GHC 7.0.1 rc1: Could not deduce (Typeable a) from the context (Typeable a, …)

[Malte Sommerkorn]

Simon Peyton-Jones wrote:
> Oh dear, that really is quite a strange error message. Something is
> definitely wrong. Can you please make a ticket for it, and include
> instructions on how to reproduce it? 

Done: http://hackage.haskell.org/trac/ghc/ticket/4355

> I gather that it depends on other packages that themselves needed changes,
> so reproduction might not be entirely easy?

I've attached a module to the bug report that triggers the problem and only
depends on base and mtl, so that should be fairly easy to reproduce.

Regards
Malte