2 % (c) The AQUA Project, Glasgow University, 1996-1998
4 \section[TcTyClsDecls]{Typecheck type and class declarations}
8 tcTyAndClassDecls, tcIdxTyInstDecl
11 #include "HsVersions.h"
13 import HsSyn ( TyClDecl(..), HsConDetails(..), HsTyVarBndr(..),
14 ConDecl(..), Sig(..), NewOrData(..), ResType(..),
15 tyClDeclTyVars, isSynDecl, isIdxTyDecl,
16 isKindSigDecl, hsConArgs, LTyClDecl, tcdName,
17 hsTyVarName, LHsTyVarBndr, LHsType
19 import HsTypes ( HsBang(..), getBangStrictness, hsLTyVarNames )
20 import BasicTypes ( RecFlag(..), StrictnessMark(..) )
21 import HscTypes ( implicitTyThings, ModDetails )
22 import BuildTyCl ( buildClass, buildAlgTyCon, buildSynTyCon, buildDataCon,
23 mkDataTyConRhs, mkNewTyConRhs )
25 import TcEnv ( TyThing(..),
26 tcLookupLocated, tcLookupLocatedGlobal,
27 tcExtendGlobalEnv, tcExtendKindEnv,
28 tcExtendKindEnvTvs, newFamInstTyConName,
29 tcExtendRecEnv, tcLookupTyVar, tcLookupLocatedTyCon )
30 import TcTyDecls ( calcRecFlags, calcClassCycles, calcSynCycles )
31 import TcClassDcl ( tcClassSigs, tcAddDeclCtxt )
32 import TcHsType ( kcHsTyVars, kcHsLiftedSigType, kcHsType,
33 kcHsContext, tcTyVarBndrs, tcHsKindedType, tcHsKindedContext,
34 kcHsSigType, tcHsBangType, tcLHsConResTy,
35 tcDataKindSig, kcCheckHsType )
36 import TcMType ( newKindVar, checkValidTheta, checkValidType,
38 UserTypeCtxt(..), SourceTyCtxt(..) )
39 import TcType ( TcKind, TcType, Type, tyVarsOfType, mkPhiTy,
40 mkArrowKind, liftedTypeKind,
41 tcSplitSigmaTy, tcGetTyVar_maybe )
42 import Type ( splitTyConApp_maybe,
43 newTyConInstRhs, isLiftedTypeKind, Kind,
44 splitKindFunTys, mkArrowKinds
45 -- pprParendType, pprThetaArrow
47 import Generics ( validGenericMethodType, canDoGenerics )
48 import Class ( Class, className, classTyCon, DefMeth(..), classBigSig, classTyVars )
49 import TyCon ( TyCon, AlgTyConRhs( AbstractTyCon, OpenDataTyCon,
51 SynTyConRhs( OpenSynTyCon, SynonymTyCon ),
52 tyConDataCons, mkForeignTyCon, isProductTyCon,
54 tyConStupidTheta, synTyConRhs, isSynTyCon, tyConName,
55 isNewTyCon, isDataTyCon, tyConKind,
57 import DataCon ( DataCon, dataConUserType, dataConName,
58 dataConFieldLabels, dataConTyCon, dataConAllTyVars,
59 dataConFieldType, dataConResTys )
60 import Var ( TyVar, idType, idName, tyVarName, setTyVarName )
61 import VarSet ( elemVarSet, mkVarSet )
62 import Name ( Name, getSrcLoc, tidyNameOcc, getOccName )
63 import OccName ( initTidyOccEnv, tidyOccName )
65 import Maybe ( isJust, fromJust, isNothing, catMaybes )
66 import Maybes ( expectJust )
67 import Monad ( unless )
68 import Unify ( tcMatchTys, tcMatchTyX )
69 import Util ( zipLazy, isSingleton, notNull, sortLe, mapAccumL )
70 import List ( partition, elemIndex )
71 import SrcLoc ( Located(..), unLoc, getLoc, srcLocSpan,
73 import ListSetOps ( equivClasses, minusList )
74 import Digraph ( SCC(..) )
75 import DynFlags ( DynFlag( Opt_GlasgowExts, Opt_Generics,
76 Opt_UnboxStrictFields, Opt_IndexedTypes ) )
80 %************************************************************************
82 \subsection{Type checking for type and class declarations}
84 %************************************************************************
88 Consider a mutually-recursive group, binding
89 a type constructor T and a class C.
91 Step 1: getInitialKind
92 Construct a KindEnv by binding T and C to a kind variable
95 In that environment, do a kind check
97 Step 3: Zonk the kinds
99 Step 4: buildTyConOrClass
100 Construct an environment binding T to a TyCon and C to a Class.
101 a) Their kinds comes from zonking the relevant kind variable
102 b) Their arity (for synonyms) comes direct from the decl
103 c) The funcional dependencies come from the decl
104 d) The rest comes a knot-tied binding of T and C, returned from Step 4
105 e) The variances of the tycons in the group is calculated from
109 In this environment, walk over the decls, constructing the TyCons and Classes.
110 This uses in a strict way items (a)-(c) above, which is why they must
111 be constructed in Step 4. Feed the results back to Step 4.
112 For this step, pass the is-recursive flag as the wimp-out flag
116 Step 6: Extend environment
117 We extend the type environment with bindings not only for the TyCons and Classes,
118 but also for their "implicit Ids" like data constructors and class selectors
120 Step 7: checkValidTyCl
121 For a recursive group only, check all the decls again, just
122 to check all the side conditions on validity. We could not
123 do this before because we were in a mutually recursive knot.
125 Identification of recursive TyCons
126 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
127 The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to
130 Identifying a TyCon as recursive serves two purposes
132 1. Avoid infinite types. Non-recursive newtypes are treated as
133 "transparent", like type synonyms, after the type checker. If we did
134 this for all newtypes, we'd get infinite types. So we figure out for
135 each newtype whether it is "recursive", and add a coercion if so. In
136 effect, we are trying to "cut the loops" by identifying a loop-breaker.
138 2. Avoid infinite unboxing. This is nothing to do with newtypes.
142 Well, this function diverges, but we don't want the strictness analyser
143 to diverge. But the strictness analyser will diverge because it looks
144 deeper and deeper into the structure of T. (I believe there are
145 examples where the function does something sane, and the strictness
146 analyser still diverges, but I can't see one now.)
148 Now, concerning (1), the FC2 branch currently adds a coercion for ALL
149 newtypes. I did this as an experiment, to try to expose cases in which
150 the coercions got in the way of optimisations. If it turns out that we
151 can indeed always use a coercion, then we don't risk recursive types,
152 and don't need to figure out what the loop breakers are.
154 For newtype *families* though, we will always have a coercion, so they
155 are always loop breakers! So you can easily adjust the current
156 algorithm by simply treating all newtype families as loop breakers (and
157 indeed type families). I think.
160 tcTyAndClassDecls :: ModDetails -> [LTyClDecl Name]
161 -> TcM TcGblEnv -- Input env extended by types and classes
162 -- and their implicit Ids,DataCons
163 tcTyAndClassDecls boot_details allDecls
164 = do { -- Omit instances of indexed types; they are handled together
165 -- with the *heads* of class instances
166 ; let decls = filter (not . isIdxTyDecl . unLoc) allDecls
168 -- First check for cyclic type synonysm or classes
169 -- See notes with checkCycleErrs
170 ; checkCycleErrs decls
172 ; traceTc (text "tcTyAndCl" <+> ppr mod)
173 ; (syn_tycons, alg_tyclss) <- fixM (\ ~(rec_syn_tycons, rec_alg_tyclss) ->
174 do { let { -- Seperate ordinary synonyms from all other type and
175 -- class declarations and add all associated type
176 -- declarations from type classes. The latter is
177 -- required so that the temporary environment for the
178 -- knot includes all associated family declarations.
179 ; (syn_decls, alg_decls) = partition (isSynDecl . unLoc)
181 ; alg_at_decls = concatMap addATs alg_decls
183 -- Extend the global env with the knot-tied results
184 -- for data types and classes
186 -- We must populate the environment with the loop-tied
187 -- T's right away, because the kind checker may "fault
188 -- in" some type constructors that recursively
190 ; let gbl_things = mkGlobalThings alg_at_decls rec_alg_tyclss
191 ; tcExtendRecEnv gbl_things $ do
193 -- Kind-check the declarations
194 { (kc_syn_decls, kc_alg_decls) <- kcTyClDecls syn_decls alg_decls
196 ; let { -- Calculate rec-flag
197 ; calc_rec = calcRecFlags boot_details rec_alg_tyclss
198 ; tc_decl = addLocM (tcTyClDecl calc_rec) }
199 -- Type-check the type synonyms, and extend the envt
200 ; syn_tycons <- tcSynDecls kc_syn_decls
201 ; tcExtendGlobalEnv syn_tycons $ do
203 -- Type-check the data types and classes
204 { alg_tyclss <- mappM tc_decl kc_alg_decls
205 ; return (syn_tycons, concat alg_tyclss)
207 -- Finished with knot-tying now
208 -- Extend the environment with the finished things
209 ; tcExtendGlobalEnv (syn_tycons ++ alg_tyclss) $ do
211 -- Perform the validity check
212 { traceTc (text "ready for validity check")
213 ; mappM_ (addLocM checkValidTyCl) decls
214 ; traceTc (text "done")
216 -- Add the implicit things;
217 -- we want them in the environment because
218 -- they may be mentioned in interface files
219 -- NB: All associated types and their implicit things will be added a
220 -- second time here. This doesn't matter as the definitions are
222 ; let { implicit_things = concatMap implicitTyThings alg_tyclss }
223 ; traceTc ((text "Adding" <+> ppr alg_tyclss)
224 $$ (text "and" <+> ppr implicit_things))
225 ; tcExtendGlobalEnv implicit_things getGblEnv
228 -- Pull associated types out of class declarations, to tie them into the
230 -- NB: We put them in the same place in the list as `tcTyClDecl' will
231 -- eventually put the matching `TyThing's. That's crucial; otherwise,
232 -- the two argument lists of `mkGlobalThings' don't match up.
233 addATs decl@(L _ (ClassDecl {tcdATs = ats})) = decl : ats
236 mkGlobalThings :: [LTyClDecl Name] -- The decls
237 -> [TyThing] -- Knot-tied, in 1-1 correspondence with the decls
239 -- Driven by the Decls, and treating the TyThings lazily
240 -- make a TypeEnv for the new things
241 mkGlobalThings decls things
242 = map mk_thing (decls `zipLazy` things)
244 mk_thing (L _ (ClassDecl {tcdLName = L _ name}), ~(AClass cl))
246 mk_thing (L _ decl, ~(ATyCon tc))
247 = (tcdName decl, ATyCon tc)
251 %************************************************************************
253 \subsection{Type checking instances of indexed types}
255 %************************************************************************
257 Instances of indexed types are somewhat of a hybrid. They are processed
258 together with class instance heads, but can contain data constructors and hence
259 they share a lot of kinding and type checking code with ordinary algebraic
260 data types (and GADTs).
263 tcIdxTyInstDecl :: LTyClDecl Name -> TcM (Maybe TyThing) -- Nothing if error
264 tcIdxTyInstDecl (L loc decl)
265 = -- Prime error recovery, set source location
266 recoverM (returnM Nothing) $
269 do { -- indexed data types require -findexed-types and can't be in an
271 ; gla_exts <- doptM Opt_IndexedTypes
272 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
273 ; checkTc gla_exts $ badIdxTyDecl (tcdLName decl)
274 ; checkTc (not is_boot) $ badBootTyIdxDeclErr
276 -- perform kind and type checking
277 ; tcIdxTyInstDecl1 decl
280 tcIdxTyInstDecl1 :: TyClDecl Name -> TcM (Maybe TyThing) -- Nothing if error
282 tcIdxTyInstDecl1 (decl@TySynonym {})
283 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
284 do { -- check that the family declaration is for a synonym
285 unless (isSynTyCon family) $
286 addErr (wrongKindOfFamily family)
288 ; -- (1) kind check the right hand side of the type equation
289 ; k_rhs <- kcCheckHsType (tcdSynRhs decl) resKind
291 -- (2) type check type equation
292 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
293 ; t_typats <- mappM tcHsKindedType k_typats
294 ; t_rhs <- tcHsKindedType k_rhs
296 -- !!!of the form: forall t_tvs. (tcdLName decl) t_typats = t_rhs
297 ; return Nothing -- !!!TODO: need TyThing for indexed synonym
300 tcIdxTyInstDecl1 (decl@TyData {tcdND = new_or_data, tcdLName = L loc tc_name,
302 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
303 do { -- check that the family declaration is for the right kind
304 unless (new_or_data == NewType && isNewTyCon family ||
305 new_or_data == DataType && isDataTyCon family) $
306 addErr (wrongKindOfFamily family)
308 ; -- (1) kind check the data declaration as usual
309 ; k_decl <- kcDataDecl decl k_tvs
310 ; let k_ctxt = tcdCtxt k_decl
311 k_cons = tcdCons k_decl
313 -- result kind must be '*' (otherwise, we have too few patterns)
314 ; checkTc (isLiftedTypeKind resKind) $ tooFewParmsErr tc_name
316 -- (2) type check indexed data type declaration
317 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
318 ; unbox_strict <- doptM Opt_UnboxStrictFields
320 -- Check that we don't use GADT syntax for indexed types
321 ; checkTc h98_syntax (badGadtIdxTyDecl tc_name)
323 -- Check that a newtype has exactly one constructor
324 ; checkTc (new_or_data == DataType || isSingleton k_cons) $
325 newtypeConError tc_name (length k_cons)
327 ; t_typats <- mappM tcHsKindedType k_typats
328 ; stupid_theta <- tcHsKindedContext k_ctxt
330 ; rep_tc_name <- newFamInstTyConName tc_name (srcSpanStart loc)
331 ; tycon <- fixM (\ tycon -> do
332 { data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data
337 DataType -> return (mkDataTyConRhs data_cons)
338 NewType -> ASSERT( isSingleton data_cons )
339 mkNewTyConRhs tc_name tycon (head data_cons)
340 ; buildAlgTyCon rep_tc_name t_tvs stupid_theta tc_rhs Recursive
341 False h98_syntax (Just (family, t_typats))
342 -- We always assume that indexed types are recursive. Why?
343 -- (1) Due to their open nature, we can never be sure that a
344 -- further instance might not introduce a new recursive
345 -- dependency. (2) They are always valid loop breakers as
346 -- they involve a coercion.
350 ; return $ Just (ATyCon tycon)
353 h98_syntax = case cons of -- All constructors have same shape
354 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
357 -- Kind checking of indexed types
360 -- Kind check type patterns and kind annotate the embedded type variables.
362 -- * Here we check that a type instance matches its kind signature, but we do
363 -- not check whether there is a pattern for each type index; the latter
364 -- check is only required for type functions.
366 kcIdxTyPats :: TyClDecl Name
367 -> ([LHsTyVarBndr Name] -> [LHsType Name] -> Kind -> TyCon -> TcM a)
368 -- ^^kinded tvs ^^kinded ty pats ^^res kind
370 kcIdxTyPats decl thing_inside
371 = kcHsTyVars (tcdTyVars decl) $ \tvs ->
372 do { family <- tcLookupLocatedTyCon (tcdLName decl)
373 ; let { (kinds, resKind) = splitKindFunTys (tyConKind family)
374 ; hs_typats = fromJust $ tcdTyPats decl }
376 -- we may not have more parameters than the kind indicates
377 ; checkTc (length kinds >= length hs_typats) $
378 tooManyParmsErr (tcdLName decl)
380 -- type functions can have a higher-kinded result
381 ; let resultKind = mkArrowKinds (drop (length hs_typats) kinds) resKind
382 ; typats <- zipWithM kcCheckHsType hs_typats kinds
383 ; thing_inside tvs typats resultKind family
389 %************************************************************************
393 %************************************************************************
395 We need to kind check all types in the mutually recursive group
396 before we know the kind of the type variables. For example:
399 op :: D b => a -> b -> b
402 bop :: (Monad c) => ...
404 Here, the kind of the locally-polymorphic type variable "b"
405 depends on *all the uses of class D*. For example, the use of
406 Monad c in bop's type signature means that D must have kind Type->Type.
408 However type synonyms work differently. They can have kinds which don't
409 just involve (->) and *:
410 type R = Int# -- Kind #
411 type S a = Array# a -- Kind * -> #
412 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
413 So we must infer their kinds from their right-hand sides *first* and then
414 use them, whereas for the mutually recursive data types D we bring into
415 scope kind bindings D -> k, where k is a kind variable, and do inference.
419 This treatment of type synonyms only applies to Haskell 98-style synonyms.
420 General type functions can be recursive, and hence, appear in `alg_decls'.
422 The kind of an indexed type is solely determinded by its kind signature;
423 hence, only kind signatures participate in the construction of the initial
424 kind environment (as constructed by `getInitialKind'). In fact, we ignore
425 instances of indexed types altogether in the following. However, we need to
426 include the kind signatures of associated types into the construction of the
427 initial kind environment. (This is handled by `allDecls').
430 kcTyClDecls syn_decls alg_decls
431 = do { -- First extend the kind env with each data type, class, and
432 -- indexed type, mapping them to a type variable
433 let initialKindDecls = concat [allDecls decl | L _ decl <- alg_decls]
434 ; alg_kinds <- mappM getInitialKind initialKindDecls
435 ; tcExtendKindEnv alg_kinds $ do
437 -- Now kind-check the type synonyms, in dependency order
438 -- We do these differently to data type and classes,
439 -- because a type synonym can be an unboxed type
441 -- and a kind variable can't unify with UnboxedTypeKind
442 -- So we infer their kinds in dependency order
443 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
444 ; tcExtendKindEnv syn_kinds $ do
446 -- Now kind-check the data type, class, and kind signatures,
447 -- returning kind-annotated decls; we don't kind-check
448 -- instances of indexed types yet, but leave this to
450 { kc_alg_decls <- mappM (wrapLocM kcTyClDecl)
451 (filter (not . isIdxTyDecl . unLoc) alg_decls)
453 ; return (kc_syn_decls, kc_alg_decls) }}}
455 -- get all declarations relevant for determining the initial kind
457 allDecls (decl@ClassDecl {tcdATs = ats}) = decl : [ at
460 allDecls decl | isIdxTyDecl decl = []
463 ------------------------------------------------------------------------
464 getInitialKind :: TyClDecl Name -> TcM (Name, TcKind)
465 -- Only for data type, class, and indexed type declarations
466 -- Get as much info as possible from the data, class, or indexed type decl,
467 -- so as to maximise usefulness of error messages
469 = do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl)
470 ; res_kind <- mk_res_kind decl
471 ; return (tcdName decl, mkArrowKinds arg_kinds res_kind) }
473 mk_arg_kind (UserTyVar _) = newKindVar
474 mk_arg_kind (KindedTyVar _ kind) = return kind
476 mk_res_kind (TyFunction { tcdKind = kind }) = return kind
477 mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
478 -- On GADT-style and data signature declarations we allow a kind
480 -- data T :: *->* where { ... }
481 mk_res_kind other = return liftedTypeKind
485 kcSynDecls :: [SCC (LTyClDecl Name)]
486 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
487 [(Name,TcKind)]) -- Kind bindings
490 kcSynDecls (group : groups)
491 = do { (decl, nk) <- kcSynDecl group
492 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
493 ; return (decl:decls, nk:nks) }
496 kcSynDecl :: SCC (LTyClDecl Name)
497 -> TcM (LTyClDecl Name, -- Kind-annotated decls
498 (Name,TcKind)) -- Kind bindings
499 kcSynDecl (AcyclicSCC ldecl@(L loc decl))
500 = tcAddDeclCtxt decl $
501 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
502 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
503 <+> brackets (ppr k_tvs))
504 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
505 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
506 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
507 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
508 (unLoc (tcdLName decl), tc_kind)) })
510 kcSynDecl (CyclicSCC decls)
511 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
512 -- of out-of-scope tycons
514 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
516 ------------------------------------------------------------------------
517 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
518 -- Not used for type synonyms (see kcSynDecl)
520 kcTyClDecl decl@(TyData {})
521 = ASSERT( not . isJust $ tcdTyPats decl ) -- must not be instance of idx ty
522 kcTyClDeclBody decl $
525 kcTyClDecl decl@(TyFunction {})
526 = kcTyClDeclBody decl $ \ tvs' ->
527 return (decl {tcdTyVars = tvs'})
529 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs, tcdATs = ats})
530 = kcTyClDeclBody decl $ \ tvs' ->
531 do { is_boot <- tcIsHsBoot
532 ; ctxt' <- kcHsContext ctxt
533 ; ats' <- mappM (wrapLocM kcTyClDecl) ats
534 ; sigs' <- mappM (wrapLocM kc_sig ) sigs
535 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs',
538 kc_sig (TypeSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
539 ; return (TypeSig nm op_ty') }
540 kc_sig other_sig = return other_sig
542 kcTyClDecl decl@(ForeignType {})
545 kcTyClDeclBody :: TyClDecl Name
546 -> ([LHsTyVarBndr Name] -> TcM a)
548 -- getInitialKind has made a suitably-shaped kind for the type or class
549 -- Unpack it, and attribute those kinds to the type variables
550 -- Extend the env with bindings for the tyvars, taken from
551 -- the kind of the tycon/class. Give it to the thing inside, and
552 -- check the result kind matches
553 kcTyClDeclBody decl thing_inside
554 = tcAddDeclCtxt decl $
555 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
556 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
557 (kinds, _) = splitKindFunTys tc_kind
558 hs_tvs = tcdTyVars decl
559 kinded_tvs = ASSERT( length kinds >= length hs_tvs )
560 [ L loc (KindedTyVar (hsTyVarName tv) k)
561 | (L loc tv, k) <- zip hs_tvs kinds]
562 ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
564 -- Kind check a data declaration, assuming that we already extended the
565 -- kind environment with the type variables of the left-hand side (these
566 -- kinded type variables are also passed as the second parameter).
568 kcDataDecl :: TyClDecl Name -> [LHsTyVarBndr Name] -> TcM (TyClDecl Name)
569 kcDataDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
571 = do { ctxt' <- kcHsContext ctxt
572 ; cons' <- mappM (wrapLocM kc_con_decl) cons
573 ; return (decl {tcdTyVars = tvs, tcdCtxt = ctxt', tcdCons = cons'}) }
575 kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res) = do
576 kcHsTyVars ex_tvs $ \ex_tvs' -> do
577 ex_ctxt' <- kcHsContext ex_ctxt
578 details' <- kc_con_details details
580 ResTyH98 -> return ResTyH98
581 ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
582 return (ConDecl name expl ex_tvs' ex_ctxt' details' res')
584 kc_con_details (PrefixCon btys)
585 = do { btys' <- mappM kc_larg_ty btys ; return (PrefixCon btys') }
586 kc_con_details (InfixCon bty1 bty2)
587 = do { bty1' <- kc_larg_ty bty1; bty2' <- kc_larg_ty bty2; return (InfixCon bty1' bty2') }
588 kc_con_details (RecCon fields)
589 = do { fields' <- mappM kc_field fields; return (RecCon fields') }
591 kc_field (fld, bty) = do { bty' <- kc_larg_ty bty ; return (fld, bty') }
593 kc_larg_ty bty = case new_or_data of
594 DataType -> kcHsSigType bty
595 NewType -> kcHsLiftedSigType bty
596 -- Can't allow an unlifted type for newtypes, because we're effectively
597 -- going to remove the constructor while coercing it to a lifted type.
598 -- And newtypes can't be bang'd
602 %************************************************************************
604 \subsection{Type checking}
606 %************************************************************************
609 tcSynDecls :: [LTyClDecl Name] -> TcM [TyThing]
610 tcSynDecls [] = return []
611 tcSynDecls (decl : decls)
612 = do { syn_tc <- addLocM tcSynDecl decl
613 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls decls)
614 ; return (syn_tc : syn_tcs) }
617 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
618 = tcTyVarBndrs tvs $ \ tvs' -> do
619 { traceTc (text "tcd1" <+> ppr tc_name)
620 ; rhs_ty' <- tcHsKindedType rhs_ty
621 ; return (ATyCon (buildSynTyCon tc_name tvs' (SynonymTyCon rhs_ty'))) }
624 tcTyClDecl :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
626 tcTyClDecl calc_isrec decl
627 = tcAddDeclCtxt decl (tcTyClDecl1 calc_isrec decl)
629 -- kind signature for a type function
630 tcTyClDecl1 _calc_isrec
631 (TyFunction {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = kind})
632 = tcTyVarBndrs tvs $ \ tvs' -> do
633 { traceTc (text "type family: " <+> ppr tc_name)
634 ; gla_exts <- doptM Opt_IndexedTypes
636 -- Check that we don't use kind signatures without Glasgow extensions
637 ; checkTc gla_exts $ badSigTyDecl tc_name
639 ; return [ATyCon $ buildSynTyCon tc_name tvs' (OpenSynTyCon kind)]
642 -- kind signature for an indexed data type
643 tcTyClDecl1 _calc_isrec
644 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
645 tcdLName = L _ tc_name, tcdKindSig = Just ksig, tcdCons = []})
646 = tcTyVarBndrs tvs $ \ tvs' -> do
647 { traceTc (text "data/newtype family: " <+> ppr tc_name)
648 ; extra_tvs <- tcDataKindSig (Just ksig)
649 ; let final_tvs = tvs' ++ extra_tvs -- we may not need these
651 ; checkTc (null . unLoc $ ctxt) $ badKindSigCtxt tc_name
652 ; gla_exts <- doptM Opt_IndexedTypes
654 -- Check that we don't use kind signatures without Glasgow extensions
655 ; checkTc gla_exts $ badSigTyDecl tc_name
657 ; tycon <- buildAlgTyCon tc_name final_tvs []
659 DataType -> OpenDataTyCon
660 NewType -> OpenNewTyCon)
661 Recursive False True Nothing
662 ; return [ATyCon tycon]
665 tcTyClDecl1 calc_isrec
666 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
667 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
668 = tcTyVarBndrs tvs $ \ tvs' -> do
669 { extra_tvs <- tcDataKindSig mb_ksig
670 ; let final_tvs = tvs' ++ extra_tvs
671 ; stupid_theta <- tcHsKindedContext ctxt
672 ; want_generic <- doptM Opt_Generics
673 ; unbox_strict <- doptM Opt_UnboxStrictFields
674 ; gla_exts <- doptM Opt_GlasgowExts
675 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
677 -- Check that we don't use GADT syntax in H98 world
678 ; checkTc (gla_exts || h98_syntax) (badGadtDecl tc_name)
680 -- Check that we don't use kind signatures without Glasgow extensions
681 ; checkTc (gla_exts || isNothing mb_ksig) (badSigTyDecl tc_name)
683 -- Check that the stupid theta is empty for a GADT-style declaration
684 ; checkTc (null stupid_theta || h98_syntax) (badStupidTheta tc_name)
686 -- Check that there's at least one condecl,
687 -- or else we're reading an hs-boot file, or -fglasgow-exts
688 ; checkTc (not (null cons) || gla_exts || is_boot)
689 (emptyConDeclsErr tc_name)
691 -- Check that a newtype has exactly one constructor
692 ; checkTc (new_or_data == DataType || isSingleton cons)
693 (newtypeConError tc_name (length cons))
695 ; tycon <- fixM (\ tycon -> do
696 { data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data
700 if null cons && is_boot -- In a hs-boot file, empty cons means
701 then return AbstractTyCon -- "don't know"; hence Abstract
702 else case new_or_data of
703 DataType -> return (mkDataTyConRhs data_cons)
705 ASSERT( isSingleton data_cons )
706 mkNewTyConRhs tc_name tycon (head data_cons)
707 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
708 (want_generic && canDoGenerics data_cons) h98_syntax Nothing
710 ; return [ATyCon tycon]
713 is_rec = calc_isrec tc_name
714 h98_syntax = case cons of -- All constructors have same shape
715 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
718 tcTyClDecl1 calc_isrec
719 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
720 tcdCtxt = ctxt, tcdMeths = meths,
721 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
722 = tcTyVarBndrs tvs $ \ tvs' -> do
723 { ctxt' <- tcHsKindedContext ctxt
724 ; fds' <- mappM (addLocM tc_fundep) fundeps
725 ; atss <- mappM (addLocM (tcTyClDecl1 (const Recursive))) ats
726 ; let ats' = zipWith setTyThingPoss atss (map (tcdTyVars . unLoc) ats)
727 ; sig_stuff <- tcClassSigs class_name sigs meths
728 ; clas <- fixM (\ clas ->
729 let -- This little knot is just so we can get
730 -- hold of the name of the class TyCon, which we
731 -- need to look up its recursiveness
732 tycon_name = tyConName (classTyCon clas)
733 tc_isrec = calc_isrec tycon_name
735 buildClass class_name tvs' ctxt' fds' ats'
737 ; return (AClass clas : ats')
738 -- NB: Order is important due to the call to `mkGlobalThings' when
739 -- tying the the type and class declaration type checking knot.
742 tc_fundep (tvs1, tvs2) = do { tvs1' <- mappM tcLookupTyVar tvs1 ;
743 ; tvs2' <- mappM tcLookupTyVar tvs2 ;
744 ; return (tvs1', tvs2') }
746 -- For each AT argument compute the position of the corresponding class
747 -- parameter in the class head. This will later serve as a permutation
748 -- vector when checking the validity of instance declarations.
749 setTyThingPoss [ATyCon tycon] atTyVars =
750 let classTyVars = hsLTyVarNames tvs
752 . map (`elemIndex` classTyVars)
755 -- There will be no Nothing, as we already passed renaming
757 ATyCon (setTyConArgPoss tycon poss)
758 setTyThingPoss _ _ = panic "TcTyClsDecls.setTyThingPoss"
760 tcTyClDecl1 calc_isrec
761 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
762 = returnM [ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0)]
764 -----------------------------------
765 tcConDecl :: Bool -- True <=> -funbox-strict_fields
771 tcConDecl unbox_strict NewType tycon tc_tvs -- Newtypes
772 (ConDecl name _ ex_tvs ex_ctxt details ResTyH98)
773 = do { let tc_datacon field_lbls arg_ty
774 = do { arg_ty' <- tcHsKindedType arg_ty -- No bang on newtype
775 ; buildDataCon (unLoc name) False {- Prefix -}
777 (map unLoc field_lbls)
778 tc_tvs [] -- No existentials
779 [] [] -- No equalities, predicates
783 -- Check that a newtype has no existential stuff
784 ; checkTc (null ex_tvs && null (unLoc ex_ctxt)) (newtypeExError name)
787 PrefixCon [arg_ty] -> tc_datacon [] arg_ty
788 RecCon [(field_lbl, arg_ty)] -> tc_datacon [field_lbl] arg_ty
790 failWithTc (newtypeFieldErr name (length (hsConArgs details)))
791 -- Check that the constructor has exactly one field
794 tcConDecl unbox_strict DataType tycon tc_tvs -- Data types
795 (ConDecl name _ tvs ctxt details res_ty)
796 = tcTyVarBndrs tvs $ \ tvs' -> do
797 { ctxt' <- tcHsKindedContext ctxt
798 ; (univ_tvs, ex_tvs, eq_preds, data_tc) <- tcResultType tycon tc_tvs tvs' res_ty
800 -- Tiresome: tidy the tyvar binders, since tc_tvs and tvs' may have the same OccNames
801 tc_datacon is_infix field_lbls btys
802 = do { let bangs = map getBangStrictness btys
803 ; arg_tys <- mappM tcHsBangType btys
804 ; buildDataCon (unLoc name) is_infix
805 (argStrictness unbox_strict bangs arg_tys)
806 (map unLoc field_lbls)
807 univ_tvs ex_tvs eq_preds ctxt' arg_tys
809 -- NB: we put data_tc, the type constructor gotten from the
810 -- constructor type signature into the data constructor;
811 -- that way checkValidDataCon can complain if it's wrong.
814 PrefixCon btys -> tc_datacon False [] btys
815 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
816 RecCon fields -> tc_datacon False field_names btys
818 (field_names, btys) = unzip fields
822 tcResultType :: TyCon
823 -> [TyVar] -- data T a b c = ...
824 -> [TyVar] -- where MkT :: forall a b c. ...
826 -> TcM ([TyVar], -- Universal
827 [TyVar], -- Existential (distinct OccNames from univs)
828 [(TyVar,Type)], -- Equality predicates
829 TyCon) -- TyCon given in the ResTy
830 -- We don't check that the TyCon given in the ResTy is
831 -- the same as the parent tycon, becuase we are in the middle
832 -- of a recursive knot; so it's postponed until checkValidDataCon
834 tcResultType decl_tycon tc_tvs dc_tvs ResTyH98
835 = return (tc_tvs, dc_tvs, [], decl_tycon)
836 -- In H98 syntax the dc_tvs are the existential ones
837 -- data T a b c = forall d e. MkT ...
838 -- The {a,b,c} are tc_tvs, and {d,e} are dc_tvs
840 tcResultType _ tc_tvs dc_tvs (ResTyGADT res_ty)
841 -- E.g. data T a b c where
842 -- MkT :: forall x y z. T (x,y) z z
844 -- ([a,z,c], [x,y], [a:=:(x,y), c:=:z], T)
846 = do { (dc_tycon, res_tys) <- tcLHsConResTy res_ty
848 ; let univ_tvs = choose_univs [] tidy_tc_tvs res_tys
849 -- Each univ_tv is either a dc_tv or a tc_tv
850 ex_tvs = dc_tvs `minusList` univ_tvs
851 eq_spec = [ (tv, ty) | (tv,ty) <- univ_tvs `zip` res_tys,
853 ; return (univ_tvs, ex_tvs, eq_spec, dc_tycon) }
855 -- choose_univs uses the res_ty itself if it's a type variable
856 -- and hasn't already been used; otherwise it uses one of the tc_tvs
857 choose_univs used tc_tvs []
858 = ASSERT( null tc_tvs ) []
859 choose_univs used (tc_tv:tc_tvs) (res_ty:res_tys)
860 | Just tv <- tcGetTyVar_maybe res_ty, not (tv `elem` used)
861 = tv : choose_univs (tv:used) tc_tvs res_tys
863 = tc_tv : choose_univs used tc_tvs res_tys
865 -- NB: tc_tvs and dc_tvs are distinct, but
866 -- we want them to be *visibly* distinct, both for
867 -- interface files and general confusion. So rename
868 -- the tc_tvs, since they are not used yet (no
869 -- consequential renaming needed)
870 init_occ_env = initTidyOccEnv (map getOccName dc_tvs)
871 (_, tidy_tc_tvs) = mapAccumL tidy_one init_occ_env tc_tvs
872 tidy_one env tv = (env', setTyVarName tv (tidyNameOcc name occ'))
875 (env', occ') = tidyOccName env (getOccName name)
878 argStrictness :: Bool -- True <=> -funbox-strict_fields
880 -> [TcType] -> [StrictnessMark]
881 argStrictness unbox_strict bangs arg_tys
882 = ASSERT( length bangs == length arg_tys )
883 zipWith (chooseBoxingStrategy unbox_strict) arg_tys bangs
885 -- We attempt to unbox/unpack a strict field when either:
886 -- (i) The field is marked '!!', or
887 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
889 -- We have turned off unboxing of newtypes because coercions make unboxing
890 -- and reboxing more complicated
891 chooseBoxingStrategy :: Bool -> TcType -> HsBang -> StrictnessMark
892 chooseBoxingStrategy unbox_strict_fields arg_ty bang
894 HsNoBang -> NotMarkedStrict
895 HsStrict | unbox_strict_fields
896 && can_unbox arg_ty -> MarkedUnboxed
897 HsUnbox | can_unbox arg_ty -> MarkedUnboxed
898 other -> MarkedStrict
900 -- we can unbox if the type is a chain of newtypes with a product tycon
902 can_unbox arg_ty = case splitTyConApp_maybe arg_ty of
904 Just (arg_tycon, tycon_args) ->
905 not (isRecursiveTyCon arg_tycon) && -- Note [Recusive unboxing]
906 isProductTyCon arg_tycon &&
907 (if isNewTyCon arg_tycon then
908 can_unbox (newTyConInstRhs arg_tycon tycon_args)
912 Note [Recursive unboxing]
913 ~~~~~~~~~~~~~~~~~~~~~~~~~
914 Be careful not to try to unbox this!
916 But it's the *argument* type that matters. This is fine:
918 because Int is non-recursive.
920 %************************************************************************
922 \subsection{Dependency analysis}
924 %************************************************************************
926 Validity checking is done once the mutually-recursive knot has been
927 tied, so we can look at things freely.
930 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
931 checkCycleErrs tyclss
935 = do { mappM_ recClsErr cls_cycles
936 ; failM } -- Give up now, because later checkValidTyCl
937 -- will loop if the synonym is recursive
939 cls_cycles = calcClassCycles tyclss
941 checkValidTyCl :: TyClDecl Name -> TcM ()
942 -- We do the validity check over declarations, rather than TyThings
943 -- only so that we can add a nice context with tcAddDeclCtxt
945 = tcAddDeclCtxt decl $
946 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
947 ; traceTc (text "Validity of" <+> ppr thing)
949 ATyCon tc -> checkValidTyCon tc
950 AClass cl -> checkValidClass cl
951 ; traceTc (text "Done validity of" <+> ppr thing)
954 -------------------------
955 -- For data types declared with record syntax, we require
956 -- that each constructor that has a field 'f'
957 -- (a) has the same result type
958 -- (b) has the same type for 'f'
959 -- module alpha conversion of the quantified type variables
960 -- of the constructor.
962 checkValidTyCon :: TyCon -> TcM ()
965 = case synTyConRhs tc of
966 OpenSynTyCon _ -> return ()
967 SynonymTyCon ty -> checkValidType syn_ctxt ty
969 = -- Check the context on the data decl
970 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
972 -- Check arg types of data constructors
973 mappM_ (checkValidDataCon tc) data_cons `thenM_`
975 -- Check that fields with the same name share a type
976 mappM_ check_fields groups
979 syn_ctxt = TySynCtxt name
981 data_cons = tyConDataCons tc
983 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
984 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
985 get_fields con = dataConFieldLabels con `zip` repeat con
986 -- dataConFieldLabels may return the empty list, which is fine
988 -- See Note [GADT record selectors] in MkId.lhs
989 -- We must check (a) that the named field has the same
990 -- type in each constructor
991 -- (b) that those constructors have the same result type
993 -- However, the constructors may have differently named type variable
994 -- and (worse) we don't know how the correspond to each other. E.g.
995 -- C1 :: forall a b. { f :: a, g :: b } -> T a b
996 -- C2 :: forall d c. { f :: c, g :: c } -> T c d
998 -- So what we do is to ust Unify.tcMatchTys to compare the first candidate's
999 -- result type against other candidates' types BOTH WAYS ROUND.
1000 -- If they magically agrees, take the substitution and
1001 -- apply them to the latter ones, and see if they match perfectly.
1002 check_fields fields@((label, con1) : other_fields)
1003 -- These fields all have the same name, but are from
1004 -- different constructors in the data type
1005 = recoverM (return ()) $ mapM_ checkOne other_fields
1006 -- Check that all the fields in the group have the same type
1007 -- NB: this check assumes that all the constructors of a given
1008 -- data type use the same type variables
1010 tvs1 = mkVarSet (dataConAllTyVars con1)
1011 res1 = dataConResTys con1
1012 fty1 = dataConFieldType con1 label
1014 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
1015 = do { checkFieldCompat label con1 con2 tvs1 res1 res2 fty1 fty2
1016 ; checkFieldCompat label con2 con1 tvs2 res2 res1 fty2 fty1 }
1018 tvs2 = mkVarSet (dataConAllTyVars con2)
1019 res2 = dataConResTys con2
1020 fty2 = dataConFieldType con2 label
1022 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
1023 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
1024 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
1026 mb_subst1 = tcMatchTys tvs1 res1 res2
1027 mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
1029 -------------------------------
1030 checkValidDataCon :: TyCon -> DataCon -> TcM ()
1031 checkValidDataCon tc con
1032 = setSrcSpan (srcLocSpan (getSrcLoc con)) $
1033 addErrCtxt (dataConCtxt con) $
1034 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
1035 ; checkValidType ctxt (dataConUserType con) }
1037 ctxt = ConArgCtxt (dataConName con)
1039 -------------------------------
1040 checkValidClass :: Class -> TcM ()
1042 = do { -- CHECK ARITY 1 FOR HASKELL 1.4
1043 gla_exts <- doptM Opt_GlasgowExts
1045 -- Check that the class is unary, unless GlaExs
1046 ; checkTc (notNull tyvars) (nullaryClassErr cls)
1047 ; checkTc (gla_exts || unary) (classArityErr cls)
1049 -- Check the super-classes
1050 ; checkValidTheta (ClassSCCtxt (className cls)) theta
1052 -- Check the class operations
1053 ; mappM_ (check_op gla_exts) op_stuff
1055 -- Check that if the class has generic methods, then the
1056 -- class has only one parameter. We can't do generic
1057 -- multi-parameter type classes!
1058 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
1061 (tyvars, theta, _, op_stuff) = classBigSig cls
1062 unary = isSingleton tyvars
1063 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
1065 check_op gla_exts (sel_id, dm)
1066 = addErrCtxt (classOpCtxt sel_id tau) $ do
1067 { checkValidTheta SigmaCtxt (tail theta)
1068 -- The 'tail' removes the initial (C a) from the
1069 -- class itself, leaving just the method type
1071 ; checkValidType (FunSigCtxt op_name) tau
1073 -- Check that the type mentions at least one of
1074 -- the class type variables
1075 ; checkTc (any (`elemVarSet` tyVarsOfType tau) tyvars)
1076 (noClassTyVarErr cls sel_id)
1078 -- Check that for a generic method, the type of
1079 -- the method is sufficiently simple
1080 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
1081 (badGenericMethodType op_name op_ty)
1084 op_name = idName sel_id
1085 op_ty = idType sel_id
1086 (_,theta1,tau1) = tcSplitSigmaTy op_ty
1087 (_,theta2,tau2) = tcSplitSigmaTy tau1
1088 (theta,tau) | gla_exts = (theta1 ++ theta2, tau2)
1089 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
1090 -- Ugh! The function might have a type like
1091 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
1092 -- With -fglasgow-exts, we want to allow this, even though the inner
1093 -- forall has an (Eq a) constraint. Whereas in general, each constraint
1094 -- in the context of a for-all must mention at least one quantified
1095 -- type variable. What a mess!
1098 ---------------------------------------------------------------------
1099 resultTypeMisMatch field_name con1 con2
1100 = vcat [sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1101 ptext SLIT("have a common field") <+> quotes (ppr field_name) <> comma],
1102 nest 2 $ ptext SLIT("but have different result types")]
1103 fieldTypeMisMatch field_name con1 con2
1104 = sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1105 ptext SLIT("give different types for field"), quotes (ppr field_name)]
1107 dataConCtxt con = ptext SLIT("In the definition of data constructor") <+> quotes (ppr con)
1109 classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
1110 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
1113 = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
1116 = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
1117 parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
1119 noClassTyVarErr clas op
1120 = sep [ptext SLIT("The class method") <+> quotes (ppr op),
1121 ptext SLIT("mentions none of the type variables of the class") <+>
1122 ppr clas <+> hsep (map ppr (classTyVars clas))]
1124 genericMultiParamErr clas
1125 = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
1126 ptext SLIT("cannot have generic methods")
1128 badGenericMethodType op op_ty
1129 = hang (ptext SLIT("Generic method type is too complex"))
1130 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
1131 ptext SLIT("You can only use type variables, arrows, lists, and tuples")])
1134 = setSrcSpan (getLoc (head sorted_decls)) $
1135 addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
1136 nest 2 (vcat (map ppr_decl sorted_decls))])
1138 sorted_decls = sortLocated syn_decls
1139 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
1142 = setSrcSpan (getLoc (head sorted_decls)) $
1143 addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
1144 nest 2 (vcat (map ppr_decl sorted_decls))])
1146 sorted_decls = sortLocated cls_decls
1147 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
1149 sortLocated :: [Located a] -> [Located a]
1150 sortLocated things = sortLe le things
1152 le (L l1 _) (L l2 _) = l1 <= l2
1154 badDataConTyCon data_con
1155 = hang (ptext SLIT("Data constructor") <+> quotes (ppr data_con) <+>
1156 ptext SLIT("returns type") <+> quotes (ppr (dataConTyCon data_con)))
1157 2 (ptext SLIT("instead of its parent type"))
1160 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
1161 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow GADTs")) ]
1163 badStupidTheta tc_name
1164 = ptext SLIT("A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
1166 newtypeConError tycon n
1167 = sep [ptext SLIT("A newtype must have exactly one constructor,"),
1168 nest 2 $ ptext SLIT("but") <+> quotes (ppr tycon) <+> ptext SLIT("has") <+> speakN n ]
1171 = sep [ptext SLIT("A newtype constructor cannot have an existential context,"),
1172 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
1174 newtypeFieldErr con_name n_flds
1175 = sep [ptext SLIT("The constructor of a newtype must have exactly one field"),
1176 nest 2 $ ptext SLIT("but") <+> quotes (ppr con_name) <+> ptext SLIT("has") <+> speakN n_flds]
1178 badSigTyDecl tc_name
1179 = vcat [ ptext SLIT("Illegal kind signature") <+>
1180 quotes (ppr tc_name)
1181 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow indexed types")) ]
1183 badKindSigCtxt tc_name
1184 = vcat [ ptext SLIT("Illegal context in kind signature") <+>
1185 quotes (ppr tc_name)
1186 , nest 2 (parens $ ptext SLIT("Currently, kind signatures cannot have a context")) ]
1188 badIdxTyDecl tc_name
1189 = vcat [ ptext SLIT("Illegal indexed type instance for") <+>
1190 quotes (ppr tc_name)
1191 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow indexed types")) ]
1193 badGadtIdxTyDecl tc_name
1194 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+>
1195 quotes (ppr tc_name)
1196 , nest 2 (parens $ ptext SLIT("Indexed types cannot use GADT declarations")) ]
1198 tooManyParmsErr tc_name
1199 = ptext SLIT("Indexed type instance has too many parameters:") <+>
1200 quotes (ppr tc_name)
1202 tooFewParmsErr tc_name
1203 = ptext SLIT("Indexed type instance has too few parameters:") <+>
1204 quotes (ppr tc_name)
1206 badBootTyIdxDeclErr =
1207 ptext SLIT("Illegal indexed type instance in hs-boot file")
1209 wrongKindOfFamily family =
1210 ptext SLIT("Wrong category of type instance; declaration was for a") <+>
1213 kindOfFamily | isSynTyCon family = ptext SLIT("type synonym")
1214 | isDataTyCon family = ptext SLIT("data type")
1215 | isNewTyCon family = ptext SLIT("newtype")
1217 emptyConDeclsErr tycon
1218 = sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
1219 nest 2 $ ptext SLIT("(-fglasgow-exts permits this)")]