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, tcFamInstDecl
13 #include "HsVersions.h"
47 import Data.List ( partition, elemIndex )
48 import Control.Monad ( mplus )
52 %************************************************************************
54 \subsection{Type checking for type and class declarations}
56 %************************************************************************
60 Consider a mutually-recursive group, binding
61 a type constructor T and a class C.
63 Step 1: getInitialKind
64 Construct a KindEnv by binding T and C to a kind variable
67 In that environment, do a kind check
69 Step 3: Zonk the kinds
71 Step 4: buildTyConOrClass
72 Construct an environment binding T to a TyCon and C to a Class.
73 a) Their kinds comes from zonking the relevant kind variable
74 b) Their arity (for synonyms) comes direct from the decl
75 c) The funcional dependencies come from the decl
76 d) The rest comes a knot-tied binding of T and C, returned from Step 4
77 e) The variances of the tycons in the group is calculated from
81 In this environment, walk over the decls, constructing the TyCons and Classes.
82 This uses in a strict way items (a)-(c) above, which is why they must
83 be constructed in Step 4. Feed the results back to Step 4.
84 For this step, pass the is-recursive flag as the wimp-out flag
88 Step 6: Extend environment
89 We extend the type environment with bindings not only for the TyCons and Classes,
90 but also for their "implicit Ids" like data constructors and class selectors
92 Step 7: checkValidTyCl
93 For a recursive group only, check all the decls again, just
94 to check all the side conditions on validity. We could not
95 do this before because we were in a mutually recursive knot.
97 Identification of recursive TyCons
98 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
99 The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to
102 Identifying a TyCon as recursive serves two purposes
104 1. Avoid infinite types. Non-recursive newtypes are treated as
105 "transparent", like type synonyms, after the type checker. If we did
106 this for all newtypes, we'd get infinite types. So we figure out for
107 each newtype whether it is "recursive", and add a coercion if so. In
108 effect, we are trying to "cut the loops" by identifying a loop-breaker.
110 2. Avoid infinite unboxing. This is nothing to do with newtypes.
114 Well, this function diverges, but we don't want the strictness analyser
115 to diverge. But the strictness analyser will diverge because it looks
116 deeper and deeper into the structure of T. (I believe there are
117 examples where the function does something sane, and the strictness
118 analyser still diverges, but I can't see one now.)
120 Now, concerning (1), the FC2 branch currently adds a coercion for ALL
121 newtypes. I did this as an experiment, to try to expose cases in which
122 the coercions got in the way of optimisations. If it turns out that we
123 can indeed always use a coercion, then we don't risk recursive types,
124 and don't need to figure out what the loop breakers are.
126 For newtype *families* though, we will always have a coercion, so they
127 are always loop breakers! So you can easily adjust the current
128 algorithm by simply treating all newtype families as loop breakers (and
129 indeed type families). I think.
132 tcTyAndClassDecls :: ModDetails -> [LTyClDecl Name]
133 -> TcM TcGblEnv -- Input env extended by types and classes
134 -- and their implicit Ids,DataCons
135 tcTyAndClassDecls boot_details allDecls
136 = do { -- Omit instances of indexed types; they are handled together
137 -- with the *heads* of class instances
138 ; let decls = filter (not . isFamInstDecl . unLoc) allDecls
140 -- First check for cyclic type synonysm or classes
141 -- See notes with checkCycleErrs
142 ; checkCycleErrs decls
144 ; traceTc (text "tcTyAndCl" <+> ppr mod)
145 ; (syn_tycons, alg_tyclss) <- fixM (\ ~(rec_syn_tycons, rec_alg_tyclss) ->
146 do { let { -- Seperate ordinary synonyms from all other type and
147 -- class declarations and add all associated type
148 -- declarations from type classes. The latter is
149 -- required so that the temporary environment for the
150 -- knot includes all associated family declarations.
151 ; (syn_decls, alg_decls) = partition (isSynDecl . unLoc)
153 ; alg_at_decls = concatMap addATs alg_decls
155 -- Extend the global env with the knot-tied results
156 -- for data types and classes
158 -- We must populate the environment with the loop-tied
159 -- T's right away, because the kind checker may "fault
160 -- in" some type constructors that recursively
162 ; let gbl_things = mkGlobalThings alg_at_decls rec_alg_tyclss
163 ; tcExtendRecEnv gbl_things $ do
165 -- Kind-check the declarations
166 { (kc_syn_decls, kc_alg_decls) <- kcTyClDecls syn_decls alg_decls
168 ; let { -- Calculate rec-flag
169 ; calc_rec = calcRecFlags boot_details rec_alg_tyclss
170 ; tc_decl = addLocM (tcTyClDecl calc_rec) }
172 -- Type-check the type synonyms, and extend the envt
173 ; syn_tycons <- tcSynDecls kc_syn_decls
174 ; tcExtendGlobalEnv syn_tycons $ do
176 -- Type-check the data types and classes
177 { alg_tyclss <- mappM tc_decl kc_alg_decls
178 ; return (syn_tycons, concat alg_tyclss)
180 -- Finished with knot-tying now
181 -- Extend the environment with the finished things
182 ; tcExtendGlobalEnv (syn_tycons ++ alg_tyclss) $ do
184 -- Perform the validity check
185 { traceTc (text "ready for validity check")
186 ; mappM_ (addLocM checkValidTyCl) decls
187 ; traceTc (text "done")
189 -- Add the implicit things;
190 -- we want them in the environment because
191 -- they may be mentioned in interface files
192 -- NB: All associated types and their implicit things will be added a
193 -- second time here. This doesn't matter as the definitions are
195 ; let { implicit_things = concatMap implicitTyThings alg_tyclss }
196 ; traceTc ((text "Adding" <+> ppr alg_tyclss)
197 $$ (text "and" <+> ppr implicit_things))
198 ; tcExtendGlobalEnv implicit_things getGblEnv
201 -- Pull associated types out of class declarations, to tie them into the
203 -- NB: We put them in the same place in the list as `tcTyClDecl' will
204 -- eventually put the matching `TyThing's. That's crucial; otherwise,
205 -- the two argument lists of `mkGlobalThings' don't match up.
206 addATs decl@(L _ (ClassDecl {tcdATs = ats})) = decl : ats
209 mkGlobalThings :: [LTyClDecl Name] -- The decls
210 -> [TyThing] -- Knot-tied, in 1-1 correspondence with the decls
212 -- Driven by the Decls, and treating the TyThings lazily
213 -- make a TypeEnv for the new things
214 mkGlobalThings decls things
215 = map mk_thing (decls `zipLazy` things)
217 mk_thing (L _ (ClassDecl {tcdLName = L _ name}), ~(AClass cl))
219 mk_thing (L _ decl, ~(ATyCon tc))
220 = (tcdName decl, ATyCon tc)
224 %************************************************************************
226 \subsection{Type checking family instances}
228 %************************************************************************
230 Family instances are somewhat of a hybrid. They are processed together with
231 class instance heads, but can contain data constructors and hence they share a
232 lot of kinding and type checking code with ordinary algebraic data types (and
236 tcFamInstDecl :: LTyClDecl Name -> TcM (Maybe TyThing) -- Nothing if error
237 tcFamInstDecl (L loc decl)
238 = -- Prime error recovery, set source location
239 recoverM (returnM Nothing) $
242 do { -- type families require -findexed-types and can't be in an
244 ; gla_exts <- doptM Opt_IndexedTypes
245 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
246 ; checkTc gla_exts $ badFamInstDecl (tcdLName decl)
247 ; checkTc (not is_boot) $ badBootFamInstDeclErr
249 -- perform kind and type checking
250 ; tcFamInstDecl1 decl
253 tcFamInstDecl1 :: TyClDecl Name -> TcM (Maybe TyThing) -- Nothing if error
255 tcFamInstDecl1 (decl@TySynonym {})
256 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
257 do { -- check that the family declaration is for a synonym
258 unless (isSynTyCon family) $
259 addErr (wrongKindOfFamily family)
261 ; -- (1) kind check the right hand side of the type equation
262 ; k_rhs <- kcCheckHsType (tcdSynRhs decl) resKind
264 -- (2) type check type equation
265 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
266 ; t_typats <- mappM tcHsKindedType k_typats
267 ; t_rhs <- tcHsKindedType k_rhs
269 -- !!!of the form: forall t_tvs. (tcdLName decl) t_typats = t_rhs
270 ; return Nothing -- !!!TODO: need TyThing for indexed synonym
273 tcFamInstDecl1 (decl@TyData {tcdND = new_or_data, tcdLName = L loc tc_name,
275 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
276 do { -- check that the family declaration is for the right kind
277 unless (new_or_data == NewType && isNewTyCon family ||
278 new_or_data == DataType && isDataTyCon family) $
279 addErr (wrongKindOfFamily family)
281 ; -- (1) kind check the data declaration as usual
282 ; k_decl <- kcDataDecl decl k_tvs
283 ; let k_ctxt = tcdCtxt k_decl
284 k_cons = tcdCons k_decl
286 -- result kind must be '*' (otherwise, we have too few patterns)
287 ; checkTc (isLiftedTypeKind resKind) $ tooFewParmsErr tc_name
289 -- (2) type check indexed data type declaration
290 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
291 ; unbox_strict <- doptM Opt_UnboxStrictFields
293 -- Check that we don't use GADT syntax for indexed types
294 ; checkTc h98_syntax (badGadtIdxTyDecl tc_name)
296 -- Check that a newtype has exactly one constructor
297 ; checkTc (new_or_data == DataType || isSingleton k_cons) $
298 newtypeConError tc_name (length k_cons)
300 ; t_typats <- mappM tcHsKindedType k_typats
301 ; stupid_theta <- tcHsKindedContext k_ctxt
303 ; rep_tc_name <- newFamInstTyConName tc_name (srcSpanStart loc)
304 ; tycon <- fixM (\ tycon -> do
305 { data_cons <- mappM (addLocM (tcConDecl unbox_strict tycon t_tvs))
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 a type family 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 families altogether in the following. However, we need to
398 include the kinds of associated families 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 . isFamInstDecl . 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 | isFamInstDecl 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 (TyFamily { tcdKind = Just kind }) = return kind
449 mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
450 -- On GADT-style declarations we allow a kind signature
451 -- data T :: *->* where { ... }
452 mk_res_kind other = return liftedTypeKind
456 kcSynDecls :: [SCC (LTyClDecl Name)]
457 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
458 [(Name,TcKind)]) -- Kind bindings
461 kcSynDecls (group : groups)
462 = do { (decl, nk) <- kcSynDecl group
463 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
464 ; return (decl:decls, nk:nks) }
467 kcSynDecl :: SCC (LTyClDecl Name)
468 -> TcM (LTyClDecl Name, -- Kind-annotated decls
469 (Name,TcKind)) -- Kind bindings
470 kcSynDecl (AcyclicSCC ldecl@(L loc decl))
471 = tcAddDeclCtxt decl $
472 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
473 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
474 <+> brackets (ppr k_tvs))
475 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
476 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
477 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
478 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
479 (unLoc (tcdLName decl), tc_kind)) })
481 kcSynDecl (CyclicSCC decls)
482 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
483 -- of out-of-scope tycons
485 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
487 ------------------------------------------------------------------------
488 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
489 -- Not used for type synonyms (see kcSynDecl)
491 kcTyClDecl decl@(TyData {})
492 = ASSERT( not . isFamInstDecl $ decl ) -- must not be a family instance
493 kcTyClDeclBody decl $
496 kcTyClDecl decl@(TyFamily {tcdKind = kind})
497 = kcTyClDeclBody decl $ \ tvs' ->
498 return (decl {tcdTyVars = tvs',
499 tcdKind = kind `mplus` Just liftedTypeKind})
500 -- default result kind is '*'
502 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs, tcdATs = ats})
503 = kcTyClDeclBody decl $ \ tvs' ->
504 do { is_boot <- tcIsHsBoot
505 ; ctxt' <- kcHsContext ctxt
506 ; ats' <- mappM (wrapLocM kcTyClDecl) ats
507 ; sigs' <- mappM (wrapLocM kc_sig ) sigs
508 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs',
511 kc_sig (TypeSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
512 ; return (TypeSig nm op_ty') }
513 kc_sig other_sig = return other_sig
515 kcTyClDecl decl@(ForeignType {})
518 kcTyClDeclBody :: TyClDecl Name
519 -> ([LHsTyVarBndr Name] -> TcM a)
521 -- getInitialKind has made a suitably-shaped kind for the type or class
522 -- Unpack it, and attribute those kinds to the type variables
523 -- Extend the env with bindings for the tyvars, taken from
524 -- the kind of the tycon/class. Give it to the thing inside, and
525 -- check the result kind matches
526 kcTyClDeclBody decl thing_inside
527 = tcAddDeclCtxt decl $
528 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
529 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
530 (kinds, _) = splitKindFunTys tc_kind
531 hs_tvs = tcdTyVars decl
532 kinded_tvs = ASSERT( length kinds >= length hs_tvs )
533 [ L loc (KindedTyVar (hsTyVarName tv) k)
534 | (L loc tv, k) <- zip hs_tvs kinds]
535 ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
537 -- Kind check a data declaration, assuming that we already extended the
538 -- kind environment with the type variables of the left-hand side (these
539 -- kinded type variables are also passed as the second parameter).
541 kcDataDecl :: TyClDecl Name -> [LHsTyVarBndr Name] -> TcM (TyClDecl Name)
542 kcDataDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
544 = do { ctxt' <- kcHsContext ctxt
545 ; cons' <- mappM (wrapLocM kc_con_decl) cons
546 ; return (decl {tcdTyVars = tvs, tcdCtxt = ctxt', tcdCons = cons'}) }
548 -- doc comments are typechecked to Nothing here
549 kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res _) = do
550 kcHsTyVars ex_tvs $ \ex_tvs' -> do
551 ex_ctxt' <- kcHsContext ex_ctxt
552 details' <- kc_con_details details
554 ResTyH98 -> return ResTyH98
555 ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
556 return (ConDecl name expl ex_tvs' ex_ctxt' details' res' Nothing)
558 kc_con_details (PrefixCon btys)
559 = do { btys' <- mappM kc_larg_ty btys ; return (PrefixCon btys') }
560 kc_con_details (InfixCon bty1 bty2)
561 = do { bty1' <- kc_larg_ty bty1; bty2' <- kc_larg_ty bty2; return (InfixCon bty1' bty2') }
562 kc_con_details (RecCon fields)
563 = do { fields' <- mappM kc_field fields; return (RecCon fields') }
565 kc_field (HsRecField fld bty d) = do { bty' <- kc_larg_ty bty ; return (HsRecField fld bty' d) }
567 kc_larg_ty bty = case new_or_data of
568 DataType -> kcHsSigType bty
569 NewType -> kcHsLiftedSigType bty
570 -- Can't allow an unlifted type for newtypes, because we're effectively
571 -- going to remove the constructor while coercing it to a lifted type.
572 -- And newtypes can't be bang'd
576 %************************************************************************
578 \subsection{Type checking}
580 %************************************************************************
583 tcSynDecls :: [LTyClDecl Name] -> TcM [TyThing]
584 tcSynDecls [] = return []
585 tcSynDecls (decl : decls)
586 = do { syn_tc <- addLocM tcSynDecl decl
587 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls decls)
588 ; return (syn_tc : syn_tcs) }
591 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
592 = tcTyVarBndrs tvs $ \ tvs' -> do
593 { traceTc (text "tcd1" <+> ppr tc_name)
594 ; rhs_ty' <- tcHsKindedType rhs_ty
595 ; return (ATyCon (buildSynTyCon tc_name tvs' (SynonymTyCon rhs_ty'))) }
598 tcTyClDecl :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
600 tcTyClDecl calc_isrec decl
601 = tcAddDeclCtxt decl (tcTyClDecl1 calc_isrec decl)
603 -- "type family" declarations
604 tcTyClDecl1 _calc_isrec
605 (TyFamily {tcdFlavour = TypeFamily,
606 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = Just kind})
607 -- NB: kind at latest
610 = tcTyVarBndrs tvs $ \ tvs' -> do
611 { traceTc (text "type family: " <+> ppr tc_name)
612 ; idx_tys <- doptM Opt_IndexedTypes
614 -- Check that we don't use families without -findexed-types
615 ; checkTc idx_tys $ badFamInstDecl tc_name
617 ; return [ATyCon $ buildSynTyCon tc_name tvs' (OpenSynTyCon kind Nothing)]
620 -- "newtype family" or "data family" declaration
621 tcTyClDecl1 _calc_isrec
622 (TyFamily {tcdFlavour = DataFamily new_or_data,
623 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = mb_kind})
624 = tcTyVarBndrs tvs $ \ tvs' -> do
625 { traceTc (text "data/newtype family: " <+> ppr tc_name)
626 ; extra_tvs <- tcDataKindSig mb_kind
627 ; let final_tvs = tvs' ++ extra_tvs -- we may not need these
629 ; idx_tys <- doptM Opt_IndexedTypes
631 -- Check that we don't use families without -findexed-types
632 ; checkTc idx_tys $ badFamInstDecl tc_name
634 ; tycon <- buildAlgTyCon tc_name final_tvs []
636 DataType -> mkOpenDataTyConRhs
637 NewType -> mkOpenNewTyConRhs)
638 Recursive False True Nothing
639 ; return [ATyCon tycon]
642 -- "newtype", "data", "newtype instance", "data instance"
643 tcTyClDecl1 calc_isrec
644 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
645 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
646 = tcTyVarBndrs tvs $ \ tvs' -> do
647 { extra_tvs <- tcDataKindSig mb_ksig
648 ; let final_tvs = tvs' ++ extra_tvs
649 ; stupid_theta <- tcHsKindedContext ctxt
650 ; want_generic <- doptM Opt_Generics
651 ; unbox_strict <- doptM Opt_UnboxStrictFields
652 ; gla_exts <- doptM Opt_GlasgowExts
653 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
655 -- Check that we don't use GADT syntax in H98 world
656 ; checkTc (gla_exts || h98_syntax) (badGadtDecl tc_name)
658 -- Check that we don't use kind signatures without Glasgow extensions
659 ; checkTc (gla_exts || isNothing mb_ksig) (badSigTyDecl tc_name)
661 -- Check that the stupid theta is empty for a GADT-style declaration
662 ; checkTc (null stupid_theta || h98_syntax) (badStupidTheta tc_name)
664 -- Check that there's at least one condecl,
665 -- or else we're reading an hs-boot file, or -fglasgow-exts
666 ; checkTc (not (null cons) || gla_exts || is_boot)
667 (emptyConDeclsErr tc_name)
669 -- Check that a newtype has exactly one constructor
670 ; checkTc (new_or_data == DataType || isSingleton cons)
671 (newtypeConError tc_name (length cons))
673 ; tycon <- fixM (\ tycon -> do
674 { data_cons <- mappM (addLocM (tcConDecl unbox_strict tycon final_tvs))
677 if null cons && is_boot -- In a hs-boot file, empty cons means
678 then return AbstractTyCon -- "don't know"; hence Abstract
679 else case new_or_data of
680 DataType -> return (mkDataTyConRhs data_cons)
682 ASSERT( isSingleton data_cons )
683 mkNewTyConRhs tc_name tycon (head data_cons)
684 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
685 (want_generic && canDoGenerics data_cons) h98_syntax Nothing
687 ; return [ATyCon tycon]
690 is_rec = calc_isrec tc_name
691 h98_syntax = case cons of -- All constructors have same shape
692 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
695 tcTyClDecl1 calc_isrec
696 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
697 tcdCtxt = ctxt, tcdMeths = meths,
698 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
699 = tcTyVarBndrs tvs $ \ tvs' -> do
700 { ctxt' <- tcHsKindedContext ctxt
701 ; fds' <- mappM (addLocM tc_fundep) fundeps
702 ; atss <- mappM (addLocM (tcTyClDecl1 (const Recursive))) ats
703 ; let ats' = zipWith setTyThingPoss atss (map (tcdTyVars . unLoc) ats)
704 ; sig_stuff <- tcClassSigs class_name sigs meths
705 ; clas <- fixM (\ clas ->
706 let -- This little knot is just so we can get
707 -- hold of the name of the class TyCon, which we
708 -- need to look up its recursiveness
709 tycon_name = tyConName (classTyCon clas)
710 tc_isrec = calc_isrec tycon_name
712 buildClass class_name tvs' ctxt' fds' ats'
714 ; return (AClass clas : ats')
715 -- NB: Order is important due to the call to `mkGlobalThings' when
716 -- tying the the type and class declaration type checking knot.
719 tc_fundep (tvs1, tvs2) = do { tvs1' <- mappM tcLookupTyVar tvs1 ;
720 ; tvs2' <- mappM tcLookupTyVar tvs2 ;
721 ; return (tvs1', tvs2') }
723 -- For each AT argument compute the position of the corresponding class
724 -- parameter in the class head. This will later serve as a permutation
725 -- vector when checking the validity of instance declarations.
726 setTyThingPoss [ATyCon tycon] atTyVars =
727 let classTyVars = hsLTyVarNames tvs
729 . map (`elemIndex` classTyVars)
732 -- There will be no Nothing, as we already passed renaming
734 ATyCon (setTyConArgPoss tycon poss)
735 setTyThingPoss _ _ = panic "TcTyClsDecls.setTyThingPoss"
737 tcTyClDecl1 calc_isrec
738 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
739 = returnM [ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0)]
741 -----------------------------------
742 tcConDecl :: Bool -- True <=> -funbox-strict_fields
747 tcConDecl unbox_strict tycon tc_tvs -- Data types
748 (ConDecl name _ tvs ctxt details res_ty _)
749 = tcTyVarBndrs tvs $ \ tvs' -> do
750 { ctxt' <- tcHsKindedContext ctxt
751 ; (univ_tvs, ex_tvs, eq_preds, data_tc) <- tcResultType tycon tc_tvs tvs' res_ty
753 -- Tiresome: tidy the tyvar binders, since tc_tvs and tvs' may have the same OccNames
754 tc_datacon is_infix field_lbls btys
755 = do { let bangs = map getBangStrictness btys
756 ; arg_tys <- mappM tcHsBangType btys
757 ; buildDataCon (unLoc name) is_infix
758 (argStrictness unbox_strict bangs arg_tys)
759 (map unLoc field_lbls)
760 univ_tvs ex_tvs eq_preds ctxt' arg_tys
762 -- NB: we put data_tc, the type constructor gotten from the
763 -- constructor type signature into the data constructor;
764 -- that way checkValidDataCon can complain if it's wrong.
767 PrefixCon btys -> tc_datacon False [] btys
768 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
769 RecCon fields -> tc_datacon False field_names btys
771 (field_names, btys) = unzip [ (n, t) | HsRecField n t _ <- fields ]
775 tcResultType :: TyCon
776 -> [TyVar] -- data T a b c = ...
777 -> [TyVar] -- where MkT :: forall a b c. ...
779 -> TcM ([TyVar], -- Universal
780 [TyVar], -- Existential (distinct OccNames from univs)
781 [(TyVar,Type)], -- Equality predicates
782 TyCon) -- TyCon given in the ResTy
783 -- We don't check that the TyCon given in the ResTy is
784 -- the same as the parent tycon, becuase we are in the middle
785 -- of a recursive knot; so it's postponed until checkValidDataCon
787 tcResultType decl_tycon tc_tvs dc_tvs ResTyH98
788 = return (tc_tvs, dc_tvs, [], decl_tycon)
789 -- In H98 syntax the dc_tvs are the existential ones
790 -- data T a b c = forall d e. MkT ...
791 -- The {a,b,c} are tc_tvs, and {d,e} are dc_tvs
793 tcResultType _ tc_tvs dc_tvs (ResTyGADT res_ty)
794 -- E.g. data T a b c where
795 -- MkT :: forall x y z. T (x,y) z z
797 -- ([a,z,c], [x,y], [a:=:(x,y), c:=:z], T)
799 = do { (dc_tycon, res_tys) <- tcLHsConResTy res_ty
801 ; let univ_tvs = choose_univs [] tidy_tc_tvs res_tys
802 -- Each univ_tv is either a dc_tv or a tc_tv
803 ex_tvs = dc_tvs `minusList` univ_tvs
804 eq_spec = [ (tv, ty) | (tv,ty) <- univ_tvs `zip` res_tys,
806 ; return (univ_tvs, ex_tvs, eq_spec, dc_tycon) }
808 -- choose_univs uses the res_ty itself if it's a type variable
809 -- and hasn't already been used; otherwise it uses one of the tc_tvs
810 choose_univs used tc_tvs []
811 = ASSERT( null tc_tvs ) []
812 choose_univs used (tc_tv:tc_tvs) (res_ty:res_tys)
813 | Just tv <- tcGetTyVar_maybe res_ty, not (tv `elem` used)
814 = tv : choose_univs (tv:used) tc_tvs res_tys
816 = tc_tv : choose_univs used tc_tvs res_tys
818 -- NB: tc_tvs and dc_tvs are distinct, but
819 -- we want them to be *visibly* distinct, both for
820 -- interface files and general confusion. So rename
821 -- the tc_tvs, since they are not used yet (no
822 -- consequential renaming needed)
823 init_occ_env = initTidyOccEnv (map getOccName dc_tvs)
824 (_, tidy_tc_tvs) = mapAccumL tidy_one init_occ_env tc_tvs
825 tidy_one env tv = (env', setTyVarName tv (tidyNameOcc name occ'))
828 (env', occ') = tidyOccName env (getOccName name)
831 argStrictness :: Bool -- True <=> -funbox-strict_fields
833 -> [TcType] -> [StrictnessMark]
834 argStrictness unbox_strict bangs arg_tys
835 = ASSERT( length bangs == length arg_tys )
836 zipWith (chooseBoxingStrategy unbox_strict) arg_tys bangs
838 -- We attempt to unbox/unpack a strict field when either:
839 -- (i) The field is marked '!!', or
840 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
842 -- We have turned off unboxing of newtypes because coercions make unboxing
843 -- and reboxing more complicated
844 chooseBoxingStrategy :: Bool -> TcType -> HsBang -> StrictnessMark
845 chooseBoxingStrategy unbox_strict_fields arg_ty bang
847 HsNoBang -> NotMarkedStrict
848 HsStrict | unbox_strict_fields
849 && can_unbox arg_ty -> MarkedUnboxed
850 HsUnbox | can_unbox arg_ty -> MarkedUnboxed
851 other -> MarkedStrict
853 -- we can unbox if the type is a chain of newtypes with a product tycon
855 can_unbox arg_ty = case splitTyConApp_maybe arg_ty of
857 Just (arg_tycon, tycon_args) ->
858 not (isRecursiveTyCon arg_tycon) && -- Note [Recusive unboxing]
859 isProductTyCon arg_tycon &&
860 (if isNewTyCon arg_tycon then
861 can_unbox (newTyConInstRhs arg_tycon tycon_args)
865 Note [Recursive unboxing]
866 ~~~~~~~~~~~~~~~~~~~~~~~~~
867 Be careful not to try to unbox this!
869 But it's the *argument* type that matters. This is fine:
871 because Int is non-recursive.
873 %************************************************************************
875 \subsection{Dependency analysis}
877 %************************************************************************
879 Validity checking is done once the mutually-recursive knot has been
880 tied, so we can look at things freely.
883 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
884 checkCycleErrs tyclss
888 = do { mappM_ recClsErr cls_cycles
889 ; failM } -- Give up now, because later checkValidTyCl
890 -- will loop if the synonym is recursive
892 cls_cycles = calcClassCycles tyclss
894 checkValidTyCl :: TyClDecl Name -> TcM ()
895 -- We do the validity check over declarations, rather than TyThings
896 -- only so that we can add a nice context with tcAddDeclCtxt
898 = tcAddDeclCtxt decl $
899 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
900 ; traceTc (text "Validity of" <+> ppr thing)
902 ATyCon tc -> checkValidTyCon tc
903 AClass cl -> checkValidClass cl
904 ; traceTc (text "Done validity of" <+> ppr thing)
907 -------------------------
908 -- For data types declared with record syntax, we require
909 -- that each constructor that has a field 'f'
910 -- (a) has the same result type
911 -- (b) has the same type for 'f'
912 -- module alpha conversion of the quantified type variables
913 -- of the constructor.
915 checkValidTyCon :: TyCon -> TcM ()
918 = case synTyConRhs tc of
919 OpenSynTyCon _ _ -> return ()
920 SynonymTyCon ty -> checkValidType syn_ctxt ty
922 = -- Check the context on the data decl
923 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
925 -- Check arg types of data constructors
926 mappM_ (checkValidDataCon tc) data_cons `thenM_`
928 -- Check that fields with the same name share a type
929 mappM_ check_fields groups
932 syn_ctxt = TySynCtxt name
934 data_cons = tyConDataCons tc
936 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
937 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
938 get_fields con = dataConFieldLabels con `zip` repeat con
939 -- dataConFieldLabels may return the empty list, which is fine
941 -- See Note [GADT record selectors] in MkId.lhs
942 -- We must check (a) that the named field has the same
943 -- type in each constructor
944 -- (b) that those constructors have the same result type
946 -- However, the constructors may have differently named type variable
947 -- and (worse) we don't know how the correspond to each other. E.g.
948 -- C1 :: forall a b. { f :: a, g :: b } -> T a b
949 -- C2 :: forall d c. { f :: c, g :: c } -> T c d
951 -- So what we do is to ust Unify.tcMatchTys to compare the first candidate's
952 -- result type against other candidates' types BOTH WAYS ROUND.
953 -- If they magically agrees, take the substitution and
954 -- apply them to the latter ones, and see if they match perfectly.
955 check_fields fields@((label, con1) : other_fields)
956 -- These fields all have the same name, but are from
957 -- different constructors in the data type
958 = recoverM (return ()) $ mapM_ checkOne other_fields
959 -- Check that all the fields in the group have the same type
960 -- NB: this check assumes that all the constructors of a given
961 -- data type use the same type variables
963 (tvs1, _, _, res1) = dataConSig con1
965 fty1 = dataConFieldType con1 label
967 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
968 = do { checkFieldCompat label con1 con2 ts1 res1 res2 fty1 fty2
969 ; checkFieldCompat label con2 con1 ts2 res2 res1 fty2 fty1 }
971 (tvs2, _, _, res2) = dataConSig con2
973 fty2 = dataConFieldType con2 label
975 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
976 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
977 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
979 mb_subst1 = tcMatchTy tvs1 res1 res2
980 mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
982 -------------------------------
983 checkValidDataCon :: TyCon -> DataCon -> TcM ()
984 checkValidDataCon tc con
985 = setSrcSpan (srcLocSpan (getSrcLoc con)) $
986 addErrCtxt (dataConCtxt con) $
987 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
988 ; checkValidType ctxt (dataConUserType con)
989 ; ifM (isNewTyCon tc) (checkNewDataCon con)
992 ctxt = ConArgCtxt (dataConName con)
994 -------------------------------
995 checkNewDataCon :: DataCon -> TcM ()
996 -- Checks for the data constructor of a newtype
998 = do { checkTc (isSingleton arg_tys) (newtypeFieldErr con (length arg_tys))
1000 ; checkTc (null eq_spec) (newtypePredError con)
1001 -- Return type is (T a b c)
1002 ; checkTc (null ex_tvs && null theta) (newtypeExError con)
1006 (_univ_tvs, ex_tvs, eq_spec, theta, arg_tys, _res_ty) = dataConFullSig con
1008 -------------------------------
1009 checkValidClass :: Class -> TcM ()
1011 = do { -- CHECK ARITY 1 FOR HASKELL 1.4
1012 gla_exts <- doptM Opt_GlasgowExts
1014 -- Check that the class is unary, unless GlaExs
1015 ; checkTc (notNull tyvars) (nullaryClassErr cls)
1016 ; checkTc (gla_exts || unary) (classArityErr cls)
1018 -- Check the super-classes
1019 ; checkValidTheta (ClassSCCtxt (className cls)) theta
1021 -- Check the class operations
1022 ; mappM_ (check_op gla_exts) op_stuff
1024 -- Check that if the class has generic methods, then the
1025 -- class has only one parameter. We can't do generic
1026 -- multi-parameter type classes!
1027 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
1030 (tyvars, theta, _, op_stuff) = classBigSig cls
1031 unary = isSingleton tyvars
1032 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
1034 check_op gla_exts (sel_id, dm)
1035 = addErrCtxt (classOpCtxt sel_id tau) $ do
1036 { checkValidTheta SigmaCtxt (tail theta)
1037 -- The 'tail' removes the initial (C a) from the
1038 -- class itself, leaving just the method type
1040 ; checkValidType (FunSigCtxt op_name) tau
1042 -- Check that the type mentions at least one of
1043 -- the class type variables...or at least one reachable
1044 -- from one of the class variables. Example: tc223
1045 -- class Error e => Game b mv e | b -> mv e where
1046 -- newBoard :: MonadState b m => m ()
1047 -- Here, MonadState has a fundep m->b, so newBoard is fine
1048 ; let grown_tyvars = grow theta (mkVarSet tyvars)
1049 ; checkTc (tyVarsOfType tau `intersectsVarSet` grown_tyvars)
1050 (noClassTyVarErr cls sel_id)
1052 -- Check that for a generic method, the type of
1053 -- the method is sufficiently simple
1054 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
1055 (badGenericMethodType op_name op_ty)
1058 op_name = idName sel_id
1059 op_ty = idType sel_id
1060 (_,theta1,tau1) = tcSplitSigmaTy op_ty
1061 (_,theta2,tau2) = tcSplitSigmaTy tau1
1062 (theta,tau) | gla_exts = (theta1 ++ theta2, tau2)
1063 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
1064 -- Ugh! The function might have a type like
1065 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
1066 -- With -fglasgow-exts, we want to allow this, even though the inner
1067 -- forall has an (Eq a) constraint. Whereas in general, each constraint
1068 -- in the context of a for-all must mention at least one quantified
1069 -- type variable. What a mess!
1072 ---------------------------------------------------------------------
1073 resultTypeMisMatch field_name con1 con2
1074 = vcat [sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1075 ptext SLIT("have a common field") <+> quotes (ppr field_name) <> comma],
1076 nest 2 $ ptext SLIT("but have different result types")]
1077 fieldTypeMisMatch field_name con1 con2
1078 = sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1079 ptext SLIT("give different types for field"), quotes (ppr field_name)]
1081 dataConCtxt con = ptext SLIT("In the definition of data constructor") <+> quotes (ppr con)
1083 classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
1084 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
1087 = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
1090 = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
1091 parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
1093 noClassTyVarErr clas op
1094 = sep [ptext SLIT("The class method") <+> quotes (ppr op),
1095 ptext SLIT("mentions none of the type variables of the class") <+>
1096 ppr clas <+> hsep (map ppr (classTyVars clas))]
1098 genericMultiParamErr clas
1099 = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
1100 ptext SLIT("cannot have generic methods")
1102 badGenericMethodType op op_ty
1103 = hang (ptext SLIT("Generic method type is too complex"))
1104 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
1105 ptext SLIT("You can only use type variables, arrows, lists, and tuples")])
1108 = setSrcSpan (getLoc (head sorted_decls)) $
1109 addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
1110 nest 2 (vcat (map ppr_decl sorted_decls))])
1112 sorted_decls = sortLocated syn_decls
1113 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
1116 = setSrcSpan (getLoc (head sorted_decls)) $
1117 addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
1118 nest 2 (vcat (map ppr_decl sorted_decls))])
1120 sorted_decls = sortLocated cls_decls
1121 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
1123 sortLocated :: [Located a] -> [Located a]
1124 sortLocated things = sortLe le things
1126 le (L l1 _) (L l2 _) = l1 <= l2
1128 badDataConTyCon data_con
1129 = hang (ptext SLIT("Data constructor") <+> quotes (ppr data_con) <+>
1130 ptext SLIT("returns type") <+> quotes (ppr (dataConTyCon data_con)))
1131 2 (ptext SLIT("instead of its parent type"))
1134 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
1135 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow GADTs")) ]
1137 badStupidTheta tc_name
1138 = ptext SLIT("A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
1140 newtypeConError tycon n
1141 = sep [ptext SLIT("A newtype must have exactly one constructor,"),
1142 nest 2 $ ptext SLIT("but") <+> quotes (ppr tycon) <+> ptext SLIT("has") <+> speakN n ]
1145 = sep [ptext SLIT("A newtype constructor cannot have an existential context,"),
1146 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
1148 newtypePredError con
1149 = sep [ptext SLIT("A newtype constructor must have a return type of form T a1 ... an"),
1150 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does not")]
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 -fglasgow-exts to allow kind signatures")) ]
1161 badFamInstDecl tc_name
1162 = vcat [ ptext SLIT("Illegal family instance for") <+>
1163 quotes (ppr tc_name)
1164 , nest 2 (parens $ ptext SLIT("Use -findexed-types to allow indexed type families")) ]
1166 badGadtIdxTyDecl tc_name
1167 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+>
1168 quotes (ppr tc_name)
1169 , nest 2 (parens $ ptext SLIT("Family instances can not yet use GADT declarations")) ]
1171 tooManyParmsErr tc_name
1172 = ptext SLIT("Family instance has too many parameters:") <+>
1173 quotes (ppr tc_name)
1175 tooFewParmsErr tc_name
1176 = ptext SLIT("Family instance has too few parameters:") <+>
1177 quotes (ppr tc_name)
1179 badBootFamInstDeclErr =
1180 ptext SLIT("Illegal family instance in hs-boot file")
1182 wrongKindOfFamily family =
1183 ptext SLIT("Wrong category of family instance; declaration was for a") <+>
1186 kindOfFamily | isSynTyCon family = ptext SLIT("type synonym")
1187 | isDataTyCon family = ptext SLIT("data type")
1188 | isNewTyCon family = ptext SLIT("newtype")
1190 emptyConDeclsErr tycon
1191 = sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
1192 nest 2 $ ptext SLIT("(-fglasgow-exts permits this)")]