testsuite/tests/typecheck/should_fail/T16512b.hs


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{-# LANGUAGE TypeFamilyDependencies #-}

module T16512b where

type family G a = r | r -> a where
  G [a] = [G a]

-- this needs -XUndecidableInstances.
-- See Note [Coverage condition for injective type families] in GHC.Tc.Instance.Family