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 ; tc <- tcFamInstDecl1 decl
264 ; checkValidTyCon tc -- Remember to check validity;
265 -- no recursion to worry about here
266 ; return (Just (ATyCon tc))
269 tcFamInstDecl1 :: TyClDecl Name -> TcM TyCon
272 tcFamInstDecl1 (decl@TySynonym {tcdLName = L loc tc_name})
273 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
274 do { -- check that the family declaration is for a synonym
275 unless (isSynTyCon family) $
276 addErr (wrongKindOfFamily family)
278 ; -- (1) kind check the right-hand side of the type equation
279 ; k_rhs <- kcCheckHsType (tcdSynRhs decl) resKind
281 -- we need the exact same number of type parameters as the family
283 ; let famArity = tyConArity family
284 ; checkTc (length k_typats == famArity) $
285 wrongNumberOfParmsErr famArity
287 -- (2) type check type equation
288 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
289 ; t_typats <- mapM tcHsKindedType k_typats
290 ; t_rhs <- tcHsKindedType k_rhs
293 -- - check the well-formedness of the instance
294 ; checkValidTypeInst t_typats t_rhs
296 -- (4) construct representation tycon
297 ; rep_tc_name <- newFamInstTyConName tc_name loc
298 ; buildSynTyCon rep_tc_name t_tvs (SynonymTyCon t_rhs)
299 (Just (family, t_typats))
302 -- "newtype instance" and "data instance"
303 tcFamInstDecl1 (decl@TyData {tcdND = new_or_data, tcdLName = L loc tc_name,
305 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
306 do { -- check that the family declaration is for the right kind
307 unless (isAlgTyCon family) $
308 addErr (wrongKindOfFamily family)
310 ; -- (1) kind check the data declaration as usual
311 ; k_decl <- kcDataDecl decl k_tvs
312 ; let k_ctxt = tcdCtxt k_decl
313 k_cons = tcdCons k_decl
315 -- result kind must be '*' (otherwise, we have too few patterns)
316 ; checkTc (isLiftedTypeKind resKind) $ tooFewParmsErr (tyConArity family)
318 -- (2) type check indexed data type declaration
319 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
320 ; unbox_strict <- doptM Opt_UnboxStrictFields
322 -- kind check the type indexes and the context
323 ; t_typats <- mapM tcHsKindedType k_typats
324 ; stupid_theta <- tcHsKindedContext k_ctxt
327 -- - left-hand side contains no type family applications
328 -- (vanilla synonyms are fine, though, and we checked for
330 ; mapM_ checkTyFamFreeness t_typats
332 -- - we don't use GADT syntax for indexed types
333 ; checkTc h98_syntax (badGadtIdxTyDecl tc_name)
335 -- - a newtype has exactly one constructor
336 ; checkTc (new_or_data == DataType || isSingleton k_cons) $
337 newtypeConError tc_name (length k_cons)
339 -- (4) construct representation tycon
340 ; rep_tc_name <- newFamInstTyConName tc_name loc
341 ; let ex_ok = True -- Existentials ok for type families!
342 ; fixM (\ tycon -> do
343 { data_cons <- mapM (addLocM (tcConDecl unbox_strict ex_ok tycon t_tvs))
347 DataType -> return (mkDataTyConRhs data_cons)
348 NewType -> ASSERT( not (null data_cons) )
349 mkNewTyConRhs rep_tc_name tycon (head data_cons)
350 ; buildAlgTyCon rep_tc_name t_tvs stupid_theta tc_rhs Recursive
351 False h98_syntax (Just (family, t_typats))
352 -- We always assume that indexed types are recursive. Why?
353 -- (1) Due to their open nature, we can never be sure that a
354 -- further instance might not introduce a new recursive
355 -- dependency. (2) They are always valid loop breakers as
356 -- they involve a coercion.
360 h98_syntax = case cons of -- All constructors have same shape
361 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
364 -- Kind checking of indexed types
367 -- Kind check type patterns and kind annotate the embedded type variables.
369 -- * Here we check that a type instance matches its kind signature, but we do
370 -- not check whether there is a pattern for each type index; the latter
371 -- check is only required for type synonym instances.
373 kcIdxTyPats :: TyClDecl Name
374 -> ([LHsTyVarBndr Name] -> [LHsType Name] -> Kind -> TyCon -> TcM a)
375 -- ^^kinded tvs ^^kinded ty pats ^^res kind
377 kcIdxTyPats decl thing_inside
378 = kcHsTyVars (tcdTyVars decl) $ \tvs ->
379 do { family <- tcLookupLocatedTyCon (tcdLName decl)
380 ; let { (kinds, resKind) = splitKindFunTys (tyConKind family)
381 ; hs_typats = fromJust $ tcdTyPats decl }
383 -- we may not have more parameters than the kind indicates
384 ; checkTc (length kinds >= length hs_typats) $
385 tooManyParmsErr (tcdLName decl)
387 -- type functions can have a higher-kinded result
388 ; let resultKind = mkArrowKinds (drop (length hs_typats) kinds) resKind
389 ; typats <- zipWithM kcCheckHsType hs_typats kinds
390 ; thing_inside tvs typats resultKind family
396 %************************************************************************
400 %************************************************************************
402 We need to kind check all types in the mutually recursive group
403 before we know the kind of the type variables. For example:
406 op :: D b => a -> b -> b
409 bop :: (Monad c) => ...
411 Here, the kind of the locally-polymorphic type variable "b"
412 depends on *all the uses of class D*. For example, the use of
413 Monad c in bop's type signature means that D must have kind Type->Type.
415 However type synonyms work differently. They can have kinds which don't
416 just involve (->) and *:
417 type R = Int# -- Kind #
418 type S a = Array# a -- Kind * -> #
419 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
420 So we must infer their kinds from their right-hand sides *first* and then
421 use them, whereas for the mutually recursive data types D we bring into
422 scope kind bindings D -> k, where k is a kind variable, and do inference.
426 This treatment of type synonyms only applies to Haskell 98-style synonyms.
427 General type functions can be recursive, and hence, appear in `alg_decls'.
429 The kind of a type family is solely determinded by its kind signature;
430 hence, only kind signatures participate in the construction of the initial
431 kind environment (as constructed by `getInitialKind'). In fact, we ignore
432 instances of families altogether in the following. However, we need to
433 include the kinds of associated families into the construction of the
434 initial kind environment. (This is handled by `allDecls').
437 kcTyClDecls syn_decls alg_decls
438 = do { -- First extend the kind env with each data type, class, and
439 -- indexed type, mapping them to a type variable
440 let initialKindDecls = concat [allDecls decl | L _ decl <- alg_decls]
441 ; alg_kinds <- mapM getInitialKind initialKindDecls
442 ; tcExtendKindEnv alg_kinds $ do
444 -- Now kind-check the type synonyms, in dependency order
445 -- We do these differently to data type and classes,
446 -- because a type synonym can be an unboxed type
448 -- and a kind variable can't unify with UnboxedTypeKind
449 -- So we infer their kinds in dependency order
450 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
451 ; tcExtendKindEnv syn_kinds $ do
453 -- Now kind-check the data type, class, and kind signatures,
454 -- returning kind-annotated decls; we don't kind-check
455 -- instances of indexed types yet, but leave this to
457 { kc_alg_decls <- mapM (wrapLocM kcTyClDecl)
458 (filter (not . isFamInstDecl . unLoc) alg_decls)
460 ; return (kc_syn_decls, kc_alg_decls) }}}
462 -- get all declarations relevant for determining the initial kind
464 allDecls (decl@ClassDecl {tcdATs = ats}) = decl : [ at
467 allDecls decl | isFamInstDecl decl = []
470 ------------------------------------------------------------------------
471 getInitialKind :: TyClDecl Name -> TcM (Name, TcKind)
472 -- Only for data type, class, and indexed type declarations
473 -- Get as much info as possible from the data, class, or indexed type decl,
474 -- so as to maximise usefulness of error messages
476 = do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl)
477 ; res_kind <- mk_res_kind decl
478 ; return (tcdName decl, mkArrowKinds arg_kinds res_kind) }
480 mk_arg_kind (UserTyVar _) = newKindVar
481 mk_arg_kind (KindedTyVar _ kind) = return kind
483 mk_res_kind (TyFamily { tcdKind = Just kind }) = return kind
484 mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
485 -- On GADT-style declarations we allow a kind signature
486 -- data T :: *->* where { ... }
487 mk_res_kind other = return liftedTypeKind
491 kcSynDecls :: [SCC (LTyClDecl Name)]
492 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
493 [(Name,TcKind)]) -- Kind bindings
496 kcSynDecls (group : groups)
497 = do { (decl, nk) <- kcSynDecl group
498 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
499 ; return (decl:decls, nk:nks) }
502 kcSynDecl :: SCC (LTyClDecl Name)
503 -> TcM (LTyClDecl Name, -- Kind-annotated decls
504 (Name,TcKind)) -- Kind bindings
505 kcSynDecl (AcyclicSCC ldecl@(L loc decl))
506 = tcAddDeclCtxt decl $
507 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
508 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
509 <+> brackets (ppr k_tvs))
510 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
511 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
512 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
513 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
514 (unLoc (tcdLName decl), tc_kind)) })
516 kcSynDecl (CyclicSCC decls)
517 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
518 -- of out-of-scope tycons
520 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
522 ------------------------------------------------------------------------
523 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
524 -- Not used for type synonyms (see kcSynDecl)
526 kcTyClDecl decl@(TyData {})
527 = ASSERT( not . isFamInstDecl $ decl ) -- must not be a family instance
528 kcTyClDeclBody decl $
531 kcTyClDecl decl@(TyFamily {})
532 = kcFamilyDecl [] decl -- the empty list signals a toplevel decl
534 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs, tcdATs = ats})
535 = kcTyClDeclBody decl $ \ tvs' ->
536 do { is_boot <- tcIsHsBoot
537 ; ctxt' <- kcHsContext ctxt
538 ; ats' <- mapM (wrapLocM (kcFamilyDecl tvs')) ats
539 ; sigs' <- mapM (wrapLocM kc_sig) sigs
540 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs',
543 kc_sig (TypeSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
544 ; return (TypeSig nm op_ty') }
545 kc_sig other_sig = return other_sig
547 kcTyClDecl decl@(ForeignType {})
550 kcTyClDeclBody :: TyClDecl Name
551 -> ([LHsTyVarBndr Name] -> TcM a)
553 -- getInitialKind has made a suitably-shaped kind for the type or class
554 -- Unpack it, and attribute those kinds to the type variables
555 -- Extend the env with bindings for the tyvars, taken from
556 -- the kind of the tycon/class. Give it to the thing inside, and
557 -- check the result kind matches
558 kcTyClDeclBody decl thing_inside
559 = tcAddDeclCtxt decl $
560 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
561 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
562 (kinds, _) = splitKindFunTys tc_kind
563 hs_tvs = tcdTyVars decl
564 kinded_tvs = ASSERT( length kinds >= length hs_tvs )
565 [ L loc (KindedTyVar (hsTyVarName tv) k)
566 | (L loc tv, k) <- zip hs_tvs kinds]
567 ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
569 -- Kind check a data declaration, assuming that we already extended the
570 -- kind environment with the type variables of the left-hand side (these
571 -- kinded type variables are also passed as the second parameter).
573 kcDataDecl :: TyClDecl Name -> [LHsTyVarBndr Name] -> TcM (TyClDecl Name)
574 kcDataDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
576 = do { ctxt' <- kcHsContext ctxt
577 ; cons' <- mapM (wrapLocM kc_con_decl) cons
578 ; return (decl {tcdTyVars = tvs, tcdCtxt = ctxt', tcdCons = cons'}) }
580 -- doc comments are typechecked to Nothing here
581 kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res _) = do
582 kcHsTyVars ex_tvs $ \ex_tvs' -> do
583 ex_ctxt' <- kcHsContext ex_ctxt
584 details' <- kc_con_details details
586 ResTyH98 -> return ResTyH98
587 ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
588 return (ConDecl name expl ex_tvs' ex_ctxt' details' res' Nothing)
590 kc_con_details (PrefixCon btys)
591 = do { btys' <- mapM kc_larg_ty btys
592 ; return (PrefixCon btys') }
593 kc_con_details (InfixCon bty1 bty2)
594 = do { bty1' <- kc_larg_ty bty1
595 ; bty2' <- kc_larg_ty bty2
596 ; return (InfixCon bty1' bty2') }
597 kc_con_details (RecCon fields)
598 = do { fields' <- mapM kc_field fields
599 ; return (RecCon fields') }
601 kc_field (ConDeclField fld bty d) = do { bty' <- kc_larg_ty bty
602 ; return (ConDeclField fld bty' d) }
604 kc_larg_ty bty = case new_or_data of
605 DataType -> kcHsSigType bty
606 NewType -> kcHsLiftedSigType bty
607 -- Can't allow an unlifted type for newtypes, because we're effectively
608 -- going to remove the constructor while coercing it to a lifted type.
609 -- And newtypes can't be bang'd
611 -- Kind check a family declaration or type family default declaration.
613 kcFamilyDecl :: [LHsTyVarBndr Name] -- tyvars of enclosing class decl if any
614 -> TyClDecl Name -> TcM (TyClDecl Name)
615 kcFamilyDecl classTvs decl@(TyFamily {tcdKind = kind})
616 = kcTyClDeclBody decl $ \tvs' ->
617 do { mapM_ unifyClassParmKinds tvs'
618 ; return (decl {tcdTyVars = tvs',
619 tcdKind = kind `mplus` Just liftedTypeKind})
620 -- default result kind is '*'
623 unifyClassParmKinds (L _ (KindedTyVar n k))
624 | Just classParmKind <- lookup n classTyKinds = unifyKind k classParmKind
625 | otherwise = return ()
626 classTyKinds = [(n, k) | L _ (KindedTyVar n k) <- classTvs]
627 kcFamilyDecl _ decl@(TySynonym {}) -- type family defaults
628 = panic "TcTyClsDecls.kcFamilyDecl: not implemented yet"
632 %************************************************************************
634 \subsection{Type checking}
636 %************************************************************************
639 tcSynDecls :: [LTyClDecl Name] -> TcM [TyThing]
640 tcSynDecls [] = return []
641 tcSynDecls (decl : decls)
642 = do { syn_tc <- addLocM tcSynDecl decl
643 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls decls)
644 ; return (syn_tc : syn_tcs) }
648 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
649 = tcTyVarBndrs tvs $ \ tvs' -> do
650 { traceTc (text "tcd1" <+> ppr tc_name)
651 ; rhs_ty' <- tcHsKindedType rhs_ty
652 ; tycon <- buildSynTyCon tc_name tvs' (SynonymTyCon rhs_ty') Nothing
653 ; return (ATyCon tycon)
657 tcTyClDecl :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
659 tcTyClDecl calc_isrec decl
660 = tcAddDeclCtxt decl (tcTyClDecl1 calc_isrec decl)
662 -- "type family" declarations
663 tcTyClDecl1 _calc_isrec
664 (TyFamily {tcdFlavour = TypeFamily,
665 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = Just kind})
666 -- NB: kind at latest
669 = tcTyVarBndrs tvs $ \ tvs' -> do
670 { traceTc (text "type family: " <+> ppr tc_name)
671 ; idx_tys <- doptM Opt_TypeFamilies
673 -- Check that we don't use families without -XTypeFamilies
674 ; checkTc idx_tys $ badFamInstDecl tc_name
676 ; tycon <- buildSynTyCon tc_name tvs' (OpenSynTyCon kind Nothing) Nothing
677 ; return [ATyCon tycon]
680 -- "data family" declaration
681 tcTyClDecl1 _calc_isrec
682 (TyFamily {tcdFlavour = DataFamily,
683 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = mb_kind})
684 = tcTyVarBndrs tvs $ \ tvs' -> do
685 { traceTc (text "data family: " <+> ppr tc_name)
686 ; extra_tvs <- tcDataKindSig mb_kind
687 ; let final_tvs = tvs' ++ extra_tvs -- we may not need these
689 ; idx_tys <- doptM Opt_TypeFamilies
691 -- Check that we don't use families without -XTypeFamilies
692 ; checkTc idx_tys $ badFamInstDecl tc_name
694 ; tycon <- buildAlgTyCon tc_name final_tvs []
695 mkOpenDataTyConRhs Recursive False True Nothing
696 ; return [ATyCon tycon]
699 -- "newtype" and "data"
700 -- NB: not used for newtype/data instances (whether associated or not)
701 tcTyClDecl1 calc_isrec
702 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
703 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
704 = tcTyVarBndrs tvs $ \ tvs' -> do
705 { extra_tvs <- tcDataKindSig mb_ksig
706 ; let final_tvs = tvs' ++ extra_tvs
707 ; stupid_theta <- tcHsKindedContext ctxt
708 ; want_generic <- doptM Opt_Generics
709 ; unbox_strict <- doptM Opt_UnboxStrictFields
710 ; empty_data_decls <- doptM Opt_EmptyDataDecls
711 ; kind_signatures <- doptM Opt_KindSignatures
712 ; existential_ok <- doptM Opt_ExistentialQuantification
713 ; gadt_ok <- doptM Opt_GADTs
714 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
715 ; let ex_ok = existential_ok || gadt_ok -- Data cons can have existential context
717 -- Check that we don't use GADT syntax in H98 world
718 ; checkTc (gadt_ok || h98_syntax) (badGadtDecl tc_name)
720 -- Check that we don't use kind signatures without Glasgow extensions
721 ; checkTc (kind_signatures || isNothing mb_ksig) (badSigTyDecl tc_name)
723 -- Check that the stupid theta is empty for a GADT-style declaration
724 ; checkTc (null stupid_theta || h98_syntax) (badStupidTheta tc_name)
726 -- Check that a newtype has exactly one constructor
727 -- Do this before checking for empty data decls, so that
728 -- we don't suggest -XEmptyDataDecls for newtypes
729 ; checkTc (new_or_data == DataType || isSingleton cons)
730 (newtypeConError tc_name (length cons))
732 -- Check that there's at least one condecl,
733 -- or else we're reading an hs-boot file, or -XEmptyDataDecls
734 ; checkTc (not (null cons) || empty_data_decls || is_boot)
735 (emptyConDeclsErr tc_name)
737 ; tycon <- fixM (\ tycon -> do
738 { data_cons <- mapM (addLocM (tcConDecl unbox_strict ex_ok tycon final_tvs))
741 if null cons && is_boot -- In a hs-boot file, empty cons means
742 then return AbstractTyCon -- "don't know"; hence Abstract
743 else case new_or_data of
744 DataType -> return (mkDataTyConRhs data_cons)
746 ASSERT( not (null data_cons) )
747 mkNewTyConRhs tc_name tycon (head data_cons)
748 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
749 (want_generic && canDoGenerics data_cons) h98_syntax Nothing
751 ; return [ATyCon tycon]
754 is_rec = calc_isrec tc_name
755 h98_syntax = case cons of -- All constructors have same shape
756 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
759 tcTyClDecl1 calc_isrec
760 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
761 tcdCtxt = ctxt, tcdMeths = meths,
762 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
763 = tcTyVarBndrs tvs $ \ tvs' -> do
764 { ctxt' <- tcHsKindedContext ctxt
765 ; fds' <- mapM (addLocM tc_fundep) fundeps
766 ; atss <- mapM (addLocM (tcTyClDecl1 (const Recursive))) ats
767 -- NB: 'ats' only contains "type family" and "data family"
768 -- declarations as well as type family defaults
769 ; let ats' = zipWith setTyThingPoss atss (map (tcdTyVars . unLoc) ats)
770 ; sig_stuff <- tcClassSigs class_name sigs meths
771 ; clas <- fixM (\ clas ->
772 let -- This little knot is just so we can get
773 -- hold of the name of the class TyCon, which we
774 -- need to look up its recursiveness
775 tycon_name = tyConName (classTyCon clas)
776 tc_isrec = calc_isrec tycon_name
778 buildClass False {- Must include unfoldings for selectors -}
779 class_name tvs' ctxt' fds' ats'
781 ; return (AClass clas : ats')
782 -- NB: Order is important due to the call to `mkGlobalThings' when
783 -- tying the the type and class declaration type checking knot.
786 tc_fundep (tvs1, tvs2) = do { tvs1' <- mapM tcLookupTyVar tvs1 ;
787 ; tvs2' <- mapM tcLookupTyVar tvs2 ;
788 ; return (tvs1', tvs2') }
790 -- For each AT argument compute the position of the corresponding class
791 -- parameter in the class head. This will later serve as a permutation
792 -- vector when checking the validity of instance declarations.
793 setTyThingPoss [ATyCon tycon] atTyVars =
794 let classTyVars = hsLTyVarNames tvs
796 . map (`elemIndex` classTyVars)
799 -- There will be no Nothing, as we already passed renaming
801 ATyCon (setTyConArgPoss tycon poss)
802 setTyThingPoss _ _ = panic "TcTyClsDecls.setTyThingPoss"
804 tcTyClDecl1 calc_isrec
805 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
806 = return [ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0)]
808 -----------------------------------
809 tcConDecl :: Bool -- True <=> -funbox-strict_fields
810 -> Bool -- True <=> -XExistentialQuantificaton or -XGADTs
815 tcConDecl unbox_strict existential_ok tycon tc_tvs -- Data types
816 (ConDecl name _ tvs ctxt details res_ty _)
817 = addErrCtxt (dataConCtxt name) $
818 tcTyVarBndrs tvs $ \ tvs' -> do
819 { ctxt' <- tcHsKindedContext ctxt
820 ; checkTc (existential_ok || (null tvs && null (unLoc ctxt)))
821 (badExistential name)
822 ; (univ_tvs, ex_tvs, eq_preds, data_tc) <- tcResultType tycon tc_tvs tvs' res_ty
824 -- Tiresome: tidy the tyvar binders, since tc_tvs and tvs' may have the same OccNames
825 tc_datacon is_infix field_lbls btys
826 = do { let bangs = map getBangStrictness btys
827 ; arg_tys <- mapM tcHsBangType btys
828 ; buildDataCon (unLoc name) is_infix
829 (argStrictness unbox_strict bangs arg_tys)
830 (map unLoc field_lbls)
831 univ_tvs ex_tvs eq_preds ctxt' arg_tys
833 -- NB: we put data_tc, the type constructor gotten from the
834 -- constructor type signature into the data constructor;
835 -- that way checkValidDataCon can complain if it's wrong.
838 PrefixCon btys -> tc_datacon False [] btys
839 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
840 RecCon fields -> tc_datacon False field_names btys
842 field_names = map cd_fld_name fields
843 btys = map cd_fld_type fields
846 tcResultType :: TyCon
847 -> [TyVar] -- data T a b c = ...
848 -> [TyVar] -- where MkT :: forall a b c. ...
850 -> TcM ([TyVar], -- Universal
851 [TyVar], -- Existential (distinct OccNames from univs)
852 [(TyVar,Type)], -- Equality predicates
853 TyCon) -- TyCon given in the ResTy
854 -- We don't check that the TyCon given in the ResTy is
855 -- the same as the parent tycon, becuase we are in the middle
856 -- of a recursive knot; so it's postponed until checkValidDataCon
858 tcResultType decl_tycon tc_tvs dc_tvs ResTyH98
859 = return (tc_tvs, dc_tvs, [], decl_tycon)
860 -- In H98 syntax the dc_tvs are the existential ones
861 -- data T a b c = forall d e. MkT ...
862 -- The {a,b,c} are tc_tvs, and {d,e} are dc_tvs
864 tcResultType _ tc_tvs dc_tvs (ResTyGADT res_ty)
865 -- E.g. data T a b c where
866 -- MkT :: forall x y z. T (x,y) z z
868 -- ([a,z,c], [x,y], [a:=:(x,y), c:=:z], T)
870 = do { (dc_tycon, res_tys) <- tcLHsConResTy res_ty
872 ; let univ_tvs = choose_univs [] tidy_tc_tvs res_tys
873 -- Each univ_tv is either a dc_tv or a tc_tv
874 ex_tvs = dc_tvs `minusList` univ_tvs
875 eq_spec = [ (tv, ty) | (tv,ty) <- univ_tvs `zip` res_tys,
877 ; return (univ_tvs, ex_tvs, eq_spec, dc_tycon) }
879 -- choose_univs uses the res_ty itself if it's a type variable
880 -- and hasn't already been used; otherwise it uses one of the tc_tvs
881 choose_univs used tc_tvs []
882 = ASSERT( null tc_tvs ) []
883 choose_univs used (tc_tv:tc_tvs) (res_ty:res_tys)
884 | Just tv <- tcGetTyVar_maybe res_ty, not (tv `elem` used)
885 = tv : choose_univs (tv:used) tc_tvs res_tys
887 = tc_tv : choose_univs used tc_tvs res_tys
889 -- NB: tc_tvs and dc_tvs are distinct, but
890 -- we want them to be *visibly* distinct, both for
891 -- interface files and general confusion. So rename
892 -- the tc_tvs, since they are not used yet (no
893 -- consequential renaming needed)
894 init_occ_env = initTidyOccEnv (map getOccName dc_tvs)
895 (_, tidy_tc_tvs) = mapAccumL tidy_one init_occ_env tc_tvs
896 tidy_one env tv = (env', setTyVarName tv (tidyNameOcc name occ'))
899 (env', occ') = tidyOccName env (getOccName name)
902 argStrictness :: Bool -- True <=> -funbox-strict_fields
904 -> [TcType] -> [StrictnessMark]
905 argStrictness unbox_strict bangs arg_tys
906 = ASSERT( length bangs == length arg_tys )
907 zipWith (chooseBoxingStrategy unbox_strict) arg_tys bangs
909 -- We attempt to unbox/unpack a strict field when either:
910 -- (i) The field is marked '!!', or
911 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
913 -- We have turned off unboxing of newtypes because coercions make unboxing
914 -- and reboxing more complicated
915 chooseBoxingStrategy :: Bool -> TcType -> HsBang -> StrictnessMark
916 chooseBoxingStrategy unbox_strict_fields arg_ty bang
918 HsNoBang -> NotMarkedStrict
919 HsStrict | unbox_strict_fields
920 && can_unbox arg_ty -> MarkedUnboxed
921 HsUnbox | can_unbox arg_ty -> MarkedUnboxed
922 other -> MarkedStrict
924 -- we can unbox if the type is a chain of newtypes with a product tycon
926 can_unbox arg_ty = case splitTyConApp_maybe arg_ty of
928 Just (arg_tycon, tycon_args) ->
929 not (isRecursiveTyCon arg_tycon) && -- Note [Recusive unboxing]
930 isProductTyCon arg_tycon &&
931 (if isNewTyCon arg_tycon then
932 can_unbox (newTyConInstRhs arg_tycon tycon_args)
936 Note [Recursive unboxing]
937 ~~~~~~~~~~~~~~~~~~~~~~~~~
938 Be careful not to try to unbox this!
940 But it's the *argument* type that matters. This is fine:
942 because Int is non-recursive.
944 %************************************************************************
946 \subsection{Dependency analysis}
948 %************************************************************************
950 Validity checking is done once the mutually-recursive knot has been
951 tied, so we can look at things freely.
954 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
955 checkCycleErrs tyclss
959 = do { mapM_ recClsErr cls_cycles
960 ; failM } -- Give up now, because later checkValidTyCl
961 -- will loop if the synonym is recursive
963 cls_cycles = calcClassCycles tyclss
965 checkValidTyCl :: TyClDecl Name -> TcM ()
966 -- We do the validity check over declarations, rather than TyThings
967 -- only so that we can add a nice context with tcAddDeclCtxt
969 = tcAddDeclCtxt decl $
970 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
971 ; traceTc (text "Validity of" <+> ppr thing)
973 ATyCon tc -> checkValidTyCon tc
974 AClass cl -> checkValidClass cl
975 ; traceTc (text "Done validity of" <+> ppr thing)
978 -------------------------
979 -- For data types declared with record syntax, we require
980 -- that each constructor that has a field 'f'
981 -- (a) has the same result type
982 -- (b) has the same type for 'f'
983 -- module alpha conversion of the quantified type variables
984 -- of the constructor.
986 checkValidTyCon :: TyCon -> TcM ()
989 = case synTyConRhs tc of
990 OpenSynTyCon _ _ -> return ()
991 SynonymTyCon ty -> checkValidType syn_ctxt ty
993 = do -- Check the context on the data decl
994 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc)
996 -- Check arg types of data constructors
997 mapM_ (checkValidDataCon tc) data_cons
999 -- Check that fields with the same name share a type
1000 mapM_ check_fields groups
1003 syn_ctxt = TySynCtxt name
1005 data_cons = tyConDataCons tc
1007 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
1008 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
1009 get_fields con = dataConFieldLabels con `zip` repeat con
1010 -- dataConFieldLabels may return the empty list, which is fine
1012 -- See Note [GADT record selectors] in MkId.lhs
1013 -- We must check (a) that the named field has the same
1014 -- type in each constructor
1015 -- (b) that those constructors have the same result type
1017 -- However, the constructors may have differently named type variable
1018 -- and (worse) we don't know how the correspond to each other. E.g.
1019 -- C1 :: forall a b. { f :: a, g :: b } -> T a b
1020 -- C2 :: forall d c. { f :: c, g :: c } -> T c d
1022 -- So what we do is to ust Unify.tcMatchTys to compare the first candidate's
1023 -- result type against other candidates' types BOTH WAYS ROUND.
1024 -- If they magically agrees, take the substitution and
1025 -- apply them to the latter ones, and see if they match perfectly.
1026 check_fields fields@((label, con1) : other_fields)
1027 -- These fields all have the same name, but are from
1028 -- different constructors in the data type
1029 = recoverM (return ()) $ mapM_ checkOne other_fields
1030 -- Check that all the fields in the group have the same type
1031 -- NB: this check assumes that all the constructors of a given
1032 -- data type use the same type variables
1034 (tvs1, _, _, res1) = dataConSig con1
1036 fty1 = dataConFieldType con1 label
1038 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
1039 = do { checkFieldCompat label con1 con2 ts1 res1 res2 fty1 fty2
1040 ; checkFieldCompat label con2 con1 ts2 res2 res1 fty2 fty1 }
1042 (tvs2, _, _, res2) = dataConSig con2
1044 fty2 = dataConFieldType con2 label
1046 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
1047 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
1048 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
1050 mb_subst1 = tcMatchTy tvs1 res1 res2
1051 mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
1053 -------------------------------
1054 checkValidDataCon :: TyCon -> DataCon -> TcM ()
1055 checkValidDataCon tc con
1056 = setSrcSpan (srcLocSpan (getSrcLoc con)) $
1057 addErrCtxt (dataConCtxt con) $
1058 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
1059 ; checkValidType ctxt (dataConUserType con)
1060 ; checkValidMonoType (dataConOrigResTy con)
1061 -- Disallow MkT :: T (forall a. a->a)
1062 -- Reason: it's really the argument of an equality constraint
1063 ; when (isNewTyCon tc) (checkNewDataCon con)
1066 ctxt = ConArgCtxt (dataConName con)
1068 -------------------------------
1069 checkNewDataCon :: DataCon -> TcM ()
1070 -- Checks for the data constructor of a newtype
1072 = do { checkTc (isSingleton arg_tys) (newtypeFieldErr con (length arg_tys))
1074 ; checkTc (null eq_spec) (newtypePredError con)
1075 -- Return type is (T a b c)
1076 ; checkTc (null ex_tvs && null eq_theta && null dict_theta) (newtypeExError con)
1078 ; checkTc (not (any isMarkedStrict (dataConStrictMarks con)))
1079 (newtypeStrictError con)
1083 (_univ_tvs, ex_tvs, eq_spec, eq_theta, dict_theta, arg_tys, _res_ty) = dataConFullSig con
1085 -------------------------------
1086 checkValidClass :: Class -> TcM ()
1088 = do { constrained_class_methods <- doptM Opt_ConstrainedClassMethods
1089 ; multi_param_type_classes <- doptM Opt_MultiParamTypeClasses
1090 ; fundep_classes <- doptM Opt_FunctionalDependencies
1092 -- Check that the class is unary, unless GlaExs
1093 ; checkTc (notNull tyvars) (nullaryClassErr cls)
1094 ; checkTc (multi_param_type_classes || unary) (classArityErr cls)
1095 ; checkTc (fundep_classes || null fundeps) (classFunDepsErr cls)
1097 -- Check the super-classes
1098 ; checkValidTheta (ClassSCCtxt (className cls)) theta
1100 -- Check the class operations
1101 ; mapM_ (check_op constrained_class_methods) op_stuff
1103 -- Check that if the class has generic methods, then the
1104 -- class has only one parameter. We can't do generic
1105 -- multi-parameter type classes!
1106 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
1109 (tyvars, fundeps, theta, _, _, op_stuff) = classExtraBigSig cls
1110 unary = isSingleton tyvars
1111 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
1113 check_op constrained_class_methods (sel_id, dm)
1114 = addErrCtxt (classOpCtxt sel_id tau) $ do
1115 { checkValidTheta SigmaCtxt (tail theta)
1116 -- The 'tail' removes the initial (C a) from the
1117 -- class itself, leaving just the method type
1119 ; traceTc (text "class op type" <+> ppr op_ty <+> ppr tau)
1120 ; checkValidType (FunSigCtxt op_name) tau
1122 -- Check that the type mentions at least one of
1123 -- the class type variables...or at least one reachable
1124 -- from one of the class variables. Example: tc223
1125 -- class Error e => Game b mv e | b -> mv e where
1126 -- newBoard :: MonadState b m => m ()
1127 -- Here, MonadState has a fundep m->b, so newBoard is fine
1128 ; let grown_tyvars = grow theta (mkVarSet tyvars)
1129 ; checkTc (tyVarsOfType tau `intersectsVarSet` grown_tyvars)
1130 (noClassTyVarErr cls sel_id)
1132 -- Check that for a generic method, the type of
1133 -- the method is sufficiently simple
1134 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
1135 (badGenericMethodType op_name op_ty)
1138 op_name = idName sel_id
1139 op_ty = idType sel_id
1140 (_,theta1,tau1) = tcSplitSigmaTy op_ty
1141 (_,theta2,tau2) = tcSplitSigmaTy tau1
1142 (theta,tau) | constrained_class_methods = (theta1 ++ theta2, tau2)
1143 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
1144 -- Ugh! The function might have a type like
1145 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
1146 -- With -XConstrainedClassMethods, we want to allow this, even though the inner
1147 -- forall has an (Eq a) constraint. Whereas in general, each constraint
1148 -- in the context of a for-all must mention at least one quantified
1149 -- type variable. What a mess!
1152 ---------------------------------------------------------------------
1153 resultTypeMisMatch field_name con1 con2
1154 = vcat [sep [ptext (sLit "Constructors") <+> ppr con1 <+> ptext (sLit "and") <+> ppr con2,
1155 ptext (sLit "have a common field") <+> quotes (ppr field_name) <> comma],
1156 nest 2 $ ptext (sLit "but have different result types")]
1157 fieldTypeMisMatch field_name con1 con2
1158 = sep [ptext (sLit "Constructors") <+> ppr con1 <+> ptext (sLit "and") <+> ppr con2,
1159 ptext (sLit "give different types for field"), quotes (ppr field_name)]
1161 dataConCtxt con = ptext (sLit "In the definition of data constructor") <+> quotes (ppr con)
1163 classOpCtxt sel_id tau = sep [ptext (sLit "When checking the class method:"),
1164 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
1167 = ptext (sLit "No parameters for class") <+> quotes (ppr cls)
1170 = vcat [ptext (sLit "Too many parameters for class") <+> quotes (ppr cls),
1171 parens (ptext (sLit "Use -XMultiParamTypeClasses to allow multi-parameter classes"))]
1174 = vcat [ptext (sLit "Fundeps in class") <+> quotes (ppr cls),
1175 parens (ptext (sLit "Use -XFunctionalDependencies to allow fundeps"))]
1177 noClassTyVarErr clas op
1178 = sep [ptext (sLit "The class method") <+> quotes (ppr op),
1179 ptext (sLit "mentions none of the type variables of the class") <+>
1180 ppr clas <+> hsep (map ppr (classTyVars clas))]
1182 genericMultiParamErr clas
1183 = ptext (sLit "The multi-parameter class") <+> quotes (ppr clas) <+>
1184 ptext (sLit "cannot have generic methods")
1186 badGenericMethodType op op_ty
1187 = hang (ptext (sLit "Generic method type is too complex"))
1188 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
1189 ptext (sLit "You can only use type variables, arrows, lists, and tuples")])
1192 = setSrcSpan (getLoc (head sorted_decls)) $
1193 addErr (sep [ptext (sLit "Cycle in type synonym declarations:"),
1194 nest 2 (vcat (map ppr_decl sorted_decls))])
1196 sorted_decls = sortLocated syn_decls
1197 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
1200 = setSrcSpan (getLoc (head sorted_decls)) $
1201 addErr (sep [ptext (sLit "Cycle in class declarations (via superclasses):"),
1202 nest 2 (vcat (map ppr_decl sorted_decls))])
1204 sorted_decls = sortLocated cls_decls
1205 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
1207 sortLocated :: [Located a] -> [Located a]
1208 sortLocated things = sortLe le things
1210 le (L l1 _) (L l2 _) = l1 <= l2
1212 badDataConTyCon data_con
1213 = hang (ptext (sLit "Data constructor") <+> quotes (ppr data_con) <+>
1214 ptext (sLit "returns type") <+> quotes (ppr (dataConTyCon data_con)))
1215 2 (ptext (sLit "instead of its parent type"))
1218 = vcat [ ptext (sLit "Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
1219 , nest 2 (parens $ ptext (sLit "Use -XGADTs to allow GADTs")) ]
1221 badExistential con_name
1222 = hang (ptext (sLit "Data constructor") <+> quotes (ppr con_name) <+>
1223 ptext (sLit "has existential type variables, or a context"))
1224 2 (parens $ ptext (sLit "Use -XExistentialQuantification or -XGADTs to allow this"))
1226 badStupidTheta tc_name
1227 = ptext (sLit "A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
1229 newtypeConError tycon n
1230 = sep [ptext (sLit "A newtype must have exactly one constructor,"),
1231 nest 2 $ ptext (sLit "but") <+> quotes (ppr tycon) <+> ptext (sLit "has") <+> speakN n ]
1234 = sep [ptext (sLit "A newtype constructor cannot have an existential context,"),
1235 nest 2 $ ptext (sLit "but") <+> quotes (ppr con) <+> ptext (sLit "does")]
1237 newtypeStrictError con
1238 = sep [ptext (sLit "A newtype constructor cannot have a strictness annotation,"),
1239 nest 2 $ ptext (sLit "but") <+> quotes (ppr con) <+> ptext (sLit "does")]
1241 newtypePredError con
1242 = sep [ptext (sLit "A newtype constructor must have a return type of form T a1 ... an"),
1243 nest 2 $ ptext (sLit "but") <+> quotes (ppr con) <+> ptext (sLit "does not")]
1245 newtypeFieldErr con_name n_flds
1246 = sep [ptext (sLit "The constructor of a newtype must have exactly one field"),
1247 nest 2 $ ptext (sLit "but") <+> quotes (ppr con_name) <+> ptext (sLit "has") <+> speakN n_flds]
1249 badSigTyDecl tc_name
1250 = vcat [ ptext (sLit "Illegal kind signature") <+>
1251 quotes (ppr tc_name)
1252 , nest 2 (parens $ ptext (sLit "Use -XKindSignatures to allow kind signatures")) ]
1254 badFamInstDecl tc_name
1255 = vcat [ ptext (sLit "Illegal family instance for") <+>
1256 quotes (ppr tc_name)
1257 , nest 2 (parens $ ptext (sLit "Use -XTypeFamilies to allow indexed type families")) ]
1259 badGadtIdxTyDecl tc_name
1260 = vcat [ ptext (sLit "Illegal generalised algebraic data declaration for") <+>
1261 quotes (ppr tc_name)
1262 , nest 2 (parens $ ptext (sLit "Family instances can not yet use GADT declarations")) ]
1264 tooManyParmsErr tc_name
1265 = ptext (sLit "Family instance has too many parameters:") <+>
1266 quotes (ppr tc_name)
1268 tooFewParmsErr arity
1269 = ptext (sLit "Family instance has too few parameters; expected") <+>
1272 wrongNumberOfParmsErr exp_arity
1273 = ptext (sLit "Number of parameters must match family declaration; expected")
1276 badBootFamInstDeclErr =
1277 ptext (sLit "Illegal family instance in hs-boot file")
1279 wrongKindOfFamily family =
1280 ptext (sLit "Wrong category of family instance; declaration was for a") <+>
1283 kindOfFamily | isSynTyCon family = ptext (sLit "type synonym")
1284 | isAlgTyCon family = ptext (sLit "data type")
1285 | otherwise = pprPanic "wrongKindOfFamily" (ppr family)
1287 emptyConDeclsErr tycon
1288 = sep [quotes (ppr tycon) <+> ptext (sLit "has no constructors"),
1289 nest 2 $ ptext (sLit "(-XEmptyDataDecls permits this)")]