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 -- - left-hand side contains no type family applications
279 -- (vanilla synonyms are fine, though)
280 ; mappM_ checkTyFamFreeness t_typats
282 -- - the right-hand side is a tau type
283 ; unless (isTauTy t_rhs) $
284 addErr (polyTyErr t_rhs)
286 -- (4) construct representation tycon
287 ; rep_tc_name <- newFamInstTyConName tc_name loc
288 ; tycon <- buildSynTyCon rep_tc_name t_tvs (SynonymTyCon t_rhs)
289 (Just (family, t_typats))
291 ; return $ Just (ATyCon tycon)
294 -- "newtype instance" and "data instance"
295 tcFamInstDecl1 (decl@TyData {tcdND = new_or_data, tcdLName = L loc tc_name,
297 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
298 do { -- check that the family declaration is for the right kind
299 unless (isAlgTyCon family) $
300 addErr (wrongKindOfFamily family)
302 ; -- (1) kind check the data declaration as usual
303 ; k_decl <- kcDataDecl decl k_tvs
304 ; let k_ctxt = tcdCtxt k_decl
305 k_cons = tcdCons k_decl
307 -- result kind must be '*' (otherwise, we have too few patterns)
308 ; checkTc (isLiftedTypeKind resKind) $ tooFewParmsErr (tyConArity family)
310 -- (2) type check indexed data type declaration
311 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
312 ; unbox_strict <- doptM Opt_UnboxStrictFields
314 -- kind check the type indexes and the context
315 ; t_typats <- mappM tcHsKindedType k_typats
316 ; stupid_theta <- tcHsKindedContext k_ctxt
319 -- - left-hand side contains no type family applications
320 -- (vanilla synonyms are fine, though)
321 ; mappM_ checkTyFamFreeness t_typats
323 -- - we don't use GADT syntax for indexed types
324 ; checkTc h98_syntax (badGadtIdxTyDecl tc_name)
326 -- - a newtype has exactly one constructor
327 ; checkTc (new_or_data == DataType || isSingleton k_cons) $
328 newtypeConError tc_name (length k_cons)
330 -- (4) construct representation tycon
331 ; rep_tc_name <- newFamInstTyConName tc_name loc
332 ; tycon <- fixM (\ tycon -> do
333 { data_cons <- mappM (addLocM (tcConDecl unbox_strict tycon t_tvs))
337 DataType -> return (mkDataTyConRhs data_cons)
338 NewType -> ASSERT( not (null data_cons) )
339 mkNewTyConRhs rep_tc_name tycon (head data_cons)
340 ; buildAlgTyCon rep_tc_name t_tvs stupid_theta tc_rhs Recursive
341 False h98_syntax (Just (family, t_typats))
342 -- We always assume that indexed types are recursive. Why?
343 -- (1) Due to their open nature, we can never be sure that a
344 -- further instance might not introduce a new recursive
345 -- dependency. (2) They are always valid loop breakers as
346 -- they involve a coercion.
350 ; return $ Just (ATyCon tycon)
353 h98_syntax = case cons of -- All constructors have same shape
354 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
357 -- Check that a type index does not contain any type family applications
359 -- * Earlier phases have already checked that there are no foralls in the
360 -- type; we also cannot have PredTys and NoteTys are being skipped by using
363 checkTyFamFreeness :: Type -> TcM ()
364 checkTyFamFreeness ty | Just (tycon, tys) <- splitTyConApp_maybe ty
365 = if isSynTyCon tycon
366 then addErr $ tyFamAppInIndexErr ty
367 else mappM_ checkTyFamFreeness tys
368 -- splitTyConApp_maybe uses the core view; hence,
369 -- any synonym tycon must be a family tycon
371 | Just (ty1, ty2) <- splitAppTy_maybe ty
372 = checkTyFamFreeness ty1 >> checkTyFamFreeness ty2
374 | otherwise -- only vars remaining
378 -- Kind checking of indexed types
381 -- Kind check type patterns and kind annotate the embedded type variables.
383 -- * Here we check that a type instance matches its kind signature, but we do
384 -- not check whether there is a pattern for each type index; the latter
385 -- check is only required for type synonym instances.
387 kcIdxTyPats :: TyClDecl Name
388 -> ([LHsTyVarBndr Name] -> [LHsType Name] -> Kind -> TyCon -> TcM a)
389 -- ^^kinded tvs ^^kinded ty pats ^^res kind
391 kcIdxTyPats decl thing_inside
392 = kcHsTyVars (tcdTyVars decl) $ \tvs ->
393 do { family <- tcLookupLocatedTyCon (tcdLName decl)
394 ; let { (kinds, resKind) = splitKindFunTys (tyConKind family)
395 ; hs_typats = fromJust $ tcdTyPats decl }
397 -- we may not have more parameters than the kind indicates
398 ; checkTc (length kinds >= length hs_typats) $
399 tooManyParmsErr (tcdLName decl)
401 -- type functions can have a higher-kinded result
402 ; let resultKind = mkArrowKinds (drop (length hs_typats) kinds) resKind
403 ; typats <- TcRnMonad.zipWithM kcCheckHsType hs_typats kinds
404 ; thing_inside tvs typats resultKind family
410 %************************************************************************
414 %************************************************************************
416 We need to kind check all types in the mutually recursive group
417 before we know the kind of the type variables. For example:
420 op :: D b => a -> b -> b
423 bop :: (Monad c) => ...
425 Here, the kind of the locally-polymorphic type variable "b"
426 depends on *all the uses of class D*. For example, the use of
427 Monad c in bop's type signature means that D must have kind Type->Type.
429 However type synonyms work differently. They can have kinds which don't
430 just involve (->) and *:
431 type R = Int# -- Kind #
432 type S a = Array# a -- Kind * -> #
433 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
434 So we must infer their kinds from their right-hand sides *first* and then
435 use them, whereas for the mutually recursive data types D we bring into
436 scope kind bindings D -> k, where k is a kind variable, and do inference.
440 This treatment of type synonyms only applies to Haskell 98-style synonyms.
441 General type functions can be recursive, and hence, appear in `alg_decls'.
443 The kind of a type family is solely determinded by its kind signature;
444 hence, only kind signatures participate in the construction of the initial
445 kind environment (as constructed by `getInitialKind'). In fact, we ignore
446 instances of families altogether in the following. However, we need to
447 include the kinds of associated families into the construction of the
448 initial kind environment. (This is handled by `allDecls').
451 kcTyClDecls syn_decls alg_decls
452 = do { -- First extend the kind env with each data type, class, and
453 -- indexed type, mapping them to a type variable
454 let initialKindDecls = concat [allDecls decl | L _ decl <- alg_decls]
455 ; alg_kinds <- mappM getInitialKind initialKindDecls
456 ; tcExtendKindEnv alg_kinds $ do
458 -- Now kind-check the type synonyms, in dependency order
459 -- We do these differently to data type and classes,
460 -- because a type synonym can be an unboxed type
462 -- and a kind variable can't unify with UnboxedTypeKind
463 -- So we infer their kinds in dependency order
464 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
465 ; tcExtendKindEnv syn_kinds $ do
467 -- Now kind-check the data type, class, and kind signatures,
468 -- returning kind-annotated decls; we don't kind-check
469 -- instances of indexed types yet, but leave this to
471 { kc_alg_decls <- mappM (wrapLocM kcTyClDecl)
472 (filter (not . isFamInstDecl . unLoc) alg_decls)
474 ; return (kc_syn_decls, kc_alg_decls) }}}
476 -- get all declarations relevant for determining the initial kind
478 allDecls (decl@ClassDecl {tcdATs = ats}) = decl : [ at
481 allDecls decl | isFamInstDecl decl = []
484 ------------------------------------------------------------------------
485 getInitialKind :: TyClDecl Name -> TcM (Name, TcKind)
486 -- Only for data type, class, and indexed type declarations
487 -- Get as much info as possible from the data, class, or indexed type decl,
488 -- so as to maximise usefulness of error messages
490 = do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl)
491 ; res_kind <- mk_res_kind decl
492 ; return (tcdName decl, mkArrowKinds arg_kinds res_kind) }
494 mk_arg_kind (UserTyVar _) = newKindVar
495 mk_arg_kind (KindedTyVar _ kind) = return kind
497 mk_res_kind (TyFamily { tcdKind = Just kind }) = return kind
498 mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
499 -- On GADT-style declarations we allow a kind signature
500 -- data T :: *->* where { ... }
501 mk_res_kind other = return liftedTypeKind
505 kcSynDecls :: [SCC (LTyClDecl Name)]
506 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
507 [(Name,TcKind)]) -- Kind bindings
510 kcSynDecls (group : groups)
511 = do { (decl, nk) <- kcSynDecl group
512 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
513 ; return (decl:decls, nk:nks) }
516 kcSynDecl :: SCC (LTyClDecl Name)
517 -> TcM (LTyClDecl Name, -- Kind-annotated decls
518 (Name,TcKind)) -- Kind bindings
519 kcSynDecl (AcyclicSCC ldecl@(L loc decl))
520 = tcAddDeclCtxt decl $
521 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
522 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
523 <+> brackets (ppr k_tvs))
524 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
525 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
526 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
527 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
528 (unLoc (tcdLName decl), tc_kind)) })
530 kcSynDecl (CyclicSCC decls)
531 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
532 -- of out-of-scope tycons
534 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
536 ------------------------------------------------------------------------
537 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
538 -- Not used for type synonyms (see kcSynDecl)
540 kcTyClDecl decl@(TyData {})
541 = ASSERT( not . isFamInstDecl $ decl ) -- must not be a family instance
542 kcTyClDeclBody decl $
545 kcTyClDecl decl@(TyFamily {})
546 = kcFamilyDecl [] decl -- the empty list signals a toplevel decl
548 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs, tcdATs = ats})
549 = kcTyClDeclBody decl $ \ tvs' ->
550 do { is_boot <- tcIsHsBoot
551 ; ctxt' <- kcHsContext ctxt
552 ; ats' <- mappM (wrapLocM (kcFamilyDecl tvs')) ats
553 ; sigs' <- mappM (wrapLocM kc_sig) sigs
554 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs',
557 kc_sig (TypeSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
558 ; return (TypeSig nm op_ty') }
559 kc_sig other_sig = return other_sig
561 kcTyClDecl decl@(ForeignType {})
564 kcTyClDeclBody :: TyClDecl Name
565 -> ([LHsTyVarBndr Name] -> TcM a)
567 -- getInitialKind has made a suitably-shaped kind for the type or class
568 -- Unpack it, and attribute those kinds to the type variables
569 -- Extend the env with bindings for the tyvars, taken from
570 -- the kind of the tycon/class. Give it to the thing inside, and
571 -- check the result kind matches
572 kcTyClDeclBody decl thing_inside
573 = tcAddDeclCtxt decl $
574 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
575 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
576 (kinds, _) = splitKindFunTys tc_kind
577 hs_tvs = tcdTyVars decl
578 kinded_tvs = ASSERT( length kinds >= length hs_tvs )
579 [ L loc (KindedTyVar (hsTyVarName tv) k)
580 | (L loc tv, k) <- zip hs_tvs kinds]
581 ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
583 -- Kind check a data declaration, assuming that we already extended the
584 -- kind environment with the type variables of the left-hand side (these
585 -- kinded type variables are also passed as the second parameter).
587 kcDataDecl :: TyClDecl Name -> [LHsTyVarBndr Name] -> TcM (TyClDecl Name)
588 kcDataDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
590 = do { ctxt' <- kcHsContext ctxt
591 ; cons' <- mappM (wrapLocM kc_con_decl) cons
592 ; return (decl {tcdTyVars = tvs, tcdCtxt = ctxt', tcdCons = cons'}) }
594 -- doc comments are typechecked to Nothing here
595 kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res _) = do
596 kcHsTyVars ex_tvs $ \ex_tvs' -> do
597 ex_ctxt' <- kcHsContext ex_ctxt
598 details' <- kc_con_details details
600 ResTyH98 -> return ResTyH98
601 ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
602 return (ConDecl name expl ex_tvs' ex_ctxt' details' res' Nothing)
604 kc_con_details (PrefixCon btys)
605 = do { btys' <- mappM kc_larg_ty btys
606 ; return (PrefixCon btys') }
607 kc_con_details (InfixCon bty1 bty2)
608 = do { bty1' <- kc_larg_ty bty1
609 ; bty2' <- kc_larg_ty bty2
610 ; return (InfixCon bty1' bty2') }
611 kc_con_details (RecCon fields)
612 = do { fields' <- mappM kc_field fields
613 ; return (RecCon fields') }
615 kc_field (ConDeclField fld bty d) = do { bty' <- kc_larg_ty bty
616 ; return (ConDeclField fld bty' d) }
618 kc_larg_ty bty = case new_or_data of
619 DataType -> kcHsSigType bty
620 NewType -> kcHsLiftedSigType bty
621 -- Can't allow an unlifted type for newtypes, because we're effectively
622 -- going to remove the constructor while coercing it to a lifted type.
623 -- And newtypes can't be bang'd
625 -- Kind check a family declaration or type family default declaration.
627 kcFamilyDecl :: [LHsTyVarBndr Name] -- tyvars of enclosing class decl if any
628 -> TyClDecl Name -> TcM (TyClDecl Name)
629 kcFamilyDecl classTvs decl@(TyFamily {tcdKind = kind})
630 = kcTyClDeclBody decl $ \tvs' ->
631 do { mapM_ unifyClassParmKinds tvs'
632 ; return (decl {tcdTyVars = tvs',
633 tcdKind = kind `mplus` Just liftedTypeKind})
634 -- default result kind is '*'
637 unifyClassParmKinds (L _ (KindedTyVar n k))
638 | Just classParmKind <- lookup n classTyKinds = unifyKind k classParmKind
639 | otherwise = return ()
640 classTyKinds = [(n, k) | L _ (KindedTyVar n k) <- classTvs]
641 kcFamilyDecl _ decl@(TySynonym {}) -- type family defaults
642 = panic "TcTyClsDecls.kcFamilyDecl: not implemented yet"
646 %************************************************************************
648 \subsection{Type checking}
650 %************************************************************************
653 tcSynDecls :: [LTyClDecl Name] -> TcM [TyThing]
654 tcSynDecls [] = return []
655 tcSynDecls (decl : decls)
656 = do { syn_tc <- addLocM tcSynDecl decl
657 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls decls)
658 ; return (syn_tc : syn_tcs) }
662 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
663 = tcTyVarBndrs tvs $ \ tvs' -> do
664 { traceTc (text "tcd1" <+> ppr tc_name)
665 ; rhs_ty' <- tcHsKindedType rhs_ty
666 ; tycon <- buildSynTyCon tc_name tvs' (SynonymTyCon rhs_ty') Nothing
667 ; return (ATyCon tycon)
671 tcTyClDecl :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
673 tcTyClDecl calc_isrec decl
674 = tcAddDeclCtxt decl (tcTyClDecl1 calc_isrec decl)
676 -- "type family" declarations
677 tcTyClDecl1 _calc_isrec
678 (TyFamily {tcdFlavour = TypeFamily,
679 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = Just kind})
680 -- NB: kind at latest
683 = tcTyVarBndrs tvs $ \ tvs' -> do
684 { traceTc (text "type family: " <+> ppr tc_name)
685 ; idx_tys <- doptM Opt_TypeFamilies
687 -- Check that we don't use families without -ftype-families
688 ; checkTc idx_tys $ badFamInstDecl tc_name
690 ; tycon <- buildSynTyCon tc_name tvs' (OpenSynTyCon kind Nothing) Nothing
691 ; return [ATyCon tycon]
694 -- "newtype family" or "data family" declaration
695 tcTyClDecl1 _calc_isrec
696 (TyFamily {tcdFlavour = DataFamily,
697 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = mb_kind})
698 = tcTyVarBndrs tvs $ \ tvs' -> do
699 { traceTc (text "data family: " <+> ppr tc_name)
700 ; extra_tvs <- tcDataKindSig mb_kind
701 ; let final_tvs = tvs' ++ extra_tvs -- we may not need these
703 ; idx_tys <- doptM Opt_TypeFamilies
705 -- Check that we don't use families without -ftype-families
706 ; checkTc idx_tys $ badFamInstDecl tc_name
708 ; tycon <- buildAlgTyCon tc_name final_tvs []
709 mkOpenDataTyConRhs Recursive False True Nothing
710 ; return [ATyCon tycon]
713 -- "newtype" and "data"
714 tcTyClDecl1 calc_isrec
715 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
716 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
717 = tcTyVarBndrs tvs $ \ tvs' -> do
718 { extra_tvs <- tcDataKindSig mb_ksig
719 ; let final_tvs = tvs' ++ extra_tvs
720 ; stupid_theta <- tcHsKindedContext ctxt
721 ; want_generic <- doptM Opt_Generics
722 ; unbox_strict <- doptM Opt_UnboxStrictFields
723 ; empty_data_decls <- doptM Opt_EmptyDataDecls
724 ; kind_signatures <- doptM Opt_KindSignatures
725 ; gadt_ok <- doptM Opt_GADTs
726 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
728 -- Check that we don't use GADT syntax in H98 world
729 ; checkTc (gadt_ok || h98_syntax) (badGadtDecl tc_name)
731 -- Check that we don't use kind signatures without Glasgow extensions
732 ; checkTc (kind_signatures || isNothing mb_ksig) (badSigTyDecl tc_name)
734 -- Check that the stupid theta is empty for a GADT-style declaration
735 ; checkTc (null stupid_theta || h98_syntax) (badStupidTheta tc_name)
737 -- Check that there's at least one condecl,
738 -- or else we're reading an hs-boot file, or -XEmptyDataDecls
739 ; checkTc (not (null cons) || empty_data_decls || is_boot)
740 (emptyConDeclsErr tc_name)
742 -- Check that a newtype has exactly one constructor
743 ; checkTc (new_or_data == DataType || isSingleton cons)
744 (newtypeConError tc_name (length cons))
746 ; tycon <- fixM (\ tycon -> do
747 { data_cons <- mappM (addLocM (tcConDecl unbox_strict tycon final_tvs))
750 if null cons && is_boot -- In a hs-boot file, empty cons means
751 then return AbstractTyCon -- "don't know"; hence Abstract
752 else case new_or_data of
753 DataType -> return (mkDataTyConRhs data_cons)
755 ASSERT( not (null data_cons) )
756 mkNewTyConRhs tc_name tycon (head data_cons)
757 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
758 (want_generic && canDoGenerics data_cons) h98_syntax Nothing
760 ; return [ATyCon tycon]
763 is_rec = calc_isrec tc_name
764 h98_syntax = case cons of -- All constructors have same shape
765 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
768 tcTyClDecl1 calc_isrec
769 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
770 tcdCtxt = ctxt, tcdMeths = meths,
771 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
772 = tcTyVarBndrs tvs $ \ tvs' -> do
773 { ctxt' <- tcHsKindedContext ctxt
774 ; fds' <- mappM (addLocM tc_fundep) fundeps
775 ; atss <- mappM (addLocM (tcTyClDecl1 (const Recursive))) ats
776 ; let ats' = zipWith setTyThingPoss atss (map (tcdTyVars . unLoc) ats)
777 ; sig_stuff <- tcClassSigs class_name sigs meths
778 ; clas <- fixM (\ clas ->
779 let -- This little knot is just so we can get
780 -- hold of the name of the class TyCon, which we
781 -- need to look up its recursiveness
782 tycon_name = tyConName (classTyCon clas)
783 tc_isrec = calc_isrec tycon_name
785 buildClass class_name tvs' ctxt' fds' ats'
787 ; return (AClass clas : ats')
788 -- NB: Order is important due to the call to `mkGlobalThings' when
789 -- tying the the type and class declaration type checking knot.
792 tc_fundep (tvs1, tvs2) = do { tvs1' <- mappM tcLookupTyVar tvs1 ;
793 ; tvs2' <- mappM tcLookupTyVar tvs2 ;
794 ; return (tvs1', tvs2') }
796 -- For each AT argument compute the position of the corresponding class
797 -- parameter in the class head. This will later serve as a permutation
798 -- vector when checking the validity of instance declarations.
799 setTyThingPoss [ATyCon tycon] atTyVars =
800 let classTyVars = hsLTyVarNames tvs
802 . map (`elemIndex` classTyVars)
805 -- There will be no Nothing, as we already passed renaming
807 ATyCon (setTyConArgPoss tycon poss)
808 setTyThingPoss _ _ = panic "TcTyClsDecls.setTyThingPoss"
810 tcTyClDecl1 calc_isrec
811 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
812 = returnM [ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0)]
814 -----------------------------------
815 tcConDecl :: Bool -- True <=> -funbox-strict_fields
820 tcConDecl unbox_strict tycon tc_tvs -- Data types
821 (ConDecl name _ tvs ctxt details res_ty _)
822 = tcTyVarBndrs tvs $ \ tvs' -> do
823 { ctxt' <- tcHsKindedContext ctxt
824 ; (univ_tvs, ex_tvs, eq_preds, data_tc) <- tcResultType tycon tc_tvs tvs' res_ty
826 -- Tiresome: tidy the tyvar binders, since tc_tvs and tvs' may have the same OccNames
827 tc_datacon is_infix field_lbls btys
828 = do { let bangs = map getBangStrictness btys
829 ; arg_tys <- mappM tcHsBangType btys
830 ; buildDataCon (unLoc name) is_infix
831 (argStrictness unbox_strict bangs arg_tys)
832 (map unLoc field_lbls)
833 univ_tvs ex_tvs eq_preds ctxt' arg_tys
835 -- NB: we put data_tc, the type constructor gotten from the
836 -- constructor type signature into the data constructor;
837 -- that way checkValidDataCon can complain if it's wrong.
840 PrefixCon btys -> tc_datacon False [] btys
841 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
842 RecCon fields -> tc_datacon False field_names btys
844 field_names = map cd_fld_name fields
845 btys = map cd_fld_type fields
848 tcResultType :: TyCon
849 -> [TyVar] -- data T a b c = ...
850 -> [TyVar] -- where MkT :: forall a b c. ...
852 -> TcM ([TyVar], -- Universal
853 [TyVar], -- Existential (distinct OccNames from univs)
854 [(TyVar,Type)], -- Equality predicates
855 TyCon) -- TyCon given in the ResTy
856 -- We don't check that the TyCon given in the ResTy is
857 -- the same as the parent tycon, becuase we are in the middle
858 -- of a recursive knot; so it's postponed until checkValidDataCon
860 tcResultType decl_tycon tc_tvs dc_tvs ResTyH98
861 = return (tc_tvs, dc_tvs, [], decl_tycon)
862 -- In H98 syntax the dc_tvs are the existential ones
863 -- data T a b c = forall d e. MkT ...
864 -- The {a,b,c} are tc_tvs, and {d,e} are dc_tvs
866 tcResultType _ tc_tvs dc_tvs (ResTyGADT res_ty)
867 -- E.g. data T a b c where
868 -- MkT :: forall x y z. T (x,y) z z
870 -- ([a,z,c], [x,y], [a:=:(x,y), c:=:z], T)
872 = do { (dc_tycon, res_tys) <- tcLHsConResTy res_ty
874 ; let univ_tvs = choose_univs [] tidy_tc_tvs res_tys
875 -- Each univ_tv is either a dc_tv or a tc_tv
876 ex_tvs = dc_tvs `minusList` univ_tvs
877 eq_spec = [ (tv, ty) | (tv,ty) <- univ_tvs `zip` res_tys,
879 ; return (univ_tvs, ex_tvs, eq_spec, dc_tycon) }
881 -- choose_univs uses the res_ty itself if it's a type variable
882 -- and hasn't already been used; otherwise it uses one of the tc_tvs
883 choose_univs used tc_tvs []
884 = ASSERT( null tc_tvs ) []
885 choose_univs used (tc_tv:tc_tvs) (res_ty:res_tys)
886 | Just tv <- tcGetTyVar_maybe res_ty, not (tv `elem` used)
887 = tv : choose_univs (tv:used) tc_tvs res_tys
889 = tc_tv : choose_univs used tc_tvs res_tys
891 -- NB: tc_tvs and dc_tvs are distinct, but
892 -- we want them to be *visibly* distinct, both for
893 -- interface files and general confusion. So rename
894 -- the tc_tvs, since they are not used yet (no
895 -- consequential renaming needed)
896 init_occ_env = initTidyOccEnv (map getOccName dc_tvs)
897 (_, tidy_tc_tvs) = mapAccumL tidy_one init_occ_env tc_tvs
898 tidy_one env tv = (env', setTyVarName tv (tidyNameOcc name occ'))
901 (env', occ') = tidyOccName env (getOccName name)
904 argStrictness :: Bool -- True <=> -funbox-strict_fields
906 -> [TcType] -> [StrictnessMark]
907 argStrictness unbox_strict bangs arg_tys
908 = ASSERT( length bangs == length arg_tys )
909 zipWith (chooseBoxingStrategy unbox_strict) arg_tys bangs
911 -- We attempt to unbox/unpack a strict field when either:
912 -- (i) The field is marked '!!', or
913 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
915 -- We have turned off unboxing of newtypes because coercions make unboxing
916 -- and reboxing more complicated
917 chooseBoxingStrategy :: Bool -> TcType -> HsBang -> StrictnessMark
918 chooseBoxingStrategy unbox_strict_fields arg_ty bang
920 HsNoBang -> NotMarkedStrict
921 HsStrict | unbox_strict_fields
922 && can_unbox arg_ty -> MarkedUnboxed
923 HsUnbox | can_unbox arg_ty -> MarkedUnboxed
924 other -> MarkedStrict
926 -- we can unbox if the type is a chain of newtypes with a product tycon
928 can_unbox arg_ty = case splitTyConApp_maybe arg_ty of
930 Just (arg_tycon, tycon_args) ->
931 not (isRecursiveTyCon arg_tycon) && -- Note [Recusive unboxing]
932 isProductTyCon arg_tycon &&
933 (if isNewTyCon arg_tycon then
934 can_unbox (newTyConInstRhs arg_tycon tycon_args)
938 Note [Recursive unboxing]
939 ~~~~~~~~~~~~~~~~~~~~~~~~~
940 Be careful not to try to unbox this!
942 But it's the *argument* type that matters. This is fine:
944 because Int is non-recursive.
946 %************************************************************************
948 \subsection{Dependency analysis}
950 %************************************************************************
952 Validity checking is done once the mutually-recursive knot has been
953 tied, so we can look at things freely.
956 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
957 checkCycleErrs tyclss
961 = do { mappM_ recClsErr cls_cycles
962 ; failM } -- Give up now, because later checkValidTyCl
963 -- will loop if the synonym is recursive
965 cls_cycles = calcClassCycles tyclss
967 checkValidTyCl :: TyClDecl Name -> TcM ()
968 -- We do the validity check over declarations, rather than TyThings
969 -- only so that we can add a nice context with tcAddDeclCtxt
971 = tcAddDeclCtxt decl $
972 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
973 ; traceTc (text "Validity of" <+> ppr thing)
975 ATyCon tc -> checkValidTyCon tc
976 AClass cl -> checkValidClass cl
977 ; traceTc (text "Done validity of" <+> ppr thing)
980 -------------------------
981 -- For data types declared with record syntax, we require
982 -- that each constructor that has a field 'f'
983 -- (a) has the same result type
984 -- (b) has the same type for 'f'
985 -- module alpha conversion of the quantified type variables
986 -- of the constructor.
988 checkValidTyCon :: TyCon -> TcM ()
991 = case synTyConRhs tc of
992 OpenSynTyCon _ _ -> return ()
993 SynonymTyCon ty -> checkValidType syn_ctxt ty
995 = -- Check the context on the data decl
996 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
998 -- Check arg types of data constructors
999 mappM_ (checkValidDataCon tc) data_cons `thenM_`
1001 -- Check that fields with the same name share a type
1002 mappM_ check_fields groups
1005 syn_ctxt = TySynCtxt name
1007 data_cons = tyConDataCons tc
1009 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
1010 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
1011 get_fields con = dataConFieldLabels con `zip` repeat con
1012 -- dataConFieldLabels may return the empty list, which is fine
1014 -- See Note [GADT record selectors] in MkId.lhs
1015 -- We must check (a) that the named field has the same
1016 -- type in each constructor
1017 -- (b) that those constructors have the same result type
1019 -- However, the constructors may have differently named type variable
1020 -- and (worse) we don't know how the correspond to each other. E.g.
1021 -- C1 :: forall a b. { f :: a, g :: b } -> T a b
1022 -- C2 :: forall d c. { f :: c, g :: c } -> T c d
1024 -- So what we do is to ust Unify.tcMatchTys to compare the first candidate's
1025 -- result type against other candidates' types BOTH WAYS ROUND.
1026 -- If they magically agrees, take the substitution and
1027 -- apply them to the latter ones, and see if they match perfectly.
1028 check_fields fields@((label, con1) : other_fields)
1029 -- These fields all have the same name, but are from
1030 -- different constructors in the data type
1031 = recoverM (return ()) $ mapM_ checkOne other_fields
1032 -- Check that all the fields in the group have the same type
1033 -- NB: this check assumes that all the constructors of a given
1034 -- data type use the same type variables
1036 (tvs1, _, _, res1) = dataConSig con1
1038 fty1 = dataConFieldType con1 label
1040 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
1041 = do { checkFieldCompat label con1 con2 ts1 res1 res2 fty1 fty2
1042 ; checkFieldCompat label con2 con1 ts2 res2 res1 fty2 fty1 }
1044 (tvs2, _, _, res2) = dataConSig con2
1046 fty2 = dataConFieldType con2 label
1048 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
1049 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
1050 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
1052 mb_subst1 = tcMatchTy tvs1 res1 res2
1053 mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
1055 -------------------------------
1056 checkValidDataCon :: TyCon -> DataCon -> TcM ()
1057 checkValidDataCon tc con
1058 = setSrcSpan (srcLocSpan (getSrcLoc con)) $
1059 addErrCtxt (dataConCtxt con) $
1060 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
1061 ; checkValidType ctxt (dataConUserType con)
1062 ; ifM (isNewTyCon tc) (checkNewDataCon con)
1065 ctxt = ConArgCtxt (dataConName con)
1067 -------------------------------
1068 checkNewDataCon :: DataCon -> TcM ()
1069 -- Checks for the data constructor of a newtype
1071 = do { checkTc (isSingleton arg_tys) (newtypeFieldErr con (length arg_tys))
1073 ; checkTc (null eq_spec) (newtypePredError con)
1074 -- Return type is (T a b c)
1075 ; checkTc (null ex_tvs && null eq_theta && null dict_theta) (newtypeExError con)
1077 ; checkTc (not (any isMarkedStrict (dataConStrictMarks con)))
1078 (newtypeStrictError con)
1082 (_univ_tvs, ex_tvs, eq_spec, eq_theta, dict_theta, arg_tys, _res_ty) = dataConFullSig con
1084 -------------------------------
1085 checkValidClass :: Class -> TcM ()
1087 = do { constrained_class_methods <- doptM Opt_ConstrainedClassMethods
1088 ; multi_param_type_classes <- doptM Opt_MultiParamTypeClasses
1089 ; fundep_classes <- doptM Opt_FunctionalDependencies
1091 -- Check that the class is unary, unless GlaExs
1092 ; checkTc (notNull tyvars) (nullaryClassErr cls)
1093 ; checkTc (multi_param_type_classes || unary) (classArityErr cls)
1094 ; checkTc (fundep_classes || null fundeps) (classFunDepsErr cls)
1096 -- Check the super-classes
1097 ; checkValidTheta (ClassSCCtxt (className cls)) theta
1099 -- Check the class operations
1100 ; mappM_ (check_op constrained_class_methods) op_stuff
1102 -- Check that if the class has generic methods, then the
1103 -- class has only one parameter. We can't do generic
1104 -- multi-parameter type classes!
1105 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
1108 (tyvars, fundeps, theta, _, _, op_stuff) = classExtraBigSig cls
1109 unary = isSingleton tyvars
1110 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
1112 check_op constrained_class_methods (sel_id, dm)
1113 = addErrCtxt (classOpCtxt sel_id tau) $ do
1114 { checkValidTheta SigmaCtxt (tail theta)
1115 -- The 'tail' removes the initial (C a) from the
1116 -- class itself, leaving just the method type
1118 ; traceTc (text "class op type" <+> ppr op_ty <+> ppr tau)
1119 ; checkValidType (FunSigCtxt op_name) tau
1121 -- Check that the type mentions at least one of
1122 -- the class type variables...or at least one reachable
1123 -- from one of the class variables. Example: tc223
1124 -- class Error e => Game b mv e | b -> mv e where
1125 -- newBoard :: MonadState b m => m ()
1126 -- Here, MonadState has a fundep m->b, so newBoard is fine
1127 ; let grown_tyvars = grow theta (mkVarSet tyvars)
1128 ; checkTc (tyVarsOfType tau `intersectsVarSet` grown_tyvars)
1129 (noClassTyVarErr cls sel_id)
1131 -- Check that for a generic method, the type of
1132 -- the method is sufficiently simple
1133 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
1134 (badGenericMethodType op_name op_ty)
1137 op_name = idName sel_id
1138 op_ty = idType sel_id
1139 (_,theta1,tau1) = tcSplitSigmaTy op_ty
1140 (_,theta2,tau2) = tcSplitSigmaTy tau1
1141 (theta,tau) | constrained_class_methods = (theta1 ++ theta2, tau2)
1142 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
1143 -- Ugh! The function might have a type like
1144 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
1145 -- With -XConstrainedClassMethods, we want to allow this, even though the inner
1146 -- forall has an (Eq a) constraint. Whereas in general, each constraint
1147 -- in the context of a for-all must mention at least one quantified
1148 -- type variable. What a mess!
1151 ---------------------------------------------------------------------
1152 resultTypeMisMatch field_name con1 con2
1153 = vcat [sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1154 ptext SLIT("have a common field") <+> quotes (ppr field_name) <> comma],
1155 nest 2 $ ptext SLIT("but have different result types")]
1156 fieldTypeMisMatch field_name con1 con2
1157 = sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1158 ptext SLIT("give different types for field"), quotes (ppr field_name)]
1160 dataConCtxt con = ptext SLIT("In the definition of data constructor") <+> quotes (ppr con)
1162 classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
1163 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
1166 = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
1169 = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
1170 parens (ptext SLIT("Use -XMultiParamTypeClasses to allow multi-parameter classes"))]
1173 = vcat [ptext SLIT("Fundeps in class") <+> quotes (ppr cls),
1174 parens (ptext SLIT("Use -XFunctionalDependencies to allow fundeps"))]
1176 noClassTyVarErr clas op
1177 = sep [ptext SLIT("The class method") <+> quotes (ppr op),
1178 ptext SLIT("mentions none of the type variables of the class") <+>
1179 ppr clas <+> hsep (map ppr (classTyVars clas))]
1181 genericMultiParamErr clas
1182 = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
1183 ptext SLIT("cannot have generic methods")
1185 badGenericMethodType op op_ty
1186 = hang (ptext SLIT("Generic method type is too complex"))
1187 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
1188 ptext SLIT("You can only use type variables, arrows, lists, and tuples")])
1191 = setSrcSpan (getLoc (head sorted_decls)) $
1192 addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
1193 nest 2 (vcat (map ppr_decl sorted_decls))])
1195 sorted_decls = sortLocated syn_decls
1196 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
1199 = setSrcSpan (getLoc (head sorted_decls)) $
1200 addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
1201 nest 2 (vcat (map ppr_decl sorted_decls))])
1203 sorted_decls = sortLocated cls_decls
1204 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
1206 sortLocated :: [Located a] -> [Located a]
1207 sortLocated things = sortLe le things
1209 le (L l1 _) (L l2 _) = l1 <= l2
1211 badDataConTyCon data_con
1212 = hang (ptext SLIT("Data constructor") <+> quotes (ppr data_con) <+>
1213 ptext SLIT("returns type") <+> quotes (ppr (dataConTyCon data_con)))
1214 2 (ptext SLIT("instead of its parent type"))
1217 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
1218 , nest 2 (parens $ ptext SLIT("Use -XGADTs to allow GADTs")) ]
1220 badStupidTheta tc_name
1221 = ptext SLIT("A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
1223 newtypeConError tycon n
1224 = sep [ptext SLIT("A newtype must have exactly one constructor,"),
1225 nest 2 $ ptext SLIT("but") <+> quotes (ppr tycon) <+> ptext SLIT("has") <+> speakN n ]
1228 = sep [ptext SLIT("A newtype constructor cannot have an existential context,"),
1229 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
1231 newtypeStrictError con
1232 = sep [ptext SLIT("A newtype constructor cannot have a strictness annotation,"),
1233 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
1235 newtypePredError con
1236 = sep [ptext SLIT("A newtype constructor must have a return type of form T a1 ... an"),
1237 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does not")]
1239 newtypeFieldErr con_name n_flds
1240 = sep [ptext SLIT("The constructor of a newtype must have exactly one field"),
1241 nest 2 $ ptext SLIT("but") <+> quotes (ppr con_name) <+> ptext SLIT("has") <+> speakN n_flds]
1243 badSigTyDecl tc_name
1244 = vcat [ ptext SLIT("Illegal kind signature") <+>
1245 quotes (ppr tc_name)
1246 , nest 2 (parens $ ptext SLIT("Use -XKindSignatures to allow kind signatures")) ]
1248 badFamInstDecl tc_name
1249 = vcat [ ptext SLIT("Illegal family instance for") <+>
1250 quotes (ppr tc_name)
1251 , nest 2 (parens $ ptext SLIT("Use -XTypeFamilies to allow indexed type families")) ]
1253 badGadtIdxTyDecl tc_name
1254 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+>
1255 quotes (ppr tc_name)
1256 , nest 2 (parens $ ptext SLIT("Family instances can not yet use GADT declarations")) ]
1258 tooManyParmsErr tc_name
1259 = ptext SLIT("Family instance has too many parameters:") <+>
1260 quotes (ppr tc_name)
1262 tooFewParmsErr arity
1263 = ptext SLIT("Family instance has too few parameters; expected") <+>
1266 wrongNumberOfParmsErr exp_arity
1267 = ptext SLIT("Number of parameters must match family declaration; expected")
1270 badBootFamInstDeclErr =
1271 ptext SLIT("Illegal family instance in hs-boot file")
1273 wrongKindOfFamily family =
1274 ptext SLIT("Wrong category of family instance; declaration was for a") <+>
1277 kindOfFamily | isSynTyCon family = ptext SLIT("type synonym")
1278 | isAlgTyCon family = ptext SLIT("data type")
1279 | otherwise = pprPanic "wrongKindOfFamily" (ppr family)
1282 = hang (ptext SLIT("Illegal polymorphic type in type instance") <> colon) 4 $
1285 tyFamAppInIndexErr ty
1286 = hang (ptext SLIT("Illegal type family application in type instance") <>
1290 emptyConDeclsErr tycon
1291 = sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
1292 nest 2 $ ptext SLIT("(-XEmptyDataDecls permits this)")]