2 % (c) The AQUA Project, Glasgow University, 1996-1998
4 \section[TcTyClsDecls]{Typecheck type and class declarations}
11 #include "HsVersions.h"
13 import HsSyn ( TyClDecl(..), HsConDetails(..), HsTyVarBndr(..),
14 ConDecl(..), Sig(..), BangType(..), HsBang(..),
15 tyClDeclTyVars, getBangType, getBangStrictness, isSynDecl,
16 LTyClDecl, tcdName, LHsTyVarBndr
18 import BasicTypes ( RecFlag(..), NewOrData(..), StrictnessMark(..) )
19 import HscTypes ( implicitTyThings )
20 import BuildTyCl ( buildClass, buildAlgTyCon, buildSynTyCon, buildDataCon )
22 import TcEnv ( TcTyThing(..), TyThing(..),
23 tcLookupLocated, tcLookupLocatedGlobal,
24 tcExtendGlobalEnv, tcExtendKindEnv,
25 tcExtendRecEnv, tcLookupTyVar )
26 import TcTyDecls ( calcTyConArgVrcs, calcRecFlags, calcClassCycles, calcSynCycles )
27 import TcClassDcl ( tcClassSigs, tcAddDeclCtxt )
28 import TcHsType ( kcHsTyVars, kcHsLiftedSigType, kcHsSigType, kcHsType,
29 kcHsContext, tcTyVarBndrs, tcHsKindedType, tcHsKindedContext )
30 import TcMType ( newKindVar, checkValidTheta, checkValidType, checkFreeness,
31 UserTypeCtxt(..), SourceTyCtxt(..) )
32 import TcUnify ( unifyKind )
33 import TcType ( TcKind, ThetaType, TcType, tyVarsOfType,
34 mkArrowKind, liftedTypeKind,
35 tcSplitSigmaTy, tcEqType )
36 import Type ( splitTyConApp_maybe, pprThetaArrow, pprParendType )
37 import FieldLabel ( fieldLabelName, fieldLabelType )
38 import Generics ( validGenericMethodType, canDoGenerics )
39 import Class ( Class, className, classTyCon, DefMeth(..), classBigSig, classTyVars )
40 import TyCon ( TyCon, ArgVrcs, DataConDetails(..),
41 tyConDataCons, mkForeignTyCon, isProductTyCon, isRecursiveTyCon,
42 tyConTheta, getSynTyConDefn, tyConDataCons, isSynTyCon, tyConName )
43 import DataCon ( DataCon, dataConWrapId, dataConName, dataConSig, dataConFieldLabels )
44 import Var ( TyVar, idType, idName )
45 import VarSet ( elemVarSet )
48 import Util ( zipLazy, isSingleton, notNull )
49 import List ( partition )
50 import SrcLoc ( Located(..), unLoc, getLoc )
51 import ListSetOps ( equivClasses )
52 import Digraph ( SCC(..) )
53 import CmdLineOpts ( DynFlag( Opt_GlasgowExts, Opt_Generics, Opt_UnboxStrictFields ) )
57 %************************************************************************
59 \subsection{Type checking for type and class declarations}
61 %************************************************************************
65 Consider a mutually-recursive group, binding
66 a type constructor T and a class C.
68 Step 1: getInitialKind
69 Construct a KindEnv by binding T and C to a kind variable
72 In that environment, do a kind check
74 Step 3: Zonk the kinds
76 Step 4: buildTyConOrClass
77 Construct an environment binding T to a TyCon and C to a Class.
78 a) Their kinds comes from zonking the relevant kind variable
79 b) Their arity (for synonyms) comes direct from the decl
80 c) The funcional dependencies come from the decl
81 d) The rest comes a knot-tied binding of T and C, returned from Step 4
82 e) The variances of the tycons in the group is calculated from
86 In this environment, walk over the decls, constructing the TyCons and Classes.
87 This uses in a strict way items (a)-(c) above, which is why they must
88 be constructed in Step 4. Feed the results back to Step 4.
89 For this step, pass the is-recursive flag as the wimp-out flag
93 Step 6: Extend environment
94 We extend the type environment with bindings not only for the TyCons and Classes,
95 but also for their "implicit Ids" like data constructors and class selectors
97 Step 7: checkValidTyCl
98 For a recursive group only, check all the decls again, just
99 to check all the side conditions on validity. We could not
100 do this before because we were in a mutually recursive knot.
103 The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to
104 @TyThing@s. @rec_vrcs@ is a finite map from @Name@s to @ArgVrcs@s.
107 tcTyAndClassDecls :: [LTyClDecl Name]
108 -> TcM TcGblEnv -- Input env extended by types and classes
109 -- and their implicit Ids,DataCons
110 tcTyAndClassDecls decls
111 = do { -- First check for cyclic type synonysm or classes
112 -- See notes with checkCycleErrs
115 ; (syn_tycons, alg_tyclss) <- fixM (\ ~(rec_syn_tycons, rec_alg_tyclss) ->
116 do { let { -- Calculate variances and rec-flag
117 ; (syn_decls, alg_decls) = partition (isSynDecl . unLoc) decls }
119 -- Extend the global env with the knot-tied results
120 -- for data types and classes
122 -- We must populate the environment with the loop-tied T's right
123 -- away, because the kind checker may "fault in" some type
124 -- constructors that recursively mention T
125 ; let { gbl_things = mkGlobalThings alg_decls rec_alg_tyclss }
126 ; tcExtendRecEnv gbl_things $ do
128 -- Kind-check the declarations
129 { (kc_syn_decls, kc_alg_decls) <- kcTyClDecls syn_decls alg_decls
131 ; let { calc_vrcs = calcTyConArgVrcs (rec_syn_tycons ++ rec_alg_tyclss)
132 ; calc_rec = calcRecFlags rec_alg_tyclss
133 ; tc_decl = addLocM (tcTyClDecl calc_vrcs calc_rec) }
134 -- Type-check the type synonyms, and extend the envt
135 ; syn_tycons <- tcSynDecls calc_vrcs kc_syn_decls
136 ; tcExtendGlobalEnv syn_tycons $ do
138 -- Type-check the data types and classes
139 { alg_tyclss <- mappM tc_decl kc_alg_decls
140 ; return (syn_tycons, alg_tyclss)
142 -- Finished with knot-tying now
143 -- Extend the environment with the finished things
144 ; tcExtendGlobalEnv (syn_tycons ++ alg_tyclss) $ do
146 -- Perform the validity check
147 { traceTc (text "ready for validity check")
148 ; mappM_ (addLocM checkValidTyCl) decls
149 ; traceTc (text "done")
151 -- Add the implicit things;
152 -- we want them in the environment because
153 -- they may be mentioned in interface files
154 ; let { implicit_things = concatMap implicitTyThings alg_tyclss }
155 ; traceTc ((text "Adding" <+> ppr alg_tyclss) $$ (text "and" <+> ppr implicit_things))
156 ; tcExtendGlobalEnv implicit_things getGblEnv
159 mkGlobalThings :: [LTyClDecl Name] -- The decls
160 -> [TyThing] -- Knot-tied, in 1-1 correspondence with the decls
162 -- Driven by the Decls, and treating the TyThings lazily
163 -- make a TypeEnv for the new things
164 mkGlobalThings decls things
165 = map mk_thing (decls `zipLazy` things)
167 mk_thing (L _ (ClassDecl {tcdLName = L _ name}), ~(AClass cl))
169 mk_thing (L _ decl, ~(ATyCon tc))
170 = (tcdName decl, ATyCon tc)
174 %************************************************************************
178 %************************************************************************
180 We need to kind check all types in the mutually recursive group
181 before we know the kind of the type variables. For example:
184 op :: D b => a -> b -> b
187 bop :: (Monad c) => ...
189 Here, the kind of the locally-polymorphic type variable "b"
190 depends on *all the uses of class D*. For example, the use of
191 Monad c in bop's type signature means that D must have kind Type->Type.
193 However type synonyms work differently. They can have kinds which don't
194 just involve (->) and *:
195 type R = Int# -- Kind #
196 type S a = Array# a -- Kind * -> #
197 type T a b = (# a,b #) -- Kind * -> * -> (# a,b #)
198 So we must infer their kinds from their right-hand sides *first* and then
199 use them, whereas for the mutually recursive data types D we bring into
200 scope kind bindings D -> k, where k is a kind variable, and do inference.
203 kcTyClDecls syn_decls alg_decls
204 = do { -- First extend the kind env with each data
205 -- type and class, mapping them to a type variable
206 alg_kinds <- mappM getInitialKind alg_decls
207 ; tcExtendKindEnv alg_kinds $ do
209 -- Now kind-check the type synonyms, in dependency order
210 -- We do these differently to data type and classes,
211 -- because a type synonym can be an unboxed type
213 -- and a kind variable can't unify with UnboxedTypeKind
214 -- So we infer their kinds in dependency order
215 { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls)
216 ; tcExtendKindEnv syn_kinds $ do
218 -- Now kind-check the data type and class declarations,
219 -- returning kind-annotated decls
220 { kc_alg_decls <- mappM (wrapLocM kcTyClDecl) alg_decls
222 ; return (kc_syn_decls, kc_alg_decls) }}}
224 ------------------------------------------------------------------------
225 getInitialKind :: LTyClDecl Name -> TcM (Name, TcKind)
228 = newKindVar `thenM` \ kind ->
229 returnM (unLoc (tcdLName (unLoc decl)), kind)
232 kcSynDecls :: [SCC (LTyClDecl Name)]
233 -> TcM ([LTyClDecl Name], -- Kind-annotated decls
234 [(Name,TcKind)]) -- Kind bindings
237 kcSynDecls (group : groups)
238 = do { (decl, nk) <- kcSynDecl group
239 ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups)
240 ; return (decl:decls, nk:nks) }
243 kcSynDecl :: SCC (LTyClDecl Name)
244 -> TcM (LTyClDecl Name, -- Kind-annotated decls
245 (Name,TcKind)) -- Kind bindings
246 kcSynDecl (AcyclicSCC ldecl@(L loc decl))
247 = tcAddDeclCtxt decl $
248 kcHsTyVars (tcdTyVars decl) (\ k_tvs ->
249 do { traceTc (text "kcd1" <+> ppr (unLoc (tcdLName decl)) <+> brackets (ppr (tcdTyVars decl))
250 <+> brackets (ppr k_tvs))
251 ; (k_rhs, rhs_kind) <- kcHsType (tcdSynRhs decl)
252 ; traceTc (text "kcd2" <+> ppr (unLoc (tcdLName decl)))
253 ; let tc_kind = foldr (mkArrowKind . kindedTyVarKind) rhs_kind k_tvs
254 ; return (L loc (decl { tcdTyVars = k_tvs, tcdSynRhs = k_rhs }),
255 (unLoc (tcdLName decl), tc_kind)) })
257 kcSynDecl (CyclicSCC decls)
258 = do { recSynErr decls; failM } -- Fail here to avoid error cascade
259 -- of out-of-scope tycons
261 ------------------------------------------------------------------------
262 kcTyClDecl :: TyClDecl Name -> TcM (TyClDecl Name)
263 -- Not used for type synonyms (see kcSynDecl)
265 kcTyClDecl decl@(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdCons = cons})
266 = kcTyClDeclBody decl $ \ tvs' ->
267 do { ctxt' <- kcHsContext ctxt
268 ; cons' <- mappM (wrapLocM kc_con_decl) cons
269 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdCons = cons'}) }
271 kc_con_decl (ConDecl name ex_tvs ex_ctxt details)
272 = kcHsTyVars ex_tvs $ \ ex_tvs' ->
273 do { ex_ctxt' <- kcHsContext ex_ctxt
274 ; details' <- kc_con_details details
275 ; return (ConDecl name ex_tvs' ex_ctxt' details')}
277 kc_con_details (PrefixCon btys)
278 = do { btys' <- mappM kc_larg_ty btys ; return (PrefixCon btys') }
279 kc_con_details (InfixCon bty1 bty2)
280 = do { bty1' <- kc_larg_ty bty1; bty2' <- kc_larg_ty bty2; return (InfixCon bty1' bty2') }
281 kc_con_details (RecCon fields)
282 = do { fields' <- mappM kc_field fields; return (RecCon fields') }
284 kc_field (fld, bty) = do { bty' <- kc_larg_ty bty ; return (fld, bty') }
286 kc_larg_ty = wrapLocM kc_arg_ty
288 kc_arg_ty (BangType str ty) = do { ty' <- kc_arg_ty_body ty; return (BangType str ty') }
289 kc_arg_ty_body = case new_or_data of
290 DataType -> kcHsSigType
291 NewType -> kcHsLiftedSigType
292 -- Can't allow an unlifted type for newtypes, because we're effectively
293 -- going to remove the constructor while coercing it to a lifted type.
295 kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs})
296 = kcTyClDeclBody decl $ \ tvs' ->
297 do { ctxt' <- kcHsContext ctxt
298 ; sigs' <- mappM (wrapLocM kc_sig) sigs
299 ; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs'}) }
301 kc_sig (Sig nm op_ty) = do { op_ty' <- kcHsLiftedSigType op_ty
302 ; return (Sig nm op_ty') }
303 kc_sig other_sig = return other_sig
305 kcTyClDecl decl@(ForeignType {})
308 kcTyClDeclBody :: TyClDecl Name
309 -> ([LHsTyVarBndr Name] -> TcM a)
311 -- Extend the env with bindings for the tyvars, taken from
312 -- the kind of the tycon/class. Give it to the thing inside, and
313 -- check the result kind matches
314 kcTyClDeclBody decl thing_inside
315 = tcAddDeclCtxt decl $
316 kcHsTyVars (tyClDeclTyVars decl) $ \ kinded_tvs ->
317 do { tc_ty_thing <- tcLookupLocated (tcdLName decl)
318 ; let tc_kind = case tc_ty_thing of { AThing k -> k }
319 ; unifyKind tc_kind (foldr (mkArrowKind . kindedTyVarKind)
320 liftedTypeKind kinded_tvs)
321 ; thing_inside kinded_tvs }
323 kindedTyVarKind (L _ (KindedTyVar _ k)) = k
327 %************************************************************************
329 \subsection{Type checking}
331 %************************************************************************
334 tcSynDecls :: (Name -> ArgVrcs) -> [LTyClDecl Name] -> TcM [TyThing]
335 tcSynDecls calc_vrcs [] = return []
336 tcSynDecls calc_vrcs (decl : decls)
337 = do { syn_tc <- addLocM (tcSynDecl calc_vrcs) decl
338 ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls calc_vrcs decls)
339 ; return (syn_tc : syn_tcs) }
342 (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty})
343 = tcTyVarBndrs tvs $ \ tvs' -> do
344 { traceTc (text "tcd1" <+> ppr tc_name)
345 ; rhs_ty' <- tcHsKindedType rhs_ty
346 ; return (ATyCon (buildSynTyCon tc_name tvs' rhs_ty' (calc_vrcs tc_name))) }
349 tcTyClDecl :: (Name -> ArgVrcs) -> (Name -> RecFlag)
350 -> TyClDecl Name -> TcM TyThing
352 tcTyClDecl calc_vrcs calc_isrec decl
353 = tcAddDeclCtxt decl (tcTyClDecl1 calc_vrcs calc_isrec decl)
355 tcTyClDecl1 calc_vrcs calc_isrec
356 (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
357 tcdLName = L _ tc_name, tcdCons = cons})
358 = tcTyVarBndrs tvs $ \ tvs' -> do
359 { ctxt' <- tcHsKindedContext ctxt
360 ; want_generic <- doptM Opt_Generics
361 ; tycon <- fixM (\ tycon -> do
362 { cons' <- mappM (addLocM (tcConDecl new_or_data tycon tvs' ctxt')) cons
363 ; buildAlgTyCon new_or_data tc_name tvs' ctxt'
364 (DataCons cons') arg_vrcs is_rec
365 (want_generic && canDoGenerics cons')
367 ; return (ATyCon tycon)
370 arg_vrcs = calc_vrcs tc_name
371 is_rec = calc_isrec tc_name
373 tcTyClDecl1 calc_vrcs calc_isrec
374 (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs,
375 tcdCtxt = ctxt, tcdMeths = meths,
376 tcdFDs = fundeps, tcdSigs = sigs} )
377 = tcTyVarBndrs tvs $ \ tvs' -> do
378 { ctxt' <- tcHsKindedContext ctxt
379 ; fds' <- mappM (addLocM tc_fundep) fundeps
380 ; sig_stuff <- tcClassSigs class_name sigs meths
381 ; clas <- fixM (\ clas ->
382 let -- This little knot is just so we can get
383 -- hold of the name of the class TyCon, which we
384 -- need to look up its recursiveness and variance
385 tycon_name = tyConName (classTyCon clas)
386 tc_isrec = calc_isrec tycon_name
387 tc_vrcs = calc_vrcs tycon_name
389 buildClass class_name tvs' ctxt' fds'
390 sig_stuff tc_isrec tc_vrcs)
391 ; return (AClass clas) }
393 tc_fundep (tvs1, tvs2) = do { tvs1' <- mappM tcLookupTyVar tvs1 ;
394 ; tvs2' <- mappM tcLookupTyVar tvs2 ;
395 ; return (tvs1', tvs2') }
398 tcTyClDecl1 calc_vrcs calc_isrec
399 (ForeignType {tcdLName = L _ tc_name, tcdExtName = tc_ext_name})
400 = returnM (ATyCon (mkForeignTyCon tc_name tc_ext_name liftedTypeKind 0 []))
402 -----------------------------------
403 tcConDecl :: NewOrData -> TyCon -> [TyVar] -> ThetaType
404 -> ConDecl Name -> TcM DataCon
406 tcConDecl new_or_data tycon tyvars ctxt
407 (ConDecl name ex_tvs ex_ctxt details)
408 = tcTyVarBndrs ex_tvs $ \ ex_tvs' -> do
409 { ex_ctxt' <- tcHsKindedContext ex_ctxt
410 ; unbox_strict <- doptM Opt_UnboxStrictFields
412 tc_datacon field_lbls btys
413 = do { let { ubtys = map unLoc btys }
414 ; arg_tys <- mappM (tcHsKindedType . getBangType) ubtys
415 ; buildDataCon (unLoc name)
416 (argStrictness unbox_strict tycon ubtys arg_tys)
417 (map unLoc field_lbls)
418 tyvars ctxt ex_tvs' ex_ctxt'
421 PrefixCon btys -> tc_datacon [] btys
422 InfixCon bty1 bty2 -> tc_datacon [] [bty1,bty2]
423 RecCon fields -> do { checkTc (null ex_tvs') (exRecConErr name)
424 ; let { (field_names, btys) = unzip fields }
425 ; tc_datacon field_names btys } }
427 argStrictness :: Bool -- True <=> -funbox-strict_fields
428 -> TyCon -> [BangType Name]
429 -> [TcType] -> [StrictnessMark]
430 argStrictness unbox_strict tycon btys arg_tys
431 = zipWith (chooseBoxingStrategy unbox_strict tycon)
433 (map getBangStrictness btys ++ repeat HsNoBang)
435 -- We attempt to unbox/unpack a strict field when either:
436 -- (i) The field is marked '!!', or
437 -- (ii) The field is marked '!', and the -funbox-strict-fields flag is on.
439 chooseBoxingStrategy :: Bool -> TyCon -> TcType -> HsBang -> StrictnessMark
440 chooseBoxingStrategy unbox_strict_fields tycon arg_ty bang
442 HsNoBang -> NotMarkedStrict
443 HsStrict | unbox_strict_fields && can_unbox -> MarkedUnboxed
444 HsUnbox | can_unbox -> MarkedUnboxed
445 other -> MarkedStrict
447 can_unbox = case splitTyConApp_maybe arg_ty of
449 Just (arg_tycon, _) -> not (isRecursiveTyCon tycon) &&
450 isProductTyCon arg_tycon
453 %************************************************************************
455 \subsection{Dependency analysis}
457 %************************************************************************
459 Validity checking is done once the mutually-recursive knot has been
460 tied, so we can look at things freely.
463 checkCycleErrs :: [LTyClDecl Name] -> TcM ()
464 checkCycleErrs tyclss
468 = do { mappM_ recClsErr cls_cycles
469 ; failM } -- Give up now, because later checkValidTyCl
470 -- will loop if the synonym is recursive
472 cls_cycles = calcClassCycles tyclss
474 checkValidTyCl :: TyClDecl Name -> TcM ()
475 -- We do the validity check over declarations, rather than TyThings
476 -- only so that we can add a nice context with tcAddDeclCtxt
478 = tcAddDeclCtxt decl $
479 do { thing <- tcLookupLocatedGlobal (tcdLName decl)
480 ; traceTc (text "Validity of" <+> ppr thing)
482 ATyCon tc -> checkValidTyCon tc
483 AClass cl -> checkValidClass cl
484 ; traceTc (text "Done validity of" <+> ppr thing)
487 -------------------------
488 checkValidTyCon :: TyCon -> TcM ()
491 = checkValidType syn_ctxt syn_rhs
493 = -- Check the context on the data decl
494 checkValidTheta (DataTyCtxt name) (tyConTheta tc) `thenM_`
496 -- Check arg types of data constructors
497 mappM_ checkValidDataCon data_cons `thenM_`
499 -- Check that fields with the same name share a type
500 mappM_ check_fields groups
503 syn_ctxt = TySynCtxt name
505 (_, syn_rhs) = getSynTyConDefn tc
506 data_cons = tyConDataCons tc
508 fields = [field | con <- data_cons, field <- dataConFieldLabels con]
509 groups = equivClasses cmp_name fields
510 cmp_name field1 field2 = fieldLabelName field1 `compare` fieldLabelName field2
512 check_fields fields@(first_field_label : other_fields)
513 -- These fields all have the same name, but are from
514 -- different constructors in the data type
515 = -- Check that all the fields in the group have the same type
516 -- NB: this check assumes that all the constructors of a given
517 -- data type use the same type variables
518 checkTc (all (tcEqType field_ty) other_tys) (fieldTypeMisMatch field_name)
520 field_ty = fieldLabelType first_field_label
521 field_name = fieldLabelName first_field_label
522 other_tys = map fieldLabelType other_fields
524 -------------------------------
525 checkValidDataCon :: DataCon -> TcM ()
526 checkValidDataCon con
527 = addErrCtxt (dataConCtxt con) (
528 checkValidType ctxt (idType (dataConWrapId con)) `thenM_`
529 -- This checks the argument types and
530 -- ambiguity of the existential context (if any)
531 checkFreeness ex_tvs ex_theta)
533 ctxt = ConArgCtxt (dataConName con)
534 (_, _, ex_tvs, ex_theta, _, _) = dataConSig con
537 -------------------------------
538 checkValidClass :: Class -> TcM ()
540 = do { -- CHECK ARITY 1 FOR HASKELL 1.4
541 gla_exts <- doptM Opt_GlasgowExts
543 -- Check that the class is unary, unless GlaExs
544 ; checkTc (notNull tyvars) (nullaryClassErr cls)
545 ; checkTc (gla_exts || unary) (classArityErr cls)
547 -- Check the super-classes
548 ; checkValidTheta (ClassSCCtxt (className cls)) theta
550 -- Check the class operations
551 ; mappM_ check_op op_stuff
553 -- Check that if the class has generic methods, then the
554 -- class has only one parameter. We can't do generic
555 -- multi-parameter type classes!
556 ; checkTc (unary || no_generics) (genericMultiParamErr cls)
559 (tyvars, theta, _, op_stuff) = classBigSig cls
560 unary = isSingleton tyvars
561 no_generics = null [() | (_, GenDefMeth) <- op_stuff]
563 check_op (sel_id, dm)
564 = addErrCtxt (classOpCtxt sel_id tau) $ do
565 { checkValidTheta SigmaCtxt (tail theta)
566 -- The 'tail' removes the initial (C a) from the
567 -- class itself, leaving just the method type
569 ; checkValidType (FunSigCtxt op_name) tau
571 -- Check that the type mentions at least one of
572 -- the class type variables
573 ; checkTc (any (`elemVarSet` tyVarsOfType tau) tyvars)
574 (noClassTyVarErr cls sel_id)
576 -- Check that for a generic method, the type of
577 -- the method is sufficiently simple
578 ; checkTc (dm /= GenDefMeth || validGenericMethodType op_ty)
579 (badGenericMethodType op_name op_ty)
582 op_name = idName sel_id
583 op_ty = idType sel_id
584 (_,theta,tau) = tcSplitSigmaTy op_ty
588 ---------------------------------------------------------------------
589 fieldTypeMisMatch field_name
590 = sep [ptext SLIT("Different constructors give different types for field"), quotes (ppr field_name)]
592 dataConCtxt con = sep [ptext SLIT("When checking the data constructor:"),
593 nest 2 (ex_part <+> pprThetaArrow ex_theta <+> ppr con <+> arg_part)]
595 (_, _, ex_tvs, ex_theta, arg_tys, _) = dataConSig con
596 ex_part | null ex_tvs = empty
597 | otherwise = ptext SLIT("forall") <+> hsep (map ppr ex_tvs) <> dot
598 -- The 'ex_theta' part could be non-empty, if the user (bogusly) wrote
599 -- data T a = Eq a => T a a
600 -- So we make sure to print it
602 fields = dataConFieldLabels con
603 arg_part | null fields = sep (map pprParendType arg_tys)
604 | otherwise = braces (sep (punctuate comma
605 [ ppr n <+> dcolon <+> ppr ty
606 | (n,ty) <- fields `zip` arg_tys]))
608 classOpCtxt sel_id tau = sep [ptext SLIT("When checking the class method:"),
609 nest 2 (ppr sel_id <+> dcolon <+> ppr tau)]
612 = ptext SLIT("No parameters for class") <+> quotes (ppr cls)
615 = vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
616 parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
618 noClassTyVarErr clas op
619 = sep [ptext SLIT("The class method") <+> quotes (ppr op),
620 ptext SLIT("mentions none of the type variables of the class") <+>
621 ppr clas <+> hsep (map ppr (classTyVars clas))]
623 genericMultiParamErr clas
624 = ptext SLIT("The multi-parameter class") <+> quotes (ppr clas) <+>
625 ptext SLIT("cannot have generic methods")
627 badGenericMethodType op op_ty
628 = hang (ptext SLIT("Generic method type is too complex"))
629 4 (vcat [ppr op <+> dcolon <+> ppr op_ty,
630 ptext SLIT("You can only use type variables, arrows, and tuples")])
633 = addSrcSpan (getLoc (head syn_decls)) $
634 addErr (sep [ptext SLIT("Cycle in type synonym declarations:"),
635 nest 2 (vcat (map ppr_decl syn_decls))])
637 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr decl
640 = addSrcSpan (getLoc (head cls_decls)) $
641 addErr (sep [ptext SLIT("Cycle in class declarations (via superclasses):"),
642 nest 2 (vcat (map ppr_decl cls_decls))])
644 ppr_decl (L loc decl) = ppr loc <> colon <+> ppr (decl { tcdSigs = [] })
647 = ptext SLIT("Can't combine named fields with locally-quantified type variables")
649 (ptext SLIT("In the declaration of data constructor") <+> ppr name)