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"
50 import Control.Monad ( mplus )
54 %************************************************************************
56 \subsection{Type checking for type and class declarations}
58 %************************************************************************
62 Consider a mutually-recursive group, binding
63 a type constructor T and a class C.
65 Step 1: getInitialKind
66 Construct a KindEnv by binding T and C to a kind variable
69 In that environment, do a kind check
71 Step 3: Zonk the kinds
73 Step 4: buildTyConOrClass
74 Construct an environment binding T to a TyCon and C to a Class.
75 a) Their kinds comes from zonking the relevant kind variable
76 b) Their arity (for synonyms) comes direct from the decl
77 c) The funcional dependencies come from the decl
78 d) The rest comes a knot-tied binding of T and C, returned from Step 4
79 e) The variances of the tycons in the group is calculated from
83 In this environment, walk over the decls, constructing the TyCons and Classes.
84 This uses in a strict way items (a)-(c) above, which is why they must
85 be constructed in Step 4. Feed the results back to Step 4.
86 For this step, pass the is-recursive flag as the wimp-out flag
90 Step 6: Extend environment
91 We extend the type environment with bindings not only for the TyCons and Classes,
92 but also for their "implicit Ids" like data constructors and class selectors
94 Step 7: checkValidTyCl
95 For a recursive group only, check all the decls again, just
96 to check all the side conditions on validity. We could not
97 do this before because we were in a mutually recursive knot.
99 Identification of recursive TyCons
100 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
101 The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to
104 Identifying a TyCon as recursive serves two purposes
106 1. Avoid infinite types. Non-recursive newtypes are treated as
107 "transparent", like type synonyms, after the type checker. If we did
108 this for all newtypes, we'd get infinite types. So we figure out for
109 each newtype whether it is "recursive", and add a coercion if so. In
110 effect, we are trying to "cut the loops" by identifying a loop-breaker.
112 2. Avoid infinite unboxing. This is nothing to do with newtypes.
116 Well, this function diverges, but we don't want the strictness analyser
117 to diverge. But the strictness analyser will diverge because it looks
118 deeper and deeper into the structure of T. (I believe there are
119 examples where the function does something sane, and the strictness
120 analyser still diverges, but I can't see one now.)
122 Now, concerning (1), the FC2 branch currently adds a coercion for ALL
123 newtypes. I did this as an experiment, to try to expose cases in which
124 the coercions got in the way of optimisations. If it turns out that we
125 can indeed always use a coercion, then we don't risk recursive types,
126 and don't need to figure out what the loop breakers are.
128 For newtype *families* though, we will always have a coercion, so they
129 are always loop breakers! So you can easily adjust the current
130 algorithm by simply treating all newtype families as loop breakers (and
131 indeed type families). I think.
134 tcTyAndClassDecls :: ModDetails -> [LTyClDecl Name]
135 -> TcM TcGblEnv -- Input env extended by types and classes
136 -- and their implicit Ids,DataCons
137 -- Fails if there are any errors
139 tcTyAndClassDecls boot_details allDecls
140 = checkNoErrs $ -- The code recovers internally, but if anything gave rise to
141 -- an error we'd better stop now, to avoid a cascade
142 do { -- Omit instances of type families; they are handled together
143 -- with the *heads* of class instances
144 ; let decls = filter (not . isFamInstDecl . unLoc) allDecls
146 -- First check for cyclic type synonysm or classes
147 -- See notes with checkCycleErrs
148 ; checkCycleErrs decls
150 ; traceTc (text "tcTyAndCl" <+> ppr mod)
151 ; (syn_tycons, alg_tyclss) <- fixM (\ ~(_rec_syn_tycons, rec_alg_tyclss) ->
152 do { let { -- Seperate ordinary synonyms from all other type and
153 -- class declarations and add all associated type
154 -- declarations from type classes. The latter is
155 -- required so that the temporary environment for the
156 -- knot includes all associated family declarations.
157 ; (syn_decls, alg_decls) = partition (isSynDecl . unLoc)
159 ; alg_at_decls = concatMap addATs alg_decls
161 -- Extend the global env with the knot-tied results
162 -- for data types and classes
164 -- We must populate the environment with the loop-tied
165 -- T's right away, because the kind checker may "fault
166 -- in" some type constructors that recursively
168 ; let gbl_things = mkGlobalThings alg_at_decls rec_alg_tyclss
169 ; tcExtendRecEnv gbl_things $ do
171 -- Kind-check the declarations
172 { (kc_syn_decls, kc_alg_decls) <- kcTyClDecls syn_decls alg_decls
174 ; let { -- Calculate rec-flag
175 ; calc_rec = calcRecFlags boot_details rec_alg_tyclss
176 ; tc_decl = addLocM (tcTyClDecl calc_rec) }
178 -- Type-check the type synonyms, and extend the envt
179 ; syn_tycons <- tcSynDecls kc_syn_decls
180 ; tcExtendGlobalEnv syn_tycons $ do
182 -- Type-check the data types and classes
183 { alg_tyclss <- mapM tc_decl kc_alg_decls
184 ; return (syn_tycons, concat alg_tyclss)
186 -- Finished with knot-tying now
187 -- Extend the environment with the finished things
188 ; tcExtendGlobalEnv (syn_tycons ++ alg_tyclss) $ do
190 -- Perform the validity check
191 { traceTc (text "ready for validity check")
192 ; mapM_ (addLocM checkValidTyCl) decls
193 ; traceTc (text "done")
195 -- Add the implicit things;
196 -- we want them in the environment because
197 -- they may be mentioned in interface files
198 -- NB: All associated types and their implicit things will be added a
199 -- second time here. This doesn't matter as the definitions are
201 ; let { implicit_things = concatMap implicitTyThings alg_tyclss }
202 ; traceTc ((text "Adding" <+> ppr alg_tyclss)
203 $$ (text "and" <+> ppr implicit_things))
204 ; tcExtendGlobalEnv implicit_things getGblEnv
207 -- Pull associated types out of class declarations, to tie them into the
209 -- NB: We put them in the same place in the list as `tcTyClDecl' will
210 -- eventually put the matching `TyThing's. That's crucial; otherwise,
211 -- the two argument lists of `mkGlobalThings' don't match up.
212 addATs decl@(L _ (ClassDecl {tcdATs = ats})) = decl : ats
215 mkGlobalThings :: [LTyClDecl Name] -- The decls
216 -> [TyThing] -- Knot-tied, in 1-1 correspondence with the decls
218 -- Driven by the Decls, and treating the TyThings lazily
219 -- make a TypeEnv for the new things
220 mkGlobalThings decls things
221 = map mk_thing (decls `zipLazy` things)
223 mk_thing (L _ (ClassDecl {tcdLName = L _ name}), ~(AClass cl))
225 mk_thing (L _ decl, ~(ATyCon tc))
226 = (tcdName decl, ATyCon tc)
230 %************************************************************************
232 \subsection{Type checking family instances}
234 %************************************************************************
236 Family instances are somewhat of a hybrid. They are processed together with
237 class instance heads, but can contain data constructors and hence they share a
238 lot of kinding and type checking code with ordinary algebraic data types (and
242 tcFamInstDecl :: LTyClDecl Name -> TcM (Maybe TyThing) -- Nothing if error
243 tcFamInstDecl (L loc decl)
244 = -- Prime error recovery, set source location
245 recoverM (return Nothing) $
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 (Just (ATyCon tc))
262 tcFamInstDecl1 :: TyClDecl Name -> TcM TyCon
265 tcFamInstDecl1 (decl@TySynonym {tcdLName = L loc tc_name})
266 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
267 do { -- check that the family declaration is for a synonym
268 unless (isSynTyCon family) $
269 addErr (wrongKindOfFamily family)
271 ; -- (1) kind check the right-hand side of the type equation
272 ; k_rhs <- kcCheckHsType (tcdSynRhs decl) resKind
274 -- we need the exact same number of type parameters as the family
276 ; let famArity = tyConArity family
277 ; checkTc (length k_typats == famArity) $
278 wrongNumberOfParmsErr famArity
280 -- (2) type check type equation
281 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
282 ; t_typats <- mapM tcHsKindedType k_typats
283 ; t_rhs <- tcHsKindedType k_rhs
286 -- - check the well-formedness of the instance
287 ; checkValidTypeInst t_typats t_rhs
289 -- (4) construct representation tycon
290 ; rep_tc_name <- newFamInstTyConName tc_name loc
291 ; buildSynTyCon rep_tc_name t_tvs (SynonymTyCon t_rhs)
292 (Just (family, t_typats))
295 -- "newtype instance" and "data instance"
296 tcFamInstDecl1 (decl@TyData {tcdND = new_or_data, tcdLName = L loc tc_name,
298 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
299 do { -- check that the family declaration is for the right kind
300 unless (isAlgTyCon family) $
301 addErr (wrongKindOfFamily family)
303 ; -- (1) kind check the data declaration as usual
304 ; k_decl <- kcDataDecl decl k_tvs
305 ; let k_ctxt = tcdCtxt k_decl
306 k_cons = tcdCons k_decl
308 -- result kind must be '*' (otherwise, we have too few patterns)
309 ; checkTc (isLiftedTypeKind resKind) $ tooFewParmsErr (tyConArity family)
311 -- (2) type check indexed data type declaration
312 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
313 ; unbox_strict <- doptM Opt_UnboxStrictFields
315 -- kind check the type indexes and the context
316 ; t_typats <- mapM tcHsKindedType k_typats
317 ; stupid_theta <- tcHsKindedContext k_ctxt
320 -- - left-hand side contains no type family applications
321 -- (vanilla synonyms are fine, though, and we checked for
323 ; mapM_ checkTyFamFreeness t_typats
325 -- - we don't use GADT syntax for indexed types
326 ; checkTc h98_syntax (badGadtIdxTyDecl tc_name)
328 -- - a newtype has exactly one constructor
329 ; checkTc (new_or_data == DataType || isSingleton k_cons) $
330 newtypeConError tc_name (length k_cons)
332 -- (4) construct representation tycon
333 ; rep_tc_name <- newFamInstTyConName tc_name loc
334 ; let ex_ok = True -- Existentials ok for type families!
335 ; fixM (\ tycon -> do
336 { data_cons <- mapM (addLocM (tcConDecl unbox_strict ex_ok tycon t_tvs))
340 DataType -> return (mkDataTyConRhs data_cons)
341 NewType -> ASSERT( not (null data_cons) )
342 mkNewTyConRhs rep_tc_name tycon (head data_cons)
343 ; buildAlgTyCon rep_tc_name t_tvs stupid_theta tc_rhs Recursive
344 False h98_syntax (Just (family, t_typats))
345 -- We always assume that indexed types are recursive. Why?
346 -- (1) Due to their open nature, we can never be sure that a
347 -- further instance might not introduce a new recursive
348 -- dependency. (2) They are always valid loop breakers as
349 -- they involve a coercion.
353 h98_syntax = case cons of -- All constructors have same shape
354 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
357 tcFamInstDecl1 d = pprPanic "tcFamInstDecl1" (ppr d)
359 -- Kind checking of indexed types
362 -- Kind check type patterns and kind annotate the embedded type variables.
364 -- * Here we check that a type instance matches its kind signature, but we do
365 -- not check whether there is a pattern for each type index; the latter
366 -- check is only required for type synonym instances.
368 kcIdxTyPats :: TyClDecl Name
369 -> ([LHsTyVarBndr Name] -> [LHsType Name] -> Kind -> TyCon -> TcM a)
370 -- ^^kinded tvs ^^kinded ty pats ^^res kind
372 kcIdxTyPats decl thing_inside
373 = kcHsTyVars (tcdTyVars decl) $ \tvs ->
374 do { family <- tcLookupLocatedTyCon (tcdLName decl)
375 ; let { (kinds, resKind) = splitKindFunTys (tyConKind family)
376 ; hs_typats = fromJust $ tcdTyPats decl }
378 -- we may not have more parameters than the kind indicates
379 ; checkTc (length kinds >= length hs_typats) $
380 tooManyParmsErr (tcdLName decl)
382 -- type functions can have a higher-kinded result
383 ; let resultKind = mkArrowKinds (drop (length hs_typats) kinds) resKind
384 ; typats <- zipWithM kcCheckHsType hs_typats kinds
385 ; thing_inside tvs typats resultKind family
391 %************************************************************************
395 %************************************************************************
397 We need to kind check all types in the mutually recursive group
398 before we know the kind of the type variables. For example:
401 op :: D b => a -> b -> b
404 bop :: (Monad c) => ...
406 Here, the kind of the locally-polymorphic type variable "b"
407 depends on *all the uses of class D*. For example, the use of
408 Monad c in bop's type signature means that D must have kind Type->Type.
410 However type synonyms work differently. They can have kinds which don't
411 just involve (->) and *:
412 type R = Int# -- Kind #
413 type S a = Array# a -- Kind * -> #
414 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
415 So we must infer their kinds from their right-hand sides *first* and then
416 use them, whereas for the mutually recursive data types D we bring into
417 scope kind bindings D -> k, where k is a kind variable, and do inference.
421 This treatment of type synonyms only applies to Haskell 98-style synonyms.
422 General type functions can be recursive, and hence, appear in `alg_decls'.
424 The kind of a type family is solely determinded by its kind signature;
425 hence, only kind signatures participate in the construction of the initial
426 kind environment (as constructed by `getInitialKind'). In fact, we ignore
427 instances of families altogether in the following. However, we need to
428 include the kinds of associated families into the construction of the
429 initial kind environment. (This is handled by `allDecls').
432 kcTyClDecls :: [LTyClDecl Name] -> [Located (TyClDecl Name)]
433 -> TcM ([LTyClDecl Name], [Located (TyClDecl Name)])
434 kcTyClDecls syn_decls alg_decls
435 = do { -- First extend the kind env with each data type, class, and
436 -- indexed type, mapping them to a type variable
437 let initialKindDecls = concat [allDecls decl | L _ decl <- alg_decls]
438 ; alg_kinds <- mapM getInitialKind initialKindDecls
439 ; tcExtendKindEnv alg_kinds $ do
441 -- Now kind-check the type synonyms, in dependency order
442 -- We do these differently to data type and classes,
443 -- because a type synonym can be an unboxed type
445 -- and a kind variable can't unify with UnboxedTypeKind
446 -- So we infer their kinds in dependency order
447 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
448 ; tcExtendKindEnv syn_kinds $ do
450 -- Now kind-check the data type, class, and kind signatures,
451 -- returning kind-annotated decls; we don't kind-check
452 -- instances of indexed types yet, but leave this to
454 { kc_alg_decls <- mapM (wrapLocM kcTyClDecl)
455 (filter (not . isFamInstDecl . unLoc) alg_decls)
457 ; return (kc_syn_decls, kc_alg_decls) }}}
459 -- get all declarations relevant for determining the initial kind
461 allDecls (decl@ClassDecl {tcdATs = ats}) = decl : [ at
464 allDecls decl | isFamInstDecl decl = []
467 ------------------------------------------------------------------------
468 getInitialKind :: TyClDecl Name -> TcM (Name, TcKind)
469 -- Only for data type, class, and indexed type declarations
470 -- Get as much info as possible from the data, class, or indexed type decl,
471 -- so as to maximise usefulness of error messages
473 = do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl)
474 ; res_kind <- mk_res_kind decl
475 ; return (tcdName decl, mkArrowKinds arg_kinds res_kind) }
477 mk_arg_kind (UserTyVar _) = newKindVar
478 mk_arg_kind (KindedTyVar _ kind) = return kind
480 mk_res_kind (TyFamily { tcdKind = Just kind }) = return kind
481 mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
482 -- On GADT-style declarations we allow a kind signature
483 -- data T :: *->* where { ... }
484 mk_res_kind _ = return liftedTypeKind
488 kcSynDecls :: [SCC (LTyClDecl Name)]
489 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
490 [(Name,TcKind)]) -- Kind bindings
493 kcSynDecls (group : groups)
494 = do { (decl, nk) <- kcSynDecl group
495 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
496 ; return (decl:decls, nk:nks) }
499 kcSynDecl :: SCC (LTyClDecl Name)
500 -> TcM (LTyClDecl Name, -- Kind-annotated decls
501 (Name,TcKind)) -- Kind bindings
502 kcSynDecl (AcyclicSCC (L loc decl))
503 = tcAddDeclCtxt decl $
504 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
505 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
506 <+> brackets (ppr k_tvs))
507 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
508 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
509 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
510 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
511 (unLoc (tcdLName decl), tc_kind)) })
513 kcSynDecl (CyclicSCC decls)
514 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
515 -- of out-of-scope tycons
517 kindedTyVarKind :: LHsTyVarBndr Name -> Kind
518 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
519 kindedTyVarKind x = pprPanic "kindedTyVarKind" (ppr x)
521 ------------------------------------------------------------------------
522 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
523 -- Not used for type synonyms (see kcSynDecl)
525 kcTyClDecl decl@(TyData {})
526 = ASSERT( not . isFamInstDecl $ decl ) -- must not be a family instance
527 kcTyClDeclBody decl $
530 kcTyClDecl decl@(TyFamily {})
531 = kcFamilyDecl [] decl -- the empty list signals a toplevel decl
533 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs, tcdATs = ats})
534 = kcTyClDeclBody decl $ \ tvs' ->
535 do { ctxt' <- kcHsContext ctxt
536 ; ats' <- mapM (wrapLocM (kcFamilyDecl tvs')) ats
537 ; sigs' <- mapM (wrapLocM kc_sig) sigs
538 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs',
541 kc_sig (TypeSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
542 ; return (TypeSig nm op_ty') }
543 kc_sig other_sig = return other_sig
545 kcTyClDecl decl@(ForeignType {})
548 kcTyClDecl (TySynonym {}) = panic "kcTyClDecl TySynonym"
550 kcTyClDeclBody :: TyClDecl Name
551 -> ([LHsTyVarBndr Name] -> TcM a)
553 -- getInitialKind has made a suitably-shaped kind for the type or class
554 -- Unpack it, and attribute those kinds to the type variables
555 -- Extend the env with bindings for the tyvars, taken from
556 -- the kind of the tycon/class. Give it to the thing inside, and
557 -- check the result kind matches
558 kcTyClDeclBody decl thing_inside
559 = tcAddDeclCtxt decl $
560 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
561 ; let tc_kind = case tc_ty_thing of
563 _ -> pprPanic "kcTyClDeclBody" (ppr tc_ty_thing)
564 (kinds, _) = splitKindFunTys tc_kind
565 hs_tvs = tcdTyVars decl
566 kinded_tvs = ASSERT( length kinds >= length hs_tvs )
567 [ L loc (KindedTyVar (hsTyVarName tv) k)
568 | (L loc tv, k) <- zip hs_tvs kinds]
569 ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
571 -- Kind check a data declaration, assuming that we already extended the
572 -- kind environment with the type variables of the left-hand side (these
573 -- kinded type variables are also passed as the second parameter).
575 kcDataDecl :: TyClDecl Name -> [LHsTyVarBndr Name] -> TcM (TyClDecl Name)
576 kcDataDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
578 = do { ctxt' <- kcHsContext ctxt
579 ; cons' <- mapM (wrapLocM kc_con_decl) cons
580 ; return (decl {tcdTyVars = tvs, tcdCtxt = ctxt', tcdCons = cons'}) }
582 -- doc comments are typechecked to Nothing here
583 kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res _) = do
584 kcHsTyVars ex_tvs $ \ex_tvs' -> do
585 ex_ctxt' <- kcHsContext ex_ctxt
586 details' <- kc_con_details details
588 ResTyH98 -> return ResTyH98
589 ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
590 return (ConDecl name expl ex_tvs' ex_ctxt' details' res' Nothing)
592 kc_con_details (PrefixCon btys)
593 = do { btys' <- mapM kc_larg_ty btys
594 ; return (PrefixCon btys') }
595 kc_con_details (InfixCon bty1 bty2)
596 = do { bty1' <- kc_larg_ty bty1
597 ; bty2' <- kc_larg_ty bty2
598 ; return (InfixCon bty1' bty2') }
599 kc_con_details (RecCon fields)
600 = do { fields' <- mapM kc_field fields
601 ; return (RecCon fields') }
603 kc_field (ConDeclField fld bty d) = do { bty' <- kc_larg_ty bty
604 ; return (ConDeclField fld bty' d) }
606 kc_larg_ty bty = case new_or_data of
607 DataType -> kcHsSigType bty
608 NewType -> kcHsLiftedSigType bty
609 -- Can't allow an unlifted type for newtypes, because we're effectively
610 -- going to remove the constructor while coercing it to a lifted type.
611 -- And newtypes can't be bang'd
612 kcDataDecl d _ = pprPanic "kcDataDecl" (ppr d)
614 -- Kind check a family declaration or type family default declaration.
616 kcFamilyDecl :: [LHsTyVarBndr Name] -- tyvars of enclosing class decl if any
617 -> TyClDecl Name -> TcM (TyClDecl Name)
618 kcFamilyDecl classTvs decl@(TyFamily {tcdKind = kind})
619 = kcTyClDeclBody decl $ \tvs' ->
620 do { mapM_ unifyClassParmKinds tvs'
621 ; return (decl {tcdTyVars = tvs',
622 tcdKind = kind `mplus` Just liftedTypeKind})
623 -- default result kind is '*'
626 unifyClassParmKinds (L _ (KindedTyVar n k))
627 | Just classParmKind <- lookup n classTyKinds = unifyKind k classParmKind
628 | otherwise = return ()
629 unifyClassParmKinds x = pprPanic "kcFamilyDecl/unifyClassParmKinds" (ppr x)
630 classTyKinds = [(n, k) | L _ (KindedTyVar n k) <- classTvs]
631 kcFamilyDecl _ (TySynonym {}) -- type family defaults
632 = panic "TcTyClsDecls.kcFamilyDecl: not implemented yet"
633 kcFamilyDecl _ d = pprPanic "kcFamilyDecl" (ppr d)
637 %************************************************************************
639 \subsection{Type checking}
641 %************************************************************************
644 tcSynDecls :: [LTyClDecl Name] -> TcM [TyThing]
645 tcSynDecls [] = return []
646 tcSynDecls (decl : decls)
647 = do { syn_tc <- addLocM tcSynDecl decl
648 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls decls)
649 ; return (syn_tc : syn_tcs) }
652 tcSynDecl :: TyClDecl Name -> TcM TyThing
654 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
655 = tcTyVarBndrs tvs $ \ tvs' -> do
656 { traceTc (text "tcd1" <+> ppr tc_name)
657 ; rhs_ty' <- tcHsKindedType rhs_ty
658 ; tycon <- buildSynTyCon tc_name tvs' (SynonymTyCon rhs_ty') Nothing
659 ; return (ATyCon tycon)
661 tcSynDecl d = pprPanic "tcSynDecl" (ppr d)
664 tcTyClDecl :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
666 tcTyClDecl calc_isrec decl
667 = tcAddDeclCtxt decl (tcTyClDecl1 calc_isrec decl)
669 -- "type family" declarations
670 tcTyClDecl1 :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
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 -XTypeFamilies
682 ; checkTc idx_tys $ badFamInstDecl tc_name
684 ; tycon <- buildSynTyCon tc_name tvs' (OpenSynTyCon kind Nothing) Nothing
685 ; return [ATyCon tycon]
688 -- "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 -XTypeFamilies
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 -- NB: not used for newtype/data instances (whether associated or not)
709 tcTyClDecl1 calc_isrec
710 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
711 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
712 = tcTyVarBndrs tvs $ \ tvs' -> do
713 { extra_tvs <- tcDataKindSig mb_ksig
714 ; let final_tvs = tvs' ++ extra_tvs
715 ; stupid_theta <- tcHsKindedContext ctxt
716 ; want_generic <- doptM Opt_Generics
717 ; unbox_strict <- doptM Opt_UnboxStrictFields
718 ; empty_data_decls <- doptM Opt_EmptyDataDecls
719 ; kind_signatures <- doptM Opt_KindSignatures
720 ; existential_ok <- doptM Opt_ExistentialQuantification
721 ; gadt_ok <- doptM Opt_GADTs
722 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
723 ; let ex_ok = existential_ok || gadt_ok -- Data cons can have existential context
725 -- Check that we don't use GADT syntax in H98 world
726 ; checkTc (gadt_ok || h98_syntax) (badGadtDecl tc_name)
728 -- Check that we don't use kind signatures without Glasgow extensions
729 ; checkTc (kind_signatures || isNothing mb_ksig) (badSigTyDecl tc_name)
731 -- Check that the stupid theta is empty for a GADT-style declaration
732 ; checkTc (null stupid_theta || h98_syntax) (badStupidTheta tc_name)
734 -- Check that a newtype has exactly one constructor
735 -- Do this before checking for empty data decls, so that
736 -- we don't suggest -XEmptyDataDecls for newtypes
737 ; checkTc (new_or_data == DataType || isSingleton cons)
738 (newtypeConError tc_name (length cons))
740 -- Check that there's at least one condecl,
741 -- or else we're reading an hs-boot file, or -XEmptyDataDecls
742 ; checkTc (not (null cons) || empty_data_decls || is_boot)
743 (emptyConDeclsErr tc_name)
745 ; tycon <- fixM (\ tycon -> do
746 { data_cons <- mapM (addLocM (tcConDecl unbox_strict ex_ok tycon final_tvs))
749 if null cons && is_boot -- In a hs-boot file, empty cons means
750 then return AbstractTyCon -- "don't know"; hence Abstract
751 else case new_or_data of
752 DataType -> return (mkDataTyConRhs data_cons)
754 ASSERT( not (null data_cons) )
755 mkNewTyConRhs tc_name tycon (head data_cons)
756 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
757 (want_generic && canDoGenerics data_cons) h98_syntax Nothing
759 ; return [ATyCon tycon]
762 is_rec = calc_isrec tc_name
763 h98_syntax = case cons of -- All constructors have same shape
764 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
767 tcTyClDecl1 calc_isrec
768 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
769 tcdCtxt = ctxt, tcdMeths = meths,
770 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
771 = tcTyVarBndrs tvs $ \ tvs' -> do
772 { ctxt' <- tcHsKindedContext ctxt
773 ; fds' <- mapM (addLocM tc_fundep) fundeps
774 ; atss <- mapM (addLocM (tcTyClDecl1 (const Recursive))) ats
775 -- NB: 'ats' only contains "type family" and "data family"
776 -- declarations as well as type family defaults
777 ; let ats' = zipWith setTyThingPoss atss (map (tcdTyVars . unLoc) ats)
778 ; sig_stuff <- tcClassSigs class_name sigs meths
779 ; clas <- fixM (\ clas ->
780 let -- This little knot is just so we can get
781 -- hold of the name of the class TyCon, which we
782 -- need to look up its recursiveness
783 tycon_name = tyConName (classTyCon clas)
784 tc_isrec = calc_isrec tycon_name
786 buildClass False {- Must include unfoldings for selectors -}
787 class_name tvs' ctxt' fds' ats'
789 ; return (AClass clas : ats')
790 -- NB: Order is important due to the call to `mkGlobalThings' when
791 -- tying the the type and class declaration type checking knot.
794 tc_fundep (tvs1, tvs2) = do { tvs1' <- mapM tcLookupTyVar tvs1 ;
795 ; tvs2' <- mapM tcLookupTyVar tvs2 ;
796 ; return (tvs1', tvs2') }
798 -- For each AT argument compute the position of the corresponding class
799 -- parameter in the class head. This will later serve as a permutation
800 -- vector when checking the validity of instance declarations.
801 setTyThingPoss [ATyCon tycon] atTyVars =
802 let classTyVars = hsLTyVarNames tvs
804 . map (`elemIndex` classTyVars)
807 -- There will be no Nothing, as we already passed renaming
809 ATyCon (setTyConArgPoss tycon poss)
810 setTyThingPoss _ _ = panic "TcTyClsDecls.setTyThingPoss"
813 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
814 = return [ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0)]
816 tcTyClDecl1 _ d = pprPanic "tcTyClDecl1" (ppr d)
818 -----------------------------------
819 tcConDecl :: Bool -- True <=> -funbox-strict_fields
820 -> Bool -- True <=> -XExistentialQuantificaton or -XGADTs
825 tcConDecl unbox_strict existential_ok tycon tc_tvs -- Data types
826 (ConDecl name _ tvs ctxt details res_ty _)
827 = addErrCtxt (dataConCtxt name) $
828 tcTyVarBndrs tvs $ \ tvs' -> do
829 { ctxt' <- tcHsKindedContext ctxt
830 ; checkTc (existential_ok || (null tvs && null (unLoc ctxt)))
831 (badExistential name)
832 ; (univ_tvs, ex_tvs, eq_preds, data_tc) <- tcResultType tycon tc_tvs tvs' res_ty
834 -- Tiresome: tidy the tyvar binders, since tc_tvs and tvs' may have the same OccNames
835 tc_datacon is_infix field_lbls btys
836 = do { let bangs = map getBangStrictness btys
837 ; arg_tys <- mapM tcHsBangType btys
838 ; buildDataCon (unLoc name) is_infix
839 (argStrictness unbox_strict bangs arg_tys)
840 (map unLoc field_lbls)
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 cd_fld_name fields
853 btys = map cd_fld_type fields
856 tcResultType :: TyCon
857 -> [TyVar] -- data T a b c = ...
858 -> [TyVar] -- where MkT :: forall a b c. ...
860 -> TcM ([TyVar], -- Universal
861 [TyVar], -- Existential (distinct OccNames from univs)
862 [(TyVar,Type)], -- Equality predicates
863 TyCon) -- TyCon given in the ResTy
864 -- We don't check that the TyCon given in the ResTy is
865 -- the same as the parent tycon, becuase we are in the middle
866 -- of a recursive knot; so it's postponed until checkValidDataCon
868 tcResultType decl_tycon tc_tvs dc_tvs ResTyH98
869 = return (tc_tvs, dc_tvs, [], decl_tycon)
870 -- In H98 syntax the dc_tvs are the existential ones
871 -- data T a b c = forall d e. MkT ...
872 -- The {a,b,c} are tc_tvs, and {d,e} are dc_tvs
874 tcResultType _ tc_tvs dc_tvs (ResTyGADT res_ty)
875 -- E.g. data T a b c where
876 -- MkT :: forall x y z. T (x,y) z z
878 -- ([a,z,c], [x,y], [a:=:(x,y), c:=:z], T)
880 = do { (dc_tycon, res_tys) <- tcLHsConResTy res_ty
882 ; let univ_tvs = choose_univs [] tidy_tc_tvs res_tys
883 -- Each univ_tv is either a dc_tv or a tc_tv
884 ex_tvs = dc_tvs `minusList` univ_tvs
885 eq_spec = [ (tv, ty) | (tv,ty) <- univ_tvs `zip` res_tys,
887 ; return (univ_tvs, ex_tvs, eq_spec, dc_tycon) }
889 -- choose_univs uses the res_ty itself if it's a type variable
890 -- and hasn't already been used; otherwise it uses one of the tc_tvs
891 choose_univs _ tc_tvs []
892 = ASSERT( null tc_tvs ) []
893 choose_univs used (tc_tv:tc_tvs) (res_ty:res_tys)
894 | Just tv <- tcGetTyVar_maybe res_ty, not (tv `elem` used)
895 = tv : choose_univs (tv:used) tc_tvs res_tys
897 = tc_tv : choose_univs used tc_tvs res_tys
899 -- NB: tc_tvs and dc_tvs are distinct, but
900 -- we want them to be *visibly* distinct, both for
901 -- interface files and general confusion. So rename
902 -- the tc_tvs, since they are not used yet (no
903 -- consequential renaming needed)
904 choose_univs _ _ _ = panic "tcResultType/choose_univs"
905 init_occ_env = initTidyOccEnv (map getOccName dc_tvs)
906 (_, tidy_tc_tvs) = mapAccumL tidy_one init_occ_env tc_tvs
907 tidy_one env tv = (env', setTyVarName tv (tidyNameOcc name occ'))
910 (env', occ') = tidyOccName env (getOccName name)
913 argStrictness :: Bool -- True <=> -funbox-strict_fields
915 -> [TcType] -> [StrictnessMark]
916 argStrictness unbox_strict bangs arg_tys
917 = ASSERT( length bangs == length arg_tys )
918 zipWith (chooseBoxingStrategy unbox_strict) arg_tys bangs
920 -- We attempt to unbox/unpack a strict field when either:
921 -- (i) The field is marked '!!', or
922 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
924 -- We have turned off unboxing of newtypes because coercions make unboxing
925 -- and reboxing more complicated
926 chooseBoxingStrategy :: Bool -> TcType -> HsBang -> StrictnessMark
927 chooseBoxingStrategy unbox_strict_fields arg_ty bang
929 HsNoBang -> NotMarkedStrict
930 HsStrict | unbox_strict_fields
931 && can_unbox arg_ty -> MarkedUnboxed
932 HsUnbox | can_unbox arg_ty -> MarkedUnboxed
935 -- we can unbox if the type is a chain of newtypes with a product tycon
937 can_unbox arg_ty = case splitTyConApp_maybe arg_ty of
939 Just (arg_tycon, tycon_args) ->
940 not (isRecursiveTyCon arg_tycon) && -- Note [Recusive unboxing]
941 isProductTyCon arg_tycon &&
942 (if isNewTyCon arg_tycon then
943 can_unbox (newTyConInstRhs arg_tycon tycon_args)
947 Note [Recursive unboxing]
948 ~~~~~~~~~~~~~~~~~~~~~~~~~
949 Be careful not to try to unbox this!
951 But it's the *argument* type that matters. This is fine:
953 because Int is non-recursive.
955 %************************************************************************
957 \subsection{Dependency analysis}
959 %************************************************************************
961 Validity checking is done once the mutually-recursive knot has been
962 tied, so we can look at things freely.
965 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
966 checkCycleErrs tyclss
970 = do { mapM_ recClsErr cls_cycles
971 ; failM } -- Give up now, because later checkValidTyCl
972 -- will loop if the synonym is recursive
974 cls_cycles = calcClassCycles tyclss
976 checkValidTyCl :: TyClDecl Name -> TcM ()
977 -- We do the validity check over declarations, rather than TyThings
978 -- only so that we can add a nice context with tcAddDeclCtxt
980 = tcAddDeclCtxt decl $
981 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
982 ; traceTc (text "Validity of" <+> ppr thing)
984 ATyCon tc -> checkValidTyCon tc
985 AClass cl -> checkValidClass cl
986 _ -> panic "checkValidTyCl"
987 ; traceTc (text "Done validity of" <+> ppr thing)
990 -------------------------
991 -- For data types declared with record syntax, we require
992 -- that each constructor that has a field 'f'
993 -- (a) has the same result type
994 -- (b) has the same type for 'f'
995 -- module alpha conversion of the quantified type variables
996 -- of the constructor.
998 checkValidTyCon :: TyCon -> TcM ()
1001 = case synTyConRhs tc of
1002 OpenSynTyCon _ _ -> return ()
1003 SynonymTyCon ty -> checkValidType syn_ctxt ty
1005 = do -- Check the context on the data decl
1006 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc)
1008 -- Check arg types of data constructors
1009 mapM_ (checkValidDataCon tc) data_cons
1011 -- Check that fields with the same name share a type
1012 mapM_ check_fields groups
1015 syn_ctxt = TySynCtxt name
1017 data_cons = tyConDataCons tc
1019 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
1020 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
1021 get_fields con = dataConFieldLabels con `zip` repeat con
1022 -- dataConFieldLabels may return the empty list, which is fine
1024 -- See Note [GADT record selectors] in MkId.lhs
1025 -- We must check (a) that the named field has the same
1026 -- type in each constructor
1027 -- (b) that those constructors have the same result type
1029 -- However, the constructors may have differently named type variable
1030 -- and (worse) we don't know how the correspond to each other. E.g.
1031 -- C1 :: forall a b. { f :: a, g :: b } -> T a b
1032 -- C2 :: forall d c. { f :: c, g :: c } -> T c d
1034 -- So what we do is to ust Unify.tcMatchTys to compare the first candidate's
1035 -- result type against other candidates' types BOTH WAYS ROUND.
1036 -- If they magically agrees, take the substitution and
1037 -- apply them to the latter ones, and see if they match perfectly.
1038 check_fields ((label, con1) : other_fields)
1039 -- These fields all have the same name, but are from
1040 -- different constructors in the data type
1041 = recoverM (return ()) $ mapM_ checkOne other_fields
1042 -- Check that all the fields in the group have the same type
1043 -- NB: this check assumes that all the constructors of a given
1044 -- data type use the same type variables
1046 (tvs1, _, _, res1) = dataConSig con1
1048 fty1 = dataConFieldType con1 label
1050 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
1051 = do { checkFieldCompat label con1 con2 ts1 res1 res2 fty1 fty2
1052 ; checkFieldCompat label con2 con1 ts2 res2 res1 fty2 fty1 }
1054 (tvs2, _, _, res2) = dataConSig con2
1056 fty2 = dataConFieldType con2 label
1057 check_fields [] = panic "checkValidTyCon/check_fields []"
1059 checkFieldCompat :: Name -> DataCon -> DataCon -> TyVarSet
1060 -> Type -> Type -> Type -> Type -> TcM ()
1061 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
1062 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
1063 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
1065 mb_subst1 = tcMatchTy tvs1 res1 res2
1066 mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
1068 -------------------------------
1069 checkValidDataCon :: TyCon -> DataCon -> TcM ()
1070 checkValidDataCon tc con
1071 = setSrcSpan (srcLocSpan (getSrcLoc con)) $
1072 addErrCtxt (dataConCtxt con) $
1073 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
1074 ; checkValidType ctxt (dataConUserType con)
1075 ; checkValidMonoType (dataConOrigResTy con)
1076 -- Disallow MkT :: T (forall a. a->a)
1077 -- Reason: it's really the argument of an equality constraint
1078 ; when (isNewTyCon tc) (checkNewDataCon con)
1081 ctxt = ConArgCtxt (dataConName con)
1083 -------------------------------
1084 checkNewDataCon :: DataCon -> TcM ()
1085 -- Checks for the data constructor of a newtype
1087 = do { checkTc (isSingleton arg_tys) (newtypeFieldErr con (length arg_tys))
1089 ; checkTc (null eq_spec) (newtypePredError con)
1090 -- Return type is (T a b c)
1091 ; checkTc (null ex_tvs && null eq_theta && null dict_theta) (newtypeExError con)
1093 ; checkTc (not (any isMarkedStrict (dataConStrictMarks con)))
1094 (newtypeStrictError con)
1098 (_univ_tvs, ex_tvs, eq_spec, eq_theta, dict_theta, arg_tys, _res_ty) = dataConFullSig con
1100 -------------------------------
1101 checkValidClass :: Class -> TcM ()
1103 = do { constrained_class_methods <- doptM Opt_ConstrainedClassMethods
1104 ; multi_param_type_classes <- doptM Opt_MultiParamTypeClasses
1105 ; fundep_classes <- doptM Opt_FunctionalDependencies
1107 -- Check that the class is unary, unless GlaExs
1108 ; checkTc (notNull tyvars) (nullaryClassErr cls)
1109 ; checkTc (multi_param_type_classes || unary) (classArityErr cls)
1110 ; checkTc (fundep_classes || null fundeps) (classFunDepsErr cls)
1112 -- Check the super-classes
1113 ; checkValidTheta (ClassSCCtxt (className cls)) theta
1115 -- Check the class operations
1116 ; mapM_ (check_op constrained_class_methods) op_stuff
1118 -- Check that if the class has generic methods, then the
1119 -- class has only one parameter. We can't do generic
1120 -- multi-parameter type classes!
1121 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
1124 (tyvars, fundeps, theta, _, _, op_stuff) = classExtraBigSig cls
1125 unary = isSingleton tyvars
1126 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
1128 check_op constrained_class_methods (sel_id, dm)
1129 = addErrCtxt (classOpCtxt sel_id tau) $ do
1130 { checkValidTheta SigmaCtxt (tail theta)
1131 -- The 'tail' removes the initial (C a) from the
1132 -- class itself, leaving just the method type
1134 ; traceTc (text "class op type" <+> ppr op_ty <+> ppr tau)
1135 ; checkValidType (FunSigCtxt op_name) tau
1137 -- Check that the type mentions at least one of
1138 -- the class type variables...or at least one reachable
1139 -- from one of the class variables. Example: tc223
1140 -- class Error e => Game b mv e | b -> mv e where
1141 -- newBoard :: MonadState b m => m ()
1142 -- Here, MonadState has a fundep m->b, so newBoard is fine
1143 ; let grown_tyvars = grow theta (mkVarSet tyvars)
1144 ; checkTc (tyVarsOfType tau `intersectsVarSet` grown_tyvars)
1145 (noClassTyVarErr cls sel_id)
1147 -- Check that for a generic method, the type of
1148 -- the method is sufficiently simple
1149 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
1150 (badGenericMethodType op_name op_ty)
1153 op_name = idName sel_id
1154 op_ty = idType sel_id
1155 (_,theta1,tau1) = tcSplitSigmaTy op_ty
1156 (_,theta2,tau2) = tcSplitSigmaTy tau1
1157 (theta,tau) | constrained_class_methods = (theta1 ++ theta2, tau2)
1158 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
1159 -- Ugh! The function might have a type like
1160 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
1161 -- With -XConstrainedClassMethods, we want to allow this, even though the inner
1162 -- forall has an (Eq a) constraint. Whereas in general, each constraint
1163 -- in the context of a for-all must mention at least one quantified
1164 -- type variable. What a mess!
1167 ---------------------------------------------------------------------
1168 resultTypeMisMatch :: Name -> DataCon -> DataCon -> SDoc
1169 resultTypeMisMatch field_name con1 con2
1170 = vcat [sep [ptext (sLit "Constructors") <+> ppr con1 <+> ptext (sLit "and") <+> ppr con2,
1171 ptext (sLit "have a common field") <+> quotes (ppr field_name) <> comma],
1172 nest 2 $ ptext (sLit "but have different result types")]
1174 fieldTypeMisMatch :: Name -> DataCon -> DataCon -> SDoc
1175 fieldTypeMisMatch field_name con1 con2
1176 = sep [ptext (sLit "Constructors") <+> ppr con1 <+> ptext (sLit "and") <+> ppr con2,
1177 ptext (sLit "give different types for field"), quotes (ppr field_name)]
1179 dataConCtxt :: Outputable a => a -> SDoc
1180 dataConCtxt con = ptext (sLit "In the definition of data constructor") <+> quotes (ppr con)
1182 classOpCtxt :: Var -> Type -> SDoc
1183 classOpCtxt sel_id tau = sep [ptext (sLit "When checking the class method:"),
1184 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
1186 nullaryClassErr :: Class -> SDoc
1188 = ptext (sLit "No parameters for class") <+> quotes (ppr cls)
1190 classArityErr :: Class -> SDoc
1192 = vcat [ptext (sLit "Too many parameters for class") <+> quotes (ppr cls),
1193 parens (ptext (sLit "Use -XMultiParamTypeClasses to allow multi-parameter classes"))]
1195 classFunDepsErr :: Class -> SDoc
1197 = vcat [ptext (sLit "Fundeps in class") <+> quotes (ppr cls),
1198 parens (ptext (sLit "Use -XFunctionalDependencies to allow fundeps"))]
1200 noClassTyVarErr :: Class -> Var -> SDoc
1201 noClassTyVarErr clas op
1202 = sep [ptext (sLit "The class method") <+> quotes (ppr op),
1203 ptext (sLit "mentions none of the type variables of the class") <+>
1204 ppr clas <+> hsep (map ppr (classTyVars clas))]
1206 genericMultiParamErr :: Class -> SDoc
1207 genericMultiParamErr clas
1208 = ptext (sLit "The multi-parameter class") <+> quotes (ppr clas) <+>
1209 ptext (sLit "cannot have generic methods")
1211 badGenericMethodType :: Name -> Kind -> SDoc
1212 badGenericMethodType op op_ty
1213 = hang (ptext (sLit "Generic method type is too complex"))
1214 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
1215 ptext (sLit "You can only use type variables, arrows, lists, and tuples")])
1217 recSynErr :: [LTyClDecl Name] -> TcRn ()
1219 = setSrcSpan (getLoc (head sorted_decls)) $
1220 addErr (sep [ptext (sLit "Cycle in type synonym declarations:"),
1221 nest 2 (vcat (map ppr_decl sorted_decls))])
1223 sorted_decls = sortLocated syn_decls
1224 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
1226 recClsErr :: [Located (TyClDecl Name)] -> TcRn ()
1228 = setSrcSpan (getLoc (head sorted_decls)) $
1229 addErr (sep [ptext (sLit "Cycle in class declarations (via superclasses):"),
1230 nest 2 (vcat (map ppr_decl sorted_decls))])
1232 sorted_decls = sortLocated cls_decls
1233 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
1235 sortLocated :: [Located a] -> [Located a]
1236 sortLocated things = sortLe le things
1238 le (L l1 _) (L l2 _) = l1 <= l2
1240 badDataConTyCon :: DataCon -> SDoc
1241 badDataConTyCon data_con
1242 = hang (ptext (sLit "Data constructor") <+> quotes (ppr data_con) <+>
1243 ptext (sLit "returns type") <+> quotes (ppr (dataConTyCon data_con)))
1244 2 (ptext (sLit "instead of its parent type"))
1246 badGadtDecl :: Name -> SDoc
1248 = vcat [ ptext (sLit "Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
1249 , nest 2 (parens $ ptext (sLit "Use -XGADTs to allow GADTs")) ]
1251 badExistential :: Located Name -> SDoc
1252 badExistential con_name
1253 = hang (ptext (sLit "Data constructor") <+> quotes (ppr con_name) <+>
1254 ptext (sLit "has existential type variables, or a context"))
1255 2 (parens $ ptext (sLit "Use -XExistentialQuantification or -XGADTs to allow this"))
1257 badStupidTheta :: Name -> SDoc
1258 badStupidTheta tc_name
1259 = ptext (sLit "A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
1261 newtypeConError :: Name -> Int -> SDoc
1262 newtypeConError tycon n
1263 = sep [ptext (sLit "A newtype must have exactly one constructor,"),
1264 nest 2 $ ptext (sLit "but") <+> quotes (ppr tycon) <+> ptext (sLit "has") <+> speakN n ]
1266 newtypeExError :: DataCon -> SDoc
1268 = sep [ptext (sLit "A newtype constructor cannot have an existential context,"),
1269 nest 2 $ ptext (sLit "but") <+> quotes (ppr con) <+> ptext (sLit "does")]
1271 newtypeStrictError :: DataCon -> SDoc
1272 newtypeStrictError con
1273 = sep [ptext (sLit "A newtype constructor cannot have a strictness annotation,"),
1274 nest 2 $ ptext (sLit "but") <+> quotes (ppr con) <+> ptext (sLit "does")]
1276 newtypePredError :: DataCon -> SDoc
1277 newtypePredError con
1278 = sep [ptext (sLit "A newtype constructor must have a return type of form T a1 ... an"),
1279 nest 2 $ ptext (sLit "but") <+> quotes (ppr con) <+> ptext (sLit "does not")]
1281 newtypeFieldErr :: DataCon -> Int -> SDoc
1282 newtypeFieldErr con_name n_flds
1283 = sep [ptext (sLit "The constructor of a newtype must have exactly one field"),
1284 nest 2 $ ptext (sLit "but") <+> quotes (ppr con_name) <+> ptext (sLit "has") <+> speakN n_flds]
1286 badSigTyDecl :: Name -> SDoc
1287 badSigTyDecl tc_name
1288 = vcat [ ptext (sLit "Illegal kind signature") <+>
1289 quotes (ppr tc_name)
1290 , nest 2 (parens $ ptext (sLit "Use -XKindSignatures to allow kind signatures")) ]
1292 badFamInstDecl :: Outputable a => a -> SDoc
1293 badFamInstDecl tc_name
1294 = vcat [ ptext (sLit "Illegal family instance for") <+>
1295 quotes (ppr tc_name)
1296 , nest 2 (parens $ ptext (sLit "Use -XTypeFamilies to allow indexed type families")) ]
1298 badGadtIdxTyDecl :: Name -> SDoc
1299 badGadtIdxTyDecl tc_name
1300 = vcat [ ptext (sLit "Illegal generalised algebraic data declaration for") <+>
1301 quotes (ppr tc_name)
1302 , nest 2 (parens $ ptext (sLit "Family instances can not yet use GADT declarations")) ]
1304 tooManyParmsErr :: Located Name -> SDoc
1305 tooManyParmsErr tc_name
1306 = ptext (sLit "Family instance has too many parameters:") <+>
1307 quotes (ppr tc_name)
1309 tooFewParmsErr :: Arity -> SDoc
1310 tooFewParmsErr arity
1311 = ptext (sLit "Family instance has too few parameters; expected") <+>
1314 wrongNumberOfParmsErr :: Arity -> SDoc
1315 wrongNumberOfParmsErr exp_arity
1316 = ptext (sLit "Number of parameters must match family declaration; expected")
1319 badBootFamInstDeclErr :: SDoc
1320 badBootFamInstDeclErr =
1321 ptext (sLit "Illegal family instance in hs-boot file")
1323 wrongKindOfFamily :: TyCon -> SDoc
1324 wrongKindOfFamily family =
1325 ptext (sLit "Wrong category of family instance; declaration was for a") <+>
1328 kindOfFamily | isSynTyCon family = ptext (sLit "type synonym")
1329 | isAlgTyCon family = ptext (sLit "data type")
1330 | otherwise = pprPanic "wrongKindOfFamily" (ppr family)
1332 emptyConDeclsErr :: Name -> SDoc
1333 emptyConDeclsErr tycon
1334 = sep [quotes (ppr tycon) <+> ptext (sLit "has no constructors"),
1335 nest 2 $ ptext (sLit "(-XEmptyDataDecls permits this)")]