patch applied (ghc): Fix egregious and long-standing tidying bug

[Simon Peyton Jones]

Thu May 25 02:43:00 PDT 2006  simonpj at microsoft.com
  * Fix egregious and long-standing tidying bug
  
  A typo in tidyAlt meant that we could get shadowing of occurrence names
  in the output of tidying.  (Specifically, of existentially bound type 
  variables.)  That in turn meant that an IfaceExpr could have shadowing, so
  when the IfaceExpr was read in, it meant something different.
  That in turn led to an obscure crash like:
  	Panic: tcIfaceTyVar
  
  Anyway, this fixes it.  MERGE into 6.4.3.
  
  

    M ./compiler/coreSyn/CoreTidy.lhs -1 +1