2 % (c) The AQUA Project, Glasgow University, 1996-1998
4 \section[TcTyClsDecls]{Typecheck type and class declarations}
8 tcTyAndClassDecls, tcIdxTyInstDecl
11 #include "HsVersions.h"
13 import HsSyn ( TyClDecl(..), HsConDetails(..), HsTyVarBndr(..),
14 ConDecl(..), Sig(..), NewOrData(..), ResType(..),
15 tyClDeclTyVars, isSynDecl, isClassDecl, isIdxTyDecl,
16 isKindSigDecl, hsConArgs, LTyClDecl, tcdName,
17 hsTyVarName, LHsTyVarBndr, LHsType, HsType(..),
20 import HsTypes ( HsBang(..), getBangStrictness, hsLTyVarNames )
21 import BasicTypes ( RecFlag(..), StrictnessMark(..) )
22 import HscTypes ( implicitTyThings, ModDetails )
23 import BuildTyCl ( buildClass, buildAlgTyCon, buildSynTyCon, buildDataCon,
24 mkDataTyConRhs, mkNewTyConRhs )
26 import TcEnv ( TyThing(..),
27 tcLookupLocated, tcLookupLocatedGlobal,
28 tcExtendGlobalEnv, tcExtendKindEnv,
29 tcExtendKindEnvTvs, newFamInstTyConName,
30 tcExtendRecEnv, tcLookupTyVar, tcLookupLocatedTyCon )
31 import TcTyDecls ( calcRecFlags, calcClassCycles, calcSynCycles )
32 import TcClassDcl ( tcClassSigs, tcAddDeclCtxt )
33 import TcHsType ( kcHsTyVars, kcHsLiftedSigType, kcHsType,
34 kcHsContext, tcTyVarBndrs, tcHsKindedType, tcHsKindedContext,
35 kcHsSigType, tcHsBangType, tcLHsConResTy,
36 tcDataKindSig, kcCheckHsType )
37 import TcMType ( newKindVar, checkValidTheta, checkValidType,
39 UserTypeCtxt(..), SourceTyCtxt(..) )
40 import TcType ( TcKind, TcType, Type, tyVarsOfType, mkPhiTy,
41 mkArrowKind, liftedTypeKind, mkTyVarTys,
42 tcSplitSigmaTy, tcEqTypes, tcGetTyVar_maybe )
43 import Type ( PredType(..), splitTyConApp_maybe, mkTyVarTy,
44 newTyConInstRhs, isLiftedTypeKind, Kind
45 -- pprParendType, pprThetaArrow
47 import Generics ( validGenericMethodType, canDoGenerics )
48 import Class ( Class, className, classTyCon, DefMeth(..), classBigSig, classTyVars )
49 import TyCon ( TyCon, AlgTyConRhs( AbstractTyCon, OpenDataTyCon,
51 SynTyConRhs( OpenSynTyCon, SynonymTyCon ),
52 tyConDataCons, mkForeignTyCon, isProductTyCon,
53 isRecursiveTyCon, isOpenTyCon,
54 tyConStupidTheta, synTyConRhs, isSynTyCon, tyConName,
55 isNewTyCon, isDataTyCon, tyConKind,
57 import DataCon ( DataCon, dataConUserType, dataConName,
58 dataConFieldLabels, dataConTyCon, dataConAllTyVars,
59 dataConFieldType, dataConResTys )
60 import Var ( TyVar, idType, idName )
61 import VarSet ( elemVarSet, mkVarSet )
62 import Name ( Name, getSrcLoc )
64 import Maybe ( isJust, fromJust, isNothing, catMaybes )
65 import Maybes ( expectJust )
66 import Monad ( unless )
67 import Unify ( tcMatchTys, tcMatchTyX )
68 import Util ( zipLazy, isSingleton, notNull, sortLe )
69 import List ( partition, elemIndex )
70 import SrcLoc ( Located(..), unLoc, getLoc, srcLocSpan,
72 import ListSetOps ( equivClasses, minusList )
73 import Digraph ( SCC(..) )
74 import DynFlags ( DynFlag( Opt_GlasgowExts, Opt_Generics,
75 Opt_UnboxStrictFields, Opt_IndexedTypes ) )
79 %************************************************************************
81 \subsection{Type checking for type and class declarations}
83 %************************************************************************
87 Consider a mutually-recursive group, binding
88 a type constructor T and a class C.
90 Step 1: getInitialKind
91 Construct a KindEnv by binding T and C to a kind variable
94 In that environment, do a kind check
96 Step 3: Zonk the kinds
98 Step 4: buildTyConOrClass
99 Construct an environment binding T to a TyCon and C to a Class.
100 a) Their kinds comes from zonking the relevant kind variable
101 b) Their arity (for synonyms) comes direct from the decl
102 c) The funcional dependencies come from the decl
103 d) The rest comes a knot-tied binding of T and C, returned from Step 4
104 e) The variances of the tycons in the group is calculated from
108 In this environment, walk over the decls, constructing the TyCons and Classes.
109 This uses in a strict way items (a)-(c) above, which is why they must
110 be constructed in Step 4. Feed the results back to Step 4.
111 For this step, pass the is-recursive flag as the wimp-out flag
115 Step 6: Extend environment
116 We extend the type environment with bindings not only for the TyCons and Classes,
117 but also for their "implicit Ids" like data constructors and class selectors
119 Step 7: checkValidTyCl
120 For a recursive group only, check all the decls again, just
121 to check all the side conditions on validity. We could not
122 do this before because we were in a mutually recursive knot.
124 Identification of recursive TyCons
125 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
126 The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to
129 Identifying a TyCon as recursive serves two purposes
131 1. Avoid infinite types. Non-recursive newtypes are treated as
132 "transparent", like type synonyms, after the type checker. If we did
133 this for all newtypes, we'd get infinite types. So we figure out for
134 each newtype whether it is "recursive", and add a coercion if so. In
135 effect, we are trying to "cut the loops" by identifying a loop-breaker.
137 2. Avoid infinite unboxing. This is nothing to do with newtypes.
141 Well, this function diverges, but we don't want the strictness analyser
142 to diverge. But the strictness analyser will diverge because it looks
143 deeper and deeper into the structure of T. (I believe there are
144 examples where the function does something sane, and the strictness
145 analyser still diverges, but I can't see one now.)
147 Now, concerning (1), the FC2 branch currently adds a coercion for ALL
148 newtypes. I did this as an experiment, to try to expose cases in which
149 the coercions got in the way of optimisations. If it turns out that we
150 can indeed always use a coercion, then we don't risk recursive types,
151 and don't need to figure out what the loop breakers are.
153 For newtype *families* though, we will always have a coercion, so they
154 are always loop breakers! So you can easily adjust the current
155 algorithm by simply treating all newtype families as loop breakers (and
156 indeed type families). I think.
159 tcTyAndClassDecls :: ModDetails -> [LTyClDecl Name]
160 -> TcM TcGblEnv -- Input env extended by types and classes
161 -- and their implicit Ids,DataCons
162 tcTyAndClassDecls boot_details allDecls
163 = do { -- Omit instances of indexed types; they are handled together
164 -- with the *heads* of class instances
165 ; let decls = filter (not . isIdxTyDecl . unLoc) allDecls
167 -- First check for cyclic type synonysm or classes
168 -- See notes with checkCycleErrs
169 ; checkCycleErrs decls
171 ; traceTc (text "tcTyAndCl" <+> ppr mod)
172 ; (syn_tycons, alg_tyclss) <- fixM (\ ~(rec_syn_tycons, rec_alg_tyclss) ->
173 do { let { -- Seperate ordinary synonyms from all other type and
174 -- class declarations and add all associated type
175 -- declarations from type classes. The latter is
176 -- required so that the temporary environment for the
177 -- knot includes all associated family declarations.
178 ; (syn_decls, alg_decls) = partition (isSynDecl . unLoc)
180 ; alg_at_decls = concatMap addATs alg_decls
182 -- Extend the global env with the knot-tied results
183 -- for data types and classes
185 -- We must populate the environment with the loop-tied
186 -- T's right away, because the kind checker may "fault
187 -- in" some type constructors that recursively
189 ; let gbl_things = mkGlobalThings alg_at_decls rec_alg_tyclss
190 ; tcExtendRecEnv gbl_things $ do
192 -- Kind-check the declarations
193 { (kc_syn_decls, kc_alg_decls) <- kcTyClDecls syn_decls alg_decls
195 ; let { -- Calculate rec-flag
196 ; calc_rec = calcRecFlags boot_details rec_alg_tyclss
197 ; tc_decl = addLocM (tcTyClDecl calc_rec) }
198 -- Type-check the type synonyms, and extend the envt
199 ; syn_tycons <- tcSynDecls kc_syn_decls
200 ; tcExtendGlobalEnv syn_tycons $ do
202 -- Type-check the data types and classes
203 { alg_tyclss <- mappM tc_decl kc_alg_decls
204 ; return (syn_tycons, concat alg_tyclss)
206 -- Finished with knot-tying now
207 -- Extend the environment with the finished things
208 ; tcExtendGlobalEnv (syn_tycons ++ alg_tyclss) $ do
210 -- Perform the validity check
211 { traceTc (text "ready for validity check")
212 ; mappM_ (addLocM checkValidTyCl) decls
213 ; traceTc (text "done")
215 -- Add the implicit things;
216 -- we want them in the environment because
217 -- they may be mentioned in interface files
218 -- NB: All associated types and their implicit things will be added a
219 -- second time here. This doesn't matter as the definitions are
221 ; let { implicit_things = concatMap implicitTyThings alg_tyclss }
222 ; traceTc ((text "Adding" <+> ppr alg_tyclss)
223 $$ (text "and" <+> ppr implicit_things))
224 ; tcExtendGlobalEnv implicit_things getGblEnv
227 -- Pull associated types out of class declarations, to tie them into the
229 -- NB: We put them in the same place in the list as `tcTyClDecl' will
230 -- eventually put the matching `TyThing's. That's crucial; otherwise,
231 -- the two argument lists of `mkGlobalThings' don't match up.
232 addATs decl@(L _ (ClassDecl {tcdATs = ats})) = decl : ats
235 mkGlobalThings :: [LTyClDecl Name] -- The decls
236 -> [TyThing] -- Knot-tied, in 1-1 correspondence with the decls
238 -- Driven by the Decls, and treating the TyThings lazily
239 -- make a TypeEnv for the new things
240 mkGlobalThings decls things
241 = map mk_thing (decls `zipLazy` things)
243 mk_thing (L _ (ClassDecl {tcdLName = L _ name}), ~(AClass cl))
245 mk_thing (L _ decl, ~(ATyCon tc))
246 = (tcdName decl, ATyCon tc)
250 %************************************************************************
252 \subsection{Type checking instances of indexed types}
254 %************************************************************************
256 Instances of indexed types are somewhat of a hybrid. They are processed
257 together with class instance heads, but can contain data constructors and hence
258 they share a lot of kinding and type checking code with ordinary algebraic
259 data types (and GADTs).
262 tcIdxTyInstDecl :: LTyClDecl Name -> TcM (Maybe TyThing) -- Nothing if error
263 tcIdxTyInstDecl (L loc decl)
264 = -- Prime error recovery, set source location
265 recoverM (returnM Nothing) $
268 do { -- indexed data types require -findexed-types and can't be in an
270 ; gla_exts <- doptM Opt_IndexedTypes
271 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
272 ; checkTc gla_exts $ badIdxTyDecl (tcdLName decl)
273 ; checkTc (not is_boot) $ badBootTyIdxDeclErr
275 -- perform kind and type checking
276 ; tcIdxTyInstDecl1 decl
279 tcIdxTyInstDecl1 :: TyClDecl Name -> TcM (Maybe TyThing) -- Nothing if error
281 tcIdxTyInstDecl1 (decl@TySynonym {})
282 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
283 do { -- check that the family declaration is for a synonym
284 unless (isSynTyCon family) $
285 addErr (wrongKindOfFamily family)
287 ; -- (1) kind check the right hand side of the type equation
288 ; k_rhs <- kcCheckHsType (tcdSynRhs decl) resKind
290 -- (2) type check type equation
291 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
292 ; t_typats <- mappM tcHsKindedType k_typats
293 ; t_rhs <- tcHsKindedType k_rhs
295 -- !!!of the form: forall t_tvs. (tcdLName decl) t_typats = t_rhs
296 ; return Nothing -- !!!TODO: need TyThing for indexed synonym
299 tcIdxTyInstDecl1 (decl@TyData {tcdND = new_or_data, tcdLName = L loc tc_name,
301 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
302 do { -- check that the family declaration is for the right kind
303 unless (new_or_data == NewType && isNewTyCon family ||
304 new_or_data == DataType && isDataTyCon family) $
305 addErr (wrongKindOfFamily family)
307 ; -- (1) kind check the data declaration as usual
308 ; k_decl <- kcDataDecl decl k_tvs
309 ; let k_ctxt = tcdCtxt k_decl
310 k_cons = tcdCons k_decl
312 -- result kind must be '*' (otherwise, we have too few patterns)
313 ; checkTc (isLiftedTypeKind resKind) $ tooFewParmsErr tc_name
315 -- (2) type check indexed data type declaration
316 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
317 ; unbox_strict <- doptM Opt_UnboxStrictFields
319 -- Check that we don't use GADT syntax for indexed types
320 ; checkTc h98_syntax (badGadtIdxTyDecl tc_name)
322 -- Check that a newtype has exactly one constructor
323 ; checkTc (new_or_data == DataType || isSingleton k_cons) $
324 newtypeConError tc_name (length k_cons)
326 ; t_typats <- mappM tcHsKindedType k_typats
327 ; stupid_theta <- tcHsKindedContext k_ctxt
329 ; rep_tc_name <- newFamInstTyConName tc_name (srcSpanStart loc)
330 ; tycon <- fixM (\ tycon -> do
331 { data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data
336 DataType -> return (mkDataTyConRhs data_cons)
337 NewType -> ASSERT( isSingleton data_cons )
338 mkNewTyConRhs tc_name tycon (head data_cons)
339 ; buildAlgTyCon rep_tc_name t_tvs stupid_theta tc_rhs Recursive
340 False h98_syntax (Just (family, t_typats))
341 -- We always assume that indexed types are recursive. Why?
342 -- (1) Due to their open nature, we can never be sure that a
343 -- further instance might not introduce a new recursive
344 -- dependency. (2) They are always valid loop breakers as
345 -- they involve a coercion.
349 ; return $ Just (ATyCon tycon)
352 h98_syntax = case cons of -- All constructors have same shape
353 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
356 -- Kind checking of indexed types
359 -- Kind check type patterns and kind annotate the embedded type variables.
361 -- * Here we check that a type instance matches its kind signature, but we do
362 -- not check whether there is a pattern for each type index; the latter
363 -- check is only required for type functions.
365 kcIdxTyPats :: TyClDecl Name
366 -> ([LHsTyVarBndr Name] -> [LHsType Name] -> Kind -> TyCon -> TcM a)
367 -- ^^kinded tvs ^^kinded ty pats ^^res kind
369 kcIdxTyPats decl thing_inside
370 = kcHsTyVars (tcdTyVars decl) $ \tvs ->
371 do { family <- tcLookupLocatedTyCon (tcdLName decl)
372 ; let { (kinds, resKind) = splitKindFunTys (tyConKind family)
373 ; hs_typats = fromJust $ tcdTyPats decl }
375 -- we may not have more parameters than the kind indicates
376 ; checkTc (length kinds >= length hs_typats) $
377 tooManyParmsErr (tcdLName decl)
379 -- type functions can have a higher-kinded result
380 ; let resultKind = mkArrowKinds (drop (length hs_typats) kinds) resKind
381 ; typats <- zipWithM kcCheckHsType hs_typats kinds
382 ; thing_inside tvs typats resultKind family
388 %************************************************************************
392 %************************************************************************
394 We need to kind check all types in the mutually recursive group
395 before we know the kind of the type variables. For example:
398 op :: D b => a -> b -> b
401 bop :: (Monad c) => ...
403 Here, the kind of the locally-polymorphic type variable "b"
404 depends on *all the uses of class D*. For example, the use of
405 Monad c in bop's type signature means that D must have kind Type->Type.
407 However type synonyms work differently. They can have kinds which don't
408 just involve (->) and *:
409 type R = Int# -- Kind #
410 type S a = Array# a -- Kind * -> #
411 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
412 So we must infer their kinds from their right-hand sides *first* and then
413 use them, whereas for the mutually recursive data types D we bring into
414 scope kind bindings D -> k, where k is a kind variable, and do inference.
418 This treatment of type synonyms only applies to Haskell 98-style synonyms.
419 General type functions can be recursive, and hence, appear in `alg_decls'.
421 The kind of an indexed type is solely determinded by its kind signature;
422 hence, only kind signatures participate in the construction of the initial
423 kind environment (as constructed by `getInitialKind'). In fact, we ignore
424 instances of indexed types altogether in the following. However, we need to
425 include the kind signatures of associated types into the construction of the
426 initial kind environment. (This is handled by `allDecls').
429 kcTyClDecls syn_decls alg_decls
430 = do { -- First extend the kind env with each data type, class, and
431 -- indexed type, mapping them to a type variable
432 let initialKindDecls = concat [allDecls decl | L _ decl <- alg_decls]
433 ; alg_kinds <- mappM getInitialKind initialKindDecls
434 ; tcExtendKindEnv alg_kinds $ do
436 -- Now kind-check the type synonyms, in dependency order
437 -- We do these differently to data type and classes,
438 -- because a type synonym can be an unboxed type
440 -- and a kind variable can't unify with UnboxedTypeKind
441 -- So we infer their kinds in dependency order
442 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
443 ; tcExtendKindEnv syn_kinds $ do
445 -- Now kind-check the data type, class, and kind signatures,
446 -- returning kind-annotated decls; we don't kind-check
447 -- instances of indexed types yet, but leave this to
449 { kc_alg_decls <- mappM (wrapLocM kcTyClDecl)
450 (filter (not . isIdxTyDecl . unLoc) alg_decls)
452 ; return (kc_syn_decls, kc_alg_decls) }}}
454 -- get all declarations relevant for determining the initial kind
456 allDecls (decl@ClassDecl {tcdATs = ats}) = decl : [ at
459 allDecls decl | isIdxTyDecl decl = []
462 ------------------------------------------------------------------------
463 getInitialKind :: TyClDecl Name -> TcM (Name, TcKind)
464 -- Only for data type, class, and indexed type declarations
465 -- Get as much info as possible from the data, class, or indexed type decl,
466 -- so as to maximise usefulness of error messages
468 = do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl)
469 ; res_kind <- mk_res_kind decl
470 ; return (tcdName decl, mkArrowKinds arg_kinds res_kind) }
472 mk_arg_kind (UserTyVar _) = newKindVar
473 mk_arg_kind (KindedTyVar _ kind) = return kind
475 mk_res_kind (TyFunction { tcdKind = kind }) = return kind
476 mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
477 -- On GADT-style and data signature declarations we allow a kind
479 -- data T :: *->* where { ... }
480 mk_res_kind other = return liftedTypeKind
484 kcSynDecls :: [SCC (LTyClDecl Name)]
485 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
486 [(Name,TcKind)]) -- Kind bindings
489 kcSynDecls (group : groups)
490 = do { (decl, nk) <- kcSynDecl group
491 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
492 ; return (decl:decls, nk:nks) }
495 kcSynDecl :: SCC (LTyClDecl Name)
496 -> TcM (LTyClDecl Name, -- Kind-annotated decls
497 (Name,TcKind)) -- Kind bindings
498 kcSynDecl (AcyclicSCC ldecl@(L loc decl))
499 = tcAddDeclCtxt decl $
500 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
501 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
502 <+> brackets (ppr k_tvs))
503 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
504 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
505 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
506 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
507 (unLoc (tcdLName decl), tc_kind)) })
509 kcSynDecl (CyclicSCC decls)
510 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
511 -- of out-of-scope tycons
513 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
515 ------------------------------------------------------------------------
516 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
517 -- Not used for type synonyms (see kcSynDecl)
519 kcTyClDecl decl@(TyData {})
520 = ASSERT( not . isJust $ tcdTyPats decl ) -- must not be instance of idx ty
521 kcTyClDeclBody decl $
524 kcTyClDecl decl@(TyFunction {})
525 = kcTyClDeclBody decl $ \ tvs' ->
526 return (decl {tcdTyVars = tvs'})
528 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs, tcdATs = ats})
529 = kcTyClDeclBody decl $ \ tvs' ->
530 do { is_boot <- tcIsHsBoot
531 ; ctxt' <- kcHsContext ctxt
532 ; ats' <- mappM (wrapLocM kcTyClDecl) ats
533 ; sigs' <- mappM (wrapLocM kc_sig ) sigs
534 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs',
537 kc_sig (TypeSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
538 ; return (TypeSig nm op_ty') }
539 kc_sig other_sig = return other_sig
541 kcTyClDecl decl@(ForeignType {})
544 kcTyClDeclBody :: TyClDecl Name
545 -> ([LHsTyVarBndr Name] -> TcM a)
547 -- getInitialKind has made a suitably-shaped kind for the type or class
548 -- Unpack it, and attribute those kinds to the type variables
549 -- Extend the env with bindings for the tyvars, taken from
550 -- the kind of the tycon/class. Give it to the thing inside, and
551 -- check the result kind matches
552 kcTyClDeclBody decl thing_inside
553 = tcAddDeclCtxt decl $
554 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
555 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
556 (kinds, _) = splitKindFunTys tc_kind
557 hs_tvs = tcdTyVars decl
558 kinded_tvs = ASSERT( length kinds >= length hs_tvs )
559 [ L loc (KindedTyVar (hsTyVarName tv) k)
560 | (L loc tv, k) <- zip hs_tvs kinds]
561 ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
563 -- Kind check a data declaration, assuming that we already extended the
564 -- kind environment with the type variables of the left-hand side (these
565 -- kinded type variables are also passed as the second parameter).
567 kcDataDecl :: TyClDecl Name -> [LHsTyVarBndr Name] -> TcM (TyClDecl Name)
568 kcDataDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
570 = do { ctxt' <- kcHsContext ctxt
571 ; cons' <- mappM (wrapLocM kc_con_decl) cons
572 ; return (decl {tcdTyVars = tvs, tcdCtxt = ctxt', tcdCons = cons'}) }
574 kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res) = do
575 kcHsTyVars ex_tvs $ \ex_tvs' -> do
576 ex_ctxt' <- kcHsContext ex_ctxt
577 details' <- kc_con_details details
579 ResTyH98 -> return ResTyH98
580 ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
581 return (ConDecl name expl ex_tvs' ex_ctxt' details' res')
583 kc_con_details (PrefixCon btys)
584 = do { btys' <- mappM kc_larg_ty btys ; return (PrefixCon btys') }
585 kc_con_details (InfixCon bty1 bty2)
586 = do { bty1' <- kc_larg_ty bty1; bty2' <- kc_larg_ty bty2; return (InfixCon bty1' bty2') }
587 kc_con_details (RecCon fields)
588 = do { fields' <- mappM kc_field fields; return (RecCon fields') }
590 kc_field (fld, bty) = do { bty' <- kc_larg_ty bty ; return (fld, bty') }
592 kc_larg_ty bty = case new_or_data of
593 DataType -> kcHsSigType bty
594 NewType -> kcHsLiftedSigType bty
595 -- Can't allow an unlifted type for newtypes, because we're effectively
596 -- going to remove the constructor while coercing it to a lifted type.
597 -- And newtypes can't be bang'd
601 %************************************************************************
603 \subsection{Type checking}
605 %************************************************************************
608 tcSynDecls :: [LTyClDecl Name] -> TcM [TyThing]
609 tcSynDecls [] = return []
610 tcSynDecls (decl : decls)
611 = do { syn_tc <- addLocM tcSynDecl decl
612 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls decls)
613 ; return (syn_tc : syn_tcs) }
616 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
617 = tcTyVarBndrs tvs $ \ tvs' -> do
618 { traceTc (text "tcd1" <+> ppr tc_name)
619 ; rhs_ty' <- tcHsKindedType rhs_ty
620 ; return (ATyCon (buildSynTyCon tc_name tvs' (SynonymTyCon rhs_ty'))) }
623 tcTyClDecl :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
625 tcTyClDecl calc_isrec decl
626 = tcAddDeclCtxt decl (tcTyClDecl1 calc_isrec decl)
628 -- kind signature for a type function
629 tcTyClDecl1 _calc_isrec
630 (TyFunction {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = kind})
631 = tcTyVarBndrs tvs $ \ tvs' -> do
632 { traceTc (text "type family: " <+> ppr tc_name)
633 ; gla_exts <- doptM Opt_IndexedTypes
635 -- Check that we don't use kind signatures without Glasgow extensions
636 ; checkTc gla_exts $ badSigTyDecl tc_name
638 ; return [ATyCon $ buildSynTyCon tc_name tvs' (OpenSynTyCon kind)]
641 -- kind signature for an indexed data type
642 tcTyClDecl1 _calc_isrec
643 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
644 tcdLName = L _ tc_name, tcdKindSig = Just ksig, tcdCons = []})
645 = tcTyVarBndrs tvs $ \ tvs' -> do
646 { traceTc (text "data/newtype family: " <+> ppr tc_name)
647 ; extra_tvs <- tcDataKindSig (Just ksig)
648 ; let final_tvs = tvs' ++ extra_tvs -- we may not need these
650 ; checkTc (null . unLoc $ ctxt) $ badKindSigCtxt tc_name
651 ; gla_exts <- doptM Opt_IndexedTypes
653 -- Check that we don't use kind signatures without Glasgow extensions
654 ; checkTc gla_exts $ badSigTyDecl tc_name
656 ; tycon <- buildAlgTyCon tc_name final_tvs []
658 DataType -> OpenDataTyCon
659 NewType -> OpenNewTyCon)
660 Recursive False True Nothing
661 ; return [ATyCon tycon]
664 tcTyClDecl1 calc_isrec
665 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
666 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
667 = tcTyVarBndrs tvs $ \ tvs' -> do
668 { extra_tvs <- tcDataKindSig mb_ksig
669 ; let final_tvs = tvs' ++ extra_tvs
670 ; stupid_theta <- tcHsKindedContext ctxt
671 ; want_generic <- doptM Opt_Generics
672 ; unbox_strict <- doptM Opt_UnboxStrictFields
673 ; gla_exts <- doptM Opt_GlasgowExts
674 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
676 -- Check that we don't use GADT syntax in H98 world
677 ; checkTc (gla_exts || h98_syntax) (badGadtDecl tc_name)
679 -- Check that we don't use kind signatures without Glasgow extensions
680 ; checkTc (gla_exts || isNothing mb_ksig) (badSigTyDecl tc_name)
682 -- Check that the stupid theta is empty for a GADT-style declaration
683 ; checkTc (null stupid_theta || h98_syntax) (badStupidTheta tc_name)
685 -- Check that there's at least one condecl,
686 -- or else we're reading an hs-boot file, or -fglasgow-exts
687 ; checkTc (not (null cons) || gla_exts || is_boot)
688 (emptyConDeclsErr tc_name)
690 -- Check that a newtype has exactly one constructor
691 ; checkTc (new_or_data == DataType || isSingleton cons)
692 (newtypeConError tc_name (length cons))
694 ; tycon <- fixM (\ tycon -> do
695 { data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data
699 if null cons && is_boot -- In a hs-boot file, empty cons means
700 then return AbstractTyCon -- "don't know"; hence Abstract
701 else case new_or_data of
702 DataType -> return (mkDataTyConRhs data_cons)
704 ASSERT( isSingleton data_cons )
705 mkNewTyConRhs tc_name tycon (head data_cons)
706 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
707 (want_generic && canDoGenerics data_cons) h98_syntax Nothing
709 ; return [ATyCon tycon]
712 is_rec = calc_isrec tc_name
713 h98_syntax = case cons of -- All constructors have same shape
714 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
717 tcTyClDecl1 calc_isrec
718 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
719 tcdCtxt = ctxt, tcdMeths = meths,
720 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
721 = tcTyVarBndrs tvs $ \ tvs' -> do
722 { ctxt' <- tcHsKindedContext ctxt
723 ; fds' <- mappM (addLocM tc_fundep) fundeps
724 ; atss <- mappM (addLocM (tcTyClDecl1 (const Recursive))) ats
725 ; let ats' = zipWith setTyThingPoss atss (map (tcdTyVars . unLoc) ats)
726 ; sig_stuff <- tcClassSigs class_name sigs meths
727 ; clas <- fixM (\ clas ->
728 let -- This little knot is just so we can get
729 -- hold of the name of the class TyCon, which we
730 -- need to look up its recursiveness
731 tycon_name = tyConName (classTyCon clas)
732 tc_isrec = calc_isrec tycon_name
734 buildClass class_name tvs' ctxt' fds' ats'
736 ; return (AClass clas : ats')
737 -- NB: Order is important due to the call to `mkGlobalThings' when
738 -- tying the the type and class declaration type checking knot.
741 tc_fundep (tvs1, tvs2) = do { tvs1' <- mappM tcLookupTyVar tvs1 ;
742 ; tvs2' <- mappM tcLookupTyVar tvs2 ;
743 ; return (tvs1', tvs2') }
745 -- For each AT argument compute the position of the corresponding class
746 -- parameter in the class head. This will later serve as a permutation
747 -- vector when checking the validity of instance declarations.
748 setTyThingPoss [ATyCon tycon] atTyVars =
749 let classTyVars = hsLTyVarNames tvs
751 . map (`elemIndex` classTyVars)
754 -- There will be no Nothing, as we already passed renaming
756 ATyCon (setTyConArgPoss tycon poss)
757 setTyThingPoss _ _ = panic "TcTyClsDecls.setTyThingPoss"
759 tcTyClDecl1 calc_isrec
760 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
761 = returnM [ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0)]
763 -----------------------------------
764 tcConDecl :: Bool -- True <=> -funbox-strict_fields
770 tcConDecl unbox_strict NewType tycon tc_tvs -- Newtypes
771 (ConDecl name _ ex_tvs ex_ctxt details ResTyH98)
772 = do { let tc_datacon field_lbls arg_ty
773 = do { arg_ty' <- tcHsKindedType arg_ty -- No bang on newtype
774 ; buildDataCon (unLoc name) False {- Prefix -}
776 (map unLoc field_lbls)
777 tc_tvs [] -- No existentials
778 [] [] -- No equalities, predicates
782 -- Check that a newtype has no existential stuff
783 ; checkTc (null ex_tvs && null (unLoc ex_ctxt)) (newtypeExError name)
786 PrefixCon [arg_ty] -> tc_datacon [] arg_ty
787 RecCon [(field_lbl, arg_ty)] -> tc_datacon [field_lbl] arg_ty
789 failWithTc (newtypeFieldErr name (length (hsConArgs details)))
790 -- Check that the constructor has exactly one field
793 tcConDecl unbox_strict DataType tycon tc_tvs -- Data types
794 (ConDecl name _ tvs ctxt details res_ty)
795 = tcTyVarBndrs tvs $ \ tvs' -> do
796 { ctxt' <- tcHsKindedContext ctxt
797 ; (univ_tvs, ex_tvs, eq_preds, data_tc) <- tcResultType tycon tc_tvs tvs' res_ty
799 tc_datacon is_infix field_lbls btys
800 = do { let bangs = map getBangStrictness btys
801 ; arg_tys <- mappM tcHsBangType btys
802 ; buildDataCon (unLoc name) is_infix
803 (argStrictness unbox_strict tycon bangs arg_tys)
804 (map unLoc field_lbls)
805 univ_tvs ex_tvs eq_preds ctxt' arg_tys
807 -- NB: we put data_tc, the type constructor gotten from the
808 -- constructor type signature into the data constructor;
809 -- that way checkValidDataCon can complain if it's wrong.
812 PrefixCon btys -> tc_datacon False [] btys
813 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
814 RecCon fields -> tc_datacon False field_names btys
816 (field_names, btys) = unzip fields
820 tcResultType :: TyCon
821 -> [TyVar] -- data T a b c = ...
822 -> [TyVar] -- where MkT :: forall a b c. ...
824 -> TcM ([TyVar], -- Universal
825 [TyVar], -- Existential
826 [(TyVar,Type)], -- Equality predicates
827 TyCon) -- TyCon given in the ResTy
828 -- We don't check that the TyCon given in the ResTy is
829 -- the same as the parent tycon, becuase we are in the middle
830 -- of a recursive knot; so it's postponed until checkValidDataCon
832 tcResultType decl_tycon tc_tvs dc_tvs ResTyH98
833 = return (tc_tvs, dc_tvs, [], decl_tycon)
834 -- In H98 syntax the dc_tvs are the existential ones
835 -- data T a b c = forall d e. MkT ...
836 -- The {a,b,c} are tc_tvs, and {d,e} are dc_tvs
838 tcResultType _ tc_tvs dc_tvs (ResTyGADT res_ty)
839 -- E.g. data T a b c where
840 -- MkT :: forall x y z. T (x,y) z z
842 -- ([a,z,c], [x,y], [a:=:(x,y), c:=:z], T)
844 = do { (dc_tycon, res_tys) <- tcLHsConResTy res_ty
845 -- NB: tc_tvs and dc_tvs are distinct
846 ; let univ_tvs = choose_univs [] tc_tvs res_tys
847 -- Each univ_tv is either a dc_tv or a tc_tv
848 ex_tvs = dc_tvs `minusList` univ_tvs
849 eq_spec = [ (tv, ty) | (tv,ty) <- univ_tvs `zip` res_tys,
851 ; return (univ_tvs, ex_tvs, eq_spec, dc_tycon) }
853 -- choose_univs uses the res_ty itself if it's a type variable
854 -- and hasn't already been used; otherwise it uses one of the tc_tvs
855 choose_univs used tc_tvs []
856 = ASSERT( null tc_tvs ) []
857 choose_univs used (tc_tv:tc_tvs) (res_ty:res_tys)
858 | Just tv <- tcGetTyVar_maybe res_ty, not (tv `elem` used)
859 = tv : choose_univs (tv:used) tc_tvs res_tys
861 = tc_tv : choose_univs used tc_tvs res_tys
864 argStrictness :: Bool -- True <=> -funbox-strict_fields
866 -> [TcType] -> [StrictnessMark]
867 argStrictness unbox_strict tycon bangs arg_tys
868 = ASSERT( length bangs == length arg_tys )
869 zipWith (chooseBoxingStrategy unbox_strict tycon) arg_tys bangs
871 -- We attempt to unbox/unpack a strict field when either:
872 -- (i) The field is marked '!!', or
873 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
875 -- We have turned off unboxing of newtypes because coercions make unboxing
876 -- and reboxing more complicated
877 chooseBoxingStrategy :: Bool -> TyCon -> TcType -> HsBang -> StrictnessMark
878 chooseBoxingStrategy unbox_strict_fields tycon arg_ty bang
880 HsNoBang -> NotMarkedStrict
881 HsStrict | unbox_strict_fields
882 && can_unbox arg_ty -> MarkedUnboxed
883 HsUnbox | can_unbox arg_ty -> MarkedUnboxed
884 other -> MarkedStrict
886 -- we can unbox if the type is a chain of newtypes with a product tycon
888 can_unbox arg_ty = case splitTyConApp_maybe arg_ty of
890 Just (arg_tycon, tycon_args) ->
891 not (isRecursiveTyCon tycon) &&
892 isProductTyCon arg_tycon &&
893 (if isNewTyCon arg_tycon then
894 can_unbox (newTyConInstRhs arg_tycon tycon_args)
898 %************************************************************************
900 \subsection{Dependency analysis}
902 %************************************************************************
904 Validity checking is done once the mutually-recursive knot has been
905 tied, so we can look at things freely.
908 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
909 checkCycleErrs tyclss
913 = do { mappM_ recClsErr cls_cycles
914 ; failM } -- Give up now, because later checkValidTyCl
915 -- will loop if the synonym is recursive
917 cls_cycles = calcClassCycles tyclss
919 checkValidTyCl :: TyClDecl Name -> TcM ()
920 -- We do the validity check over declarations, rather than TyThings
921 -- only so that we can add a nice context with tcAddDeclCtxt
923 = tcAddDeclCtxt decl $
924 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
925 ; traceTc (text "Validity of" <+> ppr thing)
927 ATyCon tc -> checkValidTyCon tc
928 AClass cl -> checkValidClass cl
929 ; traceTc (text "Done validity of" <+> ppr thing)
932 -------------------------
933 -- For data types declared with record syntax, we require
934 -- that each constructor that has a field 'f'
935 -- (a) has the same result type
936 -- (b) has the same type for 'f'
937 -- module alpha conversion of the quantified type variables
938 -- of the constructor.
940 checkValidTyCon :: TyCon -> TcM ()
943 = case synTyConRhs tc of
944 OpenSynTyCon _ -> return ()
945 SynonymTyCon ty -> checkValidType syn_ctxt ty
947 = -- Check the context on the data decl
948 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
950 -- Check arg types of data constructors
951 mappM_ (checkValidDataCon tc) data_cons `thenM_`
953 -- Check that fields with the same name share a type
954 mappM_ check_fields groups
957 syn_ctxt = TySynCtxt name
959 data_cons = tyConDataCons tc
961 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
962 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
963 get_fields con = dataConFieldLabels con `zip` repeat con
964 -- dataConFieldLabels may return the empty list, which is fine
966 -- See Note [GADT record selectors] in MkId.lhs
967 -- We must check (a) that the named field has the same
968 -- type in each constructor
969 -- (b) that those constructors have the same result type
971 -- However, the constructors may have differently named type variable
972 -- and (worse) we don't know how the correspond to each other. E.g.
973 -- C1 :: forall a b. { f :: a, g :: b } -> T a b
974 -- C2 :: forall d c. { f :: c, g :: c } -> T c d
976 -- So what we do is to ust Unify.tcMatchTys to compare the first candidate's
977 -- result type against other candidates' types BOTH WAYS ROUND.
978 -- If they magically agrees, take the substitution and
979 -- apply them to the latter ones, and see if they match perfectly.
980 check_fields fields@((label, con1) : other_fields)
981 -- These fields all have the same name, but are from
982 -- different constructors in the data type
983 = recoverM (return ()) $ mapM_ checkOne other_fields
984 -- Check that all the fields in the group have the same type
985 -- NB: this check assumes that all the constructors of a given
986 -- data type use the same type variables
988 tvs1 = mkVarSet (dataConAllTyVars con1)
989 res1 = dataConResTys con1
990 fty1 = dataConFieldType con1 label
992 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
993 = do { checkFieldCompat label con1 con2 tvs1 res1 res2 fty1 fty2
994 ; checkFieldCompat label con2 con1 tvs2 res2 res1 fty2 fty1 }
996 tvs2 = mkVarSet (dataConAllTyVars con2)
997 res2 = dataConResTys con2
998 fty2 = dataConFieldType con2 label
1000 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
1001 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
1002 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
1004 mb_subst1 = tcMatchTys tvs1 res1 res2
1005 mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
1007 -------------------------------
1008 checkValidDataCon :: TyCon -> DataCon -> TcM ()
1009 checkValidDataCon tc con
1010 = setSrcSpan (srcLocSpan (getSrcLoc con)) $
1011 addErrCtxt (dataConCtxt con) $
1012 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
1013 ; checkValidType ctxt (dataConUserType con) }
1015 ctxt = ConArgCtxt (dataConName con)
1017 -------------------------------
1018 checkValidClass :: Class -> TcM ()
1020 = do { -- CHECK ARITY 1 FOR HASKELL 1.4
1021 gla_exts <- doptM Opt_GlasgowExts
1023 -- Check that the class is unary, unless GlaExs
1024 ; checkTc (notNull tyvars) (nullaryClassErr cls)
1025 ; checkTc (gla_exts || unary) (classArityErr cls)
1027 -- Check the super-classes
1028 ; checkValidTheta (ClassSCCtxt (className cls)) theta
1030 -- Check the class operations
1031 ; mappM_ (check_op gla_exts) op_stuff
1033 -- Check that if the class has generic methods, then the
1034 -- class has only one parameter. We can't do generic
1035 -- multi-parameter type classes!
1036 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
1039 (tyvars, theta, _, op_stuff) = classBigSig cls
1040 unary = isSingleton tyvars
1041 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
1043 check_op gla_exts (sel_id, dm)
1044 = addErrCtxt (classOpCtxt sel_id tau) $ do
1045 { checkValidTheta SigmaCtxt (tail theta)
1046 -- The 'tail' removes the initial (C a) from the
1047 -- class itself, leaving just the method type
1049 ; checkValidType (FunSigCtxt op_name) tau
1051 -- Check that the type mentions at least one of
1052 -- the class type variables
1053 ; checkTc (any (`elemVarSet` tyVarsOfType tau) tyvars)
1054 (noClassTyVarErr cls sel_id)
1056 -- Check that for a generic method, the type of
1057 -- the method is sufficiently simple
1058 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
1059 (badGenericMethodType op_name op_ty)
1062 op_name = idName sel_id
1063 op_ty = idType sel_id
1064 (_,theta1,tau1) = tcSplitSigmaTy op_ty
1065 (_,theta2,tau2) = tcSplitSigmaTy tau1
1066 (theta,tau) | gla_exts = (theta1 ++ theta2, tau2)
1067 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
1068 -- Ugh! The function might have a type like
1069 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
1070 -- With -fglasgow-exts, we want to allow this, even though the inner
1071 -- forall has an (Eq a) constraint. Whereas in general, each constraint
1072 -- in the context of a for-all must mention at least one quantified
1073 -- type variable. What a mess!
1076 ---------------------------------------------------------------------
1077 resultTypeMisMatch field_name con1 con2
1078 = vcat [sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1079 ptext SLIT("have a common field") <+> quotes (ppr field_name) <> comma],
1080 nest 2 $ ptext SLIT("but have different result types")]
1081 fieldTypeMisMatch field_name con1 con2
1082 = sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1083 ptext SLIT("give different types for field"), quotes (ppr field_name)]
1085 dataConCtxt con = ptext SLIT("In the definition of data constructor") <+> quotes (ppr con)
1087 classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
1088 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
1091 = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
1094 = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
1095 parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
1097 noClassTyVarErr clas op
1098 = sep [ptext SLIT("The class method") <+> quotes (ppr op),
1099 ptext SLIT("mentions none of the type variables of the class") <+>
1100 ppr clas <+> hsep (map ppr (classTyVars clas))]
1102 genericMultiParamErr clas
1103 = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
1104 ptext SLIT("cannot have generic methods")
1106 badGenericMethodType op op_ty
1107 = hang (ptext SLIT("Generic method type is too complex"))
1108 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
1109 ptext SLIT("You can only use type variables, arrows, lists, and tuples")])
1112 = setSrcSpan (getLoc (head sorted_decls)) $
1113 addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
1114 nest 2 (vcat (map ppr_decl sorted_decls))])
1116 sorted_decls = sortLocated syn_decls
1117 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
1120 = setSrcSpan (getLoc (head sorted_decls)) $
1121 addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
1122 nest 2 (vcat (map ppr_decl sorted_decls))])
1124 sorted_decls = sortLocated cls_decls
1125 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
1127 sortLocated :: [Located a] -> [Located a]
1128 sortLocated things = sortLe le things
1130 le (L l1 _) (L l2 _) = l1 <= l2
1132 badDataConTyCon data_con
1133 = hang (ptext SLIT("Data constructor") <+> quotes (ppr data_con) <+>
1134 ptext SLIT("returns type") <+> quotes (ppr (dataConTyCon data_con)))
1135 2 (ptext SLIT("instead of its parent type"))
1138 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
1139 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow GADTs")) ]
1141 badStupidTheta tc_name
1142 = ptext SLIT("A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
1144 newtypeConError tycon n
1145 = sep [ptext SLIT("A newtype must have exactly one constructor,"),
1146 nest 2 $ ptext SLIT("but") <+> quotes (ppr tycon) <+> ptext SLIT("has") <+> speakN n ]
1149 = sep [ptext SLIT("A newtype constructor cannot have an existential context,"),
1150 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
1152 newtypeFieldErr con_name n_flds
1153 = sep [ptext SLIT("The constructor of a newtype must have exactly one field"),
1154 nest 2 $ ptext SLIT("but") <+> quotes (ppr con_name) <+> ptext SLIT("has") <+> speakN n_flds]
1156 badSigTyDecl tc_name
1157 = vcat [ ptext SLIT("Illegal kind signature") <+>
1158 quotes (ppr tc_name)
1159 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow indexed types")) ]
1161 badKindSigCtxt tc_name
1162 = vcat [ ptext SLIT("Illegal context in kind signature") <+>
1163 quotes (ppr tc_name)
1164 , nest 2 (parens $ ptext SLIT("Currently, kind signatures cannot have a context")) ]
1166 badIdxTyDecl tc_name
1167 = vcat [ ptext SLIT("Illegal indexed type instance for") <+>
1168 quotes (ppr tc_name)
1169 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow indexed types")) ]
1171 badGadtIdxTyDecl tc_name
1172 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+>
1173 quotes (ppr tc_name)
1174 , nest 2 (parens $ ptext SLIT("Indexed types cannot use GADT declarations")) ]
1176 tooManyParmsErr tc_name
1177 = ptext SLIT("Indexed type instance has too many parameters:") <+>
1178 quotes (ppr tc_name)
1180 tooFewParmsErr tc_name
1181 = ptext SLIT("Indexed type instance has too few parameters:") <+>
1182 quotes (ppr tc_name)
1184 badBootTyIdxDeclErr =
1185 ptext SLIT("Illegal indexed type instance in hs-boot file")
1187 wrongKindOfFamily family =
1188 ptext SLIT("Wrong category of type instance; declaration was for a") <+>
1191 kindOfFamily | isSynTyCon family = ptext SLIT("type synonym")
1192 | isDataTyCon family = ptext SLIT("data type")
1193 | isNewTyCon family = ptext SLIT("newtype")
1195 emptyConDeclsErr tycon
1196 = sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
1197 nest 2 $ ptext SLIT("(-fglasgow-exts permits this)")]