[Haskell-cafe] Type families versus functional dependenciesquestion

[Alexey Rodriguez]

On Thu, Jul 3, 2008 at 10:14 PM, Claus Reinke <claus.reinke at talk21.com>
wrote:

> actually, GHC gives me "could not deduce Blah f a from Blah f1 a"
>>> first. It seems that desugaring type function notation into an additional
>>> constraint helps, so there's something odd going on:
>>>
>>
>> Silly me, I didn't paste the whole type error. Yes, GHC gives both. I
>> should
>> add that I tested this under GHC 6.8.2. But this is known not to work
>> with a
>> (one/two months old) GHC head.
>>
>
> yes, I tested with 6.9.20080514. And just in case my phrasing
> was unclear: desugaring the type function application makes the
> error go away, so you have a workaround.


Thanks for highlighting this. Indeed I missed it, and it makes my example
work.

Cheers,

Alexey


>
>
> It is just confusing that this example shows that the "desugaring"
> is not a desugaring, in the current implementation..
>
> Claus
>
>
>
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