Rustdoc has a concept called "passes". These are transformations that rustdoc runs on your documentation before producing its final output.

Customizing passes is deprecated. The available passes are not considered stable and may change in any release.

In the past the most common use case for customizing passes was to omit the strip-private pass. You can do this more easily, and without risk of the pass being changed, by passing --document-private-items.