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{-# LANGUAGE TypeFamilies #-}
-- This should fail
module T3208b where
class SUBST s where
type STerm s
class OBJECT o where
type OTerm o
apply :: (SUBST s, OTerm o ~ STerm s) => s -> o
fce' :: (OTerm a ~ STerm a, OBJECT a, SUBST a) => a -> c
fce' f = fce (apply f)
-- f :: a
-- apply f :: (OBJECT a, SUBST a, OTerm o ~ STerm a) => o
-- fce called with a=o, gives wanted (OTerm o ~ STerm o, OBJECT o, SUBST o)
fce :: (OTerm a ~ STerm a, OBJECT a, SUBST a) => a -> c
fce f = fce' f
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