X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FhsSyn%2FHsPat.lhs;h=842a4f1e51e56bc652ae5ccde6cbc7fb6d23a385;hb=8a2809c29de9f23eba7ca682b48390033a9d40f6;hp=ea59e8827eade9dc485d489011b6ef60e7d93fa7;hpb=6fb1a6433a3b9e8d54abeab9d4aa7aa947140a1e;p=ghc-hetmet.git diff --git a/compiler/hsSyn/HsPat.lhs b/compiler/hsSyn/HsPat.lhs index ea59e88..842a4f1 100644 --- a/compiler/hsSyn/HsPat.lhs +++ b/compiler/hsSyn/HsPat.lhs @@ -8,8 +8,9 @@ module HsPat ( Pat(..), InPat, OutPat, LPat, - HsConDetails(..), hsConArgs, - HsRecField(..), mkRecField, + HsConDetails(..), + HsConPatDetails, hsConPatArgs, + HsRecFields(..), HsRecField(..), hsRecFields, mkPrefixConPat, mkCharLitPat, mkNilPat, mkCoPat, @@ -50,6 +51,9 @@ type LPat id = Located (Pat id) data Pat id = ------------ Simple patterns --------------- WildPat PostTcType -- Wild card + -- The sole reason for a type on a WildPat is to + -- support hsPatType :: Pat Id -> Type + | VarPat id -- Variable | VarPatOut id (DictBinds id) -- Used only for overloaded Ids; the -- bindings give its overloaded instances @@ -82,7 +86,7 @@ data Pat id ------------ Constructor patterns --------------- | ConPatIn (Located id) - (HsConDetails id (LPat id)) + (HsConPatDetails id) | ConPatOut { pat_con :: Located DataCon, @@ -90,7 +94,7 @@ data Pat id -- including any bound coercion variables pat_dicts :: [id], -- Ditto dictionaries pat_binds :: DictBinds id, -- Bindings involving those dictionaries - pat_args :: HsConDetails id (LPat id), + pat_args :: HsConPatDetails id, pat_ty :: Type -- The type of the pattern } @@ -122,40 +126,64 @@ data Pat id | SigPatOut (LPat id) -- Pattern with a type signature Type - ------------ Dictionary patterns (translation only) --------------- - | DictPat -- Used when destructing Dictionaries with an explicit case - [id] -- Superclass dicts - [id] -- Methods - ------------ Pattern coercions (translation only) --------------- | CoPat HsWrapper -- If co::t1 -> t2, p::t2, -- then (CoPat co p) :: t1 (Pat id) -- Why not LPat? Ans: existing locn will do - Type + Type -- Type of whole pattern, t1 -- During desugaring a (CoPat co pat) turns into a cast with 'co' on -- the scrutinee, followed by a match on 'pat' \end{code} -HsConDetails is use both for patterns and for data type declarations +HsConDetails is use for patterns/expressions *and* for data type declarations \begin{code} -data HsConDetails id arg - = PrefixCon [arg] -- C p1 p2 p3 - | RecCon [HsRecField id arg] -- C { x = p1, y = p2 } - | InfixCon arg arg -- p1 `C` p2 +data HsConDetails arg rec + = PrefixCon [arg] -- C p1 p2 p3 + | RecCon rec -- C { x = p1, y = p2 } + | InfixCon arg arg -- p1 `C` p2 + +type HsConPatDetails id = HsConDetails (LPat id) (HsRecFields id (LPat id)) + +hsConPatArgs :: HsConPatDetails id -> [LPat id] +hsConPatArgs (PrefixCon ps) = ps +hsConPatArgs (RecCon fs) = map hsRecFieldArg (rec_flds fs) +hsConPatArgs (InfixCon p1 p2) = [p1,p2] +\end{code} + +However HsRecFields is used only for patterns and expressions +(not data type declarations) + +\begin{code} +data HsRecFields id arg -- A bunch of record fields + -- { x = 3, y = True } + -- Used for both expressiona and patterns + = HsRecFields { rec_flds :: [HsRecField id arg], + rec_dotdot :: Maybe Int } + -- Nothing => the normal case + -- Just n => the group uses ".." notation, + -- and the first n elts of rec_flds + -- were the user-written ones + -- (In the latter case, the remaining elts of + -- rec_flds are the non-user-written ones) data HsRecField id arg = HsRecField { hsRecFieldId :: Located id, hsRecFieldArg :: arg, - hsRecFieldDoc :: Maybe (LHsDoc id) -} - -mkRecField id arg = HsRecField id arg Nothing - -hsConArgs :: HsConDetails id arg -> [arg] -hsConArgs (PrefixCon ps) = ps -hsConArgs (RecCon fs) = map hsRecFieldArg fs -hsConArgs (InfixCon p1 p2) = [p1,p2] + hsRecPun :: Bool -- Note [Punning] + } + +-- Note [Punning] +-- ~~~~~~~~~~~~~~ +-- If you write T { x, y = v+1 }, the HsRecFields will be +-- HsRecField x x True ... +-- HsRecField y (v+1) False ... +-- That is, for "punned" field x is immediately expanded to x=x +-- but with a punning flag so we can detect it later +-- (e.g. when pretty printing) + +hsRecFields :: HsRecFields id arg -> [id] +hsRecFields rbinds = map (unLoc . hsRecFieldId) (rec_flds rbinds) \end{code} @@ -208,28 +236,33 @@ pprPat (TypePat ty) = ptext SLIT("{|") <> ppr ty <> ptext SLIT("|}") pprPat (CoPat co pat _) = parens (pprHsWrapper (ppr pat) co) pprPat (SigPatIn pat ty) = ppr pat <+> dcolon <+> ppr ty pprPat (SigPatOut pat ty) = ppr pat <+> dcolon <+> ppr ty -pprPat (DictPat ds ms) = parens (sep [ptext SLIT("{-dict-}"), - brackets (interpp'SP ds), - brackets (interpp'SP ms)]) pprUserCon c (InfixCon p1 p2) = ppr p1 <+> ppr c <+> ppr p2 pprUserCon c details = ppr c <+> pprConArgs details pprConArgs (PrefixCon pats) = interppSP pats pprConArgs (InfixCon p1 p2) = interppSP [p1,p2] -pprConArgs (RecCon rpats) = braces (hsep (punctuate comma (map (pp_rpat) rpats))) - where - pp_rpat (HsRecField v p _d) = - hsep [ppr v, char '=', ppr p] +pprConArgs (RecCon rpats) = ppr rpats + +instance (OutputableBndr id, Outputable arg) + => Outputable (HsRecFields id arg) where + ppr (HsRecFields { rec_flds = flds, rec_dotdot = Nothing }) + = braces (fsep (punctuate comma (map ppr flds))) + ppr (HsRecFields { rec_flds = flds, rec_dotdot = Just n }) + = braces (fsep (punctuate comma (map ppr (take n flds) ++ [dotdot]))) + where + dotdot = ptext SLIT("..") <+> ifPprDebug (ppr (drop n flds)) + +instance (OutputableBndr id, Outputable arg) + => Outputable (HsRecField id arg) where + ppr (HsRecField { hsRecFieldId = f, hsRecFieldArg = arg, + hsRecPun = pun }) + = ppr f <+> (if pun then empty else equals <+> ppr arg) -- add parallel array brackets around a document -- pabrackets :: SDoc -> SDoc pabrackets p = ptext SLIT("[:") <> p <> ptext SLIT(":]") - -instance (OutputableBndr id, Outputable arg) => - Outputable (HsRecField id arg) where - ppr (HsRecField n ty doc) = ppr n <+> dcolon <+> ppr ty <+> ppr_mbDoc doc \end{code} @@ -302,7 +335,6 @@ isConPat (ConPatOut {}) = True isConPat (ListPat {}) = True isConPat (PArrPat {}) = True isConPat (TuplePat {}) = True -isConPat (DictPat ds ms) = (length ds + length ms) > 1 isConPat other = False isSigPat (SigPatIn _ _) = True @@ -349,13 +381,12 @@ isIrrefutableHsPat pat go1 (ConPatIn _ _) = False -- Conservative go1 (ConPatOut{ pat_con = L _ con, pat_args = details }) = isProductTyCon (dataConTyCon con) - && all go (hsConArgs details) + && all go (hsConPatArgs details) go1 (LitPat _) = False go1 (NPat _ _ _ _) = False go1 (NPlusKPat _ _ _ _) = False go1 (TypePat _) = panic "isIrrefutableHsPat: type pattern" - go1 (DictPat _ _) = panic "isIrrefutableHsPat: type pattern" \end{code}