2 % (c) The University of Glasgow 2006
3 % (c) The AQUA Project, Glasgow University, 1996-1998
6 TcTyClsDecls: Typecheck type and class declarations
10 tcTyAndClassDecls, tcFamInstDecl
13 #include "HsVersions.h"
49 import Control.Monad ( mplus )
53 %************************************************************************
55 \subsection{Type checking for type and class declarations}
57 %************************************************************************
61 Consider a mutually-recursive group, binding
62 a type constructor T and a class C.
64 Step 1: getInitialKind
65 Construct a KindEnv by binding T and C to a kind variable
68 In that environment, do a kind check
70 Step 3: Zonk the kinds
72 Step 4: buildTyConOrClass
73 Construct an environment binding T to a TyCon and C to a Class.
74 a) Their kinds comes from zonking the relevant kind variable
75 b) Their arity (for synonyms) comes direct from the decl
76 c) The funcional dependencies come from the decl
77 d) The rest comes a knot-tied binding of T and C, returned from Step 4
78 e) The variances of the tycons in the group is calculated from
82 In this environment, walk over the decls, constructing the TyCons and Classes.
83 This uses in a strict way items (a)-(c) above, which is why they must
84 be constructed in Step 4. Feed the results back to Step 4.
85 For this step, pass the is-recursive flag as the wimp-out flag
89 Step 6: Extend environment
90 We extend the type environment with bindings not only for the TyCons and Classes,
91 but also for their "implicit Ids" like data constructors and class selectors
93 Step 7: checkValidTyCl
94 For a recursive group only, check all the decls again, just
95 to check all the side conditions on validity. We could not
96 do this before because we were in a mutually recursive knot.
98 Identification of recursive TyCons
99 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
100 The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to
103 Identifying a TyCon as recursive serves two purposes
105 1. Avoid infinite types. Non-recursive newtypes are treated as
106 "transparent", like type synonyms, after the type checker. If we did
107 this for all newtypes, we'd get infinite types. So we figure out for
108 each newtype whether it is "recursive", and add a coercion if so. In
109 effect, we are trying to "cut the loops" by identifying a loop-breaker.
111 2. Avoid infinite unboxing. This is nothing to do with newtypes.
115 Well, this function diverges, but we don't want the strictness analyser
116 to diverge. But the strictness analyser will diverge because it looks
117 deeper and deeper into the structure of T. (I believe there are
118 examples where the function does something sane, and the strictness
119 analyser still diverges, but I can't see one now.)
121 Now, concerning (1), the FC2 branch currently adds a coercion for ALL
122 newtypes. I did this as an experiment, to try to expose cases in which
123 the coercions got in the way of optimisations. If it turns out that we
124 can indeed always use a coercion, then we don't risk recursive types,
125 and don't need to figure out what the loop breakers are.
127 For newtype *families* though, we will always have a coercion, so they
128 are always loop breakers! So you can easily adjust the current
129 algorithm by simply treating all newtype families as loop breakers (and
130 indeed type families). I think.
133 tcTyAndClassDecls :: ModDetails -> [LTyClDecl Name]
134 -> TcM TcGblEnv -- Input env extended by types and classes
135 -- and their implicit Ids,DataCons
136 tcTyAndClassDecls boot_details allDecls
137 = do { -- Omit instances of type families; they are handled together
138 -- with the *heads* of class instances
139 ; let decls = filter (not . isFamInstDecl . unLoc) allDecls
141 -- First check for cyclic type synonysm or classes
142 -- See notes with checkCycleErrs
143 ; checkCycleErrs decls
145 ; traceTc (text "tcTyAndCl" <+> ppr mod)
146 ; (syn_tycons, alg_tyclss) <- fixM (\ ~(rec_syn_tycons, rec_alg_tyclss) ->
147 do { let { -- Seperate ordinary synonyms from all other type and
148 -- class declarations and add all associated type
149 -- declarations from type classes. The latter is
150 -- required so that the temporary environment for the
151 -- knot includes all associated family declarations.
152 ; (syn_decls, alg_decls) = partition (isSynDecl . unLoc)
154 ; alg_at_decls = concatMap addATs alg_decls
156 -- Extend the global env with the knot-tied results
157 -- for data types and classes
159 -- We must populate the environment with the loop-tied
160 -- T's right away, because the kind checker may "fault
161 -- in" some type constructors that recursively
163 ; let gbl_things = mkGlobalThings alg_at_decls rec_alg_tyclss
164 ; tcExtendRecEnv gbl_things $ do
166 -- Kind-check the declarations
167 { (kc_syn_decls, kc_alg_decls) <- kcTyClDecls syn_decls alg_decls
169 ; let { -- Calculate rec-flag
170 ; calc_rec = calcRecFlags boot_details rec_alg_tyclss
171 ; tc_decl = addLocM (tcTyClDecl calc_rec) }
173 -- Type-check the type synonyms, and extend the envt
174 ; syn_tycons <- tcSynDecls kc_syn_decls
175 ; tcExtendGlobalEnv syn_tycons $ do
177 -- Type-check the data types and classes
178 { alg_tyclss <- mappM tc_decl kc_alg_decls
179 ; return (syn_tycons, concat alg_tyclss)
181 -- Finished with knot-tying now
182 -- Extend the environment with the finished things
183 ; tcExtendGlobalEnv (syn_tycons ++ alg_tyclss) $ do
185 -- Perform the validity check
186 { traceTc (text "ready for validity check")
187 ; mappM_ (addLocM checkValidTyCl) decls
188 ; traceTc (text "done")
190 -- Add the implicit things;
191 -- we want them in the environment because
192 -- they may be mentioned in interface files
193 -- NB: All associated types and their implicit things will be added a
194 -- second time here. This doesn't matter as the definitions are
196 ; let { implicit_things = concatMap implicitTyThings alg_tyclss }
197 ; traceTc ((text "Adding" <+> ppr alg_tyclss)
198 $$ (text "and" <+> ppr implicit_things))
199 ; tcExtendGlobalEnv implicit_things getGblEnv
202 -- Pull associated types out of class declarations, to tie them into the
204 -- NB: We put them in the same place in the list as `tcTyClDecl' will
205 -- eventually put the matching `TyThing's. That's crucial; otherwise,
206 -- the two argument lists of `mkGlobalThings' don't match up.
207 addATs decl@(L _ (ClassDecl {tcdATs = ats})) = decl : ats
210 mkGlobalThings :: [LTyClDecl Name] -- The decls
211 -> [TyThing] -- Knot-tied, in 1-1 correspondence with the decls
213 -- Driven by the Decls, and treating the TyThings lazily
214 -- make a TypeEnv for the new things
215 mkGlobalThings decls things
216 = map mk_thing (decls `zipLazy` things)
218 mk_thing (L _ (ClassDecl {tcdLName = L _ name}), ~(AClass cl))
220 mk_thing (L _ decl, ~(ATyCon tc))
221 = (tcdName decl, ATyCon tc)
225 %************************************************************************
227 \subsection{Type checking family instances}
229 %************************************************************************
231 Family instances are somewhat of a hybrid. They are processed together with
232 class instance heads, but can contain data constructors and hence they share a
233 lot of kinding and type checking code with ordinary algebraic data types (and
237 tcFamInstDecl :: LTyClDecl Name -> TcM (Maybe TyThing) -- Nothing if error
238 tcFamInstDecl (L loc decl)
239 = -- Prime error recovery, set source location
240 recoverM (returnM Nothing) $
243 do { -- type families require -ftype-families and can't be in an
245 ; type_families <- doptM Opt_TypeFamilies
246 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
247 ; checkTc type_families $ badFamInstDecl (tcdLName decl)
248 ; checkTc (not is_boot) $ badBootFamInstDeclErr
250 -- perform kind and type checking
251 ; tcFamInstDecl1 decl
254 tcFamInstDecl1 :: TyClDecl Name -> TcM (Maybe TyThing) -- Nothing if error
257 tcFamInstDecl1 (decl@TySynonym {tcdLName = L loc tc_name})
258 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
259 do { -- check that the family declaration is for a synonym
260 unless (isSynTyCon family) $
261 addErr (wrongKindOfFamily family)
263 ; -- (1) kind check the right-hand side of the type equation
264 ; k_rhs <- kcCheckHsType (tcdSynRhs decl) resKind
266 -- we need at least as many type parameters as the family declaration
268 ; let famArity = tyConArity family
269 ; checkTc (length k_typats >= famArity) $ tooFewParmsErr famArity
271 -- (2) type check type equation
272 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
273 ; t_typats <- mappM tcHsKindedType k_typats
274 ; t_rhs <- tcHsKindedType k_rhs
276 -- all parameters in excess of the family arity must be variables
277 ; checkTc (all isTyVarTy $ drop famArity t_typats) $ excessParmVarErr
280 -- - left-hand side contains no type family applications
281 -- (vanilla synonyms are fine, though)
282 ; mappM_ checkTyFamFreeness t_typats
284 -- - the right-hand side is a tau type
285 ; unless (isTauTy t_rhs) $
286 addErr (polyTyErr t_rhs)
288 -- (4) construct representation tycon
289 ; rep_tc_name <- newFamInstTyConName tc_name loc
290 ; tycon <- buildSynTyCon rep_tc_name t_tvs (SynonymTyCon t_rhs)
291 (Just (family, t_typats))
293 ; return $ Just (ATyCon tycon)
296 -- "newtype instance" and "data instance"
297 tcFamInstDecl1 (decl@TyData {tcdND = new_or_data, tcdLName = L loc tc_name,
299 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
300 do { -- check that the family declaration is for the right kind
301 unless (isAlgTyCon family) $
302 addErr (wrongKindOfFamily family)
304 ; -- (1) kind check the data declaration as usual
305 ; k_decl <- kcDataDecl decl k_tvs
306 ; let k_ctxt = tcdCtxt k_decl
307 k_cons = tcdCons k_decl
309 -- result kind must be '*' (otherwise, we have too few patterns)
310 ; checkTc (isLiftedTypeKind resKind) $ tooFewParmsErr (tyConArity family)
312 -- (2) type check indexed data type declaration
313 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
314 ; unbox_strict <- doptM Opt_UnboxStrictFields
316 -- kind check the type indexes and the context
317 ; t_typats <- mappM tcHsKindedType k_typats
318 ; stupid_theta <- tcHsKindedContext k_ctxt
321 -- - left-hand side contains no type family applications
322 -- (vanilla synonyms are fine, though)
323 ; mappM_ checkTyFamFreeness t_typats
325 -- - we don't use GADT syntax for indexed types
326 ; checkTc h98_syntax (badGadtIdxTyDecl tc_name)
328 -- - a newtype has exactly one constructor
329 ; checkTc (new_or_data == DataType || isSingleton k_cons) $
330 newtypeConError tc_name (length k_cons)
332 -- (4) construct representation tycon
333 ; rep_tc_name <- newFamInstTyConName tc_name loc
334 ; tycon <- fixM (\ tycon -> do
335 { data_cons <- mappM (addLocM (tcConDecl unbox_strict tycon t_tvs))
339 DataType -> return (mkDataTyConRhs data_cons)
340 NewType -> ASSERT( isSingleton data_cons )
341 mkNewTyConRhs rep_tc_name tycon (head data_cons)
342 ; buildAlgTyCon rep_tc_name t_tvs stupid_theta tc_rhs Recursive
343 False h98_syntax (Just (family, t_typats))
344 -- We always assume that indexed types are recursive. Why?
345 -- (1) Due to their open nature, we can never be sure that a
346 -- further instance might not introduce a new recursive
347 -- dependency. (2) They are always valid loop breakers as
348 -- they involve a coercion.
352 ; return $ Just (ATyCon tycon)
355 h98_syntax = case cons of -- All constructors have same shape
356 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
359 -- Check that a type index does not contain any type family applications
361 -- * Earlier phases have already checked that there are no foralls in the
362 -- type; we also cannot have PredTys and NoteTys are being skipped by using
365 checkTyFamFreeness :: Type -> TcM ()
366 checkTyFamFreeness ty | Just (tycon, tys) <- splitTyConApp_maybe ty
367 = if isSynTyCon tycon
368 then addErr $ tyFamAppInIndexErr ty
369 else mappM_ checkTyFamFreeness tys
370 -- splitTyConApp_maybe uses the core view; hence,
371 -- any synonym tycon must be a family tycon
373 | Just (ty1, ty2) <- splitAppTy_maybe ty
374 = checkTyFamFreeness ty1 >> checkTyFamFreeness ty2
376 | otherwise -- only vars remaining
380 -- Kind checking of indexed types
383 -- Kind check type patterns and kind annotate the embedded type variables.
385 -- * Here we check that a type instance matches its kind signature, but we do
386 -- not check whether there is a pattern for each type index; the latter
387 -- check is only required for type synonym instances.
389 kcIdxTyPats :: TyClDecl Name
390 -> ([LHsTyVarBndr Name] -> [LHsType Name] -> Kind -> TyCon -> TcM a)
391 -- ^^kinded tvs ^^kinded ty pats ^^res kind
393 kcIdxTyPats decl thing_inside
394 = kcHsTyVars (tcdTyVars decl) $ \tvs ->
395 do { family <- tcLookupLocatedTyCon (tcdLName decl)
396 ; let { (kinds, resKind) = splitKindFunTys (tyConKind family)
397 ; hs_typats = fromJust $ tcdTyPats decl }
399 -- we may not have more parameters than the kind indicates
400 ; checkTc (length kinds >= length hs_typats) $
401 tooManyParmsErr (tcdLName decl)
403 -- type functions can have a higher-kinded result
404 ; let resultKind = mkArrowKinds (drop (length hs_typats) kinds) resKind
405 ; typats <- TcRnMonad.zipWithM kcCheckHsType hs_typats kinds
406 ; thing_inside tvs typats resultKind family
412 %************************************************************************
416 %************************************************************************
418 We need to kind check all types in the mutually recursive group
419 before we know the kind of the type variables. For example:
422 op :: D b => a -> b -> b
425 bop :: (Monad c) => ...
427 Here, the kind of the locally-polymorphic type variable "b"
428 depends on *all the uses of class D*. For example, the use of
429 Monad c in bop's type signature means that D must have kind Type->Type.
431 However type synonyms work differently. They can have kinds which don't
432 just involve (->) and *:
433 type R = Int# -- Kind #
434 type S a = Array# a -- Kind * -> #
435 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
436 So we must infer their kinds from their right-hand sides *first* and then
437 use them, whereas for the mutually recursive data types D we bring into
438 scope kind bindings D -> k, where k is a kind variable, and do inference.
442 This treatment of type synonyms only applies to Haskell 98-style synonyms.
443 General type functions can be recursive, and hence, appear in `alg_decls'.
445 The kind of a type family is solely determinded by its kind signature;
446 hence, only kind signatures participate in the construction of the initial
447 kind environment (as constructed by `getInitialKind'). In fact, we ignore
448 instances of families altogether in the following. However, we need to
449 include the kinds of associated families into the construction of the
450 initial kind environment. (This is handled by `allDecls').
453 kcTyClDecls syn_decls alg_decls
454 = do { -- First extend the kind env with each data type, class, and
455 -- indexed type, mapping them to a type variable
456 let initialKindDecls = concat [allDecls decl | L _ decl <- alg_decls]
457 ; alg_kinds <- mappM getInitialKind initialKindDecls
458 ; tcExtendKindEnv alg_kinds $ do
460 -- Now kind-check the type synonyms, in dependency order
461 -- We do these differently to data type and classes,
462 -- because a type synonym can be an unboxed type
464 -- and a kind variable can't unify with UnboxedTypeKind
465 -- So we infer their kinds in dependency order
466 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
467 ; tcExtendKindEnv syn_kinds $ do
469 -- Now kind-check the data type, class, and kind signatures,
470 -- returning kind-annotated decls; we don't kind-check
471 -- instances of indexed types yet, but leave this to
473 { kc_alg_decls <- mappM (wrapLocM kcTyClDecl)
474 (filter (not . isFamInstDecl . unLoc) alg_decls)
476 ; return (kc_syn_decls, kc_alg_decls) }}}
478 -- get all declarations relevant for determining the initial kind
480 allDecls (decl@ClassDecl {tcdATs = ats}) = decl : [ at
483 allDecls decl | isFamInstDecl decl = []
486 ------------------------------------------------------------------------
487 getInitialKind :: TyClDecl Name -> TcM (Name, TcKind)
488 -- Only for data type, class, and indexed type declarations
489 -- Get as much info as possible from the data, class, or indexed type decl,
490 -- so as to maximise usefulness of error messages
492 = do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl)
493 ; res_kind <- mk_res_kind decl
494 ; return (tcdName decl, mkArrowKinds arg_kinds res_kind) }
496 mk_arg_kind (UserTyVar _) = newKindVar
497 mk_arg_kind (KindedTyVar _ kind) = return kind
499 mk_res_kind (TyFamily { tcdKind = Just kind }) = return kind
500 mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
501 -- On GADT-style declarations we allow a kind signature
502 -- data T :: *->* where { ... }
503 mk_res_kind other = return liftedTypeKind
507 kcSynDecls :: [SCC (LTyClDecl Name)]
508 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
509 [(Name,TcKind)]) -- Kind bindings
512 kcSynDecls (group : groups)
513 = do { (decl, nk) <- kcSynDecl group
514 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
515 ; return (decl:decls, nk:nks) }
518 kcSynDecl :: SCC (LTyClDecl Name)
519 -> TcM (LTyClDecl Name, -- Kind-annotated decls
520 (Name,TcKind)) -- Kind bindings
521 kcSynDecl (AcyclicSCC ldecl@(L loc decl))
522 = tcAddDeclCtxt decl $
523 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
524 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
525 <+> brackets (ppr k_tvs))
526 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
527 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
528 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
529 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
530 (unLoc (tcdLName decl), tc_kind)) })
532 kcSynDecl (CyclicSCC decls)
533 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
534 -- of out-of-scope tycons
536 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
538 ------------------------------------------------------------------------
539 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
540 -- Not used for type synonyms (see kcSynDecl)
542 kcTyClDecl decl@(TyData {})
543 = ASSERT( not . isFamInstDecl $ decl ) -- must not be a family instance
544 kcTyClDeclBody decl $
547 kcTyClDecl decl@(TyFamily {})
548 = kcFamilyDecl [] decl -- the empty list signals a toplevel decl
550 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs, tcdATs = ats})
551 = kcTyClDeclBody decl $ \ tvs' ->
552 do { is_boot <- tcIsHsBoot
553 ; ctxt' <- kcHsContext ctxt
554 ; ats' <- mappM (wrapLocM (kcFamilyDecl tvs')) ats
555 ; sigs' <- mappM (wrapLocM kc_sig) sigs
556 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs',
559 kc_sig (TypeSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
560 ; return (TypeSig nm op_ty') }
561 kc_sig other_sig = return other_sig
563 kcTyClDecl decl@(ForeignType {})
566 kcTyClDeclBody :: TyClDecl Name
567 -> ([LHsTyVarBndr Name] -> TcM a)
569 -- getInitialKind has made a suitably-shaped kind for the type or class
570 -- Unpack it, and attribute those kinds to the type variables
571 -- Extend the env with bindings for the tyvars, taken from
572 -- the kind of the tycon/class. Give it to the thing inside, and
573 -- check the result kind matches
574 kcTyClDeclBody decl thing_inside
575 = tcAddDeclCtxt decl $
576 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
577 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
578 (kinds, _) = splitKindFunTys tc_kind
579 hs_tvs = tcdTyVars decl
580 kinded_tvs = ASSERT( length kinds >= length hs_tvs )
581 [ L loc (KindedTyVar (hsTyVarName tv) k)
582 | (L loc tv, k) <- zip hs_tvs kinds]
583 ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
585 -- Kind check a data declaration, assuming that we already extended the
586 -- kind environment with the type variables of the left-hand side (these
587 -- kinded type variables are also passed as the second parameter).
589 kcDataDecl :: TyClDecl Name -> [LHsTyVarBndr Name] -> TcM (TyClDecl Name)
590 kcDataDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
592 = do { ctxt' <- kcHsContext ctxt
593 ; cons' <- mappM (wrapLocM kc_con_decl) cons
594 ; return (decl {tcdTyVars = tvs, tcdCtxt = ctxt', tcdCons = cons'}) }
596 -- doc comments are typechecked to Nothing here
597 kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res _) = do
598 kcHsTyVars ex_tvs $ \ex_tvs' -> do
599 ex_ctxt' <- kcHsContext ex_ctxt
600 details' <- kc_con_details details
602 ResTyH98 -> return ResTyH98
603 ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
604 return (ConDecl name expl ex_tvs' ex_ctxt' details' res' Nothing)
606 kc_con_details (PrefixCon btys)
607 = do { btys' <- mappM kc_larg_ty btys
608 ; return (PrefixCon btys') }
609 kc_con_details (InfixCon bty1 bty2)
610 = do { bty1' <- kc_larg_ty bty1
611 ; bty2' <- kc_larg_ty bty2
612 ; return (InfixCon bty1' bty2') }
613 kc_con_details (RecCon fields)
614 = do { fields' <- mappM kc_field fields
615 ; return (RecCon fields') }
617 kc_field (ConDeclField fld bty d) = do { bty' <- kc_larg_ty bty
618 ; return (ConDeclField fld bty' d) }
620 kc_larg_ty bty = case new_or_data of
621 DataType -> kcHsSigType bty
622 NewType -> kcHsLiftedSigType bty
623 -- Can't allow an unlifted type for newtypes, because we're effectively
624 -- going to remove the constructor while coercing it to a lifted type.
625 -- And newtypes can't be bang'd
627 -- Kind check a family declaration or type family default declaration.
629 kcFamilyDecl :: [LHsTyVarBndr Name] -- tyvars of enclosing class decl if any
630 -> TyClDecl Name -> TcM (TyClDecl Name)
631 kcFamilyDecl classTvs decl@(TyFamily {tcdKind = kind})
632 = kcTyClDeclBody decl $ \tvs' ->
633 do { mapM_ unifyClassParmKinds tvs'
634 ; return (decl {tcdTyVars = tvs',
635 tcdKind = kind `mplus` Just liftedTypeKind})
636 -- default result kind is '*'
639 unifyClassParmKinds (L _ (KindedTyVar n k))
640 | Just classParmKind <- lookup n classTyKinds = unifyKind k classParmKind
641 | otherwise = return ()
642 classTyKinds = [(n, k) | L _ (KindedTyVar n k) <- classTvs]
643 kcFamilyDecl _ decl@(TySynonym {}) -- type family defaults
644 = panic "TcTyClsDecls.kcFamilyDecl: not implemented yet"
648 %************************************************************************
650 \subsection{Type checking}
652 %************************************************************************
655 tcSynDecls :: [LTyClDecl Name] -> TcM [TyThing]
656 tcSynDecls [] = return []
657 tcSynDecls (decl : decls)
658 = do { syn_tc <- addLocM tcSynDecl decl
659 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls decls)
660 ; return (syn_tc : syn_tcs) }
664 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
665 = tcTyVarBndrs tvs $ \ tvs' -> do
666 { traceTc (text "tcd1" <+> ppr tc_name)
667 ; rhs_ty' <- tcHsKindedType rhs_ty
668 ; tycon <- buildSynTyCon tc_name tvs' (SynonymTyCon rhs_ty') Nothing
669 ; return (ATyCon tycon)
673 tcTyClDecl :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
675 tcTyClDecl calc_isrec decl
676 = tcAddDeclCtxt decl (tcTyClDecl1 calc_isrec decl)
678 -- "type family" declarations
679 tcTyClDecl1 _calc_isrec
680 (TyFamily {tcdFlavour = TypeFamily,
681 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = Just kind})
682 -- NB: kind at latest
685 = tcTyVarBndrs tvs $ \ tvs' -> do
686 { traceTc (text "type family: " <+> ppr tc_name)
687 ; idx_tys <- doptM Opt_TypeFamilies
689 -- Check that we don't use families without -ftype-families
690 ; checkTc idx_tys $ badFamInstDecl tc_name
692 ; tycon <- buildSynTyCon tc_name tvs' (OpenSynTyCon kind Nothing) Nothing
693 ; return [ATyCon tycon]
696 -- "newtype family" or "data family" declaration
697 tcTyClDecl1 _calc_isrec
698 (TyFamily {tcdFlavour = DataFamily,
699 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = mb_kind})
700 = tcTyVarBndrs tvs $ \ tvs' -> do
701 { traceTc (text "data family: " <+> ppr tc_name)
702 ; extra_tvs <- tcDataKindSig mb_kind
703 ; let final_tvs = tvs' ++ extra_tvs -- we may not need these
705 ; idx_tys <- doptM Opt_TypeFamilies
707 -- Check that we don't use families without -ftype-families
708 ; checkTc idx_tys $ badFamInstDecl tc_name
710 ; tycon <- buildAlgTyCon tc_name final_tvs []
711 mkOpenDataTyConRhs Recursive False True Nothing
712 ; return [ATyCon tycon]
715 -- "newtype" and "data"
716 tcTyClDecl1 calc_isrec
717 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
718 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
719 = tcTyVarBndrs tvs $ \ tvs' -> do
720 { extra_tvs <- tcDataKindSig mb_ksig
721 ; let final_tvs = tvs' ++ extra_tvs
722 ; stupid_theta <- tcHsKindedContext ctxt
723 ; want_generic <- doptM Opt_Generics
724 ; unbox_strict <- doptM Opt_UnboxStrictFields
725 ; empty_data_decls <- doptM Opt_EmptyDataDecls
726 ; kind_signatures <- doptM Opt_KindSignatures
727 ; gadt_ok <- doptM Opt_GADTs
728 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
730 -- Check that we don't use GADT syntax in H98 world
731 ; checkTc (gadt_ok || h98_syntax) (badGadtDecl tc_name)
733 -- Check that we don't use kind signatures without Glasgow extensions
734 ; checkTc (kind_signatures || isNothing mb_ksig) (badSigTyDecl tc_name)
736 -- Check that the stupid theta is empty for a GADT-style declaration
737 ; checkTc (null stupid_theta || h98_syntax) (badStupidTheta tc_name)
739 -- Check that there's at least one condecl,
740 -- or else we're reading an hs-boot file, or -XEmptyDataDecls
741 ; checkTc (not (null cons) || empty_data_decls || is_boot)
742 (emptyConDeclsErr tc_name)
744 -- Check that a newtype has exactly one constructor
745 ; checkTc (new_or_data == DataType || isSingleton cons)
746 (newtypeConError tc_name (length cons))
748 ; tycon <- fixM (\ tycon -> do
749 { data_cons <- mappM (addLocM (tcConDecl unbox_strict tycon final_tvs))
752 if null cons && is_boot -- In a hs-boot file, empty cons means
753 then return AbstractTyCon -- "don't know"; hence Abstract
754 else case new_or_data of
755 DataType -> return (mkDataTyConRhs data_cons)
757 ASSERT( isSingleton data_cons )
758 mkNewTyConRhs tc_name tycon (head data_cons)
759 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
760 (want_generic && canDoGenerics data_cons) h98_syntax Nothing
762 ; return [ATyCon tycon]
765 is_rec = calc_isrec tc_name
766 h98_syntax = case cons of -- All constructors have same shape
767 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
770 tcTyClDecl1 calc_isrec
771 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
772 tcdCtxt = ctxt, tcdMeths = meths,
773 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
774 = tcTyVarBndrs tvs $ \ tvs' -> do
775 { ctxt' <- tcHsKindedContext ctxt
776 ; fds' <- mappM (addLocM tc_fundep) fundeps
777 ; atss <- mappM (addLocM (tcTyClDecl1 (const Recursive))) ats
778 ; let ats' = zipWith setTyThingPoss atss (map (tcdTyVars . unLoc) ats)
779 ; sig_stuff <- tcClassSigs class_name sigs meths
780 ; clas <- fixM (\ clas ->
781 let -- This little knot is just so we can get
782 -- hold of the name of the class TyCon, which we
783 -- need to look up its recursiveness
784 tycon_name = tyConName (classTyCon clas)
785 tc_isrec = calc_isrec tycon_name
787 buildClass class_name tvs' ctxt' fds' ats'
789 ; return (AClass clas : ats')
790 -- NB: Order is important due to the call to `mkGlobalThings' when
791 -- tying the the type and class declaration type checking knot.
794 tc_fundep (tvs1, tvs2) = do { tvs1' <- mappM tcLookupTyVar tvs1 ;
795 ; tvs2' <- mappM tcLookupTyVar tvs2 ;
796 ; return (tvs1', tvs2') }
798 -- For each AT argument compute the position of the corresponding class
799 -- parameter in the class head. This will later serve as a permutation
800 -- vector when checking the validity of instance declarations.
801 setTyThingPoss [ATyCon tycon] atTyVars =
802 let classTyVars = hsLTyVarNames tvs
804 . map (`elemIndex` classTyVars)
807 -- There will be no Nothing, as we already passed renaming
809 ATyCon (setTyConArgPoss tycon poss)
810 setTyThingPoss _ _ = panic "TcTyClsDecls.setTyThingPoss"
812 tcTyClDecl1 calc_isrec
813 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
814 = returnM [ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0)]
816 -----------------------------------
817 tcConDecl :: Bool -- True <=> -funbox-strict_fields
822 tcConDecl unbox_strict tycon tc_tvs -- Data types
823 (ConDecl name _ tvs ctxt details res_ty _)
824 = tcTyVarBndrs tvs $ \ tvs' -> do
825 { ctxt' <- tcHsKindedContext ctxt
826 ; (univ_tvs, ex_tvs, eq_preds, data_tc) <- tcResultType tycon tc_tvs tvs' res_ty
828 -- Tiresome: tidy the tyvar binders, since tc_tvs and tvs' may have the same OccNames
829 tc_datacon is_infix field_lbls btys
830 = do { let bangs = map getBangStrictness btys
831 ; arg_tys <- mappM tcHsBangType btys
832 ; buildDataCon (unLoc name) is_infix
833 (argStrictness unbox_strict bangs arg_tys)
834 (map unLoc field_lbls)
835 univ_tvs ex_tvs eq_preds ctxt' arg_tys
837 -- NB: we put data_tc, the type constructor gotten from the
838 -- constructor type signature into the data constructor;
839 -- that way checkValidDataCon can complain if it's wrong.
842 PrefixCon btys -> tc_datacon False [] btys
843 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
844 RecCon fields -> tc_datacon False field_names btys
846 field_names = map cd_fld_name fields
847 btys = map cd_fld_type fields
850 tcResultType :: TyCon
851 -> [TyVar] -- data T a b c = ...
852 -> [TyVar] -- where MkT :: forall a b c. ...
854 -> TcM ([TyVar], -- Universal
855 [TyVar], -- Existential (distinct OccNames from univs)
856 [(TyVar,Type)], -- Equality predicates
857 TyCon) -- TyCon given in the ResTy
858 -- We don't check that the TyCon given in the ResTy is
859 -- the same as the parent tycon, becuase we are in the middle
860 -- of a recursive knot; so it's postponed until checkValidDataCon
862 tcResultType decl_tycon tc_tvs dc_tvs ResTyH98
863 = return (tc_tvs, dc_tvs, [], decl_tycon)
864 -- In H98 syntax the dc_tvs are the existential ones
865 -- data T a b c = forall d e. MkT ...
866 -- The {a,b,c} are tc_tvs, and {d,e} are dc_tvs
868 tcResultType _ tc_tvs dc_tvs (ResTyGADT res_ty)
869 -- E.g. data T a b c where
870 -- MkT :: forall x y z. T (x,y) z z
872 -- ([a,z,c], [x,y], [a:=:(x,y), c:=:z], T)
874 = do { (dc_tycon, res_tys) <- tcLHsConResTy res_ty
876 ; let univ_tvs = choose_univs [] tidy_tc_tvs res_tys
877 -- Each univ_tv is either a dc_tv or a tc_tv
878 ex_tvs = dc_tvs `minusList` univ_tvs
879 eq_spec = [ (tv, ty) | (tv,ty) <- univ_tvs `zip` res_tys,
881 ; return (univ_tvs, ex_tvs, eq_spec, dc_tycon) }
883 -- choose_univs uses the res_ty itself if it's a type variable
884 -- and hasn't already been used; otherwise it uses one of the tc_tvs
885 choose_univs used tc_tvs []
886 = ASSERT( null tc_tvs ) []
887 choose_univs used (tc_tv:tc_tvs) (res_ty:res_tys)
888 | Just tv <- tcGetTyVar_maybe res_ty, not (tv `elem` used)
889 = tv : choose_univs (tv:used) tc_tvs res_tys
891 = tc_tv : choose_univs used tc_tvs res_tys
893 -- NB: tc_tvs and dc_tvs are distinct, but
894 -- we want them to be *visibly* distinct, both for
895 -- interface files and general confusion. So rename
896 -- the tc_tvs, since they are not used yet (no
897 -- consequential renaming needed)
898 init_occ_env = initTidyOccEnv (map getOccName dc_tvs)
899 (_, tidy_tc_tvs) = mapAccumL tidy_one init_occ_env tc_tvs
900 tidy_one env tv = (env', setTyVarName tv (tidyNameOcc name occ'))
903 (env', occ') = tidyOccName env (getOccName name)
906 argStrictness :: Bool -- True <=> -funbox-strict_fields
908 -> [TcType] -> [StrictnessMark]
909 argStrictness unbox_strict bangs arg_tys
910 = ASSERT( length bangs == length arg_tys )
911 zipWith (chooseBoxingStrategy unbox_strict) arg_tys bangs
913 -- We attempt to unbox/unpack a strict field when either:
914 -- (i) The field is marked '!!', or
915 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
917 -- We have turned off unboxing of newtypes because coercions make unboxing
918 -- and reboxing more complicated
919 chooseBoxingStrategy :: Bool -> TcType -> HsBang -> StrictnessMark
920 chooseBoxingStrategy unbox_strict_fields arg_ty bang
922 HsNoBang -> NotMarkedStrict
923 HsStrict | unbox_strict_fields
924 && can_unbox arg_ty -> MarkedUnboxed
925 HsUnbox | can_unbox arg_ty -> MarkedUnboxed
926 other -> MarkedStrict
928 -- we can unbox if the type is a chain of newtypes with a product tycon
930 can_unbox arg_ty = case splitTyConApp_maybe arg_ty of
932 Just (arg_tycon, tycon_args) ->
933 not (isRecursiveTyCon arg_tycon) && -- Note [Recusive unboxing]
934 isProductTyCon arg_tycon &&
935 (if isNewTyCon arg_tycon then
936 can_unbox (newTyConInstRhs arg_tycon tycon_args)
940 Note [Recursive unboxing]
941 ~~~~~~~~~~~~~~~~~~~~~~~~~
942 Be careful not to try to unbox this!
944 But it's the *argument* type that matters. This is fine:
946 because Int is non-recursive.
948 %************************************************************************
950 \subsection{Dependency analysis}
952 %************************************************************************
954 Validity checking is done once the mutually-recursive knot has been
955 tied, so we can look at things freely.
958 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
959 checkCycleErrs tyclss
963 = do { mappM_ recClsErr cls_cycles
964 ; failM } -- Give up now, because later checkValidTyCl
965 -- will loop if the synonym is recursive
967 cls_cycles = calcClassCycles tyclss
969 checkValidTyCl :: TyClDecl Name -> TcM ()
970 -- We do the validity check over declarations, rather than TyThings
971 -- only so that we can add a nice context with tcAddDeclCtxt
973 = tcAddDeclCtxt decl $
974 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
975 ; traceTc (text "Validity of" <+> ppr thing)
977 ATyCon tc -> checkValidTyCon tc
978 AClass cl -> checkValidClass cl
979 ; traceTc (text "Done validity of" <+> ppr thing)
982 -------------------------
983 -- For data types declared with record syntax, we require
984 -- that each constructor that has a field 'f'
985 -- (a) has the same result type
986 -- (b) has the same type for 'f'
987 -- module alpha conversion of the quantified type variables
988 -- of the constructor.
990 checkValidTyCon :: TyCon -> TcM ()
993 = case synTyConRhs tc of
994 OpenSynTyCon _ _ -> return ()
995 SynonymTyCon ty -> checkValidType syn_ctxt ty
997 = -- Check the context on the data decl
998 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
1000 -- Check arg types of data constructors
1001 mappM_ (checkValidDataCon tc) data_cons `thenM_`
1003 -- Check that fields with the same name share a type
1004 mappM_ check_fields groups
1007 syn_ctxt = TySynCtxt name
1009 data_cons = tyConDataCons tc
1011 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
1012 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
1013 get_fields con = dataConFieldLabels con `zip` repeat con
1014 -- dataConFieldLabels may return the empty list, which is fine
1016 -- See Note [GADT record selectors] in MkId.lhs
1017 -- We must check (a) that the named field has the same
1018 -- type in each constructor
1019 -- (b) that those constructors have the same result type
1021 -- However, the constructors may have differently named type variable
1022 -- and (worse) we don't know how the correspond to each other. E.g.
1023 -- C1 :: forall a b. { f :: a, g :: b } -> T a b
1024 -- C2 :: forall d c. { f :: c, g :: c } -> T c d
1026 -- So what we do is to ust Unify.tcMatchTys to compare the first candidate's
1027 -- result type against other candidates' types BOTH WAYS ROUND.
1028 -- If they magically agrees, take the substitution and
1029 -- apply them to the latter ones, and see if they match perfectly.
1030 check_fields fields@((label, con1) : other_fields)
1031 -- These fields all have the same name, but are from
1032 -- different constructors in the data type
1033 = recoverM (return ()) $ mapM_ checkOne other_fields
1034 -- Check that all the fields in the group have the same type
1035 -- NB: this check assumes that all the constructors of a given
1036 -- data type use the same type variables
1038 (tvs1, _, _, res1) = dataConSig con1
1040 fty1 = dataConFieldType con1 label
1042 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
1043 = do { checkFieldCompat label con1 con2 ts1 res1 res2 fty1 fty2
1044 ; checkFieldCompat label con2 con1 ts2 res2 res1 fty2 fty1 }
1046 (tvs2, _, _, res2) = dataConSig con2
1048 fty2 = dataConFieldType con2 label
1050 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
1051 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
1052 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
1054 mb_subst1 = tcMatchTy tvs1 res1 res2
1055 mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
1057 -------------------------------
1058 checkValidDataCon :: TyCon -> DataCon -> TcM ()
1059 checkValidDataCon tc con
1060 = setSrcSpan (srcLocSpan (getSrcLoc con)) $
1061 addErrCtxt (dataConCtxt con) $
1062 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
1063 ; checkValidType ctxt (dataConUserType con)
1064 ; ifM (isNewTyCon tc) (checkNewDataCon con)
1067 ctxt = ConArgCtxt (dataConName con)
1069 -------------------------------
1070 checkNewDataCon :: DataCon -> TcM ()
1071 -- Checks for the data constructor of a newtype
1073 = do { checkTc (isSingleton arg_tys) (newtypeFieldErr con (length arg_tys))
1075 ; checkTc (null eq_spec) (newtypePredError con)
1076 -- Return type is (T a b c)
1077 ; checkTc (null ex_tvs && null theta) (newtypeExError con)
1079 ; checkTc (not (any isMarkedStrict (dataConStrictMarks con)))
1080 (newtypeStrictError con)
1084 (_univ_tvs, ex_tvs, eq_spec, theta, arg_tys, _res_ty) = dataConFullSig con
1086 -------------------------------
1087 checkValidClass :: Class -> TcM ()
1089 = do { constrained_class_methods <- doptM Opt_ConstrainedClassMethods
1090 ; multi_param_type_classes <- doptM Opt_MultiParamTypeClasses
1091 ; fundep_classes <- doptM Opt_FunctionalDependencies
1093 -- Check that the class is unary, unless GlaExs
1094 ; checkTc (notNull tyvars) (nullaryClassErr cls)
1095 ; checkTc (multi_param_type_classes || unary) (classArityErr cls)
1096 ; checkTc (fundep_classes || null fundeps) (classFunDepsErr cls)
1098 -- Check the super-classes
1099 ; checkValidTheta (ClassSCCtxt (className cls)) theta
1101 -- Check the class operations
1102 ; mappM_ (check_op constrained_class_methods) op_stuff
1104 -- Check that if the class has generic methods, then the
1105 -- class has only one parameter. We can't do generic
1106 -- multi-parameter type classes!
1107 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
1110 (tyvars, fundeps, theta, _, _, op_stuff) = classExtraBigSig cls
1111 unary = isSingleton tyvars
1112 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
1114 check_op constrained_class_methods (sel_id, dm)
1115 = addErrCtxt (classOpCtxt sel_id tau) $ do
1116 { checkValidTheta SigmaCtxt (tail theta)
1117 -- The 'tail' removes the initial (C a) from the
1118 -- class itself, leaving just the method type
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 badStupidTheta tc_name
1222 = ptext SLIT("A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
1224 newtypeConError tycon n
1225 = sep [ptext SLIT("A newtype must have exactly one constructor,"),
1226 nest 2 $ ptext SLIT("but") <+> quotes (ppr tycon) <+> ptext SLIT("has") <+> speakN n ]
1229 = sep [ptext SLIT("A newtype constructor cannot have an existential context,"),
1230 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
1232 newtypeStrictError con
1233 = sep [ptext SLIT("A newtype constructor cannot have a strictness annotation,"),
1234 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
1236 newtypePredError con
1237 = sep [ptext SLIT("A newtype constructor must have a return type of form T a1 ... an"),
1238 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does not")]
1240 newtypeFieldErr con_name n_flds
1241 = sep [ptext SLIT("The constructor of a newtype must have exactly one field"),
1242 nest 2 $ ptext SLIT("but") <+> quotes (ppr con_name) <+> ptext SLIT("has") <+> speakN n_flds]
1244 badSigTyDecl tc_name
1245 = vcat [ ptext SLIT("Illegal kind signature") <+>
1246 quotes (ppr tc_name)
1247 , nest 2 (parens $ ptext SLIT("Use -XKindSignatures to allow kind signatures")) ]
1249 badFamInstDecl tc_name
1250 = vcat [ ptext SLIT("Illegal family instance for") <+>
1251 quotes (ppr tc_name)
1252 , nest 2 (parens $ ptext SLIT("Use -XTypeFamilies to allow indexed type families")) ]
1254 badGadtIdxTyDecl tc_name
1255 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+>
1256 quotes (ppr tc_name)
1257 , nest 2 (parens $ ptext SLIT("Family instances can not yet use GADT declarations")) ]
1259 tooManyParmsErr tc_name
1260 = ptext SLIT("Family instance has too many parameters:") <+>
1261 quotes (ppr tc_name)
1263 tooFewParmsErr arity
1264 = ptext SLIT("Family instance has too few parameters; expected") <+>
1268 = ptext SLIT("Additional instance parameters must be variables")
1270 badBootFamInstDeclErr =
1271 ptext SLIT("Illegal family instance in hs-boot file")
1273 wrongKindOfFamily family =
1274 ptext SLIT("Wrong category of family instance; declaration was for a") <+>
1277 kindOfFamily | isSynTyCon family = ptext SLIT("type synonym")
1278 | isAlgTyCon family = ptext SLIT("data type")
1279 | otherwise = pprPanic "wrongKindOfFamily" (ppr family)
1282 = hang (ptext SLIT("Illegal polymorphic type in type instance") <> colon) 4 $
1285 tyFamAppInIndexErr ty
1286 = hang (ptext SLIT("Illegal type family application in type instance") <>
1290 emptyConDeclsErr tycon
1291 = sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
1292 nest 2 $ ptext SLIT("(-XEmptyDataDecls permits this)")]