[Haskell-cafe] Issues(Bugs?) with GHC Type Families
hpacheco at gmail.com
Wed Mar 5 20:27:47 EST 2008
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?
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