2 % (c) The AQUA Project, Glasgow University, 1996-1998
4 \section[TcTyClsDecls]{Typecheck type and class declarations}
8 tcTyAndClassDecls, tcIdxTyInstDecl
11 #include "HsVersions.h"
13 import HsSyn ( TyClDecl(..), HsConDetails(..), HsTyVarBndr(..),
14 ConDecl(..), Sig(..), NewOrData(..), ResType(..),
15 tyClDeclTyVars, isSynDecl, isClassDecl, isIdxTyDecl,
16 isKindSigDecl, hsConArgs, LTyClDecl, tcdName,
17 hsTyVarName, LHsTyVarBndr, LHsType, HsType(..),
20 import HsTypes ( HsBang(..), getBangStrictness, hsLTyVarNames )
21 import BasicTypes ( RecFlag(..), StrictnessMark(..) )
22 import HscTypes ( implicitTyThings, ModDetails )
23 import BuildTyCl ( buildClass, buildAlgTyCon, buildSynTyCon, buildDataCon,
24 mkDataTyConRhs, mkNewTyConRhs )
26 import TcEnv ( TyThing(..),
27 tcLookupLocated, tcLookupLocatedGlobal,
28 tcExtendGlobalEnv, tcExtendKindEnv, tcExtendKindEnvTvs,
29 tcExtendRecEnv, tcLookupTyVar, InstInfo )
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, mkTyVarTys,
41 tcSplitSigmaTy, tcEqTypes, tcGetTyVar_maybe )
42 import Type ( PredType(..), splitTyConApp_maybe, mkTyVarTy,
43 newTyConInstRhs, isLiftedTypeKind, Kind
44 -- pprParendType, pprThetaArrow
46 import Generics ( validGenericMethodType, canDoGenerics )
47 import Class ( Class, className, classTyCon, DefMeth(..), classBigSig, classTyVars )
48 import TyCon ( TyCon, AlgTyConRhs( AbstractTyCon, OpenDataTyCon,
50 SynTyConRhs( OpenSynTyCon, SynonymTyCon ),
51 tyConDataCons, mkForeignTyCon, isProductTyCon,
52 isRecursiveTyCon, isOpenTyCon,
53 tyConStupidTheta, synTyConRhs, isSynTyCon, tyConName,
54 isNewTyCon, isDataTyCon, tyConKind,
56 import DataCon ( DataCon, dataConUserType, dataConName,
57 dataConFieldLabels, dataConTyCon, dataConAllTyVars,
58 dataConFieldType, dataConResTys )
59 import Var ( TyVar, idType, idName )
60 import VarSet ( elemVarSet, mkVarSet )
61 import Name ( Name, getSrcLoc )
63 import Maybe ( isJust, fromJust, isNothing, catMaybes )
64 import Maybes ( expectJust )
65 import Monad ( unless )
66 import Unify ( tcMatchTys, tcMatchTyX )
67 import Util ( zipLazy, isSingleton, notNull, sortLe )
68 import List ( partition, elemIndex )
69 import SrcLoc ( Located(..), unLoc, getLoc, srcLocSpan )
70 import ListSetOps ( equivClasses, minusList )
71 import Digraph ( SCC(..) )
72 import DynFlags ( DynFlag( Opt_GlasgowExts, Opt_Generics,
73 Opt_UnboxStrictFields ) )
77 %************************************************************************
79 \subsection{Type checking for type and class declarations}
81 %************************************************************************
85 Consider a mutually-recursive group, binding
86 a type constructor T and a class C.
88 Step 1: getInitialKind
89 Construct a KindEnv by binding T and C to a kind variable
92 In that environment, do a kind check
94 Step 3: Zonk the kinds
96 Step 4: buildTyConOrClass
97 Construct an environment binding T to a TyCon and C to a Class.
98 a) Their kinds comes from zonking the relevant kind variable
99 b) Their arity (for synonyms) comes direct from the decl
100 c) The funcional dependencies come from the decl
101 d) The rest comes a knot-tied binding of T and C, returned from Step 4
102 e) The variances of the tycons in the group is calculated from
106 In this environment, walk over the decls, constructing the TyCons and Classes.
107 This uses in a strict way items (a)-(c) above, which is why they must
108 be constructed in Step 4. Feed the results back to Step 4.
109 For this step, pass the is-recursive flag as the wimp-out flag
113 Step 6: Extend environment
114 We extend the type environment with bindings not only for the TyCons and Classes,
115 but also for their "implicit Ids" like data constructors and class selectors
117 Step 7: checkValidTyCl
118 For a recursive group only, check all the decls again, just
119 to check all the side conditions on validity. We could not
120 do this before because we were in a mutually recursive knot.
122 Identification of recursive TyCons
123 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
124 The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to
127 Identifying a TyCon as recursive serves two purposes
129 1. Avoid infinite types. Non-recursive newtypes are treated as
130 "transparent", like type synonyms, after the type checker. If we did
131 this for all newtypes, we'd get infinite types. So we figure out for
132 each newtype whether it is "recursive", and add a coercion if so. In
133 effect, we are trying to "cut the loops" by identifying a loop-breaker.
135 2. Avoid infinite unboxing. This is nothing to do with newtypes.
139 Well, this function diverges, but we don't want the strictness analyser
140 to diverge. But the strictness analyser will diverge because it looks
141 deeper and deeper into the structure of T. (I believe there are
142 examples where the function does something sane, and the strictness
143 analyser still diverges, but I can't see one now.)
145 Now, concerning (1), the FC2 branch currently adds a coercion for ALL
146 newtypes. I did this as an experiment, to try to expose cases in which
147 the coercions got in the way of optimisations. If it turns out that we
148 can indeed always use a coercion, then we don't risk recursive types,
149 and don't need to figure out what the loop breakers are.
151 For newtype *families* though, we will always have a coercion, so they
152 are always loop breakers! So you can easily adjust the current
153 algorithm by simply treating all newtype families as loop breakers (and
154 indeed type families). I think.
157 tcTyAndClassDecls :: ModDetails -> [LTyClDecl Name]
158 -> TcM TcGblEnv -- Input env extended by types and classes
159 -- and their implicit Ids,DataCons
160 tcTyAndClassDecls boot_details allDecls
161 = do { -- Omit instances of indexed types; they are handled together
162 -- with the *heads* of class instances
163 ; let decls = filter (not . isIdxTyDecl . unLoc) allDecls
165 -- First check for cyclic type synonysm or classes
166 -- See notes with checkCycleErrs
167 ; checkCycleErrs decls
169 ; traceTc (text "tcTyAndCl" <+> ppr mod)
170 ; (syn_tycons, alg_tyclss) <- fixM (\ ~(rec_syn_tycons, rec_alg_tyclss) ->
171 do { let { -- Seperate ordinary synonyms from all other type and
172 -- class declarations and add all associated type
173 -- declarations from type classes. The latter is
174 -- required so that the temporary environment for the
175 -- knot includes all associated family declarations.
176 ; (syn_decls, alg_decls) = partition (isSynDecl . unLoc)
178 ; alg_at_decls = concatMap addATs alg_decls
180 -- Extend the global env with the knot-tied results
181 -- for data types and classes
183 -- We must populate the environment with the loop-tied
184 -- T's right away, because the kind checker may "fault
185 -- in" some type constructors that recursively
187 ; let gbl_things = mkGlobalThings alg_at_decls rec_alg_tyclss
188 ; tcExtendRecEnv gbl_things $ do
190 -- Kind-check the declarations
191 { (kc_syn_decls, kc_alg_decls) <- kcTyClDecls syn_decls alg_decls
193 ; let { -- Calculate rec-flag
194 ; calc_rec = calcRecFlags boot_details rec_alg_tyclss
195 ; tc_decl = addLocM (tcTyClDecl calc_rec) }
196 -- Type-check the type synonyms, and extend the envt
197 ; syn_tycons <- tcSynDecls kc_syn_decls
198 ; tcExtendGlobalEnv syn_tycons $ do
200 -- Type-check the data types and classes
201 { alg_tyclss <- mappM tc_decl kc_alg_decls
202 ; return (syn_tycons, concat alg_tyclss)
204 -- Finished with knot-tying now
205 -- Extend the environment with the finished things
206 ; tcExtendGlobalEnv (syn_tycons ++ alg_tyclss) $ do
208 -- Perform the validity check
209 { traceTc (text "ready for validity check")
210 ; mappM_ (addLocM checkValidTyCl) decls
211 ; traceTc (text "done")
213 -- Add the implicit things;
214 -- we want them in the environment because
215 -- they may be mentioned in interface files
216 ; let { implicit_things = concatMap implicitTyThings alg_tyclss }
217 ; traceTc ((text "Adding" <+> ppr alg_tyclss)
218 $$ (text "and" <+> ppr implicit_things))
219 ; tcExtendGlobalEnv implicit_things getGblEnv
222 addATs decl@(L _ (ClassDecl {tcdATs = ats})) = decl : ats
225 mkGlobalThings :: [LTyClDecl Name] -- The decls
226 -> [TyThing] -- Knot-tied, in 1-1 correspondence with the decls
228 -- Driven by the Decls, and treating the TyThings lazily
229 -- make a TypeEnv for the new things
230 mkGlobalThings decls things
231 = map mk_thing (decls `zipLazy` things)
233 mk_thing (L _ (ClassDecl {tcdLName = L _ name}), ~(AClass cl))
235 mk_thing (L _ decl, ~(ATyCon tc))
236 = (tcdName decl, ATyCon tc)
240 %************************************************************************
242 \subsection{Type checking instances of indexed types}
244 %************************************************************************
246 Instances of indexed types are somewhat of a hybrid. They are processed
247 together with class instance heads, but can contain data constructors and hence
248 they share a lot of kinding and type checking code with ordinary algebraic
249 data types (and GADTs).
252 tcIdxTyInstDecl :: LTyClDecl Name
253 -> TcM (Maybe InstInfo, Maybe TyThing) -- Nothing if error
254 tcIdxTyInstDecl (L loc decl)
255 = -- Prime error recovery, set source location
256 recoverM (returnM (Nothing, Nothing)) $
259 do { -- indexed data types require -fglasgow-exts and can't be in an
261 ; gla_exts <- doptM Opt_GlasgowExts
262 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
263 ; checkTc gla_exts $ badIdxTyDecl (tcdLName decl)
264 ; checkTc (not is_boot) $ badBootTyIdxDeclErr
266 -- perform kind and type checking
267 ; tcIdxTyInstDecl1 decl
270 tcIdxTyInstDecl1 :: TyClDecl Name
271 -> TcM (Maybe InstInfo, Maybe TyThing) -- Nothing if error
273 tcIdxTyInstDecl1 (decl@TySynonym {})
274 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
275 do { -- check that the family declaration is for a synonym
276 unless (isSynTyCon family) $
277 addErr (wrongKindOfFamily family)
279 ; -- (1) kind check the right hand side of the type equation
280 ; k_rhs <- kcCheckHsType (tcdSynRhs decl) resKind
282 -- (2) type check type equation
283 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
284 ; t_typats <- mappM tcHsKindedType k_typats
285 ; t_rhs <- tcHsKindedType k_rhs
287 -- construct type rewrite rule
288 -- !!!of the form: forall t_tvs. (tcdLName decl) t_typats = t_rhs
289 ; return (Nothing, Nothing) -- !!!TODO: need InstInfo for eq axioms
292 tcIdxTyInstDecl1 (decl@TyData {tcdND = new_or_data, tcdLName = L loc tc_name,
294 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
295 do { -- check that the family declaration is for the right kind
296 unless (new_or_data == NewType && isNewTyCon family ||
297 new_or_data == DataType && isDataTyCon family) $
298 addErr (wrongKindOfFamily family)
300 ; -- (1) kind check the data declaration as usual
301 ; k_decl <- kcDataDecl decl k_tvs
302 ; let k_ctxt = tcdCtxt k_decl
303 k_cons = tcdCons k_decl
305 -- result kind must be '*' (otherwise, we have too few patterns)
306 ; checkTc (isLiftedTypeKind resKind) $ tooFewParmsErr tc_name
308 -- (2) type check indexed data type declaration
309 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
310 ; unbox_strict <- doptM Opt_UnboxStrictFields
312 -- Check that we don't use GADT syntax for indexed types
313 ; checkTc h98_syntax (badGadtIdxTyDecl tc_name)
315 -- Check that a newtype has exactly one constructor
316 ; checkTc (new_or_data == DataType || isSingleton k_cons) $
317 newtypeConError tc_name (length k_cons)
319 ; t_typats <- mappM tcHsKindedType k_typats
320 ; stupid_theta <- tcHsKindedContext k_ctxt
322 ; tycon <- fixM (\ tycon -> do
323 { data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data
328 DataType -> return (mkDataTyConRhs data_cons)
330 ASSERT( isSingleton data_cons )
331 mkNewTyConRhs tc_name tycon (head data_cons)
332 ; buildAlgTyCon tc_name t_tvs stupid_theta tc_rhs Recursive
333 False h98_syntax (Just (family, t_typats))
334 -- We always assume that indexed types are recursive. Why?
335 -- (1) Due to their open nature, we can never be sure that a
336 -- further instance might not introduce a new recursive
337 -- dependency. (2) They are always valid loop breakers as
338 -- they involve a coercion.
342 ; return (Nothing, Just (ATyCon tycon))
345 h98_syntax = case cons of -- All constructors have same shape
346 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
349 -- Kind checking of indexed types
352 -- Kind check type patterns and kind annotate the embedded type variables.
354 -- * Here we check that a type instance matches its kind signature, but we do
355 -- not check whether there is a pattern for each type index; the latter
356 -- check is only required for type functions.
358 kcIdxTyPats :: TyClDecl Name
359 -> ([LHsTyVarBndr Name] -> [LHsType Name] -> Kind -> TyCon -> TcM a)
360 -- ^^kinded tvs ^^kinded ty pats ^^res kind
362 kcIdxTyPats decl thing_inside
363 = kcHsTyVars (tcdTyVars decl) $ \tvs ->
364 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
365 ; let { family = case tc_ty_thing of
366 AGlobal (ATyCon family) -> family
367 ; (kinds, resKind) = splitKindFunTys (tyConKind family)
368 ; hs_typats = fromJust $ tcdTyPats decl }
370 -- we may not have more parameters than the kind indicates
371 ; checkTc (length kinds >= length hs_typats) $
372 tooManyParmsErr (tcdLName decl)
374 -- type functions can have a higher-kinded result
375 ; let resultKind = mkArrowKinds (drop (length hs_typats) kinds) resKind
376 ; typats <- zipWithM kcCheckHsType hs_typats kinds
377 ; thing_inside tvs typats resultKind family
383 %************************************************************************
387 %************************************************************************
389 We need to kind check all types in the mutually recursive group
390 before we know the kind of the type variables. For example:
393 op :: D b => a -> b -> b
396 bop :: (Monad c) => ...
398 Here, the kind of the locally-polymorphic type variable "b"
399 depends on *all the uses of class D*. For example, the use of
400 Monad c in bop's type signature means that D must have kind Type->Type.
402 However type synonyms work differently. They can have kinds which don't
403 just involve (->) and *:
404 type R = Int# -- Kind #
405 type S a = Array# a -- Kind * -> #
406 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
407 So we must infer their kinds from their right-hand sides *first* and then
408 use them, whereas for the mutually recursive data types D we bring into
409 scope kind bindings D -> k, where k is a kind variable, and do inference.
413 This treatment of type synonyms only applies to Haskell 98-style synonyms.
414 General type functions can be recursive, and hence, appear in `alg_decls'.
416 The kind of an indexed type is solely determinded by its kind signature;
417 hence, only kind signatures participate in the construction of the initial
418 kind environment (as constructed by `getInitialKind'). In fact, we ignore
419 instances of indexed types altogether in the following. However, we need to
420 include the kind signatures of associated types into the construction of the
421 initial kind environment. (This is handled by `allDecls').
424 kcTyClDecls syn_decls alg_decls
425 = do { -- First extend the kind env with each data type, class, and
426 -- indexed type, mapping them to a type variable
427 let initialKindDecls = concat [allDecls decl | L _ decl <- alg_decls]
428 ; alg_kinds <- mappM getInitialKind initialKindDecls
429 ; tcExtendKindEnv alg_kinds $ do
431 -- Now kind-check the type synonyms, in dependency order
432 -- We do these differently to data type and classes,
433 -- because a type synonym can be an unboxed type
435 -- and a kind variable can't unify with UnboxedTypeKind
436 -- So we infer their kinds in dependency order
437 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
438 ; tcExtendKindEnv syn_kinds $ do
440 -- Now kind-check the data type, class, and kind signatures,
441 -- returning kind-annotated decls; we don't kind-check
442 -- instances of indexed types yet, but leave this to
444 { kc_alg_decls <- mappM (wrapLocM kcTyClDecl)
445 (filter (not . isIdxTyDecl . unLoc) alg_decls)
447 ; return (kc_syn_decls, kc_alg_decls) }}}
449 -- get all declarations relevant for determining the initial kind
451 allDecls (decl@ClassDecl {tcdATs = ats}) = decl : [ at
454 allDecls decl | isIdxTyDecl decl = []
457 ------------------------------------------------------------------------
458 getInitialKind :: TyClDecl Name -> TcM (Name, TcKind)
459 -- Only for data type, class, and indexed type declarations
460 -- Get as much info as possible from the data, class, or indexed type decl,
461 -- so as to maximise usefulness of error messages
463 = do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl)
464 ; res_kind <- mk_res_kind decl
465 ; return (tcdName decl, mkArrowKinds arg_kinds res_kind) }
467 mk_arg_kind (UserTyVar _) = newKindVar
468 mk_arg_kind (KindedTyVar _ kind) = return kind
470 mk_res_kind (TyFunction { tcdKind = kind }) = return kind
471 mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
472 -- On GADT-style and data signature declarations we allow a kind
474 -- data T :: *->* where { ... }
475 mk_res_kind other = return liftedTypeKind
479 kcSynDecls :: [SCC (LTyClDecl Name)]
480 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
481 [(Name,TcKind)]) -- Kind bindings
484 kcSynDecls (group : groups)
485 = do { (decl, nk) <- kcSynDecl group
486 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
487 ; return (decl:decls, nk:nks) }
490 kcSynDecl :: SCC (LTyClDecl Name)
491 -> TcM (LTyClDecl Name, -- Kind-annotated decls
492 (Name,TcKind)) -- Kind bindings
493 kcSynDecl (AcyclicSCC ldecl@(L loc decl))
494 = tcAddDeclCtxt decl $
495 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
496 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
497 <+> brackets (ppr k_tvs))
498 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
499 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
500 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
501 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
502 (unLoc (tcdLName decl), tc_kind)) })
504 kcSynDecl (CyclicSCC decls)
505 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
506 -- of out-of-scope tycons
508 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
510 ------------------------------------------------------------------------
511 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
512 -- Not used for type synonyms (see kcSynDecl)
514 kcTyClDecl decl@(TyData {})
515 = ASSERT( not . isJust $ tcdTyPats decl ) -- must not be instance of idx ty
516 kcTyClDeclBody decl $
519 kcTyClDecl decl@(TyFunction {})
520 = kcTyClDeclBody decl $ \ tvs' ->
521 return (decl {tcdTyVars = tvs'})
523 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs, tcdATs = ats})
524 = kcTyClDeclBody decl $ \ tvs' ->
525 do { is_boot <- tcIsHsBoot
526 ; ctxt' <- kcHsContext ctxt
527 ; ats' <- mappM (wrapLocM kcTyClDecl) ats
528 ; sigs' <- mappM (wrapLocM kc_sig ) sigs
529 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs',
532 kc_sig (TypeSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
533 ; return (TypeSig nm op_ty') }
534 kc_sig other_sig = return other_sig
536 kcTyClDecl decl@(ForeignType {})
539 kcTyClDeclBody :: TyClDecl Name
540 -> ([LHsTyVarBndr Name] -> TcM a)
542 -- getInitialKind has made a suitably-shaped kind for the type or class
543 -- Unpack it, and attribute those kinds to the type variables
544 -- Extend the env with bindings for the tyvars, taken from
545 -- the kind of the tycon/class. Give it to the thing inside, and
546 -- check the result kind matches
547 kcTyClDeclBody decl thing_inside
548 = tcAddDeclCtxt decl $
549 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
550 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
551 (kinds, _) = splitKindFunTys tc_kind
552 hs_tvs = tcdTyVars decl
553 kinded_tvs = ASSERT( length kinds >= length hs_tvs )
554 [ L loc (KindedTyVar (hsTyVarName tv) k)
555 | (L loc tv, k) <- zip hs_tvs kinds]
556 ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
558 -- Kind check a data declaration, assuming that we already extended the
559 -- kind environment with the type variables of the left-hand side (these
560 -- kinded type variables are also passed as the second parameter).
562 kcDataDecl :: TyClDecl Name -> [LHsTyVarBndr Name] -> TcM (TyClDecl Name)
563 kcDataDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
565 = do { ctxt' <- kcHsContext ctxt
566 ; cons' <- mappM (wrapLocM kc_con_decl) cons
567 ; return (decl {tcdTyVars = tvs, tcdCtxt = ctxt', tcdCons = cons'}) }
569 kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res) = do
570 kcHsTyVars ex_tvs $ \ex_tvs' -> do
571 ex_ctxt' <- kcHsContext ex_ctxt
572 details' <- kc_con_details details
574 ResTyH98 -> return ResTyH98
575 ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
576 return (ConDecl name expl ex_tvs' ex_ctxt' details' res')
578 kc_con_details (PrefixCon btys)
579 = do { btys' <- mappM kc_larg_ty btys ; return (PrefixCon btys') }
580 kc_con_details (InfixCon bty1 bty2)
581 = do { bty1' <- kc_larg_ty bty1; bty2' <- kc_larg_ty bty2; return (InfixCon bty1' bty2') }
582 kc_con_details (RecCon fields)
583 = do { fields' <- mappM kc_field fields; return (RecCon fields') }
585 kc_field (fld, bty) = do { bty' <- kc_larg_ty bty ; return (fld, bty') }
587 kc_larg_ty bty = case new_or_data of
588 DataType -> kcHsSigType bty
589 NewType -> kcHsLiftedSigType bty
590 -- Can't allow an unlifted type for newtypes, because we're effectively
591 -- going to remove the constructor while coercing it to a lifted type.
592 -- And newtypes can't be bang'd
596 %************************************************************************
598 \subsection{Type checking}
600 %************************************************************************
603 tcSynDecls :: [LTyClDecl Name] -> TcM [TyThing]
604 tcSynDecls [] = return []
605 tcSynDecls (decl : decls)
606 = do { syn_tc <- addLocM tcSynDecl decl
607 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls decls)
608 ; return (syn_tc : syn_tcs) }
611 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
612 = tcTyVarBndrs tvs $ \ tvs' -> do
613 { traceTc (text "tcd1" <+> ppr tc_name)
614 ; rhs_ty' <- tcHsKindedType rhs_ty
615 ; return (ATyCon (buildSynTyCon tc_name tvs' (SynonymTyCon rhs_ty'))) }
618 tcTyClDecl :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
620 tcTyClDecl calc_isrec decl
621 = tcAddDeclCtxt decl (tcTyClDecl1 calc_isrec decl)
623 -- kind signature for a type function
624 tcTyClDecl1 _calc_isrec
625 (TyFunction {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = kind})
626 = tcTyVarBndrs tvs $ \ tvs' -> do
627 { traceTc (text "type family: " <+> ppr tc_name)
628 ; gla_exts <- doptM Opt_GlasgowExts
630 -- Check that we don't use kind signatures without Glasgow extensions
631 ; checkTc gla_exts $ badSigTyDecl tc_name
633 ; return [ATyCon $ buildSynTyCon tc_name tvs' (OpenSynTyCon kind)]
636 -- kind signature for an indexed data type
637 tcTyClDecl1 _calc_isrec
638 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
639 tcdLName = L _ tc_name, tcdKindSig = Just ksig, tcdCons = []})
640 = tcTyVarBndrs tvs $ \ tvs' -> do
641 { traceTc (text "data/newtype family: " <+> ppr tc_name)
642 ; extra_tvs <- tcDataKindSig (Just ksig)
643 ; let final_tvs = tvs' ++ extra_tvs -- we may not need these
645 ; checkTc (null . unLoc $ ctxt) $ badKindSigCtxt tc_name
646 ; gla_exts <- doptM Opt_GlasgowExts
648 -- Check that we don't use kind signatures without Glasgow extensions
649 ; checkTc gla_exts $ badSigTyDecl tc_name
651 ; tycon <- buildAlgTyCon tc_name final_tvs []
653 DataType -> OpenDataTyCon
654 NewType -> OpenNewTyCon)
655 Recursive False True Nothing
656 ; return [ATyCon tycon]
659 tcTyClDecl1 calc_isrec
660 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
661 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
662 = tcTyVarBndrs tvs $ \ tvs' -> do
663 { extra_tvs <- tcDataKindSig mb_ksig
664 ; let final_tvs = tvs' ++ extra_tvs
665 ; stupid_theta <- tcHsKindedContext ctxt
666 ; want_generic <- doptM Opt_Generics
667 ; unbox_strict <- doptM Opt_UnboxStrictFields
668 ; gla_exts <- doptM Opt_GlasgowExts
669 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
671 -- Check that we don't use GADT syntax in H98 world
672 ; checkTc (gla_exts || h98_syntax) (badGadtDecl tc_name)
674 -- Check that we don't use kind signatures without Glasgow extensions
675 ; checkTc (gla_exts || isNothing mb_ksig) (badSigTyDecl tc_name)
677 -- Check that the stupid theta is empty for a GADT-style declaration
678 ; checkTc (null stupid_theta || h98_syntax) (badStupidTheta tc_name)
680 -- Check that there's at least one condecl,
681 -- or else we're reading an hs-boot file, or -fglasgow-exts
682 ; checkTc (not (null cons) || gla_exts || is_boot)
683 (emptyConDeclsErr tc_name)
685 -- Check that a newtype has exactly one constructor
686 ; checkTc (new_or_data == DataType || isSingleton cons)
687 (newtypeConError tc_name (length cons))
689 ; tycon <- fixM (\ tycon -> do
690 { data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data
694 if null cons && is_boot -- In a hs-boot file, empty cons means
695 then return AbstractTyCon -- "don't know"; hence Abstract
696 else case new_or_data of
697 DataType -> return (mkDataTyConRhs data_cons)
699 ASSERT( isSingleton data_cons )
700 mkNewTyConRhs tc_name tycon (head data_cons)
701 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
702 (want_generic && canDoGenerics data_cons) h98_syntax Nothing
704 ; return [ATyCon tycon]
707 is_rec = calc_isrec tc_name
708 h98_syntax = case cons of -- All constructors have same shape
709 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
712 tcTyClDecl1 calc_isrec
713 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
714 tcdCtxt = ctxt, tcdMeths = meths,
715 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
716 = tcTyVarBndrs tvs $ \ tvs' -> do
717 { ctxt' <- tcHsKindedContext ctxt
718 ; fds' <- mappM (addLocM tc_fundep) fundeps
719 ; atss <- mappM (addLocM (tcTyClDecl1 (const Recursive))) ats
720 ; let ats' = zipWith setTyThingPoss atss (map (tcdTyVars . unLoc) ats)
721 ; sig_stuff <- tcClassSigs class_name sigs meths
722 ; clas <- fixM (\ clas ->
723 let -- This little knot is just so we can get
724 -- hold of the name of the class TyCon, which we
725 -- need to look up its recursiveness
726 tycon_name = tyConName (classTyCon clas)
727 tc_isrec = calc_isrec tycon_name
729 buildClass class_name tvs' ctxt' fds' ats'
731 ; return (AClass clas : ats')
732 -- NB: Order is important due to the call to `mkGlobalThings' when
733 -- tying the the type and class declaration type checking knot.
736 tc_fundep (tvs1, tvs2) = do { tvs1' <- mappM tcLookupTyVar tvs1 ;
737 ; tvs2' <- mappM tcLookupTyVar tvs2 ;
738 ; return (tvs1', tvs2') }
740 -- For each AT argument compute the position of the corresponding class
741 -- parameter in the class head. This will later serve as a permutation
742 -- vector when checking the validity of instance declarations.
743 setTyThingPoss [ATyCon tycon] atTyVars =
744 let classTyVars = hsLTyVarNames tvs
746 . map (`elemIndex` classTyVars)
749 -- There will be no Nothing, as we already passed renaming
751 ATyCon (setTyConArgPoss tycon poss)
752 setTyThingPoss _ _ = panic "TcTyClsDecls.setTyThingPoss"
754 tcTyClDecl1 calc_isrec
755 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
756 = returnM [ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0)]
758 -----------------------------------
759 tcConDecl :: Bool -- True <=> -funbox-strict_fields
765 tcConDecl unbox_strict NewType tycon tc_tvs -- Newtypes
766 (ConDecl name _ ex_tvs ex_ctxt details ResTyH98)
767 = do { let tc_datacon field_lbls arg_ty
768 = do { arg_ty' <- tcHsKindedType arg_ty -- No bang on newtype
769 ; buildDataCon (unLoc name) False {- Prefix -}
771 (map unLoc field_lbls)
772 tc_tvs [] -- No existentials
773 [] [] -- No equalities, predicates
777 -- Check that a newtype has no existential stuff
778 ; checkTc (null ex_tvs && null (unLoc ex_ctxt)) (newtypeExError name)
781 PrefixCon [arg_ty] -> tc_datacon [] arg_ty
782 RecCon [(field_lbl, arg_ty)] -> tc_datacon [field_lbl] arg_ty
784 failWithTc (newtypeFieldErr name (length (hsConArgs details)))
785 -- Check that the constructor has exactly one field
788 tcConDecl unbox_strict DataType tycon tc_tvs -- Data types
789 (ConDecl name _ tvs ctxt details res_ty)
790 = tcTyVarBndrs tvs $ \ tvs' -> do
791 { ctxt' <- tcHsKindedContext ctxt
792 ; (univ_tvs, ex_tvs, eq_preds, data_tc) <- tcResultType tycon tc_tvs tvs' res_ty
794 tc_datacon is_infix field_lbls btys
795 = do { let bangs = map getBangStrictness btys
796 ; arg_tys <- mappM tcHsBangType btys
797 ; buildDataCon (unLoc name) is_infix
798 (argStrictness unbox_strict tycon bangs arg_tys)
799 (map unLoc field_lbls)
800 univ_tvs ex_tvs eq_preds ctxt' arg_tys
802 -- NB: we put data_tc, the type constructor gotten from the
803 -- constructor type signature into the data constructor;
804 -- that way checkValidDataCon can complain if it's wrong.
807 PrefixCon btys -> tc_datacon False [] btys
808 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
809 RecCon fields -> tc_datacon False field_names btys
811 (field_names, btys) = unzip fields
815 tcResultType :: TyCon
816 -> [TyVar] -- data T a b c = ...
817 -> [TyVar] -- where MkT :: forall a b c. ...
819 -> TcM ([TyVar], -- Universal
820 [TyVar], -- Existential
821 [(TyVar,Type)], -- Equality predicates
822 TyCon) -- TyCon given in the ResTy
823 -- We don't check that the TyCon given in the ResTy is
824 -- the same as the parent tycon, becuase we are in the middle
825 -- of a recursive knot; so it's postponed until checkValidDataCon
827 tcResultType decl_tycon tc_tvs dc_tvs ResTyH98
828 = return (tc_tvs, dc_tvs, [], decl_tycon)
829 -- In H98 syntax the dc_tvs are the existential ones
830 -- data T a b c = forall d e. MkT ...
831 -- The {a,b,c} are tc_tvs, and {d,e} are dc_tvs
833 tcResultType _ tc_tvs dc_tvs (ResTyGADT res_ty)
834 -- E.g. data T a b c where
835 -- MkT :: forall x y z. T (x,y) z z
837 -- ([a,z,c], [x,y], [a:=:(x,y), c:=:z], T)
839 = do { (dc_tycon, res_tys) <- tcLHsConResTy res_ty
840 -- NB: tc_tvs and dc_tvs are distinct
841 ; let univ_tvs = choose_univs [] tc_tvs res_tys
842 -- Each univ_tv is either a dc_tv or a tc_tv
843 ex_tvs = dc_tvs `minusList` univ_tvs
844 eq_spec = [ (tv, ty) | (tv,ty) <- univ_tvs `zip` res_tys,
846 ; return (univ_tvs, ex_tvs, eq_spec, dc_tycon) }
848 -- choose_univs uses the res_ty itself if it's a type variable
849 -- and hasn't already been used; otherwise it uses one of the tc_tvs
850 choose_univs used tc_tvs []
851 = ASSERT( null tc_tvs ) []
852 choose_univs used (tc_tv:tc_tvs) (res_ty:res_tys)
853 | Just tv <- tcGetTyVar_maybe res_ty, not (tv `elem` used)
854 = tv : choose_univs (tv:used) tc_tvs res_tys
856 = tc_tv : choose_univs used tc_tvs res_tys
859 argStrictness :: Bool -- True <=> -funbox-strict_fields
861 -> [TcType] -> [StrictnessMark]
862 argStrictness unbox_strict tycon bangs arg_tys
863 = ASSERT( length bangs == length arg_tys )
864 zipWith (chooseBoxingStrategy unbox_strict tycon) arg_tys bangs
866 -- We attempt to unbox/unpack a strict field when either:
867 -- (i) The field is marked '!!', or
868 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
870 -- We have turned off unboxing of newtypes because coercions make unboxing
871 -- and reboxing more complicated
872 chooseBoxingStrategy :: Bool -> TyCon -> TcType -> HsBang -> StrictnessMark
873 chooseBoxingStrategy unbox_strict_fields tycon arg_ty bang
875 HsNoBang -> NotMarkedStrict
876 HsStrict | unbox_strict_fields
877 && can_unbox arg_ty -> MarkedUnboxed
878 HsUnbox | can_unbox arg_ty -> MarkedUnboxed
879 other -> MarkedStrict
881 -- we can unbox if the type is a chain of newtypes with a product tycon
883 can_unbox arg_ty = case splitTyConApp_maybe arg_ty of
885 Just (arg_tycon, tycon_args) ->
886 not (isRecursiveTyCon tycon) &&
887 isProductTyCon arg_tycon &&
888 (if isNewTyCon arg_tycon then
889 can_unbox (newTyConInstRhs arg_tycon tycon_args)
893 %************************************************************************
895 \subsection{Dependency analysis}
897 %************************************************************************
899 Validity checking is done once the mutually-recursive knot has been
900 tied, so we can look at things freely.
903 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
904 checkCycleErrs tyclss
908 = do { mappM_ recClsErr cls_cycles
909 ; failM } -- Give up now, because later checkValidTyCl
910 -- will loop if the synonym is recursive
912 cls_cycles = calcClassCycles tyclss
914 checkValidTyCl :: TyClDecl Name -> TcM ()
915 -- We do the validity check over declarations, rather than TyThings
916 -- only so that we can add a nice context with tcAddDeclCtxt
918 = tcAddDeclCtxt decl $
919 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
920 ; traceTc (text "Validity of" <+> ppr thing)
922 ATyCon tc -> checkValidTyCon tc
923 AClass cl -> checkValidClass cl
924 ; traceTc (text "Done validity of" <+> ppr thing)
927 -------------------------
928 -- For data types declared with record syntax, we require
929 -- that each constructor that has a field 'f'
930 -- (a) has the same result type
931 -- (b) has the same type for 'f'
932 -- module alpha conversion of the quantified type variables
933 -- of the constructor.
935 checkValidTyCon :: TyCon -> TcM ()
938 = case synTyConRhs tc of
939 OpenSynTyCon _ -> return ()
940 SynonymTyCon ty -> checkValidType syn_ctxt ty
942 = -- Check the context on the data decl
943 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
945 -- Check arg types of data constructors
946 mappM_ (checkValidDataCon tc) data_cons `thenM_`
948 -- Check that fields with the same name share a type
949 mappM_ check_fields groups
952 syn_ctxt = TySynCtxt name
954 data_cons = tyConDataCons tc
956 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
957 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
958 get_fields con = dataConFieldLabels con `zip` repeat con
959 -- dataConFieldLabels may return the empty list, which is fine
961 -- See Note [GADT record selectors] in MkId.lhs
962 -- We must check (a) that the named field has the same
963 -- type in each constructor
964 -- (b) that those constructors have the same result type
966 -- However, the constructors may have differently named type variable
967 -- and (worse) we don't know how the correspond to each other. E.g.
968 -- C1 :: forall a b. { f :: a, g :: b } -> T a b
969 -- C2 :: forall d c. { f :: c, g :: c } -> T c d
971 -- So what we do is to ust Unify.tcMatchTys to compare the first candidate's
972 -- result type against other candidates' types BOTH WAYS ROUND.
973 -- If they magically agrees, take the substitution and
974 -- apply them to the latter ones, and see if they match perfectly.
975 check_fields fields@((label, con1) : other_fields)
976 -- These fields all have the same name, but are from
977 -- different constructors in the data type
978 = recoverM (return ()) $ mapM_ checkOne other_fields
979 -- Check that all the fields in the group have the same type
980 -- NB: this check assumes that all the constructors of a given
981 -- data type use the same type variables
983 tvs1 = mkVarSet (dataConAllTyVars con1)
984 res1 = dataConResTys con1
985 fty1 = dataConFieldType con1 label
987 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
988 = do { checkFieldCompat label con1 con2 tvs1 res1 res2 fty1 fty2
989 ; checkFieldCompat label con2 con1 tvs2 res2 res1 fty2 fty1 }
991 tvs2 = mkVarSet (dataConAllTyVars con2)
992 res2 = dataConResTys con2
993 fty2 = dataConFieldType con2 label
995 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
996 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
997 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
999 mb_subst1 = tcMatchTys tvs1 res1 res2
1000 mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
1002 -------------------------------
1003 checkValidDataCon :: TyCon -> DataCon -> TcM ()
1004 checkValidDataCon tc con
1005 = setSrcSpan (srcLocSpan (getSrcLoc con)) $
1006 addErrCtxt (dataConCtxt con) $
1007 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
1008 ; checkValidType ctxt (dataConUserType con) }
1010 ctxt = ConArgCtxt (dataConName con)
1012 -------------------------------
1013 checkValidClass :: Class -> TcM ()
1015 = do { -- CHECK ARITY 1 FOR HASKELL 1.4
1016 gla_exts <- doptM Opt_GlasgowExts
1018 -- Check that the class is unary, unless GlaExs
1019 ; checkTc (notNull tyvars) (nullaryClassErr cls)
1020 ; checkTc (gla_exts || unary) (classArityErr cls)
1022 -- Check the super-classes
1023 ; checkValidTheta (ClassSCCtxt (className cls)) theta
1025 -- Check the class operations
1026 ; mappM_ (check_op gla_exts) op_stuff
1028 -- Check that if the class has generic methods, then the
1029 -- class has only one parameter. We can't do generic
1030 -- multi-parameter type classes!
1031 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
1034 (tyvars, theta, _, op_stuff) = classBigSig cls
1035 unary = isSingleton tyvars
1036 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
1038 check_op gla_exts (sel_id, dm)
1039 = addErrCtxt (classOpCtxt sel_id tau) $ do
1040 { checkValidTheta SigmaCtxt (tail theta)
1041 -- The 'tail' removes the initial (C a) from the
1042 -- class itself, leaving just the method type
1044 ; checkValidType (FunSigCtxt op_name) tau
1046 -- Check that the type mentions at least one of
1047 -- the class type variables
1048 ; checkTc (any (`elemVarSet` tyVarsOfType tau) tyvars)
1049 (noClassTyVarErr cls sel_id)
1051 -- Check that for a generic method, the type of
1052 -- the method is sufficiently simple
1053 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
1054 (badGenericMethodType op_name op_ty)
1057 op_name = idName sel_id
1058 op_ty = idType sel_id
1059 (_,theta1,tau1) = tcSplitSigmaTy op_ty
1060 (_,theta2,tau2) = tcSplitSigmaTy tau1
1061 (theta,tau) | gla_exts = (theta1 ++ theta2, tau2)
1062 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
1063 -- Ugh! The function might have a type like
1064 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
1065 -- With -fglasgow-exts, we want to allow this, even though the inner
1066 -- forall has an (Eq a) constraint. Whereas in general, each constraint
1067 -- in the context of a for-all must mention at least one quantified
1068 -- type variable. What a mess!
1071 ---------------------------------------------------------------------
1072 resultTypeMisMatch field_name con1 con2
1073 = vcat [sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1074 ptext SLIT("have a common field") <+> quotes (ppr field_name) <> comma],
1075 nest 2 $ ptext SLIT("but have different result types")]
1076 fieldTypeMisMatch field_name con1 con2
1077 = sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1078 ptext SLIT("give different types for field"), quotes (ppr field_name)]
1080 dataConCtxt con = ptext SLIT("In the definition of data constructor") <+> quotes (ppr con)
1082 classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
1083 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
1086 = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
1089 = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
1090 parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
1092 noClassTyVarErr clas op
1093 = sep [ptext SLIT("The class method") <+> quotes (ppr op),
1094 ptext SLIT("mentions none of the type variables of the class") <+>
1095 ppr clas <+> hsep (map ppr (classTyVars clas))]
1097 genericMultiParamErr clas
1098 = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
1099 ptext SLIT("cannot have generic methods")
1101 badGenericMethodType op op_ty
1102 = hang (ptext SLIT("Generic method type is too complex"))
1103 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
1104 ptext SLIT("You can only use type variables, arrows, lists, and tuples")])
1107 = setSrcSpan (getLoc (head sorted_decls)) $
1108 addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
1109 nest 2 (vcat (map ppr_decl sorted_decls))])
1111 sorted_decls = sortLocated syn_decls
1112 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
1115 = setSrcSpan (getLoc (head sorted_decls)) $
1116 addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
1117 nest 2 (vcat (map ppr_decl sorted_decls))])
1119 sorted_decls = sortLocated cls_decls
1120 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
1122 sortLocated :: [Located a] -> [Located a]
1123 sortLocated things = sortLe le things
1125 le (L l1 _) (L l2 _) = l1 <= l2
1127 badDataConTyCon data_con
1128 = hang (ptext SLIT("Data constructor") <+> quotes (ppr data_con) <+>
1129 ptext SLIT("returns type") <+> quotes (ppr (dataConTyCon data_con)))
1130 2 (ptext SLIT("instead of its parent type"))
1133 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
1134 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow GADTs")) ]
1136 badStupidTheta tc_name
1137 = ptext SLIT("A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
1139 newtypeConError tycon n
1140 = sep [ptext SLIT("A newtype must have exactly one constructor,"),
1141 nest 2 $ ptext SLIT("but") <+> quotes (ppr tycon) <+> ptext SLIT("has") <+> speakN n ]
1144 = sep [ptext SLIT("A newtype constructor cannot have an existential context,"),
1145 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
1147 newtypeFieldErr con_name n_flds
1148 = sep [ptext SLIT("The constructor of a newtype must have exactly one field"),
1149 nest 2 $ ptext SLIT("but") <+> quotes (ppr con_name) <+> ptext SLIT("has") <+> speakN n_flds]
1151 badSigTyDecl tc_name
1152 = vcat [ ptext SLIT("Illegal kind signature") <+>
1153 quotes (ppr tc_name)
1154 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow indexed types")) ]
1156 badKindSigCtxt tc_name
1157 = vcat [ ptext SLIT("Illegal context in kind signature") <+>
1158 quotes (ppr tc_name)
1159 , nest 2 (parens $ ptext SLIT("Currently, kind signatures cannot have a context")) ]
1161 badIdxTyDecl tc_name
1162 = vcat [ ptext SLIT("Illegal indexed type instance for") <+>
1163 quotes (ppr tc_name)
1164 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow indexed types")) ]
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("Indexed types cannot use GADT declarations")) ]
1171 tooManyParmsErr tc_name
1172 = ptext SLIT("Indexed type instance has too many parameters:") <+>
1173 quotes (ppr tc_name)
1175 tooFewParmsErr tc_name
1176 = ptext SLIT("Indexed type instance has too few parameters:") <+>
1177 quotes (ppr tc_name)
1179 badBootTyIdxDeclErr =
1180 ptext SLIT("Illegal indexed type instance in hs-boot file")
1182 wrongKindOfFamily family =
1183 ptext SLIT("Wrong category of type 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)")]