Deriviable type classes

[Yitzchak Gale]

Simon Peyton-Jones wrote:
> "Generic Defaults"... will replace... the "Derivable type classes"
> stuff... in GHC 7.2 or 7.4...
> Please yell if you are a secret user of derivable type classes,
> so this change would discombobulate you.

Could you give us a preview of the parts of the syntax
spectrum that will be gobbled up by this? That is a way
that the change could affect even people who are not using
the current generics.

For example, the old generics knocked a very nice bracket
out of consideration for TH syntax. It also blessed the names
of certain magical constructors, which can be good to know
about even if the magic doesn't leak out of the generics world.

Thanks,
Yitz