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"
49 import Control.Monad ( mplus )
53 %************************************************************************
55 \subsection{Type checking for type and class declarations}
57 %************************************************************************
61 Consider a mutually-recursive group, binding
62 a type constructor T and a class C.
64 Step 1: getInitialKind
65 Construct a KindEnv by binding T and C to a kind variable
68 In that environment, do a kind check
70 Step 3: Zonk the kinds
72 Step 4: buildTyConOrClass
73 Construct an environment binding T to a TyCon and C to a Class.
74 a) Their kinds comes from zonking the relevant kind variable
75 b) Their arity (for synonyms) comes direct from the decl
76 c) The funcional dependencies come from the decl
77 d) The rest comes a knot-tied binding of T and C, returned from Step 4
78 e) The variances of the tycons in the group is calculated from
82 In this environment, walk over the decls, constructing the TyCons and Classes.
83 This uses in a strict way items (a)-(c) above, which is why they must
84 be constructed in Step 4. Feed the results back to Step 4.
85 For this step, pass the is-recursive flag as the wimp-out flag
89 Step 6: Extend environment
90 We extend the type environment with bindings not only for the TyCons and Classes,
91 but also for their "implicit Ids" like data constructors and class selectors
93 Step 7: checkValidTyCl
94 For a recursive group only, check all the decls again, just
95 to check all the side conditions on validity. We could not
96 do this before because we were in a mutually recursive knot.
98 Identification of recursive TyCons
99 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
100 The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to
103 Identifying a TyCon as recursive serves two purposes
105 1. Avoid infinite types. Non-recursive newtypes are treated as
106 "transparent", like type synonyms, after the type checker. If we did
107 this for all newtypes, we'd get infinite types. So we figure out for
108 each newtype whether it is "recursive", and add a coercion if so. In
109 effect, we are trying to "cut the loops" by identifying a loop-breaker.
111 2. Avoid infinite unboxing. This is nothing to do with newtypes.
115 Well, this function diverges, but we don't want the strictness analyser
116 to diverge. But the strictness analyser will diverge because it looks
117 deeper and deeper into the structure of T. (I believe there are
118 examples where the function does something sane, and the strictness
119 analyser still diverges, but I can't see one now.)
121 Now, concerning (1), the FC2 branch currently adds a coercion for ALL
122 newtypes. I did this as an experiment, to try to expose cases in which
123 the coercions got in the way of optimisations. If it turns out that we
124 can indeed always use a coercion, then we don't risk recursive types,
125 and don't need to figure out what the loop breakers are.
127 For newtype *families* though, we will always have a coercion, so they
128 are always loop breakers! So you can easily adjust the current
129 algorithm by simply treating all newtype families as loop breakers (and
130 indeed type families). I think.
133 tcTyAndClassDecls :: ModDetails -> [LTyClDecl Name]
134 -> TcM TcGblEnv -- Input env extended by types and classes
135 -- and their implicit Ids,DataCons
136 tcTyAndClassDecls boot_details allDecls
137 = do { -- Omit instances of type families; they are handled together
138 -- with the *heads* of class instances
139 ; let decls = filter (not . isFamInstDecl . unLoc) allDecls
141 -- First check for cyclic type synonysm or classes
142 -- See notes with checkCycleErrs
143 ; checkCycleErrs decls
145 ; traceTc (text "tcTyAndCl" <+> ppr mod)
146 ; (syn_tycons, alg_tyclss) <- fixM (\ ~(rec_syn_tycons, rec_alg_tyclss) ->
147 do { let { -- Seperate ordinary synonyms from all other type and
148 -- class declarations and add all associated type
149 -- declarations from type classes. The latter is
150 -- required so that the temporary environment for the
151 -- knot includes all associated family declarations.
152 ; (syn_decls, alg_decls) = partition (isSynDecl . unLoc)
154 ; alg_at_decls = concatMap addATs alg_decls
156 -- Extend the global env with the knot-tied results
157 -- for data types and classes
159 -- We must populate the environment with the loop-tied
160 -- T's right away, because the kind checker may "fault
161 -- in" some type constructors that recursively
163 ; let gbl_things = mkGlobalThings alg_at_decls rec_alg_tyclss
164 ; tcExtendRecEnv gbl_things $ do
166 -- Kind-check the declarations
167 { (kc_syn_decls, kc_alg_decls) <- kcTyClDecls syn_decls alg_decls
169 ; let { -- Calculate rec-flag
170 ; calc_rec = calcRecFlags boot_details rec_alg_tyclss
171 ; tc_decl = addLocM (tcTyClDecl calc_rec) }
173 -- Type-check the type synonyms, and extend the envt
174 ; syn_tycons <- tcSynDecls kc_syn_decls
175 ; tcExtendGlobalEnv syn_tycons $ do
177 -- Type-check the data types and classes
178 { alg_tyclss <- mappM tc_decl kc_alg_decls
179 ; return (syn_tycons, concat alg_tyclss)
181 -- Finished with knot-tying now
182 -- Extend the environment with the finished things
183 ; tcExtendGlobalEnv (syn_tycons ++ alg_tyclss) $ do
185 -- Perform the validity check
186 { traceTc (text "ready for validity check")
187 ; mappM_ (addLocM checkValidTyCl) decls
188 ; traceTc (text "done")
190 -- Add the implicit things;
191 -- we want them in the environment because
192 -- they may be mentioned in interface files
193 -- NB: All associated types and their implicit things will be added a
194 -- second time here. This doesn't matter as the definitions are
196 ; let { implicit_things = concatMap implicitTyThings alg_tyclss }
197 ; traceTc ((text "Adding" <+> ppr alg_tyclss)
198 $$ (text "and" <+> ppr implicit_things))
199 ; tcExtendGlobalEnv implicit_things getGblEnv
202 -- Pull associated types out of class declarations, to tie them into the
204 -- NB: We put them in the same place in the list as `tcTyClDecl' will
205 -- eventually put the matching `TyThing's. That's crucial; otherwise,
206 -- the two argument lists of `mkGlobalThings' don't match up.
207 addATs decl@(L _ (ClassDecl {tcdATs = ats})) = decl : ats
210 mkGlobalThings :: [LTyClDecl Name] -- The decls
211 -> [TyThing] -- Knot-tied, in 1-1 correspondence with the decls
213 -- Driven by the Decls, and treating the TyThings lazily
214 -- make a TypeEnv for the new things
215 mkGlobalThings decls things
216 = map mk_thing (decls `zipLazy` things)
218 mk_thing (L _ (ClassDecl {tcdLName = L _ name}), ~(AClass cl))
220 mk_thing (L _ decl, ~(ATyCon tc))
221 = (tcdName decl, ATyCon tc)
225 %************************************************************************
227 \subsection{Type checking family instances}
229 %************************************************************************
231 Family instances are somewhat of a hybrid. They are processed together with
232 class instance heads, but can contain data constructors and hence they share a
233 lot of kinding and type checking code with ordinary algebraic data types (and
237 tcFamInstDecl :: LTyClDecl Name -> TcM (Maybe TyThing) -- Nothing if error
238 tcFamInstDecl (L loc decl)
239 = -- Prime error recovery, set source location
240 recoverM (returnM Nothing) $
243 do { -- type families require -ftype-families and can't be in an
245 ; type_families <- doptM Opt_TypeFamilies
246 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
247 ; checkTc type_families $ badFamInstDecl (tcdLName decl)
248 ; checkTc (not is_boot) $ badBootFamInstDeclErr
250 -- perform kind and type checking
251 ; tcFamInstDecl1 decl
254 tcFamInstDecl1 :: TyClDecl Name -> TcM (Maybe TyThing) -- Nothing if error
257 tcFamInstDecl1 (decl@TySynonym {tcdLName = L loc tc_name})
258 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
259 do { -- check that the family declaration is for a synonym
260 unless (isSynTyCon family) $
261 addErr (wrongKindOfFamily family)
263 ; -- (1) kind check the right-hand side of the type equation
264 ; k_rhs <- kcCheckHsType (tcdSynRhs decl) resKind
266 -- we need the exact same number of type parameters as the family
268 ; let famArity = tyConArity family
269 ; checkTc (length k_typats == famArity) $
270 wrongNumberOfParmsErr famArity
272 -- (2) type check type equation
273 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
274 ; t_typats <- mappM tcHsKindedType k_typats
275 ; t_rhs <- tcHsKindedType k_rhs
278 -- - check the well-formedness of the instance
279 ; checkValidTypeInst t_typats t_rhs
281 -- (4) construct representation tycon
282 ; rep_tc_name <- newFamInstTyConName tc_name loc
283 ; tycon <- buildSynTyCon rep_tc_name t_tvs (SynonymTyCon t_rhs)
284 (Just (family, t_typats))
286 ; return $ Just (ATyCon tycon)
289 -- "newtype instance" and "data instance"
290 tcFamInstDecl1 (decl@TyData {tcdND = new_or_data, tcdLName = L loc tc_name,
292 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
293 do { -- check that the family declaration is for the right kind
294 unless (isAlgTyCon family) $
295 addErr (wrongKindOfFamily family)
297 ; -- (1) kind check the data declaration as usual
298 ; k_decl <- kcDataDecl decl k_tvs
299 ; let k_ctxt = tcdCtxt k_decl
300 k_cons = tcdCons k_decl
302 -- result kind must be '*' (otherwise, we have too few patterns)
303 ; checkTc (isLiftedTypeKind resKind) $ tooFewParmsErr (tyConArity family)
305 -- (2) type check indexed data type declaration
306 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
307 ; unbox_strict <- doptM Opt_UnboxStrictFields
309 -- kind check the type indexes and the context
310 ; t_typats <- mappM tcHsKindedType k_typats
311 ; stupid_theta <- tcHsKindedContext k_ctxt
314 -- - left-hand side contains no type family applications
315 -- (vanilla synonyms are fine, though, and we checked for
317 ; mappM_ checkTyFamFreeness t_typats
319 -- - we don't use GADT syntax for indexed types
320 ; checkTc h98_syntax (badGadtIdxTyDecl tc_name)
322 -- - a newtype has exactly one constructor
323 ; checkTc (new_or_data == DataType || isSingleton k_cons) $
324 newtypeConError tc_name (length k_cons)
326 -- (4) construct representation tycon
327 ; rep_tc_name <- newFamInstTyConName tc_name loc
328 ; tycon <- fixM (\ tycon -> do
329 { data_cons <- mappM (addLocM (tcConDecl unbox_strict tycon t_tvs))
333 DataType -> return (mkDataTyConRhs data_cons)
334 NewType -> ASSERT( not (null data_cons) )
335 mkNewTyConRhs rep_tc_name tycon (head data_cons)
336 ; buildAlgTyCon rep_tc_name t_tvs stupid_theta tc_rhs Recursive
337 False h98_syntax (Just (family, t_typats))
338 -- We always assume that indexed types are recursive. Why?
339 -- (1) Due to their open nature, we can never be sure that a
340 -- further instance might not introduce a new recursive
341 -- dependency. (2) They are always valid loop breakers as
342 -- they involve a coercion.
346 ; return $ Just (ATyCon tycon)
349 h98_syntax = case cons of -- All constructors have same shape
350 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
353 -- Kind checking of indexed types
356 -- Kind check type patterns and kind annotate the embedded type variables.
358 -- * Here we check that a type instance matches its kind signature, but we do
359 -- not check whether there is a pattern for each type index; the latter
360 -- check is only required for type synonym instances.
362 kcIdxTyPats :: TyClDecl Name
363 -> ([LHsTyVarBndr Name] -> [LHsType Name] -> Kind -> TyCon -> TcM a)
364 -- ^^kinded tvs ^^kinded ty pats ^^res kind
366 kcIdxTyPats decl thing_inside
367 = kcHsTyVars (tcdTyVars decl) $ \tvs ->
368 do { family <- tcLookupLocatedTyCon (tcdLName decl)
369 ; let { (kinds, resKind) = splitKindFunTys (tyConKind family)
370 ; hs_typats = fromJust $ tcdTyPats decl }
372 -- we may not have more parameters than the kind indicates
373 ; checkTc (length kinds >= length hs_typats) $
374 tooManyParmsErr (tcdLName decl)
376 -- type functions can have a higher-kinded result
377 ; let resultKind = mkArrowKinds (drop (length hs_typats) kinds) resKind
378 ; typats <- TcRnMonad.zipWithM kcCheckHsType hs_typats kinds
379 ; thing_inside tvs typats resultKind family
385 %************************************************************************
389 %************************************************************************
391 We need to kind check all types in the mutually recursive group
392 before we know the kind of the type variables. For example:
395 op :: D b => a -> b -> b
398 bop :: (Monad c) => ...
400 Here, the kind of the locally-polymorphic type variable "b"
401 depends on *all the uses of class D*. For example, the use of
402 Monad c in bop's type signature means that D must have kind Type->Type.
404 However type synonyms work differently. They can have kinds which don't
405 just involve (->) and *:
406 type R = Int# -- Kind #
407 type S a = Array# a -- Kind * -> #
408 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
409 So we must infer their kinds from their right-hand sides *first* and then
410 use them, whereas for the mutually recursive data types D we bring into
411 scope kind bindings D -> k, where k is a kind variable, and do inference.
415 This treatment of type synonyms only applies to Haskell 98-style synonyms.
416 General type functions can be recursive, and hence, appear in `alg_decls'.
418 The kind of a type family is solely determinded by its kind signature;
419 hence, only kind signatures participate in the construction of the initial
420 kind environment (as constructed by `getInitialKind'). In fact, we ignore
421 instances of families altogether in the following. However, we need to
422 include the kinds of associated families into the construction of the
423 initial kind environment. (This is handled by `allDecls').
426 kcTyClDecls syn_decls alg_decls
427 = do { -- First extend the kind env with each data type, class, and
428 -- indexed type, mapping them to a type variable
429 let initialKindDecls = concat [allDecls decl | L _ decl <- alg_decls]
430 ; alg_kinds <- mappM getInitialKind initialKindDecls
431 ; tcExtendKindEnv alg_kinds $ do
433 -- Now kind-check the type synonyms, in dependency order
434 -- We do these differently to data type and classes,
435 -- because a type synonym can be an unboxed type
437 -- and a kind variable can't unify with UnboxedTypeKind
438 -- So we infer their kinds in dependency order
439 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
440 ; tcExtendKindEnv syn_kinds $ do
442 -- Now kind-check the data type, class, and kind signatures,
443 -- returning kind-annotated decls; we don't kind-check
444 -- instances of indexed types yet, but leave this to
446 { kc_alg_decls <- mappM (wrapLocM kcTyClDecl)
447 (filter (not . isFamInstDecl . unLoc) alg_decls)
449 ; return (kc_syn_decls, kc_alg_decls) }}}
451 -- get all declarations relevant for determining the initial kind
453 allDecls (decl@ClassDecl {tcdATs = ats}) = decl : [ at
456 allDecls decl | isFamInstDecl decl = []
459 ------------------------------------------------------------------------
460 getInitialKind :: TyClDecl Name -> TcM (Name, TcKind)
461 -- Only for data type, class, and indexed type declarations
462 -- Get as much info as possible from the data, class, or indexed type decl,
463 -- so as to maximise usefulness of error messages
465 = do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl)
466 ; res_kind <- mk_res_kind decl
467 ; return (tcdName decl, mkArrowKinds arg_kinds res_kind) }
469 mk_arg_kind (UserTyVar _) = newKindVar
470 mk_arg_kind (KindedTyVar _ kind) = return kind
472 mk_res_kind (TyFamily { tcdKind = Just kind }) = return kind
473 mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
474 -- On GADT-style declarations we allow a kind signature
475 -- data T :: *->* where { ... }
476 mk_res_kind other = return liftedTypeKind
480 kcSynDecls :: [SCC (LTyClDecl Name)]
481 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
482 [(Name,TcKind)]) -- Kind bindings
485 kcSynDecls (group : groups)
486 = do { (decl, nk) <- kcSynDecl group
487 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
488 ; return (decl:decls, nk:nks) }
491 kcSynDecl :: SCC (LTyClDecl Name)
492 -> TcM (LTyClDecl Name, -- Kind-annotated decls
493 (Name,TcKind)) -- Kind bindings
494 kcSynDecl (AcyclicSCC ldecl@(L loc decl))
495 = tcAddDeclCtxt decl $
496 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
497 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
498 <+> brackets (ppr k_tvs))
499 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
500 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
501 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
502 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
503 (unLoc (tcdLName decl), tc_kind)) })
505 kcSynDecl (CyclicSCC decls)
506 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
507 -- of out-of-scope tycons
509 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
511 ------------------------------------------------------------------------
512 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
513 -- Not used for type synonyms (see kcSynDecl)
515 kcTyClDecl decl@(TyData {})
516 = ASSERT( not . isFamInstDecl $ decl ) -- must not be a family instance
517 kcTyClDeclBody decl $
520 kcTyClDecl decl@(TyFamily {})
521 = kcFamilyDecl [] decl -- the empty list signals a toplevel decl
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 (kcFamilyDecl tvs')) 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 -- doc comments are typechecked to Nothing here
570 kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res _) = do
571 kcHsTyVars ex_tvs $ \ex_tvs' -> do
572 ex_ctxt' <- kcHsContext ex_ctxt
573 details' <- kc_con_details details
575 ResTyH98 -> return ResTyH98
576 ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
577 return (ConDecl name expl ex_tvs' ex_ctxt' details' res' Nothing)
579 kc_con_details (PrefixCon btys)
580 = do { btys' <- mappM kc_larg_ty btys
581 ; return (PrefixCon btys') }
582 kc_con_details (InfixCon bty1 bty2)
583 = do { bty1' <- kc_larg_ty bty1
584 ; bty2' <- kc_larg_ty bty2
585 ; return (InfixCon bty1' bty2') }
586 kc_con_details (RecCon fields)
587 = do { fields' <- mappM kc_field fields
588 ; return (RecCon fields') }
590 kc_field (ConDeclField fld bty d) = do { bty' <- kc_larg_ty bty
591 ; return (ConDeclField fld bty' d) }
593 kc_larg_ty bty = case new_or_data of
594 DataType -> kcHsSigType bty
595 NewType -> kcHsLiftedSigType bty
596 -- Can't allow an unlifted type for newtypes, because we're effectively
597 -- going to remove the constructor while coercing it to a lifted type.
598 -- And newtypes can't be bang'd
600 -- Kind check a family declaration or type family default declaration.
602 kcFamilyDecl :: [LHsTyVarBndr Name] -- tyvars of enclosing class decl if any
603 -> TyClDecl Name -> TcM (TyClDecl Name)
604 kcFamilyDecl classTvs decl@(TyFamily {tcdKind = kind})
605 = kcTyClDeclBody decl $ \tvs' ->
606 do { mapM_ unifyClassParmKinds tvs'
607 ; return (decl {tcdTyVars = tvs',
608 tcdKind = kind `mplus` Just liftedTypeKind})
609 -- default result kind is '*'
612 unifyClassParmKinds (L _ (KindedTyVar n k))
613 | Just classParmKind <- lookup n classTyKinds = unifyKind k classParmKind
614 | otherwise = return ()
615 classTyKinds = [(n, k) | L _ (KindedTyVar n k) <- classTvs]
616 kcFamilyDecl _ decl@(TySynonym {}) -- type family defaults
617 = panic "TcTyClsDecls.kcFamilyDecl: not implemented yet"
621 %************************************************************************
623 \subsection{Type checking}
625 %************************************************************************
628 tcSynDecls :: [LTyClDecl Name] -> TcM [TyThing]
629 tcSynDecls [] = return []
630 tcSynDecls (decl : decls)
631 = do { syn_tc <- addLocM tcSynDecl decl
632 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls decls)
633 ; return (syn_tc : syn_tcs) }
637 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
638 = tcTyVarBndrs tvs $ \ tvs' -> do
639 { traceTc (text "tcd1" <+> ppr tc_name)
640 ; rhs_ty' <- tcHsKindedType rhs_ty
641 ; tycon <- buildSynTyCon tc_name tvs' (SynonymTyCon rhs_ty') Nothing
642 ; return (ATyCon tycon)
646 tcTyClDecl :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
648 tcTyClDecl calc_isrec decl
649 = tcAddDeclCtxt decl (tcTyClDecl1 calc_isrec decl)
651 -- "type family" declarations
652 tcTyClDecl1 _calc_isrec
653 (TyFamily {tcdFlavour = TypeFamily,
654 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = Just kind})
655 -- NB: kind at latest
658 = tcTyVarBndrs tvs $ \ tvs' -> do
659 { traceTc (text "type family: " <+> ppr tc_name)
660 ; idx_tys <- doptM Opt_TypeFamilies
662 -- Check that we don't use families without -ftype-families
663 ; checkTc idx_tys $ badFamInstDecl tc_name
665 ; tycon <- buildSynTyCon tc_name tvs' (OpenSynTyCon kind Nothing) Nothing
666 ; return [ATyCon tycon]
669 -- "newtype family" or "data family" declaration
670 tcTyClDecl1 _calc_isrec
671 (TyFamily {tcdFlavour = DataFamily,
672 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = mb_kind})
673 = tcTyVarBndrs tvs $ \ tvs' -> do
674 { traceTc (text "data family: " <+> ppr tc_name)
675 ; extra_tvs <- tcDataKindSig mb_kind
676 ; let final_tvs = tvs' ++ extra_tvs -- we may not need these
678 ; idx_tys <- doptM Opt_TypeFamilies
680 -- Check that we don't use families without -ftype-families
681 ; checkTc idx_tys $ badFamInstDecl tc_name
683 ; tycon <- buildAlgTyCon tc_name final_tvs []
684 mkOpenDataTyConRhs Recursive False True Nothing
685 ; return [ATyCon tycon]
688 -- "newtype" and "data"
689 tcTyClDecl1 calc_isrec
690 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
691 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
692 = tcTyVarBndrs tvs $ \ tvs' -> do
693 { extra_tvs <- tcDataKindSig mb_ksig
694 ; let final_tvs = tvs' ++ extra_tvs
695 ; stupid_theta <- tcHsKindedContext ctxt
696 ; want_generic <- doptM Opt_Generics
697 ; unbox_strict <- doptM Opt_UnboxStrictFields
698 ; empty_data_decls <- doptM Opt_EmptyDataDecls
699 ; kind_signatures <- doptM Opt_KindSignatures
700 ; gadt_ok <- doptM Opt_GADTs
701 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
703 -- Check that we don't use GADT syntax in H98 world
704 ; checkTc (gadt_ok || h98_syntax) (badGadtDecl tc_name)
706 -- Check that we don't use kind signatures without Glasgow extensions
707 ; checkTc (kind_signatures || isNothing mb_ksig) (badSigTyDecl tc_name)
709 -- Check that the stupid theta is empty for a GADT-style declaration
710 ; checkTc (null stupid_theta || h98_syntax) (badStupidTheta tc_name)
712 -- Check that there's at least one condecl,
713 -- or else we're reading an hs-boot file, or -XEmptyDataDecls
714 ; checkTc (not (null cons) || empty_data_decls || is_boot)
715 (emptyConDeclsErr tc_name)
717 -- Check that a newtype has exactly one constructor
718 ; checkTc (new_or_data == DataType || isSingleton cons)
719 (newtypeConError tc_name (length cons))
721 ; tycon <- fixM (\ tycon -> do
722 { data_cons <- mappM (addLocM (tcConDecl unbox_strict tycon final_tvs))
725 if null cons && is_boot -- In a hs-boot file, empty cons means
726 then return AbstractTyCon -- "don't know"; hence Abstract
727 else case new_or_data of
728 DataType -> return (mkDataTyConRhs data_cons)
730 ASSERT( not (null data_cons) )
731 mkNewTyConRhs tc_name tycon (head data_cons)
732 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
733 (want_generic && canDoGenerics data_cons) h98_syntax Nothing
735 ; return [ATyCon tycon]
738 is_rec = calc_isrec tc_name
739 h98_syntax = case cons of -- All constructors have same shape
740 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
743 tcTyClDecl1 calc_isrec
744 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
745 tcdCtxt = ctxt, tcdMeths = meths,
746 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
747 = tcTyVarBndrs tvs $ \ tvs' -> do
748 { ctxt' <- tcHsKindedContext ctxt
749 ; fds' <- mappM (addLocM tc_fundep) fundeps
750 ; atss <- mappM (addLocM (tcTyClDecl1 (const Recursive))) ats
751 ; let ats' = zipWith setTyThingPoss atss (map (tcdTyVars . unLoc) ats)
752 ; sig_stuff <- tcClassSigs class_name sigs meths
753 ; clas <- fixM (\ clas ->
754 let -- This little knot is just so we can get
755 -- hold of the name of the class TyCon, which we
756 -- need to look up its recursiveness
757 tycon_name = tyConName (classTyCon clas)
758 tc_isrec = calc_isrec tycon_name
760 buildClass class_name tvs' ctxt' fds' ats'
762 ; return (AClass clas : ats')
763 -- NB: Order is important due to the call to `mkGlobalThings' when
764 -- tying the the type and class declaration type checking knot.
767 tc_fundep (tvs1, tvs2) = do { tvs1' <- mappM tcLookupTyVar tvs1 ;
768 ; tvs2' <- mappM tcLookupTyVar tvs2 ;
769 ; return (tvs1', tvs2') }
771 -- For each AT argument compute the position of the corresponding class
772 -- parameter in the class head. This will later serve as a permutation
773 -- vector when checking the validity of instance declarations.
774 setTyThingPoss [ATyCon tycon] atTyVars =
775 let classTyVars = hsLTyVarNames tvs
777 . map (`elemIndex` classTyVars)
780 -- There will be no Nothing, as we already passed renaming
782 ATyCon (setTyConArgPoss tycon poss)
783 setTyThingPoss _ _ = panic "TcTyClsDecls.setTyThingPoss"
785 tcTyClDecl1 calc_isrec
786 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
787 = returnM [ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0)]
789 -----------------------------------
790 tcConDecl :: Bool -- True <=> -funbox-strict_fields
795 tcConDecl unbox_strict tycon tc_tvs -- Data types
796 (ConDecl name _ tvs ctxt details res_ty _)
797 = tcTyVarBndrs tvs $ \ tvs' -> do
798 { ctxt' <- tcHsKindedContext ctxt
799 ; (univ_tvs, ex_tvs, eq_preds, data_tc) <- tcResultType tycon tc_tvs tvs' res_ty
801 -- Tiresome: tidy the tyvar binders, since tc_tvs and tvs' may have the same OccNames
802 tc_datacon is_infix field_lbls btys
803 = do { let bangs = map getBangStrictness btys
804 ; arg_tys <- mappM tcHsBangType btys
805 ; buildDataCon (unLoc name) is_infix
806 (argStrictness unbox_strict bangs arg_tys)
807 (map unLoc field_lbls)
808 univ_tvs ex_tvs eq_preds ctxt' arg_tys
810 -- NB: we put data_tc, the type constructor gotten from the
811 -- constructor type signature into the data constructor;
812 -- that way checkValidDataCon can complain if it's wrong.
815 PrefixCon btys -> tc_datacon False [] btys
816 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
817 RecCon fields -> tc_datacon False field_names btys
819 field_names = map cd_fld_name fields
820 btys = map cd_fld_type fields
823 tcResultType :: TyCon
824 -> [TyVar] -- data T a b c = ...
825 -> [TyVar] -- where MkT :: forall a b c. ...
827 -> TcM ([TyVar], -- Universal
828 [TyVar], -- Existential (distinct OccNames from univs)
829 [(TyVar,Type)], -- Equality predicates
830 TyCon) -- TyCon given in the ResTy
831 -- We don't check that the TyCon given in the ResTy is
832 -- the same as the parent tycon, becuase we are in the middle
833 -- of a recursive knot; so it's postponed until checkValidDataCon
835 tcResultType decl_tycon tc_tvs dc_tvs ResTyH98
836 = return (tc_tvs, dc_tvs, [], decl_tycon)
837 -- In H98 syntax the dc_tvs are the existential ones
838 -- data T a b c = forall d e. MkT ...
839 -- The {a,b,c} are tc_tvs, and {d,e} are dc_tvs
841 tcResultType _ tc_tvs dc_tvs (ResTyGADT res_ty)
842 -- E.g. data T a b c where
843 -- MkT :: forall x y z. T (x,y) z z
845 -- ([a,z,c], [x,y], [a:=:(x,y), c:=:z], T)
847 = do { (dc_tycon, res_tys) <- tcLHsConResTy res_ty
849 ; let univ_tvs = choose_univs [] tidy_tc_tvs res_tys
850 -- Each univ_tv is either a dc_tv or a tc_tv
851 ex_tvs = dc_tvs `minusList` univ_tvs
852 eq_spec = [ (tv, ty) | (tv,ty) <- univ_tvs `zip` res_tys,
854 ; return (univ_tvs, ex_tvs, eq_spec, dc_tycon) }
856 -- choose_univs uses the res_ty itself if it's a type variable
857 -- and hasn't already been used; otherwise it uses one of the tc_tvs
858 choose_univs used tc_tvs []
859 = ASSERT( null tc_tvs ) []
860 choose_univs used (tc_tv:tc_tvs) (res_ty:res_tys)
861 | Just tv <- tcGetTyVar_maybe res_ty, not (tv `elem` used)
862 = tv : choose_univs (tv:used) tc_tvs res_tys
864 = tc_tv : choose_univs used tc_tvs res_tys
866 -- NB: tc_tvs and dc_tvs are distinct, but
867 -- we want them to be *visibly* distinct, both for
868 -- interface files and general confusion. So rename
869 -- the tc_tvs, since they are not used yet (no
870 -- consequential renaming needed)
871 init_occ_env = initTidyOccEnv (map getOccName dc_tvs)
872 (_, tidy_tc_tvs) = mapAccumL tidy_one init_occ_env tc_tvs
873 tidy_one env tv = (env', setTyVarName tv (tidyNameOcc name occ'))
876 (env', occ') = tidyOccName env (getOccName name)
879 argStrictness :: Bool -- True <=> -funbox-strict_fields
881 -> [TcType] -> [StrictnessMark]
882 argStrictness unbox_strict bangs arg_tys
883 = ASSERT( length bangs == length arg_tys )
884 zipWith (chooseBoxingStrategy unbox_strict) arg_tys bangs
886 -- We attempt to unbox/unpack a strict field when either:
887 -- (i) The field is marked '!!', or
888 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
890 -- We have turned off unboxing of newtypes because coercions make unboxing
891 -- and reboxing more complicated
892 chooseBoxingStrategy :: Bool -> TcType -> HsBang -> StrictnessMark
893 chooseBoxingStrategy unbox_strict_fields arg_ty bang
895 HsNoBang -> NotMarkedStrict
896 HsStrict | unbox_strict_fields
897 && can_unbox arg_ty -> MarkedUnboxed
898 HsUnbox | can_unbox arg_ty -> MarkedUnboxed
899 other -> MarkedStrict
901 -- we can unbox if the type is a chain of newtypes with a product tycon
903 can_unbox arg_ty = case splitTyConApp_maybe arg_ty of
905 Just (arg_tycon, tycon_args) ->
906 not (isRecursiveTyCon arg_tycon) && -- Note [Recusive unboxing]
907 isProductTyCon arg_tycon &&
908 (if isNewTyCon arg_tycon then
909 can_unbox (newTyConInstRhs arg_tycon tycon_args)
913 Note [Recursive unboxing]
914 ~~~~~~~~~~~~~~~~~~~~~~~~~
915 Be careful not to try to unbox this!
917 But it's the *argument* type that matters. This is fine:
919 because Int is non-recursive.
921 %************************************************************************
923 \subsection{Dependency analysis}
925 %************************************************************************
927 Validity checking is done once the mutually-recursive knot has been
928 tied, so we can look at things freely.
931 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
932 checkCycleErrs tyclss
936 = do { mappM_ recClsErr cls_cycles
937 ; failM } -- Give up now, because later checkValidTyCl
938 -- will loop if the synonym is recursive
940 cls_cycles = calcClassCycles tyclss
942 checkValidTyCl :: TyClDecl Name -> TcM ()
943 -- We do the validity check over declarations, rather than TyThings
944 -- only so that we can add a nice context with tcAddDeclCtxt
946 = tcAddDeclCtxt decl $
947 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
948 ; traceTc (text "Validity of" <+> ppr thing)
950 ATyCon tc -> checkValidTyCon tc
951 AClass cl -> checkValidClass cl
952 ; traceTc (text "Done validity of" <+> ppr thing)
955 -------------------------
956 -- For data types declared with record syntax, we require
957 -- that each constructor that has a field 'f'
958 -- (a) has the same result type
959 -- (b) has the same type for 'f'
960 -- module alpha conversion of the quantified type variables
961 -- of the constructor.
963 checkValidTyCon :: TyCon -> TcM ()
966 = case synTyConRhs tc of
967 OpenSynTyCon _ _ -> return ()
968 SynonymTyCon ty -> checkValidType syn_ctxt ty
970 = -- Check the context on the data decl
971 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
973 -- Check arg types of data constructors
974 mappM_ (checkValidDataCon tc) data_cons `thenM_`
976 -- Check that fields with the same name share a type
977 mappM_ check_fields groups
980 syn_ctxt = TySynCtxt name
982 data_cons = tyConDataCons tc
984 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
985 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
986 get_fields con = dataConFieldLabels con `zip` repeat con
987 -- dataConFieldLabels may return the empty list, which is fine
989 -- See Note [GADT record selectors] in MkId.lhs
990 -- We must check (a) that the named field has the same
991 -- type in each constructor
992 -- (b) that those constructors have the same result type
994 -- However, the constructors may have differently named type variable
995 -- and (worse) we don't know how the correspond to each other. E.g.
996 -- C1 :: forall a b. { f :: a, g :: b } -> T a b
997 -- C2 :: forall d c. { f :: c, g :: c } -> T c d
999 -- So what we do is to ust Unify.tcMatchTys to compare the first candidate's
1000 -- result type against other candidates' types BOTH WAYS ROUND.
1001 -- If they magically agrees, take the substitution and
1002 -- apply them to the latter ones, and see if they match perfectly.
1003 check_fields fields@((label, con1) : other_fields)
1004 -- These fields all have the same name, but are from
1005 -- different constructors in the data type
1006 = recoverM (return ()) $ mapM_ checkOne other_fields
1007 -- Check that all the fields in the group have the same type
1008 -- NB: this check assumes that all the constructors of a given
1009 -- data type use the same type variables
1011 (tvs1, _, _, res1) = dataConSig con1
1013 fty1 = dataConFieldType con1 label
1015 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
1016 = do { checkFieldCompat label con1 con2 ts1 res1 res2 fty1 fty2
1017 ; checkFieldCompat label con2 con1 ts2 res2 res1 fty2 fty1 }
1019 (tvs2, _, _, res2) = dataConSig con2
1021 fty2 = dataConFieldType con2 label
1023 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
1024 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
1025 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
1027 mb_subst1 = tcMatchTy tvs1 res1 res2
1028 mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
1030 -------------------------------
1031 checkValidDataCon :: TyCon -> DataCon -> TcM ()
1032 checkValidDataCon tc con
1033 = setSrcSpan (srcLocSpan (getSrcLoc con)) $
1034 addErrCtxt (dataConCtxt con) $
1035 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
1036 ; checkValidType ctxt (dataConUserType con)
1037 ; ifM (isNewTyCon tc) (checkNewDataCon con)
1040 ctxt = ConArgCtxt (dataConName con)
1042 -------------------------------
1043 checkNewDataCon :: DataCon -> TcM ()
1044 -- Checks for the data constructor of a newtype
1046 = do { checkTc (isSingleton arg_tys) (newtypeFieldErr con (length arg_tys))
1048 ; checkTc (null eq_spec) (newtypePredError con)
1049 -- Return type is (T a b c)
1050 ; checkTc (null ex_tvs && null eq_theta && null dict_theta) (newtypeExError con)
1052 ; checkTc (not (any isMarkedStrict (dataConStrictMarks con)))
1053 (newtypeStrictError con)
1057 (_univ_tvs, ex_tvs, eq_spec, eq_theta, dict_theta, arg_tys, _res_ty) = dataConFullSig con
1059 -------------------------------
1060 checkValidClass :: Class -> TcM ()
1062 = do { constrained_class_methods <- doptM Opt_ConstrainedClassMethods
1063 ; multi_param_type_classes <- doptM Opt_MultiParamTypeClasses
1064 ; fundep_classes <- doptM Opt_FunctionalDependencies
1066 -- Check that the class is unary, unless GlaExs
1067 ; checkTc (notNull tyvars) (nullaryClassErr cls)
1068 ; checkTc (multi_param_type_classes || unary) (classArityErr cls)
1069 ; checkTc (fundep_classes || null fundeps) (classFunDepsErr cls)
1071 -- Check the super-classes
1072 ; checkValidTheta (ClassSCCtxt (className cls)) theta
1074 -- Check the class operations
1075 ; mappM_ (check_op constrained_class_methods) op_stuff
1077 -- Check that if the class has generic methods, then the
1078 -- class has only one parameter. We can't do generic
1079 -- multi-parameter type classes!
1080 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
1083 (tyvars, fundeps, theta, _, _, op_stuff) = classExtraBigSig cls
1084 unary = isSingleton tyvars
1085 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
1087 check_op constrained_class_methods (sel_id, dm)
1088 = addErrCtxt (classOpCtxt sel_id tau) $ do
1089 { checkValidTheta SigmaCtxt (tail theta)
1090 -- The 'tail' removes the initial (C a) from the
1091 -- class itself, leaving just the method type
1093 ; traceTc (text "class op type" <+> ppr op_ty <+> ppr tau)
1094 ; checkValidType (FunSigCtxt op_name) tau
1096 -- Check that the type mentions at least one of
1097 -- the class type variables...or at least one reachable
1098 -- from one of the class variables. Example: tc223
1099 -- class Error e => Game b mv e | b -> mv e where
1100 -- newBoard :: MonadState b m => m ()
1101 -- Here, MonadState has a fundep m->b, so newBoard is fine
1102 ; let grown_tyvars = grow theta (mkVarSet tyvars)
1103 ; checkTc (tyVarsOfType tau `intersectsVarSet` grown_tyvars)
1104 (noClassTyVarErr cls sel_id)
1106 -- Check that for a generic method, the type of
1107 -- the method is sufficiently simple
1108 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
1109 (badGenericMethodType op_name op_ty)
1112 op_name = idName sel_id
1113 op_ty = idType sel_id
1114 (_,theta1,tau1) = tcSplitSigmaTy op_ty
1115 (_,theta2,tau2) = tcSplitSigmaTy tau1
1116 (theta,tau) | constrained_class_methods = (theta1 ++ theta2, tau2)
1117 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
1118 -- Ugh! The function might have a type like
1119 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
1120 -- With -XConstrainedClassMethods, we want to allow this, even though the inner
1121 -- forall has an (Eq a) constraint. Whereas in general, each constraint
1122 -- in the context of a for-all must mention at least one quantified
1123 -- type variable. What a mess!
1126 ---------------------------------------------------------------------
1127 resultTypeMisMatch field_name con1 con2
1128 = vcat [sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1129 ptext SLIT("have a common field") <+> quotes (ppr field_name) <> comma],
1130 nest 2 $ ptext SLIT("but have different result types")]
1131 fieldTypeMisMatch field_name con1 con2
1132 = sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1133 ptext SLIT("give different types for field"), quotes (ppr field_name)]
1135 dataConCtxt con = ptext SLIT("In the definition of data constructor") <+> quotes (ppr con)
1137 classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
1138 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
1141 = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
1144 = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
1145 parens (ptext SLIT("Use -XMultiParamTypeClasses to allow multi-parameter classes"))]
1148 = vcat [ptext SLIT("Fundeps in class") <+> quotes (ppr cls),
1149 parens (ptext SLIT("Use -XFunctionalDependencies to allow fundeps"))]
1151 noClassTyVarErr clas op
1152 = sep [ptext SLIT("The class method") <+> quotes (ppr op),
1153 ptext SLIT("mentions none of the type variables of the class") <+>
1154 ppr clas <+> hsep (map ppr (classTyVars clas))]
1156 genericMultiParamErr clas
1157 = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
1158 ptext SLIT("cannot have generic methods")
1160 badGenericMethodType op op_ty
1161 = hang (ptext SLIT("Generic method type is too complex"))
1162 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
1163 ptext SLIT("You can only use type variables, arrows, lists, and tuples")])
1166 = setSrcSpan (getLoc (head sorted_decls)) $
1167 addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
1168 nest 2 (vcat (map ppr_decl sorted_decls))])
1170 sorted_decls = sortLocated syn_decls
1171 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
1174 = setSrcSpan (getLoc (head sorted_decls)) $
1175 addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
1176 nest 2 (vcat (map ppr_decl sorted_decls))])
1178 sorted_decls = sortLocated cls_decls
1179 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
1181 sortLocated :: [Located a] -> [Located a]
1182 sortLocated things = sortLe le things
1184 le (L l1 _) (L l2 _) = l1 <= l2
1186 badDataConTyCon data_con
1187 = hang (ptext SLIT("Data constructor") <+> quotes (ppr data_con) <+>
1188 ptext SLIT("returns type") <+> quotes (ppr (dataConTyCon data_con)))
1189 2 (ptext SLIT("instead of its parent type"))
1192 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
1193 , nest 2 (parens $ ptext SLIT("Use -XGADTs to allow GADTs")) ]
1195 badStupidTheta tc_name
1196 = ptext SLIT("A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
1198 newtypeConError tycon n
1199 = sep [ptext SLIT("A newtype must have exactly one constructor,"),
1200 nest 2 $ ptext SLIT("but") <+> quotes (ppr tycon) <+> ptext SLIT("has") <+> speakN n ]
1203 = sep [ptext SLIT("A newtype constructor cannot have an existential context,"),
1204 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
1206 newtypeStrictError con
1207 = sep [ptext SLIT("A newtype constructor cannot have a strictness annotation,"),
1208 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
1210 newtypePredError con
1211 = sep [ptext SLIT("A newtype constructor must have a return type of form T a1 ... an"),
1212 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does not")]
1214 newtypeFieldErr con_name n_flds
1215 = sep [ptext SLIT("The constructor of a newtype must have exactly one field"),
1216 nest 2 $ ptext SLIT("but") <+> quotes (ppr con_name) <+> ptext SLIT("has") <+> speakN n_flds]
1218 badSigTyDecl tc_name
1219 = vcat [ ptext SLIT("Illegal kind signature") <+>
1220 quotes (ppr tc_name)
1221 , nest 2 (parens $ ptext SLIT("Use -XKindSignatures to allow kind signatures")) ]
1223 badFamInstDecl tc_name
1224 = vcat [ ptext SLIT("Illegal family instance for") <+>
1225 quotes (ppr tc_name)
1226 , nest 2 (parens $ ptext SLIT("Use -XTypeFamilies to allow indexed type families")) ]
1228 badGadtIdxTyDecl tc_name
1229 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+>
1230 quotes (ppr tc_name)
1231 , nest 2 (parens $ ptext SLIT("Family instances can not yet use GADT declarations")) ]
1233 tooManyParmsErr tc_name
1234 = ptext SLIT("Family instance has too many parameters:") <+>
1235 quotes (ppr tc_name)
1237 tooFewParmsErr arity
1238 = ptext SLIT("Family instance has too few parameters; expected") <+>
1241 wrongNumberOfParmsErr exp_arity
1242 = ptext SLIT("Number of parameters must match family declaration; expected")
1245 badBootFamInstDeclErr =
1246 ptext SLIT("Illegal family instance in hs-boot file")
1248 wrongKindOfFamily family =
1249 ptext SLIT("Wrong category of family instance; declaration was for a") <+>
1252 kindOfFamily | isSynTyCon family = ptext SLIT("type synonym")
1253 | isAlgTyCon family = ptext SLIT("data type")
1254 | otherwise = pprPanic "wrongKindOfFamily" (ppr family)
1256 emptyConDeclsErr tycon
1257 = sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
1258 nest 2 $ ptext SLIT("(-XEmptyDataDecls permits this)")]