2 % (c) The University of Glasgow 2006
3 % (c) The AQUA Project, Glasgow University, 1996-1998
6 TcTyClsDecls: Typecheck type and class declarations
10 tcTyAndClassDecls, tcIdxTyInstDecl
13 #include "HsVersions.h"
47 import Data.List ( partition, elemIndex )
51 %************************************************************************
53 \subsection{Type checking for type and class declarations}
55 %************************************************************************
59 Consider a mutually-recursive group, binding
60 a type constructor T and a class C.
62 Step 1: getInitialKind
63 Construct a KindEnv by binding T and C to a kind variable
66 In that environment, do a kind check
68 Step 3: Zonk the kinds
70 Step 4: buildTyConOrClass
71 Construct an environment binding T to a TyCon and C to a Class.
72 a) Their kinds comes from zonking the relevant kind variable
73 b) Their arity (for synonyms) comes direct from the decl
74 c) The funcional dependencies come from the decl
75 d) The rest comes a knot-tied binding of T and C, returned from Step 4
76 e) The variances of the tycons in the group is calculated from
80 In this environment, walk over the decls, constructing the TyCons and Classes.
81 This uses in a strict way items (a)-(c) above, which is why they must
82 be constructed in Step 4. Feed the results back to Step 4.
83 For this step, pass the is-recursive flag as the wimp-out flag
87 Step 6: Extend environment
88 We extend the type environment with bindings not only for the TyCons and Classes,
89 but also for their "implicit Ids" like data constructors and class selectors
91 Step 7: checkValidTyCl
92 For a recursive group only, check all the decls again, just
93 to check all the side conditions on validity. We could not
94 do this before because we were in a mutually recursive knot.
96 Identification of recursive TyCons
97 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
98 The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to
101 Identifying a TyCon as recursive serves two purposes
103 1. Avoid infinite types. Non-recursive newtypes are treated as
104 "transparent", like type synonyms, after the type checker. If we did
105 this for all newtypes, we'd get infinite types. So we figure out for
106 each newtype whether it is "recursive", and add a coercion if so. In
107 effect, we are trying to "cut the loops" by identifying a loop-breaker.
109 2. Avoid infinite unboxing. This is nothing to do with newtypes.
113 Well, this function diverges, but we don't want the strictness analyser
114 to diverge. But the strictness analyser will diverge because it looks
115 deeper and deeper into the structure of T. (I believe there are
116 examples where the function does something sane, and the strictness
117 analyser still diverges, but I can't see one now.)
119 Now, concerning (1), the FC2 branch currently adds a coercion for ALL
120 newtypes. I did this as an experiment, to try to expose cases in which
121 the coercions got in the way of optimisations. If it turns out that we
122 can indeed always use a coercion, then we don't risk recursive types,
123 and don't need to figure out what the loop breakers are.
125 For newtype *families* though, we will always have a coercion, so they
126 are always loop breakers! So you can easily adjust the current
127 algorithm by simply treating all newtype families as loop breakers (and
128 indeed type families). I think.
131 tcTyAndClassDecls :: ModDetails -> [LTyClDecl Name]
132 -> TcM TcGblEnv -- Input env extended by types and classes
133 -- and their implicit Ids,DataCons
134 tcTyAndClassDecls boot_details allDecls
135 = do { -- Omit instances of indexed types; they are handled together
136 -- with the *heads* of class instances
137 ; let decls = filter (not . isIdxTyDecl . unLoc) allDecls
139 -- First check for cyclic type synonysm or classes
140 -- See notes with checkCycleErrs
141 ; checkCycleErrs decls
143 ; traceTc (text "tcTyAndCl" <+> ppr mod)
144 ; (syn_tycons, alg_tyclss) <- fixM (\ ~(rec_syn_tycons, rec_alg_tyclss) ->
145 do { let { -- Seperate ordinary synonyms from all other type and
146 -- class declarations and add all associated type
147 -- declarations from type classes. The latter is
148 -- required so that the temporary environment for the
149 -- knot includes all associated family declarations.
150 ; (syn_decls, alg_decls) = partition (isSynDecl . unLoc)
152 ; alg_at_decls = concatMap addATs alg_decls
154 -- Extend the global env with the knot-tied results
155 -- for data types and classes
157 -- We must populate the environment with the loop-tied
158 -- T's right away, because the kind checker may "fault
159 -- in" some type constructors that recursively
161 ; let gbl_things = mkGlobalThings alg_at_decls rec_alg_tyclss
162 ; tcExtendRecEnv gbl_things $ do
164 -- Kind-check the declarations
165 { (kc_syn_decls, kc_alg_decls) <- kcTyClDecls syn_decls alg_decls
167 ; let { -- Calculate rec-flag
168 ; calc_rec = calcRecFlags boot_details rec_alg_tyclss
169 ; tc_decl = addLocM (tcTyClDecl calc_rec) }
171 -- Type-check the type synonyms, and extend the envt
172 ; syn_tycons <- tcSynDecls kc_syn_decls
173 ; tcExtendGlobalEnv syn_tycons $ do
175 -- Type-check the data types and classes
176 { alg_tyclss <- mappM tc_decl kc_alg_decls
177 ; return (syn_tycons, concat alg_tyclss)
179 -- Finished with knot-tying now
180 -- Extend the environment with the finished things
181 ; tcExtendGlobalEnv (syn_tycons ++ alg_tyclss) $ do
183 -- Perform the validity check
184 { traceTc (text "ready for validity check")
185 ; mappM_ (addLocM checkValidTyCl) decls
186 ; traceTc (text "done")
188 -- Add the implicit things;
189 -- we want them in the environment because
190 -- they may be mentioned in interface files
191 -- NB: All associated types and their implicit things will be added a
192 -- second time here. This doesn't matter as the definitions are
194 ; let { implicit_things = concatMap implicitTyThings alg_tyclss }
195 ; traceTc ((text "Adding" <+> ppr alg_tyclss)
196 $$ (text "and" <+> ppr implicit_things))
197 ; tcExtendGlobalEnv implicit_things getGblEnv
200 -- Pull associated types out of class declarations, to tie them into the
202 -- NB: We put them in the same place in the list as `tcTyClDecl' will
203 -- eventually put the matching `TyThing's. That's crucial; otherwise,
204 -- the two argument lists of `mkGlobalThings' don't match up.
205 addATs decl@(L _ (ClassDecl {tcdATs = ats})) = decl : ats
208 mkGlobalThings :: [LTyClDecl Name] -- The decls
209 -> [TyThing] -- Knot-tied, in 1-1 correspondence with the decls
211 -- Driven by the Decls, and treating the TyThings lazily
212 -- make a TypeEnv for the new things
213 mkGlobalThings decls things
214 = map mk_thing (decls `zipLazy` things)
216 mk_thing (L _ (ClassDecl {tcdLName = L _ name}), ~(AClass cl))
218 mk_thing (L _ decl, ~(ATyCon tc))
219 = (tcdName decl, ATyCon tc)
223 %************************************************************************
225 \subsection{Type checking instances of indexed types}
227 %************************************************************************
229 Instances of indexed types are somewhat of a hybrid. They are processed
230 together with class instance heads, but can contain data constructors and hence
231 they share a lot of kinding and type checking code with ordinary algebraic
232 data types (and GADTs).
235 tcIdxTyInstDecl :: LTyClDecl Name -> TcM (Maybe TyThing) -- Nothing if error
236 tcIdxTyInstDecl (L loc decl)
237 = -- Prime error recovery, set source location
238 recoverM (returnM Nothing) $
241 do { -- indexed data types require -findexed-types and can't be in an
243 ; gla_exts <- doptM Opt_IndexedTypes
244 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
245 ; checkTc gla_exts $ badIdxTyDecl (tcdLName decl)
246 ; checkTc (not is_boot) $ badBootTyIdxDeclErr
248 -- perform kind and type checking
249 ; tcIdxTyInstDecl1 decl
252 tcIdxTyInstDecl1 :: TyClDecl Name -> TcM (Maybe TyThing) -- Nothing if error
254 tcIdxTyInstDecl1 (decl@TySynonym {})
255 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
256 do { -- check that the family declaration is for a synonym
257 unless (isSynTyCon family) $
258 addErr (wrongKindOfFamily family)
260 ; -- (1) kind check the right hand side of the type equation
261 ; k_rhs <- kcCheckHsType (tcdSynRhs decl) resKind
263 -- (2) type check type equation
264 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
265 ; t_typats <- mappM tcHsKindedType k_typats
266 ; t_rhs <- tcHsKindedType k_rhs
268 -- !!!of the form: forall t_tvs. (tcdLName decl) t_typats = t_rhs
269 ; return Nothing -- !!!TODO: need TyThing for indexed synonym
272 tcIdxTyInstDecl1 (decl@TyData {tcdND = new_or_data, tcdLName = L loc tc_name,
274 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
275 do { -- check that the family declaration is for the right kind
276 unless (new_or_data == NewType && isNewTyCon family ||
277 new_or_data == DataType && isDataTyCon family) $
278 addErr (wrongKindOfFamily family)
280 ; -- (1) kind check the data declaration as usual
281 ; k_decl <- kcDataDecl decl k_tvs
282 ; let k_ctxt = tcdCtxt k_decl
283 k_cons = tcdCons k_decl
285 -- result kind must be '*' (otherwise, we have too few patterns)
286 ; checkTc (isLiftedTypeKind resKind) $ tooFewParmsErr tc_name
288 -- (2) type check indexed data type declaration
289 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
290 ; unbox_strict <- doptM Opt_UnboxStrictFields
292 -- Check that we don't use GADT syntax for indexed types
293 ; checkTc h98_syntax (badGadtIdxTyDecl tc_name)
295 -- Check that a newtype has exactly one constructor
296 ; checkTc (new_or_data == DataType || isSingleton k_cons) $
297 newtypeConError tc_name (length k_cons)
299 ; t_typats <- mappM tcHsKindedType k_typats
300 ; stupid_theta <- tcHsKindedContext k_ctxt
302 ; rep_tc_name <- newFamInstTyConName tc_name (srcSpanStart loc)
303 ; tycon <- fixM (\ tycon -> do
304 { data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data
309 DataType -> return (mkDataTyConRhs data_cons)
310 NewType -> ASSERT( isSingleton data_cons )
311 mkNewTyConRhs tc_name tycon (head data_cons)
312 ; buildAlgTyCon rep_tc_name t_tvs stupid_theta tc_rhs Recursive
313 False h98_syntax (Just (family, t_typats))
314 -- We always assume that indexed types are recursive. Why?
315 -- (1) Due to their open nature, we can never be sure that a
316 -- further instance might not introduce a new recursive
317 -- dependency. (2) They are always valid loop breakers as
318 -- they involve a coercion.
322 ; return $ Just (ATyCon tycon)
325 h98_syntax = case cons of -- All constructors have same shape
326 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
329 -- Kind checking of indexed types
332 -- Kind check type patterns and kind annotate the embedded type variables.
334 -- * Here we check that a type instance matches its kind signature, but we do
335 -- not check whether there is a pattern for each type index; the latter
336 -- check is only required for type functions.
338 kcIdxTyPats :: TyClDecl Name
339 -> ([LHsTyVarBndr Name] -> [LHsType Name] -> Kind -> TyCon -> TcM a)
340 -- ^^kinded tvs ^^kinded ty pats ^^res kind
342 kcIdxTyPats decl thing_inside
343 = kcHsTyVars (tcdTyVars decl) $ \tvs ->
344 do { family <- tcLookupLocatedTyCon (tcdLName decl)
345 ; let { (kinds, resKind) = splitKindFunTys (tyConKind family)
346 ; hs_typats = fromJust $ tcdTyPats decl }
348 -- we may not have more parameters than the kind indicates
349 ; checkTc (length kinds >= length hs_typats) $
350 tooManyParmsErr (tcdLName decl)
352 -- type functions can have a higher-kinded result
353 ; let resultKind = mkArrowKinds (drop (length hs_typats) kinds) resKind
354 ; typats <- TcRnMonad.zipWithM kcCheckHsType hs_typats kinds
355 ; thing_inside tvs typats resultKind family
361 %************************************************************************
365 %************************************************************************
367 We need to kind check all types in the mutually recursive group
368 before we know the kind of the type variables. For example:
371 op :: D b => a -> b -> b
374 bop :: (Monad c) => ...
376 Here, the kind of the locally-polymorphic type variable "b"
377 depends on *all the uses of class D*. For example, the use of
378 Monad c in bop's type signature means that D must have kind Type->Type.
380 However type synonyms work differently. They can have kinds which don't
381 just involve (->) and *:
382 type R = Int# -- Kind #
383 type S a = Array# a -- Kind * -> #
384 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
385 So we must infer their kinds from their right-hand sides *first* and then
386 use them, whereas for the mutually recursive data types D we bring into
387 scope kind bindings D -> k, where k is a kind variable, and do inference.
391 This treatment of type synonyms only applies to Haskell 98-style synonyms.
392 General type functions can be recursive, and hence, appear in `alg_decls'.
394 The kind of an indexed type is solely determinded by its kind signature;
395 hence, only kind signatures participate in the construction of the initial
396 kind environment (as constructed by `getInitialKind'). In fact, we ignore
397 instances of indexed types altogether in the following. However, we need to
398 include the kind signatures of associated types into the construction of the
399 initial kind environment. (This is handled by `allDecls').
402 kcTyClDecls syn_decls alg_decls
403 = do { -- First extend the kind env with each data type, class, and
404 -- indexed type, mapping them to a type variable
405 let initialKindDecls = concat [allDecls decl | L _ decl <- alg_decls]
406 ; alg_kinds <- mappM getInitialKind initialKindDecls
407 ; tcExtendKindEnv alg_kinds $ do
409 -- Now kind-check the type synonyms, in dependency order
410 -- We do these differently to data type and classes,
411 -- because a type synonym can be an unboxed type
413 -- and a kind variable can't unify with UnboxedTypeKind
414 -- So we infer their kinds in dependency order
415 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
416 ; tcExtendKindEnv syn_kinds $ do
418 -- Now kind-check the data type, class, and kind signatures,
419 -- returning kind-annotated decls; we don't kind-check
420 -- instances of indexed types yet, but leave this to
422 { kc_alg_decls <- mappM (wrapLocM kcTyClDecl)
423 (filter (not . isIdxTyDecl . unLoc) alg_decls)
425 ; return (kc_syn_decls, kc_alg_decls) }}}
427 -- get all declarations relevant for determining the initial kind
429 allDecls (decl@ClassDecl {tcdATs = ats}) = decl : [ at
432 allDecls decl | isIdxTyDecl decl = []
435 ------------------------------------------------------------------------
436 getInitialKind :: TyClDecl Name -> TcM (Name, TcKind)
437 -- Only for data type, class, and indexed type declarations
438 -- Get as much info as possible from the data, class, or indexed type decl,
439 -- so as to maximise usefulness of error messages
441 = do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl)
442 ; res_kind <- mk_res_kind decl
443 ; return (tcdName decl, mkArrowKinds arg_kinds res_kind) }
445 mk_arg_kind (UserTyVar _) = newKindVar
446 mk_arg_kind (KindedTyVar _ kind) = return kind
448 mk_res_kind (TyFunction { tcdKind = kind }) = return kind
449 mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
450 -- On GADT-style and data signature declarations we allow a kind
452 -- data T :: *->* where { ... }
453 mk_res_kind other = return liftedTypeKind
457 kcSynDecls :: [SCC (LTyClDecl Name)]
458 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
459 [(Name,TcKind)]) -- Kind bindings
462 kcSynDecls (group : groups)
463 = do { (decl, nk) <- kcSynDecl group
464 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
465 ; return (decl:decls, nk:nks) }
468 kcSynDecl :: SCC (LTyClDecl Name)
469 -> TcM (LTyClDecl Name, -- Kind-annotated decls
470 (Name,TcKind)) -- Kind bindings
471 kcSynDecl (AcyclicSCC ldecl@(L loc decl))
472 = tcAddDeclCtxt decl $
473 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
474 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
475 <+> brackets (ppr k_tvs))
476 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
477 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
478 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
479 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
480 (unLoc (tcdLName decl), tc_kind)) })
482 kcSynDecl (CyclicSCC decls)
483 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
484 -- of out-of-scope tycons
486 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
488 ------------------------------------------------------------------------
489 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
490 -- Not used for type synonyms (see kcSynDecl)
492 kcTyClDecl decl@(TyData {})
493 = ASSERT( not . isJust $ tcdTyPats decl ) -- must not be instance of idx ty
494 kcTyClDeclBody decl $
497 kcTyClDecl decl@(TyFunction {})
498 = kcTyClDeclBody decl $ \ tvs' ->
499 return (decl {tcdTyVars = tvs'})
501 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs, tcdATs = ats})
502 = kcTyClDeclBody decl $ \ tvs' ->
503 do { is_boot <- tcIsHsBoot
504 ; ctxt' <- kcHsContext ctxt
505 ; ats' <- mappM (wrapLocM kcTyClDecl) ats
506 ; sigs' <- mappM (wrapLocM kc_sig ) sigs
507 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs',
510 kc_sig (TypeSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
511 ; return (TypeSig nm op_ty') }
512 kc_sig other_sig = return other_sig
514 kcTyClDecl decl@(ForeignType {})
517 kcTyClDeclBody :: TyClDecl Name
518 -> ([LHsTyVarBndr Name] -> TcM a)
520 -- getInitialKind has made a suitably-shaped kind for the type or class
521 -- Unpack it, and attribute those kinds to the type variables
522 -- Extend the env with bindings for the tyvars, taken from
523 -- the kind of the tycon/class. Give it to the thing inside, and
524 -- check the result kind matches
525 kcTyClDeclBody decl thing_inside
526 = tcAddDeclCtxt decl $
527 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
528 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
529 (kinds, _) = splitKindFunTys tc_kind
530 hs_tvs = tcdTyVars decl
531 kinded_tvs = ASSERT( length kinds >= length hs_tvs )
532 [ L loc (KindedTyVar (hsTyVarName tv) k)
533 | (L loc tv, k) <- zip hs_tvs kinds]
534 ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
536 -- Kind check a data declaration, assuming that we already extended the
537 -- kind environment with the type variables of the left-hand side (these
538 -- kinded type variables are also passed as the second parameter).
540 kcDataDecl :: TyClDecl Name -> [LHsTyVarBndr Name] -> TcM (TyClDecl Name)
541 kcDataDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
543 = do { ctxt' <- kcHsContext ctxt
544 ; cons' <- mappM (wrapLocM kc_con_decl) cons
545 ; return (decl {tcdTyVars = tvs, tcdCtxt = ctxt', tcdCons = cons'}) }
547 -- doc comments are typechecked to Nothing here
548 kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res _) = do
549 kcHsTyVars ex_tvs $ \ex_tvs' -> do
550 ex_ctxt' <- kcHsContext ex_ctxt
551 details' <- kc_con_details details
553 ResTyH98 -> return ResTyH98
554 ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
555 return (ConDecl name expl ex_tvs' ex_ctxt' details' res' Nothing)
557 kc_con_details (PrefixCon btys)
558 = do { btys' <- mappM kc_larg_ty btys ; return (PrefixCon btys') }
559 kc_con_details (InfixCon bty1 bty2)
560 = do { bty1' <- kc_larg_ty bty1; bty2' <- kc_larg_ty bty2; return (InfixCon bty1' bty2') }
561 kc_con_details (RecCon fields)
562 = do { fields' <- mappM kc_field fields; return (RecCon fields') }
564 kc_field (HsRecField fld bty d) = do { bty' <- kc_larg_ty bty ; return (HsRecField fld bty' d) }
566 kc_larg_ty bty = case new_or_data of
567 DataType -> kcHsSigType bty
568 NewType -> kcHsLiftedSigType bty
569 -- Can't allow an unlifted type for newtypes, because we're effectively
570 -- going to remove the constructor while coercing it to a lifted type.
571 -- And newtypes can't be bang'd
575 %************************************************************************
577 \subsection{Type checking}
579 %************************************************************************
582 tcSynDecls :: [LTyClDecl Name] -> TcM [TyThing]
583 tcSynDecls [] = return []
584 tcSynDecls (decl : decls)
585 = do { syn_tc <- addLocM tcSynDecl decl
586 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls decls)
587 ; return (syn_tc : syn_tcs) }
590 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
591 = tcTyVarBndrs tvs $ \ tvs' -> do
592 { traceTc (text "tcd1" <+> ppr tc_name)
593 ; rhs_ty' <- tcHsKindedType rhs_ty
594 ; return (ATyCon (buildSynTyCon tc_name tvs' (SynonymTyCon rhs_ty'))) }
597 tcTyClDecl :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
599 tcTyClDecl calc_isrec decl
600 = tcAddDeclCtxt decl (tcTyClDecl1 calc_isrec decl)
602 -- kind signature for a type function
603 tcTyClDecl1 _calc_isrec
604 (TyFunction {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = kind})
605 = tcTyVarBndrs tvs $ \ tvs' -> do
606 { traceTc (text "type family: " <+> ppr tc_name)
607 ; gla_exts <- doptM Opt_IndexedTypes
609 -- Check that we don't use kind signatures without Glasgow extensions
610 ; checkTc gla_exts $ badSigTyDecl tc_name
612 ; return [ATyCon $ buildSynTyCon tc_name tvs' (OpenSynTyCon kind)]
615 -- kind signature for an indexed data type
616 tcTyClDecl1 _calc_isrec
617 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
618 tcdLName = L _ tc_name, tcdKindSig = Just ksig, tcdCons = []})
619 = tcTyVarBndrs tvs $ \ tvs' -> do
620 { traceTc (text "data/newtype family: " <+> ppr tc_name)
621 ; extra_tvs <- tcDataKindSig (Just ksig)
622 ; let final_tvs = tvs' ++ extra_tvs -- we may not need these
624 ; checkTc (null . unLoc $ ctxt) $ badKindSigCtxt tc_name
625 ; gla_exts <- doptM Opt_IndexedTypes
627 -- Check that we don't use kind signatures without Glasgow extensions
628 ; checkTc gla_exts $ badSigTyDecl tc_name
630 ; tycon <- buildAlgTyCon tc_name final_tvs []
632 DataType -> OpenDataTyCon
633 NewType -> OpenNewTyCon)
634 Recursive False True Nothing
635 ; return [ATyCon tycon]
638 tcTyClDecl1 calc_isrec
639 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
640 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
641 = tcTyVarBndrs tvs $ \ tvs' -> do
642 { extra_tvs <- tcDataKindSig mb_ksig
643 ; let final_tvs = tvs' ++ extra_tvs
644 ; stupid_theta <- tcHsKindedContext ctxt
645 ; want_generic <- doptM Opt_Generics
646 ; unbox_strict <- doptM Opt_UnboxStrictFields
647 ; gla_exts <- doptM Opt_GlasgowExts
648 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
650 -- Check that we don't use GADT syntax in H98 world
651 ; checkTc (gla_exts || h98_syntax) (badGadtDecl tc_name)
653 -- Check that we don't use kind signatures without Glasgow extensions
654 ; checkTc (gla_exts || isNothing mb_ksig) (badSigTyDecl tc_name)
656 -- Check that the stupid theta is empty for a GADT-style declaration
657 ; checkTc (null stupid_theta || h98_syntax) (badStupidTheta tc_name)
659 -- Check that there's at least one condecl,
660 -- or else we're reading an hs-boot file, or -fglasgow-exts
661 ; checkTc (not (null cons) || gla_exts || is_boot)
662 (emptyConDeclsErr tc_name)
664 -- Check that a newtype has exactly one constructor
665 ; checkTc (new_or_data == DataType || isSingleton cons)
666 (newtypeConError tc_name (length cons))
668 ; tycon <- fixM (\ tycon -> do
669 { data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data
673 if null cons && is_boot -- In a hs-boot file, empty cons means
674 then return AbstractTyCon -- "don't know"; hence Abstract
675 else case new_or_data of
676 DataType -> return (mkDataTyConRhs data_cons)
678 ASSERT( isSingleton data_cons )
679 mkNewTyConRhs tc_name tycon (head data_cons)
680 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
681 (want_generic && canDoGenerics data_cons) h98_syntax Nothing
683 ; return [ATyCon tycon]
686 is_rec = calc_isrec tc_name
687 h98_syntax = case cons of -- All constructors have same shape
688 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
691 tcTyClDecl1 calc_isrec
692 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
693 tcdCtxt = ctxt, tcdMeths = meths,
694 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
695 = tcTyVarBndrs tvs $ \ tvs' -> do
696 { ctxt' <- tcHsKindedContext ctxt
697 ; fds' <- mappM (addLocM tc_fundep) fundeps
698 ; atss <- mappM (addLocM (tcTyClDecl1 (const Recursive))) ats
699 ; let ats' = zipWith setTyThingPoss atss (map (tcdTyVars . unLoc) ats)
700 ; sig_stuff <- tcClassSigs class_name sigs meths
701 ; clas <- fixM (\ clas ->
702 let -- This little knot is just so we can get
703 -- hold of the name of the class TyCon, which we
704 -- need to look up its recursiveness
705 tycon_name = tyConName (classTyCon clas)
706 tc_isrec = calc_isrec tycon_name
708 buildClass class_name tvs' ctxt' fds' ats'
710 ; return (AClass clas : ats')
711 -- NB: Order is important due to the call to `mkGlobalThings' when
712 -- tying the the type and class declaration type checking knot.
715 tc_fundep (tvs1, tvs2) = do { tvs1' <- mappM tcLookupTyVar tvs1 ;
716 ; tvs2' <- mappM tcLookupTyVar tvs2 ;
717 ; return (tvs1', tvs2') }
719 -- For each AT argument compute the position of the corresponding class
720 -- parameter in the class head. This will later serve as a permutation
721 -- vector when checking the validity of instance declarations.
722 setTyThingPoss [ATyCon tycon] atTyVars =
723 let classTyVars = hsLTyVarNames tvs
725 . map (`elemIndex` classTyVars)
728 -- There will be no Nothing, as we already passed renaming
730 ATyCon (setTyConArgPoss tycon poss)
731 setTyThingPoss _ _ = panic "TcTyClsDecls.setTyThingPoss"
733 tcTyClDecl1 calc_isrec
734 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
735 = returnM [ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0)]
737 -----------------------------------
738 tcConDecl :: Bool -- True <=> -funbox-strict_fields
744 tcConDecl unbox_strict NewType tycon tc_tvs -- Newtypes
745 (ConDecl name _ ex_tvs ex_ctxt details ResTyH98 _)
746 = do { let tc_datacon field_lbls arg_ty
747 = do { arg_ty' <- tcHsKindedType arg_ty -- No bang on newtype
748 ; buildDataCon (unLoc name) False {- Prefix -}
750 (map unLoc field_lbls)
751 tc_tvs [] -- No existentials
752 [] [] -- 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 [HsRecField 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 -- 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 -- Tiresome: tidy the tyvar binders, since tc_tvs and tvs' may have the same OccNames
774 tc_datacon is_infix field_lbls btys
775 = do { let bangs = map getBangStrictness btys
776 ; arg_tys <- mappM tcHsBangType btys
777 ; buildDataCon (unLoc name) is_infix
778 (argStrictness unbox_strict bangs arg_tys)
779 (map unLoc field_lbls)
780 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 [ (n, t) | HsRecField n t _ <- 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 (distinct OccNames from univs)
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
821 ; let univ_tvs = choose_univs [] tidy_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
838 -- NB: tc_tvs and dc_tvs are distinct, but
839 -- we want them to be *visibly* distinct, both for
840 -- interface files and general confusion. So rename
841 -- the tc_tvs, since they are not used yet (no
842 -- consequential renaming needed)
843 init_occ_env = initTidyOccEnv (map getOccName dc_tvs)
844 (_, tidy_tc_tvs) = mapAccumL tidy_one init_occ_env tc_tvs
845 tidy_one env tv = (env', setTyVarName tv (tidyNameOcc name occ'))
848 (env', occ') = tidyOccName env (getOccName name)
851 argStrictness :: Bool -- True <=> -funbox-strict_fields
853 -> [TcType] -> [StrictnessMark]
854 argStrictness unbox_strict bangs arg_tys
855 = ASSERT( length bangs == length arg_tys )
856 zipWith (chooseBoxingStrategy unbox_strict) arg_tys bangs
858 -- We attempt to unbox/unpack a strict field when either:
859 -- (i) The field is marked '!!', or
860 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
862 -- We have turned off unboxing of newtypes because coercions make unboxing
863 -- and reboxing more complicated
864 chooseBoxingStrategy :: Bool -> TcType -> HsBang -> StrictnessMark
865 chooseBoxingStrategy unbox_strict_fields arg_ty bang
867 HsNoBang -> NotMarkedStrict
868 HsStrict | unbox_strict_fields
869 && can_unbox arg_ty -> MarkedUnboxed
870 HsUnbox | can_unbox arg_ty -> MarkedUnboxed
871 other -> MarkedStrict
873 -- we can unbox if the type is a chain of newtypes with a product tycon
875 can_unbox arg_ty = case splitTyConApp_maybe arg_ty of
877 Just (arg_tycon, tycon_args) ->
878 not (isRecursiveTyCon arg_tycon) && -- Note [Recusive unboxing]
879 isProductTyCon arg_tycon &&
880 (if isNewTyCon arg_tycon then
881 can_unbox (newTyConInstRhs arg_tycon tycon_args)
885 Note [Recursive unboxing]
886 ~~~~~~~~~~~~~~~~~~~~~~~~~
887 Be careful not to try to unbox this!
889 But it's the *argument* type that matters. This is fine:
891 because Int is non-recursive.
893 %************************************************************************
895 \subsection{Dependency analysis}
897 %************************************************************************
899 Validity checking is done once the mutually-recursive knot has been
900 tied, so we can look at things freely.
903 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
904 checkCycleErrs tyclss
908 = do { mappM_ recClsErr cls_cycles
909 ; failM } -- Give up now, because later checkValidTyCl
910 -- will loop if the synonym is recursive
912 cls_cycles = calcClassCycles tyclss
914 checkValidTyCl :: TyClDecl Name -> TcM ()
915 -- We do the validity check over declarations, rather than TyThings
916 -- only so that we can add a nice context with tcAddDeclCtxt
918 = tcAddDeclCtxt decl $
919 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
920 ; traceTc (text "Validity of" <+> ppr thing)
922 ATyCon tc -> checkValidTyCon tc
923 AClass cl -> checkValidClass cl
924 ; traceTc (text "Done validity of" <+> ppr thing)
927 -------------------------
928 -- For data types declared with record syntax, we require
929 -- that each constructor that has a field 'f'
930 -- (a) has the same result type
931 -- (b) has the same type for 'f'
932 -- module alpha conversion of the quantified type variables
933 -- of the constructor.
935 checkValidTyCon :: TyCon -> TcM ()
938 = case synTyConRhs tc of
939 OpenSynTyCon _ -> return ()
940 SynonymTyCon ty -> checkValidType syn_ctxt ty
942 = -- Check the context on the data decl
943 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
945 -- Check arg types of data constructors
946 mappM_ (checkValidDataCon tc) data_cons `thenM_`
948 -- Check that fields with the same name share a type
949 mappM_ check_fields groups
952 syn_ctxt = TySynCtxt name
954 data_cons = tyConDataCons tc
956 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
957 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
958 get_fields con = dataConFieldLabels con `zip` repeat con
959 -- dataConFieldLabels may return the empty list, which is fine
961 -- See Note [GADT record selectors] in MkId.lhs
962 -- We must check (a) that the named field has the same
963 -- type in each constructor
964 -- (b) that those constructors have the same result type
966 -- However, the constructors may have differently named type variable
967 -- and (worse) we don't know how the correspond to each other. E.g.
968 -- C1 :: forall a b. { f :: a, g :: b } -> T a b
969 -- C2 :: forall d c. { f :: c, g :: c } -> T c d
971 -- So what we do is to ust Unify.tcMatchTys to compare the first candidate's
972 -- result type against other candidates' types BOTH WAYS ROUND.
973 -- If they magically agrees, take the substitution and
974 -- apply them to the latter ones, and see if they match perfectly.
975 check_fields fields@((label, con1) : other_fields)
976 -- These fields all have the same name, but are from
977 -- different constructors in the data type
978 = recoverM (return ()) $ mapM_ checkOne other_fields
979 -- Check that all the fields in the group have the same type
980 -- NB: this check assumes that all the constructors of a given
981 -- data type use the same type variables
983 tvs1 = mkVarSet (dataConAllTyVars con1)
984 res1 = dataConResTys con1
985 fty1 = dataConFieldType con1 label
987 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
988 = do { checkFieldCompat label con1 con2 tvs1 res1 res2 fty1 fty2
989 ; checkFieldCompat label con2 con1 tvs2 res2 res1 fty2 fty1 }
991 tvs2 = mkVarSet (dataConAllTyVars con2)
992 res2 = dataConResTys con2
993 fty2 = dataConFieldType con2 label
995 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
996 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
997 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
999 mb_subst1 = tcMatchTys tvs1 res1 res2
1000 mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
1002 -------------------------------
1003 checkValidDataCon :: TyCon -> DataCon -> TcM ()
1004 checkValidDataCon tc con
1005 = setSrcSpan (srcLocSpan (getSrcLoc con)) $
1006 addErrCtxt (dataConCtxt con) $
1007 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
1008 ; checkValidType ctxt (dataConUserType con) }
1010 ctxt = ConArgCtxt (dataConName con)
1012 -------------------------------
1013 checkValidClass :: Class -> TcM ()
1015 = do { -- CHECK ARITY 1 FOR HASKELL 1.4
1016 gla_exts <- doptM Opt_GlasgowExts
1018 -- Check that the class is unary, unless GlaExs
1019 ; checkTc (notNull tyvars) (nullaryClassErr cls)
1020 ; checkTc (gla_exts || unary) (classArityErr cls)
1022 -- Check the super-classes
1023 ; checkValidTheta (ClassSCCtxt (className cls)) theta
1025 -- Check the class operations
1026 ; mappM_ (check_op gla_exts) op_stuff
1028 -- Check that if the class has generic methods, then the
1029 -- class has only one parameter. We can't do generic
1030 -- multi-parameter type classes!
1031 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
1034 (tyvars, theta, _, op_stuff) = classBigSig cls
1035 unary = isSingleton tyvars
1036 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
1038 check_op gla_exts (sel_id, dm)
1039 = addErrCtxt (classOpCtxt sel_id tau) $ do
1040 { checkValidTheta SigmaCtxt (tail theta)
1041 -- The 'tail' removes the initial (C a) from the
1042 -- class itself, leaving just the method type
1044 ; checkValidType (FunSigCtxt op_name) tau
1046 -- Check that the type mentions at least one of
1047 -- the class type variables...or at least one reachable
1048 -- from one of the class variables. Example: tc223
1049 -- class Error e => Game b mv e | b -> mv e where
1050 -- newBoard :: MonadState b m => m ()
1051 -- Here, MonadState has a fundep m->b, so newBoard is fine
1052 ; let grown_tyvars = grow theta (mkVarSet tyvars)
1053 ; checkTc (tyVarsOfType tau `intersectsVarSet` grown_tyvars)
1054 (noClassTyVarErr cls sel_id)
1056 -- Check that for a generic method, the type of
1057 -- the method is sufficiently simple
1058 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
1059 (badGenericMethodType op_name op_ty)
1062 op_name = idName sel_id
1063 op_ty = idType sel_id
1064 (_,theta1,tau1) = tcSplitSigmaTy op_ty
1065 (_,theta2,tau2) = tcSplitSigmaTy tau1
1066 (theta,tau) | gla_exts = (theta1 ++ theta2, tau2)
1067 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
1068 -- Ugh! The function might have a type like
1069 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
1070 -- With -fglasgow-exts, we want to allow this, even though the inner
1071 -- forall has an (Eq a) constraint. Whereas in general, each constraint
1072 -- in the context of a for-all must mention at least one quantified
1073 -- type variable. What a mess!
1076 ---------------------------------------------------------------------
1077 resultTypeMisMatch field_name con1 con2
1078 = vcat [sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1079 ptext SLIT("have a common field") <+> quotes (ppr field_name) <> comma],
1080 nest 2 $ ptext SLIT("but have different result types")]
1081 fieldTypeMisMatch field_name con1 con2
1082 = sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1083 ptext SLIT("give different types for field"), quotes (ppr field_name)]
1085 dataConCtxt con = ptext SLIT("In the definition of data constructor") <+> quotes (ppr con)
1087 classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
1088 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
1091 = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
1094 = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
1095 parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
1097 noClassTyVarErr clas op
1098 = sep [ptext SLIT("The class method") <+> quotes (ppr op),
1099 ptext SLIT("mentions none of the type variables of the class") <+>
1100 ppr clas <+> hsep (map ppr (classTyVars clas))]
1102 genericMultiParamErr clas
1103 = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
1104 ptext SLIT("cannot have generic methods")
1106 badGenericMethodType op op_ty
1107 = hang (ptext SLIT("Generic method type is too complex"))
1108 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
1109 ptext SLIT("You can only use type variables, arrows, lists, and tuples")])
1112 = setSrcSpan (getLoc (head sorted_decls)) $
1113 addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
1114 nest 2 (vcat (map ppr_decl sorted_decls))])
1116 sorted_decls = sortLocated syn_decls
1117 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
1120 = setSrcSpan (getLoc (head sorted_decls)) $
1121 addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
1122 nest 2 (vcat (map ppr_decl sorted_decls))])
1124 sorted_decls = sortLocated cls_decls
1125 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
1127 sortLocated :: [Located a] -> [Located a]
1128 sortLocated things = sortLe le things
1130 le (L l1 _) (L l2 _) = l1 <= l2
1132 badDataConTyCon data_con
1133 = hang (ptext SLIT("Data constructor") <+> quotes (ppr data_con) <+>
1134 ptext SLIT("returns type") <+> quotes (ppr (dataConTyCon data_con)))
1135 2 (ptext SLIT("instead of its parent type"))
1138 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
1139 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow GADTs")) ]
1141 badStupidTheta tc_name
1142 = ptext SLIT("A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
1144 newtypeConError tycon n
1145 = sep [ptext SLIT("A newtype must have exactly one constructor,"),
1146 nest 2 $ ptext SLIT("but") <+> quotes (ppr tycon) <+> ptext SLIT("has") <+> speakN n ]
1149 = sep [ptext SLIT("A newtype constructor cannot have an existential context,"),
1150 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
1152 newtypeFieldErr con_name n_flds
1153 = sep [ptext SLIT("The constructor of a newtype must have exactly one field"),
1154 nest 2 $ ptext SLIT("but") <+> quotes (ppr con_name) <+> ptext SLIT("has") <+> speakN n_flds]
1156 badSigTyDecl tc_name
1157 = vcat [ ptext SLIT("Illegal kind signature") <+>
1158 quotes (ppr tc_name)
1159 , nest 2 (parens $ ptext SLIT("Use -findexed-types to allow indexed types")) ]
1161 badKindSigCtxt tc_name
1162 = vcat [ ptext SLIT("Illegal context in kind signature") <+>
1163 quotes (ppr tc_name)
1164 , nest 2 (parens $ ptext SLIT("Currently, kind signatures cannot have a context")) ]
1166 badIdxTyDecl tc_name
1167 = vcat [ ptext SLIT("Illegal indexed type instance for") <+>
1168 quotes (ppr tc_name)
1169 , nest 2 (parens $ ptext SLIT("Use -findexed-types to allow indexed types")) ]
1171 badGadtIdxTyDecl tc_name
1172 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+>
1173 quotes (ppr tc_name)
1174 , nest 2 (parens $ ptext SLIT("Indexed types cannot use GADT declarations")) ]
1176 tooManyParmsErr tc_name
1177 = ptext SLIT("Indexed type instance has too many parameters:") <+>
1178 quotes (ppr tc_name)
1180 tooFewParmsErr tc_name
1181 = ptext SLIT("Indexed type instance has too few parameters:") <+>
1182 quotes (ppr tc_name)
1184 badBootTyIdxDeclErr =
1185 ptext SLIT("Illegal indexed type instance in hs-boot file")
1187 wrongKindOfFamily family =
1188 ptext SLIT("Wrong category of type instance; declaration was for a") <+>
1191 kindOfFamily | isSynTyCon family = ptext SLIT("type synonym")
1192 | isDataTyCon family = ptext SLIT("data type")
1193 | isNewTyCon family = ptext SLIT("newtype")
1195 emptyConDeclsErr tycon
1196 = sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
1197 nest 2 $ ptext SLIT("(-fglasgow-exts permits this)")]