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, tcExtendKindEnvTvs,
29 tcExtendRecEnv, tcLookupTyVar, InstInfo )
30 import TcTyDecls ( calcRecFlags, calcClassCycles, calcSynCycles )
31 import TcClassDcl ( tcClassSigs, tcAddDeclCtxt )
32 import TcHsType ( kcHsTyVars, kcHsLiftedSigType, kcHsType,
33 kcHsContext, tcTyVarBndrs, tcHsKindedType, tcHsKindedContext,
34 kcHsSigType, tcHsBangType, tcLHsConResTy,
35 tcDataKindSig, kcCheckHsType )
36 import TcMType ( newKindVar, checkValidTheta, checkValidType,
38 UserTypeCtxt(..), SourceTyCtxt(..) )
39 import TcType ( TcKind, TcType, Type, tyVarsOfType, mkPhiTy,
40 mkArrowKind, liftedTypeKind, mkTyVarTys,
41 tcSplitSigmaTy, tcEqTypes, tcGetTyVar_maybe )
42 import Type ( PredType(..), splitTyConApp_maybe, mkTyVarTy,
43 newTyConInstRhs, isLiftedTypeKind, Kind
44 -- pprParendType, pprThetaArrow
46 import Generics ( validGenericMethodType, canDoGenerics )
47 import Class ( Class, className, classTyCon, DefMeth(..), classBigSig, classTyVars )
48 import TyCon ( TyCon, AlgTyConRhs( AbstractTyCon, OpenDataTyCon,
50 SynTyConRhs( OpenSynTyCon, SynonymTyCon ),
51 tyConDataCons, mkForeignTyCon, isProductTyCon,
52 isRecursiveTyCon, isOpenTyCon,
53 tyConStupidTheta, synTyConRhs, isSynTyCon, tyConName,
54 isNewTyCon, isDataTyCon, tyConKind,
56 import DataCon ( DataCon, dataConUserType, dataConName,
57 dataConFieldLabels, dataConTyCon, dataConAllTyVars,
58 dataConFieldType, dataConResTys )
59 import Var ( TyVar, idType, idName )
60 import VarSet ( elemVarSet, mkVarSet )
61 import Name ( Name, getSrcLoc )
63 import Maybe ( isJust, fromJust, isNothing, catMaybes )
64 import Maybes ( expectJust )
65 import Monad ( unless )
66 import Unify ( tcMatchTys, tcMatchTyX )
67 import Util ( zipLazy, isSingleton, notNull, sortLe )
68 import List ( partition, elemIndex )
69 import SrcLoc ( Located(..), unLoc, getLoc, srcLocSpan )
70 import ListSetOps ( equivClasses, minusList )
71 import Digraph ( SCC(..) )
72 import DynFlags ( DynFlag( Opt_GlasgowExts, Opt_Generics,
73 Opt_UnboxStrictFields ) )
77 %************************************************************************
79 \subsection{Type checking for type and class declarations}
81 %************************************************************************
85 Consider a mutually-recursive group, binding
86 a type constructor T and a class C.
88 Step 1: getInitialKind
89 Construct a KindEnv by binding T and C to a kind variable
92 In that environment, do a kind check
94 Step 3: Zonk the kinds
96 Step 4: buildTyConOrClass
97 Construct an environment binding T to a TyCon and C to a Class.
98 a) Their kinds comes from zonking the relevant kind variable
99 b) Their arity (for synonyms) comes direct from the decl
100 c) The funcional dependencies come from the decl
101 d) The rest comes a knot-tied binding of T and C, returned from Step 4
102 e) The variances of the tycons in the group is calculated from
106 In this environment, walk over the decls, constructing the TyCons and Classes.
107 This uses in a strict way items (a)-(c) above, which is why they must
108 be constructed in Step 4. Feed the results back to Step 4.
109 For this step, pass the is-recursive flag as the wimp-out flag
113 Step 6: Extend environment
114 We extend the type environment with bindings not only for the TyCons and Classes,
115 but also for their "implicit Ids" like data constructors and class selectors
117 Step 7: checkValidTyCl
118 For a recursive group only, check all the decls again, just
119 to check all the side conditions on validity. We could not
120 do this before because we were in a mutually recursive knot.
122 Identification of recursive TyCons
123 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
124 The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to
127 Identifying a TyCon as recursive serves two purposes
129 1. Avoid infinite types. Non-recursive newtypes are treated as
130 "transparent", like type synonyms, after the type checker. If we did
131 this for all newtypes, we'd get infinite types. So we figure out for
132 each newtype whether it is "recursive", and add a coercion if so. In
133 effect, we are trying to "cut the loops" by identifying a loop-breaker.
135 2. Avoid infinite unboxing. This is nothing to do with newtypes.
139 Well, this function diverges, but we don't want the strictness analyser
140 to diverge. But the strictness analyser will diverge because it looks
141 deeper and deeper into the structure of T. (I believe there are
142 examples where the function does something sane, and the strictness
143 analyser still diverges, but I can't see one now.)
145 Now, concerning (1), the FC2 branch currently adds a coercion for ALL
146 newtypes. I did this as an experiment, to try to expose cases in which
147 the coercions got in the way of optimisations. If it turns out that we
148 can indeed always use a coercion, then we don't risk recursive types,
149 and don't need to figure out what the loop breakers are.
151 For newtype *families* though, we will always have a coercion, so they
152 are always loop breakers! So you can easily adjust the current
153 algorithm by simply treating all newtype families as loop breakers (and
154 indeed type families). I think.
157 tcTyAndClassDecls :: ModDetails -> [LTyClDecl Name]
158 -> TcM TcGblEnv -- Input env extended by types and classes
159 -- and their implicit Ids,DataCons
160 tcTyAndClassDecls boot_details allDecls
161 = do { -- Omit instances of indexed types; they are handled together
162 -- with the *heads* of class instances
163 ; let decls = filter (not . isIdxTyDecl . unLoc) allDecls
165 -- First check for cyclic type synonysm or classes
166 -- See notes with checkCycleErrs
167 ; checkCycleErrs decls
169 ; traceTc (text "tcTyAndCl" <+> ppr mod)
170 ; (syn_tycons, alg_tyclss) <- fixM (\ ~(rec_syn_tycons, rec_alg_tyclss) ->
171 do { let { -- Seperate ordinary synonyms from all other type and
172 -- class declarations and add all associated type
173 -- declarations from type classes. The latter is
174 -- required so that the temporary environment for the
175 -- knot includes all associated family declarations.
176 ; (syn_decls, alg_decls) = partition (isSynDecl . unLoc)
178 ; alg_at_decls = concatMap addATs alg_decls
180 -- Extend the global env with the knot-tied results
181 -- for data types and classes
183 -- We must populate the environment with the loop-tied
184 -- T's right away, because the kind checker may "fault
185 -- in" some type constructors that recursively
187 ; let gbl_things = mkGlobalThings alg_at_decls rec_alg_tyclss
188 ; tcExtendRecEnv gbl_things $ do
190 -- Kind-check the declarations
191 { (kc_syn_decls, kc_alg_decls) <- kcTyClDecls syn_decls alg_decls
193 ; let { -- Calculate rec-flag
194 ; calc_rec = calcRecFlags boot_details rec_alg_tyclss
195 ; tc_decl = addLocM (tcTyClDecl calc_rec) }
196 -- Type-check the type synonyms, and extend the envt
197 ; syn_tycons <- tcSynDecls kc_syn_decls
198 ; tcExtendGlobalEnv syn_tycons $ do
200 -- Type-check the data types and classes
201 { alg_tyclss <- mappM tc_decl kc_alg_decls
202 ; return (syn_tycons, concat alg_tyclss)
204 -- Finished with knot-tying now
205 -- Extend the environment with the finished things
206 ; tcExtendGlobalEnv (syn_tycons ++ alg_tyclss) $ do
208 -- Perform the validity check
209 { traceTc (text "ready for validity check")
210 ; mappM_ (addLocM checkValidTyCl) decls
211 ; traceTc (text "done")
213 -- Add the implicit things;
214 -- we want them in the environment because
215 -- they may be mentioned in interface files
216 ; let { implicit_things = concatMap implicitTyThings alg_tyclss }
217 ; traceTc ((text "Adding" <+> ppr alg_tyclss)
218 $$ (text "and" <+> ppr implicit_things))
219 ; tcExtendGlobalEnv implicit_things getGblEnv
222 addATs decl@(L _ (ClassDecl {tcdATs = ats})) = decl : ats
225 mkGlobalThings :: [LTyClDecl Name] -- The decls
226 -> [TyThing] -- Knot-tied, in 1-1 correspondence with the decls
228 -- Driven by the Decls, and treating the TyThings lazily
229 -- make a TypeEnv for the new things
230 mkGlobalThings decls things
231 = map mk_thing (decls `zipLazy` things)
233 mk_thing (L _ (ClassDecl {tcdLName = L _ name}), ~(AClass cl))
235 mk_thing (L _ decl, ~(ATyCon tc))
236 = (tcdName decl, ATyCon tc)
240 %************************************************************************
242 \subsection{Type checking instances of indexed types}
244 %************************************************************************
246 Instances of indexed types are somewhat of a hybrid. They are processed
247 together with class instance heads, but can contain data constructors and hence
248 they share a lot of kinding and type checking code with ordinary algebraic
249 data types (and GADTs).
252 tcIdxTyInstDecl :: LTyClDecl Name
253 -> TcM (Maybe InstInfo, Maybe TyThing) -- Nothing if error
254 tcIdxTyInstDecl (L loc decl)
255 = -- Prime error recovery, set source location
256 recoverM (returnM (Nothing, Nothing)) $
259 do { -- indexed data types require -fglasgow-exts and can't be in an
261 ; gla_exts <- doptM Opt_GlasgowExts
262 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
263 ; checkTc gla_exts $ badIdxTyDecl (tcdLName decl)
264 ; checkTc (not is_boot) $ badBootTyIdxDeclErr
266 -- perform kind and type checking
267 ; tcIdxTyInstDecl1 decl
270 tcIdxTyInstDecl1 :: TyClDecl Name
271 -> TcM (Maybe InstInfo, Maybe TyThing) -- Nothing if error
273 tcIdxTyInstDecl1 (decl@TySynonym {})
274 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
275 do { -- check that the family declaration is for a synonym
276 unless (isSynTyCon family) $
277 addErr (wrongKindOfFamily family)
279 ; -- (1) kind check the right hand side of the type equation
280 ; k_rhs <- kcCheckHsType (tcdSynRhs decl) resKind
282 -- (2) type check type equation
283 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
284 ; t_typats <- mappM tcHsKindedType k_typats
285 ; t_rhs <- tcHsKindedType k_rhs
287 -- construct type rewrite rule
288 -- !!!of the form: forall t_tvs. (tcdLName decl) t_typats = t_rhs
289 ; return (Nothing, Nothing) -- !!!TODO: need InstInfo for eq axioms
292 tcIdxTyInstDecl1 (decl@TyData {tcdND = new_or_data, tcdLName = L loc tc_name,
294 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
295 do { -- check that the family declaration is for the right kind
296 unless (new_or_data == NewType && isNewTyCon family ||
297 new_or_data == DataType && isDataTyCon family) $
298 addErr (wrongKindOfFamily family)
300 ; -- (1) kind check the data declaration as usual
301 ; k_decl <- kcDataDecl decl k_tvs
302 ; let k_ctxt = tcdCtxt k_decl
303 k_cons = tcdCons k_decl
305 -- result kind must be '*' (otherwise, we have too few patterns)
306 ; checkTc (isLiftedTypeKind resKind) $ tooFewParmsErr tc_name
308 -- (2) type check indexed data type declaration
309 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
310 ; unbox_strict <- doptM Opt_UnboxStrictFields
312 -- Check that we don't use GADT syntax for indexed types
313 ; checkTc h98_syntax (badGadtIdxTyDecl tc_name)
315 -- Check that a newtype has exactly one constructor
316 ; checkTc (new_or_data == DataType || isSingleton k_cons) $
317 newtypeConError tc_name (length k_cons)
319 ; t_typats <- mappM tcHsKindedType k_typats
320 ; stupid_theta <- tcHsKindedContext k_ctxt
322 ; index <- nextDFunIndex -- to generate unique names
323 ; tycon <- fixM (\ tycon -> do
324 { data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data
329 DataType -> return (mkDataTyConRhs data_cons)
331 ASSERT( isSingleton data_cons )
332 mkNewTyConRhs tc_name tycon (head data_cons)
333 ; buildAlgTyCon tc_name t_tvs stupid_theta tc_rhs Recursive
334 False h98_syntax (Just (family, t_typats, index))
335 -- We always assume that indexed types are recursive. Why?
336 -- (1) Due to their open nature, we can never be sure that a
337 -- further instance might not introduce a new recursive
338 -- dependency. (2) They are always valid loop breakers as
339 -- they involve a coercion.
343 ; return (Nothing, Just (ATyCon tycon))
346 h98_syntax = case cons of -- All constructors have same shape
347 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
350 -- Kind checking of indexed types
353 -- Kind check type patterns and kind annotate the embedded type variables.
355 -- * Here we check that a type instance matches its kind signature, but we do
356 -- not check whether there is a pattern for each type index; the latter
357 -- check is only required for type functions.
359 kcIdxTyPats :: TyClDecl Name
360 -> ([LHsTyVarBndr Name] -> [LHsType Name] -> Kind -> TyCon -> TcM a)
361 -- ^^kinded tvs ^^kinded ty pats ^^res kind
363 kcIdxTyPats decl thing_inside
364 = kcHsTyVars (tcdTyVars decl) $ \tvs ->
365 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
366 ; let { family = case tc_ty_thing of
367 AGlobal (ATyCon family) -> family
368 ; (kinds, resKind) = splitKindFunTys (tyConKind family)
369 ; hs_typats = fromJust $ tcdTyPats decl }
371 -- we may not have more parameters than the kind indicates
372 ; checkTc (length kinds >= length hs_typats) $
373 tooManyParmsErr (tcdLName decl)
375 -- type functions can have a higher-kinded result
376 ; let resultKind = mkArrowKinds (drop (length hs_typats) kinds) resKind
377 ; typats <- zipWithM kcCheckHsType hs_typats kinds
378 ; thing_inside tvs typats resultKind family
384 %************************************************************************
388 %************************************************************************
390 We need to kind check all types in the mutually recursive group
391 before we know the kind of the type variables. For example:
394 op :: D b => a -> b -> b
397 bop :: (Monad c) => ...
399 Here, the kind of the locally-polymorphic type variable "b"
400 depends on *all the uses of class D*. For example, the use of
401 Monad c in bop's type signature means that D must have kind Type->Type.
403 However type synonyms work differently. They can have kinds which don't
404 just involve (->) and *:
405 type R = Int# -- Kind #
406 type S a = Array# a -- Kind * -> #
407 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
408 So we must infer their kinds from their right-hand sides *first* and then
409 use them, whereas for the mutually recursive data types D we bring into
410 scope kind bindings D -> k, where k is a kind variable, and do inference.
414 This treatment of type synonyms only applies to Haskell 98-style synonyms.
415 General type functions can be recursive, and hence, appear in `alg_decls'.
417 The kind of an indexed type is solely determinded by its kind signature;
418 hence, only kind signatures participate in the construction of the initial
419 kind environment (as constructed by `getInitialKind'). In fact, we ignore
420 instances of indexed types altogether in the following. However, we need to
421 include the kind signatures of associated types into the construction of the
422 initial kind environment. (This is handled by `allDecls').
425 kcTyClDecls syn_decls alg_decls
426 = do { -- First extend the kind env with each data type, class, and
427 -- indexed type, mapping them to a type variable
428 let initialKindDecls = concat [allDecls decl | L _ decl <- alg_decls]
429 ; alg_kinds <- mappM getInitialKind initialKindDecls
430 ; tcExtendKindEnv alg_kinds $ do
432 -- Now kind-check the type synonyms, in dependency order
433 -- We do these differently to data type and classes,
434 -- because a type synonym can be an unboxed type
436 -- and a kind variable can't unify with UnboxedTypeKind
437 -- So we infer their kinds in dependency order
438 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
439 ; tcExtendKindEnv syn_kinds $ do
441 -- Now kind-check the data type, class, and kind signatures,
442 -- returning kind-annotated decls; we don't kind-check
443 -- instances of indexed types yet, but leave this to
445 { kc_alg_decls <- mappM (wrapLocM kcTyClDecl)
446 (filter (not . isIdxTyDecl . unLoc) alg_decls)
448 ; return (kc_syn_decls, kc_alg_decls) }}}
450 -- get all declarations relevant for determining the initial kind
452 allDecls (decl@ClassDecl {tcdATs = ats}) = decl : [ at
455 allDecls decl | isIdxTyDecl decl = []
458 ------------------------------------------------------------------------
459 getInitialKind :: TyClDecl Name -> TcM (Name, TcKind)
460 -- Only for data type, class, and indexed type declarations
461 -- Get as much info as possible from the data, class, or indexed type decl,
462 -- so as to maximise usefulness of error messages
464 = do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl)
465 ; res_kind <- mk_res_kind decl
466 ; return (tcdName decl, mkArrowKinds arg_kinds res_kind) }
468 mk_arg_kind (UserTyVar _) = newKindVar
469 mk_arg_kind (KindedTyVar _ kind) = return kind
471 mk_res_kind (TyFunction { tcdKind = kind }) = return kind
472 mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
473 -- On GADT-style and data signature declarations we allow a kind
475 -- data T :: *->* where { ... }
476 mk_res_kind other = return liftedTypeKind
480 kcSynDecls :: [SCC (LTyClDecl Name)]
481 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
482 [(Name,TcKind)]) -- Kind bindings
485 kcSynDecls (group : groups)
486 = do { (decl, nk) <- kcSynDecl group
487 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
488 ; return (decl:decls, nk:nks) }
491 kcSynDecl :: SCC (LTyClDecl Name)
492 -> TcM (LTyClDecl Name, -- Kind-annotated decls
493 (Name,TcKind)) -- Kind bindings
494 kcSynDecl (AcyclicSCC ldecl@(L loc decl))
495 = tcAddDeclCtxt decl $
496 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
497 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
498 <+> brackets (ppr k_tvs))
499 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
500 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
501 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
502 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
503 (unLoc (tcdLName decl), tc_kind)) })
505 kcSynDecl (CyclicSCC decls)
506 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
507 -- of out-of-scope tycons
509 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
511 ------------------------------------------------------------------------
512 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
513 -- Not used for type synonyms (see kcSynDecl)
515 kcTyClDecl decl@(TyData {})
516 = ASSERT( not . isJust $ tcdTyPats decl ) -- must not be instance of idx ty
517 kcTyClDeclBody decl $
520 kcTyClDecl decl@(TyFunction {})
521 = kcTyClDeclBody decl $ \ tvs' ->
522 return (decl {tcdTyVars = tvs'})
524 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs, tcdATs = ats})
525 = kcTyClDeclBody decl $ \ tvs' ->
526 do { is_boot <- tcIsHsBoot
527 ; ctxt' <- kcHsContext ctxt
528 ; ats' <- mappM (wrapLocM kcTyClDecl) ats
529 ; sigs' <- mappM (wrapLocM kc_sig ) sigs
530 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs',
533 kc_sig (TypeSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
534 ; return (TypeSig nm op_ty') }
535 kc_sig other_sig = return other_sig
537 kcTyClDecl decl@(ForeignType {})
540 kcTyClDeclBody :: TyClDecl Name
541 -> ([LHsTyVarBndr Name] -> TcM a)
543 -- getInitialKind has made a suitably-shaped kind for the type or class
544 -- Unpack it, and attribute those kinds to the type variables
545 -- Extend the env with bindings for the tyvars, taken from
546 -- the kind of the tycon/class. Give it to the thing inside, and
547 -- check the result kind matches
548 kcTyClDeclBody decl thing_inside
549 = tcAddDeclCtxt decl $
550 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
551 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
552 (kinds, _) = splitKindFunTys tc_kind
553 hs_tvs = tcdTyVars decl
554 kinded_tvs = ASSERT( length kinds >= length hs_tvs )
555 [ L loc (KindedTyVar (hsTyVarName tv) k)
556 | (L loc tv, k) <- zip hs_tvs kinds]
557 ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
559 -- Kind check a data declaration, assuming that we already extended the
560 -- kind environment with the type variables of the left-hand side (these
561 -- kinded type variables are also passed as the second parameter).
563 kcDataDecl :: TyClDecl Name -> [LHsTyVarBndr Name] -> TcM (TyClDecl Name)
564 kcDataDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
566 = do { ctxt' <- kcHsContext ctxt
567 ; cons' <- mappM (wrapLocM kc_con_decl) cons
568 ; return (decl {tcdTyVars = tvs, tcdCtxt = ctxt', tcdCons = cons'}) }
570 kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res) = do
571 kcHsTyVars ex_tvs $ \ex_tvs' -> do
572 ex_ctxt' <- kcHsContext ex_ctxt
573 details' <- kc_con_details details
575 ResTyH98 -> return ResTyH98
576 ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
577 return (ConDecl name expl ex_tvs' ex_ctxt' details' res')
579 kc_con_details (PrefixCon btys)
580 = do { btys' <- mappM kc_larg_ty btys ; return (PrefixCon btys') }
581 kc_con_details (InfixCon bty1 bty2)
582 = do { bty1' <- kc_larg_ty bty1; bty2' <- kc_larg_ty bty2; return (InfixCon bty1' bty2') }
583 kc_con_details (RecCon fields)
584 = do { fields' <- mappM kc_field fields; return (RecCon fields') }
586 kc_field (fld, bty) = do { bty' <- kc_larg_ty bty ; return (fld, bty') }
588 kc_larg_ty bty = case new_or_data of
589 DataType -> kcHsSigType bty
590 NewType -> kcHsLiftedSigType bty
591 -- Can't allow an unlifted type for newtypes, because we're effectively
592 -- going to remove the constructor while coercing it to a lifted type.
593 -- And newtypes can't be bang'd
597 %************************************************************************
599 \subsection{Type checking}
601 %************************************************************************
604 tcSynDecls :: [LTyClDecl Name] -> TcM [TyThing]
605 tcSynDecls [] = return []
606 tcSynDecls (decl : decls)
607 = do { syn_tc <- addLocM tcSynDecl decl
608 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls decls)
609 ; return (syn_tc : syn_tcs) }
612 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
613 = tcTyVarBndrs tvs $ \ tvs' -> do
614 { traceTc (text "tcd1" <+> ppr tc_name)
615 ; rhs_ty' <- tcHsKindedType rhs_ty
616 ; return (ATyCon (buildSynTyCon tc_name tvs' (SynonymTyCon rhs_ty'))) }
619 tcTyClDecl :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
621 tcTyClDecl calc_isrec decl
622 = tcAddDeclCtxt decl (tcTyClDecl1 calc_isrec decl)
624 -- kind signature for a type function
625 tcTyClDecl1 _calc_isrec
626 (TyFunction {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = kind})
627 = tcTyVarBndrs tvs $ \ tvs' -> do
628 { traceTc (text "type family: " <+> ppr tc_name)
629 ; gla_exts <- doptM Opt_GlasgowExts
631 -- Check that we don't use kind signatures without Glasgow extensions
632 ; checkTc gla_exts $ badSigTyDecl tc_name
634 ; return [ATyCon $ buildSynTyCon tc_name tvs' (OpenSynTyCon kind)]
637 -- kind signature for an indexed data type
638 tcTyClDecl1 _calc_isrec
639 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
640 tcdLName = L _ tc_name, tcdKindSig = Just ksig, tcdCons = []})
641 = tcTyVarBndrs tvs $ \ tvs' -> do
642 { traceTc (text "data/newtype family: " <+> ppr tc_name)
643 ; extra_tvs <- tcDataKindSig (Just ksig)
644 ; let final_tvs = tvs' ++ extra_tvs -- we may not need these
646 ; checkTc (null . unLoc $ ctxt) $ badKindSigCtxt tc_name
647 ; gla_exts <- doptM Opt_GlasgowExts
649 -- Check that we don't use kind signatures without Glasgow extensions
650 ; checkTc gla_exts $ badSigTyDecl tc_name
652 ; tycon <- buildAlgTyCon tc_name final_tvs []
654 DataType -> OpenDataTyCon
655 NewType -> OpenNewTyCon)
656 Recursive False True Nothing
657 ; return [ATyCon tycon]
660 tcTyClDecl1 calc_isrec
661 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
662 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
663 = tcTyVarBndrs tvs $ \ tvs' -> do
664 { extra_tvs <- tcDataKindSig mb_ksig
665 ; let final_tvs = tvs' ++ extra_tvs
666 ; stupid_theta <- tcHsKindedContext ctxt
667 ; want_generic <- doptM Opt_Generics
668 ; unbox_strict <- doptM Opt_UnboxStrictFields
669 ; gla_exts <- doptM Opt_GlasgowExts
670 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
672 -- Check that we don't use GADT syntax in H98 world
673 ; checkTc (gla_exts || h98_syntax) (badGadtDecl tc_name)
675 -- Check that we don't use kind signatures without Glasgow extensions
676 ; checkTc (gla_exts || isNothing mb_ksig) (badSigTyDecl tc_name)
678 -- Check that the stupid theta is empty for a GADT-style declaration
679 ; checkTc (null stupid_theta || h98_syntax) (badStupidTheta tc_name)
681 -- Check that there's at least one condecl,
682 -- or else we're reading an hs-boot file, or -fglasgow-exts
683 ; checkTc (not (null cons) || gla_exts || is_boot)
684 (emptyConDeclsErr tc_name)
686 -- Check that a newtype has exactly one constructor
687 ; checkTc (new_or_data == DataType || isSingleton cons)
688 (newtypeConError tc_name (length cons))
690 ; tycon <- fixM (\ tycon -> do
691 { data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data
695 if null cons && is_boot -- In a hs-boot file, empty cons means
696 then return AbstractTyCon -- "don't know"; hence Abstract
697 else case new_or_data of
698 DataType -> return (mkDataTyConRhs data_cons)
700 ASSERT( isSingleton data_cons )
701 mkNewTyConRhs tc_name tycon (head data_cons)
702 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
703 (want_generic && canDoGenerics data_cons) h98_syntax Nothing
705 ; return [ATyCon tycon]
708 is_rec = calc_isrec tc_name
709 h98_syntax = case cons of -- All constructors have same shape
710 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
713 tcTyClDecl1 calc_isrec
714 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
715 tcdCtxt = ctxt, tcdMeths = meths,
716 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
717 = tcTyVarBndrs tvs $ \ tvs' -> do
718 { ctxt' <- tcHsKindedContext ctxt
719 ; fds' <- mappM (addLocM tc_fundep) fundeps
720 ; atss <- mappM (addLocM (tcTyClDecl1 (const Recursive))) ats
721 ; let ats' = zipWith setTyThingPoss atss (map (tcdTyVars . unLoc) ats)
722 ; sig_stuff <- tcClassSigs class_name sigs meths
723 ; clas <- fixM (\ clas ->
724 let -- This little knot is just so we can get
725 -- hold of the name of the class TyCon, which we
726 -- need to look up its recursiveness
727 tycon_name = tyConName (classTyCon clas)
728 tc_isrec = calc_isrec tycon_name
730 buildClass class_name tvs' ctxt' fds' ats'
732 ; return (AClass clas : ats')
733 -- NB: Order is important due to the call to `mkGlobalThings' when
734 -- tying the the type and class declaration type checking knot.
737 tc_fundep (tvs1, tvs2) = do { tvs1' <- mappM tcLookupTyVar tvs1 ;
738 ; tvs2' <- mappM tcLookupTyVar tvs2 ;
739 ; return (tvs1', tvs2') }
741 -- For each AT argument compute the position of the corresponding class
742 -- parameter in the class head. This will later serve as a permutation
743 -- vector when checking the validity of instance declarations.
744 setTyThingPoss [ATyCon tycon] atTyVars =
745 let classTyVars = hsLTyVarNames tvs
747 . map (`elemIndex` classTyVars)
750 -- There will be no Nothing, as we already passed renaming
752 ATyCon (setTyConArgPoss tycon poss)
753 setTyThingPoss _ _ = panic "TcTyClsDecls.setTyThingPoss"
755 tcTyClDecl1 calc_isrec
756 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
757 = returnM [ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0)]
759 -----------------------------------
760 tcConDecl :: Bool -- True <=> -funbox-strict_fields
766 tcConDecl unbox_strict NewType tycon tc_tvs -- Newtypes
767 (ConDecl name _ ex_tvs ex_ctxt details ResTyH98)
768 = do { let tc_datacon field_lbls arg_ty
769 = do { arg_ty' <- tcHsKindedType arg_ty -- No bang on newtype
770 ; buildDataCon (unLoc name) False {- Prefix -}
772 (map unLoc field_lbls)
773 tc_tvs [] -- No existentials
774 [] [] -- No equalities, predicates
778 -- Check that a newtype has no existential stuff
779 ; checkTc (null ex_tvs && null (unLoc ex_ctxt)) (newtypeExError name)
782 PrefixCon [arg_ty] -> tc_datacon [] arg_ty
783 RecCon [(field_lbl, arg_ty)] -> tc_datacon [field_lbl] arg_ty
785 failWithTc (newtypeFieldErr name (length (hsConArgs details)))
786 -- Check that the constructor has exactly one field
789 tcConDecl unbox_strict DataType tycon tc_tvs -- Data types
790 (ConDecl name _ tvs ctxt details res_ty)
791 = tcTyVarBndrs tvs $ \ tvs' -> do
792 { ctxt' <- tcHsKindedContext ctxt
793 ; (univ_tvs, ex_tvs, eq_preds, data_tc) <- tcResultType tycon tc_tvs tvs' res_ty
795 tc_datacon is_infix field_lbls btys
796 = do { let bangs = map getBangStrictness btys
797 ; arg_tys <- mappM tcHsBangType btys
798 ; buildDataCon (unLoc name) is_infix
799 (argStrictness unbox_strict tycon bangs arg_tys)
800 (map unLoc field_lbls)
801 univ_tvs ex_tvs eq_preds ctxt' arg_tys
803 -- NB: we put data_tc, the type constructor gotten from the
804 -- constructor type signature into the data constructor;
805 -- that way checkValidDataCon can complain if it's wrong.
808 PrefixCon btys -> tc_datacon False [] btys
809 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
810 RecCon fields -> tc_datacon False field_names btys
812 (field_names, btys) = unzip fields
816 tcResultType :: TyCon
817 -> [TyVar] -- data T a b c = ...
818 -> [TyVar] -- where MkT :: forall a b c. ...
820 -> TcM ([TyVar], -- Universal
821 [TyVar], -- Existential
822 [(TyVar,Type)], -- Equality predicates
823 TyCon) -- TyCon given in the ResTy
824 -- We don't check that the TyCon given in the ResTy is
825 -- the same as the parent tycon, becuase we are in the middle
826 -- of a recursive knot; so it's postponed until checkValidDataCon
828 tcResultType decl_tycon tc_tvs dc_tvs ResTyH98
829 = return (tc_tvs, dc_tvs, [], decl_tycon)
830 -- In H98 syntax the dc_tvs are the existential ones
831 -- data T a b c = forall d e. MkT ...
832 -- The {a,b,c} are tc_tvs, and {d,e} are dc_tvs
834 tcResultType _ tc_tvs dc_tvs (ResTyGADT res_ty)
835 -- E.g. data T a b c where
836 -- MkT :: forall x y z. T (x,y) z z
838 -- ([a,z,c], [x,y], [a:=:(x,y), c:=:z], T)
840 = do { (dc_tycon, res_tys) <- tcLHsConResTy res_ty
841 -- NB: tc_tvs and dc_tvs are distinct
842 ; let univ_tvs = choose_univs [] tc_tvs res_tys
843 -- Each univ_tv is either a dc_tv or a tc_tv
844 ex_tvs = dc_tvs `minusList` univ_tvs
845 eq_spec = [ (tv, ty) | (tv,ty) <- univ_tvs `zip` res_tys,
847 ; return (univ_tvs, ex_tvs, eq_spec, dc_tycon) }
849 -- choose_univs uses the res_ty itself if it's a type variable
850 -- and hasn't already been used; otherwise it uses one of the tc_tvs
851 choose_univs used tc_tvs []
852 = ASSERT( null tc_tvs ) []
853 choose_univs used (tc_tv:tc_tvs) (res_ty:res_tys)
854 | Just tv <- tcGetTyVar_maybe res_ty, not (tv `elem` used)
855 = tv : choose_univs (tv:used) tc_tvs res_tys
857 = tc_tv : choose_univs used tc_tvs res_tys
860 argStrictness :: Bool -- True <=> -funbox-strict_fields
862 -> [TcType] -> [StrictnessMark]
863 argStrictness unbox_strict tycon bangs arg_tys
864 = ASSERT( length bangs == length arg_tys )
865 zipWith (chooseBoxingStrategy unbox_strict tycon) arg_tys bangs
867 -- We attempt to unbox/unpack a strict field when either:
868 -- (i) The field is marked '!!', or
869 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
871 -- We have turned off unboxing of newtypes because coercions make unboxing
872 -- and reboxing more complicated
873 chooseBoxingStrategy :: Bool -> TyCon -> TcType -> HsBang -> StrictnessMark
874 chooseBoxingStrategy unbox_strict_fields tycon arg_ty bang
876 HsNoBang -> NotMarkedStrict
877 HsStrict | unbox_strict_fields
878 && can_unbox arg_ty -> MarkedUnboxed
879 HsUnbox | can_unbox arg_ty -> MarkedUnboxed
880 other -> MarkedStrict
882 -- we can unbox if the type is a chain of newtypes with a product tycon
884 can_unbox arg_ty = case splitTyConApp_maybe arg_ty of
886 Just (arg_tycon, tycon_args) ->
887 not (isRecursiveTyCon tycon) &&
888 isProductTyCon arg_tycon &&
889 (if isNewTyCon arg_tycon then
890 can_unbox (newTyConInstRhs arg_tycon tycon_args)
894 %************************************************************************
896 \subsection{Dependency analysis}
898 %************************************************************************
900 Validity checking is done once the mutually-recursive knot has been
901 tied, so we can look at things freely.
904 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
905 checkCycleErrs tyclss
909 = do { mappM_ recClsErr cls_cycles
910 ; failM } -- Give up now, because later checkValidTyCl
911 -- will loop if the synonym is recursive
913 cls_cycles = calcClassCycles tyclss
915 checkValidTyCl :: TyClDecl Name -> TcM ()
916 -- We do the validity check over declarations, rather than TyThings
917 -- only so that we can add a nice context with tcAddDeclCtxt
919 = tcAddDeclCtxt decl $
920 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
921 ; traceTc (text "Validity of" <+> ppr thing)
923 ATyCon tc -> checkValidTyCon tc
924 AClass cl -> checkValidClass cl
925 ; traceTc (text "Done validity of" <+> ppr thing)
928 -------------------------
929 -- For data types declared with record syntax, we require
930 -- that each constructor that has a field 'f'
931 -- (a) has the same result type
932 -- (b) has the same type for 'f'
933 -- module alpha conversion of the quantified type variables
934 -- of the constructor.
936 checkValidTyCon :: TyCon -> TcM ()
939 = case synTyConRhs tc of
940 OpenSynTyCon _ -> return ()
941 SynonymTyCon ty -> checkValidType syn_ctxt ty
943 = -- Check the context on the data decl
944 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
946 -- Check arg types of data constructors
947 mappM_ (checkValidDataCon tc) data_cons `thenM_`
949 -- Check that fields with the same name share a type
950 mappM_ check_fields groups
953 syn_ctxt = TySynCtxt name
955 data_cons = tyConDataCons tc
957 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
958 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
959 get_fields con = dataConFieldLabels con `zip` repeat con
960 -- dataConFieldLabels may return the empty list, which is fine
962 -- See Note [GADT record selectors] in MkId.lhs
963 -- We must check (a) that the named field has the same
964 -- type in each constructor
965 -- (b) that those constructors have the same result type
967 -- However, the constructors may have differently named type variable
968 -- and (worse) we don't know how the correspond to each other. E.g.
969 -- C1 :: forall a b. { f :: a, g :: b } -> T a b
970 -- C2 :: forall d c. { f :: c, g :: c } -> T c d
972 -- So what we do is to ust Unify.tcMatchTys to compare the first candidate's
973 -- result type against other candidates' types BOTH WAYS ROUND.
974 -- If they magically agrees, take the substitution and
975 -- apply them to the latter ones, and see if they match perfectly.
976 check_fields fields@((label, con1) : other_fields)
977 -- These fields all have the same name, but are from
978 -- different constructors in the data type
979 = recoverM (return ()) $ mapM_ checkOne other_fields
980 -- Check that all the fields in the group have the same type
981 -- NB: this check assumes that all the constructors of a given
982 -- data type use the same type variables
984 tvs1 = mkVarSet (dataConAllTyVars con1)
985 res1 = dataConResTys con1
986 fty1 = dataConFieldType con1 label
988 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
989 = do { checkFieldCompat label con1 con2 tvs1 res1 res2 fty1 fty2
990 ; checkFieldCompat label con2 con1 tvs2 res2 res1 fty2 fty1 }
992 tvs2 = mkVarSet (dataConAllTyVars con2)
993 res2 = dataConResTys con2
994 fty2 = dataConFieldType con2 label
996 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
997 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
998 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
1000 mb_subst1 = tcMatchTys tvs1 res1 res2
1001 mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
1003 -------------------------------
1004 checkValidDataCon :: TyCon -> DataCon -> TcM ()
1005 checkValidDataCon tc con
1006 = setSrcSpan (srcLocSpan (getSrcLoc con)) $
1007 addErrCtxt (dataConCtxt con) $
1008 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
1009 ; checkValidType ctxt (dataConUserType con) }
1011 ctxt = ConArgCtxt (dataConName con)
1013 -------------------------------
1014 checkValidClass :: Class -> TcM ()
1016 = do { -- CHECK ARITY 1 FOR HASKELL 1.4
1017 gla_exts <- doptM Opt_GlasgowExts
1019 -- Check that the class is unary, unless GlaExs
1020 ; checkTc (notNull tyvars) (nullaryClassErr cls)
1021 ; checkTc (gla_exts || unary) (classArityErr cls)
1023 -- Check the super-classes
1024 ; checkValidTheta (ClassSCCtxt (className cls)) theta
1026 -- Check the class operations
1027 ; mappM_ (check_op gla_exts) op_stuff
1029 -- Check that if the class has generic methods, then the
1030 -- class has only one parameter. We can't do generic
1031 -- multi-parameter type classes!
1032 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
1035 (tyvars, theta, _, op_stuff) = classBigSig cls
1036 unary = isSingleton tyvars
1037 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
1039 check_op gla_exts (sel_id, dm)
1040 = addErrCtxt (classOpCtxt sel_id tau) $ do
1041 { checkValidTheta SigmaCtxt (tail theta)
1042 -- The 'tail' removes the initial (C a) from the
1043 -- class itself, leaving just the method type
1045 ; checkValidType (FunSigCtxt op_name) tau
1047 -- Check that the type mentions at least one of
1048 -- the class type variables
1049 ; checkTc (any (`elemVarSet` tyVarsOfType tau) tyvars)
1050 (noClassTyVarErr cls sel_id)
1052 -- Check that for a generic method, the type of
1053 -- the method is sufficiently simple
1054 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
1055 (badGenericMethodType op_name op_ty)
1058 op_name = idName sel_id
1059 op_ty = idType sel_id
1060 (_,theta1,tau1) = tcSplitSigmaTy op_ty
1061 (_,theta2,tau2) = tcSplitSigmaTy tau1
1062 (theta,tau) | gla_exts = (theta1 ++ theta2, tau2)
1063 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
1064 -- Ugh! The function might have a type like
1065 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
1066 -- With -fglasgow-exts, we want to allow this, even though the inner
1067 -- forall has an (Eq a) constraint. Whereas in general, each constraint
1068 -- in the context of a for-all must mention at least one quantified
1069 -- type variable. What a mess!
1072 ---------------------------------------------------------------------
1073 resultTypeMisMatch field_name con1 con2
1074 = vcat [sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1075 ptext SLIT("have a common field") <+> quotes (ppr field_name) <> comma],
1076 nest 2 $ ptext SLIT("but have different result types")]
1077 fieldTypeMisMatch field_name con1 con2
1078 = sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1079 ptext SLIT("give different types for field"), quotes (ppr field_name)]
1081 dataConCtxt con = ptext SLIT("In the definition of data constructor") <+> quotes (ppr con)
1083 classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
1084 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
1087 = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
1090 = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
1091 parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
1093 noClassTyVarErr clas op
1094 = sep [ptext SLIT("The class method") <+> quotes (ppr op),
1095 ptext SLIT("mentions none of the type variables of the class") <+>
1096 ppr clas <+> hsep (map ppr (classTyVars clas))]
1098 genericMultiParamErr clas
1099 = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
1100 ptext SLIT("cannot have generic methods")
1102 badGenericMethodType op op_ty
1103 = hang (ptext SLIT("Generic method type is too complex"))
1104 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
1105 ptext SLIT("You can only use type variables, arrows, lists, and tuples")])
1108 = setSrcSpan (getLoc (head sorted_decls)) $
1109 addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
1110 nest 2 (vcat (map ppr_decl sorted_decls))])
1112 sorted_decls = sortLocated syn_decls
1113 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
1116 = setSrcSpan (getLoc (head sorted_decls)) $
1117 addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
1118 nest 2 (vcat (map ppr_decl sorted_decls))])
1120 sorted_decls = sortLocated cls_decls
1121 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
1123 sortLocated :: [Located a] -> [Located a]
1124 sortLocated things = sortLe le things
1126 le (L l1 _) (L l2 _) = l1 <= l2
1128 badDataConTyCon data_con
1129 = hang (ptext SLIT("Data constructor") <+> quotes (ppr data_con) <+>
1130 ptext SLIT("returns type") <+> quotes (ppr (dataConTyCon data_con)))
1131 2 (ptext SLIT("instead of its parent type"))
1134 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
1135 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow GADTs")) ]
1137 badStupidTheta tc_name
1138 = ptext SLIT("A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
1140 newtypeConError tycon n
1141 = sep [ptext SLIT("A newtype must have exactly one constructor,"),
1142 nest 2 $ ptext SLIT("but") <+> quotes (ppr tycon) <+> ptext SLIT("has") <+> speakN n ]
1145 = sep [ptext SLIT("A newtype constructor cannot have an existential context,"),
1146 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
1148 newtypeFieldErr con_name n_flds
1149 = sep [ptext SLIT("The constructor of a newtype must have exactly one field"),
1150 nest 2 $ ptext SLIT("but") <+> quotes (ppr con_name) <+> ptext SLIT("has") <+> speakN n_flds]
1152 badSigTyDecl tc_name
1153 = vcat [ ptext SLIT("Illegal kind signature") <+>
1154 quotes (ppr tc_name)
1155 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow indexed types")) ]
1157 badKindSigCtxt tc_name
1158 = vcat [ ptext SLIT("Illegal context in kind signature") <+>
1159 quotes (ppr tc_name)
1160 , nest 2 (parens $ ptext SLIT("Currently, kind signatures cannot have a context")) ]
1162 badIdxTyDecl tc_name
1163 = vcat [ ptext SLIT("Illegal indexed type instance for") <+>
1164 quotes (ppr tc_name)
1165 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow indexed types")) ]
1167 badGadtIdxTyDecl tc_name
1168 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+>
1169 quotes (ppr tc_name)
1170 , nest 2 (parens $ ptext SLIT("Indexed types cannot use GADT declarations")) ]
1172 tooManyParmsErr tc_name
1173 = ptext SLIT("Indexed type instance has too many parameters:") <+>
1174 quotes (ppr tc_name)
1176 tooFewParmsErr tc_name
1177 = ptext SLIT("Indexed type instance has too few parameters:") <+>
1178 quotes (ppr tc_name)
1180 badBootTyIdxDeclErr =
1181 ptext SLIT("Illegal indexed type instance in hs-boot file")
1183 wrongKindOfFamily family =
1184 ptext SLIT("Wrong category of type instance; declaration was for a") <+>
1187 kindOfFamily | isSynTyCon family = ptext SLIT("type synonym")
1188 | isDataTyCon family = ptext SLIT("data type")
1189 | isNewTyCon family = ptext SLIT("newtype")
1191 emptyConDeclsErr tycon
1192 = sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
1193 nest 2 $ ptext SLIT("(-fglasgow-exts permits this)")]