T8428.hs:11:19:
    Couldn't match type ‘(forall s. ST s) a’ with ‘forall s. ST s a’
    Expected type: IdentityT (forall s. ST s) a -> forall s. ST s a
      Actual type: IdentityT (forall s. ST s) a -> (forall s. ST s) a
    Relevant bindings include
      runIdST :: IdentityT (forall s. ST s) a -> a
        (bound at T8428.hs:11:1)
    In the second argument of ‘(.)’, namely ‘runIdentityT’
    In the expression: runST . runIdentityT