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 )
33 import TcType ( Type, Kind, liftedTypeKind, eqKind )
34 import Type ( {- instance Outputable Kind -}, pprParendKind, pprKind )
35 import Name ( Name, mkInternalName )
36 import OccName ( mkVarOcc )
37 import BasicTypes ( IPName, Boxity, tupleParens )
38 import PrelNames ( unboundKey )
39 import SrcLoc ( noSrcLoc, Located(..), unLoc, noSrcSpan )
40 import CmdLineOpts ( opt_PprStyle_Debug )
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 type SyntaxName = Name -- These names are filled in by the renamer
62 -- Before then they are a placeHolderName (so that
63 -- we can still print the HsSyn)
64 -- They correspond to "rebindable syntax";
65 -- See RnEnv.lookupSyntaxName
67 placeHolderName :: SyntaxName
68 placeHolderName = mkInternalName unboundKey
69 (mkVarOcc FSLIT("syntaxPlaceHolder"))
74 %************************************************************************
76 \subsection{Data types}
78 %************************************************************************
80 This is the syntax for types as seen in type signatures.
83 type LHsContext name = Located (HsContext name)
85 type HsContext name = [LHsPred name]
87 type LHsPred name = Located (HsPred name)
89 data HsPred name = HsClassP name [LHsType name]
90 | HsIParam (IPName name) (LHsType name)
92 type LHsType name = Located (HsType name)
95 = HsForAllTy HsExplicitForAll -- Renamer leaves this flag unchanged, to record the way
96 -- the user wrote it originally, so that the printer can
97 -- print it as the user wrote it
98 [LHsTyVarBndr name] -- With ImplicitForAll, this is the empty list
99 -- until the renamer fills in the variables
103 | HsTyVar name -- Type variable or type constructor
105 | HsAppTy (LHsType name)
108 | HsFunTy (LHsType name) -- function type
111 | HsListTy (LHsType name) -- Element type
113 | HsPArrTy (LHsType name) -- Elem. type of parallel array: [:t:]
116 [LHsType name] -- Element types (length gives arity)
118 | HsOpTy (LHsType name) (Located name) (LHsType name)
120 | HsParTy (LHsType name)
121 -- Parenthesis preserved for the precedence re-arrangement in RnTypes
122 -- It's important that a * (b + c) doesn't get rearranged to (a*b) + c!
124 -- However, NB that toHsType doesn't add HsParTys (in an effort to keep
125 -- interface files smaller), so when printing a HsType we may need to
128 | HsNumTy Integer -- Generics only
130 | HsPredTy (LHsPred name) -- Only used in the type of an instance
131 -- declaration, eg. Eq [a] -> Eq a
135 | HsKindSig (LHsType name) -- (ty :: kind)
136 Kind -- A type with a kind signature
138 | HsSpliceTy (HsSplice name)
140 data HsExplicitForAll = Explicit | Implicit
142 -----------------------
143 -- Combine adjacent for-alls.
144 -- The following awkward situation can happen otherwise:
145 -- f :: forall a. ((Num a) => Int)
146 -- might generate HsForAll (Just [a]) [] (HsForAll Nothing [Num a] t)
147 -- Then a isn't discovered as ambiguous, and we abstract the AbsBinds wrt []
148 -- but the export list abstracts f wrt [a]. Disaster.
150 -- A valid type must have one for-all at the top of the type, or of the fn arg types
152 mkImplicitHsForAllTy ctxt ty = mkHsForAllTy Implicit [] ctxt ty
153 mkExplicitHsForAllTy tvs ctxt ty = mkHsForAllTy Explicit tvs ctxt ty
155 mkHsForAllTy :: HsExplicitForAll -> [LHsTyVarBndr name] -> LHsContext name -> LHsType name -> HsType name
156 -- Smart constructor for HsForAllTy
157 mkHsForAllTy exp tvs (L _ []) ty = mk_forall_ty exp tvs ty
158 mkHsForAllTy exp tvs ctxt ty = HsForAllTy exp tvs ctxt ty
160 -- mk_forall_ty makes a pure for-all type (no context)
161 mk_forall_ty Explicit [] ty = unLoc ty -- Explicit for-all with no tyvars
162 mk_forall_ty exp tvs (L _ (HsParTy ty)) = mk_forall_ty exp tvs ty
163 mk_forall_ty exp1 tvs1 (L _ (HsForAllTy exp2 tvs2 ctxt ty)) = mkHsForAllTy (exp1 `plus` exp2) (tvs1 ++ tvs2) ctxt ty
164 mk_forall_ty exp tvs ty = HsForAllTy exp tvs (L noSrcSpan []) ty
166 Implicit `plus` Implicit = Implicit
167 exp1 `plus` exp2 = Explicit
169 type LHsTyVarBndr name = Located (HsTyVarBndr name)
171 data HsTyVarBndr name
173 | KindedTyVar name Kind
174 -- *** NOTA BENE *** A "monotype" in a pragma can have
175 -- for-alls in it, (mostly to do with dictionaries). These
176 -- must be explicitly Kinded.
178 hsTyVarName :: HsTyVarBndr name -> name
179 hsTyVarName (UserTyVar n) = n
180 hsTyVarName (KindedTyVar n _) = n
182 hsLTyVarName :: LHsTyVarBndr name -> name
183 hsLTyVarName = hsTyVarName . unLoc
185 hsTyVarNames :: [HsTyVarBndr name] -> [name]
186 hsTyVarNames tvs = map hsTyVarName tvs
188 hsLTyVarNames :: [LHsTyVarBndr name] -> [name]
189 hsLTyVarNames = map hsLTyVarName
191 hsLTyVarLocName :: LHsTyVarBndr name -> Located name
192 hsLTyVarLocName = fmap hsTyVarName
194 hsLTyVarLocNames :: [LHsTyVarBndr name] -> [Located name]
195 hsLTyVarLocNames = map hsLTyVarLocName
197 replaceTyVarName :: HsTyVarBndr name1 -> name2 -> HsTyVarBndr name2
198 replaceTyVarName (UserTyVar n) n' = UserTyVar n'
199 replaceTyVarName (KindedTyVar n k) n' = KindedTyVar n' k
205 :: OutputableBndr name
207 -> ([LHsTyVarBndr name], HsContext name, name, [LHsType name])
208 -- Split up an instance decl type, returning the pieces
210 -- In interface files, the instance declaration head is created
211 -- by HsTypes.toHsType, which does not guarantee to produce a
212 -- HsForAllTy. For example, if we had the weird decl
213 -- instance Foo T => Foo [T]
214 -- then we'd get the instance type
216 -- So when colleting the instance context, to be on the safe side
217 -- we gather predicate arguments
219 -- For source code, the parser ensures the type will have the right shape.
220 -- (e.g. see ParseUtil.checkInstType)
222 splitHsInstDeclTy inst_ty
224 HsForAllTy _ tvs cxt1 tau -- The type vars should have been
225 -- computed by now, even if they were implicit
226 -> (tvs, unLoc cxt1 ++ cxt2, cls, tys)
228 (cxt2, cls, tys) = split_tau (unLoc tau)
230 other -> ([], cxt2, cls, tys)
232 (cxt2, cls, tys) = split_tau inst_ty
235 split_tau (HsFunTy (L _ (HsPredTy p)) ty) = (p:ps, cls, tys)
237 (ps, cls, tys) = split_tau (unLoc ty)
238 split_tau (HsPredTy (L _ (HsClassP cls tys))) = ([], cls, tys)
239 split_tau other = pprPanic "splitHsInstDeclTy" (ppr inst_ty)
243 %************************************************************************
245 \subsection{Pretty printing}
247 %************************************************************************
249 NB: these types get printed into interface files, so
250 don't change the printing format lightly
253 instance (OutputableBndr name) => Outputable (HsType name) where
254 ppr ty = pprHsType ty
256 instance (Outputable name) => Outputable (HsTyVarBndr name) where
257 ppr (UserTyVar name) = ppr name
258 ppr (KindedTyVar name kind) = pprHsTyVarBndr name kind
260 instance OutputableBndr name => Outputable (HsPred name) where
261 ppr (HsClassP clas tys) = ppr clas <+> hsep (map (pprParendHsType.unLoc) tys)
262 ppr (HsIParam n ty) = hsep [ppr n, dcolon, ppr ty]
264 pprHsTyVarBndr :: Outputable name => name -> Kind -> SDoc
265 pprHsTyVarBndr name kind | kind `eqKind` liftedTypeKind = ppr name
266 | otherwise = hsep [ppr name, dcolon, pprParendKind kind]
268 pprHsForAll exp tvs cxt
269 | show_forall = forall_part <+> pprHsContext (unLoc cxt)
270 | otherwise = pprHsContext (unLoc cxt)
272 show_forall = opt_PprStyle_Debug
273 || (not (null tvs) && is_explicit)
274 is_explicit = case exp of {Explicit -> True; Implicit -> False}
275 forall_part = ptext SLIT("forall") <+> interppSP tvs <> dot
277 pprHsContext :: (OutputableBndr name) => HsContext name -> SDoc
278 pprHsContext [] = empty
279 pprHsContext cxt = ppr_hs_context cxt <+> ptext SLIT("=>")
281 ppr_hs_context [] = empty
282 ppr_hs_context cxt = parens (interpp'SP cxt)
286 pREC_TOP = (0 :: Int) -- type in ParseIface.y
287 pREC_FUN = (1 :: Int) -- btype in ParseIface.y
288 -- Used for LH arg of (->)
289 pREC_OP = (2 :: Int) -- Used for arg of any infix operator
290 -- (we don't keep their fixities around)
291 pREC_CON = (3 :: Int) -- Used for arg of type applicn:
292 -- always parenthesise unless atomic
294 maybeParen :: Int -- Precedence of context
295 -> Int -- Precedence of top-level operator
296 -> SDoc -> SDoc -- Wrap in parens if (ctxt >= op)
297 maybeParen ctxt_prec op_prec p | ctxt_prec >= op_prec = parens p
300 -- printing works more-or-less as for Types
302 pprHsType, pprParendHsType :: (OutputableBndr name) => HsType name -> SDoc
304 pprHsType ty = getPprStyle $ \sty -> ppr_mono_ty pREC_TOP (prepare sty ty)
305 pprParendHsType ty = ppr_mono_ty pREC_CON ty
307 -- Before printing a type
308 -- (a) Remove outermost HsParTy parens
309 -- (b) Drop top-level for-all type variables in user style
310 -- since they are implicit in Haskell
311 prepare sty (HsParTy ty) = prepare sty (unLoc ty)
314 ppr_mono_lty ctxt_prec ty = ppr_mono_ty ctxt_prec (unLoc ty)
316 ppr_mono_ty ctxt_prec (HsForAllTy exp tvs ctxt ty)
317 = maybeParen ctxt_prec pREC_FUN $
318 sep [pprHsForAll exp tvs ctxt, ppr_mono_lty pREC_TOP ty]
320 ppr_mono_ty ctxt_prec (HsTyVar name) = ppr name
321 ppr_mono_ty ctxt_prec (HsFunTy ty1 ty2) = ppr_fun_ty ctxt_prec ty1 ty2
322 ppr_mono_ty ctxt_prec (HsTupleTy con tys) = tupleParens con (interpp'SP tys)
323 ppr_mono_ty ctxt_prec (HsKindSig ty kind) = parens (ppr_mono_lty pREC_TOP ty <+> dcolon <+> pprKind kind)
324 ppr_mono_ty ctxt_prec (HsListTy ty) = brackets (ppr_mono_lty pREC_TOP ty)
325 ppr_mono_ty ctxt_prec (HsPArrTy ty) = pabrackets (ppr_mono_lty pREC_TOP ty)
326 ppr_mono_ty ctxt_prec (HsPredTy pred) = braces (ppr pred)
327 ppr_mono_ty ctxt_prec (HsNumTy n) = integer n -- generics only
328 ppr_mono_ty ctxt_prec (HsSpliceTy s) = pprSplice s
330 ppr_mono_ty ctxt_prec (HsAppTy fun_ty arg_ty)
331 = maybeParen ctxt_prec pREC_CON $
332 hsep [ppr_mono_lty pREC_FUN fun_ty, ppr_mono_lty pREC_CON arg_ty]
334 ppr_mono_ty ctxt_prec (HsOpTy ty1 op ty2)
335 = maybeParen ctxt_prec pREC_OP $
336 ppr_mono_lty pREC_OP ty1 <+> ppr op <+> ppr_mono_lty pREC_OP ty2
338 ppr_mono_ty ctxt_prec (HsParTy ty)
339 = parens (ppr_mono_lty pREC_TOP ty)
340 -- Put the parens in where the user did
341 -- But we still use the precedence stuff to add parens because
342 -- toHsType doesn't put in any HsParTys, so we may still need them
344 --------------------------
345 ppr_fun_ty ctxt_prec ty1 ty2
346 = let p1 = ppr_mono_lty pREC_FUN ty1
347 p2 = ppr_mono_lty pREC_TOP ty2
349 maybeParen ctxt_prec pREC_FUN $
350 sep [p1, ptext SLIT("->") <+> p2]
352 --------------------------
353 pabrackets p = ptext SLIT("[:") <> p <> ptext SLIT(":]")