Record the type in TuplePat (necessary for GADTs)

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

diff --git a/ghc/compiler/hsSyn/HsPat.lhs b/ghc/compiler/hsSyn/HsPat.lhs
index 4880120..eca7dd1 100644 (file)
--- a/ghc/compiler/hsSyn/HsPat.lhs
+++ b/ghc/compiler/hsSyn/HsPat.lhs
@@ -60,6 +60,18 @@ 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
@@ -145,16 +157,16 @@ pprPatBndr var                    -- Print with type info if -dppr-debug is on
 
 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 (AsPat name pat)   = parens (hcat [ppr name, char '@', ppr pat])
-pprPat (ParPat pat)      = parens (ppr pat)
+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 (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 _) 
@@ -253,7 +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
 
@@ -279,17 +291,17 @@ isIrrefutableHsPat pat
   where
     go (L _ pat)        = go1 pat
 
-    go1 (WildPat _)       = True
-    go1 (VarPat _)        = True
-    go1 (VarPatOut _ _)   = True
-    go1 (LazyPat pat)     = True
-    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 (WildPat _)         = True
+    go1 (VarPat _)          = True
+    go1 (VarPatOut _ _)     = True
+    go1 (LazyPat pat)       = True
+    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 _)