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"
57 import Control.Monad ( mplus )
61 %************************************************************************
63 \subsection{Type checking for type and class declarations}
65 %************************************************************************
69 Consider a mutually-recursive group, binding
70 a type constructor T and a class C.
72 Step 1: getInitialKind
73 Construct a KindEnv by binding T and C to a kind variable
76 In that environment, do a kind check
78 Step 3: Zonk the kinds
80 Step 4: buildTyConOrClass
81 Construct an environment binding T to a TyCon and C to a Class.
82 a) Their kinds comes from zonking the relevant kind variable
83 b) Their arity (for synonyms) comes direct from the decl
84 c) The funcional dependencies come from the decl
85 d) The rest comes a knot-tied binding of T and C, returned from Step 4
86 e) The variances of the tycons in the group is calculated from
90 In this environment, walk over the decls, constructing the TyCons and Classes.
91 This uses in a strict way items (a)-(c) above, which is why they must
92 be constructed in Step 4. Feed the results back to Step 4.
93 For this step, pass the is-recursive flag as the wimp-out flag
97 Step 6: Extend environment
98 We extend the type environment with bindings not only for the TyCons and Classes,
99 but also for their "implicit Ids" like data constructors and class selectors
101 Step 7: checkValidTyCl
102 For a recursive group only, check all the decls again, just
103 to check all the side conditions on validity. We could not
104 do this before because we were in a mutually recursive knot.
106 Identification of recursive TyCons
107 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
108 The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to
111 Identifying a TyCon as recursive serves two purposes
113 1. Avoid infinite types. Non-recursive newtypes are treated as
114 "transparent", like type synonyms, after the type checker. If we did
115 this for all newtypes, we'd get infinite types. So we figure out for
116 each newtype whether it is "recursive", and add a coercion if so. In
117 effect, we are trying to "cut the loops" by identifying a loop-breaker.
119 2. Avoid infinite unboxing. This is nothing to do with newtypes.
123 Well, this function diverges, but we don't want the strictness analyser
124 to diverge. But the strictness analyser will diverge because it looks
125 deeper and deeper into the structure of T. (I believe there are
126 examples where the function does something sane, and the strictness
127 analyser still diverges, but I can't see one now.)
129 Now, concerning (1), the FC2 branch currently adds a coercion for ALL
130 newtypes. I did this as an experiment, to try to expose cases in which
131 the coercions got in the way of optimisations. If it turns out that we
132 can indeed always use a coercion, then we don't risk recursive types,
133 and don't need to figure out what the loop breakers are.
135 For newtype *families* though, we will always have a coercion, so they
136 are always loop breakers! So you can easily adjust the current
137 algorithm by simply treating all newtype families as loop breakers (and
138 indeed type families). I think.
141 tcTyAndClassDecls :: ModDetails -> [LTyClDecl Name]
142 -> TcM TcGblEnv -- Input env extended by types and classes
143 -- and their implicit Ids,DataCons
144 -- Fails if there are any errors
146 tcTyAndClassDecls boot_details allDecls
147 = checkNoErrs $ -- The code recovers internally, but if anything gave rise to
148 -- an error we'd better stop now, to avoid a cascade
149 do { -- Omit instances of type families; they are handled together
150 -- with the *heads* of class instances
151 ; let decls = filter (not . isFamInstDecl . unLoc) allDecls
153 -- First check for cyclic type synonysm or classes
154 -- See notes with checkCycleErrs
155 ; checkCycleErrs decls
157 ; traceTc (text "tcTyAndCl" <+> ppr mod)
158 ; (syn_tycons, alg_tyclss) <- fixM (\ ~(rec_syn_tycons, rec_alg_tyclss) ->
159 do { let { -- Seperate ordinary synonyms from all other type and
160 -- class declarations and add all associated type
161 -- declarations from type classes. The latter is
162 -- required so that the temporary environment for the
163 -- knot includes all associated family declarations.
164 ; (syn_decls, alg_decls) = partition (isSynDecl . unLoc)
166 ; alg_at_decls = concatMap addATs alg_decls
168 -- Extend the global env with the knot-tied results
169 -- for data types and classes
171 -- We must populate the environment with the loop-tied
172 -- T's right away, because the kind checker may "fault
173 -- in" some type constructors that recursively
175 ; let gbl_things = mkGlobalThings alg_at_decls rec_alg_tyclss
176 ; tcExtendRecEnv gbl_things $ do
178 -- Kind-check the declarations
179 { (kc_syn_decls, kc_alg_decls) <- kcTyClDecls syn_decls alg_decls
181 ; let { -- Calculate rec-flag
182 ; calc_rec = calcRecFlags boot_details rec_alg_tyclss
183 ; tc_decl = addLocM (tcTyClDecl calc_rec) }
185 -- Type-check the type synonyms, and extend the envt
186 ; syn_tycons <- tcSynDecls kc_syn_decls
187 ; tcExtendGlobalEnv syn_tycons $ do
189 -- Type-check the data types and classes
190 { alg_tyclss <- mapM tc_decl kc_alg_decls
191 ; return (syn_tycons, concat alg_tyclss)
193 -- Finished with knot-tying now
194 -- Extend the environment with the finished things
195 ; tcExtendGlobalEnv (syn_tycons ++ alg_tyclss) $ do
197 -- Perform the validity check
198 { traceTc (text "ready for validity check")
199 ; mapM_ (addLocM checkValidTyCl) decls
200 ; traceTc (text "done")
202 -- Add the implicit things;
203 -- we want them in the environment because
204 -- they may be mentioned in interface files
205 -- NB: All associated types and their implicit things will be added a
206 -- second time here. This doesn't matter as the definitions are
208 ; let { implicit_things = concatMap implicitTyThings alg_tyclss }
209 ; traceTc ((text "Adding" <+> ppr alg_tyclss)
210 $$ (text "and" <+> ppr implicit_things))
211 ; tcExtendGlobalEnv implicit_things getGblEnv
214 -- Pull associated types out of class declarations, to tie them into the
216 -- NB: We put them in the same place in the list as `tcTyClDecl' will
217 -- eventually put the matching `TyThing's. That's crucial; otherwise,
218 -- the two argument lists of `mkGlobalThings' don't match up.
219 addATs decl@(L _ (ClassDecl {tcdATs = ats})) = decl : ats
222 mkGlobalThings :: [LTyClDecl Name] -- The decls
223 -> [TyThing] -- Knot-tied, in 1-1 correspondence with the decls
225 -- Driven by the Decls, and treating the TyThings lazily
226 -- make a TypeEnv for the new things
227 mkGlobalThings decls things
228 = map mk_thing (decls `zipLazy` things)
230 mk_thing (L _ (ClassDecl {tcdLName = L _ name}), ~(AClass cl))
232 mk_thing (L _ decl, ~(ATyCon tc))
233 = (tcdName decl, ATyCon tc)
237 %************************************************************************
239 \subsection{Type checking family instances}
241 %************************************************************************
243 Family instances are somewhat of a hybrid. They are processed together with
244 class instance heads, but can contain data constructors and hence they share a
245 lot of kinding and type checking code with ordinary algebraic data types (and
249 tcFamInstDecl :: LTyClDecl Name -> TcM (Maybe TyThing) -- Nothing if error
250 tcFamInstDecl (L loc decl)
251 = -- Prime error recovery, set source location
252 recoverM (return Nothing) $
255 do { -- type families require -XTypeFamilies and can't be in an
257 ; type_families <- doptM Opt_TypeFamilies
258 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
259 ; checkTc type_families $ badFamInstDecl (tcdLName decl)
260 ; checkTc (not is_boot) $ badBootFamInstDeclErr
262 -- perform kind and type checking
263 ; tcFamInstDecl1 decl
266 tcFamInstDecl1 :: TyClDecl Name -> TcM (Maybe TyThing) -- Nothing if error
269 tcFamInstDecl1 (decl@TySynonym {tcdLName = L loc tc_name})
270 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
271 do { -- check that the family declaration is for a synonym
272 unless (isSynTyCon family) $
273 addErr (wrongKindOfFamily family)
275 ; -- (1) kind check the right-hand side of the type equation
276 ; k_rhs <- kcCheckHsType (tcdSynRhs decl) resKind
278 -- we need the exact same number of type parameters as the family
280 ; let famArity = tyConArity family
281 ; checkTc (length k_typats == famArity) $
282 wrongNumberOfParmsErr famArity
284 -- (2) type check type equation
285 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
286 ; t_typats <- mapM tcHsKindedType k_typats
287 ; t_rhs <- tcHsKindedType k_rhs
290 -- - check the well-formedness of the instance
291 ; checkValidTypeInst t_typats t_rhs
293 -- (4) construct representation tycon
294 ; rep_tc_name <- newFamInstTyConName tc_name loc
295 ; tycon <- buildSynTyCon rep_tc_name t_tvs (SynonymTyCon t_rhs)
296 (Just (family, t_typats))
298 ; return $ Just (ATyCon tycon)
301 -- "newtype instance" and "data instance"
302 tcFamInstDecl1 (decl@TyData {tcdND = new_or_data, tcdLName = L loc tc_name,
304 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
305 do { -- check that the family declaration is for the right kind
306 unless (isAlgTyCon family) $
307 addErr (wrongKindOfFamily family)
309 ; -- (1) kind check the data declaration as usual
310 ; k_decl <- kcDataDecl decl k_tvs
311 ; let k_ctxt = tcdCtxt k_decl
312 k_cons = tcdCons k_decl
314 -- result kind must be '*' (otherwise, we have too few patterns)
315 ; checkTc (isLiftedTypeKind resKind) $ tooFewParmsErr (tyConArity family)
317 -- (2) type check indexed data type declaration
318 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
319 ; unbox_strict <- doptM Opt_UnboxStrictFields
321 -- kind check the type indexes and the context
322 ; t_typats <- mapM tcHsKindedType k_typats
323 ; stupid_theta <- tcHsKindedContext k_ctxt
326 -- - left-hand side contains no type family applications
327 -- (vanilla synonyms are fine, though, and we checked for
329 ; mapM_ checkTyFamFreeness t_typats
331 -- - we don't use GADT syntax for indexed types
332 ; checkTc h98_syntax (badGadtIdxTyDecl tc_name)
334 -- - a newtype has exactly one constructor
335 ; checkTc (new_or_data == DataType || isSingleton k_cons) $
336 newtypeConError tc_name (length k_cons)
338 -- (4) construct representation tycon
339 ; rep_tc_name <- newFamInstTyConName tc_name loc
340 ; let ex_ok = True -- Existentials ok for type families!
341 ; tycon <- fixM (\ tycon -> do
342 { data_cons <- mapM (addLocM (tcConDecl unbox_strict ex_ok tycon t_tvs))
346 DataType -> return (mkDataTyConRhs data_cons)
347 NewType -> ASSERT( not (null data_cons) )
348 mkNewTyConRhs rep_tc_name tycon (head data_cons)
349 ; buildAlgTyCon rep_tc_name t_tvs stupid_theta tc_rhs Recursive
350 False h98_syntax (Just (family, t_typats))
351 -- We always assume that indexed types are recursive. Why?
352 -- (1) Due to their open nature, we can never be sure that a
353 -- further instance might not introduce a new recursive
354 -- dependency. (2) They are always valid loop breakers as
355 -- they involve a coercion.
359 ; return $ Just (ATyCon tycon)
362 h98_syntax = case cons of -- All constructors have same shape
363 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
366 -- Kind checking of indexed types
369 -- Kind check type patterns and kind annotate the embedded type variables.
371 -- * Here we check that a type instance matches its kind signature, but we do
372 -- not check whether there is a pattern for each type index; the latter
373 -- check is only required for type synonym instances.
375 kcIdxTyPats :: TyClDecl Name
376 -> ([LHsTyVarBndr Name] -> [LHsType Name] -> Kind -> TyCon -> TcM a)
377 -- ^^kinded tvs ^^kinded ty pats ^^res kind
379 kcIdxTyPats decl thing_inside
380 = kcHsTyVars (tcdTyVars decl) $ \tvs ->
381 do { family <- tcLookupLocatedTyCon (tcdLName decl)
382 ; let { (kinds, resKind) = splitKindFunTys (tyConKind family)
383 ; hs_typats = fromJust $ tcdTyPats decl }
385 -- we may not have more parameters than the kind indicates
386 ; checkTc (length kinds >= length hs_typats) $
387 tooManyParmsErr (tcdLName decl)
389 -- type functions can have a higher-kinded result
390 ; let resultKind = mkArrowKinds (drop (length hs_typats) kinds) resKind
391 ; typats <- zipWithM kcCheckHsType hs_typats kinds
392 ; thing_inside tvs typats resultKind family
398 %************************************************************************
402 %************************************************************************
404 We need to kind check all types in the mutually recursive group
405 before we know the kind of the type variables. For example:
408 op :: D b => a -> b -> b
411 bop :: (Monad c) => ...
413 Here, the kind of the locally-polymorphic type variable "b"
414 depends on *all the uses of class D*. For example, the use of
415 Monad c in bop's type signature means that D must have kind Type->Type.
417 However type synonyms work differently. They can have kinds which don't
418 just involve (->) and *:
419 type R = Int# -- Kind #
420 type S a = Array# a -- Kind * -> #
421 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
422 So we must infer their kinds from their right-hand sides *first* and then
423 use them, whereas for the mutually recursive data types D we bring into
424 scope kind bindings D -> k, where k is a kind variable, and do inference.
428 This treatment of type synonyms only applies to Haskell 98-style synonyms.
429 General type functions can be recursive, and hence, appear in `alg_decls'.
431 The kind of a type family is solely determinded by its kind signature;
432 hence, only kind signatures participate in the construction of the initial
433 kind environment (as constructed by `getInitialKind'). In fact, we ignore
434 instances of families altogether in the following. However, we need to
435 include the kinds of associated families into the construction of the
436 initial kind environment. (This is handled by `allDecls').
439 kcTyClDecls syn_decls alg_decls
440 = do { -- First extend the kind env with each data type, class, and
441 -- indexed type, mapping them to a type variable
442 let initialKindDecls = concat [allDecls decl | L _ decl <- alg_decls]
443 ; alg_kinds <- mapM getInitialKind initialKindDecls
444 ; tcExtendKindEnv alg_kinds $ do
446 -- Now kind-check the type synonyms, in dependency order
447 -- We do these differently to data type and classes,
448 -- because a type synonym can be an unboxed type
450 -- and a kind variable can't unify with UnboxedTypeKind
451 -- So we infer their kinds in dependency order
452 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
453 ; tcExtendKindEnv syn_kinds $ do
455 -- Now kind-check the data type, class, and kind signatures,
456 -- returning kind-annotated decls; we don't kind-check
457 -- instances of indexed types yet, but leave this to
459 { kc_alg_decls <- mapM (wrapLocM kcTyClDecl)
460 (filter (not . isFamInstDecl . unLoc) alg_decls)
462 ; return (kc_syn_decls, kc_alg_decls) }}}
464 -- get all declarations relevant for determining the initial kind
466 allDecls (decl@ClassDecl {tcdATs = ats}) = decl : [ at
469 allDecls decl | isFamInstDecl decl = []
472 ------------------------------------------------------------------------
473 getInitialKind :: TyClDecl Name -> TcM (Name, TcKind)
474 -- Only for data type, class, and indexed type declarations
475 -- Get as much info as possible from the data, class, or indexed type decl,
476 -- so as to maximise usefulness of error messages
478 = do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl)
479 ; res_kind <- mk_res_kind decl
480 ; return (tcdName decl, mkArrowKinds arg_kinds res_kind) }
482 mk_arg_kind (UserTyVar _) = newKindVar
483 mk_arg_kind (KindedTyVar _ kind) = return kind
485 mk_res_kind (TyFamily { tcdKind = Just kind }) = return kind
486 mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
487 -- On GADT-style declarations we allow a kind signature
488 -- data T :: *->* where { ... }
489 mk_res_kind other = return liftedTypeKind
493 kcSynDecls :: [SCC (LTyClDecl Name)]
494 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
495 [(Name,TcKind)]) -- Kind bindings
498 kcSynDecls (group : groups)
499 = do { (decl, nk) <- kcSynDecl group
500 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
501 ; return (decl:decls, nk:nks) }
504 kcSynDecl :: SCC (LTyClDecl Name)
505 -> TcM (LTyClDecl Name, -- Kind-annotated decls
506 (Name,TcKind)) -- Kind bindings
507 kcSynDecl (AcyclicSCC ldecl@(L loc decl))
508 = tcAddDeclCtxt decl $
509 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
510 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
511 <+> brackets (ppr k_tvs))
512 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
513 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
514 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
515 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
516 (unLoc (tcdLName decl), tc_kind)) })
518 kcSynDecl (CyclicSCC decls)
519 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
520 -- of out-of-scope tycons
522 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
524 ------------------------------------------------------------------------
525 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
526 -- Not used for type synonyms (see kcSynDecl)
528 kcTyClDecl decl@(TyData {})
529 = ASSERT( not . isFamInstDecl $ decl ) -- must not be a family instance
530 kcTyClDeclBody decl $
533 kcTyClDecl decl@(TyFamily {})
534 = kcFamilyDecl [] decl -- the empty list signals a toplevel decl
536 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs, tcdATs = ats})
537 = kcTyClDeclBody decl $ \ tvs' ->
538 do { is_boot <- tcIsHsBoot
539 ; ctxt' <- kcHsContext ctxt
540 ; ats' <- mapM (wrapLocM (kcFamilyDecl tvs')) ats
541 ; sigs' <- mapM (wrapLocM kc_sig) sigs
542 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs',
545 kc_sig (TypeSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
546 ; return (TypeSig nm op_ty') }
547 kc_sig other_sig = return other_sig
549 kcTyClDecl decl@(ForeignType {})
552 kcTyClDeclBody :: TyClDecl Name
553 -> ([LHsTyVarBndr Name] -> TcM a)
555 -- getInitialKind has made a suitably-shaped kind for the type or class
556 -- Unpack it, and attribute those kinds to the type variables
557 -- Extend the env with bindings for the tyvars, taken from
558 -- the kind of the tycon/class. Give it to the thing inside, and
559 -- check the result kind matches
560 kcTyClDeclBody decl thing_inside
561 = tcAddDeclCtxt decl $
562 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
563 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
564 (kinds, _) = splitKindFunTys tc_kind
565 hs_tvs = tcdTyVars decl
566 kinded_tvs = ASSERT( length kinds >= length hs_tvs )
567 [ L loc (KindedTyVar (hsTyVarName tv) k)
568 | (L loc tv, k) <- zip hs_tvs kinds]
569 ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
571 -- Kind check a data declaration, assuming that we already extended the
572 -- kind environment with the type variables of the left-hand side (these
573 -- kinded type variables are also passed as the second parameter).
575 kcDataDecl :: TyClDecl Name -> [LHsTyVarBndr Name] -> TcM (TyClDecl Name)
576 kcDataDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
578 = do { ctxt' <- kcHsContext ctxt
579 ; cons' <- mapM (wrapLocM kc_con_decl) cons
580 ; return (decl {tcdTyVars = tvs, tcdCtxt = ctxt', tcdCons = cons'}) }
582 -- doc comments are typechecked to Nothing here
583 kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res _) = do
584 kcHsTyVars ex_tvs $ \ex_tvs' -> do
585 ex_ctxt' <- kcHsContext ex_ctxt
586 details' <- kc_con_details details
588 ResTyH98 -> return ResTyH98
589 ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
590 return (ConDecl name expl ex_tvs' ex_ctxt' details' res' Nothing)
592 kc_con_details (PrefixCon btys)
593 = do { btys' <- mapM kc_larg_ty btys
594 ; return (PrefixCon btys') }
595 kc_con_details (InfixCon bty1 bty2)
596 = do { bty1' <- kc_larg_ty bty1
597 ; bty2' <- kc_larg_ty bty2
598 ; return (InfixCon bty1' bty2') }
599 kc_con_details (RecCon fields)
600 = do { fields' <- mapM kc_field fields
601 ; return (RecCon fields') }
603 kc_field (ConDeclField fld bty d) = do { bty' <- kc_larg_ty bty
604 ; return (ConDeclField fld bty' d) }
606 kc_larg_ty bty = case new_or_data of
607 DataType -> kcHsSigType bty
608 NewType -> kcHsLiftedSigType bty
609 -- Can't allow an unlifted type for newtypes, because we're effectively
610 -- going to remove the constructor while coercing it to a lifted type.
611 -- And newtypes can't be bang'd
613 -- Kind check a family declaration or type family default declaration.
615 kcFamilyDecl :: [LHsTyVarBndr Name] -- tyvars of enclosing class decl if any
616 -> TyClDecl Name -> TcM (TyClDecl Name)
617 kcFamilyDecl classTvs decl@(TyFamily {tcdKind = kind})
618 = kcTyClDeclBody decl $ \tvs' ->
619 do { mapM_ unifyClassParmKinds tvs'
620 ; return (decl {tcdTyVars = tvs',
621 tcdKind = kind `mplus` Just liftedTypeKind})
622 -- default result kind is '*'
625 unifyClassParmKinds (L _ (KindedTyVar n k))
626 | Just classParmKind <- lookup n classTyKinds = unifyKind k classParmKind
627 | otherwise = return ()
628 classTyKinds = [(n, k) | L _ (KindedTyVar n k) <- classTvs]
629 kcFamilyDecl _ decl@(TySynonym {}) -- type family defaults
630 = panic "TcTyClsDecls.kcFamilyDecl: not implemented yet"
634 %************************************************************************
636 \subsection{Type checking}
638 %************************************************************************
641 tcSynDecls :: [LTyClDecl Name] -> TcM [TyThing]
642 tcSynDecls [] = return []
643 tcSynDecls (decl : decls)
644 = do { syn_tc <- addLocM tcSynDecl decl
645 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls decls)
646 ; return (syn_tc : syn_tcs) }
650 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
651 = tcTyVarBndrs tvs $ \ tvs' -> do
652 { traceTc (text "tcd1" <+> ppr tc_name)
653 ; rhs_ty' <- tcHsKindedType rhs_ty
654 ; tycon <- buildSynTyCon tc_name tvs' (SynonymTyCon rhs_ty') Nothing
655 ; return (ATyCon tycon)
659 tcTyClDecl :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
661 tcTyClDecl calc_isrec decl
662 = tcAddDeclCtxt decl (tcTyClDecl1 calc_isrec decl)
664 -- "type family" declarations
665 tcTyClDecl1 _calc_isrec
666 (TyFamily {tcdFlavour = TypeFamily,
667 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = Just kind})
668 -- NB: kind at latest
671 = tcTyVarBndrs tvs $ \ tvs' -> do
672 { traceTc (text "type family: " <+> ppr tc_name)
673 ; idx_tys <- doptM Opt_TypeFamilies
675 -- Check that we don't use families without -XTypeFamilies
676 ; checkTc idx_tys $ badFamInstDecl tc_name
678 ; tycon <- buildSynTyCon tc_name tvs' (OpenSynTyCon kind Nothing) Nothing
679 ; return [ATyCon tycon]
682 -- "data family" declaration
683 tcTyClDecl1 _calc_isrec
684 (TyFamily {tcdFlavour = DataFamily,
685 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = mb_kind})
686 = tcTyVarBndrs tvs $ \ tvs' -> do
687 { traceTc (text "data family: " <+> ppr tc_name)
688 ; extra_tvs <- tcDataKindSig mb_kind
689 ; let final_tvs = tvs' ++ extra_tvs -- we may not need these
691 ; idx_tys <- doptM Opt_TypeFamilies
693 -- Check that we don't use families without -XTypeFamilies
694 ; checkTc idx_tys $ badFamInstDecl tc_name
696 ; tycon <- buildAlgTyCon tc_name final_tvs []
697 mkOpenDataTyConRhs Recursive False True Nothing
698 ; return [ATyCon tycon]
701 -- "newtype" and "data"
702 -- NB: not used for newtype/data instances (whether associated or not)
703 tcTyClDecl1 calc_isrec
704 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
705 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
706 = tcTyVarBndrs tvs $ \ tvs' -> do
707 { extra_tvs <- tcDataKindSig mb_ksig
708 ; let final_tvs = tvs' ++ extra_tvs
709 ; stupid_theta <- tcHsKindedContext ctxt
710 ; want_generic <- doptM Opt_Generics
711 ; unbox_strict <- doptM Opt_UnboxStrictFields
712 ; empty_data_decls <- doptM Opt_EmptyDataDecls
713 ; kind_signatures <- doptM Opt_KindSignatures
714 ; existential_ok <- doptM Opt_ExistentialQuantification
715 ; gadt_ok <- doptM Opt_GADTs
716 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
717 ; let ex_ok = existential_ok || gadt_ok -- Data cons can have existential context
719 -- Check that we don't use GADT syntax in H98 world
720 ; checkTc (gadt_ok || h98_syntax) (badGadtDecl tc_name)
722 -- Check that we don't use kind signatures without Glasgow extensions
723 ; checkTc (kind_signatures || isNothing mb_ksig) (badSigTyDecl tc_name)
725 -- Check that the stupid theta is empty for a GADT-style declaration
726 ; checkTc (null stupid_theta || h98_syntax) (badStupidTheta tc_name)
728 -- Check that a newtype has exactly one constructor
729 -- Do this before checking for empty data decls, so that
730 -- we don't suggest -XEmptyDataDecls for newtypes
731 ; checkTc (new_or_data == DataType || isSingleton cons)
732 (newtypeConError tc_name (length cons))
734 -- Check that there's at least one condecl,
735 -- or else we're reading an hs-boot file, or -XEmptyDataDecls
736 ; checkTc (not (null cons) || empty_data_decls || is_boot)
737 (emptyConDeclsErr tc_name)
739 ; tycon <- fixM (\ tycon -> do
740 { data_cons <- mapM (addLocM (tcConDecl unbox_strict ex_ok tycon final_tvs))
743 if null cons && is_boot -- In a hs-boot file, empty cons means
744 then return AbstractTyCon -- "don't know"; hence Abstract
745 else case new_or_data of
746 DataType -> return (mkDataTyConRhs data_cons)
748 ASSERT( not (null data_cons) )
749 mkNewTyConRhs tc_name tycon (head data_cons)
750 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
751 (want_generic && canDoGenerics data_cons) h98_syntax Nothing
753 ; return [ATyCon tycon]
756 is_rec = calc_isrec tc_name
757 h98_syntax = case cons of -- All constructors have same shape
758 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
761 tcTyClDecl1 calc_isrec
762 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
763 tcdCtxt = ctxt, tcdMeths = meths,
764 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
765 = tcTyVarBndrs tvs $ \ tvs' -> do
766 { ctxt' <- tcHsKindedContext ctxt
767 ; fds' <- mapM (addLocM tc_fundep) fundeps
768 ; atss <- mapM (addLocM (tcTyClDecl1 (const Recursive))) ats
769 -- NB: 'ats' only contains "type family" and "data family"
770 -- declarations as well as type family defaults
771 ; let ats' = zipWith setTyThingPoss atss (map (tcdTyVars . unLoc) ats)
772 ; sig_stuff <- tcClassSigs class_name sigs meths
773 ; clas <- fixM (\ clas ->
774 let -- This little knot is just so we can get
775 -- hold of the name of the class TyCon, which we
776 -- need to look up its recursiveness
777 tycon_name = tyConName (classTyCon clas)
778 tc_isrec = calc_isrec tycon_name
780 buildClass False {- Must include unfoldings for selectors -}
781 class_name tvs' ctxt' fds' ats'
783 ; return (AClass clas : ats')
784 -- NB: Order is important due to the call to `mkGlobalThings' when
785 -- tying the the type and class declaration type checking knot.
788 tc_fundep (tvs1, tvs2) = do { tvs1' <- mapM tcLookupTyVar tvs1 ;
789 ; tvs2' <- mapM tcLookupTyVar tvs2 ;
790 ; return (tvs1', tvs2') }
792 -- For each AT argument compute the position of the corresponding class
793 -- parameter in the class head. This will later serve as a permutation
794 -- vector when checking the validity of instance declarations.
795 setTyThingPoss [ATyCon tycon] atTyVars =
796 let classTyVars = hsLTyVarNames tvs
798 . map (`elemIndex` classTyVars)
801 -- There will be no Nothing, as we already passed renaming
803 ATyCon (setTyConArgPoss tycon poss)
804 setTyThingPoss _ _ = panic "TcTyClsDecls.setTyThingPoss"
806 tcTyClDecl1 calc_isrec
807 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
808 = return [ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0)]
810 -----------------------------------
811 tcConDecl :: Bool -- True <=> -funbox-strict_fields
812 -> Bool -- True <=> -XExistentialQuantificaton or -XGADTs
817 tcConDecl unbox_strict existential_ok tycon tc_tvs -- Data types
818 (ConDecl name _ tvs ctxt details res_ty _)
819 = addErrCtxt (dataConCtxt name) $
820 tcTyVarBndrs tvs $ \ tvs' -> do
821 { ctxt' <- tcHsKindedContext ctxt
822 ; checkTc (existential_ok || (null tvs && null (unLoc ctxt)))
823 (badExistential name)
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 <- mapM 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 { mapM_ 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 = do -- Check the context on the data decl
996 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc)
998 -- Check arg types of data constructors
999 mapM_ (checkValidDataCon tc) data_cons
1001 -- Check that fields with the same name share a type
1002 mapM_ 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 ; checkValidMonoType (dataConOrigResTy con)
1063 -- Disallow MkT :: T (forall a. a->a)
1064 -- Reason: it's really the argument of an equality constraint
1065 ; when (isNewTyCon tc) (checkNewDataCon con)
1068 ctxt = ConArgCtxt (dataConName con)
1070 -------------------------------
1071 checkNewDataCon :: DataCon -> TcM ()
1072 -- Checks for the data constructor of a newtype
1074 = do { checkTc (isSingleton arg_tys) (newtypeFieldErr con (length arg_tys))
1076 ; checkTc (null eq_spec) (newtypePredError con)
1077 -- Return type is (T a b c)
1078 ; checkTc (null ex_tvs && null eq_theta && null dict_theta) (newtypeExError con)
1080 ; checkTc (not (any isMarkedStrict (dataConStrictMarks con)))
1081 (newtypeStrictError con)
1085 (_univ_tvs, ex_tvs, eq_spec, eq_theta, dict_theta, arg_tys, _res_ty) = dataConFullSig con
1087 -------------------------------
1088 checkValidClass :: Class -> TcM ()
1090 = do { constrained_class_methods <- doptM Opt_ConstrainedClassMethods
1091 ; multi_param_type_classes <- doptM Opt_MultiParamTypeClasses
1092 ; fundep_classes <- doptM Opt_FunctionalDependencies
1094 -- Check that the class is unary, unless GlaExs
1095 ; checkTc (notNull tyvars) (nullaryClassErr cls)
1096 ; checkTc (multi_param_type_classes || unary) (classArityErr cls)
1097 ; checkTc (fundep_classes || null fundeps) (classFunDepsErr cls)
1099 -- Check the super-classes
1100 ; checkValidTheta (ClassSCCtxt (className cls)) theta
1102 -- Check the class operations
1103 ; mapM_ (check_op constrained_class_methods) op_stuff
1105 -- Check that if the class has generic methods, then the
1106 -- class has only one parameter. We can't do generic
1107 -- multi-parameter type classes!
1108 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
1111 (tyvars, fundeps, theta, _, _, op_stuff) = classExtraBigSig cls
1112 unary = isSingleton tyvars
1113 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
1115 check_op constrained_class_methods (sel_id, dm)
1116 = addErrCtxt (classOpCtxt sel_id tau) $ do
1117 { checkValidTheta SigmaCtxt (tail theta)
1118 -- The 'tail' removes the initial (C a) from the
1119 -- class itself, leaving just the method type
1121 ; traceTc (text "class op type" <+> ppr op_ty <+> ppr tau)
1122 ; checkValidType (FunSigCtxt op_name) tau
1124 -- Check that the type mentions at least one of
1125 -- the class type variables...or at least one reachable
1126 -- from one of the class variables. Example: tc223
1127 -- class Error e => Game b mv e | b -> mv e where
1128 -- newBoard :: MonadState b m => m ()
1129 -- Here, MonadState has a fundep m->b, so newBoard is fine
1130 ; let grown_tyvars = grow theta (mkVarSet tyvars)
1131 ; checkTc (tyVarsOfType tau `intersectsVarSet` grown_tyvars)
1132 (noClassTyVarErr cls sel_id)
1134 -- Check that for a generic method, the type of
1135 -- the method is sufficiently simple
1136 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
1137 (badGenericMethodType op_name op_ty)
1140 op_name = idName sel_id
1141 op_ty = idType sel_id
1142 (_,theta1,tau1) = tcSplitSigmaTy op_ty
1143 (_,theta2,tau2) = tcSplitSigmaTy tau1
1144 (theta,tau) | constrained_class_methods = (theta1 ++ theta2, tau2)
1145 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
1146 -- Ugh! The function might have a type like
1147 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
1148 -- With -XConstrainedClassMethods, we want to allow this, even though the inner
1149 -- forall has an (Eq a) constraint. Whereas in general, each constraint
1150 -- in the context of a for-all must mention at least one quantified
1151 -- type variable. What a mess!
1154 ---------------------------------------------------------------------
1155 resultTypeMisMatch field_name con1 con2
1156 = vcat [sep [ptext (sLit "Constructors") <+> ppr con1 <+> ptext (sLit "and") <+> ppr con2,
1157 ptext (sLit "have a common field") <+> quotes (ppr field_name) <> comma],
1158 nest 2 $ ptext (sLit "but have different result types")]
1159 fieldTypeMisMatch field_name con1 con2
1160 = sep [ptext (sLit "Constructors") <+> ppr con1 <+> ptext (sLit "and") <+> ppr con2,
1161 ptext (sLit "give different types for field"), quotes (ppr field_name)]
1163 dataConCtxt con = ptext (sLit "In the definition of data constructor") <+> quotes (ppr con)
1165 classOpCtxt sel_id tau = sep [ptext (sLit "When checking the class method:"),
1166 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
1169 = ptext (sLit "No parameters for class") <+> quotes (ppr cls)
1172 = vcat [ptext (sLit "Too many parameters for class") <+> quotes (ppr cls),
1173 parens (ptext (sLit "Use -XMultiParamTypeClasses to allow multi-parameter classes"))]
1176 = vcat [ptext (sLit "Fundeps in class") <+> quotes (ppr cls),
1177 parens (ptext (sLit "Use -XFunctionalDependencies to allow fundeps"))]
1179 noClassTyVarErr clas op
1180 = sep [ptext (sLit "The class method") <+> quotes (ppr op),
1181 ptext (sLit "mentions none of the type variables of the class") <+>
1182 ppr clas <+> hsep (map ppr (classTyVars clas))]
1184 genericMultiParamErr clas
1185 = ptext (sLit "The multi-parameter class") <+> quotes (ppr clas) <+>
1186 ptext (sLit "cannot have generic methods")
1188 badGenericMethodType op op_ty
1189 = hang (ptext (sLit "Generic method type is too complex"))
1190 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
1191 ptext (sLit "You can only use type variables, arrows, lists, and tuples")])
1194 = setSrcSpan (getLoc (head sorted_decls)) $
1195 addErr (sep [ptext (sLit "Cycle in type synonym declarations:"),
1196 nest 2 (vcat (map ppr_decl sorted_decls))])
1198 sorted_decls = sortLocated syn_decls
1199 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
1202 = setSrcSpan (getLoc (head sorted_decls)) $
1203 addErr (sep [ptext (sLit "Cycle in class declarations (via superclasses):"),
1204 nest 2 (vcat (map ppr_decl sorted_decls))])
1206 sorted_decls = sortLocated cls_decls
1207 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
1209 sortLocated :: [Located a] -> [Located a]
1210 sortLocated things = sortLe le things
1212 le (L l1 _) (L l2 _) = l1 <= l2
1214 badDataConTyCon data_con
1215 = hang (ptext (sLit "Data constructor") <+> quotes (ppr data_con) <+>
1216 ptext (sLit "returns type") <+> quotes (ppr (dataConTyCon data_con)))
1217 2 (ptext (sLit "instead of its parent type"))
1220 = vcat [ ptext (sLit "Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
1221 , nest 2 (parens $ ptext (sLit "Use -XGADTs to allow GADTs")) ]
1223 badExistential con_name
1224 = hang (ptext (sLit "Data constructor") <+> quotes (ppr con_name) <+>
1225 ptext (sLit "has existential type variables, or a context"))
1226 2 (parens $ ptext (sLit "Use -XExistentialQuantification or -XGADTs to allow this"))
1228 badStupidTheta tc_name
1229 = ptext (sLit "A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
1231 newtypeConError tycon n
1232 = sep [ptext (sLit "A newtype must have exactly one constructor,"),
1233 nest 2 $ ptext (sLit "but") <+> quotes (ppr tycon) <+> ptext (sLit "has") <+> speakN n ]
1236 = sep [ptext (sLit "A newtype constructor cannot have an existential context,"),
1237 nest 2 $ ptext (sLit "but") <+> quotes (ppr con) <+> ptext (sLit "does")]
1239 newtypeStrictError con
1240 = sep [ptext (sLit "A newtype constructor cannot have a strictness annotation,"),
1241 nest 2 $ ptext (sLit "but") <+> quotes (ppr con) <+> ptext (sLit "does")]
1243 newtypePredError con
1244 = sep [ptext (sLit "A newtype constructor must have a return type of form T a1 ... an"),
1245 nest 2 $ ptext (sLit "but") <+> quotes (ppr con) <+> ptext (sLit "does not")]
1247 newtypeFieldErr con_name n_flds
1248 = sep [ptext (sLit "The constructor of a newtype must have exactly one field"),
1249 nest 2 $ ptext (sLit "but") <+> quotes (ppr con_name) <+> ptext (sLit "has") <+> speakN n_flds]
1251 badSigTyDecl tc_name
1252 = vcat [ ptext (sLit "Illegal kind signature") <+>
1253 quotes (ppr tc_name)
1254 , nest 2 (parens $ ptext (sLit "Use -XKindSignatures to allow kind signatures")) ]
1256 badFamInstDecl tc_name
1257 = vcat [ ptext (sLit "Illegal family instance for") <+>
1258 quotes (ppr tc_name)
1259 , nest 2 (parens $ ptext (sLit "Use -XTypeFamilies to allow indexed type families")) ]
1261 badGadtIdxTyDecl tc_name
1262 = vcat [ ptext (sLit "Illegal generalised algebraic data declaration for") <+>
1263 quotes (ppr tc_name)
1264 , nest 2 (parens $ ptext (sLit "Family instances can not yet use GADT declarations")) ]
1266 tooManyParmsErr tc_name
1267 = ptext (sLit "Family instance has too many parameters:") <+>
1268 quotes (ppr tc_name)
1270 tooFewParmsErr arity
1271 = ptext (sLit "Family instance has too few parameters; expected") <+>
1274 wrongNumberOfParmsErr exp_arity
1275 = ptext (sLit "Number of parameters must match family declaration; expected")
1278 badBootFamInstDeclErr =
1279 ptext (sLit "Illegal family instance in hs-boot file")
1281 wrongKindOfFamily family =
1282 ptext (sLit "Wrong category of family instance; declaration was for a") <+>
1285 kindOfFamily | isSynTyCon family = ptext (sLit "type synonym")
1286 | isAlgTyCon family = ptext (sLit "data type")
1287 | otherwise = pprPanic "wrongKindOfFamily" (ppr family)
1289 emptyConDeclsErr tycon
1290 = sep [quotes (ppr tycon) <+> ptext (sLit "has no constructors"),
1291 nest 2 $ ptext (sLit "(-XEmptyDataDecls permits this)")]