bug with type families
pgavin at gmail.com
Mon Jun 2 20:26:32 EDT 2008
Stefan Holdermans wrote:
>> I've run into a bug that looks to be the same as the one described here:
> It does not seem like a bug, although the type-error message may be a
> bit confusing as is the fact that GHC happily infers a type for the
> signature-less function: these are I guess the real issues here. But,
> apart from that, the contents of a previous discussion seems to apply here:
> Short version: the type of isValid involves |Depend s| and not |s|.
> Since |Depend s| does not uniquely determine |s|, it is not possible to
> resolve which dictionary for Bug to supply for a particular call to
> Or---am I overlooking something?
No, that makes perfect sense to me now. Thanks.
I put up a note on #1897 pointing to that thread, but left it open
because the error message needs to be fixed :)
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