X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2FdeSugar%2FDsUtils.lhs;fp=compiler%2FdeSugar%2FDsUtils.lhs;h=6ff3916fbac7459a580971e019fb1e0632ba4d0f;hp=9a0e75279cf84b4e14174839760258b7911c9db9;hb=2ebd4bf2d64831d6363ac935efff3229aebc7530;hpb=7defebee53964996947d1dee2c6606519d796429

diff --git a/compiler/deSugar/DsUtils.lhs b/compiler/deSugar/DsUtils.lhs
index 9a0e752..6ff3916 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.