheta ctxt other -- Includes an empty constructor list
527 = ASSERT( null (unLoc ctxt) ) return Nothing
530 argStrictness :: Bool -- True <=> -funbox-strict_fields
532 -> [TcType] -> [StrictnessMark]
533 argStrictness unbox_strict tycon bangs arg_tys
534 = ASSERT( length bangs == length arg_tys )
535 zipWith (chooseBoxingStrategy unbox_strict tycon) arg_tys bangs
537 -- We attempt to unbox/unpack a strict field when either:
538 -- (i) The field is marked '!!', or
539 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
541 chooseBoxingStrategy :: Bool -> TyCon -> TcType -> HsBang -> StrictnessMark
542 chooseBoxingStrategy unbox_strict_fields tycon arg_ty bang
544 HsNoBang -> NotMarkedStrict
545 HsStrict | unbox_strict_fields && can_unbox -> MarkedUnboxed
546 HsUnbox | can_unbox -> MarkedUnboxed
547 other -> MarkedStrict
549 can_unbox = case splitTyConApp_maybe arg_ty of
551 Just (arg_tycon, _) -> not (isRecursiveTyCon tycon) &&
552 isProductTyCon arg_tycon
555 %************************************************************************
557 \subsection{Dependency analysis}
559 %************************************************************************
561 Validity checking is done once the mutually-recursive knot has been
562 tied, so we can look at things freely.
565 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
566 checkCycleErrs tyclss
570 = do { mappM_ recClsErr cls_cycles
571 ; failM } -- Give up now, because later checkValidTyCl
572 -- will loop if the synonym is recursive
574 cls_cycles = calcClassCycles tyclss
576 checkValidTyCl :: TyClDecl Name -> TcM ()
577 -- We do the validity check over declarations, rather than TyThings
578 -- only so that we can add a nice context with tcAddDeclCtxt
580 = tcAddDeclCtxt decl $
581 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
582 ; traceTc (text "Validity of" <+> ppr thing)
584 ATyCon tc -> checkValidTyCon tc
585 AClass cl -> checkValidClass cl
586 ; traceTc (text "Done validity of" <+> ppr thing)
589 -------------------------
590 checkValidTyCon :: TyCon -> TcM ()
593 = checkValidType syn_ctxt syn_rhs
595 = -- Check the context on the data decl
596 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
598 -- Check arg types of data constructors
599 mappM_ (checkValidDataCon tc) data_cons `thenM_`
601 -- Check that fields with the same name share a type
602 mappM_ check_fields groups
605 syn_ctxt = TySynCtxt name
607 (_, syn_rhs) = getSynTyConDefn tc
608 data_cons = tyConDataCons tc
610 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
611 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
612 get_fields con = dataConFieldLabels con `zip` dataConOrigArgTys con
613 -- dataConFieldLabels may return the empty list, which is fine
615 check_fields fields@((first_field_label, field_ty) : other_fields)
616 -- These fields all have the same name, but are from
617 -- different constructors in the data type
618 = -- Check that all the fields in the group have the same type
619 -- NB: this check assumes that all the constructors of a given
620 -- data type use the same type variables
621 checkTc (all (tcEqType field_ty . snd) other_fields)
622 (fieldTypeMisMatch first_field_label)
624 -------------------------------
625 checkValidDataCon :: TyCon -> DataCon -> TcM ()
626 checkValidDataCon tc con
627 = addErrCtxt (dataConCtxt con) $
628 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
629 ; checkValidType ctxt (idType (dataConWrapId con)) }
631 -- This checks the argument types and
632 -- ambiguity of the existential context (if any)
634 -- Note [Sept 04] Now that tvs is all the tvs, this
635 -- test doesn't actually check anything
636 -- ; checkFreeness tvs ex_theta }
638 ctxt = ConArgCtxt (dataConName con)
639 -- (tvs, ex_theta, _, _, _) = dataConSig con
642 -------------------------------
643 checkValidClass :: Class -> TcM ()
645 = do { -- CHECK ARITY 1 FOR HASKELL 1.4
646 gla_exts <- doptM Opt_GlasgowExts
648 -- Check that the class is unary, unless GlaExs
649 ; checkTc (notNull tyvars) (nullaryClassErr cls)
650 ; checkTc (gla_exts || unary) (classArityErr cls)
652 -- Check the super-classes
653 ; checkValidTheta (ClassSCCtxt (className cls)) theta
655 -- Check the class operations
656 ; mappM_ check_op op_stuff
658 -- Check that if the class has generic methods, then the
659 -- class has only one parameter. We can't do generic
660 -- multi-parameter type classes!
661 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
664 (tyvars, theta, _, op_stuff) = classBigSig cls
665 unary = isSingleton tyvars
666 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
668 check_op (sel_id, dm)
669 = addErrCtxt (classOpCtxt sel_id tau) $ do
670 { checkValidTheta SigmaCtxt (tail theta)
671 -- The 'tail' removes the initial (C a) from the
672 -- class itself, leaving just the method type
674 ; checkValidType (FunSigCtxt op_name) tau
676 -- Check that the type mentions at least one of
677 -- the class type variables
678 ; checkTc (any (`elemVarSet` tyVarsOfType tau) tyvars)
679 (noClassTyVarErr cls sel_id)
681 -- Check that for a generic method, the type of
682 -- the method is sufficiently simple
683 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
684 (badGenericMethodType op_name op_ty)
687 op_name = idName sel_id
688 op_ty = idType sel_id
689 (_,theta,tau) = tcSplitSigmaTy op_ty
693 ---------------------------------------------------------------------
694 fieldTypeMisMatch field_name
695 = sep [ptext SLIT("Different constructors give different types for field"), quotes (ppr field_name)]
697 dataConCtxt con = sep [ptext SLIT("When checking the data constructor:"),
698 nest 2 (ex_part <+> pprThetaArrow ex_theta <+> ppr con <+> arg_part)]
700 (ex_tvs, ex_theta, arg_tys, _, _) = dataConSig con
701 ex_part | null ex_tvs = empty
702 | otherwise = ptext SLIT("forall") <+> hsep (map ppr ex_tvs) <> dot
703 -- The 'ex_theta' part could be non-empty, if the user (bogusly) wrote
704 -- data T a = Eq a => T a a
705 -- So we make sure to print it
707 fields = dataConFieldLabels con
708 arg_part | null fields = sep (map pprParendType arg_tys)
709 | otherwise = braces (sep (punctuate comma
710 [ ppr n <+> dcolon <+> ppr ty
711 | (n,ty) <- fields `zip` arg_tys]))
713 classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
714 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
717 = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
720 = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
721 parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
723 noClassTyVarErr clas op
724 = sep [ptext SLIT("The class method") <+> quotes (ppr op),
725 ptext SLIT("mentions none of the type variables of the class") <+>
726 ppr clas <+> hsep (map ppr (classTyVars clas))]
728 genericMultiParamErr clas
729 = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
730 ptext SLIT("cannot have generic methods")
732 badGenericMethodType op op_ty
733 = hang (ptext SLIT("Generic method type is too complex"))
734 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
735 ptext SLIT("You can only use type variables, arrows, lists, and tuples")])
738 = setSrcSpan (getLoc (head sorted_decls)) $
739 addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
740 nest 2 (vcat (map ppr_decl sorted_decls))])
742 sorted_decls = sortLocated syn_decls
743 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
746 = setSrcSpan (getLoc (head sorted_decls)) $
747 addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
748 nest 2 (vcat (map ppr_decl sorted_decls))])
750 sorted_decls = sortLocated cls_decls
751 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
753 sortLocated :: [Located a] -> [Located a]
754 sortLocated things = sortLe le things
756 le (L l1 _) (L l2 _) = l1 <= l2
759 = ptext SLIT("Can't combine named fields with locally-quantified type variables or context")
761 (ptext SLIT("In the declaration of data constructor") <+> ppr name)
763 badDataConTyCon data_con
764 = hang (ptext SLIT("Data constructor") <+> quotes (ppr data_con) <+>
765 ptext SLIT("returns type") <+> quotes (ppr (dataConTyCon data_con)))
766 2 (ptext SLIT("instead of its parent type"))
769 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
770 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow GADTs")) ]
772 emptyConDeclsErr tycon
773 = sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
774 nest 4 (ptext SLIT("(-fglasgow-exts permits this)"))]