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 )
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, tyConKind )
55 import DataCon ( DataCon, dataConUserType, dataConName,
56 dataConFieldLabels, dataConTyCon, dataConAllTyVars,
57 dataConFieldType, dataConResTys )
58 import Var ( TyVar, idType, idName )
59 import VarSet ( elemVarSet, mkVarSet )
60 import Name ( Name, getSrcLoc )
62 import Maybe ( isJust, fromJust, isNothing )
63 import Maybes ( expectJust )
64 import Unify ( tcMatchTys, tcMatchTyX )
65 import Util ( zipLazy, isSingleton, notNull, sortLe )
66 import List ( partition )
67 import SrcLoc ( Located(..), unLoc, getLoc, srcLocSpan )
68 import ListSetOps ( equivClasses, minusList )
69 import List ( delete )
70 import Digraph ( SCC(..) )
71 import DynFlags ( DynFlag( Opt_GlasgowExts, Opt_Generics,
72 Opt_UnboxStrictFields ) )
76 %************************************************************************
78 \subsection{Type checking for type and class declarations}
80 %************************************************************************
84 Consider a mutually-recursive group, binding
85 a type constructor T and a class C.
87 Step 1: getInitialKind
88 Construct a KindEnv by binding T and C to a kind variable
91 In that environment, do a kind check
93 Step 3: Zonk the kinds
95 Step 4: buildTyConOrClass
96 Construct an environment binding T to a TyCon and C to a Class.
97 a) Their kinds comes from zonking the relevant kind variable
98 b) Their arity (for synonyms) comes direct from the decl
99 c) The funcional dependencies come from the decl
100 d) The rest comes a knot-tied binding of T and C, returned from Step 4
101 e) The variances of the tycons in the group is calculated from
105 In this environment, walk over the decls, constructing the TyCons and Classes.
106 This uses in a strict way items (a)-(c) above, which is why they must
107 be constructed in Step 4. Feed the results back to Step 4.
108 For this step, pass the is-recursive flag as the wimp-out flag
112 Step 6: Extend environment
113 We extend the type environment with bindings not only for the TyCons and Classes,
114 but also for their "implicit Ids" like data constructors and class selectors
116 Step 7: checkValidTyCl
117 For a recursive group only, check all the decls again, just
118 to check all the side conditions on validity. We could not
119 do this before because we were in a mutually recursive knot.
121 Identification of recursive TyCons
122 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
123 The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to
126 Identifying a TyCon as recursive serves two purposes
128 1. Avoid infinite types. Non-recursive newtypes are treated as
129 "transparent", like type synonyms, after the type checker. If we did
130 this for all newtypes, we'd get infinite types. So we figure out for
131 each newtype whether it is "recursive", and add a coercion if so. In
132 effect, we are trying to "cut the loops" by identifying a loop-breaker.
134 2. Avoid infinite unboxing. This is nothing to do with newtypes.
138 Well, this function diverges, but we don't want the strictness analyser
139 to diverge. But the strictness analyser will diverge because it looks
140 deeper and deeper into the structure of T. (I believe there are
141 examples where the function does something sane, and the strictness
142 analyser still diverges, but I can't see one now.)
144 Now, concerning (1), the FC2 branch currently adds a coercion for ALL
145 newtypes. I did this as an experiment, to try to expose cases in which
146 the coercions got in the way of optimisations. If it turns out that we
147 can indeed always use a coercion, then we don't risk recursive types,
148 and don't need to figure out what the loop breakers are.
150 For newtype *families* though, we will always have a coercion, so they
151 are always loop breakers! So you can easily adjust the current
152 algorithm by simply treating all newtype families as loop breakers (and
153 indeed type families). I think.
156 tcTyAndClassDecls :: ModDetails -> [LTyClDecl Name]
157 -> TcM TcGblEnv -- Input env extended by types and classes
158 -- and their implicit Ids,DataCons
159 tcTyAndClassDecls boot_details allDecls
160 = do { -- Omit instances of indexed types; they are handled together
161 -- with the *heads* of class instances
162 ; let decls = filter (not . isIdxTyDecl . unLoc) allDecls
164 -- First check for cyclic type synonysm or classes
165 -- See notes with checkCycleErrs
166 ; checkCycleErrs decls
168 ; traceTc (text "tcTyAndCl" <+> ppr mod)
169 ; (syn_tycons, alg_tyclss) <- fixM (\ ~(rec_syn_tycons, rec_alg_tyclss) ->
170 do { let { -- Seperate ordinary synonyms from all other type and
171 -- class declarations and add all associated type
172 -- declarations from type classes. The latter is
173 -- required so that the temporary environment for the
174 -- knot includes all associated family declarations.
175 ; (syn_decls, alg_decls) = partition (isSynDecl . unLoc)
177 ; alg_at_decls = concatMap addATs alg_decls
179 -- Extend the global env with the knot-tied results
180 -- for data types and classes
182 -- We must populate the environment with the loop-tied
183 -- T's right away, because the kind checker may "fault
184 -- in" some type constructors that recursively
186 ; let gbl_things = mkGlobalThings alg_at_decls rec_alg_tyclss
187 ; tcExtendRecEnv gbl_things $ do
189 -- Kind-check the declarations
190 { (kc_syn_decls, kc_alg_decls) <- kcTyClDecls syn_decls alg_decls
192 ; let { -- Calculate rec-flag
193 ; calc_rec = calcRecFlags boot_details rec_alg_tyclss
194 ; tc_decl = addLocM (tcTyClDecl calc_rec) }
195 -- Type-check the type synonyms, and extend the envt
196 ; syn_tycons <- tcSynDecls kc_syn_decls
197 ; tcExtendGlobalEnv syn_tycons $ do
199 -- Type-check the data types and classes
200 { alg_tyclss <- mappM tc_decl kc_alg_decls
201 ; return (syn_tycons, concat alg_tyclss)
203 -- Finished with knot-tying now
204 -- Extend the environment with the finished things
205 ; tcExtendGlobalEnv (syn_tycons ++ alg_tyclss) $ do
207 -- Perform the validity check
208 { traceTc (text "ready for validity check")
209 ; mappM_ (addLocM checkValidTyCl) decls
210 ; traceTc (text "done")
212 -- Add the implicit things;
213 -- we want them in the environment because
214 -- they may be mentioned in interface files
215 ; let { implicit_things = concatMap implicitTyThings alg_tyclss }
216 ; traceTc ((text "Adding" <+> ppr alg_tyclss)
217 $$ (text "and" <+> ppr implicit_things))
218 ; tcExtendGlobalEnv implicit_things getGblEnv
221 addATs decl@(L _ (ClassDecl {tcdATs = ats})) = decl : ats
224 mkGlobalThings :: [LTyClDecl Name] -- The decls
225 -> [TyThing] -- Knot-tied, in 1-1 correspondence with the decls
227 -- Driven by the Decls, and treating the TyThings lazily
228 -- make a TypeEnv for the new things
229 mkGlobalThings decls things
230 = map mk_thing (decls `zipLazy` things)
232 mk_thing (L _ (ClassDecl {tcdLName = L _ name}), ~(AClass cl))
234 mk_thing (L _ decl, ~(ATyCon tc))
235 = (tcdName decl, ATyCon tc)
239 %************************************************************************
241 \subsection{Type checking instances of indexed types}
243 %************************************************************************
245 Instances of indexed types are somewhat of a hybrid. They are processed
246 together with class instance heads, but can contain data constructors and hence
247 they share a lot of kinding and type checking code with ordinary algebraic
248 data types (and GADTs).
251 tcIdxTyInstDecl :: LTyClDecl Name
252 -> TcM (Maybe InstInfo, Maybe TyThing) -- Nothing if error
253 tcIdxTyInstDecl (L loc decl)
254 = -- Prime error recovery, set source location
255 recoverM (returnM (Nothing, Nothing)) $
258 do { -- indexed data types require -fglasgow-exts and can't be in an
260 ; gla_exts <- doptM Opt_GlasgowExts
261 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
262 ; checkTc gla_exts $ badIdxTyDecl (tcdLName decl)
263 ; checkTc (not is_boot) $ badBootTyIdxDeclErr
265 -- perform kind and type checking
266 ; tcIdxTyInstDecl1 decl
269 tcIdxTyInstDecl1 :: TyClDecl Name
270 -> TcM (Maybe InstInfo, Maybe TyThing) -- Nothing if error
272 tcIdxTyInstDecl1 (decl@TySynonym {})
273 = kcIdxTyPats decl $ \k_tvs k_typats resKind _ ->
274 do { -- (1) kind check the right hand side of the type equation
275 ; k_rhs <- kcCheckHsType (tcdSynRhs decl) resKind
277 -- (2) type check type equation
278 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
279 ; t_typats <- mappM tcHsKindedType k_typats
280 ; t_rhs <- tcHsKindedType k_rhs
282 -- construct type rewrite rule
283 -- !!!of the form: forall t_tvs. (tcdLName decl) t_typats = t_rhs
284 ; return (Nothing, Nothing) -- !!!TODO: need InstInfo for eq axioms
287 tcIdxTyInstDecl1 (decl@TyData {tcdND = new_or_data, tcdLName = L loc tc_name,
289 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
290 do { -- (1) kind check the data declaration as usual
291 ; k_decl <- kcDataDecl decl k_tvs
292 ; let k_ctxt = tcdCtxt k_decl
293 k_cons = tcdCons k_decl
295 -- result kind must be '*' (otherwise, we have too few patterns)
296 ; checkTc (isLiftedTypeKind resKind) $ tooFewParmsErr tc_name
298 -- (2) type check indexed data type declaration
299 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
300 ; unbox_strict <- doptM Opt_UnboxStrictFields
302 -- Check that we don't use GADT syntax for indexed types
303 ; checkTc h98_syntax (badGadtIdxTyDecl tc_name)
305 -- Check that a newtype has exactly one constructor
306 ; checkTc (new_or_data == DataType || isSingleton k_cons) $
307 newtypeConError tc_name (length k_cons)
309 ; final_tvs <- tcDataKindSig (Just $ tyConKind family)
310 ; t_typats <- mappM tcHsKindedType k_typats
311 ; stupid_theta <- tcHsKindedContext k_ctxt
313 ; tycon <- fixM (\ tycon -> do
314 { data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data
315 tycon final_tvs (Just t_typats)))
319 DataType -> return (mkDataTyConRhs data_cons)
321 ASSERT( isSingleton data_cons )
322 mkNewTyConRhs tc_name tycon (head data_cons)
323 ; buildAlgTyCon tc_name t_tvs stupid_theta tc_rhs Recursive
324 False h98_syntax (Just family)
325 -- We always assume that indexed types are recursive. Why?
326 -- (1) Due to their open nature, we can never be sure that a
327 -- further instance might not introduce a new recursive
328 -- dependency. (2) They are always valid loop breakers as
329 -- they involve a coercion.
333 -- !!!TODO: missing eq axiom
334 ; return (Nothing, Just (ATyCon tycon))
337 h98_syntax = case cons of -- All constructors have same shape
338 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
341 -- Kind checking of indexed types
344 -- Kind check type patterns and kind annotate the embedded type variables.
346 -- * Here we check that a type instance matches its kind signature, but we do
347 -- not check whether there is a pattern for each type index; the latter
348 -- check is only required for type functions.
350 kcIdxTyPats :: TyClDecl Name
351 -> ([LHsTyVarBndr Name] -> [LHsType Name] -> Kind -> TyCon -> TcM a)
352 -- ^^kinded tvs ^^kinded ty pats ^^res kind
354 kcIdxTyPats decl thing_inside
355 = kcHsTyVars (tcdTyVars decl) $ \tvs ->
356 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
357 ; let { family = case tc_ty_thing of
358 AGlobal (ATyCon family) -> family
359 ; (kinds, resKind) = splitKindFunTys (tyConKind family)
360 ; hs_typats = fromJust $ tcdTyPats decl }
362 -- we may not have more parameters than the kind indicates
363 ; checkTc (length kinds >= length hs_typats) $
364 tooManyParmsErr (tcdLName decl)
366 -- type functions can have a higher-kinded result
367 ; let resultKind = mkArrowKinds (drop (length hs_typats) kinds) resKind
368 ; typats <- zipWithM kcCheckHsType hs_typats kinds
369 ; thing_inside tvs typats resultKind family
375 %************************************************************************
379 %************************************************************************
381 We need to kind check all types in the mutually recursive group
382 before we know the kind of the type variables. For example:
385 op :: D b => a -> b -> b
388 bop :: (Monad c) => ...
390 Here, the kind of the locally-polymorphic type variable "b"
391 depends on *all the uses of class D*. For example, the use of
392 Monad c in bop's type signature means that D must have kind Type->Type.
394 However type synonyms work differently. They can have kinds which don't
395 just involve (->) and *:
396 type R = Int# -- Kind #
397 type S a = Array# a -- Kind * -> #
398 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
399 So we must infer their kinds from their right-hand sides *first* and then
400 use them, whereas for the mutually recursive data types D we bring into
401 scope kind bindings D -> k, where k is a kind variable, and do inference.
405 This treatment of type synonyms only applies to Haskell 98-style synonyms.
406 General type functions can be recursive, and hence, appear in `alg_decls'.
408 The kind of an indexed type is solely determinded by its kind signature;
409 hence, only kind signatures participate in the construction of the initial
410 kind environment (as constructed by `getInitialKind'). In fact, we ignore
411 instances of indexed types altogether in the following. However, we need to
412 include the kind signatures of associated types into the construction of the
413 initial kind environment. (This is handled by `allDecls').
416 kcTyClDecls syn_decls alg_decls
417 = do { -- First extend the kind env with each data type, class, and
418 -- indexed type, mapping them to a type variable
419 let initialKindDecls = concat [allDecls decl | L _ decl <- alg_decls]
420 ; alg_kinds <- mappM getInitialKind initialKindDecls
421 ; tcExtendKindEnv alg_kinds $ do
423 -- Now kind-check the type synonyms, in dependency order
424 -- We do these differently to data type and classes,
425 -- because a type synonym can be an unboxed type
427 -- and a kind variable can't unify with UnboxedTypeKind
428 -- So we infer their kinds in dependency order
429 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
430 ; tcExtendKindEnv syn_kinds $ do
432 -- Now kind-check the data type, class, and kind signatures,
433 -- returning kind-annotated decls; we don't kind-check
434 -- instances of indexed types yet, but leave this to
436 { kc_alg_decls <- mappM (wrapLocM kcTyClDecl)
437 (filter (not . isIdxTyDecl . unLoc) alg_decls)
439 ; return (kc_syn_decls, kc_alg_decls) }}}
441 -- get all declarations relevant for determining the initial kind
443 allDecls (decl@ClassDecl {tcdATs = ats}) = decl : [ at
446 allDecls decl | isIdxTyDecl decl = []
449 ------------------------------------------------------------------------
450 getInitialKind :: TyClDecl Name -> TcM (Name, TcKind)
451 -- Only for data type, class, and indexed type declarations
452 -- Get as much info as possible from the data, class, or indexed type decl,
453 -- so as to maximise usefulness of error messages
455 = do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl)
456 ; res_kind <- mk_res_kind decl
457 ; return (tcdName decl, mkArrowKinds arg_kinds res_kind) }
459 mk_arg_kind (UserTyVar _) = newKindVar
460 mk_arg_kind (KindedTyVar _ kind) = return kind
462 mk_res_kind (TyFunction { tcdKind = kind }) = return kind
463 mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
464 -- On GADT-style and data signature declarations we allow a kind
466 -- data T :: *->* where { ... }
467 mk_res_kind other = return liftedTypeKind
471 kcSynDecls :: [SCC (LTyClDecl Name)]
472 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
473 [(Name,TcKind)]) -- Kind bindings
476 kcSynDecls (group : groups)
477 = do { (decl, nk) <- kcSynDecl group
478 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
479 ; return (decl:decls, nk:nks) }
482 kcSynDecl :: SCC (LTyClDecl Name)
483 -> TcM (LTyClDecl Name, -- Kind-annotated decls
484 (Name,TcKind)) -- Kind bindings
485 kcSynDecl (AcyclicSCC ldecl@(L loc decl))
486 = tcAddDeclCtxt decl $
487 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
488 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
489 <+> brackets (ppr k_tvs))
490 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
491 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
492 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
493 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
494 (unLoc (tcdLName decl), tc_kind)) })
496 kcSynDecl (CyclicSCC decls)
497 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
498 -- of out-of-scope tycons
500 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
502 ------------------------------------------------------------------------
503 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
504 -- Not used for type synonyms (see kcSynDecl)
506 kcTyClDecl decl@(TyData {})
507 = ASSERT( not . isJust $ tcdTyPats decl ) -- must not be instance of idx ty
508 kcTyClDeclBody decl $
511 kcTyClDecl decl@(TyFunction {})
512 = kcTyClDeclBody decl $ \ tvs' ->
513 return (decl {tcdTyVars = tvs'})
515 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs, tcdATs = ats})
516 = kcTyClDeclBody decl $ \ tvs' ->
517 do { is_boot <- tcIsHsBoot
518 ; ctxt' <- kcHsContext ctxt
519 ; ats' <- mappM (wrapLocM kcTyClDecl) ats
520 ; sigs' <- mappM (wrapLocM kc_sig ) sigs
521 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs',
524 kc_sig (TypeSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
525 ; return (TypeSig nm op_ty') }
526 kc_sig other_sig = return other_sig
528 kcTyClDecl decl@(ForeignType {})
531 kcTyClDeclBody :: TyClDecl Name
532 -> ([LHsTyVarBndr Name] -> TcM a)
534 -- getInitialKind has made a suitably-shaped kind for the type or class
535 -- Unpack it, and attribute those kinds to the type variables
536 -- Extend the env with bindings for the tyvars, taken from
537 -- the kind of the tycon/class. Give it to the thing inside, and
538 -- check the result kind matches
539 kcTyClDeclBody decl thing_inside
540 = tcAddDeclCtxt decl $
541 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
542 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
543 (kinds, _) = splitKindFunTys tc_kind
544 hs_tvs = tcdTyVars decl
545 kinded_tvs = ASSERT( length kinds >= length hs_tvs )
546 [ L loc (KindedTyVar (hsTyVarName tv) k)
547 | (L loc tv, k) <- zip hs_tvs kinds]
548 ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
550 -- Kind check a data declaration, assuming that we already extended the
551 -- kind environment with the type variables of the left-hand side (these
552 -- kinded type variables are also passed as the second parameter).
554 kcDataDecl :: TyClDecl Name -> [LHsTyVarBndr Name] -> TcM (TyClDecl Name)
555 kcDataDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
557 = do { ctxt' <- kcHsContext ctxt
558 ; cons' <- mappM (wrapLocM kc_con_decl) cons
559 ; return (decl {tcdTyVars = tvs, tcdCtxt = ctxt', tcdCons = cons'}) }
561 kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res) = do
562 kcHsTyVars ex_tvs $ \ex_tvs' -> do
563 ex_ctxt' <- kcHsContext ex_ctxt
564 details' <- kc_con_details details
566 ResTyH98 -> return ResTyH98
567 ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
568 return (ConDecl name expl ex_tvs' ex_ctxt' details' res')
570 kc_con_details (PrefixCon btys)
571 = do { btys' <- mappM kc_larg_ty btys ; return (PrefixCon btys') }
572 kc_con_details (InfixCon bty1 bty2)
573 = do { bty1' <- kc_larg_ty bty1; bty2' <- kc_larg_ty bty2; return (InfixCon bty1' bty2') }
574 kc_con_details (RecCon fields)
575 = do { fields' <- mappM kc_field fields; return (RecCon fields') }
577 kc_field (fld, bty) = do { bty' <- kc_larg_ty bty ; return (fld, bty') }
579 kc_larg_ty bty = case new_or_data of
580 DataType -> kcHsSigType bty
581 NewType -> kcHsLiftedSigType bty
582 -- Can't allow an unlifted type for newtypes, because we're effectively
583 -- going to remove the constructor while coercing it to a lifted type.
584 -- And newtypes can't be bang'd
588 %************************************************************************
590 \subsection{Type checking}
592 %************************************************************************
595 tcSynDecls :: [LTyClDecl Name] -> TcM [TyThing]
596 tcSynDecls [] = return []
597 tcSynDecls (decl : decls)
598 = do { syn_tc <- addLocM tcSynDecl decl
599 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls decls)
600 ; return (syn_tc : syn_tcs) }
603 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
604 = tcTyVarBndrs tvs $ \ tvs' -> do
605 { traceTc (text "tcd1" <+> ppr tc_name)
606 ; rhs_ty' <- tcHsKindedType rhs_ty
607 ; return (ATyCon (buildSynTyCon tc_name tvs' (SynonymTyCon rhs_ty'))) }
610 tcTyClDecl :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
612 tcTyClDecl calc_isrec decl
613 = tcAddDeclCtxt decl (tcTyClDecl1 calc_isrec decl)
615 -- kind signature for a type function
616 tcTyClDecl1 _calc_isrec
617 (TyFunction {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = kind})
618 = tcTyVarBndrs tvs $ \ tvs' -> do
619 { gla_exts <- doptM Opt_GlasgowExts
621 -- Check that we don't use kind signatures without Glasgow extensions
622 ; checkTc gla_exts $ badSigTyDecl tc_name
624 ; return [ATyCon (buildSynTyCon tc_name tvs' (OpenSynTyCon kind))]
627 -- kind signature for an indexed data type
628 tcTyClDecl1 _calc_isrec
629 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
630 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = []})
631 = tcTyVarBndrs tvs $ \ tvs' -> do
632 { extra_tvs <- tcDataKindSig mb_ksig
633 ; let final_tvs = tvs' ++ extra_tvs -- we may not need these
635 ; checkTc (null . unLoc $ ctxt) $ badKindSigCtxt tc_name
636 ; gla_exts <- doptM Opt_GlasgowExts
638 -- Check that we don't use kind signatures without Glasgow extensions
639 ; checkTc gla_exts $ badSigTyDecl tc_name
641 ; tycon <- buildAlgTyCon tc_name final_tvs []
643 DataType -> OpenDataTyCon
644 NewType -> OpenNewTyCon)
645 Recursive False True Nothing
646 ; return [ATyCon tycon]
649 tcTyClDecl1 calc_isrec
650 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
651 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
652 = tcTyVarBndrs tvs $ \ tvs' -> do
653 { extra_tvs <- tcDataKindSig mb_ksig
654 ; let final_tvs = tvs' ++ extra_tvs
655 ; stupid_theta <- tcHsKindedContext ctxt
656 ; want_generic <- doptM Opt_Generics
657 ; unbox_strict <- doptM Opt_UnboxStrictFields
658 ; gla_exts <- doptM Opt_GlasgowExts
659 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
661 -- Check that we don't use GADT syntax in H98 world
662 ; checkTc (gla_exts || h98_syntax) (badGadtDecl tc_name)
664 -- Check that we don't use kind signatures without Glasgow extensions
665 ; checkTc (gla_exts || isNothing mb_ksig) (badSigTyDecl tc_name)
667 -- Check that the stupid theta is empty for a GADT-style declaration
668 ; checkTc (null stupid_theta || h98_syntax) (badStupidTheta tc_name)
670 -- Check that there's at least one condecl,
671 -- or else we're reading an hs-boot file, or -fglasgow-exts
672 ; checkTc (not (null cons) || gla_exts || is_boot)
673 (emptyConDeclsErr tc_name)
675 -- Check that a newtype has exactly one constructor
676 ; checkTc (new_or_data == DataType || isSingleton cons)
677 (newtypeConError tc_name (length cons))
679 ; tycon <- fixM (\ tycon -> do
680 { data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data
681 tycon final_tvs Nothing))
684 if null cons && is_boot -- In a hs-boot file, empty cons means
685 then return AbstractTyCon -- "don't know"; hence Abstract
686 else case new_or_data of
687 DataType -> return (mkDataTyConRhs data_cons)
689 ASSERT( isSingleton data_cons )
690 mkNewTyConRhs tc_name tycon (head data_cons)
691 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
692 (want_generic && canDoGenerics data_cons) h98_syntax Nothing
694 ; return [ATyCon tycon]
697 is_rec = calc_isrec tc_name
698 h98_syntax = case cons of -- All constructors have same shape
699 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
702 tcTyClDecl1 calc_isrec
703 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
704 tcdCtxt = ctxt, tcdMeths = meths,
705 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
706 = tcTyVarBndrs tvs $ \ tvs' -> do
707 { ctxt' <- tcHsKindedContext ctxt
708 ; fds' <- mappM (addLocM tc_fundep) fundeps
709 ; atss <- mappM (addLocM (tcTyClDecl1 (const Recursive))) ats
710 ; let ats' = concat atss
711 ; sig_stuff <- tcClassSigs class_name sigs meths
712 ; clas <- fixM (\ clas ->
713 let -- This little knot is just so we can get
714 -- hold of the name of the class TyCon, which we
715 -- need to look up its recursiveness
716 tycon_name = tyConName (classTyCon clas)
717 tc_isrec = calc_isrec tycon_name
719 buildClass class_name tvs' ctxt' fds' ats'
721 ; return (AClass clas : ats')
722 -- NB: Order is important due to the call to `mkGlobalThings' when
723 -- tying the the type and class declaration type checking knot.
726 tc_fundep (tvs1, tvs2) = do { tvs1' <- mappM tcLookupTyVar tvs1 ;
727 ; tvs2' <- mappM tcLookupTyVar tvs2 ;
728 ; return (tvs1', tvs2') }
731 tcTyClDecl1 calc_isrec
732 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
733 = returnM [ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0)]
735 -----------------------------------
736 tcConDecl :: Bool -- True <=> -funbox-strict_fields
739 -> Maybe [Type] -- Just ts <=> type patterns of instance type
743 tcConDecl unbox_strict NewType tycon tc_tvs mb_typats -- Newtypes
744 (ConDecl name _ ex_tvs ex_ctxt details ResTyH98)
745 = do { let tc_datacon field_lbls arg_ty
746 = do { arg_ty' <- tcHsKindedType arg_ty -- No bang on newtype
747 ; buildDataCon (unLoc name) False {- Prefix -}
749 (map unLoc field_lbls)
750 tc_tvs [] -- No existentials
751 [] [] -- No equalities, predicates
756 -- Check that a newtype has no existential stuff
757 ; checkTc (null ex_tvs && null (unLoc ex_ctxt)) (newtypeExError name)
760 PrefixCon [arg_ty] -> tc_datacon [] arg_ty
761 RecCon [(field_lbl, arg_ty)] -> tc_datacon [field_lbl] arg_ty
763 failWithTc (newtypeFieldErr name (length (hsConArgs details)))
764 -- Check that the constructor has exactly one field
767 tcConDecl unbox_strict DataType tycon tc_tvs mb_typats -- Data types
768 (ConDecl name _ tvs ctxt details res_ty)
769 = tcTyVarBndrs tvs $ \ tvs' -> do
770 { ctxt' <- tcHsKindedContext ctxt
771 ; (univ_tvs, ex_tvs, eq_preds, data_tc) <- tcResultType tycon tc_tvs tvs' res_ty
773 tc_datacon is_infix field_lbls btys
774 = do { let bangs = map getBangStrictness btys
775 ; arg_tys <- mappM tcHsBangType btys
776 ; buildDataCon (unLoc name) is_infix
777 (argStrictness unbox_strict tycon bangs arg_tys)
778 (map unLoc field_lbls)
779 univ_tvs ex_tvs eq_preds ctxt' arg_tys
782 -- NB: we put data_tc, the type constructor gotten from the
783 -- constructor type signature into the data constructor;
784 -- that way checkValidDataCon can complain if it's wrong.
787 PrefixCon btys -> tc_datacon False [] btys
788 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
789 RecCon fields -> tc_datacon False field_names btys
791 (field_names, btys) = unzip fields
795 tcResultType :: TyCon
796 -> [TyVar] -- data T a b c = ...
797 -> [TyVar] -- where MkT :: forall a b c. ...
799 -> TcM ([TyVar], -- Universal
800 [TyVar], -- Existential
801 [(TyVar,Type)], -- Equality predicates
802 TyCon) -- TyCon given in the ResTy
803 -- We don't check that the TyCon given in the ResTy is
804 -- the same as the parent tycon, becuase we are in the middle
805 -- of a recursive knot; so it's postponed until checkValidDataCon
807 tcResultType decl_tycon tc_tvs dc_tvs ResTyH98
808 = return (tc_tvs, dc_tvs, [], decl_tycon)
809 -- In H98 syntax the dc_tvs are the existential ones
810 -- data T a b c = forall d e. MkT ...
811 -- The {a,b,c} are tc_tvs, and {d,e} are dc_tvs
813 tcResultType _ tc_tvs dc_tvs (ResTyGADT res_ty)
814 -- E.g. data T a b c where
815 -- MkT :: forall x y z. T (x,y) z z
817 -- ([a,z,c], [x,y], [a:=:(x,y), c:=:z], T)
819 = do { (dc_tycon, res_tys) <- tcLHsConResTy res_ty
820 -- NB: tc_tvs and dc_tvs are distinct
821 ; let univ_tvs = choose_univs [] tc_tvs res_tys
822 -- Each univ_tv is either a dc_tv or a tc_tv
823 ex_tvs = dc_tvs `minusList` univ_tvs
824 eq_spec = [ (tv, ty) | (tv,ty) <- univ_tvs `zip` res_tys,
826 ; return (univ_tvs, ex_tvs, eq_spec, dc_tycon) }
828 -- choose_univs uses the res_ty itself if it's a type variable
829 -- and hasn't already been used; otherwise it uses one of the tc_tvs
830 choose_univs used tc_tvs []
831 = ASSERT( null tc_tvs ) []
832 choose_univs used (tc_tv:tc_tvs) (res_ty:res_tys)
833 | Just tv <- tcGetTyVar_maybe res_ty, not (tv `elem` used)
834 = tv : choose_univs (tv:used) tc_tvs res_tys
836 = tc_tv : choose_univs used tc_tvs res_tys
839 argStrictness :: Bool -- True <=> -funbox-strict_fields
841 -> [TcType] -> [StrictnessMark]
842 argStrictness unbox_strict tycon bangs arg_tys
843 = ASSERT( length bangs == length arg_tys )
844 zipWith (chooseBoxingStrategy unbox_strict tycon) arg_tys bangs
846 -- We attempt to unbox/unpack a strict field when either:
847 -- (i) The field is marked '!!', or
848 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
850 -- We have turned off unboxing of newtypes because coercions make unboxing
851 -- and reboxing more complicated
852 chooseBoxingStrategy :: Bool -> TyCon -> TcType -> HsBang -> StrictnessMark
853 chooseBoxingStrategy unbox_strict_fields tycon arg_ty bang
855 HsNoBang -> NotMarkedStrict
856 HsStrict | unbox_strict_fields
857 && can_unbox arg_ty -> MarkedUnboxed
858 HsUnbox | can_unbox arg_ty -> MarkedUnboxed
859 other -> MarkedStrict
861 -- we can unbox if the type is a chain of newtypes with a product tycon
863 can_unbox arg_ty = case splitTyConApp_maybe arg_ty of
865 Just (arg_tycon, tycon_args) ->
866 not (isRecursiveTyCon tycon) &&
867 isProductTyCon arg_tycon &&
868 (if isNewTyCon arg_tycon then
869 can_unbox (newTyConInstRhs arg_tycon tycon_args)
873 %************************************************************************
875 \subsection{Dependency analysis}
877 %************************************************************************
879 Validity checking is done once the mutually-recursive knot has been
880 tied, so we can look at things freely.
883 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
884 checkCycleErrs tyclss
888 = do { mappM_ recClsErr cls_cycles
889 ; failM } -- Give up now, because later checkValidTyCl
890 -- will loop if the synonym is recursive
892 cls_cycles = calcClassCycles tyclss
894 checkValidTyCl :: TyClDecl Name -> TcM ()
895 -- We do the validity check over declarations, rather than TyThings
896 -- only so that we can add a nice context with tcAddDeclCtxt
898 = tcAddDeclCtxt decl $
899 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
900 ; traceTc (text "Validity of" <+> ppr thing)
902 ATyCon tc -> checkValidTyCon tc
903 AClass cl -> checkValidClass cl
904 ; traceTc (text "Done validity of" <+> ppr thing)
907 -------------------------
908 -- For data types declared with record syntax, we require
909 -- that each constructor that has a field 'f'
910 -- (a) has the same result type
911 -- (b) has the same type for 'f'
912 -- module alpha conversion of the quantified type variables
913 -- of the constructor.
915 checkValidTyCon :: TyCon -> TcM ()
918 = case synTyConRhs tc of
919 OpenSynTyCon _ -> return ()
920 SynonymTyCon ty -> checkValidType syn_ctxt ty
922 = -- Check the context on the data decl
923 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
925 -- Check arg types of data constructors
926 mappM_ (checkValidDataCon tc) data_cons `thenM_`
928 -- Check that fields with the same name share a type
929 mappM_ check_fields groups
932 syn_ctxt = TySynCtxt name
934 data_cons = tyConDataCons tc
936 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
937 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
938 get_fields con = dataConFieldLabels con `zip` repeat con
939 -- dataConFieldLabels may return the empty list, which is fine
941 -- See Note [GADT record selectors] in MkId.lhs
942 -- We must check (a) that the named field has the same
943 -- type in each constructor
944 -- (b) that those constructors have the same result type
946 -- However, the constructors may have differently named type variable
947 -- and (worse) we don't know how the correspond to each other. E.g.
948 -- C1 :: forall a b. { f :: a, g :: b } -> T a b
949 -- C2 :: forall d c. { f :: c, g :: c } -> T c d
951 -- So what we do is to ust Unify.tcMatchTys to compare the first candidate's
952 -- result type against other candidates' types BOTH WAYS ROUND.
953 -- If they magically agrees, take the substitution and
954 -- apply them to the latter ones, and see if they match perfectly.
955 check_fields fields@((label, con1) : other_fields)
956 -- These fields all have the same name, but are from
957 -- different constructors in the data type
958 = recoverM (return ()) $ mapM_ checkOne other_fields
959 -- Check that all the fields in the group have the same type
960 -- NB: this check assumes that all the constructors of a given
961 -- data type use the same type variables
963 tvs1 = mkVarSet (dataConAllTyVars con1)
964 res1 = dataConResTys con1
965 fty1 = dataConFieldType con1 label
967 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
968 = do { checkFieldCompat label con1 con2 tvs1 res1 res2 fty1 fty2
969 ; checkFieldCompat label con2 con1 tvs2 res2 res1 fty2 fty1 }
971 tvs2 = mkVarSet (dataConAllTyVars con2)
972 res2 = dataConResTys con2
973 fty2 = dataConFieldType con2 label
975 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
976 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
977 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
979 mb_subst1 = tcMatchTys tvs1 res1 res2
980 mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
982 -------------------------------
983 checkValidDataCon :: TyCon -> DataCon -> TcM ()
984 checkValidDataCon tc con
985 = setSrcSpan (srcLocSpan (getSrcLoc con)) $
986 addErrCtxt (dataConCtxt con) $
987 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
988 ; checkValidType ctxt (dataConUserType con) }
990 ctxt = ConArgCtxt (dataConName con)
992 -------------------------------
993 checkValidClass :: Class -> TcM ()
995 = do { -- CHECK ARITY 1 FOR HASKELL 1.4
996 gla_exts <- doptM Opt_GlasgowExts
998 -- Check that the class is unary, unless GlaExs
999 ; checkTc (notNull tyvars) (nullaryClassErr cls)
1000 ; checkTc (gla_exts || unary) (classArityErr cls)
1002 -- Check the super-classes
1003 ; checkValidTheta (ClassSCCtxt (className cls)) theta
1005 -- Check the class operations
1006 ; mappM_ (check_op gla_exts) op_stuff
1008 -- Check that if the class has generic methods, then the
1009 -- class has only one parameter. We can't do generic
1010 -- multi-parameter type classes!
1011 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
1014 (tyvars, theta, _, op_stuff) = classBigSig cls
1015 unary = isSingleton tyvars
1016 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
1018 check_op gla_exts (sel_id, dm)
1019 = addErrCtxt (classOpCtxt sel_id tau) $ do
1020 { checkValidTheta SigmaCtxt (tail theta)
1021 -- The 'tail' removes the initial (C a) from the
1022 -- class itself, leaving just the method type
1024 ; checkValidType (FunSigCtxt op_name) tau
1026 -- Check that the type mentions at least one of
1027 -- the class type variables
1028 ; checkTc (any (`elemVarSet` tyVarsOfType tau) tyvars)
1029 (noClassTyVarErr cls sel_id)
1031 -- Check that for a generic method, the type of
1032 -- the method is sufficiently simple
1033 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
1034 (badGenericMethodType op_name op_ty)
1037 op_name = idName sel_id
1038 op_ty = idType sel_id
1039 (_,theta1,tau1) = tcSplitSigmaTy op_ty
1040 (_,theta2,tau2) = tcSplitSigmaTy tau1
1041 (theta,tau) | gla_exts = (theta1 ++ theta2, tau2)
1042 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
1043 -- Ugh! The function might have a type like
1044 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
1045 -- With -fglasgow-exts, we want to allow this, even though the inner
1046 -- forall has an (Eq a) constraint. Whereas in general, each constraint
1047 -- in the context of a for-all must mention at least one quantified
1048 -- type variable. What a mess!
1051 ---------------------------------------------------------------------
1052 resultTypeMisMatch field_name con1 con2
1053 = vcat [sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1054 ptext SLIT("have a common field") <+> quotes (ppr field_name) <> comma],
1055 nest 2 $ ptext SLIT("but have different result types")]
1056 fieldTypeMisMatch field_name con1 con2
1057 = sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1058 ptext SLIT("give different types for field"), quotes (ppr field_name)]
1060 dataConCtxt con = ptext SLIT("In the definition of data constructor") <+> quotes (ppr con)
1062 classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
1063 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
1066 = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
1069 = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
1070 parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
1072 noClassTyVarErr clas op
1073 = sep [ptext SLIT("The class method") <+> quotes (ppr op),
1074 ptext SLIT("mentions none of the type variables of the class") <+>
1075 ppr clas <+> hsep (map ppr (classTyVars clas))]
1077 genericMultiParamErr clas
1078 = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
1079 ptext SLIT("cannot have generic methods")
1081 badGenericMethodType op op_ty
1082 = hang (ptext SLIT("Generic method type is too complex"))
1083 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
1084 ptext SLIT("You can only use type variables, arrows, lists, and tuples")])
1087 = setSrcSpan (getLoc (head sorted_decls)) $
1088 addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
1089 nest 2 (vcat (map ppr_decl sorted_decls))])
1091 sorted_decls = sortLocated syn_decls
1092 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
1095 = setSrcSpan (getLoc (head sorted_decls)) $
1096 addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
1097 nest 2 (vcat (map ppr_decl sorted_decls))])
1099 sorted_decls = sortLocated cls_decls
1100 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
1102 sortLocated :: [Located a] -> [Located a]
1103 sortLocated things = sortLe le things
1105 le (L l1 _) (L l2 _) = l1 <= l2
1107 badDataConTyCon data_con
1108 = hang (ptext SLIT("Data constructor") <+> quotes (ppr data_con) <+>
1109 ptext SLIT("returns type") <+> quotes (ppr (dataConTyCon data_con)))
1110 2 (ptext SLIT("instead of its parent type"))
1113 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
1114 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow GADTs")) ]
1116 badStupidTheta tc_name
1117 = ptext SLIT("A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
1119 newtypeConError tycon n
1120 = sep [ptext SLIT("A newtype must have exactly one constructor,"),
1121 nest 2 $ ptext SLIT("but") <+> quotes (ppr tycon) <+> ptext SLIT("has") <+> speakN n ]
1124 = sep [ptext SLIT("A newtype constructor cannot have an existential context,"),
1125 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
1127 newtypeFieldErr con_name n_flds
1128 = sep [ptext SLIT("The constructor of a newtype must have exactly one field"),
1129 nest 2 $ ptext SLIT("but") <+> quotes (ppr con_name) <+> ptext SLIT("has") <+> speakN n_flds]
1131 badSigTyDecl tc_name
1132 = vcat [ ptext SLIT("Illegal kind signature") <+>
1133 quotes (ppr tc_name)
1134 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow indexed types")) ]
1136 badKindSigCtxt tc_name
1137 = vcat [ ptext SLIT("Illegal context in kind signature") <+>
1138 quotes (ppr tc_name)
1139 , nest 2 (parens $ ptext SLIT("Currently, kind signatures cannot have a context")) ]
1141 badIdxTyDecl tc_name
1142 = vcat [ ptext SLIT("Illegal indexed type instance for") <+>
1143 quotes (ppr tc_name)
1144 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow indexed types")) ]
1146 badGadtIdxTyDecl tc_name
1147 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+>
1148 quotes (ppr tc_name)
1149 , nest 2 (parens $ ptext SLIT("Indexed types cannot use GADT declarations")) ]
1151 tooManyParmsErr tc_name
1152 = ptext SLIT("Indexed type instance has too many parameters:") <+>
1153 quotes (ppr tc_name)
1155 tooFewParmsErr tc_name
1156 = ptext SLIT("Indexed type instance has too few parameters:") <+>
1157 quotes (ppr tc_name)
1159 badBootTyIdxDeclErr = ptext SLIT("Illegal indexed type instance in hs-boot file")
1161 emptyConDeclsErr tycon
1162 = sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
1163 nest 2 $ ptext SLIT("(-fglasgow-exts permits this)")]