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"
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
271 -- - left-hand side contains no type family applications
272 -- (vanilla synonyms are fine, though)
273 ; mappM_ checkTyFamFreeness t_typats
275 -- - the right-hand side is a tau type
276 ; unless (isTauTy t_rhs) $
277 addErr (polyTyErr t_rhs)
279 -- (4) construct representation tycon
280 ; rep_tc_name <- newFamInstTyConName tc_name loc
281 ; tycon <- buildSynTyCon rep_tc_name t_tvs (SynonymTyCon t_rhs)
282 (Just (family, t_typats))
284 ; return $ Just (ATyCon tycon)
287 -- "newtype instance" and "data instance"
288 tcFamInstDecl1 (decl@TyData {tcdND = new_or_data, tcdLName = L loc tc_name,
290 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
291 do { -- check that the family declaration is for the right kind
292 unless (isAlgTyCon family) $
293 addErr (wrongKindOfFamily family)
295 ; -- (1) kind check the data declaration as usual
296 ; k_decl <- kcDataDecl decl k_tvs
297 ; let k_ctxt = tcdCtxt k_decl
298 k_cons = tcdCons k_decl
300 -- result kind must be '*' (otherwise, we have too few patterns)
301 ; checkTc (isLiftedTypeKind resKind) $ tooFewParmsErr tc_name
303 -- (2) type check indexed data type declaration
304 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
305 ; unbox_strict <- doptM Opt_UnboxStrictFields
307 -- kind check the type indexes and the context
308 ; t_typats <- mappM tcHsKindedType k_typats
309 ; stupid_theta <- tcHsKindedContext k_ctxt
312 -- - left-hand side contains no type family applications
313 -- (vanilla synonyms are fine, though)
314 ; mappM_ checkTyFamFreeness t_typats
316 -- - we don't use GADT syntax for indexed types
317 ; checkTc h98_syntax (badGadtIdxTyDecl tc_name)
319 -- - a newtype has exactly one constructor
320 ; checkTc (new_or_data == DataType || isSingleton k_cons) $
321 newtypeConError tc_name (length k_cons)
323 -- (4) construct representation tycon
324 ; rep_tc_name <- newFamInstTyConName tc_name loc
325 ; tycon <- fixM (\ tycon -> do
326 { data_cons <- mappM (addLocM (tcConDecl unbox_strict tycon t_tvs))
330 DataType -> return (mkDataTyConRhs data_cons)
331 NewType -> ASSERT( isSingleton data_cons )
332 mkNewTyConRhs rep_tc_name tycon (head data_cons)
333 ; buildAlgTyCon rep_tc_name t_tvs stupid_theta tc_rhs Recursive
334 False h98_syntax (Just (family, t_typats))
335 -- We always assume that indexed types are recursive. Why?
336 -- (1) Due to their open nature, we can never be sure that a
337 -- further instance might not introduce a new recursive
338 -- dependency. (2) They are always valid loop breakers as
339 -- they involve a coercion.
343 ; return $ Just (ATyCon tycon)
346 h98_syntax = case cons of -- All constructors have same shape
347 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
350 -- Check that a type index does not contain any type family applications
352 -- * Earlier phases have already checked that there are no foralls in the
353 -- type; we also cannot have PredTys and NoteTys are being skipped by using
356 checkTyFamFreeness :: Type -> TcM ()
357 checkTyFamFreeness ty | Just (tycon, tys) <- splitTyConApp_maybe ty
358 = if isSynTyCon tycon
359 then addErr $ tyFamAppInIndexErr ty
360 else mappM_ checkTyFamFreeness tys
361 -- splitTyConApp_maybe uses the core view; hence,
362 -- any synonym tycon must be a family tycon
364 | Just (ty1, ty2) <- splitAppTy_maybe ty
365 = checkTyFamFreeness ty1 >> checkTyFamFreeness ty2
367 | otherwise -- only vars remaining
371 -- Kind checking of indexed types
374 -- Kind check type patterns and kind annotate the embedded type variables.
376 -- * Here we check that a type instance matches its kind signature, but we do
377 -- not check whether there is a pattern for each type index; the latter
378 -- check is only required for type synonym instances.
380 kcIdxTyPats :: TyClDecl Name
381 -> ([LHsTyVarBndr Name] -> [LHsType Name] -> Kind -> TyCon -> TcM a)
382 -- ^^kinded tvs ^^kinded ty pats ^^res kind
384 kcIdxTyPats decl thing_inside
385 = kcHsTyVars (tcdTyVars decl) $ \tvs ->
386 do { family <- tcLookupLocatedTyCon (tcdLName decl)
387 ; let { (kinds, resKind) = splitKindFunTys (tyConKind family)
388 ; hs_typats = fromJust $ tcdTyPats decl }
390 -- we may not have more parameters than the kind indicates
391 ; checkTc (length kinds >= length hs_typats) $
392 tooManyParmsErr (tcdLName decl)
394 -- type functions can have a higher-kinded result
395 ; let resultKind = mkArrowKinds (drop (length hs_typats) kinds) resKind
396 ; typats <- TcRnMonad.zipWithM kcCheckHsType hs_typats kinds
397 ; thing_inside tvs typats resultKind family
403 %************************************************************************
407 %************************************************************************
409 We need to kind check all types in the mutually recursive group
410 before we know the kind of the type variables. For example:
413 op :: D b => a -> b -> b
416 bop :: (Monad c) => ...
418 Here, the kind of the locally-polymorphic type variable "b"
419 depends on *all the uses of class D*. For example, the use of
420 Monad c in bop's type signature means that D must have kind Type->Type.
422 However type synonyms work differently. They can have kinds which don't
423 just involve (->) and *:
424 type R = Int# -- Kind #
425 type S a = Array# a -- Kind * -> #
426 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
427 So we must infer their kinds from their right-hand sides *first* and then
428 use them, whereas for the mutually recursive data types D we bring into
429 scope kind bindings D -> k, where k is a kind variable, and do inference.
433 This treatment of type synonyms only applies to Haskell 98-style synonyms.
434 General type functions can be recursive, and hence, appear in `alg_decls'.
436 The kind of a type family is solely determinded by its kind signature;
437 hence, only kind signatures participate in the construction of the initial
438 kind environment (as constructed by `getInitialKind'). In fact, we ignore
439 instances of families altogether in the following. However, we need to
440 include the kinds of associated families into the construction of the
441 initial kind environment. (This is handled by `allDecls').
444 kcTyClDecls syn_decls alg_decls
445 = do { -- First extend the kind env with each data type, class, and
446 -- indexed type, mapping them to a type variable
447 let initialKindDecls = concat [allDecls decl | L _ decl <- alg_decls]
448 ; alg_kinds <- mappM getInitialKind initialKindDecls
449 ; tcExtendKindEnv alg_kinds $ do
451 -- Now kind-check the type synonyms, in dependency order
452 -- We do these differently to data type and classes,
453 -- because a type synonym can be an unboxed type
455 -- and a kind variable can't unify with UnboxedTypeKind
456 -- So we infer their kinds in dependency order
457 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
458 ; tcExtendKindEnv syn_kinds $ do
460 -- Now kind-check the data type, class, and kind signatures,
461 -- returning kind-annotated decls; we don't kind-check
462 -- instances of indexed types yet, but leave this to
464 { kc_alg_decls <- mappM (wrapLocM kcTyClDecl)
465 (filter (not . isFamInstDecl . unLoc) alg_decls)
467 ; return (kc_syn_decls, kc_alg_decls) }}}
469 -- get all declarations relevant for determining the initial kind
471 allDecls (decl@ClassDecl {tcdATs = ats}) = decl : [ at
474 allDecls decl | isFamInstDecl decl = []
477 ------------------------------------------------------------------------
478 getInitialKind :: TyClDecl Name -> TcM (Name, TcKind)
479 -- Only for data type, class, and indexed type declarations
480 -- Get as much info as possible from the data, class, or indexed type decl,
481 -- so as to maximise usefulness of error messages
483 = do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl)
484 ; res_kind <- mk_res_kind decl
485 ; return (tcdName decl, mkArrowKinds arg_kinds res_kind) }
487 mk_arg_kind (UserTyVar _) = newKindVar
488 mk_arg_kind (KindedTyVar _ kind) = return kind
490 mk_res_kind (TyFamily { tcdKind = Just kind }) = return kind
491 mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
492 -- On GADT-style declarations we allow a kind signature
493 -- data T :: *->* where { ... }
494 mk_res_kind other = return liftedTypeKind
498 kcSynDecls :: [SCC (LTyClDecl Name)]
499 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
500 [(Name,TcKind)]) -- Kind bindings
503 kcSynDecls (group : groups)
504 = do { (decl, nk) <- kcSynDecl group
505 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
506 ; return (decl:decls, nk:nks) }
509 kcSynDecl :: SCC (LTyClDecl Name)
510 -> TcM (LTyClDecl Name, -- Kind-annotated decls
511 (Name,TcKind)) -- Kind bindings
512 kcSynDecl (AcyclicSCC ldecl@(L loc decl))
513 = tcAddDeclCtxt decl $
514 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
515 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
516 <+> brackets (ppr k_tvs))
517 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
518 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
519 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
520 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
521 (unLoc (tcdLName decl), tc_kind)) })
523 kcSynDecl (CyclicSCC decls)
524 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
525 -- of out-of-scope tycons
527 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
529 ------------------------------------------------------------------------
530 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
531 -- Not used for type synonyms (see kcSynDecl)
533 kcTyClDecl decl@(TyData {})
534 = ASSERT( not . isFamInstDecl $ decl ) -- must not be a family instance
535 kcTyClDeclBody decl $
538 kcTyClDecl decl@(TyFamily {tcdKind = kind})
539 = kcTyClDeclBody decl $ \ tvs' ->
540 return (decl {tcdTyVars = tvs',
541 tcdKind = kind `mplus` Just liftedTypeKind})
542 -- default result kind is '*'
544 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs, tcdATs = ats})
545 = kcTyClDeclBody decl $ \ tvs' ->
546 do { is_boot <- tcIsHsBoot
547 ; ctxt' <- kcHsContext ctxt
548 ; ats' <- mappM (wrapLocM kcTyClDecl) ats
549 ; sigs' <- mappM (wrapLocM kc_sig ) sigs
550 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs',
553 kc_sig (TypeSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
554 ; return (TypeSig nm op_ty') }
555 kc_sig other_sig = return other_sig
557 kcTyClDecl decl@(ForeignType {})
560 kcTyClDeclBody :: TyClDecl Name
561 -> ([LHsTyVarBndr Name] -> TcM a)
563 -- getInitialKind has made a suitably-shaped kind for the type or class
564 -- Unpack it, and attribute those kinds to the type variables
565 -- Extend the env with bindings for the tyvars, taken from
566 -- the kind of the tycon/class. Give it to the thing inside, and
567 -- check the result kind matches
568 kcTyClDeclBody decl thing_inside
569 = tcAddDeclCtxt decl $
570 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
571 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
572 (kinds, _) = splitKindFunTys tc_kind
573 hs_tvs = tcdTyVars decl
574 kinded_tvs = ASSERT( length kinds >= length hs_tvs )
575 [ L loc (KindedTyVar (hsTyVarName tv) k)
576 | (L loc tv, k) <- zip hs_tvs kinds]
577 ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
579 -- Kind check a data declaration, assuming that we already extended the
580 -- kind environment with the type variables of the left-hand side (these
581 -- kinded type variables are also passed as the second parameter).
583 kcDataDecl :: TyClDecl Name -> [LHsTyVarBndr Name] -> TcM (TyClDecl Name)
584 kcDataDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
586 = do { ctxt' <- kcHsContext ctxt
587 ; cons' <- mappM (wrapLocM kc_con_decl) cons
588 ; return (decl {tcdTyVars = tvs, tcdCtxt = ctxt', tcdCons = cons'}) }
590 -- doc comments are typechecked to Nothing here
591 kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res _) = do
592 kcHsTyVars ex_tvs $ \ex_tvs' -> do
593 ex_ctxt' <- kcHsContext ex_ctxt
594 details' <- kc_con_details details
596 ResTyH98 -> return ResTyH98
597 ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
598 return (ConDecl name expl ex_tvs' ex_ctxt' details' res' Nothing)
600 kc_con_details (PrefixCon btys)
601 = do { btys' <- mappM kc_larg_ty btys ; return (PrefixCon btys') }
602 kc_con_details (InfixCon bty1 bty2)
603 = do { bty1' <- kc_larg_ty bty1; bty2' <- kc_larg_ty bty2; return (InfixCon bty1' bty2') }
604 kc_con_details (RecCon fields)
605 = do { fields' <- mappM kc_field fields; return (RecCon fields') }
607 kc_field (ConDeclField fld bty d) = do { bty' <- kc_larg_ty bty
608 ; return (ConDeclField fld bty' d) }
610 kc_larg_ty bty = case new_or_data of
611 DataType -> kcHsSigType bty
612 NewType -> kcHsLiftedSigType bty
613 -- Can't allow an unlifted type for newtypes, because we're effectively
614 -- going to remove the constructor while coercing it to a lifted type.
615 -- And newtypes can't be bang'd
619 %************************************************************************
621 \subsection{Type checking}
623 %************************************************************************
626 tcSynDecls :: [LTyClDecl Name] -> TcM [TyThing]
627 tcSynDecls [] = return []
628 tcSynDecls (decl : decls)
629 = do { syn_tc <- addLocM tcSynDecl decl
630 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls decls)
631 ; return (syn_tc : syn_tcs) }
635 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
636 = tcTyVarBndrs tvs $ \ tvs' -> do
637 { traceTc (text "tcd1" <+> ppr tc_name)
638 ; rhs_ty' <- tcHsKindedType rhs_ty
639 ; tycon <- buildSynTyCon tc_name tvs' (SynonymTyCon rhs_ty') Nothing
640 ; return (ATyCon tycon)
644 tcTyClDecl :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
646 tcTyClDecl calc_isrec decl
647 = tcAddDeclCtxt decl (tcTyClDecl1 calc_isrec decl)
649 -- "type family" declarations
650 tcTyClDecl1 _calc_isrec
651 (TyFamily {tcdFlavour = TypeFamily,
652 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = Just kind})
653 -- NB: kind at latest
656 = tcTyVarBndrs tvs $ \ tvs' -> do
657 { traceTc (text "type family: " <+> ppr tc_name)
658 ; idx_tys <- doptM Opt_TypeFamilies
660 -- Check that we don't use families without -ftype-families
661 ; checkTc idx_tys $ badFamInstDecl tc_name
663 ; tycon <- buildSynTyCon tc_name tvs' (OpenSynTyCon kind Nothing) Nothing
664 ; return [ATyCon tycon]
667 -- "newtype family" or "data family" declaration
668 tcTyClDecl1 _calc_isrec
669 (TyFamily {tcdFlavour = DataFamily,
670 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = mb_kind})
671 = tcTyVarBndrs tvs $ \ tvs' -> do
672 { traceTc (text "data family: " <+> ppr tc_name)
673 ; extra_tvs <- tcDataKindSig mb_kind
674 ; let final_tvs = tvs' ++ extra_tvs -- we may not need these
676 ; idx_tys <- doptM Opt_TypeFamilies
678 -- Check that we don't use families without -ftype-families
679 ; checkTc idx_tys $ badFamInstDecl tc_name
681 ; tycon <- buildAlgTyCon tc_name final_tvs []
682 mkOpenDataTyConRhs Recursive False True Nothing
683 ; return [ATyCon tycon]
686 -- "newtype" and "data"
687 tcTyClDecl1 calc_isrec
688 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
689 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
690 = tcTyVarBndrs tvs $ \ tvs' -> do
691 { extra_tvs <- tcDataKindSig mb_ksig
692 ; let final_tvs = tvs' ++ extra_tvs
693 ; stupid_theta <- tcHsKindedContext ctxt
694 ; want_generic <- doptM Opt_Generics
695 ; unbox_strict <- doptM Opt_UnboxStrictFields
696 ; gla_exts <- doptM Opt_GlasgowExts
697 ; empty_data_decls <- doptM Opt_EmptyDataDecls
698 ; kind_signatures <- doptM Opt_KindSignatures
699 ; gadt_ok <- doptM Opt_GADTs
700 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
702 -- Check that we don't use GADT syntax in H98 world
703 ; checkTc (gadt_ok || h98_syntax) (badGadtDecl tc_name)
705 -- Check that we don't use kind signatures without Glasgow extensions
706 ; checkTc (kind_signatures || isNothing mb_ksig) (badSigTyDecl tc_name)
708 -- Check that the stupid theta is empty for a GADT-style declaration
709 ; checkTc (null stupid_theta || h98_syntax) (badStupidTheta tc_name)
711 -- Check that there's at least one condecl,
712 -- or else we're reading an hs-boot file, or -XEmptyDataDecls
713 ; checkTc (not (null cons) || empty_data_decls || is_boot)
714 (emptyConDeclsErr tc_name)
716 -- Check that a newtype has exactly one constructor
717 ; checkTc (new_or_data == DataType || isSingleton cons)
718 (newtypeConError tc_name (length cons))
720 ; tycon <- fixM (\ tycon -> do
721 { data_cons <- mappM (addLocM (tcConDecl unbox_strict tycon final_tvs))
724 if null cons && is_boot -- In a hs-boot file, empty cons means
725 then return AbstractTyCon -- "don't know"; hence Abstract
726 else case new_or_data of
727 DataType -> return (mkDataTyConRhs data_cons)
729 ASSERT( isSingleton data_cons )
730 mkNewTyConRhs tc_name tycon (head data_cons)
731 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
732 (want_generic && canDoGenerics data_cons) h98_syntax Nothing
734 ; return [ATyCon tycon]
737 is_rec = calc_isrec tc_name
738 h98_syntax = case cons of -- All constructors have same shape
739 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
742 tcTyClDecl1 calc_isrec
743 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
744 tcdCtxt = ctxt, tcdMeths = meths,
745 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
746 = tcTyVarBndrs tvs $ \ tvs' -> do
747 { ctxt' <- tcHsKindedContext ctxt
748 ; fds' <- mappM (addLocM tc_fundep) fundeps
749 ; atss <- mappM (addLocM (tcTyClDecl1 (const Recursive))) ats
750 ; let ats' = zipWith setTyThingPoss atss (map (tcdTyVars . unLoc) ats)
751 ; sig_stuff <- tcClassSigs class_name sigs meths
752 ; clas <- fixM (\ clas ->
753 let -- This little knot is just so we can get
754 -- hold of the name of the class TyCon, which we
755 -- need to look up its recursiveness
756 tycon_name = tyConName (classTyCon clas)
757 tc_isrec = calc_isrec tycon_name
759 buildClass class_name tvs' ctxt' fds' ats'
761 ; return (AClass clas : ats')
762 -- NB: Order is important due to the call to `mkGlobalThings' when
763 -- tying the the type and class declaration type checking knot.
766 tc_fundep (tvs1, tvs2) = do { tvs1' <- mappM tcLookupTyVar tvs1 ;
767 ; tvs2' <- mappM tcLookupTyVar tvs2 ;
768 ; return (tvs1', tvs2') }
770 -- For each AT argument compute the position of the corresponding class
771 -- parameter in the class head. This will later serve as a permutation
772 -- vector when checking the validity of instance declarations.
773 setTyThingPoss [ATyCon tycon] atTyVars =
774 let classTyVars = hsLTyVarNames tvs
776 . map (`elemIndex` classTyVars)
779 -- There will be no Nothing, as we already passed renaming
781 ATyCon (setTyConArgPoss tycon poss)
782 setTyThingPoss _ _ = panic "TcTyClsDecls.setTyThingPoss"
784 tcTyClDecl1 calc_isrec
785 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
786 = returnM [ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0)]
788 -----------------------------------
789 tcConDecl :: Bool -- True <=> -funbox-strict_fields
794 tcConDecl unbox_strict 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 = map cd_fld_name fields
819 btys = map cd_fld_type 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, _, _, res1) = dataConSig con1
1012 fty1 = dataConFieldType con1 label
1014 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
1015 = do { checkFieldCompat label con1 con2 ts1 res1 res2 fty1 fty2
1016 ; checkFieldCompat label con2 con1 ts2 res2 res1 fty2 fty1 }
1018 (tvs2, _, _, res2) = dataConSig 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 = tcMatchTy 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)
1036 ; ifM (isNewTyCon tc) (checkNewDataCon con)
1039 ctxt = ConArgCtxt (dataConName con)
1041 -------------------------------
1042 checkNewDataCon :: DataCon -> TcM ()
1043 -- Checks for the data constructor of a newtype
1045 = do { checkTc (isSingleton arg_tys) (newtypeFieldErr con (length arg_tys))
1047 ; checkTc (null eq_spec) (newtypePredError con)
1048 -- Return type is (T a b c)
1049 ; checkTc (null ex_tvs && null theta) (newtypeExError con)
1051 ; checkTc (not (any isMarkedStrict (dataConStrictMarks con)))
1052 (newtypeStrictError con)
1056 (_univ_tvs, ex_tvs, eq_spec, theta, arg_tys, _res_ty) = dataConFullSig con
1058 -------------------------------
1059 checkValidClass :: Class -> TcM ()
1061 = do { -- CHECK ARITY 1 FOR HASKELL 1.4
1062 gla_exts <- doptM Opt_GlasgowExts
1063 ; multi_param_type_classes <- doptM Opt_MultiParamTypeClasses
1065 -- Check that the class is unary, unless GlaExs
1066 ; checkTc (notNull tyvars) (nullaryClassErr cls)
1067 ; checkTc (multi_param_type_classes || unary) (classArityErr cls)
1069 -- Check the super-classes
1070 ; checkValidTheta (ClassSCCtxt (className cls)) theta
1072 -- Check the class operations
1073 ; mappM_ (check_op gla_exts) op_stuff
1075 -- Check that if the class has generic methods, then the
1076 -- class has only one parameter. We can't do generic
1077 -- multi-parameter type classes!
1078 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
1081 (tyvars, theta, _, op_stuff) = classBigSig cls
1082 unary = isSingleton tyvars
1083 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
1085 check_op gla_exts (sel_id, dm)
1086 = addErrCtxt (classOpCtxt sel_id tau) $ do
1087 { checkValidTheta SigmaCtxt (tail theta)
1088 -- The 'tail' removes the initial (C a) from the
1089 -- class itself, leaving just the method type
1091 ; checkValidType (FunSigCtxt op_name) tau
1093 -- Check that the type mentions at least one of
1094 -- the class type variables...or at least one reachable
1095 -- from one of the class variables. Example: tc223
1096 -- class Error e => Game b mv e | b -> mv e where
1097 -- newBoard :: MonadState b m => m ()
1098 -- Here, MonadState has a fundep m->b, so newBoard is fine
1099 ; let grown_tyvars = grow theta (mkVarSet tyvars)
1100 ; checkTc (tyVarsOfType tau `intersectsVarSet` grown_tyvars)
1101 (noClassTyVarErr cls sel_id)
1103 -- Check that for a generic method, the type of
1104 -- the method is sufficiently simple
1105 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
1106 (badGenericMethodType op_name op_ty)
1109 op_name = idName sel_id
1110 op_ty = idType sel_id
1111 (_,theta1,tau1) = tcSplitSigmaTy op_ty
1112 (_,theta2,tau2) = tcSplitSigmaTy tau1
1113 (theta,tau) | gla_exts = (theta1 ++ theta2, tau2)
1114 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
1115 -- Ugh! The function might have a type like
1116 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
1117 -- With -fglasgow-exts, we want to allow this, even though the inner
1118 -- forall has an (Eq a) constraint. Whereas in general, each constraint
1119 -- in the context of a for-all must mention at least one quantified
1120 -- type variable. What a mess!
1123 ---------------------------------------------------------------------
1124 resultTypeMisMatch field_name con1 con2
1125 = vcat [sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1126 ptext SLIT("have a common field") <+> quotes (ppr field_name) <> comma],
1127 nest 2 $ ptext SLIT("but have different result types")]
1128 fieldTypeMisMatch field_name con1 con2
1129 = sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1130 ptext SLIT("give different types for field"), quotes (ppr field_name)]
1132 dataConCtxt con = ptext SLIT("In the definition of data constructor") <+> quotes (ppr con)
1134 classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
1135 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
1138 = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
1141 = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
1142 parens (ptext SLIT("Use -XMultiParamTypeClasses to allow multi-parameter classes"))]
1144 noClassTyVarErr clas op
1145 = sep [ptext SLIT("The class method") <+> quotes (ppr op),
1146 ptext SLIT("mentions none of the type variables of the class") <+>
1147 ppr clas <+> hsep (map ppr (classTyVars clas))]
1149 genericMultiParamErr clas
1150 = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
1151 ptext SLIT("cannot have generic methods")
1153 badGenericMethodType op op_ty
1154 = hang (ptext SLIT("Generic method type is too complex"))
1155 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
1156 ptext SLIT("You can only use type variables, arrows, lists, and tuples")])
1159 = setSrcSpan (getLoc (head sorted_decls)) $
1160 addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
1161 nest 2 (vcat (map ppr_decl sorted_decls))])
1163 sorted_decls = sortLocated syn_decls
1164 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
1167 = setSrcSpan (getLoc (head sorted_decls)) $
1168 addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
1169 nest 2 (vcat (map ppr_decl sorted_decls))])
1171 sorted_decls = sortLocated cls_decls
1172 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
1174 sortLocated :: [Located a] -> [Located a]
1175 sortLocated things = sortLe le things
1177 le (L l1 _) (L l2 _) = l1 <= l2
1179 badDataConTyCon data_con
1180 = hang (ptext SLIT("Data constructor") <+> quotes (ppr data_con) <+>
1181 ptext SLIT("returns type") <+> quotes (ppr (dataConTyCon data_con)))
1182 2 (ptext SLIT("instead of its parent type"))
1185 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
1186 , nest 2 (parens $ ptext SLIT("Use -X=GADT to allow GADTs")) ]
1188 badStupidTheta tc_name
1189 = ptext SLIT("A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
1191 newtypeConError tycon n
1192 = sep [ptext SLIT("A newtype must have exactly one constructor,"),
1193 nest 2 $ ptext SLIT("but") <+> quotes (ppr tycon) <+> ptext SLIT("has") <+> speakN n ]
1196 = sep [ptext SLIT("A newtype constructor cannot have an existential context,"),
1197 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
1199 newtypeStrictError con
1200 = sep [ptext SLIT("A newtype constructor cannot have a strictness annotation,"),
1201 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
1203 newtypePredError con
1204 = sep [ptext SLIT("A newtype constructor must have a return type of form T a1 ... an"),
1205 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does not")]
1207 newtypeFieldErr con_name n_flds
1208 = sep [ptext SLIT("The constructor of a newtype must have exactly one field"),
1209 nest 2 $ ptext SLIT("but") <+> quotes (ppr con_name) <+> ptext SLIT("has") <+> speakN n_flds]
1211 badSigTyDecl tc_name
1212 = vcat [ ptext SLIT("Illegal kind signature") <+>
1213 quotes (ppr tc_name)
1214 , nest 2 (parens $ ptext SLIT("Use -XKindSignatures to allow kind signatures")) ]
1216 badFamInstDecl tc_name
1217 = vcat [ ptext SLIT("Illegal family instance for") <+>
1218 quotes (ppr tc_name)
1219 , nest 2 (parens $ ptext SLIT("Use -X=TypeFamilies to allow indexed type families")) ]
1221 badGadtIdxTyDecl tc_name
1222 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+>
1223 quotes (ppr tc_name)
1224 , nest 2 (parens $ ptext SLIT("Family instances can not yet use GADT declarations")) ]
1226 tooManyParmsErr tc_name
1227 = ptext SLIT("Family instance has too many parameters:") <+>
1228 quotes (ppr tc_name)
1230 tooFewParmsErr tc_name
1231 = ptext SLIT("Family instance has too few parameters:") <+>
1232 quotes (ppr tc_name)
1234 badBootFamInstDeclErr =
1235 ptext SLIT("Illegal family instance in hs-boot file")
1237 wrongKindOfFamily family =
1238 ptext SLIT("Wrong category of family instance; declaration was for a") <+>
1241 kindOfFamily | isSynTyCon family = ptext SLIT("type synonym")
1242 | isAlgTyCon family = ptext SLIT("data type")
1243 | otherwise = pprPanic "wrongKindOfFamily" (ppr family)
1246 = hang (ptext SLIT("Illegal polymorphic type in type instance") <> colon) 4 $
1249 tyFamAppInIndexErr ty
1250 = hang (ptext SLIT("Illegal type family application in type instance") <>
1254 emptyConDeclsErr tycon
1255 = sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
1256 nest 2 $ ptext SLIT("(-XEmptyDataDecls permits this)")]