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

Richard Eisenberg eir at
Mon Jan 11 17:42:38 UTC 2016

On Jan 9, 2016, at 6:44 PM, Henning Thielemann <lemming at> 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.


More information about the Glasgow-haskell-users mailing list