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,
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 { AThing k -> k }
342 (kinds, resKind) = splitKindFunTys tc_kind
343 hs_typats = fromJust $ tcdTyPats decl
345 -- we may not have more parameters than the kind indicates
346 ; checkTc (length kinds >= length hs_typats) $
347 tooManyParmsErr (tcdLName decl)
349 -- type functions can have a higher-kinded result
350 ; let resultKind = mkArrowKinds (drop (length hs_typats) kinds) resKind
351 ; typats <- zipWithM kcCheckHsType hs_typats kinds
352 ; thing_inside tvs typats resultKind
357 %************************************************************************
361 %************************************************************************
363 We need to kind check all types in the mutually recursive group
364 before we know the kind of the type variables. For example:
367 op :: D b => a -> b -> b
370 bop :: (Monad c) => ...
372 Here, the kind of the locally-polymorphic type variable "b"
373 depends on *all the uses of class D*. For example, the use of
374 Monad c in bop's type signature means that D must have kind Type->Type.
376 However type synonyms work differently. They can have kinds which don't
377 just involve (->) and *:
378 type R = Int# -- Kind #
379 type S a = Array# a -- Kind * -> #
380 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
381 So we must infer their kinds from their right-hand sides *first* and then
382 use them, whereas for the mutually recursive data types D we bring into
383 scope kind bindings D -> k, where k is a kind variable, and do inference.
387 This treatment of type synonyms only applies to Haskell 98-style synonyms.
388 General type functions can be recursive, and hence, appear in `alg_decls'.
390 The kind of an indexed type is solely determinded by its kind signature;
391 hence, only kind signatures participate in the construction of the initial
392 kind environment (as constructed by `getInitialKind'). In fact, we ignore
393 instances of indexed types altogether in the following. However, we need to
394 include the kind signatures of associated types into the construction of the
395 initial kind environment. (This is handled by `allDecls').
398 kcTyClDecls syn_decls alg_decls
399 = do { -- First extend the kind env with each data type, class, and
400 -- indexed type, mapping them to a type variable
401 let initialKindDecls = concat [allDecls decl | L _ decl <- alg_decls]
402 ; alg_kinds <- mappM getInitialKind initialKindDecls
403 ; tcExtendKindEnv alg_kinds $ do
405 -- Now kind-check the type synonyms, in dependency order
406 -- We do these differently to data type and classes,
407 -- because a type synonym can be an unboxed type
409 -- and a kind variable can't unify with UnboxedTypeKind
410 -- So we infer their kinds in dependency order
411 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
412 ; tcExtendKindEnv syn_kinds $ do
414 -- Now kind-check the data type, class, and kind signatures,
415 -- returning kind-annotated decls; we don't kind-check
416 -- instances of indexed types yet, but leave this to
418 { kc_alg_decls <- mappM (wrapLocM kcTyClDecl)
419 (filter (not . isIdxTyDecl . unLoc) alg_decls)
421 ; return (kc_syn_decls, kc_alg_decls) }}}
423 -- get all declarations relevant for determining the initial kind
425 allDecls (decl@ClassDecl {tcdATs = ats}) = decl : [ at
428 allDecls decl | isIdxTyDecl decl = []
431 ------------------------------------------------------------------------
432 getInitialKind :: TyClDecl Name -> TcM (Name, TcKind)
433 -- Only for data type, class, and indexed type declarations
434 -- Get as much info as possible from the data, class, or indexed type decl,
435 -- so as to maximise usefulness of error messages
437 = do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl)
438 ; res_kind <- mk_res_kind decl
439 ; return (tcdName decl, mkArrowKinds arg_kinds res_kind) }
441 mk_arg_kind (UserTyVar _) = newKindVar
442 mk_arg_kind (KindedTyVar _ kind) = return kind
444 mk_res_kind (TyFunction { tcdKind = kind }) = return kind
445 mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
446 -- On GADT-style and data signature declarations we allow a kind
448 -- data T :: *->* where { ... }
449 mk_res_kind other = return liftedTypeKind
453 kcSynDecls :: [SCC (LTyClDecl Name)]
454 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
455 [(Name,TcKind)]) -- Kind bindings
458 kcSynDecls (group : groups)
459 = do { (decl, nk) <- kcSynDecl group
460 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
461 ; return (decl:decls, nk:nks) }
464 kcSynDecl :: SCC (LTyClDecl Name)
465 -> TcM (LTyClDecl Name, -- Kind-annotated decls
466 (Name,TcKind)) -- Kind bindings
467 kcSynDecl (AcyclicSCC ldecl@(L loc decl))
468 = tcAddDeclCtxt decl $
469 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
470 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
471 <+> brackets (ppr k_tvs))
472 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
473 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
474 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
475 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
476 (unLoc (tcdLName decl), tc_kind)) })
478 kcSynDecl (CyclicSCC decls)
479 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
480 -- of out-of-scope tycons
482 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
484 ------------------------------------------------------------------------
485 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
486 -- Not used for type synonyms (see kcSynDecl)
488 kcTyClDecl decl@(TyData {})
489 = ASSERT( not . isJust $ tcdTyPats decl ) -- must not be instance of idx ty
490 kcTyClDeclBody decl $
493 kcTyClDecl decl@(TyFunction {})
494 = kcTyClDeclBody decl $ \ tvs' ->
495 return (decl {tcdTyVars = tvs'})
497 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs, tcdATs = ats})
498 = kcTyClDeclBody decl $ \ tvs' ->
499 do { is_boot <- tcIsHsBoot
500 ; ctxt' <- kcHsContext ctxt
501 ; ats' <- mappM (wrapLocM kcTyClDecl) ats
502 ; sigs' <- mappM (wrapLocM kc_sig ) sigs
503 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs',
506 kc_sig (TypeSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
507 ; return (TypeSig nm op_ty') }
508 kc_sig other_sig = return other_sig
510 kcTyClDecl decl@(ForeignType {})
513 kcTyClDeclBody :: TyClDecl Name
514 -> ([LHsTyVarBndr Name] -> TcM a)
516 -- getInitialKind has made a suitably-shaped kind for the type or class
517 -- Unpack it, and attribute those kinds to the type variables
518 -- Extend the env with bindings for the tyvars, taken from
519 -- the kind of the tycon/class. Give it to the thing inside, and
520 -- check the result kind matches
521 kcTyClDeclBody decl thing_inside
522 = tcAddDeclCtxt decl $
523 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
524 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
525 (kinds, _) = splitKindFunTys tc_kind
526 hs_tvs = tcdTyVars decl
527 kinded_tvs = ASSERT( length kinds >= length hs_tvs )
528 [ L loc (KindedTyVar (hsTyVarName tv) k)
529 | (L loc tv, k) <- zip hs_tvs kinds]
530 ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
532 -- Kind check a data declaration, assuming that we already extended the
533 -- kind environment with the type variables of the left-hand side (these
534 -- kinded type variables are also passed as the second parameter).
536 kcDataDecl :: TyClDecl Name -> [LHsTyVarBndr Name] -> TcM (TyClDecl Name)
537 kcDataDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
539 = do { ctxt' <- kcHsContext ctxt
540 ; cons' <- mappM (wrapLocM kc_con_decl) cons
541 ; return (decl {tcdTyVars = tvs, tcdCtxt = ctxt', tcdCons = cons'}) }
543 kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res) = do
544 kcHsTyVars ex_tvs $ \ex_tvs' -> do
545 ex_ctxt' <- kcHsContext ex_ctxt
546 details' <- kc_con_details details
548 ResTyH98 -> return ResTyH98
549 ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
550 return (ConDecl name expl ex_tvs' ex_ctxt' details' res')
552 kc_con_details (PrefixCon btys)
553 = do { btys' <- mappM kc_larg_ty btys ; return (PrefixCon btys') }
554 kc_con_details (InfixCon bty1 bty2)
555 = do { bty1' <- kc_larg_ty bty1; bty2' <- kc_larg_ty bty2; return (InfixCon bty1' bty2') }
556 kc_con_details (RecCon fields)
557 = do { fields' <- mappM kc_field fields; return (RecCon fields') }
559 kc_field (fld, bty) = do { bty' <- kc_larg_ty bty ; return (fld, bty') }
561 kc_larg_ty bty = case new_or_data of
562 DataType -> kcHsSigType bty
563 NewType -> kcHsLiftedSigType bty
564 -- Can't allow an unlifted type for newtypes, because we're effectively
565 -- going to remove the constructor while coercing it to a lifted type.
566 -- And newtypes can't be bang'd
570 %************************************************************************
572 \subsection{Type checking}
574 %************************************************************************
577 tcSynDecls :: [LTyClDecl Name] -> TcM [TyThing]
578 tcSynDecls [] = return []
579 tcSynDecls (decl : decls)
580 = do { syn_tc <- addLocM tcSynDecl decl
581 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls decls)
582 ; return (syn_tc : syn_tcs) }
585 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
586 = tcTyVarBndrs tvs $ \ tvs' -> do
587 { traceTc (text "tcd1" <+> ppr tc_name)
588 ; rhs_ty' <- tcHsKindedType rhs_ty
589 ; return (ATyCon (buildSynTyCon tc_name tvs' (SynonymTyCon rhs_ty'))) }
592 tcTyClDecl :: (Name -> RecFlag) -> TyClDecl Name -> TcM TyThing
594 tcTyClDecl calc_isrec decl
595 = tcAddDeclCtxt decl (tcTyClDecl1 calc_isrec decl)
597 -- kind signature for a type function
598 tcTyClDecl1 _calc_isrec
599 (TyFunction {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = kind})
600 = tcTyVarBndrs tvs $ \ tvs' -> do
601 { gla_exts <- doptM Opt_GlasgowExts
603 -- Check that we don't use kind signatures without Glasgow extensions
604 ; checkTc gla_exts $ badSigTyDecl tc_name
606 ; return (ATyCon (buildSynTyCon tc_name tvs' (OpenSynTyCon kind)))
609 -- kind signature for an indexed data type
610 tcTyClDecl1 _calc_isrec
611 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
612 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = []})
613 = tcTyVarBndrs tvs $ \ tvs' -> do
614 { extra_tvs <- tcDataKindSig mb_ksig
615 ; let final_tvs = tvs' ++ extra_tvs -- we may not need these
617 ; checkTc (null . unLoc $ ctxt) $ badKindSigCtxt tc_name
618 ; gla_exts <- doptM Opt_GlasgowExts
620 -- Check that we don't use kind signatures without Glasgow extensions
621 ; checkTc gla_exts $ badSigTyDecl tc_name
623 ; tycon <- buildAlgTyCon tc_name final_tvs []
625 DataType -> OpenDataTyCon
626 NewType -> OpenNewTyCon)
628 ; return (ATyCon tycon)
631 tcTyClDecl1 calc_isrec
632 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
633 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
634 = tcTyVarBndrs tvs $ \ tvs' -> do
635 { extra_tvs <- tcDataKindSig mb_ksig
636 ; let final_tvs = tvs' ++ extra_tvs
637 ; stupid_theta <- tcHsKindedContext ctxt
638 ; want_generic <- doptM Opt_Generics
639 ; unbox_strict <- doptM Opt_UnboxStrictFields
640 ; gla_exts <- doptM Opt_GlasgowExts
641 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
643 -- Check that we don't use GADT syntax in H98 world
644 ; checkTc (gla_exts || h98_syntax) (badGadtDecl tc_name)
646 -- Check that we don't use kind signatures without Glasgow extensions
647 ; checkTc (gla_exts || isNothing mb_ksig) (badSigTyDecl tc_name)
649 -- Check that the stupid theta is empty for a GADT-style declaration
650 ; checkTc (null stupid_theta || h98_syntax) (badStupidTheta tc_name)
652 -- Check that there's at least one condecl,
653 -- or else we're reading an hs-boot file, or -fglasgow-exts
654 ; checkTc (not (null cons) || gla_exts || is_boot)
655 (emptyConDeclsErr tc_name)
657 -- Check that a newtype has exactly one constructor
658 ; checkTc (new_or_data == DataType || isSingleton cons)
659 (newtypeConError tc_name (length cons))
661 ; tycon <- fixM (\ tycon -> do
662 { data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data
666 if null cons && is_boot -- In a hs-boot file, empty cons means
667 then return AbstractTyCon -- "don't know"; hence Abstract
668 else case new_or_data of
669 DataType -> return (mkDataTyConRhs data_cons)
671 ASSERT( isSingleton data_cons )
672 mkNewTyConRhs tc_name tycon (head data_cons)
673 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
674 (want_generic && canDoGenerics data_cons) h98_syntax
676 ; return (ATyCon tycon)
679 is_rec = calc_isrec tc_name
680 h98_syntax = case cons of -- All constructors have same shape
681 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
684 tcTyClDecl1 calc_isrec
685 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
686 tcdCtxt = ctxt, tcdMeths = meths,
687 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
688 = tcTyVarBndrs tvs $ \ tvs' -> do
689 { ctxt' <- tcHsKindedContext ctxt
690 ; fds' <- mappM (addLocM tc_fundep) fundeps
691 ; ats' <- mappM (addLocM (tcTyClDecl1 (const Recursive))) ats
692 -- ^^^^ !!!TODO: what to do with this? Need to generate FC tyfun decls.
693 ; sig_stuff <- tcClassSigs class_name sigs meths
694 ; clas <- fixM (\ clas ->
695 let -- This little knot is just so we can get
696 -- hold of the name of the class TyCon, which we
697 -- need to look up its recursiveness
698 tycon_name = tyConName (classTyCon clas)
699 tc_isrec = calc_isrec tycon_name
701 buildClass class_name tvs' ctxt' fds'
703 ; return (AClass clas) }
705 tc_fundep (tvs1, tvs2) = do { tvs1' <- mappM tcLookupTyVar tvs1 ;
706 ; tvs2' <- mappM tcLookupTyVar tvs2 ;
707 ; return (tvs1', tvs2') }
710 tcTyClDecl1 calc_isrec
711 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
712 = returnM (ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0))
714 -----------------------------------
715 tcConDecl :: Bool -- True <=> -funbox-strict_fields
716 -> NewOrData -> TyCon -> [TyVar]
717 -> ConDecl Name -> TcM DataCon
719 tcConDecl unbox_strict NewType tycon tc_tvs -- Newtypes
720 (ConDecl name _ ex_tvs ex_ctxt details ResTyH98)
721 = do { let tc_datacon field_lbls arg_ty
722 = do { arg_ty' <- tcHsKindedType arg_ty -- No bang on newtype
723 ; buildDataCon (unLoc name) False {- Prefix -}
725 (map unLoc field_lbls)
726 tc_tvs [] -- No existentials
727 [] [] -- No equalities, predicates
731 -- Check that a newtype has no existential stuff
732 ; checkTc (null ex_tvs && null (unLoc ex_ctxt)) (newtypeExError name)
735 PrefixCon [arg_ty] -> tc_datacon [] arg_ty
736 RecCon [(field_lbl, arg_ty)] -> tc_datacon [field_lbl] arg_ty
737 other -> failWithTc (newtypeFieldErr name (length (hsConArgs details)))
738 -- Check that the constructor has exactly one field
741 tcConDecl unbox_strict DataType tycon tc_tvs -- Data types
742 (ConDecl name _ tvs ctxt details res_ty)
743 = tcTyVarBndrs tvs $ \ tvs' -> do
744 { ctxt' <- tcHsKindedContext ctxt
745 ; (univ_tvs, ex_tvs, eq_preds, data_tc) <- tcResultType tycon tc_tvs tvs' res_ty
747 tc_datacon is_infix field_lbls btys
748 = do { let bangs = map getBangStrictness btys
749 ; arg_tys <- mappM tcHsBangType btys
750 ; buildDataCon (unLoc name) is_infix
751 (argStrictness unbox_strict tycon bangs arg_tys)
752 (map unLoc field_lbls)
753 univ_tvs ex_tvs eq_preds ctxt' arg_tys
755 -- NB: we put data_tc, the type constructor gotten from the constructor
756 -- type signature into the data constructor; that way
757 -- checkValidDataCon can complain if it's wrong.
760 PrefixCon btys -> tc_datacon False [] btys
761 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
762 RecCon fields -> tc_datacon False field_names btys
764 (field_names, btys) = unzip fields
768 tcResultType :: TyCon
769 -> [TyVar] -- data T a b c = ...
770 -> [TyVar] -- where MkT :: forall a b c. ...
772 -> TcM ([TyVar], -- Universal
773 [TyVar], -- Existential
774 [(TyVar,Type)], -- Equality predicates
775 TyCon) -- TyCon given in the ResTy
776 -- We don't check that the TyCon given in the ResTy is
777 -- the same as the parent tycon, becuase we are in the middle
778 -- of a recursive knot; so it's postponed until checkValidDataCon
780 tcResultType decl_tycon tc_tvs dc_tvs ResTyH98
781 = return (tc_tvs, dc_tvs, [], decl_tycon)
782 -- In H98 syntax the dc_tvs are the existential ones
783 -- data T a b c = forall d e. MkT ...
784 -- The {a,b,c} are tc_tvs, and {d,e} are dc_tvs
786 tcResultType _ tc_tvs dc_tvs (ResTyGADT res_ty)
787 -- E.g. data T a b c where
788 -- MkT :: forall x y z. T (x,y) z z
790 -- ([a,z,c], [x,y], [a:=:(x,y), c:=:z], T)
792 = do { (dc_tycon, res_tys) <- tcLHsConResTy res_ty
793 -- NB: tc_tvs and dc_tvs are distinct
794 ; let univ_tvs = choose_univs [] tc_tvs res_tys
795 -- Each univ_tv is either a dc_tv or a tc_tv
796 ex_tvs = dc_tvs `minusList` univ_tvs
797 eq_spec = [ (tv, ty) | (tv,ty) <- univ_tvs `zip` res_tys,
799 ; return (univ_tvs, ex_tvs, eq_spec, dc_tycon) }
801 -- choose_univs uses the res_ty itself if it's a type variable
802 -- and hasn't already been used; otherwise it uses one of the tc_tvs
803 choose_univs used tc_tvs []
804 = ASSERT( null tc_tvs ) []
805 choose_univs used (tc_tv:tc_tvs) (res_ty:res_tys)
806 | Just tv <- tcGetTyVar_maybe res_ty, not (tv `elem` used)
807 = tv : choose_univs (tv:used) tc_tvs res_tys
809 = tc_tv : choose_univs used tc_tvs res_tys
812 argStrictness :: Bool -- True <=> -funbox-strict_fields
814 -> [TcType] -> [StrictnessMark]
815 argStrictness unbox_strict tycon bangs arg_tys
816 = ASSERT( length bangs == length arg_tys )
817 zipWith (chooseBoxingStrategy unbox_strict tycon) arg_tys bangs
819 -- We attempt to unbox/unpack a strict field when either:
820 -- (i) The field is marked '!!', or
821 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
823 -- We have turned off unboxing of newtypes because coercions make unboxing
824 -- and reboxing more complicated
825 chooseBoxingStrategy :: Bool -> TyCon -> TcType -> HsBang -> StrictnessMark
826 chooseBoxingStrategy unbox_strict_fields tycon arg_ty bang
828 HsNoBang -> NotMarkedStrict
829 HsStrict | unbox_strict_fields
830 && can_unbox arg_ty -> MarkedUnboxed
831 HsUnbox | can_unbox arg_ty -> MarkedUnboxed
832 other -> MarkedStrict
834 -- we can unbox if the type is a chain of newtypes with a product tycon
836 can_unbox arg_ty = case splitTyConApp_maybe arg_ty of
838 Just (arg_tycon, tycon_args) ->
839 not (isRecursiveTyCon tycon) &&
840 isProductTyCon arg_tycon &&
841 (if isNewTyCon arg_tycon then
842 can_unbox (newTyConInstRhs arg_tycon tycon_args)
846 %************************************************************************
848 \subsection{Dependency analysis}
850 %************************************************************************
852 Validity checking is done once the mutually-recursive knot has been
853 tied, so we can look at things freely.
856 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
857 checkCycleErrs tyclss
861 = do { mappM_ recClsErr cls_cycles
862 ; failM } -- Give up now, because later checkValidTyCl
863 -- will loop if the synonym is recursive
865 cls_cycles = calcClassCycles tyclss
867 checkValidTyCl :: TyClDecl Name -> TcM ()
868 -- We do the validity check over declarations, rather than TyThings
869 -- only so that we can add a nice context with tcAddDeclCtxt
871 = tcAddDeclCtxt decl $
872 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
873 ; traceTc (text "Validity of" <+> ppr thing)
875 ATyCon tc -> checkValidTyCon tc
876 AClass cl -> checkValidClass cl
877 ; traceTc (text "Done validity of" <+> ppr thing)
880 -------------------------
881 -- For data types declared with record syntax, we require
882 -- that each constructor that has a field 'f'
883 -- (a) has the same result type
884 -- (b) has the same type for 'f'
885 -- module alpha conversion of the quantified type variables
886 -- of the constructor.
888 checkValidTyCon :: TyCon -> TcM ()
891 = case synTyConRhs tc of
892 OpenSynTyCon _ -> return ()
893 SynonymTyCon ty -> checkValidType syn_ctxt ty
895 = -- Check the context on the data decl
896 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
898 -- Check arg types of data constructors
899 mappM_ (checkValidDataCon tc) data_cons `thenM_`
901 -- Check that fields with the same name share a type
902 mappM_ check_fields groups
905 syn_ctxt = TySynCtxt name
907 data_cons = tyConDataCons tc
909 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
910 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
911 get_fields con = dataConFieldLabels con `zip` repeat con
912 -- dataConFieldLabels may return the empty list, which is fine
914 -- See Note [GADT record selectors] in MkId.lhs
915 -- We must check (a) that the named field has the same
916 -- type in each constructor
917 -- (b) that those constructors have the same result type
919 -- However, the constructors may have differently named type variable
920 -- and (worse) we don't know how the correspond to each other. E.g.
921 -- C1 :: forall a b. { f :: a, g :: b } -> T a b
922 -- C2 :: forall d c. { f :: c, g :: c } -> T c d
924 -- So what we do is to ust Unify.tcMatchTys to compare the first candidate's
925 -- result type against other candidates' types BOTH WAYS ROUND.
926 -- If they magically agrees, take the substitution and
927 -- apply them to the latter ones, and see if they match perfectly.
928 check_fields fields@((label, con1) : other_fields)
929 -- These fields all have the same name, but are from
930 -- different constructors in the data type
931 = recoverM (return ()) $ mapM_ checkOne other_fields
932 -- Check that all the fields in the group have the same type
933 -- NB: this check assumes that all the constructors of a given
934 -- data type use the same type variables
936 tvs1 = mkVarSet (dataConAllTyVars con1)
937 res1 = dataConResTys con1
938 fty1 = dataConFieldType con1 label
940 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
941 = do { checkFieldCompat label con1 con2 tvs1 res1 res2 fty1 fty2
942 ; checkFieldCompat label con2 con1 tvs2 res2 res1 fty2 fty1 }
944 tvs2 = mkVarSet (dataConAllTyVars con2)
945 res2 = dataConResTys con2
946 fty2 = dataConFieldType con2 label
948 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
949 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
950 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
952 mb_subst1 = tcMatchTys tvs1 res1 res2
953 mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
955 -------------------------------
956 checkValidDataCon :: TyCon -> DataCon -> TcM ()
957 checkValidDataCon tc con
958 = setSrcSpan (srcLocSpan (getSrcLoc con)) $
959 addErrCtxt (dataConCtxt con) $
960 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
961 ; checkValidType ctxt (dataConUserType con) }
963 ctxt = ConArgCtxt (dataConName con)
965 -------------------------------
966 checkValidClass :: Class -> TcM ()
968 = do { -- CHECK ARITY 1 FOR HASKELL 1.4
969 gla_exts <- doptM Opt_GlasgowExts
971 -- Check that the class is unary, unless GlaExs
972 ; checkTc (notNull tyvars) (nullaryClassErr cls)
973 ; checkTc (gla_exts || unary) (classArityErr cls)
975 -- Check the super-classes
976 ; checkValidTheta (ClassSCCtxt (className cls)) theta
978 -- Check the class operations
979 ; mappM_ (check_op gla_exts) op_stuff
981 -- Check that if the class has generic methods, then the
982 -- class has only one parameter. We can't do generic
983 -- multi-parameter type classes!
984 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
987 (tyvars, theta, _, op_stuff) = classBigSig cls
988 unary = isSingleton tyvars
989 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
991 check_op gla_exts (sel_id, dm)
992 = addErrCtxt (classOpCtxt sel_id tau) $ do
993 { checkValidTheta SigmaCtxt (tail theta)
994 -- The 'tail' removes the initial (C a) from the
995 -- class itself, leaving just the method type
997 ; checkValidType (FunSigCtxt op_name) tau
999 -- Check that the type mentions at least one of
1000 -- the class type variables
1001 ; checkTc (any (`elemVarSet` tyVarsOfType tau) tyvars)
1002 (noClassTyVarErr cls sel_id)
1004 -- Check that for a generic method, the type of
1005 -- the method is sufficiently simple
1006 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
1007 (badGenericMethodType op_name op_ty)
1010 op_name = idName sel_id
1011 op_ty = idType sel_id
1012 (_,theta1,tau1) = tcSplitSigmaTy op_ty
1013 (_,theta2,tau2) = tcSplitSigmaTy tau1
1014 (theta,tau) | gla_exts = (theta1 ++ theta2, tau2)
1015 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
1016 -- Ugh! The function might have a type like
1017 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
1018 -- With -fglasgow-exts, we want to allow this, even though the inner
1019 -- forall has an (Eq a) constraint. Whereas in general, each constraint
1020 -- in the context of a for-all must mention at least one quantified
1021 -- type variable. What a mess!
1024 ---------------------------------------------------------------------
1025 resultTypeMisMatch field_name con1 con2
1026 = vcat [sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1027 ptext SLIT("have a common field") <+> quotes (ppr field_name) <> comma],
1028 nest 2 $ ptext SLIT("but have different result types")]
1029 fieldTypeMisMatch field_name con1 con2
1030 = sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1031 ptext SLIT("give different types for field"), quotes (ppr field_name)]
1033 dataConCtxt con = ptext SLIT("In the definition of data constructor") <+> quotes (ppr con)
1035 classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
1036 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
1039 = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
1042 = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
1043 parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
1045 noClassTyVarErr clas op
1046 = sep [ptext SLIT("The class method") <+> quotes (ppr op),
1047 ptext SLIT("mentions none of the type variables of the class") <+>
1048 ppr clas <+> hsep (map ppr (classTyVars clas))]
1050 genericMultiParamErr clas
1051 = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
1052 ptext SLIT("cannot have generic methods")
1054 badGenericMethodType op op_ty
1055 = hang (ptext SLIT("Generic method type is too complex"))
1056 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
1057 ptext SLIT("You can only use type variables, arrows, lists, and tuples")])
1060 = setSrcSpan (getLoc (head sorted_decls)) $
1061 addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
1062 nest 2 (vcat (map ppr_decl sorted_decls))])
1064 sorted_decls = sortLocated syn_decls
1065 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
1068 = setSrcSpan (getLoc (head sorted_decls)) $
1069 addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
1070 nest 2 (vcat (map ppr_decl sorted_decls))])
1072 sorted_decls = sortLocated cls_decls
1073 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
1075 sortLocated :: [Located a] -> [Located a]
1076 sortLocated things = sortLe le things
1078 le (L l1 _) (L l2 _) = l1 <= l2
1080 badDataConTyCon data_con
1081 = hang (ptext SLIT("Data constructor") <+> quotes (ppr data_con) <+>
1082 ptext SLIT("returns type") <+> quotes (ppr (dataConTyCon data_con)))
1083 2 (ptext SLIT("instead of its parent type"))
1086 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
1087 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow GADTs")) ]
1089 badStupidTheta tc_name
1090 = ptext SLIT("A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
1092 newtypeConError tycon n
1093 = sep [ptext SLIT("A newtype must have exactly one constructor,"),
1094 nest 2 $ ptext SLIT("but") <+> quotes (ppr tycon) <+> ptext SLIT("has") <+> speakN n ]
1097 = sep [ptext SLIT("A newtype constructor cannot have an existential context,"),
1098 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
1100 newtypeFieldErr con_name n_flds
1101 = sep [ptext SLIT("The constructor of a newtype must have exactly one field"),
1102 nest 2 $ ptext SLIT("but") <+> quotes (ppr con_name) <+> ptext SLIT("has") <+> speakN n_flds]
1104 badSigTyDecl tc_name
1105 = vcat [ ptext SLIT("Illegal kind signature") <+>
1106 quotes (ppr tc_name)
1107 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow indexed types")) ]
1109 badKindSigCtxt tc_name
1110 = vcat [ ptext SLIT("Illegal context in kind signature") <+>
1111 quotes (ppr tc_name)
1112 , nest 2 (parens $ ptext SLIT("Currently, kind signatures cannot have a context")) ]
1114 badIdxTyDecl tc_name
1115 = vcat [ ptext SLIT("Illegal indexed type instance for") <+>
1116 quotes (ppr tc_name)
1117 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow indexed types")) ]
1119 badGadtIdxTyDecl tc_name
1120 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+>
1121 quotes (ppr tc_name)
1122 , nest 2 (parens $ ptext SLIT("Indexed types cannot use GADT declarations")) ]
1124 tooManyParmsErr tc_name
1125 = ptext SLIT("Indexed type instance has too many parameters:") <+>
1126 quotes (ppr tc_name)
1128 tooFewParmsErr tc_name
1129 = ptext SLIT("Indexed type instance has too few parameters:") <+>
1130 quotes (ppr tc_name)
1132 badBootTyIdxDeclErr = ptext SLIT("Illegal indexed type instance in hs-boot file")
1134 emptyConDeclsErr tycon
1135 = sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
1136 nest 2 $ ptext SLIT("(-fglasgow-exts permits this)")]