Core lint failure with type families, data families, and typeclasses

I haven't been able to shrink this case smaller and still fail core lint.

{-# LANGUAGE TypeFamilies, EmptyDataDecls #-}
module CoreLint where

data Eps

data family Work a v
data instance Work Eps v = Eps v

type family Dual a
type instance Dual Eps = Eps

class Connect s where
    connect :: (Dual s ~ c, Dual c ~ s) => Work s a -> Work c b -> (a,b)

instance Connect Eps where
    connect (Eps a) (Eps b) = (a,b)

Output from ghc -dcore-lint is attached

Trac metadata

Trac field	Value
Version	6.8.3
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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