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 ( 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 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 ; traceTc (text "kc_con_decl" <+> ppr name <+> ppr ty')
284 ; return (GadtDecl name ty') }
286 kc_con_details (PrefixCon btys)
287 = do { btys' <- mappM kc_larg_ty btys ; return (PrefixCon btys') }
288 kc_con_details (InfixCon bty1 bty2)
289 = do { bty1' <- kc_larg_ty bty1; bty2' <- kc_larg_ty bty2; return (InfixCon bty1' bty2') }
290 kc_con_details (RecCon fields)
291 = do { fields' <- mappM kc_field fields; return (RecCon fields') }
293 kc_field (fld, bty) = do { bty' <- kc_larg_ty bty ; return (fld, bty') }
295 kc_larg_ty bty = case new_or_data of
296 DataType -> kcHsSigType bty
297 NewType -> kcHsLiftedSigType bty
298 -- Can't allow an unlifted type for newtypes, because we're effectively
299 -- going to remove the constructor while coercing it to a lifted type.
300 -- And newtypes can't be bang'd
302 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs})
303 = kcTyClDeclBody decl $ \ tvs' ->
304 do { ctxt' <- kcHsContext ctxt
305 ; sigs' <- mappM (wrapLocM kc_sig) sigs
306 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs'}) }
308 kc_sig (Sig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
309 ; return (Sig nm op_ty') }
310 kc_sig other_sig = return other_sig
312 kcTyClDecl decl@(ForeignType {})
315 kcTyClDeclBody :: TyClDecl Name
316 -> ([LHsTyVarBndr Name] -> TcM a)
318 -- Extend the env with bindings for the tyvars, taken from
319 -- the kind of the tycon/class. Give it to the thing inside, and
320 -- check the result kind matches
321 kcTyClDeclBody decl thing_inside
322 = tcAddDeclCtxt decl $
323 kcHsTyVars (tyClDeclTyVars decl) $ \ kinded_tvs ->
324 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
325 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
327 ; traceTc (text "kcbody" <+> ppr decl <+> ppr tc_kind <+> ppr (map kindedTyVarKind kinded_tvs) <+> ppr (result_kind decl))
328 ; unifyKind tc_kind (foldr (mkArrowKind . kindedTyVarKind)
331 ; thing_inside kinded_tvs }
333 result_kind (TyData { tcdKindSig = Just kind }) = kind
334 result_kind other = liftedTypeKind
335 -- On GADT-style declarations we allow a kind signature
336 -- data T :: *->* where { ... }
338 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
342 %************************************************************************
344 \subsection{Type checking}
346 %************************************************************************
349 tcSynDecls :: (Name -> ArgVrcs) -> [LTyClDecl Name] -> TcM [TyThing]
350 tcSynDecls calc_vrcs [] = return []
351 tcSynDecls calc_vrcs (decl : decls)
352 = do { syn_tc <- addLocM (tcSynDecl calc_vrcs) decl
353 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls calc_vrcs decls)
354 ; return (syn_tc : syn_tcs) }
357 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
358 = tcTyVarBndrs tvs $ \ tvs' -> do
359 { traceTc (text "tcd1" <+> ppr tc_name)
360 ; rhs_ty' <- tcHsKindedType rhs_ty
361 ; return (ATyCon (buildSynTyCon tc_name tvs' rhs_ty' (calc_vrcs tc_name))) }
364 tcTyClDecl :: (Name -> ArgVrcs) -> (Name -> RecFlag)
365 -> TyClDecl Name -> TcM TyThing
367 tcTyClDecl calc_vrcs calc_isrec decl
368 = tcAddDeclCtxt decl (tcTyClDecl1 calc_vrcs calc_isrec decl)
370 tcTyClDecl1 calc_vrcs calc_isrec
371 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
372 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
373 = tcTyVarBndrs tvs $ \ tvs' -> do
374 { extra_tvs <- tcDataKindSig mb_ksig
375 ; let final_tvs = tvs' ++ extra_tvs
376 ; stupid_theta <- tcStupidTheta ctxt cons
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 stupid_theta data_cons
401 NewType -> ASSERT( isSingleton data_cons )
402 mkNewTyConRhs tycon (head data_cons)
403 ; buildAlgTyCon tc_name final_tvs 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 tcStupidTheta :: LHsContext Name -> [LConDecl Name] -> TcM (Maybe ThetaType)
521 -- For GADTs we don't allow a context on the data declaration
522 -- whereas for standard Haskell style data declarations, we do
523 tcStupidTheta ctxt (L _ (ConDecl _ _ _ _) : _)
524 = do { theta <- tcHsKindedContext ctxt; return (Just theta) }
525 tcStupidTheta ctxt other -- Includes an empty constructor list
526 = ASSERT( null (unLoc ctxt) ) return Nothing
529 argStrictness :: Bool -- True <=> -funbox-strict_fields
531 -> [TcType] -> [StrictnessMark]
532 argStrictness unbox_strict tycon bangs arg_tys
533 = ASSERT( length bangs == length arg_tys )
534 zipWith (chooseBoxingStrategy unbox_strict tycon) arg_tys bangs
536 -- We attempt to unbox/unpack a strict field when either:
537 -- (i) The field is marked '!!', or
538 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
540 chooseBoxingStrategy :: Bool -> TyCon -> TcType -> HsBang -> StrictnessMark
541 chooseBoxingStrategy unbox_strict_fields tycon arg_ty bang
543 HsNoBang -> NotMarkedStrict
544 HsStrict | unbox_strict_fields && can_unbox -> MarkedUnboxed
545 HsUnbox | can_unbox -> MarkedUnboxed
546 other -> MarkedStrict
548 can_unbox = case splitTyConApp_maybe arg_ty of
550 Just (arg_tycon, _) -> not (isRecursiveTyCon tycon) &&
551 isProductTyCon arg_tycon
554 %************************************************************************
556 \subsection{Dependency analysis}
558 %************************************************************************
560 Validity checking is done once the mutually-recursive knot has been
561 tied, so we can look at things freely.
564 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
565 checkCycleErrs tyclss
569 = do { mappM_ recClsErr cls_cycles
570 ; failM } -- Give up now, because later checkValidTyCl
571 -- will loop if the synonym is recursive
573 cls_cycles = calcClassCycles tyclss
575 checkValidTyCl :: TyClDecl Name -> TcM ()
576 -- We do the validity check over declarations, rather than TyThings
577 -- only so that we can add a nice context with tcAddDeclCtxt
579 = tcAddDeclCtxt decl $
580 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
581 ; traceTc (text "Validity of" <+> ppr thing)
583 ATyCon tc -> checkValidTyCon tc
584 AClass cl -> checkValidClass cl
585 ; traceTc (text "Done validity of" <+> ppr thing)
588 -------------------------
589 checkValidTyCon :: TyCon -> TcM ()
592 = checkValidType syn_ctxt syn_rhs
594 = -- Check the context on the data decl
595 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
597 -- Check arg types of data constructors
598 mappM_ (checkValidDataCon tc) data_cons `thenM_`
600 -- Check that fields with the same name share a type
601 mappM_ check_fields groups
604 syn_ctxt = TySynCtxt name
606 (_, syn_rhs) = getSynTyConDefn tc
607 data_cons = tyConDataCons tc
609 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
610 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
611 get_fields con = dataConFieldLabels con `zip` dataConOrigArgTys con
612 -- dataConFieldLabels may return the empty list, which is fine
614 check_fields fields@((first_field_label, field_ty) : other_fields)
615 -- These fields all have the same name, but are from
616 -- different constructors in the data type
617 = -- Check that all the fields in the group have the same type
618 -- NB: this check assumes that all the constructors of a given
619 -- data type use the same type variables
620 checkTc (all (tcEqType field_ty . snd) other_fields)
621 (fieldTypeMisMatch first_field_label)
623 -------------------------------
624 checkValidDataCon :: TyCon -> DataCon -> TcM ()
625 checkValidDataCon tc con
626 = addErrCtxt (dataConCtxt con) $
627 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
628 ; checkValidType ctxt (idType (dataConWrapId con)) }
630 -- This checks the argument types and
631 -- ambiguity of the existential context (if any)
633 -- Note [Sept 04] Now that tvs is all the tvs, this
634 -- test doesn't actually check anything
635 -- ; checkFreeness tvs ex_theta }
637 ctxt = ConArgCtxt (dataConName con)
638 -- (tvs, ex_theta, _, _, _) = dataConSig con
641 -------------------------------
642 checkValidClass :: Class -> TcM ()
644 = do { -- CHECK ARITY 1 FOR HASKELL 1.4
645 gla_exts <- doptM Opt_GlasgowExts
647 -- Check that the class is unary, unless GlaExs
648 ; checkTc (notNull tyvars) (nullaryClassErr cls)
649 ; checkTc (gla_exts || unary) (classArityErr cls)
651 -- Check the super-classes
652 ; checkValidTheta (ClassSCCtxt (className cls)) theta
654 -- Check the class operations
655 ; mappM_ check_op op_stuff
657 -- Check that if the class has generic methods, then the
658 -- class has only one parameter. We can't do generic
659 -- multi-parameter type classes!
660 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
663 (tyvars, theta, _, op_stuff) = classBigSig cls
664 unary = isSingleton tyvars
665 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
667 check_op (sel_id, dm)
668 = addErrCtxt (classOpCtxt sel_id tau) $ do
669 { checkValidTheta SigmaCtxt (tail theta)
670 -- The 'tail' removes the initial (C a) from the
671 -- class itself, leaving just the method type
673 ; checkValidType (FunSigCtxt op_name) tau
675 -- Check that the type mentions at least one of
676 -- the class type variables
677 ; checkTc (any (`elemVarSet` tyVarsOfType tau) tyvars)
678 (noClassTyVarErr cls sel_id)
680 -- Check that for a generic method, the type of
681 -- the method is sufficiently simple
682 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
683 (badGenericMethodType op_name op_ty)
686 op_name = idName sel_id
687 op_ty = idType sel_id
688 (_,theta,tau) = tcSplitSigmaTy op_ty
692 ---------------------------------------------------------------------
693 fieldTypeMisMatch field_name
694 = sep [ptext SLIT("Different constructors give different types for field"), quotes (ppr field_name)]
696 dataConCtxt con = sep [ptext SLIT("When checking the data constructor:"),
697 nest 2 (ex_part <+> pprThetaArrow ex_theta <+> ppr con <+> arg_part)]
699 (ex_tvs, ex_theta, arg_tys, _, _) = dataConSig con
700 ex_part | null ex_tvs = empty
701 | otherwise = ptext SLIT("forall") <+> hsep (map ppr ex_tvs) <> dot
702 -- The 'ex_theta' part could be non-empty, if the user (bogusly) wrote
703 -- data T a = Eq a => T a a
704 -- So we make sure to print it
706 fields = dataConFieldLabels con
707 arg_part | null fields = sep (map pprParendType arg_tys)
708 | otherwise = braces (sep (punctuate comma
709 [ ppr n <+> dcolon <+> ppr ty
710 | (n,ty) <- fields `zip` arg_tys]))
712 classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
713 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
716 = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
719 = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
720 parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
722 noClassTyVarErr clas op
723 = sep [ptext SLIT("The class method") <+> quotes (ppr op),
724 ptext SLIT("mentions none of the type variables of the class") <+>
725 ppr clas <+> hsep (map ppr (classTyVars clas))]
727 genericMultiParamErr clas
728 = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
729 ptext SLIT("cannot have generic methods")
731 badGenericMethodType op op_ty
732 = hang (ptext SLIT("Generic method type is too complex"))
733 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
734 ptext SLIT("You can only use type variables, arrows, lists, and tuples")])
737 = setSrcSpan (getLoc (head sorted_decls)) $
738 addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
739 nest 2 (vcat (map ppr_decl sorted_decls))])
741 sorted_decls = sortLocated syn_decls
742 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
745 = setSrcSpan (getLoc (head sorted_decls)) $
746 addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
747 nest 2 (vcat (map ppr_decl sorted_decls))])
749 sorted_decls = sortLocated cls_decls
750 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
752 sortLocated :: [Located a] -> [Located a]
753 sortLocated things = sortLe le things
755 le (L l1 _) (L l2 _) = l1 <= l2
758 = ptext SLIT("Can't combine named fields with locally-quantified type variables or context")
760 (ptext SLIT("In the declaration of data constructor") <+> ppr name)
762 badDataConTyCon data_con
763 = hang (ptext SLIT("Data constructor") <+> quotes (ppr data_con) <+>
764 ptext SLIT("returns type") <+> quotes (ppr (dataConTyCon data_con)))
765 2 (ptext SLIT("instead of its parent type"))
768 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
769 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow GADTs")) ]
771 emptyConDeclsErr tycon
772 = sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
773 nest 4 (ptext SLIT("(-fglasgow-exts permits this)"))]