X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2FdeSugar%2FDsUtils.lhs;h=25366faa597593c0e8ca92e9da03bf3c9e8da1c2;hb=920f106b8472089fb96eca537d1965256302301c;hp=9a0e75279cf84b4e14174839760258b7911c9db9;hpb=8a25c54e2df36b3fb40436e5b887dddc3c64ab54;p=ghc-hetmet.git

diff --git a/compiler/deSugar/DsUtils.lhs b/compiler/deSugar/DsUtils.lhs
index 9a0e752..25366fa 100644
--- a/compiler/deSugar/DsUtils.lhs
+++ b/compiler/deSugar/DsUtils.lhs
@@ -419,7 +419,7 @@ But that is bad for two reasons:
 Seq is very, very special!  So we recognise it right here, and desugar to
         case x of _ -> case y of _ -> (# x,y #)
 
-Note [Desugaring seq (2)]  cf Trac #2231
+Note [Desugaring seq (2)]  cf Trac #2273
 ~~~~~~~~~~~~~~~~~~~~~~~~~
 Consider
    let chp = case b of { True -> fst x; False -> 0 }
@@ -447,10 +447,14 @@ should have said explicitly
 
 But that's painful.  So the code here does a little hack to make seq
 more robust: a saturated application of 'seq' is turned *directly* into
-the case expression. So we desugar to:
+the case expression, thus:
+   x  `seq` e2 ==> case x of x -> e2    -- Note shadowing!
+   e1 `seq` e2 ==> case x of _ -> e2
+
+So we desugar our example to:
    let chp = case b of { True -> fst x; False -> 0 }
    case chp of chp { I# -> ...chp... }
-Notice the shadowing of the case binder! And now all is well.
+And now all is well.
 
 The reason it's a hack is because if you define mySeq=seq, the hack
 won't work on mySeq.  
@@ -600,7 +604,7 @@ mkLHsVarPatTup bs  = mkLHsPatTup (map nlVarPat bs)
 mkVanillaTuplePat :: [OutPat Id] -> Boxity -> Pat Id
 -- A vanilla tuple pattern simply gets its type from its sub-patterns
 mkVanillaTuplePat pats box 
-  = TuplePat pats box (mkTupleTy box (length pats) (map hsLPatType pats))
+  = TuplePat pats box (mkTupleTy box (map hsLPatType pats))
 
 -- The Big equivalents for the source tuple expressions
 mkBigLHsVarTup :: [Id] -> LHsExpr Id