2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[TcBinds]{TcBinds}
7 module TcBinds ( tcLocalBinds, tcTopBinds,
8 tcHsBootSigs, tcMonoBinds,
9 TcPragFun, tcSpecPrag, tcPrags, mkPragFun,
10 TcSigInfo(..), TcSigFun, mkTcSigFun,
11 badBootDeclErr ) where
13 #include "HsVersions.h"
15 import {-# SOURCE #-} TcMatches ( tcGRHSsPat, tcMatchesFun )
16 import {-# SOURCE #-} TcExpr ( tcMonoExpr )
18 import DynFlags ( dopt, DynFlags,
19 DynFlag(Opt_MonomorphismRestriction, Opt_MonoPatBinds, Opt_GlasgowExts) )
20 import HsSyn ( HsExpr(..), HsBind(..), LHsBinds, LHsBind, Sig(..),
21 HsLocalBinds(..), HsValBinds(..), HsIPBinds(..),
22 LSig, Match(..), IPBind(..), Prag(..),
23 HsType(..), LHsType, HsExplicitForAll(..), hsLTyVarNames,
24 isVanillaLSig, sigName, placeHolderNames, isPragLSig,
25 LPat, GRHSs, MatchGroup(..), pprLHsBinds, mkHsCoerce,
26 collectHsBindBinders, collectPatBinders, pprPatBind, isBangHsBind
28 import TcHsSyn ( zonkId )
31 import Inst ( newDictsAtLoc, newIPDict, instToId )
32 import TcEnv ( tcExtendIdEnv, tcExtendIdEnv2, tcExtendTyVarEnv2,
33 pprBinders, tcLookupLocalId_maybe, tcLookupId,
35 import TcUnify ( tcInfer, tcSubExp, unifyTheta,
36 bleatEscapedTvs, sigCtxt )
37 import TcSimplify ( tcSimplifyInfer, tcSimplifyInferCheck,
38 tcSimplifyRestricted, tcSimplifyIPs )
39 import TcHsType ( tcHsSigType, UserTypeCtxt(..) )
40 import TcPat ( tcPat, PatCtxt(..) )
41 import TcSimplify ( bindInstsOfLocalFuns )
42 import TcMType ( newFlexiTyVarTy, zonkQuantifiedTyVar, zonkSigTyVar,
43 tcInstSigTyVars, tcInstSkolTyVars, tcInstType,
44 zonkTcType, zonkTcTypes, zonkTcTyVar )
45 import TcType ( TcType, TcTyVar, TcThetaType,
46 SkolemInfo(SigSkol), UserTypeCtxt(FunSigCtxt),
47 TcTauType, TcSigmaType, isUnboxedTupleType,
48 mkTyVarTy, mkForAllTys, mkFunTys, exactTyVarsOfType,
49 mkForAllTy, isUnLiftedType, tcGetTyVar,
50 mkTyVarTys, tidyOpenTyVar )
51 import Kind ( argTypeKind )
52 import VarEnv ( TyVarEnv, emptyVarEnv, lookupVarEnv, extendVarEnv )
53 import TysWiredIn ( unitTy )
54 import TysPrim ( alphaTyVar )
55 import Id ( Id, mkLocalId, mkVanillaGlobal )
56 import IdInfo ( vanillaIdInfo )
57 import Var ( TyVar, idType, idName )
62 import SrcLoc ( Located(..), unLoc, getLoc )
64 import ErrUtils ( Message )
65 import Digraph ( SCC(..), stronglyConnComp )
66 import Maybes ( expectJust, isJust, isNothing, orElse )
67 import Util ( singleton )
68 import BasicTypes ( TopLevelFlag(..), isTopLevel, isNotTopLevel,
69 RecFlag(..), isNonRec, InlineSpec, defaultInlineSpec )
74 %************************************************************************
76 \subsection{Type-checking bindings}
78 %************************************************************************
80 @tcBindsAndThen@ typechecks a @HsBinds@. The "and then" part is because
81 it needs to know something about the {\em usage} of the things bound,
82 so that it can create specialisations of them. So @tcBindsAndThen@
83 takes a function which, given an extended environment, E, typechecks
84 the scope of the bindings returning a typechecked thing and (most
85 important) an LIE. It is this LIE which is then used as the basis for
86 specialising the things bound.
88 @tcBindsAndThen@ also takes a "combiner" which glues together the
89 bindings and the "thing" to make a new "thing".
91 The real work is done by @tcBindWithSigsAndThen@.
93 Recursive and non-recursive binds are handled in essentially the same
94 way: because of uniques there are no scoping issues left. The only
95 difference is that non-recursive bindings can bind primitive values.
97 Even for non-recursive binding groups we add typings for each binder
98 to the LVE for the following reason. When each individual binding is
99 checked the type of its LHS is unified with that of its RHS; and
100 type-checking the LHS of course requires that the binder is in scope.
102 At the top-level the LIE is sure to contain nothing but constant
103 dictionaries, which we resolve at the module level.
106 tcTopBinds :: HsValBinds Name -> TcM (LHsBinds TcId, TcLclEnv)
107 -- Note: returning the TcLclEnv is more than we really
108 -- want. The bit we care about is the local bindings
109 -- and the free type variables thereof
111 = do { (ValBindsOut prs _, env) <- tcValBinds TopLevel binds getLclEnv
112 ; return (foldr (unionBags . snd) emptyBag prs, env) }
113 -- The top level bindings are flattened into a giant
114 -- implicitly-mutually-recursive LHsBinds
116 tcHsBootSigs :: HsValBinds Name -> TcM [Id]
117 -- A hs-boot file has only one BindGroup, and it only has type
118 -- signatures in it. The renamer checked all this
119 tcHsBootSigs (ValBindsOut binds sigs)
120 = do { checkTc (null binds) badBootDeclErr
121 ; mapM (addLocM tc_boot_sig) (filter isVanillaLSig sigs) }
123 tc_boot_sig (TypeSig (L _ name) ty)
124 = do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
125 ; return (mkVanillaGlobal name sigma_ty vanillaIdInfo) }
126 -- Notice that we make GlobalIds, not LocalIds
127 tcHsBootSigs groups = pprPanic "tcHsBootSigs" (ppr groups)
129 badBootDeclErr :: Message
130 badBootDeclErr = ptext SLIT("Illegal declarations in an hs-boot file")
132 ------------------------
133 tcLocalBinds :: HsLocalBinds Name -> TcM thing
134 -> TcM (HsLocalBinds TcId, thing)
136 tcLocalBinds EmptyLocalBinds thing_inside
137 = do { thing <- thing_inside
138 ; return (EmptyLocalBinds, thing) }
140 tcLocalBinds (HsValBinds binds) thing_inside
141 = do { (binds', thing) <- tcValBinds NotTopLevel binds thing_inside
142 ; return (HsValBinds binds', thing) }
144 tcLocalBinds (HsIPBinds (IPBinds ip_binds _)) thing_inside
145 = do { (thing, lie) <- getLIE thing_inside
146 ; (avail_ips, ip_binds') <- mapAndUnzipM (wrapLocSndM tc_ip_bind) ip_binds
148 -- If the binding binds ?x = E, we must now
149 -- discharge any ?x constraints in expr_lie
150 ; dict_binds <- tcSimplifyIPs avail_ips lie
151 ; return (HsIPBinds (IPBinds ip_binds' dict_binds), thing) }
153 -- I wonder if we should do these one at at time
156 tc_ip_bind (IPBind ip expr)
157 = newFlexiTyVarTy argTypeKind `thenM` \ ty ->
158 newIPDict (IPBindOrigin ip) ip ty `thenM` \ (ip', ip_inst) ->
159 tcMonoExpr expr ty `thenM` \ expr' ->
160 returnM (ip_inst, (IPBind ip' expr'))
162 ------------------------
163 tcValBinds :: TopLevelFlag
164 -> HsValBinds Name -> TcM thing
165 -> TcM (HsValBinds TcId, thing)
167 tcValBinds top_lvl (ValBindsIn binds sigs) thing_inside
168 = pprPanic "tcValBinds" (ppr binds)
170 tcValBinds top_lvl (ValBindsOut binds sigs) thing_inside
171 = do { -- Typecheck the signature
172 ; let { prag_fn = mkPragFun sigs
173 ; ty_sigs = filter isVanillaLSig sigs
174 ; sig_fn = mkTcSigFun ty_sigs }
176 ; poly_ids <- mapM tcTySig ty_sigs
177 -- No recovery from bad signatures, because the type sigs
178 -- may bind type variables, so proceeding without them
179 -- can lead to a cascade of errors
180 -- ToDo: this means we fall over immediately if any type sig
181 -- is wrong, which is over-conservative, see Trac bug #745
183 -- Extend the envt right away with all
184 -- the Ids declared with type signatures
185 ; gla_exts <- doptM Opt_GlasgowExts
186 ; (binds', thing) <- tcExtendIdEnv poly_ids $
187 tc_val_binds gla_exts top_lvl sig_fn prag_fn
190 ; return (ValBindsOut binds' sigs, thing) }
192 ------------------------
193 tc_val_binds :: Bool -> TopLevelFlag -> TcSigFun -> TcPragFun
194 -> [(RecFlag, LHsBinds Name)] -> TcM thing
195 -> TcM ([(RecFlag, LHsBinds TcId)], thing)
196 -- Typecheck a whole lot of value bindings,
197 -- one strongly-connected component at a time
199 tc_val_binds gla_exts top_lvl sig_fn prag_fn [] thing_inside
200 = do { thing <- thing_inside
201 ; return ([], thing) }
203 tc_val_binds gla_exts top_lvl sig_fn prag_fn (group : groups) thing_inside
204 = do { (group', (groups', thing))
205 <- tc_group gla_exts top_lvl sig_fn prag_fn group $
206 tc_val_binds gla_exts top_lvl sig_fn prag_fn groups thing_inside
207 ; return (group' ++ groups', thing) }
209 ------------------------
210 tc_group :: Bool -> TopLevelFlag -> TcSigFun -> TcPragFun
211 -> (RecFlag, LHsBinds Name) -> TcM thing
212 -> TcM ([(RecFlag, LHsBinds TcId)], thing)
214 -- Typecheck one strongly-connected component of the original program.
215 -- We get a list of groups back, because there may
216 -- be specialisations etc as well
218 tc_group gla_exts top_lvl sig_fn prag_fn (NonRecursive, binds) thing_inside
219 -- A single non-recursive binding
220 -- We want to keep non-recursive things non-recursive
221 -- so that we desugar unlifted bindings correctly
222 = do { (binds, thing) <- tc_haskell98 top_lvl sig_fn prag_fn NonRecursive binds thing_inside
223 ; return ([(NonRecursive, b) | b <- binds], thing) }
225 tc_group gla_exts top_lvl sig_fn prag_fn (Recursive, binds) thing_inside
226 | not gla_exts -- Recursive group, normal Haskell 98 route
227 = do { (binds1, thing) <- tc_haskell98 top_lvl sig_fn prag_fn Recursive binds thing_inside
228 ; return ([(Recursive, unionManyBags binds1)], thing) }
230 | otherwise -- Recursive group, with gla-exts
231 = -- To maximise polymorphism (with -fglasgow-exts), we do a new
232 -- strongly-connected-component analysis, this time omitting
233 -- any references to variables with type signatures.
235 -- Notice that the bindInsts thing covers *all* the bindings in the original
236 -- group at once; an earlier one may use a later one!
237 do { traceTc (text "tc_group rec" <+> pprLHsBinds binds)
238 ; (binds1,thing) <- bindLocalInsts top_lvl $
239 go (stronglyConnComp (mkEdges sig_fn binds))
240 ; return ([(Recursive, unionManyBags binds1)], thing) }
241 -- Rec them all together
243 -- go :: SCC (LHsBind Name) -> TcM ([LHsBind TcId], [TcId], thing)
244 go (scc:sccs) = do { (binds1, ids1) <- tc_scc scc
245 ; (binds2, ids2, thing) <- tcExtendIdEnv ids1 $ go sccs
246 ; return (binds1 ++ binds2, ids1 ++ ids2, thing) }
247 go [] = do { thing <- thing_inside; return ([], [], thing) }
249 tc_scc (AcyclicSCC bind) = tc_sub_group NonRecursive (unitBag bind)
250 tc_scc (CyclicSCC binds) = tc_sub_group Recursive (listToBag binds)
252 tc_sub_group = tcPolyBinds top_lvl sig_fn prag_fn Recursive
254 tc_haskell98 top_lvl sig_fn prag_fn rec_flag binds thing_inside
255 = bindLocalInsts top_lvl $ do
256 { (binds1, ids) <- tcPolyBinds top_lvl sig_fn prag_fn rec_flag rec_flag binds
257 ; thing <- tcExtendIdEnv ids thing_inside
258 ; return (binds1, ids, thing) }
260 ------------------------
261 bindLocalInsts :: TopLevelFlag -> TcM ([LHsBinds TcId], [TcId], a) -> TcM ([LHsBinds TcId], a)
262 bindLocalInsts top_lvl thing_inside
263 | isTopLevel top_lvl = do { (binds, ids, thing) <- thing_inside; return (binds, thing) }
264 -- For the top level don't bother will all this bindInstsOfLocalFuns stuff.
265 -- All the top level things are rec'd together anyway, so it's fine to
266 -- leave them to the tcSimplifyTop, and quite a bit faster too
268 | otherwise -- Nested case
269 = do { ((binds, ids, thing), lie) <- getLIE thing_inside
270 ; lie_binds <- bindInstsOfLocalFuns lie ids
271 ; return (binds ++ [lie_binds], thing) }
273 ------------------------
274 mkEdges :: TcSigFun -> LHsBinds Name
275 -> [(LHsBind Name, BKey, [BKey])]
277 type BKey = Int -- Just number off the bindings
280 = [ (bind, key, [key | n <- nameSetToList (bind_fvs (unLoc bind)),
281 Just key <- [lookupNameEnv key_map n], no_sig n ])
282 | (bind, key) <- keyd_binds
285 no_sig :: Name -> Bool
286 no_sig n = isNothing (sig_fn n)
288 keyd_binds = bagToList binds `zip` [0::BKey ..]
290 key_map :: NameEnv BKey -- Which binding it comes from
291 key_map = mkNameEnv [(bndr, key) | (L _ bind, key) <- keyd_binds
292 , bndr <- bindersOfHsBind bind ]
294 bindersOfHsBind :: HsBind Name -> [Name]
295 bindersOfHsBind (PatBind { pat_lhs = pat }) = collectPatBinders pat
296 bindersOfHsBind (FunBind { fun_id = L _ f }) = [f]
298 ------------------------
299 tcPolyBinds :: TopLevelFlag -> TcSigFun -> TcPragFun
300 -> RecFlag -- Whether the group is really recursive
301 -> RecFlag -- Whether it's recursive after breaking
302 -- dependencies based on type signatures
304 -> TcM ([LHsBinds TcId], [TcId])
306 -- Typechecks a single bunch of bindings all together,
307 -- and generalises them. The bunch may be only part of a recursive
308 -- group, because we use type signatures to maximise polymorphism
310 -- Returns a list because the input may be a single non-recursive binding,
311 -- in which case the dependency order of the resulting bindings is
314 -- Knows nothing about the scope of the bindings
316 tcPolyBinds top_lvl sig_fn prag_fn rec_group rec_tc binds
318 bind_list = bagToList binds
319 binder_names = collectHsBindBinders binds
320 loc = getLoc (head bind_list)
321 -- TODO: location a bit awkward, but the mbinds have been
322 -- dependency analysed and may no longer be adjacent
324 -- SET UP THE MAIN RECOVERY; take advantage of any type sigs
326 recoverM (recoveryCode binder_names) $ do
328 { traceTc (ptext SLIT("------------------------------------------------"))
329 ; traceTc (ptext SLIT("Bindings for") <+> ppr binder_names)
331 -- TYPECHECK THE BINDINGS
332 ; ((binds', mono_bind_infos), lie_req)
333 <- getLIE (tcMonoBinds bind_list sig_fn rec_tc)
335 -- CHECK FOR UNLIFTED BINDINGS
336 -- These must be non-recursive etc, and are not generalised
337 -- They desugar to a case expression in the end
338 ; zonked_mono_tys <- zonkTcTypes (map getMonoType mono_bind_infos)
339 ; is_strict <- checkStrictBinds top_lvl rec_group binds'
340 zonked_mono_tys mono_bind_infos
342 do { extendLIEs lie_req
343 ; let exports = zipWith mk_export mono_bind_infos zonked_mono_tys
344 mk_export (name, Nothing, mono_id) mono_ty = ([], mkLocalId name mono_ty, mono_id, [])
345 mk_export (name, Just sig, mono_id) mono_ty = ([], sig_id sig, mono_id, [])
346 -- ToDo: prags for unlifted bindings
348 ; return ( [unitBag $ L loc $ AbsBinds [] [] exports binds'],
349 [poly_id | (_, poly_id, _, _) <- exports]) } -- Guaranteed zonked
351 else do -- The normal lifted case: GENERALISE
353 ; (tyvars_to_gen, dict_binds, dict_ids)
354 <- addErrCtxt (genCtxt (bndrNames mono_bind_infos)) $
355 generalise dflags top_lvl bind_list sig_fn mono_bind_infos lie_req
357 -- FINALISE THE QUANTIFIED TYPE VARIABLES
358 -- The quantified type variables often include meta type variables
359 -- we want to freeze them into ordinary type variables, and
360 -- default their kind (e.g. from OpenTypeKind to TypeKind)
361 ; tyvars_to_gen' <- mappM zonkQuantifiedTyVar tyvars_to_gen
363 -- BUILD THE POLYMORPHIC RESULT IDs
364 ; exports <- mapM (mkExport prag_fn tyvars_to_gen' (map idType dict_ids))
367 ; let poly_ids = [poly_id | (_, poly_id, _, _) <- exports]
368 ; traceTc (text "binding:" <+> ppr (poly_ids `zip` map idType poly_ids))
370 ; let abs_bind = L loc $ AbsBinds tyvars_to_gen'
372 (dict_binds `unionBags` binds')
374 ; return ([unitBag abs_bind], poly_ids) -- poly_ids are guaranteed zonked by mkExport
379 mkExport :: TcPragFun -> [TyVar] -> [TcType] -> MonoBindInfo
380 -> TcM ([TyVar], Id, Id, [Prag])
381 -- mkExport generates exports with
382 -- zonked type variables,
384 -- The former is just because no further unifications will change
385 -- the quantified type variables, so we can fix their final form
387 -- The latter is needed because the poly_ids are used to extend the
388 -- type environment; see the invariant on TcEnv.tcExtendIdEnv
390 -- Pre-condition: the inferred_tvs are already zonked
392 mkExport prag_fn inferred_tvs dict_tys (poly_name, mb_sig, mono_id)
393 = do { (tvs, poly_id) <- mk_poly_id mb_sig
395 ; poly_id' <- zonkId poly_id
396 ; prags <- tcPrags poly_id' (prag_fn poly_name)
397 -- tcPrags requires a zonked poly_id
399 ; return (tvs, poly_id', mono_id, prags) }
401 poly_ty = mkForAllTys inferred_tvs (mkFunTys dict_tys (idType mono_id))
403 mk_poly_id Nothing = return (inferred_tvs, mkLocalId poly_name poly_ty)
404 mk_poly_id (Just sig) = do { tvs <- mapM zonk_tv (sig_tvs sig)
405 ; return (tvs, sig_id sig) }
407 zonk_tv tv = do { ty <- zonkTcTyVar tv; return (tcGetTyVar "mkExport" ty) }
409 ------------------------
410 type TcPragFun = Name -> [LSig Name]
412 mkPragFun :: [LSig Name] -> TcPragFun
413 mkPragFun sigs = \n -> lookupNameEnv env n `orElse` []
415 prs = [(expectJust "mkPragFun" (sigName sig), sig)
416 | sig <- sigs, isPragLSig sig]
417 env = foldl add emptyNameEnv prs
418 add env (n,p) = extendNameEnv_Acc (:) singleton env n p
420 tcPrags :: Id -> [LSig Name] -> TcM [Prag]
421 tcPrags poly_id prags = mapM tc_prag prags
423 tc_prag (L loc prag) = setSrcSpan loc $
424 addErrCtxt (pragSigCtxt prag) $
427 pragSigCtxt prag = hang (ptext SLIT("In the pragma")) 2 (ppr prag)
429 tcPrag :: TcId -> Sig Name -> TcM Prag
430 -- Pre-condition: the poly_id is zonked
431 -- Reason: required by tcSubExp
432 tcPrag poly_id (SpecSig orig_name hs_ty inl) = tcSpecPrag poly_id hs_ty inl
433 tcPrag poly_id (SpecInstSig hs_ty) = tcSpecPrag poly_id hs_ty defaultInlineSpec
434 tcPrag poly_id (InlineSig v inl) = return (InlinePrag inl)
437 tcSpecPrag :: TcId -> LHsType Name -> InlineSpec -> TcM Prag
438 tcSpecPrag poly_id hs_ty inl
439 = do { spec_ty <- tcHsSigType (FunSigCtxt (idName poly_id)) hs_ty
440 ; (co_fn, lie) <- getLIE (tcSubExp (idType poly_id) spec_ty)
442 ; let const_dicts = map instToId lie
443 ; return (SpecPrag (mkHsCoerce co_fn (HsVar poly_id)) spec_ty const_dicts inl) }
444 -- Most of the work of specialisation is done by
445 -- the desugarer, guided by the SpecPrag
448 -- If typechecking the binds fails, then return with each
449 -- signature-less binder given type (forall a.a), to minimise
450 -- subsequent error messages
451 recoveryCode binder_names
452 = do { traceTc (text "tcBindsWithSigs: error recovery" <+> ppr binder_names)
453 ; poly_ids <- mapM mk_dummy binder_names
454 ; return ([], poly_ids) }
456 mk_dummy name = do { mb_id <- tcLookupLocalId_maybe name
458 Just id -> return id -- Had signature, was in envt
459 Nothing -> return (mkLocalId name forall_a_a) } -- No signature
462 forall_a_a = mkForAllTy alphaTyVar (mkTyVarTy alphaTyVar)
465 -- Check that non-overloaded unlifted bindings are
468 -- c) not a multiple-binding group (more or less implied by (a))
470 checkStrictBinds :: TopLevelFlag -> RecFlag
471 -> LHsBinds TcId -> [TcType] -> [MonoBindInfo]
473 checkStrictBinds top_lvl rec_group mbind mono_tys infos
474 | unlifted || bang_pat
475 = do { checkTc (isNotTopLevel top_lvl)
476 (strictBindErr "Top-level" unlifted mbind)
477 ; checkTc (isNonRec rec_group)
478 (strictBindErr "Recursive" unlifted mbind)
479 ; checkTc (isSingletonBag mbind)
480 (strictBindErr "Multiple" unlifted mbind)
481 ; mapM_ check_sig infos
486 unlifted = any isUnLiftedType mono_tys
487 bang_pat = anyBag (isBangHsBind . unLoc) mbind
488 check_sig (_, Just sig, _) = checkTc (null (sig_tvs sig) && null (sig_theta sig))
489 (badStrictSig unlifted sig)
490 check_sig other = return ()
492 strictBindErr flavour unlifted mbind
493 = hang (text flavour <+> msg <+> ptext SLIT("aren't allowed:"))
494 4 (pprLHsBinds mbind)
496 msg | unlifted = ptext SLIT("bindings for unlifted types")
497 | otherwise = ptext SLIT("bang-pattern bindings")
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 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 })),
552 [(name, Nothing, mono_id)]) }
554 tcMonoBinds [L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf,
555 fun_matches = matches, bind_fvs = fvs })]
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 scoped_tvs
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) <- sig_scoped tc_sig `zip` sig_tvs tc_sig ]
570 ; (co_fn, matches') <- tcExtendTyVarEnv2 rhs_tvs $
571 tcMatchesFun mono_name matches mono_ty
573 ; let fun_bind' = FunBind { fun_id = L nm_loc mono_id,
574 fun_infix = inf, fun_matches = matches',
575 bind_fvs = placeHolderNames, fun_co_fn = co_fn }
576 ; return (unitBag (L b_loc fun_bind'),
577 [(name, Just tc_sig, mono_id)]) }
579 tcMonoBinds binds sig_fn non_rec
580 = do { tc_binds <- mapM (wrapLocM (tcLhs sig_fn)) binds
582 -- Bring the monomorphic Ids, into scope for the RHSs
583 ; let mono_info = getMonoBindInfo tc_binds
584 rhs_id_env = [(name,mono_id) | (name, Nothing, mono_id) <- mono_info]
585 -- A monomorphic binding for each term variable that lacks
586 -- a type sig. (Ones with a sig are already in scope.)
588 ; binds' <- tcExtendIdEnv2 rhs_id_env $
589 traceTc (text "tcMonoBinds" <+> vcat [ ppr n <+> ppr id <+> ppr (idType id)
590 | (n,id) <- rhs_id_env]) `thenM_`
591 mapM (wrapLocM tcRhs) tc_binds
592 ; return (listToBag binds', mono_info) }
594 ------------------------
595 -- tcLhs typechecks the LHS of the bindings, to construct the environment in which
596 -- we typecheck the RHSs. Basically what we are doing is this: for each binder:
597 -- if there's a signature for it, use the instantiated signature type
598 -- otherwise invent a type variable
599 -- You see that quite directly in the FunBind case.
601 -- But there's a complication for pattern bindings:
602 -- data T = MkT (forall a. a->a)
604 -- Here we can guess a type variable for the entire LHS (which will be refined to T)
605 -- but we want to get (f::forall a. a->a) as the RHS environment.
606 -- The simplest way to do this is to typecheck the pattern, and then look up the
607 -- bound mono-ids. Then we want to retain the typechecked pattern to avoid re-doing
608 -- it; hence the TcMonoBind data type in which the LHS is done but the RHS isn't
610 data TcMonoBind -- Half completed; LHS done, RHS not done
611 = TcFunBind MonoBindInfo (Located TcId) Bool (MatchGroup Name)
612 | TcPatBind [MonoBindInfo] (LPat TcId) (GRHSs Name) TcSigmaType
614 type MonoBindInfo = (Name, Maybe TcSigInfo, TcId)
615 -- Type signature (if any), and
616 -- the monomorphic bound things
618 bndrNames :: [MonoBindInfo] -> [Name]
619 bndrNames mbi = [n | (n,_,_) <- mbi]
621 getMonoType :: MonoBindInfo -> TcTauType
622 getMonoType (_,_,mono_id) = idType mono_id
624 tcLhs :: TcSigFun -> HsBind Name -> TcM TcMonoBind
625 tcLhs sig_fn (FunBind { fun_id = L nm_loc name, fun_infix = inf, fun_matches = matches })
626 = do { mb_sig <- tcInstSig_maybe sig_fn name
627 ; mono_name <- newLocalName name
628 ; mono_ty <- mk_mono_ty mb_sig
629 ; let mono_id = mkLocalId mono_name mono_ty
630 ; return (TcFunBind (name, mb_sig, mono_id) (L nm_loc mono_id) inf matches) }
632 mk_mono_ty (Just sig) = return (sig_tau sig)
633 mk_mono_ty Nothing = newFlexiTyVarTy argTypeKind
635 tcLhs sig_fn bind@(PatBind { pat_lhs = pat, pat_rhs = grhss })
636 = do { mb_sigs <- mapM (tcInstSig_maybe sig_fn) names
637 ; mono_pat_binds <- doptM Opt_MonoPatBinds
638 -- With -fmono-pat-binds, we do no generalisation of pattern bindings
639 -- But the signature can still be polymoprhic!
640 -- data T = MkT (forall a. a->a)
641 -- x :: forall a. a->a
643 -- The function get_sig_ty decides whether the pattern-bound variables
644 -- should have exactly the type in the type signature (-fmono-pat-binds),
645 -- or the instantiated version (-fmono-pat-binds)
647 ; let nm_sig_prs = names `zip` mb_sigs
648 get_sig_ty | mono_pat_binds = idType . sig_id
649 | otherwise = sig_tau
650 tau_sig_env = mkNameEnv [ (name, get_sig_ty sig)
651 | (name, Just sig) <- nm_sig_prs]
652 sig_tau_fn = lookupNameEnv tau_sig_env
654 tc_pat exp_ty = tcPat (LetPat sig_tau_fn) pat exp_ty unitTy $ \ _ ->
655 mapM lookup_info nm_sig_prs
656 -- The unitTy is a bit bogus; it's the "result type" for lookup_info.
658 -- After typechecking the pattern, look up the binder
659 -- names, which the pattern has brought into scope.
660 lookup_info :: (Name, Maybe TcSigInfo) -> TcM MonoBindInfo
661 lookup_info (name, mb_sig) = do { mono_id <- tcLookupId name
662 ; return (name, mb_sig, mono_id) }
664 ; ((pat', infos), pat_ty) <- addErrCtxt (patMonoBindsCtxt pat grhss) $
667 ; return (TcPatBind infos pat' grhss pat_ty) }
669 names = collectPatBinders pat
672 tcLhs sig_fn other_bind = pprPanic "tcLhs" (ppr other_bind)
673 -- AbsBind, VarBind impossible
676 tcRhs :: TcMonoBind -> TcM (HsBind TcId)
677 tcRhs (TcFunBind info fun'@(L _ mono_id) inf matches)
678 = do { (co_fn, matches') <- tcMatchesFun (idName mono_id) matches
680 ; return (FunBind { fun_id = fun', fun_infix = inf, fun_matches = matches',
681 bind_fvs = placeHolderNames, fun_co_fn = co_fn }) }
683 tcRhs bind@(TcPatBind _ pat' grhss pat_ty)
684 = do { grhss' <- addErrCtxt (patMonoBindsCtxt pat' grhss) $
685 tcGRHSsPat grhss pat_ty
686 ; return (PatBind { pat_lhs = pat', pat_rhs = grhss', pat_rhs_ty = pat_ty,
687 bind_fvs = placeHolderNames }) }
690 ---------------------
691 getMonoBindInfo :: [Located TcMonoBind] -> [MonoBindInfo]
692 getMonoBindInfo tc_binds
693 = foldr (get_info . unLoc) [] tc_binds
695 get_info (TcFunBind info _ _ _) rest = info : rest
696 get_info (TcPatBind infos _ _ _) rest = infos ++ rest
700 %************************************************************************
704 %************************************************************************
707 generalise :: DynFlags -> TopLevelFlag
708 -> [LHsBind Name] -> TcSigFun
709 -> [MonoBindInfo] -> [Inst]
710 -> TcM ([TcTyVar], TcDictBinds, [TcId])
711 generalise dflags top_lvl bind_list sig_fn mono_infos lie_req
712 | isMonoGroup dflags bind_list
713 = do { extendLIEs lie_req; return ([], emptyBag, []) }
715 | isRestrictedGroup dflags bind_list sig_fn -- RESTRICTED CASE
716 = -- Check signature contexts are empty
717 do { checkTc (all is_mono_sig sigs)
718 (restrictedBindCtxtErr bndrs)
720 -- Now simplify with exactly that set of tyvars
721 -- We have to squash those Methods
722 ; (qtvs, binds) <- tcSimplifyRestricted doc top_lvl bndrs
725 -- Check that signature type variables are OK
726 ; final_qtvs <- checkSigsTyVars qtvs sigs
728 ; return (final_qtvs, binds, []) }
730 | null sigs -- UNRESTRICTED CASE, NO TYPE SIGS
731 = tcSimplifyInfer doc tau_tvs lie_req
733 | otherwise -- UNRESTRICTED CASE, WITH TYPE SIGS
734 = do { sig_lie <- unifyCtxts sigs -- sigs is non-empty
735 ; let -- The "sig_avails" is the stuff available. We get that from
736 -- the context of the type signature, BUT ALSO the lie_avail
737 -- so that polymorphic recursion works right (see Note [Polymorphic recursion])
738 local_meths = [mkMethInst sig mono_id | (_, Just sig, mono_id) <- mono_infos]
739 sig_avails = sig_lie ++ local_meths
741 -- Check that the needed dicts can be
742 -- expressed in terms of the signature ones
743 ; (forall_tvs, dict_binds) <- tcSimplifyInferCheck doc tau_tvs sig_avails lie_req
745 -- Check that signature type variables are OK
746 ; final_qtvs <- checkSigsTyVars forall_tvs sigs
748 ; returnM (final_qtvs, dict_binds, map instToId sig_lie) }
750 bndrs = bndrNames mono_infos
751 sigs = [sig | (_, Just sig, _) <- mono_infos]
752 tau_tvs = foldr (unionVarSet . exactTyVarsOfType . getMonoType) emptyVarSet mono_infos
753 -- NB: exactTyVarsOfType; see Note [Silly type synonym]
754 -- near defn of TcType.exactTyVarsOfType
755 is_mono_sig sig = null (sig_theta sig)
756 doc = ptext SLIT("type signature(s) for") <+> pprBinders bndrs
758 mkMethInst (TcSigInfo { sig_id = poly_id, sig_tvs = tvs,
759 sig_theta = theta, sig_loc = loc }) mono_id
760 = Method mono_id poly_id (mkTyVarTys tvs) theta loc
763 unifyCtxts checks that all the signature contexts are the same
764 The type signatures on a mutually-recursive group of definitions
765 must all have the same context (or none).
767 The trick here is that all the signatures should have the same
768 context, and we want to share type variables for that context, so that
769 all the right hand sides agree a common vocabulary for their type
772 We unify them because, with polymorphic recursion, their types
773 might not otherwise be related. This is a rather subtle issue.
776 unifyCtxts :: [TcSigInfo] -> TcM [Inst]
777 unifyCtxts (sig1 : sigs) -- Argument is always non-empty
778 = do { mapM unify_ctxt sigs
779 ; newDictsAtLoc (sig_loc sig1) (sig_theta sig1) }
781 theta1 = sig_theta sig1
782 unify_ctxt :: TcSigInfo -> TcM ()
783 unify_ctxt sig@(TcSigInfo { sig_theta = theta })
784 = setSrcSpan (instLocSrcSpan (sig_loc sig)) $
785 addErrCtxt (sigContextsCtxt sig1 sig) $
786 unifyTheta theta1 theta
788 checkSigsTyVars :: [TcTyVar] -> [TcSigInfo] -> TcM [TcTyVar]
789 checkSigsTyVars qtvs sigs
790 = do { gbl_tvs <- tcGetGlobalTyVars
791 ; sig_tvs_s <- mappM (check_sig gbl_tvs) sigs
793 ; let -- Sigh. Make sure that all the tyvars in the type sigs
794 -- appear in the returned ty var list, which is what we are
795 -- going to generalise over. Reason: we occasionally get
797 -- type T a = () -> ()
800 -- Here, 'a' won't appear in qtvs, so we have to add it
801 sig_tvs = foldl extendVarSetList emptyVarSet sig_tvs_s
802 all_tvs = varSetElems (extendVarSetList sig_tvs qtvs)
805 check_sig gbl_tvs (TcSigInfo {sig_id = id, sig_tvs = tvs,
806 sig_theta = theta, sig_tau = tau})
807 = addErrCtxt (ptext SLIT("In the type signature for") <+> quotes (ppr id)) $
808 addErrCtxtM (sigCtxt id tvs theta tau) $
809 do { tvs' <- checkDistinctTyVars tvs
810 ; ifM (any (`elemVarSet` gbl_tvs) tvs')
811 (bleatEscapedTvs gbl_tvs tvs tvs')
814 checkDistinctTyVars :: [TcTyVar] -> TcM [TcTyVar]
815 -- (checkDistinctTyVars tvs) checks that the tvs from one type signature
816 -- are still all type variables, and all distinct from each other.
817 -- It returns a zonked set of type variables.
818 -- For example, if the type sig is
819 -- f :: forall a b. a -> b -> b
820 -- we want to check that 'a' and 'b' haven't
821 -- (a) been unified with a non-tyvar type
822 -- (b) been unified with each other (all distinct)
824 checkDistinctTyVars sig_tvs
825 = do { zonked_tvs <- mapM zonkSigTyVar sig_tvs
826 ; foldlM check_dup emptyVarEnv (sig_tvs `zip` zonked_tvs)
827 ; return zonked_tvs }
829 check_dup :: TyVarEnv TcTyVar -> (TcTyVar, TcTyVar) -> TcM (TyVarEnv TcTyVar)
830 -- The TyVarEnv maps each zonked type variable back to its
831 -- corresponding user-written signature type variable
832 check_dup acc (sig_tv, zonked_tv)
833 = case lookupVarEnv acc zonked_tv of
834 Just sig_tv' -> bomb_out sig_tv sig_tv'
836 Nothing -> return (extendVarEnv acc zonked_tv sig_tv)
838 bomb_out sig_tv1 sig_tv2
839 = do { env0 <- tcInitTidyEnv
840 ; let (env1, tidy_tv1) = tidyOpenTyVar env0 sig_tv1
841 (env2, tidy_tv2) = tidyOpenTyVar env1 sig_tv2
842 msg = ptext SLIT("Quantified type variable") <+> quotes (ppr tidy_tv1)
843 <+> ptext SLIT("is unified with another quantified type variable")
844 <+> quotes (ppr tidy_tv2)
845 ; failWithTcM (env2, msg) }
850 @getTyVarsToGen@ decides what type variables to generalise over.
852 For a "restricted group" -- see the monomorphism restriction
853 for a definition -- we bind no dictionaries, and
854 remove from tyvars_to_gen any constrained type variables
856 *Don't* simplify dicts at this point, because we aren't going
857 to generalise over these dicts. By the time we do simplify them
858 we may well know more. For example (this actually came up)
860 f x = array ... xs where xs = [1,2,3,4,5]
861 We don't want to generate lots of (fromInt Int 1), (fromInt Int 2)
862 stuff. If we simplify only at the f-binding (not the xs-binding)
863 we'll know that the literals are all Ints, and we can just produce
866 Find all the type variables involved in overloading, the
867 "constrained_tyvars". These are the ones we *aren't* going to
868 generalise. We must be careful about doing this:
870 (a) If we fail to generalise a tyvar which is not actually
871 constrained, then it will never, ever get bound, and lands
872 up printed out in interface files! Notorious example:
873 instance Eq a => Eq (Foo a b) where ..
874 Here, b is not constrained, even though it looks as if it is.
875 Another, more common, example is when there's a Method inst in
876 the LIE, whose type might very well involve non-overloaded
878 [NOTE: Jan 2001: I don't understand the problem here so I'm doing
879 the simple thing instead]
881 (b) On the other hand, we mustn't generalise tyvars which are constrained,
882 because we are going to pass on out the unmodified LIE, with those
883 tyvars in it. They won't be in scope if we've generalised them.
885 So we are careful, and do a complete simplification just to find the
886 constrained tyvars. We don't use any of the results, except to
887 find which tyvars are constrained.
889 Note [Polymorphic recursion]
890 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
891 The game plan for polymorphic recursion in the code above is
893 * Bind any variable for which we have a type signature
894 to an Id with a polymorphic type. Then when type-checking
895 the RHSs we'll make a full polymorphic call.
897 This fine, but if you aren't a bit careful you end up with a horrendous
898 amount of partial application and (worse) a huge space leak. For example:
900 f :: Eq a => [a] -> [a]
903 If we don't take care, after typechecking we get
905 f = /\a -> \d::Eq a -> let f' = f a d
909 Notice the the stupid construction of (f a d), which is of course
910 identical to the function we're executing. In this case, the
911 polymorphic recursion isn't being used (but that's a very common case).
912 This can lead to a massive space leak, from the following top-level defn
918 Now (f dEqInt) evaluates to a lambda that has f' as a free variable; but
919 f' is another thunk which evaluates to the same thing... and you end
920 up with a chain of identical values all hung onto by the CAF ff.
924 = let f' = f Int dEqInt in \ys. ...f'...
926 = let f' = let f' = f Int dEqInt in \ys. ...f'...
931 NOTE: a bit of arity anaysis would push the (f a d) inside the (\ys...),
932 which would make the space leak go away in this case
934 Solution: when typechecking the RHSs we always have in hand the
935 *monomorphic* Ids for each binding. So we just need to make sure that
936 if (Method f a d) shows up in the constraints emerging from (...f...)
937 we just use the monomorphic Id. We achieve this by adding monomorphic Ids
938 to the "givens" when simplifying constraints. That's what the "lies_avail"
943 f = /\a -> \d::Eq a -> letrec
944 fm = \ys:[a] -> ...fm...
950 %************************************************************************
954 %************************************************************************
956 Type signatures are tricky. See Note [Signature skolems] in TcType
958 @tcSigs@ checks the signatures for validity, and returns a list of
959 {\em freshly-instantiated} signatures. That is, the types are already
960 split up, and have fresh type variables installed. All non-type-signature
961 "RenamedSigs" are ignored.
963 The @TcSigInfo@ contains @TcTypes@ because they are unified with
964 the variable's type, and after that checked to see whether they've
968 type TcSigFun = Name -> Maybe [Name] -- Maps a let-binder to the list of
969 -- type variables brought into scope
970 -- by its type signature.
971 -- Nothing => no type signature
973 mkTcSigFun :: [LSig Name] -> TcSigFun
974 -- Search for a particular type signature
975 -- Precondition: the sigs are all type sigs
976 -- Precondition: no duplicates
977 mkTcSigFun sigs = lookupNameEnv env
979 env = mkNameEnv [(name, scoped_tyvars hs_ty)
980 | L span (TypeSig (L _ name) (L _ hs_ty)) <- sigs]
981 scoped_tyvars (HsForAllTy Explicit tvs _ _) = hsLTyVarNames tvs
982 scoped_tyvars other = []
983 -- The scoped names are the ones explicitly mentioned
984 -- in the HsForAll. (There may be more in sigma_ty, because
985 -- of nested type synonyms. See Note [Scoped] with TcSigInfo.)
990 sig_id :: TcId, -- *Polymorphic* binder for this value...
992 sig_scoped :: [Name], -- Names for any scoped type variables
993 -- Invariant: correspond 1-1 with an initial
994 -- segment of sig_tvs (see Note [Scoped])
996 sig_tvs :: [TcTyVar], -- Instantiated type variables
997 -- See Note [Instantiate sig]
999 sig_theta :: TcThetaType, -- Instantiated theta
1000 sig_tau :: TcTauType, -- Instantiated tau
1001 sig_loc :: InstLoc -- The location of the signature
1005 -- There may be more instantiated type variables than scoped
1006 -- ones. For example:
1007 -- type T a = forall b. b -> (a,b)
1008 -- f :: forall c. T c
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 sig_scoped
1015 -- Note [Instantiate sig]
1016 -- It's vital to instantiate a type signature with fresh variable.
1018 -- type S = forall a. a->a
1022 -- Here, we must use distinct type variables when checking f,g's right hand sides.
1023 -- (Instantiation is only necessary because of type synonyms. Otherwise,
1024 -- it's all cool; each signature has distinct type variables from the renamer.)
1026 instance Outputable TcSigInfo where
1027 ppr (TcSigInfo { sig_id = id, sig_tvs = tyvars, sig_theta = theta, sig_tau = tau})
1028 = ppr id <+> ptext SLIT("::") <+> ppr tyvars <+> ppr theta <+> ptext SLIT("=>") <+> ppr tau
1032 tcTySig :: LSig Name -> TcM TcId
1033 tcTySig (L span (TypeSig (L _ name) ty))
1035 do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
1036 ; return (mkLocalId name sigma_ty) }
1039 tcInstSig_maybe :: TcSigFun -> Name -> TcM (Maybe TcSigInfo)
1040 -- Instantiate with *meta* type variables;
1041 -- this signature is part of a multi-signature group
1042 tcInstSig_maybe sig_fn name
1043 = case sig_fn name of
1044 Nothing -> return Nothing
1045 Just tvs -> do { tc_sig <- tcInstSig False name tvs
1046 ; return (Just tc_sig) }
1048 tcInstSig :: Bool -> Name -> [Name] -> TcM TcSigInfo
1049 -- Instantiate the signature, with either skolems or meta-type variables
1050 -- depending on the use_skols boolean. This variable is set True
1051 -- when we are typechecking a single function binding; and False for
1052 -- pattern bindigs and a group of several function bindings.
1053 -- Reason: in the latter cases, the "skolems" can be unified together,
1054 -- so they aren't properly rigid in the type-refinement sense.
1055 -- NB: unless we are doing H98, each function with a sig will be done
1056 -- separately, even if it's mutually recursive, so use_skols will be True
1058 -- We always instantiate with fresh uniques,
1059 -- although we keep the same print-name
1061 -- type T = forall a. [a] -> [a]
1063 -- f = g where { g :: T; g = <rhs> }
1065 -- We must not use the same 'a' from the defn of T at both places!!
1067 tcInstSig use_skols name scoped_names
1068 = do { poly_id <- tcLookupId name -- Cannot fail; the poly ids are put into
1069 -- scope when starting the binding group
1070 ; let skol_info = SigSkol (FunSigCtxt name)
1071 inst_tyvars | use_skols = tcInstSkolTyVars skol_info
1072 | otherwise = tcInstSigTyVars skol_info
1073 ; (tvs, theta, tau) <- tcInstType inst_tyvars (idType poly_id)
1074 ; loc <- getInstLoc (SigOrigin skol_info)
1075 ; return (TcSigInfo { sig_id = poly_id,
1076 sig_tvs = tvs, sig_theta = theta, sig_tau = tau,
1077 sig_scoped = final_scoped_names, sig_loc = loc }) }
1078 -- Note that the scoped_names and the sig_tvs will have
1079 -- different Names. That's quite ok; when we bring the
1080 -- scoped_names into scope, we just bind them to the sig_tvs
1082 -- We also only have scoped type variables when we are instantiating
1083 -- with true skolems
1084 final_scoped_names | use_skols = scoped_names
1088 isMonoGroup :: DynFlags -> [LHsBind Name] -> Bool
1089 -- No generalisation at all
1090 isMonoGroup dflags binds
1091 = dopt Opt_MonoPatBinds dflags && any is_pat_bind binds
1093 is_pat_bind (L _ (PatBind {})) = True
1094 is_pat_bind other = False
1097 isRestrictedGroup :: DynFlags -> [LHsBind Name] -> TcSigFun -> Bool
1098 isRestrictedGroup dflags binds sig_fn
1099 = mono_restriction && not all_unrestricted
1101 mono_restriction = dopt Opt_MonomorphismRestriction dflags
1102 all_unrestricted = all (unrestricted . unLoc) binds
1103 has_sig n = isJust (sig_fn n)
1105 unrestricted (PatBind {}) = False
1106 unrestricted (VarBind { var_id = v }) = has_sig v
1107 unrestricted (FunBind { fun_id = v, fun_matches = matches }) = unrestricted_match matches
1108 || has_sig (unLoc v)
1110 unrestricted_match (MatchGroup (L _ (Match [] _ _) : _) _) = False
1111 -- No args => like a pattern binding
1112 unrestricted_match other = True
1113 -- Some args => a function binding
1117 %************************************************************************
1119 \subsection[TcBinds-errors]{Error contexts and messages}
1121 %************************************************************************
1125 -- This one is called on LHS, when pat and grhss are both Name
1126 -- and on RHS, when pat is TcId and grhss is still Name
1127 patMonoBindsCtxt pat grhss
1128 = hang (ptext SLIT("In a pattern binding:")) 4 (pprPatBind pat grhss)
1130 -----------------------------------------------
1131 sigContextsCtxt sig1 sig2
1132 = vcat [ptext SLIT("When matching the contexts of the signatures for"),
1133 nest 2 (vcat [ppr id1 <+> dcolon <+> ppr (idType id1),
1134 ppr id2 <+> dcolon <+> ppr (idType id2)]),
1135 ptext SLIT("The signature contexts in a mutually recursive group should all be identical")]
1141 -----------------------------------------------
1142 unboxedTupleErr name ty
1143 = hang (ptext SLIT("Illegal binding of unboxed tuple"))
1144 4 (ppr name <+> dcolon <+> ppr ty)
1146 -----------------------------------------------
1147 restrictedBindCtxtErr binder_names
1148 = hang (ptext SLIT("Illegal overloaded type signature(s)"))
1149 4 (vcat [ptext SLIT("in a binding group for") <+> pprBinders binder_names,
1150 ptext SLIT("that falls under the monomorphism restriction")])
1152 genCtxt binder_names
1153 = ptext SLIT("When generalising the type(s) for") <+> pprBinders binder_names