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"
51 import Control.Monad ( mplus )
55 %************************************************************************
57 \subsection{Type checking for type and class declarations}
59 %************************************************************************
63 Consider a mutually-recursive group, binding
64 a type constructor T and a class C.
66 Step 1: getInitialKind
67 Construct a KindEnv by binding T and C to a kind variable
70 In that environment, do a kind check
72 Step 3: Zonk the kinds
74 Step 4: buildTyConOrClass
75 Construct an environment binding T to a TyCon and C to a Class.
76 a) Their kinds comes from zonking the relevant kind variable
77 b) Their arity (for synonyms) comes direct from the decl
78 c) The funcional dependencies come from the decl
79 d) The rest comes a knot-tied binding of T and C, returned from Step 4
80 e) The variances of the tycons in the group is calculated from
84 In this environment, walk over the decls, constructing the TyCons and Classes.
85 This uses in a strict way items (a)-(c) above, which is why they must
86 be constructed in Step 4. Feed the results back to Step 4.
87 For this step, pass the is-recursive flag as the wimp-out flag
91 Step 6: Extend environment
92 We extend the type environment with bindings not only for the TyCons and Classes,
93 but also for their "implicit Ids" like data constructors and class selectors
95 Step 7: checkValidTyCl
96 For a recursive group only, check all the decls again, just
97 to check all the side conditions on validity. We could not
98 do this before because we were in a mutually recursive knot.
100 Identification of recursive TyCons
101 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
102 The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to
105 Identifying a TyCon as recursive serves two purposes
107 1. Avoid infinite types. Non-recursive newtypes are treated as
108 "transparent", like type synonyms, after the type checker. If we did
109 this for all newtypes, we'd get infinite types. So we figure out for
110 each newtype whether it is "recursive", and add a coercion if so. In
111 effect, we are trying to "cut the loops" by identifying a loop-breaker.
113 2. Avoid infinite unboxing. This is nothing to do with newtypes.
117 Well, this function diverges, but we don't want the strictness analyser
118 to diverge. But the strictness analyser will diverge because it looks
119 deeper and deeper into the structure of T. (I believe there are
120 examples where the function does something sane, and the strictness
121 analyser still diverges, but I can't see one now.)
123 Now, concerning (1), the FC2 branch currently adds a coercion for ALL
124 newtypes. I did this as an experiment, to try to expose cases in which
125 the coercions got in the way of optimisations. If it turns out that we
126 can indeed always use a coercion, then we don't risk recursive types,
127 and don't need to figure out what the loop breakers are.
129 For newtype *families* though, we will always have a coercion, so they
130 are always loop breakers! So you can easily adjust the current
131 algorithm by simply treating all newtype families as loop breakers (and
132 indeed type families). I think.
135 tcTyAndClassDecls :: ModDetails -> [LTyClDecl Name]
136 -> TcM TcGblEnv -- Input env extended by types and classes
137 -- and their implicit Ids,DataCons
138 -- Fails if there are any errors
140 tcTyAndClassDecls boot_details allDecls
141 = checkNoErrs $ -- The code recovers internally, but if anything gave rise to
142 -- an error we'd better stop now, to avoid a cascade
143 do { -- Omit instances of type families; they are handled together
144 -- with the *heads* of class instances
145 ; let decls = filter (not . isFamInstDecl . unLoc) allDecls
147 -- First check for cyclic type synonysm or classes
148 -- See notes with checkCycleErrs
149 ; checkCycleErrs decls
151 ; traceTc (text "tcTyAndCl" <+> ppr mod)
152 ; (syn_tycons, alg_tyclss) <- fixM (\ ~(_rec_syn_tycons, rec_alg_tyclss) ->
153 do { let { -- Seperate ordinary synonyms from all other type and
154 -- class declarations and add all associated type
155 -- declarations from type classes. The latter is
156 -- required so that the temporary environment for the
157 -- knot includes all associated family declarations.
158 ; (syn_decls, alg_decls) = partition (isSynDecl . unLoc)
160 ; alg_at_decls = concatMap addATs alg_decls
162 -- Extend the global env with the knot-tied results
163 -- for data types and classes
165 -- We must populate the environment with the loop-tied
166 -- T's right away, because the kind checker may "fault
167 -- in" some type constructors that recursively
169 ; let gbl_things = mkGlobalThings alg_at_decls rec_alg_tyclss
170 ; tcExtendRecEnv gbl_things $ do
172 -- Kind-check the declarations
173 { (kc_syn_decls, kc_alg_decls) <- kcTyClDecls syn_decls alg_decls
175 ; let { -- Calculate rec-flag
176 ; calc_rec = calcRecFlags boot_details rec_alg_tyclss
177 ; tc_decl = addLocM (tcTyClDecl calc_rec) }
179 -- Type-check the type synonyms, and extend the envt
180 ; syn_tycons <- tcSynDecls kc_syn_decls
181 ; tcExtendGlobalEnv syn_tycons $ do
183 -- Type-check the data types and classes
184 { alg_tyclss <- mapM tc_decl kc_alg_decls
185 ; return (syn_tycons, concat alg_tyclss)
187 -- Finished with knot-tying now
188 -- Extend the environment with the finished things
189 ; tcExtendGlobalEnv (syn_tycons ++ alg_tyclss) $ do
191 -- Perform the validity check
192 { traceTc (text "ready for validity check")
193 ; mapM_ (addLocM checkValidTyCl) decls
194 ; traceTc (text "done")
196 -- Add the implicit things;
197 -- we want them in the environment because
198 -- they may be mentioned in interface files
199 -- NB: All associated types and their implicit things will be added a
200 -- second time here. This doesn't matter as the definitions are
202 ; let { implicit_things = concatMap implicitTyThings alg_tyclss }
203 ; traceTc ((text "Adding" <+> ppr alg_tyclss)
204 $$ (text "and" <+> ppr implicit_things))
205 ; tcExtendGlobalEnv implicit_things getGblEnv
208 -- Pull associated types out of class declarations, to tie them into the
210 -- NB: We put them in the same place in the list as `tcTyClDecl' will
211 -- eventually put the matching `TyThing's. That's crucial; otherwise,
212 -- the two argument lists of `mkGlobalThings' don't match up.
213 addATs decl@(L _ (ClassDecl {tcdATs = ats})) = decl : ats
216 mkGlobalThings :: [LTyClDecl Name] -- The decls
217 -> [TyThing] -- Knot-tied, in 1-1 correspondence with the decls
219 -- Driven by the Decls, and treating the TyThings lazily
220 -- make a TypeEnv for the new things
221 mkGlobalThings decls things
222 = map mk_thing (decls `zipLazy` things)
224 mk_thing (L _ (ClassDecl {tcdLName = L _ name}), ~(AClass cl))
226 mk_thing (L _ decl, ~(ATyCon tc))
227 = (tcdName decl, ATyCon tc)
231 %************************************************************************
233 \subsection{Type checking family instances}
235 %************************************************************************
237 Family instances are somewhat of a hybrid. They are processed together with
238 class instance heads, but can contain data constructors and hence they share a
239 lot of kinding and type checking code with ordinary algebraic data types (and
243 tcFamInstDecl :: LTyClDecl Name -> TcM TyThing
244 tcFamInstDecl (L loc decl)
245 = -- Prime error recovery, set source location
248 do { -- type families require -XTypeFamilies and can't be in an
250 ; type_families <- doptM Opt_TypeFamilies
251 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
252 ; checkTc type_families $ badFamInstDecl (tcdLName decl)
253 ; checkTc (not is_boot) $ badBootFamInstDeclErr
255 -- Perform kind and type checking
256 ; tc <- tcFamInstDecl1 decl
257 ; checkValidTyCon tc -- Remember to check validity;
258 -- no recursion to worry about here
259 ; return (ATyCon tc) }
261 tcFamInstDecl1 :: TyClDecl Name -> TcM TyCon
264 tcFamInstDecl1 (decl@TySynonym {tcdLName = L loc tc_name})
265 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
266 do { -- check that the family declaration is for a synonym
267 unless (isSynTyCon family) $
268 addErr (wrongKindOfFamily family)
270 ; -- (1) kind check the right-hand side of the type equation
271 ; k_rhs <- kcCheckHsType (tcdSynRhs decl) resKind
273 -- we need the exact same number of type parameters as the family
275 ; let famArity = tyConArity family
276 ; checkTc (length k_typats == famArity) $
277 wrongNumberOfParmsErr famArity
279 -- (2) type check type equation
280 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
281 ; t_typats <- mapM tcHsKindedType k_typats
282 ; t_rhs <- tcHsKindedType k_rhs
284 -- (3) check the well-formedness of the instance
285 ; checkValidTypeInst t_typats t_rhs
287 -- (4) construct representation tycon
288 ; rep_tc_name <- newFamInstTyConName tc_name loc
289 ; buildSynTyCon rep_tc_name t_tvs (SynonymTyCon t_rhs)
290 (typeKind t_rhs) (Just (family, t_typats))
293 -- "newtype instance" and "data instance"
294 tcFamInstDecl1 (decl@TyData {tcdND = new_or_data, tcdLName = L loc tc_name,
296 = kcIdxTyPats decl $ \k_tvs k_typats resKind fam_tycon ->
297 do { -- check that the family declaration is for the right kind
298 unless (isAlgTyCon fam_tycon) $
299 addErr (wrongKindOfFamily fam_tycon)
301 ; -- (1) kind check the data declaration as usual
302 ; k_decl <- kcDataDecl decl k_tvs
303 ; let k_ctxt = tcdCtxt k_decl
304 k_cons = tcdCons k_decl
306 -- result kind must be '*' (otherwise, we have too few patterns)
307 ; checkTc (isLiftedTypeKind resKind) $ tooFewParmsErr (tyConArity fam_tycon)
309 -- (2) type check indexed data type declaration
310 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
311 ; unbox_strict <- doptM Opt_UnboxStrictFields
313 -- kind check the type indexes and the context
314 ; t_typats <- mapM tcHsKindedType k_typats
315 ; stupid_theta <- tcHsKindedContext k_ctxt
318 -- (a) left-hand side contains no type family applications
319 -- (vanilla synonyms are fine, though, and we checked for
321 ; mapM_ checkTyFamFreeness t_typats
323 -- (b) a newtype has exactly one constructor
324 ; checkTc (new_or_data == DataType || isSingleton k_cons) $
325 newtypeConError tc_name (length k_cons)
327 -- (4) construct representation tycon
328 ; rep_tc_name <- newFamInstTyConName tc_name loc
329 ; let ex_ok = True -- Existentials ok for type families!
330 ; fixM (\ rep_tycon -> do
331 { let orig_res_ty = mkTyConApp fam_tycon t_typats
332 ; data_cons <- tcConDecls unbox_strict ex_ok rep_tycon
333 (t_tvs, orig_res_ty) k_cons
336 DataType -> return (mkDataTyConRhs data_cons)
337 NewType -> ASSERT( not (null data_cons) )
338 mkNewTyConRhs rep_tc_name rep_tycon (head data_cons)
339 ; buildAlgTyCon rep_tc_name t_tvs stupid_theta tc_rhs Recursive
340 False h98_syntax (Just (fam_tycon, t_typats))
341 -- We always assume that indexed types are recursive. Why?
342 -- (1) Due to their open nature, we can never be sure that a
343 -- further instance might not introduce a new recursive
344 -- dependency. (2) They are always valid loop breakers as
345 -- they involve a coercion.
349 h98_syntax = case cons of -- All constructors have same shape
350 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
353 tcFamInstDecl1 d = pprPanic "tcFamInstDecl1" (ppr d)
355 -- Kind checking of indexed types
358 -- Kind check type patterns and kind annotate the embedded type variables.
360 -- * Here we check that a type instance matches its kind signature, but we do
361 -- not check whether there is a pattern for each type index; the latter
362 -- check is only required for type synonym instances.
364 kcIdxTyPats :: TyClDecl Name
365 -> ([LHsTyVarBndr Name] -> [LHsType Name] -> Kind -> TyCon -> TcM a)
366 -- ^^kinded tvs ^^kinded ty pats ^^res kind
368 kcIdxTyPats decl thing_inside
369 = kcHsTyVars (tcdTyVars decl) $ \tvs ->
370 do { fam_tycon <- tcLookupLocatedTyCon (tcdLName decl)
371 ; let { (kinds, resKind) = splitKindFunTys (tyConKind fam_tycon)
372 ; hs_typats = fromJust $ tcdTyPats decl }
374 -- we may not have more parameters than the kind indicates
375 ; checkTc (length kinds >= length hs_typats) $
376 tooManyParmsErr (tcdLName decl)
378 -- type functions can have a higher-kinded result
379 ; let resultKind = mkArrowKinds (drop (length hs_typats) kinds) resKind
380 ; typats <- zipWithM kcCheckHsType hs_typats kinds
381 ; thing_inside tvs typats resultKind fam_tycon
387 %************************************************************************
391 %************************************************************************
393 We need to kind check all types in the mutually recursive group
394 before we know the kind of the type variables. For example:
397 op :: D b => a -> b -> b
400 bop :: (Monad c) => ...
402 Here, the kind of the locally-polymorphic type variable "b"
403 depends on *all the uses of class D*. For example, the use of
404 Monad c in bop's type signature means that D must have kind Type->Type.
406 However type synonyms work differently. They can have kinds which don't
407 just involve (->) and *:
408 type R = Int# -- Kind #
409 type S a = Array# a -- Kind * -> #
410 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
411 So we must infer their kinds from their right-hand sides *first* and then
412 use them, whereas for the mutually recursive data types D we bring into
413 scope kind bindings D -> k, where k is a kind variable, and do inference.
417 This treatment of type synonyms only applies to Haskell 98-style synonyms.
418 General type functions can be recursive, and hence, appear in `alg_decls'.
420 The kind of a type family is solely determinded by its kind signature;
421 hence, only kind signatures participate in the construction of the initial
422 kind environment (as constructed by `getInitialKind'). In fact, we ignore
423 instances of families altogether in the following. However, we need to
424 include the kinds of associated families into the construction of the
425 initial kind environment. (This is handled by `allDecls').
428 kcTyClDecls :: [LTyClDecl Name] -> [Located (TyClDecl Name)]
429 -> TcM ([LTyClDecl Name], [Located (TyClDecl Name)])
430 kcTyClDecls syn_decls alg_decls
431 = do { -- First extend the kind env with each data type, class, and
432 -- indexed type, mapping them to a type variable
433 let initialKindDecls = concat [allDecls decl | L _ decl <- alg_decls]
434 ; alg_kinds <- mapM getInitialKind initialKindDecls
435 ; tcExtendKindEnv alg_kinds $ do
437 -- Now kind-check the type synonyms, in dependency order
438 -- We do these differently to data type and classes,
439 -- because a type synonym can be an unboxed type
441 -- and a kind variable can't unify with UnboxedTypeKind
442 -- So we infer their kinds in dependency order
443 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
444 ; tcExtendKindEnv syn_kinds $ do
446 -- Now kind-check the data type, class, and kind signatures,
447 -- returning kind-annotated decls; we don't kind-check
448 -- instances of indexed types yet, but leave this to
450 { kc_alg_decls <- mapM (wrapLocM kcTyClDecl)
451 (filter (not . isFamInstDecl . unLoc) alg_decls)
453 ; return (kc_syn_decls, kc_alg_decls) }}}
455 -- get all declarations relevant for determining the initial kind
457 allDecls (decl@ClassDecl {tcdATs = ats}) = decl : [ at
460 allDecls decl | isFamInstDecl decl = []
463 ------------------------------------------------------------------------
464 getInitialKind :: TyClDecl Name -> TcM (Name, TcKind)
465 -- Only for data type, class, and indexed type declarations
466 -- Get as much info as possible from the data, class, or indexed type decl,
467 -- so as to maximise usefulness of error messages
469 = do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl)
470 ; res_kind <- mk_res_kind decl
471 ; return (tcdName decl, mkArrowKinds arg_kinds res_kind) }
473 mk_arg_kind (UserTyVar _) = newKindVar
474 mk_arg_kind (KindedTyVar _ kind) = return kind
476 mk_res_kind (TyFamily { tcdKind = Just kind }) = return kind
477 mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
478 -- On GADT-style declarations we allow a kind signature
479 -- data T :: *->* where { ... }
480 mk_res_kind _ = return liftedTypeKind
484 kcSynDecls :: [SCC (LTyClDecl Name)]
485 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
486 [(Name,TcKind)]) -- Kind bindings
489 kcSynDecls (group : groups)
490 = do { (decl, nk) <- kcSynDecl group
491 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
492 ; return (decl:decls, nk:nks) }
495 kcSynDecl :: SCC (LTyClDecl Name)
496 -> TcM (LTyClDecl Name, -- Kind-annotated decls
497 (Name,TcKind)) -- Kind bindings
498 kcSynDecl (AcyclicSCC (L loc decl))
499 = tcAddDeclCtxt decl $
500 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
501 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
502 <+> brackets (ppr k_tvs))
503 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
504 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
505 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
506 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
507 (unLoc (tcdLName decl), tc_kind)) })
509 kcSynDecl (CyclicSCC decls)
510 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
511 -- of out-of-scope tycons
513 kindedTyVarKind :: LHsTyVarBndr Name -> Kind
514 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
515 kindedTyVarKind x = pprPanic "kindedTyVarKind" (ppr x)
517 ------------------------------------------------------------------------
518 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
519 -- Not used for type synonyms (see kcSynDecl)
521 kcTyClDecl decl@(TyData {})
522 = ASSERT( not . isFamInstDecl $ decl ) -- must not be a family instance
523 kcTyClDeclBody decl $
526 kcTyClDecl decl@(TyFamily {})
527 = kcFamilyDecl [] decl -- the empty list signals a toplevel decl
529 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs, tcdATs = ats})
530 = kcTyClDeclBody decl $ \ tvs' ->
531 do { ctxt' <- kcHsContext ctxt
532 ; ats' <- mapM (wrapLocM (kcFamilyDecl tvs')) ats
533 ; sigs' <- mapM (wrapLocM kc_sig) sigs
534 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs',
537 kc_sig (TypeSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
538 ; return (TypeSig nm op_ty') }
539 kc_sig other_sig = return other_sig
541 kcTyClDecl decl@(ForeignType {})
544 kcTyClDecl (TySynonym {}) = panic "kcTyClDecl TySynonym"
546 kcTyClDeclBody :: TyClDecl Name
547 -> ([LHsTyVarBndr Name] -> TcM a)
549 -- getInitialKind has made a suitably-shaped kind for the type or class
550 -- Unpack it, and attribute those kinds to the type variables
551 -- Extend the env with bindings for the tyvars, taken from
552 -- the kind of the tycon/class. Give it to the thing inside, and
553 -- check the result kind matches
554 kcTyClDeclBody decl thing_inside
555 = tcAddDeclCtxt decl $
556 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
557 ; let tc_kind = case tc_ty_thing of
559 _ -> pprPanic "kcTyClDeclBody" (ppr tc_ty_thing)
560 (kinds, _) = splitKindFunTys tc_kind
561 hs_tvs = tcdTyVars decl
562 kinded_tvs = ASSERT( length kinds >= length hs_tvs )
563 [ L loc (KindedTyVar (hsTyVarName tv) k)
564 | (L loc tv, k) <- zip hs_tvs kinds]
565 ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
567 -- Kind check a data declaration, assuming that we already extended the
568 -- kind environment with the type variables of the left-hand side (these
569 -- kinded type variables are also passed as the second parameter).
571 kcDataDecl :: TyClDecl Name -> [LHsTyVarBndr Name] -> TcM (TyClDecl Name)
572 kcDataDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
574 = do { ctxt' <- kcHsContext ctxt
575 ; cons' <- mapM (wrapLocM kc_con_decl) cons
576 ; return (decl {tcdTyVars = tvs, tcdCtxt = ctxt', tcdCons = cons'}) }
578 -- doc comments are typechecked to Nothing here
579 kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res _) = do
580 kcHsTyVars ex_tvs $ \ex_tvs' -> do
581 ex_ctxt' <- kcHsContext ex_ctxt
582 details' <- kc_con_details details
584 ResTyH98 -> return ResTyH98
585 ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
586 return (ConDecl name expl ex_tvs' ex_ctxt' details' res' Nothing)
588 kc_con_details (PrefixCon btys)
589 = do { btys' <- mapM kc_larg_ty btys
590 ; return (PrefixCon btys') }
591 kc_con_details (InfixCon bty1 bty2)
592 = do { bty1' <- kc_larg_ty bty1
593 ; bty2' <- kc_larg_ty bty2
594 ; return (InfixCon bty1' bty2') }
595 kc_con_details (RecCon fields)
596 = do { fields' <- mapM kc_field fields
597 ; return (RecCon fields') }
599 kc_field (ConDeclField fld bty d) = do { bty' <- kc_larg_ty bty
600 ; return (ConDeclField fld bty' d) }
602 kc_larg_ty bty = case new_or_data of
603 DataType -> kcHsSigType bty
604 NewType -> kcHsLiftedSigType bty
605 -- Can't allow an unlifted type for newtypes, because we're effectively
606 -- going to remove the constructor while coercing it to a lifted type.
607 -- And newtypes can't be bang'd
608 kcDataDecl d _ = pprPanic "kcDataDecl" (ppr d)
610 -- Kind check a family declaration or type family default declaration.
612 kcFamilyDecl :: [LHsTyVarBndr Name] -- tyvars of enclosing class decl if any
613 -> TyClDecl Name -> TcM (TyClDecl Name)
614 kcFamilyDecl classTvs decl@(TyFamily {tcdKind = kind})
615 = kcTyClDeclBody decl $ \tvs' ->
616 do { mapM_ unifyClassParmKinds tvs'
617 ; return (decl {tcdTyVars = tvs',
618 tcdKind = kind `mplus` Just liftedTypeKind})
619 -- default result kind is '*'
622 unifyClassParmKinds (L _ (KindedTyVar n k))
623 | Just classParmKind <- lookup n classTyKinds = unifyKind k classParmKind
624 | otherwise = return ()
625 unifyClassParmKinds x = pprPanic "kcFamilyDecl/unifyClassParmKinds" (ppr x)
626 classTyKinds = [(n, k) | L _ (KindedTyVar n k) <- classTvs]
627 kcFamilyDecl _ (TySynonym {}) -- type family defaults
628 = panic "TcTyClsDecls.kcFamilyDecl: not implemented yet"
629 kcFamilyDecl _ d = pprPanic "kcFamilyDecl" (ppr d)
633 %************************************************************************
635 \subsection{Type checking}
637 %************************************************************************
640 tcSynDecls :: [LTyClDecl Name] -> TcM [TyThing]
641 tcSynDecls [] = return []
642 tcSynDecls (decl : decls)
643 = do { syn_tc <- addLocM tcSynDecl decl
644 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls decls)
645 ; return (syn_tc : syn_tcs) }
648 tcSynDecl :: TyClDecl Name -> TcM TyThing
650 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
651 = tcTyVarBndrs tvs $ \ tvs' -> do
652 { traceTc (text "tcd1" <+> ppr tc_name)
653 ; rhs_ty' <- tcHsKindedType rhs_ty
654 ; tycon <- buildSynTyCon tc_name tvs' (SynonymTyCon rhs_ty')
655 (typeKind rhs_ty') Nothing
656 ; return (ATyCon tycon)
658 tcSynDecl d = pprPanic "tcSynDecl" (ppr d)
661 tcTyClDecl :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
663 tcTyClDecl calc_isrec decl
664 = tcAddDeclCtxt decl (tcTyClDecl1 calc_isrec decl)
666 -- "type family" declarations
667 tcTyClDecl1 :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
668 tcTyClDecl1 _calc_isrec
669 (TyFamily {tcdFlavour = TypeFamily,
670 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = Just kind})
671 -- NB: kind at latest
674 = tcTyVarBndrs tvs $ \ tvs' -> do
675 { traceTc (text "type family: " <+> ppr tc_name)
676 ; idx_tys <- doptM Opt_TypeFamilies
678 -- Check that we don't use families without -XTypeFamilies
679 ; checkTc idx_tys $ badFamInstDecl tc_name
681 ; tycon <- buildSynTyCon tc_name tvs' (OpenSynTyCon kind Nothing) kind Nothing
682 ; return [ATyCon tycon]
685 -- "data family" declaration
686 tcTyClDecl1 _calc_isrec
687 (TyFamily {tcdFlavour = DataFamily,
688 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = mb_kind})
689 = tcTyVarBndrs tvs $ \ tvs' -> do
690 { traceTc (text "data family: " <+> ppr tc_name)
691 ; extra_tvs <- tcDataKindSig mb_kind
692 ; let final_tvs = tvs' ++ extra_tvs -- we may not need these
694 ; idx_tys <- doptM Opt_TypeFamilies
696 -- Check that we don't use families without -XTypeFamilies
697 ; checkTc idx_tys $ badFamInstDecl tc_name
699 ; tycon <- buildAlgTyCon tc_name final_tvs []
700 mkOpenDataTyConRhs Recursive False True Nothing
701 ; return [ATyCon tycon]
704 -- "newtype" and "data"
705 -- NB: not used for newtype/data instances (whether associated or not)
706 tcTyClDecl1 calc_isrec
707 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
708 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
709 = tcTyVarBndrs tvs $ \ tvs' -> do
710 { extra_tvs <- tcDataKindSig mb_ksig
711 ; let final_tvs = tvs' ++ extra_tvs
712 ; stupid_theta <- tcHsKindedContext ctxt
713 ; want_generic <- doptM Opt_Generics
714 ; unbox_strict <- doptM Opt_UnboxStrictFields
715 ; empty_data_decls <- doptM Opt_EmptyDataDecls
716 ; kind_signatures <- doptM Opt_KindSignatures
717 ; existential_ok <- doptM Opt_ExistentialQuantification
718 ; gadt_ok <- doptM Opt_GADTs
719 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
720 ; let ex_ok = existential_ok || gadt_ok -- Data cons can have existential context
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 a newtype has exactly one constructor
732 -- Do this before checking for empty data decls, so that
733 -- we don't suggest -XEmptyDataDecls for newtypes
734 ; checkTc (new_or_data == DataType || isSingleton cons)
735 (newtypeConError tc_name (length cons))
737 -- Check that there's at least one condecl,
738 -- or else we're reading an hs-boot file, or -XEmptyDataDecls
739 ; checkTc (not (null cons) || empty_data_decls || is_boot)
740 (emptyConDeclsErr tc_name)
742 ; tycon <- fixM (\ tycon -> do
743 { let res_ty = mkTyConApp tycon (mkTyVarTys final_tvs)
744 ; data_cons <- tcConDecls unbox_strict ex_ok
745 tycon (final_tvs, res_ty) cons
747 if null cons && is_boot -- In a hs-boot file, empty cons means
748 then return AbstractTyCon -- "don't know"; hence Abstract
749 else case new_or_data of
750 DataType -> return (mkDataTyConRhs data_cons)
751 NewType -> ASSERT( not (null data_cons) )
752 mkNewTyConRhs tc_name tycon (head data_cons)
753 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
754 (want_generic && canDoGenerics data_cons) h98_syntax Nothing
756 ; return [ATyCon tycon]
759 is_rec = calc_isrec tc_name
760 h98_syntax = case cons of -- All constructors have same shape
761 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
764 tcTyClDecl1 calc_isrec
765 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
766 tcdCtxt = ctxt, tcdMeths = meths,
767 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
768 = tcTyVarBndrs tvs $ \ tvs' -> do
769 { ctxt' <- tcHsKindedContext ctxt
770 ; fds' <- mapM (addLocM tc_fundep) fundeps
771 ; atss <- mapM (addLocM (tcTyClDecl1 (const Recursive))) ats
772 -- NB: 'ats' only contains "type family" and "data family"
773 -- declarations as well as type family defaults
774 ; let ats' = zipWith setTyThingPoss atss (map (tcdTyVars . unLoc) ats)
775 ; sig_stuff <- tcClassSigs class_name sigs meths
776 ; clas <- fixM (\ clas ->
777 let -- This little knot is just so we can get
778 -- hold of the name of the class TyCon, which we
779 -- need to look up its recursiveness
780 tycon_name = tyConName (classTyCon clas)
781 tc_isrec = calc_isrec tycon_name
783 buildClass False {- Must include unfoldings for selectors -}
784 class_name tvs' ctxt' fds' ats'
786 ; return (AClass clas : ats')
787 -- NB: Order is important due to the call to `mkGlobalThings' when
788 -- tying the the type and class declaration type checking knot.
791 tc_fundep (tvs1, tvs2) = do { tvs1' <- mapM tcLookupTyVar tvs1 ;
792 ; tvs2' <- mapM tcLookupTyVar tvs2 ;
793 ; return (tvs1', tvs2') }
795 -- For each AT argument compute the position of the corresponding class
796 -- parameter in the class head. This will later serve as a permutation
797 -- vector when checking the validity of instance declarations.
798 setTyThingPoss [ATyCon tycon] atTyVars =
799 let classTyVars = hsLTyVarNames tvs
801 . map (`elemIndex` classTyVars)
804 -- There will be no Nothing, as we already passed renaming
806 ATyCon (setTyConArgPoss tycon poss)
807 setTyThingPoss _ _ = panic "TcTyClsDecls.setTyThingPoss"
810 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
811 = return [ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0)]
813 tcTyClDecl1 _ d = pprPanic "tcTyClDecl1" (ppr d)
815 -----------------------------------
816 tcConDecls :: Bool -> Bool -> TyCon -> ([TyVar], Type)
817 -> [LConDecl Name] -> TcM [DataCon]
818 tcConDecls unbox ex_ok rep_tycon res_tmpl cons
819 = mapM (addLocM (tcConDecl unbox ex_ok rep_tycon res_tmpl)) cons
821 tcConDecl :: Bool -- True <=> -funbox-strict_fields
822 -> Bool -- True <=> -XExistentialQuantificaton or -XGADTs
823 -> TyCon -- Representation tycon
824 -> ([TyVar], Type) -- Return type template (with its template tyvars)
828 tcConDecl unbox_strict existential_ok rep_tycon res_tmpl -- Data types
829 (ConDecl name _ tvs ctxt details res_ty _)
830 = addErrCtxt (dataConCtxt name) $
831 tcTyVarBndrs tvs $ \ tvs' -> do
832 { ctxt' <- tcHsKindedContext ctxt
833 ; checkTc (existential_ok || (null tvs && null (unLoc ctxt)))
834 (badExistential name)
835 ; (univ_tvs, ex_tvs, eq_preds, res_ty') <- tcResultType res_tmpl tvs' res_ty
837 tc_datacon is_infix field_lbls btys
838 = do { (arg_tys, stricts) <- mapAndUnzipM (tcConArg unbox_strict) btys
839 ; buildDataCon (unLoc name) is_infix
841 univ_tvs ex_tvs eq_preds ctxt' arg_tys
843 -- NB: we put data_tc, the type constructor gotten from the
844 -- constructor type signature into the data constructor;
845 -- that way checkValidDataCon can complain if it's wrong.
848 PrefixCon btys -> tc_datacon False [] btys
849 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
850 RecCon fields -> tc_datacon False field_names btys
852 field_names = map (unLoc . cd_fld_name) fields
853 btys = map cd_fld_type fields
857 -- data instance T (b,c) where
858 -- TI :: forall e. e -> T (e,e)
860 -- The representation tycon looks like this:
861 -- data :R7T b c where
862 -- TI :: forall b1 c1. (b1 ~ c1) => b1 -> :R7T b1 c1
863 -- In this case orig_res_ty = T (e,e)
865 tcResultType :: ([TyVar], Type) -- Template for result type; e.g.
866 -- data T a b c = ... gives ([a,b,c], T a b)
867 -> [TyVar] -- where MkT :: forall a b c. ...
869 -> TcM ([TyVar], -- Universal
870 [TyVar], -- Existential (distinct OccNames from univs)
871 [(TyVar,Type)], -- Equality predicates
872 Type) -- Typechecked return type
873 -- We don't check that the TyCon given in the ResTy is
874 -- the same as the parent tycon, becuase we are in the middle
875 -- of a recursive knot; so it's postponed until checkValidDataCon
877 tcResultType (tmpl_tvs, res_ty) dc_tvs ResTyH98
878 = return (tmpl_tvs, dc_tvs, [], res_ty)
879 -- In H98 syntax the dc_tvs are the existential ones
880 -- data T a b c = forall d e. MkT ...
881 -- The {a,b,c} are tc_tvs, and {d,e} are dc_tvs
883 tcResultType (tmpl_tvs, res_tmpl) dc_tvs (ResTyGADT res_ty)
884 -- E.g. data T [a] b c where
885 -- MkT :: forall x y z. T [(x,y)] z z
887 -- Univ tyvars Eq-spec
891 -- Existentials are the leftover type vars: [x,y]
892 = do { res_ty' <- tcHsKindedType res_ty
893 ; let Just subst = tcMatchTy (mkVarSet tmpl_tvs) res_tmpl res_ty'
895 -- /Lazily/ figure out the univ_tvs etc
896 -- Each univ_tv is either a dc_tv or a tmpl_tv
897 (univ_tvs, eq_spec) = foldr choose ([], []) tidy_tmpl_tvs
898 choose tmpl (univs, eqs)
899 | Just ty <- lookupTyVar subst tmpl
900 = case tcGetTyVar_maybe ty of
901 Just tv | not (tv `elem` univs)
903 _other -> (tmpl:univs, (tmpl,ty):eqs)
904 | otherwise = pprPanic "tcResultType" (ppr res_ty)
905 ex_tvs = dc_tvs `minusList` univ_tvs
907 ; return (univ_tvs, ex_tvs, eq_spec, res_ty') }
909 -- NB: tmpl_tvs and dc_tvs are distinct, but
910 -- we want them to be *visibly* distinct, both for
911 -- interface files and general confusion. So rename
912 -- the tc_tvs, since they are not used yet (no
913 -- consequential renaming needed)
914 (_, tidy_tmpl_tvs) = mapAccumL tidy_one init_occ_env tmpl_tvs
915 init_occ_env = initTidyOccEnv (map getOccName dc_tvs)
916 tidy_one env tv = (env', setTyVarName tv (tidyNameOcc name occ'))
919 (env', occ') = tidyOccName env (getOccName name)
922 tcConArg :: Bool -- True <=> -funbox-strict_fields
924 -> TcM (TcType, StrictnessMark)
925 tcConArg unbox_strict bty
926 = do { arg_ty <- tcHsBangType bty
927 ; let bang = getBangStrictness bty
928 ; return (arg_ty, chooseBoxingStrategy unbox_strict arg_ty bang) }
930 -- We attempt to unbox/unpack a strict field when either:
931 -- (i) The field is marked '!!', or
932 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
934 -- We have turned off unboxing of newtypes because coercions make unboxing
935 -- and reboxing more complicated
936 chooseBoxingStrategy :: Bool -> TcType -> HsBang -> StrictnessMark
937 chooseBoxingStrategy unbox_strict_fields arg_ty bang
939 HsNoBang -> NotMarkedStrict
940 HsStrict | unbox_strict_fields
941 && can_unbox arg_ty -> MarkedUnboxed
942 HsUnbox | can_unbox arg_ty -> MarkedUnboxed
945 -- we can unbox if the type is a chain of newtypes with a product tycon
947 can_unbox arg_ty = case splitTyConApp_maybe arg_ty of
949 Just (arg_tycon, tycon_args) ->
950 not (isRecursiveTyCon arg_tycon) && -- Note [Recusive unboxing]
951 isProductTyCon arg_tycon &&
952 (if isNewTyCon arg_tycon then
953 can_unbox (newTyConInstRhs arg_tycon tycon_args)
957 Note [Recursive unboxing]
958 ~~~~~~~~~~~~~~~~~~~~~~~~~
959 Be careful not to try to unbox this!
961 But it's the *argument* type that matters. This is fine:
963 because Int is non-recursive.
965 %************************************************************************
967 \subsection{Dependency analysis}
969 %************************************************************************
971 Validity checking is done once the mutually-recursive knot has been
972 tied, so we can look at things freely.
975 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
976 checkCycleErrs tyclss
980 = do { mapM_ recClsErr cls_cycles
981 ; failM } -- Give up now, because later checkValidTyCl
982 -- will loop if the synonym is recursive
984 cls_cycles = calcClassCycles tyclss
986 checkValidTyCl :: TyClDecl Name -> TcM ()
987 -- We do the validity check over declarations, rather than TyThings
988 -- only so that we can add a nice context with tcAddDeclCtxt
990 = tcAddDeclCtxt decl $
991 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
992 ; traceTc (text "Validity of" <+> ppr thing)
994 ATyCon tc -> checkValidTyCon tc
995 AClass cl -> checkValidClass cl
996 _ -> panic "checkValidTyCl"
997 ; traceTc (text "Done validity of" <+> ppr thing)
1000 -------------------------
1001 -- For data types declared with record syntax, we require
1002 -- that each constructor that has a field 'f'
1003 -- (a) has the same result type
1004 -- (b) has the same type for 'f'
1005 -- module alpha conversion of the quantified type variables
1006 -- of the constructor.
1008 -- Note that we allow existentials to match becuase the
1009 -- fields can never meet. E.g
1011 -- T1 { f1 :: b, f2 :: a, f3 ::Int } :: T
1012 -- T2 { f1 :: c, f2 :: c, f3 ::Int } :: T
1013 -- Here we do not complain about f1,f2 because they are existential
1015 checkValidTyCon :: TyCon -> TcM ()
1018 = case synTyConRhs tc of
1019 OpenSynTyCon _ _ -> return ()
1020 SynonymTyCon ty -> checkValidType syn_ctxt ty
1022 = do -- Check the context on the data decl
1023 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc)
1025 -- Check arg types of data constructors
1026 mapM_ (checkValidDataCon tc) data_cons
1028 -- Check that fields with the same name share a type
1029 mapM_ check_fields groups
1032 syn_ctxt = TySynCtxt name
1034 data_cons = tyConDataCons tc
1036 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
1037 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
1038 get_fields con = dataConFieldLabels con `zip` repeat con
1039 -- dataConFieldLabels may return the empty list, which is fine
1041 -- See Note [GADT record selectors] in MkId.lhs
1042 -- We must check (a) that the named field has the same
1043 -- type in each constructor
1044 -- (b) that those constructors have the same result type
1046 -- However, the constructors may have differently named type variable
1047 -- and (worse) we don't know how the correspond to each other. E.g.
1048 -- C1 :: forall a b. { f :: a, g :: b } -> T a b
1049 -- C2 :: forall d c. { f :: c, g :: c } -> T c d
1051 -- So what we do is to ust Unify.tcMatchTys to compare the first candidate's
1052 -- result type against other candidates' types BOTH WAYS ROUND.
1053 -- If they magically agrees, take the substitution and
1054 -- apply them to the latter ones, and see if they match perfectly.
1055 check_fields ((label, con1) : other_fields)
1056 -- These fields all have the same name, but are from
1057 -- different constructors in the data type
1058 = recoverM (return ()) $ mapM_ checkOne other_fields
1059 -- Check that all the fields in the group have the same type
1060 -- NB: this check assumes that all the constructors of a given
1061 -- data type use the same type variables
1063 (tvs1, _, _, res1) = dataConSig con1
1065 fty1 = dataConFieldType con1 label
1067 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
1068 = do { checkFieldCompat label con1 con2 ts1 res1 res2 fty1 fty2
1069 ; checkFieldCompat label con2 con1 ts2 res2 res1 fty2 fty1 }
1071 (tvs2, _, _, res2) = dataConSig con2
1073 fty2 = dataConFieldType con2 label
1074 check_fields [] = panic "checkValidTyCon/check_fields []"
1076 checkFieldCompat :: Name -> DataCon -> DataCon -> TyVarSet
1077 -> Type -> Type -> Type -> Type -> TcM ()
1078 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
1079 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
1080 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
1082 mb_subst1 = tcMatchTy tvs1 res1 res2
1083 mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
1085 -------------------------------
1086 checkValidDataCon :: TyCon -> DataCon -> TcM ()
1087 checkValidDataCon tc con
1088 = setSrcSpan (srcLocSpan (getSrcLoc con)) $
1089 addErrCtxt (dataConCtxt con) $
1090 do { let tc_tvs = tyConTyVars tc
1091 res_ty_tmpl = mkFamilyTyConApp tc (mkTyVarTys tc_tvs)
1092 actual_res_ty = dataConOrigResTy con
1093 ; checkTc (isJust (tcMatchTy (mkVarSet tc_tvs)
1096 (badDataConTyCon con res_ty_tmpl actual_res_ty)
1097 ; checkValidMonoType (dataConOrigResTy con)
1098 -- Disallow MkT :: T (forall a. a->a)
1099 -- Reason: it's really the argument of an equality constraint
1100 ; checkValidType ctxt (dataConUserType con)
1101 ; when (isNewTyCon tc) (checkNewDataCon con)
1104 ctxt = ConArgCtxt (dataConName con)
1106 -------------------------------
1107 checkNewDataCon :: DataCon -> TcM ()
1108 -- Checks for the data constructor of a newtype
1110 = do { checkTc (isSingleton arg_tys) (newtypeFieldErr con (length arg_tys))
1112 ; checkTc (null eq_spec) (newtypePredError con)
1113 -- Return type is (T a b c)
1114 ; checkTc (null ex_tvs && null eq_theta && null dict_theta) (newtypeExError con)
1116 ; checkTc (not (any isMarkedStrict (dataConStrictMarks con)))
1117 (newtypeStrictError con)
1121 (_univ_tvs, ex_tvs, eq_spec, eq_theta, dict_theta, arg_tys, _res_ty) = dataConFullSig con
1123 -------------------------------
1124 checkValidClass :: Class -> TcM ()
1126 = do { constrained_class_methods <- doptM Opt_ConstrainedClassMethods
1127 ; multi_param_type_classes <- doptM Opt_MultiParamTypeClasses
1128 ; fundep_classes <- doptM Opt_FunctionalDependencies
1130 -- Check that the class is unary, unless GlaExs
1131 ; checkTc (notNull tyvars) (nullaryClassErr cls)
1132 ; checkTc (multi_param_type_classes || unary) (classArityErr cls)
1133 ; checkTc (fundep_classes || null fundeps) (classFunDepsErr cls)
1135 -- Check the super-classes
1136 ; checkValidTheta (ClassSCCtxt (className cls)) theta
1138 -- Check the class operations
1139 ; mapM_ (check_op constrained_class_methods) op_stuff
1141 -- Check that if the class has generic methods, then the
1142 -- class has only one parameter. We can't do generic
1143 -- multi-parameter type classes!
1144 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
1147 (tyvars, fundeps, theta, _, _, op_stuff) = classExtraBigSig cls
1148 unary = isSingleton tyvars
1149 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
1151 check_op constrained_class_methods (sel_id, dm)
1152 = addErrCtxt (classOpCtxt sel_id tau) $ do
1153 { checkValidTheta SigmaCtxt (tail theta)
1154 -- The 'tail' removes the initial (C a) from the
1155 -- class itself, leaving just the method type
1157 ; traceTc (text "class op type" <+> ppr op_ty <+> ppr tau)
1158 ; checkValidType (FunSigCtxt op_name) tau
1160 -- Check that the type mentions at least one of
1161 -- the class type variables...or at least one reachable
1162 -- from one of the class variables. Example: tc223
1163 -- class Error e => Game b mv e | b -> mv e where
1164 -- newBoard :: MonadState b m => m ()
1165 -- Here, MonadState has a fundep m->b, so newBoard is fine
1166 ; let grown_tyvars = grow theta (mkVarSet tyvars)
1167 ; checkTc (tyVarsOfType tau `intersectsVarSet` grown_tyvars)
1168 (noClassTyVarErr cls sel_id)
1170 -- Check that for a generic method, the type of
1171 -- the method is sufficiently simple
1172 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
1173 (badGenericMethodType op_name op_ty)
1176 op_name = idName sel_id
1177 op_ty = idType sel_id
1178 (_,theta1,tau1) = tcSplitSigmaTy op_ty
1179 (_,theta2,tau2) = tcSplitSigmaTy tau1
1180 (theta,tau) | constrained_class_methods = (theta1 ++ theta2, tau2)
1181 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
1182 -- Ugh! The function might have a type like
1183 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
1184 -- With -XConstrainedClassMethods, we want to allow this, even though the inner
1185 -- forall has an (Eq a) constraint. Whereas in general, each constraint
1186 -- in the context of a for-all must mention at least one quantified
1187 -- type variable. What a mess!
1190 ---------------------------------------------------------------------
1191 resultTypeMisMatch :: Name -> DataCon -> DataCon -> SDoc
1192 resultTypeMisMatch field_name con1 con2
1193 = vcat [sep [ptext (sLit "Constructors") <+> ppr con1 <+> ptext (sLit "and") <+> ppr con2,
1194 ptext (sLit "have a common field") <+> quotes (ppr field_name) <> comma],
1195 nest 2 $ ptext (sLit "but have different result types")]
1197 fieldTypeMisMatch :: Name -> DataCon -> DataCon -> SDoc
1198 fieldTypeMisMatch field_name con1 con2
1199 = sep [ptext (sLit "Constructors") <+> ppr con1 <+> ptext (sLit "and") <+> ppr con2,
1200 ptext (sLit "give different types for field"), quotes (ppr field_name)]
1202 dataConCtxt :: Outputable a => a -> SDoc
1203 dataConCtxt con = ptext (sLit "In the definition of data constructor") <+> quotes (ppr con)
1205 classOpCtxt :: Var -> Type -> SDoc
1206 classOpCtxt sel_id tau = sep [ptext (sLit "When checking the class method:"),
1207 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
1209 nullaryClassErr :: Class -> SDoc
1211 = ptext (sLit "No parameters for class") <+> quotes (ppr cls)
1213 classArityErr :: Class -> SDoc
1215 = vcat [ptext (sLit "Too many parameters for class") <+> quotes (ppr cls),
1216 parens (ptext (sLit "Use -XMultiParamTypeClasses to allow multi-parameter classes"))]
1218 classFunDepsErr :: Class -> SDoc
1220 = vcat [ptext (sLit "Fundeps in class") <+> quotes (ppr cls),
1221 parens (ptext (sLit "Use -XFunctionalDependencies to allow fundeps"))]
1223 noClassTyVarErr :: Class -> Var -> SDoc
1224 noClassTyVarErr clas op
1225 = sep [ptext (sLit "The class method") <+> quotes (ppr op),
1226 ptext (sLit "mentions none of the type variables of the class") <+>
1227 ppr clas <+> hsep (map ppr (classTyVars clas))]
1229 genericMultiParamErr :: Class -> SDoc
1230 genericMultiParamErr clas
1231 = ptext (sLit "The multi-parameter class") <+> quotes (ppr clas) <+>
1232 ptext (sLit "cannot have generic methods")
1234 badGenericMethodType :: Name -> Kind -> SDoc
1235 badGenericMethodType op op_ty
1236 = hang (ptext (sLit "Generic method type is too complex"))
1237 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
1238 ptext (sLit "You can only use type variables, arrows, lists, and tuples")])
1240 recSynErr :: [LTyClDecl Name] -> TcRn ()
1242 = setSrcSpan (getLoc (head sorted_decls)) $
1243 addErr (sep [ptext (sLit "Cycle in type synonym declarations:"),
1244 nest 2 (vcat (map ppr_decl sorted_decls))])
1246 sorted_decls = sortLocated syn_decls
1247 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
1249 recClsErr :: [Located (TyClDecl Name)] -> TcRn ()
1251 = setSrcSpan (getLoc (head sorted_decls)) $
1252 addErr (sep [ptext (sLit "Cycle in class declarations (via superclasses):"),
1253 nest 2 (vcat (map ppr_decl sorted_decls))])
1255 sorted_decls = sortLocated cls_decls
1256 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
1258 sortLocated :: [Located a] -> [Located a]
1259 sortLocated things = sortLe le things
1261 le (L l1 _) (L l2 _) = l1 <= l2
1263 badDataConTyCon :: DataCon -> Type -> Type -> SDoc
1264 badDataConTyCon data_con res_ty_tmpl actual_res_ty
1265 = hang (ptext (sLit "Data constructor") <+> quotes (ppr data_con) <+>
1266 ptext (sLit "returns type") <+> quotes (ppr actual_res_ty))
1267 2 (ptext (sLit "instead of an instance of its parent type") <+> quotes (ppr res_ty_tmpl))
1269 badGadtDecl :: Name -> SDoc
1271 = vcat [ ptext (sLit "Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
1272 , nest 2 (parens $ ptext (sLit "Use -XGADTs to allow GADTs")) ]
1274 badExistential :: Located Name -> SDoc
1275 badExistential con_name
1276 = hang (ptext (sLit "Data constructor") <+> quotes (ppr con_name) <+>
1277 ptext (sLit "has existential type variables, or a context"))
1278 2 (parens $ ptext (sLit "Use -XExistentialQuantification or -XGADTs to allow this"))
1280 badStupidTheta :: Name -> SDoc
1281 badStupidTheta tc_name
1282 = ptext (sLit "A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
1284 newtypeConError :: Name -> Int -> SDoc
1285 newtypeConError tycon n
1286 = sep [ptext (sLit "A newtype must have exactly one constructor,"),
1287 nest 2 $ ptext (sLit "but") <+> quotes (ppr tycon) <+> ptext (sLit "has") <+> speakN n ]
1289 newtypeExError :: DataCon -> SDoc
1291 = sep [ptext (sLit "A newtype constructor cannot have an existential context,"),
1292 nest 2 $ ptext (sLit "but") <+> quotes (ppr con) <+> ptext (sLit "does")]
1294 newtypeStrictError :: DataCon -> SDoc
1295 newtypeStrictError con
1296 = sep [ptext (sLit "A newtype constructor cannot have a strictness annotation,"),
1297 nest 2 $ ptext (sLit "but") <+> quotes (ppr con) <+> ptext (sLit "does")]
1299 newtypePredError :: DataCon -> SDoc
1300 newtypePredError con
1301 = sep [ptext (sLit "A newtype constructor must have a return type of form T a1 ... an"),
1302 nest 2 $ ptext (sLit "but") <+> quotes (ppr con) <+> ptext (sLit "does not")]
1304 newtypeFieldErr :: DataCon -> Int -> SDoc
1305 newtypeFieldErr con_name n_flds
1306 = sep [ptext (sLit "The constructor of a newtype must have exactly one field"),
1307 nest 2 $ ptext (sLit "but") <+> quotes (ppr con_name) <+> ptext (sLit "has") <+> speakN n_flds]
1309 badSigTyDecl :: Name -> SDoc
1310 badSigTyDecl tc_name
1311 = vcat [ ptext (sLit "Illegal kind signature") <+>
1312 quotes (ppr tc_name)
1313 , nest 2 (parens $ ptext (sLit "Use -XKindSignatures to allow kind signatures")) ]
1315 badFamInstDecl :: Outputable a => a -> SDoc
1316 badFamInstDecl tc_name
1317 = vcat [ ptext (sLit "Illegal family instance for") <+>
1318 quotes (ppr tc_name)
1319 , nest 2 (parens $ ptext (sLit "Use -XTypeFamilies to allow indexed type families")) ]
1322 badGadtIdxTyDecl :: Name -> SDoc
1323 badGadtIdxTyDecl tc_name
1324 = vcat [ ptext (sLit "Illegal generalised algebraic data declaration for") <+>
1325 quotes (ppr tc_name)
1326 , nest 2 (parens $ ptext (sLit "Family instances can not yet use GADT declarations")) ]
1328 tooManyParmsErr :: Located Name -> SDoc
1329 tooManyParmsErr tc_name
1330 = ptext (sLit "Family instance has too many parameters:") <+>
1331 quotes (ppr tc_name)
1333 tooFewParmsErr :: Arity -> SDoc
1334 tooFewParmsErr arity
1335 = ptext (sLit "Family instance has too few parameters; expected") <+>
1338 wrongNumberOfParmsErr :: Arity -> SDoc
1339 wrongNumberOfParmsErr exp_arity
1340 = ptext (sLit "Number of parameters must match family declaration; expected")
1343 badBootFamInstDeclErr :: SDoc
1344 badBootFamInstDeclErr =
1345 ptext (sLit "Illegal family instance in hs-boot file")
1347 wrongKindOfFamily :: TyCon -> SDoc
1348 wrongKindOfFamily family =
1349 ptext (sLit "Wrong category of family instance; declaration was for a") <+>
1352 kindOfFamily | isSynTyCon family = ptext (sLit "type synonym")
1353 | isAlgTyCon family = ptext (sLit "data type")
1354 | otherwise = pprPanic "wrongKindOfFamily" (ppr family)
1356 emptyConDeclsErr :: Name -> SDoc
1357 emptyConDeclsErr tycon
1358 = sep [quotes (ppr tycon) <+> ptext (sLit "has no constructors"),
1359 nest 2 $ ptext (sLit "(-XEmptyDataDecls permits this)")]