2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[HsBinds]{Abstract syntax: top-level bindings and signatures}
6 Datatype for: @BindGroup@, @Bind@, @Sig@, @Bind@.
11 #include "HsVersions.h"
13 import {-# SOURCE #-} HsExpr ( HsExpr, pprExpr, LHsExpr,
14 MatchGroup, pprFunBind,
16 import {-# SOURCE #-} HsPat ( LPat )
18 import HsTypes ( LHsType, PostTcType )
21 import NameSet ( NameSet, elemNameSet )
22 import BasicTypes ( IPName, RecFlag(..), InlineSpec(..), Fixity )
24 import SrcLoc ( Located(..), SrcSpan, unLoc )
25 import Util ( sortLe )
26 import Var ( TyVar, DictId, Id )
27 import Bag ( Bag, emptyBag, isEmptyBag, bagToList, unionBags, unionManyBags )
30 %************************************************************************
32 \subsection{Bindings: @BindGroup@}
34 %************************************************************************
36 Global bindings (where clauses)
39 data HsLocalBinds id -- Bindings in a 'let' expression
40 -- or a 'where' clause
41 = HsValBinds (HsValBinds id)
42 | HsIPBinds (HsIPBinds id)
45 data HsValBinds id -- Value bindings (not implicit parameters)
46 = ValBindsIn -- Before typechecking
47 (LHsBinds id) [LSig id] -- Not dependency analysed
48 -- Recursive by default
50 | ValBindsOut -- After renaming
51 [(RecFlag, LHsBinds id)] -- Dependency analysed
54 type LHsBinds id = Bag (LHsBind id)
55 type DictBinds id = LHsBinds id -- Used for dictionary or method bindings
56 type LHsBind id = Located (HsBind id)
59 = FunBind { -- FunBind is used for both functions f x = e
60 -- and variables f = \x -> e
61 -- Reason: the Match stuff lets us have an optional
62 -- result type sig f :: a->a = ...mentions a...
64 -- This also means that instance decls can only have
65 -- FunBinds, so if you change this, you'll need to
66 -- change e.g. rnMethodBinds
70 fun_infix :: Bool, -- True => infix declaration
72 fun_matches :: MatchGroup id, -- The payload
74 fun_co_fn :: ExprCoFn, -- Coercion from the type of the MatchGroup to the type of
76 -- f :: Int -> forall a. a -> a
78 -- Then the MatchGroup will have type (Int -> a' -> a')
79 -- (with a free type variable a'). The coercion will take
80 -- a CoreExpr of this type and convert it to a CoreExpr of
81 -- type Int -> forall a'. a' -> a'
82 -- Notice that the coercion captures the free a'. That's
83 -- why coercions are (CoreExpr -> CoreExpr), rather than
84 -- just CoreExpr (with a functional type)
86 bind_fvs :: NameSet -- After the renamer, this contains a superset of the
87 -- Names of the other binders in this binding group that
88 -- are free in the RHS of the defn
89 -- Before renaming, and after typechecking,
90 -- the field is unused; it's just an error thunk
93 | PatBind { -- The pattern is never a simple variable;
94 -- That case is done by FunBind
97 pat_rhs_ty :: PostTcType, -- Type of the GRHSs
98 bind_fvs :: NameSet -- Same as for FunBind
101 | VarBind { -- Dictionary binding and suchlike
102 var_id :: id, -- All VarBinds are introduced by the type checker
103 var_rhs :: LHsExpr id -- Located only for consistency
106 | AbsBinds { -- Binds abstraction; TRANSLATION
108 abs_dicts :: [DictId],
109 abs_exports :: [([TyVar], id, id, [Prag])], -- (tvs, poly_id, mono_id, prags)
110 abs_binds :: LHsBinds id -- The dictionary bindings and typechecked user bindings
111 -- mixed up together; you can tell the dict bindings because
112 -- they are all VarBinds
114 -- Consider (AbsBinds tvs ds [(ftvs, poly_f, mono_f) binds]
116 -- Creates bindings for (polymorphic, overloaded) poly_f
117 -- in terms of monomorphic, non-overloaded mono_f
120 -- 1. 'binds' binds mono_f
121 -- 2. ftvs is a subset of tvs
122 -- 3. ftvs includes all tyvars free in ds
124 -- See section 9 of static semantics paper for more details.
125 -- (You can get a PhD for explaining the True Meaning
126 -- of this last construct.)
128 placeHolderNames :: NameSet
129 -- Used for the NameSet in FunBind and PatBind prior to the renamer
130 placeHolderNames = panic "placeHolderNames"
133 instance OutputableBndr id => Outputable (HsLocalBinds id) where
134 ppr (HsValBinds bs) = ppr bs
135 ppr (HsIPBinds bs) = ppr bs
136 ppr EmptyLocalBinds = empty
138 instance OutputableBndr id => Outputable (HsValBinds id) where
139 ppr (ValBindsIn binds sigs)
140 = pprValBindsForUser binds sigs
142 ppr (ValBindsOut sccs sigs)
143 = getPprStyle $ \ sty ->
144 if debugStyle sty then -- Print with sccs showing
145 vcat (map ppr sigs) $$ vcat (map ppr_scc sccs)
147 pprValBindsForUser (unionManyBags (map snd sccs)) sigs
149 ppr_scc (rec_flag, binds) = pp_rec rec_flag <+> pprLHsBinds binds
150 pp_rec Recursive = ptext SLIT("rec")
151 pp_rec NonRecursive = ptext SLIT("nonrec")
153 -- *not* pprLHsBinds because we don't want braces; 'let' and
154 -- 'where' include a list of HsBindGroups and we don't want
155 -- several groups of bindings each with braces around.
156 -- Sort by location before printing
157 pprValBindsForUser binds sigs
158 = vcat (map snd (sort_by_loc decls))
161 decls :: [(SrcSpan, SDoc)]
162 decls = [(loc, ppr sig) | L loc sig <- sigs] ++
163 [(loc, ppr bind) | L loc bind <- bagToList binds]
165 sort_by_loc decls = sortLe (\(l1,_) (l2,_) -> l1 <= l2) decls
167 pprLHsBinds :: OutputableBndr id => LHsBinds id -> SDoc
169 | isEmptyLHsBinds binds = empty
170 | otherwise = lbrace <+> vcat (map ppr (bagToList binds)) <+> rbrace
173 emptyLocalBinds :: HsLocalBinds a
174 emptyLocalBinds = EmptyLocalBinds
176 isEmptyLocalBinds :: HsLocalBinds a -> Bool
177 isEmptyLocalBinds (HsValBinds ds) = isEmptyValBinds ds
178 isEmptyLocalBinds (HsIPBinds ds) = isEmptyIPBinds ds
179 isEmptyLocalBinds EmptyLocalBinds = True
181 isEmptyValBinds :: HsValBinds a -> Bool
182 isEmptyValBinds (ValBindsIn ds sigs) = isEmptyLHsBinds ds && null sigs
183 isEmptyValBinds (ValBindsOut ds sigs) = null ds && null sigs
185 emptyValBindsIn, emptyValBindsOut :: HsValBinds a
186 emptyValBindsIn = ValBindsIn emptyBag []
187 emptyValBindsOut = ValBindsOut [] []
189 emptyLHsBinds :: LHsBinds id
190 emptyLHsBinds = emptyBag
192 isEmptyLHsBinds :: LHsBinds id -> Bool
193 isEmptyLHsBinds = isEmptyBag
196 plusHsValBinds :: HsValBinds a -> HsValBinds a -> HsValBinds a
197 plusHsValBinds (ValBindsIn ds1 sigs1) (ValBindsIn ds2 sigs2)
198 = ValBindsIn (ds1 `unionBags` ds2) (sigs1 ++ sigs2)
199 plusHsValBinds (ValBindsOut ds1 sigs1) (ValBindsOut ds2 sigs2)
200 = ValBindsOut (ds1 ++ ds2) (sigs1 ++ sigs2)
212 f1p = /\ tvs -> \ [d1,d2] -> letrec DBINDS and BIND
215 gp = ...same again, with gm instead of fm
217 This is a pretty bad translation, because it duplicates all the bindings.
218 So the desugarer tries to do a better job:
220 fp = /\ [a,b] -> \ [d1,d2] -> case tp [a,b] [d1,d2] of
224 tp = /\ [a,b] -> \ [d1,d2] -> letrec DBINDS and BIND
228 instance OutputableBndr id => Outputable (HsBind id) where
229 ppr mbind = ppr_monobind mbind
231 ppr_monobind :: OutputableBndr id => HsBind id -> SDoc
233 ppr_monobind (PatBind { pat_lhs = pat, pat_rhs = grhss }) = pprPatBind pat grhss
234 ppr_monobind (VarBind { var_id = var, var_rhs = rhs }) = ppr var <+> equals <+> pprExpr (unLoc rhs)
235 ppr_monobind (FunBind { fun_id = fun, fun_matches = matches }) = pprFunBind (unLoc fun) matches
236 -- ToDo: print infix if appropriate
238 ppr_monobind (AbsBinds { abs_tvs = tyvars, abs_dicts = dictvars,
239 abs_exports = exports, abs_binds = val_binds })
240 = sep [ptext SLIT("AbsBinds"),
241 brackets (interpp'SP tyvars),
242 brackets (interpp'SP dictvars),
243 brackets (sep (punctuate comma (map ppr_exp exports)))]
245 nest 2 ( vcat [pprBndr LetBind x | (_,x,_,_) <- exports]
246 -- Print type signatures
247 $$ pprLHsBinds val_binds )
249 ppr_exp (tvs, gbl, lcl, prags)
250 = vcat [ppr gbl <+> ptext SLIT("<=") <+> ppr tvs <+> ppr lcl,
251 nest 2 (vcat (map (pprPrag gbl) prags))]
254 %************************************************************************
256 Implicit parameter bindings
258 %************************************************************************
264 (DictBinds id) -- Only in typechecker output; binds
265 -- uses of the implicit parameters
267 isEmptyIPBinds :: HsIPBinds id -> Bool
268 isEmptyIPBinds (IPBinds is ds) = null is && isEmptyBag ds
270 type LIPBind id = Located (IPBind id)
272 -- | Implicit parameter bindings.
278 instance (OutputableBndr id) => Outputable (HsIPBinds id) where
279 ppr (IPBinds bs ds) = vcat (map ppr bs)
282 instance (OutputableBndr id) => Outputable (IPBind id) where
283 ppr (IPBind id rhs) = pprBndr LetBind id <+> equals <+> pprExpr (unLoc rhs)
287 %************************************************************************
289 \subsection{Coercion functions}
291 %************************************************************************
294 -- A Coercion is an expression with a hole in it
295 -- We need coercions to have concrete form so that we can zonk them
298 = CoHole -- The identity coercion
299 | CoCompose ExprCoFn ExprCoFn
300 | CoApps ExprCoFn [Id] -- Non-empty list
301 | CoTyApps ExprCoFn [Type] -- in all of these
302 | CoLams [Id] ExprCoFn -- so that the identity coercion
303 | CoTyLams [TyVar] ExprCoFn -- is just Hole
304 | CoLet (LHsBinds Id) ExprCoFn -- Would be nicer to be core bindings
306 (<.>) :: ExprCoFn -> ExprCoFn -> ExprCoFn
309 idCoercion :: ExprCoFn
312 isIdCoercion :: ExprCoFn -> Bool
313 isIdCoercion CoHole = True
314 isIdCoercion other = False
318 %************************************************************************
320 \subsection{@Sig@: type signatures and value-modifying user pragmas}
322 %************************************************************************
324 It is convenient to lump ``value-modifying'' user-pragmas (e.g.,
325 ``specialise this function to these four types...'') in with type
326 signatures. Then all the machinery to move them into place, etc.,
330 type LSig name = Located (Sig name)
333 = TypeSig (Located name) -- A bog-std type signature
336 | SpecSig (Located name) -- Specialise a function or datatype ...
337 (LHsType name) -- ... to these types
340 | InlineSig (Located name) -- Function name
343 | SpecInstSig (LHsType name) -- (Class tys); should be a specialisation of the
344 -- current instance decl
346 | FixSig (FixitySig name) -- Fixity declaration
348 type LFixitySig name = Located (FixitySig name)
349 data FixitySig name = FixitySig (Located name) Fixity
351 -- A Prag conveys pragmas from the type checker to the desugarer
357 (HsExpr Id) -- An expression, of the given specialised type, which
358 PostTcType -- specialises the polymorphic function
359 [Id] -- Dicts mentioned free in the expression
360 InlineSpec -- Inlining spec for the specialised function
362 isInlinePrag (InlinePrag _) = True
363 isInlinePrag prag = False
365 isSpecPrag (SpecPrag _ _ _ _) = True
366 isSpecPrag prag = False
370 okBindSig :: NameSet -> LSig Name -> Bool
371 okBindSig ns sig = sigForThisGroup ns sig
373 okHsBootSig :: LSig Name -> Bool
374 okHsBootSig (L _ (TypeSig _ _)) = True
375 okHsBootSig (L _ (FixSig _)) = True
376 okHsBootSig sig = False
378 okClsDclSig :: LSig Name -> Bool
379 okClsDclSig (L _ (SpecInstSig _)) = False
380 okClsDclSig sig = True -- All others OK
382 okInstDclSig :: NameSet -> LSig Name -> Bool
383 okInstDclSig ns lsig@(L _ sig) = ok ns sig
385 ok ns (TypeSig _ _) = False
386 ok ns (FixSig _) = False
387 ok ns (SpecInstSig _) = True
388 ok ns sig = sigForThisGroup ns lsig
390 sigForThisGroup :: NameSet -> LSig Name -> Bool
391 sigForThisGroup ns sig
392 = case sigName sig of
394 Just n -> n `elemNameSet` ns
396 sigName :: LSig name -> Maybe name
397 sigName (L _ sig) = f sig
399 f (TypeSig n _) = Just (unLoc n)
400 f (SpecSig n _ _) = Just (unLoc n)
401 f (InlineSig n _) = Just (unLoc n)
402 f (FixSig (FixitySig n _)) = Just (unLoc n)
405 isFixityLSig :: LSig name -> Bool
406 isFixityLSig (L _ (FixSig {})) = True
407 isFixityLSig _ = False
409 isVanillaLSig :: LSig name -> Bool
410 isVanillaLSig (L _(TypeSig {})) = True
411 isVanillaLSig sig = False
413 isSpecLSig :: LSig name -> Bool
414 isSpecLSig (L _(SpecSig {})) = True
415 isSpecLSig sig = False
417 isSpecInstLSig (L _ (SpecInstSig {})) = True
418 isSpecInstLSig sig = False
420 isPragLSig :: LSig name -> Bool
421 -- Identifies pragmas
422 isPragLSig (L _ (SpecSig {})) = True
423 isPragLSig (L _ (InlineSig {})) = True
424 isPragLSig other = False
426 isInlineLSig :: LSig name -> Bool
427 -- Identifies inline pragmas
428 isInlineLSig (L _ (InlineSig {})) = True
429 isInlineLSig other = False
431 hsSigDoc (TypeSig {}) = ptext SLIT("type signature")
432 hsSigDoc (SpecSig {}) = ptext SLIT("SPECIALISE pragma")
433 hsSigDoc (InlineSig _ spec) = ppr spec <+> ptext SLIT("pragma")
434 hsSigDoc (SpecInstSig {}) = ptext SLIT("SPECIALISE instance pragma")
435 hsSigDoc (FixSig {}) = ptext SLIT("fixity declaration")
438 Signature equality is used when checking for duplicate signatures
441 eqHsSig :: LSig Name -> LSig Name -> Bool
442 eqHsSig (L _ (FixSig (FixitySig n1 _))) (L _ (FixSig (FixitySig n2 _))) = unLoc n1 == unLoc n2
443 eqHsSig (L _ (TypeSig n1 _)) (L _ (TypeSig n2 _)) = unLoc n1 == unLoc n2
444 eqHsSig (L _ (InlineSig n1 s1)) (L _ (InlineSig n2 s2)) = s1 == s2 && unLoc n1 == unLoc n2
445 -- For specialisations, we don't have equality over
446 -- HsType, so it's not convenient to spot duplicate
447 -- specialisations here. Check for this later, when we're in Type land
448 eqHsSig _other1 _other2 = False
452 instance (OutputableBndr name) => Outputable (Sig name) where
453 ppr sig = ppr_sig sig
455 ppr_sig :: OutputableBndr name => Sig name -> SDoc
456 ppr_sig (TypeSig var ty) = pprVarSig (unLoc var) ty
457 ppr_sig (FixSig fix_sig) = ppr fix_sig
458 ppr_sig (SpecSig var ty inl) = pragBrackets (pprSpec var ty inl)
459 ppr_sig (InlineSig var inl) = pragBrackets (ppr inl <+> ppr var)
460 ppr_sig (SpecInstSig ty) = pragBrackets (ptext SLIT("SPECIALIZE instance") <+> ppr ty)
462 instance Outputable name => Outputable (FixitySig name) where
463 ppr (FixitySig name fixity) = sep [ppr fixity, ppr name]
465 pragBrackets :: SDoc -> SDoc
466 pragBrackets doc = ptext SLIT("{-#") <+> doc <+> ptext SLIT("#-}")
468 pprVarSig :: (Outputable id, Outputable ty) => id -> ty -> SDoc
469 pprVarSig var ty = sep [ppr var <+> dcolon, nest 2 (ppr ty)]
471 pprSpec :: (Outputable id, Outputable ty) => id -> ty -> InlineSpec -> SDoc
472 pprSpec var ty inl = sep [ptext SLIT("SPECIALIZE") <+> ppr inl <+> pprVarSig var ty]
474 pprPrag :: Outputable id => id -> Prag -> SDoc
475 pprPrag var (InlinePrag inl) = ppr inl <+> ppr var
476 pprPrag var (SpecPrag expr ty _ inl) = pprSpec var ty inl