rustdoc removes feature flag labels for re-exports

[andrewbanchich]

tower::service_fn, for example, says nothing about feature flags you need to enable, even though it is behind the utils flag. This makes it fairly confusing.

The service_fn in the crate root is just a reexport of tower::utils::service_fn, which is correctly marked as behind a feature flag.

[GuillaumeGomez]

Another re-export issue. I'll take a look at it.

[GuillaumeGomez]

Just to be sure: did you try with a more recent nightly? I fixed a similar issue in #101006.

[andrewbanchich]

It does seem to be fixed on nightly. Thanks!