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, tcSpecPrags, tcVectDecls, mkPragFun,
11 TcSigInfo(..), SigFun, mkSigFun,
12 badBootDeclErr ) where
14 import {-# SOURCE #-} TcMatches ( tcGRHSsPat, tcMatchesFun )
15 import {-# SOURCE #-} TcExpr ( tcMonoExpr )
48 #include "HsVersions.h"
52 %************************************************************************
54 \subsection{Type-checking bindings}
56 %************************************************************************
58 @tcBindsAndThen@ typechecks a @HsBinds@. The "and then" part is because
59 it needs to know something about the {\em usage} of the things bound,
60 so that it can create specialisations of them. So @tcBindsAndThen@
61 takes a function which, given an extended environment, E, typechecks
62 the scope of the bindings returning a typechecked thing and (most
63 important) an LIE. It is this LIE which is then used as the basis for
64 specialising the things bound.
66 @tcBindsAndThen@ also takes a "combiner" which glues together the
67 bindings and the "thing" to make a new "thing".
69 The real work is done by @tcBindWithSigsAndThen@.
71 Recursive and non-recursive binds are handled in essentially the same
72 way: because of uniques there are no scoping issues left. The only
73 difference is that non-recursive bindings can bind primitive values.
75 Even for non-recursive binding groups we add typings for each binder
76 to the LVE for the following reason. When each individual binding is
77 checked the type of its LHS is unified with that of its RHS; and
78 type-checking the LHS of course requires that the binder is in scope.
80 At the top-level the LIE is sure to contain nothing but constant
81 dictionaries, which we resolve at the module level.
84 tcTopBinds :: HsValBinds Name
85 -> TcM ( LHsBinds TcId -- Typechecked bindings
86 , [LTcSpecPrag] -- SPECIALISE prags for imported Ids
87 , TcLclEnv) -- Augmented environment
89 -- Note: returning the TcLclEnv is more than we really
90 -- want. The bit we care about is the local bindings
91 -- and the free type variables thereof
93 = do { (ValBindsOut prs sigs, env) <- tcValBinds TopLevel binds getLclEnv
94 ; let binds = foldr (unionBags . snd) emptyBag prs
95 ; specs <- tcImpPrags sigs
96 ; return (binds, specs, env) }
97 -- The top level bindings are flattened into a giant
98 -- implicitly-mutually-recursive LHsBinds
100 tcHsBootSigs :: HsValBinds Name -> TcM [Id]
101 -- A hs-boot file has only one BindGroup, and it only has type
102 -- signatures in it. The renamer checked all this
103 tcHsBootSigs (ValBindsOut binds sigs)
104 = do { checkTc (null binds) badBootDeclErr
105 ; mapM (addLocM tc_boot_sig) (filter isTypeLSig sigs) }
107 tc_boot_sig (TypeSig (L _ name) ty)
108 = do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
109 ; return (mkVanillaGlobal name sigma_ty) }
110 -- Notice that we make GlobalIds, not LocalIds
111 tc_boot_sig s = pprPanic "tcHsBootSigs/tc_boot_sig" (ppr s)
112 tcHsBootSigs groups = pprPanic "tcHsBootSigs" (ppr groups)
114 badBootDeclErr :: Message
115 badBootDeclErr = ptext (sLit "Illegal declarations in an hs-boot file")
117 ------------------------
118 tcLocalBinds :: HsLocalBinds Name -> TcM thing
119 -> TcM (HsLocalBinds TcId, thing)
121 tcLocalBinds EmptyLocalBinds thing_inside
122 = do { thing <- thing_inside
123 ; return (EmptyLocalBinds, thing) }
125 tcLocalBinds (HsValBinds binds) thing_inside
126 = do { (binds', thing) <- tcValBinds NotTopLevel binds thing_inside
127 ; return (HsValBinds binds', thing) }
129 tcLocalBinds (HsIPBinds (IPBinds ip_binds _)) thing_inside
130 = do { (given_ips, ip_binds') <- mapAndUnzipM (wrapLocSndM tc_ip_bind) ip_binds
132 -- If the binding binds ?x = E, we must now
133 -- discharge any ?x constraints in expr_lie
134 -- See Note [Implicit parameter untouchables]
135 ; (ev_binds, result) <- checkConstraints (IPSkol ips)
136 [] given_ips thing_inside
138 ; return (HsIPBinds (IPBinds ip_binds' ev_binds), result) }
140 ips = [ip | L _ (IPBind ip _) <- ip_binds]
142 -- I wonder if we should do these one at at time
145 tc_ip_bind (IPBind ip expr)
146 = do { ty <- newFlexiTyVarTy argTypeKind
147 ; ip_id <- newIP ip ty
148 ; expr' <- tcMonoExpr expr ty
149 ; return (ip_id, (IPBind (IPName ip_id) expr')) }
152 Note [Implicit parameter untouchables]
153 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
154 We add the type variables in the types of the implicit parameters
155 as untouchables, not so much because we really must not unify them,
156 but rather because we otherwise end up with constraints like this
157 Num alpha, Implic { wanted = alpha ~ Int }
158 The constraint solver solves alpha~Int by unification, but then
159 doesn't float that solved constraint out (it's not an unsolved
160 wanted. Result disaster: the (Num alpha) is again solved, this
161 time by defaulting. No no no.
163 However [Oct 10] this is all handled automatically by the
164 untouchable-range idea.
167 tcValBinds :: TopLevelFlag
168 -> HsValBinds Name -> TcM thing
169 -> TcM (HsValBinds TcId, thing)
171 tcValBinds _ (ValBindsIn binds _) _
172 = pprPanic "tcValBinds" (ppr binds)
174 tcValBinds top_lvl (ValBindsOut binds sigs) thing_inside
175 = do { -- Typecheck the signature
176 ; let { prag_fn = mkPragFun sigs (foldr (unionBags . snd) emptyBag binds)
177 ; ty_sigs = filter isTypeLSig sigs
178 ; sig_fn = mkSigFun ty_sigs }
180 ; poly_ids <- checkNoErrs (mapAndRecoverM tcTySig ty_sigs)
181 -- No recovery from bad signatures, because the type sigs
182 -- may bind type variables, so proceeding without them
183 -- can lead to a cascade of errors
184 -- ToDo: this means we fall over immediately if any type sig
185 -- is wrong, which is over-conservative, see Trac bug #745
187 -- Extend the envt right away with all
188 -- the Ids declared with type signatures
189 ; (binds', thing) <- tcExtendIdEnv poly_ids $
190 tcBindGroups top_lvl sig_fn prag_fn
193 ; return (ValBindsOut binds' sigs, thing) }
195 ------------------------
196 tcBindGroups :: TopLevelFlag -> SigFun -> PragFun
197 -> [(RecFlag, LHsBinds Name)] -> TcM thing
198 -> TcM ([(RecFlag, LHsBinds TcId)], thing)
199 -- Typecheck a whole lot of value bindings,
200 -- one strongly-connected component at a time
201 -- Here a "strongly connected component" has the strightforward
202 -- meaning of a group of bindings that mention each other,
203 -- ignoring type signatures (that part comes later)
205 tcBindGroups _ _ _ [] thing_inside
206 = do { thing <- thing_inside
207 ; return ([], thing) }
209 tcBindGroups top_lvl sig_fn prag_fn (group : groups) thing_inside
210 = do { (group', (groups', thing))
211 <- tc_group top_lvl sig_fn prag_fn group $
212 tcBindGroups top_lvl sig_fn prag_fn groups thing_inside
213 ; return (group' ++ groups', thing) }
215 ------------------------
216 tc_group :: forall thing.
217 TopLevelFlag -> SigFun -> PragFun
218 -> (RecFlag, LHsBinds Name) -> TcM thing
219 -> TcM ([(RecFlag, LHsBinds TcId)], thing)
221 -- Typecheck one strongly-connected component of the original program.
222 -- We get a list of groups back, because there may
223 -- be specialisations etc as well
225 tc_group top_lvl sig_fn prag_fn (NonRecursive, binds) thing_inside
226 -- A single non-recursive binding
227 -- We want to keep non-recursive things non-recursive
228 -- so that we desugar unlifted bindings correctly
229 = do { (binds1, ids) <- tcPolyBinds top_lvl sig_fn prag_fn NonRecursive NonRecursive
231 ; thing <- tcExtendIdEnv ids thing_inside
232 ; return ( [(NonRecursive, binds1)], thing) }
234 tc_group top_lvl sig_fn prag_fn (Recursive, binds) thing_inside
235 = -- To maximise polymorphism (assumes -XRelaxedPolyRec), we do a new
236 -- strongly-connected-component analysis, this time omitting
237 -- any references to variables with type signatures.
238 do { traceTc "tc_group rec" (pprLHsBinds binds)
239 ; (binds1, _ids, thing) <- go sccs
240 -- Here is where we should do bindInstsOfLocalFuns
241 -- if we start having Methods again
242 ; return ([(Recursive, binds1)], thing) }
243 -- Rec them all together
245 sccs :: [SCC (LHsBind Name)]
246 sccs = stronglyConnCompFromEdgedVertices (mkEdges sig_fn binds)
248 go :: [SCC (LHsBind Name)] -> TcM (LHsBinds TcId, [TcId], thing)
249 go (scc:sccs) = do { (binds1, ids1) <- tc_scc scc
250 ; (binds2, ids2, thing) <- tcExtendIdEnv ids1 $ go sccs
251 ; return (binds1 `unionBags` binds2, ids1 ++ ids2, thing) }
252 go [] = do { thing <- thing_inside; return (emptyBag, [], thing) }
254 tc_scc (AcyclicSCC bind) = tc_sub_group NonRecursive [bind]
255 tc_scc (CyclicSCC binds) = tc_sub_group Recursive binds
257 tc_sub_group = tcPolyBinds top_lvl sig_fn prag_fn Recursive
260 ------------------------
262 bindLocalInsts :: TopLevelFlag
263 -> TcM (LHsBinds TcId, [TcId], a)
264 -> TcM (LHsBinds TcId, TcEvBinds, a)
265 bindLocalInsts top_lvl thing_inside
267 = do { (binds, _, thing) <- thing_inside; return (binds, emptyBag, thing) }
268 -- For the top level don't bother with all this bindInstsOfLocalFuns stuff.
269 -- All the top level things are rec'd together anyway, so it's fine to
270 -- leave them to the tcSimplifyTop, and quite a bit faster too
272 | otherwise -- Nested case
273 = do { ((binds, ids, thing), lie) <- captureConstraints thing_inside
274 ; lie_binds <- bindLocalMethods lie ids
275 ; return (binds, lie_binds, thing) }
278 ------------------------
279 mkEdges :: SigFun -> LHsBinds Name
280 -> [(LHsBind Name, BKey, [BKey])]
282 type BKey = Int -- Just number off the bindings
285 = [ (bind, key, [key | n <- nameSetToList (bind_fvs (unLoc bind)),
286 Just key <- [lookupNameEnv key_map n], no_sig n ])
287 | (bind, key) <- keyd_binds
290 no_sig :: Name -> Bool
291 no_sig n = isNothing (sig_fn n)
293 keyd_binds = bagToList binds `zip` [0::BKey ..]
295 key_map :: NameEnv BKey -- Which binding it comes from
296 key_map = mkNameEnv [(bndr, key) | (L _ bind, key) <- keyd_binds
297 , bndr <- bindersOfHsBind bind ]
299 bindersOfHsBind :: HsBind Name -> [Name]
300 bindersOfHsBind (PatBind { pat_lhs = pat }) = collectPatBinders pat
301 bindersOfHsBind (FunBind { fun_id = L _ f }) = [f]
302 bindersOfHsBind (AbsBinds {}) = panic "bindersOfHsBind AbsBinds"
303 bindersOfHsBind (VarBind {}) = panic "bindersOfHsBind VarBind"
305 ------------------------
306 tcPolyBinds :: TopLevelFlag -> SigFun -> PragFun
307 -> RecFlag -- Whether the group is really recursive
308 -> RecFlag -- Whether it's recursive after breaking
309 -- dependencies based on type signatures
311 -> TcM (LHsBinds TcId, [TcId])
313 -- Typechecks a single bunch of bindings all together,
314 -- and generalises them. The bunch may be only part of a recursive
315 -- group, because we use type signatures to maximise polymorphism
317 -- Returns a list because the input may be a single non-recursive binding,
318 -- in which case the dependency order of the resulting bindings is
321 -- Knows nothing about the scope of the bindings
323 tcPolyBinds top_lvl sig_fn prag_fn rec_group rec_tc bind_list
325 recoverM (recoveryCode binder_names sig_fn) $ do
326 -- Set up main recover; take advantage of any type sigs
328 { traceTc "------------------------------------------------" empty
329 ; traceTc "Bindings for" (ppr binder_names)
331 -- Instantiate the polytypes of any binders that have signatures
332 -- (as determined by sig_fn), returning a TcSigInfo for each
333 ; tc_sig_fn <- tcInstSigs sig_fn binder_names
336 ; let plan = decideGeneralisationPlan dflags top_lvl binder_names bind_list tc_sig_fn
337 ; traceTc "Generalisation plan" (ppr plan)
338 ; (binds, poly_ids) <- case plan of
339 NoGen -> tcPolyNoGen tc_sig_fn prag_fn rec_tc bind_list
340 InferGen mono -> tcPolyInfer top_lvl mono tc_sig_fn prag_fn rec_tc bind_list
341 CheckGen sig -> tcPolyCheck sig prag_fn rec_tc bind_list
343 -- Check whether strict bindings are ok
344 -- These must be non-recursive etc, and are not generalised
345 -- They desugar to a case expression in the end
346 ; checkStrictBinds top_lvl rec_group bind_list poly_ids
348 ; return (binds, poly_ids) }
350 binder_names = collectHsBindListBinders bind_list
351 loc = foldr1 combineSrcSpans (map getLoc bind_list)
352 -- The mbinds have been dependency analysed and
353 -- may no longer be adjacent; so find the narrowest
354 -- span that includes them all
358 :: TcSigFun -> PragFun
359 -> RecFlag -- Whether it's recursive after breaking
360 -- dependencies based on type signatures
362 -> TcM (LHsBinds TcId, [TcId])
363 -- No generalisation whatsoever
365 tcPolyNoGen tc_sig_fn prag_fn rec_tc bind_list
366 = do { (binds', mono_infos) <- tcMonoBinds tc_sig_fn (LetGblBndr prag_fn)
368 ; mono_ids' <- mapM tc_mono_info mono_infos
369 ; return (binds', mono_ids') }
371 tc_mono_info (name, _, mono_id)
372 = do { mono_ty' <- zonkTcTypeCarefully (idType mono_id)
373 -- Zonk, mainly to expose unboxed types to checkStrictBinds
374 ; let mono_id' = setIdType mono_id mono_ty'
375 ; _specs <- tcSpecPrags mono_id' (prag_fn name)
377 -- NB: tcPrags generates error messages for
378 -- specialisation pragmas for non-overloaded sigs
379 -- Indeed that is why we call it here!
380 -- So we can safely ignore _specs
383 tcPolyCheck :: TcSigInfo -> PragFun
384 -> RecFlag -- Whether it's recursive after breaking
385 -- dependencies based on type signatures
387 -> TcM (LHsBinds TcId, [TcId])
388 -- There is just one binding,
389 -- it binds a single variable,
390 -- it has a signature,
391 tcPolyCheck sig@(TcSigInfo { sig_id = id, sig_tvs = tvs, sig_scoped = scoped
392 , sig_theta = theta, sig_tau = tau })
393 prag_fn rec_tc bind_list
394 = do { ev_vars <- newEvVars theta
395 ; let skol_info = SigSkol (FunSigCtxt (idName id)) (mkPhiTy theta tau)
396 ; (ev_binds, (binds', [mono_info]))
397 <- checkConstraints skol_info tvs ev_vars $
398 tcExtendTyVarEnv2 (scoped `zip` mkTyVarTys tvs) $
399 tcMonoBinds (\_ -> Just sig) LetLclBndr rec_tc bind_list
401 ; export <- mkExport prag_fn tvs theta mono_info
404 ; let (_, poly_id, _, _) = export
405 abs_bind = L loc $ AbsBinds
407 , abs_ev_vars = ev_vars, abs_ev_binds = ev_binds
408 , abs_exports = [export], abs_binds = binds' }
409 ; return (unitBag abs_bind, [poly_id]) }
414 -> Bool -- True <=> apply the monomorphism restriction
415 -> TcSigFun -> PragFun
416 -> RecFlag -- Whether it's recursive after breaking
417 -- dependencies based on type signatures
419 -> TcM (LHsBinds TcId, [TcId])
420 tcPolyInfer top_lvl mono tc_sig_fn prag_fn rec_tc bind_list
421 = do { ((binds', mono_infos), wanted)
422 <- captureConstraints $
423 tcMonoBinds tc_sig_fn LetLclBndr rec_tc bind_list
425 ; unifyCtxts [sig | (_, Just sig, _) <- mono_infos]
427 ; let name_taus = [(name, idType mono_id) | (name, _, mono_id) <- mono_infos]
428 ; (qtvs, givens, ev_binds) <- simplifyInfer top_lvl mono name_taus wanted
430 ; exports <- mapM (mkExport prag_fn qtvs (map evVarPred givens))
433 ; let poly_ids = [poly_id | (_, poly_id, _, _) <- exports]
434 ; traceTc "Binding:" (ppr (poly_ids `zip` map idType poly_ids))
437 ; let abs_bind = L loc $ AbsBinds { abs_tvs = qtvs
438 , abs_ev_vars = givens, abs_ev_binds = ev_binds
439 , abs_exports = exports, abs_binds = binds' }
441 ; return (unitBag abs_bind, poly_ids) -- poly_ids are guaranteed zonked by mkExport
446 mkExport :: PragFun -> [TyVar] -> TcThetaType
448 -> TcM ([TyVar], Id, Id, TcSpecPrags)
449 -- mkExport generates exports with
450 -- zonked type variables,
452 -- The former is just because no further unifications will change
453 -- the quantified type variables, so we can fix their final form
455 -- The latter is needed because the poly_ids are used to extend the
456 -- type environment; see the invariant on TcEnv.tcExtendIdEnv
458 -- Pre-condition: the inferred_tvs are already zonked
460 mkExport prag_fn inferred_tvs theta
461 (poly_name, mb_sig, mono_id)
462 = do { (tvs, poly_id) <- mk_poly_id mb_sig
463 -- poly_id has a zonked type
465 ; poly_id' <- addInlinePrags poly_id prag_sigs
467 ; spec_prags <- tcSpecPrags poly_id prag_sigs
468 -- tcPrags requires a zonked poly_id
470 ; return (tvs, poly_id', mono_id, SpecPrags spec_prags) }
472 prag_sigs = prag_fn poly_name
473 poly_ty = mkSigmaTy inferred_tvs theta (idType mono_id)
475 mk_poly_id Nothing = do { poly_ty' <- zonkTcTypeCarefully poly_ty
476 ; return (inferred_tvs, mkLocalId poly_name poly_ty') }
477 mk_poly_id (Just sig) = do { tvs <- mapM zonk_tv (sig_tvs sig)
478 ; return (tvs, sig_id sig) }
480 zonk_tv tv = do { ty <- zonkTcTyVar tv; return (tcGetTyVar "mkExport" ty) }
482 ------------------------
483 type PragFun = Name -> [LSig Name]
485 mkPragFun :: [LSig Name] -> LHsBinds Name -> PragFun
486 mkPragFun sigs binds = \n -> lookupNameEnv prag_env n `orElse` []
488 prs = mapCatMaybes get_sig sigs
490 get_sig :: LSig Name -> Maybe (Located Name, LSig Name)
491 get_sig (L l (SpecSig nm ty inl)) = Just (nm, L l $ SpecSig nm ty (add_arity nm inl))
492 get_sig (L l (InlineSig nm inl)) = Just (nm, L l $ InlineSig nm (add_arity nm inl))
495 add_arity (L _ n) inl_prag -- Adjust inl_sat field to match visible arity of function
496 | Just ar <- lookupNameEnv ar_env n,
497 Inline <- inl_inline inl_prag = inl_prag { inl_sat = Just ar }
498 -- add arity only for real INLINE pragmas, not INLINABLE
499 | otherwise = inl_prag
501 prag_env :: NameEnv [LSig Name]
502 prag_env = foldl add emptyNameEnv prs
503 add env (L _ n,p) = extendNameEnv_Acc (:) singleton env n p
505 -- ar_env maps a local to the arity of its definition
506 ar_env :: NameEnv Arity
507 ar_env = foldrBag lhsBindArity emptyNameEnv binds
509 lhsBindArity :: LHsBind Name -> NameEnv Arity -> NameEnv Arity
510 lhsBindArity (L _ (FunBind { fun_id = id, fun_matches = ms })) env
511 = extendNameEnv env (unLoc id) (matchGroupArity ms)
512 lhsBindArity _ env = env -- PatBind/VarBind
515 tcSpecPrags :: Id -> [LSig Name]
517 -- Add INLINE and SPECIALSE pragmas
518 -- INLINE prags are added to the (polymorphic) Id directly
519 -- SPECIALISE prags are passed to the desugarer via TcSpecPrags
520 -- Pre-condition: the poly_id is zonked
521 -- Reason: required by tcSubExp
522 tcSpecPrags poly_id prag_sigs
523 = do { unless (null bad_sigs) warn_discarded_sigs
524 ; mapAndRecoverM (wrapLocM (tcSpec poly_id)) spec_sigs }
526 spec_sigs = filter isSpecLSig prag_sigs
527 bad_sigs = filter is_bad_sig prag_sigs
528 is_bad_sig s = not (isSpecLSig s || isInlineLSig s)
530 warn_discarded_sigs = warnPrags poly_id bad_sigs $
531 ptext (sLit "Discarding unexpected pragmas for")
535 tcSpec :: TcId -> Sig Name -> TcM TcSpecPrag
536 tcSpec poly_id prag@(SpecSig _ hs_ty inl)
537 -- The Name in the SpecSig may not be the same as that of the poly_id
538 -- Example: SPECIALISE for a class method: the Name in the SpecSig is
539 -- for the selector Id, but the poly_id is something like $cop
540 = addErrCtxt (spec_ctxt prag) $
541 do { spec_ty <- tcHsSigType sig_ctxt hs_ty
542 ; warnIf (not (isOverloadedTy poly_ty || isInlinePragma inl))
543 (ptext (sLit "SPECIALISE pragma for non-overloaded function") <+> quotes (ppr poly_id))
544 -- Note [SPECIALISE pragmas]
545 ; wrap <- tcSubType origin sig_ctxt (idType poly_id) spec_ty
546 ; return (SpecPrag poly_id wrap inl) }
548 name = idName poly_id
549 poly_ty = idType poly_id
550 origin = SpecPragOrigin name
551 sig_ctxt = FunSigCtxt name
552 spec_ctxt prag = hang (ptext (sLit "In the SPECIALISE pragma")) 2 (ppr prag)
554 tcSpec _ prag = pprPanic "tcSpec" (ppr prag)
557 tcImpPrags :: [LSig Name] -> TcM [LTcSpecPrag]
559 = do { this_mod <- getModule
560 ; mapAndRecoverM (wrapLocM tcImpSpec)
561 [L loc (name,prag) | (L loc prag@(SpecSig (L _ name) _ _)) <- prags
562 , not (nameIsLocalOrFrom this_mod name) ] }
564 tcImpSpec :: (Name, Sig Name) -> TcM TcSpecPrag
565 tcImpSpec (name, prag)
566 = do { id <- tcLookupId name
567 ; checkTc (isAnyInlinePragma (idInlinePragma id))
571 impSpecErr :: Name -> SDoc
573 = hang (ptext (sLit "You cannot SPECIALISE") <+> quotes (ppr name))
574 2 (vcat [ ptext (sLit "because its definition has no INLINE/INLINABLE pragma")
575 , ptext (sLit "(or you compiled its defining module without -O)")])
578 tcVectDecls :: [LVectDecl Name] -> TcM ([LVectDecl TcId])
580 = do { decls' <- mapM (wrapLocM tcVect) decls
581 ; let ids = [unLoc id | L _ (HsVect id _) <- decls']
582 dups = findDupsEq (==) ids
583 ; mapM_ reportVectDups dups
584 ; traceTcConstraints "End of tcVectDecls"
588 reportVectDups (first:_second:_more)
589 = addErrAt (getSrcSpan first) $
590 ptext (sLit "Duplicate vectorisation declarations for") <+> ppr first
591 reportVectDups _ = return ()
594 tcVect :: VectDecl Name -> TcM (VectDecl TcId)
595 -- We can't typecheck the expression of a vectorisation declaration against the vectorised type
596 -- of the original definition as this requires internals of the vectoriser not available during
597 -- type checking. Instead, we infer the type of the expression and leave it to the vectoriser
598 -- to check the compatibility of the Core types.
599 tcVect (HsVect name Nothing)
600 = addErrCtxt (vectCtxt name) $
601 do { id <- wrapLocM tcLookupId name
602 ; return $ HsVect id Nothing
604 tcVect (HsVect name@(L loc _) (Just rhs))
605 = addErrCtxt (vectCtxt name) $
606 do { _id <- wrapLocM tcLookupId name -- need to ensure that the name is already defined
608 -- turn the vectorisation declaration into a single non-recursive binding
609 ; let bind = L loc $ mkFunBind name [mkSimpleMatch [] rhs]
610 sigFun = const Nothing
611 pragFun = mkPragFun [] (unitBag bind)
613 -- perform type inference (including generalisation)
614 ; (binds, [id']) <- tcPolyInfer TopLevel False sigFun pragFun NonRecursive [bind]
616 ; traceTc "tcVect inferred type" $ ppr (varType id')
617 ; traceTc "tcVect bindings" $ ppr binds
619 -- add all bindings, including the type variable and dictionary bindings produced by type
620 -- generalisation to the right-hand side of the vectorisation declaration
621 ; let [AbsBinds tvs evs _ evBinds actualBinds] = (map unLoc . bagToList) binds
622 ; let [bind'] = bagToList actualBinds
624 [L _ (Match _ _ (GRHSs [L _ (GRHS _ rhs')] _))]
625 _ = (fun_matches . unLoc) bind'
626 rhsWrapped = mkHsLams tvs evs (mkHsDictLet evBinds rhs')
628 -- We return the type-checked 'Id', to propagate the inferred signature
629 -- to the vectoriser - see "Note [Typechecked vectorisation pragmas]" in HsDecls
630 ; return $ HsVect (L loc id') (Just rhsWrapped)
633 vectCtxt :: Located Name -> SDoc
634 vectCtxt name = ptext (sLit "When checking the vectorisation declaration for") <+> ppr name
637 -- If typechecking the binds fails, then return with each
638 -- signature-less binder given type (forall a.a), to minimise
639 -- subsequent error messages
640 recoveryCode :: [Name] -> SigFun -> TcM (LHsBinds TcId, [Id])
641 recoveryCode binder_names sig_fn
642 = do { traceTc "tcBindsWithSigs: error recovery" (ppr binder_names)
643 ; poly_ids <- mapM mk_dummy binder_names
644 ; return (emptyBag, poly_ids) }
647 | isJust (sig_fn name) = tcLookupId name -- Had signature; look it up
648 | otherwise = return (mkLocalId name forall_a_a) -- No signature
651 forall_a_a = mkForAllTy openAlphaTyVar (mkTyVarTy openAlphaTyVar)
654 Note [SPECIALISE pragmas]
655 ~~~~~~~~~~~~~~~~~~~~~~~~~
656 There is no point in a SPECIALISE pragma for a non-overloaded function:
657 reverse :: [a] -> [a]
658 {-# SPECIALISE reverse :: [Int] -> [Int] #-}
660 But SPECIALISE INLINE *can* make sense for GADTS:
662 ArrInt :: !Int -> ByteArray# -> Arr Int
663 ArrPair :: !Int -> Arr e1 -> Arr e2 -> Arr (e1, e2)
665 (!:) :: Arr e -> Int -> e
666 {-# SPECIALISE INLINE (!:) :: Arr Int -> Int -> Int #-}
667 {-# SPECIALISE INLINE (!:) :: Arr (a, b) -> Int -> (a, b) #-}
668 (ArrInt _ ba) !: (I# i) = I# (indexIntArray# ba i)
669 (ArrPair _ a1 a2) !: i = (a1 !: i, a2 !: i)
671 When (!:) is specialised it becomes non-recursive, and can usefully
672 be inlined. Scary! So we only warn for SPECIALISE *without* INLINE
673 for a non-overloaded function.
675 %************************************************************************
677 \subsection{tcMonoBind}
679 %************************************************************************
681 @tcMonoBinds@ deals with a perhaps-recursive group of HsBinds.
682 The signatures have been dealt with already.
685 tcMonoBinds :: TcSigFun -> LetBndrSpec
686 -> RecFlag -- Whether the binding is recursive for typechecking purposes
687 -- i.e. the binders are mentioned in their RHSs, and
688 -- we are not resuced by a type signature
690 -> TcM (LHsBinds TcId, [MonoBindInfo])
692 tcMonoBinds sig_fn no_gen is_rec
693 [ L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf,
694 fun_matches = matches, bind_fvs = fvs })]
695 -- Single function binding,
696 | NonRecursive <- is_rec -- ...binder isn't mentioned in RHS
697 , Nothing <- sig_fn name -- ...with no type signature
698 = -- In this very special case we infer the type of the
699 -- right hand side first (it may have a higher-rank type)
700 -- and *then* make the monomorphic Id for the LHS
701 -- e.g. f = \(x::forall a. a->a) -> <body>
702 -- We want to infer a higher-rank type for f
704 do { ((co_fn, matches'), rhs_ty) <- tcInfer (tcMatchesFun name inf matches)
706 ; mono_id <- newNoSigLetBndr no_gen name rhs_ty
707 ; return (unitBag (L b_loc (FunBind { fun_id = L nm_loc mono_id, fun_infix = inf,
708 fun_matches = matches', bind_fvs = fvs,
709 fun_co_fn = co_fn, fun_tick = Nothing })),
710 [(name, Nothing, mono_id)]) }
712 tcMonoBinds sig_fn no_gen _ binds
713 = do { tc_binds <- mapM (wrapLocM (tcLhs sig_fn no_gen)) binds
715 -- Bring the monomorphic Ids, into scope for the RHSs
716 ; let mono_info = getMonoBindInfo tc_binds
717 rhs_id_env = [(name,mono_id) | (name, Nothing, mono_id) <- mono_info]
718 -- A monomorphic binding for each term variable that lacks
719 -- a type sig. (Ones with a sig are already in scope.)
721 ; binds' <- tcExtendIdEnv2 rhs_id_env $ do
722 traceTc "tcMonoBinds" $ vcat [ ppr n <+> ppr id <+> ppr (idType id)
723 | (n,id) <- rhs_id_env]
724 mapM (wrapLocM tcRhs) tc_binds
725 ; return (listToBag binds', mono_info) }
727 ------------------------
728 -- tcLhs typechecks the LHS of the bindings, to construct the environment in which
729 -- we typecheck the RHSs. Basically what we are doing is this: for each binder:
730 -- if there's a signature for it, use the instantiated signature type
731 -- otherwise invent a type variable
732 -- You see that quite directly in the FunBind case.
734 -- But there's a complication for pattern bindings:
735 -- data T = MkT (forall a. a->a)
737 -- Here we can guess a type variable for the entire LHS (which will be refined to T)
738 -- but we want to get (f::forall a. a->a) as the RHS environment.
739 -- The simplest way to do this is to typecheck the pattern, and then look up the
740 -- bound mono-ids. Then we want to retain the typechecked pattern to avoid re-doing
741 -- it; hence the TcMonoBind data type in which the LHS is done but the RHS isn't
743 data TcMonoBind -- Half completed; LHS done, RHS not done
744 = TcFunBind MonoBindInfo SrcSpan Bool (MatchGroup Name)
745 | TcPatBind [MonoBindInfo] (LPat TcId) (GRHSs Name) TcSigmaType
747 type MonoBindInfo = (Name, Maybe TcSigInfo, TcId)
748 -- Type signature (if any), and
749 -- the monomorphic bound things
751 tcLhs :: TcSigFun -> LetBndrSpec -> HsBind Name -> TcM TcMonoBind
752 tcLhs sig_fn no_gen (FunBind { fun_id = L nm_loc name, fun_infix = inf, fun_matches = matches })
753 | Just sig <- sig_fn name
754 = do { mono_id <- newSigLetBndr no_gen name sig
755 ; return (TcFunBind (name, Just sig, mono_id) nm_loc inf matches) }
757 = do { mono_ty <- newFlexiTyVarTy argTypeKind
758 ; mono_id <- newNoSigLetBndr no_gen name mono_ty
759 ; return (TcFunBind (name, Nothing, mono_id) nm_loc inf matches) }
761 tcLhs sig_fn no_gen (PatBind { pat_lhs = pat, pat_rhs = grhss })
762 = do { let tc_pat exp_ty = tcLetPat sig_fn no_gen pat exp_ty $
763 mapM lookup_info (collectPatBinders pat)
765 -- After typechecking the pattern, look up the binder
766 -- names, which the pattern has brought into scope.
767 lookup_info :: Name -> TcM MonoBindInfo
768 lookup_info name = do { mono_id <- tcLookupId name
769 ; return (name, sig_fn name, mono_id) }
771 ; ((pat', infos), pat_ty) <- addErrCtxt (patMonoBindsCtxt pat grhss) $
774 ; return (TcPatBind infos pat' grhss pat_ty) }
776 tcLhs _ _ other_bind = pprPanic "tcLhs" (ppr other_bind)
777 -- AbsBind, VarBind impossible
780 tcRhs :: TcMonoBind -> TcM (HsBind TcId)
781 -- When we are doing pattern bindings, or multiple function bindings at a time
782 -- we *don't* bring any scoped type variables into scope
783 -- Wny not? They are not completely rigid.
784 -- That's why we have the special case for a single FunBind in tcMonoBinds
785 tcRhs (TcFunBind (_,_,mono_id) loc inf matches)
786 = do { (co_fn, matches') <- tcMatchesFun (idName mono_id) inf
787 matches (idType mono_id)
788 ; return (FunBind { fun_id = L loc mono_id, fun_infix = inf
789 , fun_matches = matches'
791 , bind_fvs = placeHolderNames, fun_tick = Nothing }) }
793 tcRhs (TcPatBind _ pat' grhss pat_ty)
794 = do { grhss' <- addErrCtxt (patMonoBindsCtxt pat' grhss) $
795 tcGRHSsPat grhss pat_ty
796 ; return (PatBind { pat_lhs = pat', pat_rhs = grhss', pat_rhs_ty = pat_ty
797 , bind_fvs = placeHolderNames }) }
800 ---------------------
801 getMonoBindInfo :: [Located TcMonoBind] -> [MonoBindInfo]
802 getMonoBindInfo tc_binds
803 = foldr (get_info . unLoc) [] tc_binds
805 get_info (TcFunBind info _ _ _) rest = info : rest
806 get_info (TcPatBind infos _ _ _) rest = infos ++ rest
810 %************************************************************************
814 %************************************************************************
816 unifyCtxts checks that all the signature contexts are the same
817 The type signatures on a mutually-recursive group of definitions
818 must all have the same context (or none).
820 The trick here is that all the signatures should have the same
821 context, and we want to share type variables for that context, so that
822 all the right hand sides agree a common vocabulary for their type
825 We unify them because, with polymorphic recursion, their types
826 might not otherwise be related. This is a rather subtle issue.
829 unifyCtxts :: [TcSigInfo] -> TcM ()
830 -- Post-condition: the returned Insts are full zonked
831 unifyCtxts [] = return ()
832 unifyCtxts (sig1 : sigs)
833 = do { traceTc "unifyCtxts" (ppr (sig1 : sigs))
834 ; mapM_ unify_ctxt sigs }
836 theta1 = sig_theta sig1
837 unify_ctxt :: TcSigInfo -> TcM ()
838 unify_ctxt sig@(TcSigInfo { sig_theta = theta })
839 = setSrcSpan (sig_loc sig) $
840 addErrCtxt (sigContextsCtxt sig1 sig) $
841 do { cois <- unifyTheta theta1 theta
842 ; -- Check whether all coercions are identity coercions
843 -- That can happen if we have, say
845 -- g :: C (F a) => ...
846 -- where F is a type function and (F a ~ [a])
847 -- Then unification might succeed with a coercion. But it's much
848 -- much simpler to require that such signatures have identical contexts
849 checkTc (all isReflCo cois)
850 (ptext (sLit "Mutually dependent functions have syntactically distinct contexts"))
855 @getTyVarsToGen@ decides what type variables to generalise over.
857 For a "restricted group" -- see the monomorphism restriction
858 for a definition -- we bind no dictionaries, and
859 remove from tyvars_to_gen any constrained type variables
861 *Don't* simplify dicts at this point, because we aren't going
862 to generalise over these dicts. By the time we do simplify them
863 we may well know more. For example (this actually came up)
865 f x = array ... xs where xs = [1,2,3,4,5]
866 We don't want to generate lots of (fromInt Int 1), (fromInt Int 2)
867 stuff. If we simplify only at the f-binding (not the xs-binding)
868 we'll know that the literals are all Ints, and we can just produce
871 Find all the type variables involved in overloading, the
872 "constrained_tyvars". These are the ones we *aren't* going to
873 generalise. We must be careful about doing this:
875 (a) If we fail to generalise a tyvar which is not actually
876 constrained, then it will never, ever get bound, and lands
877 up printed out in interface files! Notorious example:
878 instance Eq a => Eq (Foo a b) where ..
879 Here, b is not constrained, even though it looks as if it is.
880 Another, more common, example is when there's a Method inst in
881 the LIE, whose type might very well involve non-overloaded
883 [NOTE: Jan 2001: I don't understand the problem here so I'm doing
884 the simple thing instead]
886 (b) On the other hand, we mustn't generalise tyvars which are constrained,
887 because we are going to pass on out the unmodified LIE, with those
888 tyvars in it. They won't be in scope if we've generalised them.
890 So we are careful, and do a complete simplification just to find the
891 constrained tyvars. We don't use any of the results, except to
892 find which tyvars are constrained.
894 Note [Polymorphic recursion]
895 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
896 The game plan for polymorphic recursion in the code above is
898 * Bind any variable for which we have a type signature
899 to an Id with a polymorphic type. Then when type-checking
900 the RHSs we'll make a full polymorphic call.
902 This fine, but if you aren't a bit careful you end up with a horrendous
903 amount of partial application and (worse) a huge space leak. For example:
905 f :: Eq a => [a] -> [a]
908 If we don't take care, after typechecking we get
910 f = /\a -> \d::Eq a -> let f' = f a d
914 Notice the the stupid construction of (f a d), which is of course
915 identical to the function we're executing. In this case, the
916 polymorphic recursion isn't being used (but that's a very common case).
917 This can lead to a massive space leak, from the following top-level defn
923 Now (f dEqInt) evaluates to a lambda that has f' as a free variable; but
924 f' is another thunk which evaluates to the same thing... and you end
925 up with a chain of identical values all hung onto by the CAF ff.
929 = let f' = f Int dEqInt in \ys. ...f'...
931 = let f' = let f' = f Int dEqInt in \ys. ...f'...
936 NOTE: a bit of arity anaysis would push the (f a d) inside the (\ys...),
937 which would make the space leak go away in this case
939 Solution: when typechecking the RHSs we always have in hand the
940 *monomorphic* Ids for each binding. So we just need to make sure that
941 if (Method f a d) shows up in the constraints emerging from (...f...)
942 we just use the monomorphic Id. We achieve this by adding monomorphic Ids
943 to the "givens" when simplifying constraints. That's what the "lies_avail"
948 f = /\a -> \d::Eq a -> letrec
949 fm = \ys:[a] -> ...fm...
953 %************************************************************************
957 %************************************************************************
959 Type signatures are tricky. See Note [Signature skolems] in TcType
961 @tcSigs@ checks the signatures for validity, and returns a list of
962 {\em freshly-instantiated} signatures. That is, the types are already
963 split up, and have fresh type variables installed. All non-type-signature
964 "RenamedSigs" are ignored.
966 The @TcSigInfo@ contains @TcTypes@ because they are unified with
967 the variable's type, and after that checked to see whether they've
972 The -XScopedTypeVariables flag brings lexically-scoped type variables
973 into scope for any explicitly forall-quantified type variables:
974 f :: forall a. a -> a
976 Then 'a' is in scope inside 'e'.
978 However, we do *not* support this
979 - For pattern bindings e.g
983 - For multiple function bindings, unless Opt_RelaxedPolyRec is on
984 f :: forall a. a -> a
986 g :: forall b. b -> b
988 Reason: we use mutable variables for 'a' and 'b', since they may
989 unify to each other, and that means the scoped type variable would
990 not stand for a completely rigid variable.
992 Currently, we simply make Opt_ScopedTypeVariables imply Opt_RelaxedPolyRec
995 Note [More instantiated than scoped]
996 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
997 There may be more instantiated type variables than lexically-scoped
999 type T a = forall b. b -> (a,b)
1001 Here, the signature for f will have one scoped type variable, c,
1002 but two instantiated type variables, c' and b'.
1004 We assume that the scoped ones are at the *front* of sig_tvs,
1005 and remember the names from the original HsForAllTy in the TcSigFun.
1007 Note [Signature skolems]
1008 ~~~~~~~~~~~~~~~~~~~~~~~~
1009 When instantiating a type signature, we do so with either skolems or
1010 SigTv meta-type variables depending on the use_skols boolean. This
1011 variable is set True when we are typechecking a single function
1012 binding; and False for pattern bindings and a group of several
1015 Reason: in the latter cases, the "skolems" can be unified together,
1016 so they aren't properly rigid in the type-refinement sense.
1017 NB: unless we are doing H98, each function with a sig will be done
1018 separately, even if it's mutually recursive, so use_skols will be True
1021 Note [Only scoped tyvars are in the TyVarEnv]
1022 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1023 We are careful to keep only the *lexically scoped* type variables in
1024 the type environment. Why? After all, the renamer has ensured
1025 that only legal occurrences occur, so we could put all type variables
1028 But we want to check that two distinct lexically scoped type variables
1029 do not map to the same internal type variable. So we need to know which
1030 the lexically-scoped ones are... and at the moment we do that by putting
1031 only the lexically scoped ones into the environment.
1033 Note [Instantiate sig with fresh variables]
1034 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1035 It's vital to instantiate a type signature with fresh variables.
1037 type T = forall a. [a] -> [a]
1039 f = g where { g :: T; g = <rhs> }
1041 We must not use the same 'a' from the defn of T at both places!!
1042 (Instantiation is only necessary because of type synonyms. Otherwise,
1043 it's all cool; each signature has distinct type variables from the renamer.)
1046 type SigFun = Name -> Maybe ([Name], SrcSpan)
1047 -- Maps a let-binder to the list of
1048 -- type variables brought into scope
1049 -- by its type signature, plus location
1050 -- Nothing => no type signature
1052 mkSigFun :: [LSig Name] -> SigFun
1053 -- Search for a particular type signature
1054 -- Precondition: the sigs are all type sigs
1055 -- Precondition: no duplicates
1056 mkSigFun sigs = lookupNameEnv env
1058 env = mkNameEnv (mapCatMaybes mk_pair sigs)
1059 mk_pair (L loc (TypeSig (L _ name) lhs_ty)) = Just (name, (hsExplicitTvs lhs_ty, loc))
1060 mk_pair (L loc (IdSig id)) = Just (idName id, ([], loc))
1062 -- The scoped names are the ones explicitly mentioned
1063 -- in the HsForAll. (There may be more in sigma_ty, because
1064 -- of nested type synonyms. See Note [More instantiated than scoped].)
1065 -- See Note [Only scoped tyvars are in the TyVarEnv]
1069 tcTySig :: LSig Name -> TcM TcId
1070 tcTySig (L span (TypeSig (L _ name) ty))
1072 do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
1073 ; return (mkLocalId name sigma_ty) }
1074 tcTySig (L _ (IdSig id))
1076 tcTySig s = pprPanic "tcTySig" (ppr s)
1079 tcInstSigs :: SigFun -> [Name] -> TcM TcSigFun
1080 tcInstSigs sig_fn bndrs
1081 = do { prs <- mapMaybeM (tcInstSig sig_fn use_skols) bndrs
1082 ; return (lookupNameEnv (mkNameEnv prs)) }
1084 use_skols = isSingleton bndrs -- See Note [Signature skolems]
1086 tcInstSig :: SigFun -> Bool -> Name -> TcM (Maybe (Name, TcSigInfo))
1087 -- For use_skols :: Bool see Note [Signature skolems]
1089 -- We must instantiate with fresh uniques,
1090 -- (see Note [Instantiate sig with fresh variables])
1091 -- although we keep the same print-name.
1093 tcInstSig sig_fn use_skols name
1094 | Just (scoped_tvs, loc) <- sig_fn name
1095 = do { poly_id <- tcLookupId name -- Cannot fail; the poly ids are put into
1096 -- scope when starting the binding group
1097 ; let poly_ty = idType poly_id
1098 ; (tvs, theta, tau) <- if use_skols
1099 then tcInstType tcInstSkolTyVars poly_ty
1100 else tcInstType tcInstSigTyVars poly_ty
1101 ; let sig = TcSigInfo { sig_id = poly_id
1102 , sig_scoped = scoped_tvs
1103 , sig_tvs = tvs, sig_theta = theta, sig_tau = tau
1105 ; return (Just (name, sig)) }
1109 -------------------------------
1110 data GeneralisationPlan
1111 = NoGen -- No generalisation, no AbsBinds
1112 | InferGen Bool -- Implicit generalisation; there is an AbsBinds
1113 -- True <=> apply the MR; generalise only unconstrained type vars
1114 | CheckGen TcSigInfo -- Explicit generalisation; there is an AbsBinds
1116 -- A consequence of the no-AbsBinds choice (NoGen) is that there is
1117 -- no "polymorphic Id" and "monmomorphic Id"; there is just the one
1119 instance Outputable GeneralisationPlan where
1120 ppr NoGen = ptext (sLit "NoGen")
1121 ppr (InferGen b) = ptext (sLit "InferGen") <+> ppr b
1122 ppr (CheckGen s) = ptext (sLit "CheckGen") <+> ppr s
1124 decideGeneralisationPlan
1125 :: DynFlags -> TopLevelFlag -> [Name] -> [LHsBind Name] -> TcSigFun -> GeneralisationPlan
1126 decideGeneralisationPlan dflags top_lvl _bndrs binds sig_fn
1127 | bang_pat_binds = NoGen
1128 | mono_pat_binds = NoGen
1129 | Just sig <- one_funbind_with_sig binds = if null (sig_tvs sig) && null (sig_theta sig)
1130 then NoGen -- Optimise common case
1132 | (xopt Opt_MonoLocalBinds dflags
1133 && isNotTopLevel top_lvl) = NoGen
1134 | otherwise = InferGen mono_restriction
1137 bang_pat_binds = any (isBangHsBind . unLoc) binds
1138 -- Bang patterns must not be polymorphic,
1139 -- because we are going to force them
1142 mono_pat_binds = xopt Opt_MonoPatBinds dflags
1143 && any (is_pat_bind . unLoc) binds
1145 mono_restriction = xopt Opt_MonomorphismRestriction dflags
1146 && any (restricted . unLoc) binds
1148 no_sig n = isNothing (sig_fn n)
1150 -- With OutsideIn, all nested bindings are monomorphic
1151 -- except a single function binding with a signature
1152 one_funbind_with_sig [L _ FunBind { fun_id = v }] = sig_fn (unLoc v)
1153 one_funbind_with_sig _ = Nothing
1155 -- The Haskell 98 monomorphism resetriction
1156 restricted (PatBind {}) = True
1157 restricted (VarBind { var_id = v }) = no_sig v
1158 restricted (FunBind { fun_id = v, fun_matches = m }) = restricted_match m
1160 restricted (AbsBinds {}) = panic "isRestrictedGroup/unrestricted AbsBinds"
1162 restricted_match (MatchGroup (L _ (Match [] _ _) : _) _) = True
1163 restricted_match _ = False
1164 -- No args => like a pattern binding
1165 -- Some args => a function binding
1167 is_pat_bind (PatBind {}) = True
1168 is_pat_bind _ = False
1171 checkStrictBinds :: TopLevelFlag -> RecFlag
1172 -> [LHsBind Name] -> [Id]
1174 -- Check that non-overloaded unlifted bindings are
1175 -- a) non-recursive,
1176 -- b) not top level,
1177 -- c) not a multiple-binding group (more or less implied by (a))
1179 checkStrictBinds top_lvl rec_group binds poly_ids
1180 | unlifted || bang_pat
1181 = do { checkTc (isNotTopLevel top_lvl)
1182 (strictBindErr "Top-level" unlifted binds)
1183 ; checkTc (isNonRec rec_group)
1184 (strictBindErr "Recursive" unlifted binds)
1185 ; checkTc (isSingleton binds)
1186 (strictBindErr "Multiple" unlifted binds)
1187 -- This should be a checkTc, not a warnTc, but as of GHC 6.11
1188 -- the versions of alex and happy available have non-conforming
1189 -- templates, so the GHC build fails if it's an error:
1190 ; warnUnlifted <- doptM Opt_WarnLazyUnliftedBindings
1191 ; warnTc (warnUnlifted && not bang_pat && lifted_pat)
1192 -- No outer bang, but it's a compound pattern
1193 -- E.g (I# x#) = blah
1194 -- Warn about this, but not about
1197 (unliftedMustBeBang binds) }
1201 unlifted = any is_unlifted poly_ids
1202 bang_pat = any (isBangHsBind . unLoc) binds
1203 lifted_pat = any (isLiftedPatBind . unLoc) binds
1204 is_unlifted id = case tcSplitForAllTys (idType id) of
1205 (_, rho) -> isUnLiftedType rho
1207 unliftedMustBeBang :: [LHsBind Name] -> SDoc
1208 unliftedMustBeBang binds
1209 = hang (text "Pattern bindings containing unlifted types should use an outermost bang pattern:")
1210 2 (pprBindList binds)
1212 strictBindErr :: String -> Bool -> [LHsBind Name] -> SDoc
1213 strictBindErr flavour unlifted binds
1214 = hang (text flavour <+> msg <+> ptext (sLit "aren't allowed:"))
1215 2 (pprBindList binds)
1217 msg | unlifted = ptext (sLit "bindings for unlifted types")
1218 | otherwise = ptext (sLit "bang-pattern bindings")
1220 pprBindList :: [LHsBind Name] -> SDoc
1221 pprBindList binds = vcat (map ppr binds)
1225 %************************************************************************
1227 \subsection[TcBinds-errors]{Error contexts and messages}
1229 %************************************************************************
1233 -- This one is called on LHS, when pat and grhss are both Name
1234 -- and on RHS, when pat is TcId and grhss is still Name
1235 patMonoBindsCtxt :: OutputableBndr id => LPat id -> GRHSs Name -> SDoc
1236 patMonoBindsCtxt pat grhss
1237 = hang (ptext (sLit "In a pattern binding:")) 2 (pprPatBind pat grhss)
1239 -----------------------------------------------
1240 sigContextsCtxt :: TcSigInfo -> TcSigInfo -> SDoc
1241 sigContextsCtxt sig1 sig2
1242 = vcat [ptext (sLit "When matching the contexts of the signatures for"),
1243 nest 2 (vcat [ppr id1 <+> dcolon <+> ppr (idType id1),
1244 ppr id2 <+> dcolon <+> ppr (idType id2)]),
1245 ptext (sLit "The signature contexts in a mutually recursive group should all be identical")]