patch applied (ghc): Improve error messages

[Simon Peyton Jones]

Mon Nov  1 09:46:30 PDT 2010  simonpj at microsoft.com
  * Improve error messages
  
  In particular, instead of
     Cannot match 'a' with 'b'
  we get
     Could not deduce (a~b) from context (F a ~ b)
  or whatever

    M ./compiler/typecheck/TcErrors.lhs -19 +27

View patch online:
http://darcs.haskell.org/cgi-bin/darcsweb.cgi?r=ghc;a=darcs_commitdiff;h=20101101164630-1287e-28f8b473470d8b5f8e2b16d8e59aba9a81d4e7cd.gz