patch applied (ghc): Fix Trac #4099: better error message for type functions

[Simon Peyton Jones]

Mon May 31 07:04:13 PDT 2010  simonpj at microsoft.com
  * Fix Trac #4099: better error message for type functions
  
  Now we only want about "T is a type function and might not be
  injective" when matchin (T x) against (T y), which is the case
  that is really confusing.

    M ./compiler/typecheck/TcTyFuns.lhs -14 +9

View patch online:
http://darcs.haskell.org/cgi-bin/darcsweb.cgi?r=ghc;a=darcs_commitdiff;h=20100531140413-1287e-907572f6b1d7fd57cf9a936e5e7d795cbf59d5e4.gz