patch applied (ghc): Fix an old but subtle bug in the Simplifier

[Simon Peyton Jones]

Mon Nov  5 08:13:14 PST 2007  simonpj at microsoft.com
  * Fix an old but subtle bug in the Simplifier
  
  I got a Core Lint failure when compiling System.Win32.Info in the
  Win32 package.  It was very delicate: adding or removing a function
  definition elsewhere in the module (unrelated to the error) made the
  error go away.
  
  Happily, I found it.  In SimplUtils.prepareDefault I was comparing an
  InId with an OutId.  We were getting a spurious hit, and hence doing
  a bogus CaseMerge.
  
  This bug has been lurking ever since I re-factored the way that case
  expressions were simplified, about 6 months ago!
  

    M ./compiler/simplCore/SimplEnv.lhs -3 +5
    M ./compiler/simplCore/SimplUtils.lhs -18 +17
    M ./compiler/simplCore/Simplify.lhs -2 +2