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 mkExplicitHsForAllTy, mkImplicitHsForAllTy,
15 hsTyVarName, hsTyVarNames, replaceTyVarName,
16 hsLTyVarName, hsLTyVarNames, hsLTyVarLocName, hsLTyVarLocNames,
20 PostTcType, placeHolderType,
23 SyntaxName, placeHolderName,
26 pprParendHsType, pprHsForAll, pprHsContext, ppr_hs_context, pprHsTyVarBndr
29 #include "HsVersions.h"
31 import {-# SOURCE #-} HsExpr ( HsSplice, pprSplice )
34 import Kind ( {- instance Outputable Kind -}, Kind,
35 pprParendKind, pprKind, isLiftedTypeKind )
36 import Name ( Name, mkInternalName )
37 import OccName ( mkVarOcc )
38 import BasicTypes ( IPName, Boxity, tupleParens )
39 import PrelNames ( unboundKey )
40 import SrcLoc ( noSrcLoc, Located(..), unLoc, noSrcSpan )
41 import CmdLineOpts ( opt_PprStyle_Debug )
46 %************************************************************************
48 \subsection{Annotating the syntax}
50 %************************************************************************
53 type PostTcType = Type -- Used for slots in the abstract syntax
54 -- where we want to keep slot for a type
55 -- to be added by the type checker...but
56 -- before typechecking it's just bogus
58 placeHolderType :: PostTcType -- Used before typechecking
59 placeHolderType = panic "Evaluated the place holder for a PostTcType"
62 type SyntaxName = Name -- These names are filled in by the renamer
63 -- Before then they are a placeHolderName (so that
64 -- we can still print the HsSyn)
65 -- They correspond to "rebindable syntax";
66 -- See RnEnv.lookupSyntaxName
68 placeHolderName :: SyntaxName
69 placeHolderName = mkInternalName unboundKey
70 (mkVarOcc FSLIT("syntaxPlaceHolder"))
75 %************************************************************************
77 \subsection{Data types}
79 %************************************************************************
81 This is the syntax for types as seen in type signatures.
84 type LHsContext name = Located (HsContext name)
86 type HsContext name = [LHsPred name]
88 type LHsPred name = Located (HsPred name)
90 data HsPred name = HsClassP name [LHsType name]
91 | HsIParam (IPName name) (LHsType name)
93 type LHsType name = Located (HsType name)
96 = HsForAllTy HsExplicitForAll -- Renamer leaves this flag unchanged, to record the way
97 -- the user wrote it originally, so that the printer can
98 -- print it as the user wrote it
99 [LHsTyVarBndr name] -- With ImplicitForAll, this is the empty list
100 -- until the renamer fills in the variables
104 | HsTyVar name -- Type variable or type constructor
106 | HsAppTy (LHsType name)
109 | HsFunTy (LHsType name) -- function type
112 | HsListTy (LHsType name) -- Element type
114 | HsPArrTy (LHsType name) -- Elem. type of parallel array: [:t:]
117 [LHsType name] -- Element types (length gives arity)
119 | HsOpTy (LHsType name) (Located name) (LHsType name)
121 | HsParTy (LHsType name)
122 -- Parenthesis preserved for the precedence re-arrangement in RnTypes
123 -- It's important that a * (b + c) doesn't get rearranged to (a*b) + c!
125 -- However, NB that toHsType doesn't add HsParTys (in an effort to keep
126 -- interface files smaller), so when printing a HsType we may need to
129 | HsNumTy Integer -- Generics only
131 | HsPredTy (LHsPred name) -- Only used in the type of an instance
132 -- declaration, eg. Eq [a] -> Eq a
136 | HsKindSig (LHsType name) -- (ty :: kind)
137 Kind -- A type with a kind signature
139 | HsSpliceTy (HsSplice name)
141 data HsExplicitForAll = Explicit | Implicit
143 -----------------------
144 -- Combine adjacent for-alls.
145 -- The following awkward situation can happen otherwise:
146 -- f :: forall a. ((Num a) => Int)
147 -- might generate HsForAll (Just [a]) [] (HsForAll Nothing [Num a] t)
148 -- Then a isn't discovered as ambiguous, and we abstract the AbsBinds wrt []
149 -- but the export list abstracts f wrt [a]. Disaster.
151 -- A valid type must have one for-all at the top of the type, or of the fn arg types
153 mkImplicitHsForAllTy ctxt ty = mkHsForAllTy Implicit [] ctxt ty
154 mkExplicitHsForAllTy tvs ctxt ty = mkHsForAllTy Explicit tvs ctxt ty
156 mkHsForAllTy :: HsExplicitForAll -> [LHsTyVarBndr name] -> LHsContext name -> LHsType name -> HsType name
157 -- Smart constructor for HsForAllTy
158 mkHsForAllTy exp tvs (L _ []) ty = mk_forall_ty exp tvs ty
159 mkHsForAllTy exp tvs ctxt ty = HsForAllTy exp tvs ctxt ty
161 -- mk_forall_ty makes a pure for-all type (no context)
162 mk_forall_ty Explicit [] ty = unLoc ty -- Explicit for-all with no tyvars
163 mk_forall_ty exp tvs (L _ (HsParTy ty)) = mk_forall_ty exp tvs ty
164 mk_forall_ty exp1 tvs1 (L _ (HsForAllTy exp2 tvs2 ctxt ty)) = mkHsForAllTy (exp1 `plus` exp2) (tvs1 ++ tvs2) ctxt ty
165 mk_forall_ty exp tvs ty = HsForAllTy exp tvs (L noSrcSpan []) ty
167 Implicit `plus` Implicit = Implicit
168 exp1 `plus` exp2 = Explicit
170 type LHsTyVarBndr name = Located (HsTyVarBndr name)
172 data HsTyVarBndr name
174 | KindedTyVar name Kind
175 -- *** NOTA BENE *** A "monotype" in a pragma can have
176 -- for-alls in it, (mostly to do with dictionaries). These
177 -- must be explicitly Kinded.
179 hsTyVarName :: HsTyVarBndr name -> name
180 hsTyVarName (UserTyVar n) = n
181 hsTyVarName (KindedTyVar n _) = n
183 hsLTyVarName :: LHsTyVarBndr name -> name
184 hsLTyVarName = hsTyVarName . unLoc
186 hsTyVarNames :: [HsTyVarBndr name] -> [name]
187 hsTyVarNames tvs = map hsTyVarName tvs
189 hsLTyVarNames :: [LHsTyVarBndr name] -> [name]
190 hsLTyVarNames = map hsLTyVarName
192 hsLTyVarLocName :: LHsTyVarBndr name -> Located name
193 hsLTyVarLocName = fmap hsTyVarName
195 hsLTyVarLocNames :: [LHsTyVarBndr name] -> [Located name]
196 hsLTyVarLocNames = map hsLTyVarLocName
198 replaceTyVarName :: HsTyVarBndr name1 -> name2 -> HsTyVarBndr name2
199 replaceTyVarName (UserTyVar n) n' = UserTyVar n'
200 replaceTyVarName (KindedTyVar n k) n' = KindedTyVar n' k
206 :: OutputableBndr name
208 -> ([LHsTyVarBndr name], HsContext name, name, [LHsType name])
209 -- Split up an instance decl type, returning the pieces
211 -- In interface files, the instance declaration head is created
212 -- by HsTypes.toHsType, which does not guarantee to produce a
213 -- HsForAllTy. For example, if we had the weird decl
214 -- instance Foo T => Foo [T]
215 -- then we'd get the instance type
217 -- So when colleting the instance context, to be on the safe side
218 -- we gather predicate arguments
220 -- For source code, the parser ensures the type will have the right shape.
221 -- (e.g. see ParseUtil.checkInstType)
223 splitHsInstDeclTy inst_ty
225 HsForAllTy _ tvs cxt1 tau -- The type vars should have been
226 -- computed by now, even if they were implicit
227 -> (tvs, unLoc cxt1 ++ cxt2, cls, tys)
229 (cxt2, cls, tys) = split_tau (unLoc tau)
231 other -> ([], cxt2, cls, tys)
233 (cxt2, cls, tys) = split_tau inst_ty
236 split_tau (HsFunTy (L _ (HsPredTy p)) ty) = (p:ps, cls, tys)
238 (ps, cls, tys) = split_tau (unLoc ty)
239 split_tau (HsPredTy (L _ (HsClassP cls tys))) = ([], cls, tys)
240 split_tau other = pprPanic "splitHsInstDeclTy" (ppr inst_ty)
244 %************************************************************************
246 \subsection{Pretty printing}
248 %************************************************************************
250 NB: these types get printed into interface files, so
251 don't change the printing format lightly
254 instance (OutputableBndr name) => Outputable (HsType name) where
255 ppr ty = pprHsType ty
257 instance (Outputable name) => Outputable (HsTyVarBndr name) where
258 ppr (UserTyVar name) = ppr name
259 ppr (KindedTyVar name kind) = pprHsTyVarBndr name kind
261 instance OutputableBndr name => Outputable (HsPred name) where
262 ppr (HsClassP clas tys) = ppr clas <+> hsep (map (pprParendHsType.unLoc) tys)
263 ppr (HsIParam n ty) = hsep [ppr n, dcolon, ppr ty]
265 pprHsTyVarBndr :: Outputable name => name -> Kind -> SDoc
266 pprHsTyVarBndr name kind | isLiftedTypeKind kind = ppr name
267 | otherwise = hsep [ppr name, dcolon, pprParendKind kind]
269 pprHsForAll exp tvs cxt
270 | show_forall = forall_part <+> pprHsContext (unLoc cxt)
271 | otherwise = pprHsContext (unLoc cxt)
273 show_forall = opt_PprStyle_Debug
274 || (not (null tvs) && is_explicit)
275 is_explicit = case exp of {Explicit -> True; Implicit -> False}
276 forall_part = ptext SLIT("forall") <+> interppSP tvs <> dot
278 pprHsContext :: (OutputableBndr name) => HsContext name -> SDoc
279 pprHsContext [] = empty
280 pprHsContext cxt = ppr_hs_context cxt <+> ptext SLIT("=>")
282 ppr_hs_context [] = empty
283 ppr_hs_context cxt = parens (interpp'SP cxt)
287 pREC_TOP = (0 :: Int) -- type in ParseIface.y
288 pREC_FUN = (1 :: Int) -- btype in ParseIface.y
289 -- Used for LH arg of (->)
290 pREC_OP = (2 :: Int) -- Used for arg of any infix operator
291 -- (we don't keep their fixities around)
292 pREC_CON = (3 :: Int) -- Used for arg of type applicn:
293 -- always parenthesise unless atomic
295 maybeParen :: Int -- Precedence of context
296 -> Int -- Precedence of top-level operator
297 -> SDoc -> SDoc -- Wrap in parens if (ctxt >= op)
298 maybeParen ctxt_prec op_prec p | ctxt_prec >= op_prec = parens p
301 -- printing works more-or-less as for Types
303 pprHsType, pprParendHsType :: (OutputableBndr name) => HsType name -> SDoc
305 pprHsType ty = getPprStyle $ \sty -> ppr_mono_ty pREC_TOP (prepare sty ty)
306 pprParendHsType ty = ppr_mono_ty pREC_CON ty
308 -- Before printing a type
309 -- (a) Remove outermost HsParTy parens
310 -- (b) Drop top-level for-all type variables in user style
311 -- since they are implicit in Haskell
312 prepare sty (HsParTy ty) = prepare sty (unLoc ty)
315 ppr_mono_lty ctxt_prec ty = ppr_mono_ty ctxt_prec (unLoc ty)
317 ppr_mono_ty ctxt_prec (HsForAllTy exp tvs ctxt ty)
318 = maybeParen ctxt_prec pREC_FUN $
319 sep [pprHsForAll exp tvs ctxt, ppr_mono_lty pREC_TOP ty]
321 ppr_mono_ty ctxt_prec (HsTyVar name) = ppr name
322 ppr_mono_ty ctxt_prec (HsFunTy ty1 ty2) = ppr_fun_ty ctxt_prec ty1 ty2
323 ppr_mono_ty ctxt_prec (HsTupleTy con tys) = tupleParens con (interpp'SP tys)
324 ppr_mono_ty ctxt_prec (HsKindSig ty kind) = parens (ppr_mono_lty pREC_TOP ty <+> dcolon <+> pprKind kind)
325 ppr_mono_ty ctxt_prec (HsListTy ty) = brackets (ppr_mono_lty pREC_TOP ty)
326 ppr_mono_ty ctxt_prec (HsPArrTy ty) = pabrackets (ppr_mono_lty pREC_TOP ty)
327 ppr_mono_ty ctxt_prec (HsPredTy pred) = braces (ppr pred)
328 ppr_mono_ty ctxt_prec (HsNumTy n) = integer n -- generics only
329 ppr_mono_ty ctxt_prec (HsSpliceTy s) = pprSplice s
331 ppr_mono_ty ctxt_prec (HsAppTy fun_ty arg_ty)
332 = maybeParen ctxt_prec pREC_CON $
333 hsep [ppr_mono_lty pREC_FUN fun_ty, ppr_mono_lty pREC_CON arg_ty]
335 ppr_mono_ty ctxt_prec (HsOpTy ty1 op ty2)
336 = maybeParen ctxt_prec pREC_OP $
337 ppr_mono_lty pREC_OP ty1 <+> ppr op <+> ppr_mono_lty pREC_OP ty2
339 ppr_mono_ty ctxt_prec (HsParTy ty)
340 = parens (ppr_mono_lty pREC_TOP ty)
341 -- Put the parens in where the user did
342 -- But we still use the precedence stuff to add parens because
343 -- toHsType doesn't put in any HsParTys, so we may still need them
345 --------------------------
346 ppr_fun_ty ctxt_prec ty1 ty2
347 = let p1 = ppr_mono_lty pREC_FUN ty1
348 p2 = ppr_mono_lty pREC_TOP ty2
350 maybeParen ctxt_prec pREC_FUN $
351 sep [p1, ptext SLIT("->") <+> p2]
353 --------------------------
354 pabrackets p = ptext SLIT("[:") <> p <> ptext SLIT(":]")