Wrong "Private type in exported type signature" error

[netvl]

Consider this code:

mod a {
    pub mod x {
        pub fn return_x() -> ::X { ::X }
    }
}

struct X;

fn main() {
    let _value = a::x::return_x();
}

It fails to compile with the following error:

test.rs:3:30: 3:33 error: private type in exported type signature
test.rs:3         pub fn return_x() -> ::X { ::X }
                                       ^~~

However, while fn return_x() is pub and mod x is also pub, this function never gets exported from the crate because mod a is private. Therefore, X, being private, is also not available outside the crate. I think that such code should be allowed.

[crumblingstatue]

I have run into this as well.

mod foo {
    // Private implementation detail struct
    struct Strut;
    fn doit() {
        self::bar::fun();
    }
    mod bar {
        // bar::fun() is a private implementation detail of mod foo
        pub fn fun() -> super::Strut {
            unimplemented!()
        }
    }
}

fn main() {
    // foo::bar::fun(); // inaccessible outside of `foo`
}

<anon>:9:25: 9:37 error: private type in exported type signature
<anon>:9         pub fn fun() -> super::Strut {
                                 ^~~~~~~~~~~~

[alexcrichton]

This has been filed before and the gist is that the definition of a "public signature" is that the type is marked pub, so it's considered a public type subject to the privacy rules. You can find more details in the associated RFC