Just something I have been wondering. I would like to implement somehting like:
type family F a :: * -> * ... class C a b where ... instance (F a ~ F b) => C a b where ... But apparently type equality coercions can not be used as a single context. If I enable -fallow-undecidable-instances, whenever the equality does not hold, the instance returns a compile error, what does make sense. Is there any way I could overcome this? Thanks, hugo
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