Rustdoc is showing definitions of "private" types in type def documentation

[weiznich]

I tried this code:

diesel-rs/diesel@116e868

cargo +nightly doc --open -p diesel --no-deps

Search for diesel::dsl::Eq afterwards to get to this page

I expected to see this happen: Rustdoc hides the aliased type + tuple field sections as the Grouped by type is not exposed as part of the public API. (That type is in a crate local module)

Instead, this happened: Rustdoc shows information about private types.

Meta

rustdoc --version --verbose:

rustdoc 1.89.0-nightly (59aa1e873 2025-06-03)
binary: rustdoc
commit-hash: 59aa1e873028948faaf8b97e5e02d4db340ad7b1
commit-date: 2025-06-03
host: x86_64-unknown-linux-gnu
release: 1.89.0-nightly
LLVM version: 20.1.5

[bjorn3]

Does it work correctly if you mark the field as pub(crate)? The Grouped type is a public part of the api, even if the user can't directly reference the type. It seems like you can do my_eq.0.0 to access the field of the Grouped type if my_eq is an instance of the public diesel::dsl::Eq type.

[weiznich]

I added a #[doc(hidden)] attribute to the Grouped struct and now the output looks somewhat better. That results in the following output:

This is still not perfect as it now seems to claim that type Eq = Grouped<> is just an alias to the type struct Eq which is rather wrong. (It's an alias to Grouped).

You are correct that you could access the inner fields of that type. For diesel we just decided at some point that only what's visible in the documentation is considered to be part of the public API, anything else is: Use it at your own risk.

[weiznich]

The following code placed in a new crate in a lib.rs file reproduces the problem:

mod my_eq {
    #[doc(hidden)]
    pub struct Eq<L, R> {
        l: L,
        r: R,
    }
}

mod my_grouped {
    pub struct Grouped<I>(pub I);
}

pub type Eq<L, R> = self::my_grouped::Grouped<self::my_eq::Eq<L, R>>;