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, InstInfo )
28 import TcTyDecls ( 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, 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.
114 Identification of recursive TyCons
115 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
116 The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to
119 Identifying a TyCon as recursive serves two purposes
121 1. Avoid infinite types. Non-recursive newtypes are treated as
122 "transparent", like type synonyms, after the type checker. If we did
123 this for all newtypes, we'd get infinite types. So we figure out for
124 each newtype whether it is "recursive", and add a coercion if so. In
125 effect, we are trying to "cut the loops" by identifying a loop-breaker.
127 2. Avoid infinite unboxing. This is nothing to do with newtypes.
131 Well, this function diverges, but we don't want the strictness analyser
132 to diverge. But the strictness analyser will diverge because it looks
133 deeper and deeper into the structure of T. (I believe there are
134 examples where the function does something sane, and the strictness
135 analyser still diverges, but I can't see one now.)
137 Now, concerning (1), the FC2 branch currently adds a coercion for ALL
138 newtypes. I did this as an experiment, to try to expose cases in which
139 the coercions got in the way of optimisations. If it turns out that we
140 can indeed always use a coercion, then we don't risk recursive types,
141 and don't need to figure out what the loop breakers are.
143 For newtype *families* though, we will always have a coercion, so they
144 are always loop breakers! So you can easily adjust the current
145 algorithm by simply treating all newtype families as loop breakers (and
146 indeed type families). I think.
149 tcTyAndClassDecls :: ModDetails -> [LTyClDecl Name]
150 -> TcM TcGblEnv -- Input env extended by types and classes
151 -- and their implicit Ids,DataCons
152 tcTyAndClassDecls boot_details decls
153 = do { -- First check for cyclic type synonysm or classes
154 -- See notes with checkCycleErrs
157 ; traceTc (text "tcTyAndCl" <+> ppr mod)
158 ; (syn_tycons, alg_tyclss) <- fixM (\ ~(rec_syn_tycons, rec_alg_tyclss) ->
159 do { let { -- Calculate variances and rec-flag
160 ; (syn_decls, alg_decls) = partition (isSynDecl . unLoc)
162 -- Extend the global env with the knot-tied results
163 -- for data types and classes
165 -- We must populate the environment with the loop-tied T's right
166 -- away, because the kind checker may "fault in" some type
167 -- constructors that recursively mention T
168 ; let { gbl_things = mkGlobalThings alg_decls rec_alg_tyclss }
169 ; tcExtendRecEnv gbl_things $ do
171 -- Kind-check the declarations
172 { (kc_syn_decls, kc_alg_decls) <- kcTyClDecls syn_decls alg_decls
174 ; let { calc_rec = calcRecFlags boot_details rec_alg_tyclss
175 ; tc_decl = addLocM (tcTyClDecl calc_rec) }
176 -- Type-check the type synonyms, and extend the envt
177 ; syn_tycons <- tcSynDecls kc_syn_decls
178 ; tcExtendGlobalEnv syn_tycons $ do
180 -- Type-check the data types and classes
181 { alg_tyclss <- mappM tc_decl kc_alg_decls
182 ; return (syn_tycons, alg_tyclss)
184 -- Finished with knot-tying now
185 -- Extend the environment with the finished things
186 ; tcExtendGlobalEnv (syn_tycons ++ alg_tyclss) $ do
188 -- Perform the validity check
189 { traceTc (text "ready for validity check")
190 ; mappM_ (addLocM checkValidTyCl) decls
191 ; traceTc (text "done")
193 -- Add the implicit things;
194 -- we want them in the environment because
195 -- they may be mentioned in interface files
196 ; let { implicit_things = concatMap implicitTyThings alg_tyclss }
197 ; traceTc ((text "Adding" <+> ppr alg_tyclss) $$ (text "and" <+> ppr implicit_things))
198 ; tcExtendGlobalEnv implicit_things getGblEnv
201 mkGlobalThings :: [LTyClDecl Name] -- The decls
202 -> [TyThing] -- Knot-tied, in 1-1 correspondence with the decls
204 -- Driven by the Decls, and treating the TyThings lazily
205 -- make a TypeEnv for the new things
206 mkGlobalThings decls things
207 = map mk_thing (decls `zipLazy` things)
209 mk_thing (L _ (ClassDecl {tcdLName = L _ name}), ~(AClass cl))
211 mk_thing (L _ decl, ~(ATyCon tc))
212 = (tcdName decl, ATyCon tc)
216 %************************************************************************
220 %************************************************************************
222 We need to kind check all types in the mutually recursive group
223 before we know the kind of the type variables. For example:
226 op :: D b => a -> b -> b
229 bop :: (Monad c) => ...
231 Here, the kind of the locally-polymorphic type variable "b"
232 depends on *all the uses of class D*. For example, the use of
233 Monad c in bop's type signature means that D must have kind Type->Type.
235 However type synonyms work differently. They can have kinds which don't
236 just involve (->) and *:
237 type R = Int# -- Kind #
238 type S a = Array# a -- Kind * -> #
239 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
240 So we must infer their kinds from their right-hand sides *first* and then
241 use them, whereas for the mutually recursive data types D we bring into
242 scope kind bindings D -> k, where k is a kind variable, and do inference.
245 kcTyClDecls syn_decls alg_decls
246 = do { -- First extend the kind env with each data
247 -- type and class, mapping them to a type variable
248 alg_kinds <- mappM getInitialKind alg_decls
249 ; tcExtendKindEnv alg_kinds $ do
251 -- Now kind-check the type synonyms, in dependency order
252 -- We do these differently to data type and classes,
253 -- because a type synonym can be an unboxed type
255 -- and a kind variable can't unify with UnboxedTypeKind
256 -- So we infer their kinds in dependency order
257 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
258 ; tcExtendKindEnv syn_kinds $ do
260 -- Now kind-check the data type and class declarations,
261 -- returning kind-annotated decls
262 { kc_alg_decls <- mappM (wrapLocM kcTyClDecl) alg_decls
264 ; return (kc_syn_decls, kc_alg_decls) }}}
266 ------------------------------------------------------------------------
267 getInitialKind :: LTyClDecl Name -> TcM (Name, TcKind)
268 -- Only for data type and class declarations
269 -- Get as much info as possible from the data or class decl,
270 -- so as to maximise usefulness of error messages
271 getInitialKind (L _ decl)
272 = do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl)
273 ; res_kind <- mk_res_kind decl
274 ; return (tcdName decl, mkArrowKinds arg_kinds res_kind) }
276 mk_arg_kind (UserTyVar _) = newKindVar
277 mk_arg_kind (KindedTyVar _ kind) = return kind
279 mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
280 -- On GADT-style declarations we allow a kind signature
281 -- data T :: *->* where { ... }
282 mk_res_kind other = return liftedTypeKind
286 kcSynDecls :: [SCC (LTyClDecl Name)]
287 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
288 [(Name,TcKind)]) -- Kind bindings
291 kcSynDecls (group : groups)
292 = do { (decl, nk) <- kcSynDecl group
293 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
294 ; return (decl:decls, nk:nks) }
297 kcSynDecl :: SCC (LTyClDecl Name)
298 -> TcM (LTyClDecl Name, -- Kind-annotated decls
299 (Name,TcKind)) -- Kind bindings
300 kcSynDecl (AcyclicSCC ldecl@(L loc decl))
301 = tcAddDeclCtxt decl $
302 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
303 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
304 <+> brackets (ppr k_tvs))
305 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
306 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
307 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
308 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
309 (unLoc (tcdLName decl), tc_kind)) })
311 kcSynDecl (CyclicSCC decls)
312 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
313 -- of out-of-scope tycons
315 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
317 ------------------------------------------------------------------------
318 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
319 -- Not used for type synonyms (see kcSynDecl)
321 kcTyClDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
322 = kcTyClDeclBody decl $ \ tvs' ->
323 do { ctxt' <- kcHsContext ctxt
324 ; cons' <- mappM (wrapLocM kc_con_decl) cons
325 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdCons = cons'}) }
327 kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res) = do
328 kcHsTyVars ex_tvs $ \ex_tvs' -> do
329 ex_ctxt' <- kcHsContext ex_ctxt
330 details' <- kc_con_details details
332 ResTyH98 -> return ResTyH98
333 ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
334 return (ConDecl name expl ex_tvs' ex_ctxt' details' res')
336 kc_con_details (PrefixCon btys)
337 = do { btys' <- mappM kc_larg_ty btys ; return (PrefixCon btys') }
338 kc_con_details (InfixCon bty1 bty2)
339 = do { bty1' <- kc_larg_ty bty1; bty2' <- kc_larg_ty bty2; return (InfixCon bty1' bty2') }
340 kc_con_details (RecCon fields)
341 = do { fields' <- mappM kc_field fields; return (RecCon fields') }
343 kc_field (fld, bty) = do { bty' <- kc_larg_ty bty ; return (fld, bty') }
345 kc_larg_ty bty = case new_or_data of
346 DataType -> kcHsSigType bty
347 NewType -> kcHsLiftedSigType bty
348 -- Can't allow an unlifted type for newtypes, because we're effectively
349 -- going to remove the constructor while coercing it to a lifted type.
350 -- And newtypes can't be bang'd
353 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs})
354 = kcTyClDeclBody decl $ \ tvs' ->
355 do { is_boot <- tcIsHsBoot
356 ; ctxt' <- kcHsContext ctxt
357 ; sigs' <- mappM (wrapLocM kc_sig) sigs
358 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs'}) }
360 kc_sig (TypeSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
361 ; return (TypeSig nm op_ty') }
362 kc_sig other_sig = return other_sig
364 kcTyClDecl decl@(ForeignType {})
367 kcTyClDeclBody :: TyClDecl Name
368 -> ([LHsTyVarBndr Name] -> TcM a)
370 -- getInitialKind has made a suitably-shaped kind for the type or class
371 -- Unpack it, and attribute those kinds to the type variables
372 -- Extend the env with bindings for the tyvars, taken from
373 -- the kind of the tycon/class. Give it to the thing inside, and
374 -- check the result kind matches
375 kcTyClDeclBody decl thing_inside
376 = tcAddDeclCtxt decl $
377 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
378 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
379 (kinds, _) = splitKindFunTys tc_kind
380 hs_tvs = tcdTyVars decl
381 kinded_tvs = ASSERT( length kinds >= length hs_tvs )
382 [ L loc (KindedTyVar (hsTyVarName tv) k)
383 | (L loc tv, k) <- zip hs_tvs kinds]
384 ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
388 %************************************************************************
390 \subsection{Type checking}
392 %************************************************************************
395 tcSynDecls :: [LTyClDecl Name] -> TcM [TyThing]
396 tcSynDecls [] = return []
397 tcSynDecls (decl : decls)
398 = do { syn_tc <- addLocM tcSynDecl decl
399 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls decls)
400 ; return (syn_tc : syn_tcs) }
403 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
404 = tcTyVarBndrs tvs $ \ tvs' -> do
405 { traceTc (text "tcd1" <+> ppr tc_name)
406 ; rhs_ty' <- tcHsKindedType rhs_ty
407 ; return (ATyCon (buildSynTyCon tc_name tvs' rhs_ty')) }
410 tcTyClDecl :: (Name -> RecFlag) -> TyClDecl Name -> TcM TyThing
412 tcTyClDecl calc_isrec decl
413 = tcAddDeclCtxt decl (tcTyClDecl1 calc_isrec decl)
415 tcTyClDecl1 calc_isrec
416 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
417 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
418 = tcTyVarBndrs tvs $ \ tvs' -> do
419 { extra_tvs <- tcDataKindSig mb_ksig
420 ; let final_tvs = tvs' ++ extra_tvs
421 ; stupid_theta <- tcHsKindedContext ctxt
422 ; want_generic <- doptM Opt_Generics
423 ; unbox_strict <- doptM Opt_UnboxStrictFields
424 ; gla_exts <- doptM Opt_GlasgowExts
425 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
427 -- Check that we don't use GADT syntax in H98 world
428 ; checkTc (gla_exts || h98_syntax) (badGadtDecl tc_name)
430 -- Check that there's at least one condecl,
431 -- or else we're reading an interface file, or -fglasgow-exts
432 ; checkTc (not (null cons) || gla_exts || is_boot)
433 (emptyConDeclsErr tc_name)
435 -- Check that a newtype has exactly one constructor
436 ; checkTc (new_or_data == DataType || isSingleton cons)
437 (newtypeConError tc_name (length cons))
439 ; tycon <- fixM (\ tycon -> do
440 { data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data
444 | null cons && is_boot -- In a hs-boot file, empty cons means
445 = AbstractTyCon -- "don't know"; hence Abstract
447 = case new_or_data of
448 DataType -> mkDataTyConRhs data_cons
449 NewType -> ASSERT( isSingleton data_cons )
450 mkNewTyConRhs tycon (head data_cons)
451 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
452 (want_generic && canDoGenerics data_cons)
454 ; return (ATyCon tycon)
457 is_rec = calc_isrec tc_name
458 h98_syntax = case cons of -- All constructors have same shape
459 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
462 tcTyClDecl1 calc_isrec
463 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
464 tcdCtxt = ctxt, tcdMeths = meths,
465 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
466 = tcTyVarBndrs tvs $ \ tvs' -> do
467 { ctxt' <- tcHsKindedContext ctxt
468 ; fds' <- mappM (addLocM tc_fundep) fundeps
469 -- !!!TODO: process `ats`; what do we want to store in the `Class'? -=chak
470 ; sig_stuff <- tcClassSigs class_name sigs meths
471 ; clas <- fixM (\ clas ->
472 let -- This little knot is just so we can get
473 -- hold of the name of the class TyCon, which we
474 -- need to look up its recursiveness and variance
475 tycon_name = tyConName (classTyCon clas)
476 tc_isrec = calc_isrec tycon_name
478 buildClass class_name tvs' ctxt' fds'
480 ; return (AClass clas) }
482 tc_fundep (tvs1, tvs2) = do { tvs1' <- mappM tcLookupTyVar tvs1 ;
483 ; tvs2' <- mappM tcLookupTyVar tvs2 ;
484 ; return (tvs1', tvs2') }
487 tcTyClDecl1 calc_isrec
488 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
489 = returnM (ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0))
491 -----------------------------------
492 tcConDecl :: Bool -- True <=> -funbox-strict_fields
493 -> NewOrData -> TyCon -> [TyVar]
494 -> ConDecl Name -> TcM DataCon
496 tcConDecl unbox_strict NewType tycon tc_tvs -- Newtypes
497 (ConDecl name _ ex_tvs ex_ctxt details ResTyH98)
498 = do { let tc_datacon field_lbls arg_ty
499 = do { arg_ty' <- tcHsKindedType arg_ty -- No bang on newtype
500 ; buildDataCon (unLoc name) False {- Prefix -}
501 True {- Vanilla -} [NotMarkedStrict]
502 (map unLoc field_lbls)
504 tycon (mkTyVarTys tc_tvs) }
506 -- Check that a newtype has no existential stuff
507 ; checkTc (null ex_tvs && null (unLoc ex_ctxt)) (newtypeExError name)
510 PrefixCon [arg_ty] -> tc_datacon [] arg_ty
511 RecCon [(field_lbl, arg_ty)] -> tc_datacon [field_lbl] arg_ty
512 other -> failWithTc (newtypeFieldErr name (length (hsConArgs details)))
513 -- Check that the constructor has exactly one field
516 tcConDecl unbox_strict DataType tycon tc_tvs -- Data types
517 (ConDecl name _ tvs ctxt details res_ty)
518 = tcTyVarBndrs tvs $ \ tvs' -> do
519 { ctxt' <- tcHsKindedContext ctxt
520 ; (data_tc, res_ty_args) <- tcResultType tycon tc_tvs res_ty
522 con_tvs = case res_ty of
523 ResTyH98 -> tc_tvs ++ tvs'
524 ResTyGADT _ -> tryVanilla tvs' res_ty_args
526 -- Vanilla iff result type matches the quantified vars exactly,
527 -- and there is no existential context
528 -- Must check the context too because of implicit params; e.g.
529 -- data T = (?x::Int) => MkT Int
530 is_vanilla = res_ty_args `tcEqTypes` mkTyVarTys con_tvs
533 tc_datacon is_infix field_lbls btys
534 = do { let bangs = map getBangStrictness btys
535 ; arg_tys <- mappM tcHsBangType btys
536 ; buildDataCon (unLoc name) is_infix is_vanilla
537 (argStrictness unbox_strict tycon bangs arg_tys)
538 (map unLoc field_lbls)
539 con_tvs ctxt' arg_tys
540 data_tc res_ty_args }
541 -- NB: we put data_tc, the type constructor gotten from the constructor
542 -- type signature into the data constructor; that way
543 -- checkValidDataCon can complain if it's wrong.
546 PrefixCon btys -> tc_datacon False [] btys
547 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
548 RecCon fields -> tc_datacon False field_names btys
550 (field_names, btys) = unzip fields
554 tcResultType :: TyCon -> [TyVar] -> ResType Name -> TcM (TyCon, [TcType])
555 tcResultType tycon tvs ResTyH98 = return (tycon, mkTyVarTys tvs)
556 tcResultType _ _ (ResTyGADT res_ty) = tcLHsConResTy res_ty
558 tryVanilla :: [TyVar] -> [TcType] -> [TyVar]
559 -- (tryVanilla tvs tys) returns a permutation of tvs.
560 -- It tries to re-order the tvs so that it exactly
561 -- matches the [Type], if that is possible
562 tryVanilla tvs (ty:tys) | Just tv <- tcGetTyVar_maybe ty -- The type is a tyvar
563 , tv `elem` tvs -- That tyvar is in the list
564 = tv : tryVanilla (delete tv tvs) tys
565 tryVanilla tvs tys = tvs -- Fall through case
569 argStrictness :: Bool -- True <=> -funbox-strict_fields
571 -> [TcType] -> [StrictnessMark]
572 argStrictness unbox_strict tycon bangs arg_tys
573 = ASSERT( length bangs == length arg_tys )
574 zipWith (chooseBoxingStrategy unbox_strict tycon) arg_tys bangs
576 -- We attempt to unbox/unpack a strict field when either:
577 -- (i) The field is marked '!!', or
578 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
580 chooseBoxingStrategy :: Bool -> TyCon -> TcType -> HsBang -> StrictnessMark
581 chooseBoxingStrategy unbox_strict_fields tycon arg_ty bang
583 HsNoBang -> NotMarkedStrict
584 HsStrict | unbox_strict_fields && can_unbox -> MarkedUnboxed
585 HsUnbox | can_unbox -> MarkedUnboxed
586 other -> MarkedStrict
588 can_unbox = case splitTyConApp_maybe arg_ty of
590 Just (arg_tycon, _) -> not (isRecursiveTyCon tycon) &&
591 isProductTyCon arg_tycon
594 %************************************************************************
596 \subsection{Dependency analysis}
598 %************************************************************************
600 Validity checking is done once the mutually-recursive knot has been
601 tied, so we can look at things freely.
604 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
605 checkCycleErrs tyclss
609 = do { mappM_ recClsErr cls_cycles
610 ; failM } -- Give up now, because later checkValidTyCl
611 -- will loop if the synonym is recursive
613 cls_cycles = calcClassCycles tyclss
615 checkValidTyCl :: TyClDecl Name -> TcM ()
616 -- We do the validity check over declarations, rather than TyThings
617 -- only so that we can add a nice context with tcAddDeclCtxt
619 = tcAddDeclCtxt decl $
620 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
621 ; traceTc (text "Validity of" <+> ppr thing)
623 ATyCon tc -> checkValidTyCon tc
624 AClass cl -> checkValidClass cl
625 ; traceTc (text "Done validity of" <+> ppr thing)
628 -------------------------
629 -- For data types declared with record syntax, we require
630 -- that each constructor that has a field 'f'
631 -- (a) has the same result type
632 -- (b) has the same type for 'f'
633 -- module alpha conversion of the quantified type variables
634 -- of the constructor.
636 checkValidTyCon :: TyCon -> TcM ()
639 = checkValidType syn_ctxt syn_rhs
641 = -- Check the context on the data decl
642 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
644 -- Check arg types of data constructors
645 mappM_ (checkValidDataCon tc) data_cons `thenM_`
647 -- Check that fields with the same name share a type
648 mappM_ check_fields groups
651 syn_ctxt = TySynCtxt name
653 syn_rhs = synTyConRhs tc
654 data_cons = tyConDataCons tc
656 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
657 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
658 get_fields con = dataConFieldLabels con `zip` repeat con
659 -- dataConFieldLabels may return the empty list, which is fine
661 -- Note: The complicated checkOne logic below is there to accomodate
662 -- for different return types. Add res_ty to the mix,
663 -- comparing them in two steps, all for good error messages.
664 -- Plan: Use Unify.tcMatchTys to compare the first candidate's
665 -- result type against other candidates' types (check bothways).
666 -- If they magically agrees, take the substitution and
667 -- apply them to the latter ones, and see if they match perfectly.
668 -- check_fields fields@((first_field_label, field_ty) : other_fields)
669 check_fields fields@((label, con1) : other_fields)
670 -- These fields all have the same name, but are from
671 -- different constructors in the data type
672 = recoverM (return ()) $ mapM_ checkOne other_fields
673 -- Check that all the fields in the group have the same type
674 -- NB: this check assumes that all the constructors of a given
675 -- data type use the same type variables
677 tvs1 = mkVarSet (dataConTyVars con1)
678 res1 = dataConResTys con1
679 fty1 = dataConFieldType con1 label
681 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
682 = do { checkFieldCompat label con1 con2 tvs1 res1 res2 fty1 fty2
683 ; checkFieldCompat label con2 con1 tvs2 res2 res1 fty2 fty1 }
685 tvs2 = mkVarSet (dataConTyVars con2)
686 res2 = dataConResTys con2
687 fty2 = dataConFieldType con2 label
689 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
690 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
691 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
693 mb_subst1 = tcMatchTys tvs1 res1 res2
694 mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
696 -------------------------------
697 checkValidDataCon :: TyCon -> DataCon -> TcM ()
698 checkValidDataCon tc con
699 = setSrcSpan (srcLocSpan (getSrcLoc con)) $
700 addErrCtxt (dataConCtxt con) $
701 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
702 ; checkValidType ctxt (idType (dataConWrapId con)) }
704 -- This checks the argument types and
705 -- ambiguity of the existential context (if any)
707 -- Note [Sept 04] Now that tvs is all the tvs, this
708 -- test doesn't actually check anything
709 -- ; checkFreeness tvs ex_theta }
711 ctxt = ConArgCtxt (dataConName con)
712 -- (tvs, ex_theta, _, _, _) = dataConSig con
715 -------------------------------
716 checkValidClass :: Class -> TcM ()
718 = do { -- CHECK ARITY 1 FOR HASKELL 1.4
719 gla_exts <- doptM Opt_GlasgowExts
721 -- Check that the class is unary, unless GlaExs
722 ; checkTc (notNull tyvars) (nullaryClassErr cls)
723 ; checkTc (gla_exts || unary) (classArityErr cls)
725 -- Check the super-classes
726 ; checkValidTheta (ClassSCCtxt (className cls)) theta
728 -- Check the class operations
729 ; mappM_ (check_op gla_exts) op_stuff
731 -- Check that if the class has generic methods, then the
732 -- class has only one parameter. We can't do generic
733 -- multi-parameter type classes!
734 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
736 -- Check that the class has no associated types, unless GlaExs
737 ; checkTc (gla_exts || no_ats) (badATDecl cls)
740 (tyvars, theta, _, op_stuff) = classBigSig cls
741 unary = isSingleton tyvars
742 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
743 no_ats = True -- !!!TODO: determine whether the class has ATs -=chak
745 check_op gla_exts (sel_id, dm)
746 = addErrCtxt (classOpCtxt sel_id tau) $ do
747 { checkValidTheta SigmaCtxt (tail theta)
748 -- The 'tail' removes the initial (C a) from the
749 -- class itself, leaving just the method type
751 ; checkValidType (FunSigCtxt op_name) tau
753 -- Check that the type mentions at least one of
754 -- the class type variables
755 ; checkTc (any (`elemVarSet` tyVarsOfType tau) tyvars)
756 (noClassTyVarErr cls sel_id)
758 -- Check that for a generic method, the type of
759 -- the method is sufficiently simple
760 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
761 (badGenericMethodType op_name op_ty)
764 op_name = idName sel_id
765 op_ty = idType sel_id
766 (_,theta1,tau1) = tcSplitSigmaTy op_ty
767 (_,theta2,tau2) = tcSplitSigmaTy tau1
768 (theta,tau) | gla_exts = (theta1 ++ theta2, tau2)
769 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
770 -- Ugh! The function might have a type like
771 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
772 -- With -fglasgow-exts, we want to allow this, even though the inner
773 -- forall has an (Eq a) constraint. Whereas in general, each constraint
774 -- in the context of a for-all must mention at least one quantified
775 -- type variable. What a mess!
778 ---------------------------------------------------------------------
779 resultTypeMisMatch field_name con1 con2
780 = vcat [sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
781 ptext SLIT("have a common field") <+> quotes (ppr field_name) <> comma],
782 nest 2 $ ptext SLIT("but have different result types")]
783 fieldTypeMisMatch field_name con1 con2
784 = sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
785 ptext SLIT("give different types for field"), quotes (ppr field_name)]
787 dataConCtxt con = ptext SLIT("In the definition of data constructor") <+> quotes (ppr con)
789 classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
790 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
793 = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
796 = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
797 parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
799 noClassTyVarErr clas op
800 = sep [ptext SLIT("The class method") <+> quotes (ppr op),
801 ptext SLIT("mentions none of the type variables of the class") <+>
802 ppr clas <+> hsep (map ppr (classTyVars clas))]
804 genericMultiParamErr clas
805 = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
806 ptext SLIT("cannot have generic methods")
808 badGenericMethodType op op_ty
809 = hang (ptext SLIT("Generic method type is too complex"))
810 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
811 ptext SLIT("You can only use type variables, arrows, lists, and tuples")])
814 = setSrcSpan (getLoc (head sorted_decls)) $
815 addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
816 nest 2 (vcat (map ppr_decl sorted_decls))])
818 sorted_decls = sortLocated syn_decls
819 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
822 = setSrcSpan (getLoc (head sorted_decls)) $
823 addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
824 nest 2 (vcat (map ppr_decl sorted_decls))])
826 sorted_decls = sortLocated cls_decls
827 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
829 sortLocated :: [Located a] -> [Located a]
830 sortLocated things = sortLe le things
832 le (L l1 _) (L l2 _) = l1 <= l2
834 badDataConTyCon data_con
835 = hang (ptext SLIT("Data constructor") <+> quotes (ppr data_con) <+>
836 ptext SLIT("returns type") <+> quotes (ppr (dataConTyCon data_con)))
837 2 (ptext SLIT("instead of its parent type"))
840 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
841 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow GADTs")) ]
843 newtypeConError tycon n
844 = sep [ptext SLIT("A newtype must have exactly one constructor,"),
845 nest 2 $ ptext SLIT("but") <+> quotes (ppr tycon) <+> ptext SLIT("has") <+> speakN n ]
848 = sep [ptext SLIT("A newtype constructor cannot have an existential context,"),
849 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
851 newtypeFieldErr con_name n_flds
852 = sep [ptext SLIT("The constructor of a newtype must have exactly one field"),
853 nest 2 $ ptext SLIT("but") <+> quotes (ppr con_name) <+> ptext SLIT("has") <+> speakN n_flds]
856 = vcat [ ptext SLIT("Illegal associated type declaration in") <+> quotes (ppr cl_name)
857 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow ATs")) ]
859 emptyConDeclsErr tycon
860 = sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
861 nest 2 $ ptext SLIT("(-fglasgow-exts permits this)")]