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, tcPolyBinds,
10 PragFun, tcPrags, mkPragFun,
11 TcSigInfo(..), SigFun, mkSigFun,
12 badBootDeclErr ) where
14 import {-# SOURCE #-} TcMatches ( tcGRHSsPat, tcMatchesFun )
15 import {-# SOURCE #-} TcExpr ( tcMonoExpr )
46 import Data.List( partition )
51 %************************************************************************
53 \subsection{Type-checking bindings}
55 %************************************************************************
57 @tcBindsAndThen@ typechecks a @HsBinds@. The "and then" part is because
58 it needs to know something about the {\em usage} of the things bound,
59 so that it can create specialisations of them. So @tcBindsAndThen@
60 takes a function which, given an extended environment, E, typechecks
61 the scope of the bindings returning a typechecked thing and (most
62 important) an LIE. It is this LIE which is then used as the basis for
63 specialising the things bound.
65 @tcBindsAndThen@ also takes a "combiner" which glues together the
66 bindings and the "thing" to make a new "thing".
68 The real work is done by @tcBindWithSigsAndThen@.
70 Recursive and non-recursive binds are handled in essentially the same
71 way: because of uniques there are no scoping issues left. The only
72 difference is that non-recursive bindings can bind primitive values.
74 Even for non-recursive binding groups we add typings for each binder
75 to the LVE for the following reason. When each individual binding is
76 checked the type of its LHS is unified with that of its RHS; and
77 type-checking the LHS of course requires that the binder is in scope.
79 At the top-level the LIE is sure to contain nothing but constant
80 dictionaries, which we resolve at the module level.
83 tcTopBinds :: HsValBinds Name -> TcM (LHsBinds TcId, TcLclEnv)
84 -- Note: returning the TcLclEnv is more than we really
85 -- want. The bit we care about is the local bindings
86 -- and the free type variables thereof
88 = do { (ValBindsOut prs _, env) <- tcValBinds TopLevel binds getLclEnv
89 ; return (foldr (unionBags . snd) emptyBag prs, env) }
90 -- The top level bindings are flattened into a giant
91 -- implicitly-mutually-recursive LHsBinds
93 tcHsBootSigs :: HsValBinds Name -> TcM [Id]
94 -- A hs-boot file has only one BindGroup, and it only has type
95 -- signatures in it. The renamer checked all this
96 tcHsBootSigs (ValBindsOut binds sigs)
97 = do { checkTc (null binds) badBootDeclErr
98 ; mapM (addLocM tc_boot_sig) (filter isTypeLSig sigs) }
100 tc_boot_sig (TypeSig (L _ name) ty)
101 = do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
102 ; return (mkVanillaGlobal name sigma_ty) }
103 -- Notice that we make GlobalIds, not LocalIds
104 tc_boot_sig s = pprPanic "tcHsBootSigs/tc_boot_sig" (ppr s)
105 tcHsBootSigs groups = pprPanic "tcHsBootSigs" (ppr groups)
107 badBootDeclErr :: Message
108 badBootDeclErr = ptext (sLit "Illegal declarations in an hs-boot file")
110 ------------------------
111 tcLocalBinds :: HsLocalBinds Name -> TcM thing
112 -> TcM (HsLocalBinds TcId, thing)
114 tcLocalBinds EmptyLocalBinds thing_inside
115 = do { thing <- thing_inside
116 ; return (EmptyLocalBinds, thing) }
118 tcLocalBinds (HsValBinds binds) thing_inside
119 = do { (binds', thing) <- tcValBinds NotTopLevel binds thing_inside
120 ; return (HsValBinds binds', thing) }
122 tcLocalBinds (HsIPBinds (IPBinds ip_binds _)) thing_inside
123 = do { (given_ips, ip_binds') <- mapAndUnzipM (wrapLocSndM tc_ip_bind) ip_binds
124 ; let ip_tvs = foldr (unionVarSet . tyVarsOfType . idType) emptyVarSet given_ips
126 -- If the binding binds ?x = E, we must now
127 -- discharge any ?x constraints in expr_lie
128 ; (ev_binds, result) <- checkConstraints (IPSkol ips)
129 ip_tvs -- See Note [Implicit parameter untouchables]
133 ; return (HsIPBinds (IPBinds ip_binds' ev_binds), result) }
135 ips = [ip | L _ (IPBind ip _) <- ip_binds]
137 -- I wonder if we should do these one at at time
140 tc_ip_bind (IPBind ip expr)
141 = do { ty <- newFlexiTyVarTy argTypeKind
142 ; ip_id <- newIP ip ty
143 ; expr' <- tcMonoExpr expr ty
144 ; return (ip_id, (IPBind (IPName ip_id) expr')) }
147 Note [Implicit parameter untouchables]
148 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
149 We add the type variables in the types of the implicit parameters
150 as untouchables, not so much because we really must not unify them,
151 but rather because we otherwise end up with constraints like this
152 Num alpha, Implic { wanted = alpha ~ Int }
153 The constraint solver solves alpha~Int by unification, but then
154 doesn't float that solved constraint out (it's not an unsolved
155 wanted. Result disaster: the (Num alpha) is again solved, this
156 time by defaulting. No no no.
159 tcValBinds :: TopLevelFlag
160 -> HsValBinds Name -> TcM thing
161 -> TcM (HsValBinds TcId, thing)
163 tcValBinds _ (ValBindsIn binds _) _
164 = pprPanic "tcValBinds" (ppr binds)
166 tcValBinds top_lvl (ValBindsOut binds sigs) thing_inside
167 = do { -- Typecheck the signature
168 ; let { prag_fn = mkPragFun sigs (foldr (unionBags . snd) emptyBag binds)
169 ; ty_sigs = filter isTypeLSig sigs
170 ; sig_fn = mkSigFun ty_sigs }
172 ; poly_ids <- checkNoErrs (mapAndRecoverM tcTySig ty_sigs)
173 -- No recovery from bad signatures, because the type sigs
174 -- may bind type variables, so proceeding without them
175 -- can lead to a cascade of errors
176 -- ToDo: this means we fall over immediately if any type sig
177 -- is wrong, which is over-conservative, see Trac bug #745
179 -- Extend the envt right away with all
180 -- the Ids declared with type signatures
181 ; (binds', thing) <- tcExtendIdEnv poly_ids $
182 tcBindGroups top_lvl sig_fn prag_fn
185 ; return (ValBindsOut binds' sigs, thing) }
187 ------------------------
188 tcBindGroups :: TopLevelFlag -> SigFun -> PragFun
189 -> [(RecFlag, LHsBinds Name)] -> TcM thing
190 -> TcM ([(RecFlag, LHsBinds TcId)], thing)
191 -- Typecheck a whole lot of value bindings,
192 -- one strongly-connected component at a time
193 -- Here a "strongly connected component" has the strightforward
194 -- meaning of a group of bindings that mention each other,
195 -- ignoring type signatures (that part comes later)
197 tcBindGroups _ _ _ [] thing_inside
198 = do { thing <- thing_inside
199 ; return ([], thing) }
201 tcBindGroups top_lvl sig_fn prag_fn (group : groups) thing_inside
202 = do { (group', (groups', thing))
203 <- tc_group top_lvl sig_fn prag_fn group $
204 tcBindGroups top_lvl sig_fn prag_fn groups thing_inside
205 ; return (group' ++ groups', thing) }
207 ------------------------
208 tc_group :: forall thing.
209 TopLevelFlag -> SigFun -> PragFun
210 -> (RecFlag, LHsBinds Name) -> TcM thing
211 -> TcM ([(RecFlag, LHsBinds TcId)], thing)
213 -- Typecheck one strongly-connected component of the original program.
214 -- We get a list of groups back, because there may
215 -- be specialisations etc as well
217 tc_group top_lvl sig_fn prag_fn (NonRecursive, binds) thing_inside
218 -- A single non-recursive binding
219 -- We want to keep non-recursive things non-recursive
220 -- so that we desugar unlifted bindings correctly
221 = do { (binds1, ids) <- tcPolyBinds top_lvl sig_fn prag_fn NonRecursive NonRecursive
223 ; thing <- tcExtendIdEnv ids thing_inside
224 ; return ( [(NonRecursive, binds1)], thing) }
226 tc_group top_lvl sig_fn prag_fn (Recursive, binds) thing_inside
227 = -- To maximise polymorphism (assumes -XRelaxedPolyRec), we do a new
228 -- strongly-connected-component analysis, this time omitting
229 -- any references to variables with type signatures.
230 do { traceTc "tc_group rec" (pprLHsBinds binds)
231 ; (binds1, _ids, thing) <- go sccs
232 -- Here is where we should do bindInstsOfLocalFuns
233 -- if we start having Methods again
234 ; return ([(Recursive, binds1)], thing) }
235 -- Rec them all together
237 sccs :: [SCC (LHsBind Name)]
238 sccs = stronglyConnCompFromEdgedVertices (mkEdges sig_fn binds)
240 go :: [SCC (LHsBind Name)] -> TcM (LHsBinds TcId, [TcId], thing)
241 go (scc:sccs) = do { (binds1, ids1) <- tc_scc scc
242 ; (binds2, ids2, thing) <- tcExtendIdEnv ids1 $ go sccs
243 ; return (binds1 `unionBags` binds2, ids1 ++ ids2, thing) }
244 go [] = do { thing <- thing_inside; return (emptyBag, [], thing) }
246 tc_scc (AcyclicSCC bind) = tc_sub_group NonRecursive [bind]
247 tc_scc (CyclicSCC binds) = tc_sub_group Recursive binds
249 tc_sub_group = tcPolyBinds top_lvl sig_fn prag_fn Recursive
252 ------------------------
254 bindLocalInsts :: TopLevelFlag
255 -> TcM (LHsBinds TcId, [TcId], a)
256 -> TcM (LHsBinds TcId, TcEvBinds, a)
257 bindLocalInsts top_lvl thing_inside
259 = do { (binds, _, thing) <- thing_inside; return (binds, emptyBag, thing) }
260 -- For the top level don't bother with all this bindInstsOfLocalFuns stuff.
261 -- All the top level things are rec'd together anyway, so it's fine to
262 -- leave them to the tcSimplifyTop, and quite a bit faster too
264 | otherwise -- Nested case
265 = do { ((binds, ids, thing), lie) <- getConstraints thing_inside
266 ; lie_binds <- bindLocalMethods lie ids
267 ; return (binds, lie_binds, thing) }
270 ------------------------
271 mkEdges :: SigFun -> LHsBinds Name
272 -> [(LHsBind Name, BKey, [BKey])]
274 type BKey = Int -- Just number off the bindings
277 = [ (bind, key, [key | n <- nameSetToList (bind_fvs (unLoc bind)),
278 Just key <- [lookupNameEnv key_map n], no_sig n ])
279 | (bind, key) <- keyd_binds
282 no_sig :: Name -> Bool
283 no_sig n = isNothing (sig_fn n)
285 keyd_binds = bagToList binds `zip` [0::BKey ..]
287 key_map :: NameEnv BKey -- Which binding it comes from
288 key_map = mkNameEnv [(bndr, key) | (L _ bind, key) <- keyd_binds
289 , bndr <- bindersOfHsBind bind ]
291 bindersOfHsBind :: HsBind Name -> [Name]
292 bindersOfHsBind (PatBind { pat_lhs = pat }) = collectPatBinders pat
293 bindersOfHsBind (FunBind { fun_id = L _ f }) = [f]
294 bindersOfHsBind (AbsBinds {}) = panic "bindersOfHsBind AbsBinds"
295 bindersOfHsBind (VarBind {}) = panic "bindersOfHsBind VarBind"
297 ------------------------
298 tcPolyBinds :: TopLevelFlag -> SigFun -> PragFun
299 -> RecFlag -- Whether the group is really recursive
300 -> RecFlag -- Whether it's recursive after breaking
301 -- dependencies based on type signatures
303 -> TcM (LHsBinds TcId, [TcId])
305 -- Typechecks a single bunch of bindings all together,
306 -- and generalises them. The bunch may be only part of a recursive
307 -- group, because we use type signatures to maximise polymorphism
309 -- Returns a list because the input may be a single non-recursive binding,
310 -- in which case the dependency order of the resulting bindings is
313 -- Knows nothing about the scope of the bindings
315 tcPolyBinds top_lvl sig_fn prag_fn rec_group rec_tc bind_list
317 recoverM (recoveryCode binder_names sig_fn) $ do
318 -- Set up main recoer; take advantage of any type sigs
320 { traceTc "------------------------------------------------" empty
321 ; traceTc "Bindings for" (ppr binder_names)
323 ; tc_sig_fn <- tcInstSigs sig_fn binder_names
326 ; let plan = decideGeneralisationPlan dflags top_lvl binder_names bind_list tc_sig_fn
327 ; traceTc "Generalisation plan" (ppr plan)
328 ; (binds, poly_ids) <- case plan of
329 NoGen -> tcPolyNoGen tc_sig_fn prag_fn rec_group rec_tc bind_list
330 InferGen mono -> tcPolyInfer top_lvl mono tc_sig_fn prag_fn rec_group rec_tc bind_list
331 CheckGen sig -> tcPolyCheck sig prag_fn rec_group rec_tc bind_list
333 -- Check whether strict bindings are ok
334 -- These must be non-recursive etc, and are not generalised
335 -- They desugar to a case expression in the end
336 ; checkStrictBinds top_lvl rec_group bind_list poly_ids
338 -- Warn about missing signatures
339 -- Do this only when we we have a type to offer
340 ; warn_missing_sigs <- doptM Opt_WarnMissingSigs
341 ; when (isTopLevel top_lvl && warn_missing_sigs) $
342 mapM_ missingSigWarn (filter no_sig poly_ids)
344 ; return (binds, poly_ids) }
346 no_sig id = isNothing (sig_fn (idName id))
348 binder_names = collectHsBindListBinders bind_list
349 loc = getLoc (head bind_list)
350 -- TODO: location a bit awkward, but the mbinds have been
351 -- dependency analysed and may no longer be adjacent
354 :: TcSigFun -> PragFun
355 -> RecFlag -- Whether the group is really recursive
356 -> RecFlag -- Whether it's recursive after breaking
357 -- dependencies based on type signatures
359 -> TcM (LHsBinds TcId, [TcId])
360 -- No generalisation whatsoever
362 tcPolyNoGen tc_sig_fn prag_fn rec_group rec_tc bind_list
363 = do { (binds', mono_infos) <- tcMonoBinds tc_sig_fn True rec_tc bind_list
364 ; mono_ids' <- mapM tc_mono_info mono_infos
365 ; return (binds', mono_ids') }
367 tc_mono_info (name, _, mono_id)
368 = do { mono_ty' <- zonkTcTypeCarefully (idType mono_id)
369 -- Zonk, mainly to expose unboxed types to checkStrictBinds
370 ; let mono_id' = setIdType mono_id mono_ty'
371 ; (mono_id'', _specs) <- tcPrags rec_group False False
372 mono_id' (prag_fn name)
374 -- NB: tcPrags generates and error message for
375 -- specialisation pragmas for non-overloaded sigs
376 -- So we can safely ignore _specs
379 tcPolyCheck :: TcSigInfo -> PragFun
380 -> RecFlag -- Whether the group is really recursive
381 -> RecFlag -- Whether it's recursive after breaking
382 -- dependencies based on type signatures
384 -> TcM (LHsBinds TcId, [TcId])
385 -- There is just one binding,
386 -- it binds a single variable,
387 -- it has a signature,
388 tcPolyCheck sig@(TcSigInfo { sig_id = id, sig_tvs = tvs, sig_scoped = scoped
389 , sig_theta = theta, sig_loc = loc })
390 prag_fn rec_group rec_tc bind_list
391 = do { ev_vars <- newEvVars theta
393 ; let skol_info = SigSkol (FunSigCtxt (idName id))
394 ; (ev_binds, (binds', [mono_info]))
395 <- checkConstraints skol_info emptyVarSet tvs ev_vars $
396 tcExtendTyVarEnv2 (scoped `zip` mkTyVarTys tvs) $
397 tcMonoBinds (\_ -> Just sig) False rec_tc bind_list
399 ; export <- mkExport rec_group False prag_fn tvs theta mono_info
401 ; let (_, poly_id, _, _) = export
402 abs_bind = L loc $ AbsBinds
404 , abs_ev_vars = ev_vars, abs_ev_binds = ev_binds
405 , abs_exports = [export], abs_binds = binds' }
406 ; return (unitBag abs_bind, [poly_id]) }
410 -> Bool -- True <=> apply the monomorphism restriction
411 -> TcSigFun -> PragFun
412 -> RecFlag -- Whether the group is really recursive
413 -> RecFlag -- Whether it's recursive after breaking
414 -- dependencies based on type signatures
416 -> TcM (LHsBinds TcId, [TcId])
417 tcPolyInfer top_lvl mono sig_fn prag_fn rec_group rec_tc bind_list
418 = do { ((binds', mono_infos), wanted)
420 tcMonoBinds sig_fn False rec_tc bind_list
422 ; unifyCtxts [sig | (_, Just sig, _) <- mono_infos]
424 ; let get_tvs | isTopLevel top_lvl = tyVarsOfType
425 | otherwise = exactTyVarsOfType
426 -- See Note [Silly type synonym] in TcType
427 tau_tvs = foldr (unionVarSet . get_tvs . getMonoType) emptyVarSet mono_infos
429 ; (qtvs, givens, ev_binds) <- simplifyInfer mono tau_tvs wanted
431 ; exports <- mapM (mkExport rec_group (length mono_infos > 1)
432 prag_fn qtvs (map evVarPred givens))
435 ; let poly_ids = [poly_id | (_, poly_id, _, _) <- exports]
436 ; traceTc "Binding:" (ppr (poly_ids `zip` map idType poly_ids))
439 ; let abs_bind = L loc $ AbsBinds { abs_tvs = qtvs
440 , abs_ev_vars = givens, abs_ev_binds = ev_binds
441 , abs_exports = exports, abs_binds = binds' }
443 ; return (unitBag abs_bind, poly_ids) -- poly_ids are guaranteed zonked by mkExport
449 -> Bool -- More than one variable is bound, so we'll desugar to
450 -- a tuple, so INLINE pragmas won't work
451 -> PragFun -> [TyVar] -> TcThetaType
453 -> TcM ([TyVar], Id, Id, TcSpecPrags)
454 -- mkExport generates exports with
455 -- zonked type variables,
457 -- The former is just because no further unifications will change
458 -- the quantified type variables, so we can fix their final form
460 -- The latter is needed because the poly_ids are used to extend the
461 -- type environment; see the invariant on TcEnv.tcExtendIdEnv
463 -- Pre-condition: the inferred_tvs are already zonked
465 mkExport rec_group multi_bind prag_fn inferred_tvs theta
466 (poly_name, mb_sig, mono_id)
467 = do { (tvs, poly_id) <- mk_poly_id mb_sig
468 -- poly_id has a zonked type
470 ; (poly_id', spec_prags) <- tcPrags rec_group multi_bind (notNull theta)
471 poly_id (prag_fn poly_name)
472 -- tcPrags requires a zonked poly_id
474 ; return (tvs, poly_id', mono_id, SpecPrags spec_prags) }
476 poly_ty = mkSigmaTy inferred_tvs theta (idType mono_id)
478 mk_poly_id Nothing = do { poly_ty' <- zonkTcTypeCarefully poly_ty
479 ; return (inferred_tvs, mkLocalId poly_name poly_ty') }
480 mk_poly_id (Just sig) = do { tvs <- mapM zonk_tv (sig_tvs sig)
481 ; return (tvs, sig_id sig) }
483 zonk_tv tv = do { ty <- zonkTcTyVar tv; return (tcGetTyVar "mkExport" ty) }
485 ------------------------
486 type PragFun = Name -> [LSig Name]
488 mkPragFun :: [LSig Name] -> LHsBinds Name -> PragFun
489 mkPragFun sigs binds = \n -> lookupNameEnv prag_env n `orElse` []
491 prs = mapCatMaybes get_sig sigs
493 get_sig :: LSig Name -> Maybe (Located Name, LSig Name)
494 get_sig (L l (SpecSig nm ty inl)) = Just (nm, L l $ SpecSig nm ty (add_arity nm inl))
495 get_sig (L l (InlineSig nm inl)) = Just (nm, L l $ InlineSig nm (add_arity nm inl))
498 add_arity (L _ n) inl_prag -- Adjust inl_sat field to match visible arity of function
499 | Just ar <- lookupNameEnv ar_env n = inl_prag { inl_sat = Just ar }
500 | otherwise = inl_prag
502 prag_env :: NameEnv [LSig Name]
503 prag_env = foldl add emptyNameEnv prs
504 add env (L _ n,p) = extendNameEnv_Acc (:) singleton env n p
506 -- ar_env maps a local to the arity of its definition
507 ar_env :: NameEnv Arity
508 ar_env = foldrBag lhsBindArity emptyNameEnv binds
510 lhsBindArity :: LHsBind Name -> NameEnv Arity -> NameEnv Arity
511 lhsBindArity (L _ (FunBind { fun_id = id, fun_matches = ms })) env
512 = extendNameEnv env (unLoc id) (matchGroupArity ms)
513 lhsBindArity _ env = env -- PatBind/VarBind
516 -> Bool -- True <=> AbsBinds binds more than one variable
517 -> Bool -- True <=> function is overloaded
519 -> TcM (Id, [Located TcSpecPrag])
520 -- Add INLINE and SPECIALSE pragmas
521 -- INLINE prags are added to the (polymorphic) Id directly
522 -- SPECIALISE prags are passed to the desugarer via TcSpecPrags
523 -- Pre-condition: the poly_id is zonked
524 -- Reason: required by tcSubExp
525 tcPrags _rec_group _multi_bind is_overloaded_id poly_id prag_sigs
526 = do { poly_id' <- tc_inl inl_sigs
528 ; spec_prags <- mapM (wrapLocM (tcSpecPrag poly_id')) spec_sigs
530 ; unless (null spec_sigs || is_overloaded_id) warn_discarded_spec
532 ; unless (null bad_sigs) warn_discarded_sigs
534 ; return (poly_id', spec_prags) }
536 (inl_sigs, other_sigs) = partition isInlineLSig prag_sigs
537 (spec_sigs, bad_sigs) = partition isSpecLSig other_sigs
539 warn_discarded_spec = warnPrags poly_id spec_sigs $
540 ptext (sLit "SPECIALISE pragmas for non-overloaded function")
541 warn_dup_inline = warnPrags poly_id inl_sigs $
542 ptext (sLit "Duplicate INLINE pragmas for")
543 warn_discarded_sigs = warnPrags poly_id bad_sigs $
544 ptext (sLit "Discarding unexpected pragmas for")
547 tc_inl [] = return poly_id
548 tc_inl (L loc (InlineSig _ prag) : other_inls)
549 = do { unless (null other_inls) (setSrcSpan loc warn_dup_inline)
550 ; return (poly_id `setInlinePragma` prag) }
551 tc_inl _ = panic "tc_inl"
553 {- Earlier we tried to warn about
554 (a) INLINE for recursive function
555 (b) INLINE for function that is part of a multi-binder group
556 Code fragments below. But we want to allow
560 even though they are mutually recursive.
561 So I'm just omitting the warnings for now
563 | multi_bind && isInlinePragma prag
564 = do { setSrcSpan loc $ addWarnTc multi_bind_warn
567 ; when (isInlinePragma prag && isRec rec_group)
568 (setSrcSpan loc (addWarnTc rec_inline_warn))
570 rec_inline_warn = ptext (sLit "INLINE pragma for recursive binder")
571 <+> quotes (ppr poly_id) <+> ptext (sLit "may be discarded")
573 multi_bind_warn = hang (ptext (sLit "Discarding INLINE pragma for") <+> quotes (ppr poly_id))
574 2 (ptext (sLit "because it is bound by a pattern, or mutual recursion") )
578 warnPrags :: Id -> [LSig Name] -> SDoc -> TcM ()
579 warnPrags id bad_sigs herald
580 = addWarnTc (hang (herald <+> quotes (ppr id))
581 2 (ppr_sigs bad_sigs))
583 ppr_sigs sigs = vcat (map (ppr . getLoc) sigs)
586 tcSpecPrag :: TcId -> Sig Name -> TcM TcSpecPrag
587 tcSpecPrag poly_id prag@(SpecSig _ hs_ty inl)
588 = addErrCtxt (spec_ctxt prag) $
589 do { let name = idName poly_id
590 sig_ctxt = FunSigCtxt name
591 ; spec_ty <- tcHsSigType sig_ctxt hs_ty
592 ; wrap <- tcSubType (SpecPragOrigin name) (SigSkol sig_ctxt)
593 (idType poly_id) spec_ty
594 ; return (SpecPrag wrap inl) }
596 spec_ctxt prag = hang (ptext (sLit "In the SPECIALISE pragma")) 2 (ppr prag)
597 tcSpecPrag _ sig = pprPanic "tcSpecPrag" (ppr sig)
600 -- If typechecking the binds fails, then return with each
601 -- signature-less binder given type (forall a.a), to minimise
602 -- subsequent error messages
603 recoveryCode :: [Name] -> SigFun -> TcM (LHsBinds TcId, [Id])
604 recoveryCode binder_names sig_fn
605 = do { traceTc "tcBindsWithSigs: error recovery" (ppr binder_names)
606 ; poly_ids <- mapM mk_dummy binder_names
607 ; return (emptyBag, poly_ids) }
610 | isJust (sig_fn name) = tcLookupId name -- Had signature; look it up
611 | otherwise = return (mkLocalId name forall_a_a) -- No signature
614 forall_a_a = mkForAllTy openAlphaTyVar (mkTyVarTy openAlphaTyVar)
618 %************************************************************************
620 \subsection{tcMonoBind}
622 %************************************************************************
624 @tcMonoBinds@ deals with a perhaps-recursive group of HsBinds.
625 The signatures have been dealt with already.
628 tcMonoBinds :: TcSigFun
629 -> Bool -- True <=> no generalisation will be done for this binding
630 -> RecFlag -- Whether the binding is recursive for typechecking purposes
631 -- i.e. the binders are mentioned in their RHSs, and
632 -- we are not resuced by a type signature
634 -> TcM (LHsBinds TcId, [MonoBindInfo])
636 tcMonoBinds sig_fn no_gen is_rec
637 [ L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf,
638 fun_matches = matches, bind_fvs = fvs })]
639 -- Single function binding,
640 | NonRecursive <- is_rec -- ...binder isn't mentioned in RHS
641 , Nothing <- sig_fn name -- ...with no type signature
642 = -- In this very special case we infer the type of the
643 -- right hand side first (it may have a higher-rank type)
644 -- and *then* make the monomorphic Id for the LHS
645 -- e.g. f = \(x::forall a. a->a) -> <body>
646 -- We want to infer a higher-rank type for f
648 do { ((co_fn, matches'), rhs_ty) <- tcInfer (tcMatchesFun name inf matches)
650 ; mono_id <- newLetBndr no_gen name rhs_ty
651 ; return (unitBag (L b_loc (FunBind { fun_id = L nm_loc mono_id, fun_infix = inf,
652 fun_matches = matches', bind_fvs = fvs,
653 fun_co_fn = co_fn, fun_tick = Nothing })),
654 [(name, Nothing, mono_id)]) }
656 tcMonoBinds sig_fn no_gen _ binds
657 = do { tc_binds <- mapM (wrapLocM (tcLhs sig_fn no_gen)) binds
659 -- Bring the monomorphic Ids, into scope for the RHSs
660 ; let mono_info = getMonoBindInfo tc_binds
661 rhs_id_env = [(name,mono_id) | (name, Nothing, mono_id) <- mono_info]
662 -- A monomorphic binding for each term variable that lacks
663 -- a type sig. (Ones with a sig are already in scope.)
665 ; binds' <- tcExtendIdEnv2 rhs_id_env $ do
666 traceTc "tcMonoBinds" $ vcat [ ppr n <+> ppr id <+> ppr (idType id)
667 | (n,id) <- rhs_id_env]
668 mapM (wrapLocM tcRhs) tc_binds
669 ; return (listToBag binds', mono_info) }
671 ------------------------
672 -- tcLhs typechecks the LHS of the bindings, to construct the environment in which
673 -- we typecheck the RHSs. Basically what we are doing is this: for each binder:
674 -- if there's a signature for it, use the instantiated signature type
675 -- otherwise invent a type variable
676 -- You see that quite directly in the FunBind case.
678 -- But there's a complication for pattern bindings:
679 -- data T = MkT (forall a. a->a)
681 -- Here we can guess a type variable for the entire LHS (which will be refined to T)
682 -- but we want to get (f::forall a. a->a) as the RHS environment.
683 -- The simplest way to do this is to typecheck the pattern, and then look up the
684 -- bound mono-ids. Then we want to retain the typechecked pattern to avoid re-doing
685 -- it; hence the TcMonoBind data type in which the LHS is done but the RHS isn't
687 data TcMonoBind -- Half completed; LHS done, RHS not done
688 = TcFunBind MonoBindInfo (Located TcId) Bool (MatchGroup Name)
689 | TcPatBind [MonoBindInfo] (LPat TcId) (GRHSs Name) TcSigmaType
691 type MonoBindInfo = (Name, Maybe TcSigInfo, TcId)
692 -- Type signature (if any), and
693 -- the monomorphic bound things
695 getMonoType :: MonoBindInfo -> TcTauType
696 getMonoType (_,_,mono_id) = idType mono_id
698 tcLhs :: TcSigFun -> Bool -> HsBind Name -> TcM TcMonoBind
699 tcLhs sig_fn no_gen (FunBind { fun_id = L nm_loc name, fun_infix = inf, fun_matches = matches })
700 = do { mono_id <- newLhsBndr mb_sig no_gen name
701 ; return (TcFunBind (name, mb_sig, mono_id) (L nm_loc mono_id) inf matches) }
705 tcLhs sig_fn no_gen (PatBind { pat_lhs = pat, pat_rhs = grhss })
706 = do { let tc_pat exp_ty = tcLetPat sig_fn no_gen pat exp_ty $
707 mapM lookup_info (collectPatBinders pat)
709 -- After typechecking the pattern, look up the binder
710 -- names, which the pattern has brought into scope.
711 lookup_info :: Name -> TcM MonoBindInfo
712 lookup_info name = do { mono_id <- tcLookupId name
713 ; return (name, sig_fn name, mono_id) }
715 ; ((pat', infos), pat_ty) <- addErrCtxt (patMonoBindsCtxt pat grhss) $
718 ; return (TcPatBind infos pat' grhss pat_ty) }
720 tcLhs _ _ other_bind = pprPanic "tcLhs" (ppr other_bind)
721 -- AbsBind, VarBind impossible
724 newLhsBndr :: Maybe TcSigInfo -> Bool -> Name -> TcM TcId
725 -- cf TcPat.tcPatBndr (LetPat case)
726 newLhsBndr (Just sig) no_gen name
727 | no_gen = return (sig_id sig)
728 | otherwise = do { mono_name <- newLocalName name
729 ; return (mkLocalId mono_name (sig_tau sig)) }
731 newLhsBndr Nothing no_gen name
732 = do { mono_ty <- newFlexiTyVarTy argTypeKind
733 ; newLetBndr no_gen name mono_ty }
736 tcRhs :: TcMonoBind -> TcM (HsBind TcId)
737 -- When we are doing pattern bindings, or multiple function bindings at a time
738 -- we *don't* bring any scoped type variables into scope
739 -- Wny not? They are not completely rigid.
740 -- That's why we have the special case for a single FunBind in tcMonoBinds
741 tcRhs (TcFunBind (_,_,mono_id) fun' inf matches)
742 = do { (co_fn, matches') <- tcMatchesFun (idName mono_id) inf
743 matches (idType mono_id)
744 ; return (FunBind { fun_id = fun', fun_infix = inf, fun_matches = matches'
746 , bind_fvs = placeHolderNames, fun_tick = Nothing }) }
748 tcRhs (TcPatBind _ pat' grhss pat_ty)
749 = do { grhss' <- addErrCtxt (patMonoBindsCtxt pat' grhss) $
750 tcGRHSsPat grhss pat_ty
751 ; return (PatBind { pat_lhs = pat', pat_rhs = grhss', pat_rhs_ty = pat_ty
752 , bind_fvs = placeHolderNames }) }
755 ---------------------
756 getMonoBindInfo :: [Located TcMonoBind] -> [MonoBindInfo]
757 getMonoBindInfo tc_binds
758 = foldr (get_info . unLoc) [] tc_binds
760 get_info (TcFunBind info _ _ _) rest = info : rest
761 get_info (TcPatBind infos _ _ _) rest = infos ++ rest
765 %************************************************************************
769 %************************************************************************
771 unifyCtxts checks that all the signature contexts are the same
772 The type signatures on a mutually-recursive group of definitions
773 must all have the same context (or none).
775 The trick here is that all the signatures should have the same
776 context, and we want to share type variables for that context, so that
777 all the right hand sides agree a common vocabulary for their type
780 We unify them because, with polymorphic recursion, their types
781 might not otherwise be related. This is a rather subtle issue.
784 unifyCtxts :: [TcSigInfo] -> TcM ()
785 -- Post-condition: the returned Insts are full zonked
786 unifyCtxts [] = return ()
787 unifyCtxts (sig1 : sigs)
788 = do { traceTc "unifyCtxts" (ppr (sig1 : sigs))
789 ; mapM_ unify_ctxt sigs }
791 theta1 = sig_theta sig1
792 unify_ctxt :: TcSigInfo -> TcM ()
793 unify_ctxt sig@(TcSigInfo { sig_theta = theta })
794 = setSrcSpan (sig_loc sig) $
795 addErrCtxt (sigContextsCtxt sig1 sig) $
796 do { cois <- unifyTheta theta1 theta
797 ; -- Check whether all coercions are identity coercions
798 -- That can happen if we have, say
800 -- g :: C (F a) => ...
801 -- where F is a type function and (F a ~ [a])
802 -- Then unification might succeed with a coercion. But it's much
803 -- much simpler to require that such signatures have identical contexts
804 checkTc (all isIdentityCoI cois)
805 (ptext (sLit "Mutually dependent functions have syntactically distinct contexts"))
810 @getTyVarsToGen@ decides what type variables to generalise over.
812 For a "restricted group" -- see the monomorphism restriction
813 for a definition -- we bind no dictionaries, and
814 remove from tyvars_to_gen any constrained type variables
816 *Don't* simplify dicts at this point, because we aren't going
817 to generalise over these dicts. By the time we do simplify them
818 we may well know more. For example (this actually came up)
820 f x = array ... xs where xs = [1,2,3,4,5]
821 We don't want to generate lots of (fromInt Int 1), (fromInt Int 2)
822 stuff. If we simplify only at the f-binding (not the xs-binding)
823 we'll know that the literals are all Ints, and we can just produce
826 Find all the type variables involved in overloading, the
827 "constrained_tyvars". These are the ones we *aren't* going to
828 generalise. We must be careful about doing this:
830 (a) If we fail to generalise a tyvar which is not actually
831 constrained, then it will never, ever get bound, and lands
832 up printed out in interface files! Notorious example:
833 instance Eq a => Eq (Foo a b) where ..
834 Here, b is not constrained, even though it looks as if it is.
835 Another, more common, example is when there's a Method inst in
836 the LIE, whose type might very well involve non-overloaded
838 [NOTE: Jan 2001: I don't understand the problem here so I'm doing
839 the simple thing instead]
841 (b) On the other hand, we mustn't generalise tyvars which are constrained,
842 because we are going to pass on out the unmodified LIE, with those
843 tyvars in it. They won't be in scope if we've generalised them.
845 So we are careful, and do a complete simplification just to find the
846 constrained tyvars. We don't use any of the results, except to
847 find which tyvars are constrained.
849 Note [Polymorphic recursion]
850 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
851 The game plan for polymorphic recursion in the code above is
853 * Bind any variable for which we have a type signature
854 to an Id with a polymorphic type. Then when type-checking
855 the RHSs we'll make a full polymorphic call.
857 This fine, but if you aren't a bit careful you end up with a horrendous
858 amount of partial application and (worse) a huge space leak. For example:
860 f :: Eq a => [a] -> [a]
863 If we don't take care, after typechecking we get
865 f = /\a -> \d::Eq a -> let f' = f a d
869 Notice the the stupid construction of (f a d), which is of course
870 identical to the function we're executing. In this case, the
871 polymorphic recursion isn't being used (but that's a very common case).
872 This can lead to a massive space leak, from the following top-level defn
878 Now (f dEqInt) evaluates to a lambda that has f' as a free variable; but
879 f' is another thunk which evaluates to the same thing... and you end
880 up with a chain of identical values all hung onto by the CAF ff.
884 = let f' = f Int dEqInt in \ys. ...f'...
886 = let f' = let f' = f Int dEqInt in \ys. ...f'...
891 NOTE: a bit of arity anaysis would push the (f a d) inside the (\ys...),
892 which would make the space leak go away in this case
894 Solution: when typechecking the RHSs we always have in hand the
895 *monomorphic* Ids for each binding. So we just need to make sure that
896 if (Method f a d) shows up in the constraints emerging from (...f...)
897 we just use the monomorphic Id. We achieve this by adding monomorphic Ids
898 to the "givens" when simplifying constraints. That's what the "lies_avail"
903 f = /\a -> \d::Eq a -> letrec
904 fm = \ys:[a] -> ...fm...
910 %************************************************************************
914 %************************************************************************
916 Type signatures are tricky. See Note [Signature skolems] in TcType
918 @tcSigs@ checks the signatures for validity, and returns a list of
919 {\em freshly-instantiated} signatures. That is, the types are already
920 split up, and have fresh type variables installed. All non-type-signature
921 "RenamedSigs" are ignored.
923 The @TcSigInfo@ contains @TcTypes@ because they are unified with
924 the variable's type, and after that checked to see whether they've
929 The -XScopedTypeVariables flag brings lexically-scoped type variables
930 into scope for any explicitly forall-quantified type variables:
931 f :: forall a. a -> a
933 Then 'a' is in scope inside 'e'.
935 However, we do *not* support this
936 - For pattern bindings e.g
940 - For multiple function bindings, unless Opt_RelaxedPolyRec is on
941 f :: forall a. a -> a
943 g :: forall b. b -> b
945 Reason: we use mutable variables for 'a' and 'b', since they may
946 unify to each other, and that means the scoped type variable would
947 not stand for a completely rigid variable.
949 Currently, we simply make Opt_ScopedTypeVariables imply Opt_RelaxedPolyRec
952 Note [More instantiated than scoped]
953 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
954 There may be more instantiated type variables than lexically-scoped
956 type T a = forall b. b -> (a,b)
958 Here, the signature for f will have one scoped type variable, c,
959 but two instantiated type variables, c' and b'.
961 We assume that the scoped ones are at the *front* of sig_tvs,
962 and remember the names from the original HsForAllTy in the TcSigFun.
964 Note [Signature skolems]
965 ~~~~~~~~~~~~~~~~~~~~~~~~
966 When instantiating a type signature, we do so with either skolems or
967 SigTv meta-type variables depending on the use_skols boolean. This
968 variable is set True when we are typechecking a single function
969 binding; and False for pattern bindings and a group of several
972 Reason: in the latter cases, the "skolems" can be unified together,
973 so they aren't properly rigid in the type-refinement sense.
974 NB: unless we are doing H98, each function with a sig will be done
975 separately, even if it's mutually recursive, so use_skols will be True
978 Note [Only scoped tyvars are in the TyVarEnv]
979 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
980 We are careful to keep only the *lexically scoped* type variables in
981 the type environment. Why? After all, the renamer has ensured
982 that only legal occurrences occur, so we could put all type variables
985 But we want to check that two distinct lexically scoped type variables
986 do not map to the same internal type variable. So we need to know which
987 the lexically-scoped ones are... and at the moment we do that by putting
988 only the lexically scoped ones into the environment.
990 Note [Instantiate sig with fresh variables]
991 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
992 It's vital to instantiate a type signature with fresh variables.
994 type T = forall a. [a] -> [a]
996 f = g where { g :: T; g = <rhs> }
998 We must not use the same 'a' from the defn of T at both places!!
999 (Instantiation is only necessary because of type synonyms. Otherwise,
1000 it's all cool; each signature has distinct type variables from the renamer.)
1003 type SigFun = Name -> Maybe ([Name], SrcSpan)
1004 -- Maps a let-binder to the list of
1005 -- type variables brought into scope
1006 -- by its type signature, plus location
1007 -- Nothing => no type signature
1009 mkSigFun :: [LSig Name] -> SigFun
1010 -- Search for a particular type signature
1011 -- Precondition: the sigs are all type sigs
1012 -- Precondition: no duplicates
1013 mkSigFun sigs = lookupNameEnv env
1015 env = mkNameEnv (mapCatMaybes mk_pair sigs)
1016 mk_pair (L loc (TypeSig (L _ name) lhs_ty)) = Just (name, (hsExplicitTvs lhs_ty, loc))
1017 mk_pair (L loc (IdSig id)) = Just (idName id, ([], loc))
1019 -- The scoped names are the ones explicitly mentioned
1020 -- in the HsForAll. (There may be more in sigma_ty, because
1021 -- of nested type synonyms. See Note [More instantiated than scoped].)
1022 -- See Note [Only scoped tyvars are in the TyVarEnv]
1026 tcTySig :: LSig Name -> TcM TcId
1027 tcTySig (L span (TypeSig (L _ name) ty))
1029 do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
1030 ; return (mkLocalId name sigma_ty) }
1031 tcTySig (L _ (IdSig id))
1033 tcTySig s = pprPanic "tcTySig" (ppr s)
1036 tcInstSigs :: SigFun -> [Name] -> TcM TcSigFun
1037 tcInstSigs sig_fn bndrs
1038 = do { prs <- mapMaybeM (tcInstSig sig_fn use_skols) bndrs
1039 ; return (lookupNameEnv (mkNameEnv prs)) }
1041 use_skols = isSingleton bndrs -- See Note [Signature skolems]
1043 tcInstSig :: SigFun -> Bool -> Name -> TcM (Maybe (Name, TcSigInfo))
1044 -- For use_skols :: Bool see Note [Signature skolems]
1046 -- We must instantiate with fresh uniques,
1047 -- (see Note [Instantiate sig with fresh variables])
1048 -- although we keep the same print-name.
1050 tcInstSig sig_fn use_skols name
1051 | Just (scoped_tvs, loc) <- sig_fn name
1052 = do { poly_id <- tcLookupId name -- Cannot fail; the poly ids are put into
1053 -- scope when starting the binding group
1054 ; (tvs, theta, tau) <- tcInstSigType use_skols name (idType poly_id)
1055 ; let sig = TcSigInfo { sig_id = poly_id
1056 , sig_scoped = scoped_tvs
1057 , sig_tvs = tvs, sig_theta = theta, sig_tau = tau
1059 ; return (Just (name, sig)) }
1063 -------------------------------
1064 data GeneralisationPlan
1065 = NoGen -- No generalisation, no AbsBinds
1066 | InferGen Bool -- Implicit generalisation; there is an AbsBinds
1067 -- True <=> apply the MR; generalise only unconstrained type vars
1068 | CheckGen TcSigInfo -- Explicit generalisation; there is an AbsBinds
1070 -- A consequence of the no-AbsBinds choice (NoGen) is that there is
1071 -- no "polymorphic Id" and "monmomorphic Id"; there is just the one
1073 instance Outputable GeneralisationPlan where
1074 ppr NoGen = ptext (sLit "NoGen")
1075 ppr (InferGen b) = ptext (sLit "InferGen") <+> ppr b
1076 ppr (CheckGen s) = ptext (sLit "CheckGen") <+> ppr s
1078 decideGeneralisationPlan
1079 :: DynFlags -> TopLevelFlag -> [Name] -> [LHsBind Name] -> TcSigFun -> GeneralisationPlan
1080 decideGeneralisationPlan dflags top_lvl _bndrs binds sig_fn
1081 | mono_pat_binds = NoGen
1082 | Just sig <- one_funbind_with_sig binds = if null (sig_tvs sig) && null (sig_theta sig)
1083 then NoGen -- Optimise common case
1085 | (xopt Opt_MonoLocalBinds dflags
1086 && isNotTopLevel top_lvl) = NoGen
1087 | otherwise = InferGen mono_restriction
1089 -- | all no_sig bndrs = InferGen mono_restriction
1090 -- | otherwise = NoGen -- A mixture of function
1091 -- -- and pattern bindings
1093 mono_pat_binds = xopt Opt_MonoPatBinds dflags
1094 && any (is_pat_bind . unLoc) binds
1096 mono_restriction = xopt Opt_MonomorphismRestriction dflags
1097 && any (restricted . unLoc) binds
1099 no_sig n = isNothing (sig_fn n)
1101 -- With OutsideIn, all nested bindings are monomorphic
1102 -- except a single function binding with a signature
1103 one_funbind_with_sig [L _ FunBind { fun_id = v }] = sig_fn (unLoc v)
1104 one_funbind_with_sig _ = Nothing
1106 -- The Haskell 98 monomorphism resetriction
1107 restricted (PatBind {}) = True
1108 restricted (VarBind { var_id = v }) = no_sig v
1109 restricted (FunBind { fun_id = v, fun_matches = m }) = restricted_match m
1111 restricted (AbsBinds {}) = panic "isRestrictedGroup/unrestricted AbsBinds"
1113 restricted_match (MatchGroup (L _ (Match [] _ _) : _) _) = True
1114 restricted_match _ = False
1115 -- No args => like a pattern binding
1116 -- Some args => a function binding
1118 is_pat_bind (PatBind {}) = True
1119 is_pat_bind _ = False
1122 checkStrictBinds :: TopLevelFlag -> RecFlag
1123 -> [LHsBind Name] -> [Id]
1125 -- Check that non-overloaded unlifted bindings are
1126 -- a) non-recursive,
1127 -- b) not top level,
1128 -- c) not a multiple-binding group (more or less implied by (a))
1130 checkStrictBinds top_lvl rec_group binds poly_ids
1131 | unlifted || bang_pat
1132 = do { checkTc (isNotTopLevel top_lvl)
1133 (strictBindErr "Top-level" unlifted binds)
1134 ; checkTc (isNonRec rec_group)
1135 (strictBindErr "Recursive" unlifted binds)
1136 ; checkTc (isSingleton binds)
1137 (strictBindErr "Multiple" unlifted binds)
1138 -- This should be a checkTc, not a warnTc, but as of GHC 6.11
1139 -- the versions of alex and happy available have non-conforming
1140 -- templates, so the GHC build fails if it's an error:
1141 ; warnUnlifted <- doptM Opt_WarnLazyUnliftedBindings
1142 ; warnTc (warnUnlifted && not bang_pat)
1143 (unliftedMustBeBang binds) }
1147 unlifted = any is_unlifted poly_ids
1148 bang_pat = any (isBangHsBind . unLoc) binds
1149 is_unlifted id = case tcSplitForAllTys (idType id) of
1150 (_, rho) -> isUnLiftedType rho
1152 unliftedMustBeBang :: [LHsBind Name] -> SDoc
1153 unliftedMustBeBang binds
1154 = hang (text "Bindings containing unlifted types should use an outermost bang pattern:")
1155 2 (pprBindList binds)
1157 strictBindErr :: String -> Bool -> [LHsBind Name] -> SDoc
1158 strictBindErr flavour unlifted binds
1159 = hang (text flavour <+> msg <+> ptext (sLit "aren't allowed:"))
1160 2 (pprBindList binds)
1162 msg | unlifted = ptext (sLit "bindings for unlifted types")
1163 | otherwise = ptext (sLit "bang-pattern bindings")
1165 pprBindList :: [LHsBind Name] -> SDoc
1166 pprBindList binds = vcat (map ppr binds)
1170 %************************************************************************
1172 \subsection[TcBinds-errors]{Error contexts and messages}
1174 %************************************************************************
1178 -- This one is called on LHS, when pat and grhss are both Name
1179 -- and on RHS, when pat is TcId and grhss is still Name
1180 patMonoBindsCtxt :: OutputableBndr id => LPat id -> GRHSs Name -> SDoc
1181 patMonoBindsCtxt pat grhss
1182 = hang (ptext (sLit "In a pattern binding:")) 2 (pprPatBind pat grhss)
1184 -----------------------------------------------
1185 sigContextsCtxt :: TcSigInfo -> TcSigInfo -> SDoc
1186 sigContextsCtxt sig1 sig2
1187 = vcat [ptext (sLit "When matching the contexts of the signatures for"),
1188 nest 2 (vcat [ppr id1 <+> dcolon <+> ppr (idType id1),
1189 ppr id2 <+> dcolon <+> ppr (idType id2)]),
1190 ptext (sLit "The signature contexts in a mutually recursive group should all be identical")]
1195 -----------------------------------------------
1197 badStrictSig :: Bool -> TcSigInfo -> SDoc
1198 badStrictSig unlifted sig
1199 = hang (ptext (sLit "Illegal polymorphic signature in") <+> msg)
1202 msg | unlifted = ptext (sLit "an unlifted binding")
1203 | otherwise = ptext (sLit "a bang-pattern binding")
1205 restrictedBindSigErr :: [Name] -> SDoc
1206 restrictedBindSigErr binder_names
1207 = hang (ptext (sLit "Illegal type signature(s)"))
1208 2 (vcat [ptext (sLit "in a binding group for") <+> pprBinders binder_names,
1209 ptext (sLit "that falls under the monomorphism restriction")])
1211 genCtxt :: [Name] -> SDoc
1212 genCtxt binder_names
1213 = ptext (sLit "When generalising the type(s) for") <+> pprBinders binder_names
1216 missingSigWarn :: TcId -> TcM ()
1218 = do { env0 <- tcInitTidyEnv
1219 ; let (env1, tidy_ty) = tidyOpenType env0 (idType id)
1220 ; addWarnTcM (env1, mk_msg tidy_ty) }
1223 mk_msg ty = vcat [ptext (sLit "Definition but no type signature for") <+> quotes (ppr name),
1224 sep [ptext (sLit "Inferred type:") <+> pprHsVar name <+> dcolon <+> ppr ty]]