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)
228 #if __GLASGOW_HASKELL__ < 605
229 -- Old GHCs don't understand that ~... matches anything
230 mk_thing _ = panic "mkGlobalThings: Can't happen"
235 %************************************************************************
237 \subsection{Type checking family instances}
239 %************************************************************************
241 Family instances are somewhat of a hybrid. They are processed together with
242 class instance heads, but can contain data constructors and hence they share a
243 lot of kinding and type checking code with ordinary algebraic data types (and
247 tcFamInstDecl :: LTyClDecl Name -> TcM TyThing
248 tcFamInstDecl (L loc decl)
249 = -- Prime error recovery, set source location
252 do { -- type families require -XTypeFamilies and can't be in an
254 ; type_families <- doptM Opt_TypeFamilies
255 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
256 ; checkTc type_families $ badFamInstDecl (tcdLName decl)
257 ; checkTc (not is_boot) $ badBootFamInstDeclErr
259 -- Perform kind and type checking
260 ; tc <- tcFamInstDecl1 decl
261 ; checkValidTyCon tc -- Remember to check validity;
262 -- no recursion to worry about here
263 ; return (ATyCon tc) }
265 tcFamInstDecl1 :: TyClDecl Name -> TcM TyCon
268 tcFamInstDecl1 (decl@TySynonym {tcdLName = L loc tc_name})
269 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
270 do { -- check that the family declaration is for a synonym
271 unless (isSynTyCon family) $
272 addErr (wrongKindOfFamily family)
274 ; -- (1) kind check the right-hand side of the type equation
275 ; k_rhs <- kcCheckHsType (tcdSynRhs decl) resKind
277 -- we need the exact same number of type parameters as the family
279 ; let famArity = tyConArity family
280 ; checkTc (length k_typats == famArity) $
281 wrongNumberOfParmsErr famArity
283 -- (2) type check type equation
284 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
285 ; t_typats <- mapM tcHsKindedType k_typats
286 ; t_rhs <- tcHsKindedType k_rhs
288 -- (3) check the well-formedness of the instance
289 ; checkValidTypeInst t_typats t_rhs
291 -- (4) construct representation tycon
292 ; rep_tc_name <- newFamInstTyConName tc_name loc
293 ; buildSynTyCon rep_tc_name t_tvs (SynonymTyCon t_rhs)
294 (typeKind t_rhs) (Just (family, t_typats))
297 -- "newtype instance" and "data instance"
298 tcFamInstDecl1 (decl@TyData {tcdND = new_or_data, tcdLName = L loc tc_name,
300 = kcIdxTyPats decl $ \k_tvs k_typats resKind fam_tycon ->
301 do { -- check that the family declaration is for the right kind
302 unless (isAlgTyCon fam_tycon) $
303 addErr (wrongKindOfFamily fam_tycon)
305 ; -- (1) kind check the data declaration as usual
306 ; k_decl <- kcDataDecl decl k_tvs
307 ; let k_ctxt = tcdCtxt k_decl
308 k_cons = tcdCons k_decl
310 -- result kind must be '*' (otherwise, we have too few patterns)
311 ; checkTc (isLiftedTypeKind resKind) $ tooFewParmsErr (tyConArity fam_tycon)
313 -- (2) type check indexed data type declaration
314 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
315 ; unbox_strict <- doptM Opt_UnboxStrictFields
317 -- kind check the type indexes and the context
318 ; t_typats <- mapM tcHsKindedType k_typats
319 ; stupid_theta <- tcHsKindedContext k_ctxt
322 -- (a) left-hand side contains no type family applications
323 -- (vanilla synonyms are fine, though, and we checked for
325 ; mapM_ checkTyFamFreeness t_typats
327 -- (b) a newtype has exactly one constructor
328 ; checkTc (new_or_data == DataType || isSingleton k_cons) $
329 newtypeConError tc_name (length k_cons)
331 -- (4) construct representation tycon
332 ; rep_tc_name <- newFamInstTyConName tc_name loc
333 ; let ex_ok = True -- Existentials ok for type families!
334 ; fixM (\ rep_tycon -> do
335 { let orig_res_ty = mkTyConApp fam_tycon t_typats
336 ; data_cons <- tcConDecls unbox_strict ex_ok rep_tycon
337 (t_tvs, orig_res_ty) k_cons
340 DataType -> return (mkDataTyConRhs data_cons)
341 NewType -> ASSERT( not (null data_cons) )
342 mkNewTyConRhs rep_tc_name rep_tycon (head data_cons)
343 ; buildAlgTyCon rep_tc_name t_tvs stupid_theta tc_rhs Recursive
344 False h98_syntax (Just (fam_tycon, 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 { fam_tycon <- tcLookupLocatedTyCon (tcdLName decl)
375 ; let { (kinds, resKind) = splitKindFunTys (tyConKind fam_tycon)
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 fam_tycon
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')
659 (typeKind rhs_ty') Nothing
660 ; return (ATyCon tycon)
662 tcSynDecl d = pprPanic "tcSynDecl" (ppr d)
665 tcTyClDecl :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
667 tcTyClDecl calc_isrec decl
668 = tcAddDeclCtxt decl (tcTyClDecl1 calc_isrec decl)
670 -- "type family" declarations
671 tcTyClDecl1 :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
672 tcTyClDecl1 _calc_isrec
673 (TyFamily {tcdFlavour = TypeFamily,
674 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = Just kind})
675 -- NB: kind at latest
678 = tcTyVarBndrs tvs $ \ tvs' -> do
679 { traceTc (text "type family: " <+> ppr tc_name)
680 ; idx_tys <- doptM Opt_TypeFamilies
682 -- Check that we don't use families without -XTypeFamilies
683 ; checkTc idx_tys $ badFamInstDecl tc_name
685 ; tycon <- buildSynTyCon tc_name tvs' (OpenSynTyCon kind Nothing) kind Nothing
686 ; return [ATyCon tycon]
689 -- "data family" declaration
690 tcTyClDecl1 _calc_isrec
691 (TyFamily {tcdFlavour = DataFamily,
692 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = mb_kind})
693 = tcTyVarBndrs tvs $ \ tvs' -> do
694 { traceTc (text "data family: " <+> ppr tc_name)
695 ; extra_tvs <- tcDataKindSig mb_kind
696 ; let final_tvs = tvs' ++ extra_tvs -- we may not need these
698 ; idx_tys <- doptM Opt_TypeFamilies
700 -- Check that we don't use families without -XTypeFamilies
701 ; checkTc idx_tys $ badFamInstDecl tc_name
703 ; tycon <- buildAlgTyCon tc_name final_tvs []
704 mkOpenDataTyConRhs Recursive False True Nothing
705 ; return [ATyCon tycon]
708 -- "newtype" and "data"
709 -- NB: not used for newtype/data instances (whether associated or not)
710 tcTyClDecl1 calc_isrec
711 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
712 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
713 = tcTyVarBndrs tvs $ \ tvs' -> do
714 { extra_tvs <- tcDataKindSig mb_ksig
715 ; let final_tvs = tvs' ++ extra_tvs
716 ; stupid_theta <- tcHsKindedContext ctxt
717 ; want_generic <- doptM Opt_Generics
718 ; unbox_strict <- doptM Opt_UnboxStrictFields
719 ; empty_data_decls <- doptM Opt_EmptyDataDecls
720 ; kind_signatures <- doptM Opt_KindSignatures
721 ; existential_ok <- doptM Opt_ExistentialQuantification
722 ; gadt_ok <- doptM Opt_GADTs
723 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
724 ; let ex_ok = existential_ok || gadt_ok -- Data cons can have existential context
726 -- Check that we don't use GADT syntax in H98 world
727 ; checkTc (gadt_ok || h98_syntax) (badGadtDecl tc_name)
729 -- Check that we don't use kind signatures without Glasgow extensions
730 ; checkTc (kind_signatures || isNothing mb_ksig) (badSigTyDecl tc_name)
732 -- Check that the stupid theta is empty for a GADT-style declaration
733 ; checkTc (null stupid_theta || h98_syntax) (badStupidTheta tc_name)
735 -- Check that a newtype has exactly one constructor
736 -- Do this before checking for empty data decls, so that
737 -- we don't suggest -XEmptyDataDecls for newtypes
738 ; checkTc (new_or_data == DataType || isSingleton cons)
739 (newtypeConError tc_name (length cons))
741 -- Check that there's at least one condecl,
742 -- or else we're reading an hs-boot file, or -XEmptyDataDecls
743 ; checkTc (not (null cons) || empty_data_decls || is_boot)
744 (emptyConDeclsErr tc_name)
746 ; tycon <- fixM (\ tycon -> do
747 { let res_ty = mkTyConApp tycon (mkTyVarTys final_tvs)
748 ; data_cons <- tcConDecls unbox_strict ex_ok
749 tycon (final_tvs, res_ty) cons
751 if null cons && is_boot -- In a hs-boot file, empty cons means
752 then return AbstractTyCon -- "don't know"; hence Abstract
753 else case new_or_data of
754 DataType -> return (mkDataTyConRhs data_cons)
755 NewType -> ASSERT( not (null data_cons) )
756 mkNewTyConRhs tc_name tycon (head data_cons)
757 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
758 (want_generic && canDoGenerics data_cons) h98_syntax Nothing
760 ; return [ATyCon tycon]
763 is_rec = calc_isrec tc_name
764 h98_syntax = case cons of -- All constructors have same shape
765 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
768 tcTyClDecl1 calc_isrec
769 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
770 tcdCtxt = ctxt, tcdMeths = meths,
771 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
772 = tcTyVarBndrs tvs $ \ tvs' -> do
773 { ctxt' <- tcHsKindedContext ctxt
774 ; fds' <- mapM (addLocM tc_fundep) fundeps
775 ; atss <- mapM (addLocM (tcTyClDecl1 (const Recursive))) ats
776 -- NB: 'ats' only contains "type family" and "data family"
777 -- declarations as well as type family defaults
778 ; let ats' = zipWith setTyThingPoss atss (map (tcdTyVars . unLoc) ats)
779 ; sig_stuff <- tcClassSigs class_name sigs meths
780 ; clas <- fixM (\ clas ->
781 let -- This little knot is just so we can get
782 -- hold of the name of the class TyCon, which we
783 -- need to look up its recursiveness
784 tycon_name = tyConName (classTyCon clas)
785 tc_isrec = calc_isrec tycon_name
787 buildClass False {- Must include unfoldings for selectors -}
788 class_name tvs' ctxt' fds' ats'
790 ; return (AClass clas : ats')
791 -- NB: Order is important due to the call to `mkGlobalThings' when
792 -- tying the the type and class declaration type checking knot.
795 tc_fundep (tvs1, tvs2) = do { tvs1' <- mapM tcLookupTyVar tvs1 ;
796 ; tvs2' <- mapM tcLookupTyVar tvs2 ;
797 ; return (tvs1', tvs2') }
799 -- For each AT argument compute the position of the corresponding class
800 -- parameter in the class head. This will later serve as a permutation
801 -- vector when checking the validity of instance declarations.
802 setTyThingPoss [ATyCon tycon] atTyVars =
803 let classTyVars = hsLTyVarNames tvs
805 . map (`elemIndex` classTyVars)
808 -- There will be no Nothing, as we already passed renaming
810 ATyCon (setTyConArgPoss tycon poss)
811 setTyThingPoss _ _ = panic "TcTyClsDecls.setTyThingPoss"
814 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
815 = return [ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0)]
817 tcTyClDecl1 _ d = pprPanic "tcTyClDecl1" (ppr d)
819 -----------------------------------
820 tcConDecls :: Bool -> Bool -> TyCon -> ([TyVar], Type)
821 -> [LConDecl Name] -> TcM [DataCon]
822 tcConDecls unbox ex_ok rep_tycon res_tmpl cons
823 = mapM (addLocM (tcConDecl unbox ex_ok rep_tycon res_tmpl)) cons
825 tcConDecl :: Bool -- True <=> -funbox-strict_fields
826 -> Bool -- True <=> -XExistentialQuantificaton or -XGADTs
827 -> TyCon -- Representation tycon
828 -> ([TyVar], Type) -- Return type template (with its template tyvars)
832 tcConDecl unbox_strict existential_ok rep_tycon res_tmpl -- Data types
833 (ConDecl name _ tvs ctxt details res_ty _)
834 = addErrCtxt (dataConCtxt name) $
835 tcTyVarBndrs tvs $ \ tvs' -> do
836 { ctxt' <- tcHsKindedContext ctxt
837 ; checkTc (existential_ok || (null tvs && null (unLoc ctxt)))
838 (badExistential name)
839 ; (univ_tvs, ex_tvs, eq_preds, res_ty') <- tcResultType res_tmpl tvs' res_ty
841 tc_datacon is_infix field_lbls btys
842 = do { (arg_tys, stricts) <- mapAndUnzipM (tcConArg unbox_strict) btys
843 ; buildDataCon (unLoc name) is_infix
845 univ_tvs ex_tvs eq_preds ctxt' arg_tys
847 -- NB: we put data_tc, the type constructor gotten from the
848 -- constructor type signature into the data constructor;
849 -- that way checkValidDataCon can complain if it's wrong.
852 PrefixCon btys -> tc_datacon False [] btys
853 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
854 RecCon fields -> tc_datacon False field_names btys
856 field_names = map (unLoc . cd_fld_name) fields
857 btys = map cd_fld_type fields
861 -- data instance T (b,c) where
862 -- TI :: forall e. e -> T (e,e)
864 -- The representation tycon looks like this:
865 -- data :R7T b c where
866 -- TI :: forall b1 c1. (b1 ~ c1) => b1 -> :R7T b1 c1
867 -- In this case orig_res_ty = T (e,e)
869 tcResultType :: ([TyVar], Type) -- Template for result type; e.g.
870 -- data T a b c = ... gives ([a,b,c], T a b)
871 -> [TyVar] -- where MkT :: forall a b c. ...
873 -> TcM ([TyVar], -- Universal
874 [TyVar], -- Existential (distinct OccNames from univs)
875 [(TyVar,Type)], -- Equality predicates
876 Type) -- Typechecked return type
877 -- We don't check that the TyCon given in the ResTy is
878 -- the same as the parent tycon, becuase we are in the middle
879 -- of a recursive knot; so it's postponed until checkValidDataCon
881 tcResultType (tmpl_tvs, res_ty) dc_tvs ResTyH98
882 = return (tmpl_tvs, dc_tvs, [], res_ty)
883 -- In H98 syntax the dc_tvs are the existential ones
884 -- data T a b c = forall d e. MkT ...
885 -- The {a,b,c} are tc_tvs, and {d,e} are dc_tvs
887 tcResultType (tmpl_tvs, res_tmpl) dc_tvs (ResTyGADT res_ty)
888 -- E.g. data T [a] b c where
889 -- MkT :: forall x y z. T [(x,y)] z z
891 -- Univ tyvars Eq-spec
895 -- Existentials are the leftover type vars: [x,y]
896 = do { res_ty' <- tcHsKindedType res_ty
897 ; let Just subst = tcMatchTy (mkVarSet tmpl_tvs) res_tmpl res_ty'
899 -- *Lazily* figure out the univ_tvs etc
900 -- Each univ_tv is either a dc_tv or a tmpl_tv
901 (univ_tvs, eq_spec) = foldr choose ([], []) tidy_tmpl_tvs
902 choose tmpl (univs, eqs)
903 | Just ty <- lookupTyVar subst tmpl
904 = case tcGetTyVar_maybe ty of
905 Just tv | not (tv `elem` univs)
907 _other -> (tmpl:univs, (tmpl,ty):eqs)
908 | otherwise = pprPanic "tcResultType" (ppr res_ty)
909 ex_tvs = dc_tvs `minusList` univ_tvs
911 ; return (univ_tvs, ex_tvs, eq_spec, res_ty') }
913 -- NB: tmpl_tvs and dc_tvs are distinct, but
914 -- we want them to be *visibly* distinct, both for
915 -- interface files and general confusion. So rename
916 -- the tc_tvs, since they are not used yet (no
917 -- consequential renaming needed)
918 (_, tidy_tmpl_tvs) = mapAccumL tidy_one init_occ_env tmpl_tvs
919 init_occ_env = initTidyOccEnv (map getOccName dc_tvs)
920 tidy_one env tv = (env', setTyVarName tv (tidyNameOcc name occ'))
923 (env', occ') = tidyOccName env (getOccName name)
926 tcConArg :: Bool -- True <=> -funbox-strict_fields
928 -> TcM (TcType, StrictnessMark)
929 tcConArg unbox_strict bty
930 = do { arg_ty <- tcHsBangType bty
931 ; let bang = getBangStrictness bty
932 ; return (arg_ty, chooseBoxingStrategy unbox_strict arg_ty bang) }
934 -- We attempt to unbox/unpack a strict field when either:
935 -- (i) The field is marked '!!', or
936 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
938 -- We have turned off unboxing of newtypes because coercions make unboxing
939 -- and reboxing more complicated
940 chooseBoxingStrategy :: Bool -> TcType -> HsBang -> StrictnessMark
941 chooseBoxingStrategy unbox_strict_fields arg_ty bang
943 HsNoBang -> NotMarkedStrict
944 HsStrict | unbox_strict_fields
945 && can_unbox arg_ty -> MarkedUnboxed
946 HsUnbox | can_unbox arg_ty -> MarkedUnboxed
949 -- we can unbox if the type is a chain of newtypes with a product tycon
951 can_unbox arg_ty = case splitTyConApp_maybe arg_ty of
953 Just (arg_tycon, tycon_args) ->
954 not (isRecursiveTyCon arg_tycon) && -- Note [Recusive unboxing]
955 isProductTyCon arg_tycon &&
956 (if isNewTyCon arg_tycon then
957 can_unbox (newTyConInstRhs arg_tycon tycon_args)
961 Note [Recursive unboxing]
962 ~~~~~~~~~~~~~~~~~~~~~~~~~
963 Be careful not to try to unbox this!
965 But it's the *argument* type that matters. This is fine:
967 because Int is non-recursive.
969 %************************************************************************
971 \subsection{Dependency analysis}
973 %************************************************************************
975 Validity checking is done once the mutually-recursive knot has been
976 tied, so we can look at things freely.
979 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
980 checkCycleErrs tyclss
984 = do { mapM_ recClsErr cls_cycles
985 ; failM } -- Give up now, because later checkValidTyCl
986 -- will loop if the synonym is recursive
988 cls_cycles = calcClassCycles tyclss
990 checkValidTyCl :: TyClDecl Name -> TcM ()
991 -- We do the validity check over declarations, rather than TyThings
992 -- only so that we can add a nice context with tcAddDeclCtxt
994 = tcAddDeclCtxt decl $
995 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
996 ; traceTc (text "Validity of" <+> ppr thing)
998 ATyCon tc -> checkValidTyCon tc
999 AClass cl -> checkValidClass cl
1000 _ -> panic "checkValidTyCl"
1001 ; traceTc (text "Done validity of" <+> ppr thing)
1004 -------------------------
1005 -- For data types declared with record syntax, we require
1006 -- that each constructor that has a field 'f'
1007 -- (a) has the same result type
1008 -- (b) has the same type for 'f'
1009 -- module alpha conversion of the quantified type variables
1010 -- of the constructor.
1012 -- Note that we allow existentials to match becuase the
1013 -- fields can never meet. E.g
1015 -- T1 { f1 :: b, f2 :: a, f3 ::Int } :: T
1016 -- T2 { f1 :: c, f2 :: c, f3 ::Int } :: T
1017 -- Here we do not complain about f1,f2 because they are existential
1019 checkValidTyCon :: TyCon -> TcM ()
1022 = case synTyConRhs tc of
1023 OpenSynTyCon _ _ -> return ()
1024 SynonymTyCon ty -> checkValidType syn_ctxt ty
1026 = do -- Check the context on the data decl
1027 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc)
1029 -- Check arg types of data constructors
1030 mapM_ (checkValidDataCon tc) data_cons
1032 -- Check that fields with the same name share a type
1033 mapM_ check_fields groups
1036 syn_ctxt = TySynCtxt name
1038 data_cons = tyConDataCons tc
1040 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
1041 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
1042 get_fields con = dataConFieldLabels con `zip` repeat con
1043 -- dataConFieldLabels may return the empty list, which is fine
1045 -- See Note [GADT record selectors] in MkId.lhs
1046 -- We must check (a) that the named field has the same
1047 -- type in each constructor
1048 -- (b) that those constructors have the same result type
1050 -- However, the constructors may have differently named type variable
1051 -- and (worse) we don't know how the correspond to each other. E.g.
1052 -- C1 :: forall a b. { f :: a, g :: b } -> T a b
1053 -- C2 :: forall d c. { f :: c, g :: c } -> T c d
1055 -- So what we do is to ust Unify.tcMatchTys to compare the first candidate's
1056 -- result type against other candidates' types BOTH WAYS ROUND.
1057 -- If they magically agrees, take the substitution and
1058 -- apply them to the latter ones, and see if they match perfectly.
1059 check_fields ((label, con1) : other_fields)
1060 -- These fields all have the same name, but are from
1061 -- different constructors in the data type
1062 = recoverM (return ()) $ mapM_ checkOne other_fields
1063 -- Check that all the fields in the group have the same type
1064 -- NB: this check assumes that all the constructors of a given
1065 -- data type use the same type variables
1067 (tvs1, _, _, res1) = dataConSig con1
1069 fty1 = dataConFieldType con1 label
1071 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
1072 = do { checkFieldCompat label con1 con2 ts1 res1 res2 fty1 fty2
1073 ; checkFieldCompat label con2 con1 ts2 res2 res1 fty2 fty1 }
1075 (tvs2, _, _, res2) = dataConSig con2
1077 fty2 = dataConFieldType con2 label
1078 check_fields [] = panic "checkValidTyCon/check_fields []"
1080 checkFieldCompat :: Name -> DataCon -> DataCon -> TyVarSet
1081 -> Type -> Type -> Type -> Type -> TcM ()
1082 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
1083 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
1084 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
1086 mb_subst1 = tcMatchTy tvs1 res1 res2
1087 mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
1089 -------------------------------
1090 checkValidDataCon :: TyCon -> DataCon -> TcM ()
1091 checkValidDataCon tc con
1092 = setSrcSpan (srcLocSpan (getSrcLoc con)) $
1093 addErrCtxt (dataConCtxt con) $
1094 do { let tc_tvs = tyConTyVars tc
1095 res_ty_tmpl = mkFamilyTyConApp tc (mkTyVarTys tc_tvs)
1096 actual_res_ty = dataConOrigResTy con
1097 ; checkTc (isJust (tcMatchTy (mkVarSet tc_tvs)
1100 (badDataConTyCon con res_ty_tmpl actual_res_ty)
1101 ; checkValidMonoType (dataConOrigResTy con)
1102 -- Disallow MkT :: T (forall a. a->a)
1103 -- Reason: it's really the argument of an equality constraint
1104 ; checkValidType ctxt (dataConUserType con)
1105 ; when (isNewTyCon tc) (checkNewDataCon con)
1108 ctxt = ConArgCtxt (dataConName con)
1110 -------------------------------
1111 checkNewDataCon :: DataCon -> TcM ()
1112 -- Checks for the data constructor of a newtype
1114 = do { checkTc (isSingleton arg_tys) (newtypeFieldErr con (length arg_tys))
1116 ; checkTc (null eq_spec) (newtypePredError con)
1117 -- Return type is (T a b c)
1118 ; checkTc (null ex_tvs && null eq_theta && null dict_theta) (newtypeExError con)
1120 ; checkTc (not (any isMarkedStrict (dataConStrictMarks con)))
1121 (newtypeStrictError con)
1125 (_univ_tvs, ex_tvs, eq_spec, eq_theta, dict_theta, arg_tys, _res_ty) = dataConFullSig con
1127 -------------------------------
1128 checkValidClass :: Class -> TcM ()
1130 = do { constrained_class_methods <- doptM Opt_ConstrainedClassMethods
1131 ; multi_param_type_classes <- doptM Opt_MultiParamTypeClasses
1132 ; fundep_classes <- doptM Opt_FunctionalDependencies
1134 -- Check that the class is unary, unless GlaExs
1135 ; checkTc (notNull tyvars) (nullaryClassErr cls)
1136 ; checkTc (multi_param_type_classes || unary) (classArityErr cls)
1137 ; checkTc (fundep_classes || null fundeps) (classFunDepsErr cls)
1139 -- Check the super-classes
1140 ; checkValidTheta (ClassSCCtxt (className cls)) theta
1142 -- Check the class operations
1143 ; mapM_ (check_op constrained_class_methods) op_stuff
1145 -- Check that if the class has generic methods, then the
1146 -- class has only one parameter. We can't do generic
1147 -- multi-parameter type classes!
1148 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
1151 (tyvars, fundeps, theta, _, _, op_stuff) = classExtraBigSig cls
1152 unary = isSingleton tyvars
1153 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
1155 check_op constrained_class_methods (sel_id, dm)
1156 = addErrCtxt (classOpCtxt sel_id tau) $ do
1157 { checkValidTheta SigmaCtxt (tail theta)
1158 -- The 'tail' removes the initial (C a) from the
1159 -- class itself, leaving just the method type
1161 ; traceTc (text "class op type" <+> ppr op_ty <+> ppr tau)
1162 ; checkValidType (FunSigCtxt op_name) tau
1164 -- Check that the type mentions at least one of
1165 -- the class type variables...or at least one reachable
1166 -- from one of the class variables. Example: tc223
1167 -- class Error e => Game b mv e | b -> mv e where
1168 -- newBoard :: MonadState b m => m ()
1169 -- Here, MonadState has a fundep m->b, so newBoard is fine
1170 ; let grown_tyvars = grow theta (mkVarSet tyvars)
1171 ; checkTc (tyVarsOfType tau `intersectsVarSet` grown_tyvars)
1172 (noClassTyVarErr cls sel_id)
1174 -- Check that for a generic method, the type of
1175 -- the method is sufficiently simple
1176 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
1177 (badGenericMethodType op_name op_ty)
1180 op_name = idName sel_id
1181 op_ty = idType sel_id
1182 (_,theta1,tau1) = tcSplitSigmaTy op_ty
1183 (_,theta2,tau2) = tcSplitSigmaTy tau1
1184 (theta,tau) | constrained_class_methods = (theta1 ++ theta2, tau2)
1185 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
1186 -- Ugh! The function might have a type like
1187 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
1188 -- With -XConstrainedClassMethods, we want to allow this, even though the inner
1189 -- forall has an (Eq a) constraint. Whereas in general, each constraint
1190 -- in the context of a for-all must mention at least one quantified
1191 -- type variable. What a mess!
1194 ---------------------------------------------------------------------
1195 resultTypeMisMatch :: Name -> DataCon -> DataCon -> SDoc
1196 resultTypeMisMatch field_name con1 con2
1197 = vcat [sep [ptext (sLit "Constructors") <+> ppr con1 <+> ptext (sLit "and") <+> ppr con2,
1198 ptext (sLit "have a common field") <+> quotes (ppr field_name) <> comma],
1199 nest 2 $ ptext (sLit "but have different result types")]
1201 fieldTypeMisMatch :: Name -> DataCon -> DataCon -> SDoc
1202 fieldTypeMisMatch field_name con1 con2
1203 = sep [ptext (sLit "Constructors") <+> ppr con1 <+> ptext (sLit "and") <+> ppr con2,
1204 ptext (sLit "give different types for field"), quotes (ppr field_name)]
1206 dataConCtxt :: Outputable a => a -> SDoc
1207 dataConCtxt con = ptext (sLit "In the definition of data constructor") <+> quotes (ppr con)
1209 classOpCtxt :: Var -> Type -> SDoc
1210 classOpCtxt sel_id tau = sep [ptext (sLit "When checking the class method:"),
1211 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
1213 nullaryClassErr :: Class -> SDoc
1215 = ptext (sLit "No parameters for class") <+> quotes (ppr cls)
1217 classArityErr :: Class -> SDoc
1219 = vcat [ptext (sLit "Too many parameters for class") <+> quotes (ppr cls),
1220 parens (ptext (sLit "Use -XMultiParamTypeClasses to allow multi-parameter classes"))]
1222 classFunDepsErr :: Class -> SDoc
1224 = vcat [ptext (sLit "Fundeps in class") <+> quotes (ppr cls),
1225 parens (ptext (sLit "Use -XFunctionalDependencies to allow fundeps"))]
1227 noClassTyVarErr :: Class -> Var -> SDoc
1228 noClassTyVarErr clas op
1229 = sep [ptext (sLit "The class method") <+> quotes (ppr op),
1230 ptext (sLit "mentions none of the type variables of the class") <+>
1231 ppr clas <+> hsep (map ppr (classTyVars clas))]
1233 genericMultiParamErr :: Class -> SDoc
1234 genericMultiParamErr clas
1235 = ptext (sLit "The multi-parameter class") <+> quotes (ppr clas) <+>
1236 ptext (sLit "cannot have generic methods")
1238 badGenericMethodType :: Name -> Kind -> SDoc
1239 badGenericMethodType op op_ty
1240 = hang (ptext (sLit "Generic method type is too complex"))
1241 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
1242 ptext (sLit "You can only use type variables, arrows, lists, and tuples")])
1244 recSynErr :: [LTyClDecl Name] -> TcRn ()
1246 = setSrcSpan (getLoc (head sorted_decls)) $
1247 addErr (sep [ptext (sLit "Cycle in type synonym declarations:"),
1248 nest 2 (vcat (map ppr_decl sorted_decls))])
1250 sorted_decls = sortLocated syn_decls
1251 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
1253 recClsErr :: [Located (TyClDecl Name)] -> TcRn ()
1255 = setSrcSpan (getLoc (head sorted_decls)) $
1256 addErr (sep [ptext (sLit "Cycle in class declarations (via superclasses):"),
1257 nest 2 (vcat (map ppr_decl sorted_decls))])
1259 sorted_decls = sortLocated cls_decls
1260 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
1262 sortLocated :: [Located a] -> [Located a]
1263 sortLocated things = sortLe le things
1265 le (L l1 _) (L l2 _) = l1 <= l2
1267 badDataConTyCon :: DataCon -> Type -> Type -> SDoc
1268 badDataConTyCon data_con res_ty_tmpl actual_res_ty
1269 = hang (ptext (sLit "Data constructor") <+> quotes (ppr data_con) <+>
1270 ptext (sLit "returns type") <+> quotes (ppr actual_res_ty))
1271 2 (ptext (sLit "instead of an instance of its parent type") <+> quotes (ppr res_ty_tmpl))
1273 badGadtDecl :: Name -> SDoc
1275 = vcat [ ptext (sLit "Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
1276 , nest 2 (parens $ ptext (sLit "Use -XGADTs to allow GADTs")) ]
1278 badExistential :: Located Name -> SDoc
1279 badExistential con_name
1280 = hang (ptext (sLit "Data constructor") <+> quotes (ppr con_name) <+>
1281 ptext (sLit "has existential type variables, or a context"))
1282 2 (parens $ ptext (sLit "Use -XExistentialQuantification or -XGADTs to allow this"))
1284 badStupidTheta :: Name -> SDoc
1285 badStupidTheta tc_name
1286 = ptext (sLit "A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
1288 newtypeConError :: Name -> Int -> SDoc
1289 newtypeConError tycon n
1290 = sep [ptext (sLit "A newtype must have exactly one constructor,"),
1291 nest 2 $ ptext (sLit "but") <+> quotes (ppr tycon) <+> ptext (sLit "has") <+> speakN n ]
1293 newtypeExError :: DataCon -> SDoc
1295 = sep [ptext (sLit "A newtype constructor cannot have an existential context,"),
1296 nest 2 $ ptext (sLit "but") <+> quotes (ppr con) <+> ptext (sLit "does")]
1298 newtypeStrictError :: DataCon -> SDoc
1299 newtypeStrictError con
1300 = sep [ptext (sLit "A newtype constructor cannot have a strictness annotation,"),
1301 nest 2 $ ptext (sLit "but") <+> quotes (ppr con) <+> ptext (sLit "does")]
1303 newtypePredError :: DataCon -> SDoc
1304 newtypePredError con
1305 = sep [ptext (sLit "A newtype constructor must have a return type of form T a1 ... an"),
1306 nest 2 $ ptext (sLit "but") <+> quotes (ppr con) <+> ptext (sLit "does not")]
1308 newtypeFieldErr :: DataCon -> Int -> SDoc
1309 newtypeFieldErr con_name n_flds
1310 = sep [ptext (sLit "The constructor of a newtype must have exactly one field"),
1311 nest 2 $ ptext (sLit "but") <+> quotes (ppr con_name) <+> ptext (sLit "has") <+> speakN n_flds]
1313 badSigTyDecl :: Name -> SDoc
1314 badSigTyDecl tc_name
1315 = vcat [ ptext (sLit "Illegal kind signature") <+>
1316 quotes (ppr tc_name)
1317 , nest 2 (parens $ ptext (sLit "Use -XKindSignatures to allow kind signatures")) ]
1319 badFamInstDecl :: Outputable a => a -> SDoc
1320 badFamInstDecl tc_name
1321 = vcat [ ptext (sLit "Illegal family instance for") <+>
1322 quotes (ppr tc_name)
1323 , nest 2 (parens $ ptext (sLit "Use -XTypeFamilies to allow indexed type families")) ]
1326 badGadtIdxTyDecl :: Name -> SDoc
1327 badGadtIdxTyDecl tc_name
1328 = vcat [ ptext (sLit "Illegal generalised algebraic data declaration for") <+>
1329 quotes (ppr tc_name)
1330 , nest 2 (parens $ ptext (sLit "Family instances can not yet use GADT declarations")) ]
1332 tooManyParmsErr :: Located Name -> SDoc
1333 tooManyParmsErr tc_name
1334 = ptext (sLit "Family instance has too many parameters:") <+>
1335 quotes (ppr tc_name)
1337 tooFewParmsErr :: Arity -> SDoc
1338 tooFewParmsErr arity
1339 = ptext (sLit "Family instance has too few parameters; expected") <+>
1342 wrongNumberOfParmsErr :: Arity -> SDoc
1343 wrongNumberOfParmsErr exp_arity
1344 = ptext (sLit "Number of parameters must match family declaration; expected")
1347 badBootFamInstDeclErr :: SDoc
1348 badBootFamInstDeclErr =
1349 ptext (sLit "Illegal family instance in hs-boot file")
1351 wrongKindOfFamily :: TyCon -> SDoc
1352 wrongKindOfFamily family =
1353 ptext (sLit "Wrong category of family instance; declaration was for a") <+>
1356 kindOfFamily | isSynTyCon family = ptext (sLit "type synonym")
1357 | isAlgTyCon family = ptext (sLit "data type")
1358 | otherwise = pprPanic "wrongKindOfFamily" (ppr family)
1360 emptyConDeclsErr :: Name -> SDoc
1361 emptyConDeclsErr tycon
1362 = sep [quotes (ppr tycon) <+> ptext (sLit "has no constructors"),
1363 nest 2 $ ptext (sLit "(-XEmptyDataDecls permits this)")]