seemingly inconsistent behavior for "kind-indexed" type constraints in GHC 7.6

Nicolas Frisby nicolas.frisby at
Fri Oct 5 23:49:51 CEST 2012

GHC 7.6 is rejecting some programs that I think ought to be well-typed.

Details here

I find this behavior particularly odd because I can get GHC to deduce
the type equalities in some contexts but not in others. In particular,
it does not deduce them inside of type class instances.

Is this a known issue? I'll create a Trac ticket if that's appropriate.

Thanks for your time.

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