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, hsConArgs,
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,
35 UserTypeCtxt(..), SourceTyCtxt(..) )
36 import TcType ( TcKind, TcType, tyVarsOfType, mkPhiTy,
37 mkArrowKind, liftedTypeKind, mkTyVarTys,
38 tcSplitSigmaTy, tcEqTypes, tcGetTyVar_maybe )
39 import Type ( splitTyConApp_maybe,
40 -- pprParendType, pprThetaArrow
42 import Kind ( mkArrowKinds, splitKindFunTys )
43 import Generics ( validGenericMethodType, canDoGenerics )
44 import Class ( Class, className, classTyCon, DefMeth(..), classBigSig, classTyVars )
45 import TyCon ( TyCon, ArgVrcs, AlgTyConRhs( AbstractTyCon ),
46 tyConDataCons, mkForeignTyCon, isProductTyCon, isRecursiveTyCon,
47 tyConStupidTheta, synTyConRhs, isSynTyCon, tyConName )
48 import DataCon ( DataCon, dataConWrapId, dataConName,
49 dataConFieldLabels, dataConTyCon,
50 dataConTyVars, dataConFieldType, dataConResTys )
51 import Var ( TyVar, idType, idName )
52 import VarSet ( elemVarSet, mkVarSet )
53 import Name ( Name, getSrcLoc )
55 import Maybe ( isJust )
56 import Maybes ( expectJust )
57 import Unify ( tcMatchTys, tcMatchTyX )
58 import Util ( zipLazy, isSingleton, notNull, sortLe )
59 import List ( partition )
60 import SrcLoc ( Located(..), unLoc, getLoc, srcLocSpan )
61 import ListSetOps ( equivClasses )
62 import List ( delete )
63 import Digraph ( SCC(..) )
64 import DynFlags ( DynFlag( Opt_GlasgowExts, Opt_Generics,
65 Opt_UnboxStrictFields ) )
69 %************************************************************************
71 \subsection{Type checking for type and class declarations}
73 %************************************************************************
77 Consider a mutually-recursive group, binding
78 a type constructor T and a class C.
80 Step 1: getInitialKind
81 Construct a KindEnv by binding T and C to a kind variable
84 In that environment, do a kind check
86 Step 3: Zonk the kinds
88 Step 4: buildTyConOrClass
89 Construct an environment binding T to a TyCon and C to a Class.
90 a) Their kinds comes from zonking the relevant kind variable
91 b) Their arity (for synonyms) comes direct from the decl
92 c) The funcional dependencies come from the decl
93 d) The rest comes a knot-tied binding of T and C, returned from Step 4
94 e) The variances of the tycons in the group is calculated from
98 In this environment, walk over the decls, constructing the TyCons and Classes.
99 This uses in a strict way items (a)-(c) above, which is why they must
100 be constructed in Step 4. Feed the results back to Step 4.
101 For this step, pass the is-recursive flag as the wimp-out flag
105 Step 6: Extend environment
106 We extend the type environment with bindings not only for the TyCons and Classes,
107 but also for their "implicit Ids" like data constructors and class selectors
109 Step 7: checkValidTyCl
110 For a recursive group only, check all the decls again, just
111 to check all the side conditions on validity. We could not
112 do this before because we were in a mutually recursive knot.
115 The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to
116 @TyThing@s. @rec_vrcs@ is a finite map from @Name@s to @ArgVrcs@s.
119 tcTyAndClassDecls :: ModDetails -> [LTyClDecl Name]
120 -> TcM TcGblEnv -- Input env extended by types and classes
121 -- and their implicit Ids,DataCons
122 tcTyAndClassDecls boot_details decls
123 = do { -- First check for cyclic type synonysm or classes
124 -- See notes with checkCycleErrs
127 ; traceTc (text "tcTyAndCl" <+> ppr mod)
128 ; (syn_tycons, alg_tyclss) <- fixM (\ ~(rec_syn_tycons, rec_alg_tyclss) ->
129 do { let { -- Calculate variances and rec-flag
130 ; (syn_decls, alg_decls) = partition (isSynDecl . unLoc) decls }
132 -- Extend the global env with the knot-tied results
133 -- for data types and classes
135 -- We must populate the environment with the loop-tied T's right
136 -- away, because the kind checker may "fault in" some type
137 -- constructors that recursively mention T
138 ; let { gbl_things = mkGlobalThings alg_decls rec_alg_tyclss }
139 ; tcExtendRecEnv gbl_things $ do
141 -- Kind-check the declarations
142 { (kc_syn_decls, kc_alg_decls) <- kcTyClDecls syn_decls alg_decls
144 ; let { calc_vrcs = calcTyConArgVrcs (rec_syn_tycons ++ rec_alg_tyclss)
145 ; calc_rec = calcRecFlags boot_details rec_alg_tyclss
146 ; tc_decl = addLocM (tcTyClDecl calc_vrcs calc_rec) }
147 -- Type-check the type synonyms, and extend the envt
148 ; syn_tycons <- tcSynDecls calc_vrcs kc_syn_decls
149 ; tcExtendGlobalEnv syn_tycons $ do
151 -- Type-check the data types and classes
152 { alg_tyclss <- mappM tc_decl kc_alg_decls
153 ; return (syn_tycons, alg_tyclss)
155 -- Finished with knot-tying now
156 -- Extend the environment with the finished things
157 ; tcExtendGlobalEnv (syn_tycons ++ alg_tyclss) $ do
159 -- Perform the validity check
160 { traceTc (text "ready for validity check")
161 ; mappM_ (addLocM checkValidTyCl) decls
162 ; traceTc (text "done")
164 -- Add the implicit things;
165 -- we want them in the environment because
166 -- they may be mentioned in interface files
167 ; let { implicit_things = concatMap implicitTyThings alg_tyclss }
168 ; traceTc ((text "Adding" <+> ppr alg_tyclss) $$ (text "and" <+> ppr implicit_things))
169 ; tcExtendGlobalEnv implicit_things getGblEnv
172 mkGlobalThings :: [LTyClDecl Name] -- The decls
173 -> [TyThing] -- Knot-tied, in 1-1 correspondence with the decls
175 -- Driven by the Decls, and treating the TyThings lazily
176 -- make a TypeEnv for the new things
177 mkGlobalThings decls things
178 = map mk_thing (decls `zipLazy` things)
180 mk_thing (L _ (ClassDecl {tcdLName = L _ name}), ~(AClass cl))
182 mk_thing (L _ decl, ~(ATyCon tc))
183 = (tcdName decl, ATyCon tc)
187 %************************************************************************
191 %************************************************************************
193 We need to kind check all types in the mutually recursive group
194 before we know the kind of the type variables. For example:
197 op :: D b => a -> b -> b
200 bop :: (Monad c) => ...
202 Here, the kind of the locally-polymorphic type variable "b"
203 depends on *all the uses of class D*. For example, the use of
204 Monad c in bop's type signature means that D must have kind Type->Type.
206 However type synonyms work differently. They can have kinds which don't
207 just involve (->) and *:
208 type R = Int# -- Kind #
209 type S a = Array# a -- Kind * -> #
210 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
211 So we must infer their kinds from their right-hand sides *first* and then
212 use them, whereas for the mutually recursive data types D we bring into
213 scope kind bindings D -> k, where k is a kind variable, and do inference.
216 kcTyClDecls syn_decls alg_decls
217 = do { -- First extend the kind env with each data
218 -- type and class, mapping them to a type variable
219 alg_kinds <- mappM getInitialKind alg_decls
220 ; tcExtendKindEnv alg_kinds $ do
222 -- Now kind-check the type synonyms, in dependency order
223 -- We do these differently to data type and classes,
224 -- because a type synonym can be an unboxed type
226 -- and a kind variable can't unify with UnboxedTypeKind
227 -- So we infer their kinds in dependency order
228 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
229 ; tcExtendKindEnv syn_kinds $ do
231 -- Now kind-check the data type and class declarations,
232 -- returning kind-annotated decls
233 { kc_alg_decls <- mappM (wrapLocM kcTyClDecl) alg_decls
235 ; return (kc_syn_decls, kc_alg_decls) }}}
237 ------------------------------------------------------------------------
238 getInitialKind :: LTyClDecl Name -> TcM (Name, TcKind)
239 -- Only for data type and class declarations
240 -- Get as much info as possible from the data or class decl,
241 -- so as to maximise usefulness of error messages
242 getInitialKind (L _ decl)
243 = do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl)
244 ; res_kind <- mk_res_kind decl
245 ; return (tcdName decl, mkArrowKinds arg_kinds res_kind) }
247 mk_arg_kind (UserTyVar _) = newKindVar
248 mk_arg_kind (KindedTyVar _ kind) = return kind
250 mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
251 -- On GADT-style declarations we allow a kind signature
252 -- data T :: *->* where { ... }
253 mk_res_kind other = return liftedTypeKind
257 kcSynDecls :: [SCC (LTyClDecl Name)]
258 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
259 [(Name,TcKind)]) -- Kind bindings
262 kcSynDecls (group : groups)
263 = do { (decl, nk) <- kcSynDecl group
264 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
265 ; return (decl:decls, nk:nks) }
268 kcSynDecl :: SCC (LTyClDecl Name)
269 -> TcM (LTyClDecl Name, -- Kind-annotated decls
270 (Name,TcKind)) -- Kind bindings
271 kcSynDecl (AcyclicSCC ldecl@(L loc decl))
272 = tcAddDeclCtxt decl $
273 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
274 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
275 <+> brackets (ppr k_tvs))
276 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
277 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
278 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
279 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
280 (unLoc (tcdLName decl), tc_kind)) })
282 kcSynDecl (CyclicSCC decls)
283 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
284 -- of out-of-scope tycons
286 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
288 ------------------------------------------------------------------------
289 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
290 -- Not used for type synonyms (see kcSynDecl)
292 kcTyClDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
293 = kcTyClDeclBody decl $ \ tvs' ->
294 do { ctxt' <- kcHsContext ctxt
295 ; cons' <- mappM (wrapLocM kc_con_decl) cons
296 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdCons = cons'}) }
298 kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res) = do
299 kcHsTyVars ex_tvs $ \ex_tvs' -> do
300 ex_ctxt' <- kcHsContext ex_ctxt
301 details' <- kc_con_details details
303 ResTyH98 -> return ResTyH98
304 ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
305 return (ConDecl name expl ex_tvs' ex_ctxt' details' res')
307 kc_con_details (PrefixCon btys)
308 = do { btys' <- mappM kc_larg_ty btys ; return (PrefixCon btys') }
309 kc_con_details (InfixCon bty1 bty2)
310 = do { bty1' <- kc_larg_ty bty1; bty2' <- kc_larg_ty bty2; return (InfixCon bty1' bty2') }
311 kc_con_details (RecCon fields)
312 = do { fields' <- mappM kc_field fields; return (RecCon fields') }
314 kc_field (fld, bty) = do { bty' <- kc_larg_ty bty ; return (fld, bty') }
316 kc_larg_ty bty = case new_or_data of
317 DataType -> kcHsSigType bty
318 NewType -> kcHsLiftedSigType bty
319 -- Can't allow an unlifted type for newtypes, because we're effectively
320 -- going to remove the constructor while coercing it to a lifted type.
321 -- And newtypes can't be bang'd
323 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs})
324 = kcTyClDeclBody decl $ \ tvs' ->
325 do { is_boot <- tcIsHsBoot
326 ; ctxt' <- kcHsContext ctxt
327 ; sigs' <- mappM (wrapLocM kc_sig) sigs
328 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs'}) }
330 kc_sig (TypeSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
331 ; return (TypeSig nm op_ty') }
332 kc_sig other_sig = return other_sig
334 kcTyClDecl decl@(ForeignType {})
337 kcTyClDeclBody :: TyClDecl Name
338 -> ([LHsTyVarBndr Name] -> TcM a)
340 -- getInitialKind has made a suitably-shaped kind for the type or class
341 -- Unpack it, and attribute those kinds to the type variables
342 -- Extend the env with bindings for the tyvars, taken from
343 -- the kind of the tycon/class. Give it to the thing inside, and
344 -- check the result kind matches
345 kcTyClDeclBody decl thing_inside
346 = tcAddDeclCtxt decl $
347 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
348 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
349 (kinds, _) = splitKindFunTys tc_kind
350 hs_tvs = tcdTyVars decl
351 kinded_tvs = ASSERT( length kinds >= length hs_tvs )
352 [ L loc (KindedTyVar (hsTyVarName tv) k)
353 | (L loc tv, k) <- zip hs_tvs kinds]
354 ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
358 %************************************************************************
360 \subsection{Type checking}
362 %************************************************************************
365 tcSynDecls :: (Name -> ArgVrcs) -> [LTyClDecl Name] -> TcM [TyThing]
366 tcSynDecls calc_vrcs [] = return []
367 tcSynDecls calc_vrcs (decl : decls)
368 = do { syn_tc <- addLocM (tcSynDecl calc_vrcs) decl
369 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls calc_vrcs decls)
370 ; return (syn_tc : syn_tcs) }
373 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
374 = tcTyVarBndrs tvs $ \ tvs' -> do
375 { traceTc (text "tcd1" <+> ppr tc_name)
376 ; rhs_ty' <- tcHsKindedType rhs_ty
377 ; return (ATyCon (buildSynTyCon tc_name tvs' rhs_ty' (calc_vrcs tc_name))) }
380 tcTyClDecl :: (Name -> ArgVrcs) -> (Name -> RecFlag)
381 -> TyClDecl Name -> TcM TyThing
383 tcTyClDecl calc_vrcs calc_isrec decl
384 = tcAddDeclCtxt decl (tcTyClDecl1 calc_vrcs calc_isrec decl)
386 tcTyClDecl1 calc_vrcs calc_isrec
387 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
388 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
389 = tcTyVarBndrs tvs $ \ tvs' -> do
390 { extra_tvs <- tcDataKindSig mb_ksig
391 ; let final_tvs = tvs' ++ extra_tvs
392 ; stupid_theta <- tcHsKindedContext ctxt
393 ; want_generic <- doptM Opt_Generics
394 ; unbox_strict <- doptM Opt_UnboxStrictFields
395 ; gla_exts <- doptM Opt_GlasgowExts
396 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
398 -- Check that we don't use GADT syntax in H98 world
399 ; checkTc (gla_exts || h98_syntax) (badGadtDecl tc_name)
401 -- Check that there's at least one condecl,
402 -- or else we're reading an interface file, or -fglasgow-exts
403 ; checkTc (not (null cons) || gla_exts || is_boot)
404 (emptyConDeclsErr tc_name)
406 -- Check that a newtype has exactly one constructor
407 ; checkTc (new_or_data == DataType || isSingleton cons)
408 (newtypeConError tc_name (length cons))
410 ; tycon <- fixM (\ tycon -> do
411 { data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data
415 | null cons && is_boot -- In a hs-boot file, empty cons means
416 = AbstractTyCon -- "don't know"; hence Abstract
418 = case new_or_data of
419 DataType -> mkDataTyConRhs data_cons
420 NewType -> ASSERT( isSingleton data_cons )
421 mkNewTyConRhs tycon (head data_cons)
422 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs arg_vrcs is_rec
423 (want_generic && canDoGenerics data_cons)
425 ; return (ATyCon tycon)
428 arg_vrcs = calc_vrcs tc_name
429 is_rec = calc_isrec tc_name
430 h98_syntax = case cons of -- All constructors have same shape
431 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
434 tcTyClDecl1 calc_vrcs calc_isrec
435 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
436 tcdCtxt = ctxt, tcdMeths = meths,
437 tcdFDs = fundeps, tcdSigs = sigs} )
438 = tcTyVarBndrs tvs $ \ tvs' -> do
439 { ctxt' <- tcHsKindedContext ctxt
440 ; fds' <- mappM (addLocM tc_fundep) fundeps
441 ; sig_stuff <- tcClassSigs class_name sigs meths
442 ; clas <- fixM (\ clas ->
443 let -- This little knot is just so we can get
444 -- hold of the name of the class TyCon, which we
445 -- need to look up its recursiveness and variance
446 tycon_name = tyConName (classTyCon clas)
447 tc_isrec = calc_isrec tycon_name
448 tc_vrcs = calc_vrcs tycon_name
450 buildClass class_name tvs' ctxt' fds'
451 sig_stuff tc_isrec tc_vrcs)
452 ; return (AClass clas) }
454 tc_fundep (tvs1, tvs2) = do { tvs1' <- mappM tcLookupTyVar tvs1 ;
455 ; tvs2' <- mappM tcLookupTyVar tvs2 ;
456 ; return (tvs1', tvs2') }
459 tcTyClDecl1 calc_vrcs calc_isrec
460 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
461 = returnM (ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0 []))
463 -----------------------------------
464 tcConDecl :: Bool -- True <=> -funbox-strict_fields
465 -> NewOrData -> TyCon -> [TyVar]
466 -> ConDecl Name -> TcM DataCon
468 tcConDecl unbox_strict NewType tycon tc_tvs -- Newtypes
469 (ConDecl name _ ex_tvs ex_ctxt details ResTyH98)
470 = do { let tc_datacon field_lbls arg_ty
471 = do { arg_ty' <- tcHsKindedType arg_ty -- No bang on newtype
472 ; buildDataCon (unLoc name) False {- Prefix -}
473 True {- Vanilla -} [NotMarkedStrict]
474 (map unLoc field_lbls)
476 tycon (mkTyVarTys tc_tvs) }
478 -- Check that a newtype has no existential stuff
479 ; checkTc (null ex_tvs && null (unLoc ex_ctxt)) (newtypeExError name)
482 PrefixCon [arg_ty] -> tc_datacon [] arg_ty
483 RecCon [(field_lbl, arg_ty)] -> tc_datacon [field_lbl] arg_ty
484 other -> failWithTc (newtypeFieldErr name (length (hsConArgs details)))
485 -- Check that the constructor has exactly one field
488 tcConDecl unbox_strict DataType tycon tc_tvs -- Data types
489 (ConDecl name _ tvs ctxt details res_ty)
490 = tcTyVarBndrs tvs $ \ tvs' -> do
491 { ctxt' <- tcHsKindedContext ctxt
492 ; (data_tc, res_ty_args) <- tcResultType tycon tc_tvs res_ty
494 con_tvs = case res_ty of
495 ResTyH98 -> tc_tvs ++ tvs'
496 ResTyGADT _ -> tryVanilla tvs' res_ty_args
498 -- Vanilla iff result type matches the quantified vars exactly,
499 -- and there is no existential context
500 -- Must check the context too because of implicit params; e.g.
501 -- data T = (?x::Int) => MkT Int
502 is_vanilla = res_ty_args `tcEqTypes` mkTyVarTys con_tvs
505 tc_datacon is_infix field_lbls btys
506 = do { let bangs = map getBangStrictness btys
507 ; arg_tys <- mappM tcHsBangType btys
508 ; buildDataCon (unLoc name) is_infix is_vanilla
509 (argStrictness unbox_strict tycon bangs arg_tys)
510 (map unLoc field_lbls)
511 con_tvs ctxt' arg_tys
512 data_tc res_ty_args }
513 -- NB: we put data_tc, the type constructor gotten from the constructor
514 -- type signature into the data constructor; that way
515 -- checkValidDataCon can complain if it's wrong.
518 PrefixCon btys -> tc_datacon False [] btys
519 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
520 RecCon fields -> tc_datacon False field_names btys
522 (field_names, btys) = unzip fields
526 tcResultType :: TyCon -> [TyVar] -> ResType Name -> TcM (TyCon, [TcType])
527 tcResultType tycon tvs ResTyH98 = return (tycon, mkTyVarTys tvs)
528 tcResultType _ _ (ResTyGADT res_ty) = tcLHsConResTy res_ty
530 tryVanilla :: [TyVar] -> [TcType] -> [TyVar]
531 -- (tryVanilla tvs tys) returns a permutation of tvs.
532 -- It tries to re-order the tvs so that it exactly
533 -- matches the [Type], if that is possible
534 tryVanilla tvs (ty:tys) | Just tv <- tcGetTyVar_maybe ty -- The type is a tyvar
535 , tv `elem` tvs -- That tyvar is in the list
536 = tv : tryVanilla (delete tv tvs) tys
537 tryVanilla tvs tys = tvs -- Fall through case
541 argStrictness :: Bool -- True <=> -funbox-strict_fields
543 -> [TcType] -> [StrictnessMark]
544 argStrictness unbox_strict tycon bangs arg_tys
545 = ASSERT( length bangs == length arg_tys )
546 zipWith (chooseBoxingStrategy unbox_strict tycon) arg_tys bangs
548 -- We attempt to unbox/unpack a strict field when either:
549 -- (i) The field is marked '!!', or
550 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
552 chooseBoxingStrategy :: Bool -> TyCon -> TcType -> HsBang -> StrictnessMark
553 chooseBoxingStrategy unbox_strict_fields tycon arg_ty bang
555 HsNoBang -> NotMarkedStrict
556 HsStrict | unbox_strict_fields && can_unbox -> MarkedUnboxed
557 HsUnbox | can_unbox -> MarkedUnboxed
558 other -> MarkedStrict
560 can_unbox = case splitTyConApp_maybe arg_ty of
562 Just (arg_tycon, _) -> not (isRecursiveTyCon tycon) &&
563 isProductTyCon arg_tycon
566 %************************************************************************
568 \subsection{Dependency analysis}
570 %************************************************************************
572 Validity checking is done once the mutually-recursive knot has been
573 tied, so we can look at things freely.
576 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
577 checkCycleErrs tyclss
581 = do { mappM_ recClsErr cls_cycles
582 ; failM } -- Give up now, because later checkValidTyCl
583 -- will loop if the synonym is recursive
585 cls_cycles = calcClassCycles tyclss
587 checkValidTyCl :: TyClDecl Name -> TcM ()
588 -- We do the validity check over declarations, rather than TyThings
589 -- only so that we can add a nice context with tcAddDeclCtxt
591 = tcAddDeclCtxt decl $
592 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
593 ; traceTc (text "Validity of" <+> ppr thing)
595 ATyCon tc -> checkValidTyCon tc
596 AClass cl -> checkValidClass cl
597 ; traceTc (text "Done validity of" <+> ppr thing)
600 -------------------------
601 -- For data types declared with record syntax, we require
602 -- that each constructor that has a field 'f'
603 -- (a) has the same result type
604 -- (b) has the same type for 'f'
605 -- module alpha conversion of the quantified type variables
606 -- of the constructor.
608 checkValidTyCon :: TyCon -> TcM ()
611 = checkValidType syn_ctxt syn_rhs
613 = -- Check the context on the data decl
614 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
616 -- Check arg types of data constructors
617 mappM_ (checkValidDataCon tc) data_cons `thenM_`
619 -- Check that fields with the same name share a type
620 mappM_ check_fields groups
623 syn_ctxt = TySynCtxt name
625 syn_rhs = synTyConRhs tc
626 data_cons = tyConDataCons tc
628 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
629 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
630 get_fields con = dataConFieldLabels con `zip` repeat con
631 -- dataConFieldLabels may return the empty list, which is fine
633 -- Note: The complicated checkOne logic below is there to accomodate
634 -- for different return types. Add res_ty to the mix,
635 -- comparing them in two steps, all for good error messages.
636 -- Plan: Use Unify.tcMatchTys to compare the first candidate's
637 -- result type against other candidates' types (check bothways).
638 -- If they magically agrees, take the substitution and
639 -- apply them to the latter ones, and see if they match perfectly.
640 -- check_fields fields@((first_field_label, field_ty) : other_fields)
641 check_fields fields@((label, con1) : other_fields)
642 -- These fields all have the same name, but are from
643 -- different constructors in the data type
644 = recoverM (return ()) $ mapM_ checkOne other_fields
645 -- Check that all the fields in the group have the same type
646 -- NB: this check assumes that all the constructors of a given
647 -- data type use the same type variables
649 tvs1 = mkVarSet (dataConTyVars con1)
650 res1 = dataConResTys con1
651 fty1 = dataConFieldType con1 label
653 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
654 = do { checkFieldCompat label con1 con2 tvs1 res1 res2 fty1 fty2
655 ; checkFieldCompat label con2 con1 tvs2 res2 res1 fty2 fty1 }
657 tvs2 = mkVarSet (dataConTyVars con2)
658 res2 = dataConResTys con2
659 fty2 = dataConFieldType con2 label
661 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
662 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
663 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
665 mb_subst1 = tcMatchTys tvs1 res1 res2
666 mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
668 -------------------------------
669 checkValidDataCon :: TyCon -> DataCon -> TcM ()
670 checkValidDataCon tc con
671 = setSrcSpan (srcLocSpan (getSrcLoc con)) $
672 addErrCtxt (dataConCtxt con) $
673 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
674 ; checkValidType ctxt (idType (dataConWrapId con)) }
676 -- This checks the argument types and
677 -- ambiguity of the existential context (if any)
679 -- Note [Sept 04] Now that tvs is all the tvs, this
680 -- test doesn't actually check anything
681 -- ; checkFreeness tvs ex_theta }
683 ctxt = ConArgCtxt (dataConName con)
684 -- (tvs, ex_theta, _, _, _) = dataConSig con
687 -------------------------------
688 checkValidClass :: Class -> TcM ()
690 = do { -- CHECK ARITY 1 FOR HASKELL 1.4
691 gla_exts <- doptM Opt_GlasgowExts
693 -- Check that the class is unary, unless GlaExs
694 ; checkTc (notNull tyvars) (nullaryClassErr cls)
695 ; checkTc (gla_exts || unary) (classArityErr cls)
697 -- Check the super-classes
698 ; checkValidTheta (ClassSCCtxt (className cls)) theta
700 -- Check the class operations
701 ; mappM_ (check_op gla_exts) op_stuff
703 -- Check that if the class has generic methods, then the
704 -- class has only one parameter. We can't do generic
705 -- multi-parameter type classes!
706 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
709 (tyvars, theta, _, op_stuff) = classBigSig cls
710 unary = isSingleton tyvars
711 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
713 check_op gla_exts (sel_id, dm)
714 = addErrCtxt (classOpCtxt sel_id tau) $ do
715 { checkValidTheta SigmaCtxt (tail theta)
716 -- The 'tail' removes the initial (C a) from the
717 -- class itself, leaving just the method type
719 ; checkValidType (FunSigCtxt op_name) tau
721 -- Check that the type mentions at least one of
722 -- the class type variables
723 ; checkTc (any (`elemVarSet` tyVarsOfType tau) tyvars)
724 (noClassTyVarErr cls sel_id)
726 -- Check that for a generic method, the type of
727 -- the method is sufficiently simple
728 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
729 (badGenericMethodType op_name op_ty)
732 op_name = idName sel_id
733 op_ty = idType sel_id
734 (_,theta1,tau1) = tcSplitSigmaTy op_ty
735 (_,theta2,tau2) = tcSplitSigmaTy tau1
736 (theta,tau) | gla_exts = (theta1 ++ theta2, tau2)
737 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
738 -- Ugh! The function might have a type like
739 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
740 -- With -fglasgow-exts, we want to allow this, even though the inner
741 -- forall has an (Eq a) constraint. Whereas in general, each constraint
742 -- in the context of a for-all must mention at least one quantified
743 -- type variable. What a mess!
746 ---------------------------------------------------------------------
747 resultTypeMisMatch field_name con1 con2
748 = vcat [sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
749 ptext SLIT("have a common field") <+> quotes (ppr field_name) <> comma],
750 nest 2 $ ptext SLIT("but have different result types")]
751 fieldTypeMisMatch field_name con1 con2
752 = sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
753 ptext SLIT("give different types for field"), quotes (ppr field_name)]
755 dataConCtxt con = ptext SLIT("In the definition of data constructor") <+> quotes (ppr con)
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 newtypeConError tycon n
812 = sep [ptext SLIT("A newtype must have exactly one constructor,"),
813 nest 2 $ ptext SLIT("but") <+> quotes (ppr tycon) <+> ptext SLIT("has") <+> speakN n ]
816 = sep [ptext SLIT("A newtype constructor cannot have an existential context,"),
817 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
819 newtypeFieldErr con_name n_flds
820 = sep [ptext SLIT("The constructor of a newtype must have exactly one field"),
821 nest 2 $ ptext SLIT("but") <+> quotes (ppr con_name) <+> ptext SLIT("has") <+> speakN n_flds]
823 emptyConDeclsErr tycon
824 = sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
825 nest 2 $ ptext SLIT("(-fglasgow-exts permits this)")]