base-3.0.3.0 not backwards compatible with base-3.0.2.0

[Ian Lynagh]

On Wed, Nov 19, 2008 at 03:06:04PM +0100, Stefan Holdermans wrote:
> 
> Could anyone confirm the following claims?
> 
> * base-3.0.3.0 (shipped with GHC 6.10.1) is supposed to be backwards  
> compatible with base-3.0.2.0 (shipped with GHC 6.8.3) ...

Yes.

> * ... but it isn't! (For example, the Arrow class from Control.Arrow  
> is a subclass of Category from Control.Category in base-3.0.3.0, but  
> not in base-3.0.2.0.)

Yes. It wasn't possible to handle this change in a compatible way, I'm
afraid.

> Do we know of any similar issues?

I think the Arrow/Category changes are the only issue. I think one of
the methods moved from one class to the other as well.

> What's the recommended workaround  
> when shipping code that is to support both GHC 6.8.* and GHC 6.10.*?)

CPP is the best solution I can think of.


Thanks
Ian