T15552a.hs:26:9: error:
    • Illegal nested use of type family ‘FirstEntryOfVal’
        in the arguments of the type-family application ‘GetEntryOfVal
                                                           (FirstEntryOfVal v kvs)’
      (Use UndecidableInstances to permit this)
    • In the equations for closed type family ‘FirstEntryOfVal’
      In the type family declaration for ‘FirstEntryOfVal’

T15552a.hs:26:9: error:
    • Illegal nested use of type family ‘FirstEntryOfVal’
        in the arguments of the type-family application ‘EntryOfValKey
                                                           (FirstEntryOfVal v kvs)’
      (Use UndecidableInstances to permit this)
    • In the equations for closed type family ‘FirstEntryOfVal’
      In the type family declaration for ‘FirstEntryOfVal’

T15552a.hs:26:9: error:
    • Illegal nested use of type family ‘FirstEntryOfVal’
        in the arguments of the type-family application ‘EntryOfValKey
                                                           (FirstEntryOfVal v kvs)’
      (Use UndecidableInstances to permit this)
    • In the equations for closed type family ‘FirstEntryOfVal’
      In the type family declaration for ‘FirstEntryOfVal’