[ghc-steering-committee] Mind the gap

[Chris Dornan]

Richard are you satisfied that my example program is invalid under PolyKinds?

> On 6 Jul 2022, at 12:51, Richard Eisenberg <lists at richarde.dev> wrote:
> 
> 
> 
>> On Jul 6, 2022, at 4:35 AM, Simon Peyton Jones <simon.peytonjones at gmail.com <mailto:simon.peytonjones at gmail.com>> wrote:
>> 
>> I sort of wonder: if we have (Typeable t) should that not give us (Typeable k) where (t :: k)?  That would require us to have a function typeRepKind :: TypeRep (a::k) -> TypeRep k, and I don't know how hard that is to get.
> 
> We have that function. It's called typeRepKind. What we need for this example is a superclass constraint:
> 
> class Typeable k => Typeable (a :: k)
> 
> which would probably require UndecidableSuperClasses, but otherwise might just work.
> 
> Richard
> 

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