2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
6 HsTypes: Abstract syntax: user-defined types
9 {-# LANGUAGE DeriveDataTypeable #-}
13 HsTyVarBndr(..), LHsTyVarBndr,
15 HsContext, LHsContext,
19 LBangType, BangType, HsBang(..),
20 getBangType, getBangStrictness,
22 ConDeclField(..), pprConDeclFields,
24 mkExplicitHsForAllTy, mkImplicitHsForAllTy, hsExplicitTvs,
25 hsTyVarName, hsTyVarNames, replaceTyVarName,
26 hsTyVarKind, hsTyVarNameKind,
27 hsLTyVarName, hsLTyVarNames, hsLTyVarLocName, hsLTyVarLocNames,
28 splitHsInstDeclTy, splitHsFunType,
31 PostTcType, placeHolderType, PostTcKind, placeHolderKind,
34 pprParendHsType, pprHsForAll, pprHsContext, ppr_hs_context,
37 import {-# SOURCE #-} HsExpr ( HsSplice, pprSplice )
39 import NameSet( FreeVars )
52 %************************************************************************
54 \subsection{Annotating the syntax}
56 %************************************************************************
59 type PostTcKind = Kind
60 type PostTcType = Type -- Used for slots in the abstract syntax
61 -- where we want to keep slot for a type
62 -- to be added by the type checker...but
63 -- before typechecking it's just bogus
65 placeHolderType :: PostTcType -- Used before typechecking
66 placeHolderType = panic "Evaluated the place holder for a PostTcType"
68 placeHolderKind :: PostTcKind -- Used before typechecking
69 placeHolderKind = panic "Evaluated the place holder for a PostTcKind"
72 %************************************************************************
74 Quasi quotes; used in types and elsewhere
76 %************************************************************************
79 data HsQuasiQuote id = HsQuasiQuote
80 id -- The quasi-quoter
81 SrcSpan -- The span of the enclosed string
82 FastString -- The enclosed string
83 deriving (Data, Typeable)
85 instance OutputableBndr id => Outputable (HsQuasiQuote id) where
88 ppr_qq :: OutputableBndr id => HsQuasiQuote id -> SDoc
89 ppr_qq (HsQuasiQuote quoter _ quote) =
90 char '[' <> ppr quoter <> ptext (sLit "|") <>
91 ppr quote <> ptext (sLit "|]")
95 %************************************************************************
97 \subsection{Bang annotations}
99 %************************************************************************
102 type LBangType name = Located (BangType name)
103 type BangType name = HsType name -- Bangs are in the HsType data type
105 getBangType :: LHsType a -> LHsType a
106 getBangType (L _ (HsBangTy _ ty)) = ty
109 getBangStrictness :: LHsType a -> HsBang
110 getBangStrictness (L _ (HsBangTy s _)) = s
111 getBangStrictness _ = HsNoBang
115 %************************************************************************
117 \subsection{Data types}
119 %************************************************************************
121 This is the syntax for types as seen in type signatures.
124 type LHsContext name = Located (HsContext name)
126 type HsContext name = [LHsPred name]
128 type LHsPred name = Located (HsPred name)
130 data HsPred name = HsClassP name [LHsType name] -- class constraint
131 | HsEqualP (LHsType name) (LHsType name)-- equality constraint
132 | HsIParam (IPName name) (LHsType name)
133 deriving (Data, Typeable)
135 type LHsType name = Located (HsType name)
138 = HsForAllTy HsExplicitFlag -- Renamer leaves this flag unchanged, to record the way
139 -- the user wrote it originally, so that the printer can
140 -- print it as the user wrote it
141 [LHsTyVarBndr name] -- With ImplicitForAll, this is the empty list
142 -- until the renamer fills in the variables
146 | HsTyVar name -- Type variable or type constructor
148 | HsAppTy (LHsType name)
151 | HsFunTy (LHsType name) -- function type
154 | HsListTy (LHsType name) -- Element type
156 | HsPArrTy (LHsType name) -- Elem. type of parallel array: [:t:]
159 [LHsType name] -- Element types (length gives arity)
161 | HsOpTy (LHsType name) (Located name) (LHsType name)
163 | HsParTy (LHsType name)
164 -- Parenthesis preserved for the precedence re-arrangement in RnTypes
165 -- It's important that a * (b + c) doesn't get rearranged to (a*b) + c!
167 -- However, NB that toHsType doesn't add HsParTys (in an effort to keep
168 -- interface files smaller), so when printing a HsType we may need to
171 | HsPredTy (HsPred name) -- Only used in the type of an instance
172 -- declaration, eg. Eq [a] -> Eq a
175 -- Note no need for location info on the
176 -- Enclosed HsPred; the one on the type will do
178 | HsKindSig (LHsType name) -- (ty :: kind)
179 Kind -- A type with a kind signature
181 | HsQuasiQuoteTy (HsQuasiQuote name)
183 | HsSpliceTy (HsSplice name)
184 FreeVars -- Variables free in the splice (filled in by renamer)
187 | HsDocTy (LHsType name) LHsDocString -- A documented type
189 | HsBangTy HsBang (LHsType name) -- Bang-style type annotations
190 | HsRecTy [ConDeclField name] -- Only in data type declarations
192 | HsCoreTy Type -- An escape hatch for tunnelling a *closed*
193 -- Core Type through HsSyn.
195 deriving (Data, Typeable)
197 data HsExplicitFlag = Explicit | Implicit deriving (Data, Typeable)
199 data ConDeclField name -- Record fields have Haddoc docs on them
200 = ConDeclField { cd_fld_name :: Located name,
201 cd_fld_type :: LBangType name,
202 cd_fld_doc :: Maybe LHsDocString }
203 deriving (Data, Typeable)
205 -----------------------
206 -- Combine adjacent for-alls.
207 -- The following awkward situation can happen otherwise:
208 -- f :: forall a. ((Num a) => Int)
209 -- might generate HsForAll (Just [a]) [] (HsForAll Nothing [Num a] t)
210 -- Then a isn't discovered as ambiguous, and we abstract the AbsBinds wrt []
211 -- but the export list abstracts f wrt [a]. Disaster.
213 -- A valid type must have one for-all at the top of the type, or of the fn arg types
215 mkImplicitHsForAllTy :: LHsContext name -> LHsType name -> HsType name
216 mkExplicitHsForAllTy :: [LHsTyVarBndr name] -> LHsContext name -> LHsType name -> HsType name
217 mkImplicitHsForAllTy ctxt ty = mkHsForAllTy Implicit [] ctxt ty
218 mkExplicitHsForAllTy tvs ctxt ty = mkHsForAllTy Explicit tvs ctxt ty
220 mkHsForAllTy :: HsExplicitFlag -> [LHsTyVarBndr name] -> LHsContext name -> LHsType name -> HsType name
221 -- Smart constructor for HsForAllTy
222 mkHsForAllTy exp tvs (L _ []) ty = mk_forall_ty exp tvs ty
223 mkHsForAllTy exp tvs ctxt ty = HsForAllTy exp tvs ctxt ty
225 -- mk_forall_ty makes a pure for-all type (no context)
226 mk_forall_ty :: HsExplicitFlag -> [LHsTyVarBndr name] -> LHsType name -> HsType name
227 mk_forall_ty exp tvs (L _ (HsParTy ty)) = mk_forall_ty exp tvs ty
228 mk_forall_ty exp1 tvs1 (L _ (HsForAllTy exp2 tvs2 ctxt ty)) = mkHsForAllTy (exp1 `plus` exp2) (tvs1 ++ tvs2) ctxt ty
229 mk_forall_ty exp tvs ty = HsForAllTy exp tvs (L noSrcSpan []) ty
230 -- Even if tvs is empty, we still make a HsForAll!
231 -- In the Implicit case, this signals the place to do implicit quantification
232 -- In the Explicit case, it prevents implicit quantification
233 -- (see the sigtype production in Parser.y.pp)
234 -- so that (forall. ty) isn't implicitly quantified
236 plus :: HsExplicitFlag -> HsExplicitFlag -> HsExplicitFlag
237 Implicit `plus` Implicit = Implicit
238 _ `plus` _ = Explicit
240 hsExplicitTvs :: LHsType name -> [name]
241 -- The explicitly-given forall'd type variables of a HsType
242 hsExplicitTvs (L _ (HsForAllTy Explicit tvs _ _)) = hsLTyVarNames tvs
245 ---------------------
246 type LHsTyVarBndr name = Located (HsTyVarBndr name)
248 data HsTyVarBndr name
249 = UserTyVar -- No explicit kinding
250 name -- See Note [Printing KindedTyVars]
256 -- *** NOTA BENE *** A "monotype" in a pragma can have
257 -- for-alls in it, (mostly to do with dictionaries). These
258 -- must be explicitly Kinded.
259 deriving (Data, Typeable)
261 hsTyVarName :: HsTyVarBndr name -> name
262 hsTyVarName (UserTyVar n _) = n
263 hsTyVarName (KindedTyVar n _) = n
265 hsTyVarKind :: HsTyVarBndr name -> Kind
266 hsTyVarKind (UserTyVar _ k) = k
267 hsTyVarKind (KindedTyVar _ k) = k
269 hsTyVarNameKind :: HsTyVarBndr name -> (name, Kind)
270 hsTyVarNameKind (UserTyVar n k) = (n,k)
271 hsTyVarNameKind (KindedTyVar n k) = (n,k)
273 hsLTyVarName :: LHsTyVarBndr name -> name
274 hsLTyVarName = hsTyVarName . unLoc
276 hsTyVarNames :: [HsTyVarBndr name] -> [name]
277 hsTyVarNames tvs = map hsTyVarName tvs
279 hsLTyVarNames :: [LHsTyVarBndr name] -> [name]
280 hsLTyVarNames = map hsLTyVarName
282 hsLTyVarLocName :: LHsTyVarBndr name -> Located name
283 hsLTyVarLocName = fmap hsTyVarName
285 hsLTyVarLocNames :: [LHsTyVarBndr name] -> [Located name]
286 hsLTyVarLocNames = map hsLTyVarLocName
288 replaceTyVarName :: HsTyVarBndr name1 -> name2 -> HsTyVarBndr name2
289 replaceTyVarName (UserTyVar _ k) n' = UserTyVar n' k
290 replaceTyVarName (KindedTyVar _ k) n' = KindedTyVar n' k
296 :: OutputableBndr name
298 -> ([LHsTyVarBndr name], HsContext name, name, [LHsType name])
299 -- Split up an instance decl type, returning the pieces
301 splitHsInstDeclTy inst_ty
303 HsParTy (L _ ty) -> splitHsInstDeclTy ty
304 HsForAllTy _ tvs cxt (L _ ty) -> split_tau tvs (unLoc cxt) ty
305 other -> split_tau [] [] other
306 -- The type vars should have been computed by now, even if they were implicit
308 split_tau tvs cxt (HsPredTy (HsClassP cls tys)) = (tvs, cxt, cls, tys)
309 split_tau tvs cxt (HsParTy (L _ ty)) = split_tau tvs cxt ty
310 split_tau _ _ _ = pprPanic "splitHsInstDeclTy" (ppr inst_ty)
312 -- Splits HsType into the (init, last) parts
313 -- Breaks up any parens in the result type:
314 -- splitHsFunType (a -> (b -> c)) = ([a,b], c)
315 splitHsFunType :: LHsType name -> ([LHsType name], LHsType name)
316 splitHsFunType (L _ (HsFunTy x y)) = (x:args, res)
318 (args, res) = splitHsFunType y
319 splitHsFunType (L _ (HsParTy ty)) = splitHsFunType ty
320 splitHsFunType other = ([], other)
324 %************************************************************************
326 \subsection{Pretty printing}
328 %************************************************************************
331 instance (OutputableBndr name) => Outputable (HsType name) where
332 ppr ty = pprHsType ty
334 instance (Outputable name) => Outputable (HsTyVarBndr name) where
335 ppr (UserTyVar name _) = ppr name
336 ppr (KindedTyVar name kind) = hsep [ppr name, dcolon, pprParendKind kind]
338 instance OutputableBndr name => Outputable (HsPred name) where
339 ppr (HsClassP clas tys) = ppr clas <+> hsep (map pprLHsType tys)
340 ppr (HsEqualP t1 t2) = hsep [pprLHsType t1, ptext (sLit "~"),
342 ppr (HsIParam n ty) = hsep [ppr n, dcolon, ppr ty]
344 pprLHsType :: OutputableBndr name => LHsType name -> SDoc
345 pprLHsType = pprParendHsType . unLoc
347 pprHsForAll :: OutputableBndr name => HsExplicitFlag -> [LHsTyVarBndr name] -> LHsContext name -> SDoc
348 pprHsForAll exp tvs cxt
349 | show_forall = forall_part <+> pprHsContext (unLoc cxt)
350 | otherwise = pprHsContext (unLoc cxt)
352 show_forall = opt_PprStyle_Debug
353 || (not (null tvs) && is_explicit)
354 is_explicit = case exp of {Explicit -> True; Implicit -> False}
355 forall_part = ptext (sLit "forall") <+> interppSP tvs <> dot
357 pprHsContext :: (OutputableBndr name) => HsContext name -> SDoc
358 pprHsContext [] = empty
359 pprHsContext [L _ pred]
360 | noParenHsPred pred = ppr pred <+> darrow
361 pprHsContext cxt = ppr_hs_context cxt <+> darrow
363 noParenHsPred :: HsPred name -> Bool
364 -- c.f. TypeRep.noParenPred
365 noParenHsPred (HsClassP {}) = True
366 noParenHsPred (HsEqualP {}) = True
367 noParenHsPred (HsIParam {}) = False
369 ppr_hs_context :: (OutputableBndr name) => HsContext name -> SDoc
370 ppr_hs_context [] = empty
371 ppr_hs_context cxt = parens (interpp'SP cxt)
373 pprConDeclFields :: OutputableBndr name => [ConDeclField name] -> SDoc
374 pprConDeclFields fields = braces (sep (punctuate comma (map ppr_fld fields)))
376 ppr_fld (ConDeclField { cd_fld_name = n, cd_fld_type = ty,
378 = ppr n <+> dcolon <+> ppr ty <+> ppr_mbDoc doc
381 Note [Printing KindedTyVars]
382 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
383 Trac #3830 reminded me that we should really only print the kind
384 signature on a KindedTyVar if the kind signature was put there by the
385 programmer. During kind inference GHC now adds a PostTcKind to UserTyVars,
386 rather than converting to KindedTyVars as before.
388 (As it happens, the message in #3830 comes out a different way now,
389 and the problem doesn't show up; but having the flag on a KindedTyVar
390 seems like the Right Thing anyway.)
393 pREC_TOP, pREC_FUN, pREC_OP, pREC_CON :: Int
394 pREC_TOP = 0 -- type in ParseIface.y
395 pREC_FUN = 1 -- btype in ParseIface.y
396 -- Used for LH arg of (->)
397 pREC_OP = 2 -- Used for arg of any infix operator
398 -- (we don't keep their fixities around)
399 pREC_CON = 3 -- Used for arg of type applicn:
400 -- always parenthesise unless atomic
402 maybeParen :: Int -- Precedence of context
403 -> Int -- Precedence of top-level operator
404 -> SDoc -> SDoc -- Wrap in parens if (ctxt >= op)
405 maybeParen ctxt_prec op_prec p | ctxt_prec >= op_prec = parens p
408 -- printing works more-or-less as for Types
410 pprHsType, pprParendHsType :: (OutputableBndr name) => HsType name -> SDoc
412 pprHsType ty = getPprStyle $ \sty -> ppr_mono_ty pREC_TOP (prepare sty ty)
413 pprParendHsType ty = ppr_mono_ty pREC_CON ty
415 -- Before printing a type
416 -- (a) Remove outermost HsParTy parens
417 -- (b) Drop top-level for-all type variables in user style
418 -- since they are implicit in Haskell
419 prepare :: PprStyle -> HsType name -> HsType name
420 prepare sty (HsParTy ty) = prepare sty (unLoc ty)
423 ppr_mono_lty :: (OutputableBndr name) => Int -> LHsType name -> SDoc
424 ppr_mono_lty ctxt_prec ty = ppr_mono_ty ctxt_prec (unLoc ty)
426 ppr_mono_ty :: (OutputableBndr name) => Int -> HsType name -> SDoc
427 ppr_mono_ty ctxt_prec (HsForAllTy exp tvs ctxt ty)
428 = maybeParen ctxt_prec pREC_FUN $
429 sep [pprHsForAll exp tvs ctxt, ppr_mono_lty pREC_TOP ty]
431 ppr_mono_ty _ (HsBangTy b ty) = ppr b <> ppr ty
432 ppr_mono_ty _ (HsQuasiQuoteTy qq) = ppr qq
433 ppr_mono_ty _ (HsRecTy flds) = pprConDeclFields flds
434 ppr_mono_ty _ (HsTyVar name) = ppr name
435 ppr_mono_ty prec (HsFunTy ty1 ty2) = ppr_fun_ty prec ty1 ty2
436 ppr_mono_ty _ (HsTupleTy con tys) = tupleParens con (interpp'SP tys)
437 ppr_mono_ty _ (HsKindSig ty kind) = parens (ppr_mono_lty pREC_TOP ty <+> dcolon <+> pprKind kind)
438 ppr_mono_ty _ (HsListTy ty) = brackets (ppr_mono_lty pREC_TOP ty)
439 ppr_mono_ty _ (HsPArrTy ty) = pabrackets (ppr_mono_lty pREC_TOP ty)
440 ppr_mono_ty _ (HsPredTy pred) = ppr pred
441 ppr_mono_ty _ (HsSpliceTy s _ _) = pprSplice s
442 ppr_mono_ty _ (HsCoreTy ty) = ppr ty
444 ppr_mono_ty ctxt_prec (HsAppTy fun_ty arg_ty)
445 = maybeParen ctxt_prec pREC_CON $
446 hsep [ppr_mono_lty pREC_FUN fun_ty, ppr_mono_lty pREC_CON arg_ty]
448 ppr_mono_ty ctxt_prec (HsOpTy ty1 op ty2)
449 = maybeParen ctxt_prec pREC_OP $
450 ppr_mono_lty pREC_OP ty1 <+> ppr op <+> ppr_mono_lty pREC_OP ty2
452 ppr_mono_ty _ (HsParTy ty)
453 = parens (ppr_mono_lty pREC_TOP ty)
454 -- Put the parens in where the user did
455 -- But we still use the precedence stuff to add parens because
456 -- toHsType doesn't put in any HsParTys, so we may still need them
458 ppr_mono_ty ctxt_prec (HsDocTy ty doc)
459 = maybeParen ctxt_prec pREC_OP $
460 ppr_mono_lty pREC_OP ty <+> ppr (unLoc doc)
461 -- we pretty print Haddock comments on types as if they were
464 --------------------------
465 ppr_fun_ty :: (OutputableBndr name) => Int -> LHsType name -> LHsType name -> SDoc
466 ppr_fun_ty ctxt_prec ty1 ty2
467 = let p1 = ppr_mono_lty pREC_FUN ty1
468 p2 = ppr_mono_lty pREC_TOP ty2
470 maybeParen ctxt_prec pREC_FUN $
471 sep [p1, ptext (sLit "->") <+> p2]
473 --------------------------
474 pabrackets :: SDoc -> SDoc
475 pabrackets p = ptext (sLit "[:") <> p <> ptext (sLit ":]")