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, isClassDecl, 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)
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
324 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs})
325 = kcTyClDeclBody decl $ \ tvs' ->
326 do { is_boot <- tcIsHsBoot
327 ; ctxt' <- kcHsContext ctxt
328 ; sigs' <- mappM (wrapLocM kc_sig) sigs
329 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs'}) }
331 kc_sig (TypeSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
332 ; return (TypeSig nm op_ty') }
333 kc_sig other_sig = return other_sig
335 kcTyClDecl decl@(ForeignType {})
338 kcTyClDeclBody :: TyClDecl Name
339 -> ([LHsTyVarBndr Name] -> TcM a)
341 -- getInitialKind has made a suitably-shaped kind for the type or class
342 -- Unpack it, and attribute those kinds to the type variables
343 -- Extend the env with bindings for the tyvars, taken from
344 -- the kind of the tycon/class. Give it to the thing inside, and
345 -- check the result kind matches
346 kcTyClDeclBody decl thing_inside
347 = tcAddDeclCtxt decl $
348 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
349 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
350 (kinds, _) = splitKindFunTys tc_kind
351 hs_tvs = tcdTyVars decl
352 kinded_tvs = ASSERT( length kinds >= length hs_tvs )
353 [ L loc (KindedTyVar (hsTyVarName tv) k)
354 | (L loc tv, k) <- zip hs_tvs kinds]
355 ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
359 %************************************************************************
361 \subsection{Type checking}
363 %************************************************************************
366 tcSynDecls :: (Name -> ArgVrcs) -> [LTyClDecl Name] -> TcM [TyThing]
367 tcSynDecls calc_vrcs [] = return []
368 tcSynDecls calc_vrcs (decl : decls)
369 = do { syn_tc <- addLocM (tcSynDecl calc_vrcs) decl
370 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls calc_vrcs decls)
371 ; return (syn_tc : syn_tcs) }
374 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
375 = tcTyVarBndrs tvs $ \ tvs' -> do
376 { traceTc (text "tcd1" <+> ppr tc_name)
377 ; rhs_ty' <- tcHsKindedType rhs_ty
378 ; return (ATyCon (buildSynTyCon tc_name tvs' rhs_ty' (calc_vrcs tc_name))) }
381 tcTyClDecl :: (Name -> ArgVrcs) -> (Name -> RecFlag)
382 -> TyClDecl Name -> TcM TyThing
384 tcTyClDecl calc_vrcs calc_isrec decl
385 = tcAddDeclCtxt decl (tcTyClDecl1 calc_vrcs calc_isrec decl)
387 tcTyClDecl1 calc_vrcs calc_isrec
388 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
389 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
390 = tcTyVarBndrs tvs $ \ tvs' -> do
391 { extra_tvs <- tcDataKindSig mb_ksig
392 ; let final_tvs = tvs' ++ extra_tvs
393 ; stupid_theta <- tcHsKindedContext ctxt
394 ; want_generic <- doptM Opt_Generics
395 ; unbox_strict <- doptM Opt_UnboxStrictFields
396 ; gla_exts <- doptM Opt_GlasgowExts
397 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
399 -- Check that we don't use GADT syntax in H98 world
400 ; checkTc (gla_exts || h98_syntax) (badGadtDecl tc_name)
402 -- Check that there's at least one condecl,
403 -- or else we're reading an interface file, or -fglasgow-exts
404 ; checkTc (not (null cons) || gla_exts || is_boot)
405 (emptyConDeclsErr tc_name)
407 -- Check that a newtype has exactly one constructor
408 ; checkTc (new_or_data == DataType || isSingleton cons)
409 (newtypeConError tc_name (length cons))
411 ; tycon <- fixM (\ tycon -> do
412 { data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data
416 | null cons && is_boot -- In a hs-boot file, empty cons means
417 = AbstractTyCon -- "don't know"; hence Abstract
419 = case new_or_data of
420 DataType -> mkDataTyConRhs data_cons
421 NewType -> ASSERT( isSingleton data_cons )
422 mkNewTyConRhs tycon (head data_cons)
423 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs arg_vrcs is_rec
424 (want_generic && canDoGenerics data_cons)
426 ; return (ATyCon tycon)
429 arg_vrcs = calc_vrcs tc_name
430 is_rec = calc_isrec tc_name
431 h98_syntax = case cons of -- All constructors have same shape
432 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
435 tcTyClDecl1 calc_vrcs calc_isrec
436 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
437 tcdCtxt = ctxt, tcdMeths = meths,
438 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
439 = tcTyVarBndrs tvs $ \ tvs' -> do
440 { ctxt' <- tcHsKindedContext ctxt
441 ; fds' <- mappM (addLocM tc_fundep) fundeps
442 -- !!!TODO: process `ats`; what do we want to store in the `Class'? -=chak
443 ; sig_stuff <- tcClassSigs class_name sigs meths
444 ; clas <- fixM (\ clas ->
445 let -- This little knot is just so we can get
446 -- hold of the name of the class TyCon, which we
447 -- need to look up its recursiveness and variance
448 tycon_name = tyConName (classTyCon clas)
449 tc_isrec = calc_isrec tycon_name
450 tc_vrcs = calc_vrcs tycon_name
452 buildClass class_name tvs' ctxt' fds'
453 sig_stuff tc_isrec tc_vrcs)
454 ; return (AClass clas) }
456 tc_fundep (tvs1, tvs2) = do { tvs1' <- mappM tcLookupTyVar tvs1 ;
457 ; tvs2' <- mappM tcLookupTyVar tvs2 ;
458 ; return (tvs1', tvs2') }
461 tcTyClDecl1 calc_vrcs calc_isrec
462 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
463 = returnM (ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0 []))
465 -----------------------------------
466 tcConDecl :: Bool -- True <=> -funbox-strict_fields
467 -> NewOrData -> TyCon -> [TyVar]
468 -> ConDecl Name -> TcM DataCon
470 tcConDecl unbox_strict NewType tycon tc_tvs -- Newtypes
471 (ConDecl name _ ex_tvs ex_ctxt details ResTyH98)
472 = do { let tc_datacon field_lbls arg_ty
473 = do { arg_ty' <- tcHsKindedType arg_ty -- No bang on newtype
474 ; buildDataCon (unLoc name) False {- Prefix -}
475 True {- Vanilla -} [NotMarkedStrict]
476 (map unLoc field_lbls)
478 tycon (mkTyVarTys tc_tvs) }
480 -- Check that a newtype has no existential stuff
481 ; checkTc (null ex_tvs && null (unLoc ex_ctxt)) (newtypeExError name)
484 PrefixCon [arg_ty] -> tc_datacon [] arg_ty
485 RecCon [(field_lbl, arg_ty)] -> tc_datacon [field_lbl] arg_ty
486 other -> failWithTc (newtypeFieldErr name (length (hsConArgs details)))
487 -- Check that the constructor has exactly one field
490 tcConDecl unbox_strict DataType tycon tc_tvs -- Data types
491 (ConDecl name _ tvs ctxt details res_ty)
492 = tcTyVarBndrs tvs $ \ tvs' -> do
493 { ctxt' <- tcHsKindedContext ctxt
494 ; (data_tc, res_ty_args) <- tcResultType tycon tc_tvs res_ty
496 con_tvs = case res_ty of
497 ResTyH98 -> tc_tvs ++ tvs'
498 ResTyGADT _ -> tryVanilla tvs' res_ty_args
500 -- Vanilla iff result type matches the quantified vars exactly,
501 -- and there is no existential context
502 -- Must check the context too because of implicit params; e.g.
503 -- data T = (?x::Int) => MkT Int
504 is_vanilla = res_ty_args `tcEqTypes` mkTyVarTys con_tvs
507 tc_datacon is_infix field_lbls btys
508 = do { let bangs = map getBangStrictness btys
509 ; arg_tys <- mappM tcHsBangType btys
510 ; buildDataCon (unLoc name) is_infix is_vanilla
511 (argStrictness unbox_strict tycon bangs arg_tys)
512 (map unLoc field_lbls)
513 con_tvs ctxt' arg_tys
514 data_tc res_ty_args }
515 -- NB: we put data_tc, the type constructor gotten from the constructor
516 -- type signature into the data constructor; that way
517 -- checkValidDataCon can complain if it's wrong.
520 PrefixCon btys -> tc_datacon False [] btys
521 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
522 RecCon fields -> tc_datacon False field_names btys
524 (field_names, btys) = unzip fields
528 tcResultType :: TyCon -> [TyVar] -> ResType Name -> TcM (TyCon, [TcType])
529 tcResultType tycon tvs ResTyH98 = return (tycon, mkTyVarTys tvs)
530 tcResultType _ _ (ResTyGADT res_ty) = tcLHsConResTy res_ty
532 tryVanilla :: [TyVar] -> [TcType] -> [TyVar]
533 -- (tryVanilla tvs tys) returns a permutation of tvs.
534 -- It tries to re-order the tvs so that it exactly
535 -- matches the [Type], if that is possible
536 tryVanilla tvs (ty:tys) | Just tv <- tcGetTyVar_maybe ty -- The type is a tyvar
537 , tv `elem` tvs -- That tyvar is in the list
538 = tv : tryVanilla (delete tv tvs) tys
539 tryVanilla tvs tys = tvs -- Fall through case
543 argStrictness :: Bool -- True <=> -funbox-strict_fields
545 -> [TcType] -> [StrictnessMark]
546 argStrictness unbox_strict tycon bangs arg_tys
547 = ASSERT( length bangs == length arg_tys )
548 zipWith (chooseBoxingStrategy unbox_strict tycon) arg_tys bangs
550 -- We attempt to unbox/unpack a strict field when either:
551 -- (i) The field is marked '!!', or
552 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
554 chooseBoxingStrategy :: Bool -> TyCon -> TcType -> HsBang -> StrictnessMark
555 chooseBoxingStrategy unbox_strict_fields tycon arg_ty bang
557 HsNoBang -> NotMarkedStrict
558 HsStrict | unbox_strict_fields && can_unbox -> MarkedUnboxed
559 HsUnbox | can_unbox -> MarkedUnboxed
560 other -> MarkedStrict
562 can_unbox = case splitTyConApp_maybe arg_ty of
564 Just (arg_tycon, _) -> not (isRecursiveTyCon tycon) &&
565 isProductTyCon arg_tycon
568 %************************************************************************
570 \subsection{Dependency analysis}
572 %************************************************************************
574 Validity checking is done once the mutually-recursive knot has been
575 tied, so we can look at things freely.
578 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
579 checkCycleErrs tyclss
583 = do { mappM_ recClsErr cls_cycles
584 ; failM } -- Give up now, because later checkValidTyCl
585 -- will loop if the synonym is recursive
587 cls_cycles = calcClassCycles tyclss
589 checkValidTyCl :: TyClDecl Name -> TcM ()
590 -- We do the validity check over declarations, rather than TyThings
591 -- only so that we can add a nice context with tcAddDeclCtxt
593 = tcAddDeclCtxt decl $
594 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
595 ; traceTc (text "Validity of" <+> ppr thing)
597 ATyCon tc -> checkValidTyCon tc
598 AClass cl -> checkValidClass cl
599 ; traceTc (text "Done validity of" <+> ppr thing)
602 -------------------------
603 -- For data types declared with record syntax, we require
604 -- that each constructor that has a field 'f'
605 -- (a) has the same result type
606 -- (b) has the same type for 'f'
607 -- module alpha conversion of the quantified type variables
608 -- of the constructor.
610 checkValidTyCon :: TyCon -> TcM ()
613 = checkValidType syn_ctxt syn_rhs
615 = -- Check the context on the data decl
616 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
618 -- Check arg types of data constructors
619 mappM_ (checkValidDataCon tc) data_cons `thenM_`
621 -- Check that fields with the same name share a type
622 mappM_ check_fields groups
625 syn_ctxt = TySynCtxt name
627 syn_rhs = synTyConRhs tc
628 data_cons = tyConDataCons tc
630 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
631 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
632 get_fields con = dataConFieldLabels con `zip` repeat con
633 -- dataConFieldLabels may return the empty list, which is fine
635 -- Note: The complicated checkOne logic below is there to accomodate
636 -- for different return types. Add res_ty to the mix,
637 -- comparing them in two steps, all for good error messages.
638 -- Plan: Use Unify.tcMatchTys to compare the first candidate's
639 -- result type against other candidates' types (check bothways).
640 -- If they magically agrees, take the substitution and
641 -- apply them to the latter ones, and see if they match perfectly.
642 -- check_fields fields@((first_field_label, field_ty) : other_fields)
643 check_fields fields@((label, con1) : other_fields)
644 -- These fields all have the same name, but are from
645 -- different constructors in the data type
646 = recoverM (return ()) $ mapM_ checkOne other_fields
647 -- Check that all the fields in the group have the same type
648 -- NB: this check assumes that all the constructors of a given
649 -- data type use the same type variables
651 tvs1 = mkVarSet (dataConTyVars con1)
652 res1 = dataConResTys con1
653 fty1 = dataConFieldType con1 label
655 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
656 = do { checkFieldCompat label con1 con2 tvs1 res1 res2 fty1 fty2
657 ; checkFieldCompat label con2 con1 tvs2 res2 res1 fty2 fty1 }
659 tvs2 = mkVarSet (dataConTyVars con2)
660 res2 = dataConResTys con2
661 fty2 = dataConFieldType con2 label
663 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
664 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
665 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
667 mb_subst1 = tcMatchTys tvs1 res1 res2
668 mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
670 -------------------------------
671 checkValidDataCon :: TyCon -> DataCon -> TcM ()
672 checkValidDataCon tc con
673 = setSrcSpan (srcLocSpan (getSrcLoc con)) $
674 addErrCtxt (dataConCtxt con) $
675 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
676 ; checkValidType ctxt (idType (dataConWrapId con)) }
678 -- This checks the argument types and
679 -- ambiguity of the existential context (if any)
681 -- Note [Sept 04] Now that tvs is all the tvs, this
682 -- test doesn't actually check anything
683 -- ; checkFreeness tvs ex_theta }
685 ctxt = ConArgCtxt (dataConName con)
686 -- (tvs, ex_theta, _, _, _) = dataConSig con
689 -------------------------------
690 checkValidClass :: Class -> TcM ()
692 = do { -- CHECK ARITY 1 FOR HASKELL 1.4
693 gla_exts <- doptM Opt_GlasgowExts
695 -- Check that the class is unary, unless GlaExs
696 ; checkTc (notNull tyvars) (nullaryClassErr cls)
697 ; checkTc (gla_exts || unary) (classArityErr cls)
699 -- Check the super-classes
700 ; checkValidTheta (ClassSCCtxt (className cls)) theta
702 -- Check the class operations
703 ; mappM_ (check_op gla_exts) op_stuff
705 -- Check that if the class has generic methods, then the
706 -- class has only one parameter. We can't do generic
707 -- multi-parameter type classes!
708 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
710 -- Check that the class has no associated types, unless GlaExs
711 ; checkTc (gla_exts || no_ats) (badATDecl cls)
714 (tyvars, theta, _, op_stuff) = classBigSig cls
715 unary = isSingleton tyvars
716 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
717 no_ats = True -- !!!TODO: determine whether the class has ATs -=chak
719 check_op gla_exts (sel_id, dm)
720 = addErrCtxt (classOpCtxt sel_id tau) $ do
721 { checkValidTheta SigmaCtxt (tail theta)
722 -- The 'tail' removes the initial (C a) from the
723 -- class itself, leaving just the method type
725 ; checkValidType (FunSigCtxt op_name) tau
727 -- Check that the type mentions at least one of
728 -- the class type variables
729 ; checkTc (any (`elemVarSet` tyVarsOfType tau) tyvars)
730 (noClassTyVarErr cls sel_id)
732 -- Check that for a generic method, the type of
733 -- the method is sufficiently simple
734 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
735 (badGenericMethodType op_name op_ty)
738 op_name = idName sel_id
739 op_ty = idType sel_id
740 (_,theta1,tau1) = tcSplitSigmaTy op_ty
741 (_,theta2,tau2) = tcSplitSigmaTy tau1
742 (theta,tau) | gla_exts = (theta1 ++ theta2, tau2)
743 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
744 -- Ugh! The function might have a type like
745 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
746 -- With -fglasgow-exts, we want to allow this, even though the inner
747 -- forall has an (Eq a) constraint. Whereas in general, each constraint
748 -- in the context of a for-all must mention at least one quantified
749 -- type variable. What a mess!
752 ---------------------------------------------------------------------
753 resultTypeMisMatch field_name con1 con2
754 = vcat [sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
755 ptext SLIT("have a common field") <+> quotes (ppr field_name) <> comma],
756 nest 2 $ ptext SLIT("but have different result types")]
757 fieldTypeMisMatch field_name con1 con2
758 = sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
759 ptext SLIT("give different types for field"), quotes (ppr field_name)]
761 dataConCtxt con = ptext SLIT("In the definition of data constructor") <+> quotes (ppr con)
763 classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
764 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
767 = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
770 = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
771 parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
773 noClassTyVarErr clas op
774 = sep [ptext SLIT("The class method") <+> quotes (ppr op),
775 ptext SLIT("mentions none of the type variables of the class") <+>
776 ppr clas <+> hsep (map ppr (classTyVars clas))]
778 genericMultiParamErr clas
779 = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
780 ptext SLIT("cannot have generic methods")
782 badGenericMethodType op op_ty
783 = hang (ptext SLIT("Generic method type is too complex"))
784 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
785 ptext SLIT("You can only use type variables, arrows, lists, and tuples")])
788 = setSrcSpan (getLoc (head sorted_decls)) $
789 addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
790 nest 2 (vcat (map ppr_decl sorted_decls))])
792 sorted_decls = sortLocated syn_decls
793 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
796 = setSrcSpan (getLoc (head sorted_decls)) $
797 addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
798 nest 2 (vcat (map ppr_decl sorted_decls))])
800 sorted_decls = sortLocated cls_decls
801 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
803 sortLocated :: [Located a] -> [Located a]
804 sortLocated things = sortLe le things
806 le (L l1 _) (L l2 _) = l1 <= l2
808 badDataConTyCon data_con
809 = hang (ptext SLIT("Data constructor") <+> quotes (ppr data_con) <+>
810 ptext SLIT("returns type") <+> quotes (ppr (dataConTyCon data_con)))
811 2 (ptext SLIT("instead of its parent type"))
814 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
815 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow GADTs")) ]
817 newtypeConError tycon n
818 = sep [ptext SLIT("A newtype must have exactly one constructor,"),
819 nest 2 $ ptext SLIT("but") <+> quotes (ppr tycon) <+> ptext SLIT("has") <+> speakN n ]
822 = sep [ptext SLIT("A newtype constructor cannot have an existential context,"),
823 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
825 newtypeFieldErr con_name n_flds
826 = sep [ptext SLIT("The constructor of a newtype must have exactly one field"),
827 nest 2 $ ptext SLIT("but") <+> quotes (ppr con_name) <+> ptext SLIT("has") <+> speakN n_flds]
830 = vcat [ ptext SLIT("Illegal associated type declaration in") <+> quotes (ppr cl_name)
831 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow ATs")) ]
833 emptyConDeclsErr tycon
834 = sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
835 nest 2 $ ptext SLIT("(-fglasgow-exts permits this)")]