-- any warnings in the module. See
-- http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
-- for details
+{-# LANGUAGE DeriveDataTypeable #-}
module HsPat (
Pat(..), InPat, OutPat, LPat,
HsConPatDetails, hsConPatArgs,
HsRecFields(..), HsRecField(..), hsRecFields,
- mkPrefixConPat, mkCharLitPat, mkNilPat, mkCoPat, mkCoPatCoI,
+ mkPrefixConPat, mkCharLitPat, mkNilPat,
- isBangHsBind, hsPatNeedsParens,
- patsAreAllCons, isConPat, isSigPat, isWildPat,
- patsAreAllLits, isLitPat, isIrrefutableHsPat,
+ isBangHsBind, isLiftedPatBind,
+ isBangLPat, hsPatNeedsParens,
+ isIrrefutableHsPat,
pprParendLPat
) where
import HsTypes
import BasicTypes
-- others:
-import Coercion
import PprCore ( {- instance OutputableBndr TyVar -} )
import TysWiredIn
import Var
import Type
import SrcLoc
import FastString
+-- libraries:
+import Data.Data hiding (TyCon)
+import Data.Maybe
\end{code}
-- support hsPatType :: Pat Id -> Type
| VarPat id -- Variable
- | VarPatOut id (DictBinds id) -- Used only for overloaded Ids; the
- -- bindings give its overloaded instances
- | LazyPat (LPat id) -- Lazy pattern
+ | LazyPat (LPat id) -- Lazy pattern
| AsPat (Located id) (LPat id) -- As pattern
| ParPat (LPat id) -- Parenthesised pattern
| BangPat (LPat id) -- Bang pattern
| ConPatOut {
pat_con :: Located DataCon,
pat_tvs :: [TyVar], -- Existentially bound type variables (tyvars only)
- pat_dicts :: [id], -- Ditto *coercion variables* and *dictionaries*
+ pat_dicts :: [EvVar], -- Ditto *coercion variables* and *dictionaries*
-- One reason for putting coercion variable here, I think,
-- is to ensure their kinds are zonked
- pat_binds :: DictBinds id, -- Bindings involving those dictionaries
+ pat_binds :: TcEvBinds, -- Bindings involving those dictionaries
pat_args :: HsConPatDetails id,
pat_ty :: Type -- The type of the pattern
}
| LitPat HsLit -- Used for *non-overloaded* literal patterns:
-- Int#, Char#, Int, Char, String, etc.
- | NPat (HsOverLit id) -- ALWAYS positive
+ | NPat -- Used for all overloaded literals,
+ -- including overloaded strings with -XOverloadedStrings
+ (HsOverLit id) -- ALWAYS positive
(Maybe (SyntaxExpr id)) -- Just (Name of 'negate') for negative
-- patterns, Nothing otherwise
(SyntaxExpr id) -- Equality checker, of type t->t->Bool
(SyntaxExpr id) -- (>=) function, of type t->t->Bool
(SyntaxExpr id) -- Name of '-' (see RnEnv.lookupSyntaxName)
- ------------ Generics ---------------
- | TypePat (LHsType id) -- Type pattern for generic definitions
- -- e.g f{| a+b |} = ...
- -- These show up only in class declarations,
- -- and should be a top-level pattern
-
------------ Pattern type signatures ---------------
| SigPatIn (LPat id) -- Pattern with a type signature
(LHsType id)
Type
------------ Pattern coercions (translation only) ---------------
- | CoPat HsWrapper -- If co::t1 -> t2, p::t2,
+ | 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 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'
+ deriving (Data, Typeable)
\end{code}
HsConDetails is use for patterns/expressions *and* for data type declarations
= PrefixCon [arg] -- C p1 p2 p3
| RecCon rec -- C { x = p1, y = p2 }
| InfixCon arg arg -- p1 `C` p2
+ deriving (Data, Typeable)
type HsConPatDetails id = HsConDetails (LPat id) (HsRecFields id (LPat id))
-- Used for both expressions and patterns
= HsRecFields { rec_flds :: [HsRecField id arg],
rec_dotdot :: Maybe Int } -- Note [DotDot fields]
+ deriving (Data, Typeable)
-- Note [DotDot fields]
-- ~~~~~~~~~~~~~~~~~~~~
hsRecFieldId :: Located id,
hsRecFieldArg :: arg, -- Filled in by renamer
hsRecPun :: Bool -- Note [Punning]
- }
+ } deriving (Data, Typeable)
-- Note [Punning]
-- ~~~~~~~~~~~~~~
pprPat :: (OutputableBndr name) => Pat name -> SDoc
pprPat (VarPat var) = pprPatBndr var
-pprPat (VarPatOut var bs) = pprPatBndr var <+> braces (ppr bs)
pprPat (WildPat _) = char '_'
pprPat (LazyPat pat) = char '~' <> pprParendLPat pat
pprPat (BangPat pat) = char '!' <> pprParendLPat pat
if debugStyle sty then -- typechecked Pat in an error message,
-- and we want to make sure it prints nicely
ppr con <+> sep [ hsep (map pprPatBndr tvs) <+> hsep (map pprPatBndr dicts),
- pprLHsBinds binds, pprConArgs details]
+ ppr binds, pprConArgs details]
else pprUserCon con details
pprPat (LitPat s) = ppr s
pprPat (NPat l (Just _) _) = char '-' <> ppr l
pprPat (NPlusKPat n k _ _) = hcat [ppr n, char '+', ppr k]
pprPat (QuasiQuotePat qq) = ppr qq
-pprPat (TypePat ty) = ptext (sLit "{|") <> ppr ty <> ptext (sLit "|}")
pprPat (CoPat co pat _) = pprHsWrapper (ppr pat) co
pprPat (SigPatIn pat ty) = ppr pat <+> dcolon <+> ppr ty
pprPat (SigPatOut pat ty) = ppr pat <+> dcolon <+> ppr ty
-- Make a vanilla Prefix constructor pattern
mkPrefixConPat dc pats ty
= noLoc $ ConPatOut { pat_con = noLoc dc, pat_tvs = [], pat_dicts = [],
- pat_binds = emptyLHsBinds, pat_args = PrefixCon pats,
+ pat_binds = emptyTcEvBinds, pat_args = PrefixCon pats,
pat_ty = ty }
mkNilPat :: Type -> OutPat id
mkCharLitPat :: Char -> OutPat id
mkCharLitPat c = mkPrefixConPat charDataCon [noLoc $ LitPat (HsCharPrim c)] charTy
-
-mkCoPat :: HsWrapper -> Pat id -> Type -> Pat id
-mkCoPat co pat ty
- | isIdHsWrapper co = pat
- | otherwise = CoPat co pat ty
-
-mkCoPatCoI :: CoercionI -> Pat id -> Type -> Pat id
-mkCoPatCoI IdCo pat _ = pat
-mkCoPatCoI (ACo co) pat ty = mkCoPat (WpCast co) pat ty
\end{code}
The 1.3 report defines what ``irrefutable'' and ``failure-free'' patterns are.
\begin{code}
-isWildPat :: Pat id -> Bool
-isWildPat (WildPat _) = True
-isWildPat _ = False
-
-patsAreAllCons :: [Pat id] -> Bool
-patsAreAllCons pat_list = all isConPat pat_list
-
-isConPat :: Pat id -> Bool
-isConPat (AsPat _ pat) = isConPat (unLoc pat)
-isConPat (ConPatIn {}) = True
-isConPat (ConPatOut {}) = True
-isConPat (ListPat {}) = True
-isConPat (PArrPat {}) = True
-isConPat (TuplePat {}) = True
-isConPat _ = False
-
-isSigPat :: Pat id -> Bool
-isSigPat (SigPatIn _ _) = True
-isSigPat (SigPatOut _ _) = True
-isSigPat _ = False
-
-patsAreAllLits :: [Pat id] -> Bool
-patsAreAllLits pat_list = all isLitPat pat_list
-
-isLitPat :: Pat id -> Bool
-isLitPat (AsPat _ pat) = isLitPat (unLoc pat)
-isLitPat (LitPat _) = True
-isLitPat (NPat _ _ _) = True
-isLitPat (NPlusKPat _ _ _ _) = True
-isLitPat _ = False
+isBangLPat :: LPat id -> Bool
+isBangLPat (L _ (BangPat {})) = True
+isBangLPat (L _ (ParPat p)) = isBangLPat p
+isBangLPat _ = False
isBangHsBind :: HsBind id -> Bool
--- In this module because HsPat is above HsBinds in the import graph
-isBangHsBind (PatBind { pat_lhs = L _ (BangPat _) }) = True
-isBangHsBind _ = False
+-- A pattern binding with an outermost bang
+-- Defined in this module because HsPat is above HsBinds in the import graph
+isBangHsBind (PatBind { pat_lhs = p }) = isBangLPat p
+isBangHsBind _ = False
+
+isLiftedPatBind :: HsBind id -> Bool
+-- A pattern binding with a compound pattern, not just a variable
+-- (I# x) yes
+-- (# a, b #) no, even if a::Int#
+-- x no, even if x::Int#
+-- We want to warn about a missing bang-pattern on the yes's
+isLiftedPatBind (PatBind { pat_lhs = p }) = isLiftedLPat p
+isLiftedPatBind _ = False
+
+isLiftedLPat :: LPat id -> Bool
+isLiftedLPat (L _ (ParPat p)) = isLiftedLPat p
+isLiftedLPat (L _ (BangPat p)) = isLiftedLPat p
+isLiftedLPat (L _ (AsPat _ p)) = isLiftedLPat p
+isLiftedLPat (L _ (TuplePat _ Unboxed _)) = False
+isLiftedLPat (L _ (VarPat {})) = False
+isLiftedLPat (L _ (WildPat {})) = False
+isLiftedLPat _ = True
isIrrefutableHsPat :: OutputableBndr id => LPat id -> Bool
-- (isIrrefutableHsPat p) is true if matching against p cannot fail,
go1 (WildPat {}) = True
go1 (VarPat {}) = True
- go1 (VarPatOut {}) = True
go1 (LazyPat {}) = True
go1 (BangPat pat) = go pat
go1 (CoPat _ pat _) = go1 pat
go1 (ConPatIn {}) = False -- Conservative
go1 (ConPatOut{ pat_con = L _ con, pat_args = details })
- = isProductTyCon (dataConTyCon con)
+ = isJust (tyConSingleDataCon_maybe (dataConTyCon con))
+ -- NB: tyConSingleDataCon_maybe, *not* isProductTyCon, because
+ -- the latter is false of existentials. See Trac #4439
&& all go (hsConPatArgs details)
go1 (LitPat {}) = False
go1 (QuasiQuotePat {}) = urk pat -- Gotten rid of by renamer, before
-- isIrrefutablePat is called
- go1 (TypePat {}) = urk pat
urk pat = pprPanic "isIrrefutableHsPat:" (ppr pat)
hsPatNeedsParens :: Pat a -> Bool
hsPatNeedsParens (WildPat {}) = False
hsPatNeedsParens (VarPat {}) = False
-hsPatNeedsParens (VarPatOut {}) = True
hsPatNeedsParens (LazyPat {}) = False
hsPatNeedsParens (BangPat {}) = False
hsPatNeedsParens (CoPat {}) = True
hsPatNeedsParens (NPat {}) = False
hsPatNeedsParens (NPlusKPat {}) = True
hsPatNeedsParens (QuasiQuotePat {}) = True
-hsPatNeedsParens (TypePat {}) = False
conPatNeedsParens :: HsConDetails a b -> Bool
conPatNeedsParens (PrefixCon args) = not (null args)
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