2 % (c) The University of Glasgow 2006
3 % (c) The AQUA Project, Glasgow University, 1996-1998
6 TcTyClsDecls: Typecheck type and class declarations
10 tcTyAndClassDecls, tcFamInstDecl
13 #include "HsVersions.h"
50 import Control.Monad ( mplus )
54 %************************************************************************
56 \subsection{Type checking for type and class declarations}
58 %************************************************************************
62 Consider a mutually-recursive group, binding
63 a type constructor T and a class C.
65 Step 1: getInitialKind
66 Construct a KindEnv by binding T and C to a kind variable
69 In that environment, do a kind check
71 Step 3: Zonk the kinds
73 Step 4: buildTyConOrClass
74 Construct an environment binding T to a TyCon and C to a Class.
75 a) Their kinds comes from zonking the relevant kind variable
76 b) Their arity (for synonyms) comes direct from the decl
77 c) The funcional dependencies come from the decl
78 d) The rest comes a knot-tied binding of T and C, returned from Step 4
79 e) The variances of the tycons in the group is calculated from
83 In this environment, walk over the decls, constructing the TyCons and Classes.
84 This uses in a strict way items (a)-(c) above, which is why they must
85 be constructed in Step 4. Feed the results back to Step 4.
86 For this step, pass the is-recursive flag as the wimp-out flag
90 Step 6: Extend environment
91 We extend the type environment with bindings not only for the TyCons and Classes,
92 but also for their "implicit Ids" like data constructors and class selectors
94 Step 7: checkValidTyCl
95 For a recursive group only, check all the decls again, just
96 to check all the side conditions on validity. We could not
97 do this before because we were in a mutually recursive knot.
99 Identification of recursive TyCons
100 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
101 The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to
104 Identifying a TyCon as recursive serves two purposes
106 1. Avoid infinite types. Non-recursive newtypes are treated as
107 "transparent", like type synonyms, after the type checker. If we did
108 this for all newtypes, we'd get infinite types. So we figure out for
109 each newtype whether it is "recursive", and add a coercion if so. In
110 effect, we are trying to "cut the loops" by identifying a loop-breaker.
112 2. Avoid infinite unboxing. This is nothing to do with newtypes.
116 Well, this function diverges, but we don't want the strictness analyser
117 to diverge. But the strictness analyser will diverge because it looks
118 deeper and deeper into the structure of T. (I believe there are
119 examples where the function does something sane, and the strictness
120 analyser still diverges, but I can't see one now.)
122 Now, concerning (1), the FC2 branch currently adds a coercion for ALL
123 newtypes. I did this as an experiment, to try to expose cases in which
124 the coercions got in the way of optimisations. If it turns out that we
125 can indeed always use a coercion, then we don't risk recursive types,
126 and don't need to figure out what the loop breakers are.
128 For newtype *families* though, we will always have a coercion, so they
129 are always loop breakers! So you can easily adjust the current
130 algorithm by simply treating all newtype families as loop breakers (and
131 indeed type families). I think.
134 tcTyAndClassDecls :: ModDetails -> [LTyClDecl Name]
135 -> TcM TcGblEnv -- Input env extended by types and classes
136 -- and their implicit Ids,DataCons
137 -- Fails if there are any errors
139 tcTyAndClassDecls boot_details allDecls
140 = checkNoErrs $ -- The code recovers internally, but if anything gave rise to
141 -- an error we'd better stop now, to avoid a cascade
142 do { -- Omit instances of type families; they are handled together
143 -- with the *heads* of class instances
144 ; let decls = filter (not . isFamInstDecl . unLoc) allDecls
146 -- First check for cyclic type synonysm or classes
147 -- See notes with checkCycleErrs
148 ; checkCycleErrs decls
150 ; traceTc (text "tcTyAndCl" <+> ppr mod)
151 ; (syn_tycons, alg_tyclss) <- fixM (\ ~(_rec_syn_tycons, rec_alg_tyclss) ->
152 do { let { -- Seperate ordinary synonyms from all other type and
153 -- class declarations and add all associated type
154 -- declarations from type classes. The latter is
155 -- required so that the temporary environment for the
156 -- knot includes all associated family declarations.
157 ; (syn_decls, alg_decls) = partition (isSynDecl . unLoc)
159 ; alg_at_decls = concatMap addATs alg_decls
161 -- Extend the global env with the knot-tied results
162 -- for data types and classes
164 -- We must populate the environment with the loop-tied
165 -- T's right away, because the kind checker may "fault
166 -- in" some type constructors that recursively
168 ; let gbl_things = mkGlobalThings alg_at_decls rec_alg_tyclss
169 ; tcExtendRecEnv gbl_things $ do
171 -- Kind-check the declarations
172 { (kc_syn_decls, kc_alg_decls) <- kcTyClDecls syn_decls alg_decls
174 ; let { -- Calculate rec-flag
175 ; calc_rec = calcRecFlags boot_details rec_alg_tyclss
176 ; tc_decl = addLocM (tcTyClDecl calc_rec) }
178 -- Type-check the type synonyms, and extend the envt
179 ; syn_tycons <- tcSynDecls kc_syn_decls
180 ; tcExtendGlobalEnv syn_tycons $ do
182 -- Type-check the data types and classes
183 { alg_tyclss <- mapM tc_decl kc_alg_decls
184 ; return (syn_tycons, concat alg_tyclss)
186 -- Finished with knot-tying now
187 -- Extend the environment with the finished things
188 ; tcExtendGlobalEnv (syn_tycons ++ alg_tyclss) $ do
190 -- Perform the validity check
191 { traceTc (text "ready for validity check")
192 ; mapM_ (addLocM checkValidTyCl) decls
193 ; traceTc (text "done")
195 -- Add the implicit things;
196 -- we want them in the environment because
197 -- they may be mentioned in interface files
198 -- NB: All associated types and their implicit things will be added a
199 -- second time here. This doesn't matter as the definitions are
201 ; let { implicit_things = concatMap implicitTyThings alg_tyclss }
202 ; traceTc ((text "Adding" <+> ppr alg_tyclss)
203 $$ (text "and" <+> ppr implicit_things))
204 ; tcExtendGlobalEnv implicit_things getGblEnv
207 -- Pull associated types out of class declarations, to tie them into the
209 -- NB: We put them in the same place in the list as `tcTyClDecl' will
210 -- eventually put the matching `TyThing's. That's crucial; otherwise,
211 -- the two argument lists of `mkGlobalThings' don't match up.
212 addATs decl@(L _ (ClassDecl {tcdATs = ats})) = decl : ats
215 mkGlobalThings :: [LTyClDecl Name] -- The decls
216 -> [TyThing] -- Knot-tied, in 1-1 correspondence with the decls
218 -- Driven by the Decls, and treating the TyThings lazily
219 -- make a TypeEnv for the new things
220 mkGlobalThings decls things
221 = map mk_thing (decls `zipLazy` things)
223 mk_thing (L _ (ClassDecl {tcdLName = L _ name}), ~(AClass cl))
225 mk_thing (L _ decl, ~(ATyCon tc))
226 = (tcdName decl, ATyCon tc)
227 #if __GLASGOW_HASKELL__ < 605
228 -- Old GHCs don't understand that ~... matches anything
229 mk_thing _ = panic "mkGlobalThings: Can't happen"
234 %************************************************************************
236 \subsection{Type checking family instances}
238 %************************************************************************
240 Family instances are somewhat of a hybrid. They are processed together with
241 class instance heads, but can contain data constructors and hence they share a
242 lot of kinding and type checking code with ordinary algebraic data types (and
246 tcFamInstDecl :: LTyClDecl Name -> TcM (Maybe TyThing) -- Nothing if error
247 tcFamInstDecl (L loc decl)
248 = -- Prime error recovery, set source location
249 recoverM (return Nothing) $
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 (Just (ATyCon tc))
266 tcFamInstDecl1 :: TyClDecl Name -> TcM TyCon
269 tcFamInstDecl1 (decl@TySynonym {tcdLName = L loc tc_name})
270 = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
271 do { -- check that the family declaration is for a synonym
272 unless (isSynTyCon family) $
273 addErr (wrongKindOfFamily family)
275 ; -- (1) kind check the right-hand side of the type equation
276 ; k_rhs <- kcCheckHsType (tcdSynRhs decl) resKind
278 -- we need the exact same number of type parameters as the family
280 ; let famArity = tyConArity family
281 ; checkTc (length k_typats == famArity) $
282 wrongNumberOfParmsErr famArity
284 -- (2) type check type equation
285 ; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
286 ; t_typats <- mapM tcHsKindedType k_typats
287 ; t_rhs <- tcHsKindedType k_rhs
290 -- - 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 (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') Nothing
663 ; return (ATyCon tycon)
665 tcSynDecl d = pprPanic "tcSynDecl" (ppr d)
668 tcTyClDecl :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
670 tcTyClDecl calc_isrec decl
671 = tcAddDeclCtxt decl (tcTyClDecl1 calc_isrec decl)
673 -- "type family" declarations
674 tcTyClDecl1 :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing]
675 tcTyClDecl1 _calc_isrec
676 (TyFamily {tcdFlavour = TypeFamily,
677 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = Just kind})
678 -- NB: kind at latest
681 = tcTyVarBndrs tvs $ \ tvs' -> do
682 { traceTc (text "type family: " <+> ppr tc_name)
683 ; idx_tys <- doptM Opt_TypeFamilies
685 -- Check that we don't use families without -XTypeFamilies
686 ; checkTc idx_tys $ badFamInstDecl tc_name
688 ; tycon <- buildSynTyCon tc_name tvs' (OpenSynTyCon kind Nothing) Nothing
689 ; return [ATyCon tycon]
692 -- "data family" declaration
693 tcTyClDecl1 _calc_isrec
694 (TyFamily {tcdFlavour = DataFamily,
695 tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = mb_kind})
696 = tcTyVarBndrs tvs $ \ tvs' -> do
697 { traceTc (text "data family: " <+> ppr tc_name)
698 ; extra_tvs <- tcDataKindSig mb_kind
699 ; let final_tvs = tvs' ++ extra_tvs -- we may not need these
701 ; idx_tys <- doptM Opt_TypeFamilies
703 -- Check that we don't use families without -XTypeFamilies
704 ; checkTc idx_tys $ badFamInstDecl tc_name
706 ; tycon <- buildAlgTyCon tc_name final_tvs []
707 mkOpenDataTyConRhs Recursive False True Nothing
708 ; return [ATyCon tycon]
711 -- "newtype" and "data"
712 -- NB: not used for newtype/data instances (whether associated or not)
713 tcTyClDecl1 calc_isrec
714 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
715 tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
716 = tcTyVarBndrs tvs $ \ tvs' -> do
717 { extra_tvs <- tcDataKindSig mb_ksig
718 ; let final_tvs = tvs' ++ extra_tvs
719 ; stupid_theta <- tcHsKindedContext ctxt
720 ; want_generic <- doptM Opt_Generics
721 ; unbox_strict <- doptM Opt_UnboxStrictFields
722 ; empty_data_decls <- doptM Opt_EmptyDataDecls
723 ; kind_signatures <- doptM Opt_KindSignatures
724 ; existential_ok <- doptM Opt_ExistentialQuantification
725 ; gadt_ok <- doptM Opt_GADTs
726 ; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
727 ; let ex_ok = existential_ok || gadt_ok -- Data cons can have existential context
729 -- Check that we don't use GADT syntax in H98 world
730 ; checkTc (gadt_ok || h98_syntax) (badGadtDecl tc_name)
732 -- Check that we don't use kind signatures without Glasgow extensions
733 ; checkTc (kind_signatures || isNothing mb_ksig) (badSigTyDecl tc_name)
735 -- Check that the stupid theta is empty for a GADT-style declaration
736 ; checkTc (null stupid_theta || h98_syntax) (badStupidTheta tc_name)
738 -- Check that a newtype has exactly one constructor
739 -- Do this before checking for empty data decls, so that
740 -- we don't suggest -XEmptyDataDecls for newtypes
741 ; checkTc (new_or_data == DataType || isSingleton cons)
742 (newtypeConError tc_name (length cons))
744 -- Check that there's at least one condecl,
745 -- or else we're reading an hs-boot file, or -XEmptyDataDecls
746 ; checkTc (not (null cons) || empty_data_decls || is_boot)
747 (emptyConDeclsErr tc_name)
749 ; tycon <- fixM (\ tycon -> do
750 { data_cons <- mapM (addLocM (tcConDecl unbox_strict ex_ok tycon final_tvs))
753 if null cons && is_boot -- In a hs-boot file, empty cons means
754 then return AbstractTyCon -- "don't know"; hence Abstract
755 else case new_or_data of
756 DataType -> return (mkDataTyConRhs data_cons)
758 ASSERT( not (null data_cons) )
759 mkNewTyConRhs tc_name tycon (head data_cons)
760 ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
761 (want_generic && canDoGenerics data_cons) h98_syntax Nothing
763 ; return [ATyCon tycon]
766 is_rec = calc_isrec tc_name
767 h98_syntax = case cons of -- All constructors have same shape
768 L _ (ConDecl { con_res = ResTyGADT _ }) : _ -> False
771 tcTyClDecl1 calc_isrec
772 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
773 tcdCtxt = ctxt, tcdMeths = meths,
774 tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} )
775 = tcTyVarBndrs tvs $ \ tvs' -> do
776 { ctxt' <- tcHsKindedContext ctxt
777 ; fds' <- mapM (addLocM tc_fundep) fundeps
778 ; atss <- mapM (addLocM (tcTyClDecl1 (const Recursive))) ats
779 -- NB: 'ats' only contains "type family" and "data family"
780 -- declarations as well as type family defaults
781 ; let ats' = zipWith setTyThingPoss atss (map (tcdTyVars . unLoc) ats)
782 ; sig_stuff <- tcClassSigs class_name sigs meths
783 ; clas <- fixM (\ clas ->
784 let -- This little knot is just so we can get
785 -- hold of the name of the class TyCon, which we
786 -- need to look up its recursiveness
787 tycon_name = tyConName (classTyCon clas)
788 tc_isrec = calc_isrec tycon_name
790 buildClass False {- Must include unfoldings for selectors -}
791 class_name tvs' ctxt' fds' ats'
793 ; return (AClass clas : ats')
794 -- NB: Order is important due to the call to `mkGlobalThings' when
795 -- tying the the type and class declaration type checking knot.
798 tc_fundep (tvs1, tvs2) = do { tvs1' <- mapM tcLookupTyVar tvs1 ;
799 ; tvs2' <- mapM tcLookupTyVar tvs2 ;
800 ; return (tvs1', tvs2') }
802 -- For each AT argument compute the position of the corresponding class
803 -- parameter in the class head. This will later serve as a permutation
804 -- vector when checking the validity of instance declarations.
805 setTyThingPoss [ATyCon tycon] atTyVars =
806 let classTyVars = hsLTyVarNames tvs
808 . map (`elemIndex` classTyVars)
811 -- There will be no Nothing, as we already passed renaming
813 ATyCon (setTyConArgPoss tycon poss)
814 setTyThingPoss _ _ = panic "TcTyClsDecls.setTyThingPoss"
817 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
818 = return [ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0)]
820 tcTyClDecl1 _ d = pprPanic "tcTyClDecl1" (ppr d)
822 -----------------------------------
823 tcConDecl :: Bool -- True <=> -funbox-strict_fields
824 -> Bool -- True <=> -XExistentialQuantificaton or -XGADTs
829 tcConDecl unbox_strict existential_ok tycon tc_tvs -- Data types
830 (ConDecl name _ tvs ctxt details res_ty _)
831 = addErrCtxt (dataConCtxt name) $
832 tcTyVarBndrs tvs $ \ tvs' -> do
833 { ctxt' <- tcHsKindedContext ctxt
834 ; checkTc (existential_ok || (null tvs && null (unLoc ctxt)))
835 (badExistential name)
836 ; (univ_tvs, ex_tvs, eq_preds, data_tc) <- tcResultType tycon tc_tvs tvs' res_ty
838 -- Tiresome: tidy the tyvar binders, since tc_tvs and tvs' may have the same OccNames
839 tc_datacon is_infix field_lbls btys
840 = do { let bangs = map getBangStrictness btys
841 ; arg_tys <- mapM tcHsBangType btys
842 ; buildDataCon (unLoc name) is_infix
843 (argStrictness unbox_strict bangs arg_tys)
844 (map unLoc field_lbls)
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 cd_fld_name fields
857 btys = map cd_fld_type fields
860 tcResultType :: TyCon
861 -> [TyVar] -- data T a b c = ...
862 -> [TyVar] -- where MkT :: forall a b c. ...
864 -> TcM ([TyVar], -- Universal
865 [TyVar], -- Existential (distinct OccNames from univs)
866 [(TyVar,Type)], -- Equality predicates
867 TyCon) -- TyCon given in the ResTy
868 -- We don't check that the TyCon given in the ResTy is
869 -- the same as the parent tycon, becuase we are in the middle
870 -- of a recursive knot; so it's postponed until checkValidDataCon
872 tcResultType decl_tycon tc_tvs dc_tvs ResTyH98
873 = return (tc_tvs, dc_tvs, [], decl_tycon)
874 -- In H98 syntax the dc_tvs are the existential ones
875 -- data T a b c = forall d e. MkT ...
876 -- The {a,b,c} are tc_tvs, and {d,e} are dc_tvs
878 tcResultType _ tc_tvs dc_tvs (ResTyGADT res_ty)
879 -- E.g. data T a b c where
880 -- MkT :: forall x y z. T (x,y) z z
882 -- ([a,z,c], [x,y], [a:=:(x,y), c:=:z], T)
884 = do { (dc_tycon, res_tys) <- tcLHsConResTy res_ty
886 ; let univ_tvs = choose_univs [] tidy_tc_tvs res_tys
887 -- Each univ_tv is either a dc_tv or a tc_tv
888 ex_tvs = dc_tvs `minusList` univ_tvs
889 eq_spec = [ (tv, ty) | (tv,ty) <- univ_tvs `zip` res_tys,
891 ; return (univ_tvs, ex_tvs, eq_spec, dc_tycon) }
893 -- choose_univs uses the res_ty itself if it's a type variable
894 -- and hasn't already been used; otherwise it uses one of the tc_tvs
895 choose_univs _ tc_tvs []
896 = ASSERT( null tc_tvs ) []
897 choose_univs used (tc_tv:tc_tvs) (res_ty:res_tys)
898 | Just tv <- tcGetTyVar_maybe res_ty, not (tv `elem` used)
899 = tv : choose_univs (tv:used) tc_tvs res_tys
901 = tc_tv : choose_univs used tc_tvs res_tys
903 -- NB: tc_tvs and dc_tvs are distinct, but
904 -- we want them to be *visibly* distinct, both for
905 -- interface files and general confusion. So rename
906 -- the tc_tvs, since they are not used yet (no
907 -- consequential renaming needed)
908 choose_univs _ _ _ = panic "tcResultType/choose_univs"
909 init_occ_env = initTidyOccEnv (map getOccName dc_tvs)
910 (_, tidy_tc_tvs) = mapAccumL tidy_one init_occ_env tc_tvs
911 tidy_one env tv = (env', setTyVarName tv (tidyNameOcc name occ'))
914 (env', occ') = tidyOccName env (getOccName name)
917 argStrictness :: Bool -- True <=> -funbox-strict_fields
919 -> [TcType] -> [StrictnessMark]
920 argStrictness unbox_strict bangs arg_tys
921 = ASSERT( length bangs == length arg_tys )
922 zipWith (chooseBoxingStrategy unbox_strict) arg_tys bangs
924 -- We attempt to unbox/unpack a strict field when either:
925 -- (i) The field is marked '!!', or
926 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
928 -- We have turned off unboxing of newtypes because coercions make unboxing
929 -- and reboxing more complicated
930 chooseBoxingStrategy :: Bool -> TcType -> HsBang -> StrictnessMark
931 chooseBoxingStrategy unbox_strict_fields arg_ty bang
933 HsNoBang -> NotMarkedStrict
934 HsStrict | unbox_strict_fields
935 && can_unbox arg_ty -> MarkedUnboxed
936 HsUnbox | can_unbox arg_ty -> MarkedUnboxed
939 -- we can unbox if the type is a chain of newtypes with a product tycon
941 can_unbox arg_ty = case splitTyConApp_maybe arg_ty of
943 Just (arg_tycon, tycon_args) ->
944 not (isRecursiveTyCon arg_tycon) && -- Note [Recusive unboxing]
945 isProductTyCon arg_tycon &&
946 (if isNewTyCon arg_tycon then
947 can_unbox (newTyConInstRhs arg_tycon tycon_args)
951 Note [Recursive unboxing]
952 ~~~~~~~~~~~~~~~~~~~~~~~~~
953 Be careful not to try to unbox this!
955 But it's the *argument* type that matters. This is fine:
957 because Int is non-recursive.
959 %************************************************************************
961 \subsection{Dependency analysis}
963 %************************************************************************
965 Validity checking is done once the mutually-recursive knot has been
966 tied, so we can look at things freely.
969 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
970 checkCycleErrs tyclss
974 = do { mapM_ recClsErr cls_cycles
975 ; failM } -- Give up now, because later checkValidTyCl
976 -- will loop if the synonym is recursive
978 cls_cycles = calcClassCycles tyclss
980 checkValidTyCl :: TyClDecl Name -> TcM ()
981 -- We do the validity check over declarations, rather than TyThings
982 -- only so that we can add a nice context with tcAddDeclCtxt
984 = tcAddDeclCtxt decl $
985 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
986 ; traceTc (text "Validity of" <+> ppr thing)
988 ATyCon tc -> checkValidTyCon tc
989 AClass cl -> checkValidClass cl
990 _ -> panic "checkValidTyCl"
991 ; traceTc (text "Done validity of" <+> ppr thing)
994 -------------------------
995 -- For data types declared with record syntax, we require
996 -- that each constructor that has a field 'f'
997 -- (a) has the same result type
998 -- (b) has the same type for 'f'
999 -- module alpha conversion of the quantified type variables
1000 -- of the constructor.
1002 checkValidTyCon :: TyCon -> TcM ()
1005 = case synTyConRhs tc of
1006 OpenSynTyCon _ _ -> return ()
1007 SynonymTyCon ty -> checkValidType syn_ctxt ty
1009 = do -- Check the context on the data decl
1010 checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc)
1012 -- Check arg types of data constructors
1013 mapM_ (checkValidDataCon tc) data_cons
1015 -- Check that fields with the same name share a type
1016 mapM_ check_fields groups
1019 syn_ctxt = TySynCtxt name
1021 data_cons = tyConDataCons tc
1023 groups = equivClasses cmp_fld (concatMap get_fields data_cons)
1024 cmp_fld (f1,_) (f2,_) = f1 `compare` f2
1025 get_fields con = dataConFieldLabels con `zip` repeat con
1026 -- dataConFieldLabels may return the empty list, which is fine
1028 -- See Note [GADT record selectors] in MkId.lhs
1029 -- We must check (a) that the named field has the same
1030 -- type in each constructor
1031 -- (b) that those constructors have the same result type
1033 -- However, the constructors may have differently named type variable
1034 -- and (worse) we don't know how the correspond to each other. E.g.
1035 -- C1 :: forall a b. { f :: a, g :: b } -> T a b
1036 -- C2 :: forall d c. { f :: c, g :: c } -> T c d
1038 -- So what we do is to ust Unify.tcMatchTys to compare the first candidate's
1039 -- result type against other candidates' types BOTH WAYS ROUND.
1040 -- If they magically agrees, take the substitution and
1041 -- apply them to the latter ones, and see if they match perfectly.
1042 check_fields ((label, con1) : other_fields)
1043 -- These fields all have the same name, but are from
1044 -- different constructors in the data type
1045 = recoverM (return ()) $ mapM_ checkOne other_fields
1046 -- Check that all the fields in the group have the same type
1047 -- NB: this check assumes that all the constructors of a given
1048 -- data type use the same type variables
1050 (tvs1, _, _, res1) = dataConSig con1
1052 fty1 = dataConFieldType con1 label
1054 checkOne (_, con2) -- Do it bothways to ensure they are structurally identical
1055 = do { checkFieldCompat label con1 con2 ts1 res1 res2 fty1 fty2
1056 ; checkFieldCompat label con2 con1 ts2 res2 res1 fty2 fty1 }
1058 (tvs2, _, _, res2) = dataConSig con2
1060 fty2 = dataConFieldType con2 label
1061 check_fields [] = panic "checkValidTyCon/check_fields []"
1063 checkFieldCompat :: Name -> DataCon -> DataCon -> TyVarSet
1064 -> Type -> Type -> Type -> Type -> TcM ()
1065 checkFieldCompat fld con1 con2 tvs1 res1 res2 fty1 fty2
1066 = do { checkTc (isJust mb_subst1) (resultTypeMisMatch fld con1 con2)
1067 ; checkTc (isJust mb_subst2) (fieldTypeMisMatch fld con1 con2) }
1069 mb_subst1 = tcMatchTy tvs1 res1 res2
1070 mb_subst2 = tcMatchTyX tvs1 (expectJust "checkFieldCompat" mb_subst1) fty1 fty2
1072 -------------------------------
1073 checkValidDataCon :: TyCon -> DataCon -> TcM ()
1074 checkValidDataCon tc con
1075 = setSrcSpan (srcLocSpan (getSrcLoc con)) $
1076 addErrCtxt (dataConCtxt con) $
1077 do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
1078 ; checkValidType ctxt (dataConUserType con)
1079 ; checkValidMonoType (dataConOrigResTy con)
1080 -- Disallow MkT :: T (forall a. a->a)
1081 -- Reason: it's really the argument of an equality constraint
1082 ; when (isNewTyCon tc) (checkNewDataCon con)
1085 ctxt = ConArgCtxt (dataConName con)
1087 -------------------------------
1088 checkNewDataCon :: DataCon -> TcM ()
1089 -- Checks for the data constructor of a newtype
1091 = do { checkTc (isSingleton arg_tys) (newtypeFieldErr con (length arg_tys))
1093 ; checkTc (null eq_spec) (newtypePredError con)
1094 -- Return type is (T a b c)
1095 ; checkTc (null ex_tvs && null eq_theta && null dict_theta) (newtypeExError con)
1097 ; checkTc (not (any isMarkedStrict (dataConStrictMarks con)))
1098 (newtypeStrictError con)
1102 (_univ_tvs, ex_tvs, eq_spec, eq_theta, dict_theta, arg_tys, _res_ty) = dataConFullSig con
1104 -------------------------------
1105 checkValidClass :: Class -> TcM ()
1107 = do { constrained_class_methods <- doptM Opt_ConstrainedClassMethods
1108 ; multi_param_type_classes <- doptM Opt_MultiParamTypeClasses
1109 ; fundep_classes <- doptM Opt_FunctionalDependencies
1111 -- Check that the class is unary, unless GlaExs
1112 ; checkTc (notNull tyvars) (nullaryClassErr cls)
1113 ; checkTc (multi_param_type_classes || unary) (classArityErr cls)
1114 ; checkTc (fundep_classes || null fundeps) (classFunDepsErr cls)
1116 -- Check the super-classes
1117 ; checkValidTheta (ClassSCCtxt (className cls)) theta
1119 -- Check the class operations
1120 ; mapM_ (check_op constrained_class_methods) op_stuff
1122 -- Check that if the class has generic methods, then the
1123 -- class has only one parameter. We can't do generic
1124 -- multi-parameter type classes!
1125 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
1128 (tyvars, fundeps, theta, _, _, op_stuff) = classExtraBigSig cls
1129 unary = isSingleton tyvars
1130 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
1132 check_op constrained_class_methods (sel_id, dm)
1133 = addErrCtxt (classOpCtxt sel_id tau) $ do
1134 { checkValidTheta SigmaCtxt (tail theta)
1135 -- The 'tail' removes the initial (C a) from the
1136 -- class itself, leaving just the method type
1138 ; traceTc (text "class op type" <+> ppr op_ty <+> ppr tau)
1139 ; checkValidType (FunSigCtxt op_name) tau
1141 -- Check that the type mentions at least one of
1142 -- the class type variables...or at least one reachable
1143 -- from one of the class variables. Example: tc223
1144 -- class Error e => Game b mv e | b -> mv e where
1145 -- newBoard :: MonadState b m => m ()
1146 -- Here, MonadState has a fundep m->b, so newBoard is fine
1147 ; let grown_tyvars = grow theta (mkVarSet tyvars)
1148 ; checkTc (tyVarsOfType tau `intersectsVarSet` grown_tyvars)
1149 (noClassTyVarErr cls sel_id)
1151 -- Check that for a generic method, the type of
1152 -- the method is sufficiently simple
1153 ; checkTc (dm /= GenDefMeth || validGenericMethodType tau)
1154 (badGenericMethodType op_name op_ty)
1157 op_name = idName sel_id
1158 op_ty = idType sel_id
1159 (_,theta1,tau1) = tcSplitSigmaTy op_ty
1160 (_,theta2,tau2) = tcSplitSigmaTy tau1
1161 (theta,tau) | constrained_class_methods = (theta1 ++ theta2, tau2)
1162 | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
1163 -- Ugh! The function might have a type like
1164 -- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
1165 -- With -XConstrainedClassMethods, we want to allow this, even though the inner
1166 -- forall has an (Eq a) constraint. Whereas in general, each constraint
1167 -- in the context of a for-all must mention at least one quantified
1168 -- type variable. What a mess!
1171 ---------------------------------------------------------------------
1172 resultTypeMisMatch :: Name -> DataCon -> DataCon -> SDoc
1173 resultTypeMisMatch field_name con1 con2
1174 = vcat [sep [ptext (sLit "Constructors") <+> ppr con1 <+> ptext (sLit "and") <+> ppr con2,
1175 ptext (sLit "have a common field") <+> quotes (ppr field_name) <> comma],
1176 nest 2 $ ptext (sLit "but have different result types")]
1178 fieldTypeMisMatch :: Name -> DataCon -> DataCon -> SDoc
1179 fieldTypeMisMatch field_name con1 con2
1180 = sep [ptext (sLit "Constructors") <+> ppr con1 <+> ptext (sLit "and") <+> ppr con2,
1181 ptext (sLit "give different types for field"), quotes (ppr field_name)]
1183 dataConCtxt :: Outputable a => a -> SDoc
1184 dataConCtxt con = ptext (sLit "In the definition of data constructor") <+> quotes (ppr con)
1186 classOpCtxt :: Var -> Type -> SDoc
1187 classOpCtxt sel_id tau = sep [ptext (sLit "When checking the class method:"),
1188 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
1190 nullaryClassErr :: Class -> SDoc
1192 = ptext (sLit "No parameters for class") <+> quotes (ppr cls)
1194 classArityErr :: Class -> SDoc
1196 = vcat [ptext (sLit "Too many parameters for class") <+> quotes (ppr cls),
1197 parens (ptext (sLit "Use -XMultiParamTypeClasses to allow multi-parameter classes"))]
1199 classFunDepsErr :: Class -> SDoc
1201 = vcat [ptext (sLit "Fundeps in class") <+> quotes (ppr cls),
1202 parens (ptext (sLit "Use -XFunctionalDependencies to allow fundeps"))]
1204 noClassTyVarErr :: Class -> Var -> SDoc
1205 noClassTyVarErr clas op
1206 = sep [ptext (sLit "The class method") <+> quotes (ppr op),
1207 ptext (sLit "mentions none of the type variables of the class") <+>
1208 ppr clas <+> hsep (map ppr (classTyVars clas))]
1210 genericMultiParamErr :: Class -> SDoc
1211 genericMultiParamErr clas
1212 = ptext (sLit "The multi-parameter class") <+> quotes (ppr clas) <+>
1213 ptext (sLit "cannot have generic methods")
1215 badGenericMethodType :: Name -> Kind -> SDoc
1216 badGenericMethodType op op_ty
1217 = hang (ptext (sLit "Generic method type is too complex"))
1218 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
1219 ptext (sLit "You can only use type variables, arrows, lists, and tuples")])
1221 recSynErr :: [LTyClDecl Name] -> TcRn ()
1223 = setSrcSpan (getLoc (head sorted_decls)) $
1224 addErr (sep [ptext (sLit "Cycle in type synonym declarations:"),
1225 nest 2 (vcat (map ppr_decl sorted_decls))])
1227 sorted_decls = sortLocated syn_decls
1228 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
1230 recClsErr :: [Located (TyClDecl Name)] -> TcRn ()
1232 = setSrcSpan (getLoc (head sorted_decls)) $
1233 addErr (sep [ptext (sLit "Cycle in class declarations (via superclasses):"),
1234 nest 2 (vcat (map ppr_decl sorted_decls))])
1236 sorted_decls = sortLocated cls_decls
1237 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
1239 sortLocated :: [Located a] -> [Located a]
1240 sortLocated things = sortLe le things
1242 le (L l1 _) (L l2 _) = l1 <= l2
1244 badDataConTyCon :: DataCon -> SDoc
1245 badDataConTyCon data_con
1246 = hang (ptext (sLit "Data constructor") <+> quotes (ppr data_con) <+>
1247 ptext (sLit "returns type") <+> quotes (ppr (dataConTyCon data_con)))
1248 2 (ptext (sLit "instead of its parent type"))
1250 badGadtDecl :: Name -> SDoc
1252 = vcat [ ptext (sLit "Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
1253 , nest 2 (parens $ ptext (sLit "Use -XGADTs to allow GADTs")) ]
1255 badExistential :: Located Name -> SDoc
1256 badExistential con_name
1257 = hang (ptext (sLit "Data constructor") <+> quotes (ppr con_name) <+>
1258 ptext (sLit "has existential type variables, or a context"))
1259 2 (parens $ ptext (sLit "Use -XExistentialQuantification or -XGADTs to allow this"))
1261 badStupidTheta :: Name -> SDoc
1262 badStupidTheta tc_name
1263 = ptext (sLit "A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
1265 newtypeConError :: Name -> Int -> SDoc
1266 newtypeConError tycon n
1267 = sep [ptext (sLit "A newtype must have exactly one constructor,"),
1268 nest 2 $ ptext (sLit "but") <+> quotes (ppr tycon) <+> ptext (sLit "has") <+> speakN n ]
1270 newtypeExError :: DataCon -> SDoc
1272 = sep [ptext (sLit "A newtype constructor cannot have an existential context,"),
1273 nest 2 $ ptext (sLit "but") <+> quotes (ppr con) <+> ptext (sLit "does")]
1275 newtypeStrictError :: DataCon -> SDoc
1276 newtypeStrictError con
1277 = sep [ptext (sLit "A newtype constructor cannot have a strictness annotation,"),
1278 nest 2 $ ptext (sLit "but") <+> quotes (ppr con) <+> ptext (sLit "does")]
1280 newtypePredError :: DataCon -> SDoc
1281 newtypePredError con
1282 = sep [ptext (sLit "A newtype constructor must have a return type of form T a1 ... an"),
1283 nest 2 $ ptext (sLit "but") <+> quotes (ppr con) <+> ptext (sLit "does not")]
1285 newtypeFieldErr :: DataCon -> Int -> SDoc
1286 newtypeFieldErr con_name n_flds
1287 = sep [ptext (sLit "The constructor of a newtype must have exactly one field"),
1288 nest 2 $ ptext (sLit "but") <+> quotes (ppr con_name) <+> ptext (sLit "has") <+> speakN n_flds]
1290 badSigTyDecl :: Name -> SDoc
1291 badSigTyDecl tc_name
1292 = vcat [ ptext (sLit "Illegal kind signature") <+>
1293 quotes (ppr tc_name)
1294 , nest 2 (parens $ ptext (sLit "Use -XKindSignatures to allow kind signatures")) ]
1296 badFamInstDecl :: Outputable a => a -> SDoc
1297 badFamInstDecl tc_name
1298 = vcat [ ptext (sLit "Illegal family instance for") <+>
1299 quotes (ppr tc_name)
1300 , nest 2 (parens $ ptext (sLit "Use -XTypeFamilies to allow indexed type families")) ]
1302 badGadtIdxTyDecl :: Name -> SDoc
1303 badGadtIdxTyDecl tc_name
1304 = vcat [ ptext (sLit "Illegal generalised algebraic data declaration for") <+>
1305 quotes (ppr tc_name)
1306 , nest 2 (parens $ ptext (sLit "Family instances can not yet use GADT declarations")) ]
1308 tooManyParmsErr :: Located Name -> SDoc
1309 tooManyParmsErr tc_name
1310 = ptext (sLit "Family instance has too many parameters:") <+>
1311 quotes (ppr tc_name)
1313 tooFewParmsErr :: Arity -> SDoc
1314 tooFewParmsErr arity
1315 = ptext (sLit "Family instance has too few parameters; expected") <+>
1318 wrongNumberOfParmsErr :: Arity -> SDoc
1319 wrongNumberOfParmsErr exp_arity
1320 = ptext (sLit "Number of parameters must match family declaration; expected")
1323 badBootFamInstDeclErr :: SDoc
1324 badBootFamInstDeclErr =
1325 ptext (sLit "Illegal family instance in hs-boot file")
1327 wrongKindOfFamily :: TyCon -> SDoc
1328 wrongKindOfFamily family =
1329 ptext (sLit "Wrong category of family instance; declaration was for a") <+>
1332 kindOfFamily | isSynTyCon family = ptext (sLit "type synonym")
1333 | isAlgTyCon family = ptext (sLit "data type")
1334 | otherwise = pprPanic "wrongKindOfFamily" (ppr family)
1336 emptyConDeclsErr :: Name -> SDoc
1337 emptyConDeclsErr tycon
1338 = sep [quotes (ppr tycon) <+> ptext (sLit "has no constructors"),
1339 nest 2 $ ptext (sLit "(-XEmptyDataDecls permits this)")]