module HsPat (
Pat(..), InPat, OutPat, LPat,
- HsConDetails(..), hsConArgs,
- HsRecField(..), mkRecField,
+ HsConDetails(..),
+ HsConPatDetails, hsConPatArgs,
+ HsRecFields(..), HsRecField(..), hsRecFields,
mkPrefixConPat, mkCharLitPat, mkNilPat, mkCoPat,
import HsBinds
import HsLit
import HsTypes
-import HsDoc
import BasicTypes
-- others:
import PprCore ( {- instance OutputableBndr TyVar -} )
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
------------ Constructor patterns ---------------
| ConPatIn (Located id)
- (HsConDetails id (LPat id))
+ (HsConPatDetails id)
| ConPatOut {
pat_con :: Located DataCon,
-- 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
}
| 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}
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 d, 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}
isConPat (ListPat {}) = True
isConPat (PArrPat {}) = True
isConPat (TuplePat {}) = True
-isConPat (DictPat ds ms) = (length ds + length ms) > 1
isConPat other = False
isSigPat (SigPatIn _ _) = True
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}