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 (Maybe TyThing) -- Nothing if error
248 tcFamInstDecl (L loc decl)
249 = -- Prime error recovery, set source location
250 recoverM (return Nothing) $
253 do { -- type families require -XTypeFamilies and can't be in an
255 ; type_families <- doptM Opt_TypeFamilies
256 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
257 ; checkTc type_families $ badFamInstDecl (tcdLName decl)
258 ; checkTc (not is_boot) $ badBootFamInstDeclErr
260 -- Perform kind and type checking
261 ; tc <- tcFamInstDecl1 decl
262 ; checkValidTyCon tc -- Remember to check validity;
263 -- no recursion to worry about here
264 ; return (Just (ATyCon tc))
267 tcFamInstDecl1 :: TyClDecl Name -> TcM TyCon
270 tcFamInstDecl1 (decl@TySynonym {tcdLName = L loc tc_name})
271 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
272 do { -- check that the family declaration is for a synonym
273 unless (isSynTyCon family) $
274 addErr (wrongKindOfFamily family)
276 ; -- (1) kind check the right-hand side of the type equation
277 ; k_rhs <- kcCheckHsType (tcdSynRhs decl) resKind
279 -- we need the exact same number of type parameters as the family
281 ; let famArity = tyConArity family
282 ; checkTc (length k_typats == famArity) $
283 wrongNumberOfParmsErr famArity
285 -- (2) type check type equation
286 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
287 ; t_typats <- mapM tcHsKindedType k_typats
288 ; t_rhs <- tcHsKindedType k_rhs
290 -- (3) check the well-formedness of the instance
291 ; checkValidTypeInst t_typats t_rhs
293 -- (4) construct representation tycon
294 ; rep_tc_name <- newFamInstTyConName tc_name loc
295 ; buildSynTyCon rep_tc_name t_tvs (SynonymTyCon t_rhs)
296 (typeKind t_rhs) (Just (family, t_typats))
299 -- "newtype instance" and "data instance"
300 tcFamInstDecl1 (decl@TyData {tcdND = new_or_data, tcdLName = L loc tc_name,
302 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
303 do { -- check that the family declaration is for the right kind
304 unless (isAlgTyCon family) $
305 addErr (wrongKindOfFamily family)
307 ; -- (1) kind check the data declaration as usual
308 ; k_decl <- kcDataDecl decl k_tvs
309 ; let k_ctxt = tcdCtxt k_decl
310 k_cons = tcdCons k_decl
312 -- result kind must be '*' (otherwise, we have too few patterns)
313 ; checkTc (isLiftedTypeKind resKind) $ tooFewParmsErr (tyConArity family)
315 -- (2) type check indexed data type declaration
316 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
317 ; unbox_strict <- doptM Opt_UnboxStrictFields
319 -- kind check the type indexes and the context
320 ; t_typats <- mapM tcHsKindedType k_typats
321 ; stupid_theta <- tcHsKindedContext k_ctxt
324 -- - left-hand side contains no type family applications
325 -- (vanilla synonyms are fine, though, and we checked for
327 ; mapM_ checkTyFamFreeness t_typats
329 -- - we don't use GADT syntax for indexed types
330 ; checkTc h98_syntax (badGadtIdxTyDecl tc_name)
332 -- - a newtype has exactly one constructor
333 ; checkTc (new_or_data == DataType || isSingleton k_cons) $
334 newtypeConError tc_name (length k_cons)
336 -- (4) construct representation tycon
337 ; rep_tc_name <- newFamInstTyConName tc_name loc
338 ; let ex_ok = True -- Existentials ok for type families!
339 ; fixM (\ tycon -> do
340 { data_cons <- mapM (addLocM (tcConDecl unbox_strict ex_ok tycon t_tvs))
344 DataType -> return (mkDataTyConRhs data_cons)
345 NewType -> ASSERT( not (null data_cons) )
346 mkNewTyConRhs rep_tc_name tycon (head data_cons)
347 ; buildAlgTyCon rep_tc_name t_tvs stupid_theta tc_rhs Recursive
348 False h98_syntax (Just (family, t_typats))
349 -- We always assume that indexed types are recursive. Why?
350 -- (1) Due to their open nature, we can never be sure that a
351 -- further instance might not introduce a new recursive
352 -- dependency. (2) They are always valid loop breakers as
353 -- they involve a coercion.
357 h98_syntax = case cons of -- All constructors have same shape
358 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
361 tcFamInstDecl1 d = pprPanic "tcFamInstDecl1" (ppr d)
363 -- Kind checking of indexed types
366 -- Kind check type patterns and kind annotate the embedded type variables.
368 -- * Here we check that a type instance matches its kind signature, but we do
369 -- not check whether there is a pattern for each type index; the latter
370 -- check is only required for type synonym instances.
372 kcIdxTyPats :: TyClDecl Name
373 -> ([LHsTyVarBndr Name] -> [LHsType Name] -> Kind -> TyCon -> TcM a)
374 -- ^^kinded tvs ^^kinded ty pats ^^res kind
376 kcIdxTyPats decl thing_inside
377 = kcHsTyVars (tcdTyVars decl) $ \tvs ->
378 do { family <- tcLookupLocatedTyCon (tcdLName decl)
379 ; let { (kinds, resKind) = splitKindFunTys (tyConKind family)
380 ; hs_typats = fromJust $ tcdTyPats decl }
382 -- we may not have more parameters than the kind indicates
383 ; checkTc (length kinds >= length hs_typats) $
384 tooManyParmsErr (tcdLName decl)
386 -- type functions can have a higher-kinded result
387 ; let resultKind = mkArrowKinds (drop (length hs_typats) kinds) resKind
388 ; typats <- zipWithM kcCheckHsType hs_typats kinds
389 ; thing_inside tvs typats resultKind family
395 %************************************************************************
399 %************************************************************************
401 We need to kind check all types in the mutually recursive group
402 before we know the kind of the type variables. For example:
405 op :: D b => a -> b -> b
408 bop :: (Monad c) => ...
410 Here, the kind of the locally-polymorphic type variable "b"
411 depends on *all the uses of class D*. For example, the use of
412 Monad c in bop's type signature means that D must have kind Type->Type.
414 However type synonyms work differently. They can have kinds which don't
415 just involve (->) and *:
416 type R = Int# -- Kind #
417 type S a = Array# a -- Kind * -> #
418 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
419 So we must infer their kinds from their right-hand sides *first* and then
420 use them, whereas for the mutually recursive data types D we bring into
421 scope kind bindings D -> k, where k is a kind variable, and do inference.
425 This treatment of type synonyms only applies to Haskell 98-style synonyms.
426 General type functions can be recursive, and hence, appear in `alg_decls'.
428 The kind of a type family is solely determinded by its kind signature;
429 hence, only kind signatures participate in the construction of the initial
430 kind environment (as constructed by `getInitialKind'). In fact, we ignore
431 instances of families altogether in the following. However, we need to
432 include the kinds of associated families into the construction of the
433 initial kind environment. (This is handled by `allDecls').
436 kcTyClDecls :: [LTyClDecl Name] -> [Located (TyClDecl Name)]
437 -> TcM ([LTyClDecl Name], [Located (TyClDecl Name)])
438 kcTyClDecls syn_decls alg_decls
439 = do { -- First extend the kind env with each data type, class, and
440 -- indexed type, mapping them to a type variable
441 let initialKindDecls = concat [allDecls decl | L _ decl <- alg_decls]
442 ; alg_kinds <- mapM getInitialKind initialKindDecls
443 ; tcExtendKindEnv alg_kinds $ do
445 -- Now kind-check the type synonyms, in dependency order
446 -- We do these differently to data type and classes,
447 -- because a type synonym can be an unboxed type
449 -- and a kind variable can't unify with UnboxedTypeKind
450 -- So we infer their kinds in dependency order
451 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
452 ; tcExtendKindEnv syn_kinds $ do
454 -- Now kind-check the data type, class, and kind signatures,
455 -- returning kind-annotated decls; we don't kind-check
456 -- instances of indexed types yet, but leave this to
458 { kc_alg_decls <- mapM (wrapLocM kcTyClDecl)
459 (filter (not . isFamInstDecl . unLoc) alg_decls)
461 ; return (kc_syn_decls, kc_alg_decls) }}}
463 -- get all declarations relevant for determining the initial kind
465 allDecls (decl@ClassDecl {tcdATs = ats}) = decl : [ at
468 allDecls decl | isFamInstDecl decl = []
471 ------------------------------------------------------------------------
472 getInitialKind :: TyClDecl Name -> TcM (Name, TcKind)
473 -- Only for data type, class, and indexed type declarations
474 -- Get as much info as possible from the data, class, or indexed type decl,
475 -- so as to maximise usefulness of error messages
477 = do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl)
478 ; res_kind <- mk_res_kind decl
479 ; return (tcdName decl, mkArrowKinds arg_kinds res_kind) }
481 mk_arg_kind (UserTyVar _) = newKindVar
482 mk_arg_kind (KindedTyVar _ kind) = return kind
484 mk_res_kind (TyFamily { tcdKind = Just kind }) = return kind
485 mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
486 -- On GADT-style declarations we allow a kind signature
487 -- data T :: *->* where { ... }
488 mk_res_kind _ = return liftedTypeKind
492 kcSynDecls :: [SCC (LTyClDecl Name)]
493 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
494 [(Name,TcKind)]) -- Kind bindings
497 kcSynDecls (group : groups)
498 = do { (decl, nk) <- kcSynDecl group
499 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
500 ; return (decl:decls, nk:nks) }
503 kcSynDecl :: SCC (LTyClDecl Name)
504 -> TcM (LTyClDecl Name, -- Kind-annotated decls
505 (Name,TcKind)) -- Kind bindings
506 kcSynDecl (AcyclicSCC (L loc decl))
507 = tcAddDeclCtxt decl $
508 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
509 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
510 <+> brackets (ppr k_tvs))
511 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
512 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
513 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
514 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
515 (unLoc (tcdLName decl), tc_kind)) })
517 kcSynDecl (CyclicSCC decls)
518 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
519 -- of out-of-scope tycons
521 kindedTyVarKind :: LHsTyVarBndr Name -> Kind
522 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
523 kindedTyVarKind x = pprPanic "kindedTyVarKind" (ppr x)
525 ------------------------------------------------------------------------
526 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
527 -- Not used for type synonyms (see kcSynDecl)
529 kcTyClDecl decl@(TyData {})
530 = ASSERT( not . isFamInstDecl $ decl ) -- must not be a family instance
531 kcTyClDeclBody decl $
534 kcTyClDecl decl@(TyFamily {})
535 = kcFamilyDecl [] decl -- the empty list signals a toplevel decl
537 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs, tcdATs = ats})
538 = kcTyClDeclBody decl $ \ tvs' ->
539 do { ctxt' <- kcHsContext ctxt
540 ; ats' <- mapM (wrapLocM (kcFamilyDecl tvs')) ats
541 ; sigs' <- mapM (wrapLocM kc_sig) sigs
542 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs',
545 kc_sig (TypeSig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
546 ; return (TypeSig nm op_ty') }
547 kc_sig other_sig = return other_sig
549 kcTyClDecl decl@(ForeignType {})
552 kcTyClDecl (TySynonym {}) = panic "kcTyClDecl TySynonym"
554 kcTyClDeclBody :: TyClDecl Name
555 -> ([LHsTyVarBndr Name] -> TcM a)
557 -- getInitialKind has made a suitably-shaped kind for the type or class
558 -- Unpack it, and attribute those kinds to the type variables
559 -- Extend the env with bindings for the tyvars, taken from
560 -- the kind of the tycon/class. Give it to the thing inside, and
561 -- check the result kind matches
562 kcTyClDeclBody decl thing_inside
563 = tcAddDeclCtxt decl $
564 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
565 ; let tc_kind = case tc_ty_thing of
567 _ -> pprPanic "kcTyClDeclBody" (ppr tc_ty_thing)
568 (kinds, _) = splitKindFunTys tc_kind
569 hs_tvs = tcdTyVars decl
570 kinded_tvs = ASSERT( length kinds >= length hs_tvs )
571 [ L loc (KindedTyVar (hsTyVarName tv) k)
572 | (L loc tv, k) <- zip hs_tvs kinds]
573 ; tcExtendKindEnvTvs kinded_tvs (thing_inside kinded_tvs) }
575 -- Kind check a data declaration, assuming that we already extended the
576 -- kind environment with the type variables of the left-hand side (these
577 -- kinded type variables are also passed as the second parameter).
579 kcDataDecl :: TyClDecl Name -> [LHsTyVarBndr Name] -> TcM (TyClDecl Name)
580 kcDataDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
582 = do { ctxt' <- kcHsContext ctxt
583 ; cons' <- mapM (wrapLocM kc_con_decl) cons
584 ; return (decl {tcdTyVars = tvs, tcdCtxt = ctxt', tcdCons = cons'}) }
586 -- doc comments are typechecked to Nothing here
587 kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res _) = do
588 kcHsTyVars ex_tvs $ \ex_tvs' -> do
589 ex_ctxt' <- kcHsContext ex_ctxt
590 details' <- kc_con_details details
592 ResTyH98 -> return ResTyH98
593 ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
594 return (ConDecl name expl ex_tvs' ex_ctxt' details' res' Nothing)
596 kc_con_details (PrefixCon btys)
597 = do { btys' <- mapM kc_larg_ty btys
598 ; return (PrefixCon btys') }
599 kc_con_details (InfixCon bty1 bty2)
600 = do { bty1' <- kc_larg_ty bty1
601 ; bty2' <- kc_larg_ty bty2
602 ; return (InfixCon bty1' bty2') }
603 kc_con_details (RecCon fields)
604 = do { fields' <- mapM kc_field fields
605 ; return (RecCon fields') }
607 kc_field (ConDeclField fld bty d) = do { bty' <- kc_larg_ty bty
608 ; return (ConDeclField fld bty' d) }
610 kc_larg_ty bty = case new_or_data of
611 DataType -> kcHsSigType bty
612 NewType -> kcHsLiftedSigType bty
613 -- Can't allow an unlifted type for newtypes, because we're effectively
614 -- going to remove the constructor while coercing it to a lifted type.
615 -- And newtypes can't be bang'd
616 kcDataDecl d _ = pprPanic "kcDataDecl" (ppr d)
618 -- Kind check a family declaration or type family default declaration.
620 kcFamilyDecl :: [LHsTyVarBndr Name] -- tyvars of enclosing class decl if any
621 -> TyClDecl Name -> TcM (TyClDecl Name)
622 kcFamilyDecl classTvs decl@(TyFamily {tcdKind = kind})
623 = kcTyClDeclBody decl $ \tvs' ->
624 do { mapM_ unifyClassParmKinds tvs'
625 ; return (decl {tcdTyVars = tvs',
626 tcdKind = kind `mplus` Just liftedTypeKind})
627 -- default result kind is '*'
630 unifyClassParmKinds (L _ (KindedTyVar n k))
631 | Just classParmKind <- lookup n classTyKinds = unifyKind k classParmKind
632 | otherwise = return ()
633 unifyClassParmKinds x = pprPanic "kcFamilyDecl/unifyClassParmKinds" (ppr x)
634 classTyKinds = [(n, k) | L _ (KindedTyVar n k) <- classTvs]
635 kcFamilyDecl _ (TySynonym {}) -- type family defaults
636 = panic "TcTyClsDecls.kcFamilyDecl: not implemented yet"
637 kcFamilyDecl _ d = pprPanic "kcFamilyDecl" (ppr d)
641 %************************************************************************
643 \subsection{Type checking}
645 %************************************************************************
648 tcSynDecls :: [LTyClDecl Name] -> TcM [TyThing]
649 tcSynDecls [] = return []
650 tcSynDecls (decl : decls)
651 = do { syn_tc <- addLocM tcSynDecl decl
652 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls decls)
653 ; return (syn_tc : syn_tcs) }
656 tcSynDecl :: TyClDecl Name -> TcM TyThing
658 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
659 = tcTyVarBndrs tvs $ \ tvs' -> do
660 { traceTc (text "tcd1" <+> ppr tc_name)
661 ; rhs_ty' <- tcHsKindedType rhs_ty
662 ; tycon <- buildSynTyCon tc_name tvs' (SynonymTyCon rhs_ty')
663 (typeKind rhs_ty') Nothing
664 ; return (ATyCon tycon)
666 tcSynDecl d = pprPanic "tcSynDecl" (ppr d)
669 tcTyClDecl :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
671 tcTyClDecl calc_isrec decl
672 = tcAddDeclCtxt decl (tcTyClDecl1 calc_isrec decl)
674 -- "type family" declarations
675 tcTyClDecl1 :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
676 tcTyClDecl1 _calc_isrec
677 (TyFamily {tcdFlavour = TypeFamily,
678 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = Just kind})
679 -- NB: kind at latest
682 = tcTyVarBndrs tvs $ \ tvs' -> do
683 { traceTc (text "type family: " <+> ppr tc_name)
684 ; idx_tys <- doptM Opt_TypeFamilies
686 -- Check that we don't use families without -XTypeFamilies
687 ; checkTc idx_tys $ badFamInstDecl tc_name
689 ; tycon <- buildSynTyCon tc_name tvs' (OpenSynTyCon kind Nothing) kind Nothing
690 ; return [ATyCon tycon]
693 -- "data family" declaration
694 tcTyClDecl1 _calc_isrec
695 (TyFamily {tcdFlavour = DataFamily,
696 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = mb_kind})
697 = tcTyVarBndrs tvs $ \ tvs' -> do
698 { traceTc (text "data family: " <+> ppr tc_name)
699 ; extra_tvs <- tcDataKindSig mb_kind
700 ; let final_tvs = tvs' ++ extra_tvs -- we may not need these
702 ; idx_tys <- doptM Opt_TypeFamilies
704 -- Check that we don't use families without -XTypeFamilies
705 ; checkTc idx_tys $ badFamInstDecl tc_name
707 ; tycon <- buildAlgTyCon tc_name final_tvs []
708 mkOpenDataTyConRhs Recursive False True Nothing
709 ; return [ATyCon tycon]
712 -- "newtype" and "data"
713 -- NB: not used for newtype/data instances (whether associated or not)
714 tcTyClDecl1 calc_isrec
715 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
716 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
717 = tcTyVarBndrs tvs $ \ tvs' -> do
718 { extra_tvs <- tcDataKindSig mb_ksig
719 ; let final_tvs = tvs' ++ extra_tvs
720 ; stupid_theta <- tcHsKindedContext ctxt
721 ; want_generic <- doptM Opt_Generics
722 ; unbox_strict <- doptM Opt_UnboxStrictFields
723 ; empty_data_decls <- doptM Opt_EmptyDataDecls
724 ; kind_signatures <- doptM Opt_KindSignatures
725 ; existential_ok <- doptM Opt_ExistentialQuantification
726 ; gadt_ok <- doptM Opt_GADTs
727 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
728 ; let ex_ok = existential_ok || gadt_ok -- Data cons can have existential context
730 -- Check that we don't use GADT syntax in H98 world
731 ; checkTc (gadt_ok || h98_syntax) (badGadtDecl tc_name)
733 -- Check that we don't use kind signatures without Glasgow extensions
734 ; checkTc (kind_signatures || isNothing mb_ksig) (badSigTyDecl tc_name)
736 -- Check that the stupid theta is empty for a GADT-style declaration
737 ; checkTc (null stupid_theta || h98_syntax) (badStupidTheta tc_name)
739 -- Check that a newtype has exactly one constructor
740 -- Do this before checking for empty data decls, so that
741 -- we don't suggest -XEmptyDataDecls for newtypes
742 ; checkTc (new_or_data == DataType || isSingleton cons)
743 (newtypeConError tc_name (length cons))
745 -- Check that there's at least one condecl,
746 -- or else we're reading an hs-boot file, or -XEmptyDataDecls
747 ; checkTc (not (null cons) || empty_data_decls || is_boot)
748 (emptyConDeclsErr tc_name)
750 ; tycon <- fixM (\ tycon -> do
751 { data_cons <- mapM (addLocM (tcConDecl unbox_strict ex_ok tycon final_tvs))
754 if null cons && is_boot -- In a hs-boot file, empty cons means
755 then return AbstractTyCon -- "don't know"; hence Abstract
756 else case new_or_data of
757 DataType -> return (mkDataTyConRhs data_cons)
759 ASSERT( not (null data_cons) )
760 mkNewTyConRhs tc_name tycon (head data_cons)
761 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
762 (want_generic && canDoGenerics data_cons) h98_syntax Nothing
764 ; return [ATyCon tycon]
767 is_rec = calc_isrec tc_name
768 h98_syntax = case cons of -- All constructors have same shape
769 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
772 tcTyClDecl1 calc_isrec
773 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
774 tcdCtxt = ctxt, tcdMeths = meths,
775 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
776 = tcTyVarBndrs tvs $ \ tvs' -> do
777 { ctxt' <- tcHsKindedContext ctxt
778 ; fds' <- mapM (addLocM tc_fundep) fundeps
779 ; atss <- mapM (addLocM (tcTyClDecl1 (const Recursive))) ats
780 -- NB: 'ats' only contains "type family" and "data family"
781 -- declarations as well as type family defaults
782 ; let ats' = zipWith setTyThingPoss atss (map (tcdTyVars . unLoc) ats)
783 ; sig_stuff <- tcClassSigs class_name sigs meths
784 ; clas <- fixM (\ clas ->
785 let -- This little knot is just so we can get
786 -- hold of the name of the class TyCon, which we
787 -- need to look up its recursiveness
788 tycon_name = tyConName (classTyCon clas)
789 tc_isrec = calc_isrec tycon_name
791 buildClass False {- Must include unfoldings for selectors -}
792 class_name tvs' ctxt' fds' ats'
794 ; return (AClass clas : ats')
795 -- NB: Order is important due to the call to `mkGlobalThings' when
796 -- tying the the type and class declaration type checking knot.
799 tc_fundep (tvs1, tvs2) = do { tvs1' <- mapM tcLookupTyVar tvs1 ;
800 ; tvs2' <- mapM tcLookupTyVar tvs2 ;
801 ; return (tvs1', tvs2') }
803 -- For each AT argument compute the position of the corresponding class
804 -- parameter in the class head. This will later serve as a permutation
805 -- vector when checking the validity of instance declarations.
806 setTyThingPoss [ATyCon tycon] atTyVars =
807 let classTyVars = hsLTyVarNames tvs
809 . map (`elemIndex` classTyVars)
812 -- There will be no Nothing, as we already passed renaming
814 ATyCon (setTyConArgPoss tycon poss)
815 setTyThingPoss _ _ = panic "TcTyClsDecls.setTyThingPoss"
818 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
819 = return [ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0)]
821 tcTyClDecl1 _ d = pprPanic "tcTyClDecl1" (ppr d)
823 -----------------------------------
824 tcConDecl :: Bool -- True <=> -funbox-strict_fields
825 -> Bool -- True <=> -XExistentialQuantificaton or -XGADTs
830 tcConDecl unbox_strict existential_ok tycon tc_tvs -- Data types
831 (ConDecl name _ tvs ctxt details res_ty _)
832 = addErrCtxt (dataConCtxt name) $
833 tcTyVarBndrs tvs $ \ tvs' -> do
834 { ctxt' <- tcHsKindedContext ctxt
835 ; checkTc (existential_ok || (null tvs && null (unLoc ctxt)))
836 (badExistential name)
837 ; (univ_tvs, ex_tvs, eq_preds, data_tc) <- tcResultType tycon tc_tvs tvs' res_ty
839 -- Tiresome: tidy the tyvar binders, since tc_tvs and tvs' may have the same OccNames
840 tc_datacon is_infix field_lbls btys
841 = do { let bangs = map getBangStrictness btys
842 ; arg_tys <- mapM tcHsBangType btys
843 ; buildDataCon (unLoc name) is_infix
844 (argStrictness unbox_strict bangs arg_tys)
845 (map unLoc field_lbls)
846 univ_tvs ex_tvs eq_preds ctxt' arg_tys
848 -- NB: we put data_tc, the type constructor gotten from the
849 -- constructor type signature into the data constructor;
850 -- that way checkValidDataCon can complain if it's wrong.
853 PrefixCon btys -> tc_datacon False [] btys
854 InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
855 RecCon fields -> tc_datacon False field_names btys
857 field_names = map cd_fld_name fields
858 btys = map cd_fld_type fields
861 tcResultType :: TyCon
862 -> [TyVar] -- data T a b c = ...
863 -> [TyVar] -- where MkT :: forall a b c. ...
865 -> TcM ([TyVar], -- Universal
866 [TyVar], -- Existential (distinct OccNames from univs)
867 [(TyVar,Type)], -- Equality predicates
868 TyCon) -- TyCon given in the ResTy
869 -- We don't check that the TyCon given in the ResTy is
870 -- the same as the parent tycon, becuase we are in the middle
871 -- of a recursive knot; so it's postponed until checkValidDataCon
873 tcResultType decl_tycon tc_tvs dc_tvs ResTyH98
874 = return (tc_tvs, dc_tvs, [], decl_tycon)
875 -- In H98 syntax the dc_tvs are the existential ones
876 -- data T a b c = forall d e. MkT ...
877 -- The {a,b,c} are tc_tvs, and {d,e} are dc_tvs
879 tcResultType _ tc_tvs dc_tvs (ResTyGADT res_ty)
880 -- E.g. data T a b c where
881 -- MkT :: forall x y z. T (x,y) z z
883 -- ([a,z,c], [x,y], [a:=:(x,y), c:=:z], T)
885 = do { (dc_tycon, res_tys) <- tcLHsConResTy res_ty
887 ; let univ_tvs = choose_univs [] tidy_tc_tvs res_tys
888 -- Each univ_tv is either a dc_tv or a tc_tv
889 ex_tvs = dc_tvs `minusList` univ_tvs
890 eq_spec = [ (tv, ty) | (tv,ty) <- univ_tvs `zip` res_tys,
892 ; return (univ_tvs, ex_tvs, eq_spec, dc_tycon) }
894 -- choose_univs uses the res_ty itself if it's a type variable
895 -- and hasn't already been used; otherwise it uses one of the tc_tvs
896 choose_univs _ tc_tvs []
897 = ASSERT( null tc_tvs ) []
898 choose_univs used (tc_tv:tc_tvs) (res_ty:res_tys)
899 | Just tv <- tcGetTyVar_maybe res_ty, not (tv `elem` used)
900 = tv : choose_univs (tv:used) tc_tvs res_tys
902 = tc_tv : choose_univs used tc_tvs res_tys
904 -- NB: tc_tvs and dc_tvs are distinct, but
905 -- we want them to be *visibly* distinct, both for
906 -- interface files and general confusion. So rename
907 -- the tc_tvs, since they are not used yet (no
908 -- consequential renaming needed)
909 choose_univs _ _ _ = panic "tcResultType/choose_univs"
910 init_occ_env = initTidyOccEnv (map getOccName dc_tvs)
911 (_, tidy_tc_tvs) = mapAccumL tidy_one init_occ_env tc_tvs
912 tidy_one env tv = (env', setTyVarName tv (tidyNameOcc name occ'))
915 (env', occ') = tidyOccName env (getOccName name)
918 argStrictness :: Bool -- True <=> -funbox-strict_fields
920 -> [TcType] -> [StrictnessMark]
921 argStrictness unbox_strict bangs arg_tys
922 = ASSERT( length bangs == length arg_tys )
923 zipWith (chooseBoxingStrategy unbox_strict) arg_tys bangs
925 -- We attempt to unbox/unpack a strict field when either:
926 -- (i) The field is marked '!!', or
927 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
929 -- We have turned off unboxing of newtypes because coercions make unboxing
930 -- and reboxing more complicated
931 chooseBoxingStrategy :: Bool -> TcType -> HsBang -> StrictnessMark
932 chooseBoxingStrategy unbox_strict_fields arg_ty bang
934 HsNoBang -> NotMarkedStrict
935 HsStrict | unbox_strict_fields
936 && can_unbox arg_ty -> MarkedUnboxed
937 HsUnbox | can_unbox arg_ty -> MarkedUnboxed
940 -- we can unbox if the type is a chain of newtypes with a product tycon
942 can_unbox arg_ty = case splitTyConApp_maybe arg_ty of
944 Just (arg_tycon, tycon_args) ->
945 not (isRecursiveTyCon arg_tycon) && -- Note [Recusive unboxing]
946 isProductTyCon arg_tycon &&
947 (if isNewTyCon arg_tycon then
948 can_unbox (newTyConInstRhs arg_tycon tycon_args)
952 Note [Recursive unboxing]
953 ~~~~~~~~~~~~~~~~~~~~~~~~~
954 Be careful not to try to unbox this!
956 But it's the *argument* type that matters. This is fine:
958 because Int is non-recursive.
960 %************************************************************************
962 \subsection{Dependency analysis}
964 %************************************************************************
966 Validity checking is done once the mutually-recursive knot has been
967 tied, so we can look at things freely.
970 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
971 checkCycleErrs tyclss
975 = do { mapM_ recClsErr cls_cycles
976 ; failM } -- Give up now, because later checkValidTyCl
977 -- will loop if the synonym is recursive
979 cls_cycles = calcClassCycles tyclss
981 checkValidTyCl :: TyClDecl Name -> TcM ()
982 -- We do the validity check over declarations, rather than TyThings
983 -- only so that we can add a nice context with tcAddDeclCtxt
985 = tcAddDeclCtxt decl $
986 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
987 ; traceTc (text "Validity of" <+> ppr thing)
989 ATyCon tc -> checkValidTyCon tc
990 AClass cl -> checkValidClass cl
991 _ -> panic "checkValidTyCl"
992 ; traceTc (text "Done validity of" <+> ppr thing)
995 -------------------------
996 -- For data types declared with record syntax, we require
997 -- that each constructor that has a field 'f'
998 -- (a) has the same result type
999 -- (b) has the same type for 'f'
1000 -- module alpha conversion of the quantified type variables
1001 -- of the constructor.
1003 checkValidTyCon :: TyCon -> TcM ()
1006 = case synTyConRhs tc of
1007 OpenSynTyCon _ _ -> return ()
1008 SynonymTyCon ty -> checkValidType syn_ctxt ty
1010 = do -- Check the context on the data decl
1011 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc)
1013 -- Check arg types of data constructors
1014 mapM_ (checkValidDataCon tc) data_cons
1016 -- Check that fields with the same name share a type
1017 mapM_ check_fields groups
1020 syn_ctxt = TySynCtxt name
1022 data_cons = tyConDataCons tc
1024 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
1025 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
1026 get_fields con = dataConFieldLabels con `zip` repeat con
1027 -- dataConFieldLabels may return the empty list, which is fine
1029 -- See Note [GADT record selectors] in MkId.lhs
1030 -- We must check (a) that the named field has the same
1031 -- type in each constructor
1032 -- (b) that those constructors have the same result type
1034 -- However, the constructors may have differently named type variable
1035 -- and (worse) we don't know how the correspond to each other. E.g.
1036 -- C1 :: forall a b. { f :: a, g :: b } -> T a b
1037 -- C2 :: forall d c. { f :: c, g :: c } -> T c d
1039 -- So what we do is to ust Unify.tcMatchTys to compare the first candidate's
1040 -- result type against other candidates' types BOTH WAYS ROUND.
1041 -- If they magically agrees, take the substitution and
1042 -- apply them to the latter ones, and see if they match perfectly.
1043 check_fields ((label, con1) : other_fields)
1044 -- These fields all have the same name, but are from
1045 -- different constructors in the data type
1046 = recoverM (return ()) $ mapM_ checkOne other_fields
1047 -- Check that all the fields in the group have the same type
1048 -- NB: this check assumes that all the constructors of a given
1049 -- data type use the same type variables
1051 (tvs1, _, _, res1) = dataConSig con1
1053 fty1 = dataConFieldType con1 label
1055 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
1056 = do { checkFieldCompat label con1 con2 ts1 res1 res2 fty1 fty2
1057 ; checkFieldCompat label con2 con1 ts2 res2 res1 fty2 fty1 }
1059 (tvs2, _, _, res2) = dataConSig con2
1061 fty2 = dataConFieldType con2 label
1062 check_fields [] = panic "checkValidTyCon/check_fields []"
1064 checkFieldCompat :: Name -> DataCon -> DataCon -> TyVarSet
1065 -> Type -> Type -> Type -> Type -> TcM ()
1066 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
1067 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
1068 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
1070 mb_subst1 = tcMatchTy tvs1 res1 res2
1071 mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
1073 -------------------------------
1074 checkValidDataCon :: TyCon -> DataCon -> TcM ()
1075 checkValidDataCon tc con
1076 = setSrcSpan (srcLocSpan (getSrcLoc con)) $
1077 addErrCtxt (dataConCtxt con) $
1078 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
1079 ; checkValidType ctxt (dataConUserType con)
1080 ; checkValidMonoType (dataConOrigResTy con)
1081 -- Disallow MkT :: T (forall a. a->a)
1082 -- Reason: it's really the argument of an equality constraint
1083 ; when (isNewTyCon tc) (checkNewDataCon con)
1086 ctxt = ConArgCtxt (dataConName con)
1088 -------------------------------
1089 checkNewDataCon :: DataCon -> TcM ()
1090 -- Checks for the data constructor of a newtype
1092 = do { checkTc (isSingleton arg_tys) (newtypeFieldErr con (length arg_tys))
1094 ; checkTc (null eq_spec) (newtypePredError con)
1095 -- Return type is (T a b c)
1096 ; checkTc (null ex_tvs && null eq_theta && null dict_theta) (newtypeExError con)
1098 ; checkTc (not (any isMarkedStrict (dataConStrictMarks con)))
1099 (newtypeStrictError con)
1103 (_univ_tvs, ex_tvs, eq_spec, eq_theta, dict_theta, arg_tys, _res_ty) = dataConFullSig con
1105 -------------------------------
1106 checkValidClass :: Class -> TcM ()
1108 = do { constrained_class_methods <- doptM Opt_ConstrainedClassMethods
1109 ; multi_param_type_classes <- doptM Opt_MultiParamTypeClasses
1110 ; fundep_classes <- doptM Opt_FunctionalDependencies
1112 -- Check that the class is unary, unless GlaExs
1113 ; checkTc (notNull tyvars) (nullaryClassErr cls)
1114 ; checkTc (multi_param_type_classes || unary) (classArityErr cls)
1115 ; checkTc (fundep_classes || null fundeps) (classFunDepsErr cls)
1117 -- Check the super-classes
1118 ; checkValidTheta (ClassSCCtxt (className cls)) theta
1120 -- Check the class operations
1121 ; mapM_ (check_op constrained_class_methods) op_stuff
1123 -- Check that if the class has generic methods, then the
1124 -- class has only one parameter. We can't do generic
1125 -- multi-parameter type classes!
1126 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
1129 (tyvars, fundeps, theta, _, _, op_stuff) = classExtraBigSig cls
1130 unary = isSingleton tyvars
1131 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
1133 check_op constrained_class_methods (sel_id, dm)
1134 = addErrCtxt (classOpCtxt sel_id tau) $ do
1135 { checkValidTheta SigmaCtxt (tail theta)
1136 -- The 'tail' removes the initial (C a) from the
1137 -- class itself, leaving just the method type
1139 ; traceTc (text "class op type" <+> ppr op_ty <+> ppr tau)
1140 ; checkValidType (FunSigCtxt op_name) tau
1142 -- Check that the type mentions at least one of
1143 -- the class type variables...or at least one reachable
1144 -- from one of the class variables. Example: tc223
1145 -- class Error e => Game b mv e | b -> mv e where
1146 -- newBoard :: MonadState b m => m ()
1147 -- Here, MonadState has a fundep m->b, so newBoard is fine
1148 ; let grown_tyvars = grow theta (mkVarSet tyvars)
1149 ; checkTc (tyVarsOfType tau `intersectsVarSet` grown_tyvars)
1150 (noClassTyVarErr cls sel_id)
1152 -- Check that for a generic method, the type of
1153 -- the method is sufficiently simple
1154 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
1155 (badGenericMethodType op_name op_ty)
1158 op_name = idName sel_id
1159 op_ty = idType sel_id
1160 (_,theta1,tau1) = tcSplitSigmaTy op_ty
1161 (_,theta2,tau2) = tcSplitSigmaTy tau1
1162 (theta,tau) | constrained_class_methods = (theta1 ++ theta2, tau2)
1163 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
1164 -- Ugh! The function might have a type like
1165 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
1166 -- With -XConstrainedClassMethods, we want to allow this, even though the inner
1167 -- forall has an (Eq a) constraint. Whereas in general, each constraint
1168 -- in the context of a for-all must mention at least one quantified
1169 -- type variable. What a mess!
1172 ---------------------------------------------------------------------
1173 resultTypeMisMatch :: Name -> DataCon -> DataCon -> SDoc
1174 resultTypeMisMatch field_name con1 con2
1175 = vcat [sep [ptext (sLit "Constructors") <+> ppr con1 <+> ptext (sLit "and") <+> ppr con2,
1176 ptext (sLit "have a common field") <+> quotes (ppr field_name) <> comma],
1177 nest 2 $ ptext (sLit "but have different result types")]
1179 fieldTypeMisMatch :: Name -> DataCon -> DataCon -> SDoc
1180 fieldTypeMisMatch field_name con1 con2
1181 = sep [ptext (sLit "Constructors") <+> ppr con1 <+> ptext (sLit "and") <+> ppr con2,
1182 ptext (sLit "give different types for field"), quotes (ppr field_name)]
1184 dataConCtxt :: Outputable a => a -> SDoc
1185 dataConCtxt con = ptext (sLit "In the definition of data constructor") <+> quotes (ppr con)
1187 classOpCtxt :: Var -> Type -> SDoc
1188 classOpCtxt sel_id tau = sep [ptext (sLit "When checking the class method:"),
1189 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
1191 nullaryClassErr :: Class -> SDoc
1193 = ptext (sLit "No parameters for class") <+> quotes (ppr cls)
1195 classArityErr :: Class -> SDoc
1197 = vcat [ptext (sLit "Too many parameters for class") <+> quotes (ppr cls),
1198 parens (ptext (sLit "Use -XMultiParamTypeClasses to allow multi-parameter classes"))]
1200 classFunDepsErr :: Class -> SDoc
1202 = vcat [ptext (sLit "Fundeps in class") <+> quotes (ppr cls),
1203 parens (ptext (sLit "Use -XFunctionalDependencies to allow fundeps"))]
1205 noClassTyVarErr :: Class -> Var -> SDoc
1206 noClassTyVarErr clas op
1207 = sep [ptext (sLit "The class method") <+> quotes (ppr op),
1208 ptext (sLit "mentions none of the type variables of the class") <+>
1209 ppr clas <+> hsep (map ppr (classTyVars clas))]
1211 genericMultiParamErr :: Class -> SDoc
1212 genericMultiParamErr clas
1213 = ptext (sLit "The multi-parameter class") <+> quotes (ppr clas) <+>
1214 ptext (sLit "cannot have generic methods")
1216 badGenericMethodType :: Name -> Kind -> SDoc
1217 badGenericMethodType op op_ty
1218 = hang (ptext (sLit "Generic method type is too complex"))
1219 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
1220 ptext (sLit "You can only use type variables, arrows, lists, and tuples")])
1222 recSynErr :: [LTyClDecl Name] -> TcRn ()
1224 = setSrcSpan (getLoc (head sorted_decls)) $
1225 addErr (sep [ptext (sLit "Cycle in type synonym declarations:"),
1226 nest 2 (vcat (map ppr_decl sorted_decls))])
1228 sorted_decls = sortLocated syn_decls
1229 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
1231 recClsErr :: [Located (TyClDecl Name)] -> TcRn ()
1233 = setSrcSpan (getLoc (head sorted_decls)) $
1234 addErr (sep [ptext (sLit "Cycle in class declarations (via superclasses):"),
1235 nest 2 (vcat (map ppr_decl sorted_decls))])
1237 sorted_decls = sortLocated cls_decls
1238 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
1240 sortLocated :: [Located a] -> [Located a]
1241 sortLocated things = sortLe le things
1243 le (L l1 _) (L l2 _) = l1 <= l2
1245 badDataConTyCon :: DataCon -> SDoc
1246 badDataConTyCon data_con
1247 = hang (ptext (sLit "Data constructor") <+> quotes (ppr data_con) <+>
1248 ptext (sLit "returns type") <+> quotes (ppr (dataConTyCon data_con)))
1249 2 (ptext (sLit "instead of its parent type"))
1251 badGadtDecl :: Name -> SDoc
1253 = vcat [ ptext (sLit "Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
1254 , nest 2 (parens $ ptext (sLit "Use -XGADTs to allow GADTs")) ]
1256 badExistential :: Located Name -> SDoc
1257 badExistential con_name
1258 = hang (ptext (sLit "Data constructor") <+> quotes (ppr con_name) <+>
1259 ptext (sLit "has existential type variables, or a context"))
1260 2 (parens $ ptext (sLit "Use -XExistentialQuantification or -XGADTs to allow this"))
1262 badStupidTheta :: Name -> SDoc
1263 badStupidTheta tc_name
1264 = ptext (sLit "A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
1266 newtypeConError :: Name -> Int -> SDoc
1267 newtypeConError tycon n
1268 = sep [ptext (sLit "A newtype must have exactly one constructor,"),
1269 nest 2 $ ptext (sLit "but") <+> quotes (ppr tycon) <+> ptext (sLit "has") <+> speakN n ]
1271 newtypeExError :: DataCon -> SDoc
1273 = sep [ptext (sLit "A newtype constructor cannot have an existential context,"),
1274 nest 2 $ ptext (sLit "but") <+> quotes (ppr con) <+> ptext (sLit "does")]
1276 newtypeStrictError :: DataCon -> SDoc
1277 newtypeStrictError con
1278 = sep [ptext (sLit "A newtype constructor cannot have a strictness annotation,"),
1279 nest 2 $ ptext (sLit "but") <+> quotes (ppr con) <+> ptext (sLit "does")]
1281 newtypePredError :: DataCon -> SDoc
1282 newtypePredError con
1283 = sep [ptext (sLit "A newtype constructor must have a return type of form T a1 ... an"),
1284 nest 2 $ ptext (sLit "but") <+> quotes (ppr con) <+> ptext (sLit "does not")]
1286 newtypeFieldErr :: DataCon -> Int -> SDoc
1287 newtypeFieldErr con_name n_flds
1288 = sep [ptext (sLit "The constructor of a newtype must have exactly one field"),
1289 nest 2 $ ptext (sLit "but") <+> quotes (ppr con_name) <+> ptext (sLit "has") <+> speakN n_flds]
1291 badSigTyDecl :: Name -> SDoc
1292 badSigTyDecl tc_name
1293 = vcat [ ptext (sLit "Illegal kind signature") <+>
1294 quotes (ppr tc_name)
1295 , nest 2 (parens $ ptext (sLit "Use -XKindSignatures to allow kind signatures")) ]
1297 badFamInstDecl :: Outputable a => a -> SDoc
1298 badFamInstDecl tc_name
1299 = vcat [ ptext (sLit "Illegal family instance for") <+>
1300 quotes (ppr tc_name)
1301 , nest 2 (parens $ ptext (sLit "Use -XTypeFamilies to allow indexed type families")) ]
1303 badGadtIdxTyDecl :: Name -> SDoc
1304 badGadtIdxTyDecl tc_name
1305 = vcat [ ptext (sLit "Illegal generalised algebraic data declaration for") <+>
1306 quotes (ppr tc_name)
1307 , nest 2 (parens $ ptext (sLit "Family instances can not yet use GADT declarations")) ]
1309 tooManyParmsErr :: Located Name -> SDoc
1310 tooManyParmsErr tc_name
1311 = ptext (sLit "Family instance has too many parameters:") <+>
1312 quotes (ppr tc_name)
1314 tooFewParmsErr :: Arity -> SDoc
1315 tooFewParmsErr arity
1316 = ptext (sLit "Family instance has too few parameters; expected") <+>
1319 wrongNumberOfParmsErr :: Arity -> SDoc
1320 wrongNumberOfParmsErr exp_arity
1321 = ptext (sLit "Number of parameters must match family declaration; expected")
1324 badBootFamInstDeclErr :: SDoc
1325 badBootFamInstDeclErr =
1326 ptext (sLit "Illegal family instance in hs-boot file")
1328 wrongKindOfFamily :: TyCon -> SDoc
1329 wrongKindOfFamily family =
1330 ptext (sLit "Wrong category of family instance; declaration was for a") <+>
1333 kindOfFamily | isSynTyCon family = ptext (sLit "type synonym")
1334 | isAlgTyCon family = ptext (sLit "data type")
1335 | otherwise = pprPanic "wrongKindOfFamily" (ppr family)
1337 emptyConDeclsErr :: Name -> SDoc
1338 emptyConDeclsErr tycon
1339 = sep [quotes (ppr tycon) <+> ptext (sLit "has no constructors"),
1340 nest 2 $ ptext (sLit "(-XEmptyDataDecls permits this)")]