[GHC] #5051: Typechecker behaviour change

[Serge D. Mechveliani]

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 at 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.
> [..]