2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[HsDecls]{Abstract syntax: global declarations}
6 Definitions for: @TyDecl@ and @oCnDecl@, @ClassDecl@,
7 @InstDecl@, @DefaultDecl@ and @ForeignDecl@.
11 HsDecl(..), LHsDecl, TyClDecl(..), LTyClDecl,
12 InstDecl(..), LInstDecl, NewOrData(..),
13 RuleDecl(..), LRuleDecl, RuleBndr(..),
14 DefaultDecl(..), LDefaultDecl, HsGroup(..), SpliceDecl(..),
15 ForeignDecl(..), LForeignDecl, ForeignImport(..), ForeignExport(..),
16 CImportSpec(..), FoType(..),
17 ConDecl(..), LConDecl,
18 LBangType, BangType(..), HsBang(..),
19 getBangType, getBangStrictness, unbangedType,
20 DeprecDecl(..), LDeprecDecl,
21 tcdName, tyClDeclNames, tyClDeclTyVars,
22 isClassDecl, isSynDecl, isDataDecl,
25 collectRuleBndrSigTys,
28 #include "HsVersions.h"
31 import {-# SOURCE #-} HsExpr( HsExpr, pprExpr )
32 -- Because Expr imports Decls via HsBracket
34 import HsBinds ( HsBindGroup, HsBind, LHsBinds,
35 Sig(..), LSig, LFixitySig, pprLHsBinds )
36 import HsPat ( HsConDetails(..), hsConArgs )
37 import HsImpExp ( pprHsVar )
39 import HscTypes ( DeprecTxt )
40 import CoreSyn ( RuleName )
41 import BasicTypes ( Activation(..) )
42 import ForeignCall ( CCallTarget(..), DNCallSpec, CCallConv, Safety,
46 import FunDeps ( pprFundeps )
47 import Class ( FunDep )
48 import CStrings ( CLabelString )
51 import SrcLoc ( Located(..), unLoc )
56 %************************************************************************
58 \subsection[HsDecl]{Declarations}
60 %************************************************************************
63 type LHsDecl id = Located (HsDecl id)
70 | DefD (DefaultDecl id)
71 | ForD (ForeignDecl id)
72 | DeprecD (DeprecDecl id)
74 | SpliceD (SpliceDecl id)
76 -- NB: all top-level fixity decls are contained EITHER
78 -- OR in the ClassDecls in TyClDs
81 -- a) data constructors
82 -- b) class methods (but they can be also done in the
83 -- signatures of class decls)
84 -- c) imported functions (that have an IfacSig)
87 -- The latter is for class methods only
89 -- A [HsDecl] is categorised into a HsGroup before being
90 -- fed to the renamer.
93 hs_valds :: [HsBindGroup id],
94 -- Before the renamer, this is a single big HsBindGroup,
95 -- with all the bindings, and all the signatures.
96 -- The renamer does dependency analysis, splitting it up
97 -- into several HsBindGroups.
99 hs_tyclds :: [LTyClDecl id],
100 hs_instds :: [LInstDecl id],
102 hs_fixds :: [LFixitySig id],
103 -- Snaffled out of both top-level fixity signatures,
104 -- and those in class declarations
106 hs_defds :: [LDefaultDecl id],
107 hs_fords :: [LForeignDecl id],
108 hs_depds :: [LDeprecDecl id],
109 hs_ruleds :: [LRuleDecl id]
114 instance OutputableBndr name => Outputable (HsDecl name) where
115 ppr (TyClD dcl) = ppr dcl
116 ppr (ValD binds) = ppr binds
117 ppr (DefD def) = ppr def
118 ppr (InstD inst) = ppr inst
119 ppr (ForD fd) = ppr fd
120 ppr (SigD sd) = ppr sd
121 ppr (RuleD rd) = ppr rd
122 ppr (DeprecD dd) = ppr dd
123 ppr (SpliceD dd) = ppr dd
125 instance OutputableBndr name => Outputable (HsGroup name) where
126 ppr (HsGroup { hs_valds = val_decls,
127 hs_tyclds = tycl_decls,
128 hs_instds = inst_decls,
129 hs_fixds = fix_decls,
130 hs_depds = deprec_decls,
131 hs_fords = foreign_decls,
132 hs_defds = default_decls,
133 hs_ruleds = rule_decls })
134 = vcat [ppr_ds fix_decls, ppr_ds default_decls,
135 ppr_ds deprec_decls, ppr_ds rule_decls,
137 ppr_ds tycl_decls, ppr_ds inst_decls,
138 ppr_ds foreign_decls]
141 ppr_ds ds = text "" $$ vcat (map ppr ds)
143 data SpliceDecl id = SpliceDecl (Located (HsExpr id)) -- Top level splice
145 instance OutputableBndr name => Outputable (SpliceDecl name) where
146 ppr (SpliceDecl e) = ptext SLIT("$") <> parens (pprExpr (unLoc e))
150 %************************************************************************
152 \subsection[TyDecl]{@data@, @newtype@ or @type@ (synonym) type declaration}
154 %************************************************************************
156 --------------------------------
158 --------------------------------
160 Here is the story about the implicit names that go with type, class,
161 and instance decls. It's a bit tricky, so pay attention!
163 "Implicit" (or "system") binders
164 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
165 Each data type decl defines
166 a worker name for each constructor
167 to-T and from-T convertors
168 Each class decl defines
169 a tycon for the class
170 a data constructor for that tycon
171 the worker for that constructor
172 a selector for each superclass
174 All have occurrence names that are derived uniquely from their parent
177 None of these get separate definitions in an interface file; they are
178 fully defined by the data or class decl. But they may *occur* in
179 interface files, of course. Any such occurrence must haul in the
180 relevant type or class decl.
183 - Ensure they "point to" the parent data/class decl
184 when loading that decl from an interface file
185 (See RnHiFiles.getSysBinders)
187 - When typechecking the decl, we build the implicit TyCons and Ids.
188 When doing so we look them up in the name cache (RnEnv.lookupSysName),
189 to ensure correct module and provenance is set
191 These are the two places that we have to conjure up the magic derived
192 names. (The actual magic is in OccName.mkWorkerOcc, etc.)
196 - Occurrence name is derived uniquely from the method name
199 - If there is a default method name at all, it's recorded in
200 the ClassOpSig (in HsBinds), in the DefMeth field.
201 (DefMeth is defined in Class.lhs)
203 Source-code class decls and interface-code class decls are treated subtly
204 differently, which has given me a great deal of confusion over the years.
205 Here's the deal. (We distinguish the two cases because source-code decls
206 have (Just binds) in the tcdMeths field, whereas interface decls have Nothing.
208 In *source-code* class declarations:
210 - When parsing, every ClassOpSig gets a DefMeth with a suitable RdrName
211 This is done by RdrHsSyn.mkClassOpSigDM
213 - The renamer renames it to a Name
215 - During typechecking, we generate a binding for each $dm for
216 which there's a programmer-supplied default method:
221 We generate a binding for $dmop1 but not for $dmop2.
222 The Class for Foo has a NoDefMeth for op2 and a DefMeth for op1.
223 The Name for $dmop2 is simply discarded.
225 In *interface-file* class declarations:
226 - When parsing, we see if there's an explicit programmer-supplied default method
227 because there's an '=' sign to indicate it:
229 op1 = :: <type> -- NB the '='
231 We use this info to generate a DefMeth with a suitable RdrName for op1,
232 and a NoDefMeth for op2
233 - The interface file has a separate definition for $dmop1, with unfolding etc.
234 - The renamer renames it to a Name.
235 - The renamer treats $dmop1 as a free variable of the declaration, so that
236 the binding for $dmop1 will be sucked in. (See RnHsSyn.tyClDeclFVs)
237 This doesn't happen for source code class decls, because they *bind* the default method.
241 Each instance declaration gives rise to one dictionary function binding.
243 The type checker makes up new source-code instance declarations
244 (e.g. from 'deriving' or generic default methods --- see
245 TcInstDcls.tcInstDecls1). So we can't generate the names for
246 dictionary functions in advance (we don't know how many we need).
248 On the other hand for interface-file instance declarations, the decl
249 specifies the name of the dictionary function, and it has a binding elsewhere
250 in the interface file:
251 instance {Eq Int} = dEqInt
252 dEqInt :: {Eq Int} <pragma info>
254 So again we treat source code and interface file code slightly differently.
257 - Source code instance decls have a Nothing in the (Maybe name) field
258 (see data InstDecl below)
260 - The typechecker makes up a Local name for the dict fun for any source-code
261 instance decl, whether it comes from a source-code instance decl, or whether
262 the instance decl is derived from some other construct (e.g. 'deriving').
264 - The occurrence name it chooses is derived from the instance decl (just for
265 documentation really) --- e.g. dNumInt. Two dict funs may share a common
266 occurrence name, but will have different uniques. E.g.
267 instance Foo [Int] where ...
268 instance Foo [Bool] where ...
269 These might both be dFooList
271 - The CoreTidy phase externalises the name, and ensures the occurrence name is
272 unique (this isn't special to dict funs). So we'd get dFooList and dFooList1.
274 - We can take this relaxed approach (changing the occurrence name later)
275 because dict fun Ids are not captured in a TyCon or Class (unlike default
276 methods, say). Instead, they are kept separately in the InstEnv. This
277 makes it easy to adjust them after compiling a module. (Once we've finished
278 compiling that module, they don't change any more.)
282 - The instance decl gives the dict fun name, so the InstDecl has a (Just name)
283 in the (Maybe name) field.
285 - RnHsSyn.instDeclFVs treats the dict fun name as free in the decl, so that we
286 suck in the dfun binding
290 -- TyClDecls are precisely the kind of declarations that can
291 -- appear in interface files; or (internally) in GHC's interface
292 -- for a module. That's why (despite the misnomer) IfaceSig and ForeignType
293 -- are both in TyClDecl
295 type LTyClDecl name = Located (TyClDecl name)
299 tcdLName :: Located name,
300 tcdExtName :: Maybe FastString,
304 | TyData { tcdND :: NewOrData,
305 tcdCtxt :: LHsContext name, -- Context
306 tcdLName :: Located name, -- Type constructor
307 tcdTyVars :: [LHsTyVarBndr name], -- Type variables
308 tcdCons :: [LConDecl name], -- Data constructors
309 tcdDerivs :: Maybe (LHsContext name)
310 -- Derivings; Nothing => not specified
311 -- Just [] => derive exactly what is asked
314 | TySynonym { tcdLName :: Located name, -- type constructor
315 tcdTyVars :: [LHsTyVarBndr name], -- type variables
316 tcdSynRhs :: LHsType name -- synonym expansion
319 | ClassDecl { tcdCtxt :: LHsContext name, -- Context...
320 tcdLName :: Located name, -- Name of the class
321 tcdTyVars :: [LHsTyVarBndr name], -- Class type variables
322 tcdFDs :: [Located (FunDep name)], -- Functional deps
323 tcdSigs :: [LSig name], -- Methods' signatures
324 tcdMeths :: LHsBinds name -- Default methods
328 = NewType -- "newtype Blah ..."
329 | DataType -- "data Blah ..."
330 deriving( Eq ) -- Needed because Demand derives Eq
336 isDataDecl, isSynDecl, isClassDecl :: TyClDecl name -> Bool
338 isSynDecl (TySynonym {}) = True
339 isSynDecl other = False
341 isDataDecl (TyData {}) = True
342 isDataDecl other = False
344 isClassDecl (ClassDecl {}) = True
345 isClassDecl other = False
351 tcdName :: TyClDecl name -> name
352 tcdName decl = unLoc (tcdLName decl)
354 tyClDeclNames :: Eq name => TyClDecl name -> [Located name]
355 -- Returns all the *binding* names of the decl, along with their SrcLocs
356 -- The first one is guaranteed to be the name of the decl
357 -- For record fields, the first one counts as the SrcLoc
358 -- We use the equality to filter out duplicate field names
360 tyClDeclNames (TySynonym {tcdLName = name}) = [name]
361 tyClDeclNames (ForeignType {tcdLName = name}) = [name]
363 tyClDeclNames (ClassDecl {tcdLName = cls_name, tcdSigs = sigs})
364 = cls_name : [n | L _ (Sig n _) <- sigs]
366 tyClDeclNames (TyData {tcdLName = tc_name, tcdCons = cons})
367 = tc_name : conDeclsNames (map unLoc cons)
369 tyClDeclTyVars (TySynonym {tcdTyVars = tvs}) = tvs
370 tyClDeclTyVars (TyData {tcdTyVars = tvs}) = tvs
371 tyClDeclTyVars (ClassDecl {tcdTyVars = tvs}) = tvs
372 tyClDeclTyVars (ForeignType {}) = []
376 countTyClDecls :: [TyClDecl name] -> (Int, Int, Int, Int)
377 -- class, data, newtype, synonym decls
379 = (count isClassDecl decls,
380 count isSynDecl decls,
381 count isDataTy decls,
384 isDataTy TyData{tcdND=DataType} = True
387 isNewTy TyData{tcdND=NewType} = True
392 instance OutputableBndr name
393 => Outputable (TyClDecl name) where
395 ppr (ForeignType {tcdLName = ltycon})
396 = hsep [ptext SLIT("foreign import type dotnet"), ppr ltycon]
398 ppr (TySynonym {tcdLName = ltycon, tcdTyVars = tyvars, tcdSynRhs = mono_ty})
399 = hang (ptext SLIT("type") <+> pp_decl_head [] ltycon tyvars <+> equals)
402 ppr (TyData {tcdND = new_or_data, tcdCtxt = context, tcdLName = ltycon,
403 tcdTyVars = tyvars, tcdCons = condecls,
404 tcdDerivs = derivings})
405 = pp_tydecl (ppr new_or_data <+> pp_decl_head (unLoc context) ltycon tyvars)
406 (pp_condecls condecls)
409 ppr (ClassDecl {tcdCtxt = context, tcdLName = lclas, tcdTyVars = tyvars, tcdFDs = fds,
410 tcdSigs = sigs, tcdMeths = methods})
411 | null sigs -- No "where" part
414 | otherwise -- Laid out
415 = sep [hsep [top_matter, ptext SLIT("where {")],
416 nest 4 (sep [sep (map ppr_sig sigs), ppr methods, char '}'])]
418 top_matter = ptext SLIT("class") <+> pp_decl_head (unLoc context) lclas tyvars <+> pprFundeps (map unLoc fds)
419 ppr_sig sig = ppr sig <> semi
421 pp_decl_head :: OutputableBndr name
424 -> [LHsTyVarBndr name]
426 pp_decl_head context thing tyvars
427 = hsep [pprHsContext context, ppr thing, interppSP tyvars]
429 pp_condecls cs = equals <+> sep (punctuate (ptext SLIT(" |")) (map ppr cs))
431 pp_tydecl pp_head pp_decl_rhs derivings
432 = hang pp_head 4 (sep [
436 Just ds -> hsep [ptext SLIT("deriving"),
437 ppr_hs_context (unLoc ds)]
440 instance Outputable NewOrData where
441 ppr NewType = ptext SLIT("newtype")
442 ppr DataType = ptext SLIT("data")
446 %************************************************************************
448 \subsection[ConDecl]{A data-constructor declaration}
450 %************************************************************************
453 type LConDecl name = Located (ConDecl name)
456 = ConDecl (Located name) -- Constructor name; this is used for the
457 -- DataCon itself, and for the user-callable wrapper Id
459 [LHsTyVarBndr name] -- Existentially quantified type variables
460 (LHsContext name) -- ...and context
461 -- If both are empty then there are no existentials
463 (HsConDetails name (LBangType name))
467 conDeclsNames :: Eq name => [ConDecl name] -> [Located name]
468 -- See tyClDeclNames for what this does
469 -- The function is boringly complicated because of the records
470 -- And since we only have equality, we have to be a little careful
472 = snd (foldl do_one ([], []) cons)
474 do_one (flds_seen, acc) (ConDecl lname _ _ (RecCon flds))
475 = (map unLoc new_flds ++ flds_seen, lname : [f | f <- new_flds] ++ acc)
477 new_flds = [ f | (f,_) <- flds, not (unLoc f `elem` flds_seen) ]
479 do_one (flds_seen, acc) (ConDecl lname _ _ _)
480 = (flds_seen, lname:acc)
482 conDetailsTys details = map getBangType (hsConArgs details)
486 type LBangType name = Located (BangType name)
488 data BangType name = BangType HsBang (LHsType name)
490 data HsBang = HsNoBang
492 | HsUnbox -- {-# UNPACK #-} ! (GHC extension, meaning "unbox")
494 getBangType (BangType _ ty) = ty
495 getBangStrictness (BangType s _) = s
497 unbangedType :: LHsType id -> LBangType id
498 unbangedType ty@(L loc _) = L loc (BangType HsNoBang ty)
502 instance (OutputableBndr name) => Outputable (ConDecl name) where
503 ppr (ConDecl con tvs cxt con_details)
504 = sep [pprHsForAll Explicit tvs cxt, ppr_con_details con con_details]
506 ppr_con_details con (InfixCon ty1 ty2)
507 = hsep [ppr ty1, ppr con, ppr ty2]
509 -- ConDecls generated by MkIface.ifaceTyThing always have a PrefixCon, even
510 -- if the constructor is an infix one. This is because in an interface file
511 -- we don't distinguish between the two. Hence when printing these for the
512 -- user, we need to parenthesise infix constructor names.
513 ppr_con_details con (PrefixCon tys)
514 = hsep (pprHsVar con : map ppr tys)
516 ppr_con_details con (RecCon fields)
517 = ppr con <+> braces (sep (punctuate comma (map ppr_field fields)))
519 ppr_field (n, ty) = ppr n <+> dcolon <+> ppr ty
521 instance OutputableBndr name => Outputable (BangType name) where
522 ppr (BangType is_strict ty)
523 = bang <> pprParendHsType (unLoc ty)
525 bang = case is_strict of
528 HsUnbox -> ptext SLIT("!!")
532 %************************************************************************
534 \subsection[InstDecl]{An instance declaration
536 %************************************************************************
539 type LInstDecl name = Located (InstDecl name)
542 = InstDecl (LHsType name) -- Context => Class Instance-type
543 -- Using a polytype means that the renamer conveniently
544 -- figures out the quantified type variables for us.
546 [LSig name] -- User-supplied pragmatic info
548 instance (OutputableBndr name) => Outputable (InstDecl name) where
550 ppr (InstDecl inst_ty binds uprags)
551 = vcat [hsep [ptext SLIT("instance"), ppr inst_ty, ptext SLIT("where")],
553 nest 4 (pprLHsBinds binds) ]
556 %************************************************************************
558 \subsection[DefaultDecl]{A @default@ declaration}
560 %************************************************************************
562 There can only be one default declaration per module, but it is hard
563 for the parser to check that; we pass them all through in the abstract
564 syntax, and that restriction must be checked in the front end.
567 type LDefaultDecl name = Located (DefaultDecl name)
569 data DefaultDecl name
570 = DefaultDecl [LHsType name]
572 instance (OutputableBndr name)
573 => Outputable (DefaultDecl name) where
575 ppr (DefaultDecl tys)
576 = ptext SLIT("default") <+> parens (interpp'SP tys)
579 %************************************************************************
581 \subsection{Foreign function interface declaration}
583 %************************************************************************
587 -- foreign declarations are distinguished as to whether they define or use a
590 -- * the Boolean value indicates whether the pre-standard deprecated syntax
593 type LForeignDecl name = Located (ForeignDecl name)
595 data ForeignDecl name
596 = ForeignImport (Located name) (LHsType name) ForeignImport Bool -- defines name
597 | ForeignExport (Located name) (LHsType name) ForeignExport Bool -- uses name
599 -- specification of an imported external entity in dependence on the calling
602 data ForeignImport = -- import of a C entity
604 -- * the two strings specifying a header file or library
605 -- may be empty, which indicates the absence of a
606 -- header or object specification (both are not used
607 -- in the case of `CWrapper' and when `CFunction'
608 -- has a dynamic target)
610 -- * the calling convention is irrelevant for code
611 -- generation in the case of `CLabel', but is needed
612 -- for pretty printing
614 -- * `Safety' is irrelevant for `CLabel' and `CWrapper'
616 CImport CCallConv -- ccall or stdcall
617 Safety -- safe or unsafe
618 FastString -- name of C header
619 FastString -- name of library object
620 CImportSpec -- details of the C entity
622 -- import of a .NET function
624 | DNImport DNCallSpec
626 -- details of an external C entity
628 data CImportSpec = CLabel CLabelString -- import address of a C label
629 | CFunction CCallTarget -- static or dynamic function
630 | CWrapper -- wrapper to expose closures
633 -- specification of an externally exported entity in dependence on the calling
636 data ForeignExport = CExport CExportSpec -- contains the calling convention
637 | DNExport -- presently unused
639 -- abstract type imported from .NET
641 data FoType = DNType -- In due course we'll add subtype stuff
642 deriving (Eq) -- Used for equality instance for TyClDecl
645 -- pretty printing of foreign declarations
648 instance OutputableBndr name => Outputable (ForeignDecl name) where
649 ppr (ForeignImport n ty fimport _) =
650 ptext SLIT("foreign import") <+> ppr fimport <+>
651 ppr n <+> dcolon <+> ppr ty
652 ppr (ForeignExport n ty fexport _) =
653 ptext SLIT("foreign export") <+> ppr fexport <+>
654 ppr n <+> dcolon <+> ppr ty
656 instance Outputable ForeignImport where
657 ppr (DNImport spec) =
658 ptext SLIT("dotnet") <+> ppr spec
659 ppr (CImport cconv safety header lib spec) =
660 ppr cconv <+> ppr safety <+>
661 char '"' <> pprCEntity header lib spec <> char '"'
663 pprCEntity header lib (CLabel lbl) =
664 ptext SLIT("static") <+> ftext header <+> char '&' <>
665 pprLib lib <> ppr lbl
666 pprCEntity header lib (CFunction (StaticTarget lbl)) =
667 ptext SLIT("static") <+> ftext header <+> char '&' <>
668 pprLib lib <> ppr lbl
669 pprCEntity header lib (CFunction (DynamicTarget)) =
670 ptext SLIT("dynamic")
671 pprCEntity _ _ (CWrapper) = ptext SLIT("wrapper")
673 pprLib lib | nullFastString lib = empty
674 | otherwise = char '[' <> ppr lib <> char ']'
676 instance Outputable ForeignExport where
677 ppr (CExport (CExportStatic lbl cconv)) =
678 ppr cconv <+> char '"' <> ppr lbl <> char '"'
680 ptext SLIT("dotnet") <+> ptext SLIT("\"<unused>\"")
682 instance Outputable FoType where
683 ppr DNType = ptext SLIT("type dotnet")
687 %************************************************************************
689 \subsection{Transformation rules}
691 %************************************************************************
694 type LRuleDecl name = Located (RuleDecl name)
697 = HsRule -- Source rule
698 RuleName -- Rule name
700 [RuleBndr name] -- Forall'd vars; after typechecking this includes tyvars
701 (Located (HsExpr name)) -- LHS
702 (Located (HsExpr name)) -- RHS
705 = RuleBndr (Located name)
706 | RuleBndrSig (Located name) (LHsType name)
708 collectRuleBndrSigTys :: [RuleBndr name] -> [LHsType name]
709 collectRuleBndrSigTys bndrs = [ty | RuleBndrSig _ ty <- bndrs]
711 instance OutputableBndr name => Outputable (RuleDecl name) where
712 ppr (HsRule name act ns lhs rhs)
713 = sep [text "{-# RULES" <+> doubleQuotes (ftext name) <+> ppr act,
714 nest 4 (pp_forall <+> pprExpr (unLoc lhs)),
715 nest 4 (equals <+> pprExpr (unLoc rhs) <+> text "#-}") ]
717 pp_forall | null ns = empty
718 | otherwise = text "forall" <+> fsep (map ppr ns) <> dot
720 instance OutputableBndr name => Outputable (RuleBndr name) where
721 ppr (RuleBndr name) = ppr name
722 ppr (RuleBndrSig name ty) = ppr name <> dcolon <> ppr ty
726 %************************************************************************
728 \subsection[DeprecDecl]{Deprecations}
730 %************************************************************************
732 We use exported entities for things to deprecate.
735 type LDeprecDecl name = Located (DeprecDecl name)
737 data DeprecDecl name = Deprecation name DeprecTxt
739 instance OutputableBndr name => Outputable (DeprecDecl name) where
740 ppr (Deprecation thing txt)
741 = hsep [text "{-# DEPRECATED", ppr thing, doubleQuotes (ppr txt), text "#-}"]