The 1.3 report defines what ``irrefutable'' and ``failure-free'' patterns are.
\begin{code}
-hasViewPat :: Pat id -> Bool
-hasViewPat p = hasViewPat' (L undefined p)
-
-hasViewPat' :: LPat id -> Bool
-hasViewPat' (L _ p) = go p where
- go (WildPat _) = False
- go (VarPat _) = False
- go (VarPatOut _ _) = False
- go (LazyPat p) = hasViewPat' p
- go (AsPat _ p) = hasViewPat' p
- go (ParPat p) = hasViewPat' p
- go (BangPat p) = hasViewPat' p
- go (ListPat p _) = any hasViewPat' p
- go (TuplePat p _ _) = any hasViewPat' p
- go (PArrPat p _) = any hasViewPat' p
- go (ConPatIn _ p) = go' p
+hasViewPat :: LPat id -> Bool
+hasViewPat (L _ p) = go p where
+ go (WildPat _) = False
+ go (VarPat _) = False
+ go (VarPatOut _ _) = False
+ go (LazyPat p) = hasViewPat p
+ go (AsPat _ p) = hasViewPat p
+ go (ParPat p) = hasViewPat p
+ go (BangPat p) = hasViewPat p
+ go (ListPat p _) = any hasViewPat p
+ go (TuplePat p _ _) = any hasViewPat p
+ go (PArrPat p _) = any hasViewPat p
+ go (ConPatIn _ p) = go' p
go (ConPatOut _ _ _ _ p _) = go' p
- go (ViewPat _ _ _) = True
- go (QuasiQuotePat _) = False
- go (LitPat _) = False
- go (NPat _ _ _) = False
- go (NPlusKPat _ _ _ _) = False
- go (TypePat _) = False
- go (SigPatIn p _) = hasViewPat' p
- go (SigPatOut p _) = hasViewPat' p
- go (CoPat _ _ _) = False
+ go (ViewPat _ _ _) = True
+ go (QuasiQuotePat _) = False
+ go (LitPat _) = False
+ go (NPat _ _ _) = False
+ go (NPlusKPat _ _ _ _) = False
+ go (TypePat _) = False
+ go (SigPatIn p _) = hasViewPat p
+ go (SigPatOut p _) = hasViewPat p
+ go (CoPat _ _ _) = False
go' p = case p of
- PrefixCon ps -> any hasViewPat' ps
- RecCon (HsRecFields fs _) -> any (hasViewPat' . hsRecFieldArg) fs
- InfixCon p1 p2 -> hasViewPat' p1 || hasViewPat' p2
+ PrefixCon ps -> any hasViewPat ps
+ RecCon (HsRecFields fs _) -> any (hasViewPat . hsRecFieldArg) fs
+ InfixCon p1 p2 -> hasViewPat p1 || hasViewPat p2
isWildPat :: Pat id -> Bool
isWildPat (WildPat _) = True