2 % (c) The University of Glasgow 2006
3 % (c) The AQUA Project, Glasgow University, 1996-1998
6 TcTyClsDecls: Typecheck type and class declarations
10 -- The above warning supression flag is a temporary kludge.
11 -- While working on this module you are encouraged to remove it and fix
12 -- any warnings in the module. See
13 -- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
17 tcTyAndClassDecls, tcFamInstDecl
20 #include "HsVersions.h"
56 import Control.Monad ( mplus )
60 %************************************************************************
62 \subsection{Type checking for type and class declarations}
64 %************************************************************************
68 Consider a mutually-recursive group, binding
69 a type constructor T and a class C.
71 Step 1: getInitialKind
72 Construct a KindEnv by binding T and C to a kind variable
75 In that environment, do a kind check
77 Step 3: Zonk the kinds
79 Step 4: buildTyConOrClass
80 Construct an environment binding T to a TyCon and C to a Class.
81 a) Their kinds comes from zonking the relevant kind variable
82 b) Their arity (for synonyms) comes direct from the decl
83 c) The funcional dependencies come from the decl
84 d) The rest comes a knot-tied binding of T and C, returned from Step 4
85 e) The variances of the tycons in the group is calculated from
89 In this environment, walk over the decls, constructing the TyCons and Classes.
90 This uses in a strict way items (a)-(c) above, which is why they must
91 be constructed in Step 4. Feed the results back to Step 4.
92 For this step, pass the is-recursive flag as the wimp-out flag
96 Step 6: Extend environment
97 We extend the type environment with bindings not only for the TyCons and Classes,
98 but also for their "implicit Ids" like data constructors and class selectors
100 Step 7: checkValidTyCl
101 For a recursive group only, check all the decls again, just
102 to check all the side conditions on validity. We could not
103 do this before because we were in a mutually recursive knot.
105 Identification of recursive TyCons
106 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
107 The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to
110 Identifying a TyCon as recursive serves two purposes
112 1. Avoid infinite types. Non-recursive newtypes are treated as
113 "transparent", like type synonyms, after the type checker. If we did
114 this for all newtypes, we'd get infinite types. So we figure out for
115 each newtype whether it is "recursive", and add a coercion if so. In
116 effect, we are trying to "cut the loops" by identifying a loop-breaker.
118 2. Avoid infinite unboxing. This is nothing to do with newtypes.
122 Well, this function diverges, but we don't want the strictness analyser
123 to diverge. But the strictness analyser will diverge because it looks
124 deeper and deeper into the structure of T. (I believe there are
125 examples where the function does something sane, and the strictness
126 analyser still diverges, but I can't see one now.)
128 Now, concerning (1), the FC2 branch currently adds a coercion for ALL
129 newtypes. I did this as an experiment, to try to expose cases in which
130 the coercions got in the way of optimisations. If it turns out that we
131 can indeed always use a coercion, then we don't risk recursive types,
132 and don't need to figure out what the loop breakers are.
134 For newtype *families* though, we will always have a coercion, so they
135 are always loop breakers! So you can easily adjust the current
136 algorithm by simply treating all newtype families as loop breakers (and
137 indeed type families). I think.
140 tcTyAndClassDecls :: ModDetails -> [LTyClDecl Name]
141 -> TcM TcGblEnv -- Input env extended by types and classes
142 -- and their implicit Ids,DataCons
143 -- Fails if there are any errors
145 tcTyAndClassDecls boot_details allDecls
146 = checkNoErrs $ -- The code recovers internally, but if anything gave rise to
147 -- an error we'd better stop now, to avoid a cascade
148 do { -- Omit instances of type families; they are handled together
149 -- with the *heads* of class instances
150 ; let decls = filter (not . isFamInstDecl . unLoc) allDecls
152 -- First check for cyclic type synonysm or classes
153 -- See notes with checkCycleErrs
154 ; checkCycleErrs decls
156 ; traceTc (text "tcTyAndCl" <+> ppr mod)
157 ; (syn_tycons, alg_tyclss) <- fixM (\ ~(rec_syn_tycons, rec_alg_tyclss) ->
158 do { let { -- Seperate ordinary synonyms from all other type and
159 -- class declarations and add all associated type
160 -- declarations from type classes. The latter is
161 -- required so that the temporary environment for the
162 -- knot includes all associated family declarations.
163 ; (syn_decls, alg_decls) = partition (isSynDecl . unLoc)
165 ; alg_at_decls = concatMap addATs alg_decls
167 -- Extend the global env with the knot-tied results
168 -- for data types and classes
170 -- We must populate the environment with the loop-tied
171 -- T's right away, because the kind checker may "fault
172 -- in" some type constructors that recursively
174 ; let gbl_things = mkGlobalThings alg_at_decls rec_alg_tyclss
175 ; tcExtendRecEnv gbl_things $ do
177 -- Kind-check the declarations
178 { (kc_syn_decls, kc_alg_decls) <- kcTyClDecls syn_decls alg_decls
180 ; let { -- Calculate rec-flag
181 ; calc_rec = calcRecFlags boot_details rec_alg_tyclss
182 ; tc_decl = addLocM (tcTyClDecl calc_rec) }
184 -- Type-check the type synonyms, and extend the envt
185 ; syn_tycons <- tcSynDecls kc_syn_decls
186 ; tcExtendGlobalEnv syn_tycons $ do
188 -- Type-check the data types and classes
189 { alg_tyclss <- mapM tc_decl kc_alg_decls
190 ; return (syn_tycons, concat alg_tyclss)
192 -- Finished with knot-tying now
193 -- Extend the environment with the finished things
194 ; tcExtendGlobalEnv (syn_tycons ++ alg_tyclss) $ do
196 -- Perform the validity check
197 { traceTc (text "ready for validity check")
198 ; mapM_ (addLocM checkValidTyCl) decls
199 ; traceTc (text "done")
201 -- Add the implicit things;
202 -- we want them in the environment because
203 -- they may be mentioned in interface files
204 -- NB: All associated types and their implicit things will be added a
205 -- second time here. This doesn't matter as the definitions are
207 ; let { implicit_things = concatMap implicitTyThings alg_tyclss }
208 ; traceTc ((text "Adding" <+> ppr alg_tyclss)
209 $$ (text "and" <+> ppr implicit_things))
210 ; tcExtendGlobalEnv implicit_things getGblEnv
213 -- Pull associated types out of class declarations, to tie them into the
215 -- NB: We put them in the same place in the list as `tcTyClDecl' will
216 -- eventually put the matching `TyThing's. That's crucial; otherwise,
217 -- the two argument lists of `mkGlobalThings' don't match up.
218 addATs decl@(L _ (ClassDecl {tcdATs = ats})) = decl : ats
221 mkGlobalThings :: [LTyClDecl Name] -- The decls
222 -> [TyThing] -- Knot-tied, in 1-1 correspondence with the decls
224 -- Driven by the Decls, and treating the TyThings lazily
225 -- make a TypeEnv for the new things
226 mkGlobalThings decls things
227 = map mk_thing (decls `zipLazy` things)
229 mk_thing (L _ (ClassDecl {tcdLName = L _ name}), ~(AClass cl))
231 mk_thing (L _ decl, ~(ATyCon tc))
232 = (tcdName decl, ATyCon tc)
236 %************************************************************************
238 \subsection{Type checking family instances}
240 %************************************************************************
242 Family instances are somewhat of a hybrid. They are processed together with
243 class instance heads, but can contain data constructors and hence they share a
244 lot of kinding and type checking code with ordinary algebraic data types (and
248 tcFamInstDecl :: LTyClDecl Name -> TcM (Maybe TyThing) -- Nothing if error
249 tcFamInstDecl (L loc decl)
250 = -- Prime error recovery, set source location
251 recoverM (return Nothing) $
254 do { -- type families require -XTypeFamilies and can't be in an
256 ; type_families <- doptM Opt_TypeFamilies
257 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
258 ; checkTc type_families $ badFamInstDecl (tcdLName decl)
259 ; checkTc (not is_boot) $ badBootFamInstDeclErr
261 -- perform kind and type checking
262 ; tcFamInstDecl1 decl
265 tcFamInstDecl1 :: TyClDecl Name -> TcM (Maybe TyThing) -- Nothing if error
268 tcFamInstDecl1 (decl@TySynonym {tcdLName = L loc tc_name})
269 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
270 do { -- check that the family declaration is for a synonym
271 unless (isSynTyCon family) $
272 addErr (wrongKindOfFamily family)
274 ; -- (1) kind check the right-hand side of the type equation
275 ; k_rhs <- kcCheckHsType (tcdSynRhs decl) resKind
277 -- we need the exact same number of type parameters as the family
279 ; let famArity = tyConArity family
280 ; checkTc (length k_typats == famArity) $
281 wrongNumberOfParmsErr famArity
283 -- (2) type check type equation
284 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
285 ; t_typats <- mapM tcHsKindedType k_typats
286 ; t_rhs <- tcHsKindedType k_rhs
289 -- - check the well-formedness of the instance
290 ; checkValidTypeInst t_typats t_rhs
292 -- (4) construct representation tycon
293 ; rep_tc_name <- newFamInstTyConName tc_name loc
294 ; tycon <- buildSynTyCon rep_tc_name t_tvs (SynonymTyCon t_rhs)
295 (Just (family, t_typats))
297 ; return $ Just (ATyCon tycon)
300 -- "newtype instance" and "data instance"
301 tcFamInstDecl1 (decl@TyData {tcdND = new_or_data, tcdLName = L loc tc_name,
303 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
304 do { -- check that the family declaration is for the right kind
305 unless (isAlgTyCon family) $
306 addErr (wrongKindOfFamily family)
308 ; -- (1) kind check the data declaration as usual
309 ; k_decl <- kcDataDecl decl k_tvs
310 ; let k_ctxt = tcdCtxt k_decl
311 k_cons = tcdCons k_decl
313 -- result kind must be '*' (otherwise, we have too few patterns)
314 ; checkTc (isLiftedTypeKind resKind) $ tooFewParmsErr (tyConArity family)
316 -- (2) type check indexed data type declaration
317 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
318 ; unbox_strict <- doptM Opt_UnboxStrictFields
320 -- kind check the type indexes and the context
321 ; t_typats <- mapM tcHsKindedType k_typats
322 ; stupid_theta <- tcHsKindedContext k_ctxt
325 -- - left-hand side contains no type family applications
326 -- (vanilla synonyms are fine, though, and we checked for
328 ; mapM_ checkTyFamFreeness t_typats
330 -- - we don't use GADT syntax for indexed types
331 ; checkTc h98_syntax (badGadtIdxTyDecl tc_name)
333 -- - a newtype has exactly one constructor
334 ; checkTc (new_or_data == DataType || isSingleton k_cons) $
335 newtypeConError tc_name (length k_cons)
337 -- (4) construct representation tycon
338 ; rep_tc_name <- newFamInstTyConName tc_name loc
339 ; let ex_ok = True -- Existentials ok for type families!
340 ; tycon <- fixM (\ tycon -> do
341 { data_cons <- mapM (addLocM (tcConDecl unbox_strict ex_ok tycon t_tvs))
345 DataType -> return (mkDataTyConRhs data_cons)
346 NewType -> ASSERT( not (null data_cons) )
347 mkNewTyConRhs rep_tc_name tycon (head data_cons)
348 ; buildAlgTyCon rep_tc_name t_tvs stupid_theta tc_rhs Recursive
349 False h98_syntax (Just (family, t_typats))
350 -- We always assume that indexed types are recursive. Why?
351 -- (1) Due to their open nature, we can never be sure that a
352 -- further instance might not introduce a new recursive
353 -- dependency. (2) They are always valid loop breakers as
354 -- they involve a coercion.
358 ; return $ Just (ATyCon tycon)
361 h98_syntax = case cons of -- All constructors have same shape
362 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
365 -- Kind checking of indexed types
368 -- Kind check type patterns and kind annotate the embedded type variables.
370 -- * Here we check that a type instance matches its kind signature, but we do
371 -- not check whether there is a pattern for each type index; the latter
372 -- check is only required for type synonym instances.
374 kcIdxTyPats :: TyClDecl Name
375 -> ([LHsTyVarBndr Name] -> [LHsType Name] -> Kind -> TyCon -> TcM a)
376 -- ^^kinded tvs ^^kinded ty pats ^^res kind
378 kcIdxTyPats decl thing_inside
379 = kcHsTyVars (tcdTyVars decl) $ \tvs ->
380 do { family <- tcLookupLocatedTyCon (tcdLName decl)
381 ; let { (kinds, resKind) = splitKindFunTys (tyConKind family)
382 ; hs_typats = fromJust $ tcdTyPats decl }
384 -- we may not have more parameters than the kind indicates
385 ; checkTc (length kinds >= length hs_typats) $
386 tooManyParmsErr (tcdLName decl)
388 -- type functions can have a higher-kinded result
389 ; let resultKind = mkArrowKinds (drop (length hs_typats) kinds) resKind
390 ; typats <- zipWithM kcCheckHsType hs_typats kinds
391 ; thing_inside tvs typats resultKind family
397 %************************************************************************
401 %************************************************************************
403 We need to kind check all types in the mutually recursive group
404 before we know the kind of the type variables. For example:
407 op :: D b => a -> b -> b
410 bop :: (Monad c) => ...
412 Here, the kind of the locally-polymorphic type variable "b"
413 depends on *all the uses of class D*. For example, the use of
414 Monad c in bop's type signature means that D must have kind Type->Type.
416 However type synonyms work differently. They can have kinds which don't
417 just involve (->) and *:
418 type R = Int# -- Kind #
419 type S a = Array# a -- Kind * -> #
420 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
421 So we must infer their kinds from their right-hand sides *first* and then
422 use them, whereas for the mutually recursive data types D we bring into
423 scope kind bindings D -> k, where k is a kind variable, and do inference.
427 This treatment of type synonyms only applies to Haskell 98-style synonyms.
428 General type functions can be recursive, and hence, appear in `alg_decls'.
430 The kind of a type family is solely determinded by its kind signature;
431 hence, only kind signatures participate in the construction of the initial
432 kind environment (as constructed by `getInitialKind'). In fact, we ignore
433 instances of families altogether in the following. However, we need to
434 include the kinds of associated families into the construction of the
435 initial kind environment. (This is handled by `allDecls').
438 kcTyClDecls syn_decls alg_decls
439 = do { -- First extend the kind env with each data type, class, and
440 -- indexed type, mapping them to a type variable
441 let initialKindDecls = concat [allDecls decl | L _ decl <- alg_decls]
442 ; alg_kinds <- mapM getInitialKind initialKindDecls
443 ; tcExtendKindEnv alg_kinds $ do
445 -- Now kind-check the type synonyms, in dependency order
446 -- We do these differently to data type and classes,
447 -- because a type synonym can be an unboxed type
449 -- and a kind variable can't unify with UnboxedTypeKind
450 -- So we infer their kinds in dependency order
451 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
452 ; tcExtendKindEnv syn_kinds $ do
454 -- Now kind-check the data type, class, and kind signatures,
455 -- returning kind-annotated decls; we don't kind-check
456 -- instances of indexed types yet, but leave this to
458 { kc_alg_decls <- mapM (wrapLocM kcTyClDecl)
459 (filter (not . isFamInstDecl . unLoc) alg_decls)
461 ; return (kc_syn_decls, kc_alg_decls) }}}
463 -- get all declarations relevant for determining the initial kind
465 allDecls (decl@ClassDecl {tcdATs = ats}) = decl : [ at
468 allDecls decl | isFamInstDecl decl = []
471 ------------------------------------------------------------------------
472 getInitialKind :: TyClDecl Name -> TcM (Name, TcKind)
473 -- Only for data type, class, and indexed type declarations
474 -- Get as much info as possible from the data, class, or indexed type decl,
475 -- so as to maximise usefulness of error messages
477 = do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl)
478 ; res_kind <- mk_res_kind decl
479 ; return (tcdName decl, mkArrowKinds arg_kinds res_kind) }
481 mk_arg_kind (UserTyVar _) = newKindVar
482 mk_arg_kind (KindedTyVar _ kind) = return kind
484 mk_res_kind (TyFamily { tcdKind = Just kind }) = return kind
485 mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
486 -- On GADT-style declarations we allow a kind signature
487 -- data T :: *->* where { ... }
488 mk_res_kind other = return liftedTypeKind
492 kcSynDecls :: [SCC (LTyClDecl Name)]
493 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
494 [(Name,TcKind)]) -- Kind bindings
497 kcSynDecls (group : groups)
498 = do { (decl, nk) <- kcSynDecl group
499 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
500 ; return (decl:decls, nk:nks) }
503 kcSynDecl :: SCC (LTyClDecl Name)
504 -> TcM (LTyClDecl Name, -- Kind-annotated decls
505 (Name,TcKind)) -- Kind bindings
506 kcSynDecl (AcyclicSCC ldecl@(L loc decl))
507 = tcAddDeclCtxt decl $
508 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
509 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
510 <+> brackets (ppr k_tvs))
511 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
512 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
513 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
514 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
515 (unLoc (tcdLName decl), tc_kind)) })
517 kcSynDecl (CyclicSCC decls)
518 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
519 -- of out-of-scope tycons
521 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
523 ------------------------------------------------------------------------
524 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
525 -- Not used for type synonyms (see kcSynDecl)
527 kcTyClDecl decl@(TyData {})
528 = ASSERT( not . isFamInstDecl $ decl ) -- must not be a family instance
529 kcTyClDeclBody decl $
532 kcTyClDecl decl@(TyFamily {})
533 = kcFamilyDecl [] decl -- the empty list signals a toplevel decl
535 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs, tcdATs = ats})
536 = kcTyClDeclBody decl $ \ tvs' ->
537 do { is_boot <- tcIsHsBoot
538 ; ctxt' <- kcHsContext ctxt
539 ; ats' <- mapM (wrapLocM (kcFamilyDecl tvs')) ats
540 ; sigs' <- mapM (wrapLocM kc_sig) sigs
541 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs',
544 kc_sig (TypeSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
545 ; return (TypeSig nm op_ty') }
546 kc_sig other_sig = return other_sig
548 kcTyClDecl decl@(ForeignType {})
551 kcTyClDeclBody :: TyClDecl Name
552 -> ([LHsTyVarBndr Name] -> TcM a)
554 -- getInitialKind has made a suitably-shaped kind for the type or class
555 -- Unpack it, and attribute those kinds to the type variables
556 -- Extend the env with bindings for the tyvars, taken from
557 -- the kind of the tycon/class. Give it to the thing inside, and
558 -- check the result kind matches
559 kcTyClDeclBody decl thing_inside
560 = tcAddDeclCtxt decl $
561 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
562 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
563 (kinds, _) = splitKindFunTys tc_kind
564 hs_tvs = tcdTyVars decl
565 kinded_tvs = ASSERT( length kinds >= length hs_tvs )
566 [ L loc (KindedTyVar (hsTyVarName tv) k)
567 | (L loc tv, k) <- zip hs_tvs kinds]
568 ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
570 -- Kind check a data declaration, assuming that we already extended the
571 -- kind environment with the type variables of the left-hand side (these
572 -- kinded type variables are also passed as the second parameter).
574 kcDataDecl :: TyClDecl Name -> [LHsTyVarBndr Name] -> TcM (TyClDecl Name)
575 kcDataDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
577 = do { ctxt' <- kcHsContext ctxt
578 ; cons' <- mapM (wrapLocM kc_con_decl) cons
579 ; return (decl {tcdTyVars = tvs, tcdCtxt = ctxt', tcdCons = cons'}) }
581 -- doc comments are typechecked to Nothing here
582 kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res _) = do
583 kcHsTyVars ex_tvs $ \ex_tvs' -> do
584 ex_ctxt' <- kcHsContext ex_ctxt
585 details' <- kc_con_details details
587 ResTyH98 -> return ResTyH98
588 ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
589 return (ConDecl name expl ex_tvs' ex_ctxt' details' res' Nothing)
591 kc_con_details (PrefixCon btys)
592 = do { btys' <- mapM kc_larg_ty btys
593 ; return (PrefixCon btys') }
594 kc_con_details (InfixCon bty1 bty2)
595 = do { bty1' <- kc_larg_ty bty1
596 ; bty2' <- kc_larg_ty bty2
597 ; return (InfixCon bty1' bty2') }
598 kc_con_details (RecCon fields)
599 = do { fields' <- mapM kc_field fields
600 ; return (RecCon fields') }
602 kc_field (ConDeclField fld bty d) = do { bty' <- kc_larg_ty bty
603 ; return (ConDeclField fld bty' d) }
605 kc_larg_ty bty = case new_or_data of
606 DataType -> kcHsSigType bty
607 NewType -> kcHsLiftedSigType bty
608 -- Can't allow an unlifted type for newtypes, because we're effectively
609 -- going to remove the constructor while coercing it to a lifted type.
610 -- And newtypes can't be bang'd
612 -- Kind check a family declaration or type family default declaration.
614 kcFamilyDecl :: [LHsTyVarBndr Name] -- tyvars of enclosing class decl if any
615 -> TyClDecl Name -> TcM (TyClDecl Name)
616 kcFamilyDecl classTvs decl@(TyFamily {tcdKind = kind})
617 = kcTyClDeclBody decl $ \tvs' ->
618 do { mapM_ unifyClassParmKinds tvs'
619 ; return (decl {tcdTyVars = tvs',
620 tcdKind = kind `mplus` Just liftedTypeKind})
621 -- default result kind is '*'
624 unifyClassParmKinds (L _ (KindedTyVar n k))
625 | Just classParmKind <- lookup n classTyKinds = unifyKind k classParmKind
626 | otherwise = return ()
627 classTyKinds = [(n, k) | L _ (KindedTyVar n k) <- classTvs]
628 kcFamilyDecl _ decl@(TySynonym {}) -- type family defaults
629 = panic "TcTyClsDecls.kcFamilyDecl: not implemented yet"
633 %************************************************************************
635 \subsection{Type checking}
637 %************************************************************************
640 tcSynDecls :: [LTyClDecl Name] -> TcM [TyThing]
641 tcSynDecls [] = return []
642 tcSynDecls (decl : decls)
643 = do { syn_tc <- addLocM tcSynDecl decl
644 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls decls)
645 ; return (syn_tc : syn_tcs) }
649 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
650 = tcTyVarBndrs tvs $ \ tvs' -> do
651 { traceTc (text "tcd1" <+> ppr tc_name)
652 ; rhs_ty' <- tcHsKindedType rhs_ty
653 ; tycon <- buildSynTyCon tc_name tvs' (SynonymTyCon rhs_ty') Nothing
654 ; return (ATyCon tycon)
658 tcTyClDecl :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
660 tcTyClDecl calc_isrec decl
661 = tcAddDeclCtxt decl (tcTyClDecl1 calc_isrec decl)
663 -- "type family" declarations
664 tcTyClDecl1 _calc_isrec
665 (TyFamily {tcdFlavour = TypeFamily,
666 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = Just kind})
667 -- NB: kind at latest
670 = tcTyVarBndrs tvs $ \ tvs' -> do
671 { traceTc (text "type family: " <+> ppr tc_name)
672 ; idx_tys <- doptM Opt_TypeFamilies
674 -- Check that we don't use families without -XTypeFamilies
675 ; checkTc idx_tys $ badFamInstDecl tc_name
677 ; tycon <- buildSynTyCon tc_name tvs' (OpenSynTyCon kind Nothing) Nothing
678 ; return [ATyCon tycon]
681 -- "data family" declaration
682 tcTyClDecl1 _calc_isrec
683 (TyFamily {tcdFlavour = DataFamily,
684 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = mb_kind})
685 = tcTyVarBndrs tvs $ \ tvs' -> do
686 { traceTc (text "data family: " <+> ppr tc_name)
687 ; extra_tvs <- tcDataKindSig mb_kind
688 ; let final_tvs = tvs' ++ extra_tvs -- we may not need these
690 ; idx_tys <- doptM Opt_TypeFamilies
692 -- Check that we don't use families without -XTypeFamilies
693 ; checkTc idx_tys $ badFamInstDecl tc_name
695 ; tycon <- buildAlgTyCon tc_name final_tvs []
696 mkOpenDataTyConRhs Recursive False True Nothing
697 ; return [ATyCon tycon]
700 -- "newtype" and "data"
701 -- NB: not used for newtype/data instances (whether associated or not)
702 tcTyClDecl1 calc_isrec
703 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
704 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
705 = tcTyVarBndrs tvs $ \ tvs' -> do
706 { extra_tvs <- tcDataKindSig mb_ksig
707 ; let final_tvs = tvs' ++ extra_tvs
708 ; stupid_theta <- tcHsKindedContext ctxt
709 ; want_generic <- doptM Opt_Generics
710 ; unbox_strict <- doptM Opt_UnboxStrictFields
711 ; empty_data_decls <- doptM Opt_EmptyDataDecls
712 ; kind_signatures <- doptM Opt_KindSignatures
713 ; existential_ok <- doptM Opt_ExistentialQuantification
714 ; gadt_ok <- doptM Opt_GADTs
715 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
716 ; let ex_ok = existential_ok || gadt_ok -- Data cons can have existential context
718 -- Check that we don't use GADT syntax in H98 world
719 ; checkTc (gadt_ok || h98_syntax) (badGadtDecl tc_name)
721 -- Check that we don't use kind signatures without Glasgow extensions
722 ; checkTc (kind_signatures || isNothing mb_ksig) (badSigTyDecl tc_name)
724 -- Check that the stupid theta is empty for a GADT-style declaration
725 ; checkTc (null stupid_theta || h98_syntax) (badStupidTheta tc_name)
727 -- Check that there's at least one condecl,
728 -- or else we're reading an hs-boot file, or -XEmptyDataDecls
729 ; checkTc (not (null cons) || empty_data_decls || is_boot)
730 (emptyConDeclsErr tc_name)
732 -- Check that a newtype has exactly one constructor
733 ; checkTc (new_or_data == DataType || isSingleton cons)
734 (newtypeConError tc_name (length cons))
736 ; tycon <- fixM (\ tycon -> do
737 { data_cons <- mapM (addLocM (tcConDecl unbox_strict ex_ok tycon final_tvs))
740 if null cons && is_boot -- In a hs-boot file, empty cons means
741 then return AbstractTyCon -- "don't know"; hence Abstract
742 else case new_or_data of
743 DataType -> return (mkDataTyConRhs data_cons)
745 ASSERT( not (null data_cons) )
746 mkNewTyConRhs tc_name tycon (head data_cons)
747 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
748 (want_generic && canDoGenerics data_cons) h98_syntax Nothing
750 ; return [ATyCon tycon]
753 is_rec = calc_isrec tc_name
754 h98_syntax = case cons of -- All constructors have same shape
755 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
758 tcTyClDecl1 calc_isrec
759 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
760 tcdCtxt = ctxt, tcdMeths = meths,
761 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
762 = tcTyVarBndrs tvs $ \ tvs' -> do
763 { ctxt' <- tcHsKindedContext ctxt
764 ; fds' <- mapM (addLocM tc_fundep) fundeps
765 ; atss <- mapM (addLocM (tcTyClDecl1 (const Recursive))) ats
766 -- NB: 'ats' only contains "type family" and "data family"
767 -- declarations as well as type family defaults
768 ; let ats' = zipWith setTyThingPoss atss (map (tcdTyVars . unLoc) ats)
769 ; sig_stuff <- tcClassSigs class_name sigs meths
770 ; clas <- fixM (\ clas ->
771 let -- This little knot is just so we can get
772 -- hold of the name of the class TyCon, which we
773 -- need to look up its recursiveness
774 tycon_name = tyConName (classTyCon clas)
775 tc_isrec = calc_isrec tycon_name
777 buildClass class_name tvs' ctxt' fds' ats'
779 ; return (AClass clas : ats')
780 -- NB: Order is important due to the call to `mkGlobalThings' when
781 -- tying the the type and class declaration type checking knot.
784 tc_fundep (tvs1, tvs2) = do { tvs1' <- mapM tcLookupTyVar tvs1 ;
785 ; tvs2' <- mapM tcLookupTyVar tvs2 ;
786 ; return (tvs1', tvs2') }
788 -- For each AT argument compute the position of the corresponding class
789 -- parameter in the class head. This will later serve as a permutation
790 -- vector when checking the validity of instance declarations.
791 setTyThingPoss [ATyCon tycon] atTyVars =
792 let classTyVars = hsLTyVarNames tvs
794 . map (`elemIndex` classTyVars)
797 -- There will be no Nothing, as we already passed renaming
799 ATyCon (setTyConArgPoss tycon poss)
800 setTyThingPoss _ _ = panic "TcTyClsDecls.setTyThingPoss"
802 tcTyClDecl1 calc_isrec
803 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
804 = return [ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0)]
806 -----------------------------------
807 tcConDecl :: Bool -- True <=> -funbox-strict_fields
808 -> Bool -- True <=> -XExistentialQuantificaton or -XGADTs
813 tcConDecl unbox_strict existential_ok tycon tc_tvs -- Data types
814 (ConDecl name _ tvs ctxt details res_ty _)
815 = tcTyVarBndrs tvs $ \ tvs' -> do
816 { ctxt' <- tcHsKindedContext ctxt
817 ; checkTc (existential_ok || (null tvs && null (unLoc ctxt)))
818 (badExistential name)
819 ; (univ_tvs, ex_tvs, eq_preds, data_tc) <- tcResultType tycon tc_tvs tvs' res_ty
821 -- Tiresome: tidy the tyvar binders, since tc_tvs and tvs' may have the same OccNames
822 tc_datacon is_infix field_lbls btys
823 = do { let bangs = map getBangStrictness btys
824 ; arg_tys <- mapM tcHsBangType btys
825 ; buildDataCon (unLoc name) is_infix
826 (argStrictness unbox_strict bangs arg_tys)
827 (map unLoc field_lbls)
828 univ_tvs ex_tvs eq_preds ctxt' arg_tys
830 -- NB: we put data_tc, the type constructor gotten from the
831 -- constructor type signature into the data constructor;
832 -- that way checkValidDataCon can complain if it's wrong.
835 PrefixCon btys -> tc_datacon False [] btys
836 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
837 RecCon fields -> tc_datacon False field_names btys
839 field_names = map cd_fld_name fields
840 btys = map cd_fld_type fields
843 tcResultType :: TyCon
844 -> [TyVar] -- data T a b c = ...
845 -> [TyVar] -- where MkT :: forall a b c. ...
847 -> TcM ([TyVar], -- Universal
848 [TyVar], -- Existential (distinct OccNames from univs)
849 [(TyVar,Type)], -- Equality predicates
850 TyCon) -- TyCon given in the ResTy
851 -- We don't check that the TyCon given in the ResTy is
852 -- the same as the parent tycon, becuase we are in the middle
853 -- of a recursive knot; so it's postponed until checkValidDataCon
855 tcResultType decl_tycon tc_tvs dc_tvs ResTyH98
856 = return (tc_tvs, dc_tvs, [], decl_tycon)
857 -- In H98 syntax the dc_tvs are the existential ones
858 -- data T a b c = forall d e. MkT ...
859 -- The {a,b,c} are tc_tvs, and {d,e} are dc_tvs
861 tcResultType _ tc_tvs dc_tvs (ResTyGADT res_ty)
862 -- E.g. data T a b c where
863 -- MkT :: forall x y z. T (x,y) z z
865 -- ([a,z,c], [x,y], [a:=:(x,y), c:=:z], T)
867 = do { (dc_tycon, res_tys) <- tcLHsConResTy res_ty
869 ; let univ_tvs = choose_univs [] tidy_tc_tvs res_tys
870 -- Each univ_tv is either a dc_tv or a tc_tv
871 ex_tvs = dc_tvs `minusList` univ_tvs
872 eq_spec = [ (tv, ty) | (tv,ty) <- univ_tvs `zip` res_tys,
874 ; return (univ_tvs, ex_tvs, eq_spec, dc_tycon) }
876 -- choose_univs uses the res_ty itself if it's a type variable
877 -- and hasn't already been used; otherwise it uses one of the tc_tvs
878 choose_univs used tc_tvs []
879 = ASSERT( null tc_tvs ) []
880 choose_univs used (tc_tv:tc_tvs) (res_ty:res_tys)
881 | Just tv <- tcGetTyVar_maybe res_ty, not (tv `elem` used)
882 = tv : choose_univs (tv:used) tc_tvs res_tys
884 = tc_tv : choose_univs used tc_tvs res_tys
886 -- NB: tc_tvs and dc_tvs are distinct, but
887 -- we want them to be *visibly* distinct, both for
888 -- interface files and general confusion. So rename
889 -- the tc_tvs, since they are not used yet (no
890 -- consequential renaming needed)
891 init_occ_env = initTidyOccEnv (map getOccName dc_tvs)
892 (_, tidy_tc_tvs) = mapAccumL tidy_one init_occ_env tc_tvs
893 tidy_one env tv = (env', setTyVarName tv (tidyNameOcc name occ'))
896 (env', occ') = tidyOccName env (getOccName name)
899 argStrictness :: Bool -- True <=> -funbox-strict_fields
901 -> [TcType] -> [StrictnessMark]
902 argStrictness unbox_strict bangs arg_tys
903 = ASSERT( length bangs == length arg_tys )
904 zipWith (chooseBoxingStrategy unbox_strict) arg_tys bangs
906 -- We attempt to unbox/unpack a strict field when either:
907 -- (i) The field is marked '!!', or
908 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
910 -- We have turned off unboxing of newtypes because coercions make unboxing
911 -- and reboxing more complicated
912 chooseBoxingStrategy :: Bool -> TcType -> HsBang -> StrictnessMark
913 chooseBoxingStrategy unbox_strict_fields arg_ty bang
915 HsNoBang -> NotMarkedStrict
916 HsStrict | unbox_strict_fields
917 && can_unbox arg_ty -> MarkedUnboxed
918 HsUnbox | can_unbox arg_ty -> MarkedUnboxed
919 other -> MarkedStrict
921 -- we can unbox if the type is a chain of newtypes with a product tycon
923 can_unbox arg_ty = case splitTyConApp_maybe arg_ty of
925 Just (arg_tycon, tycon_args) ->
926 not (isRecursiveTyCon arg_tycon) && -- Note [Recusive unboxing]
927 isProductTyCon arg_tycon &&
928 (if isNewTyCon arg_tycon then
929 can_unbox (newTyConInstRhs arg_tycon tycon_args)
933 Note [Recursive unboxing]
934 ~~~~~~~~~~~~~~~~~~~~~~~~~
935 Be careful not to try to unbox this!
937 But it's the *argument* type that matters. This is fine:
939 because Int is non-recursive.
941 %************************************************************************
943 \subsection{Dependency analysis}
945 %************************************************************************
947 Validity checking is done once the mutually-recursive knot has been
948 tied, so we can look at things freely.
951 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
952 checkCycleErrs tyclss
956 = do { mapM_ recClsErr cls_cycles
957 ; failM } -- Give up now, because later checkValidTyCl
958 -- will loop if the synonym is recursive
960 cls_cycles = calcClassCycles tyclss
962 checkValidTyCl :: TyClDecl Name -> TcM ()
963 -- We do the validity check over declarations, rather than TyThings
964 -- only so that we can add a nice context with tcAddDeclCtxt
966 = tcAddDeclCtxt decl $
967 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
968 ; traceTc (text "Validity of" <+> ppr thing)
970 ATyCon tc -> checkValidTyCon tc
971 AClass cl -> checkValidClass cl
972 ; traceTc (text "Done validity of" <+> ppr thing)
975 -------------------------
976 -- For data types declared with record syntax, we require
977 -- that each constructor that has a field 'f'
978 -- (a) has the same result type
979 -- (b) has the same type for 'f'
980 -- module alpha conversion of the quantified type variables
981 -- of the constructor.
983 checkValidTyCon :: TyCon -> TcM ()
986 = case synTyConRhs tc of
987 OpenSynTyCon _ _ -> return ()
988 SynonymTyCon ty -> checkValidType syn_ctxt ty
990 = do -- Check the context on the data decl
991 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc)
993 -- Check arg types of data constructors
994 mapM_ (checkValidDataCon tc) data_cons
996 -- Check that fields with the same name share a type
997 mapM_ check_fields groups
1000 syn_ctxt = TySynCtxt name
1002 data_cons = tyConDataCons tc
1004 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
1005 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
1006 get_fields con = dataConFieldLabels con `zip` repeat con
1007 -- dataConFieldLabels may return the empty list, which is fine
1009 -- See Note [GADT record selectors] in MkId.lhs
1010 -- We must check (a) that the named field has the same
1011 -- type in each constructor
1012 -- (b) that those constructors have the same result type
1014 -- However, the constructors may have differently named type variable
1015 -- and (worse) we don't know how the correspond to each other. E.g.
1016 -- C1 :: forall a b. { f :: a, g :: b } -> T a b
1017 -- C2 :: forall d c. { f :: c, g :: c } -> T c d
1019 -- So what we do is to ust Unify.tcMatchTys to compare the first candidate's
1020 -- result type against other candidates' types BOTH WAYS ROUND.
1021 -- If they magically agrees, take the substitution and
1022 -- apply them to the latter ones, and see if they match perfectly.
1023 check_fields fields@((label, con1) : other_fields)
1024 -- These fields all have the same name, but are from
1025 -- different constructors in the data type
1026 = recoverM (return ()) $ mapM_ checkOne other_fields
1027 -- Check that all the fields in the group have the same type
1028 -- NB: this check assumes that all the constructors of a given
1029 -- data type use the same type variables
1031 (tvs1, _, _, res1) = dataConSig con1
1033 fty1 = dataConFieldType con1 label
1035 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
1036 = do { checkFieldCompat label con1 con2 ts1 res1 res2 fty1 fty2
1037 ; checkFieldCompat label con2 con1 ts2 res2 res1 fty2 fty1 }
1039 (tvs2, _, _, res2) = dataConSig con2
1041 fty2 = dataConFieldType con2 label
1043 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
1044 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
1045 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
1047 mb_subst1 = tcMatchTy tvs1 res1 res2
1048 mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
1050 -------------------------------
1051 checkValidDataCon :: TyCon -> DataCon -> TcM ()
1052 checkValidDataCon tc con
1053 = setSrcSpan (srcLocSpan (getSrcLoc con)) $
1054 addErrCtxt (dataConCtxt con) $
1055 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
1056 ; checkValidType ctxt (dataConUserType con)
1057 ; checkValidMonoType (dataConOrigResTy con)
1058 -- Disallow MkT :: T (forall a. a->a)
1059 -- Reason: it's really the argument of an equality constraint
1060 ; when (isNewTyCon tc) (checkNewDataCon con)
1063 ctxt = ConArgCtxt (dataConName con)
1065 -------------------------------
1066 checkNewDataCon :: DataCon -> TcM ()
1067 -- Checks for the data constructor of a newtype
1069 = do { checkTc (isSingleton arg_tys) (newtypeFieldErr con (length arg_tys))
1071 ; checkTc (null eq_spec) (newtypePredError con)
1072 -- Return type is (T a b c)
1073 ; checkTc (null ex_tvs && null eq_theta && null dict_theta) (newtypeExError con)
1075 ; checkTc (not (any isMarkedStrict (dataConStrictMarks con)))
1076 (newtypeStrictError con)
1080 (_univ_tvs, ex_tvs, eq_spec, eq_theta, dict_theta, arg_tys, _res_ty) = dataConFullSig con
1082 -------------------------------
1083 checkValidClass :: Class -> TcM ()
1085 = do { constrained_class_methods <- doptM Opt_ConstrainedClassMethods
1086 ; multi_param_type_classes <- doptM Opt_MultiParamTypeClasses
1087 ; fundep_classes <- doptM Opt_FunctionalDependencies
1089 -- Check that the class is unary, unless GlaExs
1090 ; checkTc (notNull tyvars) (nullaryClassErr cls)
1091 ; checkTc (multi_param_type_classes || unary) (classArityErr cls)
1092 ; checkTc (fundep_classes || null fundeps) (classFunDepsErr cls)
1094 -- Check the super-classes
1095 ; checkValidTheta (ClassSCCtxt (className cls)) theta
1097 -- Check the class operations
1098 ; mapM_ (check_op constrained_class_methods) op_stuff
1100 -- Check that if the class has generic methods, then the
1101 -- class has only one parameter. We can't do generic
1102 -- multi-parameter type classes!
1103 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
1106 (tyvars, fundeps, theta, _, _, op_stuff) = classExtraBigSig cls
1107 unary = isSingleton tyvars
1108 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
1110 check_op constrained_class_methods (sel_id, dm)
1111 = addErrCtxt (classOpCtxt sel_id tau) $ do
1112 { checkValidTheta SigmaCtxt (tail theta)
1113 -- The 'tail' removes the initial (C a) from the
1114 -- class itself, leaving just the method type
1116 ; traceTc (text "class op type" <+> ppr op_ty <+> ppr tau)
1117 ; checkValidType (FunSigCtxt op_name) tau
1119 -- Check that the type mentions at least one of
1120 -- the class type variables...or at least one reachable
1121 -- from one of the class variables. Example: tc223
1122 -- class Error e => Game b mv e | b -> mv e where
1123 -- newBoard :: MonadState b m => m ()
1124 -- Here, MonadState has a fundep m->b, so newBoard is fine
1125 ; let grown_tyvars = grow theta (mkVarSet tyvars)
1126 ; checkTc (tyVarsOfType tau `intersectsVarSet` grown_tyvars)
1127 (noClassTyVarErr cls sel_id)
1129 -- Check that for a generic method, the type of
1130 -- the method is sufficiently simple
1131 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
1132 (badGenericMethodType op_name op_ty)
1135 op_name = idName sel_id
1136 op_ty = idType sel_id
1137 (_,theta1,tau1) = tcSplitSigmaTy op_ty
1138 (_,theta2,tau2) = tcSplitSigmaTy tau1
1139 (theta,tau) | constrained_class_methods = (theta1 ++ theta2, tau2)
1140 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
1141 -- Ugh! The function might have a type like
1142 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
1143 -- With -XConstrainedClassMethods, we want to allow this, even though the inner
1144 -- forall has an (Eq a) constraint. Whereas in general, each constraint
1145 -- in the context of a for-all must mention at least one quantified
1146 -- type variable. What a mess!
1149 ---------------------------------------------------------------------
1150 resultTypeMisMatch field_name con1 con2
1151 = vcat [sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1152 ptext SLIT("have a common field") <+> quotes (ppr field_name) <> comma],
1153 nest 2 $ ptext SLIT("but have different result types")]
1154 fieldTypeMisMatch field_name con1 con2
1155 = sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1156 ptext SLIT("give different types for field"), quotes (ppr field_name)]
1158 dataConCtxt con = ptext SLIT("In the definition of data constructor") <+> quotes (ppr con)
1160 classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
1161 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
1164 = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
1167 = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
1168 parens (ptext SLIT("Use -XMultiParamTypeClasses to allow multi-parameter classes"))]
1171 = vcat [ptext SLIT("Fundeps in class") <+> quotes (ppr cls),
1172 parens (ptext SLIT("Use -XFunctionalDependencies to allow fundeps"))]
1174 noClassTyVarErr clas op
1175 = sep [ptext SLIT("The class method") <+> quotes (ppr op),
1176 ptext SLIT("mentions none of the type variables of the class") <+>
1177 ppr clas <+> hsep (map ppr (classTyVars clas))]
1179 genericMultiParamErr clas
1180 = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
1181 ptext SLIT("cannot have generic methods")
1183 badGenericMethodType op op_ty
1184 = hang (ptext SLIT("Generic method type is too complex"))
1185 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
1186 ptext SLIT("You can only use type variables, arrows, lists, and tuples")])
1189 = setSrcSpan (getLoc (head sorted_decls)) $
1190 addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
1191 nest 2 (vcat (map ppr_decl sorted_decls))])
1193 sorted_decls = sortLocated syn_decls
1194 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
1197 = setSrcSpan (getLoc (head sorted_decls)) $
1198 addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
1199 nest 2 (vcat (map ppr_decl sorted_decls))])
1201 sorted_decls = sortLocated cls_decls
1202 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
1204 sortLocated :: [Located a] -> [Located a]
1205 sortLocated things = sortLe le things
1207 le (L l1 _) (L l2 _) = l1 <= l2
1209 badDataConTyCon data_con
1210 = hang (ptext SLIT("Data constructor") <+> quotes (ppr data_con) <+>
1211 ptext SLIT("returns type") <+> quotes (ppr (dataConTyCon data_con)))
1212 2 (ptext SLIT("instead of its parent type"))
1215 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
1216 , nest 2 (parens $ ptext SLIT("Use -XGADTs to allow GADTs")) ]
1218 badExistential con_name
1219 = hang (ptext SLIT("Data constructor") <+> quotes (ppr con_name) <+>
1220 ptext SLIT("has existential type variables, or a context"))
1221 2 (parens $ ptext SLIT("Use -XExistentialQuantification or -XGADTs to allow this"))
1223 badStupidTheta tc_name
1224 = ptext SLIT("A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
1226 newtypeConError tycon n
1227 = sep [ptext SLIT("A newtype must have exactly one constructor,"),
1228 nest 2 $ ptext SLIT("but") <+> quotes (ppr tycon) <+> ptext SLIT("has") <+> speakN n ]
1231 = sep [ptext SLIT("A newtype constructor cannot have an existential context,"),
1232 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
1234 newtypeStrictError con
1235 = sep [ptext SLIT("A newtype constructor cannot have a strictness annotation,"),
1236 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
1238 newtypePredError con
1239 = sep [ptext SLIT("A newtype constructor must have a return type of form T a1 ... an"),
1240 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does not")]
1242 newtypeFieldErr con_name n_flds
1243 = sep [ptext SLIT("The constructor of a newtype must have exactly one field"),
1244 nest 2 $ ptext SLIT("but") <+> quotes (ppr con_name) <+> ptext SLIT("has") <+> speakN n_flds]
1246 badSigTyDecl tc_name
1247 = vcat [ ptext SLIT("Illegal kind signature") <+>
1248 quotes (ppr tc_name)
1249 , nest 2 (parens $ ptext SLIT("Use -XKindSignatures to allow kind signatures")) ]
1251 badFamInstDecl tc_name
1252 = vcat [ ptext SLIT("Illegal family instance for") <+>
1253 quotes (ppr tc_name)
1254 , nest 2 (parens $ ptext SLIT("Use -XTypeFamilies to allow indexed type families")) ]
1256 badGadtIdxTyDecl tc_name
1257 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+>
1258 quotes (ppr tc_name)
1259 , nest 2 (parens $ ptext SLIT("Family instances can not yet use GADT declarations")) ]
1261 tooManyParmsErr tc_name
1262 = ptext SLIT("Family instance has too many parameters:") <+>
1263 quotes (ppr tc_name)
1265 tooFewParmsErr arity
1266 = ptext SLIT("Family instance has too few parameters; expected") <+>
1269 wrongNumberOfParmsErr exp_arity
1270 = ptext SLIT("Number of parameters must match family declaration; expected")
1273 badBootFamInstDeclErr =
1274 ptext SLIT("Illegal family instance in hs-boot file")
1276 wrongKindOfFamily family =
1277 ptext SLIT("Wrong category of family instance; declaration was for a") <+>
1280 kindOfFamily | isSynTyCon family = ptext SLIT("type synonym")
1281 | isAlgTyCon family = ptext SLIT("data type")
1282 | otherwise = pprPanic "wrongKindOfFamily" (ppr family)
1284 emptyConDeclsErr tycon
1285 = sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
1286 nest 2 $ ptext SLIT("(-XEmptyDataDecls permits this)")]