Add bang patterns

[ghc-hetmet.git] / ghc / compiler / hsSyn / HsPat.lhs

diff --git a/ghc/compiler/hsSyn/HsPat.lhs b/ghc/compiler/hsSyn/HsPat.lhs
index 4d64a46..953d228 100644 (file)
--- a/ghc/compiler/hsSyn/HsPat.lhs
+++ b/ghc/compiler/hsSyn/HsPat.lhs
@@ -11,8 +11,8 @@ module HsPat (
 
        mkPrefixConPat, mkCharLitPat, mkNilPat, 
 
-       isWildPat, 
-       patsAreAllCons, isConPat, isSigPat,
+       isBangHsBind,   
+       patsAreAllCons, isConPat, isSigPat, isWildPat,
        patsAreAllLits, isLitPat, isIrrefutableHsPat
     ) where
 
@@ -22,7 +22,7 @@ module HsPat (
 import {-# SOURCE #-} HsExpr           ( SyntaxExpr )
 
 -- friends:
-import HsBinds         ( DictBinds, emptyLHsBinds, pprLHsBinds )
+import HsBinds         ( DictBinds, HsBind(..), emptyLHsBinds, pprLHsBinds )
 import HsLit           ( HsLit(HsCharPrim), HsOverLit )
 import HsTypes         ( LHsType, PostTcType )
 import BasicTypes      ( Boxity, tupleParens )
@@ -53,6 +53,7 @@ data Pat id
   | LazyPat    (LPat id)               -- Lazy pattern
   | AsPat      (Located id) (LPat id)  -- As pattern
   | ParPat      (LPat id)              -- Parenthesised pattern
+  | BangPat    (LPat id)               -- Bang patterng
 
        ------------ Lists, tuples, arrays ---------------
   | ListPat    [LPat id]               -- Syntactic list
@@ -60,6 +61,18 @@ data Pat id
                    
   | TuplePat   [LPat id]               -- Tuple
                Boxity                  -- UnitPat is TuplePat []
+               PostTcType
+       -- You might think that the PostTcType was redundant, but it's essential
+       --      data T a where
+       --        T1 :: Int -> T Int
+       --      f :: (T a, a) -> Int
+       --      f (T1 x, z) = z
+       -- When desugaring, we must generate
+       --      f = /\a. \v::a.  case v of (t::T a, w::a) ->
+       --                       case t of (T1 (x::Int)) -> 
+       -- Note the (w::a), NOT (w::Int), because we have not yet
+       -- refined 'a' to Int.  So we must know that the second component
+       -- of the tuple is of type 'a' not Int.  See selectMatchVar
 
   | PArrPat    [LPat id]               -- Syntactic parallel array
                PostTcType              -- The type of the elements
@@ -79,7 +92,7 @@ data Pat id
   | LitPat         HsLit               -- Used for *non-overloaded* literal patterns:
                                        -- Int#, Char#, Int, Char, String, etc.
 
-  | NPat           (HsOverLit id)              -- *Always* positive
+  | NPat           (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
@@ -144,17 +157,16 @@ pprPatBndr var                    -- Print with type info if -dppr-debug is on
        ppr var
 
 pprPat :: (OutputableBndr name) => Pat name -> SDoc
-
 pprPat (VarPat var)      = pprPatBndr var
 pprPat (VarPatOut var bs) = parens (pprPatBndr var <+> braces (ppr bs))
 pprPat (WildPat _)       = char '_'
 pprPat (LazyPat pat)      = char '~' <> ppr pat
+pprPat (BangPat pat)      = char '!' <> ppr pat
 pprPat (AsPat name pat)   = parens (hcat [ppr name, char '@', ppr pat])
 pprPat (ParPat pat)      = parens (ppr pat)
-
-pprPat (ListPat pats _)   = brackets (interpp'SP pats)
-pprPat (PArrPat pats _)   = pabrackets (interpp'SP pats)
-pprPat (TuplePat pats bx) = tupleParens bx (interpp'SP pats)
+pprPat (ListPat pats _)     = brackets (interpp'SP pats)
+pprPat (PArrPat pats _)     = pabrackets (interpp'SP pats)
+pprPat (TuplePat pats bx _) = tupleParens bx (interpp'SP pats)
 
 pprPat (ConPatIn con details) = pprUserCon con details
 pprPat (ConPatOut con tvs dicts binds details _) 
@@ -166,7 +178,8 @@ pprPat (ConPatOut con tvs dicts binds details _)
     else pprUserCon con details
 
 pprPat (LitPat s)            = ppr s
-pprPat (NPat l _ _ _)        = ppr l
+pprPat (NPat l Nothing  _ _)  = ppr l
+pprPat (NPat l (Just _) _ _)  = char '-' <> ppr l
 pprPat (NPlusKPat n k _ _)    = hcat [ppr n, char '+', ppr k]
 pprPat (TypePat ty)          = ptext SLIT("{|") <> ppr ty <> ptext SLIT("|}")
 pprPat (SigPatIn pat ty)      = ppr pat <+> dcolon <+> ppr ty
@@ -252,7 +265,7 @@ isConPat (ConPatIn _ _)              = True
 isConPat (ConPatOut _ _ _ _ _ _) = True
 isConPat (ListPat _ _)          = True
 isConPat (PArrPat _ _)          = True
-isConPat (TuplePat _ _)                 = True
+isConPat (TuplePat _ _ _)       = True
 isConPat (DictPat ds ms)        = (length ds + length ms) > 1
 isConPat other                  = False
 
@@ -269,26 +282,32 @@ isLitPat (NPat _ _ _ _)           = True
 isLitPat (NPlusKPat _ _ _ _)    = True
 isLitPat other                 = False
 
+isBangHsBind :: HsBind id -> Bool
+-- In this module because HsPat is above HsBinds in the import graph
+isBangHsBind (PatBind { pat_lhs = L _ (BangPat p) }) = True
+isBangHsBind bind                                   = False
+
 isIrrefutableHsPat :: LPat id -> Bool
 -- This function returns False if it's in doubt; specifically
--- on a ConPatIn it doesn't know th size of the constructor family
+-- on a ConPatIn it doesn't know the size of the constructor family
 -- But if it returns True, the pattern is definitely irrefutable
 isIrrefutableHsPat pat
   = go pat
   where
     go (L _ pat)        = go1 pat
 
-    go1 (WildPat _)       = True
-    go1 (VarPat _)        = True
-    go1 (VarPatOut _ _)   = True
-    go1 (LazyPat _)       = True
-    go1 (ParPat pat)      = go pat
-    go1 (AsPat _ pat)     = go pat
-    go1 (SigPatIn pat _)  = go pat
-    go1 (SigPatOut pat _) = go pat
-    go1 (ListPat pats _)  = all go pats
-    go1 (TuplePat pats _) = all go pats
-    go1 (PArrPat pats _)  = all go pats
+    go1 (WildPat _)         = True
+    go1 (VarPat _)          = True
+    go1 (VarPatOut _ _)     = True
+    go1 (LazyPat pat)       = True
+    go1 (BangPat pat)       = go pat
+    go1 (ParPat pat)        = go pat
+    go1 (AsPat _ pat)       = go pat
+    go1 (SigPatIn pat _)    = go pat
+    go1 (SigPatOut pat _)   = go pat
+    go1 (TuplePat pats _ _) = all go pats
+    go1 (ListPat pats _)    = False
+    go1 (PArrPat pats _)    = False    -- ?
 
     go1 (ConPatIn _ _) = False -- Conservative
     go1 (ConPatOut (L _ con) _ _ _ details _)