2 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
4 \section[HsTypes]{Abstract syntax: user-defined types}
9 HsTyVarBndr(..), LHsTyVarBndr,
11 HsContext, LHsContext,
14 LBangType, BangType, HsBang(..),
15 getBangType, getBangStrictness,
17 mkExplicitHsForAllTy, mkImplicitHsForAllTy, hsExplicitTvs,
18 hsTyVarName, hsTyVarNames, replaceTyVarName,
19 hsLTyVarName, hsLTyVarNames, hsLTyVarLocName, hsLTyVarLocNames,
20 splitHsInstDeclTy, splitHsFunType,
23 PostTcType, placeHolderType,
26 pprParendHsType, pprHsForAll, pprHsContext, ppr_hs_context, pprHsTyVarBndr
29 #include "HsVersions.h"
31 import {-# SOURCE #-} HsExpr ( HsSplice, pprSplice )
34 import {- Kind parts of -}
35 Type ( {- instance Outputable Kind -} Kind,
36 pprParendKind, pprKind, isLiftedTypeKind )
37 import BasicTypes ( IPName, Boxity, tupleParens )
38 import SrcLoc ( Located(..), unLoc, noSrcSpan )
39 import StaticFlags ( opt_PprStyle_Debug )
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 data HsExplicitForAll = Explicit | Implicit
162 -----------------------
163 -- Combine adjacent for-alls.
164 -- The following awkward situation can happen otherwise:
165 -- f :: forall a. ((Num a) => Int)
166 -- might generate HsForAll (Just [a]) [] (HsForAll Nothing [Num a] t)
167 -- Then a isn't discovered as ambiguous, and we abstract the AbsBinds wrt []
168 -- but the export list abstracts f wrt [a]. Disaster.
170 -- A valid type must have one for-all at the top of the type, or of the fn arg types
172 mkImplicitHsForAllTy ctxt ty = mkHsForAllTy Implicit [] ctxt ty
173 mkExplicitHsForAllTy tvs ctxt ty = mkHsForAllTy Explicit tvs ctxt ty
175 mkHsForAllTy :: HsExplicitForAll -> [LHsTyVarBndr name] -> LHsContext name -> LHsType name -> HsType name
176 -- Smart constructor for HsForAllTy
177 mkHsForAllTy exp tvs (L _ []) ty = mk_forall_ty exp tvs ty
178 mkHsForAllTy exp tvs ctxt ty = HsForAllTy exp tvs ctxt ty
180 -- mk_forall_ty makes a pure for-all type (no context)
181 mk_forall_ty exp tvs (L _ (HsParTy ty)) = mk_forall_ty exp tvs ty
182 mk_forall_ty exp1 tvs1 (L _ (HsForAllTy exp2 tvs2 ctxt ty)) = mkHsForAllTy (exp1 `plus` exp2) (tvs1 ++ tvs2) ctxt ty
183 mk_forall_ty exp tvs ty = HsForAllTy exp tvs (L noSrcSpan []) ty
184 -- Even if tvs is empty, we still make a HsForAll!
185 -- In the Implicit case, this signals the place to do implicit quantification
186 -- In the Explicit case, it prevents implicit quantification
187 -- (see the sigtype production in Parser.y.pp)
188 -- so that (forall. ty) isn't implicitly quantified
190 Implicit `plus` Implicit = Implicit
191 exp1 `plus` exp2 = Explicit
193 hsExplicitTvs :: LHsType name -> [name]
194 -- The explicitly-given forall'd type variables of a HsType
195 hsExplicitTvs (L _ (HsForAllTy Explicit tvs _ _)) = hsLTyVarNames tvs
196 hsExplicitTvs other = []
198 ---------------------
199 type LHsTyVarBndr name = Located (HsTyVarBndr name)
201 data HsTyVarBndr name
203 | KindedTyVar name Kind
204 -- *** NOTA BENE *** A "monotype" in a pragma can have
205 -- for-alls in it, (mostly to do with dictionaries). These
206 -- must be explicitly Kinded.
208 hsTyVarName :: HsTyVarBndr name -> name
209 hsTyVarName (UserTyVar n) = n
210 hsTyVarName (KindedTyVar n _) = n
212 hsLTyVarName :: LHsTyVarBndr name -> name
213 hsLTyVarName = hsTyVarName . unLoc
215 hsTyVarNames :: [HsTyVarBndr name] -> [name]
216 hsTyVarNames tvs = map hsTyVarName tvs
218 hsLTyVarNames :: [LHsTyVarBndr name] -> [name]
219 hsLTyVarNames = map hsLTyVarName
221 hsLTyVarLocName :: LHsTyVarBndr name -> Located name
222 hsLTyVarLocName = fmap hsTyVarName
224 hsLTyVarLocNames :: [LHsTyVarBndr name] -> [Located name]
225 hsLTyVarLocNames = map hsLTyVarLocName
227 replaceTyVarName :: HsTyVarBndr name1 -> name2 -> HsTyVarBndr name2
228 replaceTyVarName (UserTyVar n) n' = UserTyVar n'
229 replaceTyVarName (KindedTyVar n k) n' = KindedTyVar n' k
235 :: OutputableBndr name
237 -> ([LHsTyVarBndr name], HsContext name, name, [LHsType name])
238 -- Split up an instance decl type, returning the pieces
240 splitHsInstDeclTy inst_ty
242 HsParTy (L _ ty) -> splitHsInstDeclTy ty
243 HsForAllTy _ tvs cxt (L _ ty) -> split_tau tvs (unLoc cxt) ty
244 other -> split_tau [] [] other
245 -- The type vars should have been computed by now, even if they were implicit
247 split_tau tvs cxt (HsPredTy (HsClassP cls tys)) = (tvs, cxt, cls, tys)
248 split_tau tvs cxt (HsParTy (L _ ty)) = split_tau tvs cxt ty
249 split_tau _ _ other = pprPanic "splitHsInstDeclTy" (ppr inst_ty)
251 -- Splits HsType into the (init, last) parts
252 -- Breaks up any parens in the result type:
253 -- splitHsFunType (a -> (b -> c)) = ([a,b], c)
254 splitHsFunType :: LHsType name -> ([LHsType name], LHsType name)
255 splitHsFunType (L l (HsFunTy x y)) = (x:args, res)
257 (args, res) = splitHsFunType y
258 splitHsFunType (L _ (HsParTy ty)) = splitHsFunType ty
259 splitHsFunType other = ([], other)
263 %************************************************************************
265 \subsection{Pretty printing}
267 %************************************************************************
269 NB: these types get printed into interface files, so
270 don't change the printing format lightly
273 instance (OutputableBndr name) => Outputable (HsType name) where
274 ppr ty = pprHsType ty
276 instance (Outputable name) => Outputable (HsTyVarBndr name) where
277 ppr (UserTyVar name) = ppr name
278 ppr (KindedTyVar name kind) = pprHsTyVarBndr name kind
280 instance OutputableBndr name => Outputable (HsPred name) where
281 ppr (HsClassP clas tys) = ppr clas <+> hsep (map (pprParendHsType.unLoc) tys)
282 ppr (HsIParam n ty) = hsep [ppr n, dcolon, ppr ty]
284 pprHsTyVarBndr :: Outputable name => name -> Kind -> SDoc
285 pprHsTyVarBndr name kind | isLiftedTypeKind kind = ppr name
286 | otherwise = hsep [ppr name, dcolon, pprParendKind kind]
288 pprHsForAll exp tvs cxt
289 | show_forall = forall_part <+> pprHsContext (unLoc cxt)
290 | otherwise = pprHsContext (unLoc cxt)
292 show_forall = opt_PprStyle_Debug
293 || (not (null tvs) && is_explicit)
294 is_explicit = case exp of {Explicit -> True; Implicit -> False}
295 forall_part = ptext SLIT("forall") <+> interppSP tvs <> dot
297 pprHsContext :: (OutputableBndr name) => HsContext name -> SDoc
298 pprHsContext [] = empty
299 pprHsContext cxt = ppr_hs_context cxt <+> ptext SLIT("=>")
301 ppr_hs_context [] = empty
302 ppr_hs_context cxt = parens (interpp'SP cxt)
306 pREC_TOP = (0 :: Int) -- type in ParseIface.y
307 pREC_FUN = (1 :: Int) -- btype in ParseIface.y
308 -- Used for LH arg of (->)
309 pREC_OP = (2 :: Int) -- Used for arg of any infix operator
310 -- (we don't keep their fixities around)
311 pREC_CON = (3 :: Int) -- Used for arg of type applicn:
312 -- always parenthesise unless atomic
314 maybeParen :: Int -- Precedence of context
315 -> Int -- Precedence of top-level operator
316 -> SDoc -> SDoc -- Wrap in parens if (ctxt >= op)
317 maybeParen ctxt_prec op_prec p | ctxt_prec >= op_prec = parens p
320 -- printing works more-or-less as for Types
322 pprHsType, pprParendHsType :: (OutputableBndr name) => HsType name -> SDoc
324 pprHsType ty = getPprStyle $ \sty -> ppr_mono_ty pREC_TOP (prepare sty ty)
325 pprParendHsType ty = ppr_mono_ty pREC_CON ty
327 -- Before printing a type
328 -- (a) Remove outermost HsParTy parens
329 -- (b) Drop top-level for-all type variables in user style
330 -- since they are implicit in Haskell
331 prepare sty (HsParTy ty) = prepare sty (unLoc ty)
334 ppr_mono_lty ctxt_prec ty = ppr_mono_ty ctxt_prec (unLoc ty)
336 ppr_mono_ty ctxt_prec (HsForAllTy exp tvs ctxt ty)
337 = maybeParen ctxt_prec pREC_FUN $
338 sep [pprHsForAll exp tvs ctxt, ppr_mono_lty pREC_TOP ty]
341 ppr_mono_ty ctxt_prec (HsBangTy b ty) = ppr b <> ppr ty
342 ppr_mono_ty ctxt_prec (HsTyVar name) = ppr name
343 ppr_mono_ty ctxt_prec (HsFunTy ty1 ty2) = ppr_fun_ty ctxt_prec ty1 ty2
344 ppr_mono_ty ctxt_prec (HsTupleTy con tys) = tupleParens con (interpp'SP tys)
345 ppr_mono_ty ctxt_prec (HsKindSig ty kind) = parens (ppr_mono_lty pREC_TOP ty <+> dcolon <+> pprKind kind)
346 ppr_mono_ty ctxt_prec (HsListTy ty) = brackets (ppr_mono_lty pREC_TOP ty)
347 ppr_mono_ty ctxt_prec (HsPArrTy ty) = pabrackets (ppr_mono_lty pREC_TOP ty)
348 ppr_mono_ty ctxt_prec (HsPredTy pred) = braces (ppr pred)
349 ppr_mono_ty ctxt_prec (HsNumTy n) = integer n -- generics only
350 ppr_mono_ty ctxt_prec (HsSpliceTy s) = pprSplice s
352 ppr_mono_ty ctxt_prec (HsAppTy fun_ty arg_ty)
353 = maybeParen ctxt_prec pREC_CON $
354 hsep [ppr_mono_lty pREC_FUN fun_ty, ppr_mono_lty pREC_CON arg_ty]
356 ppr_mono_ty ctxt_prec (HsOpTy ty1 op ty2)
357 = maybeParen ctxt_prec pREC_OP $
358 ppr_mono_lty pREC_OP ty1 <+> ppr op <+> ppr_mono_lty pREC_OP ty2
360 ppr_mono_ty ctxt_prec (HsParTy ty)
361 = parens (ppr_mono_lty pREC_TOP ty)
362 -- Put the parens in where the user did
363 -- But we still use the precedence stuff to add parens because
364 -- toHsType doesn't put in any HsParTys, so we may still need them
366 --------------------------
367 ppr_fun_ty ctxt_prec ty1 ty2
368 = let p1 = ppr_mono_lty pREC_FUN ty1
369 p2 = ppr_mono_lty pREC_TOP ty2
371 maybeParen ctxt_prec pREC_FUN $
372 sep [p1, ptext SLIT("->") <+> p2]
374 --------------------------
375 pabrackets p = ptext SLIT("[:") <> p <> ptext SLIT(":]")