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
19 import HsTypes ( HsBang(..), getBangStrictness )
20 import BasicTypes ( RecFlag(..), StrictnessMark(..) )
21 import HscTypes ( implicitTyThings, ModDetails )
22 import BuildTyCl ( buildClass, buildAlgTyCon, buildSynTyCon, buildDataCon,
23 mkDataTyConRhs, mkNewTyConRhs )
25 import TcEnv ( TyThing(..),
26 tcLookupLocated, tcLookupLocatedGlobal,
27 tcExtendGlobalEnv, tcExtendKindEnv, tcExtendKindEnvTvs,
28 tcExtendRecEnv, tcLookupTyVar, InstInfo )
29 import TcTyDecls ( calcRecFlags, calcClassCycles, calcSynCycles )
30 import TcClassDcl ( tcClassSigs, tcAddDeclCtxt )
31 import TcHsType ( kcHsTyVars, kcHsLiftedSigType, kcHsType,
32 kcHsContext, tcTyVarBndrs, tcHsKindedType, tcHsKindedContext,
33 kcHsSigType, tcHsBangType, tcLHsConResTy,
34 tcDataKindSig, kcCheckHsType )
35 import TcMType ( newKindVar, checkValidTheta, checkValidType,
37 UserTypeCtxt(..), SourceTyCtxt(..) )
38 import TcType ( TcKind, TcType, Type, tyVarsOfType, mkPhiTy,
39 mkArrowKind, liftedTypeKind, mkTyVarTys,
40 tcSplitSigmaTy, tcEqTypes, tcGetTyVar_maybe )
41 import Type ( PredType(..), splitTyConApp_maybe, mkTyVarTy,
42 newTyConInstRhs, isLiftedTypeKind, Kind
43 -- pprParendType, pprThetaArrow
45 import Generics ( validGenericMethodType, canDoGenerics )
46 import Class ( Class, className, classTyCon, DefMeth(..), classBigSig, classTyVars )
47 import TyCon ( TyCon, AlgTyConRhs( AbstractTyCon, OpenDataTyCon,
49 SynTyConRhs( OpenSynTyCon, SynonymTyCon ),
50 tyConDataCons, mkForeignTyCon, isProductTyCon,
51 isRecursiveTyCon, isOpenTyCon,
52 tyConStupidTheta, synTyConRhs, isSynTyCon, tyConName,
53 isNewTyCon, tyConKind )
54 import DataCon ( DataCon, dataConUserType, dataConName,
55 dataConFieldLabels, dataConTyCon, dataConAllTyVars,
56 dataConFieldType, dataConResTys )
57 import Var ( TyVar, idType, idName )
58 import VarSet ( elemVarSet, mkVarSet )
59 import Name ( Name, getSrcLoc )
61 import Maybe ( isJust, fromJust, isNothing )
62 import Maybes ( expectJust )
63 import Unify ( tcMatchTys, tcMatchTyX )
64 import Util ( zipLazy, isSingleton, notNull, sortLe )
65 import List ( partition )
66 import SrcLoc ( Located(..), unLoc, getLoc, srcLocSpan )
67 import ListSetOps ( equivClasses, minusList )
68 import List ( delete )
69 import Digraph ( SCC(..) )
70 import DynFlags ( DynFlag( Opt_GlasgowExts, Opt_Generics,
71 Opt_UnboxStrictFields ) )
75 %************************************************************************
77 \subsection{Type checking for type and class declarations}
79 %************************************************************************
83 Consider a mutually-recursive group, binding
84 a type constructor T and a class C.
86 Step 1: getInitialKind
87 Construct a KindEnv by binding T and C to a kind variable
90 In that environment, do a kind check
92 Step 3: Zonk the kinds
94 Step 4: buildTyConOrClass
95 Construct an environment binding T to a TyCon and C to a Class.
96 a) Their kinds comes from zonking the relevant kind variable
97 b) Their arity (for synonyms) comes direct from the decl
98 c) The funcional dependencies come from the decl
99 d) The rest comes a knot-tied binding of T and C, returned from Step 4
100 e) The variances of the tycons in the group is calculated from
104 In this environment, walk over the decls, constructing the TyCons and Classes.
105 This uses in a strict way items (a)-(c) above, which is why they must
106 be constructed in Step 4. Feed the results back to Step 4.
107 For this step, pass the is-recursive flag as the wimp-out flag
111 Step 6: Extend environment
112 We extend the type environment with bindings not only for the TyCons and Classes,
113 but also for their "implicit Ids" like data constructors and class selectors
115 Step 7: checkValidTyCl
116 For a recursive group only, check all the decls again, just
117 to check all the side conditions on validity. We could not
118 do this before because we were in a mutually recursive knot.
120 Identification of recursive TyCons
121 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
122 The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to
125 Identifying a TyCon as recursive serves two purposes
127 1. Avoid infinite types. Non-recursive newtypes are treated as
128 "transparent", like type synonyms, after the type checker. If we did
129 this for all newtypes, we'd get infinite types. So we figure out for
130 each newtype whether it is "recursive", and add a coercion if so. In
131 effect, we are trying to "cut the loops" by identifying a loop-breaker.
133 2. Avoid infinite unboxing. This is nothing to do with newtypes.
137 Well, this function diverges, but we don't want the strictness analyser
138 to diverge. But the strictness analyser will diverge because it looks
139 deeper and deeper into the structure of T. (I believe there are
140 examples where the function does something sane, and the strictness
141 analyser still diverges, but I can't see one now.)
143 Now, concerning (1), the FC2 branch currently adds a coercion for ALL
144 newtypes. I did this as an experiment, to try to expose cases in which
145 the coercions got in the way of optimisations. If it turns out that we
146 can indeed always use a coercion, then we don't risk recursive types,
147 and don't need to figure out what the loop breakers are.
149 For newtype *families* though, we will always have a coercion, so they
150 are always loop breakers! So you can easily adjust the current
151 algorithm by simply treating all newtype families as loop breakers (and
152 indeed type families). I think.
155 tcTyAndClassDecls :: ModDetails -> [LTyClDecl Name]
156 -> TcM TcGblEnv -- Input env extended by types and classes
157 -- and their implicit Ids,DataCons
158 tcTyAndClassDecls boot_details allDecls
159 = do { -- Omit instances of indexed types; they are handled together
160 -- with the *heads* of class instances
161 ; let decls = filter (not . isIdxTyDecl . unLoc) allDecls
163 -- First check for cyclic type synonysm or classes
164 -- See notes with checkCycleErrs
165 ; checkCycleErrs decls
167 ; traceTc (text "tcTyAndCl" <+> ppr mod)
168 ; (syn_tycons, alg_tyclss) <- fixM (\ ~(rec_syn_tycons, rec_alg_tyclss) ->
169 do { let { -- Calculate variances and rec-flag
170 ; (syn_decls, alg_decls) = partition (isSynDecl . unLoc)
172 -- Extend the global env with the knot-tied results
173 -- for data types and classes
175 -- We must populate the environment with the loop-tied T's right
176 -- away, because the kind checker may "fault in" some type
177 -- constructors that recursively mention T
178 ; let { gbl_things = mkGlobalThings alg_decls rec_alg_tyclss }
179 ; tcExtendRecEnv gbl_things $ do
181 -- Kind-check the declarations
182 { (kc_syn_decls, kc_alg_decls) <- kcTyClDecls syn_decls alg_decls
184 ; let { calc_rec = calcRecFlags boot_details rec_alg_tyclss
185 ; tc_decl = addLocM (tcTyClDecl calc_rec) }
186 -- Type-check the type synonyms, and extend the envt
187 ; syn_tycons <- tcSynDecls kc_syn_decls
188 ; tcExtendGlobalEnv syn_tycons $ do
190 -- Type-check the data types and classes
191 { alg_tyclss <- mappM tc_decl kc_alg_decls
192 ; return (syn_tycons, alg_tyclss)
194 -- Finished with knot-tying now
195 -- Extend the environment with the finished things
196 ; tcExtendGlobalEnv (syn_tycons ++ alg_tyclss) $ do
198 -- Perform the validity check
199 { traceTc (text "ready for validity check")
200 ; mappM_ (addLocM checkValidTyCl) decls
201 ; traceTc (text "done")
203 -- Add the implicit things;
204 -- we want them in the environment because
205 -- they may be mentioned in interface files
206 ; let { implicit_things = concatMap implicitTyThings alg_tyclss }
207 ; traceTc ((text "Adding" <+> ppr alg_tyclss) $$ (text "and" <+> ppr implicit_things))
208 ; tcExtendGlobalEnv implicit_things getGblEnv
211 mkGlobalThings :: [LTyClDecl Name] -- The decls
212 -> [TyThing] -- Knot-tied, in 1-1 correspondence with the decls
214 -- Driven by the Decls, and treating the TyThings lazily
215 -- make a TypeEnv for the new things
216 mkGlobalThings decls things
217 = map mk_thing (decls `zipLazy` things)
219 mk_thing (L _ (ClassDecl {tcdLName = L _ name}), ~(AClass cl))
221 mk_thing (L _ decl, ~(ATyCon tc))
222 = (tcdName decl, ATyCon tc)
226 %************************************************************************
228 \subsection{Type checking instances of indexed types}
230 %************************************************************************
232 Instances of indexed types are somewhat of a hybrid. They are processed
233 together with class instance heads, but can contain data constructors and hence
234 they share a lot of kinding and type checking code with ordinary algebraic
235 data types (and GADTs).
238 tcIdxTyInstDecl :: LTyClDecl Name -> TcM (Maybe InstInfo) -- Nothing if error
239 tcIdxTyInstDecl (L loc decl)
240 = -- Prime error recovery, set source location
241 recoverM (returnM Nothing) $
244 do { -- indexed data types require -fglasgow-exts and can't be in an
246 ; gla_exts <- doptM Opt_GlasgowExts
247 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
248 ; checkTc gla_exts $ badIdxTyDecl (tcdLName decl)
249 ; checkTc (not is_boot) $ badBootTyIdxDeclErr
251 -- perform kind and type checking
252 ; tcIdxTyInstDecl1 decl
255 tcIdxTyInstDecl1 :: TyClDecl Name -> TcM (Maybe InstInfo) -- Nothing if error
257 tcIdxTyInstDecl1 (decl@TySynonym {})
258 = kcIdxTyPats decl $ \k_tvs k_typats resKind ->
259 do { -- kind check the right hand side of the type equation
260 ; k_rhs <- kcCheckHsType (tcdSynRhs decl) resKind
262 -- type check type equation
263 ; tcTyVarBndrs k_tvs $ \t_tvs -> do {
264 ; t_typats <- mappM tcHsKindedType k_typats
265 ; t_rhs <- tcHsKindedType k_rhs
267 -- construct type rewrite rule
268 -- !!!of the form: forall t_tvs. (tcdLName decl) t_typats = t_rhs
269 ; return Nothing -- !!!TODO: need InstInfo for indexed types
272 tcIdxTyInstDecl1 (decl@TyData {tcdND = new_or_data, tcdLName = L _ tc_name,
274 = kcIdxTyPats decl $ \k_tvs k_typats resKind ->
275 do { -- kind check the data declaration as usual
276 ; k_decl <- kcDataDecl decl k_tvs
277 ; k_typats <- mappM tcHsKindedType k_typats
278 ; let k_ctxt = tcdCtxt decl
279 k_cons = tcdCons decl
281 -- result kind must be '*' (otherwise, we have too few patterns)
282 ; checkTc (isLiftedTypeKind resKind) $ tooFewParmsErr tc_name
284 -- type check indexed data type declaration
285 ; tcTyVarBndrs k_tvs $ \t_tvs -> do {
286 ; unbox_strict <- doptM Opt_UnboxStrictFields
288 -- Check that we don't use GADT syntax for indexed types
289 ; checkTc h98_syntax (badGadtIdxTyDecl tc_name)
291 -- Check that a newtype has exactly one constructor
292 ; checkTc (new_or_data == DataType || isSingleton cons) $
293 newtypeConError tc_name (length cons)
295 ; stupid_theta <- tcHsKindedContext k_ctxt
296 ; tycon <- fixM (\ tycon -> do
297 { data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data
302 DataType -> return (mkDataTyConRhs data_cons)
304 ASSERT( isSingleton data_cons )
305 mkNewTyConRhs tc_name tycon (head data_cons)
306 --vvvvvvv !!! need a new derived tc_name here
307 ; buildAlgTyCon tc_name t_tvs stupid_theta tc_rhs Recursive
309 -- We always assume that indexed types are recursive. Why?
310 -- (1) Due to their open nature, we can never be sure that a
311 -- further instance might not introduce a new recursive
312 -- dependency. (2) They are always valid loop breakers as
313 -- they involve a coercion.
317 -- !!!twofold: (1) (ATyCon tycon) and (2) an equality axiom
318 ; return Nothing -- !!!TODO: need InstInfo for indexed types
321 h98_syntax = case cons of -- All constructors have same shape
322 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
325 -- Kind checking of indexed types
328 -- Kind check type patterns and kind annotate the embedded type variables.
330 -- * Here we check that a type instance matches its kind signature, but we do
331 -- not check whether there is a pattern for each type index; the latter
332 -- check is only required for type functions.
334 kcIdxTyPats :: TyClDecl Name
335 -> ([LHsTyVarBndr Name] -> [LHsType Name] -> Kind -> TcM a)
336 -- ^^kinded tvs ^^kinded ty pats ^^res kind
338 kcIdxTyPats decl thing_inside
339 = kcHsTyVars (tcdTyVars decl) $ \tvs ->
340 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
341 ; let { tc_kind = case tc_ty_thing of
342 AGlobal (ATyCon tycon) -> tyConKind tycon
343 ; (kinds, resKind) = splitKindFunTys tc_kind
344 ; hs_typats = fromJust $ tcdTyPats decl }
346 -- we may not have more parameters than the kind indicates
347 ; checkTc (length kinds >= length hs_typats) $
348 tooManyParmsErr (tcdLName decl)
350 -- type functions can have a higher-kinded result
351 ; let resultKind = mkArrowKinds (drop (length hs_typats) kinds) resKind
352 ; typats <- zipWithM kcCheckHsType hs_typats kinds
353 ; thing_inside tvs typats resultKind
359 %************************************************************************
363 %************************************************************************
365 We need to kind check all types in the mutually recursive group
366 before we know the kind of the type variables. For example:
369 op :: D b => a -> b -> b
372 bop :: (Monad c) => ...
374 Here, the kind of the locally-polymorphic type variable "b"
375 depends on *all the uses of class D*. For example, the use of
376 Monad c in bop's type signature means that D must have kind Type->Type.
378 However type synonyms work differently. They can have kinds which don't
379 just involve (->) and *:
380 type R = Int# -- Kind #
381 type S a = Array# a -- Kind * -> #
382 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
383 So we must infer their kinds from their right-hand sides *first* and then
384 use them, whereas for the mutually recursive data types D we bring into
385 scope kind bindings D -> k, where k is a kind variable, and do inference.
389 This treatment of type synonyms only applies to Haskell 98-style synonyms.
390 General type functions can be recursive, and hence, appear in `alg_decls'.
392 The kind of an indexed type is solely determinded by its kind signature;
393 hence, only kind signatures participate in the construction of the initial
394 kind environment (as constructed by `getInitialKind'). In fact, we ignore
395 instances of indexed types altogether in the following. However, we need to
396 include the kind signatures of associated types into the construction of the
397 initial kind environment. (This is handled by `allDecls').
400 kcTyClDecls syn_decls alg_decls
401 = do { -- First extend the kind env with each data type, class, and
402 -- indexed type, mapping them to a type variable
403 let initialKindDecls = concat [allDecls decl | L _ decl <- alg_decls]
404 ; alg_kinds <- mappM getInitialKind initialKindDecls
405 ; tcExtendKindEnv alg_kinds $ do
407 -- Now kind-check the type synonyms, in dependency order
408 -- We do these differently to data type and classes,
409 -- because a type synonym can be an unboxed type
411 -- and a kind variable can't unify with UnboxedTypeKind
412 -- So we infer their kinds in dependency order
413 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
414 ; tcExtendKindEnv syn_kinds $ do
416 -- Now kind-check the data type, class, and kind signatures,
417 -- returning kind-annotated decls; we don't kind-check
418 -- instances of indexed types yet, but leave this to
420 { kc_alg_decls <- mappM (wrapLocM kcTyClDecl)
421 (filter (not . isIdxTyDecl . unLoc) alg_decls)
423 ; return (kc_syn_decls, kc_alg_decls) }}}
425 -- get all declarations relevant for determining the initial kind
427 allDecls (decl@ClassDecl {tcdATs = ats}) = decl : [ at
430 allDecls decl | isIdxTyDecl decl = []
433 ------------------------------------------------------------------------
434 getInitialKind :: TyClDecl Name -> TcM (Name, TcKind)
435 -- Only for data type, class, and indexed type declarations
436 -- Get as much info as possible from the data, class, or indexed type decl,
437 -- so as to maximise usefulness of error messages
439 = do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl)
440 ; res_kind <- mk_res_kind decl
441 ; return (tcdName decl, mkArrowKinds arg_kinds res_kind) }
443 mk_arg_kind (UserTyVar _) = newKindVar
444 mk_arg_kind (KindedTyVar _ kind) = return kind
446 mk_res_kind (TyFunction { tcdKind = kind }) = return kind
447 mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
448 -- On GADT-style and data signature declarations we allow a kind
450 -- data T :: *->* where { ... }
451 mk_res_kind other = return liftedTypeKind
455 kcSynDecls :: [SCC (LTyClDecl Name)]
456 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
457 [(Name,TcKind)]) -- Kind bindings
460 kcSynDecls (group : groups)
461 = do { (decl, nk) <- kcSynDecl group
462 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
463 ; return (decl:decls, nk:nks) }
466 kcSynDecl :: SCC (LTyClDecl Name)
467 -> TcM (LTyClDecl Name, -- Kind-annotated decls
468 (Name,TcKind)) -- Kind bindings
469 kcSynDecl (AcyclicSCC ldecl@(L loc decl))
470 = tcAddDeclCtxt decl $
471 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
472 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
473 <+> brackets (ppr k_tvs))
474 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
475 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
476 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
477 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
478 (unLoc (tcdLName decl), tc_kind)) })
480 kcSynDecl (CyclicSCC decls)
481 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
482 -- of out-of-scope tycons
484 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
486 ------------------------------------------------------------------------
487 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
488 -- Not used for type synonyms (see kcSynDecl)
490 kcTyClDecl decl@(TyData {})
491 = ASSERT( not . isJust $ tcdTyPats decl ) -- must not be instance of idx ty
492 kcTyClDeclBody decl $
495 kcTyClDecl decl@(TyFunction {})
496 = kcTyClDeclBody decl $ \ tvs' ->
497 return (decl {tcdTyVars = tvs'})
499 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs, tcdATs = ats})
500 = kcTyClDeclBody decl $ \ tvs' ->
501 do { is_boot <- tcIsHsBoot
502 ; ctxt' <- kcHsContext ctxt
503 ; ats' <- mappM (wrapLocM kcTyClDecl) ats
504 ; sigs' <- mappM (wrapLocM kc_sig ) sigs
505 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs',
508 kc_sig (TypeSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
509 ; return (TypeSig nm op_ty') }
510 kc_sig other_sig = return other_sig
512 kcTyClDecl decl@(ForeignType {})
515 kcTyClDeclBody :: TyClDecl Name
516 -> ([LHsTyVarBndr Name] -> TcM a)
518 -- getInitialKind has made a suitably-shaped kind for the type or class
519 -- Unpack it, and attribute those kinds to the type variables
520 -- Extend the env with bindings for the tyvars, taken from
521 -- the kind of the tycon/class. Give it to the thing inside, and
522 -- check the result kind matches
523 kcTyClDeclBody decl thing_inside
524 = tcAddDeclCtxt decl $
525 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
526 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
527 (kinds, _) = splitKindFunTys tc_kind
528 hs_tvs = tcdTyVars decl
529 kinded_tvs = ASSERT( length kinds >= length hs_tvs )
530 [ L loc (KindedTyVar (hsTyVarName tv) k)
531 | (L loc tv, k) <- zip hs_tvs kinds]
532 ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
534 -- Kind check a data declaration, assuming that we already extended the
535 -- kind environment with the type variables of the left-hand side (these
536 -- kinded type variables are also passed as the second parameter).
538 kcDataDecl :: TyClDecl Name -> [LHsTyVarBndr Name] -> TcM (TyClDecl Name)
539 kcDataDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
541 = do { ctxt' <- kcHsContext ctxt
542 ; cons' <- mappM (wrapLocM kc_con_decl) cons
543 ; return (decl {tcdTyVars = tvs, tcdCtxt = ctxt', tcdCons = cons'}) }
545 kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res) = do
546 kcHsTyVars ex_tvs $ \ex_tvs' -> do
547 ex_ctxt' <- kcHsContext ex_ctxt
548 details' <- kc_con_details details
550 ResTyH98 -> return ResTyH98
551 ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
552 return (ConDecl name expl ex_tvs' ex_ctxt' details' res')
554 kc_con_details (PrefixCon btys)
555 = do { btys' <- mappM kc_larg_ty btys ; return (PrefixCon btys') }
556 kc_con_details (InfixCon bty1 bty2)
557 = do { bty1' <- kc_larg_ty bty1; bty2' <- kc_larg_ty bty2; return (InfixCon bty1' bty2') }
558 kc_con_details (RecCon fields)
559 = do { fields' <- mappM kc_field fields; return (RecCon fields') }
561 kc_field (fld, bty) = do { bty' <- kc_larg_ty bty ; return (fld, bty') }
563 kc_larg_ty bty = case new_or_data of
564 DataType -> kcHsSigType bty
565 NewType -> kcHsLiftedSigType bty
566 -- Can't allow an unlifted type for newtypes, because we're effectively
567 -- going to remove the constructor while coercing it to a lifted type.
568 -- And newtypes can't be bang'd
572 %************************************************************************
574 \subsection{Type checking}
576 %************************************************************************
579 tcSynDecls :: [LTyClDecl Name] -> TcM [TyThing]
580 tcSynDecls [] = return []
581 tcSynDecls (decl : decls)
582 = do { syn_tc <- addLocM tcSynDecl decl
583 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls decls)
584 ; return (syn_tc : syn_tcs) }
587 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
588 = tcTyVarBndrs tvs $ \ tvs' -> do
589 { traceTc (text "tcd1" <+> ppr tc_name)
590 ; rhs_ty' <- tcHsKindedType rhs_ty
591 ; return (ATyCon (buildSynTyCon tc_name tvs' (SynonymTyCon rhs_ty'))) }
594 tcTyClDecl :: (Name -> RecFlag) -> TyClDecl Name -> TcM TyThing
596 tcTyClDecl calc_isrec decl
597 = tcAddDeclCtxt decl (tcTyClDecl1 calc_isrec decl)
599 -- kind signature for a type function
600 tcTyClDecl1 _calc_isrec
601 (TyFunction {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = kind})
602 = tcTyVarBndrs tvs $ \ tvs' -> do
603 { gla_exts <- doptM Opt_GlasgowExts
605 -- Check that we don't use kind signatures without Glasgow extensions
606 ; checkTc gla_exts $ badSigTyDecl tc_name
608 ; return (ATyCon (buildSynTyCon tc_name tvs' (OpenSynTyCon kind)))
611 -- kind signature for an indexed data type
612 tcTyClDecl1 _calc_isrec
613 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
614 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = []})
615 = tcTyVarBndrs tvs $ \ tvs' -> do
616 { extra_tvs <- tcDataKindSig mb_ksig
617 ; let final_tvs = tvs' ++ extra_tvs -- we may not need these
619 ; checkTc (null . unLoc $ ctxt) $ badKindSigCtxt tc_name
620 ; gla_exts <- doptM Opt_GlasgowExts
622 -- Check that we don't use kind signatures without Glasgow extensions
623 ; checkTc gla_exts $ badSigTyDecl tc_name
625 ; tycon <- buildAlgTyCon tc_name final_tvs []
627 DataType -> OpenDataTyCon
628 NewType -> OpenNewTyCon)
630 ; return (ATyCon tycon)
633 tcTyClDecl1 calc_isrec
634 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
635 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
636 = tcTyVarBndrs tvs $ \ tvs' -> do
637 { extra_tvs <- tcDataKindSig mb_ksig
638 ; let final_tvs = tvs' ++ extra_tvs
639 ; stupid_theta <- tcHsKindedContext ctxt
640 ; want_generic <- doptM Opt_Generics
641 ; unbox_strict <- doptM Opt_UnboxStrictFields
642 ; gla_exts <- doptM Opt_GlasgowExts
643 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
645 -- Check that we don't use GADT syntax in H98 world
646 ; checkTc (gla_exts || h98_syntax) (badGadtDecl tc_name)
648 -- Check that we don't use kind signatures without Glasgow extensions
649 ; checkTc (gla_exts || isNothing mb_ksig) (badSigTyDecl tc_name)
651 -- Check that the stupid theta is empty for a GADT-style declaration
652 ; checkTc (null stupid_theta || h98_syntax) (badStupidTheta tc_name)
654 -- Check that there's at least one condecl,
655 -- or else we're reading an hs-boot file, or -fglasgow-exts
656 ; checkTc (not (null cons) || gla_exts || is_boot)
657 (emptyConDeclsErr tc_name)
659 -- Check that a newtype has exactly one constructor
660 ; checkTc (new_or_data == DataType || isSingleton cons)
661 (newtypeConError tc_name (length cons))
663 ; tycon <- fixM (\ tycon -> do
664 { data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data
668 if null cons && is_boot -- In a hs-boot file, empty cons means
669 then return AbstractTyCon -- "don't know"; hence Abstract
670 else case new_or_data of
671 DataType -> return (mkDataTyConRhs data_cons)
673 ASSERT( isSingleton data_cons )
674 mkNewTyConRhs tc_name tycon (head data_cons)
675 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
676 (want_generic && canDoGenerics data_cons) h98_syntax
678 ; return (ATyCon tycon)
681 is_rec = calc_isrec tc_name
682 h98_syntax = case cons of -- All constructors have same shape
683 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
686 tcTyClDecl1 calc_isrec
687 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
688 tcdCtxt = ctxt, tcdMeths = meths,
689 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
690 = tcTyVarBndrs tvs $ \ tvs' -> do
691 { ctxt' <- tcHsKindedContext ctxt
692 ; fds' <- mappM (addLocM tc_fundep) fundeps
693 ; ats' <- mappM (addLocM (tcTyClDecl1 (const Recursive))) ats
694 -- ^^^^ !!!TODO: what to do with this? Need to generate FC tyfun decls.
695 ; sig_stuff <- tcClassSigs class_name sigs meths
696 ; clas <- fixM (\ clas ->
697 let -- This little knot is just so we can get
698 -- hold of the name of the class TyCon, which we
699 -- need to look up its recursiveness
700 tycon_name = tyConName (classTyCon clas)
701 tc_isrec = calc_isrec tycon_name
703 buildClass class_name tvs' ctxt' fds'
705 ; return (AClass clas) }
707 tc_fundep (tvs1, tvs2) = do { tvs1' <- mappM tcLookupTyVar tvs1 ;
708 ; tvs2' <- mappM tcLookupTyVar tvs2 ;
709 ; return (tvs1', tvs2') }
712 tcTyClDecl1 calc_isrec
713 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
714 = returnM (ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0))
716 -----------------------------------
717 tcConDecl :: Bool -- True <=> -funbox-strict_fields
718 -> NewOrData -> TyCon -> [TyVar]
719 -> ConDecl Name -> TcM DataCon
721 tcConDecl unbox_strict NewType tycon tc_tvs -- Newtypes
722 (ConDecl name _ ex_tvs ex_ctxt details ResTyH98)
723 = do { let tc_datacon field_lbls arg_ty
724 = do { arg_ty' <- tcHsKindedType arg_ty -- No bang on newtype
725 ; buildDataCon (unLoc name) False {- Prefix -}
727 (map unLoc field_lbls)
728 tc_tvs [] -- No existentials
729 [] [] -- No equalities, predicates
733 -- Check that a newtype has no existential stuff
734 ; checkTc (null ex_tvs && null (unLoc ex_ctxt)) (newtypeExError name)
737 PrefixCon [arg_ty] -> tc_datacon [] arg_ty
738 RecCon [(field_lbl, arg_ty)] -> tc_datacon [field_lbl] arg_ty
739 other -> failWithTc (newtypeFieldErr name (length (hsConArgs details)))
740 -- Check that the constructor has exactly one field
743 tcConDecl unbox_strict DataType tycon tc_tvs -- Data types
744 (ConDecl name _ tvs ctxt details res_ty)
745 = tcTyVarBndrs tvs $ \ tvs' -> do
746 { ctxt' <- tcHsKindedContext ctxt
747 ; (univ_tvs, ex_tvs, eq_preds, data_tc) <- tcResultType tycon tc_tvs tvs' res_ty
749 tc_datacon is_infix field_lbls btys
750 = do { let bangs = map getBangStrictness btys
751 ; arg_tys <- mappM tcHsBangType btys
752 ; buildDataCon (unLoc name) is_infix
753 (argStrictness unbox_strict tycon bangs arg_tys)
754 (map unLoc field_lbls)
755 univ_tvs ex_tvs eq_preds ctxt' arg_tys
757 -- NB: we put data_tc, the type constructor gotten from the constructor
758 -- type signature into the data constructor; that way
759 -- checkValidDataCon can complain if it's wrong.
762 PrefixCon btys -> tc_datacon False [] btys
763 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
764 RecCon fields -> tc_datacon False field_names btys
766 (field_names, btys) = unzip fields
770 tcResultType :: TyCon
771 -> [TyVar] -- data T a b c = ...
772 -> [TyVar] -- where MkT :: forall a b c. ...
774 -> TcM ([TyVar], -- Universal
775 [TyVar], -- Existential
776 [(TyVar,Type)], -- Equality predicates
777 TyCon) -- TyCon given in the ResTy
778 -- We don't check that the TyCon given in the ResTy is
779 -- the same as the parent tycon, becuase we are in the middle
780 -- of a recursive knot; so it's postponed until checkValidDataCon
782 tcResultType decl_tycon tc_tvs dc_tvs ResTyH98
783 = return (tc_tvs, dc_tvs, [], decl_tycon)
784 -- In H98 syntax the dc_tvs are the existential ones
785 -- data T a b c = forall d e. MkT ...
786 -- The {a,b,c} are tc_tvs, and {d,e} are dc_tvs
788 tcResultType _ tc_tvs dc_tvs (ResTyGADT res_ty)
789 -- E.g. data T a b c where
790 -- MkT :: forall x y z. T (x,y) z z
792 -- ([a,z,c], [x,y], [a:=:(x,y), c:=:z], T)
794 = do { (dc_tycon, res_tys) <- tcLHsConResTy res_ty
795 -- NB: tc_tvs and dc_tvs are distinct
796 ; let univ_tvs = choose_univs [] tc_tvs res_tys
797 -- Each univ_tv is either a dc_tv or a tc_tv
798 ex_tvs = dc_tvs `minusList` univ_tvs
799 eq_spec = [ (tv, ty) | (tv,ty) <- univ_tvs `zip` res_tys,
801 ; return (univ_tvs, ex_tvs, eq_spec, dc_tycon) }
803 -- choose_univs uses the res_ty itself if it's a type variable
804 -- and hasn't already been used; otherwise it uses one of the tc_tvs
805 choose_univs used tc_tvs []
806 = ASSERT( null tc_tvs ) []
807 choose_univs used (tc_tv:tc_tvs) (res_ty:res_tys)
808 | Just tv <- tcGetTyVar_maybe res_ty, not (tv `elem` used)
809 = tv : choose_univs (tv:used) tc_tvs res_tys
811 = tc_tv : choose_univs used tc_tvs res_tys
814 argStrictness :: Bool -- True <=> -funbox-strict_fields
816 -> [TcType] -> [StrictnessMark]
817 argStrictness unbox_strict tycon bangs arg_tys
818 = ASSERT( length bangs == length arg_tys )
819 zipWith (chooseBoxingStrategy unbox_strict tycon) arg_tys bangs
821 -- We attempt to unbox/unpack a strict field when either:
822 -- (i) The field is marked '!!', or
823 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
825 -- We have turned off unboxing of newtypes because coercions make unboxing
826 -- and reboxing more complicated
827 chooseBoxingStrategy :: Bool -> TyCon -> TcType -> HsBang -> StrictnessMark
828 chooseBoxingStrategy unbox_strict_fields tycon arg_ty bang
830 HsNoBang -> NotMarkedStrict
831 HsStrict | unbox_strict_fields
832 && can_unbox arg_ty -> MarkedUnboxed
833 HsUnbox | can_unbox arg_ty -> MarkedUnboxed
834 other -> MarkedStrict
836 -- we can unbox if the type is a chain of newtypes with a product tycon
838 can_unbox arg_ty = case splitTyConApp_maybe arg_ty of
840 Just (arg_tycon, tycon_args) ->
841 not (isRecursiveTyCon tycon) &&
842 isProductTyCon arg_tycon &&
843 (if isNewTyCon arg_tycon then
844 can_unbox (newTyConInstRhs arg_tycon tycon_args)
848 %************************************************************************
850 \subsection{Dependency analysis}
852 %************************************************************************
854 Validity checking is done once the mutually-recursive knot has been
855 tied, so we can look at things freely.
858 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
859 checkCycleErrs tyclss
863 = do { mappM_ recClsErr cls_cycles
864 ; failM } -- Give up now, because later checkValidTyCl
865 -- will loop if the synonym is recursive
867 cls_cycles = calcClassCycles tyclss
869 checkValidTyCl :: TyClDecl Name -> TcM ()
870 -- We do the validity check over declarations, rather than TyThings
871 -- only so that we can add a nice context with tcAddDeclCtxt
873 = tcAddDeclCtxt decl $
874 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
875 ; traceTc (text "Validity of" <+> ppr thing)
877 ATyCon tc -> checkValidTyCon tc
878 AClass cl -> checkValidClass cl
879 ; traceTc (text "Done validity of" <+> ppr thing)
882 -------------------------
883 -- For data types declared with record syntax, we require
884 -- that each constructor that has a field 'f'
885 -- (a) has the same result type
886 -- (b) has the same type for 'f'
887 -- module alpha conversion of the quantified type variables
888 -- of the constructor.
890 checkValidTyCon :: TyCon -> TcM ()
893 = case synTyConRhs tc of
894 OpenSynTyCon _ -> return ()
895 SynonymTyCon ty -> checkValidType syn_ctxt ty
897 = -- Check the context on the data decl
898 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
900 -- Check arg types of data constructors
901 mappM_ (checkValidDataCon tc) data_cons `thenM_`
903 -- Check that fields with the same name share a type
904 mappM_ check_fields groups
907 syn_ctxt = TySynCtxt name
909 data_cons = tyConDataCons tc
911 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
912 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
913 get_fields con = dataConFieldLabels con `zip` repeat con
914 -- dataConFieldLabels may return the empty list, which is fine
916 -- See Note [GADT record selectors] in MkId.lhs
917 -- We must check (a) that the named field has the same
918 -- type in each constructor
919 -- (b) that those constructors have the same result type
921 -- However, the constructors may have differently named type variable
922 -- and (worse) we don't know how the correspond to each other. E.g.
923 -- C1 :: forall a b. { f :: a, g :: b } -> T a b
924 -- C2 :: forall d c. { f :: c, g :: c } -> T c d
926 -- So what we do is to ust Unify.tcMatchTys to compare the first candidate's
927 -- result type against other candidates' types BOTH WAYS ROUND.
928 -- If they magically agrees, take the substitution and
929 -- apply them to the latter ones, and see if they match perfectly.
930 check_fields fields@((label, con1) : other_fields)
931 -- These fields all have the same name, but are from
932 -- different constructors in the data type
933 = recoverM (return ()) $ mapM_ checkOne other_fields
934 -- Check that all the fields in the group have the same type
935 -- NB: this check assumes that all the constructors of a given
936 -- data type use the same type variables
938 tvs1 = mkVarSet (dataConAllTyVars con1)
939 res1 = dataConResTys con1
940 fty1 = dataConFieldType con1 label
942 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
943 = do { checkFieldCompat label con1 con2 tvs1 res1 res2 fty1 fty2
944 ; checkFieldCompat label con2 con1 tvs2 res2 res1 fty2 fty1 }
946 tvs2 = mkVarSet (dataConAllTyVars con2)
947 res2 = dataConResTys con2
948 fty2 = dataConFieldType con2 label
950 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
951 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
952 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
954 mb_subst1 = tcMatchTys tvs1 res1 res2
955 mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
957 -------------------------------
958 checkValidDataCon :: TyCon -> DataCon -> TcM ()
959 checkValidDataCon tc con
960 = setSrcSpan (srcLocSpan (getSrcLoc con)) $
961 addErrCtxt (dataConCtxt con) $
962 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
963 ; checkValidType ctxt (dataConUserType con) }
965 ctxt = ConArgCtxt (dataConName con)
967 -------------------------------
968 checkValidClass :: Class -> TcM ()
970 = do { -- CHECK ARITY 1 FOR HASKELL 1.4
971 gla_exts <- doptM Opt_GlasgowExts
973 -- Check that the class is unary, unless GlaExs
974 ; checkTc (notNull tyvars) (nullaryClassErr cls)
975 ; checkTc (gla_exts || unary) (classArityErr cls)
977 -- Check the super-classes
978 ; checkValidTheta (ClassSCCtxt (className cls)) theta
980 -- Check the class operations
981 ; mappM_ (check_op gla_exts) op_stuff
983 -- Check that if the class has generic methods, then the
984 -- class has only one parameter. We can't do generic
985 -- multi-parameter type classes!
986 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
989 (tyvars, theta, _, op_stuff) = classBigSig cls
990 unary = isSingleton tyvars
991 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
993 check_op gla_exts (sel_id, dm)
994 = addErrCtxt (classOpCtxt sel_id tau) $ do
995 { checkValidTheta SigmaCtxt (tail theta)
996 -- The 'tail' removes the initial (C a) from the
997 -- class itself, leaving just the method type
999 ; checkValidType (FunSigCtxt op_name) tau
1001 -- Check that the type mentions at least one of
1002 -- the class type variables
1003 ; checkTc (any (`elemVarSet` tyVarsOfType tau) tyvars)
1004 (noClassTyVarErr cls sel_id)
1006 -- Check that for a generic method, the type of
1007 -- the method is sufficiently simple
1008 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
1009 (badGenericMethodType op_name op_ty)
1012 op_name = idName sel_id
1013 op_ty = idType sel_id
1014 (_,theta1,tau1) = tcSplitSigmaTy op_ty
1015 (_,theta2,tau2) = tcSplitSigmaTy tau1
1016 (theta,tau) | gla_exts = (theta1 ++ theta2, tau2)
1017 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
1018 -- Ugh! The function might have a type like
1019 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
1020 -- With -fglasgow-exts, we want to allow this, even though the inner
1021 -- forall has an (Eq a) constraint. Whereas in general, each constraint
1022 -- in the context of a for-all must mention at least one quantified
1023 -- type variable. What a mess!
1026 ---------------------------------------------------------------------
1027 resultTypeMisMatch field_name con1 con2
1028 = vcat [sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1029 ptext SLIT("have a common field") <+> quotes (ppr field_name) <> comma],
1030 nest 2 $ ptext SLIT("but have different result types")]
1031 fieldTypeMisMatch field_name con1 con2
1032 = sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1033 ptext SLIT("give different types for field"), quotes (ppr field_name)]
1035 dataConCtxt con = ptext SLIT("In the definition of data constructor") <+> quotes (ppr con)
1037 classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
1038 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
1041 = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
1044 = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
1045 parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
1047 noClassTyVarErr clas op
1048 = sep [ptext SLIT("The class method") <+> quotes (ppr op),
1049 ptext SLIT("mentions none of the type variables of the class") <+>
1050 ppr clas <+> hsep (map ppr (classTyVars clas))]
1052 genericMultiParamErr clas
1053 = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
1054 ptext SLIT("cannot have generic methods")
1056 badGenericMethodType op op_ty
1057 = hang (ptext SLIT("Generic method type is too complex"))
1058 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
1059 ptext SLIT("You can only use type variables, arrows, lists, and tuples")])
1062 = setSrcSpan (getLoc (head sorted_decls)) $
1063 addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
1064 nest 2 (vcat (map ppr_decl sorted_decls))])
1066 sorted_decls = sortLocated syn_decls
1067 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
1070 = setSrcSpan (getLoc (head sorted_decls)) $
1071 addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
1072 nest 2 (vcat (map ppr_decl sorted_decls))])
1074 sorted_decls = sortLocated cls_decls
1075 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
1077 sortLocated :: [Located a] -> [Located a]
1078 sortLocated things = sortLe le things
1080 le (L l1 _) (L l2 _) = l1 <= l2
1082 badDataConTyCon data_con
1083 = hang (ptext SLIT("Data constructor") <+> quotes (ppr data_con) <+>
1084 ptext SLIT("returns type") <+> quotes (ppr (dataConTyCon data_con)))
1085 2 (ptext SLIT("instead of its parent type"))
1088 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
1089 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow GADTs")) ]
1091 badStupidTheta tc_name
1092 = ptext SLIT("A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
1094 newtypeConError tycon n
1095 = sep [ptext SLIT("A newtype must have exactly one constructor,"),
1096 nest 2 $ ptext SLIT("but") <+> quotes (ppr tycon) <+> ptext SLIT("has") <+> speakN n ]
1099 = sep [ptext SLIT("A newtype constructor cannot have an existential context,"),
1100 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
1102 newtypeFieldErr con_name n_flds
1103 = sep [ptext SLIT("The constructor of a newtype must have exactly one field"),
1104 nest 2 $ ptext SLIT("but") <+> quotes (ppr con_name) <+> ptext SLIT("has") <+> speakN n_flds]
1106 badSigTyDecl tc_name
1107 = vcat [ ptext SLIT("Illegal kind signature") <+>
1108 quotes (ppr tc_name)
1109 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow indexed types")) ]
1111 badKindSigCtxt tc_name
1112 = vcat [ ptext SLIT("Illegal context in kind signature") <+>
1113 quotes (ppr tc_name)
1114 , nest 2 (parens $ ptext SLIT("Currently, kind signatures cannot have a context")) ]
1116 badIdxTyDecl tc_name
1117 = vcat [ ptext SLIT("Illegal indexed type instance for") <+>
1118 quotes (ppr tc_name)
1119 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow indexed types")) ]
1121 badGadtIdxTyDecl tc_name
1122 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+>
1123 quotes (ppr tc_name)
1124 , nest 2 (parens $ ptext SLIT("Indexed types cannot use GADT declarations")) ]
1126 tooManyParmsErr tc_name
1127 = ptext SLIT("Indexed type instance has too many parameters:") <+>
1128 quotes (ppr tc_name)
1130 tooFewParmsErr tc_name
1131 = ptext SLIT("Indexed type instance has too few parameters:") <+>
1132 quotes (ppr tc_name)
1134 badBootTyIdxDeclErr = ptext SLIT("Illegal indexed type instance in hs-boot file")
1136 emptyConDeclsErr tycon
1137 = sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
1138 nest 2 $ ptext SLIT("(-fglasgow-exts permits this)")]