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, hsTyVarName, 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, tcExtendKindEnvTvs,
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 TcType ( TcKind, TcType, tyVarsOfType,
36 mkArrowKind, liftedTypeKind, mkTyVarTys, tcEqTypes,
37 tcSplitSigmaTy, tcEqType )
38 import Type ( splitTyConApp_maybe, pprThetaArrow, pprParendType )
39 import Kind ( mkArrowKinds, splitKindFunTys )
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)
232 -- Only for data type and class declarations
233 -- Get as much info as possible from the data or class decl,
234 -- so as to maximise usefulness of error messages
235 getInitialKind (L _ decl)
236 = do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl)
237 ; res_kind <- mk_res_kind decl
238 ; return (tcdName decl, mkArrowKinds arg_kinds res_kind) }
240 mk_arg_kind (UserTyVar _) = newKindVar
241 mk_arg_kind (KindedTyVar _ kind) = return kind
243 mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
244 -- On GADT-style declarations we allow a kind signature
245 -- data T :: *->* where { ... }
246 mk_res_kind other = return liftedTypeKind
250 kcSynDecls :: [SCC (LTyClDecl Name)]
251 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
252 [(Name,TcKind)]) -- Kind bindings
255 kcSynDecls (group : groups)
256 = do { (decl, nk) <- kcSynDecl group
257 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
258 ; return (decl:decls, nk:nks) }
261 kcSynDecl :: SCC (LTyClDecl Name)
262 -> TcM (LTyClDecl Name, -- Kind-annotated decls
263 (Name,TcKind)) -- Kind bindings
264 kcSynDecl (AcyclicSCC ldecl@(L loc decl))
265 = tcAddDeclCtxt decl $
266 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
267 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
268 <+> brackets (ppr k_tvs))
269 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
270 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
271 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
272 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
273 (unLoc (tcdLName decl), tc_kind)) })
275 kcSynDecl (CyclicSCC decls)
276 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
277 -- of out-of-scope tycons
279 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
281 ------------------------------------------------------------------------
282 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
283 -- Not used for type synonyms (see kcSynDecl)
285 kcTyClDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
286 = kcTyClDeclBody decl $ \ tvs' ->
287 do { ctxt' <- kcHsContext ctxt
288 ; cons' <- mappM (wrapLocM kc_con_decl) cons
289 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdCons = cons'}) }
291 kc_con_decl (ConDecl name ex_tvs ex_ctxt details)
292 = kcHsTyVars ex_tvs $ \ ex_tvs' ->
293 do { ex_ctxt' <- kcHsContext ex_ctxt
294 ; details' <- kc_con_details details
295 ; return (ConDecl name ex_tvs' ex_ctxt' details')}
296 kc_con_decl (GadtDecl name ty)
297 = do { ty' <- kcHsSigType ty
298 ; traceTc (text "kc_con_decl" <+> ppr name <+> ppr ty')
299 ; return (GadtDecl name ty') }
301 kc_con_details (PrefixCon btys)
302 = do { btys' <- mappM kc_larg_ty btys ; return (PrefixCon btys') }
303 kc_con_details (InfixCon bty1 bty2)
304 = do { bty1' <- kc_larg_ty bty1; bty2' <- kc_larg_ty bty2; return (InfixCon bty1' bty2') }
305 kc_con_details (RecCon fields)
306 = do { fields' <- mappM kc_field fields; return (RecCon fields') }
308 kc_field (fld, bty) = do { bty' <- kc_larg_ty bty ; return (fld, bty') }
310 kc_larg_ty bty = case new_or_data of
311 DataType -> kcHsSigType bty
312 NewType -> kcHsLiftedSigType bty
313 -- Can't allow an unlifted type for newtypes, because we're effectively
314 -- going to remove the constructor while coercing it to a lifted type.
315 -- And newtypes can't be bang'd
317 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs})
318 = kcTyClDeclBody decl $ \ tvs' ->
319 do { ctxt' <- kcHsContext ctxt
320 ; sigs' <- mappM (wrapLocM kc_sig) sigs
321 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs'}) }
323 kc_sig (Sig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
324 ; return (Sig nm op_ty') }
325 kc_sig other_sig = return other_sig
327 kcTyClDecl decl@(ForeignType {})
330 kcTyClDeclBody :: TyClDecl Name
331 -> ([LHsTyVarBndr Name] -> TcM a)
333 -- getInitialKind has made a suitably-shaped kind for the type or class
334 -- Unpack it, and attribute those kinds to the type variables
335 -- Extend the env with bindings for the tyvars, taken from
336 -- the kind of the tycon/class. Give it to the thing inside, and
337 -- check the result kind matches
338 kcTyClDeclBody decl thing_inside
339 = tcAddDeclCtxt decl $
340 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
341 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
342 (kinds, _) = splitKindFunTys tc_kind
343 hs_tvs = tcdTyVars decl
344 kinded_tvs = ASSERT( length kinds >= length hs_tvs )
345 [ L loc (KindedTyVar (hsTyVarName tv) k)
346 | (L loc tv, k) <- zip hs_tvs kinds]
347 ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
351 %************************************************************************
353 \subsection{Type checking}
355 %************************************************************************
358 tcSynDecls :: (Name -> ArgVrcs) -> [LTyClDecl Name] -> TcM [TyThing]
359 tcSynDecls calc_vrcs [] = return []
360 tcSynDecls calc_vrcs (decl : decls)
361 = do { syn_tc <- addLocM (tcSynDecl calc_vrcs) decl
362 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls calc_vrcs decls)
363 ; return (syn_tc : syn_tcs) }
366 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
367 = tcTyVarBndrs tvs $ \ tvs' -> do
368 { traceTc (text "tcd1" <+> ppr tc_name)
369 ; rhs_ty' <- tcHsKindedType rhs_ty
370 ; return (ATyCon (buildSynTyCon tc_name tvs' rhs_ty' (calc_vrcs tc_name))) }
373 tcTyClDecl :: (Name -> ArgVrcs) -> (Name -> RecFlag)
374 -> TyClDecl Name -> TcM TyThing
376 tcTyClDecl calc_vrcs calc_isrec decl
377 = tcAddDeclCtxt decl (tcTyClDecl1 calc_vrcs calc_isrec decl)
379 tcTyClDecl1 calc_vrcs calc_isrec
380 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
381 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
382 = tcTyVarBndrs tvs $ \ tvs' -> do
383 { extra_tvs <- tcDataKindSig mb_ksig
384 ; let final_tvs = tvs' ++ extra_tvs
385 ; stupid_theta <- tcHsKindedContext ctxt
386 ; want_generic <- doptM Opt_Generics
387 ; unbox_strict <- doptM Opt_UnboxStrictFields
388 ; gla_exts <- doptM Opt_GlasgowExts
389 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
391 -- Check that we don't use GADT syntax in H98 world
392 ; checkTc (gla_exts || h98_syntax) (badGadtDecl tc_name)
394 -- Check that there's at least one condecl,
395 -- or else we're reading an interface file, or -fglasgow-exts
396 ; checkTc (not (null cons) || gla_exts || is_boot)
397 (emptyConDeclsErr tc_name)
399 ; tycon <- fixM (\ tycon -> do
400 { data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data
404 | null cons && is_boot -- In a hs-boot file, empty cons means
405 = AbstractTyCon -- "don't know"; hence Abstract
407 = case new_or_data of
408 DataType -> mkDataTyConRhs data_cons
409 NewType -> ASSERT( isSingleton data_cons )
410 mkNewTyConRhs tycon (head data_cons)
411 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs arg_vrcs is_rec
412 (want_generic && canDoGenerics data_cons)
414 ; return (ATyCon tycon)
417 arg_vrcs = calc_vrcs tc_name
418 is_rec = calc_isrec tc_name
419 h98_syntax = case cons of -- All constructors have same shape
420 L _ (GadtDecl {}) : _ -> False
423 tcTyClDecl1 calc_vrcs calc_isrec
424 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
425 tcdCtxt = ctxt, tcdMeths = meths,
426 tcdFDs = fundeps, tcdSigs = sigs} )
427 = tcTyVarBndrs tvs $ \ tvs' -> do
428 { ctxt' <- tcHsKindedContext ctxt
429 ; fds' <- mappM (addLocM tc_fundep) fundeps
430 ; sig_stuff <- tcClassSigs class_name sigs meths
431 ; clas <- fixM (\ clas ->
432 let -- This little knot is just so we can get
433 -- hold of the name of the class TyCon, which we
434 -- need to look up its recursiveness and variance
435 tycon_name = tyConName (classTyCon clas)
436 tc_isrec = calc_isrec tycon_name
437 tc_vrcs = calc_vrcs tycon_name
439 buildClass class_name tvs' ctxt' fds'
440 sig_stuff tc_isrec tc_vrcs)
441 ; return (AClass clas) }
443 tc_fundep (tvs1, tvs2) = do { tvs1' <- mappM tcLookupTyVar tvs1 ;
444 ; tvs2' <- mappM tcLookupTyVar tvs2 ;
445 ; return (tvs1', tvs2') }
448 tcTyClDecl1 calc_vrcs calc_isrec
449 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
450 = returnM (ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0 []))
452 -----------------------------------
453 tcConDecl :: Bool -- True <=> -funbox-strict_fields
454 -> NewOrData -> TyCon -> [TyVar]
455 -> ConDecl Name -> TcM DataCon
457 tcConDecl unbox_strict NewType tycon tc_tvs -- Newtypes
458 (ConDecl name ex_tvs ex_ctxt details)
459 = ASSERT( null ex_tvs && null (unLoc ex_ctxt) )
460 do { let tc_datacon field_lbls arg_ty
461 = do { arg_ty' <- tcHsKindedType arg_ty -- No bang on newtype
462 ; buildDataCon (unLoc name) False {- Prefix -}
463 True {- Vanilla -} [NotMarkedStrict]
464 (map unLoc field_lbls)
466 tycon (mkTyVarTys tc_tvs) }
468 PrefixCon [arg_ty] -> tc_datacon [] arg_ty
469 RecCon [(field_lbl, arg_ty)] -> tc_datacon [field_lbl] arg_ty }
471 tcConDecl unbox_strict DataType tycon tc_tvs -- Ordinary data types
472 (ConDecl name ex_tvs ex_ctxt details)
473 = tcTyVarBndrs ex_tvs $ \ ex_tvs' -> do
474 { ex_ctxt' <- tcHsKindedContext ex_ctxt
476 is_vanilla = null ex_tvs && null (unLoc ex_ctxt)
477 -- Vanilla iff no ex_tvs and no context
478 -- Must check the context too because of
479 -- implicit params; e.g.
480 -- data T = (?x::Int) => MkT Int
482 tc_datacon is_infix field_lbls btys
483 = do { let { bangs = map getBangStrictness btys }
484 ; arg_tys <- mappM tcHsBangType btys
485 ; buildDataCon (unLoc name) is_infix is_vanilla
486 (argStrictness unbox_strict tycon bangs arg_tys)
487 (map unLoc field_lbls)
491 tycon (mkTyVarTys tc_tvs) }
493 PrefixCon btys -> tc_datacon False [] btys
494 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
495 RecCon fields -> do { checkTc (null ex_tvs) (exRecConErr name)
496 -- It's ok to have an implicit-parameter context
497 -- for the data constructor, provided it binds
499 ; let { (field_names, btys) = unzip fields }
500 ; tc_datacon False field_names btys } }
502 tcConDecl unbox_strict DataType tycon tc_tvs -- GADTs
503 decl@(GadtDecl name con_ty)
504 = do { traceTc (text "tcConDecl" <+> ppr name)
505 ; (tvs, theta, bangs, arg_tys, data_tc, res_tys) <- tcLHsConSig con_ty
507 ; traceTc (text "tcConDecl1" <+> ppr name)
508 ; let -- Now dis-assemble the type, and check its form
509 is_vanilla = null theta && mkTyVarTys tvs `tcEqTypes` res_tys
511 -- Vanilla datacons guarantee to use the same
512 -- type variables as the parent tycon
513 (tvs', arg_tys', res_tys')
514 | is_vanilla = (tc_tvs, substTys subst arg_tys, substTys subst res_tys)
515 | otherwise = (tvs, arg_tys, res_tys)
516 subst = zipTopTvSubst tvs (mkTyVarTys tc_tvs)
518 ; traceTc (text "tcConDecl3" <+> ppr name)
519 ; buildDataCon (unLoc name) False {- Not infix -} is_vanilla
520 (argStrictness unbox_strict tycon bangs arg_tys)
521 [{- No field labels -}]
522 tvs' theta arg_tys' data_tc res_tys' }
523 -- NB: we put data_tc, the type constructor gotten from the constructor
524 -- type signature into the data constructor; that way checkValidDataCon
525 -- can complain if it's wrong.
528 argStrictness :: Bool -- True <=> -funbox-strict_fields
530 -> [TcType] -> [StrictnessMark]
531 argStrictness unbox_strict tycon bangs arg_tys
532 = ASSERT( length bangs == length arg_tys )
533 zipWith (chooseBoxingStrategy unbox_strict tycon) arg_tys bangs
535 -- We attempt to unbox/unpack a strict field when either:
536 -- (i) The field is marked '!!', or
537 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
539 chooseBoxingStrategy :: Bool -> TyCon -> TcType -> HsBang -> StrictnessMark
540 chooseBoxingStrategy unbox_strict_fields tycon arg_ty bang
542 HsNoBang -> NotMarkedStrict
543 HsStrict | unbox_strict_fields && can_unbox -> MarkedUnboxed
544 HsUnbox | can_unbox -> MarkedUnboxed
545 other -> MarkedStrict
547 can_unbox = case splitTyConApp_maybe arg_ty of
549 Just (arg_tycon, _) -> not (isRecursiveTyCon tycon) &&
550 isProductTyCon arg_tycon
553 %************************************************************************
555 \subsection{Dependency analysis}
557 %************************************************************************
559 Validity checking is done once the mutually-recursive knot has been
560 tied, so we can look at things freely.
563 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
564 checkCycleErrs tyclss
568 = do { mappM_ recClsErr cls_cycles
569 ; failM } -- Give up now, because later checkValidTyCl
570 -- will loop if the synonym is recursive
572 cls_cycles = calcClassCycles tyclss
574 checkValidTyCl :: TyClDecl Name -> TcM ()
575 -- We do the validity check over declarations, rather than TyThings
576 -- only so that we can add a nice context with tcAddDeclCtxt
578 = tcAddDeclCtxt decl $
579 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
580 ; traceTc (text "Validity of" <+> ppr thing)
582 ATyCon tc -> checkValidTyCon tc
583 AClass cl -> checkValidClass cl
584 ; traceTc (text "Done validity of" <+> ppr thing)
587 -------------------------
588 checkValidTyCon :: TyCon -> TcM ()
591 = checkValidType syn_ctxt syn_rhs
593 = -- Check the context on the data decl
594 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
596 -- Check arg types of data constructors
597 mappM_ (checkValidDataCon tc) data_cons `thenM_`
599 -- Check that fields with the same name share a type
600 mappM_ check_fields groups
603 syn_ctxt = TySynCtxt name
605 (_, syn_rhs) = getSynTyConDefn tc
606 data_cons = tyConDataCons tc
608 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
609 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
610 get_fields con = dataConFieldLabels con `zip` dataConOrigArgTys con
611 -- dataConFieldLabels may return the empty list, which is fine
613 check_fields fields@((first_field_label, field_ty) : other_fields)
614 -- These fields all have the same name, but are from
615 -- different constructors in the data type
616 = -- Check that all the fields in the group have the same type
617 -- NB: this check assumes that all the constructors of a given
618 -- data type use the same type variables
619 checkTc (all (tcEqType field_ty . snd) other_fields)
620 (fieldTypeMisMatch first_field_label)
622 -------------------------------
623 checkValidDataCon :: TyCon -> DataCon -> TcM ()
624 checkValidDataCon tc con
625 = addErrCtxt (dataConCtxt con) $
626 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
627 ; checkValidType ctxt (idType (dataConWrapId con)) }
629 -- This checks the argument types and
630 -- ambiguity of the existential context (if any)
632 -- Note [Sept 04] Now that tvs is all the tvs, this
633 -- test doesn't actually check anything
634 -- ; checkFreeness tvs ex_theta }
636 ctxt = ConArgCtxt (dataConName con)
637 -- (tvs, ex_theta, _, _, _) = dataConSig con
640 -------------------------------
641 checkValidClass :: Class -> TcM ()
643 = do { -- CHECK ARITY 1 FOR HASKELL 1.4
644 gla_exts <- doptM Opt_GlasgowExts
646 -- Check that the class is unary, unless GlaExs
647 ; checkTc (notNull tyvars) (nullaryClassErr cls)
648 ; checkTc (gla_exts || unary) (classArityErr cls)
650 -- Check the super-classes
651 ; checkValidTheta (ClassSCCtxt (className cls)) theta
653 -- Check the class operations
654 ; mappM_ check_op op_stuff
656 -- Check that if the class has generic methods, then the
657 -- class has only one parameter. We can't do generic
658 -- multi-parameter type classes!
659 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
662 (tyvars, theta, _, op_stuff) = classBigSig cls
663 unary = isSingleton tyvars
664 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
666 check_op (sel_id, dm)
667 = addErrCtxt (classOpCtxt sel_id tau) $ do
668 { checkValidTheta SigmaCtxt (tail theta)
669 -- The 'tail' removes the initial (C a) from the
670 -- class itself, leaving just the method type
672 ; checkValidType (FunSigCtxt op_name) tau
674 -- Check that the type mentions at least one of
675 -- the class type variables
676 ; checkTc (any (`elemVarSet` tyVarsOfType tau) tyvars)
677 (noClassTyVarErr cls sel_id)
679 -- Check that for a generic method, the type of
680 -- the method is sufficiently simple
681 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
682 (badGenericMethodType op_name op_ty)
685 op_name = idName sel_id
686 op_ty = idType sel_id
687 (_,theta,tau) = tcSplitSigmaTy op_ty
691 ---------------------------------------------------------------------
692 fieldTypeMisMatch field_name
693 = sep [ptext SLIT("Different constructors give different types for field"), quotes (ppr field_name)]
695 dataConCtxt con = sep [ptext SLIT("When checking the data constructor:"),
696 nest 2 (ex_part <+> pprThetaArrow ex_theta <+> ppr con <+> arg_part)]
698 (ex_tvs, ex_theta, arg_tys, _, _) = dataConSig con
699 ex_part | null ex_tvs = empty
700 | otherwise = ptext SLIT("forall") <+> hsep (map ppr ex_tvs) <> dot
701 -- The 'ex_theta' part could be non-empty, if the user (bogusly) wrote
702 -- data T a = Eq a => T a a
703 -- So we make sure to print it
705 fields = dataConFieldLabels con
706 arg_part | null fields = sep (map pprParendType arg_tys)
707 | otherwise = braces (sep (punctuate comma
708 [ ppr n <+> dcolon <+> ppr ty
709 | (n,ty) <- fields `zip` arg_tys]))
711 classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
712 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
715 = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
718 = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
719 parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
721 noClassTyVarErr clas op
722 = sep [ptext SLIT("The class method") <+> quotes (ppr op),
723 ptext SLIT("mentions none of the type variables of the class") <+>
724 ppr clas <+> hsep (map ppr (classTyVars clas))]
726 genericMultiParamErr clas
727 = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
728 ptext SLIT("cannot have generic methods")
730 badGenericMethodType op op_ty
731 = hang (ptext SLIT("Generic method type is too complex"))
732 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
733 ptext SLIT("You can only use type variables, arrows, lists, and tuples")])
736 = setSrcSpan (getLoc (head sorted_decls)) $
737 addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
738 nest 2 (vcat (map ppr_decl sorted_decls))])
740 sorted_decls = sortLocated syn_decls
741 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
744 = setSrcSpan (getLoc (head sorted_decls)) $
745 addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
746 nest 2 (vcat (map ppr_decl sorted_decls))])
748 sorted_decls = sortLocated cls_decls
749 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
751 sortLocated :: [Located a] -> [Located a]
752 sortLocated things = sortLe le things
754 le (L l1 _) (L l2 _) = l1 <= l2
757 = ptext SLIT("Can't combine named fields with locally-quantified type variables or context")
759 (ptext SLIT("In the declaration of data constructor") <+> ppr name)
761 badDataConTyCon data_con
762 = hang (ptext SLIT("Data constructor") <+> quotes (ppr data_con) <+>
763 ptext SLIT("returns type") <+> quotes (ppr (dataConTyCon data_con)))
764 2 (ptext SLIT("instead of its parent type"))
767 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
768 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow GADTs")) ]
770 emptyConDeclsErr tycon
771 = sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
772 nest 4 (ptext SLIT("(-fglasgow-exts permits this)"))]