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(..), ResType(..),
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, tcLHsConResTy, tcDataKindSig )
33 import TcMType ( newKindVar, checkValidTheta, checkValidType, checkFreeness,
34 UserTypeCtxt(..), SourceTyCtxt(..) )
35 import TcType ( TcKind, TcType, tyVarsOfType, mkPhiTy,
36 mkArrowKind, liftedTypeKind, mkTyVarTys,
37 tcSplitSigmaTy, tcEqTypes, tcGetTyVar_maybe )
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, dataConTyCon,
47 dataConTyVars, dataConFieldType, dataConResTys )
48 import Var ( TyVar, idType, idName )
49 import VarSet ( elemVarSet, mkVarSet )
52 import Maybe ( isJust, fromJust )
53 import Unify ( tcMatchTys, tcMatchTyX )
54 import Util ( zipLazy, isSingleton, notNull, sortLe )
55 import List ( partition )
56 import SrcLoc ( Located(..), unLoc, getLoc )
57 import ListSetOps ( equivClasses )
58 import List ( delete )
59 import Digraph ( SCC(..) )
60 import DynFlags ( DynFlag( Opt_GlasgowExts, Opt_Generics,
61 Opt_UnboxStrictFields ) )
65 %************************************************************************
67 \subsection{Type checking for type and class declarations}
69 %************************************************************************
73 Consider a mutually-recursive group, binding
74 a type constructor T and a class C.
76 Step 1: getInitialKind
77 Construct a KindEnv by binding T and C to a kind variable
80 In that environment, do a kind check
82 Step 3: Zonk the kinds
84 Step 4: buildTyConOrClass
85 Construct an environment binding T to a TyCon and C to a Class.
86 a) Their kinds comes from zonking the relevant kind variable
87 b) Their arity (for synonyms) comes direct from the decl
88 c) The funcional dependencies come from the decl
89 d) The rest comes a knot-tied binding of T and C, returned from Step 4
90 e) The variances of the tycons in the group is calculated from
94 In this environment, walk over the decls, constructing the TyCons and Classes.
95 This uses in a strict way items (a)-(c) above, which is why they must
96 be constructed in Step 4. Feed the results back to Step 4.
97 For this step, pass the is-recursive flag as the wimp-out flag
101 Step 6: Extend environment
102 We extend the type environment with bindings not only for the TyCons and Classes,
103 but also for their "implicit Ids" like data constructors and class selectors
105 Step 7: checkValidTyCl
106 For a recursive group only, check all the decls again, just
107 to check all the side conditions on validity. We could not
108 do this before because we were in a mutually recursive knot.
111 The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to
112 @TyThing@s. @rec_vrcs@ is a finite map from @Name@s to @ArgVrcs@s.
115 tcTyAndClassDecls :: ModDetails -> [LTyClDecl Name]
116 -> TcM TcGblEnv -- Input env extended by types and classes
117 -- and their implicit Ids,DataCons
118 tcTyAndClassDecls boot_details decls
119 = do { -- First check for cyclic type synonysm or classes
120 -- See notes with checkCycleErrs
123 ; traceTc (text "tcTyAndCl" <+> ppr mod)
124 ; (syn_tycons, alg_tyclss) <- fixM (\ ~(rec_syn_tycons, rec_alg_tyclss) ->
125 do { let { -- Calculate variances and rec-flag
126 ; (syn_decls, alg_decls) = partition (isSynDecl . unLoc) decls }
128 -- Extend the global env with the knot-tied results
129 -- for data types and classes
131 -- We must populate the environment with the loop-tied T's right
132 -- away, because the kind checker may "fault in" some type
133 -- constructors that recursively mention T
134 ; let { gbl_things = mkGlobalThings alg_decls rec_alg_tyclss }
135 ; tcExtendRecEnv gbl_things $ do
137 -- Kind-check the declarations
138 { (kc_syn_decls, kc_alg_decls) <- kcTyClDecls syn_decls alg_decls
140 ; let { calc_vrcs = calcTyConArgVrcs (rec_syn_tycons ++ rec_alg_tyclss)
141 ; calc_rec = calcRecFlags boot_details rec_alg_tyclss
142 ; tc_decl = addLocM (tcTyClDecl calc_vrcs calc_rec) }
143 -- Type-check the type synonyms, and extend the envt
144 ; syn_tycons <- tcSynDecls calc_vrcs kc_syn_decls
145 ; tcExtendGlobalEnv syn_tycons $ do
147 -- Type-check the data types and classes
148 { alg_tyclss <- mappM tc_decl kc_alg_decls
149 ; return (syn_tycons, alg_tyclss)
151 -- Finished with knot-tying now
152 -- Extend the environment with the finished things
153 ; tcExtendGlobalEnv (syn_tycons ++ alg_tyclss) $ do
155 -- Perform the validity check
156 { traceTc (text "ready for validity check")
157 ; mappM_ (addLocM checkValidTyCl) decls
158 ; traceTc (text "done")
160 -- Add the implicit things;
161 -- we want them in the environment because
162 -- they may be mentioned in interface files
163 ; let { implicit_things = concatMap implicitTyThings alg_tyclss }
164 ; traceTc ((text "Adding" <+> ppr alg_tyclss) $$ (text "and" <+> ppr implicit_things))
165 ; tcExtendGlobalEnv implicit_things getGblEnv
168 mkGlobalThings :: [LTyClDecl Name] -- The decls
169 -> [TyThing] -- Knot-tied, in 1-1 correspondence with the decls
171 -- Driven by the Decls, and treating the TyThings lazily
172 -- make a TypeEnv for the new things
173 mkGlobalThings decls things
174 = map mk_thing (decls `zipLazy` things)
176 mk_thing (L _ (ClassDecl {tcdLName = L _ name}), ~(AClass cl))
178 mk_thing (L _ decl, ~(ATyCon tc))
179 = (tcdName decl, ATyCon tc)
183 %************************************************************************
187 %************************************************************************
189 We need to kind check all types in the mutually recursive group
190 before we know the kind of the type variables. For example:
193 op :: D b => a -> b -> b
196 bop :: (Monad c) => ...
198 Here, the kind of the locally-polymorphic type variable "b"
199 depends on *all the uses of class D*. For example, the use of
200 Monad c in bop's type signature means that D must have kind Type->Type.
202 However type synonyms work differently. They can have kinds which don't
203 just involve (->) and *:
204 type R = Int# -- Kind #
205 type S a = Array# a -- Kind * -> #
206 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
207 So we must infer their kinds from their right-hand sides *first* and then
208 use them, whereas for the mutually recursive data types D we bring into
209 scope kind bindings D -> k, where k is a kind variable, and do inference.
212 kcTyClDecls syn_decls alg_decls
213 = do { -- First extend the kind env with each data
214 -- type and class, mapping them to a type variable
215 alg_kinds <- mappM getInitialKind alg_decls
216 ; tcExtendKindEnv alg_kinds $ do
218 -- Now kind-check the type synonyms, in dependency order
219 -- We do these differently to data type and classes,
220 -- because a type synonym can be an unboxed type
222 -- and a kind variable can't unify with UnboxedTypeKind
223 -- So we infer their kinds in dependency order
224 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
225 ; tcExtendKindEnv syn_kinds $ do
227 -- Now kind-check the data type and class declarations,
228 -- returning kind-annotated decls
229 { kc_alg_decls <- mappM (wrapLocM kcTyClDecl) alg_decls
231 ; return (kc_syn_decls, kc_alg_decls) }}}
233 ------------------------------------------------------------------------
234 getInitialKind :: LTyClDecl Name -> TcM (Name, TcKind)
235 -- Only for data type and class declarations
236 -- Get as much info as possible from the data or class decl,
237 -- so as to maximise usefulness of error messages
238 getInitialKind (L _ decl)
239 = do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl)
240 ; res_kind <- mk_res_kind decl
241 ; return (tcdName decl, mkArrowKinds arg_kinds res_kind) }
243 mk_arg_kind (UserTyVar _) = newKindVar
244 mk_arg_kind (KindedTyVar _ kind) = return kind
246 mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
247 -- On GADT-style declarations we allow a kind signature
248 -- data T :: *->* where { ... }
249 mk_res_kind other = return liftedTypeKind
253 kcSynDecls :: [SCC (LTyClDecl Name)]
254 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
255 [(Name,TcKind)]) -- Kind bindings
258 kcSynDecls (group : groups)
259 = do { (decl, nk) <- kcSynDecl group
260 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
261 ; return (decl:decls, nk:nks) }
264 kcSynDecl :: SCC (LTyClDecl Name)
265 -> TcM (LTyClDecl Name, -- Kind-annotated decls
266 (Name,TcKind)) -- Kind bindings
267 kcSynDecl (AcyclicSCC ldecl@(L loc decl))
268 = tcAddDeclCtxt decl $
269 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
270 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
271 <+> brackets (ppr k_tvs))
272 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
273 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
274 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
275 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
276 (unLoc (tcdLName decl), tc_kind)) })
278 kcSynDecl (CyclicSCC decls)
279 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
280 -- of out-of-scope tycons
282 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
284 ------------------------------------------------------------------------
285 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
286 -- Not used for type synonyms (see kcSynDecl)
288 kcTyClDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
289 = kcTyClDeclBody decl $ \ tvs' ->
290 do { ctxt' <- kcHsContext ctxt
291 ; cons' <- mappM (wrapLocM kc_con_decl) cons
292 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdCons = cons'}) }
294 kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res) = do
295 kcHsTyVars ex_tvs $ \ex_tvs' -> do
296 ex_ctxt' <- kcHsContext ex_ctxt
297 details' <- kc_con_details details
299 ResTyH98 -> return ResTyH98
300 ResTyGADT ty -> return . ResTyGADT =<< kcHsSigType ty
301 return (ConDecl name expl ex_tvs' ex_ctxt' details' res')
303 kc_con_details (PrefixCon btys)
304 = do { btys' <- mappM kc_larg_ty btys ; return (PrefixCon btys') }
305 kc_con_details (InfixCon bty1 bty2)
306 = do { bty1' <- kc_larg_ty bty1; bty2' <- kc_larg_ty bty2; return (InfixCon bty1' bty2') }
307 kc_con_details (RecCon fields)
308 = do { fields' <- mappM kc_field fields; return (RecCon fields') }
310 kc_field (fld, bty) = do { bty' <- kc_larg_ty bty ; return (fld, bty') }
312 kc_larg_ty bty = case new_or_data of
313 DataType -> kcHsSigType bty
314 NewType -> kcHsLiftedSigType bty
315 -- Can't allow an unlifted type for newtypes, because we're effectively
316 -- going to remove the constructor while coercing it to a lifted type.
317 -- And newtypes can't be bang'd
319 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs})
320 = kcTyClDeclBody decl $ \ tvs' ->
321 do { is_boot <- tcIsHsBoot
322 ; checkTc (not is_boot) badBootClassDeclErr
323 ; ctxt' <- kcHsContext ctxt
324 ; sigs' <- mappM (wrapLocM kc_sig) sigs
325 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs'}) }
327 kc_sig (TypeSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
328 ; return (TypeSig nm op_ty') }
329 kc_sig other_sig = return other_sig
331 kcTyClDecl decl@(ForeignType {})
334 kcTyClDeclBody :: TyClDecl Name
335 -> ([LHsTyVarBndr Name] -> TcM a)
337 -- getInitialKind has made a suitably-shaped kind for the type or class
338 -- Unpack it, and attribute those kinds to the type variables
339 -- Extend the env with bindings for the tyvars, taken from
340 -- the kind of the tycon/class. Give it to the thing inside, and
341 -- check the result kind matches
342 kcTyClDeclBody decl thing_inside
343 = tcAddDeclCtxt decl $
344 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
345 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
346 (kinds, _) = splitKindFunTys tc_kind
347 hs_tvs = tcdTyVars decl
348 kinded_tvs = ASSERT( length kinds >= length hs_tvs )
349 [ L loc (KindedTyVar (hsTyVarName tv) k)
350 | (L loc tv, k) <- zip hs_tvs kinds]
351 ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
355 %************************************************************************
357 \subsection{Type checking}
359 %************************************************************************
362 tcSynDecls :: (Name -> ArgVrcs) -> [LTyClDecl Name] -> TcM [TyThing]
363 tcSynDecls calc_vrcs [] = return []
364 tcSynDecls calc_vrcs (decl : decls)
365 = do { syn_tc <- addLocM (tcSynDecl calc_vrcs) decl
366 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls calc_vrcs decls)
367 ; return (syn_tc : syn_tcs) }
370 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
371 = tcTyVarBndrs tvs $ \ tvs' -> do
372 { traceTc (text "tcd1" <+> ppr tc_name)
373 ; rhs_ty' <- tcHsKindedType rhs_ty
374 ; return (ATyCon (buildSynTyCon tc_name tvs' rhs_ty' (calc_vrcs tc_name))) }
377 tcTyClDecl :: (Name -> ArgVrcs) -> (Name -> RecFlag)
378 -> TyClDecl Name -> TcM TyThing
380 tcTyClDecl calc_vrcs calc_isrec decl
381 = tcAddDeclCtxt decl (tcTyClDecl1 calc_vrcs calc_isrec decl)
383 tcTyClDecl1 calc_vrcs calc_isrec
384 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
385 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
386 = tcTyVarBndrs tvs $ \ tvs' -> do
387 { extra_tvs <- tcDataKindSig mb_ksig
388 ; let final_tvs = tvs' ++ extra_tvs
389 ; stupid_theta <- tcHsKindedContext ctxt
390 ; want_generic <- doptM Opt_Generics
391 ; unbox_strict <- doptM Opt_UnboxStrictFields
392 ; gla_exts <- doptM Opt_GlasgowExts
393 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
395 -- Check that we don't use GADT syntax in H98 world
396 ; checkTc (gla_exts || h98_syntax) (badGadtDecl tc_name)
398 -- Check that there's at least one condecl,
399 -- or else we're reading an interface file, or -fglasgow-exts
400 ; checkTc (not (null cons) || gla_exts || is_boot)
401 (emptyConDeclsErr tc_name)
403 ; tycon <- fixM (\ tycon -> do
404 { data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data
408 | null cons && is_boot -- In a hs-boot file, empty cons means
409 = AbstractTyCon -- "don't know"; hence Abstract
411 = case new_or_data of
412 DataType -> mkDataTyConRhs data_cons
413 NewType -> ASSERT( isSingleton data_cons )
414 mkNewTyConRhs tycon (head data_cons)
415 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs arg_vrcs is_rec
416 (want_generic && canDoGenerics data_cons)
418 ; return (ATyCon tycon)
421 arg_vrcs = calc_vrcs tc_name
422 is_rec = calc_isrec tc_name
423 h98_syntax = case cons of -- All constructors have same shape
424 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
427 tcTyClDecl1 calc_vrcs calc_isrec
428 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
429 tcdCtxt = ctxt, tcdMeths = meths,
430 tcdFDs = fundeps, tcdSigs = sigs} )
431 = tcTyVarBndrs tvs $ \ tvs' -> do
432 { ctxt' <- tcHsKindedContext ctxt
433 ; fds' <- mappM (addLocM tc_fundep) fundeps
434 ; sig_stuff <- tcClassSigs class_name sigs meths
435 ; clas <- fixM (\ clas ->
436 let -- This little knot is just so we can get
437 -- hold of the name of the class TyCon, which we
438 -- need to look up its recursiveness and variance
439 tycon_name = tyConName (classTyCon clas)
440 tc_isrec = calc_isrec tycon_name
441 tc_vrcs = calc_vrcs tycon_name
443 buildClass class_name tvs' ctxt' fds'
444 sig_stuff tc_isrec tc_vrcs)
445 ; return (AClass clas) }
447 tc_fundep (tvs1, tvs2) = do { tvs1' <- mappM tcLookupTyVar tvs1 ;
448 ; tvs2' <- mappM tcLookupTyVar tvs2 ;
449 ; return (tvs1', tvs2') }
452 tcTyClDecl1 calc_vrcs calc_isrec
453 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
454 = returnM (ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0 []))
456 -----------------------------------
457 tcConDecl :: Bool -- True <=> -funbox-strict_fields
458 -> NewOrData -> TyCon -> [TyVar]
459 -> ConDecl Name -> TcM DataCon
461 tcConDecl unbox_strict NewType tycon tc_tvs -- Newtypes
462 (ConDecl name _ ex_tvs ex_ctxt details ResTyH98)
463 = ASSERT( null ex_tvs && null (unLoc ex_ctxt) )
464 do { let tc_datacon field_lbls arg_ty
465 = do { arg_ty' <- tcHsKindedType arg_ty -- No bang on newtype
466 ; buildDataCon (unLoc name) False {- Prefix -}
467 True {- Vanilla -} [NotMarkedStrict]
468 (map unLoc field_lbls)
470 tycon (mkTyVarTys tc_tvs) }
472 PrefixCon [arg_ty] -> tc_datacon [] arg_ty
473 RecCon [(field_lbl, arg_ty)] -> tc_datacon [field_lbl] arg_ty }
475 tcConDecl unbox_strict DataType tycon tc_tvs -- Data types
476 (ConDecl name _ tvs ctxt details res_ty)
477 = tcTyVarBndrs tvs $ \ tvs' -> do
478 { ctxt' <- tcHsKindedContext ctxt
479 ; (data_tc, res_ty_args) <- tcResultType tycon tc_tvs res_ty
481 con_tvs = case res_ty of
482 ResTyH98 -> tc_tvs ++ tvs'
483 ResTyGADT _ -> tryVanilla tvs' res_ty_args
485 -- Vanilla iff result type matches the quantified vars exactly,
486 -- and there is no existential context
487 -- Must check the context too because of implicit params; e.g.
488 -- data T = (?x::Int) => MkT Int
489 is_vanilla = res_ty_args `tcEqTypes` mkTyVarTys con_tvs
492 tc_datacon is_infix field_lbls btys
493 = do { let bangs = map getBangStrictness btys
494 ; arg_tys <- mappM tcHsBangType btys
495 ; buildDataCon (unLoc name) is_infix is_vanilla
496 (argStrictness unbox_strict tycon bangs arg_tys)
497 (map unLoc field_lbls)
498 con_tvs ctxt' arg_tys
499 data_tc res_ty_args }
500 -- NB: we put data_tc, the type constructor gotten from the constructor
501 -- type signature into the data constructor; that way
502 -- checkValidDataCon can complain if it's wrong.
505 PrefixCon btys -> tc_datacon False [] btys
506 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
507 RecCon fields -> tc_datacon False field_names btys
509 (field_names, btys) = unzip fields
513 tcResultType :: TyCon -> [TyVar] -> ResType Name -> TcM (TyCon, [TcType])
514 tcResultType tycon tvs ResTyH98 = return (tycon, mkTyVarTys tvs)
515 tcResultType _ _ (ResTyGADT res_ty) = tcLHsConResTy res_ty
517 tryVanilla :: [TyVar] -> [TcType] -> [TyVar]
518 -- (tryVanilla tvs tys) returns a permutation of tvs.
519 -- It tries to re-order the tvs so that it exactly
520 -- matches the [Type], if that is possible
521 tryVanilla tvs (ty:tys) | Just tv <- tcGetTyVar_maybe ty -- The type is a tyvar
522 , tv `elem` tvs -- That tyvar is in the list
523 = tv : tryVanilla (delete tv tvs) tys
524 tryVanilla tvs tys = tvs -- Fall through case
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 -- For data types declared with record syntax, we require
589 -- that each constructor that has a field 'f'
590 -- (a) has the same result type
591 -- (b) has the same type for 'f'
592 -- module alpha conversion of the quantified type variables
593 -- of the constructor.
595 checkValidTyCon :: TyCon -> TcM ()
598 = checkValidType syn_ctxt syn_rhs
600 = -- Check the context on the data decl
601 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
603 -- Check arg types of data constructors
604 mappM_ (checkValidDataCon tc) data_cons `thenM_`
606 -- Check that fields with the same name share a type
607 mappM_ check_fields groups
610 syn_ctxt = TySynCtxt name
612 (_, syn_rhs) = getSynTyConDefn tc
613 data_cons = tyConDataCons tc
615 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
616 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
617 get_fields con = dataConFieldLabels con `zip` repeat con
618 -- dataConFieldLabels may return the empty list, which is fine
620 -- XXX - autrijus - Make this far more complex to acommodate
621 -- for different return types. Add res_ty to the mix,
622 -- comparing them in two steps, all for good error messages.
623 -- Plan: Use Unify.tcMatchTys to compare the first candidate's
624 -- result type against other candidates' types (check bothways).
625 -- If they magically agrees, take the substitution and
626 -- apply them to the latter ones, and see if they match perfectly.
627 -- check_fields fields@((first_field_label, field_ty) : other_fields)
628 check_fields fields@((label, con1) : other_fields)
629 -- These fields all have the same name, but are from
630 -- different constructors in the data type
631 = recoverM (return ()) $ mapM_ checkOne other_fields
632 -- Check that all the fields in the group have the same type
633 -- NB: this check assumes that all the constructors of a given
634 -- data type use the same type variables
636 tvs1 = mkVarSet (dataConTyVars con1)
637 res1 = dataConResTys con1
638 fty1 = dataConFieldType con1 label
640 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
641 = do { checkFieldCompat label con1 con2 tvs1 res1 res2 fty1 fty2
642 ; checkFieldCompat label con2 con1 tvs2 res2 res1 fty2 fty1 }
644 tvs2 = mkVarSet (dataConTyVars con2)
645 res2 = dataConResTys con2
646 fty2 = dataConFieldType con2 label
648 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
649 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
650 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
652 mb_subst1 = tcMatchTys tvs1 res1 res2
653 mb_subst2 = tcMatchTyX tvs1 (fromJust mb_subst1) fty1 fty2
655 -------------------------------
656 checkValidDataCon :: TyCon -> DataCon -> TcM ()
657 checkValidDataCon tc con
658 = addErrCtxt (dataConCtxt con) $
659 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
660 ; checkValidType ctxt (idType (dataConWrapId con)) }
662 -- This checks the argument types and
663 -- ambiguity of the existential context (if any)
665 -- Note [Sept 04] Now that tvs is all the tvs, this
666 -- test doesn't actually check anything
667 -- ; checkFreeness tvs ex_theta }
669 ctxt = ConArgCtxt (dataConName con)
670 -- (tvs, ex_theta, _, _, _) = dataConSig con
673 -------------------------------
674 checkValidClass :: Class -> TcM ()
676 = do { -- CHECK ARITY 1 FOR HASKELL 1.4
677 gla_exts <- doptM Opt_GlasgowExts
679 -- Check that the class is unary, unless GlaExs
680 ; checkTc (notNull tyvars) (nullaryClassErr cls)
681 ; checkTc (gla_exts || unary) (classArityErr cls)
683 -- Check the super-classes
684 ; checkValidTheta (ClassSCCtxt (className cls)) theta
686 -- Check the class operations
687 ; mappM_ (check_op gla_exts) op_stuff
689 -- Check that if the class has generic methods, then the
690 -- class has only one parameter. We can't do generic
691 -- multi-parameter type classes!
692 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
695 (tyvars, theta, _, op_stuff) = classBigSig cls
696 unary = isSingleton tyvars
697 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
699 check_op gla_exts (sel_id, dm)
700 = addErrCtxt (classOpCtxt sel_id tau) $ do
701 { checkValidTheta SigmaCtxt (tail theta)
702 -- The 'tail' removes the initial (C a) from the
703 -- class itself, leaving just the method type
705 ; checkValidType (FunSigCtxt op_name) tau
707 -- Check that the type mentions at least one of
708 -- the class type variables
709 ; checkTc (any (`elemVarSet` tyVarsOfType tau) tyvars)
710 (noClassTyVarErr cls sel_id)
712 -- Check that for a generic method, the type of
713 -- the method is sufficiently simple
714 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
715 (badGenericMethodType op_name op_ty)
718 op_name = idName sel_id
719 op_ty = idType sel_id
720 (_,theta1,tau1) = tcSplitSigmaTy op_ty
721 (_,theta2,tau2) = tcSplitSigmaTy tau1
722 (theta,tau) | gla_exts = (theta1 ++ theta2, tau2)
723 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
724 -- Ugh! The function might have a type like
725 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
726 -- With -fglasgow-exts, we want to allow this, even though the inner
727 -- forall has an (Eq a) constraint. Whereas in general, each constraint
728 -- in the context of a for-all must mention at least one quantified
729 -- type variable. What a mess!
732 ---------------------------------------------------------------------
733 resultTypeMisMatch field_name con1 con2
734 = vcat [sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
735 ptext SLIT("have a common field") <+> quotes (ppr field_name) <> comma],
736 nest 2 $ ptext SLIT("but have different result types")]
737 fieldTypeMisMatch field_name con1 con2
738 = sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
739 ptext SLIT("give different types for field"), quotes (ppr field_name)]
741 dataConCtxt con = sep [ptext SLIT("When checking the data constructor:"),
742 nest 2 (ex_part <+> pprThetaArrow ex_theta <+> ppr con <+> arg_part)]
744 (ex_tvs, ex_theta, arg_tys, _, _) = dataConSig con
745 ex_part | null ex_tvs = empty
746 | otherwise = ptext SLIT("forall") <+> hsep (map ppr ex_tvs) <> dot
747 -- The 'ex_theta' part could be non-empty, if the user (bogusly) wrote
748 -- data T a = Eq a => T a a
749 -- So we make sure to print it
751 fields = dataConFieldLabels con
752 arg_part | null fields = sep (map pprParendType arg_tys)
753 | otherwise = braces (sep (punctuate comma
754 [ ppr n <+> dcolon <+> ppr ty
755 | (n,ty) <- fields `zip` arg_tys]))
757 classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
758 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
761 = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
764 = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
765 parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
767 noClassTyVarErr clas op
768 = sep [ptext SLIT("The class method") <+> quotes (ppr op),
769 ptext SLIT("mentions none of the type variables of the class") <+>
770 ppr clas <+> hsep (map ppr (classTyVars clas))]
772 genericMultiParamErr clas
773 = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
774 ptext SLIT("cannot have generic methods")
776 badGenericMethodType op op_ty
777 = hang (ptext SLIT("Generic method type is too complex"))
778 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
779 ptext SLIT("You can only use type variables, arrows, lists, and tuples")])
782 = setSrcSpan (getLoc (head sorted_decls)) $
783 addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
784 nest 2 (vcat (map ppr_decl sorted_decls))])
786 sorted_decls = sortLocated syn_decls
787 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
790 = setSrcSpan (getLoc (head sorted_decls)) $
791 addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
792 nest 2 (vcat (map ppr_decl sorted_decls))])
794 sorted_decls = sortLocated cls_decls
795 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
797 sortLocated :: [Located a] -> [Located a]
798 sortLocated things = sortLe le things
800 le (L l1 _) (L l2 _) = l1 <= l2
802 badDataConTyCon data_con
803 = hang (ptext SLIT("Data constructor") <+> quotes (ppr data_con) <+>
804 ptext SLIT("returns type") <+> quotes (ppr (dataConTyCon data_con)))
805 2 (ptext SLIT("instead of its parent type"))
808 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
809 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow GADTs")) ]
811 emptyConDeclsErr tycon
812 = sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
813 nest 4 (ptext SLIT("(-fglasgow-exts permits this)"))]
815 badBootClassDeclErr = ptext SLIT("Illegal class declaration in hs-boot file")