missing_docs false positive on re-export in module with #![allow(missing_docs)]

[abonander]

This one might be a bit complex to solve. This affects both 2015 and 2018 editions on stable/nightly.

When a pub item from a private module in a crate with #![deny(missing_docs)] is reexported in a pub module marked #![allow(missing_docs)], the lint still fires.

2015 (Playground) (2018 just needs the crate:: prefix on the use path)

//! docs for crate
#![deny(missing_docs)]

#[allow(missing_docs)]
pub mod undoc {
    #[allow(missing_docs)] // no effect
    pub use nonpub::Foo;
}

mod nonpub {
    pub struct Foo;
    
    impl Foo {
        pub fn bar() {}
    }
}

Both report the same error. The lint marks the original definition point of the item; if it has associated items, those are hit too:

error: missing documentation for a struct
  --> src/lib.rs:11:5
   |
11 |     pub struct Foo;
   |     ^^^^^^^^^^^^^^^
   |
note: lint level defined here
  --> src/lib.rs:2:9
   |
2  | #![deny(missing_docs)]
   |         ^^^^^^^^^^^^

error: missing documentation for a method
  --> src/lib.rs:14:9
   |
14 |         pub fn bar() {}
   |         ^^^^^^^^^^^^

error: aborting due to 2 previous errors

Interestingly, marking the item's source module with #[allow(missing_docs)] silences the error: Playground

//! docs for crate
#![deny(missing_docs)]

#[allow(missing_docs)]
pub mod undoc {
    pub use nonpub::Foo;
}

#[allow(missing_docs)]
mod nonpub {
    pub struct Foo;
    
    impl Foo {
        pub fn bar() {}
    }
}

[abonander]

@estebank this is a lint error, not a Rustdoc error

[estebank]

@abonander good catch, I misread the ticket while grooming. Thanks for the correction!

[petrochenkov]

struct Foo and fn bar are 1) reachable from other crates, 2) have no doc comments and 3) are not in scope of #[allow(missing_docs)].
So they are reported by the missing doc lint.

Looks like everything is working correctly to me.

[GuillaumeGomez]

I'm the one who wrote this lint and it seems to be working correctly to me as well...

[abonander]

Except that they're reexported from a module marked #[allow(missing_docs)] which I would expect not to require documentation on items reachable inside it.

Moreover, #[allow(missing_docs)] on the reexport does nothing but is not at least marked as an unused attribute.