Stance on the API compatibility of `#[doc(hidden)]` `pub` items

[ROMemories]

The #[doc(hidden)] attribute allows to hide items from the rendered documentation generated by rustdoc (with some subtleties regarding re-exports).

It is my opinion that this excludes the decorated item from the crate's SemVer commitment.
This opinion seems to be shared by rust-analyzer, where such items have been excluded from the auto-completion mechanism (rust-lang/rust-analyzer#9719, rust-lang/rust-analyzer#15473). Additionally, cargo-semver-checks also worked on taking into account this attribute when checking for breaking changes.

However, the Cargo reference regarding SemVer only states that removing/renaming pub items is a major change, making no difference for #[doc(hidden)] items.

Is there an official stance on the compatibility guarantees of #[doc(hidden)] pub items and, if so, should the reference be updated?

[epage]

There are many reasons to #[doc(hidden)] something. For example, I think I've done it for deprecated items in the past. I don't think we can fully infer intent behind something behind hidden.

However, there is room for crates to say that parts of their API are unstable. There are not currently built-in ways to express this (e.g. stabilizing #[unstable], #10881). Some are done through documentation while others are done through naming.