dhall-1.25.0: dhall-lang/tests/semantic-hash/success/simple/optionalFoldA.dhall

    let f =
            λ(o : Optional Text)
          → Optional/fold Text o Natural (λ(j : Text) → 1) 2

in  { example0 = f (Some "foo")
    , example1 = f (None Text)
    }