T1900.hs:8:3: error: [GHC-83865]
    • Couldn't match type: Depend s0
                     with: Depend s
      Expected: Depend s -> Depend s
        Actual: Depend s0 -> Depend s0
        NB: ‘Depend’ is a non-injective type family
        The type variable ‘s0’ is ambiguous
    • In the ambiguity check for ‘trans’
      To defer the ambiguity check to use sites, enable AllowAmbiguousTypes
      When checking the class method:
        trans :: forall s. Bug s => Depend s -> Depend s
      In the class declaration for ‘Bug’