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 mkExplicitHsForAllTy, mkImplicitHsForAllTy, hsExplicitTvs,
20 hsTyVarName, hsTyVarNames, replaceTyVarName,
21 hsLTyVarName, hsLTyVarNames, hsLTyVarLocName, hsLTyVarLocNames,
22 splitHsInstDeclTy, splitHsFunType,
25 PostTcType, placeHolderType,
28 pprParendHsType, pprHsForAll, pprHsContext, ppr_hs_context, pprHsTyVarBndr
31 #include "HsVersions.h"
33 import {-# SOURCE #-} HsExpr ( HsSplice, pprSplice )
44 %************************************************************************
46 \subsection{Annotating the syntax}
48 %************************************************************************
51 type PostTcType = Type -- Used for slots in the abstract syntax
52 -- where we want to keep slot for a type
53 -- to be added by the type checker...but
54 -- before typechecking it's just bogus
56 placeHolderType :: PostTcType -- Used before typechecking
57 placeHolderType = panic "Evaluated the place holder for a PostTcType"
60 %************************************************************************
62 \subsection{Bang annotations}
64 %************************************************************************
67 type LBangType name = Located (BangType name)
68 type BangType name = HsType name -- Bangs are in the HsType data type
70 data HsBang = HsNoBang -- Only used as a return value for getBangStrictness,
71 -- never appears on a HsBangTy
73 | HsUnbox -- {-# UNPACK #-} ! (GHC extension, meaning "unbox")
75 instance Outputable HsBang where
76 ppr (HsNoBang) = empty
77 ppr (HsStrict) = char '!'
78 ppr (HsUnbox) = ptext SLIT("!!")
80 getBangType :: LHsType a -> LHsType a
81 getBangType (L _ (HsBangTy _ ty)) = ty
84 getBangStrictness :: LHsType a -> HsBang
85 getBangStrictness (L _ (HsBangTy s _)) = s
86 getBangStrictness _ = HsNoBang
90 %************************************************************************
92 \subsection{Data types}
94 %************************************************************************
96 This is the syntax for types as seen in type signatures.
99 type LHsContext name = Located (HsContext name)
101 type HsContext name = [LHsPred name]
103 type LHsPred name = Located (HsPred name)
105 data HsPred name = HsClassP name [LHsType name]
106 | HsIParam (IPName name) (LHsType name)
108 type LHsType name = Located (HsType name)
111 = HsForAllTy HsExplicitForAll -- Renamer leaves this flag unchanged, to record the way
112 -- the user wrote it originally, so that the printer can
113 -- print it as the user wrote it
114 [LHsTyVarBndr name] -- With ImplicitForAll, this is the empty list
115 -- until the renamer fills in the variables
119 | HsTyVar name -- Type variable or type constructor
121 | HsBangTy HsBang (LHsType name) -- Bang-style type annotations
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 data HsExplicitForAll = Explicit | Implicit
164 -----------------------
165 -- Combine adjacent for-alls.
166 -- The following awkward situation can happen otherwise:
167 -- f :: forall a. ((Num a) => Int)
168 -- might generate HsForAll (Just [a]) [] (HsForAll Nothing [Num a] t)
169 -- Then a isn't discovered as ambiguous, and we abstract the AbsBinds wrt []
170 -- but the export list abstracts f wrt [a]. Disaster.
172 -- A valid type must have one for-all at the top of the type, or of the fn arg types
174 mkImplicitHsForAllTy ctxt ty = mkHsForAllTy Implicit [] ctxt ty
175 mkExplicitHsForAllTy tvs ctxt ty = mkHsForAllTy Explicit tvs ctxt ty
177 mkHsForAllTy :: HsExplicitForAll -> [LHsTyVarBndr name] -> LHsContext name -> LHsType name -> HsType name
178 -- Smart constructor for HsForAllTy
179 mkHsForAllTy exp tvs (L _ []) ty = mk_forall_ty exp tvs ty
180 mkHsForAllTy exp tvs ctxt ty = HsForAllTy exp tvs ctxt ty
182 -- mk_forall_ty makes a pure for-all type (no context)
183 mk_forall_ty exp tvs (L _ (HsParTy ty)) = mk_forall_ty exp tvs ty
184 mk_forall_ty exp1 tvs1 (L _ (HsForAllTy exp2 tvs2 ctxt ty)) = mkHsForAllTy (exp1 `plus` exp2) (tvs1 ++ tvs2) ctxt ty
185 mk_forall_ty exp tvs ty = HsForAllTy exp tvs (L noSrcSpan []) ty
186 -- Even if tvs is empty, we still make a HsForAll!
187 -- In the Implicit case, this signals the place to do implicit quantification
188 -- In the Explicit case, it prevents implicit quantification
189 -- (see the sigtype production in Parser.y.pp)
190 -- so that (forall. ty) isn't implicitly quantified
192 Implicit `plus` Implicit = Implicit
193 exp1 `plus` exp2 = Explicit
195 hsExplicitTvs :: LHsType name -> [name]
196 -- The explicitly-given forall'd type variables of a HsType
197 hsExplicitTvs (L _ (HsForAllTy Explicit tvs _ _)) = hsLTyVarNames tvs
198 hsExplicitTvs other = []
200 ---------------------
201 type LHsTyVarBndr name = Located (HsTyVarBndr name)
203 data HsTyVarBndr name
205 | KindedTyVar name Kind
206 -- *** NOTA BENE *** A "monotype" in a pragma can have
207 -- for-alls in it, (mostly to do with dictionaries). These
208 -- must be explicitly Kinded.
210 hsTyVarName :: HsTyVarBndr name -> name
211 hsTyVarName (UserTyVar n) = n
212 hsTyVarName (KindedTyVar n _) = n
214 hsLTyVarName :: LHsTyVarBndr name -> name
215 hsLTyVarName = hsTyVarName . unLoc
217 hsTyVarNames :: [HsTyVarBndr name] -> [name]
218 hsTyVarNames tvs = map hsTyVarName tvs
220 hsLTyVarNames :: [LHsTyVarBndr name] -> [name]
221 hsLTyVarNames = map hsLTyVarName
223 hsLTyVarLocName :: LHsTyVarBndr name -> Located name
224 hsLTyVarLocName = fmap hsTyVarName
226 hsLTyVarLocNames :: [LHsTyVarBndr name] -> [Located name]
227 hsLTyVarLocNames = map hsLTyVarLocName
229 replaceTyVarName :: HsTyVarBndr name1 -> name2 -> HsTyVarBndr name2
230 replaceTyVarName (UserTyVar n) n' = UserTyVar n'
231 replaceTyVarName (KindedTyVar n k) n' = KindedTyVar n' k
237 :: OutputableBndr name
239 -> ([LHsTyVarBndr name], HsContext name, name, [LHsType name])
240 -- Split up an instance decl type, returning the pieces
242 splitHsInstDeclTy inst_ty
244 HsParTy (L _ ty) -> splitHsInstDeclTy ty
245 HsForAllTy _ tvs cxt (L _ ty) -> split_tau tvs (unLoc cxt) ty
246 other -> split_tau [] [] other
247 -- The type vars should have been computed by now, even if they were implicit
249 split_tau tvs cxt (HsPredTy (HsClassP cls tys)) = (tvs, cxt, cls, tys)
250 split_tau tvs cxt (HsParTy (L _ ty)) = split_tau tvs cxt ty
251 split_tau _ _ other = pprPanic "splitHsInstDeclTy" (ppr inst_ty)
253 -- Splits HsType into the (init, last) parts
254 -- Breaks up any parens in the result type:
255 -- splitHsFunType (a -> (b -> c)) = ([a,b], c)
256 splitHsFunType :: LHsType name -> ([LHsType name], LHsType name)
257 splitHsFunType (L l (HsFunTy x y)) = (x:args, res)
259 (args, res) = splitHsFunType y
260 splitHsFunType (L _ (HsParTy ty)) = splitHsFunType ty
261 splitHsFunType other = ([], other)
265 %************************************************************************
267 \subsection{Pretty printing}
269 %************************************************************************
271 NB: these types get printed into interface files, so
272 don't change the printing format lightly
275 instance (OutputableBndr name) => Outputable (HsType name) where
276 ppr ty = pprHsType ty
278 instance (Outputable name) => Outputable (HsTyVarBndr name) where
279 ppr (UserTyVar name) = ppr name
280 ppr (KindedTyVar name kind) = pprHsTyVarBndr name kind
282 instance OutputableBndr name => Outputable (HsPred name) where
283 ppr (HsClassP clas tys) = ppr clas <+> hsep (map (pprParendHsType.unLoc) tys)
284 ppr (HsIParam n ty) = hsep [ppr n, dcolon, ppr ty]
286 pprHsTyVarBndr :: Outputable name => name -> Kind -> SDoc
287 pprHsTyVarBndr name kind | isLiftedTypeKind kind = ppr name
288 | otherwise = hsep [ppr name, dcolon, pprParendKind kind]
290 pprHsForAll exp tvs cxt
291 | show_forall = forall_part <+> pprHsContext (unLoc cxt)
292 | otherwise = pprHsContext (unLoc cxt)
294 show_forall = opt_PprStyle_Debug
295 || (not (null tvs) && is_explicit)
296 is_explicit = case exp of {Explicit -> True; Implicit -> False}
297 forall_part = ptext SLIT("forall") <+> interppSP tvs <> dot
299 pprHsContext :: (OutputableBndr name) => HsContext name -> SDoc
300 pprHsContext [] = empty
301 pprHsContext cxt = ppr_hs_context cxt <+> ptext SLIT("=>")
303 ppr_hs_context [] = empty
304 ppr_hs_context cxt = parens (interpp'SP cxt)
308 pREC_TOP = (0 :: Int) -- type in ParseIface.y
309 pREC_FUN = (1 :: Int) -- btype in ParseIface.y
310 -- Used for LH arg of (->)
311 pREC_OP = (2 :: Int) -- Used for arg of any infix operator
312 -- (we don't keep their fixities around)
313 pREC_CON = (3 :: Int) -- Used for arg of type applicn:
314 -- always parenthesise unless atomic
316 maybeParen :: Int -- Precedence of context
317 -> Int -- Precedence of top-level operator
318 -> SDoc -> SDoc -- Wrap in parens if (ctxt >= op)
319 maybeParen ctxt_prec op_prec p | ctxt_prec >= op_prec = parens p
322 -- printing works more-or-less as for Types
324 pprHsType, pprParendHsType :: (OutputableBndr name) => HsType name -> SDoc
326 pprHsType ty = getPprStyle $ \sty -> ppr_mono_ty pREC_TOP (prepare sty ty)
327 pprParendHsType ty = ppr_mono_ty pREC_CON ty
329 -- Before printing a type
330 -- (a) Remove outermost HsParTy parens
331 -- (b) Drop top-level for-all type variables in user style
332 -- since they are implicit in Haskell
333 prepare sty (HsParTy ty) = prepare sty (unLoc ty)
336 ppr_mono_lty ctxt_prec ty = ppr_mono_ty ctxt_prec (unLoc ty)
338 ppr_mono_ty ctxt_prec (HsForAllTy exp tvs ctxt ty)
339 = maybeParen ctxt_prec pREC_FUN $
340 sep [pprHsForAll exp tvs ctxt, ppr_mono_lty pREC_TOP ty]
343 ppr_mono_ty ctxt_prec (HsBangTy b ty) = ppr b <> ppr ty
344 ppr_mono_ty ctxt_prec (HsTyVar name) = ppr name
345 ppr_mono_ty ctxt_prec (HsFunTy ty1 ty2) = ppr_fun_ty ctxt_prec ty1 ty2
346 ppr_mono_ty ctxt_prec (HsTupleTy con tys) = tupleParens con (interpp'SP tys)
347 ppr_mono_ty ctxt_prec (HsKindSig ty kind) = parens (ppr_mono_lty pREC_TOP ty <+> dcolon <+> pprKind kind)
348 ppr_mono_ty ctxt_prec (HsListTy ty) = brackets (ppr_mono_lty pREC_TOP ty)
349 ppr_mono_ty ctxt_prec (HsPArrTy ty) = pabrackets (ppr_mono_lty pREC_TOP ty)
350 ppr_mono_ty ctxt_prec (HsPredTy pred) = braces (ppr pred)
351 ppr_mono_ty ctxt_prec (HsNumTy n) = integer n -- generics only
352 ppr_mono_ty ctxt_prec (HsSpliceTy s) = pprSplice s
354 ppr_mono_ty ctxt_prec (HsAppTy fun_ty arg_ty)
355 = maybeParen ctxt_prec pREC_CON $
356 hsep [ppr_mono_lty pREC_FUN fun_ty, ppr_mono_lty pREC_CON arg_ty]
358 ppr_mono_ty ctxt_prec (HsOpTy ty1 op ty2)
359 = maybeParen ctxt_prec pREC_OP $
360 ppr_mono_lty pREC_OP ty1 <+> ppr op <+> ppr_mono_lty pREC_OP ty2
362 ppr_mono_ty ctxt_prec (HsParTy ty)
363 = parens (ppr_mono_lty pREC_TOP ty)
364 -- Put the parens in where the user did
365 -- But we still use the precedence stuff to add parens because
366 -- toHsType doesn't put in any HsParTys, so we may still need them
368 ppr_mono_ty ctxt_prec (HsDocTy ty doc)
369 = ppr ty <+> ppr (unLoc doc)
371 --------------------------
372 ppr_fun_ty ctxt_prec ty1 ty2
373 = let p1 = ppr_mono_lty pREC_FUN ty1
374 p2 = ppr_mono_lty pREC_TOP ty2
376 maybeParen ctxt_prec pREC_FUN $
377 sep [p1, ptext SLIT("->") <+> p2]
379 --------------------------
380 pabrackets p = ptext SLIT("[:") <> p <> ptext SLIT(":]")