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]
558 -- SPECIALISE pragamas for imported things
560 = do { this_mod <- getModule
562 ; if not (dopt Opt_Specialise dflags) then
563 return [] -- Ignore SPECIALISE pragmas for imported things
564 -- when -O is not on; otherwise we get bogus
565 -- complaints about lack of INLINABLE pragmas
566 -- in the imported module (also compiled without -O)
567 -- Notably, when Haddocking the base library
569 mapAndRecoverM (wrapLocM tcImpSpec)
570 [L loc (name,prag) | (L loc prag@(SpecSig (L _ name) _ _)) <- prags
571 , not (nameIsLocalOrFrom this_mod name) ] }
573 tcImpSpec :: (Name, Sig Name) -> TcM TcSpecPrag
574 tcImpSpec (name, prag)
575 = do { id <- tcLookupId name
576 ; checkTc (isAnyInlinePragma (idInlinePragma id))
580 impSpecErr :: Name -> SDoc
582 = hang (ptext (sLit "You cannot SPECIALISE") <+> quotes (ppr name))
583 2 (vcat [ ptext (sLit "because its definition has no INLINE/INLINABLE pragma")
585 [ ptext (sLit "or its defining module") <+> quotes (ppr mod)
586 , ptext (sLit "was compiled without -O")]])
588 mod = nameModule name
591 tcVectDecls :: [LVectDecl Name] -> TcM ([LVectDecl TcId])
593 = do { decls' <- mapM (wrapLocM tcVect) decls
594 ; let ids = [unLoc id | L _ (HsVect id _) <- decls']
595 dups = findDupsEq (==) ids
596 ; mapM_ reportVectDups dups
597 ; traceTcConstraints "End of tcVectDecls"
601 reportVectDups (first:_second:_more)
602 = addErrAt (getSrcSpan first) $
603 ptext (sLit "Duplicate vectorisation declarations for") <+> ppr first
604 reportVectDups _ = return ()
607 tcVect :: VectDecl Name -> TcM (VectDecl TcId)
608 -- We can't typecheck the expression of a vectorisation declaration against the vectorised type
609 -- of the original definition as this requires internals of the vectoriser not available during
610 -- type checking. Instead, we infer the type of the expression and leave it to the vectoriser
611 -- to check the compatibility of the Core types.
612 tcVect (HsVect name Nothing)
613 = addErrCtxt (vectCtxt name) $
614 do { id <- wrapLocM tcLookupId name
615 ; return $ HsVect id Nothing
617 tcVect (HsVect name@(L loc _) (Just rhs))
618 = addErrCtxt (vectCtxt name) $
619 do { _id <- wrapLocM tcLookupId name -- need to ensure that the name is already defined
621 -- turn the vectorisation declaration into a single non-recursive binding
622 ; let bind = L loc $ mkFunBind name [mkSimpleMatch [] rhs]
623 sigFun = const Nothing
624 pragFun = mkPragFun [] (unitBag bind)
626 -- perform type inference (including generalisation)
627 ; (binds, [id']) <- tcPolyInfer TopLevel False sigFun pragFun NonRecursive [bind]
629 ; traceTc "tcVect inferred type" $ ppr (varType id')
630 ; traceTc "tcVect bindings" $ ppr binds
632 -- add all bindings, including the type variable and dictionary bindings produced by type
633 -- generalisation to the right-hand side of the vectorisation declaration
634 ; let [AbsBinds tvs evs _ evBinds actualBinds] = (map unLoc . bagToList) binds
635 ; let [bind'] = bagToList actualBinds
637 [L _ (Match _ _ (GRHSs [L _ (GRHS _ rhs')] _))]
638 _ = (fun_matches . unLoc) bind'
639 rhsWrapped = mkHsLams tvs evs (mkHsDictLet evBinds rhs')
641 -- We return the type-checked 'Id', to propagate the inferred signature
642 -- to the vectoriser - see "Note [Typechecked vectorisation pragmas]" in HsDecls
643 ; return $ HsVect (L loc id') (Just rhsWrapped)
646 vectCtxt :: Located Name -> SDoc
647 vectCtxt name = ptext (sLit "When checking the vectorisation declaration for") <+> ppr name
650 -- If typechecking the binds fails, then return with each
651 -- signature-less binder given type (forall a.a), to minimise
652 -- subsequent error messages
653 recoveryCode :: [Name] -> SigFun -> TcM (LHsBinds TcId, [Id])
654 recoveryCode binder_names sig_fn
655 = do { traceTc "tcBindsWithSigs: error recovery" (ppr binder_names)
656 ; poly_ids <- mapM mk_dummy binder_names
657 ; return (emptyBag, poly_ids) }
660 | isJust (sig_fn name) = tcLookupId name -- Had signature; look it up
661 | otherwise = return (mkLocalId name forall_a_a) -- No signature
664 forall_a_a = mkForAllTy openAlphaTyVar (mkTyVarTy openAlphaTyVar)
667 Note [SPECIALISE pragmas]
668 ~~~~~~~~~~~~~~~~~~~~~~~~~
669 There is no point in a SPECIALISE pragma for a non-overloaded function:
670 reverse :: [a] -> [a]
671 {-# SPECIALISE reverse :: [Int] -> [Int] #-}
673 But SPECIALISE INLINE *can* make sense for GADTS:
675 ArrInt :: !Int -> ByteArray# -> Arr Int
676 ArrPair :: !Int -> Arr e1 -> Arr e2 -> Arr (e1, e2)
678 (!:) :: Arr e -> Int -> e
679 {-# SPECIALISE INLINE (!:) :: Arr Int -> Int -> Int #-}
680 {-# SPECIALISE INLINE (!:) :: Arr (a, b) -> Int -> (a, b) #-}
681 (ArrInt _ ba) !: (I# i) = I# (indexIntArray# ba i)
682 (ArrPair _ a1 a2) !: i = (a1 !: i, a2 !: i)
684 When (!:) is specialised it becomes non-recursive, and can usefully
685 be inlined. Scary! So we only warn for SPECIALISE *without* INLINE
686 for a non-overloaded function.
688 %************************************************************************
690 \subsection{tcMonoBind}
692 %************************************************************************
694 @tcMonoBinds@ deals with a perhaps-recursive group of HsBinds.
695 The signatures have been dealt with already.
698 tcMonoBinds :: TcSigFun -> LetBndrSpec
699 -> RecFlag -- Whether the binding is recursive for typechecking purposes
700 -- i.e. the binders are mentioned in their RHSs, and
701 -- we are not resuced by a type signature
703 -> TcM (LHsBinds TcId, [MonoBindInfo])
705 tcMonoBinds sig_fn no_gen is_rec
706 [ L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf,
707 fun_matches = matches, bind_fvs = fvs })]
708 -- Single function binding,
709 | NonRecursive <- is_rec -- ...binder isn't mentioned in RHS
710 , Nothing <- sig_fn name -- ...with no type signature
711 = -- In this very special case we infer the type of the
712 -- right hand side first (it may have a higher-rank type)
713 -- and *then* make the monomorphic Id for the LHS
714 -- e.g. f = \(x::forall a. a->a) -> <body>
715 -- We want to infer a higher-rank type for f
717 do { ((co_fn, matches'), rhs_ty) <- tcInfer (tcMatchesFun name inf matches)
719 ; mono_id <- newNoSigLetBndr no_gen name rhs_ty
720 ; return (unitBag (L b_loc (FunBind { fun_id = L nm_loc mono_id, fun_infix = inf,
721 fun_matches = matches', bind_fvs = fvs,
722 fun_co_fn = co_fn, fun_tick = Nothing })),
723 [(name, Nothing, mono_id)]) }
725 tcMonoBinds sig_fn no_gen _ binds
726 = do { tc_binds <- mapM (wrapLocM (tcLhs sig_fn no_gen)) binds
728 -- Bring the monomorphic Ids, into scope for the RHSs
729 ; let mono_info = getMonoBindInfo tc_binds
730 rhs_id_env = [(name,mono_id) | (name, Nothing, mono_id) <- mono_info]
731 -- A monomorphic binding for each term variable that lacks
732 -- a type sig. (Ones with a sig are already in scope.)
734 ; binds' <- tcExtendIdEnv2 rhs_id_env $ do
735 traceTc "tcMonoBinds" $ vcat [ ppr n <+> ppr id <+> ppr (idType id)
736 | (n,id) <- rhs_id_env]
737 mapM (wrapLocM tcRhs) tc_binds
738 ; return (listToBag binds', mono_info) }
740 ------------------------
741 -- tcLhs typechecks the LHS of the bindings, to construct the environment in which
742 -- we typecheck the RHSs. Basically what we are doing is this: for each binder:
743 -- if there's a signature for it, use the instantiated signature type
744 -- otherwise invent a type variable
745 -- You see that quite directly in the FunBind case.
747 -- But there's a complication for pattern bindings:
748 -- data T = MkT (forall a. a->a)
750 -- Here we can guess a type variable for the entire LHS (which will be refined to T)
751 -- but we want to get (f::forall a. a->a) as the RHS environment.
752 -- The simplest way to do this is to typecheck the pattern, and then look up the
753 -- bound mono-ids. Then we want to retain the typechecked pattern to avoid re-doing
754 -- it; hence the TcMonoBind data type in which the LHS is done but the RHS isn't
756 data TcMonoBind -- Half completed; LHS done, RHS not done
757 = TcFunBind MonoBindInfo SrcSpan Bool (MatchGroup Name)
758 | TcPatBind [MonoBindInfo] (LPat TcId) (GRHSs Name) TcSigmaType
760 type MonoBindInfo = (Name, Maybe TcSigInfo, TcId)
761 -- Type signature (if any), and
762 -- the monomorphic bound things
764 tcLhs :: TcSigFun -> LetBndrSpec -> HsBind Name -> TcM TcMonoBind
765 tcLhs sig_fn no_gen (FunBind { fun_id = L nm_loc name, fun_infix = inf, fun_matches = matches })
766 | Just sig <- sig_fn name
767 = do { mono_id <- newSigLetBndr no_gen name sig
768 ; return (TcFunBind (name, Just sig, mono_id) nm_loc inf matches) }
770 = do { mono_ty <- newFlexiTyVarTy argTypeKind
771 ; mono_id <- newNoSigLetBndr no_gen name mono_ty
772 ; return (TcFunBind (name, Nothing, mono_id) nm_loc inf matches) }
774 tcLhs sig_fn no_gen (PatBind { pat_lhs = pat, pat_rhs = grhss })
775 = do { let tc_pat exp_ty = tcLetPat sig_fn no_gen pat exp_ty $
776 mapM lookup_info (collectPatBinders pat)
778 -- After typechecking the pattern, look up the binder
779 -- names, which the pattern has brought into scope.
780 lookup_info :: Name -> TcM MonoBindInfo
781 lookup_info name = do { mono_id <- tcLookupId name
782 ; return (name, sig_fn name, mono_id) }
784 ; ((pat', infos), pat_ty) <- addErrCtxt (patMonoBindsCtxt pat grhss) $
787 ; return (TcPatBind infos pat' grhss pat_ty) }
789 tcLhs _ _ other_bind = pprPanic "tcLhs" (ppr other_bind)
790 -- AbsBind, VarBind impossible
793 tcRhs :: TcMonoBind -> TcM (HsBind TcId)
794 -- When we are doing pattern bindings, or multiple function bindings at a time
795 -- we *don't* bring any scoped type variables into scope
796 -- Wny not? They are not completely rigid.
797 -- That's why we have the special case for a single FunBind in tcMonoBinds
798 tcRhs (TcFunBind (_,_,mono_id) loc inf matches)
799 = do { (co_fn, matches') <- tcMatchesFun (idName mono_id) inf
800 matches (idType mono_id)
801 ; return (FunBind { fun_id = L loc mono_id, fun_infix = inf
802 , fun_matches = matches'
804 , bind_fvs = placeHolderNames, fun_tick = Nothing }) }
806 tcRhs (TcPatBind _ pat' grhss pat_ty)
807 = do { grhss' <- addErrCtxt (patMonoBindsCtxt pat' grhss) $
808 tcGRHSsPat grhss pat_ty
809 ; return (PatBind { pat_lhs = pat', pat_rhs = grhss', pat_rhs_ty = pat_ty
810 , bind_fvs = placeHolderNames }) }
813 ---------------------
814 getMonoBindInfo :: [Located TcMonoBind] -> [MonoBindInfo]
815 getMonoBindInfo tc_binds
816 = foldr (get_info . unLoc) [] tc_binds
818 get_info (TcFunBind info _ _ _) rest = info : rest
819 get_info (TcPatBind infos _ _ _) rest = infos ++ rest
823 %************************************************************************
827 %************************************************************************
829 unifyCtxts checks that all the signature contexts are the same
830 The type signatures on a mutually-recursive group of definitions
831 must all have the same context (or none).
833 The trick here is that all the signatures should have the same
834 context, and we want to share type variables for that context, so that
835 all the right hand sides agree a common vocabulary for their type
838 We unify them because, with polymorphic recursion, their types
839 might not otherwise be related. This is a rather subtle issue.
842 unifyCtxts :: [TcSigInfo] -> TcM ()
843 -- Post-condition: the returned Insts are full zonked
844 unifyCtxts [] = return ()
845 unifyCtxts (sig1 : sigs)
846 = do { traceTc "unifyCtxts" (ppr (sig1 : sigs))
847 ; mapM_ unify_ctxt sigs }
849 theta1 = sig_theta sig1
850 unify_ctxt :: TcSigInfo -> TcM ()
851 unify_ctxt sig@(TcSigInfo { sig_theta = theta })
852 = setSrcSpan (sig_loc sig) $
853 addErrCtxt (sigContextsCtxt sig1 sig) $
854 do { cois <- unifyTheta theta1 theta
855 ; -- Check whether all coercions are identity coercions
856 -- That can happen if we have, say
858 -- g :: C (F a) => ...
859 -- where F is a type function and (F a ~ [a])
860 -- Then unification might succeed with a coercion. But it's much
861 -- much simpler to require that such signatures have identical contexts
862 checkTc (all isReflCo cois)
863 (ptext (sLit "Mutually dependent functions have syntactically distinct contexts"))
868 @getTyVarsToGen@ decides what type variables to generalise over.
870 For a "restricted group" -- see the monomorphism restriction
871 for a definition -- we bind no dictionaries, and
872 remove from tyvars_to_gen any constrained type variables
874 *Don't* simplify dicts at this point, because we aren't going
875 to generalise over these dicts. By the time we do simplify them
876 we may well know more. For example (this actually came up)
878 f x = array ... xs where xs = [1,2,3,4,5]
879 We don't want to generate lots of (fromInt Int 1), (fromInt Int 2)
880 stuff. If we simplify only at the f-binding (not the xs-binding)
881 we'll know that the literals are all Ints, and we can just produce
884 Find all the type variables involved in overloading, the
885 "constrained_tyvars". These are the ones we *aren't* going to
886 generalise. We must be careful about doing this:
888 (a) If we fail to generalise a tyvar which is not actually
889 constrained, then it will never, ever get bound, and lands
890 up printed out in interface files! Notorious example:
891 instance Eq a => Eq (Foo a b) where ..
892 Here, b is not constrained, even though it looks as if it is.
893 Another, more common, example is when there's a Method inst in
894 the LIE, whose type might very well involve non-overloaded
896 [NOTE: Jan 2001: I don't understand the problem here so I'm doing
897 the simple thing instead]
899 (b) On the other hand, we mustn't generalise tyvars which are constrained,
900 because we are going to pass on out the unmodified LIE, with those
901 tyvars in it. They won't be in scope if we've generalised them.
903 So we are careful, and do a complete simplification just to find the
904 constrained tyvars. We don't use any of the results, except to
905 find which tyvars are constrained.
907 Note [Polymorphic recursion]
908 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
909 The game plan for polymorphic recursion in the code above is
911 * Bind any variable for which we have a type signature
912 to an Id with a polymorphic type. Then when type-checking
913 the RHSs we'll make a full polymorphic call.
915 This fine, but if you aren't a bit careful you end up with a horrendous
916 amount of partial application and (worse) a huge space leak. For example:
918 f :: Eq a => [a] -> [a]
921 If we don't take care, after typechecking we get
923 f = /\a -> \d::Eq a -> let f' = f a d
927 Notice the the stupid construction of (f a d), which is of course
928 identical to the function we're executing. In this case, the
929 polymorphic recursion isn't being used (but that's a very common case).
930 This can lead to a massive space leak, from the following top-level defn
936 Now (f dEqInt) evaluates to a lambda that has f' as a free variable; but
937 f' is another thunk which evaluates to the same thing... and you end
938 up with a chain of identical values all hung onto by the CAF ff.
942 = let f' = f Int dEqInt in \ys. ...f'...
944 = let f' = let f' = f Int dEqInt in \ys. ...f'...
949 NOTE: a bit of arity anaysis would push the (f a d) inside the (\ys...),
950 which would make the space leak go away in this case
952 Solution: when typechecking the RHSs we always have in hand the
953 *monomorphic* Ids for each binding. So we just need to make sure that
954 if (Method f a d) shows up in the constraints emerging from (...f...)
955 we just use the monomorphic Id. We achieve this by adding monomorphic Ids
956 to the "givens" when simplifying constraints. That's what the "lies_avail"
961 f = /\a -> \d::Eq a -> letrec
962 fm = \ys:[a] -> ...fm...
966 %************************************************************************
970 %************************************************************************
972 Type signatures are tricky. See Note [Signature skolems] in TcType
974 @tcSigs@ checks the signatures for validity, and returns a list of
975 {\em freshly-instantiated} signatures. That is, the types are already
976 split up, and have fresh type variables installed. All non-type-signature
977 "RenamedSigs" are ignored.
979 The @TcSigInfo@ contains @TcTypes@ because they are unified with
980 the variable's type, and after that checked to see whether they've
985 The -XScopedTypeVariables flag brings lexically-scoped type variables
986 into scope for any explicitly forall-quantified type variables:
987 f :: forall a. a -> a
989 Then 'a' is in scope inside 'e'.
991 However, we do *not* support this
992 - For pattern bindings e.g
996 - For multiple function bindings, unless Opt_RelaxedPolyRec is on
997 f :: forall a. a -> a
999 g :: forall b. b -> b
1001 Reason: we use mutable variables for 'a' and 'b', since they may
1002 unify to each other, and that means the scoped type variable would
1003 not stand for a completely rigid variable.
1005 Currently, we simply make Opt_ScopedTypeVariables imply Opt_RelaxedPolyRec
1008 Note [More instantiated than scoped]
1009 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1010 There may be more instantiated type variables than lexically-scoped
1012 type T a = forall b. b -> (a,b)
1014 Here, the signature for f will have one scoped type variable, c,
1015 but two instantiated type variables, c' and b'.
1017 We assume that the scoped ones are at the *front* of sig_tvs,
1018 and remember the names from the original HsForAllTy in the TcSigFun.
1020 Note [Signature skolems]
1021 ~~~~~~~~~~~~~~~~~~~~~~~~
1022 When instantiating a type signature, we do so with either skolems or
1023 SigTv meta-type variables depending on the use_skols boolean. This
1024 variable is set True when we are typechecking a single function
1025 binding; and False for pattern bindings and a group of several
1028 Reason: in the latter cases, the "skolems" can be unified together,
1029 so they aren't properly rigid in the type-refinement sense.
1030 NB: unless we are doing H98, each function with a sig will be done
1031 separately, even if it's mutually recursive, so use_skols will be True
1034 Note [Only scoped tyvars are in the TyVarEnv]
1035 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1036 We are careful to keep only the *lexically scoped* type variables in
1037 the type environment. Why? After all, the renamer has ensured
1038 that only legal occurrences occur, so we could put all type variables
1041 But we want to check that two distinct lexically scoped type variables
1042 do not map to the same internal type variable. So we need to know which
1043 the lexically-scoped ones are... and at the moment we do that by putting
1044 only the lexically scoped ones into the environment.
1046 Note [Instantiate sig with fresh variables]
1047 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1048 It's vital to instantiate a type signature with fresh variables.
1050 type T = forall a. [a] -> [a]
1052 f = g where { g :: T; g = <rhs> }
1054 We must not use the same 'a' from the defn of T at both places!!
1055 (Instantiation is only necessary because of type synonyms. Otherwise,
1056 it's all cool; each signature has distinct type variables from the renamer.)
1059 type SigFun = Name -> Maybe ([Name], SrcSpan)
1060 -- Maps a let-binder to the list of
1061 -- type variables brought into scope
1062 -- by its type signature, plus location
1063 -- Nothing => no type signature
1065 mkSigFun :: [LSig Name] -> SigFun
1066 -- Search for a particular type signature
1067 -- Precondition: the sigs are all type sigs
1068 -- Precondition: no duplicates
1069 mkSigFun sigs = lookupNameEnv env
1071 env = mkNameEnv (mapCatMaybes mk_pair sigs)
1072 mk_pair (L loc (TypeSig (L _ name) lhs_ty)) = Just (name, (hsExplicitTvs lhs_ty, loc))
1073 mk_pair (L loc (IdSig id)) = Just (idName id, ([], loc))
1075 -- The scoped names are the ones explicitly mentioned
1076 -- in the HsForAll. (There may be more in sigma_ty, because
1077 -- of nested type synonyms. See Note [More instantiated than scoped].)
1078 -- See Note [Only scoped tyvars are in the TyVarEnv]
1082 tcTySig :: LSig Name -> TcM TcId
1083 tcTySig (L span (TypeSig (L _ name) ty))
1085 do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
1086 ; return (mkLocalId name sigma_ty) }
1087 tcTySig (L _ (IdSig id))
1089 tcTySig s = pprPanic "tcTySig" (ppr s)
1092 tcInstSigs :: SigFun -> [Name] -> TcM TcSigFun
1093 tcInstSigs sig_fn bndrs
1094 = do { prs <- mapMaybeM (tcInstSig sig_fn use_skols) bndrs
1095 ; return (lookupNameEnv (mkNameEnv prs)) }
1097 use_skols = isSingleton bndrs -- See Note [Signature skolems]
1099 tcInstSig :: SigFun -> Bool -> Name -> TcM (Maybe (Name, TcSigInfo))
1100 -- For use_skols :: Bool see Note [Signature skolems]
1102 -- We must instantiate with fresh uniques,
1103 -- (see Note [Instantiate sig with fresh variables])
1104 -- although we keep the same print-name.
1106 tcInstSig sig_fn use_skols name
1107 | Just (scoped_tvs, loc) <- sig_fn name
1108 = do { poly_id <- tcLookupId name -- Cannot fail; the poly ids are put into
1109 -- scope when starting the binding group
1110 ; let poly_ty = idType poly_id
1111 ; (tvs, theta, tau) <- if use_skols
1112 then tcInstType tcInstSkolTyVars poly_ty
1113 else tcInstType tcInstSigTyVars poly_ty
1114 ; let sig = TcSigInfo { sig_id = poly_id
1115 , sig_scoped = scoped_tvs
1116 , sig_tvs = tvs, sig_theta = theta, sig_tau = tau
1118 ; return (Just (name, sig)) }
1122 -------------------------------
1123 data GeneralisationPlan
1124 = NoGen -- No generalisation, no AbsBinds
1125 | InferGen Bool -- Implicit generalisation; there is an AbsBinds
1126 -- True <=> apply the MR; generalise only unconstrained type vars
1127 | CheckGen TcSigInfo -- Explicit generalisation; there is an AbsBinds
1129 -- A consequence of the no-AbsBinds choice (NoGen) is that there is
1130 -- no "polymorphic Id" and "monmomorphic Id"; there is just the one
1132 instance Outputable GeneralisationPlan where
1133 ppr NoGen = ptext (sLit "NoGen")
1134 ppr (InferGen b) = ptext (sLit "InferGen") <+> ppr b
1135 ppr (CheckGen s) = ptext (sLit "CheckGen") <+> ppr s
1137 decideGeneralisationPlan
1138 :: DynFlags -> TopLevelFlag -> [Name] -> [LHsBind Name] -> TcSigFun -> GeneralisationPlan
1139 decideGeneralisationPlan dflags top_lvl _bndrs binds sig_fn
1140 | bang_pat_binds = NoGen
1141 | mono_pat_binds = NoGen
1142 | Just sig <- one_funbind_with_sig binds = if null (sig_tvs sig) && null (sig_theta sig)
1143 then NoGen -- Optimise common case
1145 | (xopt Opt_MonoLocalBinds dflags
1146 && isNotTopLevel top_lvl) = NoGen
1147 | otherwise = InferGen mono_restriction
1150 bang_pat_binds = any (isBangHsBind . unLoc) binds
1151 -- Bang patterns must not be polymorphic,
1152 -- because we are going to force them
1155 mono_pat_binds = xopt Opt_MonoPatBinds dflags
1156 && any (is_pat_bind . unLoc) binds
1158 mono_restriction = xopt Opt_MonomorphismRestriction dflags
1159 && any (restricted . unLoc) binds
1161 no_sig n = isNothing (sig_fn n)
1163 -- With OutsideIn, all nested bindings are monomorphic
1164 -- except a single function binding with a signature
1165 one_funbind_with_sig [L _ FunBind { fun_id = v }] = sig_fn (unLoc v)
1166 one_funbind_with_sig _ = Nothing
1168 -- The Haskell 98 monomorphism resetriction
1169 restricted (PatBind {}) = True
1170 restricted (VarBind { var_id = v }) = no_sig v
1171 restricted (FunBind { fun_id = v, fun_matches = m }) = restricted_match m
1173 restricted (AbsBinds {}) = panic "isRestrictedGroup/unrestricted AbsBinds"
1175 restricted_match (MatchGroup (L _ (Match [] _ _) : _) _) = True
1176 restricted_match _ = False
1177 -- No args => like a pattern binding
1178 -- Some args => a function binding
1180 is_pat_bind (PatBind {}) = True
1181 is_pat_bind _ = False
1184 checkStrictBinds :: TopLevelFlag -> RecFlag
1185 -> [LHsBind Name] -> [Id]
1187 -- Check that non-overloaded unlifted bindings are
1188 -- a) non-recursive,
1189 -- b) not top level,
1190 -- c) not a multiple-binding group (more or less implied by (a))
1192 checkStrictBinds top_lvl rec_group binds poly_ids
1193 | unlifted || bang_pat
1194 = do { checkTc (isNotTopLevel top_lvl)
1195 (strictBindErr "Top-level" unlifted binds)
1196 ; checkTc (isNonRec rec_group)
1197 (strictBindErr "Recursive" unlifted binds)
1198 ; checkTc (isSingleton binds)
1199 (strictBindErr "Multiple" unlifted binds)
1200 -- This should be a checkTc, not a warnTc, but as of GHC 6.11
1201 -- the versions of alex and happy available have non-conforming
1202 -- templates, so the GHC build fails if it's an error:
1203 ; warnUnlifted <- doptM Opt_WarnLazyUnliftedBindings
1204 ; warnTc (warnUnlifted && not bang_pat && lifted_pat)
1205 -- No outer bang, but it's a compound pattern
1206 -- E.g (I# x#) = blah
1207 -- Warn about this, but not about
1210 (unliftedMustBeBang binds) }
1214 unlifted = any is_unlifted poly_ids
1215 bang_pat = any (isBangHsBind . unLoc) binds
1216 lifted_pat = any (isLiftedPatBind . unLoc) binds
1217 is_unlifted id = case tcSplitForAllTys (idType id) of
1218 (_, rho) -> isUnLiftedType rho
1220 unliftedMustBeBang :: [LHsBind Name] -> SDoc
1221 unliftedMustBeBang binds
1222 = hang (text "Pattern bindings containing unlifted types should use an outermost bang pattern:")
1223 2 (pprBindList binds)
1225 strictBindErr :: String -> Bool -> [LHsBind Name] -> SDoc
1226 strictBindErr flavour unlifted binds
1227 = hang (text flavour <+> msg <+> ptext (sLit "aren't allowed:"))
1228 2 (pprBindList binds)
1230 msg | unlifted = ptext (sLit "bindings for unlifted types")
1231 | otherwise = ptext (sLit "bang-pattern bindings")
1233 pprBindList :: [LHsBind Name] -> SDoc
1234 pprBindList binds = vcat (map ppr binds)
1238 %************************************************************************
1240 \subsection[TcBinds-errors]{Error contexts and messages}
1242 %************************************************************************
1246 -- This one is called on LHS, when pat and grhss are both Name
1247 -- and on RHS, when pat is TcId and grhss is still Name
1248 patMonoBindsCtxt :: OutputableBndr id => LPat id -> GRHSs Name -> SDoc
1249 patMonoBindsCtxt pat grhss
1250 = hang (ptext (sLit "In a pattern binding:")) 2 (pprPatBind pat grhss)
1252 -----------------------------------------------
1253 sigContextsCtxt :: TcSigInfo -> TcSigInfo -> SDoc
1254 sigContextsCtxt sig1 sig2
1255 = vcat [ptext (sLit "When matching the contexts of the signatures for"),
1256 nest 2 (vcat [ppr id1 <+> dcolon <+> ppr (idType id1),
1257 ppr id2 <+> dcolon <+> ppr (idType id2)]),
1258 ptext (sLit "The signature contexts in a mutually recursive group should all be identical")]