2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
5 \section[TcBinds]{TcBinds}
8 module TcBinds ( tcLocalBinds, tcTopBinds,
9 tcHsBootSigs, tcMonoBinds,
10 TcPragFun, tcSpecPrag, tcPrags, mkPragFun,
11 TcSigInfo(..), TcSigFun, mkTcSigFun,
12 badBootDeclErr ) where
14 import {-# SOURCE #-} TcMatches ( tcGRHSsPat, tcMatchesFun )
15 import {-# SOURCE #-} TcExpr ( tcMonoExpr )
29 import {- Kind parts of -} Type
54 %************************************************************************
56 \subsection{Type-checking bindings}
58 %************************************************************************
60 @tcBindsAndThen@ typechecks a @HsBinds@. The "and then" part is because
61 it needs to know something about the {\em usage} of the things bound,
62 so that it can create specialisations of them. So @tcBindsAndThen@
63 takes a function which, given an extended environment, E, typechecks
64 the scope of the bindings returning a typechecked thing and (most
65 important) an LIE. It is this LIE which is then used as the basis for
66 specialising the things bound.
68 @tcBindsAndThen@ also takes a "combiner" which glues together the
69 bindings and the "thing" to make a new "thing".
71 The real work is done by @tcBindWithSigsAndThen@.
73 Recursive and non-recursive binds are handled in essentially the same
74 way: because of uniques there are no scoping issues left. The only
75 difference is that non-recursive bindings can bind primitive values.
77 Even for non-recursive binding groups we add typings for each binder
78 to the LVE for the following reason. When each individual binding is
79 checked the type of its LHS is unified with that of its RHS; and
80 type-checking the LHS of course requires that the binder is in scope.
82 At the top-level the LIE is sure to contain nothing but constant
83 dictionaries, which we resolve at the module level.
86 tcTopBinds :: HsValBinds Name -> TcM (LHsBinds TcId, TcLclEnv)
87 -- Note: returning the TcLclEnv is more than we really
88 -- want. The bit we care about is the local bindings
89 -- and the free type variables thereof
91 = do { (ValBindsOut prs _, env) <- tcValBinds TopLevel binds getLclEnv
92 ; return (foldr (unionBags . snd) emptyBag prs, env) }
93 -- The top level bindings are flattened into a giant
94 -- implicitly-mutually-recursive LHsBinds
96 tcHsBootSigs :: HsValBinds Name -> TcM [Id]
97 -- A hs-boot file has only one BindGroup, and it only has type
98 -- signatures in it. The renamer checked all this
99 tcHsBootSigs (ValBindsOut binds sigs)
100 = do { checkTc (null binds) badBootDeclErr
101 ; mapM (addLocM tc_boot_sig) (filter isVanillaLSig sigs) }
103 tc_boot_sig (TypeSig (L _ name) ty)
104 = do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
105 ; return (mkVanillaGlobal name sigma_ty) }
106 -- Notice that we make GlobalIds, not LocalIds
107 tc_boot_sig s = pprPanic "tcHsBootSigs/tc_boot_sig" (ppr s)
108 tcHsBootSigs groups = pprPanic "tcHsBootSigs" (ppr groups)
110 badBootDeclErr :: Message
111 badBootDeclErr = ptext (sLit "Illegal declarations in an hs-boot file")
113 ------------------------
114 tcLocalBinds :: HsLocalBinds Name -> TcM thing
115 -> TcM (HsLocalBinds TcId, thing)
117 tcLocalBinds EmptyLocalBinds thing_inside
118 = do { thing <- thing_inside
119 ; return (EmptyLocalBinds, thing) }
121 tcLocalBinds (HsValBinds binds) thing_inside
122 = do { (binds', thing) <- tcValBinds NotTopLevel binds thing_inside
123 ; return (HsValBinds binds', thing) }
125 tcLocalBinds (HsIPBinds (IPBinds ip_binds _)) thing_inside
126 = do { (thing, lie) <- getLIE thing_inside
127 ; (avail_ips, ip_binds') <- mapAndUnzipM (wrapLocSndM tc_ip_bind) ip_binds
129 -- If the binding binds ?x = E, we must now
130 -- discharge any ?x constraints in expr_lie
131 ; dict_binds <- tcSimplifyIPs avail_ips lie
132 ; return (HsIPBinds (IPBinds ip_binds' dict_binds), thing) }
134 -- I wonder if we should do these one at at time
137 tc_ip_bind (IPBind ip expr) = do
138 ty <- newFlexiTyVarTy argTypeKind
139 (ip', ip_inst) <- newIPDict (IPBindOrigin ip) ip ty
140 expr' <- tcMonoExpr expr ty
141 return (ip_inst, (IPBind ip' expr'))
143 ------------------------
144 tcValBinds :: TopLevelFlag
145 -> HsValBinds Name -> TcM thing
146 -> TcM (HsValBinds TcId, thing)
148 tcValBinds _ (ValBindsIn binds _) _
149 = pprPanic "tcValBinds" (ppr binds)
151 tcValBinds top_lvl (ValBindsOut binds sigs) thing_inside
152 = do { -- Typecheck the signature
153 ; let { prag_fn = mkPragFun sigs
154 ; ty_sigs = filter isVanillaLSig sigs
155 ; sig_fn = mkTcSigFun ty_sigs }
157 ; poly_ids <- mapM tcTySig ty_sigs
158 -- No recovery from bad signatures, because the type sigs
159 -- may bind type variables, so proceeding without them
160 -- can lead to a cascade of errors
161 -- ToDo: this means we fall over immediately if any type sig
162 -- is wrong, which is over-conservative, see Trac bug #745
164 -- Extend the envt right away with all
165 -- the Ids declared with type signatures
166 ; poly_rec <- doptM Opt_RelaxedPolyRec
167 ; (binds', thing) <- tcExtendIdEnv poly_ids $
168 tc_val_binds poly_rec top_lvl sig_fn prag_fn
171 ; return (ValBindsOut binds' sigs, thing) }
173 ------------------------
174 tc_val_binds :: Bool -> TopLevelFlag -> TcSigFun -> TcPragFun
175 -> [(RecFlag, LHsBinds Name)] -> TcM thing
176 -> TcM ([(RecFlag, LHsBinds TcId)], thing)
177 -- Typecheck a whole lot of value bindings,
178 -- one strongly-connected component at a time
180 tc_val_binds _ _ _ _ [] thing_inside
181 = do { thing <- thing_inside
182 ; return ([], thing) }
184 tc_val_binds poly_rec top_lvl sig_fn prag_fn (group : groups) thing_inside
185 = do { (group', (groups', thing))
186 <- tc_group poly_rec top_lvl sig_fn prag_fn group $
187 tc_val_binds poly_rec top_lvl sig_fn prag_fn groups thing_inside
188 ; return (group' ++ groups', thing) }
190 ------------------------
191 tc_group :: Bool -> TopLevelFlag -> TcSigFun -> TcPragFun
192 -> (RecFlag, LHsBinds Name) -> TcM thing
193 -> TcM ([(RecFlag, LHsBinds TcId)], thing)
195 -- Typecheck one strongly-connected component of the original program.
196 -- We get a list of groups back, because there may
197 -- be specialisations etc as well
199 tc_group _ top_lvl sig_fn prag_fn (NonRecursive, binds) thing_inside
200 -- A single non-recursive binding
201 -- We want to keep non-recursive things non-recursive
202 -- so that we desugar unlifted bindings correctly
203 = do { (binds, thing) <- tc_haskell98 top_lvl sig_fn prag_fn NonRecursive binds thing_inside
204 ; return ([(NonRecursive, b) | b <- binds], thing) }
206 tc_group poly_rec top_lvl sig_fn prag_fn (Recursive, binds) thing_inside
207 | not poly_rec -- Recursive group, normal Haskell 98 route
208 = do { (binds1, thing) <- tc_haskell98 top_lvl sig_fn prag_fn Recursive binds thing_inside
209 ; return ([(Recursive, unionManyBags binds1)], thing) }
211 | otherwise -- Recursive group, with gla-exts
212 = -- To maximise polymorphism (with -fglasgow-exts), we do a new
213 -- strongly-connected-component analysis, this time omitting
214 -- any references to variables with type signatures.
216 -- Notice that the bindInsts thing covers *all* the bindings in the original
217 -- group at once; an earlier one may use a later one!
218 do { traceTc (text "tc_group rec" <+> pprLHsBinds binds)
219 ; (binds1,thing) <- bindLocalInsts top_lvl $
220 go (stronglyConnCompFromEdgedVertices (mkEdges sig_fn binds))
221 ; return ([(Recursive, unionManyBags binds1)], thing) }
222 -- Rec them all together
224 -- go :: SCC (LHsBind Name) -> TcM ([LHsBind TcId], [TcId], thing)
225 go (scc:sccs) = do { (binds1, ids1) <- tc_scc scc
226 ; (binds2, ids2, thing) <- tcExtendIdEnv ids1 $ go sccs
227 ; return (binds1 ++ binds2, ids1 ++ ids2, thing) }
228 go [] = do { thing <- thing_inside; return ([], [], thing) }
230 tc_scc (AcyclicSCC bind) = tc_sub_group NonRecursive (unitBag bind)
231 tc_scc (CyclicSCC binds) = tc_sub_group Recursive (listToBag binds)
233 tc_sub_group = tcPolyBinds top_lvl sig_fn prag_fn Recursive
235 tc_haskell98 :: TopLevelFlag -> TcSigFun -> TcPragFun -> RecFlag
236 -> LHsBinds Name -> TcM a -> TcM ([LHsBinds TcId], a)
237 tc_haskell98 top_lvl sig_fn prag_fn rec_flag binds thing_inside
238 = bindLocalInsts top_lvl $ do
239 { (binds1, ids) <- tcPolyBinds top_lvl sig_fn prag_fn rec_flag rec_flag binds
240 ; thing <- tcExtendIdEnv ids thing_inside
241 ; return (binds1, ids, thing) }
243 ------------------------
244 bindLocalInsts :: TopLevelFlag -> TcM ([LHsBinds TcId], [TcId], a) -> TcM ([LHsBinds TcId], a)
245 bindLocalInsts top_lvl thing_inside
246 | isTopLevel top_lvl = do { (binds, _, thing) <- thing_inside; return (binds, thing) }
247 -- For the top level don't bother with all this bindInstsOfLocalFuns stuff.
248 -- All the top level things are rec'd together anyway, so it's fine to
249 -- leave them to the tcSimplifyTop, and quite a bit faster too
251 | otherwise -- Nested case
252 = do { ((binds, ids, thing), lie) <- getLIE thing_inside
253 ; lie_binds <- bindInstsOfLocalFuns lie ids
254 ; return (binds ++ [lie_binds], thing) }
256 ------------------------
257 mkEdges :: TcSigFun -> LHsBinds Name
258 -> [(LHsBind Name, BKey, [BKey])]
260 type BKey = Int -- Just number off the bindings
263 = [ (bind, key, [key | n <- nameSetToList (bind_fvs (unLoc bind)),
264 Just key <- [lookupNameEnv key_map n], no_sig n ])
265 | (bind, key) <- keyd_binds
268 no_sig :: Name -> Bool
269 no_sig n = isNothing (sig_fn n)
271 keyd_binds = bagToList binds `zip` [0::BKey ..]
273 key_map :: NameEnv BKey -- Which binding it comes from
274 key_map = mkNameEnv [(bndr, key) | (L _ bind, key) <- keyd_binds
275 , bndr <- bindersOfHsBind bind ]
277 bindersOfHsBind :: HsBind Name -> [Name]
278 bindersOfHsBind (PatBind { pat_lhs = pat }) = collectPatBinders pat
279 bindersOfHsBind (FunBind { fun_id = L _ f }) = [f]
280 bindersOfHsBind (AbsBinds {}) = panic "bindersOfHsBind AbsBinds"
281 bindersOfHsBind (VarBind {}) = panic "bindersOfHsBind VarBind"
283 ------------------------
284 tcPolyBinds :: TopLevelFlag -> TcSigFun -> TcPragFun
285 -> RecFlag -- Whether the group is really recursive
286 -> RecFlag -- Whether it's recursive after breaking
287 -- dependencies based on type signatures
289 -> TcM ([LHsBinds TcId], [TcId])
291 -- Typechecks a single bunch of bindings all together,
292 -- and generalises them. The bunch may be only part of a recursive
293 -- group, because we use type signatures to maximise polymorphism
295 -- Returns a list because the input may be a single non-recursive binding,
296 -- in which case the dependency order of the resulting bindings is
299 -- Knows nothing about the scope of the bindings
301 tcPolyBinds top_lvl sig_fn prag_fn rec_group rec_tc binds
303 bind_list = bagToList binds
304 binder_names = collectHsBindBinders binds
305 loc = getLoc (head bind_list)
306 -- TODO: location a bit awkward, but the mbinds have been
307 -- dependency analysed and may no longer be adjacent
309 -- SET UP THE MAIN RECOVERY; take advantage of any type sigs
311 recoverM (recoveryCode binder_names sig_fn) $ do
313 { traceTc (ptext (sLit "------------------------------------------------"))
314 ; traceTc (ptext (sLit "Bindings for") <+> ppr binder_names)
316 -- TYPECHECK THE BINDINGS
317 ; ((binds', mono_bind_infos), lie_req)
318 <- getLIE (tcMonoBinds bind_list sig_fn rec_tc)
319 ; traceTc (text "temp" <+> (ppr binds' $$ ppr lie_req))
321 -- CHECK FOR UNLIFTED BINDINGS
322 -- These must be non-recursive etc, and are not generalised
323 -- They desugar to a case expression in the end
324 ; zonked_mono_tys <- zonkTcTypes (map getMonoType mono_bind_infos)
325 ; is_strict <- checkStrictBinds top_lvl rec_group binds'
326 zonked_mono_tys mono_bind_infos
328 do { extendLIEs lie_req
329 ; let exports = zipWith mk_export mono_bind_infos zonked_mono_tys
330 mk_export (name, Nothing, mono_id) mono_ty = ([], mkLocalId name mono_ty, mono_id, [])
331 mk_export (_, Just sig, mono_id) _ = ([], sig_id sig, mono_id, [])
332 -- ToDo: prags for unlifted bindings
334 ; return ( [unitBag $ L loc $ AbsBinds [] [] exports binds'],
335 [poly_id | (_, poly_id, _, _) <- exports]) } -- Guaranteed zonked
337 else do -- The normal lifted case: GENERALISE
339 ; (tyvars_to_gen, dicts, dict_binds)
340 <- addErrCtxt (genCtxt (bndrNames mono_bind_infos)) $
341 generalise dflags top_lvl bind_list sig_fn mono_bind_infos lie_req
343 -- BUILD THE POLYMORPHIC RESULT IDs
344 ; let dict_vars = map instToVar dicts -- May include equality constraints
345 ; exports <- mapM (mkExport top_lvl prag_fn tyvars_to_gen (map varType dict_vars))
348 ; let poly_ids = [poly_id | (_, poly_id, _, _) <- exports]
349 ; traceTc (text "binding:" <+> ppr (poly_ids `zip` map idType poly_ids))
351 ; let abs_bind = L loc $ AbsBinds tyvars_to_gen
353 (dict_binds `unionBags` binds')
355 ; return ([unitBag abs_bind], poly_ids) -- poly_ids are guaranteed zonked by mkExport
360 mkExport :: TopLevelFlag -> TcPragFun -> [TyVar] -> [TcType]
362 -> TcM ([TyVar], Id, Id, [LPrag])
363 -- mkExport generates exports with
364 -- zonked type variables,
366 -- The former is just because no further unifications will change
367 -- the quantified type variables, so we can fix their final form
369 -- The latter is needed because the poly_ids are used to extend the
370 -- type environment; see the invariant on TcEnv.tcExtendIdEnv
372 -- Pre-condition: the inferred_tvs are already zonked
374 mkExport top_lvl prag_fn inferred_tvs dict_tys (poly_name, mb_sig, mono_id)
375 = do { warn_missing_sigs <- doptM Opt_WarnMissingSigs
376 ; let warn = isTopLevel top_lvl && warn_missing_sigs
377 ; (tvs, poly_id) <- mk_poly_id warn mb_sig
378 -- poly_id has a zonked type
380 ; prags <- tcPrags poly_id (prag_fn poly_name)
381 -- tcPrags requires a zonked poly_id
383 ; return (tvs, poly_id, mono_id, prags) }
385 poly_ty = mkForAllTys inferred_tvs (mkFunTys dict_tys (idType mono_id))
387 mk_poly_id warn Nothing = do { poly_ty' <- zonkTcType poly_ty
388 ; missingSigWarn warn poly_name poly_ty'
389 ; return (inferred_tvs, mkLocalId poly_name poly_ty') }
390 mk_poly_id _ (Just sig) = do { tvs <- mapM zonk_tv (sig_tvs sig)
391 ; return (tvs, sig_id sig) }
393 zonk_tv tv = do { ty <- zonkTcTyVar tv; return (tcGetTyVar "mkExport" ty) }
395 ------------------------
396 type TcPragFun = Name -> [LSig Name]
398 mkPragFun :: [LSig Name] -> TcPragFun
399 mkPragFun sigs = \n -> lookupNameEnv env n `orElse` []
401 prs = [(expectJust "mkPragFun" (sigName sig), sig)
402 | sig <- sigs, isPragLSig sig]
403 env = foldl add emptyNameEnv prs
404 add env (n,p) = extendNameEnv_Acc (:) singleton env n p
406 tcPrags :: Id -> [LSig Name] -> TcM [LPrag]
407 tcPrags poly_id prags = mapM (wrapLocM tc_prag) prags
409 tc_prag prag = addErrCtxt (pragSigCtxt prag) $
412 pragSigCtxt :: Sig Name -> SDoc
413 pragSigCtxt prag = hang (ptext (sLit "In the pragma")) 2 (ppr prag)
415 tcPrag :: TcId -> Sig Name -> TcM Prag
416 -- Pre-condition: the poly_id is zonked
417 -- Reason: required by tcSubExp
418 tcPrag poly_id (SpecSig _ hs_ty inl) = tcSpecPrag poly_id hs_ty inl
419 tcPrag poly_id (SpecInstSig hs_ty) = tcSpecPrag poly_id hs_ty defaultInlineSpec
420 tcPrag _ (InlineSig _ inl) = return (InlinePrag inl)
421 tcPrag _ (FixSig {}) = panic "tcPrag FixSig"
422 tcPrag _ (TypeSig {}) = panic "tcPrag TypeSig"
425 tcSpecPrag :: TcId -> LHsType Name -> InlineSpec -> TcM Prag
426 tcSpecPrag poly_id hs_ty inl
427 = do { let name = idName poly_id
428 ; spec_ty <- tcHsSigType (FunSigCtxt name) hs_ty
429 ; co_fn <- tcSubExp (SpecPragOrigin name) (idType poly_id) spec_ty
430 ; return (SpecPrag (mkHsWrap co_fn (HsVar poly_id)) spec_ty inl) }
431 -- Most of the work of specialisation is done by
432 -- the desugarer, guided by the SpecPrag
435 -- If typechecking the binds fails, then return with each
436 -- signature-less binder given type (forall a.a), to minimise
437 -- subsequent error messages
438 recoveryCode :: [Name] -> (Name -> Maybe [Name])
439 -> TcM ([Bag (LHsBindLR Id Var)], [Id])
440 recoveryCode binder_names sig_fn
441 = do { traceTc (text "tcBindsWithSigs: error recovery" <+> ppr binder_names)
442 ; poly_ids <- mapM mk_dummy binder_names
443 ; return ([], poly_ids) }
446 | isJust (sig_fn name) = tcLookupId name -- Had signature; look it up
447 | otherwise = return (mkLocalId name forall_a_a) -- No signature
450 forall_a_a = mkForAllTy alphaTyVar (mkTyVarTy alphaTyVar)
453 -- Check that non-overloaded unlifted bindings are
456 -- c) not a multiple-binding group (more or less implied by (a))
458 checkStrictBinds :: TopLevelFlag -> RecFlag
459 -> LHsBinds TcId -> [TcType] -> [MonoBindInfo]
461 checkStrictBinds top_lvl rec_group mbind mono_tys infos
462 | unlifted || bang_pat
463 = do { checkTc (isNotTopLevel top_lvl)
464 (strictBindErr "Top-level" unlifted mbind)
465 ; checkTc (isNonRec rec_group)
466 (strictBindErr "Recursive" unlifted mbind)
467 ; checkTc (isSingletonBag mbind)
468 (strictBindErr "Multiple" unlifted mbind)
469 ; mapM_ check_sig infos
474 unlifted = any isUnLiftedType mono_tys
475 bang_pat = anyBag (isBangHsBind . unLoc) mbind
476 check_sig (_, Just sig, _) = checkTc (null (sig_tvs sig) && null (sig_theta sig))
477 (badStrictSig unlifted sig)
478 check_sig _ = return ()
480 strictBindErr :: String -> Bool -> LHsBindsLR Var Var -> SDoc
481 strictBindErr flavour unlifted mbind
482 = hang (text flavour <+> msg <+> ptext (sLit "aren't allowed:"))
483 4 (pprLHsBinds mbind)
485 msg | unlifted = ptext (sLit "bindings for unlifted types")
486 | otherwise = ptext (sLit "bang-pattern bindings")
488 badStrictSig :: Bool -> TcSigInfo -> SDoc
489 badStrictSig unlifted sig
490 = hang (ptext (sLit "Illegal polymorphic signature in") <+> msg)
493 msg | unlifted = ptext (sLit "an unlifted binding")
494 | otherwise = ptext (sLit "a bang-pattern binding")
498 %************************************************************************
500 \subsection{tcMonoBind}
502 %************************************************************************
504 @tcMonoBinds@ deals with a perhaps-recursive group of HsBinds.
505 The signatures have been dealt with already.
508 tcMonoBinds :: [LHsBind Name]
510 -> RecFlag -- Whether the binding is recursive for typechecking purposes
511 -- i.e. the binders are mentioned in their RHSs, and
512 -- we are not resuced by a type signature
513 -> TcM (LHsBinds TcId, [MonoBindInfo])
515 tcMonoBinds [L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf,
516 fun_matches = matches, bind_fvs = fvs })]
517 sig_fn -- Single function binding,
518 NonRecursive -- binder isn't mentioned in RHS,
519 | Nothing <- sig_fn name -- ...with no type signature
520 = -- In this very special case we infer the type of the
521 -- right hand side first (it may have a higher-rank type)
522 -- and *then* make the monomorphic Id for the LHS
523 -- e.g. f = \(x::forall a. a->a) -> <body>
524 -- We want to infer a higher-rank type for f
526 do { ((co_fn, matches'), rhs_ty) <- tcInfer (tcMatchesFun name inf matches)
528 -- Check for an unboxed tuple type
529 -- f = (# True, False #)
530 -- Zonk first just in case it's hidden inside a meta type variable
531 -- (This shows up as a (more obscure) kind error
532 -- in the 'otherwise' case of tcMonoBinds.)
533 ; zonked_rhs_ty <- zonkTcType rhs_ty
534 ; checkTc (not (isUnboxedTupleType zonked_rhs_ty))
535 (unboxedTupleErr name zonked_rhs_ty)
537 ; mono_name <- newLocalName name
538 ; let mono_id = mkLocalId mono_name zonked_rhs_ty
539 ; return (unitBag (L b_loc (FunBind { fun_id = L nm_loc mono_id, fun_infix = inf,
540 fun_matches = matches', bind_fvs = fvs,
541 fun_co_fn = co_fn, fun_tick = Nothing })),
542 [(name, Nothing, mono_id)]) }
544 tcMonoBinds [L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf,
545 fun_matches = matches })]
546 sig_fn -- Single function binding
548 | Just scoped_tvs <- sig_fn name -- ...with a type signature
549 = -- When we have a single function binding, with a type signature
550 -- we can (a) use genuine, rigid skolem constants for the type variables
551 -- (b) bring (rigid) scoped type variables into scope
553 do { tc_sig <- tcInstSig True name
554 ; mono_name <- newLocalName name
555 ; let mono_ty = sig_tau tc_sig
556 mono_id = mkLocalId mono_name mono_ty
557 rhs_tvs = [ (name, mkTyVarTy tv)
558 | (name, tv) <- scoped_tvs `zip` sig_tvs tc_sig ]
559 -- See Note [More instantiated than scoped]
560 -- Note that the scoped_tvs and the (sig_tvs sig)
561 -- may have different Names. That's quite ok.
563 ; (co_fn, matches') <- tcExtendTyVarEnv2 rhs_tvs $
564 tcMatchesFun mono_name inf matches mono_ty
566 ; let fun_bind' = FunBind { fun_id = L nm_loc mono_id,
567 fun_infix = inf, fun_matches = matches',
568 bind_fvs = placeHolderNames, fun_co_fn = co_fn,
570 ; return (unitBag (L b_loc fun_bind'),
571 [(name, Just tc_sig, mono_id)]) }
573 tcMonoBinds binds sig_fn _
574 = do { tc_binds <- mapM (wrapLocM (tcLhs sig_fn)) binds
576 -- Bring the monomorphic Ids, into scope for the RHSs
577 ; let mono_info = getMonoBindInfo tc_binds
578 rhs_id_env = [(name,mono_id) | (name, Nothing, mono_id) <- mono_info]
579 -- A monomorphic binding for each term variable that lacks
580 -- a type sig. (Ones with a sig are already in scope.)
582 ; binds' <- tcExtendIdEnv2 rhs_id_env $ do
583 traceTc (text "tcMonoBinds" <+> vcat [ ppr n <+> ppr id <+> ppr (idType id)
584 | (n,id) <- rhs_id_env])
585 mapM (wrapLocM tcRhs) tc_binds
586 ; return (listToBag binds', mono_info) }
588 ------------------------
589 -- tcLhs typechecks the LHS of the bindings, to construct the environment in which
590 -- we typecheck the RHSs. Basically what we are doing is this: for each binder:
591 -- if there's a signature for it, use the instantiated signature type
592 -- otherwise invent a type variable
593 -- You see that quite directly in the FunBind case.
595 -- But there's a complication for pattern bindings:
596 -- data T = MkT (forall a. a->a)
598 -- Here we can guess a type variable for the entire LHS (which will be refined to T)
599 -- but we want to get (f::forall a. a->a) as the RHS environment.
600 -- The simplest way to do this is to typecheck the pattern, and then look up the
601 -- bound mono-ids. Then we want to retain the typechecked pattern to avoid re-doing
602 -- it; hence the TcMonoBind data type in which the LHS is done but the RHS isn't
604 data TcMonoBind -- Half completed; LHS done, RHS not done
605 = TcFunBind MonoBindInfo (Located TcId) Bool (MatchGroup Name)
606 | TcPatBind [MonoBindInfo] (LPat TcId) (GRHSs Name) TcSigmaType
608 type MonoBindInfo = (Name, Maybe TcSigInfo, TcId)
609 -- Type signature (if any), and
610 -- the monomorphic bound things
612 bndrNames :: [MonoBindInfo] -> [Name]
613 bndrNames mbi = [n | (n,_,_) <- mbi]
615 getMonoType :: MonoBindInfo -> TcTauType
616 getMonoType (_,_,mono_id) = idType mono_id
618 tcLhs :: TcSigFun -> HsBind Name -> TcM TcMonoBind
619 tcLhs sig_fn (FunBind { fun_id = L nm_loc name, fun_infix = inf, fun_matches = matches })
620 = do { mb_sig <- tcInstSig_maybe sig_fn name
621 ; mono_name <- newLocalName name
622 ; mono_ty <- mk_mono_ty mb_sig
623 ; let mono_id = mkLocalId mono_name mono_ty
624 ; return (TcFunBind (name, mb_sig, mono_id) (L nm_loc mono_id) inf matches) }
626 mk_mono_ty (Just sig) = return (sig_tau sig)
627 mk_mono_ty Nothing = newFlexiTyVarTy argTypeKind
629 tcLhs sig_fn (PatBind { pat_lhs = pat, pat_rhs = grhss })
630 = do { mb_sigs <- mapM (tcInstSig_maybe sig_fn) names
631 ; mono_pat_binds <- doptM Opt_MonoPatBinds
632 -- With -XMonoPatBinds, we do no generalisation of pattern bindings
633 -- But the signature can still be polymoprhic!
634 -- data T = MkT (forall a. a->a)
635 -- x :: forall a. a->a
637 -- The function get_sig_ty decides whether the pattern-bound variables
638 -- should have exactly the type in the type signature (-XMonoPatBinds),
639 -- or the instantiated version (-XMonoPatBinds)
641 ; let nm_sig_prs = names `zip` mb_sigs
642 get_sig_ty | mono_pat_binds = idType . sig_id
643 | otherwise = sig_tau
644 tau_sig_env = mkNameEnv [ (name, get_sig_ty sig)
645 | (name, Just sig) <- nm_sig_prs]
646 sig_tau_fn = lookupNameEnv tau_sig_env
648 tc_pat exp_ty = tcLetPat sig_tau_fn pat exp_ty $
649 mapM lookup_info nm_sig_prs
651 -- After typechecking the pattern, look up the binder
652 -- names, which the pattern has brought into scope.
653 lookup_info :: (Name, Maybe TcSigInfo) -> TcM MonoBindInfo
654 lookup_info (name, mb_sig) = do { mono_id <- tcLookupId name
655 ; return (name, mb_sig, mono_id) }
657 ; ((pat', infos), pat_ty) <- addErrCtxt (patMonoBindsCtxt pat grhss) $
660 ; return (TcPatBind infos pat' grhss pat_ty) }
662 names = collectPatBinders pat
665 tcLhs _ other_bind = pprPanic "tcLhs" (ppr other_bind)
666 -- AbsBind, VarBind impossible
669 tcRhs :: TcMonoBind -> TcM (HsBind TcId)
670 -- When we are doing pattern bindings, or multiple function bindings at a time
671 -- we *don't* bring any scoped type variables into scope
672 -- Wny not? They are not completely rigid.
673 -- That's why we have the special case for a single FunBind in tcMonoBinds
674 tcRhs (TcFunBind (_,_,mono_id) fun' inf matches)
675 = do { (co_fn, matches') <- tcMatchesFun (idName mono_id) inf
676 matches (idType mono_id)
677 ; return (FunBind { fun_id = fun', fun_infix = inf, fun_matches = matches',
678 bind_fvs = placeHolderNames, fun_co_fn = co_fn,
679 fun_tick = Nothing }) }
681 tcRhs (TcPatBind _ pat' grhss pat_ty)
682 = do { grhss' <- addErrCtxt (patMonoBindsCtxt pat' grhss) $
683 tcGRHSsPat grhss pat_ty
684 ; return (PatBind { pat_lhs = pat', pat_rhs = grhss', pat_rhs_ty = pat_ty,
685 bind_fvs = placeHolderNames }) }
688 ---------------------
689 getMonoBindInfo :: [Located TcMonoBind] -> [MonoBindInfo]
690 getMonoBindInfo tc_binds
691 = foldr (get_info . unLoc) [] tc_binds
693 get_info (TcFunBind info _ _ _) rest = info : rest
694 get_info (TcPatBind infos _ _ _) rest = infos ++ rest
698 %************************************************************************
702 %************************************************************************
705 generalise :: DynFlags -> TopLevelFlag
706 -> [LHsBind Name] -> TcSigFun
707 -> [MonoBindInfo] -> [Inst]
708 -> TcM ([TyVar], [Inst], TcDictBinds)
709 -- The returned [TyVar] are all ready to quantify
711 generalise dflags top_lvl bind_list sig_fn mono_infos lie_req
712 | isMonoGroup dflags bind_list
713 = do { extendLIEs lie_req
714 ; return ([], [], emptyBag) }
716 | isRestrictedGroup dflags bind_list sig_fn -- RESTRICTED CASE
717 = -- Check signature contexts are empty
718 do { checkTc (all is_mono_sig sigs)
719 (restrictedBindCtxtErr bndrs)
721 -- Now simplify with exactly that set of tyvars
722 -- We have to squash those Methods
723 ; (qtvs, binds) <- tcSimplifyRestricted doc top_lvl bndrs
726 -- Check that signature type variables are OK
727 ; final_qtvs <- checkSigsTyVars qtvs sigs
729 ; return (final_qtvs, [], binds) }
731 | null sigs -- UNRESTRICTED CASE, NO TYPE SIGS
732 = tcSimplifyInfer doc tau_tvs lie_req
734 | otherwise -- UNRESTRICTED CASE, WITH TYPE SIGS
735 = do { sig_lie <- unifyCtxts sigs -- sigs is non-empty; sig_lie is zonked
736 ; let -- The "sig_avails" is the stuff available. We get that from
737 -- the context of the type signature, BUT ALSO the lie_avail
738 -- so that polymorphic recursion works right (see Note [Polymorphic recursion])
739 local_meths = [mkMethInst sig mono_id | (_, Just sig, mono_id) <- mono_infos]
740 sig_avails = sig_lie ++ local_meths
741 loc = sig_loc (head sigs)
743 -- Check that the needed dicts can be
744 -- expressed in terms of the signature ones
745 ; (qtvs, binds) <- tcSimplifyInferCheck loc tau_tvs sig_avails lie_req
747 -- Check that signature type variables are OK
748 ; final_qtvs <- checkSigsTyVars qtvs sigs
750 ; return (final_qtvs, sig_lie, binds) }
752 bndrs = bndrNames mono_infos
753 sigs = [sig | (_, Just sig, _) <- mono_infos]
754 get_tvs | isTopLevel top_lvl = tyVarsOfType -- See Note [Silly type synonym] in TcType
755 | otherwise = exactTyVarsOfType
756 tau_tvs = foldr (unionVarSet . get_tvs . getMonoType) emptyVarSet mono_infos
757 is_mono_sig sig = null (sig_theta sig)
758 doc = ptext (sLit "type signature(s) for") <+> pprBinders bndrs
760 mkMethInst (TcSigInfo { sig_id = poly_id, sig_tvs = tvs,
761 sig_theta = theta, sig_loc = loc }) mono_id
762 = Method {tci_id = mono_id, tci_oid = poly_id, tci_tys = mkTyVarTys tvs,
763 tci_theta = theta, tci_loc = loc}
766 unifyCtxts checks that all the signature contexts are the same
767 The type signatures on a mutually-recursive group of definitions
768 must all have the same context (or none).
770 The trick here is that all the signatures should have the same
771 context, and we want to share type variables for that context, so that
772 all the right hand sides agree a common vocabulary for their type
775 We unify them because, with polymorphic recursion, their types
776 might not otherwise be related. This is a rather subtle issue.
779 unifyCtxts :: [TcSigInfo] -> TcM [Inst]
780 -- Post-condition: the returned Insts are full zonked
781 unifyCtxts [] = panic "unifyCtxts []"
782 unifyCtxts (sig1 : sigs) -- Argument is always non-empty
783 = do { mapM unify_ctxt sigs
784 ; theta <- zonkTcThetaType (sig_theta sig1)
785 ; newDictBndrs (sig_loc sig1) theta }
787 theta1 = sig_theta sig1
788 unify_ctxt :: TcSigInfo -> TcM ()
789 unify_ctxt sig@(TcSigInfo { sig_theta = theta })
790 = setSrcSpan (instLocSpan (sig_loc sig)) $
791 addErrCtxt (sigContextsCtxt sig1 sig) $
792 do { cois <- unifyTheta theta1 theta
793 ; -- Check whether all coercions are identity coercions
794 -- That can happen if we have, say
796 -- g :: C (F a) => ...
797 -- where F is a type function and (F a ~ [a])
798 -- Then unification might succeed with a coercion. But it's much
799 -- much simpler to require that such signatures have identical contexts
800 checkTc (all isIdentityCoercion cois)
801 (ptext (sLit "Mutually dependent functions have syntactically distinct contexts"))
804 checkSigsTyVars :: [TcTyVar] -> [TcSigInfo] -> TcM [TcTyVar]
805 checkSigsTyVars qtvs sigs
806 = do { gbl_tvs <- tcGetGlobalTyVars
807 ; sig_tvs_s <- mapM (check_sig gbl_tvs) sigs
809 ; let -- Sigh. Make sure that all the tyvars in the type sigs
810 -- appear in the returned ty var list, which is what we are
811 -- going to generalise over. Reason: we occasionally get
813 -- type T a = () -> ()
816 -- Here, 'a' won't appear in qtvs, so we have to add it
817 sig_tvs = foldl extendVarSetList emptyVarSet sig_tvs_s
818 all_tvs = varSetElems (extendVarSetList sig_tvs qtvs)
821 check_sig gbl_tvs (TcSigInfo {sig_id = id, sig_tvs = tvs,
822 sig_theta = theta, sig_tau = tau})
823 = addErrCtxt (ptext (sLit "In the type signature for") <+> quotes (ppr id)) $
824 addErrCtxtM (sigCtxt id tvs theta tau) $
825 do { tvs' <- checkDistinctTyVars tvs
826 ; when (any (`elemVarSet` gbl_tvs) tvs')
827 (bleatEscapedTvs gbl_tvs tvs tvs')
830 checkDistinctTyVars :: [TcTyVar] -> TcM [TcTyVar]
831 -- (checkDistinctTyVars tvs) checks that the tvs from one type signature
832 -- are still all type variables, and all distinct from each other.
833 -- It returns a zonked set of type variables.
834 -- For example, if the type sig is
835 -- f :: forall a b. a -> b -> b
836 -- we want to check that 'a' and 'b' haven't
837 -- (a) been unified with a non-tyvar type
838 -- (b) been unified with each other (all distinct)
840 checkDistinctTyVars sig_tvs
841 = do { zonked_tvs <- mapM zonkSigTyVar sig_tvs
842 ; foldlM check_dup emptyVarEnv (sig_tvs `zip` zonked_tvs)
843 ; return zonked_tvs }
845 check_dup :: TyVarEnv TcTyVar -> (TcTyVar, TcTyVar) -> TcM (TyVarEnv TcTyVar)
846 -- The TyVarEnv maps each zonked type variable back to its
847 -- corresponding user-written signature type variable
848 check_dup acc (sig_tv, zonked_tv)
849 = case lookupVarEnv acc zonked_tv of
850 Just sig_tv' -> bomb_out sig_tv sig_tv'
852 Nothing -> return (extendVarEnv acc zonked_tv sig_tv)
854 bomb_out sig_tv1 sig_tv2
855 = do { env0 <- tcInitTidyEnv
856 ; let (env1, tidy_tv1) = tidyOpenTyVar env0 sig_tv1
857 (env2, tidy_tv2) = tidyOpenTyVar env1 sig_tv2
858 msg = ptext (sLit "Quantified type variable") <+> quotes (ppr tidy_tv1)
859 <+> ptext (sLit "is unified with another quantified type variable")
860 <+> quotes (ppr tidy_tv2)
861 ; failWithTcM (env2, msg) }
865 @getTyVarsToGen@ decides what type variables to generalise over.
867 For a "restricted group" -- see the monomorphism restriction
868 for a definition -- we bind no dictionaries, and
869 remove from tyvars_to_gen any constrained type variables
871 *Don't* simplify dicts at this point, because we aren't going
872 to generalise over these dicts. By the time we do simplify them
873 we may well know more. For example (this actually came up)
875 f x = array ... xs where xs = [1,2,3,4,5]
876 We don't want to generate lots of (fromInt Int 1), (fromInt Int 2)
877 stuff. If we simplify only at the f-binding (not the xs-binding)
878 we'll know that the literals are all Ints, and we can just produce
881 Find all the type variables involved in overloading, the
882 "constrained_tyvars". These are the ones we *aren't* going to
883 generalise. We must be careful about doing this:
885 (a) If we fail to generalise a tyvar which is not actually
886 constrained, then it will never, ever get bound, and lands
887 up printed out in interface files! Notorious example:
888 instance Eq a => Eq (Foo a b) where ..
889 Here, b is not constrained, even though it looks as if it is.
890 Another, more common, example is when there's a Method inst in
891 the LIE, whose type might very well involve non-overloaded
893 [NOTE: Jan 2001: I don't understand the problem here so I'm doing
894 the simple thing instead]
896 (b) On the other hand, we mustn't generalise tyvars which are constrained,
897 because we are going to pass on out the unmodified LIE, with those
898 tyvars in it. They won't be in scope if we've generalised them.
900 So we are careful, and do a complete simplification just to find the
901 constrained tyvars. We don't use any of the results, except to
902 find which tyvars are constrained.
904 Note [Polymorphic recursion]
905 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
906 The game plan for polymorphic recursion in the code above is
908 * Bind any variable for which we have a type signature
909 to an Id with a polymorphic type. Then when type-checking
910 the RHSs we'll make a full polymorphic call.
912 This fine, but if you aren't a bit careful you end up with a horrendous
913 amount of partial application and (worse) a huge space leak. For example:
915 f :: Eq a => [a] -> [a]
918 If we don't take care, after typechecking we get
920 f = /\a -> \d::Eq a -> let f' = f a d
924 Notice the the stupid construction of (f a d), which is of course
925 identical to the function we're executing. In this case, the
926 polymorphic recursion isn't being used (but that's a very common case).
927 This can lead to a massive space leak, from the following top-level defn
933 Now (f dEqInt) evaluates to a lambda that has f' as a free variable; but
934 f' is another thunk which evaluates to the same thing... and you end
935 up with a chain of identical values all hung onto by the CAF ff.
939 = let f' = f Int dEqInt in \ys. ...f'...
941 = let f' = let f' = f Int dEqInt in \ys. ...f'...
946 NOTE: a bit of arity anaysis would push the (f a d) inside the (\ys...),
947 which would make the space leak go away in this case
949 Solution: when typechecking the RHSs we always have in hand the
950 *monomorphic* Ids for each binding. So we just need to make sure that
951 if (Method f a d) shows up in the constraints emerging from (...f...)
952 we just use the monomorphic Id. We achieve this by adding monomorphic Ids
953 to the "givens" when simplifying constraints. That's what the "lies_avail"
958 f = /\a -> \d::Eq a -> letrec
959 fm = \ys:[a] -> ...fm...
965 %************************************************************************
969 %************************************************************************
971 Type signatures are tricky. See Note [Signature skolems] in TcType
973 @tcSigs@ checks the signatures for validity, and returns a list of
974 {\em freshly-instantiated} signatures. That is, the types are already
975 split up, and have fresh type variables installed. All non-type-signature
976 "RenamedSigs" are ignored.
978 The @TcSigInfo@ contains @TcTypes@ because they are unified with
979 the variable's type, and after that checked to see whether they've
984 The -XScopedTypeVariables flag brings lexically-scoped type variables
985 into scope for any explicitly forall-quantified type variables:
986 f :: forall a. a -> a
988 Then 'a' is in scope inside 'e'.
990 However, we do *not* support this
991 - For pattern bindings e.g
995 - For multiple function bindings, unless Opt_RelaxedPolyRec is on
996 f :: forall a. a -> a
998 g :: forall b. b -> b
1000 Reason: we use mutable variables for 'a' and 'b', since they may
1001 unify to each other, and that means the scoped type variable would
1002 not stand for a completely rigid variable.
1004 Currently, we simply make Opt_ScopedTypeVariables imply Opt_RelaxedPolyRec
1007 Note [More instantiated than scoped]
1008 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1009 There may be more instantiated type variables than lexically-scoped
1011 type T a = forall b. b -> (a,b)
1013 Here, the signature for f will have one scoped type variable, c,
1014 but two instantiated type variables, c' and b'.
1016 We assume that the scoped ones are at the *front* of sig_tvs,
1017 and remember the names from the original HsForAllTy in the TcSigFun.
1021 type TcSigFun = Name -> Maybe [Name] -- Maps a let-binder to the list of
1022 -- type variables brought into scope
1023 -- by its type signature.
1024 -- Nothing => no type signature
1026 mkTcSigFun :: [LSig Name] -> TcSigFun
1027 -- Search for a particular type signature
1028 -- Precondition: the sigs are all type sigs
1029 -- Precondition: no duplicates
1030 mkTcSigFun sigs = lookupNameEnv env
1032 env = mkNameEnv [(name, hsExplicitTvs lhs_ty)
1033 | L _ (TypeSig (L _ name) lhs_ty) <- sigs]
1034 -- The scoped names are the ones explicitly mentioned
1035 -- in the HsForAll. (There may be more in sigma_ty, because
1036 -- of nested type synonyms. See Note [More instantiated than scoped].)
1037 -- See Note [Only scoped tyvars are in the TyVarEnv]
1042 sig_id :: TcId, -- *Polymorphic* binder for this value...
1044 sig_tvs :: [TcTyVar], -- Instantiated type variables
1045 -- See Note [Instantiate sig]
1047 sig_theta :: TcThetaType, -- Instantiated theta
1048 sig_tau :: TcTauType, -- Instantiated tau
1049 sig_loc :: InstLoc -- The location of the signature
1053 -- Note [Only scoped tyvars are in the TyVarEnv]
1054 -- We are careful to keep only the *lexically scoped* type variables in
1055 -- the type environment. Why? After all, the renamer has ensured
1056 -- that only legal occurrences occur, so we could put all type variables
1057 -- into the type env.
1059 -- But we want to check that two distinct lexically scoped type variables
1060 -- do not map to the same internal type variable. So we need to know which
1061 -- the lexically-scoped ones are... and at the moment we do that by putting
1062 -- only the lexically scoped ones into the environment.
1065 -- Note [Instantiate sig]
1066 -- It's vital to instantiate a type signature with fresh variables.
1068 -- type S = forall a. a->a
1072 -- Here, we must use distinct type variables when checking f,g's right hand sides.
1073 -- (Instantiation is only necessary because of type synonyms. Otherwise,
1074 -- it's all cool; each signature has distinct type variables from the renamer.)
1076 instance Outputable TcSigInfo where
1077 ppr (TcSigInfo { sig_id = id, sig_tvs = tyvars, sig_theta = theta, sig_tau = tau})
1078 = ppr id <+> ptext (sLit "::") <+> ppr tyvars <+> ppr theta <+> ptext (sLit "=>") <+> ppr tau
1082 tcTySig :: LSig Name -> TcM TcId
1083 tcTySig (L span (TypeSig (L _ name) ty))
1085 do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
1086 ; return (mkLocalId name sigma_ty) }
1087 tcTySig s = pprPanic "tcTySig" (ppr s)
1090 tcInstSig_maybe :: TcSigFun -> Name -> TcM (Maybe TcSigInfo)
1091 -- Instantiate with *meta* type variables;
1092 -- this signature is part of a multi-signature group
1093 tcInstSig_maybe sig_fn name
1094 = case sig_fn name of
1095 Nothing -> return Nothing
1096 Just _scoped_tvs -> do { tc_sig <- tcInstSig False name
1097 ; return (Just tc_sig) }
1098 -- NB: the _scoped_tvs may be non-empty, but we can
1099 -- just ignore them. See Note [Scoped tyvars].
1101 tcInstSig :: Bool -> Name -> TcM TcSigInfo
1102 -- Instantiate the signature, with either skolems or meta-type variables
1103 -- depending on the use_skols boolean. This variable is set True
1104 -- when we are typechecking a single function binding; and False for
1105 -- pattern bindings and a group of several function bindings.
1106 -- Reason: in the latter cases, the "skolems" can be unified together,
1107 -- so they aren't properly rigid in the type-refinement sense.
1108 -- NB: unless we are doing H98, each function with a sig will be done
1109 -- separately, even if it's mutually recursive, so use_skols will be True
1111 -- We always instantiate with fresh uniques,
1112 -- although we keep the same print-name
1114 -- type T = forall a. [a] -> [a]
1116 -- f = g where { g :: T; g = <rhs> }
1118 -- We must not use the same 'a' from the defn of T at both places!!
1120 tcInstSig use_skols name
1121 = do { poly_id <- tcLookupId name -- Cannot fail; the poly ids are put into
1122 -- scope when starting the binding group
1123 ; let skol_info = SigSkol (FunSigCtxt name)
1124 inst_tyvars = tcInstSigTyVars use_skols skol_info
1125 ; (tvs, theta, tau) <- tcInstType inst_tyvars (idType poly_id)
1126 ; loc <- getInstLoc (SigOrigin skol_info)
1127 ; return (TcSigInfo { sig_id = poly_id,
1128 sig_tvs = tvs, sig_theta = theta, sig_tau = tau,
1132 isMonoGroup :: DynFlags -> [LHsBind Name] -> Bool
1133 -- No generalisation at all
1134 isMonoGroup dflags binds
1135 = dopt Opt_MonoPatBinds dflags && any is_pat_bind binds
1137 is_pat_bind (L _ (PatBind {})) = True
1138 is_pat_bind _ = False
1141 isRestrictedGroup :: DynFlags -> [LHsBind Name] -> TcSigFun -> Bool
1142 isRestrictedGroup dflags binds sig_fn
1143 = mono_restriction && not all_unrestricted
1145 mono_restriction = dopt Opt_MonomorphismRestriction dflags
1146 all_unrestricted = all (unrestricted . unLoc) binds
1147 has_sig n = isJust (sig_fn n)
1149 unrestricted (PatBind {}) = False
1150 unrestricted (VarBind { var_id = v }) = has_sig v
1151 unrestricted (FunBind { fun_id = v, fun_matches = matches }) = unrestricted_match matches
1152 || has_sig (unLoc v)
1153 unrestricted (AbsBinds {})
1154 = panic "isRestrictedGroup/unrestricted AbsBinds"
1156 unrestricted_match (MatchGroup (L _ (Match [] _ _) : _) _) = False
1157 -- No args => like a pattern binding
1158 unrestricted_match _ = True
1159 -- Some args => a function binding
1163 %************************************************************************
1165 \subsection[TcBinds-errors]{Error contexts and messages}
1167 %************************************************************************
1171 -- This one is called on LHS, when pat and grhss are both Name
1172 -- and on RHS, when pat is TcId and grhss is still Name
1173 patMonoBindsCtxt :: OutputableBndr id => LPat id -> GRHSs Name -> SDoc
1174 patMonoBindsCtxt pat grhss
1175 = hang (ptext (sLit "In a pattern binding:")) 4 (pprPatBind pat grhss)
1177 -----------------------------------------------
1178 sigContextsCtxt :: TcSigInfo -> TcSigInfo -> SDoc
1179 sigContextsCtxt sig1 sig2
1180 = vcat [ptext (sLit "When matching the contexts of the signatures for"),
1181 nest 2 (vcat [ppr id1 <+> dcolon <+> ppr (idType id1),
1182 ppr id2 <+> dcolon <+> ppr (idType id2)]),
1183 ptext (sLit "The signature contexts in a mutually recursive group should all be identical")]
1189 -----------------------------------------------
1190 unboxedTupleErr :: Name -> Type -> SDoc
1191 unboxedTupleErr name ty
1192 = hang (ptext (sLit "Illegal binding of unboxed tuple"))
1193 4 (ppr name <+> dcolon <+> ppr ty)
1195 -----------------------------------------------
1196 restrictedBindCtxtErr :: [Name] -> SDoc
1197 restrictedBindCtxtErr binder_names
1198 = hang (ptext (sLit "Illegal overloaded type signature(s)"))
1199 4 (vcat [ptext (sLit "in a binding group for") <+> pprBinders binder_names,
1200 ptext (sLit "that falls under the monomorphism restriction")])
1202 genCtxt :: [Name] -> SDoc
1203 genCtxt binder_names
1204 = ptext (sLit "When generalising the type(s) for") <+> pprBinders binder_names
1206 missingSigWarn :: Bool -> Name -> Type -> TcM ()
1207 missingSigWarn False _ _ = return ()
1208 missingSigWarn True name ty
1209 = do { env0 <- tcInitTidyEnv
1210 ; let (env1, tidy_ty) = tidyOpenType env0 ty
1211 ; addWarnTcM (env1, mk_msg tidy_ty) }
1213 mk_msg ty = vcat [ptext (sLit "Definition but no type signature for") <+> quotes (ppr name),
1214 sep [ptext (sLit "Inferred type:") <+> pprHsVar name <+> dcolon <+> ppr ty]]