Re: suppress warning "Defined but not used: type variable ‘x’" in GHC-8.0

[Henning Thielemann]

On Mon, 11 Jan 2016, Richard Eisenberg wrote:

> On Jan 9, 2016, at 6:44 PM, Henning Thielemann <lemming at henning-thielemann.de> wrote:
>>
>> instance (Natural n) => Num.Integer (Un n) where
>>    type Repr (Un _n) = Unary
>>
>>
>> GHC-7.6.3 and GHC-7.4.2 complain:
>>    Type indexes must match class instance head
>>    Found `Un _n' but expected `Un n'
>>    In the type synonym instance declaration for `Num.Repr'
>>    In the instance declaration for `Num.Integer (Un n)'
>>
>>
>> GHC-7.8.4, GHC-7.10.3 and GHC-8.0 are happy with the difference.
>
> I'm surprised this is accepted at all. Looks like hogwash to me. I think you should post a bug report.

Ok, but then GHC must not warn about the unused argument of Repr.