Simon, thank you. Currently, DoCon works under ghc-7.0.1. And as I understand, the next release which is going to support DoCon (with its heavy use of overlapping instances) will be ghc-7.2. Regards, -------- Serge Mechveliani, mechvel@botik.ru On Wed, Jun 22, 2011 at 11:01:53AM -0000, GHC wrote:
#5051: Typechecker behaviour change ---------------------------+------------------------------------------------ Reporter: igloo | Owner: simonpj Type: bug | Status: closed Priority: high | Milestone: 7.2.1 Component: Compiler | Version: 7.0.2 Resolution: fixed | Keywords:
[..]
GHC 7 indeed falls over on `DoCon` 2.12. It turns out to be a rather subtle interaction of overlapping instances with the ill-fated "silent superclass parameters" I introduced to solve a problem in the typechecker's constraint solver. [..]