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 type families; 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 -ftype-families and can't be in an
244 ; gla_exts <- doptM Opt_TypeFamilies
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
256 tcFamInstDecl1 (decl@TySynonym {tcdLName = L loc tc_name})
257 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
258 do { -- check that the family declaration is for a synonym
259 unless (isSynTyCon family) $
260 addErr (wrongKindOfFamily family)
262 ; -- (1) kind check the right-hand side of the type equation
263 ; k_rhs <- kcCheckHsType (tcdSynRhs decl) resKind
265 -- (2) type check type equation
266 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
267 ; t_typats <- mappM tcHsKindedType k_typats
268 ; t_rhs <- tcHsKindedType k_rhs
270 ; -- (3) check that the right-hand side is a tau type
271 ; unless (isTauTy t_rhs) $
272 addErr (polyTyErr t_rhs)
274 -- (4) construct representation tycon
275 ; rep_tc_name <- newFamInstTyConName tc_name loc
276 ; tycon <- buildSynTyCon rep_tc_name t_tvs (SynonymTyCon t_rhs)
277 (Just (family, t_typats))
279 ; return $ Just (ATyCon tycon)
282 -- "newtype instance" and "data instance"
283 tcFamInstDecl1 (decl@TyData {tcdND = new_or_data, tcdLName = L loc tc_name,
285 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
286 do { -- check that the family declaration is for the right kind
287 unless (isAlgTyCon family) $
288 addErr (wrongKindOfFamily family)
290 ; -- (1) kind check the data declaration as usual
291 ; k_decl <- kcDataDecl decl k_tvs
292 ; let k_ctxt = tcdCtxt k_decl
293 k_cons = tcdCons k_decl
295 -- result kind must be '*' (otherwise, we have too few patterns)
296 ; checkTc (isLiftedTypeKind resKind) $ tooFewParmsErr tc_name
298 -- (2) type check indexed data type declaration
299 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
300 ; unbox_strict <- doptM Opt_UnboxStrictFields
302 -- Check that we don't use GADT syntax for indexed types
303 ; checkTc h98_syntax (badGadtIdxTyDecl tc_name)
305 -- Check that a newtype has exactly one constructor
306 ; checkTc (new_or_data == DataType || isSingleton k_cons) $
307 newtypeConError tc_name (length k_cons)
309 ; t_typats <- mappM tcHsKindedType k_typats
310 ; stupid_theta <- tcHsKindedContext k_ctxt
312 -- (3) construct representation tycon
313 ; rep_tc_name <- newFamInstTyConName tc_name loc
314 ; tycon <- fixM (\ tycon -> do
315 { data_cons <- mappM (addLocM (tcConDecl unbox_strict tycon t_tvs))
319 DataType -> return (mkDataTyConRhs data_cons)
320 NewType -> ASSERT( isSingleton data_cons )
321 mkNewTyConRhs rep_tc_name tycon (head data_cons)
322 ; buildAlgTyCon rep_tc_name t_tvs stupid_theta tc_rhs Recursive
323 False h98_syntax (Just (family, t_typats))
324 -- We always assume that indexed types are recursive. Why?
325 -- (1) Due to their open nature, we can never be sure that a
326 -- further instance might not introduce a new recursive
327 -- dependency. (2) They are always valid loop breakers as
328 -- they involve a coercion.
332 ; return $ Just (ATyCon tycon)
335 h98_syntax = case cons of -- All constructors have same shape
336 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
339 -- Kind checking of indexed types
342 -- Kind check type patterns and kind annotate the embedded type variables.
344 -- * Here we check that a type instance matches its kind signature, but we do
345 -- not check whether there is a pattern for each type index; the latter
346 -- check is only required for type synonym instances.
348 kcIdxTyPats :: TyClDecl Name
349 -> ([LHsTyVarBndr Name] -> [LHsType Name] -> Kind -> TyCon -> TcM a)
350 -- ^^kinded tvs ^^kinded ty pats ^^res kind
352 kcIdxTyPats decl thing_inside
353 = kcHsTyVars (tcdTyVars decl) $ \tvs ->
354 do { family <- tcLookupLocatedTyCon (tcdLName decl)
355 ; let { (kinds, resKind) = splitKindFunTys (tyConKind family)
356 ; hs_typats = fromJust $ tcdTyPats decl }
358 -- we may not have more parameters than the kind indicates
359 ; checkTc (length kinds >= length hs_typats) $
360 tooManyParmsErr (tcdLName decl)
362 -- type functions can have a higher-kinded result
363 ; let resultKind = mkArrowKinds (drop (length hs_typats) kinds) resKind
364 ; typats <- TcRnMonad.zipWithM kcCheckHsType hs_typats kinds
365 ; thing_inside tvs typats resultKind family
371 %************************************************************************
375 %************************************************************************
377 We need to kind check all types in the mutually recursive group
378 before we know the kind of the type variables. For example:
381 op :: D b => a -> b -> b
384 bop :: (Monad c) => ...
386 Here, the kind of the locally-polymorphic type variable "b"
387 depends on *all the uses of class D*. For example, the use of
388 Monad c in bop's type signature means that D must have kind Type->Type.
390 However type synonyms work differently. They can have kinds which don't
391 just involve (->) and *:
392 type R = Int# -- Kind #
393 type S a = Array# a -- Kind * -> #
394 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
395 So we must infer their kinds from their right-hand sides *first* and then
396 use them, whereas for the mutually recursive data types D we bring into
397 scope kind bindings D -> k, where k is a kind variable, and do inference.
401 This treatment of type synonyms only applies to Haskell 98-style synonyms.
402 General type functions can be recursive, and hence, appear in `alg_decls'.
404 The kind of a type family is solely determinded by its kind signature;
405 hence, only kind signatures participate in the construction of the initial
406 kind environment (as constructed by `getInitialKind'). In fact, we ignore
407 instances of families altogether in the following. However, we need to
408 include the kinds of associated families into the construction of the
409 initial kind environment. (This is handled by `allDecls').
412 kcTyClDecls syn_decls alg_decls
413 = do { -- First extend the kind env with each data type, class, and
414 -- indexed type, mapping them to a type variable
415 let initialKindDecls = concat [allDecls decl | L _ decl <- alg_decls]
416 ; alg_kinds <- mappM getInitialKind initialKindDecls
417 ; tcExtendKindEnv alg_kinds $ do
419 -- Now kind-check the type synonyms, in dependency order
420 -- We do these differently to data type and classes,
421 -- because a type synonym can be an unboxed type
423 -- and a kind variable can't unify with UnboxedTypeKind
424 -- So we infer their kinds in dependency order
425 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
426 ; tcExtendKindEnv syn_kinds $ do
428 -- Now kind-check the data type, class, and kind signatures,
429 -- returning kind-annotated decls; we don't kind-check
430 -- instances of indexed types yet, but leave this to
432 { kc_alg_decls <- mappM (wrapLocM kcTyClDecl)
433 (filter (not . isFamInstDecl . unLoc) alg_decls)
435 ; return (kc_syn_decls, kc_alg_decls) }}}
437 -- get all declarations relevant for determining the initial kind
439 allDecls (decl@ClassDecl {tcdATs = ats}) = decl : [ at
442 allDecls decl | isFamInstDecl decl = []
445 ------------------------------------------------------------------------
446 getInitialKind :: TyClDecl Name -> TcM (Name, TcKind)
447 -- Only for data type, class, and indexed type declarations
448 -- Get as much info as possible from the data, class, or indexed type decl,
449 -- so as to maximise usefulness of error messages
451 = do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl)
452 ; res_kind <- mk_res_kind decl
453 ; return (tcdName decl, mkArrowKinds arg_kinds res_kind) }
455 mk_arg_kind (UserTyVar _) = newKindVar
456 mk_arg_kind (KindedTyVar _ kind) = return kind
458 mk_res_kind (TyFamily { tcdKind = Just kind }) = return kind
459 mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
460 -- On GADT-style declarations we allow a kind signature
461 -- data T :: *->* where { ... }
462 mk_res_kind other = return liftedTypeKind
466 kcSynDecls :: [SCC (LTyClDecl Name)]
467 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
468 [(Name,TcKind)]) -- Kind bindings
471 kcSynDecls (group : groups)
472 = do { (decl, nk) <- kcSynDecl group
473 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
474 ; return (decl:decls, nk:nks) }
477 kcSynDecl :: SCC (LTyClDecl Name)
478 -> TcM (LTyClDecl Name, -- Kind-annotated decls
479 (Name,TcKind)) -- Kind bindings
480 kcSynDecl (AcyclicSCC ldecl@(L loc decl))
481 = tcAddDeclCtxt decl $
482 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
483 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
484 <+> brackets (ppr k_tvs))
485 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
486 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
487 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
488 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
489 (unLoc (tcdLName decl), tc_kind)) })
491 kcSynDecl (CyclicSCC decls)
492 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
493 -- of out-of-scope tycons
495 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
497 ------------------------------------------------------------------------
498 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
499 -- Not used for type synonyms (see kcSynDecl)
501 kcTyClDecl decl@(TyData {})
502 = ASSERT( not . isFamInstDecl $ decl ) -- must not be a family instance
503 kcTyClDeclBody decl $
506 kcTyClDecl decl@(TyFamily {tcdKind = kind})
507 = kcTyClDeclBody decl $ \ tvs' ->
508 return (decl {tcdTyVars = tvs',
509 tcdKind = kind `mplus` Just liftedTypeKind})
510 -- default result kind is '*'
512 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs, tcdATs = ats})
513 = kcTyClDeclBody decl $ \ tvs' ->
514 do { is_boot <- tcIsHsBoot
515 ; ctxt' <- kcHsContext ctxt
516 ; ats' <- mappM (wrapLocM kcTyClDecl) ats
517 ; sigs' <- mappM (wrapLocM kc_sig ) sigs
518 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs',
521 kc_sig (TypeSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
522 ; return (TypeSig nm op_ty') }
523 kc_sig other_sig = return other_sig
525 kcTyClDecl decl@(ForeignType {})
528 kcTyClDeclBody :: TyClDecl Name
529 -> ([LHsTyVarBndr Name] -> TcM a)
531 -- getInitialKind has made a suitably-shaped kind for the type or class
532 -- Unpack it, and attribute those kinds to the type variables
533 -- Extend the env with bindings for the tyvars, taken from
534 -- the kind of the tycon/class. Give it to the thing inside, and
535 -- check the result kind matches
536 kcTyClDeclBody decl thing_inside
537 = tcAddDeclCtxt decl $
538 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
539 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
540 (kinds, _) = splitKindFunTys tc_kind
541 hs_tvs = tcdTyVars decl
542 kinded_tvs = ASSERT( length kinds >= length hs_tvs )
543 [ L loc (KindedTyVar (hsTyVarName tv) k)
544 | (L loc tv, k) <- zip hs_tvs kinds]
545 ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
547 -- Kind check a data declaration, assuming that we already extended the
548 -- kind environment with the type variables of the left-hand side (these
549 -- kinded type variables are also passed as the second parameter).
551 kcDataDecl :: TyClDecl Name -> [LHsTyVarBndr Name] -> TcM (TyClDecl Name)
552 kcDataDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
554 = do { ctxt' <- kcHsContext ctxt
555 ; cons' <- mappM (wrapLocM kc_con_decl) cons
556 ; return (decl {tcdTyVars = tvs, tcdCtxt = ctxt', tcdCons = cons'}) }
558 -- doc comments are typechecked to Nothing here
559 kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res _) = do
560 kcHsTyVars ex_tvs $ \ex_tvs' -> do
561 ex_ctxt' <- kcHsContext ex_ctxt
562 details' <- kc_con_details details
564 ResTyH98 -> return ResTyH98
565 ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
566 return (ConDecl name expl ex_tvs' ex_ctxt' details' res' Nothing)
568 kc_con_details (PrefixCon btys)
569 = do { btys' <- mappM kc_larg_ty btys ; return (PrefixCon btys') }
570 kc_con_details (InfixCon bty1 bty2)
571 = do { bty1' <- kc_larg_ty bty1; bty2' <- kc_larg_ty bty2; return (InfixCon bty1' bty2') }
572 kc_con_details (RecCon fields)
573 = do { fields' <- mappM kc_field fields; return (RecCon fields') }
575 kc_field (ConDeclField fld bty d) = do { bty' <- kc_larg_ty bty
576 ; return (ConDeclField fld bty' d) }
578 kc_larg_ty bty = case new_or_data of
579 DataType -> kcHsSigType bty
580 NewType -> kcHsLiftedSigType bty
581 -- Can't allow an unlifted type for newtypes, because we're effectively
582 -- going to remove the constructor while coercing it to a lifted type.
583 -- And newtypes can't be bang'd
587 %************************************************************************
589 \subsection{Type checking}
591 %************************************************************************
594 tcSynDecls :: [LTyClDecl Name] -> TcM [TyThing]
595 tcSynDecls [] = return []
596 tcSynDecls (decl : decls)
597 = do { syn_tc <- addLocM tcSynDecl decl
598 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls decls)
599 ; return (syn_tc : syn_tcs) }
603 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
604 = tcTyVarBndrs tvs $ \ tvs' -> do
605 { traceTc (text "tcd1" <+> ppr tc_name)
606 ; rhs_ty' <- tcHsKindedType rhs_ty
607 ; tycon <- buildSynTyCon tc_name tvs' (SynonymTyCon rhs_ty') Nothing
608 ; return (ATyCon tycon)
612 tcTyClDecl :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
614 tcTyClDecl calc_isrec decl
615 = tcAddDeclCtxt decl (tcTyClDecl1 calc_isrec decl)
617 -- "type family" declarations
618 tcTyClDecl1 _calc_isrec
619 (TyFamily {tcdFlavour = TypeFamily,
620 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = Just kind})
621 -- NB: kind at latest
624 = tcTyVarBndrs tvs $ \ tvs' -> do
625 { traceTc (text "type family: " <+> ppr tc_name)
626 ; idx_tys <- doptM Opt_TypeFamilies
628 -- Check that we don't use families without -ftype-families
629 ; checkTc idx_tys $ badFamInstDecl tc_name
631 ; tycon <- buildSynTyCon tc_name tvs' (OpenSynTyCon kind Nothing) Nothing
632 ; return [ATyCon tycon]
635 -- "newtype family" or "data family" declaration
636 tcTyClDecl1 _calc_isrec
637 (TyFamily {tcdFlavour = DataFamily,
638 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = mb_kind})
639 = tcTyVarBndrs tvs $ \ tvs' -> do
640 { traceTc (text "data family: " <+> ppr tc_name)
641 ; extra_tvs <- tcDataKindSig mb_kind
642 ; let final_tvs = tvs' ++ extra_tvs -- we may not need these
644 ; idx_tys <- doptM Opt_TypeFamilies
646 -- Check that we don't use families without -ftype-families
647 ; checkTc idx_tys $ badFamInstDecl tc_name
649 ; tycon <- buildAlgTyCon tc_name final_tvs []
650 mkOpenDataTyConRhs Recursive False True Nothing
651 ; return [ATyCon tycon]
654 -- "newtype" and "data"
655 tcTyClDecl1 calc_isrec
656 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
657 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
658 = tcTyVarBndrs tvs $ \ tvs' -> do
659 { extra_tvs <- tcDataKindSig mb_ksig
660 ; let final_tvs = tvs' ++ extra_tvs
661 ; stupid_theta <- tcHsKindedContext ctxt
662 ; want_generic <- doptM Opt_Generics
663 ; unbox_strict <- doptM Opt_UnboxStrictFields
664 ; gla_exts <- doptM Opt_GlasgowExts
665 ; gadt_ok <- doptM Opt_GADTs
666 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
668 -- Check that we don't use GADT syntax in H98 world
669 ; checkTc (gadt_ok || h98_syntax) (badGadtDecl tc_name)
671 -- Check that we don't use kind signatures without Glasgow extensions
672 ; checkTc (gla_exts || isNothing mb_ksig) (badSigTyDecl tc_name)
674 -- Check that the stupid theta is empty for a GADT-style declaration
675 ; checkTc (null stupid_theta || h98_syntax) (badStupidTheta tc_name)
677 -- Check that there's at least one condecl,
678 -- or else we're reading an hs-boot file, or -fglasgow-exts
679 ; checkTc (not (null cons) || gla_exts || is_boot)
680 (emptyConDeclsErr tc_name)
682 -- Check that a newtype has exactly one constructor
683 ; checkTc (new_or_data == DataType || isSingleton cons)
684 (newtypeConError tc_name (length cons))
686 ; tycon <- fixM (\ tycon -> do
687 { data_cons <- mappM (addLocM (tcConDecl unbox_strict tycon final_tvs))
690 if null cons && is_boot -- In a hs-boot file, empty cons means
691 then return AbstractTyCon -- "don't know"; hence Abstract
692 else case new_or_data of
693 DataType -> return (mkDataTyConRhs data_cons)
695 ASSERT( isSingleton data_cons )
696 mkNewTyConRhs tc_name tycon (head data_cons)
697 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
698 (want_generic && canDoGenerics data_cons) h98_syntax Nothing
700 ; return [ATyCon tycon]
703 is_rec = calc_isrec tc_name
704 h98_syntax = case cons of -- All constructors have same shape
705 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
708 tcTyClDecl1 calc_isrec
709 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
710 tcdCtxt = ctxt, tcdMeths = meths,
711 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
712 = tcTyVarBndrs tvs $ \ tvs' -> do
713 { ctxt' <- tcHsKindedContext ctxt
714 ; fds' <- mappM (addLocM tc_fundep) fundeps
715 ; atss <- mappM (addLocM (tcTyClDecl1 (const Recursive))) ats
716 ; let ats' = zipWith setTyThingPoss atss (map (tcdTyVars . unLoc) ats)
717 ; sig_stuff <- tcClassSigs class_name sigs meths
718 ; clas <- fixM (\ clas ->
719 let -- This little knot is just so we can get
720 -- hold of the name of the class TyCon, which we
721 -- need to look up its recursiveness
722 tycon_name = tyConName (classTyCon clas)
723 tc_isrec = calc_isrec tycon_name
725 buildClass class_name tvs' ctxt' fds' ats'
727 ; return (AClass clas : ats')
728 -- NB: Order is important due to the call to `mkGlobalThings' when
729 -- tying the the type and class declaration type checking knot.
732 tc_fundep (tvs1, tvs2) = do { tvs1' <- mappM tcLookupTyVar tvs1 ;
733 ; tvs2' <- mappM tcLookupTyVar tvs2 ;
734 ; return (tvs1', tvs2') }
736 -- For each AT argument compute the position of the corresponding class
737 -- parameter in the class head. This will later serve as a permutation
738 -- vector when checking the validity of instance declarations.
739 setTyThingPoss [ATyCon tycon] atTyVars =
740 let classTyVars = hsLTyVarNames tvs
742 . map (`elemIndex` classTyVars)
745 -- There will be no Nothing, as we already passed renaming
747 ATyCon (setTyConArgPoss tycon poss)
748 setTyThingPoss _ _ = panic "TcTyClsDecls.setTyThingPoss"
750 tcTyClDecl1 calc_isrec
751 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
752 = returnM [ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0)]
754 -----------------------------------
755 tcConDecl :: Bool -- True <=> -funbox-strict_fields
760 tcConDecl unbox_strict tycon tc_tvs -- Data types
761 (ConDecl name _ tvs ctxt details res_ty _)
762 = tcTyVarBndrs tvs $ \ tvs' -> do
763 { ctxt' <- tcHsKindedContext ctxt
764 ; (univ_tvs, ex_tvs, eq_preds, data_tc) <- tcResultType tycon tc_tvs tvs' res_ty
766 -- Tiresome: tidy the tyvar binders, since tc_tvs and tvs' may have the same OccNames
767 tc_datacon is_infix field_lbls btys
768 = do { let bangs = map getBangStrictness btys
769 ; arg_tys <- mappM tcHsBangType btys
770 ; buildDataCon (unLoc name) is_infix
771 (argStrictness unbox_strict bangs arg_tys)
772 (map unLoc field_lbls)
773 univ_tvs ex_tvs eq_preds ctxt' arg_tys
775 -- NB: we put data_tc, the type constructor gotten from the
776 -- constructor type signature into the data constructor;
777 -- that way checkValidDataCon can complain if it's wrong.
780 PrefixCon btys -> tc_datacon False [] btys
781 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
782 RecCon fields -> tc_datacon False field_names btys
784 field_names = map cd_fld_name fields
785 btys = map cd_fld_type fields
788 tcResultType :: TyCon
789 -> [TyVar] -- data T a b c = ...
790 -> [TyVar] -- where MkT :: forall a b c. ...
792 -> TcM ([TyVar], -- Universal
793 [TyVar], -- Existential (distinct OccNames from univs)
794 [(TyVar,Type)], -- Equality predicates
795 TyCon) -- TyCon given in the ResTy
796 -- We don't check that the TyCon given in the ResTy is
797 -- the same as the parent tycon, becuase we are in the middle
798 -- of a recursive knot; so it's postponed until checkValidDataCon
800 tcResultType decl_tycon tc_tvs dc_tvs ResTyH98
801 = return (tc_tvs, dc_tvs, [], decl_tycon)
802 -- In H98 syntax the dc_tvs are the existential ones
803 -- data T a b c = forall d e. MkT ...
804 -- The {a,b,c} are tc_tvs, and {d,e} are dc_tvs
806 tcResultType _ tc_tvs dc_tvs (ResTyGADT res_ty)
807 -- E.g. data T a b c where
808 -- MkT :: forall x y z. T (x,y) z z
810 -- ([a,z,c], [x,y], [a:=:(x,y), c:=:z], T)
812 = do { (dc_tycon, res_tys) <- tcLHsConResTy res_ty
814 ; let univ_tvs = choose_univs [] tidy_tc_tvs res_tys
815 -- Each univ_tv is either a dc_tv or a tc_tv
816 ex_tvs = dc_tvs `minusList` univ_tvs
817 eq_spec = [ (tv, ty) | (tv,ty) <- univ_tvs `zip` res_tys,
819 ; return (univ_tvs, ex_tvs, eq_spec, dc_tycon) }
821 -- choose_univs uses the res_ty itself if it's a type variable
822 -- and hasn't already been used; otherwise it uses one of the tc_tvs
823 choose_univs used tc_tvs []
824 = ASSERT( null tc_tvs ) []
825 choose_univs used (tc_tv:tc_tvs) (res_ty:res_tys)
826 | Just tv <- tcGetTyVar_maybe res_ty, not (tv `elem` used)
827 = tv : choose_univs (tv:used) tc_tvs res_tys
829 = tc_tv : choose_univs used tc_tvs res_tys
831 -- NB: tc_tvs and dc_tvs are distinct, but
832 -- we want them to be *visibly* distinct, both for
833 -- interface files and general confusion. So rename
834 -- the tc_tvs, since they are not used yet (no
835 -- consequential renaming needed)
836 init_occ_env = initTidyOccEnv (map getOccName dc_tvs)
837 (_, tidy_tc_tvs) = mapAccumL tidy_one init_occ_env tc_tvs
838 tidy_one env tv = (env', setTyVarName tv (tidyNameOcc name occ'))
841 (env', occ') = tidyOccName env (getOccName name)
844 argStrictness :: Bool -- True <=> -funbox-strict_fields
846 -> [TcType] -> [StrictnessMark]
847 argStrictness unbox_strict bangs arg_tys
848 = ASSERT( length bangs == length arg_tys )
849 zipWith (chooseBoxingStrategy unbox_strict) arg_tys bangs
851 -- We attempt to unbox/unpack a strict field when either:
852 -- (i) The field is marked '!!', or
853 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
855 -- We have turned off unboxing of newtypes because coercions make unboxing
856 -- and reboxing more complicated
857 chooseBoxingStrategy :: Bool -> TcType -> HsBang -> StrictnessMark
858 chooseBoxingStrategy unbox_strict_fields arg_ty bang
860 HsNoBang -> NotMarkedStrict
861 HsStrict | unbox_strict_fields
862 && can_unbox arg_ty -> MarkedUnboxed
863 HsUnbox | can_unbox arg_ty -> MarkedUnboxed
864 other -> MarkedStrict
866 -- we can unbox if the type is a chain of newtypes with a product tycon
868 can_unbox arg_ty = case splitTyConApp_maybe arg_ty of
870 Just (arg_tycon, tycon_args) ->
871 not (isRecursiveTyCon arg_tycon) && -- Note [Recusive unboxing]
872 isProductTyCon arg_tycon &&
873 (if isNewTyCon arg_tycon then
874 can_unbox (newTyConInstRhs arg_tycon tycon_args)
878 Note [Recursive unboxing]
879 ~~~~~~~~~~~~~~~~~~~~~~~~~
880 Be careful not to try to unbox this!
882 But it's the *argument* type that matters. This is fine:
884 because Int is non-recursive.
886 %************************************************************************
888 \subsection{Dependency analysis}
890 %************************************************************************
892 Validity checking is done once the mutually-recursive knot has been
893 tied, so we can look at things freely.
896 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
897 checkCycleErrs tyclss
901 = do { mappM_ recClsErr cls_cycles
902 ; failM } -- Give up now, because later checkValidTyCl
903 -- will loop if the synonym is recursive
905 cls_cycles = calcClassCycles tyclss
907 checkValidTyCl :: TyClDecl Name -> TcM ()
908 -- We do the validity check over declarations, rather than TyThings
909 -- only so that we can add a nice context with tcAddDeclCtxt
911 = tcAddDeclCtxt decl $
912 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
913 ; traceTc (text "Validity of" <+> ppr thing)
915 ATyCon tc -> checkValidTyCon tc
916 AClass cl -> checkValidClass cl
917 ; traceTc (text "Done validity of" <+> ppr thing)
920 -------------------------
921 -- For data types declared with record syntax, we require
922 -- that each constructor that has a field 'f'
923 -- (a) has the same result type
924 -- (b) has the same type for 'f'
925 -- module alpha conversion of the quantified type variables
926 -- of the constructor.
928 checkValidTyCon :: TyCon -> TcM ()
931 = case synTyConRhs tc of
932 OpenSynTyCon _ _ -> return ()
933 SynonymTyCon ty -> checkValidType syn_ctxt ty
935 = -- Check the context on the data decl
936 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
938 -- Check arg types of data constructors
939 mappM_ (checkValidDataCon tc) data_cons `thenM_`
941 -- Check that fields with the same name share a type
942 mappM_ check_fields groups
945 syn_ctxt = TySynCtxt name
947 data_cons = tyConDataCons tc
949 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
950 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
951 get_fields con = dataConFieldLabels con `zip` repeat con
952 -- dataConFieldLabels may return the empty list, which is fine
954 -- See Note [GADT record selectors] in MkId.lhs
955 -- We must check (a) that the named field has the same
956 -- type in each constructor
957 -- (b) that those constructors have the same result type
959 -- However, the constructors may have differently named type variable
960 -- and (worse) we don't know how the correspond to each other. E.g.
961 -- C1 :: forall a b. { f :: a, g :: b } -> T a b
962 -- C2 :: forall d c. { f :: c, g :: c } -> T c d
964 -- So what we do is to ust Unify.tcMatchTys to compare the first candidate's
965 -- result type against other candidates' types BOTH WAYS ROUND.
966 -- If they magically agrees, take the substitution and
967 -- apply them to the latter ones, and see if they match perfectly.
968 check_fields fields@((label, con1) : other_fields)
969 -- These fields all have the same name, but are from
970 -- different constructors in the data type
971 = recoverM (return ()) $ mapM_ checkOne other_fields
972 -- Check that all the fields in the group have the same type
973 -- NB: this check assumes that all the constructors of a given
974 -- data type use the same type variables
976 (tvs1, _, _, res1) = dataConSig con1
978 fty1 = dataConFieldType con1 label
980 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
981 = do { checkFieldCompat label con1 con2 ts1 res1 res2 fty1 fty2
982 ; checkFieldCompat label con2 con1 ts2 res2 res1 fty2 fty1 }
984 (tvs2, _, _, res2) = dataConSig con2
986 fty2 = dataConFieldType con2 label
988 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
989 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
990 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
992 mb_subst1 = tcMatchTy tvs1 res1 res2
993 mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
995 -------------------------------
996 checkValidDataCon :: TyCon -> DataCon -> TcM ()
997 checkValidDataCon tc con
998 = setSrcSpan (srcLocSpan (getSrcLoc con)) $
999 addErrCtxt (dataConCtxt con) $
1000 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
1001 ; checkValidType ctxt (dataConUserType con)
1002 ; ifM (isNewTyCon tc) (checkNewDataCon con)
1005 ctxt = ConArgCtxt (dataConName con)
1007 -------------------------------
1008 checkNewDataCon :: DataCon -> TcM ()
1009 -- Checks for the data constructor of a newtype
1011 = do { checkTc (isSingleton arg_tys) (newtypeFieldErr con (length arg_tys))
1013 ; checkTc (null eq_spec) (newtypePredError con)
1014 -- Return type is (T a b c)
1015 ; checkTc (null ex_tvs && null theta) (newtypeExError con)
1017 ; checkTc (not (any isMarkedStrict (dataConStrictMarks con)))
1018 (newtypeStrictError con)
1022 (_univ_tvs, ex_tvs, eq_spec, theta, arg_tys, _res_ty) = dataConFullSig con
1024 -------------------------------
1025 checkValidClass :: Class -> TcM ()
1027 = do { -- CHECK ARITY 1 FOR HASKELL 1.4
1028 gla_exts <- doptM Opt_GlasgowExts
1030 -- Check that the class is unary, unless GlaExs
1031 ; checkTc (notNull tyvars) (nullaryClassErr cls)
1032 ; checkTc (gla_exts || unary) (classArityErr cls)
1034 -- Check the super-classes
1035 ; checkValidTheta (ClassSCCtxt (className cls)) theta
1037 -- Check the class operations
1038 ; mappM_ (check_op gla_exts) op_stuff
1040 -- Check that if the class has generic methods, then the
1041 -- class has only one parameter. We can't do generic
1042 -- multi-parameter type classes!
1043 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
1046 (tyvars, theta, _, op_stuff) = classBigSig cls
1047 unary = isSingleton tyvars
1048 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
1050 check_op gla_exts (sel_id, dm)
1051 = addErrCtxt (classOpCtxt sel_id tau) $ do
1052 { checkValidTheta SigmaCtxt (tail theta)
1053 -- The 'tail' removes the initial (C a) from the
1054 -- class itself, leaving just the method type
1056 ; checkValidType (FunSigCtxt op_name) tau
1058 -- Check that the type mentions at least one of
1059 -- the class type variables...or at least one reachable
1060 -- from one of the class variables. Example: tc223
1061 -- class Error e => Game b mv e | b -> mv e where
1062 -- newBoard :: MonadState b m => m ()
1063 -- Here, MonadState has a fundep m->b, so newBoard is fine
1064 ; let grown_tyvars = grow theta (mkVarSet tyvars)
1065 ; checkTc (tyVarsOfType tau `intersectsVarSet` grown_tyvars)
1066 (noClassTyVarErr cls sel_id)
1068 -- Check that for a generic method, the type of
1069 -- the method is sufficiently simple
1070 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
1071 (badGenericMethodType op_name op_ty)
1074 op_name = idName sel_id
1075 op_ty = idType sel_id
1076 (_,theta1,tau1) = tcSplitSigmaTy op_ty
1077 (_,theta2,tau2) = tcSplitSigmaTy tau1
1078 (theta,tau) | gla_exts = (theta1 ++ theta2, tau2)
1079 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
1080 -- Ugh! The function might have a type like
1081 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
1082 -- With -fglasgow-exts, we want to allow this, even though the inner
1083 -- forall has an (Eq a) constraint. Whereas in general, each constraint
1084 -- in the context of a for-all must mention at least one quantified
1085 -- type variable. What a mess!
1088 ---------------------------------------------------------------------
1089 resultTypeMisMatch field_name con1 con2
1090 = vcat [sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1091 ptext SLIT("have a common field") <+> quotes (ppr field_name) <> comma],
1092 nest 2 $ ptext SLIT("but have different result types")]
1093 fieldTypeMisMatch field_name con1 con2
1094 = sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1095 ptext SLIT("give different types for field"), quotes (ppr field_name)]
1097 dataConCtxt con = ptext SLIT("In the definition of data constructor") <+> quotes (ppr con)
1099 classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
1100 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
1103 = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
1106 = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
1107 parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
1109 noClassTyVarErr clas op
1110 = sep [ptext SLIT("The class method") <+> quotes (ppr op),
1111 ptext SLIT("mentions none of the type variables of the class") <+>
1112 ppr clas <+> hsep (map ppr (classTyVars clas))]
1114 genericMultiParamErr clas
1115 = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
1116 ptext SLIT("cannot have generic methods")
1118 badGenericMethodType op op_ty
1119 = hang (ptext SLIT("Generic method type is too complex"))
1120 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
1121 ptext SLIT("You can only use type variables, arrows, lists, and tuples")])
1124 = setSrcSpan (getLoc (head sorted_decls)) $
1125 addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
1126 nest 2 (vcat (map ppr_decl sorted_decls))])
1128 sorted_decls = sortLocated syn_decls
1129 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
1132 = setSrcSpan (getLoc (head sorted_decls)) $
1133 addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
1134 nest 2 (vcat (map ppr_decl sorted_decls))])
1136 sorted_decls = sortLocated cls_decls
1137 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
1139 sortLocated :: [Located a] -> [Located a]
1140 sortLocated things = sortLe le things
1142 le (L l1 _) (L l2 _) = l1 <= l2
1144 badDataConTyCon data_con
1145 = hang (ptext SLIT("Data constructor") <+> quotes (ppr data_con) <+>
1146 ptext SLIT("returns type") <+> quotes (ppr (dataConTyCon data_con)))
1147 2 (ptext SLIT("instead of its parent type"))
1150 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
1151 , nest 2 (parens $ ptext SLIT("Use -X=GADT to allow GADTs")) ]
1153 badStupidTheta tc_name
1154 = ptext SLIT("A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
1156 newtypeConError tycon n
1157 = sep [ptext SLIT("A newtype must have exactly one constructor,"),
1158 nest 2 $ ptext SLIT("but") <+> quotes (ppr tycon) <+> ptext SLIT("has") <+> speakN n ]
1161 = sep [ptext SLIT("A newtype constructor cannot have an existential context,"),
1162 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
1164 newtypeStrictError con
1165 = sep [ptext SLIT("A newtype constructor cannot have a strictness annotation,"),
1166 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
1168 newtypePredError con
1169 = sep [ptext SLIT("A newtype constructor must have a return type of form T a1 ... an"),
1170 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does not")]
1172 newtypeFieldErr con_name n_flds
1173 = sep [ptext SLIT("The constructor of a newtype must have exactly one field"),
1174 nest 2 $ ptext SLIT("but") <+> quotes (ppr con_name) <+> ptext SLIT("has") <+> speakN n_flds]
1176 badSigTyDecl tc_name
1177 = vcat [ ptext SLIT("Illegal kind signature") <+>
1178 quotes (ppr tc_name)
1179 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow kind signatures")) ]
1181 badFamInstDecl tc_name
1182 = vcat [ ptext SLIT("Illegal family instance for") <+>
1183 quotes (ppr tc_name)
1184 , nest 2 (parens $ ptext SLIT("Use -X=TypeFamilies to allow indexed type families")) ]
1186 badGadtIdxTyDecl tc_name
1187 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+>
1188 quotes (ppr tc_name)
1189 , nest 2 (parens $ ptext SLIT("Family instances can not yet use GADT declarations")) ]
1191 tooManyParmsErr tc_name
1192 = ptext SLIT("Family instance has too many parameters:") <+>
1193 quotes (ppr tc_name)
1195 tooFewParmsErr tc_name
1196 = ptext SLIT("Family instance has too few parameters:") <+>
1197 quotes (ppr tc_name)
1199 badBootFamInstDeclErr =
1200 ptext SLIT("Illegal family instance in hs-boot file")
1202 wrongKindOfFamily family =
1203 ptext SLIT("Wrong category of family instance; declaration was for a") <+>
1206 kindOfFamily | isSynTyCon family = ptext SLIT("type synonym")
1207 | isAlgTyCon family = ptext SLIT("data type")
1208 | otherwise = pprPanic "wrongKindOfFamily" (ppr family)
1211 = hang (ptext SLIT("Illegal polymorphic type in type instance") <> colon) 4 $
1214 emptyConDeclsErr tycon
1215 = sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
1216 nest 2 $ ptext SLIT("(-fglasgow-exts permits this)")]