2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
5 \section[HsBinds]{Abstract syntax: top-level bindings and signatures}
7 Datatype for: @BindGroup@, @Bind@, @Sig@, @Bind@.
10 {-# OPTIONS -fno-warn-incomplete-patterns #-}
11 -- The above warning supression flag is a temporary kludge.
12 -- While working on this module you are encouraged to remove it and fix
13 -- any warnings in the module. See
14 -- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
19 import {-# SOURCE #-} HsExpr ( HsExpr, pprExpr, LHsExpr,
20 MatchGroup, pprFunBind,
22 import {-# SOURCE #-} HsPat ( LPat )
39 %************************************************************************
41 \subsection{Bindings: @BindGroup@}
43 %************************************************************************
45 Global bindings (where clauses)
48 -- During renaming, we need bindings where the left-hand sides
49 -- have been renamed but the the right-hand sides have not.
50 -- the ...LR datatypes are parametrized by two id types,
51 -- one for the left and one for the right.
52 -- Other than during renaming, these will be the same.
54 type HsLocalBinds id = HsLocalBindsLR id id
56 data HsLocalBindsLR idL idR -- Bindings in a 'let' expression
57 -- or a 'where' clause
58 = HsValBinds (HsValBindsLR idL idR)
59 | HsIPBinds (HsIPBinds idR)
62 type HsValBinds id = HsValBindsLR id id
64 data HsValBindsLR idL idR -- Value bindings (not implicit parameters)
65 = ValBindsIn -- Before typechecking
66 (LHsBindsLR idL idR) [LSig idR] -- Not dependency analysed
67 -- Recursive by default
69 | ValBindsOut -- After renaming
70 [(RecFlag, LHsBinds idL)] -- Dependency analysed, later bindings
71 -- in the list may depend on earlier
75 type LHsBinds id = Bag (LHsBind id)
76 type DictBinds id = LHsBinds id -- Used for dictionary or method bindings
77 type LHsBind id = Located (HsBind id)
78 type HsBind id = HsBindLR id id
80 type LHsBindLR idL idR = Located (HsBindLR idL idR)
81 type LHsBindsLR idL idR = Bag (LHsBindLR idL idR)
84 = FunBind { -- FunBind is used for both functions f x = e
85 -- and variables f = \x -> e
86 -- Reason 1: Special case for type inference: see TcBinds.tcMonoBinds
88 -- Reason 2: instance decls can only have FunBinds, which is convenient
89 -- If you change this, you'll need to change e.g. rnMethodBinds
91 -- But note that the form f :: a->a = ...
92 -- parses as a pattern binding, just like
93 -- (f :: a -> a) = ...
95 fun_id :: Located idL,
97 fun_infix :: Bool, -- True => infix declaration
99 fun_matches :: MatchGroup idR, -- The payload
101 fun_co_fn :: HsWrapper, -- Coercion from the type of the MatchGroup to the type of
103 -- f :: Int -> forall a. a -> a
105 -- Then the MatchGroup will have type (Int -> a' -> a')
106 -- (with a free type variable a'). The coercion will take
107 -- a CoreExpr of this type and convert it to a CoreExpr of
108 -- type Int -> forall a'. a' -> a'
109 -- Notice that the coercion captures the free a'.
111 bind_fvs :: NameSet, -- After the renamer, this contains a superset of the
112 -- Names of the other binders in this binding group that
113 -- are free in the RHS of the defn
114 -- Before renaming, and after typechecking,
115 -- the field is unused; it's just an error thunk
117 fun_tick :: Maybe (Int,[idR]) -- This is the (optional) module-local tick number.
120 | PatBind { -- The pattern is never a simple variable;
121 -- That case is done by FunBind
123 pat_rhs :: GRHSs idR,
124 pat_rhs_ty :: PostTcType, -- Type of the GRHSs
125 bind_fvs :: NameSet -- Same as for FunBind
128 | VarBind { -- Dictionary binding and suchlike
129 var_id :: idL, -- All VarBinds are introduced by the type checker
130 var_rhs :: LHsExpr idR -- Located only for consistency
133 | AbsBinds { -- Binds abstraction; TRANSLATION
135 abs_dicts :: [DictId],
136 -- AbsBinds only gets used when idL = idR after renaming,
137 -- but these need to be idL's for the collect... code in HsUtil to have
139 abs_exports :: [([TyVar], idL, idL, [LPrag])], -- (tvs, poly_id, mono_id, prags)
140 abs_binds :: LHsBinds idL -- The dictionary bindings and typechecked user bindings
141 -- mixed up together; you can tell the dict bindings because
142 -- they are all VarBinds
144 -- Consider (AbsBinds tvs ds [(ftvs, poly_f, mono_f) binds]
146 -- Creates bindings for (polymorphic, overloaded) poly_f
147 -- in terms of monomorphic, non-overloaded mono_f
150 -- 1. 'binds' binds mono_f
151 -- 2. ftvs is a subset of tvs
152 -- 3. ftvs includes all tyvars free in ds
154 -- See section 9 of static semantics paper for more details.
155 -- (You can get a PhD for explaining the True Meaning
156 -- of this last construct.)
158 placeHolderNames :: NameSet
159 -- Used for the NameSet in FunBind and PatBind prior to the renamer
160 placeHolderNames = panic "placeHolderNames"
163 instance (OutputableBndr idL, OutputableBndr idR) => Outputable (HsLocalBindsLR idL idR) where
164 ppr (HsValBinds bs) = ppr bs
165 ppr (HsIPBinds bs) = ppr bs
166 ppr EmptyLocalBinds = empty
168 instance (OutputableBndr idL, OutputableBndr idR) => Outputable (HsValBindsLR idL idR) where
169 ppr (ValBindsIn binds sigs)
170 = pprValBindsForUser binds sigs
172 ppr (ValBindsOut sccs sigs)
173 = getPprStyle $ \ sty ->
174 if debugStyle sty then -- Print with sccs showing
175 vcat (map ppr sigs) $$ vcat (map ppr_scc sccs)
177 pprValBindsForUser (unionManyBags (map snd sccs)) sigs
179 ppr_scc (rec_flag, binds) = pp_rec rec_flag <+> pprLHsBinds binds
180 pp_rec Recursive = ptext (sLit "rec")
181 pp_rec NonRecursive = ptext (sLit "nonrec")
183 -- *not* pprLHsBinds because we don't want braces; 'let' and
184 -- 'where' include a list of HsBindGroups and we don't want
185 -- several groups of bindings each with braces around.
186 -- Sort by location before printing
187 pprValBindsForUser :: (OutputableBndr idL, OutputableBndr idR, OutputableBndr id2)
188 => LHsBindsLR idL idR -> [LSig id2] -> SDoc
189 pprValBindsForUser binds sigs
190 = pprDeeperList vcat (map snd (sort_by_loc decls))
193 decls :: [(SrcSpan, SDoc)]
194 decls = [(loc, ppr sig) | L loc sig <- sigs] ++
195 [(loc, ppr bind) | L loc bind <- bagToList binds]
197 sort_by_loc decls = sortLe (\(l1,_) (l2,_) -> l1 <= l2) decls
199 pprLHsBinds :: (OutputableBndr idL, OutputableBndr idR) => LHsBindsLR idL idR -> SDoc
201 | isEmptyLHsBinds binds = empty
202 | otherwise = lbrace <+> pprDeeperList vcat (map ppr (bagToList binds)) <+> rbrace
205 emptyLocalBinds :: HsLocalBindsLR a b
206 emptyLocalBinds = EmptyLocalBinds
208 isEmptyLocalBinds :: HsLocalBindsLR a b -> Bool
209 isEmptyLocalBinds (HsValBinds ds) = isEmptyValBinds ds
210 isEmptyLocalBinds (HsIPBinds ds) = isEmptyIPBinds ds
211 isEmptyLocalBinds EmptyLocalBinds = True
213 isEmptyValBinds :: HsValBindsLR a b -> Bool
214 isEmptyValBinds (ValBindsIn ds sigs) = isEmptyLHsBinds ds && null sigs
215 isEmptyValBinds (ValBindsOut ds sigs) = null ds && null sigs
217 emptyValBindsIn, emptyValBindsOut :: HsValBindsLR a b
218 emptyValBindsIn = ValBindsIn emptyBag []
219 emptyValBindsOut = ValBindsOut [] []
221 emptyLHsBinds :: LHsBindsLR idL idR
222 emptyLHsBinds = emptyBag
224 isEmptyLHsBinds :: LHsBindsLR idL idR -> Bool
225 isEmptyLHsBinds = isEmptyBag
228 plusHsValBinds :: HsValBinds a -> HsValBinds a -> HsValBinds a
229 plusHsValBinds (ValBindsIn ds1 sigs1) (ValBindsIn ds2 sigs2)
230 = ValBindsIn (ds1 `unionBags` ds2) (sigs1 ++ sigs2)
231 plusHsValBinds (ValBindsOut ds1 sigs1) (ValBindsOut ds2 sigs2)
232 = ValBindsOut (ds1 ++ ds2) (sigs1 ++ sigs2)
244 f1p = /\ tvs -> \ [d1,d2] -> letrec DBINDS and BIND
247 gp = ...same again, with gm instead of fm
249 This is a pretty bad translation, because it duplicates all the bindings.
250 So the desugarer tries to do a better job:
252 fp = /\ [a,b] -> \ [d1,d2] -> case tp [a,b] [d1,d2] of
256 tp = /\ [a,b] -> \ [d1,d2] -> letrec DBINDS and BIND
260 instance (OutputableBndr idL, OutputableBndr idR) => Outputable (HsBindLR idL idR) where
261 ppr mbind = ppr_monobind mbind
263 ppr_monobind :: (OutputableBndr idL, OutputableBndr idR) => HsBindLR idL idR -> SDoc
265 ppr_monobind (PatBind { pat_lhs = pat, pat_rhs = grhss }) = pprPatBind pat grhss
266 ppr_monobind (VarBind { var_id = var, var_rhs = rhs }) = pprBndr CaseBind var <+> equals <+> pprExpr (unLoc rhs)
267 ppr_monobind (FunBind { fun_id = fun, fun_infix = inf,
268 fun_matches = matches,
272 Just t -> text "-- tick id = " <> ppr t
273 ) $$ pprFunBind (unLoc fun) inf matches
275 ppr_monobind (AbsBinds { abs_tvs = tyvars, abs_dicts = dictvars,
276 abs_exports = exports, abs_binds = val_binds })
277 = sep [ptext (sLit "AbsBinds"),
278 brackets (interpp'SP tyvars),
279 brackets (interpp'SP dictvars),
280 brackets (sep (punctuate comma (map ppr_exp exports)))]
282 nest 2 ( vcat [pprBndr LetBind x | (_,x,_,_) <- exports]
283 -- Print type signatures
284 $$ pprLHsBinds val_binds )
286 ppr_exp (tvs, gbl, lcl, prags)
287 = vcat [ppr gbl <+> ptext (sLit "<=") <+> ppr tvs <+> ppr lcl,
288 nest 2 (vcat (map (pprPrag gbl) prags))]
291 %************************************************************************
293 Implicit parameter bindings
295 %************************************************************************
301 (DictBinds id) -- Only in typechecker output; binds
302 -- uses of the implicit parameters
304 isEmptyIPBinds :: HsIPBinds id -> Bool
305 isEmptyIPBinds (IPBinds is ds) = null is && isEmptyBag ds
307 type LIPBind id = Located (IPBind id)
309 -- | Implicit parameter bindings.
315 instance (OutputableBndr id) => Outputable (HsIPBinds id) where
316 ppr (IPBinds bs ds) = pprDeeperList vcat (map ppr bs)
319 instance (OutputableBndr id) => Outputable (IPBind id) where
320 ppr (IPBind id rhs) = pprBndr LetBind id <+> equals <+> pprExpr (unLoc rhs)
324 %************************************************************************
326 \subsection{Coercion functions}
328 %************************************************************************
331 -- A HsWrapper is an expression with a hole in it
332 -- We need coercions to have concrete form so that we can zonk them
335 = WpHole -- The identity coercion
337 | WpCompose HsWrapper HsWrapper -- (\a1..an. []) `WpCompose` (\x1..xn. [])
338 -- = (\a1..an \x1..xn. [])
340 | WpCast Coercion -- A cast: [] `cast` co
341 -- Guaranteed not the identity coercion
343 | WpApp Var -- [] d the 'd' is a type-class dictionary
344 | WpTyApp Type -- [] t the 't' is a type or corecion
345 | WpLam Var -- \d. [] the 'd' is a type-class dictionary or coercion variable
346 | WpTyLam TyVar -- \a. [] the 'a' is a type variable (not coercion var)
347 | WpInline -- inline_me [] Wrap inline around the thing
349 -- Non-empty bindings, so that the identity coercion
350 -- is always exactly WpHole
351 | WpLet (LHsBinds Id) -- let binds in []
352 -- (would be nicer to be core bindings)
354 instance Outputable HsWrapper where
355 ppr co_fn = pprHsWrapper (ptext (sLit "<>")) co_fn
357 pprHsWrapper :: SDoc -> HsWrapper -> SDoc
358 pprHsWrapper it wrap =
361 help it (WpCompose f1 f2) = help (help it f2) f1
362 help it (WpCast co) = sep [it, nest 2 (ptext (sLit "`cast`") <+> pprParendType co)]
363 help it (WpApp id) = sep [it, nest 2 (ppr id)]
364 help it (WpTyApp ty) = sep [it, ptext (sLit "@") <+> pprParendType ty]
365 help it (WpLam id) = sep [ptext (sLit "\\") <> pprBndr LambdaBind id <> dot, it]
366 help it (WpTyLam tv) = sep [ptext (sLit "/\\") <> pprBndr LambdaBind tv <> dot, it]
367 help it (WpLet binds) = sep [ptext (sLit "let") <+> braces (ppr binds), it]
368 help it WpInline = sep [ptext (sLit "_inline_me_"), it]
370 -- in debug mode, print the wrapper
371 -- otherwise just print what's inside
372 getPprStyle (\ s -> if debugStyle s then (help it wrap) else it)
374 (<.>) :: HsWrapper -> HsWrapper -> HsWrapper
377 c1 <.> c2 = c1 `WpCompose` c2
379 mkWpTyApps :: [Type] -> HsWrapper
380 mkWpTyApps tys = mk_co_fn WpTyApp (reverse tys)
382 mkWpApps :: [Id] -> HsWrapper
383 mkWpApps ids = mk_co_fn WpApp (reverse ids)
385 mkWpTyLams :: [TyVar] -> HsWrapper
386 mkWpTyLams ids = mk_co_fn WpTyLam ids
388 mkWpLams :: [Id] -> HsWrapper
389 mkWpLams ids = mk_co_fn WpLam ids
391 mk_co_fn :: (a -> HsWrapper) -> [a] -> HsWrapper
392 mk_co_fn f as = foldr (WpCompose . f) WpHole as
394 idHsWrapper :: HsWrapper
397 isIdHsWrapper :: HsWrapper -> Bool
398 isIdHsWrapper WpHole = True
399 isIdHsWrapper _ = False
403 %************************************************************************
405 \subsection{@Sig@: type signatures and value-modifying user pragmas}
407 %************************************************************************
409 It is convenient to lump ``value-modifying'' user-pragmas (e.g.,
410 ``specialise this function to these four types...'') in with type
411 signatures. Then all the machinery to move them into place, etc.,
415 type LSig name = Located (Sig name)
417 data Sig name -- Signatures and pragmas
418 = -- An ordinary type signature
419 -- f :: Num a => a -> a
420 TypeSig (Located name) -- A bog-std type signature
423 -- An ordinary fixity declaration
425 | FixSig (FixitySig name) -- Fixity declaration
429 | InlineSig (Located name) -- Function name
432 -- A specialisation pragma
433 -- {-# SPECIALISE f :: Int -> Int #-}
434 | SpecSig (Located name) -- Specialise a function or datatype ...
435 (LHsType name) -- ... to these types
438 -- A specialisation pragma for instance declarations only
439 -- {-# SPECIALISE instance Eq [Int] #-}
440 | SpecInstSig (LHsType name) -- (Class tys); should be a specialisation of the
441 -- current instance decl
444 type LFixitySig name = Located (FixitySig name)
445 data FixitySig name = FixitySig (Located name) Fixity
447 -- A Prag conveys pragmas from the type checker to the desugarer
448 type LPrag = Located Prag
454 (HsExpr Id) -- An expression, of the given specialised type, which
455 PostTcType -- specialises the polymorphic function
456 InlineSpec -- Inlining spec for the specialised function
458 isInlinePrag :: Prag -> Bool
459 isInlinePrag (InlinePrag _) = True
460 isInlinePrag _ = False
462 isSpecPrag :: Prag -> Bool
463 isSpecPrag (SpecPrag {}) = True
468 okBindSig :: Sig a -> Bool
471 okHsBootSig :: Sig a -> Bool
472 okHsBootSig (TypeSig _ _) = True
473 okHsBootSig (FixSig _) = True
474 okHsBootSig _ = False
476 okClsDclSig :: Sig a -> Bool
477 okClsDclSig (SpecInstSig _) = False
478 okClsDclSig _ = True -- All others OK
480 okInstDclSig :: Sig a -> Bool
481 okInstDclSig (TypeSig _ _) = False
482 okInstDclSig (FixSig _) = False
483 okInstDclSig _ = True
485 sigForThisGroup :: NameSet -> LSig Name -> Bool
486 sigForThisGroup ns sig
487 = case sigName sig of
489 Just n -> n `elemNameSet` ns
491 sigName :: LSig name -> Maybe name
492 sigName (L _ sig) = sigNameNoLoc sig
494 sigNameNoLoc :: Sig name -> Maybe name
495 sigNameNoLoc (TypeSig n _) = Just (unLoc n)
496 sigNameNoLoc (SpecSig n _ _) = Just (unLoc n)
497 sigNameNoLoc (InlineSig n _) = Just (unLoc n)
498 sigNameNoLoc (FixSig (FixitySig n _)) = Just (unLoc n)
499 sigNameNoLoc _ = Nothing
501 isFixityLSig :: LSig name -> Bool
502 isFixityLSig (L _ (FixSig {})) = True
503 isFixityLSig _ = False
505 isVanillaLSig :: LSig name -> Bool
506 isVanillaLSig (L _(TypeSig {})) = True
507 isVanillaLSig _ = False
509 isSpecLSig :: LSig name -> Bool
510 isSpecLSig (L _(SpecSig {})) = True
513 isSpecInstLSig :: LSig name -> Bool
514 isSpecInstLSig (L _ (SpecInstSig {})) = True
515 isSpecInstLSig _ = False
517 isPragLSig :: LSig name -> Bool
518 -- Identifies pragmas
519 isPragLSig (L _ (SpecSig {})) = True
520 isPragLSig (L _ (InlineSig {})) = True
523 isInlineLSig :: LSig name -> Bool
524 -- Identifies inline pragmas
525 isInlineLSig (L _ (InlineSig {})) = True
526 isInlineLSig _ = False
528 hsSigDoc :: Sig name -> SDoc
529 hsSigDoc (TypeSig {}) = ptext (sLit "type signature")
530 hsSigDoc (SpecSig {}) = ptext (sLit "SPECIALISE pragma")
531 hsSigDoc (InlineSig {}) = ptext (sLit "INLINE pragma")
532 hsSigDoc (SpecInstSig {}) = ptext (sLit "SPECIALISE instance pragma")
533 hsSigDoc (FixSig {}) = ptext (sLit "fixity declaration")
536 Signature equality is used when checking for duplicate signatures
539 eqHsSig :: Eq a => LSig a -> LSig a -> Bool
540 eqHsSig (L _ (FixSig (FixitySig n1 _))) (L _ (FixSig (FixitySig n2 _))) = unLoc n1 == unLoc n2
541 eqHsSig (L _ (TypeSig n1 _)) (L _ (TypeSig n2 _)) = unLoc n1 == unLoc n2
542 eqHsSig (L _ (InlineSig n1 _)) (L _ (InlineSig n2 _)) = unLoc n1 == unLoc n2
543 -- For specialisations, we don't have equality over
544 -- HsType, so it's not convenient to spot duplicate
545 -- specialisations here. Check for this later, when we're in Type land
546 eqHsSig _other1 _other2 = False
550 instance (OutputableBndr name) => Outputable (Sig name) where
551 ppr sig = ppr_sig sig
553 ppr_sig :: OutputableBndr name => Sig name -> SDoc
554 ppr_sig (TypeSig var ty) = pprVarSig (unLoc var) ty
555 ppr_sig (FixSig fix_sig) = ppr fix_sig
556 ppr_sig (SpecSig var ty inl) = pragBrackets (pprSpec var ty inl)
557 ppr_sig (InlineSig var inl) = pragBrackets (ppr inl <+> ppr var)
558 ppr_sig (SpecInstSig ty) = pragBrackets (ptext (sLit "SPECIALIZE instance") <+> ppr ty)
560 instance Outputable name => Outputable (FixitySig name) where
561 ppr (FixitySig name fixity) = sep [ppr fixity, ppr name]
563 pragBrackets :: SDoc -> SDoc
564 pragBrackets doc = ptext (sLit "{-#") <+> doc <+> ptext (sLit "#-}")
566 pprVarSig :: (Outputable id, Outputable ty) => id -> ty -> SDoc
567 pprVarSig var ty = sep [ppr var <+> dcolon, nest 2 (ppr ty)]
569 pprSpec :: (Outputable id, Outputable ty) => id -> ty -> InlineSpec -> SDoc
570 pprSpec var ty inl = sep [ptext (sLit "SPECIALIZE") <+> ppr inl <+> pprVarSig var ty]
572 pprPrag :: Outputable id => id -> LPrag -> SDoc
573 pprPrag var (L _ (InlinePrag inl)) = ppr inl <+> ppr var
574 pprPrag var (L _ (SpecPrag _expr ty inl)) = pprSpec var ty inl