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{-# LANGUAGE Haskell2010 #-}
{-# LANGUAGE TypeFamilies, TypeFamilyDependencies #-}
module T13651 where
type family F r s = f | f -> r s
type instance F (Bar h (Foo r)) (Bar h (Foo s)) = Bar h (Bar r s)
data Bar s b
data Foo a
foo :: (F cr cu ~ Bar h (Bar r u),
F cu cs ~ Bar (Foo h) (Bar u s))
=> Bar h (Bar r u) -> Bar (Foo h) (Bar u s) -> cu -> Foo (cr -> cs)
-- A variant of T13651 which fixes 'cu'
-- as well as the other type args
foo = undefined
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