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
35 import Var hiding (mkLocalId)
55 %************************************************************************
57 \subsection{Type-checking bindings}
59 %************************************************************************
61 @tcBindsAndThen@ typechecks a @HsBinds@. The "and then" part is because
62 it needs to know something about the {\em usage} of the things bound,
63 so that it can create specialisations of them. So @tcBindsAndThen@
64 takes a function which, given an extended environment, E, typechecks
65 the scope of the bindings returning a typechecked thing and (most
66 important) an LIE. It is this LIE which is then used as the basis for
67 specialising the things bound.
69 @tcBindsAndThen@ also takes a "combiner" which glues together the
70 bindings and the "thing" to make a new "thing".
72 The real work is done by @tcBindWithSigsAndThen@.
74 Recursive and non-recursive binds are handled in essentially the same
75 way: because of uniques there are no scoping issues left. The only
76 difference is that non-recursive bindings can bind primitive values.
78 Even for non-recursive binding groups we add typings for each binder
79 to the LVE for the following reason. When each individual binding is
80 checked the type of its LHS is unified with that of its RHS; and
81 type-checking the LHS of course requires that the binder is in scope.
83 At the top-level the LIE is sure to contain nothing but constant
84 dictionaries, which we resolve at the module level.
87 tcTopBinds :: HsValBinds Name -> TcM (LHsBinds TcId, TcLclEnv)
88 -- Note: returning the TcLclEnv is more than we really
89 -- want. The bit we care about is the local bindings
90 -- and the free type variables thereof
92 = do { (ValBindsOut prs _, env) <- tcValBinds TopLevel binds getLclEnv
93 ; return (foldr (unionBags . snd) emptyBag prs, env) }
94 -- The top level bindings are flattened into a giant
95 -- implicitly-mutually-recursive LHsBinds
97 tcHsBootSigs :: HsValBinds Name -> TcM [Id]
98 -- A hs-boot file has only one BindGroup, and it only has type
99 -- signatures in it. The renamer checked all this
100 tcHsBootSigs (ValBindsOut binds sigs)
101 = do { checkTc (null binds) badBootDeclErr
102 ; mapM (addLocM tc_boot_sig) (filter isVanillaLSig sigs) }
104 tc_boot_sig (TypeSig (L _ name) ty)
105 = do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
106 ; return (mkVanillaGlobal name sigma_ty vanillaIdInfo) }
107 -- Notice that we make GlobalIds, not LocalIds
108 tc_boot_sig s = pprPanic "tcHsBootSigs/tc_boot_sig" (ppr s)
109 tcHsBootSigs groups = pprPanic "tcHsBootSigs" (ppr groups)
111 badBootDeclErr :: Message
112 badBootDeclErr = ptext (sLit "Illegal declarations in an hs-boot file")
114 ------------------------
115 tcLocalBinds :: HsLocalBinds Name -> TcM thing
116 -> TcM (HsLocalBinds TcId, thing)
118 tcLocalBinds EmptyLocalBinds thing_inside
119 = do { thing <- thing_inside
120 ; return (EmptyLocalBinds, thing) }
122 tcLocalBinds (HsValBinds binds) thing_inside
123 = do { (binds', thing) <- tcValBinds NotTopLevel binds thing_inside
124 ; return (HsValBinds binds', thing) }
126 tcLocalBinds (HsIPBinds (IPBinds ip_binds _)) thing_inside
127 = do { (thing, lie) <- getLIE thing_inside
128 ; (avail_ips, ip_binds') <- mapAndUnzipM (wrapLocSndM tc_ip_bind) ip_binds
130 -- If the binding binds ?x = E, we must now
131 -- discharge any ?x constraints in expr_lie
132 ; dict_binds <- tcSimplifyIPs avail_ips lie
133 ; return (HsIPBinds (IPBinds ip_binds' dict_binds), thing) }
135 -- I wonder if we should do these one at at time
138 tc_ip_bind (IPBind ip expr) = do
139 ty <- newFlexiTyVarTy argTypeKind
140 (ip', ip_inst) <- newIPDict (IPBindOrigin ip) ip ty
141 expr' <- tcMonoExpr expr ty
142 return (ip_inst, (IPBind ip' expr'))
144 ------------------------
145 tcValBinds :: TopLevelFlag
146 -> HsValBinds Name -> TcM thing
147 -> TcM (HsValBinds TcId, thing)
149 tcValBinds _ (ValBindsIn binds _) _
150 = pprPanic "tcValBinds" (ppr binds)
152 tcValBinds top_lvl (ValBindsOut binds sigs) thing_inside
153 = do { -- Typecheck the signature
154 ; let { prag_fn = mkPragFun sigs
155 ; ty_sigs = filter isVanillaLSig sigs
156 ; sig_fn = mkTcSigFun ty_sigs }
158 ; poly_ids <- mapM tcTySig ty_sigs
159 -- No recovery from bad signatures, because the type sigs
160 -- may bind type variables, so proceeding without them
161 -- can lead to a cascade of errors
162 -- ToDo: this means we fall over immediately if any type sig
163 -- is wrong, which is over-conservative, see Trac bug #745
165 -- Extend the envt right away with all
166 -- the Ids declared with type signatures
167 ; poly_rec <- doptM Opt_RelaxedPolyRec
168 ; (binds', thing) <- tcExtendIdEnv poly_ids $
169 tc_val_binds poly_rec top_lvl sig_fn prag_fn
172 ; return (ValBindsOut binds' sigs, thing) }
174 ------------------------
175 tc_val_binds :: Bool -> TopLevelFlag -> TcSigFun -> TcPragFun
176 -> [(RecFlag, LHsBinds Name)] -> TcM thing
177 -> TcM ([(RecFlag, LHsBinds TcId)], thing)
178 -- Typecheck a whole lot of value bindings,
179 -- one strongly-connected component at a time
181 tc_val_binds _ _ _ _ [] thing_inside
182 = do { thing <- thing_inside
183 ; return ([], thing) }
185 tc_val_binds poly_rec top_lvl sig_fn prag_fn (group : groups) thing_inside
186 = do { (group', (groups', thing))
187 <- tc_group poly_rec top_lvl sig_fn prag_fn group $
188 tc_val_binds poly_rec top_lvl sig_fn prag_fn groups thing_inside
189 ; return (group' ++ groups', thing) }
191 ------------------------
192 tc_group :: Bool -> TopLevelFlag -> TcSigFun -> TcPragFun
193 -> (RecFlag, LHsBinds Name) -> TcM thing
194 -> TcM ([(RecFlag, LHsBinds TcId)], thing)
196 -- Typecheck one strongly-connected component of the original program.
197 -- We get a list of groups back, because there may
198 -- be specialisations etc as well
200 tc_group _ top_lvl sig_fn prag_fn (NonRecursive, binds) thing_inside
201 -- A single non-recursive binding
202 -- We want to keep non-recursive things non-recursive
203 -- so that we desugar unlifted bindings correctly
204 = do { (binds, thing) <- tc_haskell98 top_lvl sig_fn prag_fn NonRecursive binds thing_inside
205 ; return ([(NonRecursive, b) | b <- binds], thing) }
207 tc_group poly_rec top_lvl sig_fn prag_fn (Recursive, binds) thing_inside
208 | not poly_rec -- Recursive group, normal Haskell 98 route
209 = do { (binds1, thing) <- tc_haskell98 top_lvl sig_fn prag_fn Recursive binds thing_inside
210 ; return ([(Recursive, unionManyBags binds1)], thing) }
212 | otherwise -- Recursive group, with gla-exts
213 = -- To maximise polymorphism (with -fglasgow-exts), we do a new
214 -- strongly-connected-component analysis, this time omitting
215 -- any references to variables with type signatures.
217 -- Notice that the bindInsts thing covers *all* the bindings in the original
218 -- group at once; an earlier one may use a later one!
219 do { traceTc (text "tc_group rec" <+> pprLHsBinds binds)
220 ; (binds1,thing) <- bindLocalInsts top_lvl $
221 go (stronglyConnComp (mkEdges sig_fn binds))
222 ; return ([(Recursive, unionManyBags binds1)], thing) }
223 -- Rec them all together
225 -- go :: SCC (LHsBind Name) -> TcM ([LHsBind TcId], [TcId], thing)
226 go (scc:sccs) = do { (binds1, ids1) <- tc_scc scc
227 ; (binds2, ids2, thing) <- tcExtendIdEnv ids1 $ go sccs
228 ; return (binds1 ++ binds2, ids1 ++ ids2, thing) }
229 go [] = do { thing <- thing_inside; return ([], [], thing) }
231 tc_scc (AcyclicSCC bind) = tc_sub_group NonRecursive (unitBag bind)
232 tc_scc (CyclicSCC binds) = tc_sub_group Recursive (listToBag binds)
234 tc_sub_group = tcPolyBinds top_lvl sig_fn prag_fn Recursive
236 tc_haskell98 :: TopLevelFlag -> TcSigFun -> TcPragFun -> RecFlag
237 -> LHsBinds Name -> TcM a -> TcM ([LHsBinds TcId], a)
238 tc_haskell98 top_lvl sig_fn prag_fn rec_flag binds thing_inside
239 = bindLocalInsts top_lvl $ do
240 { (binds1, ids) <- tcPolyBinds top_lvl sig_fn prag_fn rec_flag rec_flag binds
241 ; thing <- tcExtendIdEnv ids thing_inside
242 ; return (binds1, ids, thing) }
244 ------------------------
245 bindLocalInsts :: TopLevelFlag -> TcM ([LHsBinds TcId], [TcId], a) -> TcM ([LHsBinds TcId], a)
246 bindLocalInsts top_lvl thing_inside
247 | isTopLevel top_lvl = do { (binds, _, thing) <- thing_inside; return (binds, thing) }
248 -- For the top level don't bother with all this bindInstsOfLocalFuns stuff.
249 -- All the top level things are rec'd together anyway, so it's fine to
250 -- leave them to the tcSimplifyTop, and quite a bit faster too
252 | otherwise -- Nested case
253 = do { ((binds, ids, thing), lie) <- getLIE thing_inside
254 ; lie_binds <- bindInstsOfLocalFuns lie ids
255 ; return (binds ++ [lie_binds], thing) }
257 ------------------------
258 mkEdges :: TcSigFun -> LHsBinds Name
259 -> [(LHsBind Name, BKey, [BKey])]
261 type BKey = Int -- Just number off the bindings
264 = [ (bind, key, [key | n <- nameSetToList (bind_fvs (unLoc bind)),
265 Just key <- [lookupNameEnv key_map n], no_sig n ])
266 | (bind, key) <- keyd_binds
269 no_sig :: Name -> Bool
270 no_sig n = isNothing (sig_fn n)
272 keyd_binds = bagToList binds `zip` [0::BKey ..]
274 key_map :: NameEnv BKey -- Which binding it comes from
275 key_map = mkNameEnv [(bndr, key) | (L _ bind, key) <- keyd_binds
276 , bndr <- bindersOfHsBind bind ]
278 bindersOfHsBind :: HsBind Name -> [Name]
279 bindersOfHsBind (PatBind { pat_lhs = pat }) = collectPatBinders pat
280 bindersOfHsBind (FunBind { fun_id = L _ f }) = [f]
281 bindersOfHsBind (AbsBinds {}) = panic "bindersOfHsBind AbsBinds"
282 bindersOfHsBind (VarBind {}) = panic "bindersOfHsBind VarBind"
284 ------------------------
285 tcPolyBinds :: TopLevelFlag -> TcSigFun -> TcPragFun
286 -> RecFlag -- Whether the group is really recursive
287 -> RecFlag -- Whether it's recursive after breaking
288 -- dependencies based on type signatures
290 -> TcM ([LHsBinds TcId], [TcId])
292 -- Typechecks a single bunch of bindings all together,
293 -- and generalises them. The bunch may be only part of a recursive
294 -- group, because we use type signatures to maximise polymorphism
296 -- Returns a list because the input may be a single non-recursive binding,
297 -- in which case the dependency order of the resulting bindings is
300 -- Knows nothing about the scope of the bindings
302 tcPolyBinds top_lvl sig_fn prag_fn rec_group rec_tc binds
304 bind_list = bagToList binds
305 binder_names = collectHsBindBinders binds
306 loc = getLoc (head bind_list)
307 -- TODO: location a bit awkward, but the mbinds have been
308 -- dependency analysed and may no longer be adjacent
310 -- SET UP THE MAIN RECOVERY; take advantage of any type sigs
312 recoverM (recoveryCode binder_names sig_fn) $ do
314 { traceTc (ptext (sLit "------------------------------------------------"))
315 ; traceTc (ptext (sLit "Bindings for") <+> ppr binder_names)
317 -- TYPECHECK THE BINDINGS
318 ; ((binds', mono_bind_infos), lie_req)
319 <- getLIE (tcMonoBinds bind_list sig_fn rec_tc)
320 ; traceTc (text "temp" <+> (ppr binds' $$ ppr lie_req))
322 -- CHECK FOR UNLIFTED BINDINGS
323 -- These must be non-recursive etc, and are not generalised
324 -- They desugar to a case expression in the end
325 ; zonked_mono_tys <- zonkTcTypes (map getMonoType mono_bind_infos)
326 ; is_strict <- checkStrictBinds top_lvl rec_group binds'
327 zonked_mono_tys mono_bind_infos
329 do { extendLIEs lie_req
330 ; let exports = zipWith mk_export mono_bind_infos zonked_mono_tys
331 mk_export (name, Nothing, mono_id) mono_ty = ([], mkLocalId name mono_ty, mono_id, [])
332 mk_export (_, Just sig, mono_id) _ = ([], sig_id sig, mono_id, [])
333 -- ToDo: prags for unlifted bindings
335 ; return ( [unitBag $ L loc $ AbsBinds [] [] exports binds'],
336 [poly_id | (_, poly_id, _, _) <- exports]) } -- Guaranteed zonked
338 else do -- The normal lifted case: GENERALISE
340 ; (tyvars_to_gen, dicts, dict_binds)
341 <- addErrCtxt (genCtxt (bndrNames mono_bind_infos)) $
342 generalise dflags top_lvl bind_list sig_fn mono_bind_infos lie_req
344 -- BUILD THE POLYMORPHIC RESULT IDs
345 ; let dict_vars = map instToVar dicts -- May include equality constraints
346 ; exports <- mapM (mkExport top_lvl prag_fn tyvars_to_gen (map varType dict_vars))
349 ; let poly_ids = [poly_id | (_, poly_id, _, _) <- exports]
350 ; traceTc (text "binding:" <+> ppr (poly_ids `zip` map idType poly_ids))
352 ; let abs_bind = L loc $ AbsBinds tyvars_to_gen
354 (dict_binds `unionBags` binds')
356 ; return ([unitBag abs_bind], poly_ids) -- poly_ids are guaranteed zonked by mkExport
361 mkExport :: TopLevelFlag -> TcPragFun -> [TyVar] -> [TcType]
363 -> TcM ([TyVar], Id, Id, [LPrag])
364 -- mkExport generates exports with
365 -- zonked type variables,
367 -- The former is just because no further unifications will change
368 -- the quantified type variables, so we can fix their final form
370 -- The latter is needed because the poly_ids are used to extend the
371 -- type environment; see the invariant on TcEnv.tcExtendIdEnv
373 -- Pre-condition: the inferred_tvs are already zonked
375 mkExport top_lvl prag_fn inferred_tvs dict_tys (poly_name, mb_sig, mono_id)
376 = do { warn_missing_sigs <- doptM Opt_WarnMissingSigs
377 ; let warn = isTopLevel top_lvl && warn_missing_sigs
378 ; (tvs, poly_id) <- mk_poly_id warn mb_sig
379 -- poly_id has a zonked type
381 ; prags <- tcPrags poly_id (prag_fn poly_name)
382 -- tcPrags requires a zonked poly_id
384 ; return (tvs, poly_id, mono_id, prags) }
386 poly_ty = mkForAllTys inferred_tvs (mkFunTys dict_tys (idType mono_id))
388 mk_poly_id warn Nothing = do { poly_ty' <- zonkTcType poly_ty
389 ; missingSigWarn warn poly_name poly_ty'
390 ; return (inferred_tvs, mkLocalId poly_name poly_ty') }
391 mk_poly_id _ (Just sig) = do { tvs <- mapM zonk_tv (sig_tvs sig)
392 ; return (tvs, sig_id sig) }
394 zonk_tv tv = do { ty <- zonkTcTyVar tv; return (tcGetTyVar "mkExport" ty) }
396 ------------------------
397 type TcPragFun = Name -> [LSig Name]
399 mkPragFun :: [LSig Name] -> TcPragFun
400 mkPragFun sigs = \n -> lookupNameEnv env n `orElse` []
402 prs = [(expectJust "mkPragFun" (sigName sig), sig)
403 | sig <- sigs, isPragLSig sig]
404 env = foldl add emptyNameEnv prs
405 add env (n,p) = extendNameEnv_Acc (:) singleton env n p
407 tcPrags :: Id -> [LSig Name] -> TcM [LPrag]
408 tcPrags poly_id prags = mapM (wrapLocM tc_prag) prags
410 tc_prag prag = addErrCtxt (pragSigCtxt prag) $
413 pragSigCtxt :: Sig Name -> SDoc
414 pragSigCtxt prag = hang (ptext (sLit "In the pragma")) 2 (ppr prag)
416 tcPrag :: TcId -> Sig Name -> TcM Prag
417 -- Pre-condition: the poly_id is zonked
418 -- Reason: required by tcSubExp
419 tcPrag poly_id (SpecSig _ hs_ty inl) = tcSpecPrag poly_id hs_ty inl
420 tcPrag poly_id (SpecInstSig hs_ty) = tcSpecPrag poly_id hs_ty defaultInlineSpec
421 tcPrag _ (InlineSig _ inl) = return (InlinePrag inl)
422 tcPrag _ (FixSig {}) = panic "tcPrag FixSig"
423 tcPrag _ (TypeSig {}) = panic "tcPrag TypeSig"
426 tcSpecPrag :: TcId -> LHsType Name -> InlineSpec -> TcM Prag
427 tcSpecPrag poly_id hs_ty inl
428 = do { let name = idName poly_id
429 ; spec_ty <- tcHsSigType (FunSigCtxt name) hs_ty
430 ; co_fn <- tcSubExp (SpecPragOrigin name) (idType poly_id) spec_ty
431 ; return (SpecPrag (mkHsWrap co_fn (HsVar poly_id)) spec_ty inl) }
432 -- Most of the work of specialisation is done by
433 -- the desugarer, guided by the SpecPrag
436 -- If typechecking the binds fails, then return with each
437 -- signature-less binder given type (forall a.a), to minimise
438 -- subsequent error messages
439 recoveryCode :: [Name] -> (Name -> Maybe [Name])
440 -> TcM ([Bag (LHsBindLR Id Var)], [Id])
441 recoveryCode binder_names sig_fn
442 = do { traceTc (text "tcBindsWithSigs: error recovery" <+> ppr binder_names)
443 ; poly_ids <- mapM mk_dummy binder_names
444 ; return ([], poly_ids) }
447 | isJust (sig_fn name) = tcLookupId name -- Had signature; look it up
448 | otherwise = return (mkLocalId name forall_a_a) -- No signature
451 forall_a_a = mkForAllTy alphaTyVar (mkTyVarTy alphaTyVar)
454 -- Check that non-overloaded unlifted bindings are
457 -- c) not a multiple-binding group (more or less implied by (a))
459 checkStrictBinds :: TopLevelFlag -> RecFlag
460 -> LHsBinds TcId -> [TcType] -> [MonoBindInfo]
462 checkStrictBinds top_lvl rec_group mbind mono_tys infos
463 | unlifted || bang_pat
464 = do { checkTc (isNotTopLevel top_lvl)
465 (strictBindErr "Top-level" unlifted mbind)
466 ; checkTc (isNonRec rec_group)
467 (strictBindErr "Recursive" unlifted mbind)
468 ; checkTc (isSingletonBag mbind)
469 (strictBindErr "Multiple" unlifted mbind)
470 ; mapM_ check_sig infos
475 unlifted = any isUnLiftedType mono_tys
476 bang_pat = anyBag (isBangHsBind . unLoc) mbind
477 check_sig (_, Just sig, _) = checkTc (null (sig_tvs sig) && null (sig_theta sig))
478 (badStrictSig unlifted sig)
479 check_sig _ = return ()
481 strictBindErr :: String -> Bool -> LHsBindsLR Var Var -> SDoc
482 strictBindErr flavour unlifted mbind
483 = hang (text flavour <+> msg <+> ptext (sLit "aren't allowed:"))
484 4 (pprLHsBinds mbind)
486 msg | unlifted = ptext (sLit "bindings for unlifted types")
487 | otherwise = ptext (sLit "bang-pattern bindings")
489 badStrictSig :: Bool -> TcSigInfo -> SDoc
490 badStrictSig unlifted sig
491 = hang (ptext (sLit "Illegal polymorphic signature in") <+> msg)
494 msg | unlifted = ptext (sLit "an unlifted binding")
495 | otherwise = ptext (sLit "a bang-pattern binding")
499 %************************************************************************
501 \subsection{tcMonoBind}
503 %************************************************************************
505 @tcMonoBinds@ deals with a perhaps-recursive group of HsBinds.
506 The signatures have been dealt with already.
509 tcMonoBinds :: [LHsBind Name]
511 -> RecFlag -- Whether the binding is recursive for typechecking purposes
512 -- i.e. the binders are mentioned in their RHSs, and
513 -- we are not resuced by a type signature
514 -> TcM (LHsBinds TcId, [MonoBindInfo])
516 tcMonoBinds [L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf,
517 fun_matches = matches, bind_fvs = fvs })]
518 sig_fn -- Single function binding,
519 NonRecursive -- binder isn't mentioned in RHS,
520 | Nothing <- sig_fn name -- ...with no type signature
521 = -- In this very special case we infer the type of the
522 -- right hand side first (it may have a higher-rank type)
523 -- and *then* make the monomorphic Id for the LHS
524 -- e.g. f = \(x::forall a. a->a) -> <body>
525 -- We want to infer a higher-rank type for f
527 do { ((co_fn, matches'), rhs_ty) <- tcInfer (tcMatchesFun name inf matches)
529 -- Check for an unboxed tuple type
530 -- f = (# True, False #)
531 -- Zonk first just in case it's hidden inside a meta type variable
532 -- (This shows up as a (more obscure) kind error
533 -- in the 'otherwise' case of tcMonoBinds.)
534 ; zonked_rhs_ty <- zonkTcType rhs_ty
535 ; checkTc (not (isUnboxedTupleType zonked_rhs_ty))
536 (unboxedTupleErr name zonked_rhs_ty)
538 ; mono_name <- newLocalName name
539 ; let mono_id = mkLocalId mono_name zonked_rhs_ty
540 ; return (unitBag (L b_loc (FunBind { fun_id = L nm_loc mono_id, fun_infix = inf,
541 fun_matches = matches', bind_fvs = fvs,
542 fun_co_fn = co_fn, fun_tick = Nothing })),
543 [(name, Nothing, mono_id)]) }
545 tcMonoBinds [L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf,
546 fun_matches = matches })]
547 sig_fn -- Single function binding
549 | Just scoped_tvs <- sig_fn name -- ...with a type signature
550 = -- When we have a single function binding, with a type signature
551 -- we can (a) use genuine, rigid skolem constants for the type variables
552 -- (b) bring (rigid) scoped type variables into scope
554 do { tc_sig <- tcInstSig True name
555 ; mono_name <- newLocalName name
556 ; let mono_ty = sig_tau tc_sig
557 mono_id = mkLocalId mono_name mono_ty
558 rhs_tvs = [ (name, mkTyVarTy tv)
559 | (name, tv) <- scoped_tvs `zip` sig_tvs tc_sig ]
560 -- See Note [More instantiated than scoped]
561 -- Note that the scoped_tvs and the (sig_tvs sig)
562 -- may have different Names. That's quite ok.
564 ; (co_fn, matches') <- tcExtendTyVarEnv2 rhs_tvs $
565 tcMatchesFun mono_name inf matches mono_ty
567 ; let fun_bind' = FunBind { fun_id = L nm_loc mono_id,
568 fun_infix = inf, fun_matches = matches',
569 bind_fvs = placeHolderNames, fun_co_fn = co_fn,
571 ; return (unitBag (L b_loc fun_bind'),
572 [(name, Just tc_sig, mono_id)]) }
574 tcMonoBinds binds sig_fn _
575 = do { tc_binds <- mapM (wrapLocM (tcLhs sig_fn)) binds
577 -- Bring the monomorphic Ids, into scope for the RHSs
578 ; let mono_info = getMonoBindInfo tc_binds
579 rhs_id_env = [(name,mono_id) | (name, Nothing, mono_id) <- mono_info]
580 -- A monomorphic binding for each term variable that lacks
581 -- a type sig. (Ones with a sig are already in scope.)
583 ; binds' <- tcExtendIdEnv2 rhs_id_env $ do
584 traceTc (text "tcMonoBinds" <+> vcat [ ppr n <+> ppr id <+> ppr (idType id)
585 | (n,id) <- rhs_id_env])
586 mapM (wrapLocM tcRhs) tc_binds
587 ; return (listToBag binds', mono_info) }
589 ------------------------
590 -- tcLhs typechecks the LHS of the bindings, to construct the environment in which
591 -- we typecheck the RHSs. Basically what we are doing is this: for each binder:
592 -- if there's a signature for it, use the instantiated signature type
593 -- otherwise invent a type variable
594 -- You see that quite directly in the FunBind case.
596 -- But there's a complication for pattern bindings:
597 -- data T = MkT (forall a. a->a)
599 -- Here we can guess a type variable for the entire LHS (which will be refined to T)
600 -- but we want to get (f::forall a. a->a) as the RHS environment.
601 -- The simplest way to do this is to typecheck the pattern, and then look up the
602 -- bound mono-ids. Then we want to retain the typechecked pattern to avoid re-doing
603 -- it; hence the TcMonoBind data type in which the LHS is done but the RHS isn't
605 data TcMonoBind -- Half completed; LHS done, RHS not done
606 = TcFunBind MonoBindInfo (Located TcId) Bool (MatchGroup Name)
607 | TcPatBind [MonoBindInfo] (LPat TcId) (GRHSs Name) TcSigmaType
609 type MonoBindInfo = (Name, Maybe TcSigInfo, TcId)
610 -- Type signature (if any), and
611 -- the monomorphic bound things
613 bndrNames :: [MonoBindInfo] -> [Name]
614 bndrNames mbi = [n | (n,_,_) <- mbi]
616 getMonoType :: MonoBindInfo -> TcTauType
617 getMonoType (_,_,mono_id) = idType mono_id
619 tcLhs :: TcSigFun -> HsBind Name -> TcM TcMonoBind
620 tcLhs sig_fn (FunBind { fun_id = L nm_loc name, fun_infix = inf, fun_matches = matches })
621 = do { mb_sig <- tcInstSig_maybe sig_fn name
622 ; mono_name <- newLocalName name
623 ; mono_ty <- mk_mono_ty mb_sig
624 ; let mono_id = mkLocalId mono_name mono_ty
625 ; return (TcFunBind (name, mb_sig, mono_id) (L nm_loc mono_id) inf matches) }
627 mk_mono_ty (Just sig) = return (sig_tau sig)
628 mk_mono_ty Nothing = newFlexiTyVarTy argTypeKind
630 tcLhs sig_fn (PatBind { pat_lhs = pat, pat_rhs = grhss })
631 = do { mb_sigs <- mapM (tcInstSig_maybe sig_fn) names
632 ; mono_pat_binds <- doptM Opt_MonoPatBinds
633 -- With -XMonoPatBinds, we do no generalisation of pattern bindings
634 -- But the signature can still be polymoprhic!
635 -- data T = MkT (forall a. a->a)
636 -- x :: forall a. a->a
638 -- The function get_sig_ty decides whether the pattern-bound variables
639 -- should have exactly the type in the type signature (-XMonoPatBinds),
640 -- or the instantiated version (-XMonoPatBinds)
642 ; let nm_sig_prs = names `zip` mb_sigs
643 get_sig_ty | mono_pat_binds = idType . sig_id
644 | otherwise = sig_tau
645 tau_sig_env = mkNameEnv [ (name, get_sig_ty sig)
646 | (name, Just sig) <- nm_sig_prs]
647 sig_tau_fn = lookupNameEnv tau_sig_env
649 tc_pat exp_ty = tcLetPat sig_tau_fn pat exp_ty $
650 mapM lookup_info nm_sig_prs
652 -- After typechecking the pattern, look up the binder
653 -- names, which the pattern has brought into scope.
654 lookup_info :: (Name, Maybe TcSigInfo) -> TcM MonoBindInfo
655 lookup_info (name, mb_sig) = do { mono_id <- tcLookupId name
656 ; return (name, mb_sig, mono_id) }
658 ; ((pat', infos), pat_ty) <- addErrCtxt (patMonoBindsCtxt pat grhss) $
661 ; return (TcPatBind infos pat' grhss pat_ty) }
663 names = collectPatBinders pat
666 tcLhs _ other_bind = pprPanic "tcLhs" (ppr other_bind)
667 -- AbsBind, VarBind impossible
670 tcRhs :: TcMonoBind -> TcM (HsBind TcId)
671 -- When we are doing pattern bindings, or multiple function bindings at a time
672 -- we *don't* bring any scoped type variables into scope
673 -- Wny not? They are not completely rigid.
674 -- That's why we have the special case for a single FunBind in tcMonoBinds
675 tcRhs (TcFunBind (_,_,mono_id) fun' inf matches)
676 = do { (co_fn, matches') <- tcMatchesFun (idName mono_id) inf
677 matches (idType mono_id)
678 ; return (FunBind { fun_id = fun', fun_infix = inf, fun_matches = matches',
679 bind_fvs = placeHolderNames, fun_co_fn = co_fn,
680 fun_tick = Nothing }) }
682 tcRhs (TcPatBind _ pat' grhss pat_ty)
683 = do { grhss' <- addErrCtxt (patMonoBindsCtxt pat' grhss) $
684 tcGRHSsPat grhss pat_ty
685 ; return (PatBind { pat_lhs = pat', pat_rhs = grhss', pat_rhs_ty = pat_ty,
686 bind_fvs = placeHolderNames }) }
689 ---------------------
690 getMonoBindInfo :: [Located TcMonoBind] -> [MonoBindInfo]
691 getMonoBindInfo tc_binds
692 = foldr (get_info . unLoc) [] tc_binds
694 get_info (TcFunBind info _ _ _) rest = info : rest
695 get_info (TcPatBind infos _ _ _) rest = infos ++ rest
699 %************************************************************************
703 %************************************************************************
706 generalise :: DynFlags -> TopLevelFlag
707 -> [LHsBind Name] -> TcSigFun
708 -> [MonoBindInfo] -> [Inst]
709 -> TcM ([TyVar], [Inst], TcDictBinds)
710 -- The returned [TyVar] are all ready to quantify
712 generalise dflags top_lvl bind_list sig_fn mono_infos lie_req
713 | isMonoGroup dflags bind_list
714 = do { extendLIEs lie_req
715 ; return ([], [], emptyBag) }
717 | isRestrictedGroup dflags bind_list sig_fn -- RESTRICTED CASE
718 = -- Check signature contexts are empty
719 do { checkTc (all is_mono_sig sigs)
720 (restrictedBindCtxtErr bndrs)
722 -- Now simplify with exactly that set of tyvars
723 -- We have to squash those Methods
724 ; (qtvs, binds) <- tcSimplifyRestricted doc top_lvl bndrs
727 -- Check that signature type variables are OK
728 ; final_qtvs <- checkSigsTyVars qtvs sigs
730 ; return (final_qtvs, [], binds) }
732 | null sigs -- UNRESTRICTED CASE, NO TYPE SIGS
733 = tcSimplifyInfer doc tau_tvs lie_req
735 | otherwise -- UNRESTRICTED CASE, WITH TYPE SIGS
736 = do { sig_lie <- unifyCtxts sigs -- sigs is non-empty; sig_lie is zonked
737 ; let -- The "sig_avails" is the stuff available. We get that from
738 -- the context of the type signature, BUT ALSO the lie_avail
739 -- so that polymorphic recursion works right (see Note [Polymorphic recursion])
740 local_meths = [mkMethInst sig mono_id | (_, Just sig, mono_id) <- mono_infos]
741 sig_avails = sig_lie ++ local_meths
742 loc = sig_loc (head sigs)
744 -- Check that the needed dicts can be
745 -- expressed in terms of the signature ones
746 ; (qtvs, binds) <- tcSimplifyInferCheck loc tau_tvs sig_avails lie_req
748 -- Check that signature type variables are OK
749 ; final_qtvs <- checkSigsTyVars qtvs sigs
751 ; return (final_qtvs, sig_lie, binds) }
753 bndrs = bndrNames mono_infos
754 sigs = [sig | (_, Just sig, _) <- mono_infos]
755 get_tvs | isTopLevel top_lvl = tyVarsOfType -- See Note [Silly type synonym] in TcType
756 | otherwise = exactTyVarsOfType
757 tau_tvs = foldr (unionVarSet . get_tvs . getMonoType) emptyVarSet mono_infos
758 is_mono_sig sig = null (sig_theta sig)
759 doc = ptext (sLit "type signature(s) for") <+> pprBinders bndrs
761 mkMethInst (TcSigInfo { sig_id = poly_id, sig_tvs = tvs,
762 sig_theta = theta, sig_loc = loc }) mono_id
763 = Method {tci_id = mono_id, tci_oid = poly_id, tci_tys = mkTyVarTys tvs,
764 tci_theta = theta, tci_loc = loc}
767 unifyCtxts checks that all the signature contexts are the same
768 The type signatures on a mutually-recursive group of definitions
769 must all have the same context (or none).
771 The trick here is that all the signatures should have the same
772 context, and we want to share type variables for that context, so that
773 all the right hand sides agree a common vocabulary for their type
776 We unify them because, with polymorphic recursion, their types
777 might not otherwise be related. This is a rather subtle issue.
780 unifyCtxts :: [TcSigInfo] -> TcM [Inst]
781 -- Post-condition: the returned Insts are full zonked
782 unifyCtxts [] = panic "unifyCtxts []"
783 unifyCtxts (sig1 : sigs) -- Argument is always non-empty
784 = do { mapM unify_ctxt sigs
785 ; theta <- zonkTcThetaType (sig_theta sig1)
786 ; newDictBndrs (sig_loc sig1) theta }
788 theta1 = sig_theta sig1
789 unify_ctxt :: TcSigInfo -> TcM ()
790 unify_ctxt sig@(TcSigInfo { sig_theta = theta })
791 = setSrcSpan (instLocSpan (sig_loc sig)) $
792 addErrCtxt (sigContextsCtxt sig1 sig) $
793 do { cois <- unifyTheta theta1 theta
794 ; -- Check whether all coercions are identity coercions
795 -- That can happen if we have, say
797 -- g :: C (F a) => ...
798 -- where F is a type function and (F a ~ [a])
799 -- Then unification might succeed with a coercion. But it's much
800 -- much simpler to require that such signatures have identical contexts
801 checkTc (all isIdentityCoercion cois)
802 (ptext (sLit "Mutually dependent functions have syntactically distinct contexts"))
805 checkSigsTyVars :: [TcTyVar] -> [TcSigInfo] -> TcM [TcTyVar]
806 checkSigsTyVars qtvs sigs
807 = do { gbl_tvs <- tcGetGlobalTyVars
808 ; sig_tvs_s <- mapM (check_sig gbl_tvs) sigs
810 ; let -- Sigh. Make sure that all the tyvars in the type sigs
811 -- appear in the returned ty var list, which is what we are
812 -- going to generalise over. Reason: we occasionally get
814 -- type T a = () -> ()
817 -- Here, 'a' won't appear in qtvs, so we have to add it
818 sig_tvs = foldl extendVarSetList emptyVarSet sig_tvs_s
819 all_tvs = varSetElems (extendVarSetList sig_tvs qtvs)
822 check_sig gbl_tvs (TcSigInfo {sig_id = id, sig_tvs = tvs,
823 sig_theta = theta, sig_tau = tau})
824 = addErrCtxt (ptext (sLit "In the type signature for") <+> quotes (ppr id)) $
825 addErrCtxtM (sigCtxt id tvs theta tau) $
826 do { tvs' <- checkDistinctTyVars tvs
827 ; when (any (`elemVarSet` gbl_tvs) tvs')
828 (bleatEscapedTvs gbl_tvs tvs tvs')
831 checkDistinctTyVars :: [TcTyVar] -> TcM [TcTyVar]
832 -- (checkDistinctTyVars tvs) checks that the tvs from one type signature
833 -- are still all type variables, and all distinct from each other.
834 -- It returns a zonked set of type variables.
835 -- For example, if the type sig is
836 -- f :: forall a b. a -> b -> b
837 -- we want to check that 'a' and 'b' haven't
838 -- (a) been unified with a non-tyvar type
839 -- (b) been unified with each other (all distinct)
841 checkDistinctTyVars sig_tvs
842 = do { zonked_tvs <- mapM zonkSigTyVar sig_tvs
843 ; foldlM check_dup emptyVarEnv (sig_tvs `zip` zonked_tvs)
844 ; return zonked_tvs }
846 check_dup :: TyVarEnv TcTyVar -> (TcTyVar, TcTyVar) -> TcM (TyVarEnv TcTyVar)
847 -- The TyVarEnv maps each zonked type variable back to its
848 -- corresponding user-written signature type variable
849 check_dup acc (sig_tv, zonked_tv)
850 = case lookupVarEnv acc zonked_tv of
851 Just sig_tv' -> bomb_out sig_tv sig_tv'
853 Nothing -> return (extendVarEnv acc zonked_tv sig_tv)
855 bomb_out sig_tv1 sig_tv2
856 = do { env0 <- tcInitTidyEnv
857 ; let (env1, tidy_tv1) = tidyOpenTyVar env0 sig_tv1
858 (env2, tidy_tv2) = tidyOpenTyVar env1 sig_tv2
859 msg = ptext (sLit "Quantified type variable") <+> quotes (ppr tidy_tv1)
860 <+> ptext (sLit "is unified with another quantified type variable")
861 <+> quotes (ppr tidy_tv2)
862 ; failWithTcM (env2, msg) }
867 @getTyVarsToGen@ decides what type variables to generalise over.
869 For a "restricted group" -- see the monomorphism restriction
870 for a definition -- we bind no dictionaries, and
871 remove from tyvars_to_gen any constrained type variables
873 *Don't* simplify dicts at this point, because we aren't going
874 to generalise over these dicts. By the time we do simplify them
875 we may well know more. For example (this actually came up)
877 f x = array ... xs where xs = [1,2,3,4,5]
878 We don't want to generate lots of (fromInt Int 1), (fromInt Int 2)
879 stuff. If we simplify only at the f-binding (not the xs-binding)
880 we'll know that the literals are all Ints, and we can just produce
883 Find all the type variables involved in overloading, the
884 "constrained_tyvars". These are the ones we *aren't* going to
885 generalise. We must be careful about doing this:
887 (a) If we fail to generalise a tyvar which is not actually
888 constrained, then it will never, ever get bound, and lands
889 up printed out in interface files! Notorious example:
890 instance Eq a => Eq (Foo a b) where ..
891 Here, b is not constrained, even though it looks as if it is.
892 Another, more common, example is when there's a Method inst in
893 the LIE, whose type might very well involve non-overloaded
895 [NOTE: Jan 2001: I don't understand the problem here so I'm doing
896 the simple thing instead]
898 (b) On the other hand, we mustn't generalise tyvars which are constrained,
899 because we are going to pass on out the unmodified LIE, with those
900 tyvars in it. They won't be in scope if we've generalised them.
902 So we are careful, and do a complete simplification just to find the
903 constrained tyvars. We don't use any of the results, except to
904 find which tyvars are constrained.
906 Note [Polymorphic recursion]
907 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
908 The game plan for polymorphic recursion in the code above is
910 * Bind any variable for which we have a type signature
911 to an Id with a polymorphic type. Then when type-checking
912 the RHSs we'll make a full polymorphic call.
914 This fine, but if you aren't a bit careful you end up with a horrendous
915 amount of partial application and (worse) a huge space leak. For example:
917 f :: Eq a => [a] -> [a]
920 If we don't take care, after typechecking we get
922 f = /\a -> \d::Eq a -> let f' = f a d
926 Notice the the stupid construction of (f a d), which is of course
927 identical to the function we're executing. In this case, the
928 polymorphic recursion isn't being used (but that's a very common case).
929 This can lead to a massive space leak, from the following top-level defn
935 Now (f dEqInt) evaluates to a lambda that has f' as a free variable; but
936 f' is another thunk which evaluates to the same thing... and you end
937 up with a chain of identical values all hung onto by the CAF ff.
941 = let f' = f Int dEqInt in \ys. ...f'...
943 = let f' = let f' = f Int dEqInt in \ys. ...f'...
948 NOTE: a bit of arity anaysis would push the (f a d) inside the (\ys...),
949 which would make the space leak go away in this case
951 Solution: when typechecking the RHSs we always have in hand the
952 *monomorphic* Ids for each binding. So we just need to make sure that
953 if (Method f a d) shows up in the constraints emerging from (...f...)
954 we just use the monomorphic Id. We achieve this by adding monomorphic Ids
955 to the "givens" when simplifying constraints. That's what the "lies_avail"
960 f = /\a -> \d::Eq a -> letrec
961 fm = \ys:[a] -> ...fm...
967 %************************************************************************
971 %************************************************************************
973 Type signatures are tricky. See Note [Signature skolems] in TcType
975 @tcSigs@ checks the signatures for validity, and returns a list of
976 {\em freshly-instantiated} signatures. That is, the types are already
977 split up, and have fresh type variables installed. All non-type-signature
978 "RenamedSigs" are ignored.
980 The @TcSigInfo@ contains @TcTypes@ because they are unified with
981 the variable's type, and after that checked to see whether they've
986 The -XScopedTypeVariables flag brings lexically-scoped type variables
987 into scope for any explicitly forall-quantified type variables:
988 f :: forall a. a -> a
990 Then 'a' is in scope inside 'e'.
992 However, we do *not* support this
993 - For pattern bindings e.g
997 - For multiple function bindings, unless Opt_RelaxedPolyRec is on
998 f :: forall a. a -> a
1000 g :: forall b. b -> b
1002 Reason: we use mutable variables for 'a' and 'b', since they may
1003 unify to each other, and that means the scoped type variable would
1004 not stand for a completely rigid variable.
1006 Currently, we simply make Opt_ScopedTypeVariables imply Opt_RelaxedPolyRec
1009 Note [More instantiated than scoped]
1010 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1011 There may be more instantiated type variables than lexically-scoped
1013 type T a = forall b. b -> (a,b)
1015 Here, the signature for f will have one scoped type variable, c,
1016 but two instantiated type variables, c' and b'.
1018 We assume that the scoped ones are at the *front* of sig_tvs,
1019 and remember the names from the original HsForAllTy in the TcSigFun.
1023 type TcSigFun = Name -> Maybe [Name] -- Maps a let-binder to the list of
1024 -- type variables brought into scope
1025 -- by its type signature.
1026 -- Nothing => no type signature
1028 mkTcSigFun :: [LSig Name] -> TcSigFun
1029 -- Search for a particular type signature
1030 -- Precondition: the sigs are all type sigs
1031 -- Precondition: no duplicates
1032 mkTcSigFun sigs = lookupNameEnv env
1034 env = mkNameEnv [(name, hsExplicitTvs lhs_ty)
1035 | L _ (TypeSig (L _ name) lhs_ty) <- sigs]
1036 -- The scoped names are the ones explicitly mentioned
1037 -- in the HsForAll. (There may be more in sigma_ty, because
1038 -- of nested type synonyms. See Note [More instantiated than scoped].)
1039 -- See Note [Only scoped tyvars are in the TyVarEnv]
1044 sig_id :: TcId, -- *Polymorphic* binder for this value...
1046 sig_tvs :: [TcTyVar], -- Instantiated type variables
1047 -- See Note [Instantiate sig]
1049 sig_theta :: TcThetaType, -- Instantiated theta
1050 sig_tau :: TcTauType, -- Instantiated tau
1051 sig_loc :: InstLoc -- The location of the signature
1055 -- Note [Only scoped tyvars are in the TyVarEnv]
1056 -- We are careful to keep only the *lexically scoped* type variables in
1057 -- the type environment. Why? After all, the renamer has ensured
1058 -- that only legal occurrences occur, so we could put all type variables
1059 -- into the type env.
1061 -- But we want to check that two distinct lexically scoped type variables
1062 -- do not map to the same internal type variable. So we need to know which
1063 -- the lexically-scoped ones are... and at the moment we do that by putting
1064 -- only the lexically scoped ones into the environment.
1067 -- Note [Instantiate sig]
1068 -- It's vital to instantiate a type signature with fresh variables.
1070 -- type S = forall a. a->a
1074 -- Here, we must use distinct type variables when checking f,g's right hand sides.
1075 -- (Instantiation is only necessary because of type synonyms. Otherwise,
1076 -- it's all cool; each signature has distinct type variables from the renamer.)
1078 instance Outputable TcSigInfo where
1079 ppr (TcSigInfo { sig_id = id, sig_tvs = tyvars, sig_theta = theta, sig_tau = tau})
1080 = ppr id <+> ptext (sLit "::") <+> ppr tyvars <+> ppr theta <+> ptext (sLit "=>") <+> ppr tau
1084 tcTySig :: LSig Name -> TcM TcId
1085 tcTySig (L span (TypeSig (L _ name) ty))
1087 do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
1088 ; return (mkLocalId name sigma_ty) }
1089 tcTySig s = pprPanic "tcTySig" (ppr s)
1092 tcInstSig_maybe :: TcSigFun -> Name -> TcM (Maybe TcSigInfo)
1093 -- Instantiate with *meta* type variables;
1094 -- this signature is part of a multi-signature group
1095 tcInstSig_maybe sig_fn name
1096 = case sig_fn name of
1097 Nothing -> return Nothing
1098 Just _scoped_tvs -> do { tc_sig <- tcInstSig False name
1099 ; return (Just tc_sig) }
1100 -- NB: the _scoped_tvs may be non-empty, but we can
1101 -- just ignore them. See Note [Scoped tyvars].
1103 tcInstSig :: Bool -> Name -> TcM TcSigInfo
1104 -- Instantiate the signature, with either skolems or meta-type variables
1105 -- depending on the use_skols boolean. This variable is set True
1106 -- when we are typechecking a single function binding; and False for
1107 -- pattern bindings and a group of several function bindings.
1108 -- Reason: in the latter cases, the "skolems" can be unified together,
1109 -- so they aren't properly rigid in the type-refinement sense.
1110 -- NB: unless we are doing H98, each function with a sig will be done
1111 -- separately, even if it's mutually recursive, so use_skols will be True
1113 -- We always instantiate with fresh uniques,
1114 -- although we keep the same print-name
1116 -- type T = forall a. [a] -> [a]
1118 -- f = g where { g :: T; g = <rhs> }
1120 -- We must not use the same 'a' from the defn of T at both places!!
1122 tcInstSig use_skols name
1123 = do { poly_id <- tcLookupId name -- Cannot fail; the poly ids are put into
1124 -- scope when starting the binding group
1125 ; let skol_info = SigSkol (FunSigCtxt name)
1126 inst_tyvars = tcInstSigTyVars use_skols skol_info
1127 ; (tvs, theta, tau) <- tcInstType inst_tyvars (idType poly_id)
1128 ; loc <- getInstLoc (SigOrigin skol_info)
1129 ; return (TcSigInfo { sig_id = poly_id,
1130 sig_tvs = tvs, sig_theta = theta, sig_tau = tau,
1134 isMonoGroup :: DynFlags -> [LHsBind Name] -> Bool
1135 -- No generalisation at all
1136 isMonoGroup dflags binds
1137 = dopt Opt_MonoPatBinds dflags && any is_pat_bind binds
1139 is_pat_bind (L _ (PatBind {})) = True
1140 is_pat_bind _ = False
1143 isRestrictedGroup :: DynFlags -> [LHsBind Name] -> TcSigFun -> Bool
1144 isRestrictedGroup dflags binds sig_fn
1145 = mono_restriction && not all_unrestricted
1147 mono_restriction = dopt Opt_MonomorphismRestriction dflags
1148 all_unrestricted = all (unrestricted . unLoc) binds
1149 has_sig n = isJust (sig_fn n)
1151 unrestricted (PatBind {}) = False
1152 unrestricted (VarBind { var_id = v }) = has_sig v
1153 unrestricted (FunBind { fun_id = v, fun_matches = matches }) = unrestricted_match matches
1154 || has_sig (unLoc v)
1155 unrestricted (AbsBinds {})
1156 = panic "isRestrictedGroup/unrestricted AbsBinds"
1158 unrestricted_match (MatchGroup (L _ (Match [] _ _) : _) _) = False
1159 -- No args => like a pattern binding
1160 unrestricted_match _ = True
1161 -- Some args => a function binding
1165 %************************************************************************
1167 \subsection[TcBinds-errors]{Error contexts and messages}
1169 %************************************************************************
1173 -- This one is called on LHS, when pat and grhss are both Name
1174 -- and on RHS, when pat is TcId and grhss is still Name
1175 patMonoBindsCtxt :: OutputableBndr id => LPat id -> GRHSs Name -> SDoc
1176 patMonoBindsCtxt pat grhss
1177 = hang (ptext (sLit "In a pattern binding:")) 4 (pprPatBind pat grhss)
1179 -----------------------------------------------
1180 sigContextsCtxt :: TcSigInfo -> TcSigInfo -> SDoc
1181 sigContextsCtxt sig1 sig2
1182 = vcat [ptext (sLit "When matching the contexts of the signatures for"),
1183 nest 2 (vcat [ppr id1 <+> dcolon <+> ppr (idType id1),
1184 ppr id2 <+> dcolon <+> ppr (idType id2)]),
1185 ptext (sLit "The signature contexts in a mutually recursive group should all be identical")]
1191 -----------------------------------------------
1192 unboxedTupleErr :: Name -> Type -> SDoc
1193 unboxedTupleErr name ty
1194 = hang (ptext (sLit "Illegal binding of unboxed tuple"))
1195 4 (ppr name <+> dcolon <+> ppr ty)
1197 -----------------------------------------------
1198 restrictedBindCtxtErr :: [Name] -> SDoc
1199 restrictedBindCtxtErr binder_names
1200 = hang (ptext (sLit "Illegal overloaded type signature(s)"))
1201 4 (vcat [ptext (sLit "in a binding group for") <+> pprBinders binder_names,
1202 ptext (sLit "that falls under the monomorphism restriction")])
1204 genCtxt :: [Name] -> SDoc
1205 genCtxt binder_names
1206 = ptext (sLit "When generalising the type(s) for") <+> pprBinders binder_names
1208 missingSigWarn :: Bool -> Name -> Type -> TcM ()
1209 missingSigWarn False _ _ = return ()
1210 missingSigWarn True name ty
1211 = do { env0 <- tcInitTidyEnv
1212 ; let (env1, tidy_ty) = tidyOpenType env0 ty
1213 ; addWarnTcM (env1, mk_msg tidy_ty) }
1215 mk_msg ty = vcat [ptext (sLit "Definition but no type signature for") <+> quotes (ppr name),
1216 sep [ptext (sLit "Inferred type:") <+> pprHsVar name <+> dcolon <+> ppr ty]]