patch applied (ghc): Fix Trac #3057 in deriving Functor

[Simon Peyton Jones]

Tue Mar  3 09:06:12 PST 2009  simonpj at microsoft.com
  * Fix Trac #3057 in deriving Functor 
  Ignore-this: 7d7783868e4684930f75c3b35c18c586
  
  The universal type variables of a data constructor are not necessarily
  identical to those of its parent type constructor, especially if the
  data type is imported.
  
  While I was at it, I did a significant refactoring to make all this
  traversal of types more comprehensible, by adding the data type
  FFoldType.
  

    M ./compiler/typecheck/TcDeriv.lhs -12 +11
    M ./compiler/typecheck/TcGenDeriv.lhs -69 +89

View patch online:
http://darcs.haskell.org/ghc/_darcs/patches/20090303170612-1287e-ec15ef29119f8a036cd841495958202b9f5b2ee1.gz