2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
5 \section[TcBinds]{TcBinds}
8 module TcBinds ( tcLocalBinds, tcTopBinds,
9 tcHsBootSigs, tcMonoBinds, tcPolyBinds,
10 TcPragFun, tcSpecPrag, tcPrags, mkPragFun,
11 TcSigInfo(..), TcSigFun, mkTcSigFun,
12 badBootDeclErr ) where
14 import {-# SOURCE #-} TcMatches ( tcGRHSsPat, tcMatchesFun )
15 import {-# SOURCE #-} TcExpr ( tcMonoExpr )
29 import {- Kind parts of -} Type
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 -> TcM (LHsBinds TcId, TcLclEnv)
87 -- Note: returning the TcLclEnv is more than we really
88 -- want. The bit we care about is the local bindings
89 -- and the free type variables thereof
91 = do { (ValBindsOut prs _, env) <- tcValBinds TopLevel binds getLclEnv
92 ; return (foldr (unionBags . snd) emptyBag prs, env) }
93 -- The top level bindings are flattened into a giant
94 -- implicitly-mutually-recursive LHsBinds
96 tcHsBootSigs :: HsValBinds Name -> TcM [Id]
97 -- A hs-boot file has only one BindGroup, and it only has type
98 -- signatures in it. The renamer checked all this
99 tcHsBootSigs (ValBindsOut binds sigs)
100 = do { checkTc (null binds) badBootDeclErr
101 ; mapM (addLocM tc_boot_sig) (filter isVanillaLSig sigs) }
103 tc_boot_sig (TypeSig (L _ name) ty)
104 = do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
105 ; return (mkVanillaGlobal name sigma_ty) }
106 -- Notice that we make GlobalIds, not LocalIds
107 tc_boot_sig s = pprPanic "tcHsBootSigs/tc_boot_sig" (ppr s)
108 tcHsBootSigs groups = pprPanic "tcHsBootSigs" (ppr groups)
110 badBootDeclErr :: Message
111 badBootDeclErr = ptext (sLit "Illegal declarations in an hs-boot file")
113 ------------------------
114 tcLocalBinds :: HsLocalBinds Name -> TcM thing
115 -> TcM (HsLocalBinds TcId, thing)
117 tcLocalBinds EmptyLocalBinds thing_inside
118 = do { thing <- thing_inside
119 ; return (EmptyLocalBinds, thing) }
121 tcLocalBinds (HsValBinds binds) thing_inside
122 = do { (binds', thing) <- tcValBinds NotTopLevel binds thing_inside
123 ; return (HsValBinds binds', thing) }
125 tcLocalBinds (HsIPBinds (IPBinds ip_binds _)) thing_inside
126 = do { (thing, lie) <- getLIE thing_inside
127 ; (avail_ips, ip_binds') <- mapAndUnzipM (wrapLocSndM tc_ip_bind) ip_binds
129 -- If the binding binds ?x = E, we must now
130 -- discharge any ?x constraints in expr_lie
131 ; dict_binds <- tcSimplifyIPs avail_ips lie
132 ; return (HsIPBinds (IPBinds ip_binds' dict_binds), thing) }
134 -- I wonder if we should do these one at at time
137 tc_ip_bind (IPBind ip expr) = do
138 ty <- newFlexiTyVarTy argTypeKind
139 (ip', ip_inst) <- newIPDict (IPBindOrigin ip) ip ty
140 expr' <- tcMonoExpr expr ty
141 return (ip_inst, (IPBind ip' expr'))
143 ------------------------
144 tcValBinds :: TopLevelFlag
145 -> HsValBinds Name -> TcM thing
146 -> TcM (HsValBinds TcId, thing)
148 tcValBinds _ (ValBindsIn binds _) _
149 = pprPanic "tcValBinds" (ppr binds)
151 tcValBinds top_lvl (ValBindsOut binds sigs) thing_inside
152 = do { -- Typecheck the signature
153 ; let { prag_fn = mkPragFun sigs
154 ; ty_sigs = filter isVanillaLSig sigs
155 ; sig_fn = mkTcSigFun ty_sigs }
157 ; poly_ids <- checkNoErrs (mapAndRecoverM tcTySig ty_sigs)
158 -- No recovery from bad signatures, because the type sigs
159 -- may bind type variables, so proceeding without them
160 -- can lead to a cascade of errors
161 -- ToDo: this means we fall over immediately if any type sig
162 -- is wrong, which is over-conservative, see Trac bug #745
164 -- Extend the envt right away with all
165 -- the Ids declared with type signatures
166 ; poly_rec <- doptM Opt_RelaxedPolyRec
167 ; (binds', thing) <- tcExtendIdEnv poly_ids $
168 tcBindGroups poly_rec top_lvl sig_fn prag_fn
171 ; return (ValBindsOut binds' sigs, thing) }
173 ------------------------
174 tcBindGroups :: Bool -> TopLevelFlag -> TcSigFun -> TcPragFun
175 -> [(RecFlag, LHsBinds Name)] -> TcM thing
176 -> TcM ([(RecFlag, LHsBinds TcId)], thing)
177 -- Typecheck a whole lot of value bindings,
178 -- one strongly-connected component at a time
179 -- Here a "strongly connected component" has the strightforward
180 -- meaning of a group of bindings that mention each other,
181 -- ignoring type signatures (that part comes later)
183 tcBindGroups _ _ _ _ [] thing_inside
184 = do { thing <- thing_inside
185 ; return ([], thing) }
187 tcBindGroups poly_rec top_lvl sig_fn prag_fn (group : groups) thing_inside
188 = do { (group', (groups', thing))
189 <- tc_group poly_rec top_lvl sig_fn prag_fn group $
190 tcBindGroups poly_rec top_lvl sig_fn prag_fn groups thing_inside
191 ; return (group' ++ groups', thing) }
193 ------------------------
194 tc_group :: Bool -> TopLevelFlag -> TcSigFun -> TcPragFun
195 -> (RecFlag, LHsBinds Name) -> TcM thing
196 -> TcM ([(RecFlag, LHsBinds TcId)], thing)
198 -- Typecheck one strongly-connected component of the original program.
199 -- We get a list of groups back, because there may
200 -- be specialisations etc as well
202 tc_group _ top_lvl sig_fn prag_fn (NonRecursive, binds) thing_inside
203 -- A single non-recursive binding
204 -- We want to keep non-recursive things non-recursive
205 -- so that we desugar unlifted bindings correctly
206 = do { (binds1, lie_binds, thing) <- tc_haskell98 top_lvl sig_fn prag_fn
207 NonRecursive binds thing_inside
208 ; return ( [(NonRecursive, unitBag b) | b <- bagToList binds1]
209 ++ [(Recursive, lie_binds)] -- TcDictBinds have scrambled dependency order
212 tc_group poly_rec top_lvl sig_fn prag_fn (Recursive, binds) thing_inside
213 | not poly_rec -- Recursive group, normal Haskell 98 route
214 = do { (binds1, lie_binds, thing) <- tc_haskell98 top_lvl sig_fn prag_fn
215 Recursive binds thing_inside
216 ; return ([(Recursive, binds1 `unionBags` lie_binds)], thing) }
218 | otherwise -- Recursive group, with -XRelaxedPolyRec
219 = -- To maximise polymorphism (with -XRelaxedPolyRec), we do a new
220 -- strongly-connected-component analysis, this time omitting
221 -- any references to variables with type signatures.
223 -- Notice that the bindInsts thing covers *all* the bindings in
224 -- the original group at once; an earlier one may use a later one!
225 do { traceTc (text "tc_group rec" <+> pprLHsBinds binds)
226 ; (binds1,lie_binds,thing) <- bindLocalInsts top_lvl $
227 go (stronglyConnCompFromEdgedVertices (mkEdges sig_fn binds))
228 ; return ([(Recursive, binds1 `unionBags` lie_binds)], thing) }
229 -- Rec them all together
231 -- go :: SCC (LHsBind Name) -> TcM (LHsBinds TcId, [TcId], thing)
232 go (scc:sccs) = do { (binds1, ids1) <- tc_scc scc
233 ; (binds2, ids2, thing) <- tcExtendIdEnv ids1 $ go sccs
234 ; return (binds1 `unionBags` binds2, ids1 ++ ids2, thing) }
235 go [] = do { thing <- thing_inside; return (emptyBag, [], thing) }
237 tc_scc (AcyclicSCC bind) = tc_sub_group NonRecursive (unitBag bind)
238 tc_scc (CyclicSCC binds) = tc_sub_group Recursive (listToBag binds)
240 tc_sub_group = tcPolyBinds top_lvl sig_fn prag_fn Recursive
242 tc_haskell98 :: TopLevelFlag -> TcSigFun -> TcPragFun -> RecFlag
243 -> LHsBinds Name -> TcM a -> TcM (LHsBinds TcId, TcDictBinds, a)
244 tc_haskell98 top_lvl sig_fn prag_fn rec_flag binds thing_inside
245 = bindLocalInsts top_lvl $
246 do { (binds1, ids) <- tcPolyBinds top_lvl sig_fn prag_fn rec_flag rec_flag binds
247 ; thing <- tcExtendIdEnv ids thing_inside
248 ; return (binds1, ids, thing) }
250 ------------------------
251 bindLocalInsts :: TopLevelFlag
252 -> TcM (LHsBinds TcId, [TcId], a)
253 -> TcM (LHsBinds TcId, TcDictBinds, a)
254 bindLocalInsts top_lvl thing_inside
256 = do { (binds, _, thing) <- thing_inside; return (binds, emptyBag, thing) }
257 -- For the top level don't bother with all this bindInstsOfLocalFuns stuff.
258 -- All the top level things are rec'd together anyway, so it's fine to
259 -- leave them to the tcSimplifyTop, and quite a bit faster too
261 | otherwise -- Nested case
262 = do { ((binds, ids, thing), lie) <- getLIE thing_inside
263 ; lie_binds <- bindInstsOfLocalFuns lie ids
264 ; return (binds, lie_binds, thing) }
266 ------------------------
267 mkEdges :: TcSigFun -> LHsBinds Name
268 -> [(LHsBind Name, BKey, [BKey])]
270 type BKey = Int -- Just number off the bindings
273 = [ (bind, key, [key | n <- nameSetToList (bind_fvs (unLoc bind)),
274 Just key <- [lookupNameEnv key_map n], no_sig n ])
275 | (bind, key) <- keyd_binds
278 no_sig :: Name -> Bool
279 no_sig n = isNothing (sig_fn n)
281 keyd_binds = bagToList binds `zip` [0::BKey ..]
283 key_map :: NameEnv BKey -- Which binding it comes from
284 key_map = mkNameEnv [(bndr, key) | (L _ bind, key) <- keyd_binds
285 , bndr <- bindersOfHsBind bind ]
287 bindersOfHsBind :: HsBind Name -> [Name]
288 bindersOfHsBind (PatBind { pat_lhs = pat }) = collectPatBinders pat
289 bindersOfHsBind (FunBind { fun_id = L _ f }) = [f]
290 bindersOfHsBind (AbsBinds {}) = panic "bindersOfHsBind AbsBinds"
291 bindersOfHsBind (VarBind {}) = panic "bindersOfHsBind VarBind"
293 ------------------------
294 tcPolyBinds :: TopLevelFlag -> TcSigFun -> TcPragFun
295 -> RecFlag -- Whether the group is really recursive
296 -> RecFlag -- Whether it's recursive after breaking
297 -- dependencies based on type signatures
299 -> TcM (LHsBinds TcId, [TcId])
301 -- Typechecks a single bunch of bindings all together,
302 -- and generalises them. The bunch may be only part of a recursive
303 -- group, because we use type signatures to maximise polymorphism
305 -- Returns a list because the input may be a single non-recursive binding,
306 -- in which case the dependency order of the resulting bindings is
309 -- Knows nothing about the scope of the bindings
311 tcPolyBinds top_lvl sig_fn prag_fn rec_group rec_tc binds
313 bind_list = bagToList binds
314 binder_names = collectHsBindBinders binds
315 loc = getLoc (head bind_list)
316 -- TODO: location a bit awkward, but the mbinds have been
317 -- dependency analysed and may no longer be adjacent
319 -- SET UP THE MAIN RECOVERY; take advantage of any type sigs
321 recoverM (recoveryCode binder_names sig_fn) $ do
323 { traceTc (ptext (sLit "------------------------------------------------"))
324 ; traceTc (ptext (sLit "Bindings for") <+> ppr binder_names)
326 -- TYPECHECK THE BINDINGS
327 ; ((binds', mono_bind_infos), lie_req)
328 <- getLIE (tcMonoBinds bind_list sig_fn rec_tc)
329 ; traceTc (text "temp" <+> (ppr binds' $$ ppr lie_req))
331 -- CHECK FOR UNLIFTED BINDINGS
332 -- These must be non-recursive etc, and are not generalised
333 -- They desugar to a case expression in the end
334 ; zonked_mono_tys <- zonkTcTypes (map getMonoType mono_bind_infos)
335 ; is_strict <- checkStrictBinds top_lvl rec_group binds'
336 zonked_mono_tys mono_bind_infos
338 do { extendLIEs lie_req
339 ; let exports = zipWith mk_export mono_bind_infos zonked_mono_tys
340 mk_export (name, Nothing, mono_id) mono_ty = ([], mkLocalId name mono_ty, mono_id, [])
341 mk_export (_, Just sig, mono_id) _ = ([], sig_id sig, mono_id, [])
342 -- ToDo: prags for unlifted bindings
344 ; return ( unitBag $ L loc $ AbsBinds [] [] exports binds',
345 [poly_id | (_, poly_id, _, _) <- exports]) } -- Guaranteed zonked
347 else do -- The normal lifted case: GENERALISE
349 ; (tyvars_to_gen, dicts, dict_binds)
350 <- addErrCtxt (genCtxt (bndrNames mono_bind_infos)) $
351 generalise dflags top_lvl bind_list sig_fn mono_bind_infos lie_req
353 -- BUILD THE POLYMORPHIC RESULT IDs
354 ; let dict_vars = map instToVar dicts -- May include equality constraints
355 ; exports <- mapM (mkExport top_lvl prag_fn tyvars_to_gen (map varType dict_vars))
358 ; let poly_ids = [poly_id | (_, poly_id, _, _) <- exports]
359 ; traceTc (text "binding:" <+> ppr (poly_ids `zip` map idType poly_ids))
361 ; let abs_bind = L loc $ AbsBinds tyvars_to_gen
363 (dict_binds `unionBags` binds')
365 ; return (unitBag abs_bind, poly_ids) -- poly_ids are guaranteed zonked by mkExport
370 mkExport :: TopLevelFlag -> TcPragFun -> [TyVar] -> [TcType]
372 -> TcM ([TyVar], Id, Id, [LPrag])
373 -- mkExport generates exports with
374 -- zonked type variables,
376 -- The former is just because no further unifications will change
377 -- the quantified type variables, so we can fix their final form
379 -- The latter is needed because the poly_ids are used to extend the
380 -- type environment; see the invariant on TcEnv.tcExtendIdEnv
382 -- Pre-condition: the inferred_tvs are already zonked
384 mkExport top_lvl prag_fn inferred_tvs dict_tys (poly_name, mb_sig, mono_id)
385 = do { warn_missing_sigs <- doptM Opt_WarnMissingSigs
386 ; let warn = isTopLevel top_lvl && warn_missing_sigs
387 ; (tvs, poly_id) <- mk_poly_id warn mb_sig
388 -- poly_id has a zonked type
390 ; prags <- tcPrags poly_id (prag_fn poly_name)
391 -- tcPrags requires a zonked poly_id
393 ; return (tvs, poly_id, mono_id, prags) }
395 poly_ty = mkForAllTys inferred_tvs (mkFunTys dict_tys (idType mono_id))
397 mk_poly_id warn Nothing = do { poly_ty' <- zonkTcType poly_ty
398 ; missingSigWarn warn poly_name poly_ty'
399 ; return (inferred_tvs, mkLocalId poly_name poly_ty') }
400 mk_poly_id _ (Just sig) = do { tvs <- mapM zonk_tv (sig_tvs sig)
401 ; return (tvs, sig_id sig) }
403 zonk_tv tv = do { ty <- zonkTcTyVar tv; return (tcGetTyVar "mkExport" ty) }
405 ------------------------
406 type TcPragFun = Name -> [LSig Name]
408 mkPragFun :: [LSig Name] -> TcPragFun
409 mkPragFun sigs = \n -> lookupNameEnv env n `orElse` []
411 prs = [(expectJust "mkPragFun" (sigName sig), sig)
412 | sig <- sigs, isPragLSig sig]
413 env = foldl add emptyNameEnv prs
414 add env (n,p) = extendNameEnv_Acc (:) singleton env n p
416 tcPrags :: Id -> [LSig Name] -> TcM [LPrag]
417 tcPrags poly_id prags = mapM (wrapLocM tc_prag) prags
419 tc_prag prag = addErrCtxt (pragSigCtxt prag) $
422 pragSigCtxt :: Sig Name -> SDoc
423 pragSigCtxt prag = hang (ptext (sLit "In the pragma")) 2 (ppr prag)
425 tcPrag :: TcId -> Sig Name -> TcM Prag
426 -- Pre-condition: the poly_id is zonked
427 -- Reason: required by tcSubExp
428 tcPrag poly_id (SpecSig _ hs_ty inl) = tcSpecPrag poly_id hs_ty inl
429 tcPrag poly_id (SpecInstSig hs_ty) = tcSpecPrag poly_id hs_ty defaultInlineSpec
430 tcPrag _ (InlineSig _ inl) = return (InlinePrag inl)
431 tcPrag _ (FixSig {}) = panic "tcPrag FixSig"
432 tcPrag _ (TypeSig {}) = panic "tcPrag TypeSig"
435 tcSpecPrag :: TcId -> LHsType Name -> InlineSpec -> TcM Prag
436 tcSpecPrag poly_id hs_ty inl
437 = do { let name = idName poly_id
438 ; spec_ty <- tcHsSigType (FunSigCtxt name) hs_ty
439 ; co_fn <- tcSubExp (SpecPragOrigin name) (idType poly_id) spec_ty
440 ; return (SpecPrag (mkHsWrap co_fn (HsVar poly_id)) spec_ty inl) }
441 -- Most of the work of specialisation is done by
442 -- the desugarer, guided by the SpecPrag
445 -- If typechecking the binds fails, then return with each
446 -- signature-less binder given type (forall a.a), to minimise
447 -- subsequent error messages
448 recoveryCode :: [Name] -> (Name -> Maybe [Name])
449 -> TcM (LHsBinds TcId, [Id])
450 recoveryCode binder_names sig_fn
451 = do { traceTc (text "tcBindsWithSigs: error recovery" <+> ppr binder_names)
452 ; poly_ids <- mapM mk_dummy binder_names
453 ; return (emptyBag, poly_ids) }
456 | isJust (sig_fn name) = tcLookupId name -- Had signature; look it up
457 | otherwise = return (mkLocalId name forall_a_a) -- No signature
460 forall_a_a = mkForAllTy alphaTyVar (mkTyVarTy alphaTyVar)
463 -- Check that non-overloaded unlifted bindings are
466 -- c) not a multiple-binding group (more or less implied by (a))
468 checkStrictBinds :: TopLevelFlag -> RecFlag
469 -> LHsBinds TcId -> [TcType] -> [MonoBindInfo]
471 checkStrictBinds top_lvl rec_group mbind mono_tys infos
472 | unlifted || bang_pat
473 = do { checkTc (isNotTopLevel top_lvl)
474 (strictBindErr "Top-level" unlifted mbind)
475 ; checkTc (isNonRec rec_group)
476 (strictBindErr "Recursive" unlifted mbind)
477 ; checkTc (isSingletonBag mbind)
478 (strictBindErr "Multiple" unlifted mbind)
479 ; mapM_ check_sig infos
484 unlifted = any isUnLiftedType mono_tys
485 bang_pat = anyBag (isBangHsBind . unLoc) mbind
486 check_sig (_, Just sig, _) = checkTc (null (sig_tvs sig) && null (sig_theta sig))
487 (badStrictSig unlifted sig)
488 check_sig _ = return ()
490 strictBindErr :: String -> Bool -> LHsBindsLR Var Var -> SDoc
491 strictBindErr flavour unlifted mbind
492 = hang (text flavour <+> msg <+> ptext (sLit "aren't allowed:"))
493 4 (pprLHsBinds mbind)
495 msg | unlifted = ptext (sLit "bindings for unlifted types")
496 | otherwise = ptext (sLit "bang-pattern bindings")
498 badStrictSig :: Bool -> TcSigInfo -> SDoc
499 badStrictSig unlifted sig
500 = hang (ptext (sLit "Illegal polymorphic signature in") <+> msg)
503 msg | unlifted = ptext (sLit "an unlifted binding")
504 | otherwise = ptext (sLit "a bang-pattern binding")
508 %************************************************************************
510 \subsection{tcMonoBind}
512 %************************************************************************
514 @tcMonoBinds@ deals with a perhaps-recursive group of HsBinds.
515 The signatures have been dealt with already.
518 tcMonoBinds :: [LHsBind Name]
520 -> RecFlag -- Whether the binding is recursive for typechecking purposes
521 -- i.e. the binders are mentioned in their RHSs, and
522 -- we are not resuced by a type signature
523 -> TcM (LHsBinds TcId, [MonoBindInfo])
525 tcMonoBinds [L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf,
526 fun_matches = matches, bind_fvs = fvs })]
527 sig_fn -- Single function binding,
528 NonRecursive -- binder isn't mentioned in RHS,
529 | Nothing <- sig_fn name -- ...with no type signature
530 = -- In this very special case we infer the type of the
531 -- right hand side first (it may have a higher-rank type)
532 -- and *then* make the monomorphic Id for the LHS
533 -- e.g. f = \(x::forall a. a->a) -> <body>
534 -- We want to infer a higher-rank type for f
536 do { ((co_fn, matches'), rhs_ty) <- tcInfer (tcMatchesFun name inf matches)
538 -- Check for an unboxed tuple type
539 -- f = (# True, False #)
540 -- Zonk first just in case it's hidden inside a meta type variable
541 -- (This shows up as a (more obscure) kind error
542 -- in the 'otherwise' case of tcMonoBinds.)
543 ; zonked_rhs_ty <- zonkTcType rhs_ty
544 ; checkTc (not (isUnboxedTupleType zonked_rhs_ty))
545 (unboxedTupleErr name zonked_rhs_ty)
547 ; mono_name <- newLocalName name
548 ; let mono_id = mkLocalId mono_name zonked_rhs_ty
549 ; return (unitBag (L b_loc (FunBind { fun_id = L nm_loc mono_id, fun_infix = inf,
550 fun_matches = matches', bind_fvs = fvs,
551 fun_co_fn = co_fn, fun_tick = Nothing })),
552 [(name, Nothing, mono_id)]) }
554 tcMonoBinds [L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf,
555 fun_matches = matches })]
556 sig_fn -- Single function binding
558 | Just scoped_tvs <- sig_fn name -- ...with a type signature
559 = -- When we have a single function binding, with a type signature
560 -- we can (a) use genuine, rigid skolem constants for the type variables
561 -- (b) bring (rigid) scoped type variables into scope
563 do { tc_sig <- tcInstSig True name
564 ; mono_name <- newLocalName name
565 ; let mono_ty = sig_tau tc_sig
566 mono_id = mkLocalId mono_name mono_ty
567 rhs_tvs = [ (name, mkTyVarTy tv)
568 | (name, tv) <- scoped_tvs `zip` sig_tvs tc_sig ]
569 -- See Note [More instantiated than scoped]
570 -- Note that the scoped_tvs and the (sig_tvs sig)
571 -- may have different Names. That's quite ok.
573 ; traceTc (text "tcMoonBinds" <+> ppr scoped_tvs $$ ppr tc_sig)
574 ; (co_fn, matches') <- tcExtendTyVarEnv2 rhs_tvs $
575 tcMatchesFun mono_name inf matches mono_ty
576 -- Note that "mono_ty" might actually be a polymorphic type,
577 -- if the original function had a signature like
578 -- forall a. Eq a => forall b. Ord b => ....
579 -- But that's ok: tcMatchesFun can deal with that
580 -- It happens, too! See Note [Polymorphic methods] in TcClassDcl.
582 ; let fun_bind' = FunBind { fun_id = L nm_loc mono_id,
583 fun_infix = inf, fun_matches = matches',
584 bind_fvs = placeHolderNames, fun_co_fn = co_fn,
586 ; return (unitBag (L b_loc fun_bind'),
587 [(name, Just tc_sig, mono_id)]) }
589 tcMonoBinds binds sig_fn _
590 = do { tc_binds <- mapM (wrapLocM (tcLhs sig_fn)) binds
592 -- Bring the monomorphic Ids, into scope for the RHSs
593 ; let mono_info = getMonoBindInfo tc_binds
594 rhs_id_env = [(name,mono_id) | (name, Nothing, mono_id) <- mono_info]
595 -- A monomorphic binding for each term variable that lacks
596 -- a type sig. (Ones with a sig are already in scope.)
598 ; binds' <- tcExtendIdEnv2 rhs_id_env $ do
599 traceTc (text "tcMonoBinds" <+> vcat [ ppr n <+> ppr id <+> ppr (idType id)
600 | (n,id) <- rhs_id_env])
601 mapM (wrapLocM tcRhs) tc_binds
602 ; return (listToBag binds', mono_info) }
604 ------------------------
605 -- tcLhs typechecks the LHS of the bindings, to construct the environment in which
606 -- we typecheck the RHSs. Basically what we are doing is this: for each binder:
607 -- if there's a signature for it, use the instantiated signature type
608 -- otherwise invent a type variable
609 -- You see that quite directly in the FunBind case.
611 -- But there's a complication for pattern bindings:
612 -- data T = MkT (forall a. a->a)
614 -- Here we can guess a type variable for the entire LHS (which will be refined to T)
615 -- but we want to get (f::forall a. a->a) as the RHS environment.
616 -- The simplest way to do this is to typecheck the pattern, and then look up the
617 -- bound mono-ids. Then we want to retain the typechecked pattern to avoid re-doing
618 -- it; hence the TcMonoBind data type in which the LHS is done but the RHS isn't
620 data TcMonoBind -- Half completed; LHS done, RHS not done
621 = TcFunBind MonoBindInfo (Located TcId) Bool (MatchGroup Name)
622 | TcPatBind [MonoBindInfo] (LPat TcId) (GRHSs Name) TcSigmaType
624 type MonoBindInfo = (Name, Maybe TcSigInfo, TcId)
625 -- Type signature (if any), and
626 -- the monomorphic bound things
628 bndrNames :: [MonoBindInfo] -> [Name]
629 bndrNames mbi = [n | (n,_,_) <- mbi]
631 getMonoType :: MonoBindInfo -> TcTauType
632 getMonoType (_,_,mono_id) = idType mono_id
634 tcLhs :: TcSigFun -> HsBind Name -> TcM TcMonoBind
635 tcLhs sig_fn (FunBind { fun_id = L nm_loc name, fun_infix = inf, fun_matches = matches })
636 = do { mb_sig <- tcInstSig_maybe sig_fn name
637 ; mono_name <- newLocalName name
638 ; mono_ty <- mk_mono_ty mb_sig
639 ; let mono_id = mkLocalId mono_name mono_ty
640 ; return (TcFunBind (name, mb_sig, mono_id) (L nm_loc mono_id) inf matches) }
642 mk_mono_ty (Just sig) = return (sig_tau sig)
643 mk_mono_ty Nothing = newFlexiTyVarTy argTypeKind
645 tcLhs sig_fn (PatBind { pat_lhs = pat, pat_rhs = grhss })
646 = do { mb_sigs <- mapM (tcInstSig_maybe sig_fn) names
647 ; mono_pat_binds <- doptM Opt_MonoPatBinds
648 -- With -XMonoPatBinds, we do no generalisation of pattern bindings
649 -- But the signature can still be polymoprhic!
650 -- data T = MkT (forall a. a->a)
651 -- x :: forall a. a->a
653 -- The function get_sig_ty decides whether the pattern-bound variables
654 -- should have exactly the type in the type signature (-XMonoPatBinds),
655 -- or the instantiated version (-XMonoPatBinds)
657 ; let nm_sig_prs = names `zip` mb_sigs
658 get_sig_ty | mono_pat_binds = idType . sig_id
659 | otherwise = sig_tau
660 tau_sig_env = mkNameEnv [ (name, get_sig_ty sig)
661 | (name, Just sig) <- nm_sig_prs]
662 sig_tau_fn = lookupNameEnv tau_sig_env
664 tc_pat exp_ty = tcLetPat sig_tau_fn pat exp_ty $
665 mapM lookup_info nm_sig_prs
667 -- After typechecking the pattern, look up the binder
668 -- names, which the pattern has brought into scope.
669 lookup_info :: (Name, Maybe TcSigInfo) -> TcM MonoBindInfo
670 lookup_info (name, mb_sig) = do { mono_id <- tcLookupId name
671 ; return (name, mb_sig, mono_id) }
673 ; ((pat', infos), pat_ty) <- addErrCtxt (patMonoBindsCtxt pat grhss) $
676 ; return (TcPatBind infos pat' grhss pat_ty) }
678 names = collectPatBinders pat
681 tcLhs _ other_bind = pprPanic "tcLhs" (ppr other_bind)
682 -- AbsBind, VarBind impossible
685 tcRhs :: TcMonoBind -> TcM (HsBind TcId)
686 -- When we are doing pattern bindings, or multiple function bindings at a time
687 -- we *don't* bring any scoped type variables into scope
688 -- Wny not? They are not completely rigid.
689 -- That's why we have the special case for a single FunBind in tcMonoBinds
690 tcRhs (TcFunBind (_,_,mono_id) fun' inf matches)
691 = do { (co_fn, matches') <- tcMatchesFun (idName mono_id) inf
692 matches (idType mono_id)
693 ; return (FunBind { fun_id = fun', fun_infix = inf, fun_matches = matches',
694 bind_fvs = placeHolderNames, fun_co_fn = co_fn,
695 fun_tick = Nothing }) }
697 tcRhs (TcPatBind _ pat' grhss pat_ty)
698 = do { grhss' <- addErrCtxt (patMonoBindsCtxt pat' grhss) $
699 tcGRHSsPat grhss pat_ty
700 ; return (PatBind { pat_lhs = pat', pat_rhs = grhss', pat_rhs_ty = pat_ty,
701 bind_fvs = placeHolderNames }) }
704 ---------------------
705 getMonoBindInfo :: [Located TcMonoBind] -> [MonoBindInfo]
706 getMonoBindInfo tc_binds
707 = foldr (get_info . unLoc) [] tc_binds
709 get_info (TcFunBind info _ _ _) rest = info : rest
710 get_info (TcPatBind infos _ _ _) rest = infos ++ rest
714 %************************************************************************
718 %************************************************************************
721 generalise :: DynFlags -> TopLevelFlag
722 -> [LHsBind Name] -> TcSigFun
723 -> [MonoBindInfo] -> [Inst]
724 -> TcM ([TyVar], [Inst], TcDictBinds)
725 -- The returned [TyVar] are all ready to quantify
727 generalise dflags top_lvl bind_list sig_fn mono_infos lie_req
728 | isMonoGroup dflags bind_list
729 = do { extendLIEs lie_req
730 ; return ([], [], emptyBag) }
732 | isRestrictedGroup dflags bind_list sig_fn -- RESTRICTED CASE
733 = -- Check signature contexts are empty
734 do { checkTc (all is_mono_sig sigs)
735 (restrictedBindCtxtErr bndrs)
737 -- Now simplify with exactly that set of tyvars
738 -- We have to squash those Methods
739 ; (qtvs, binds) <- tcSimplifyRestricted doc top_lvl bndrs
742 -- Check that signature type variables are OK
743 ; final_qtvs <- checkSigsTyVars qtvs sigs
745 ; return (final_qtvs, [], binds) }
747 | null sigs -- UNRESTRICTED CASE, NO TYPE SIGS
748 = tcSimplifyInfer doc tau_tvs lie_req
750 | otherwise -- UNRESTRICTED CASE, WITH TYPE SIGS
751 = do { sig_lie <- unifyCtxts sigs -- sigs is non-empty; sig_lie is zonked
752 ; let -- The "sig_avails" is the stuff available. We get that from
753 -- the context of the type signature, BUT ALSO the lie_avail
754 -- so that polymorphic recursion works right (see Note [Polymorphic recursion])
755 local_meths = [mkMethInst sig mono_id | (_, Just sig, mono_id) <- mono_infos]
756 sig_avails = sig_lie ++ local_meths
757 loc = sig_loc (head sigs)
759 -- Check that the needed dicts can be
760 -- expressed in terms of the signature ones
761 ; (qtvs, binds) <- tcSimplifyInferCheck loc tau_tvs sig_avails lie_req
763 -- Check that signature type variables are OK
764 ; final_qtvs <- checkSigsTyVars qtvs sigs
766 ; return (final_qtvs, sig_lie, binds) }
768 bndrs = bndrNames mono_infos
769 sigs = [sig | (_, Just sig, _) <- mono_infos]
770 get_tvs | isTopLevel top_lvl = tyVarsOfType -- See Note [Silly type synonym] in TcType
771 | otherwise = exactTyVarsOfType
772 tau_tvs = foldr (unionVarSet . get_tvs . getMonoType) emptyVarSet mono_infos
773 is_mono_sig sig = null (sig_theta sig)
774 doc = ptext (sLit "type signature(s) for") <+> pprBinders bndrs
776 mkMethInst (TcSigInfo { sig_id = poly_id, sig_tvs = tvs,
777 sig_theta = theta, sig_loc = loc }) mono_id
778 = Method {tci_id = mono_id, tci_oid = poly_id, tci_tys = mkTyVarTys tvs,
779 tci_theta = theta, tci_loc = loc}
782 unifyCtxts checks that all the signature contexts are the same
783 The type signatures on a mutually-recursive group of definitions
784 must all have the same context (or none).
786 The trick here is that all the signatures should have the same
787 context, and we want to share type variables for that context, so that
788 all the right hand sides agree a common vocabulary for their type
791 We unify them because, with polymorphic recursion, their types
792 might not otherwise be related. This is a rather subtle issue.
795 unifyCtxts :: [TcSigInfo] -> TcM [Inst]
796 -- Post-condition: the returned Insts are full zonked
797 unifyCtxts [] = panic "unifyCtxts []"
798 unifyCtxts (sig1 : sigs) -- Argument is always non-empty
799 = do { mapM unify_ctxt sigs
800 ; theta <- zonkTcThetaType (sig_theta sig1)
801 ; newDictBndrs (sig_loc sig1) theta }
803 theta1 = sig_theta sig1
804 unify_ctxt :: TcSigInfo -> TcM ()
805 unify_ctxt sig@(TcSigInfo { sig_theta = theta })
806 = setSrcSpan (instLocSpan (sig_loc sig)) $
807 addErrCtxt (sigContextsCtxt sig1 sig) $
808 do { cois <- unifyTheta theta1 theta
809 ; -- Check whether all coercions are identity coercions
810 -- That can happen if we have, say
812 -- g :: C (F a) => ...
813 -- where F is a type function and (F a ~ [a])
814 -- Then unification might succeed with a coercion. But it's much
815 -- much simpler to require that such signatures have identical contexts
816 checkTc (all isIdentityCoercion cois)
817 (ptext (sLit "Mutually dependent functions have syntactically distinct contexts"))
820 checkSigsTyVars :: [TcTyVar] -> [TcSigInfo] -> TcM [TcTyVar]
821 checkSigsTyVars qtvs sigs
822 = do { gbl_tvs <- tcGetGlobalTyVars
823 ; sig_tvs_s <- mapM (check_sig gbl_tvs) sigs
825 ; let -- Sigh. Make sure that all the tyvars in the type sigs
826 -- appear in the returned ty var list, which is what we are
827 -- going to generalise over. Reason: we occasionally get
829 -- type T a = () -> ()
832 -- Here, 'a' won't appear in qtvs, so we have to add it
833 sig_tvs = foldl extendVarSetList emptyVarSet sig_tvs_s
834 all_tvs = varSetElems (extendVarSetList sig_tvs qtvs)
837 check_sig gbl_tvs (TcSigInfo {sig_id = id, sig_tvs = tvs,
838 sig_theta = theta, sig_tau = tau})
839 = addErrCtxt (ptext (sLit "In the type signature for") <+> quotes (ppr id)) $
840 addErrCtxtM (sigCtxt id tvs theta tau) $
841 do { tvs' <- checkDistinctTyVars tvs
842 ; when (any (`elemVarSet` gbl_tvs) tvs')
843 (bleatEscapedTvs gbl_tvs tvs tvs')
846 checkDistinctTyVars :: [TcTyVar] -> TcM [TcTyVar]
847 -- (checkDistinctTyVars tvs) checks that the tvs from one type signature
848 -- are still all type variables, and all distinct from each other.
849 -- It returns a zonked set of type variables.
850 -- For example, if the type sig is
851 -- f :: forall a b. a -> b -> b
852 -- we want to check that 'a' and 'b' haven't
853 -- (a) been unified with a non-tyvar type
854 -- (b) been unified with each other (all distinct)
856 checkDistinctTyVars sig_tvs
857 = do { zonked_tvs <- mapM zonkSigTyVar sig_tvs
858 ; foldlM check_dup emptyVarEnv (sig_tvs `zip` zonked_tvs)
859 ; return zonked_tvs }
861 check_dup :: TyVarEnv TcTyVar -> (TcTyVar, TcTyVar) -> TcM (TyVarEnv TcTyVar)
862 -- The TyVarEnv maps each zonked type variable back to its
863 -- corresponding user-written signature type variable
864 check_dup acc (sig_tv, zonked_tv)
865 = case lookupVarEnv acc zonked_tv of
866 Just sig_tv' -> bomb_out sig_tv sig_tv'
868 Nothing -> return (extendVarEnv acc zonked_tv sig_tv)
870 bomb_out sig_tv1 sig_tv2
871 = do { env0 <- tcInitTidyEnv
872 ; let (env1, tidy_tv1) = tidyOpenTyVar env0 sig_tv1
873 (env2, tidy_tv2) = tidyOpenTyVar env1 sig_tv2
874 msg = ptext (sLit "Quantified type variable") <+> quotes (ppr tidy_tv1)
875 <+> ptext (sLit "is unified with another quantified type variable")
876 <+> quotes (ppr tidy_tv2)
877 ; failWithTcM (env2, msg) }
881 @getTyVarsToGen@ decides what type variables to generalise over.
883 For a "restricted group" -- see the monomorphism restriction
884 for a definition -- we bind no dictionaries, and
885 remove from tyvars_to_gen any constrained type variables
887 *Don't* simplify dicts at this point, because we aren't going
888 to generalise over these dicts. By the time we do simplify them
889 we may well know more. For example (this actually came up)
891 f x = array ... xs where xs = [1,2,3,4,5]
892 We don't want to generate lots of (fromInt Int 1), (fromInt Int 2)
893 stuff. If we simplify only at the f-binding (not the xs-binding)
894 we'll know that the literals are all Ints, and we can just produce
897 Find all the type variables involved in overloading, the
898 "constrained_tyvars". These are the ones we *aren't* going to
899 generalise. We must be careful about doing this:
901 (a) If we fail to generalise a tyvar which is not actually
902 constrained, then it will never, ever get bound, and lands
903 up printed out in interface files! Notorious example:
904 instance Eq a => Eq (Foo a b) where ..
905 Here, b is not constrained, even though it looks as if it is.
906 Another, more common, example is when there's a Method inst in
907 the LIE, whose type might very well involve non-overloaded
909 [NOTE: Jan 2001: I don't understand the problem here so I'm doing
910 the simple thing instead]
912 (b) On the other hand, we mustn't generalise tyvars which are constrained,
913 because we are going to pass on out the unmodified LIE, with those
914 tyvars in it. They won't be in scope if we've generalised them.
916 So we are careful, and do a complete simplification just to find the
917 constrained tyvars. We don't use any of the results, except to
918 find which tyvars are constrained.
920 Note [Polymorphic recursion]
921 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
922 The game plan for polymorphic recursion in the code above is
924 * Bind any variable for which we have a type signature
925 to an Id with a polymorphic type. Then when type-checking
926 the RHSs we'll make a full polymorphic call.
928 This fine, but if you aren't a bit careful you end up with a horrendous
929 amount of partial application and (worse) a huge space leak. For example:
931 f :: Eq a => [a] -> [a]
934 If we don't take care, after typechecking we get
936 f = /\a -> \d::Eq a -> let f' = f a d
940 Notice the the stupid construction of (f a d), which is of course
941 identical to the function we're executing. In this case, the
942 polymorphic recursion isn't being used (but that's a very common case).
943 This can lead to a massive space leak, from the following top-level defn
949 Now (f dEqInt) evaluates to a lambda that has f' as a free variable; but
950 f' is another thunk which evaluates to the same thing... and you end
951 up with a chain of identical values all hung onto by the CAF ff.
955 = let f' = f Int dEqInt in \ys. ...f'...
957 = let f' = let f' = f Int dEqInt in \ys. ...f'...
962 NOTE: a bit of arity anaysis would push the (f a d) inside the (\ys...),
963 which would make the space leak go away in this case
965 Solution: when typechecking the RHSs we always have in hand the
966 *monomorphic* Ids for each binding. So we just need to make sure that
967 if (Method f a d) shows up in the constraints emerging from (...f...)
968 we just use the monomorphic Id. We achieve this by adding monomorphic Ids
969 to the "givens" when simplifying constraints. That's what the "lies_avail"
974 f = /\a -> \d::Eq a -> letrec
975 fm = \ys:[a] -> ...fm...
981 %************************************************************************
985 %************************************************************************
987 Type signatures are tricky. See Note [Signature skolems] in TcType
989 @tcSigs@ checks the signatures for validity, and returns a list of
990 {\em freshly-instantiated} signatures. That is, the types are already
991 split up, and have fresh type variables installed. All non-type-signature
992 "RenamedSigs" are ignored.
994 The @TcSigInfo@ contains @TcTypes@ because they are unified with
995 the variable's type, and after that checked to see whether they've
1000 The -XScopedTypeVariables flag brings lexically-scoped type variables
1001 into scope for any explicitly forall-quantified type variables:
1002 f :: forall a. a -> a
1004 Then 'a' is in scope inside 'e'.
1006 However, we do *not* support this
1007 - For pattern bindings e.g
1011 - For multiple function bindings, unless Opt_RelaxedPolyRec is on
1012 f :: forall a. a -> a
1014 g :: forall b. b -> b
1016 Reason: we use mutable variables for 'a' and 'b', since they may
1017 unify to each other, and that means the scoped type variable would
1018 not stand for a completely rigid variable.
1020 Currently, we simply make Opt_ScopedTypeVariables imply Opt_RelaxedPolyRec
1023 Note [More instantiated than scoped]
1024 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1025 There may be more instantiated type variables than lexically-scoped
1027 type T a = forall b. b -> (a,b)
1029 Here, the signature for f will have one scoped type variable, c,
1030 but two instantiated type variables, c' and b'.
1032 We assume that the scoped ones are at the *front* of sig_tvs,
1033 and remember the names from the original HsForAllTy in the TcSigFun.
1037 type TcSigFun = Name -> Maybe [Name] -- Maps a let-binder to the list of
1038 -- type variables brought into scope
1039 -- by its type signature.
1040 -- Nothing => no type signature
1042 mkTcSigFun :: [LSig Name] -> TcSigFun
1043 -- Search for a particular type signature
1044 -- Precondition: the sigs are all type sigs
1045 -- Precondition: no duplicates
1046 mkTcSigFun sigs = lookupNameEnv env
1048 env = mkNameEnv [(name, hsExplicitTvs lhs_ty)
1049 | L _ (TypeSig (L _ name) lhs_ty) <- sigs]
1050 -- The scoped names are the ones explicitly mentioned
1051 -- in the HsForAll. (There may be more in sigma_ty, because
1052 -- of nested type synonyms. See Note [More instantiated than scoped].)
1053 -- See Note [Only scoped tyvars are in the TyVarEnv]
1058 sig_id :: TcId, -- *Polymorphic* binder for this value...
1060 sig_tvs :: [TcTyVar], -- Instantiated type variables
1061 -- See Note [Instantiate sig]
1063 sig_theta :: TcThetaType, -- Instantiated theta
1064 sig_tau :: TcTauType, -- Instantiated tau
1065 sig_loc :: InstLoc -- The location of the signature
1069 -- Note [Only scoped tyvars are in the TyVarEnv]
1070 -- We are careful to keep only the *lexically scoped* type variables in
1071 -- the type environment. Why? After all, the renamer has ensured
1072 -- that only legal occurrences occur, so we could put all type variables
1073 -- into the type env.
1075 -- But we want to check that two distinct lexically scoped type variables
1076 -- do not map to the same internal type variable. So we need to know which
1077 -- the lexically-scoped ones are... and at the moment we do that by putting
1078 -- only the lexically scoped ones into the environment.
1081 -- Note [Instantiate sig]
1082 -- It's vital to instantiate a type signature with fresh variables.
1084 -- type S = forall a. a->a
1088 -- Here, we must use distinct type variables when checking f,g's right hand sides.
1089 -- (Instantiation is only necessary because of type synonyms. Otherwise,
1090 -- it's all cool; each signature has distinct type variables from the renamer.)
1092 instance Outputable TcSigInfo where
1093 ppr (TcSigInfo { sig_id = id, sig_tvs = tyvars, sig_theta = theta, sig_tau = tau})
1094 = ppr id <+> ptext (sLit "::") <+> ppr tyvars <+> ppr theta <+> ptext (sLit "=>") <+> ppr tau
1098 tcTySig :: LSig Name -> TcM TcId
1099 tcTySig (L span (TypeSig (L _ name) ty))
1101 do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
1102 ; return (mkLocalId name sigma_ty) }
1103 tcTySig s = pprPanic "tcTySig" (ppr s)
1106 tcInstSig_maybe :: TcSigFun -> Name -> TcM (Maybe TcSigInfo)
1107 -- Instantiate with *meta* type variables;
1108 -- this signature is part of a multi-signature group
1109 tcInstSig_maybe sig_fn name
1110 = case sig_fn name of
1111 Nothing -> return Nothing
1112 Just _scoped_tvs -> do { tc_sig <- tcInstSig False name
1113 ; return (Just tc_sig) }
1114 -- NB: the _scoped_tvs may be non-empty, but we can
1115 -- just ignore them. See Note [Scoped tyvars].
1117 tcInstSig :: Bool -> Name -> TcM TcSigInfo
1118 -- Instantiate the signature, with either skolems or meta-type variables
1119 -- depending on the use_skols boolean. This variable is set True
1120 -- when we are typechecking a single function binding; and False for
1121 -- pattern bindings and a group of several function bindings.
1122 -- Reason: in the latter cases, the "skolems" can be unified together,
1123 -- so they aren't properly rigid in the type-refinement sense.
1124 -- NB: unless we are doing H98, each function with a sig will be done
1125 -- separately, even if it's mutually recursive, so use_skols will be True
1127 -- We always instantiate with fresh uniques,
1128 -- although we keep the same print-name
1130 -- type T = forall a. [a] -> [a]
1132 -- f = g where { g :: T; g = <rhs> }
1134 -- We must not use the same 'a' from the defn of T at both places!!
1136 tcInstSig use_skols name
1137 = do { poly_id <- tcLookupId name -- Cannot fail; the poly ids are put into
1138 -- scope when starting the binding group
1139 ; let skol_info = SigSkol (FunSigCtxt name)
1140 ; (tvs, theta, tau) <- tcInstSigType use_skols skol_info (idType poly_id)
1141 ; loc <- getInstLoc (SigOrigin skol_info)
1142 ; return (TcSigInfo { sig_id = poly_id,
1143 sig_tvs = tvs, sig_theta = theta, sig_tau = tau,
1147 isMonoGroup :: DynFlags -> [LHsBind Name] -> Bool
1148 -- No generalisation at all
1149 isMonoGroup dflags binds
1150 = dopt Opt_MonoPatBinds dflags && any is_pat_bind binds
1152 is_pat_bind (L _ (PatBind {})) = True
1153 is_pat_bind _ = False
1156 isRestrictedGroup :: DynFlags -> [LHsBind Name] -> TcSigFun -> Bool
1157 isRestrictedGroup dflags binds sig_fn
1158 = mono_restriction && not all_unrestricted
1160 mono_restriction = dopt Opt_MonomorphismRestriction dflags
1161 all_unrestricted = all (unrestricted . unLoc) binds
1162 has_sig n = isJust (sig_fn n)
1164 unrestricted (PatBind {}) = False
1165 unrestricted (VarBind { var_id = v }) = has_sig v
1166 unrestricted (FunBind { fun_id = v, fun_matches = matches }) = unrestricted_match matches
1167 || has_sig (unLoc v)
1168 unrestricted (AbsBinds {})
1169 = panic "isRestrictedGroup/unrestricted AbsBinds"
1171 unrestricted_match (MatchGroup (L _ (Match [] _ _) : _) _) = False
1172 -- No args => like a pattern binding
1173 unrestricted_match _ = True
1174 -- Some args => a function binding
1178 %************************************************************************
1180 \subsection[TcBinds-errors]{Error contexts and messages}
1182 %************************************************************************
1186 -- This one is called on LHS, when pat and grhss are both Name
1187 -- and on RHS, when pat is TcId and grhss is still Name
1188 patMonoBindsCtxt :: OutputableBndr id => LPat id -> GRHSs Name -> SDoc
1189 patMonoBindsCtxt pat grhss
1190 = hang (ptext (sLit "In a pattern binding:")) 4 (pprPatBind pat grhss)
1192 -----------------------------------------------
1193 sigContextsCtxt :: TcSigInfo -> TcSigInfo -> SDoc
1194 sigContextsCtxt sig1 sig2
1195 = vcat [ptext (sLit "When matching the contexts of the signatures for"),
1196 nest 2 (vcat [ppr id1 <+> dcolon <+> ppr (idType id1),
1197 ppr id2 <+> dcolon <+> ppr (idType id2)]),
1198 ptext (sLit "The signature contexts in a mutually recursive group should all be identical")]
1204 -----------------------------------------------
1205 unboxedTupleErr :: Name -> Type -> SDoc
1206 unboxedTupleErr name ty
1207 = hang (ptext (sLit "Illegal binding of unboxed tuple"))
1208 4 (ppr name <+> dcolon <+> ppr ty)
1210 -----------------------------------------------
1211 restrictedBindCtxtErr :: [Name] -> SDoc
1212 restrictedBindCtxtErr binder_names
1213 = hang (ptext (sLit "Illegal overloaded type signature(s)"))
1214 4 (vcat [ptext (sLit "in a binding group for") <+> pprBinders binder_names,
1215 ptext (sLit "that falls under the monomorphism restriction")])
1217 genCtxt :: [Name] -> SDoc
1218 genCtxt binder_names
1219 = ptext (sLit "When generalising the type(s) for") <+> pprBinders binder_names
1221 missingSigWarn :: Bool -> Name -> Type -> TcM ()
1222 missingSigWarn False _ _ = return ()
1223 missingSigWarn True name ty
1224 = do { env0 <- tcInitTidyEnv
1225 ; let (env1, tidy_ty) = tidyOpenType env0 ty
1226 ; addWarnTcM (env1, mk_msg tidy_ty) }
1228 mk_msg ty = vcat [ptext (sLit "Definition but no type signature for") <+> quotes (ppr name),
1229 sep [ptext (sLit "Inferred type:") <+> pprHsVar name <+> dcolon <+> ppr ty]]