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 -- (2) type check type equation
267 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
268 ; t_typats <- mappM tcHsKindedType k_typats
269 ; t_rhs <- tcHsKindedType k_rhs
272 -- - left-hand side contains no type family applications
273 -- (vanilla synonyms are fine, though)
274 ; mappM_ checkTyFamFreeness t_typats
276 -- - the right-hand side is a tau type
277 ; unless (isTauTy t_rhs) $
278 addErr (polyTyErr t_rhs)
280 -- (4) construct representation tycon
281 ; rep_tc_name <- newFamInstTyConName tc_name loc
282 ; tycon <- buildSynTyCon rep_tc_name t_tvs (SynonymTyCon t_rhs)
283 (Just (family, t_typats))
285 ; return $ Just (ATyCon tycon)
288 -- "newtype instance" and "data instance"
289 tcFamInstDecl1 (decl@TyData {tcdND = new_or_data, tcdLName = L loc tc_name,
291 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
292 do { -- check that the family declaration is for the right kind
293 unless (isAlgTyCon family) $
294 addErr (wrongKindOfFamily family)
296 ; -- (1) kind check the data declaration as usual
297 ; k_decl <- kcDataDecl decl k_tvs
298 ; let k_ctxt = tcdCtxt k_decl
299 k_cons = tcdCons k_decl
301 -- result kind must be '*' (otherwise, we have too few patterns)
302 ; checkTc (isLiftedTypeKind resKind) $ tooFewParmsErr tc_name
304 -- (2) type check indexed data type declaration
305 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
306 ; unbox_strict <- doptM Opt_UnboxStrictFields
308 -- kind check the type indexes and the context
309 ; t_typats <- mappM tcHsKindedType k_typats
310 ; stupid_theta <- tcHsKindedContext k_ctxt
313 -- - left-hand side contains no type family applications
314 -- (vanilla synonyms are fine, though)
315 ; mappM_ checkTyFamFreeness t_typats
317 -- - we don't use GADT syntax for indexed types
318 ; checkTc h98_syntax (badGadtIdxTyDecl tc_name)
320 -- - a newtype has exactly one constructor
321 ; checkTc (new_or_data == DataType || isSingleton k_cons) $
322 newtypeConError tc_name (length k_cons)
324 -- (4) construct representation tycon
325 ; rep_tc_name <- newFamInstTyConName tc_name loc
326 ; tycon <- fixM (\ tycon -> do
327 { data_cons <- mappM (addLocM (tcConDecl unbox_strict tycon t_tvs))
331 DataType -> return (mkDataTyConRhs data_cons)
332 NewType -> ASSERT( isSingleton data_cons )
333 mkNewTyConRhs rep_tc_name tycon (head data_cons)
334 ; buildAlgTyCon rep_tc_name t_tvs stupid_theta tc_rhs Recursive
335 False h98_syntax (Just (family, t_typats))
336 -- We always assume that indexed types are recursive. Why?
337 -- (1) Due to their open nature, we can never be sure that a
338 -- further instance might not introduce a new recursive
339 -- dependency. (2) They are always valid loop breakers as
340 -- they involve a coercion.
344 ; return $ Just (ATyCon tycon)
347 h98_syntax = case cons of -- All constructors have same shape
348 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
351 -- Check that a type index does not contain any type family applications
353 -- * Earlier phases have already checked that there are no foralls in the
354 -- type; we also cannot have PredTys and NoteTys are being skipped by using
357 checkTyFamFreeness :: Type -> TcM ()
358 checkTyFamFreeness ty | Just (tycon, tys) <- splitTyConApp_maybe ty
359 = if isSynTyCon tycon
360 then addErr $ tyFamAppInIndexErr ty
361 else mappM_ checkTyFamFreeness tys
362 -- splitTyConApp_maybe uses the core view; hence,
363 -- any synonym tycon must be a family tycon
365 | Just (ty1, ty2) <- splitAppTy_maybe ty
366 = checkTyFamFreeness ty1 >> checkTyFamFreeness ty2
368 | otherwise -- only vars remaining
372 -- Kind checking of indexed types
375 -- Kind check type patterns and kind annotate the embedded type variables.
377 -- * Here we check that a type instance matches its kind signature, but we do
378 -- not check whether there is a pattern for each type index; the latter
379 -- check is only required for type synonym instances.
381 kcIdxTyPats :: TyClDecl Name
382 -> ([LHsTyVarBndr Name] -> [LHsType Name] -> Kind -> TyCon -> TcM a)
383 -- ^^kinded tvs ^^kinded ty pats ^^res kind
385 kcIdxTyPats decl thing_inside
386 = kcHsTyVars (tcdTyVars decl) $ \tvs ->
387 do { family <- tcLookupLocatedTyCon (tcdLName decl)
388 ; let { (kinds, resKind) = splitKindFunTys (tyConKind family)
389 ; hs_typats = fromJust $ tcdTyPats decl }
391 -- we may not have more parameters than the kind indicates
392 ; checkTc (length kinds >= length hs_typats) $
393 tooManyParmsErr (tcdLName decl)
395 -- type functions can have a higher-kinded result
396 ; let resultKind = mkArrowKinds (drop (length hs_typats) kinds) resKind
397 ; typats <- TcRnMonad.zipWithM kcCheckHsType hs_typats kinds
398 ; thing_inside tvs typats resultKind family
404 %************************************************************************
408 %************************************************************************
410 We need to kind check all types in the mutually recursive group
411 before we know the kind of the type variables. For example:
414 op :: D b => a -> b -> b
417 bop :: (Monad c) => ...
419 Here, the kind of the locally-polymorphic type variable "b"
420 depends on *all the uses of class D*. For example, the use of
421 Monad c in bop's type signature means that D must have kind Type->Type.
423 However type synonyms work differently. They can have kinds which don't
424 just involve (->) and *:
425 type R = Int# -- Kind #
426 type S a = Array# a -- Kind * -> #
427 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
428 So we must infer their kinds from their right-hand sides *first* and then
429 use them, whereas for the mutually recursive data types D we bring into
430 scope kind bindings D -> k, where k is a kind variable, and do inference.
434 This treatment of type synonyms only applies to Haskell 98-style synonyms.
435 General type functions can be recursive, and hence, appear in `alg_decls'.
437 The kind of a type family is solely determinded by its kind signature;
438 hence, only kind signatures participate in the construction of the initial
439 kind environment (as constructed by `getInitialKind'). In fact, we ignore
440 instances of families altogether in the following. However, we need to
441 include the kinds of associated families into the construction of the
442 initial kind environment. (This is handled by `allDecls').
445 kcTyClDecls syn_decls alg_decls
446 = do { -- First extend the kind env with each data type, class, and
447 -- indexed type, mapping them to a type variable
448 let initialKindDecls = concat [allDecls decl | L _ decl <- alg_decls]
449 ; alg_kinds <- mappM getInitialKind initialKindDecls
450 ; tcExtendKindEnv alg_kinds $ do
452 -- Now kind-check the type synonyms, in dependency order
453 -- We do these differently to data type and classes,
454 -- because a type synonym can be an unboxed type
456 -- and a kind variable can't unify with UnboxedTypeKind
457 -- So we infer their kinds in dependency order
458 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
459 ; tcExtendKindEnv syn_kinds $ do
461 -- Now kind-check the data type, class, and kind signatures,
462 -- returning kind-annotated decls; we don't kind-check
463 -- instances of indexed types yet, but leave this to
465 { kc_alg_decls <- mappM (wrapLocM kcTyClDecl)
466 (filter (not . isFamInstDecl . unLoc) alg_decls)
468 ; return (kc_syn_decls, kc_alg_decls) }}}
470 -- get all declarations relevant for determining the initial kind
472 allDecls (decl@ClassDecl {tcdATs = ats}) = decl : [ at
475 allDecls decl | isFamInstDecl decl = []
478 ------------------------------------------------------------------------
479 getInitialKind :: TyClDecl Name -> TcM (Name, TcKind)
480 -- Only for data type, class, and indexed type declarations
481 -- Get as much info as possible from the data, class, or indexed type decl,
482 -- so as to maximise usefulness of error messages
484 = do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl)
485 ; res_kind <- mk_res_kind decl
486 ; return (tcdName decl, mkArrowKinds arg_kinds res_kind) }
488 mk_arg_kind (UserTyVar _) = newKindVar
489 mk_arg_kind (KindedTyVar _ kind) = return kind
491 mk_res_kind (TyFamily { tcdKind = Just kind }) = return kind
492 mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
493 -- On GADT-style declarations we allow a kind signature
494 -- data T :: *->* where { ... }
495 mk_res_kind other = return liftedTypeKind
499 kcSynDecls :: [SCC (LTyClDecl Name)]
500 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
501 [(Name,TcKind)]) -- Kind bindings
504 kcSynDecls (group : groups)
505 = do { (decl, nk) <- kcSynDecl group
506 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
507 ; return (decl:decls, nk:nks) }
510 kcSynDecl :: SCC (LTyClDecl Name)
511 -> TcM (LTyClDecl Name, -- Kind-annotated decls
512 (Name,TcKind)) -- Kind bindings
513 kcSynDecl (AcyclicSCC ldecl@(L loc decl))
514 = tcAddDeclCtxt decl $
515 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
516 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
517 <+> brackets (ppr k_tvs))
518 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
519 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
520 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
521 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
522 (unLoc (tcdLName decl), tc_kind)) })
524 kcSynDecl (CyclicSCC decls)
525 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
526 -- of out-of-scope tycons
528 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
530 ------------------------------------------------------------------------
531 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
532 -- Not used for type synonyms (see kcSynDecl)
534 kcTyClDecl decl@(TyData {})
535 = ASSERT( not . isFamInstDecl $ decl ) -- must not be a family instance
536 kcTyClDeclBody decl $
539 kcTyClDecl decl@(TyFamily {})
540 = kcFamilyDecl [] decl -- the empty list signals a toplevel decl
542 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs, tcdATs = ats})
543 = kcTyClDeclBody decl $ \ tvs' ->
544 do { is_boot <- tcIsHsBoot
545 ; ctxt' <- kcHsContext ctxt
546 ; ats' <- mappM (wrapLocM (kcFamilyDecl tvs')) ats
547 ; sigs' <- mappM (wrapLocM kc_sig) sigs
548 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs',
551 kc_sig (TypeSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
552 ; return (TypeSig nm op_ty') }
553 kc_sig other_sig = return other_sig
555 kcTyClDecl decl@(ForeignType {})
558 kcTyClDeclBody :: TyClDecl Name
559 -> ([LHsTyVarBndr Name] -> TcM a)
561 -- getInitialKind has made a suitably-shaped kind for the type or class
562 -- Unpack it, and attribute those kinds to the type variables
563 -- Extend the env with bindings for the tyvars, taken from
564 -- the kind of the tycon/class. Give it to the thing inside, and
565 -- check the result kind matches
566 kcTyClDeclBody decl thing_inside
567 = tcAddDeclCtxt decl $
568 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
569 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
570 (kinds, _) = splitKindFunTys tc_kind
571 hs_tvs = tcdTyVars decl
572 kinded_tvs = ASSERT( length kinds >= length hs_tvs )
573 [ L loc (KindedTyVar (hsTyVarName tv) k)
574 | (L loc tv, k) <- zip hs_tvs kinds]
575 ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
577 -- Kind check a data declaration, assuming that we already extended the
578 -- kind environment with the type variables of the left-hand side (these
579 -- kinded type variables are also passed as the second parameter).
581 kcDataDecl :: TyClDecl Name -> [LHsTyVarBndr Name] -> TcM (TyClDecl Name)
582 kcDataDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
584 = do { ctxt' <- kcHsContext ctxt
585 ; cons' <- mappM (wrapLocM kc_con_decl) cons
586 ; return (decl {tcdTyVars = tvs, tcdCtxt = ctxt', tcdCons = cons'}) }
588 -- doc comments are typechecked to Nothing here
589 kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res _) = do
590 kcHsTyVars ex_tvs $ \ex_tvs' -> do
591 ex_ctxt' <- kcHsContext ex_ctxt
592 details' <- kc_con_details details
594 ResTyH98 -> return ResTyH98
595 ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
596 return (ConDecl name expl ex_tvs' ex_ctxt' details' res' Nothing)
598 kc_con_details (PrefixCon btys)
599 = do { btys' <- mappM kc_larg_ty btys
600 ; return (PrefixCon btys') }
601 kc_con_details (InfixCon bty1 bty2)
602 = do { bty1' <- kc_larg_ty bty1
603 ; bty2' <- kc_larg_ty bty2
604 ; return (InfixCon bty1' bty2') }
605 kc_con_details (RecCon fields)
606 = do { fields' <- mappM kc_field fields
607 ; return (RecCon fields') }
609 kc_field (ConDeclField fld bty d) = do { bty' <- kc_larg_ty bty
610 ; return (ConDeclField fld bty' d) }
612 kc_larg_ty bty = case new_or_data of
613 DataType -> kcHsSigType bty
614 NewType -> kcHsLiftedSigType bty
615 -- Can't allow an unlifted type for newtypes, because we're effectively
616 -- going to remove the constructor while coercing it to a lifted type.
617 -- And newtypes can't be bang'd
619 -- Kind check a family declaration or type family default declaration.
621 kcFamilyDecl :: [LHsTyVarBndr Name] -- tyvars of enclosing class decl if any
622 -> TyClDecl Name -> TcM (TyClDecl Name)
623 kcFamilyDecl classTvs decl@(TyFamily {tcdKind = kind})
624 = kcTyClDeclBody decl $ \tvs' ->
625 do { mapM_ unifyClassParmKinds tvs'
626 ; return (decl {tcdTyVars = tvs',
627 tcdKind = kind `mplus` Just liftedTypeKind})
628 -- default result kind is '*'
631 unifyClassParmKinds (L _ (KindedTyVar n k))
632 | Just classParmKind <- lookup n classTyKinds = unifyKind k classParmKind
633 | otherwise = return ()
634 classTyKinds = [(n, k) | L _ (KindedTyVar n k) <- classTvs]
635 kcFamilyDecl _ decl@(TySynonym {}) -- type family defaults
636 = panic "TcTyClsDecls.kcFamilyDecl: not implemented yet"
640 %************************************************************************
642 \subsection{Type checking}
644 %************************************************************************
647 tcSynDecls :: [LTyClDecl Name] -> TcM [TyThing]
648 tcSynDecls [] = return []
649 tcSynDecls (decl : decls)
650 = do { syn_tc <- addLocM tcSynDecl decl
651 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls decls)
652 ; return (syn_tc : syn_tcs) }
656 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
657 = tcTyVarBndrs tvs $ \ tvs' -> do
658 { traceTc (text "tcd1" <+> ppr tc_name)
659 ; rhs_ty' <- tcHsKindedType rhs_ty
660 ; tycon <- buildSynTyCon tc_name tvs' (SynonymTyCon rhs_ty') Nothing
661 ; return (ATyCon tycon)
665 tcTyClDecl :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
667 tcTyClDecl calc_isrec decl
668 = tcAddDeclCtxt decl (tcTyClDecl1 calc_isrec decl)
670 -- "type family" declarations
671 tcTyClDecl1 _calc_isrec
672 (TyFamily {tcdFlavour = TypeFamily,
673 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = Just kind})
674 -- NB: kind at latest
677 = tcTyVarBndrs tvs $ \ tvs' -> do
678 { traceTc (text "type family: " <+> ppr tc_name)
679 ; idx_tys <- doptM Opt_TypeFamilies
681 -- Check that we don't use families without -ftype-families
682 ; checkTc idx_tys $ badFamInstDecl tc_name
684 ; tycon <- buildSynTyCon tc_name tvs' (OpenSynTyCon kind Nothing) Nothing
685 ; return [ATyCon tycon]
688 -- "newtype family" or "data family" declaration
689 tcTyClDecl1 _calc_isrec
690 (TyFamily {tcdFlavour = DataFamily,
691 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = mb_kind})
692 = tcTyVarBndrs tvs $ \ tvs' -> do
693 { traceTc (text "data family: " <+> ppr tc_name)
694 ; extra_tvs <- tcDataKindSig mb_kind
695 ; let final_tvs = tvs' ++ extra_tvs -- we may not need these
697 ; idx_tys <- doptM Opt_TypeFamilies
699 -- Check that we don't use families without -ftype-families
700 ; checkTc idx_tys $ badFamInstDecl tc_name
702 ; tycon <- buildAlgTyCon tc_name final_tvs []
703 mkOpenDataTyConRhs Recursive False True Nothing
704 ; return [ATyCon tycon]
707 -- "newtype" and "data"
708 tcTyClDecl1 calc_isrec
709 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
710 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
711 = tcTyVarBndrs tvs $ \ tvs' -> do
712 { extra_tvs <- tcDataKindSig mb_ksig
713 ; let final_tvs = tvs' ++ extra_tvs
714 ; stupid_theta <- tcHsKindedContext ctxt
715 ; want_generic <- doptM Opt_Generics
716 ; unbox_strict <- doptM Opt_UnboxStrictFields
717 ; empty_data_decls <- doptM Opt_EmptyDataDecls
718 ; kind_signatures <- doptM Opt_KindSignatures
719 ; gadt_ok <- doptM Opt_GADTs
720 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
722 -- Check that we don't use GADT syntax in H98 world
723 ; checkTc (gadt_ok || h98_syntax) (badGadtDecl tc_name)
725 -- Check that we don't use kind signatures without Glasgow extensions
726 ; checkTc (kind_signatures || isNothing mb_ksig) (badSigTyDecl tc_name)
728 -- Check that the stupid theta is empty for a GADT-style declaration
729 ; checkTc (null stupid_theta || h98_syntax) (badStupidTheta tc_name)
731 -- Check that there's at least one condecl,
732 -- or else we're reading an hs-boot file, or -XEmptyDataDecls
733 ; checkTc (not (null cons) || empty_data_decls || is_boot)
734 (emptyConDeclsErr tc_name)
736 -- Check that a newtype has exactly one constructor
737 ; checkTc (new_or_data == DataType || isSingleton cons)
738 (newtypeConError tc_name (length cons))
740 ; tycon <- fixM (\ tycon -> do
741 { data_cons <- mappM (addLocM (tcConDecl unbox_strict tycon final_tvs))
744 if null cons && is_boot -- In a hs-boot file, empty cons means
745 then return AbstractTyCon -- "don't know"; hence Abstract
746 else case new_or_data of
747 DataType -> return (mkDataTyConRhs data_cons)
749 ASSERT( isSingleton data_cons )
750 mkNewTyConRhs tc_name tycon (head data_cons)
751 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
752 (want_generic && canDoGenerics data_cons) h98_syntax Nothing
754 ; return [ATyCon tycon]
757 is_rec = calc_isrec tc_name
758 h98_syntax = case cons of -- All constructors have same shape
759 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
762 tcTyClDecl1 calc_isrec
763 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
764 tcdCtxt = ctxt, tcdMeths = meths,
765 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
766 = tcTyVarBndrs tvs $ \ tvs' -> do
767 { ctxt' <- tcHsKindedContext ctxt
768 ; fds' <- mappM (addLocM tc_fundep) fundeps
769 ; atss <- mappM (addLocM (tcTyClDecl1 (const Recursive))) ats
770 ; let ats' = zipWith setTyThingPoss atss (map (tcdTyVars . unLoc) ats)
771 ; sig_stuff <- tcClassSigs class_name sigs meths
772 ; clas <- fixM (\ clas ->
773 let -- This little knot is just so we can get
774 -- hold of the name of the class TyCon, which we
775 -- need to look up its recursiveness
776 tycon_name = tyConName (classTyCon clas)
777 tc_isrec = calc_isrec tycon_name
779 buildClass 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' <- mappM tcLookupTyVar tvs1 ;
787 ; tvs2' <- mappM 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 = returnM [ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0)]
808 -----------------------------------
809 tcConDecl :: Bool -- True <=> -funbox-strict_fields
814 tcConDecl unbox_strict tycon tc_tvs -- Data types
815 (ConDecl name _ tvs ctxt details res_ty _)
816 = tcTyVarBndrs tvs $ \ tvs' -> do
817 { ctxt' <- tcHsKindedContext ctxt
818 ; (univ_tvs, ex_tvs, eq_preds, data_tc) <- tcResultType tycon tc_tvs tvs' res_ty
820 -- Tiresome: tidy the tyvar binders, since tc_tvs and tvs' may have the same OccNames
821 tc_datacon is_infix field_lbls btys
822 = do { let bangs = map getBangStrictness btys
823 ; arg_tys <- mappM tcHsBangType btys
824 ; buildDataCon (unLoc name) is_infix
825 (argStrictness unbox_strict bangs arg_tys)
826 (map unLoc field_lbls)
827 univ_tvs ex_tvs eq_preds ctxt' arg_tys
829 -- NB: we put data_tc, the type constructor gotten from the
830 -- constructor type signature into the data constructor;
831 -- that way checkValidDataCon can complain if it's wrong.
834 PrefixCon btys -> tc_datacon False [] btys
835 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
836 RecCon fields -> tc_datacon False field_names btys
838 field_names = map cd_fld_name fields
839 btys = map cd_fld_type fields
842 tcResultType :: TyCon
843 -> [TyVar] -- data T a b c = ...
844 -> [TyVar] -- where MkT :: forall a b c. ...
846 -> TcM ([TyVar], -- Universal
847 [TyVar], -- Existential (distinct OccNames from univs)
848 [(TyVar,Type)], -- Equality predicates
849 TyCon) -- TyCon given in the ResTy
850 -- We don't check that the TyCon given in the ResTy is
851 -- the same as the parent tycon, becuase we are in the middle
852 -- of a recursive knot; so it's postponed until checkValidDataCon
854 tcResultType decl_tycon tc_tvs dc_tvs ResTyH98
855 = return (tc_tvs, dc_tvs, [], decl_tycon)
856 -- In H98 syntax the dc_tvs are the existential ones
857 -- data T a b c = forall d e. MkT ...
858 -- The {a,b,c} are tc_tvs, and {d,e} are dc_tvs
860 tcResultType _ tc_tvs dc_tvs (ResTyGADT res_ty)
861 -- E.g. data T a b c where
862 -- MkT :: forall x y z. T (x,y) z z
864 -- ([a,z,c], [x,y], [a:=:(x,y), c:=:z], T)
866 = do { (dc_tycon, res_tys) <- tcLHsConResTy res_ty
868 ; let univ_tvs = choose_univs [] tidy_tc_tvs res_tys
869 -- Each univ_tv is either a dc_tv or a tc_tv
870 ex_tvs = dc_tvs `minusList` univ_tvs
871 eq_spec = [ (tv, ty) | (tv,ty) <- univ_tvs `zip` res_tys,
873 ; return (univ_tvs, ex_tvs, eq_spec, dc_tycon) }
875 -- choose_univs uses the res_ty itself if it's a type variable
876 -- and hasn't already been used; otherwise it uses one of the tc_tvs
877 choose_univs used tc_tvs []
878 = ASSERT( null tc_tvs ) []
879 choose_univs used (tc_tv:tc_tvs) (res_ty:res_tys)
880 | Just tv <- tcGetTyVar_maybe res_ty, not (tv `elem` used)
881 = tv : choose_univs (tv:used) tc_tvs res_tys
883 = tc_tv : choose_univs used tc_tvs res_tys
885 -- NB: tc_tvs and dc_tvs are distinct, but
886 -- we want them to be *visibly* distinct, both for
887 -- interface files and general confusion. So rename
888 -- the tc_tvs, since they are not used yet (no
889 -- consequential renaming needed)
890 init_occ_env = initTidyOccEnv (map getOccName dc_tvs)
891 (_, tidy_tc_tvs) = mapAccumL tidy_one init_occ_env tc_tvs
892 tidy_one env tv = (env', setTyVarName tv (tidyNameOcc name occ'))
895 (env', occ') = tidyOccName env (getOccName name)
898 argStrictness :: Bool -- True <=> -funbox-strict_fields
900 -> [TcType] -> [StrictnessMark]
901 argStrictness unbox_strict bangs arg_tys
902 = ASSERT( length bangs == length arg_tys )
903 zipWith (chooseBoxingStrategy unbox_strict) arg_tys bangs
905 -- We attempt to unbox/unpack a strict field when either:
906 -- (i) The field is marked '!!', or
907 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
909 -- We have turned off unboxing of newtypes because coercions make unboxing
910 -- and reboxing more complicated
911 chooseBoxingStrategy :: Bool -> TcType -> HsBang -> StrictnessMark
912 chooseBoxingStrategy unbox_strict_fields arg_ty bang
914 HsNoBang -> NotMarkedStrict
915 HsStrict | unbox_strict_fields
916 && can_unbox arg_ty -> MarkedUnboxed
917 HsUnbox | can_unbox arg_ty -> MarkedUnboxed
918 other -> MarkedStrict
920 -- we can unbox if the type is a chain of newtypes with a product tycon
922 can_unbox arg_ty = case splitTyConApp_maybe arg_ty of
924 Just (arg_tycon, tycon_args) ->
925 not (isRecursiveTyCon arg_tycon) && -- Note [Recusive unboxing]
926 isProductTyCon arg_tycon &&
927 (if isNewTyCon arg_tycon then
928 can_unbox (newTyConInstRhs arg_tycon tycon_args)
932 Note [Recursive unboxing]
933 ~~~~~~~~~~~~~~~~~~~~~~~~~
934 Be careful not to try to unbox this!
936 But it's the *argument* type that matters. This is fine:
938 because Int is non-recursive.
940 %************************************************************************
942 \subsection{Dependency analysis}
944 %************************************************************************
946 Validity checking is done once the mutually-recursive knot has been
947 tied, so we can look at things freely.
950 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
951 checkCycleErrs tyclss
955 = do { mappM_ recClsErr cls_cycles
956 ; failM } -- Give up now, because later checkValidTyCl
957 -- will loop if the synonym is recursive
959 cls_cycles = calcClassCycles tyclss
961 checkValidTyCl :: TyClDecl Name -> TcM ()
962 -- We do the validity check over declarations, rather than TyThings
963 -- only so that we can add a nice context with tcAddDeclCtxt
965 = tcAddDeclCtxt decl $
966 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
967 ; traceTc (text "Validity of" <+> ppr thing)
969 ATyCon tc -> checkValidTyCon tc
970 AClass cl -> checkValidClass cl
971 ; traceTc (text "Done validity of" <+> ppr thing)
974 -------------------------
975 -- For data types declared with record syntax, we require
976 -- that each constructor that has a field 'f'
977 -- (a) has the same result type
978 -- (b) has the same type for 'f'
979 -- module alpha conversion of the quantified type variables
980 -- of the constructor.
982 checkValidTyCon :: TyCon -> TcM ()
985 = case synTyConRhs tc of
986 OpenSynTyCon _ _ -> return ()
987 SynonymTyCon ty -> checkValidType syn_ctxt ty
989 = -- Check the context on the data decl
990 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
992 -- Check arg types of data constructors
993 mappM_ (checkValidDataCon tc) data_cons `thenM_`
995 -- Check that fields with the same name share a type
996 mappM_ check_fields groups
999 syn_ctxt = TySynCtxt name
1001 data_cons = tyConDataCons tc
1003 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
1004 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
1005 get_fields con = dataConFieldLabels con `zip` repeat con
1006 -- dataConFieldLabels may return the empty list, which is fine
1008 -- See Note [GADT record selectors] in MkId.lhs
1009 -- We must check (a) that the named field has the same
1010 -- type in each constructor
1011 -- (b) that those constructors have the same result type
1013 -- However, the constructors may have differently named type variable
1014 -- and (worse) we don't know how the correspond to each other. E.g.
1015 -- C1 :: forall a b. { f :: a, g :: b } -> T a b
1016 -- C2 :: forall d c. { f :: c, g :: c } -> T c d
1018 -- So what we do is to ust Unify.tcMatchTys to compare the first candidate's
1019 -- result type against other candidates' types BOTH WAYS ROUND.
1020 -- If they magically agrees, take the substitution and
1021 -- apply them to the latter ones, and see if they match perfectly.
1022 check_fields fields@((label, con1) : other_fields)
1023 -- These fields all have the same name, but are from
1024 -- different constructors in the data type
1025 = recoverM (return ()) $ mapM_ checkOne other_fields
1026 -- Check that all the fields in the group have the same type
1027 -- NB: this check assumes that all the constructors of a given
1028 -- data type use the same type variables
1030 (tvs1, _, _, res1) = dataConSig con1
1032 fty1 = dataConFieldType con1 label
1034 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
1035 = do { checkFieldCompat label con1 con2 ts1 res1 res2 fty1 fty2
1036 ; checkFieldCompat label con2 con1 ts2 res2 res1 fty2 fty1 }
1038 (tvs2, _, _, res2) = dataConSig con2
1040 fty2 = dataConFieldType con2 label
1042 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
1043 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
1044 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
1046 mb_subst1 = tcMatchTy tvs1 res1 res2
1047 mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
1049 -------------------------------
1050 checkValidDataCon :: TyCon -> DataCon -> TcM ()
1051 checkValidDataCon tc con
1052 = setSrcSpan (srcLocSpan (getSrcLoc con)) $
1053 addErrCtxt (dataConCtxt con) $
1054 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
1055 ; checkValidType ctxt (dataConUserType con)
1056 ; ifM (isNewTyCon tc) (checkNewDataCon con)
1059 ctxt = ConArgCtxt (dataConName con)
1061 -------------------------------
1062 checkNewDataCon :: DataCon -> TcM ()
1063 -- Checks for the data constructor of a newtype
1065 = do { checkTc (isSingleton arg_tys) (newtypeFieldErr con (length arg_tys))
1067 ; checkTc (null eq_spec) (newtypePredError con)
1068 -- Return type is (T a b c)
1069 ; checkTc (null ex_tvs && null theta) (newtypeExError con)
1071 ; checkTc (not (any isMarkedStrict (dataConStrictMarks con)))
1072 (newtypeStrictError con)
1076 (_univ_tvs, ex_tvs, eq_spec, theta, arg_tys, _res_ty) = dataConFullSig con
1078 -------------------------------
1079 checkValidClass :: Class -> TcM ()
1081 = do { constrained_class_methods <- doptM Opt_ConstrainedClassMethods
1082 ; multi_param_type_classes <- doptM Opt_MultiParamTypeClasses
1083 ; fundep_classes <- doptM Opt_FunctionalDependencies
1085 -- Check that the class is unary, unless GlaExs
1086 ; checkTc (notNull tyvars) (nullaryClassErr cls)
1087 ; checkTc (multi_param_type_classes || unary) (classArityErr cls)
1088 ; checkTc (fundep_classes || null fundeps) (classFunDepsErr cls)
1090 -- Check the super-classes
1091 ; checkValidTheta (ClassSCCtxt (className cls)) theta
1093 -- Check the class operations
1094 ; mappM_ (check_op constrained_class_methods) op_stuff
1096 -- Check that if the class has generic methods, then the
1097 -- class has only one parameter. We can't do generic
1098 -- multi-parameter type classes!
1099 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
1102 (tyvars, fundeps, theta, _, _, op_stuff) = classExtraBigSig cls
1103 unary = isSingleton tyvars
1104 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
1106 check_op constrained_class_methods (sel_id, dm)
1107 = addErrCtxt (classOpCtxt sel_id tau) $ do
1108 { checkValidTheta SigmaCtxt (tail theta)
1109 -- The 'tail' removes the initial (C a) from the
1110 -- class itself, leaving just the method type
1112 ; checkValidType (FunSigCtxt op_name) tau
1114 -- Check that the type mentions at least one of
1115 -- the class type variables...or at least one reachable
1116 -- from one of the class variables. Example: tc223
1117 -- class Error e => Game b mv e | b -> mv e where
1118 -- newBoard :: MonadState b m => m ()
1119 -- Here, MonadState has a fundep m->b, so newBoard is fine
1120 ; let grown_tyvars = grow theta (mkVarSet tyvars)
1121 ; checkTc (tyVarsOfType tau `intersectsVarSet` grown_tyvars)
1122 (noClassTyVarErr cls sel_id)
1124 -- Check that for a generic method, the type of
1125 -- the method is sufficiently simple
1126 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
1127 (badGenericMethodType op_name op_ty)
1130 op_name = idName sel_id
1131 op_ty = idType sel_id
1132 (_,theta1,tau1) = tcSplitSigmaTy op_ty
1133 (_,theta2,tau2) = tcSplitSigmaTy tau1
1134 (theta,tau) | constrained_class_methods = (theta1 ++ theta2, tau2)
1135 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
1136 -- Ugh! The function might have a type like
1137 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
1138 -- With -XConstrainedClassMethods, we want to allow this, even though the inner
1139 -- forall has an (Eq a) constraint. Whereas in general, each constraint
1140 -- in the context of a for-all must mention at least one quantified
1141 -- type variable. What a mess!
1144 ---------------------------------------------------------------------
1145 resultTypeMisMatch field_name con1 con2
1146 = vcat [sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1147 ptext SLIT("have a common field") <+> quotes (ppr field_name) <> comma],
1148 nest 2 $ ptext SLIT("but have different result types")]
1149 fieldTypeMisMatch field_name con1 con2
1150 = sep [ptext SLIT("Constructors") <+> ppr con1 <+> ptext SLIT("and") <+> ppr con2,
1151 ptext SLIT("give different types for field"), quotes (ppr field_name)]
1153 dataConCtxt con = ptext SLIT("In the definition of data constructor") <+> quotes (ppr con)
1155 classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
1156 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
1159 = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
1162 = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
1163 parens (ptext SLIT("Use -XMultiParamTypeClasses to allow multi-parameter classes"))]
1166 = vcat [ptext SLIT("Fundeps in class") <+> quotes (ppr cls),
1167 parens (ptext SLIT("Use -XFunctionalDependencies to allow fundeps"))]
1169 noClassTyVarErr clas op
1170 = sep [ptext SLIT("The class method") <+> quotes (ppr op),
1171 ptext SLIT("mentions none of the type variables of the class") <+>
1172 ppr clas <+> hsep (map ppr (classTyVars clas))]
1174 genericMultiParamErr clas
1175 = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
1176 ptext SLIT("cannot have generic methods")
1178 badGenericMethodType op op_ty
1179 = hang (ptext SLIT("Generic method type is too complex"))
1180 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
1181 ptext SLIT("You can only use type variables, arrows, lists, and tuples")])
1184 = setSrcSpan (getLoc (head sorted_decls)) $
1185 addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
1186 nest 2 (vcat (map ppr_decl sorted_decls))])
1188 sorted_decls = sortLocated syn_decls
1189 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
1192 = setSrcSpan (getLoc (head sorted_decls)) $
1193 addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
1194 nest 2 (vcat (map ppr_decl sorted_decls))])
1196 sorted_decls = sortLocated cls_decls
1197 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
1199 sortLocated :: [Located a] -> [Located a]
1200 sortLocated things = sortLe le things
1202 le (L l1 _) (L l2 _) = l1 <= l2
1204 badDataConTyCon data_con
1205 = hang (ptext SLIT("Data constructor") <+> quotes (ppr data_con) <+>
1206 ptext SLIT("returns type") <+> quotes (ppr (dataConTyCon data_con)))
1207 2 (ptext SLIT("instead of its parent type"))
1210 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
1211 , nest 2 (parens $ ptext SLIT("Use -XGADTs to allow GADTs")) ]
1213 badStupidTheta tc_name
1214 = ptext SLIT("A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
1216 newtypeConError tycon n
1217 = sep [ptext SLIT("A newtype must have exactly one constructor,"),
1218 nest 2 $ ptext SLIT("but") <+> quotes (ppr tycon) <+> ptext SLIT("has") <+> speakN n ]
1221 = sep [ptext SLIT("A newtype constructor cannot have an existential context,"),
1222 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
1224 newtypeStrictError con
1225 = sep [ptext SLIT("A newtype constructor cannot have a strictness annotation,"),
1226 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
1228 newtypePredError con
1229 = sep [ptext SLIT("A newtype constructor must have a return type of form T a1 ... an"),
1230 nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does not")]
1232 newtypeFieldErr con_name n_flds
1233 = sep [ptext SLIT("The constructor of a newtype must have exactly one field"),
1234 nest 2 $ ptext SLIT("but") <+> quotes (ppr con_name) <+> ptext SLIT("has") <+> speakN n_flds]
1236 badSigTyDecl tc_name
1237 = vcat [ ptext SLIT("Illegal kind signature") <+>
1238 quotes (ppr tc_name)
1239 , nest 2 (parens $ ptext SLIT("Use -XKindSignatures to allow kind signatures")) ]
1241 badFamInstDecl tc_name
1242 = vcat [ ptext SLIT("Illegal family instance for") <+>
1243 quotes (ppr tc_name)
1244 , nest 2 (parens $ ptext SLIT("Use -XTypeFamilies to allow indexed type families")) ]
1246 badGadtIdxTyDecl tc_name
1247 = vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+>
1248 quotes (ppr tc_name)
1249 , nest 2 (parens $ ptext SLIT("Family instances can not yet use GADT declarations")) ]
1251 tooManyParmsErr tc_name
1252 = ptext SLIT("Family instance has too many parameters:") <+>
1253 quotes (ppr tc_name)
1255 tooFewParmsErr tc_name
1256 = ptext SLIT("Family instance has too few parameters:") <+>
1257 quotes (ppr tc_name)
1259 badBootFamInstDeclErr =
1260 ptext SLIT("Illegal family instance in hs-boot file")
1262 wrongKindOfFamily family =
1263 ptext SLIT("Wrong category of family instance; declaration was for a") <+>
1266 kindOfFamily | isSynTyCon family = ptext SLIT("type synonym")
1267 | isAlgTyCon family = ptext SLIT("data type")
1268 | otherwise = pprPanic "wrongKindOfFamily" (ppr family)
1271 = hang (ptext SLIT("Illegal polymorphic type in type instance") <> colon) 4 $
1274 tyFamAppInIndexErr ty
1275 = hang (ptext SLIT("Illegal type family application in type instance") <>
1279 emptyConDeclsErr tycon
1280 = sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
1281 nest 2 $ ptext SLIT("(-XEmptyDataDecls permits this)")]