instance overlap in 6.6 candidate

[Simon Peyton-Jones]

| ------------------------------------------------
| data Equation = ...
| instance Show Equation where ...
| 
| instance Show [Equation]
|   where
|   showsPrec _ eqs =  <certain program which prints a list of equation
|                       in a `nicer' way than by the default list
printing
|                      >
| ------------------------------------------------
| 
| This gives the user possibility to redefine a certain part of the
| library instance.
| Is not  ghc-6.4.1  better at this point?

Perhaps.  That's what I'd like feedback about.  What do others think?
(Incidentally, 6.5 has been like this for about a year without
complaints.  Also I made the change because people wanted to be able to
*use* overlapping instances (defined in a library) without having to
give the -fallow-overlapping-instances flag.)

Simon