patch applied (ghc): Fix Trac #4966

[Simon Peyton Jones]

Thu Feb 17 06:10:00 PST 2011  simonpj at microsoft.com
  * Fix Trac #4966
  
  This is just a program that exploits overlapping
  instances in a delicate way. The fix makes GHC
  a bit more friendly towards such programs. 
  
  See Note [Overlap and deriving] in TcSimplify

    M ./compiler/typecheck/TcSimplify.lhs -5 +30

View patch online:
http://darcs.haskell.org/cgi-bin/darcsweb.cgi?r=ghc;a=darcs_commitdiff;h=20110217141000-1287e-fc0ddc3002c298da5bacefd9f6f64b584d755437.gz