orphans

[Ian Lynagh]

On Sat, Aug 16, 2008 at 12:00:07AM +0100, Simon Peyton-Jones wrote:
> It's only an orphan if the rule's LHS mentions no locally-defined type. In this case, the LHS doesn't appear to mention IOArray, but it does really because there's an invisible type argument.

Aha! I hadn't noticed how the rule got desugared.

> However IOArray is defined in GHC.IOBase, so indeed the rule is an orphan.  Why can't the instance be put with the class decl?

OK, yes, I think we're fine then. We'll just have to move thawIOArray
into GHC.IOBase too, but that seems fine given it's specific to GHC
and its definition of IOArray.


Thanks
Ian