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, zonkTcTyVars )
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 ; (binds', thing) <- tcExtendIdEnv poly_ids $
186 tc_val_binds top_lvl sig_fn prag_fn
189 ; return (ValBindsOut binds' sigs, thing) }
191 ------------------------
192 tc_val_binds :: TopLevelFlag -> TcSigFun -> TcPragFun
193 -> [(RecFlag, LHsBinds Name)] -> TcM thing
194 -> TcM ([(RecFlag, LHsBinds TcId)], thing)
195 -- Typecheck a whole lot of value bindings,
196 -- one strongly-connected component at a time
198 tc_val_binds top_lvl sig_fn prag_fn [] thing_inside
199 = do { thing <- thing_inside
200 ; return ([], thing) }
202 tc_val_binds top_lvl sig_fn prag_fn (group : groups) thing_inside
203 = do { (group', (groups', thing))
204 <- tc_group top_lvl sig_fn prag_fn group $
205 tc_val_binds top_lvl sig_fn prag_fn groups thing_inside
206 ; return (group' ++ groups', thing) }
208 ------------------------
209 tc_group :: TopLevelFlag -> TcSigFun -> TcPragFun
210 -> (RecFlag, LHsBinds Name) -> TcM thing
211 -> TcM ([(RecFlag, LHsBinds TcId)], thing)
213 -- Typecheck one strongly-connected component of the original program.
214 -- We get a list of groups back, because there may
215 -- be specialisations etc as well
217 tc_group top_lvl sig_fn prag_fn (NonRecursive, binds) thing_inside
218 = -- A single non-recursive binding
219 -- We want to keep non-recursive things non-recursive
220 -- so that we desugar unlifted bindings correctly
221 do { (binds, thing) <- tcPolyBinds top_lvl NonRecursive NonRecursive
222 sig_fn prag_fn binds thing_inside
223 ; return ([(NonRecursive, b) | b <- binds], thing) }
225 tc_group top_lvl sig_fn prag_fn (Recursive, binds) thing_inside
226 = -- A recursive strongly-connected component
227 -- To maximise polymorphism (with -fglasgow-exts), we do a new
228 -- strongly-connected-component analysis, this time omitting
229 -- any references to variables with type signatures.
231 -- Then we bring into scope all the variables with type signatures
232 do { traceTc (text "tc_group rec" <+> pprLHsBinds binds)
233 ; gla_exts <- doptM Opt_GlasgowExts
234 ; (binds,thing) <- if gla_exts
236 else tc_binds Recursive binds thing_inside
237 ; return ([(Recursive, unionManyBags binds)], thing) }
238 -- Rec them all together
240 new_sccs :: [SCC (LHsBind Name)]
241 new_sccs = stronglyConnComp (mkEdges sig_fn binds)
243 -- go :: SCC (LHsBind Name) -> TcM ([LHsBind TcId], thing)
244 go (scc:sccs) = do { (binds1, (binds2, thing)) <- go1 scc (go sccs)
245 ; return (binds1 ++ binds2, thing) }
246 go [] = do { thing <- thing_inside; return ([], thing) }
248 go1 (AcyclicSCC bind) = tc_binds NonRecursive (unitBag bind)
249 go1 (CyclicSCC binds) = tc_binds Recursive (listToBag binds)
251 tc_binds rec_tc binds = tcPolyBinds top_lvl Recursive rec_tc sig_fn prag_fn binds
253 ------------------------
254 mkEdges :: TcSigFun -> LHsBinds Name
255 -> [(LHsBind Name, BKey, [BKey])]
257 type BKey = Int -- Just number off the bindings
260 = [ (bind, key, [key | n <- nameSetToList (bind_fvs (unLoc bind)),
261 Just key <- [lookupNameEnv key_map n], no_sig n ])
262 | (bind, key) <- keyd_binds
265 no_sig :: Name -> Bool
266 no_sig n = isNothing (sig_fn n)
268 keyd_binds = bagToList binds `zip` [0::BKey ..]
270 key_map :: NameEnv BKey -- Which binding it comes from
271 key_map = mkNameEnv [(bndr, key) | (L _ bind, key) <- keyd_binds
272 , bndr <- bindersOfHsBind bind ]
274 bindersOfHsBind :: HsBind Name -> [Name]
275 bindersOfHsBind (PatBind { pat_lhs = pat }) = collectPatBinders pat
276 bindersOfHsBind (FunBind { fun_id = L _ f }) = [f]
278 ------------------------
279 tcPolyBinds :: TopLevelFlag
280 -> RecFlag -- Whether the group is really recursive
281 -> RecFlag -- Whether it's recursive for typechecking purposes
282 -> TcSigFun -> TcPragFun
285 -> TcM ([LHsBinds TcId], thing)
287 -- Typechecks a single bunch of bindings all together,
288 -- and generalises them. The bunch may be only part of a recursive
289 -- group, because we use type signatures to maximise polymorphism
291 -- Deals with the bindInstsOfLocalFuns thing too
293 -- Returns a list because the input may be a single non-recursive binding,
294 -- in which case the dependency order of the resulting bindings is
297 tcPolyBinds top_lvl rec_group rec_tc sig_fn prag_fn scc thing_inside
298 = -- NB: polymorphic recursion means that a function
299 -- may use an instance of itself, we must look at the LIE arising
300 -- from the function's own right hand side. Hence the getLIE
301 -- encloses the tc_poly_binds.
302 do { traceTc (text "tcPolyBinds" <+> ppr scc)
303 ; ((binds1, poly_ids, thing), lie) <- getLIE $
304 do { (binds1, poly_ids) <- tc_poly_binds top_lvl rec_group rec_tc
306 ; thing <- tcExtendIdEnv poly_ids thing_inside
307 ; return (binds1, poly_ids, thing) }
309 ; if isTopLevel top_lvl
310 then -- For the top level don't bother will all this
311 -- bindInstsOfLocalFuns stuff. All the top level
312 -- things are rec'd together anyway, so it's fine to
313 -- leave them to the tcSimplifyTop,
314 -- and quite a bit faster too
315 do { extendLIEs lie; return (binds1, thing) }
317 else do -- Nested case
318 { lie_binds <- bindInstsOfLocalFuns lie poly_ids
319 ; return (binds1 ++ [lie_binds], thing) }}
321 ------------------------
322 tc_poly_binds :: TopLevelFlag -- See comments on tcPolyBinds
323 -> RecFlag -> RecFlag
324 -> TcSigFun -> TcPragFun
326 -> TcM ([LHsBinds TcId], [TcId])
327 -- Typechecks the bindings themselves
328 -- Knows nothing about the scope of the bindings
330 tc_poly_binds top_lvl rec_group rec_tc sig_fn prag_fn binds
332 binder_names = collectHsBindBinders binds
333 bind_list = bagToList binds
335 loc = getLoc (head bind_list)
336 -- TODO: location a bit awkward, but the mbinds have been
337 -- dependency analysed and may no longer be adjacent
339 -- SET UP THE MAIN RECOVERY; take advantage of any type sigs
341 recoverM (recoveryCode binder_names) $ do
343 { traceTc (ptext SLIT("------------------------------------------------"))
344 ; traceTc (ptext SLIT("Bindings for") <+> ppr binder_names)
346 -- TYPECHECK THE BINDINGS
347 ; ((binds', mono_bind_infos), lie_req)
348 <- getLIE (tcMonoBinds bind_list sig_fn rec_tc)
350 -- CHECK FOR UNLIFTED BINDINGS
351 -- These must be non-recursive etc, and are not generalised
352 -- They desugar to a case expression in the end
353 ; zonked_mono_tys <- zonkTcTypes (map getMonoType mono_bind_infos)
354 ; is_strict <- checkStrictBinds top_lvl rec_group binds'
355 zonked_mono_tys mono_bind_infos
357 do { extendLIEs lie_req
358 ; let exports = zipWith mk_export mono_bind_infos zonked_mono_tys
359 mk_export (name, Nothing, mono_id) mono_ty = ([], mkLocalId name mono_ty, mono_id, [])
360 mk_export (name, Just sig, mono_id) mono_ty = ([], sig_id sig, mono_id, [])
361 -- ToDo: prags for unlifted bindings
363 ; return ( [unitBag $ L loc $ AbsBinds [] [] exports binds'],
364 [poly_id | (_, poly_id, _, _) <- exports]) } -- Guaranteed zonked
366 else do -- The normal lifted case: GENERALISE
368 ; (tyvars_to_gen, dict_binds, dict_ids)
369 <- addErrCtxt (genCtxt (bndrNames mono_bind_infos)) $
370 generalise dflags top_lvl bind_list sig_fn mono_bind_infos lie_req
372 -- FINALISE THE QUANTIFIED TYPE VARIABLES
373 -- The quantified type variables often include meta type variables
374 -- we want to freeze them into ordinary type variables, and
375 -- default their kind (e.g. from OpenTypeKind to TypeKind)
376 ; tyvars_to_gen' <- mappM zonkQuantifiedTyVar tyvars_to_gen
378 -- BUILD THE POLYMORPHIC RESULT IDs
379 ; exports <- mapM (mkExport prag_fn tyvars_to_gen' (map idType dict_ids))
382 -- ZONK THE poly_ids, because they are used to extend the type
383 -- environment; see the invariant on TcEnv.tcExtendIdEnv
384 ; let poly_ids = [poly_id | (_, poly_id, _, _) <- exports]
385 ; zonked_poly_ids <- mappM zonkId poly_ids
387 ; traceTc (text "binding:" <+> ppr (zonked_poly_ids `zip` map idType zonked_poly_ids))
389 ; let abs_bind = L loc $ AbsBinds tyvars_to_gen'
391 (dict_binds `unionBags` binds')
393 ; return ([unitBag abs_bind], zonked_poly_ids)
398 mkExport :: TcPragFun -> [TyVar] -> [TcType] -> MonoBindInfo
399 -> TcM ([TyVar], Id, Id, [Prag])
400 mkExport prag_fn inferred_tvs dict_tys (poly_name, mb_sig, mono_id)
402 Nothing -> do { prags <- tcPrags poly_id (prag_fn poly_name)
403 ; return (inferred_tvs, poly_id, mono_id, prags) }
405 poly_id = mkLocalId poly_name poly_ty
406 poly_ty = mkForAllTys inferred_tvs
410 Just sig -> do { let poly_id = sig_id sig
411 ; prags <- tcPrags poly_id (prag_fn poly_name)
412 ; sig_tys <- zonkTcTyVars (sig_tvs sig)
413 ; let sig_tvs' = map (tcGetTyVar "mkExport") sig_tys
414 ; return (sig_tvs', poly_id, mono_id, prags) }
415 -- We zonk the sig_tvs here so that the export triple
416 -- always has zonked type variables;
417 -- a convenient invariant
420 ------------------------
421 type TcPragFun = Name -> [LSig Name]
423 mkPragFun :: [LSig Name] -> TcPragFun
424 mkPragFun sigs = \n -> lookupNameEnv env n `orElse` []
426 prs = [(expectJust "mkPragFun" (sigName sig), sig)
427 | sig <- sigs, isPragLSig sig]
428 env = foldl add emptyNameEnv prs
429 add env (n,p) = extendNameEnv_Acc (:) singleton env n p
431 tcPrags :: Id -> [LSig Name] -> TcM [Prag]
432 tcPrags poly_id prags = mapM tc_prag prags
434 tc_prag (L loc prag) = setSrcSpan loc $
435 addErrCtxt (pragSigCtxt prag) $
438 pragSigCtxt prag = hang (ptext SLIT("In the pragma")) 2 (ppr prag)
440 tcPrag :: TcId -> Sig Name -> TcM Prag
441 tcPrag poly_id (SpecSig orig_name hs_ty inl) = tcSpecPrag poly_id hs_ty inl
442 tcPrag poly_id (SpecInstSig hs_ty) = tcSpecPrag poly_id hs_ty defaultInlineSpec
443 tcPrag poly_id (InlineSig v inl) = return (InlinePrag inl)
446 tcSpecPrag :: TcId -> LHsType Name -> InlineSpec -> TcM Prag
447 tcSpecPrag poly_id hs_ty inl
448 = do { spec_ty <- tcHsSigType (FunSigCtxt (idName poly_id)) hs_ty
449 ; (co_fn, lie) <- getLIE (tcSubExp (idType poly_id) spec_ty)
451 ; let const_dicts = map instToId lie
452 ; return (SpecPrag (mkHsCoerce co_fn (HsVar poly_id)) spec_ty const_dicts inl) }
453 -- Most of the work of specialisation is done by
454 -- the desugarer, guided by the SpecPrag
457 -- If typechecking the binds fails, then return with each
458 -- signature-less binder given type (forall a.a), to minimise
459 -- subsequent error messages
460 recoveryCode binder_names
461 = do { traceTc (text "tcBindsWithSigs: error recovery" <+> ppr binder_names)
462 ; poly_ids <- mapM mk_dummy binder_names
463 ; return ([], poly_ids) }
465 mk_dummy name = do { mb_id <- tcLookupLocalId_maybe name
467 Just id -> return id -- Had signature, was in envt
468 Nothing -> return (mkLocalId name forall_a_a) } -- No signature
471 forall_a_a = mkForAllTy alphaTyVar (mkTyVarTy alphaTyVar)
474 -- Check that non-overloaded unlifted bindings are
477 -- c) not a multiple-binding group (more or less implied by (a))
479 checkStrictBinds :: TopLevelFlag -> RecFlag
480 -> LHsBinds TcId -> [TcType] -> [MonoBindInfo]
482 checkStrictBinds top_lvl rec_group mbind mono_tys infos
483 | unlifted || bang_pat
484 = do { checkTc (isNotTopLevel top_lvl)
485 (strictBindErr "Top-level" unlifted mbind)
486 ; checkTc (isNonRec rec_group)
487 (strictBindErr "Recursive" unlifted mbind)
488 ; checkTc (isSingletonBag mbind)
489 (strictBindErr "Multiple" unlifted mbind)
490 ; mapM_ check_sig infos
495 unlifted = any isUnLiftedType mono_tys
496 bang_pat = anyBag (isBangHsBind . unLoc) mbind
497 check_sig (_, Just sig, _) = checkTc (null (sig_tvs sig) && null (sig_theta sig))
498 (badStrictSig unlifted sig)
499 check_sig other = return ()
501 strictBindErr flavour unlifted mbind
502 = hang (text flavour <+> msg <+> ptext SLIT("aren't allowed:"))
503 4 (pprLHsBinds mbind)
505 msg | unlifted = ptext SLIT("bindings for unlifted types")
506 | otherwise = ptext SLIT("bang-pattern bindings")
508 badStrictSig unlifted sig
509 = hang (ptext SLIT("Illegal polymorphic signature in") <+> msg)
512 msg | unlifted = ptext SLIT("an unlifted binding")
513 | otherwise = ptext SLIT("a bang-pattern binding")
517 %************************************************************************
519 \subsection{tcMonoBind}
521 %************************************************************************
523 @tcMonoBinds@ deals with a perhaps-recursive group of HsBinds.
524 The signatures have been dealt with already.
527 tcMonoBinds :: [LHsBind Name]
529 -> RecFlag -- Whether the binding is recursive for typechecking purposes
530 -- i.e. the binders are mentioned in their RHSs, and
531 -- we are not resuced by a type signature
532 -> TcM (LHsBinds TcId, [MonoBindInfo])
534 tcMonoBinds [L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf,
535 fun_matches = matches, bind_fvs = fvs })]
536 sig_fn -- Single function binding,
537 NonRecursive -- binder isn't mentioned in RHS,
538 | Nothing <- sig_fn name -- ...with no type signature
539 = -- In this very special case we infer the type of the
540 -- right hand side first (it may have a higher-rank type)
541 -- and *then* make the monomorphic Id for the LHS
542 -- e.g. f = \(x::forall a. a->a) -> <body>
543 -- We want to infer a higher-rank type for f
545 do { ((co_fn, matches'), rhs_ty) <- tcInfer (tcMatchesFun name matches)
547 -- Check for an unboxed tuple type
548 -- f = (# True, False #)
549 -- Zonk first just in case it's hidden inside a meta type variable
550 -- (This shows up as a (more obscure) kind error
551 -- in the 'otherwise' case of tcMonoBinds.)
552 ; zonked_rhs_ty <- zonkTcType rhs_ty
553 ; checkTc (not (isUnboxedTupleType zonked_rhs_ty))
554 (unboxedTupleErr name zonked_rhs_ty)
556 ; mono_name <- newLocalName name
557 ; let mono_id = mkLocalId mono_name zonked_rhs_ty
558 ; return (unitBag (L b_loc (FunBind { fun_id = L nm_loc mono_id, fun_infix = inf,
559 fun_matches = matches', bind_fvs = fvs,
560 fun_co_fn = co_fn })),
561 [(name, Nothing, mono_id)]) }
563 tcMonoBinds [L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf,
564 fun_matches = matches, bind_fvs = fvs })]
565 sig_fn -- Single function binding
567 | Just scoped_tvs <- sig_fn name -- ...with a type signature
568 = -- When we have a single function binding, with a type signature
569 -- we can (a) use genuine, rigid skolem constants for the type variables
570 -- (b) bring (rigid) scoped type variables into scope
572 do { tc_sig <- tcInstSig True name scoped_tvs
573 ; mono_name <- newLocalName name
574 ; let mono_ty = sig_tau tc_sig
575 mono_id = mkLocalId mono_name mono_ty
576 rhs_tvs = [ (name, mkTyVarTy tv)
577 | (name, tv) <- sig_scoped tc_sig `zip` sig_tvs tc_sig ]
579 ; (co_fn, matches') <- tcExtendTyVarEnv2 rhs_tvs $
580 tcMatchesFun mono_name matches mono_ty
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 }
585 ; return (unitBag (L b_loc fun_bind'),
586 [(name, Just tc_sig, mono_id)]) }
588 tcMonoBinds binds sig_fn non_rec
589 = do { tc_binds <- mapM (wrapLocM (tcLhs sig_fn)) binds
591 -- Bring the monomorphic Ids, into scope for the RHSs
592 ; let mono_info = getMonoBindInfo tc_binds
593 rhs_id_env = [(name,mono_id) | (name, Nothing, mono_id) <- mono_info]
594 -- A monomorphic binding for each term variable that lacks
595 -- a type sig. (Ones with a sig are already in scope.)
597 ; binds' <- tcExtendIdEnv2 rhs_id_env $
598 traceTc (text "tcMonoBinds" <+> vcat [ ppr n <+> ppr id <+> ppr (idType id)
599 | (n,id) <- rhs_id_env]) `thenM_`
600 mapM (wrapLocM tcRhs) tc_binds
601 ; return (listToBag binds', mono_info) }
603 ------------------------
604 -- tcLhs typechecks the LHS of the bindings, to construct the environment in which
605 -- we typecheck the RHSs. Basically what we are doing is this: for each binder:
606 -- if there's a signature for it, use the instantiated signature type
607 -- otherwise invent a type variable
608 -- You see that quite directly in the FunBind case.
610 -- But there's a complication for pattern bindings:
611 -- data T = MkT (forall a. a->a)
613 -- Here we can guess a type variable for the entire LHS (which will be refined to T)
614 -- but we want to get (f::forall a. a->a) as the RHS environment.
615 -- The simplest way to do this is to typecheck the pattern, and then look up the
616 -- bound mono-ids. Then we want to retain the typechecked pattern to avoid re-doing
617 -- it; hence the TcMonoBind data type in which the LHS is done but the RHS isn't
619 data TcMonoBind -- Half completed; LHS done, RHS not done
620 = TcFunBind MonoBindInfo (Located TcId) Bool (MatchGroup Name)
621 | TcPatBind [MonoBindInfo] (LPat TcId) (GRHSs Name) TcSigmaType
623 type MonoBindInfo = (Name, Maybe TcSigInfo, TcId)
624 -- Type signature (if any), and
625 -- the monomorphic bound things
627 bndrNames :: [MonoBindInfo] -> [Name]
628 bndrNames mbi = [n | (n,_,_) <- mbi]
630 getMonoType :: MonoBindInfo -> TcTauType
631 getMonoType (_,_,mono_id) = idType mono_id
633 tcLhs :: TcSigFun -> HsBind Name -> TcM TcMonoBind
634 tcLhs sig_fn (FunBind { fun_id = L nm_loc name, fun_infix = inf, fun_matches = matches })
635 = do { mb_sig <- tcInstSig_maybe sig_fn name
636 ; mono_name <- newLocalName name
637 ; mono_ty <- mk_mono_ty mb_sig
638 ; let mono_id = mkLocalId mono_name mono_ty
639 ; return (TcFunBind (name, mb_sig, mono_id) (L nm_loc mono_id) inf matches) }
641 mk_mono_ty (Just sig) = return (sig_tau sig)
642 mk_mono_ty Nothing = newFlexiTyVarTy argTypeKind
644 tcLhs sig_fn bind@(PatBind { pat_lhs = pat, pat_rhs = grhss })
645 = do { mb_sigs <- mapM (tcInstSig_maybe sig_fn) names
647 ; let nm_sig_prs = names `zip` mb_sigs
648 tau_sig_env = mkNameEnv [ (name, sig_tau sig) | (name, Just sig) <- nm_sig_prs]
649 sig_tau_fn = lookupNameEnv tau_sig_env
651 tc_pat exp_ty = tcPat (LetPat sig_tau_fn) pat exp_ty unitTy $ \ _ ->
652 mapM lookup_info nm_sig_prs
653 -- The unitTy is a bit bogus; it's the "result type" for lookup_info.
655 -- After typechecking the pattern, look up the binder
656 -- names, which the pattern has brought into scope.
657 lookup_info :: (Name, Maybe TcSigInfo) -> TcM MonoBindInfo
658 lookup_info (name, mb_sig) = do { mono_id <- tcLookupId name
659 ; return (name, mb_sig, mono_id) }
661 ; ((pat', infos), pat_ty) <- addErrCtxt (patMonoBindsCtxt pat grhss) $
664 ; return (TcPatBind infos pat' grhss pat_ty) }
666 names = collectPatBinders pat
669 tcLhs sig_fn other_bind = pprPanic "tcLhs" (ppr other_bind)
670 -- AbsBind, VarBind impossible
673 tcRhs :: TcMonoBind -> TcM (HsBind TcId)
674 tcRhs (TcFunBind info fun'@(L _ mono_id) inf matches)
675 = do { (co_fn, matches') <- tcMatchesFun (idName mono_id) matches
677 ; return (FunBind { fun_id = fun', fun_infix = inf, fun_matches = matches',
678 bind_fvs = placeHolderNames, fun_co_fn = co_fn }) }
680 tcRhs bind@(TcPatBind _ pat' grhss pat_ty)
681 = do { grhss' <- addErrCtxt (patMonoBindsCtxt pat' grhss) $
682 tcGRHSsPat grhss pat_ty
683 ; return (PatBind { pat_lhs = pat', pat_rhs = grhss', pat_rhs_ty = pat_ty,
684 bind_fvs = placeHolderNames }) }
687 ---------------------
688 getMonoBindInfo :: [Located TcMonoBind] -> [MonoBindInfo]
689 getMonoBindInfo tc_binds
690 = foldr (get_info . unLoc) [] tc_binds
692 get_info (TcFunBind info _ _ _) rest = info : rest
693 get_info (TcPatBind infos _ _ _) rest = infos ++ rest
697 %************************************************************************
701 %************************************************************************
704 generalise :: DynFlags -> TopLevelFlag
705 -> [LHsBind Name] -> TcSigFun
706 -> [MonoBindInfo] -> [Inst]
707 -> TcM ([TcTyVar], TcDictBinds, [TcId])
708 generalise dflags top_lvl bind_list sig_fn mono_infos lie_req
709 | isMonoGroup dflags bind_list
710 = do { extendLIEs lie_req; return ([], emptyBag, []) }
712 | isRestrictedGroup dflags bind_list sig_fn -- RESTRICTED CASE
713 = -- Check signature contexts are empty
714 do { checkTc (all is_mono_sig sigs)
715 (restrictedBindCtxtErr bndrs)
717 -- Now simplify with exactly that set of tyvars
718 -- We have to squash those Methods
719 ; (qtvs, binds) <- tcSimplifyRestricted doc top_lvl bndrs
722 -- Check that signature type variables are OK
723 ; final_qtvs <- checkSigsTyVars qtvs sigs
725 ; return (final_qtvs, binds, []) }
727 | null sigs -- UNRESTRICTED CASE, NO TYPE SIGS
728 = tcSimplifyInfer doc tau_tvs lie_req
730 | otherwise -- UNRESTRICTED CASE, WITH TYPE SIGS
731 = do { sig_lie <- unifyCtxts sigs -- sigs is non-empty
732 ; let -- The "sig_avails" is the stuff available. We get that from
733 -- the context of the type signature, BUT ALSO the lie_avail
734 -- so that polymorphic recursion works right (see Note [Polymorphic recursion])
735 local_meths = [mkMethInst sig mono_id | (_, Just sig, mono_id) <- mono_infos]
736 sig_avails = sig_lie ++ local_meths
738 -- Check that the needed dicts can be
739 -- expressed in terms of the signature ones
740 ; (forall_tvs, dict_binds) <- tcSimplifyInferCheck doc tau_tvs sig_avails lie_req
742 -- Check that signature type variables are OK
743 ; final_qtvs <- checkSigsTyVars forall_tvs sigs
745 ; returnM (final_qtvs, dict_binds, map instToId sig_lie) }
747 bndrs = bndrNames mono_infos
748 sigs = [sig | (_, Just sig, _) <- mono_infos]
749 tau_tvs = foldr (unionVarSet . exactTyVarsOfType . getMonoType) emptyVarSet mono_infos
750 -- NB: exactTyVarsOfType; see Note [Silly type synonym]
751 -- near defn of TcType.exactTyVarsOfType
752 is_mono_sig sig = null (sig_theta sig)
753 doc = ptext SLIT("type signature(s) for") <+> pprBinders bndrs
755 mkMethInst (TcSigInfo { sig_id = poly_id, sig_tvs = tvs,
756 sig_theta = theta, sig_loc = loc }) mono_id
757 = Method mono_id poly_id (mkTyVarTys tvs) theta loc
760 unifyCtxts checks that all the signature contexts are the same
761 The type signatures on a mutually-recursive group of definitions
762 must all have the same context (or none).
764 The trick here is that all the signatures should have the same
765 context, and we want to share type variables for that context, so that
766 all the right hand sides agree a common vocabulary for their type
769 We unify them because, with polymorphic recursion, their types
770 might not otherwise be related. This is a rather subtle issue.
773 unifyCtxts :: [TcSigInfo] -> TcM [Inst]
774 unifyCtxts (sig1 : sigs) -- Argument is always non-empty
775 = do { mapM unify_ctxt sigs
776 ; newDictsAtLoc (sig_loc sig1) (sig_theta sig1) }
778 theta1 = sig_theta sig1
779 unify_ctxt :: TcSigInfo -> TcM ()
780 unify_ctxt sig@(TcSigInfo { sig_theta = theta })
781 = setSrcSpan (instLocSrcSpan (sig_loc sig)) $
782 addErrCtxt (sigContextsCtxt sig1 sig) $
783 unifyTheta theta1 theta
785 checkSigsTyVars :: [TcTyVar] -> [TcSigInfo] -> TcM [TcTyVar]
786 checkSigsTyVars qtvs sigs
787 = do { gbl_tvs <- tcGetGlobalTyVars
788 ; sig_tvs_s <- mappM (check_sig gbl_tvs) sigs
790 ; let -- Sigh. Make sure that all the tyvars in the type sigs
791 -- appear in the returned ty var list, which is what we are
792 -- going to generalise over. Reason: we occasionally get
794 -- type T a = () -> ()
797 -- Here, 'a' won't appear in qtvs, so we have to add it
798 sig_tvs = foldl extendVarSetList emptyVarSet sig_tvs_s
799 all_tvs = varSetElems (extendVarSetList sig_tvs qtvs)
802 check_sig gbl_tvs (TcSigInfo {sig_id = id, sig_tvs = tvs,
803 sig_theta = theta, sig_tau = tau})
804 = addErrCtxt (ptext SLIT("In the type signature for") <+> quotes (ppr id)) $
805 addErrCtxtM (sigCtxt id tvs theta tau) $
806 do { tvs' <- checkDistinctTyVars tvs
807 ; ifM (any (`elemVarSet` gbl_tvs) tvs')
808 (bleatEscapedTvs gbl_tvs tvs tvs')
811 checkDistinctTyVars :: [TcTyVar] -> TcM [TcTyVar]
812 -- (checkDistinctTyVars tvs) checks that the tvs from one type signature
813 -- are still all type variables, and all distinct from each other.
814 -- It returns a zonked set of type variables.
815 -- For example, if the type sig is
816 -- f :: forall a b. a -> b -> b
817 -- we want to check that 'a' and 'b' haven't
818 -- (a) been unified with a non-tyvar type
819 -- (b) been unified with each other (all distinct)
821 checkDistinctTyVars sig_tvs
822 = do { zonked_tvs <- mapM zonkSigTyVar sig_tvs
823 ; foldlM check_dup emptyVarEnv (sig_tvs `zip` zonked_tvs)
824 ; return zonked_tvs }
826 check_dup :: TyVarEnv TcTyVar -> (TcTyVar, TcTyVar) -> TcM (TyVarEnv TcTyVar)
827 -- The TyVarEnv maps each zonked type variable back to its
828 -- corresponding user-written signature type variable
829 check_dup acc (sig_tv, zonked_tv)
830 = case lookupVarEnv acc zonked_tv of
831 Just sig_tv' -> bomb_out sig_tv sig_tv'
833 Nothing -> return (extendVarEnv acc zonked_tv sig_tv)
835 bomb_out sig_tv1 sig_tv2
836 = do { env0 <- tcInitTidyEnv
837 ; let (env1, tidy_tv1) = tidyOpenTyVar env0 sig_tv1
838 (env2, tidy_tv2) = tidyOpenTyVar env1 sig_tv2
839 msg = ptext SLIT("Quantified type variable") <+> quotes (ppr tidy_tv1)
840 <+> ptext SLIT("is unified with another quantified type variable")
841 <+> quotes (ppr tidy_tv2)
842 ; failWithTcM (env2, msg) }
847 @getTyVarsToGen@ decides what type variables to generalise over.
849 For a "restricted group" -- see the monomorphism restriction
850 for a definition -- we bind no dictionaries, and
851 remove from tyvars_to_gen any constrained type variables
853 *Don't* simplify dicts at this point, because we aren't going
854 to generalise over these dicts. By the time we do simplify them
855 we may well know more. For example (this actually came up)
857 f x = array ... xs where xs = [1,2,3,4,5]
858 We don't want to generate lots of (fromInt Int 1), (fromInt Int 2)
859 stuff. If we simplify only at the f-binding (not the xs-binding)
860 we'll know that the literals are all Ints, and we can just produce
863 Find all the type variables involved in overloading, the
864 "constrained_tyvars". These are the ones we *aren't* going to
865 generalise. We must be careful about doing this:
867 (a) If we fail to generalise a tyvar which is not actually
868 constrained, then it will never, ever get bound, and lands
869 up printed out in interface files! Notorious example:
870 instance Eq a => Eq (Foo a b) where ..
871 Here, b is not constrained, even though it looks as if it is.
872 Another, more common, example is when there's a Method inst in
873 the LIE, whose type might very well involve non-overloaded
875 [NOTE: Jan 2001: I don't understand the problem here so I'm doing
876 the simple thing instead]
878 (b) On the other hand, we mustn't generalise tyvars which are constrained,
879 because we are going to pass on out the unmodified LIE, with those
880 tyvars in it. They won't be in scope if we've generalised them.
882 So we are careful, and do a complete simplification just to find the
883 constrained tyvars. We don't use any of the results, except to
884 find which tyvars are constrained.
886 Note [Polymorphic recursion]
887 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
888 The game plan for polymorphic recursion in the code above is
890 * Bind any variable for which we have a type signature
891 to an Id with a polymorphic type. Then when type-checking
892 the RHSs we'll make a full polymorphic call.
894 This fine, but if you aren't a bit careful you end up with a horrendous
895 amount of partial application and (worse) a huge space leak. For example:
897 f :: Eq a => [a] -> [a]
900 If we don't take care, after typechecking we get
902 f = /\a -> \d::Eq a -> let f' = f a d
906 Notice the the stupid construction of (f a d), which is of course
907 identical to the function we're executing. In this case, the
908 polymorphic recursion isn't being used (but that's a very common case).
909 This can lead to a massive space leak, from the following top-level defn
915 Now (f dEqInt) evaluates to a lambda that has f' as a free variable; but
916 f' is another thunk which evaluates to the same thing... and you end
917 up with a chain of identical values all hung onto by the CAF ff.
921 = let f' = f Int dEqInt in \ys. ...f'...
923 = let f' = let f' = f Int dEqInt in \ys. ...f'...
928 NOTE: a bit of arity anaysis would push the (f a d) inside the (\ys...),
929 which would make the space leak go away in this case
931 Solution: when typechecking the RHSs we always have in hand the
932 *monomorphic* Ids for each binding. So we just need to make sure that
933 if (Method f a d) shows up in the constraints emerging from (...f...)
934 we just use the monomorphic Id. We achieve this by adding monomorphic Ids
935 to the "givens" when simplifying constraints. That's what the "lies_avail"
940 f = /\a -> \d::Eq a -> letrec
941 fm = \ys:[a] -> ...fm...
947 %************************************************************************
951 %************************************************************************
953 Type signatures are tricky. See Note [Signature skolems] in TcType
955 @tcSigs@ checks the signatures for validity, and returns a list of
956 {\em freshly-instantiated} signatures. That is, the types are already
957 split up, and have fresh type variables installed. All non-type-signature
958 "RenamedSigs" are ignored.
960 The @TcSigInfo@ contains @TcTypes@ because they are unified with
961 the variable's type, and after that checked to see whether they've
965 type TcSigFun = Name -> Maybe [Name] -- Maps a let-binder to the list of
966 -- type variables brought into scope
967 -- by its type signature.
968 -- Nothing => no type signature
970 mkTcSigFun :: [LSig Name] -> TcSigFun
971 -- Search for a particular type signature
972 -- Precondition: the sigs are all type sigs
973 -- Precondition: no duplicates
974 mkTcSigFun sigs = lookupNameEnv env
976 env = mkNameEnv [(name, scoped_tyvars hs_ty)
977 | L span (TypeSig (L _ name) (L _ hs_ty)) <- sigs]
978 scoped_tyvars (HsForAllTy Explicit tvs _ _) = hsLTyVarNames tvs
979 scoped_tyvars other = []
980 -- The scoped names are the ones explicitly mentioned
981 -- in the HsForAll. (There may be more in sigma_ty, because
982 -- of nested type synonyms. See Note [Scoped] with TcSigInfo.)
987 sig_id :: TcId, -- *Polymorphic* binder for this value...
989 sig_scoped :: [Name], -- Names for any scoped type variables
990 -- Invariant: correspond 1-1 with an initial
991 -- segment of sig_tvs (see Note [Scoped])
993 sig_tvs :: [TcTyVar], -- Instantiated type variables
994 -- See Note [Instantiate sig]
996 sig_theta :: TcThetaType, -- Instantiated theta
997 sig_tau :: TcTauType, -- Instantiated tau
998 sig_loc :: InstLoc -- The location of the signature
1002 -- There may be more instantiated type variables than scoped
1003 -- ones. For example:
1004 -- type T a = forall b. b -> (a,b)
1005 -- f :: forall c. T c
1006 -- Here, the signature for f will have one scoped type variable, c,
1007 -- but two instantiated type variables, c' and b'.
1009 -- We assume that the scoped ones are at the *front* of sig_tvs,
1010 -- and remember the names from the original HsForAllTy in sig_scoped
1012 -- Note [Instantiate sig]
1013 -- It's vital to instantiate a type signature with fresh variable.
1015 -- type S = forall a. a->a
1019 -- Here, we must use distinct type variables when checking f,g's right hand sides.
1020 -- (Instantiation is only necessary because of type synonyms. Otherwise,
1021 -- it's all cool; each signature has distinct type variables from the renamer.)
1023 instance Outputable TcSigInfo where
1024 ppr (TcSigInfo { sig_id = id, sig_tvs = tyvars, sig_theta = theta, sig_tau = tau})
1025 = ppr id <+> ptext SLIT("::") <+> ppr tyvars <+> ppr theta <+> ptext SLIT("=>") <+> ppr tau
1029 tcTySig :: LSig Name -> TcM TcId
1030 tcTySig (L span (TypeSig (L _ name) ty))
1032 do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
1033 ; return (mkLocalId name sigma_ty) }
1036 tcInstSig_maybe :: TcSigFun -> Name -> TcM (Maybe TcSigInfo)
1037 -- Instantiate with *meta* type variables;
1038 -- this signature is part of a multi-signature group
1039 tcInstSig_maybe sig_fn name
1040 = case sig_fn name of
1041 Nothing -> return Nothing
1042 Just tvs -> do { tc_sig <- tcInstSig False name tvs
1043 ; return (Just tc_sig) }
1045 tcInstSig :: Bool -> Name -> [Name] -> TcM TcSigInfo
1046 -- Instantiate the signature, with either skolems or meta-type variables
1047 -- depending on the use_skols boolean
1049 -- We always instantiate with freshs uniques,
1050 -- although we keep the same print-name
1052 -- type T = forall a. [a] -> [a]
1054 -- f = g where { g :: T; g = <rhs> }
1056 -- We must not use the same 'a' from the defn of T at both places!!
1058 tcInstSig use_skols name scoped_names
1059 = do { poly_id <- tcLookupId name -- Cannot fail; the poly ids are put into
1060 -- scope when starting the binding group
1061 ; let skol_info = SigSkol (FunSigCtxt name)
1062 inst_tyvars | use_skols = tcInstSkolTyVars skol_info
1063 | otherwise = tcInstSigTyVars skol_info
1064 ; (tvs, theta, tau) <- tcInstType inst_tyvars (idType poly_id)
1065 ; loc <- getInstLoc (SigOrigin skol_info)
1066 ; return (TcSigInfo { sig_id = poly_id,
1067 sig_tvs = tvs, sig_theta = theta, sig_tau = tau,
1068 sig_scoped = final_scoped_names, sig_loc = loc }) }
1069 -- Note that the scoped_names and the sig_tvs will have
1070 -- different Names. That's quite ok; when we bring the
1071 -- scoped_names into scope, we just bind them to the sig_tvs
1073 -- We also only have scoped type variables when we are instantiating
1074 -- with true skolems
1075 final_scoped_names | use_skols = scoped_names
1079 isMonoGroup :: DynFlags -> [LHsBind Name] -> Bool
1080 -- No generalisation at all
1081 isMonoGroup dflags binds
1082 = dopt Opt_MonoPatBinds dflags && any is_pat_bind binds
1084 is_pat_bind (L _ (PatBind {})) = True
1085 is_pat_bind other = False
1088 isRestrictedGroup :: DynFlags -> [LHsBind Name] -> TcSigFun -> Bool
1089 isRestrictedGroup dflags binds sig_fn
1090 = mono_restriction && not all_unrestricted
1092 mono_restriction = dopt Opt_MonomorphismRestriction dflags
1093 all_unrestricted = all (unrestricted . unLoc) binds
1094 has_sig n = isJust (sig_fn n)
1096 unrestricted (PatBind {}) = False
1097 unrestricted (VarBind { var_id = v }) = has_sig v
1098 unrestricted (FunBind { fun_id = v, fun_matches = matches }) = unrestricted_match matches
1099 || has_sig (unLoc v)
1101 unrestricted_match (MatchGroup (L _ (Match [] _ _) : _) _) = False
1102 -- No args => like a pattern binding
1103 unrestricted_match other = True
1104 -- Some args => a function binding
1108 %************************************************************************
1110 \subsection[TcBinds-errors]{Error contexts and messages}
1112 %************************************************************************
1116 -- This one is called on LHS, when pat and grhss are both Name
1117 -- and on RHS, when pat is TcId and grhss is still Name
1118 patMonoBindsCtxt pat grhss
1119 = hang (ptext SLIT("In a pattern binding:")) 4 (pprPatBind pat grhss)
1121 -----------------------------------------------
1122 sigContextsCtxt sig1 sig2
1123 = vcat [ptext SLIT("When matching the contexts of the signatures for"),
1124 nest 2 (vcat [ppr id1 <+> dcolon <+> ppr (idType id1),
1125 ppr id2 <+> dcolon <+> ppr (idType id2)]),
1126 ptext SLIT("The signature contexts in a mutually recursive group should all be identical")]
1132 -----------------------------------------------
1133 unboxedTupleErr name ty
1134 = hang (ptext SLIT("Illegal binding of unboxed tuple"))
1135 4 (ppr name <+> dcolon <+> ppr ty)
1137 -----------------------------------------------
1138 restrictedBindCtxtErr binder_names
1139 = hang (ptext SLIT("Illegal overloaded type signature(s)"))
1140 4 (vcat [ptext SLIT("in a binding group for") <+> pprBinders binder_names,
1141 ptext SLIT("that falls under the monomorphism restriction")])
1143 genCtxt binder_names
1144 = ptext SLIT("When generalising the type(s) for") <+> pprBinders binder_names