2 % (c) The University of Glasgow 2006
3 % (c) The AQUA Project, Glasgow University, 1996-1998
6 TcTyClsDecls: Typecheck type and class declarations
10 tcTyAndClassDecls, tcFamInstDecl
13 #include "HsVersions.h"
47 import Data.List ( partition, elemIndex )
48 import Control.Monad ( mplus )
52 %************************************************************************
54 \subsection{Type checking for type and class declarations}
56 %************************************************************************
60 Consider a mutually-recursive group, binding
61 a type constructor T and a class C.
63 Step 1: getInitialKind
64 Construct a KindEnv by binding T and C to a kind variable
67 In that environment, do a kind check
69 Step 3: Zonk the kinds
71 Step 4: buildTyConOrClass
72 Construct an environment binding T to a TyCon and C to a Class.
73 a) Their kinds comes from zonking the relevant kind variable
74 b) Their arity (for synonyms) comes direct from the decl
75 c) The funcional dependencies come from the decl
76 d) The rest comes a knot-tied binding of T and C, returned from Step 4
77 e) The variances of the tycons in the group is calculated from
81 In this environment, walk over the decls, constructing the TyCons and Classes.
82 This uses in a strict way items (a)-(c) above, which is why they must
83 be constructed in Step 4. Feed the results back to Step 4.
84 For this step, pass the is-recursive flag as the wimp-out flag
88 Step 6: Extend environment
89 We extend the type environment with bindings not only for the TyCons and Classes,
90 but also for their "implicit Ids" like data constructors and class selectors
92 Step 7: checkValidTyCl
93 For a recursive group only, check all the decls again, just
94 to check all the side conditions on validity. We could not
95 do this before because we were in a mutually recursive knot.
97 Identification of recursive TyCons
98 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
99 The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to
102 Identifying a TyCon as recursive serves two purposes
104 1. Avoid infinite types. Non-recursive newtypes are treated as
105 "transparent", like type synonyms, after the type checker. If we did
106 this for all newtypes, we'd get infinite types. So we figure out for
107 each newtype whether it is "recursive", and add a coercion if so. In
108 effect, we are trying to "cut the loops" by identifying a loop-breaker.
110 2. Avoid infinite unboxing. This is nothing to do with newtypes.
114 Well, this function diverges, but we don't want the strictness analyser
115 to diverge. But the strictness analyser will diverge because it looks
116 deeper and deeper into the structure of T. (I believe there are
117 examples where the function does something sane, and the strictness
118 analyser still diverges, but I can't see one now.)
120 Now, concerning (1), the FC2 branch currently adds a coercion for ALL
121 newtypes. I did this as an experiment, to try to expose cases in which
122 the coercions got in the way of optimisations. If it turns out that we
123 can indeed always use a coercion, then we don't risk recursive types,
124 and don't need to figure out what the loop breakers are.
126 For newtype *families* though, we will always have a coercion, so they
127 are always loop breakers! So you can easily adjust the current
128 algorithm by simply treating all newtype families as loop breakers (and
129 indeed type families). I think.
132 tcTyAndClassDecls :: ModDetails -> [LTyClDecl Name]
133 -> TcM TcGblEnv -- Input env extended by types and classes
134 -- and their implicit Ids,DataCons
135 tcTyAndClassDecls boot_details allDecls
136 = do { -- Omit instances of type families; they are handled together
137 -- with the *heads* of class instances
138 ; let decls = filter (not . isFamInstDecl . unLoc) allDecls
140 -- First check for cyclic type synonysm or classes
141 -- See notes with checkCycleErrs
142 ; checkCycleErrs decls
144 ; traceTc (text "tcTyAndCl" <+> ppr mod)
145 ; (syn_tycons, alg_tyclss) <- fixM (\ ~(rec_syn_tycons, rec_alg_tyclss) ->
146 do { let { -- Seperate ordinary synonyms from all other type and
147 -- class declarations and add all associated type
148 -- declarations from type classes. The latter is
149 -- required so that the temporary environment for the
150 -- knot includes all associated family declarations.
151 ; (syn_decls, alg_decls) = partition (isSynDecl . unLoc)
153 ; alg_at_decls = concatMap addATs alg_decls
155 -- Extend the global env with the knot-tied results
156 -- for data types and classes
158 -- We must populate the environment with the loop-tied
159 -- T's right away, because the kind checker may "fault
160 -- in" some type constructors that recursively
162 ; let gbl_things = mkGlobalThings alg_at_decls rec_alg_tyclss
163 ; tcExtendRecEnv gbl_things $ do
165 -- Kind-check the declarations
166 { (kc_syn_decls, kc_alg_decls) <- kcTyClDecls syn_decls alg_decls
168 ; let { -- Calculate rec-flag
169 ; calc_rec = calcRecFlags boot_details rec_alg_tyclss
170 ; tc_decl = addLocM (tcTyClDecl calc_rec) }
172 -- Type-check the type synonyms, and extend the envt
173 ; syn_tycons <- tcSynDecls kc_syn_decls
174 ; tcExtendGlobalEnv syn_tycons $ do
176 -- Type-check the data types and classes
177 { alg_tyclss <- mappM tc_decl kc_alg_decls
178 ; return (syn_tycons, concat alg_tyclss)
180 -- Finished with knot-tying now
181 -- Extend the environment with the finished things
182 ; tcExtendGlobalEnv (syn_tycons ++ alg_tyclss) $ do
184 -- Perform the validity check
185 { traceTc (text "ready for validity check")
186 ; mappM_ (addLocM checkValidTyCl) decls
187 ; traceTc (text "done")
189 -- Add the implicit things;
190 -- we want them in the environment because
191 -- they may be mentioned in interface files
192 -- NB: All associated types and their implicit things will be added a
193 -- second time here. This doesn't matter as the definitions are
195 ; let { implicit_things = concatMap implicitTyThings alg_tyclss }
196 ; traceTc ((text "Adding" <+> ppr alg_tyclss)
197 $$ (text "and" <+> ppr implicit_things))
198 ; tcExtendGlobalEnv implicit_things getGblEnv
201 -- Pull associated types out of class declarations, to tie them into the
203 -- NB: We put them in the same place in the list as `tcTyClDecl' will
204 -- eventually put the matching `TyThing's. That's crucial; otherwise,
205 -- the two argument lists of `mkGlobalThings' don't match up.
206 addATs decl@(L _ (ClassDecl {tcdATs = ats})) = decl : ats
209 mkGlobalThings :: [LTyClDecl Name] -- The decls
210 -> [TyThing] -- Knot-tied, in 1-1 correspondence with the decls
212 -- Driven by the Decls, and treating the TyThings lazily
213 -- make a TypeEnv for the new things
214 mkGlobalThings decls things
215 = map mk_thing (decls `zipLazy` things)
217 mk_thing (L _ (ClassDecl {tcdLName = L _ name}), ~(AClass cl))
219 mk_thing (L _ decl, ~(ATyCon tc))
220 = (tcdName decl, ATyCon tc)
224 %************************************************************************
226 \subsection{Type checking family instances}
228 %************************************************************************
230 Family instances are somewhat of a hybrid. They are processed together with
231 class instance heads, but can contain data constructors and hence they share a
232 lot of kinding and type checking code with ordinary algebraic data types (and
236 tcFamInstDecl :: LTyClDecl Name -> TcM (Maybe TyThing) -- Nothing if error
237 tcFamInstDecl (L loc decl)
238 = -- Prime error recovery, set source location
239 recoverM (returnM Nothing) $
242 do { -- type families require -ftype-families and can't be in an
244 ; gla_exts <- doptM Opt_TypeFamilies
245 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
246 ; checkTc gla_exts $ badFamInstDecl (tcdLName decl)
247 ; checkTc (not is_boot) $ badBootFamInstDeclErr
249 -- perform kind and type checking
250 ; tcFamInstDecl1 decl
253 tcFamInstDecl1 :: TyClDecl Name -> TcM (Maybe TyThing) -- Nothing if error
256 tcFamInstDecl1 (decl@TySynonym {tcdLName = L loc tc_name})
257 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
258 do { -- check that the family declaration is for a synonym
259 unless (isSynTyCon family) $
260 addErr (wrongKindOfFamily family)
262 ; -- (1) kind check the right-hand side of the type equation
263 ; k_rhs <- kcCheckHsType (tcdSynRhs decl) resKind
265 -- (2) type check type equation
266 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
267 ; t_typats <- mappM tcHsKindedType k_typats
268 ; t_rhs <- tcHsKindedType k_rhs
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 ; gadt_ok <- doptM Opt_GADTs
698 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
700 -- Check that we don't use GADT syntax in H98 world
701 ; checkTc (gadt_ok || h98_syntax) (badGadtDecl tc_name)
703 -- Check that we don't use kind signatures without Glasgow extensions
704 ; checkTc (gla_exts || isNothing mb_ksig) (badSigTyDecl tc_name)
706 -- Check that the stupid theta is empty for a GADT-style declaration
707 ; checkTc (null stupid_theta || h98_syntax) (badStupidTheta tc_name)
709 -- Check that there's at least one condecl,
710 -- or else we're reading an hs-boot file, or -fglasgow-exts
711 ; checkTc (not (null cons) || gla_exts || is_boot)
712 (emptyConDeclsErr tc_name)
714 -- Check that a newtype has exactly one constructor
715 ; checkTc (new_or_data == DataType || isSingleton cons)
716 (newtypeConError tc_name (length cons))
718 ; tycon <- fixM (\ tycon -> do
719 { data_cons <- mappM (addLocM (tcConDecl unbox_strict tycon final_tvs))
722 if null cons && is_boot -- In a hs-boot file, empty cons means
723 then return AbstractTyCon -- "don't know"; hence Abstract
724 else case new_or_data of
725 DataType -> return (mkDataTyConRhs data_cons)
727 ASSERT( isSingleton data_cons )
728 mkNewTyConRhs tc_name tycon (head data_cons)
729 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
730 (want_generic && canDoGenerics data_cons) h98_syntax Nothing
732 ; return [ATyCon tycon]
735 is_rec = calc_isrec tc_name
736 h98_syntax = case cons of -- All constructors have same shape
737 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
740 tcTyClDecl1 calc_isrec
741 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
742 tcdCtxt = ctxt, tcdMeths = meths,
743 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
744 = tcTyVarBndrs tvs $ \ tvs' -> do
745 { ctxt' <- tcHsKindedContext ctxt
746 ; fds' <- mappM (addLocM tc_fundep) fundeps
747 ; atss <- mappM (addLocM (tcTyClDecl1 (const Recursive))) ats
748 ; let ats' = zipWith setTyThingPoss atss (map (tcdTyVars . unLoc) ats)
749 ; sig_stuff <- tcClassSigs class_name sigs meths
750 ; clas <- fixM (\ clas ->
751 let -- This little knot is just so we can get
752 -- hold of the name of the class TyCon, which we
753 -- need to look up its recursiveness
754 tycon_name = tyConName (classTyCon clas)
755 tc_isrec = calc_isrec tycon_name
757 buildClass class_name tvs' ctxt' fds' ats'
759 ; return (AClass clas : ats')
760 -- NB: Order is important due to the call to `mkGlobalThings' when
761 -- tying the the type and class declaration type checking knot.
764 tc_fundep (tvs1, tvs2) = do { tvs1' <- mappM tcLookupTyVar tvs1 ;
765 ; tvs2' <- mappM tcLookupTyVar tvs2 ;
766 ; return (tvs1', tvs2') }
768 -- For each AT argument compute the position of the corresponding class
769 -- parameter in the class head. This will later serve as a permutation
770 -- vector when checking the validity of instance declarations.
771 setTyThingPoss [ATyCon tycon] atTyVars =
772 let classTyVars = hsLTyVarNames tvs
774 . map (`elemIndex` classTyVars)
777 -- There will be no Nothing, as we already passed renaming
779 ATyCon (setTyConArgPoss tycon poss)
780 setTyThingPoss _ _ = panic "TcTyClsDecls.setTyThingPoss"
782 tcTyClDecl1 calc_isrec
783 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
784 = returnM [ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0)]
786 -----------------------------------
787 tcConDecl :: Bool -- True <=> -funbox-strict_fields
792 tcConDecl unbox_strict tycon tc_tvs -- Data types
793 (ConDecl name _ tvs ctxt details res_ty _)
794 = tcTyVarBndrs tvs $ \ tvs' -> do
795 { ctxt' <- tcHsKindedContext ctxt
796 ; (univ_tvs, ex_tvs, eq_preds, data_tc) <- tcResultType tycon tc_tvs tvs' res_ty
798 -- Tiresome: tidy the tyvar binders, since tc_tvs and tvs' may have the same OccNames
799 tc_datacon is_infix field_lbls btys
800 = do { let bangs = map getBangStrictness btys
801 ; arg_tys <- mappM tcHsBangType btys
802 ; buildDataCon (unLoc name) is_infix
803 (argStrictness unbox_strict bangs arg_tys)
804 (map unLoc field_lbls)
805 univ_tvs ex_tvs eq_preds ctxt' arg_tys
807 -- NB: we put data_tc, the type constructor gotten from the
808 -- constructor type signature into the data constructor;
809 -- that way checkValidDataCon can complain if it's wrong.
812 PrefixCon btys -> tc_datacon False [] btys
813 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
814 RecCon fields -> tc_datacon False field_names btys
816 field_names = map cd_fld_name fields
817 btys = map cd_fld_type fields
820 tcResultType :: TyCon
821 -> [TyVar] -- data T a b c = ...
822 -> [TyVar] -- where MkT :: forall a b c. ...
824 -> TcM ([TyVar], -- Universal
825 [TyVar], -- Existential (distinct OccNames from univs)
826 [(TyVar,Type)], -- Equality predicates
827 TyCon) -- TyCon given in the ResTy
828 -- We don't check that the TyCon given in the ResTy is
829 -- the same as the parent tycon, becuase we are in the middle
830 -- of a recursive knot; so it's postponed until checkValidDataCon
832 tcResultType decl_tycon tc_tvs dc_tvs ResTyH98
833 = return (tc_tvs, dc_tvs, [], decl_tycon)
834 -- In H98 syntax the dc_tvs are the existential ones
835 -- data T a b c = forall d e. MkT ...
836 -- The {a,b,c} are tc_tvs, and {d,e} are dc_tvs
838 tcResultType _ tc_tvs dc_tvs (ResTyGADT res_ty)
839 -- E.g. data T a b c where
840 -- MkT :: forall x y z. T (x,y) z z
842 -- ([a,z,c], [x,y], [a:=:(x,y), c:=:z], T)
844 = do { (dc_tycon, res_tys) <- tcLHsConResTy res_ty
846 ; let univ_tvs = choose_univs [] tidy_tc_tvs res_tys
847 -- Each univ_tv is either a dc_tv or a tc_tv
848 ex_tvs = dc_tvs `minusList` univ_tvs
849 eq_spec = [ (tv, ty) | (tv,ty) <- univ_tvs `zip` res_tys,
851 ; return (univ_tvs, ex_tvs, eq_spec, dc_tycon) }
853 -- choose_univs uses the res_ty itself if it's a type variable
854 -- and hasn't already been used; otherwise it uses one of the tc_tvs
855 choose_univs used tc_tvs []
856 = ASSERT( null tc_tvs ) []
857 choose_univs used (tc_tv:tc_tvs) (res_ty:res_tys)
858 | Just tv <- tcGetTyVar_maybe res_ty, not (tv `elem` used)
859 = tv : choose_univs (tv:used) tc_tvs res_tys
861 = tc_tv : choose_univs used tc_tvs res_tys
863 -- NB: tc_tvs and dc_tvs are distinct, but
864 -- we want them to be *visibly* distinct, both for
865 -- interface files and general confusion. So rename
866 -- the tc_tvs, since they are not used yet (no
867 -- consequential renaming needed)
868 init_occ_env = initTidyOccEnv (map getOccName dc_tvs)
869 (_, tidy_tc_tvs) = mapAccumL tidy_one init_occ_env tc_tvs
870 tidy_one env tv = (env', setTyVarName tv (tidyNameOcc name occ'))
873 (env', occ') = tidyOccName env (getOccName name)
876 argStrictness :: Bool -- True <=> -funbox-strict_fields
878 -> [TcType] -> [StrictnessMark]
879 argStrictness unbox_strict bangs arg_tys
880 = ASSERT( length bangs == length arg_tys )
881 zipWith (chooseBoxingStrategy unbox_strict) arg_tys bangs
883 -- We attempt to unbox/unpack a strict field when either:
884 -- (i) The field is marked '!!', or
885 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
887 -- We have turned off unboxing of newtypes because coercions make unboxing
888 -- and reboxing more complicated
889 chooseBoxingStrategy :: Bool -> TcType -> HsBang -> StrictnessMark
890 chooseBoxingStrategy unbox_strict_fields arg_ty bang
892 HsNoBang -> NotMarkedStrict
893 HsStrict | unbox_strict_fields
894 && can_unbox arg_ty -> MarkedUnboxed
895 HsUnbox | can_unbox arg_ty -> MarkedUnboxed
896 other -> MarkedStrict
898 -- we can unbox if the type is a chain of newtypes with a product tycon
900 can_unbox arg_ty = case splitTyConApp_maybe arg_ty of
902 Just (arg_tycon, tycon_args) ->
903 not (isRecursiveTyCon arg_tycon) && -- Note [Recusive unboxing]
904 isProductTyCon arg_tycon &&
905 (if isNewTyCon arg_tycon then
906 can_unbox (newTyConInstRhs arg_tycon tycon_args)
910 Note [Recursive unboxing]
911 ~~~~~~~~~~~~~~~~~~~~~~~~~
912 Be careful not to try to unbox this!
914 But it's the *argument* type that matters. This is fine:
916 because Int is non-recursive.
918 %************************************************************************
920 \subsection{Dependency analysis}
922 %************************************************************************
924 Validity checking is done once the mutually-recursive knot has been
925 tied, so we can look at things freely.
928 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
929 checkCycleErrs tyclss
933 = do { mappM_ recClsErr cls_cycles
934 ; failM } -- Give up now, because later checkValidTyCl
935 -- will loop if the synonym is recursive
937 cls_cycles = calcClassCycles tyclss
939 checkValidTyCl :: TyClDecl Name -> TcM ()
940 -- We do the validity check over declarations, rather than TyThings
941 -- only so that we can add a nice context with tcAddDeclCtxt
943 = tcAddDeclCtxt decl $
944 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
945 ; traceTc (text "Validity of" <+> ppr thing)
947 ATyCon tc -> checkValidTyCon tc
948 AClass cl -> checkValidClass cl
949 ; traceTc (text "Done validity of" <+> ppr thing)
952 -------------------------
953 -- For data types declared with record syntax, we require
954 -- that each constructor that has a field 'f'
955 -- (a) has the same result type
956 -- (b) has the same type for 'f'
957 -- module alpha conversion of the quantified type variables
958 -- of the constructor.
960 checkValidTyCon :: TyCon -> TcM ()
963 = case synTyConRhs tc of
964 OpenSynTyCon _ _ -> return ()
965 SynonymTyCon ty -> checkValidType syn_ctxt ty
967 = -- Check the context on the data decl
968 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
970 -- Check arg types of data constructors
971 mappM_ (checkValidDataCon tc) data_cons `thenM_`
973 -- Check that fields with the same name share a type
974 mappM_ check_fields groups
977 syn_ctxt = TySynCtxt name
979 data_cons = tyConDataCons tc
981 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
982 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
983 get_fields con = dataConFieldLabels con `zip` repeat con
984 -- dataConFieldLabels may return the empty list, which is fine
986 -- See Note [GADT record selectors] in MkId.lhs
987 -- We must check (a) that the named field has the same
988 -- type in each constructor
989 -- (b) that those constructors have the same result type
991 -- However, the constructors may have differently named type variable
992 -- and (worse) we don't know how the correspond to each other. E.g.
993 -- C1 :: forall a b. { f :: a, g :: b } -> T a b
994 -- C2 :: forall d c. { f :: c, g :: c } -> T c d
996 -- So what we do is to ust Unify.tcMatchTys to compare the first candidate's
997 -- result type against other candidates' types BOTH WAYS ROUND.
998 -- If they magically agrees, take the substitution and
999 -- apply them to the latter ones, and see if they match perfectly.
1000 check_fields fields@((label, con1) : other_fields)
1001 -- These fields all have the same name, but are from
1002 -- different constructors in the data type
1003 = recoverM (return ()) $ mapM_ checkOne other_fields
1004 -- Check that all the fields in the group have the same type
1005 -- NB: this check assumes that all the constructors of a given
1006 -- data type use the same type variables
1008 (tvs1, _, _, res1) = dataConSig con1
1010 fty1 = dataConFieldType con1 label
1012 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
1013 = do { checkFieldCompat label con1 con2 ts1 res1 res2 fty1 fty2
1014 ; checkFieldCompat label con2 con1 ts2 res2 res1 fty2 fty1 }
1016 (tvs2, _, _, res2) = dataConSig con2
1018 fty2 = dataConFieldType con2 label
1020 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
1021 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
1022 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
1024 mb_subst1 = tcMatchTy tvs1 res1 res2
1025 mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
1027 -------------------------------
1028 checkValidDataCon :: TyCon -> DataCon -> TcM ()
1029 checkValidDataCon tc con
1030 = setSrcSpan (srcLocSpan (getSrcLoc con)) $
1031 addErrCtxt (dataConCtxt con) $
1032 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
1033 ; checkValidType ctxt (dataConUserType con)
1034 ; ifM (isNewTyCon tc) (checkNewDataCon con)
1037 ctxt = ConArgCtxt (dataConName con)
1039 -------------------------------
1040 checkNewDataCon :: DataCon -> TcM ()
1041 -- Checks for the data constructor of a newtype
1043 = do { checkTc (isSingleton arg_tys) (newtypeFieldErr con (length arg_tys))
1045 ; checkTc (null eq_spec) (newtypePredError con)
1046 -- Return type is (T a b c)
1047 ; checkTc (null ex_tvs && null theta) (newtypeExError con)
1049 ; checkTc (not (any isMarkedStrict (dataConStrictMarks con)))
1050 (newtypeStrictError con)
1054 (_univ_tvs, ex_tvs, eq_spec, theta, arg_tys, _res_ty) = dataConFullSig con
1056 -------------------------------
1057 checkValidClass :: Class -> TcM ()
1059 = do { -- CHECK ARITY 1 FOR HASKELL 1.4
1060 gla_exts <- doptM Opt_GlasgowExts
1062 -- Check that the class is unary, unless GlaExs
1063 ; checkTc (notNull tyvars) (nullaryClassErr cls)
1064 ; checkTc (gla_exts || unary) (classArityErr cls)
1066 -- Check the super-classes
1067 ; checkValidTheta (ClassSCCtxt (className cls)) theta
1069 -- Check the class operations
1070 ; mappM_ (check_op gla_exts) op_stuff
1072 -- Check that if the class has generic methods, then the
1073 -- class has only one parameter. We can't do generic
1074 -- multi-parameter type classes!
1075 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
1078 (tyvars, theta, _, op_stuff) = classBigSig cls
1079 unary = isSingleton tyvars
1080 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
1082 check_op gla_exts (sel_id, dm)
1083 = addErrCtxt (classOpCtxt sel_id tau) $ do
1084 { checkValidTheta SigmaCtxt (tail theta)
1085 -- The 'tail' removes the initial (C a) from the
1086 -- class itself, leaving just the method type
1088 ; checkValidType (FunSigCtxt op_name) tau
1090 -- Check that the type mentions at least one of
1091 -- the class type variables...or at least one reachable
1092 -- from one of the class variables. Example: tc223
1093 -- class Error e => Game b mv e | b -> mv e where
1094 -- newBoard :: MonadState b m => m ()
1095 -- Here, MonadState has a fundep m->b, so newBoard is fine
1096 ; let grown_tyvars = grow theta (mkVarSet tyvars)
1097 ; checkTc (tyVarsOfType tau `intersectsVarSet` grown_tyvars)
1098 (noClassTyVarErr cls sel_id)
1100 -- Check that for a generic method, the type of
1101 -- the method is sufficiently simple
1102 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
1103 (badGenericMethodType op_name op_ty)
1106 op_name = idName sel_id
1107 op_ty = idType sel_id
1108 (_,theta1,tau1) = tcSplitSigmaTy op_ty
1109 (_,theta2,tau2) = tcSplitSigmaTy tau1
1110 (theta,tau) | gla_exts = (theta1 ++ theta2, tau2)
1111 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
1112 -- Ugh! The function might have a type like
1113 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
1114 -- With -fglasgow-exts, we want to allow this, even though the inner
1115 -- forall has an (Eq a) constraint. Whereas in general, each constraint
1116 -- in the context of a for-all must mention at least one quantified
1117 -- type variable. What a mess!
1120 ---------------------------------------------------------------------
1121 resultTypeMisMatch field_name con1 con2
1122 = vcat [sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1123 ptext SLIT("have a common field") <+> quotes (ppr field_name) <> comma],
1124 nest 2 $ ptext SLIT("but have different result types")]
1125 fieldTypeMisMatch field_name con1 con2
1126 = sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1127 ptext SLIT("give different types for field"), quotes (ppr field_name)]
1129 dataConCtxt con = ptext SLIT("In the definition of data constructor") <+> quotes (ppr con)
1131 classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
1132 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
1135 = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
1138 = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
1139 parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
1141 noClassTyVarErr clas op
1142 = sep [ptext SLIT("The class method") <+> quotes (ppr op),
1143 ptext SLIT("mentions none of the type variables of the class") <+>
1144 ppr clas <+> hsep (map ppr (classTyVars clas))]
1146 genericMultiParamErr clas
1147 = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
1148 ptext SLIT("cannot have generic methods")
1150 badGenericMethodType op op_ty
1151 = hang (ptext SLIT("Generic method type is too complex"))
1152 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
1153 ptext SLIT("You can only use type variables, arrows, lists, and tuples")])
1156 = setSrcSpan (getLoc (head sorted_decls)) $
1157 addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
1158 nest 2 (vcat (map ppr_decl sorted_decls))])
1160 sorted_decls = sortLocated syn_decls
1161 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
1164 = setSrcSpan (getLoc (head sorted_decls)) $
1165 addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
1166 nest 2 (vcat (map ppr_decl sorted_decls))])
1168 sorted_decls = sortLocated cls_decls
1169 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
1171 sortLocated :: [Located a] -> [Located a]
1172 sortLocated things = sortLe le things
1174 le (L l1 _) (L l2 _) = l1 <= l2
1176 badDataConTyCon data_con
1177 = hang (ptext SLIT("Data constructor") <+> quotes (ppr data_con) <+>
1178 ptext SLIT("returns type") <+> quotes (ppr (dataConTyCon data_con)))
1179 2 (ptext SLIT("instead of its parent type"))
1182 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
1183 , nest 2 (parens $ ptext SLIT("Use -X=GADT to allow GADTs")) ]
1185 badStupidTheta tc_name
1186 = ptext SLIT("A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
1188 newtypeConError tycon n
1189 = sep [ptext SLIT("A newtype must have exactly one constructor,"),
1190 nest 2 $ ptext SLIT("but") <+> quotes (ppr tycon) <+> ptext SLIT("has") <+> speakN n ]
1193 = sep [ptext SLIT("A newtype constructor cannot have an existential context,"),
1194 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
1196 newtypeStrictError con
1197 = sep [ptext SLIT("A newtype constructor cannot have a strictness annotation,"),
1198 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
1200 newtypePredError con
1201 = sep [ptext SLIT("A newtype constructor must have a return type of form T a1 ... an"),
1202 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does not")]
1204 newtypeFieldErr con_name n_flds
1205 = sep [ptext SLIT("The constructor of a newtype must have exactly one field"),
1206 nest 2 $ ptext SLIT("but") <+> quotes (ppr con_name) <+> ptext SLIT("has") <+> speakN n_flds]
1208 badSigTyDecl tc_name
1209 = vcat [ ptext SLIT("Illegal kind signature") <+>
1210 quotes (ppr tc_name)
1211 , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow kind signatures")) ]
1213 badFamInstDecl tc_name
1214 = vcat [ ptext SLIT("Illegal family instance for") <+>
1215 quotes (ppr tc_name)
1216 , nest 2 (parens $ ptext SLIT("Use -X=TypeFamilies to allow indexed type families")) ]
1218 badGadtIdxTyDecl tc_name
1219 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+>
1220 quotes (ppr tc_name)
1221 , nest 2 (parens $ ptext SLIT("Family instances can not yet use GADT declarations")) ]
1223 tooManyParmsErr tc_name
1224 = ptext SLIT("Family instance has too many parameters:") <+>
1225 quotes (ppr tc_name)
1227 tooFewParmsErr tc_name
1228 = ptext SLIT("Family instance has too few parameters:") <+>
1229 quotes (ppr tc_name)
1231 badBootFamInstDeclErr =
1232 ptext SLIT("Illegal family instance in hs-boot file")
1234 wrongKindOfFamily family =
1235 ptext SLIT("Wrong category of family instance; declaration was for a") <+>
1238 kindOfFamily | isSynTyCon family = ptext SLIT("type synonym")
1239 | isAlgTyCon family = ptext SLIT("data type")
1240 | otherwise = pprPanic "wrongKindOfFamily" (ppr family)
1243 = hang (ptext SLIT("Illegal polymorphic type in type instance") <> colon) 4 $
1246 tyFamAppInIndexErr ty
1247 = hang (ptext SLIT("Illegal type family application in type instance") <>
1251 emptyConDeclsErr tycon
1252 = sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
1253 nest 2 $ ptext SLIT("(-fglasgow-exts permits this)")]