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 )
28 import RnBinds( misplacedSigErr )
47 import Data.List( partition )
50 #include "HsVersions.h"
54 %************************************************************************
56 \subsection{Type-checking bindings}
58 %************************************************************************
60 @tcBindsAndThen@ typechecks a @HsBinds@. The "and then" part is because
61 it needs to know something about the {\em usage} of the things bound,
62 so that it can create specialisations of them. So @tcBindsAndThen@
63 takes a function which, given an extended environment, E, typechecks
64 the scope of the bindings returning a typechecked thing and (most
65 important) an LIE. It is this LIE which is then used as the basis for
66 specialising the things bound.
68 @tcBindsAndThen@ also takes a "combiner" which glues together the
69 bindings and the "thing" to make a new "thing".
71 The real work is done by @tcBindWithSigsAndThen@.
73 Recursive and non-recursive binds are handled in essentially the same
74 way: because of uniques there are no scoping issues left. The only
75 difference is that non-recursive bindings can bind primitive values.
77 Even for non-recursive binding groups we add typings for each binder
78 to the LVE for the following reason. When each individual binding is
79 checked the type of its LHS is unified with that of its RHS; and
80 type-checking the LHS of course requires that the binder is in scope.
82 At the top-level the LIE is sure to contain nothing but constant
83 dictionaries, which we resolve at the module level.
86 tcTopBinds :: HsValBinds Name
87 -> TcM ( LHsBinds TcId -- Typechecked bindings
88 , [LTcSpecPrag] -- SPECIALISE prags for imported Ids
89 , TcLclEnv) -- Augmented environment
91 -- Note: returning the TcLclEnv is more than we really
92 -- want. The bit we care about is the local bindings
93 -- and the free type variables thereof
95 = do { (ValBindsOut prs sigs, env) <- tcValBinds TopLevel binds getLclEnv
96 ; let binds = foldr (unionBags . snd) emptyBag prs
97 ; specs <- tcImpPrags sigs
98 ; return (binds, specs, env) }
99 -- The top level bindings are flattened into a giant
100 -- implicitly-mutually-recursive LHsBinds
102 tcHsBootSigs :: HsValBinds Name -> TcM [Id]
103 -- A hs-boot file has only one BindGroup, and it only has type
104 -- signatures in it. The renamer checked all this
105 tcHsBootSigs (ValBindsOut binds sigs)
106 = do { checkTc (null binds) badBootDeclErr
107 ; mapM (addLocM tc_boot_sig) (filter isTypeLSig sigs) }
109 tc_boot_sig (TypeSig (L _ name) ty)
110 = do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
111 ; return (mkVanillaGlobal name sigma_ty) }
112 -- Notice that we make GlobalIds, not LocalIds
113 tc_boot_sig s = pprPanic "tcHsBootSigs/tc_boot_sig" (ppr s)
114 tcHsBootSigs groups = pprPanic "tcHsBootSigs" (ppr groups)
116 badBootDeclErr :: Message
117 badBootDeclErr = ptext (sLit "Illegal declarations in an hs-boot file")
119 ------------------------
120 tcLocalBinds :: HsLocalBinds Name -> TcM thing
121 -> TcM (HsLocalBinds TcId, thing)
123 tcLocalBinds EmptyLocalBinds thing_inside
124 = do { thing <- thing_inside
125 ; return (EmptyLocalBinds, thing) }
127 tcLocalBinds (HsValBinds binds) thing_inside
128 = do { (binds', thing) <- tcValBinds NotTopLevel binds thing_inside
129 ; return (HsValBinds binds', thing) }
131 tcLocalBinds (HsIPBinds (IPBinds ip_binds _)) thing_inside
132 = do { (given_ips, ip_binds') <- mapAndUnzipM (wrapLocSndM tc_ip_bind) ip_binds
134 -- If the binding binds ?x = E, we must now
135 -- discharge any ?x constraints in expr_lie
136 -- See Note [Implicit parameter untouchables]
137 ; (ev_binds, result) <- checkConstraints (IPSkol ips)
138 [] given_ips thing_inside
140 ; return (HsIPBinds (IPBinds ip_binds' ev_binds), result) }
142 ips = [ip | L _ (IPBind ip _) <- ip_binds]
144 -- I wonder if we should do these one at at time
147 tc_ip_bind (IPBind ip expr)
148 = do { ty <- newFlexiTyVarTy argTypeKind
149 ; ip_id <- newIP ip ty
150 ; expr' <- tcMonoExpr expr ty
151 ; return (ip_id, (IPBind (IPName ip_id) expr')) }
154 Note [Implicit parameter untouchables]
155 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
156 We add the type variables in the types of the implicit parameters
157 as untouchables, not so much because we really must not unify them,
158 but rather because we otherwise end up with constraints like this
159 Num alpha, Implic { wanted = alpha ~ Int }
160 The constraint solver solves alpha~Int by unification, but then
161 doesn't float that solved constraint out (it's not an unsolved
162 wanted. Result disaster: the (Num alpha) is again solved, this
163 time by defaulting. No no no.
165 However [Oct 10] this is all handled automatically by the
166 untouchable-range idea.
169 tcValBinds :: TopLevelFlag
170 -> HsValBinds Name -> TcM thing
171 -> TcM (HsValBinds TcId, thing)
173 tcValBinds _ (ValBindsIn binds _) _
174 = pprPanic "tcValBinds" (ppr binds)
176 tcValBinds top_lvl (ValBindsOut binds sigs) thing_inside
177 = do { -- Typecheck the signature
178 ; let { prag_fn = mkPragFun sigs (foldr (unionBags . snd) emptyBag binds)
179 ; ty_sigs = filter isTypeLSig sigs
180 ; sig_fn = mkSigFun ty_sigs }
182 ; poly_ids <- checkNoErrs (mapAndRecoverM tcTySig ty_sigs)
183 -- No recovery from bad signatures, because the type sigs
184 -- may bind type variables, so proceeding without them
185 -- can lead to a cascade of errors
186 -- ToDo: this means we fall over immediately if any type sig
187 -- is wrong, which is over-conservative, see Trac bug #745
189 -- Extend the envt right away with all
190 -- the Ids declared with type signatures
191 ; (binds', thing) <- tcExtendIdEnv poly_ids $
192 tcBindGroups top_lvl sig_fn prag_fn
195 ; return (ValBindsOut binds' sigs, thing) }
197 ------------------------
198 tcBindGroups :: TopLevelFlag -> SigFun -> PragFun
199 -> [(RecFlag, LHsBinds Name)] -> TcM thing
200 -> TcM ([(RecFlag, LHsBinds TcId)], thing)
201 -- Typecheck a whole lot of value bindings,
202 -- one strongly-connected component at a time
203 -- Here a "strongly connected component" has the strightforward
204 -- meaning of a group of bindings that mention each other,
205 -- ignoring type signatures (that part comes later)
207 tcBindGroups _ _ _ [] thing_inside
208 = do { thing <- thing_inside
209 ; return ([], thing) }
211 tcBindGroups top_lvl sig_fn prag_fn (group : groups) thing_inside
212 = do { (group', (groups', thing))
213 <- tc_group top_lvl sig_fn prag_fn group $
214 tcBindGroups top_lvl sig_fn prag_fn groups thing_inside
215 ; return (group' ++ groups', thing) }
217 ------------------------
218 tc_group :: forall thing.
219 TopLevelFlag -> SigFun -> PragFun
220 -> (RecFlag, LHsBinds Name) -> TcM thing
221 -> TcM ([(RecFlag, LHsBinds TcId)], thing)
223 -- Typecheck one strongly-connected component of the original program.
224 -- We get a list of groups back, because there may
225 -- be specialisations etc as well
227 tc_group top_lvl sig_fn prag_fn (NonRecursive, binds) thing_inside
228 -- A single non-recursive binding
229 -- We want to keep non-recursive things non-recursive
230 -- so that we desugar unlifted bindings correctly
231 = do { (binds1, ids) <- tcPolyBinds top_lvl sig_fn prag_fn NonRecursive NonRecursive
233 ; thing <- tcExtendIdEnv ids thing_inside
234 ; return ( [(NonRecursive, binds1)], thing) }
236 tc_group top_lvl sig_fn prag_fn (Recursive, binds) thing_inside
237 = -- To maximise polymorphism (assumes -XRelaxedPolyRec), we do a new
238 -- strongly-connected-component analysis, this time omitting
239 -- any references to variables with type signatures.
240 do { traceTc "tc_group rec" (pprLHsBinds binds)
241 ; (binds1, _ids, thing) <- go sccs
242 -- Here is where we should do bindInstsOfLocalFuns
243 -- if we start having Methods again
244 ; return ([(Recursive, binds1)], thing) }
245 -- Rec them all together
247 sccs :: [SCC (LHsBind Name)]
248 sccs = stronglyConnCompFromEdgedVertices (mkEdges sig_fn binds)
250 go :: [SCC (LHsBind Name)] -> TcM (LHsBinds TcId, [TcId], thing)
251 go (scc:sccs) = do { (binds1, ids1) <- tc_scc scc
252 ; (binds2, ids2, thing) <- tcExtendIdEnv ids1 $ go sccs
253 ; return (binds1 `unionBags` binds2, ids1 ++ ids2, thing) }
254 go [] = do { thing <- thing_inside; return (emptyBag, [], thing) }
256 tc_scc (AcyclicSCC bind) = tc_sub_group NonRecursive [bind]
257 tc_scc (CyclicSCC binds) = tc_sub_group Recursive binds
259 tc_sub_group = tcPolyBinds top_lvl sig_fn prag_fn Recursive
262 ------------------------
264 bindLocalInsts :: TopLevelFlag
265 -> TcM (LHsBinds TcId, [TcId], a)
266 -> TcM (LHsBinds TcId, TcEvBinds, a)
267 bindLocalInsts top_lvl thing_inside
269 = do { (binds, _, thing) <- thing_inside; return (binds, emptyBag, thing) }
270 -- For the top level don't bother with all this bindInstsOfLocalFuns stuff.
271 -- All the top level things are rec'd together anyway, so it's fine to
272 -- leave them to the tcSimplifyTop, and quite a bit faster too
274 | otherwise -- Nested case
275 = do { ((binds, ids, thing), lie) <- captureConstraints thing_inside
276 ; lie_binds <- bindLocalMethods lie ids
277 ; return (binds, lie_binds, thing) }
280 ------------------------
281 mkEdges :: SigFun -> LHsBinds Name
282 -> [(LHsBind Name, BKey, [BKey])]
284 type BKey = Int -- Just number off the bindings
287 = [ (bind, key, [key | n <- nameSetToList (bind_fvs (unLoc bind)),
288 Just key <- [lookupNameEnv key_map n], no_sig n ])
289 | (bind, key) <- keyd_binds
292 no_sig :: Name -> Bool
293 no_sig n = isNothing (sig_fn n)
295 keyd_binds = bagToList binds `zip` [0::BKey ..]
297 key_map :: NameEnv BKey -- Which binding it comes from
298 key_map = mkNameEnv [(bndr, key) | (L _ bind, key) <- keyd_binds
299 , bndr <- bindersOfHsBind bind ]
301 bindersOfHsBind :: HsBind Name -> [Name]
302 bindersOfHsBind (PatBind { pat_lhs = pat }) = collectPatBinders pat
303 bindersOfHsBind (FunBind { fun_id = L _ f }) = [f]
304 bindersOfHsBind (AbsBinds {}) = panic "bindersOfHsBind AbsBinds"
305 bindersOfHsBind (VarBind {}) = panic "bindersOfHsBind VarBind"
307 ------------------------
308 tcPolyBinds :: TopLevelFlag -> SigFun -> PragFun
309 -> RecFlag -- Whether the group is really recursive
310 -> RecFlag -- Whether it's recursive after breaking
311 -- dependencies based on type signatures
313 -> TcM (LHsBinds TcId, [TcId])
315 -- Typechecks a single bunch of bindings all together,
316 -- and generalises them. The bunch may be only part of a recursive
317 -- group, because we use type signatures to maximise polymorphism
319 -- Returns a list because the input may be a single non-recursive binding,
320 -- in which case the dependency order of the resulting bindings is
323 -- Knows nothing about the scope of the bindings
325 tcPolyBinds top_lvl sig_fn prag_fn rec_group rec_tc bind_list
327 recoverM (recoveryCode binder_names sig_fn) $ do
328 -- Set up main recover; take advantage of any type sigs
330 { traceTc "------------------------------------------------" empty
331 ; traceTc "Bindings for" (ppr binder_names)
333 -- Instantiate the polytypes of any binders that have signatures
334 -- (as determined by sig_fn), returning a TcSigInfo for each
335 ; tc_sig_fn <- tcInstSigs sig_fn binder_names
338 ; let plan = decideGeneralisationPlan dflags top_lvl binder_names bind_list tc_sig_fn
339 ; traceTc "Generalisation plan" (ppr plan)
340 ; (binds, poly_ids) <- case plan of
341 NoGen -> tcPolyNoGen tc_sig_fn prag_fn rec_tc bind_list
342 InferGen mono -> tcPolyInfer top_lvl mono tc_sig_fn prag_fn rec_tc bind_list
343 CheckGen sig -> tcPolyCheck sig prag_fn rec_tc bind_list
345 -- Check whether strict bindings are ok
346 -- These must be non-recursive etc, and are not generalised
347 -- They desugar to a case expression in the end
348 ; checkStrictBinds top_lvl rec_group bind_list poly_ids
350 ; return (binds, poly_ids) }
352 binder_names = collectHsBindListBinders bind_list
353 loc = foldr1 combineSrcSpans (map getLoc bind_list)
354 -- The mbinds have been dependency analysed and
355 -- may no longer be adjacent; so find the narrowest
356 -- span that includes them all
360 :: TcSigFun -> PragFun
361 -> RecFlag -- Whether it's recursive after breaking
362 -- dependencies based on type signatures
364 -> TcM (LHsBinds TcId, [TcId])
365 -- No generalisation whatsoever
367 tcPolyNoGen tc_sig_fn prag_fn rec_tc bind_list
368 = do { (binds', mono_infos) <- tcMonoBinds tc_sig_fn (LetGblBndr prag_fn)
370 ; mono_ids' <- mapM tc_mono_info mono_infos
371 ; return (binds', mono_ids') }
373 tc_mono_info (name, _, mono_id)
374 = do { mono_ty' <- zonkTcTypeCarefully (idType mono_id)
375 -- Zonk, mainly to expose unboxed types to checkStrictBinds
376 ; let mono_id' = setIdType mono_id mono_ty'
377 ; _specs <- tcSpecPrags mono_id' (prag_fn name)
379 -- NB: tcPrags generates error messages for
380 -- specialisation pragmas for non-overloaded sigs
381 -- Indeed that is why we call it here!
382 -- So we can safely ignore _specs
385 tcPolyCheck :: TcSigInfo -> PragFun
386 -> RecFlag -- Whether it's recursive after breaking
387 -- dependencies based on type signatures
389 -> TcM (LHsBinds TcId, [TcId])
390 -- There is just one binding,
391 -- it binds a single variable,
392 -- it has a signature,
393 tcPolyCheck sig@(TcSigInfo { sig_id = id, sig_tvs = tvs, sig_scoped = scoped
394 , sig_theta = theta, sig_tau = tau })
395 prag_fn rec_tc bind_list
396 = do { ev_vars <- newEvVars theta
397 ; let skol_info = SigSkol (FunSigCtxt (idName id)) (mkPhiTy theta tau)
398 ; (ev_binds, (binds', [mono_info]))
399 <- checkConstraints skol_info tvs ev_vars $
400 tcExtendTyVarEnv2 (scoped `zip` mkTyVarTys tvs) $
401 tcMonoBinds (\_ -> Just sig) LetLclBndr rec_tc bind_list
403 ; export <- mkExport prag_fn tvs theta mono_info
406 ; let (_, poly_id, _, _) = export
407 abs_bind = L loc $ AbsBinds
409 , abs_ev_vars = ev_vars, abs_ev_binds = ev_binds
410 , abs_exports = [export], abs_binds = binds' }
411 ; return (unitBag abs_bind, [poly_id]) }
416 -> Bool -- True <=> apply the monomorphism restriction
417 -> TcSigFun -> PragFun
418 -> RecFlag -- Whether it's recursive after breaking
419 -- dependencies based on type signatures
421 -> TcM (LHsBinds TcId, [TcId])
422 tcPolyInfer top_lvl mono tc_sig_fn prag_fn rec_tc bind_list
423 = do { ((binds', mono_infos), wanted)
424 <- captureConstraints $
425 tcMonoBinds tc_sig_fn LetLclBndr rec_tc bind_list
427 ; unifyCtxts [sig | (_, Just sig, _) <- mono_infos]
429 ; let name_taus = [(name, idType mono_id) | (name, _, mono_id) <- mono_infos]
430 ; (qtvs, givens, ev_binds) <- simplifyInfer top_lvl mono name_taus wanted
432 ; exports <- mapM (mkExport 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
448 mkExport :: PragFun -> [TyVar] -> TcThetaType
450 -> TcM ([TyVar], Id, Id, TcSpecPrags)
451 -- mkExport generates exports with
452 -- zonked type variables,
454 -- The former is just because no further unifications will change
455 -- the quantified type variables, so we can fix their final form
457 -- The latter is needed because the poly_ids are used to extend the
458 -- type environment; see the invariant on TcEnv.tcExtendIdEnv
460 -- Pre-condition: the inferred_tvs are already zonked
462 mkExport prag_fn inferred_tvs theta
463 (poly_name, mb_sig, mono_id)
464 = do { (tvs, poly_id) <- mk_poly_id mb_sig
465 -- poly_id has a zonked type
467 ; poly_id' <- addInlinePrags poly_id prag_sigs
469 ; spec_prags <- tcSpecPrags poly_id prag_sigs
470 -- tcPrags requires a zonked poly_id
472 ; return (tvs, poly_id', mono_id, SpecPrags spec_prags) }
474 prag_sigs = prag_fn poly_name
475 poly_ty = mkSigmaTy inferred_tvs theta (idType mono_id)
477 mk_poly_id Nothing = do { poly_ty' <- zonkTcTypeCarefully poly_ty
478 ; return (inferred_tvs, mkLocalId poly_name poly_ty') }
479 mk_poly_id (Just sig) = do { tvs <- mapM zonk_tv (sig_tvs sig)
480 ; return (tvs, sig_id sig) }
482 zonk_tv tv = do { ty <- zonkTcTyVar tv; return (tcGetTyVar "mkExport" ty) }
484 ------------------------
485 type PragFun = Name -> [LSig Name]
487 mkPragFun :: [LSig Name] -> LHsBinds Name -> PragFun
488 mkPragFun sigs binds = \n -> lookupNameEnv prag_env n `orElse` []
490 prs = mapCatMaybes get_sig sigs
492 get_sig :: LSig Name -> Maybe (Located Name, LSig Name)
493 get_sig (L l (SpecSig nm ty inl)) = Just (nm, L l $ SpecSig nm ty (add_arity nm inl))
494 get_sig (L l (InlineSig nm inl)) = Just (nm, L l $ InlineSig nm (add_arity nm inl))
497 add_arity (L _ n) inl_prag -- Adjust inl_sat field to match visible arity of function
498 | Just ar <- lookupNameEnv ar_env n,
499 Inline <- inl_inline inl_prag = inl_prag { inl_sat = Just ar }
500 -- add arity only for real INLINE pragmas, not INLINABLE
501 | otherwise = inl_prag
503 prag_env :: NameEnv [LSig Name]
504 prag_env = foldl add emptyNameEnv prs
505 add env (L _ n,p) = extendNameEnv_Acc (:) singleton env n p
507 -- ar_env maps a local to the arity of its definition
508 ar_env :: NameEnv Arity
509 ar_env = foldrBag lhsBindArity emptyNameEnv binds
511 lhsBindArity :: LHsBind Name -> NameEnv Arity -> NameEnv Arity
512 lhsBindArity (L _ (FunBind { fun_id = id, fun_matches = ms })) env
513 = extendNameEnv env (unLoc id) (matchGroupArity ms)
514 lhsBindArity _ env = env -- PatBind/VarBind
517 tcSpecPrags :: Id -> [LSig Name]
519 -- Add INLINE and SPECIALSE pragmas
520 -- INLINE prags are added to the (polymorphic) Id directly
521 -- SPECIALISE prags are passed to the desugarer via TcSpecPrags
522 -- Pre-condition: the poly_id is zonked
523 -- Reason: required by tcSubExp
524 tcSpecPrags poly_id prag_sigs
525 = do { unless (null bad_sigs) warn_discarded_sigs
526 ; mapAndRecoverM (wrapLocM (tcSpec poly_id)) spec_sigs }
528 spec_sigs = filter isSpecLSig prag_sigs
529 bad_sigs = filter is_bad_sig prag_sigs
530 is_bad_sig s = not (isSpecLSig s || isInlineLSig s)
532 warn_discarded_sigs = warnPrags poly_id bad_sigs $
533 ptext (sLit "Discarding unexpected pragmas for")
537 tcSpec :: TcId -> Sig Name -> TcM TcSpecPrag
538 tcSpec poly_id prag@(SpecSig _ hs_ty inl)
539 -- The Name in the SpecSig may not be the same as that of the poly_id
540 -- Example: SPECIALISE for a class method: the Name in the SpecSig is
541 -- for the selector Id, but the poly_id is something like $cop
542 = addErrCtxt (spec_ctxt prag) $
543 do { spec_ty <- tcHsSigType sig_ctxt hs_ty
544 ; warnIf (not (isOverloadedTy poly_ty || isInlinePragma inl))
545 (ptext (sLit "SPECIALISE pragma for non-overloaded function") <+> quotes (ppr poly_id))
546 -- Note [SPECIALISE pragmas]
547 ; wrap <- tcSubType origin sig_ctxt (idType poly_id) spec_ty
548 ; return (SpecPrag poly_id wrap inl) }
550 name = idName poly_id
551 poly_ty = idType poly_id
552 origin = SpecPragOrigin name
553 sig_ctxt = FunSigCtxt name
554 spec_ctxt prag = hang (ptext (sLit "In the SPECIALISE pragma")) 2 (ppr prag)
556 tcSpec _ prag = pprPanic "tcSpec" (ppr prag)
559 tcImpPrags :: [LSig Name] -> TcM [LTcSpecPrag]
561 = do { this_mod <- getModule
563 = case sigName prag of
565 Just name -> not (nameIsLocalOrFrom this_mod name)
566 (spec_prags, others) = partition isSpecLSig $
568 ; mapM_ misplacedSigErr others
569 -- Messy that this misplaced-sig error comes here
570 -- but the others come from the renamer
571 ; mapAndRecoverM (wrapLocM tcImpSpec) spec_prags }
573 tcImpSpec :: Sig Name -> TcM TcSpecPrag
574 tcImpSpec prag@(SpecSig (L _ name) _ _)
575 = do { id <- tcLookupId name
576 ; checkTc (isAnyInlinePragma (idInlinePragma id))
579 tcImpSpec p = pprPanic "tcImpSpec" (ppr p)
581 impSpecErr :: Name -> SDoc
583 = hang (ptext (sLit "You cannot SPECIALISE") <+> quotes (ppr name))
584 2 (vcat [ ptext (sLit "because its definition has no INLINE/INLINABLE pragma")
585 , ptext (sLit "(or you compiled its defining module without -O)")])
588 tcVectDecls :: [LVectDecl Name] -> TcM [LVectDecl TcId]
590 = do { decls' <- mapM (wrapLocM tcVect) decls
591 ; let ids = [unLoc id | L _ (HsVect id _) <- decls']
592 dups = findDupsEq (==) ids
593 ; mapM_ reportVectDups dups
597 reportVectDups (first:_second:_more)
598 = addErrAt (getSrcSpan first) $
599 ptext (sLit "Duplicate vectorisation declarations for") <+> ppr first
600 reportVectDups _ = return ()
603 tcVect :: VectDecl Name -> TcM (VectDecl TcId)
604 -- We can't typecheck the expression of a vectorisation declaration against the vectorised type
605 -- of the original definition as this requires internals of the vectoriser not available during
606 -- type checking. Instead, we infer the type of the expression and leave it to the vectoriser
607 -- to check the compatibility of the Core types.
608 tcVect (HsVect name Nothing)
609 = addErrCtxt (vectCtxt name) $
610 do { id <- wrapLocM tcLookupId name
611 ; return (HsVect id Nothing)
613 tcVect (HsVect name@(L loc _) (Just rhs))
614 = addErrCtxt (vectCtxt name) $
615 do { _id <- wrapLocM tcLookupId name -- need to ensure that the name is already defined
617 -- turn the vectorisation declaration into a single non-recursive binding
618 ; let bind = L loc $ mkFunBind name [mkSimpleMatch [] rhs]
619 sigFun = const Nothing
620 pragFun = mkPragFun [] (unitBag bind)
622 -- perform type inference (including generalisation)
623 ; (binds, [id']) <- tcPolyInfer TopLevel False sigFun pragFun NonRecursive [bind]
625 ; traceTc "tcVect inferred type" $ ppr (varType id')
627 -- add the type variable and dictionary bindings produced by type generalisation to the
628 -- right-hand side of the vectorisation declaration
629 ; let [AbsBinds tvs evs _ evBinds actualBinds] = (map unLoc . bagToList) binds
630 ; let [bind'] = bagToList actualBinds
632 [L _ (Match _ _ (GRHSs [L _ (GRHS _ rhs')] _))]
633 _ = (fun_matches . unLoc) bind'
634 rhsWrapped = mkHsLams tvs evs (mkHsDictLet evBinds rhs')
636 -- We return the type-checked 'Id', to propagate the inferred signature
637 -- to the vectoriser - see "Note [Typechecked vectorisation pragmas]" in HsDecls
638 ; return $ HsVect (L loc id') (Just rhsWrapped)
641 vectCtxt :: Located Name -> SDoc
642 vectCtxt name = ptext (sLit "When checking the vectorisation declaration for") <+> ppr name
645 -- If typechecking the binds fails, then return with each
646 -- signature-less binder given type (forall a.a), to minimise
647 -- subsequent error messages
648 recoveryCode :: [Name] -> SigFun -> TcM (LHsBinds TcId, [Id])
649 recoveryCode binder_names sig_fn
650 = do { traceTc "tcBindsWithSigs: error recovery" (ppr binder_names)
651 ; poly_ids <- mapM mk_dummy binder_names
652 ; return (emptyBag, poly_ids) }
655 | isJust (sig_fn name) = tcLookupId name -- Had signature; look it up
656 | otherwise = return (mkLocalId name forall_a_a) -- No signature
659 forall_a_a = mkForAllTy openAlphaTyVar (mkTyVarTy openAlphaTyVar)
662 Note [SPECIALISE pragmas]
663 ~~~~~~~~~~~~~~~~~~~~~~~~~
664 There is no point in a SPECIALISE pragma for a non-overloaded function:
665 reverse :: [a] -> [a]
666 {-# SPECIALISE reverse :: [Int] -> [Int] #-}
668 But SPECIALISE INLINE *can* make sense for GADTS:
670 ArrInt :: !Int -> ByteArray# -> Arr Int
671 ArrPair :: !Int -> Arr e1 -> Arr e2 -> Arr (e1, e2)
673 (!:) :: Arr e -> Int -> e
674 {-# SPECIALISE INLINE (!:) :: Arr Int -> Int -> Int #-}
675 {-# SPECIALISE INLINE (!:) :: Arr (a, b) -> Int -> (a, b) #-}
676 (ArrInt _ ba) !: (I# i) = I# (indexIntArray# ba i)
677 (ArrPair _ a1 a2) !: i = (a1 !: i, a2 !: i)
679 When (!:) is specialised it becomes non-recursive, and can usefully
680 be inlined. Scary! So we only warn for SPECIALISE *without* INLINE
681 for a non-overloaded function.
683 %************************************************************************
685 \subsection{tcMonoBind}
687 %************************************************************************
689 @tcMonoBinds@ deals with a perhaps-recursive group of HsBinds.
690 The signatures have been dealt with already.
693 tcMonoBinds :: TcSigFun -> LetBndrSpec
694 -> RecFlag -- Whether the binding is recursive for typechecking purposes
695 -- i.e. the binders are mentioned in their RHSs, and
696 -- we are not resuced by a type signature
698 -> TcM (LHsBinds TcId, [MonoBindInfo])
700 tcMonoBinds sig_fn no_gen is_rec
701 [ L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf,
702 fun_matches = matches, bind_fvs = fvs })]
703 -- Single function binding,
704 | NonRecursive <- is_rec -- ...binder isn't mentioned in RHS
705 , Nothing <- sig_fn name -- ...with no type signature
706 = -- In this very special case we infer the type of the
707 -- right hand side first (it may have a higher-rank type)
708 -- and *then* make the monomorphic Id for the LHS
709 -- e.g. f = \(x::forall a. a->a) -> <body>
710 -- We want to infer a higher-rank type for f
712 do { ((co_fn, matches'), rhs_ty) <- tcInfer (tcMatchesFun name inf matches)
714 ; mono_id <- newNoSigLetBndr no_gen name rhs_ty
715 ; return (unitBag (L b_loc (FunBind { fun_id = L nm_loc mono_id, fun_infix = inf,
716 fun_matches = matches', bind_fvs = fvs,
717 fun_co_fn = co_fn, fun_tick = Nothing })),
718 [(name, Nothing, mono_id)]) }
720 tcMonoBinds sig_fn no_gen _ binds
721 = do { tc_binds <- mapM (wrapLocM (tcLhs sig_fn no_gen)) binds
723 -- Bring the monomorphic Ids, into scope for the RHSs
724 ; let mono_info = getMonoBindInfo tc_binds
725 rhs_id_env = [(name,mono_id) | (name, Nothing, mono_id) <- mono_info]
726 -- A monomorphic binding for each term variable that lacks
727 -- a type sig. (Ones with a sig are already in scope.)
729 ; binds' <- tcExtendIdEnv2 rhs_id_env $ do
730 traceTc "tcMonoBinds" $ vcat [ ppr n <+> ppr id <+> ppr (idType id)
731 | (n,id) <- rhs_id_env]
732 mapM (wrapLocM tcRhs) tc_binds
733 ; return (listToBag binds', mono_info) }
735 ------------------------
736 -- tcLhs typechecks the LHS of the bindings, to construct the environment in which
737 -- we typecheck the RHSs. Basically what we are doing is this: for each binder:
738 -- if there's a signature for it, use the instantiated signature type
739 -- otherwise invent a type variable
740 -- You see that quite directly in the FunBind case.
742 -- But there's a complication for pattern bindings:
743 -- data T = MkT (forall a. a->a)
745 -- Here we can guess a type variable for the entire LHS (which will be refined to T)
746 -- but we want to get (f::forall a. a->a) as the RHS environment.
747 -- The simplest way to do this is to typecheck the pattern, and then look up the
748 -- bound mono-ids. Then we want to retain the typechecked pattern to avoid re-doing
749 -- it; hence the TcMonoBind data type in which the LHS is done but the RHS isn't
751 data TcMonoBind -- Half completed; LHS done, RHS not done
752 = TcFunBind MonoBindInfo SrcSpan Bool (MatchGroup Name)
753 | TcPatBind [MonoBindInfo] (LPat TcId) (GRHSs Name) TcSigmaType
755 type MonoBindInfo = (Name, Maybe TcSigInfo, TcId)
756 -- Type signature (if any), and
757 -- the monomorphic bound things
759 tcLhs :: TcSigFun -> LetBndrSpec -> HsBind Name -> TcM TcMonoBind
760 tcLhs sig_fn no_gen (FunBind { fun_id = L nm_loc name, fun_infix = inf, fun_matches = matches })
761 | Just sig <- sig_fn name
762 = do { mono_id <- newSigLetBndr no_gen name sig
763 ; return (TcFunBind (name, Just sig, mono_id) nm_loc inf matches) }
765 = do { mono_ty <- newFlexiTyVarTy argTypeKind
766 ; mono_id <- newNoSigLetBndr no_gen name mono_ty
767 ; return (TcFunBind (name, Nothing, mono_id) nm_loc inf matches) }
769 tcLhs sig_fn no_gen (PatBind { pat_lhs = pat, pat_rhs = grhss })
770 = do { let tc_pat exp_ty = tcLetPat sig_fn no_gen pat exp_ty $
771 mapM lookup_info (collectPatBinders pat)
773 -- After typechecking the pattern, look up the binder
774 -- names, which the pattern has brought into scope.
775 lookup_info :: Name -> TcM MonoBindInfo
776 lookup_info name = do { mono_id <- tcLookupId name
777 ; return (name, sig_fn name, mono_id) }
779 ; ((pat', infos), pat_ty) <- addErrCtxt (patMonoBindsCtxt pat grhss) $
782 ; return (TcPatBind infos pat' grhss pat_ty) }
784 tcLhs _ _ other_bind = pprPanic "tcLhs" (ppr other_bind)
785 -- AbsBind, VarBind impossible
788 tcRhs :: TcMonoBind -> TcM (HsBind TcId)
789 -- When we are doing pattern bindings, or multiple function bindings at a time
790 -- we *don't* bring any scoped type variables into scope
791 -- Wny not? They are not completely rigid.
792 -- That's why we have the special case for a single FunBind in tcMonoBinds
793 tcRhs (TcFunBind (_,_,mono_id) loc inf matches)
794 = do { (co_fn, matches') <- tcMatchesFun (idName mono_id) inf
795 matches (idType mono_id)
796 ; return (FunBind { fun_id = L loc mono_id, fun_infix = inf
797 , fun_matches = matches'
799 , bind_fvs = placeHolderNames, fun_tick = Nothing }) }
801 tcRhs (TcPatBind _ pat' grhss pat_ty)
802 = do { grhss' <- addErrCtxt (patMonoBindsCtxt pat' grhss) $
803 tcGRHSsPat grhss pat_ty
804 ; return (PatBind { pat_lhs = pat', pat_rhs = grhss', pat_rhs_ty = pat_ty
805 , bind_fvs = placeHolderNames }) }
808 ---------------------
809 getMonoBindInfo :: [Located TcMonoBind] -> [MonoBindInfo]
810 getMonoBindInfo tc_binds
811 = foldr (get_info . unLoc) [] tc_binds
813 get_info (TcFunBind info _ _ _) rest = info : rest
814 get_info (TcPatBind infos _ _ _) rest = infos ++ rest
818 %************************************************************************
822 %************************************************************************
824 unifyCtxts checks that all the signature contexts are the same
825 The type signatures on a mutually-recursive group of definitions
826 must all have the same context (or none).
828 The trick here is that all the signatures should have the same
829 context, and we want to share type variables for that context, so that
830 all the right hand sides agree a common vocabulary for their type
833 We unify them because, with polymorphic recursion, their types
834 might not otherwise be related. This is a rather subtle issue.
837 unifyCtxts :: [TcSigInfo] -> TcM ()
838 -- Post-condition: the returned Insts are full zonked
839 unifyCtxts [] = return ()
840 unifyCtxts (sig1 : sigs)
841 = do { traceTc "unifyCtxts" (ppr (sig1 : sigs))
842 ; mapM_ unify_ctxt sigs }
844 theta1 = sig_theta sig1
845 unify_ctxt :: TcSigInfo -> TcM ()
846 unify_ctxt sig@(TcSigInfo { sig_theta = theta })
847 = setSrcSpan (sig_loc sig) $
848 addErrCtxt (sigContextsCtxt sig1 sig) $
849 do { cois <- unifyTheta theta1 theta
850 ; -- Check whether all coercions are identity coercions
851 -- That can happen if we have, say
853 -- g :: C (F a) => ...
854 -- where F is a type function and (F a ~ [a])
855 -- Then unification might succeed with a coercion. But it's much
856 -- much simpler to require that such signatures have identical contexts
857 checkTc (all isIdentityCoI cois)
858 (ptext (sLit "Mutually dependent functions have syntactically distinct contexts"))
863 @getTyVarsToGen@ decides what type variables to generalise over.
865 For a "restricted group" -- see the monomorphism restriction
866 for a definition -- we bind no dictionaries, and
867 remove from tyvars_to_gen any constrained type variables
869 *Don't* simplify dicts at this point, because we aren't going
870 to generalise over these dicts. By the time we do simplify them
871 we may well know more. For example (this actually came up)
873 f x = array ... xs where xs = [1,2,3,4,5]
874 We don't want to generate lots of (fromInt Int 1), (fromInt Int 2)
875 stuff. If we simplify only at the f-binding (not the xs-binding)
876 we'll know that the literals are all Ints, and we can just produce
879 Find all the type variables involved in overloading, the
880 "constrained_tyvars". These are the ones we *aren't* going to
881 generalise. We must be careful about doing this:
883 (a) If we fail to generalise a tyvar which is not actually
884 constrained, then it will never, ever get bound, and lands
885 up printed out in interface files! Notorious example:
886 instance Eq a => Eq (Foo a b) where ..
887 Here, b is not constrained, even though it looks as if it is.
888 Another, more common, example is when there's a Method inst in
889 the LIE, whose type might very well involve non-overloaded
891 [NOTE: Jan 2001: I don't understand the problem here so I'm doing
892 the simple thing instead]
894 (b) On the other hand, we mustn't generalise tyvars which are constrained,
895 because we are going to pass on out the unmodified LIE, with those
896 tyvars in it. They won't be in scope if we've generalised them.
898 So we are careful, and do a complete simplification just to find the
899 constrained tyvars. We don't use any of the results, except to
900 find which tyvars are constrained.
902 Note [Polymorphic recursion]
903 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
904 The game plan for polymorphic recursion in the code above is
906 * Bind any variable for which we have a type signature
907 to an Id with a polymorphic type. Then when type-checking
908 the RHSs we'll make a full polymorphic call.
910 This fine, but if you aren't a bit careful you end up with a horrendous
911 amount of partial application and (worse) a huge space leak. For example:
913 f :: Eq a => [a] -> [a]
916 If we don't take care, after typechecking we get
918 f = /\a -> \d::Eq a -> let f' = f a d
922 Notice the the stupid construction of (f a d), which is of course
923 identical to the function we're executing. In this case, the
924 polymorphic recursion isn't being used (but that's a very common case).
925 This can lead to a massive space leak, from the following top-level defn
931 Now (f dEqInt) evaluates to a lambda that has f' as a free variable; but
932 f' is another thunk which evaluates to the same thing... and you end
933 up with a chain of identical values all hung onto by the CAF ff.
937 = let f' = f Int dEqInt in \ys. ...f'...
939 = let f' = let f' = f Int dEqInt in \ys. ...f'...
944 NOTE: a bit of arity anaysis would push the (f a d) inside the (\ys...),
945 which would make the space leak go away in this case
947 Solution: when typechecking the RHSs we always have in hand the
948 *monomorphic* Ids for each binding. So we just need to make sure that
949 if (Method f a d) shows up in the constraints emerging from (...f...)
950 we just use the monomorphic Id. We achieve this by adding monomorphic Ids
951 to the "givens" when simplifying constraints. That's what the "lies_avail"
956 f = /\a -> \d::Eq a -> letrec
957 fm = \ys:[a] -> ...fm...
961 %************************************************************************
965 %************************************************************************
967 Type signatures are tricky. See Note [Signature skolems] in TcType
969 @tcSigs@ checks the signatures for validity, and returns a list of
970 {\em freshly-instantiated} signatures. That is, the types are already
971 split up, and have fresh type variables installed. All non-type-signature
972 "RenamedSigs" are ignored.
974 The @TcSigInfo@ contains @TcTypes@ because they are unified with
975 the variable's type, and after that checked to see whether they've
980 The -XScopedTypeVariables flag brings lexically-scoped type variables
981 into scope for any explicitly forall-quantified type variables:
982 f :: forall a. a -> a
984 Then 'a' is in scope inside 'e'.
986 However, we do *not* support this
987 - For pattern bindings e.g
991 - For multiple function bindings, unless Opt_RelaxedPolyRec is on
992 f :: forall a. a -> a
994 g :: forall b. b -> b
996 Reason: we use mutable variables for 'a' and 'b', since they may
997 unify to each other, and that means the scoped type variable would
998 not stand for a completely rigid variable.
1000 Currently, we simply make Opt_ScopedTypeVariables imply Opt_RelaxedPolyRec
1003 Note [More instantiated than scoped]
1004 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1005 There may be more instantiated type variables than lexically-scoped
1007 type T a = forall b. b -> (a,b)
1009 Here, the signature for f will have one scoped type variable, c,
1010 but two instantiated type variables, c' and b'.
1012 We assume that the scoped ones are at the *front* of sig_tvs,
1013 and remember the names from the original HsForAllTy in the TcSigFun.
1015 Note [Signature skolems]
1016 ~~~~~~~~~~~~~~~~~~~~~~~~
1017 When instantiating a type signature, we do so with either skolems or
1018 SigTv meta-type variables depending on the use_skols boolean. This
1019 variable is set True when we are typechecking a single function
1020 binding; and False for pattern bindings and a group of several
1023 Reason: in the latter cases, the "skolems" can be unified together,
1024 so they aren't properly rigid in the type-refinement sense.
1025 NB: unless we are doing H98, each function with a sig will be done
1026 separately, even if it's mutually recursive, so use_skols will be True
1029 Note [Only scoped tyvars are in the TyVarEnv]
1030 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1031 We are careful to keep only the *lexically scoped* type variables in
1032 the type environment. Why? After all, the renamer has ensured
1033 that only legal occurrences occur, so we could put all type variables
1036 But we want to check that two distinct lexically scoped type variables
1037 do not map to the same internal type variable. So we need to know which
1038 the lexically-scoped ones are... and at the moment we do that by putting
1039 only the lexically scoped ones into the environment.
1041 Note [Instantiate sig with fresh variables]
1042 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1043 It's vital to instantiate a type signature with fresh variables.
1045 type T = forall a. [a] -> [a]
1047 f = g where { g :: T; g = <rhs> }
1049 We must not use the same 'a' from the defn of T at both places!!
1050 (Instantiation is only necessary because of type synonyms. Otherwise,
1051 it's all cool; each signature has distinct type variables from the renamer.)
1054 type SigFun = Name -> Maybe ([Name], SrcSpan)
1055 -- Maps a let-binder to the list of
1056 -- type variables brought into scope
1057 -- by its type signature, plus location
1058 -- Nothing => no type signature
1060 mkSigFun :: [LSig Name] -> SigFun
1061 -- Search for a particular type signature
1062 -- Precondition: the sigs are all type sigs
1063 -- Precondition: no duplicates
1064 mkSigFun sigs = lookupNameEnv env
1066 env = mkNameEnv (mapCatMaybes mk_pair sigs)
1067 mk_pair (L loc (TypeSig (L _ name) lhs_ty)) = Just (name, (hsExplicitTvs lhs_ty, loc))
1068 mk_pair (L loc (IdSig id)) = Just (idName id, ([], loc))
1070 -- The scoped names are the ones explicitly mentioned
1071 -- in the HsForAll. (There may be more in sigma_ty, because
1072 -- of nested type synonyms. See Note [More instantiated than scoped].)
1073 -- See Note [Only scoped tyvars are in the TyVarEnv]
1077 tcTySig :: LSig Name -> TcM TcId
1078 tcTySig (L span (TypeSig (L _ name) ty))
1080 do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
1081 ; return (mkLocalId name sigma_ty) }
1082 tcTySig (L _ (IdSig id))
1084 tcTySig s = pprPanic "tcTySig" (ppr s)
1087 tcInstSigs :: SigFun -> [Name] -> TcM TcSigFun
1088 tcInstSigs sig_fn bndrs
1089 = do { prs <- mapMaybeM (tcInstSig sig_fn use_skols) bndrs
1090 ; return (lookupNameEnv (mkNameEnv prs)) }
1092 use_skols = isSingleton bndrs -- See Note [Signature skolems]
1094 tcInstSig :: SigFun -> Bool -> Name -> TcM (Maybe (Name, TcSigInfo))
1095 -- For use_skols :: Bool see Note [Signature skolems]
1097 -- We must instantiate with fresh uniques,
1098 -- (see Note [Instantiate sig with fresh variables])
1099 -- although we keep the same print-name.
1101 tcInstSig sig_fn use_skols name
1102 | Just (scoped_tvs, loc) <- sig_fn name
1103 = do { poly_id <- tcLookupId name -- Cannot fail; the poly ids are put into
1104 -- scope when starting the binding group
1105 ; let poly_ty = idType poly_id
1106 ; (tvs, theta, tau) <- if use_skols
1107 then tcInstType tcInstSkolTyVars poly_ty
1108 else tcInstType tcInstSigTyVars poly_ty
1109 ; let sig = TcSigInfo { sig_id = poly_id
1110 , sig_scoped = scoped_tvs
1111 , sig_tvs = tvs, sig_theta = theta, sig_tau = tau
1113 ; return (Just (name, sig)) }
1117 -------------------------------
1118 data GeneralisationPlan
1119 = NoGen -- No generalisation, no AbsBinds
1120 | InferGen Bool -- Implicit generalisation; there is an AbsBinds
1121 -- True <=> apply the MR; generalise only unconstrained type vars
1122 | CheckGen TcSigInfo -- Explicit generalisation; there is an AbsBinds
1124 -- A consequence of the no-AbsBinds choice (NoGen) is that there is
1125 -- no "polymorphic Id" and "monmomorphic Id"; there is just the one
1127 instance Outputable GeneralisationPlan where
1128 ppr NoGen = ptext (sLit "NoGen")
1129 ppr (InferGen b) = ptext (sLit "InferGen") <+> ppr b
1130 ppr (CheckGen s) = ptext (sLit "CheckGen") <+> ppr s
1132 decideGeneralisationPlan
1133 :: DynFlags -> TopLevelFlag -> [Name] -> [LHsBind Name] -> TcSigFun -> GeneralisationPlan
1134 decideGeneralisationPlan dflags top_lvl _bndrs binds sig_fn
1135 | bang_pat_binds = NoGen
1136 | mono_pat_binds = NoGen
1137 | Just sig <- one_funbind_with_sig binds = if null (sig_tvs sig) && null (sig_theta sig)
1138 then NoGen -- Optimise common case
1140 | (xopt Opt_MonoLocalBinds dflags
1141 && isNotTopLevel top_lvl) = NoGen
1142 | otherwise = InferGen mono_restriction
1145 bang_pat_binds = any (isBangHsBind . unLoc) binds
1146 -- Bang patterns must not be polymorphic,
1147 -- because we are going to force them
1150 mono_pat_binds = xopt Opt_MonoPatBinds dflags
1151 && any (is_pat_bind . unLoc) binds
1153 mono_restriction = xopt Opt_MonomorphismRestriction dflags
1154 && any (restricted . unLoc) binds
1156 no_sig n = isNothing (sig_fn n)
1158 -- With OutsideIn, all nested bindings are monomorphic
1159 -- except a single function binding with a signature
1160 one_funbind_with_sig [L _ FunBind { fun_id = v }] = sig_fn (unLoc v)
1161 one_funbind_with_sig _ = Nothing
1163 -- The Haskell 98 monomorphism resetriction
1164 restricted (PatBind {}) = True
1165 restricted (VarBind { var_id = v }) = no_sig v
1166 restricted (FunBind { fun_id = v, fun_matches = m }) = restricted_match m
1168 restricted (AbsBinds {}) = panic "isRestrictedGroup/unrestricted AbsBinds"
1170 restricted_match (MatchGroup (L _ (Match [] _ _) : _) _) = True
1171 restricted_match _ = False
1172 -- No args => like a pattern binding
1173 -- Some args => a function binding
1175 is_pat_bind (PatBind {}) = True
1176 is_pat_bind _ = False
1179 checkStrictBinds :: TopLevelFlag -> RecFlag
1180 -> [LHsBind Name] -> [Id]
1182 -- Check that non-overloaded unlifted bindings are
1183 -- a) non-recursive,
1184 -- b) not top level,
1185 -- c) not a multiple-binding group (more or less implied by (a))
1187 checkStrictBinds top_lvl rec_group binds poly_ids
1188 | unlifted || bang_pat
1189 = do { checkTc (isNotTopLevel top_lvl)
1190 (strictBindErr "Top-level" unlifted binds)
1191 ; checkTc (isNonRec rec_group)
1192 (strictBindErr "Recursive" unlifted binds)
1193 ; checkTc (isSingleton binds)
1194 (strictBindErr "Multiple" unlifted binds)
1195 -- This should be a checkTc, not a warnTc, but as of GHC 6.11
1196 -- the versions of alex and happy available have non-conforming
1197 -- templates, so the GHC build fails if it's an error:
1198 ; warnUnlifted <- doptM Opt_WarnLazyUnliftedBindings
1199 ; warnTc (warnUnlifted && not bang_pat && lifted_pat)
1200 -- No outer bang, but it's a compound pattern
1201 -- E.g (I# x#) = blah
1202 -- Warn about this, but not about
1205 (unliftedMustBeBang binds) }
1209 unlifted = any is_unlifted poly_ids
1210 bang_pat = any (isBangHsBind . unLoc) binds
1211 lifted_pat = any (isLiftedPatBind . unLoc) binds
1212 is_unlifted id = case tcSplitForAllTys (idType id) of
1213 (_, rho) -> isUnLiftedType rho
1215 unliftedMustBeBang :: [LHsBind Name] -> SDoc
1216 unliftedMustBeBang binds
1217 = hang (text "Pattern bindings containing unlifted types should use an outermost bang pattern:")
1218 2 (pprBindList binds)
1220 strictBindErr :: String -> Bool -> [LHsBind Name] -> SDoc
1221 strictBindErr flavour unlifted binds
1222 = hang (text flavour <+> msg <+> ptext (sLit "aren't allowed:"))
1223 2 (pprBindList binds)
1225 msg | unlifted = ptext (sLit "bindings for unlifted types")
1226 | otherwise = ptext (sLit "bang-pattern bindings")
1228 pprBindList :: [LHsBind Name] -> SDoc
1229 pprBindList binds = vcat (map ppr binds)
1233 %************************************************************************
1235 \subsection[TcBinds-errors]{Error contexts and messages}
1237 %************************************************************************
1241 -- This one is called on LHS, when pat and grhss are both Name
1242 -- and on RHS, when pat is TcId and grhss is still Name
1243 patMonoBindsCtxt :: OutputableBndr id => LPat id -> GRHSs Name -> SDoc
1244 patMonoBindsCtxt pat grhss
1245 = hang (ptext (sLit "In a pattern binding:")) 2 (pprPatBind pat grhss)
1247 -----------------------------------------------
1248 sigContextsCtxt :: TcSigInfo -> TcSigInfo -> SDoc
1249 sigContextsCtxt sig1 sig2
1250 = vcat [ptext (sLit "When matching the contexts of the signatures for"),
1251 nest 2 (vcat [ppr id1 <+> dcolon <+> ppr (idType id1),
1252 ppr id2 <+> dcolon <+> ppr (idType id2)]),
1253 ptext (sLit "The signature contexts in a mutually recursive group should all be identical")]