2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
6 HsTypes: Abstract syntax: user-defined types
11 HsTyVarBndr(..), LHsTyVarBndr,
13 HsContext, LHsContext,
16 LBangType, BangType, HsBang(..),
17 getBangType, getBangStrictness,
19 ConDeclField(..), pprConDeclFields,
21 mkExplicitHsForAllTy, mkImplicitHsForAllTy, hsExplicitTvs,
22 hsTyVarName, hsTyVarNames, replaceTyVarName,
23 hsLTyVarName, hsLTyVarNames, hsLTyVarLocName, hsLTyVarLocNames,
24 splitHsInstDeclTy, splitHsFunType,
27 PostTcType, placeHolderType,
30 pprParendHsType, pprHsForAll, pprHsContext, ppr_hs_context, pprHsTyVarBndr
33 import {-# SOURCE #-} HsExpr ( HsSplice, pprSplice )
45 %************************************************************************
47 \subsection{Annotating the syntax}
49 %************************************************************************
52 type PostTcType = Type -- Used for slots in the abstract syntax
53 -- where we want to keep slot for a type
54 -- to be added by the type checker...but
55 -- before typechecking it's just bogus
57 placeHolderType :: PostTcType -- Used before typechecking
58 placeHolderType = panic "Evaluated the place holder for a PostTcType"
61 %************************************************************************
63 \subsection{Bang annotations}
65 %************************************************************************
68 type LBangType name = Located (BangType name)
69 type BangType name = HsType name -- Bangs are in the HsType data type
71 data HsBang = HsNoBang -- Only used as a return value for getBangStrictness,
72 -- never appears on a HsBangTy
74 | HsUnbox -- {-# UNPACK #-} ! (GHC extension, meaning "unbox")
76 instance Outputable HsBang where
77 ppr (HsNoBang) = empty
78 ppr (HsStrict) = char '!'
79 ppr (HsUnbox) = ptext (sLit "!!")
81 getBangType :: LHsType a -> LHsType a
82 getBangType (L _ (HsBangTy _ ty)) = ty
85 getBangStrictness :: LHsType a -> HsBang
86 getBangStrictness (L _ (HsBangTy s _)) = s
87 getBangStrictness _ = HsNoBang
91 %************************************************************************
93 \subsection{Data types}
95 %************************************************************************
97 This is the syntax for types as seen in type signatures.
100 type LHsContext name = Located (HsContext name)
102 type HsContext name = [LHsPred name]
104 type LHsPred name = Located (HsPred name)
106 data HsPred name = HsClassP name [LHsType name] -- class constraint
107 | HsEqualP (LHsType name) (LHsType name)-- equality constraint
108 | HsIParam (IPName name) (LHsType name)
110 type LHsType name = Located (HsType name)
113 = HsForAllTy HsExplicitForAll -- Renamer leaves this flag unchanged, to record the way
114 -- the user wrote it originally, so that the printer can
115 -- print it as the user wrote it
116 [LHsTyVarBndr name] -- With ImplicitForAll, this is the empty list
117 -- until the renamer fills in the variables
121 | HsTyVar name -- Type variable or type constructor
123 | HsAppTy (LHsType name)
126 | HsFunTy (LHsType name) -- function type
129 | HsListTy (LHsType name) -- Element type
131 | HsPArrTy (LHsType name) -- Elem. type of parallel array: [:t:]
134 [LHsType name] -- Element types (length gives arity)
136 | HsOpTy (LHsType name) (Located name) (LHsType name)
138 | HsParTy (LHsType name)
139 -- Parenthesis preserved for the precedence re-arrangement in RnTypes
140 -- It's important that a * (b + c) doesn't get rearranged to (a*b) + c!
142 -- However, NB that toHsType doesn't add HsParTys (in an effort to keep
143 -- interface files smaller), so when printing a HsType we may need to
146 | HsNumTy Integer -- Generics only
148 | HsPredTy (HsPred name) -- Only used in the type of an instance
149 -- declaration, eg. Eq [a] -> Eq a
152 -- Note no need for location info on the
153 -- enclosed HsPred; the one on the type will do
155 | HsKindSig (LHsType name) -- (ty :: kind)
156 Kind -- A type with a kind signature
158 | HsSpliceTy (HsSplice name)
160 | HsDocTy (LHsType name) (LHsDoc name) -- A documented type
162 | HsBangTy HsBang (LHsType name) -- Bang-style type annotations
163 | HsRecTy [ConDeclField name] -- Only in data type declarations
165 data HsExplicitForAll = Explicit | Implicit
169 data ConDeclField name -- Record fields have Haddoc docs on them
170 = ConDeclField { cd_fld_name :: Located name,
171 cd_fld_type :: LBangType name,
172 cd_fld_doc :: Maybe (LHsDoc name) }
175 -----------------------
176 -- Combine adjacent for-alls.
177 -- The following awkward situation can happen otherwise:
178 -- f :: forall a. ((Num a) => Int)
179 -- might generate HsForAll (Just [a]) [] (HsForAll Nothing [Num a] t)
180 -- Then a isn't discovered as ambiguous, and we abstract the AbsBinds wrt []
181 -- but the export list abstracts f wrt [a]. Disaster.
183 -- A valid type must have one for-all at the top of the type, or of the fn arg types
185 mkImplicitHsForAllTy :: LHsContext name -> LHsType name -> HsType name
186 mkExplicitHsForAllTy :: [LHsTyVarBndr name] -> LHsContext name -> LHsType name -> HsType name
187 mkImplicitHsForAllTy ctxt ty = mkHsForAllTy Implicit [] ctxt ty
188 mkExplicitHsForAllTy tvs ctxt ty = mkHsForAllTy Explicit tvs ctxt ty
190 mkHsForAllTy :: HsExplicitForAll -> [LHsTyVarBndr name] -> LHsContext name -> LHsType name -> HsType name
191 -- Smart constructor for HsForAllTy
192 mkHsForAllTy exp tvs (L _ []) ty = mk_forall_ty exp tvs ty
193 mkHsForAllTy exp tvs ctxt ty = HsForAllTy exp tvs ctxt ty
195 -- mk_forall_ty makes a pure for-all type (no context)
196 mk_forall_ty :: HsExplicitForAll -> [LHsTyVarBndr name] -> LHsType name -> HsType name
197 mk_forall_ty exp tvs (L _ (HsParTy ty)) = mk_forall_ty exp tvs ty
198 mk_forall_ty exp1 tvs1 (L _ (HsForAllTy exp2 tvs2 ctxt ty)) = mkHsForAllTy (exp1 `plus` exp2) (tvs1 ++ tvs2) ctxt ty
199 mk_forall_ty exp tvs ty = HsForAllTy exp tvs (L noSrcSpan []) ty
200 -- Even if tvs is empty, we still make a HsForAll!
201 -- In the Implicit case, this signals the place to do implicit quantification
202 -- In the Explicit case, it prevents implicit quantification
203 -- (see the sigtype production in Parser.y.pp)
204 -- so that (forall. ty) isn't implicitly quantified
206 plus :: HsExplicitForAll -> HsExplicitForAll -> HsExplicitForAll
207 Implicit `plus` Implicit = Implicit
208 _ `plus` _ = Explicit
210 hsExplicitTvs :: LHsType name -> [name]
211 -- The explicitly-given forall'd type variables of a HsType
212 hsExplicitTvs (L _ (HsForAllTy Explicit tvs _ _)) = hsLTyVarNames tvs
215 ---------------------
216 type LHsTyVarBndr name = Located (HsTyVarBndr name)
218 data HsTyVarBndr name
220 | KindedTyVar name Kind
221 -- *** NOTA BENE *** A "monotype" in a pragma can have
222 -- for-alls in it, (mostly to do with dictionaries). These
223 -- must be explicitly Kinded.
225 hsTyVarName :: HsTyVarBndr name -> name
226 hsTyVarName (UserTyVar n) = n
227 hsTyVarName (KindedTyVar n _) = n
229 hsLTyVarName :: LHsTyVarBndr name -> name
230 hsLTyVarName = hsTyVarName . unLoc
232 hsTyVarNames :: [HsTyVarBndr name] -> [name]
233 hsTyVarNames tvs = map hsTyVarName tvs
235 hsLTyVarNames :: [LHsTyVarBndr name] -> [name]
236 hsLTyVarNames = map hsLTyVarName
238 hsLTyVarLocName :: LHsTyVarBndr name -> Located name
239 hsLTyVarLocName = fmap hsTyVarName
241 hsLTyVarLocNames :: [LHsTyVarBndr name] -> [Located name]
242 hsLTyVarLocNames = map hsLTyVarLocName
244 replaceTyVarName :: HsTyVarBndr name1 -> name2 -> HsTyVarBndr name2
245 replaceTyVarName (UserTyVar _) n' = UserTyVar n'
246 replaceTyVarName (KindedTyVar _ k) n' = KindedTyVar n' k
252 :: OutputableBndr name
254 -> ([LHsTyVarBndr name], HsContext name, name, [LHsType name])
255 -- Split up an instance decl type, returning the pieces
257 splitHsInstDeclTy inst_ty
259 HsParTy (L _ ty) -> splitHsInstDeclTy ty
260 HsForAllTy _ tvs cxt (L _ ty) -> split_tau tvs (unLoc cxt) ty
261 other -> split_tau [] [] other
262 -- The type vars should have been computed by now, even if they were implicit
264 split_tau tvs cxt (HsPredTy (HsClassP cls tys)) = (tvs, cxt, cls, tys)
265 split_tau tvs cxt (HsParTy (L _ ty)) = split_tau tvs cxt ty
266 split_tau _ _ _ = pprPanic "splitHsInstDeclTy" (ppr inst_ty)
268 -- Splits HsType into the (init, last) parts
269 -- Breaks up any parens in the result type:
270 -- splitHsFunType (a -> (b -> c)) = ([a,b], c)
271 splitHsFunType :: LHsType name -> ([LHsType name], LHsType name)
272 splitHsFunType (L _ (HsFunTy x y)) = (x:args, res)
274 (args, res) = splitHsFunType y
275 splitHsFunType (L _ (HsParTy ty)) = splitHsFunType ty
276 splitHsFunType other = ([], other)
280 %************************************************************************
282 \subsection{Pretty printing}
284 %************************************************************************
287 instance (OutputableBndr name) => Outputable (HsType name) where
288 ppr ty = pprHsType ty
290 instance (Outputable name) => Outputable (HsTyVarBndr name) where
291 ppr (UserTyVar name) = ppr name
292 ppr (KindedTyVar name kind) = pprHsTyVarBndr name kind
294 instance OutputableBndr name => Outputable (HsPred name) where
295 ppr (HsClassP clas tys) = ppr clas <+> hsep (map pprLHsType tys)
296 ppr (HsEqualP t1 t2) = hsep [pprLHsType t1, ptext (sLit "~"),
298 ppr (HsIParam n ty) = hsep [ppr n, dcolon, ppr ty]
300 pprLHsType :: OutputableBndr name => LHsType name -> SDoc
301 pprLHsType = pprParendHsType . unLoc
303 pprHsTyVarBndr :: Outputable name => name -> Kind -> SDoc
304 pprHsTyVarBndr name kind | isLiftedTypeKind kind = ppr name
305 | otherwise = hsep [ppr name, dcolon, pprParendKind kind]
307 pprHsForAll :: OutputableBndr name => HsExplicitForAll -> [LHsTyVarBndr name] -> LHsContext name -> SDoc
308 pprHsForAll exp tvs cxt
309 | show_forall = forall_part <+> pprHsContext (unLoc cxt)
310 | otherwise = pprHsContext (unLoc cxt)
312 show_forall = opt_PprStyle_Debug
313 || (not (null tvs) && is_explicit)
314 is_explicit = case exp of {Explicit -> True; Implicit -> False}
315 forall_part = ptext (sLit "forall") <+> interppSP tvs <> dot
317 pprHsContext :: (OutputableBndr name) => HsContext name -> SDoc
318 pprHsContext [] = empty
319 pprHsContext cxt = ppr_hs_context cxt <+> ptext (sLit "=>")
321 ppr_hs_context :: (OutputableBndr name) => HsContext name -> SDoc
322 ppr_hs_context [] = empty
323 ppr_hs_context cxt = parens (interpp'SP cxt)
325 pprConDeclFields :: OutputableBndr name => [ConDeclField name] -> SDoc
326 pprConDeclFields fields = braces (sep (punctuate comma (map ppr_fld fields)))
328 ppr_fld (ConDeclField { cd_fld_name = n, cd_fld_type = ty,
330 = ppr n <+> dcolon <+> ppr ty <+> ppr_mbDoc doc
334 pREC_TOP, pREC_FUN, pREC_OP, pREC_CON :: Int
335 pREC_TOP = 0 -- type in ParseIface.y
336 pREC_FUN = 1 -- btype in ParseIface.y
337 -- Used for LH arg of (->)
338 pREC_OP = 2 -- Used for arg of any infix operator
339 -- (we don't keep their fixities around)
340 pREC_CON = 3 -- Used for arg of type applicn:
341 -- always parenthesise unless atomic
343 maybeParen :: Int -- Precedence of context
344 -> Int -- Precedence of top-level operator
345 -> SDoc -> SDoc -- Wrap in parens if (ctxt >= op)
346 maybeParen ctxt_prec op_prec p | ctxt_prec >= op_prec = parens p
349 -- printing works more-or-less as for Types
351 pprHsType, pprParendHsType :: (OutputableBndr name) => HsType name -> SDoc
353 pprHsType ty = getPprStyle $ \sty -> ppr_mono_ty pREC_TOP (prepare sty ty)
354 pprParendHsType ty = ppr_mono_ty pREC_CON ty
356 -- Before printing a type
357 -- (a) Remove outermost HsParTy parens
358 -- (b) Drop top-level for-all type variables in user style
359 -- since they are implicit in Haskell
360 prepare :: PprStyle -> HsType name -> HsType name
361 prepare sty (HsParTy ty) = prepare sty (unLoc ty)
364 ppr_mono_lty :: (OutputableBndr name) => Int -> LHsType name -> SDoc
365 ppr_mono_lty ctxt_prec ty = ppr_mono_ty ctxt_prec (unLoc ty)
367 ppr_mono_ty :: (OutputableBndr name) => Int -> HsType name -> SDoc
368 ppr_mono_ty ctxt_prec (HsForAllTy exp tvs ctxt ty)
369 = maybeParen ctxt_prec pREC_FUN $
370 sep [pprHsForAll exp tvs ctxt, ppr_mono_lty pREC_TOP ty]
372 ppr_mono_ty _ (HsBangTy b ty) = ppr b <> ppr ty
373 ppr_mono_ty _ (HsRecTy flds) = pprConDeclFields flds
374 ppr_mono_ty _ (HsTyVar name) = ppr name
375 ppr_mono_ty ctxt_prec (HsFunTy ty1 ty2) = ppr_fun_ty ctxt_prec ty1 ty2
376 ppr_mono_ty _ (HsTupleTy con tys) = tupleParens con (interpp'SP tys)
377 ppr_mono_ty _ (HsKindSig ty kind) = parens (ppr_mono_lty pREC_TOP ty <+> dcolon <+> pprKind kind)
378 ppr_mono_ty _ (HsListTy ty) = brackets (ppr_mono_lty pREC_TOP ty)
379 ppr_mono_ty _ (HsPArrTy ty) = pabrackets (ppr_mono_lty pREC_TOP ty)
380 ppr_mono_ty _ (HsPredTy pred) = ppr pred
381 ppr_mono_ty _ (HsNumTy n) = integer n -- generics only
382 ppr_mono_ty _ (HsSpliceTy s) = pprSplice s
384 ppr_mono_ty ctxt_prec (HsAppTy fun_ty arg_ty)
385 = maybeParen ctxt_prec pREC_CON $
386 hsep [ppr_mono_lty pREC_FUN fun_ty, ppr_mono_lty pREC_CON arg_ty]
388 ppr_mono_ty ctxt_prec (HsOpTy ty1 op ty2)
389 = maybeParen ctxt_prec pREC_OP $
390 ppr_mono_lty pREC_OP ty1 <+> ppr op <+> ppr_mono_lty pREC_OP ty2
392 ppr_mono_ty _ (HsParTy ty)
393 = parens (ppr_mono_lty pREC_TOP ty)
394 -- Put the parens in where the user did
395 -- But we still use the precedence stuff to add parens because
396 -- toHsType doesn't put in any HsParTys, so we may still need them
398 ppr_mono_ty ctxt_prec (HsDocTy ty doc)
399 = maybeParen ctxt_prec pREC_OP $
400 ppr_mono_lty pREC_OP ty <+> ppr (unLoc doc)
401 -- we pretty print Haddock comments on types as if they were
404 --------------------------
405 ppr_fun_ty :: (OutputableBndr name) => Int -> LHsType name -> LHsType name -> SDoc
406 ppr_fun_ty ctxt_prec ty1 ty2
407 = let p1 = ppr_mono_lty pREC_FUN ty1
408 p2 = ppr_mono_lty pREC_TOP ty2
410 maybeParen ctxt_prec pREC_FUN $
411 sep [p1, ptext (sLit "->") <+> p2]
413 --------------------------
414 pabrackets :: SDoc -> SDoc
415 pabrackets p = ptext (sLit "[:") <> p <> ptext (sLit ":]")