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 ( newDictBndrs, newIPDict, instToId )
32 import TcEnv ( tcExtendIdEnv, tcExtendIdEnv2, tcExtendTyVarEnv2,
33 pprBinders, 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 ( tcLetPat )
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 parts of -} Type ( argTypeKind )
52 import VarEnv ( TyVarEnv, emptyVarEnv, lookupVarEnv, extendVarEnv )
53 import TysPrim ( alphaTyVar )
54 import Id ( Id, mkLocalId, mkVanillaGlobal )
55 import IdInfo ( vanillaIdInfo )
56 import Var ( TyVar, idType, idName )
61 import SrcLoc ( Located(..), unLoc, getLoc )
63 import ErrUtils ( Message )
64 import Digraph ( SCC(..), stronglyConnComp )
65 import Maybes ( expectJust, isJust, isNothing, orElse )
66 import Util ( singleton )
67 import BasicTypes ( TopLevelFlag(..), isTopLevel, isNotTopLevel,
68 RecFlag(..), isNonRec, InlineSpec, defaultInlineSpec )
73 %************************************************************************
75 \subsection{Type-checking bindings}
77 %************************************************************************
79 @tcBindsAndThen@ typechecks a @HsBinds@. The "and then" part is because
80 it needs to know something about the {\em usage} of the things bound,
81 so that it can create specialisations of them. So @tcBindsAndThen@
82 takes a function which, given an extended environment, E, typechecks
83 the scope of the bindings returning a typechecked thing and (most
84 important) an LIE. It is this LIE which is then used as the basis for
85 specialising the things bound.
87 @tcBindsAndThen@ also takes a "combiner" which glues together the
88 bindings and the "thing" to make a new "thing".
90 The real work is done by @tcBindWithSigsAndThen@.
92 Recursive and non-recursive binds are handled in essentially the same
93 way: because of uniques there are no scoping issues left. The only
94 difference is that non-recursive bindings can bind primitive values.
96 Even for non-recursive binding groups we add typings for each binder
97 to the LVE for the following reason. When each individual binding is
98 checked the type of its LHS is unified with that of its RHS; and
99 type-checking the LHS of course requires that the binder is in scope.
101 At the top-level the LIE is sure to contain nothing but constant
102 dictionaries, which we resolve at the module level.
105 tcTopBinds :: HsValBinds Name -> TcM (LHsBinds TcId, TcLclEnv)
106 -- Note: returning the TcLclEnv is more than we really
107 -- want. The bit we care about is the local bindings
108 -- and the free type variables thereof
110 = do { (ValBindsOut prs _, env) <- tcValBinds TopLevel binds getLclEnv
111 ; return (foldr (unionBags . snd) emptyBag prs, env) }
112 -- The top level bindings are flattened into a giant
113 -- implicitly-mutually-recursive LHsBinds
115 tcHsBootSigs :: HsValBinds Name -> TcM [Id]
116 -- A hs-boot file has only one BindGroup, and it only has type
117 -- signatures in it. The renamer checked all this
118 tcHsBootSigs (ValBindsOut binds sigs)
119 = do { checkTc (null binds) badBootDeclErr
120 ; mapM (addLocM tc_boot_sig) (filter isVanillaLSig sigs) }
122 tc_boot_sig (TypeSig (L _ name) ty)
123 = do { sigma_ty <- tcHsSigType (FunSigCtxt name) ty
124 ; return (mkVanillaGlobal name sigma_ty vanillaIdInfo) }
125 -- Notice that we make GlobalIds, not LocalIds
126 tcHsBootSigs groups = pprPanic "tcHsBootSigs" (ppr groups)
128 badBootDeclErr :: Message
129 badBootDeclErr = ptext SLIT("Illegal declarations in an hs-boot file")
131 ------------------------
132 tcLocalBinds :: HsLocalBinds Name -> TcM thing
133 -> TcM (HsLocalBinds TcId, thing)
135 tcLocalBinds EmptyLocalBinds thing_inside
136 = do { thing <- thing_inside
137 ; return (EmptyLocalBinds, thing) }
139 tcLocalBinds (HsValBinds binds) thing_inside
140 = do { (binds', thing) <- tcValBinds NotTopLevel binds thing_inside
141 ; return (HsValBinds binds', thing) }
143 tcLocalBinds (HsIPBinds (IPBinds ip_binds _)) thing_inside
144 = do { (thing, lie) <- getLIE thing_inside
145 ; (avail_ips, ip_binds') <- mapAndUnzipM (wrapLocSndM tc_ip_bind) ip_binds
147 -- If the binding binds ?x = E, we must now
148 -- discharge any ?x constraints in expr_lie
149 ; dict_binds <- tcSimplifyIPs avail_ips lie
150 ; return (HsIPBinds (IPBinds ip_binds' dict_binds), thing) }
152 -- I wonder if we should do these one at at time
155 tc_ip_bind (IPBind ip expr)
156 = newFlexiTyVarTy argTypeKind `thenM` \ ty ->
157 newIPDict (IPBindOrigin ip) ip ty `thenM` \ (ip', ip_inst) ->
158 tcMonoExpr expr ty `thenM` \ expr' ->
159 returnM (ip_inst, (IPBind ip' expr'))
161 ------------------------
162 tcValBinds :: TopLevelFlag
163 -> HsValBinds Name -> TcM thing
164 -> TcM (HsValBinds TcId, thing)
166 tcValBinds top_lvl (ValBindsIn binds sigs) thing_inside
167 = pprPanic "tcValBinds" (ppr binds)
169 tcValBinds top_lvl (ValBindsOut binds sigs) thing_inside
170 = do { -- Typecheck the signature
171 ; let { prag_fn = mkPragFun sigs
172 ; ty_sigs = filter isVanillaLSig sigs
173 ; sig_fn = mkTcSigFun ty_sigs }
175 ; poly_ids <- mapM tcTySig ty_sigs
176 -- No recovery from bad signatures, because the type sigs
177 -- may bind type variables, so proceeding without them
178 -- can lead to a cascade of errors
179 -- ToDo: this means we fall over immediately if any type sig
180 -- is wrong, which is over-conservative, see Trac bug #745
182 -- Extend the envt right away with all
183 -- the Ids declared with type signatures
184 ; gla_exts <- doptM Opt_GlasgowExts
185 ; (binds', thing) <- tcExtendIdEnv poly_ids $
186 tc_val_binds gla_exts top_lvl sig_fn prag_fn
189 ; return (ValBindsOut binds' sigs, thing) }
191 ------------------------
192 tc_val_binds :: Bool -> 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 gla_exts top_lvl sig_fn prag_fn [] thing_inside
199 = do { thing <- thing_inside
200 ; return ([], thing) }
202 tc_val_binds gla_exts top_lvl sig_fn prag_fn (group : groups) thing_inside
203 = do { (group', (groups', thing))
204 <- tc_group gla_exts top_lvl sig_fn prag_fn group $
205 tc_val_binds gla_exts top_lvl sig_fn prag_fn groups thing_inside
206 ; return (group' ++ groups', thing) }
208 ------------------------
209 tc_group :: Bool -> 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 gla_exts 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) <- tc_haskell98 top_lvl sig_fn prag_fn NonRecursive binds thing_inside
222 ; return ([(NonRecursive, b) | b <- binds], thing) }
224 tc_group gla_exts top_lvl sig_fn prag_fn (Recursive, binds) thing_inside
225 | not gla_exts -- Recursive group, normal Haskell 98 route
226 = do { (binds1, thing) <- tc_haskell98 top_lvl sig_fn prag_fn Recursive binds thing_inside
227 ; return ([(Recursive, unionManyBags binds1)], thing) }
229 | otherwise -- Recursive group, with gla-exts
230 = -- To maximise polymorphism (with -fglasgow-exts), we do a new
231 -- strongly-connected-component analysis, this time omitting
232 -- any references to variables with type signatures.
234 -- Notice that the bindInsts thing covers *all* the bindings in the original
235 -- group at once; an earlier one may use a later one!
236 do { traceTc (text "tc_group rec" <+> pprLHsBinds binds)
237 ; (binds1,thing) <- bindLocalInsts top_lvl $
238 go (stronglyConnComp (mkEdges sig_fn binds))
239 ; return ([(Recursive, unionManyBags binds1)], thing) }
240 -- Rec them all together
242 -- go :: SCC (LHsBind Name) -> TcM ([LHsBind TcId], [TcId], thing)
243 go (scc:sccs) = do { (binds1, ids1) <- tc_scc scc
244 ; (binds2, ids2, thing) <- tcExtendIdEnv ids1 $ go sccs
245 ; return (binds1 ++ binds2, ids1 ++ ids2, thing) }
246 go [] = do { thing <- thing_inside; return ([], [], thing) }
248 tc_scc (AcyclicSCC bind) = tc_sub_group NonRecursive (unitBag bind)
249 tc_scc (CyclicSCC binds) = tc_sub_group Recursive (listToBag binds)
251 tc_sub_group = tcPolyBinds top_lvl sig_fn prag_fn Recursive
253 tc_haskell98 top_lvl sig_fn prag_fn rec_flag binds thing_inside
254 = bindLocalInsts top_lvl $ do
255 { (binds1, ids) <- tcPolyBinds top_lvl sig_fn prag_fn rec_flag rec_flag binds
256 ; thing <- tcExtendIdEnv ids thing_inside
257 ; return (binds1, ids, thing) }
259 ------------------------
260 bindLocalInsts :: TopLevelFlag -> TcM ([LHsBinds TcId], [TcId], a) -> TcM ([LHsBinds TcId], a)
261 bindLocalInsts top_lvl thing_inside
262 | isTopLevel top_lvl = do { (binds, ids, thing) <- thing_inside; return (binds, thing) }
263 -- For the top level don't bother will all this bindInstsOfLocalFuns stuff.
264 -- All the top level things are rec'd together anyway, so it's fine to
265 -- leave them to the tcSimplifyTop, and quite a bit faster too
267 | otherwise -- Nested case
268 = do { ((binds, ids, thing), lie) <- getLIE thing_inside
269 ; lie_binds <- bindInstsOfLocalFuns lie ids
270 ; return (binds ++ [lie_binds], thing) }
272 ------------------------
273 mkEdges :: TcSigFun -> LHsBinds Name
274 -> [(LHsBind Name, BKey, [BKey])]
276 type BKey = Int -- Just number off the bindings
279 = [ (bind, key, [key | n <- nameSetToList (bind_fvs (unLoc bind)),
280 Just key <- [lookupNameEnv key_map n], no_sig n ])
281 | (bind, key) <- keyd_binds
284 no_sig :: Name -> Bool
285 no_sig n = isNothing (sig_fn n)
287 keyd_binds = bagToList binds `zip` [0::BKey ..]
289 key_map :: NameEnv BKey -- Which binding it comes from
290 key_map = mkNameEnv [(bndr, key) | (L _ bind, key) <- keyd_binds
291 , bndr <- bindersOfHsBind bind ]
293 bindersOfHsBind :: HsBind Name -> [Name]
294 bindersOfHsBind (PatBind { pat_lhs = pat }) = collectPatBinders pat
295 bindersOfHsBind (FunBind { fun_id = L _ f }) = [f]
297 ------------------------
298 tcPolyBinds :: TopLevelFlag -> TcSigFun -> TcPragFun
299 -> RecFlag -- Whether the group is really recursive
300 -> RecFlag -- Whether it's recursive after breaking
301 -- dependencies based on type signatures
303 -> TcM ([LHsBinds TcId], [TcId])
305 -- Typechecks a single bunch of bindings all together,
306 -- and generalises them. The bunch may be only part of a recursive
307 -- group, because we use type signatures to maximise polymorphism
309 -- Returns a list because the input may be a single non-recursive binding,
310 -- in which case the dependency order of the resulting bindings is
313 -- Knows nothing about the scope of the bindings
315 tcPolyBinds top_lvl sig_fn prag_fn rec_group rec_tc binds
317 bind_list = bagToList binds
318 binder_names = collectHsBindBinders binds
319 loc = getLoc (head bind_list)
320 -- TODO: location a bit awkward, but the mbinds have been
321 -- dependency analysed and may no longer be adjacent
323 -- SET UP THE MAIN RECOVERY; take advantage of any type sigs
325 recoverM (recoveryCode binder_names sig_fn) $ do
327 { traceTc (ptext SLIT("------------------------------------------------"))
328 ; traceTc (ptext SLIT("Bindings for") <+> ppr binder_names)
330 -- TYPECHECK THE BINDINGS
331 ; ((binds', mono_bind_infos), lie_req)
332 <- getLIE (tcMonoBinds bind_list sig_fn rec_tc)
334 -- CHECK FOR UNLIFTED BINDINGS
335 -- These must be non-recursive etc, and are not generalised
336 -- They desugar to a case expression in the end
337 ; zonked_mono_tys <- zonkTcTypes (map getMonoType mono_bind_infos)
338 ; is_strict <- checkStrictBinds top_lvl rec_group binds'
339 zonked_mono_tys mono_bind_infos
341 do { extendLIEs lie_req
342 ; let exports = zipWith mk_export mono_bind_infos zonked_mono_tys
343 mk_export (name, Nothing, mono_id) mono_ty = ([], mkLocalId name mono_ty, mono_id, [])
344 mk_export (name, Just sig, mono_id) mono_ty = ([], sig_id sig, mono_id, [])
345 -- ToDo: prags for unlifted bindings
347 ; return ( [unitBag $ L loc $ AbsBinds [] [] exports binds'],
348 [poly_id | (_, poly_id, _, _) <- exports]) } -- Guaranteed zonked
350 else do -- The normal lifted case: GENERALISE
352 ; (tyvars_to_gen, dict_binds, dict_ids)
353 <- addErrCtxt (genCtxt (bndrNames mono_bind_infos)) $
354 generalise dflags top_lvl bind_list sig_fn mono_bind_infos lie_req
356 -- FINALISE THE QUANTIFIED TYPE VARIABLES
357 -- The quantified type variables often include meta type variables
358 -- we want to freeze them into ordinary type variables, and
359 -- default their kind (e.g. from OpenTypeKind to TypeKind)
360 ; tyvars_to_gen' <- mappM zonkQuantifiedTyVar tyvars_to_gen
362 -- BUILD THE POLYMORPHIC RESULT IDs
363 ; exports <- mapM (mkExport prag_fn tyvars_to_gen' (map idType dict_ids))
366 ; let poly_ids = [poly_id | (_, poly_id, _, _) <- exports]
367 ; traceTc (text "binding:" <+> ppr (poly_ids `zip` map idType poly_ids))
369 ; let abs_bind = L loc $ AbsBinds tyvars_to_gen'
371 (dict_binds `unionBags` binds')
373 ; return ([unitBag abs_bind], poly_ids) -- poly_ids are guaranteed zonked by mkExport
378 mkExport :: TcPragFun -> [TyVar] -> [TcType] -> MonoBindInfo
379 -> TcM ([TyVar], Id, Id, [Prag])
380 -- mkExport generates exports with
381 -- zonked type variables,
383 -- The former is just because no further unifications will change
384 -- the quantified type variables, so we can fix their final form
386 -- The latter is needed because the poly_ids are used to extend the
387 -- type environment; see the invariant on TcEnv.tcExtendIdEnv
389 -- Pre-condition: the inferred_tvs are already zonked
391 mkExport prag_fn inferred_tvs dict_tys (poly_name, mb_sig, mono_id)
392 = do { (tvs, poly_id) <- mk_poly_id mb_sig
394 ; poly_id' <- zonkId poly_id
395 ; prags <- tcPrags poly_id' (prag_fn poly_name)
396 -- tcPrags requires a zonked poly_id
398 ; return (tvs, poly_id', mono_id, prags) }
400 poly_ty = mkForAllTys inferred_tvs (mkFunTys dict_tys (idType mono_id))
402 mk_poly_id Nothing = return (inferred_tvs, mkLocalId poly_name poly_ty)
403 mk_poly_id (Just sig) = do { tvs <- mapM zonk_tv (sig_tvs sig)
404 ; return (tvs, sig_id sig) }
406 zonk_tv tv = do { ty <- zonkTcTyVar tv; return (tcGetTyVar "mkExport" ty) }
408 ------------------------
409 type TcPragFun = Name -> [LSig Name]
411 mkPragFun :: [LSig Name] -> TcPragFun
412 mkPragFun sigs = \n -> lookupNameEnv env n `orElse` []
414 prs = [(expectJust "mkPragFun" (sigName sig), sig)
415 | sig <- sigs, isPragLSig sig]
416 env = foldl add emptyNameEnv prs
417 add env (n,p) = extendNameEnv_Acc (:) singleton env n p
419 tcPrags :: Id -> [LSig Name] -> TcM [Prag]
420 tcPrags poly_id prags = mapM tc_prag prags
422 tc_prag (L loc prag) = setSrcSpan loc $
423 addErrCtxt (pragSigCtxt prag) $
426 pragSigCtxt prag = hang (ptext SLIT("In the pragma")) 2 (ppr prag)
428 tcPrag :: TcId -> Sig Name -> TcM Prag
429 -- Pre-condition: the poly_id is zonked
430 -- Reason: required by tcSubExp
431 tcPrag poly_id (SpecSig orig_name hs_ty inl) = tcSpecPrag poly_id hs_ty inl
432 tcPrag poly_id (SpecInstSig hs_ty) = tcSpecPrag poly_id hs_ty defaultInlineSpec
433 tcPrag poly_id (InlineSig v inl) = return (InlinePrag inl)
436 tcSpecPrag :: TcId -> LHsType Name -> InlineSpec -> TcM Prag
437 tcSpecPrag poly_id hs_ty inl
438 = do { spec_ty <- tcHsSigType (FunSigCtxt (idName poly_id)) hs_ty
439 ; (co_fn, lie) <- getLIE (tcSubExp (idType poly_id) spec_ty)
441 ; let const_dicts = map instToId lie
442 ; return (SpecPrag (mkHsCoerce co_fn (HsVar poly_id)) spec_ty const_dicts inl) }
443 -- Most of the work of specialisation is done by
444 -- the desugarer, guided by the SpecPrag
447 -- If typechecking the binds fails, then return with each
448 -- signature-less binder given type (forall a.a), to minimise
449 -- subsequent error messages
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 ([], 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 other = return ()
490 strictBindErr flavour unlifted mbind
491 = hang (text flavour <+> msg <+> ptext SLIT("aren't allowed:"))
492 4 (pprLHsBinds mbind)
494 msg | unlifted = ptext SLIT("bindings for unlifted types")
495 | otherwise = ptext SLIT("bang-pattern bindings")
497 badStrictSig unlifted sig
498 = hang (ptext SLIT("Illegal polymorphic signature in") <+> msg)
501 msg | unlifted = ptext SLIT("an unlifted binding")
502 | otherwise = ptext SLIT("a bang-pattern binding")
506 %************************************************************************
508 \subsection{tcMonoBind}
510 %************************************************************************
512 @tcMonoBinds@ deals with a perhaps-recursive group of HsBinds.
513 The signatures have been dealt with already.
516 tcMonoBinds :: [LHsBind Name]
518 -> RecFlag -- Whether the binding is recursive for typechecking purposes
519 -- i.e. the binders are mentioned in their RHSs, and
520 -- we are not resuced by a type signature
521 -> TcM (LHsBinds TcId, [MonoBindInfo])
523 tcMonoBinds [L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf,
524 fun_matches = matches, bind_fvs = fvs })]
525 sig_fn -- Single function binding,
526 NonRecursive -- binder isn't mentioned in RHS,
527 | Nothing <- sig_fn name -- ...with no type signature
528 = -- In this very special case we infer the type of the
529 -- right hand side first (it may have a higher-rank type)
530 -- and *then* make the monomorphic Id for the LHS
531 -- e.g. f = \(x::forall a. a->a) -> <body>
532 -- We want to infer a higher-rank type for f
534 do { ((co_fn, matches'), rhs_ty) <- tcInfer (tcMatchesFun name matches)
536 -- Check for an unboxed tuple type
537 -- f = (# True, False #)
538 -- Zonk first just in case it's hidden inside a meta type variable
539 -- (This shows up as a (more obscure) kind error
540 -- in the 'otherwise' case of tcMonoBinds.)
541 ; zonked_rhs_ty <- zonkTcType rhs_ty
542 ; checkTc (not (isUnboxedTupleType zonked_rhs_ty))
543 (unboxedTupleErr name zonked_rhs_ty)
545 ; mono_name <- newLocalName name
546 ; let mono_id = mkLocalId mono_name zonked_rhs_ty
547 ; return (unitBag (L b_loc (FunBind { fun_id = L nm_loc mono_id, fun_infix = inf,
548 fun_matches = matches', bind_fvs = fvs,
549 fun_co_fn = co_fn })),
550 [(name, Nothing, mono_id)]) }
552 tcMonoBinds [L b_loc (FunBind { fun_id = L nm_loc name, fun_infix = inf,
553 fun_matches = matches, bind_fvs = fvs })]
554 sig_fn -- Single function binding
556 | Just scoped_tvs <- sig_fn name -- ...with a type signature
557 = -- When we have a single function binding, with a type signature
558 -- we can (a) use genuine, rigid skolem constants for the type variables
559 -- (b) bring (rigid) scoped type variables into scope
561 do { tc_sig <- tcInstSig True name scoped_tvs
562 ; mono_name <- newLocalName name
563 ; let mono_ty = sig_tau tc_sig
564 mono_id = mkLocalId mono_name mono_ty
565 rhs_tvs = [ (name, mkTyVarTy tv)
566 | (name, tv) <- sig_scoped tc_sig `zip` sig_tvs tc_sig ]
568 ; (co_fn, matches') <- tcExtendTyVarEnv2 rhs_tvs $
569 tcMatchesFun mono_name matches mono_ty
571 ; let fun_bind' = FunBind { fun_id = L nm_loc mono_id,
572 fun_infix = inf, fun_matches = matches',
573 bind_fvs = placeHolderNames, fun_co_fn = co_fn }
574 ; return (unitBag (L b_loc fun_bind'),
575 [(name, Just tc_sig, mono_id)]) }
577 tcMonoBinds binds sig_fn non_rec
578 = do { tc_binds <- mapM (wrapLocM (tcLhs sig_fn)) binds
580 -- Bring the monomorphic Ids, into scope for the RHSs
581 ; let mono_info = getMonoBindInfo tc_binds
582 rhs_id_env = [(name,mono_id) | (name, Nothing, mono_id) <- mono_info]
583 -- A monomorphic binding for each term variable that lacks
584 -- a type sig. (Ones with a sig are already in scope.)
586 ; binds' <- tcExtendIdEnv2 rhs_id_env $
587 traceTc (text "tcMonoBinds" <+> vcat [ ppr n <+> ppr id <+> ppr (idType id)
588 | (n,id) <- rhs_id_env]) `thenM_`
589 mapM (wrapLocM tcRhs) tc_binds
590 ; return (listToBag binds', mono_info) }
592 ------------------------
593 -- tcLhs typechecks the LHS of the bindings, to construct the environment in which
594 -- we typecheck the RHSs. Basically what we are doing is this: for each binder:
595 -- if there's a signature for it, use the instantiated signature type
596 -- otherwise invent a type variable
597 -- You see that quite directly in the FunBind case.
599 -- But there's a complication for pattern bindings:
600 -- data T = MkT (forall a. a->a)
602 -- Here we can guess a type variable for the entire LHS (which will be refined to T)
603 -- but we want to get (f::forall a. a->a) as the RHS environment.
604 -- The simplest way to do this is to typecheck the pattern, and then look up the
605 -- bound mono-ids. Then we want to retain the typechecked pattern to avoid re-doing
606 -- it; hence the TcMonoBind data type in which the LHS is done but the RHS isn't
608 data TcMonoBind -- Half completed; LHS done, RHS not done
609 = TcFunBind MonoBindInfo (Located TcId) Bool (MatchGroup Name)
610 | TcPatBind [MonoBindInfo] (LPat TcId) (GRHSs Name) TcSigmaType
612 type MonoBindInfo = (Name, Maybe TcSigInfo, TcId)
613 -- Type signature (if any), and
614 -- the monomorphic bound things
616 bndrNames :: [MonoBindInfo] -> [Name]
617 bndrNames mbi = [n | (n,_,_) <- mbi]
619 getMonoType :: MonoBindInfo -> TcTauType
620 getMonoType (_,_,mono_id) = idType mono_id
622 tcLhs :: TcSigFun -> HsBind Name -> TcM TcMonoBind
623 tcLhs sig_fn (FunBind { fun_id = L nm_loc name, fun_infix = inf, fun_matches = matches })
624 = do { mb_sig <- tcInstSig_maybe sig_fn name
625 ; mono_name <- newLocalName name
626 ; mono_ty <- mk_mono_ty mb_sig
627 ; let mono_id = mkLocalId mono_name mono_ty
628 ; return (TcFunBind (name, mb_sig, mono_id) (L nm_loc mono_id) inf matches) }
630 mk_mono_ty (Just sig) = return (sig_tau sig)
631 mk_mono_ty Nothing = newFlexiTyVarTy argTypeKind
633 tcLhs sig_fn bind@(PatBind { pat_lhs = pat, pat_rhs = grhss })
634 = do { mb_sigs <- mapM (tcInstSig_maybe sig_fn) names
635 ; mono_pat_binds <- doptM Opt_MonoPatBinds
636 -- With -fmono-pat-binds, we do no generalisation of pattern bindings
637 -- But the signature can still be polymoprhic!
638 -- data T = MkT (forall a. a->a)
639 -- x :: forall a. a->a
641 -- The function get_sig_ty decides whether the pattern-bound variables
642 -- should have exactly the type in the type signature (-fmono-pat-binds),
643 -- or the instantiated version (-fmono-pat-binds)
645 ; let nm_sig_prs = names `zip` mb_sigs
646 get_sig_ty | mono_pat_binds = idType . sig_id
647 | otherwise = sig_tau
648 tau_sig_env = mkNameEnv [ (name, get_sig_ty sig)
649 | (name, Just sig) <- nm_sig_prs]
650 sig_tau_fn = lookupNameEnv tau_sig_env
652 tc_pat exp_ty = tcLetPat sig_tau_fn pat exp_ty $
653 mapM lookup_info nm_sig_prs
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 ; newDictBndrs (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. This variable is set True
1048 -- when we are typechecking a single function binding; and False for
1049 -- pattern bindigs and a group of several function bindings.
1050 -- Reason: in the latter cases, the "skolems" can be unified together,
1051 -- so they aren't properly rigid in the type-refinement sense.
1052 -- NB: unless we are doing H98, each function with a sig will be done
1053 -- separately, even if it's mutually recursive, so use_skols will be True
1055 -- We always instantiate with fresh uniques,
1056 -- although we keep the same print-name
1058 -- type T = forall a. [a] -> [a]
1060 -- f = g where { g :: T; g = <rhs> }
1062 -- We must not use the same 'a' from the defn of T at both places!!
1064 tcInstSig use_skols name scoped_names
1065 = do { poly_id <- tcLookupId name -- Cannot fail; the poly ids are put into
1066 -- scope when starting the binding group
1067 ; let skol_info = SigSkol (FunSigCtxt name)
1068 inst_tyvars | use_skols = tcInstSkolTyVars skol_info
1069 | otherwise = tcInstSigTyVars skol_info
1070 ; (tvs, theta, tau) <- tcInstType inst_tyvars (idType poly_id)
1071 ; loc <- getInstLoc (SigOrigin skol_info)
1072 ; return (TcSigInfo { sig_id = poly_id,
1073 sig_tvs = tvs, sig_theta = theta, sig_tau = tau,
1074 sig_scoped = final_scoped_names, sig_loc = loc }) }
1075 -- Note that the scoped_names and the sig_tvs will have
1076 -- different Names. That's quite ok; when we bring the
1077 -- scoped_names into scope, we just bind them to the sig_tvs
1079 -- We also only have scoped type variables when we are instantiating
1080 -- with true skolems
1081 final_scoped_names | use_skols = scoped_names
1085 isMonoGroup :: DynFlags -> [LHsBind Name] -> Bool
1086 -- No generalisation at all
1087 isMonoGroup dflags binds
1088 = dopt Opt_MonoPatBinds dflags && any is_pat_bind binds
1090 is_pat_bind (L _ (PatBind {})) = True
1091 is_pat_bind other = False
1094 isRestrictedGroup :: DynFlags -> [LHsBind Name] -> TcSigFun -> Bool
1095 isRestrictedGroup dflags binds sig_fn
1096 = mono_restriction && not all_unrestricted
1098 mono_restriction = dopt Opt_MonomorphismRestriction dflags
1099 all_unrestricted = all (unrestricted . unLoc) binds
1100 has_sig n = isJust (sig_fn n)
1102 unrestricted (PatBind {}) = False
1103 unrestricted (VarBind { var_id = v }) = has_sig v
1104 unrestricted (FunBind { fun_id = v, fun_matches = matches }) = unrestricted_match matches
1105 || has_sig (unLoc v)
1107 unrestricted_match (MatchGroup (L _ (Match [] _ _) : _) _) = False
1108 -- No args => like a pattern binding
1109 unrestricted_match other = True
1110 -- Some args => a function binding
1114 %************************************************************************
1116 \subsection[TcBinds-errors]{Error contexts and messages}
1118 %************************************************************************
1122 -- This one is called on LHS, when pat and grhss are both Name
1123 -- and on RHS, when pat is TcId and grhss is still Name
1124 patMonoBindsCtxt pat grhss
1125 = hang (ptext SLIT("In a pattern binding:")) 4 (pprPatBind pat grhss)
1127 -----------------------------------------------
1128 sigContextsCtxt sig1 sig2
1129 = vcat [ptext SLIT("When matching the contexts of the signatures for"),
1130 nest 2 (vcat [ppr id1 <+> dcolon <+> ppr (idType id1),
1131 ppr id2 <+> dcolon <+> ppr (idType id2)]),
1132 ptext SLIT("The signature contexts in a mutually recursive group should all be identical")]
1138 -----------------------------------------------
1139 unboxedTupleErr name ty
1140 = hang (ptext SLIT("Illegal binding of unboxed tuple"))
1141 4 (ppr name <+> dcolon <+> ppr ty)
1143 -----------------------------------------------
1144 restrictedBindCtxtErr binder_names
1145 = hang (ptext SLIT("Illegal overloaded type signature(s)"))
1146 4 (vcat [ptext SLIT("in a binding group for") <+> pprBinders binder_names,
1147 ptext SLIT("that falls under the monomorphism restriction")])
1149 genCtxt binder_names
1150 = ptext SLIT("When generalising the type(s) for") <+> pprBinders binder_names