Completes 08e6491 in reusing `maybe_visit`

:sweat: I don't know why the tests did not fail, but to keep the same syntax as before 08e6491, `collector =` is required.

Maybe `visit` changes `collector` in-place, so the result is the same, but since I'm not sure about the side effects, I think this PR is needed too. Sorry! :sweat: