Public function is allowed to return private struct, results in cc linking error

[daboross]

This error can be shown with two rust files compiled directly via rustc (or cargo, but just using rustc is simpler for showing the error).

cratea.rs:

#![crate_name = "cratea"]
#![crate_type = "lib"]

pub mod pub_dispatch {
    use dispatch;

    pub fn create_dispatch() -> dispatch::Dispatch {
        return dispatch::Dispatch;
    }
}

mod dispatch {
    pub struct Dispatch;

    impl Dispatch {
        pub fn dispatch(self) {
        }
    }
}

crateb.rs:

#![crate_name = "crateb"]
extern crate cratea;

fn main() {
    let dispatch = cratea::pub_dispatch::create_dispatch();

    dispatch.dispatch();
}

Output from compiling:

$ rustc cratea.rs
cratea.rs:16:9: 17:10 warning: method is never used: `dispatch`, #[warn(dead_code)] on by default
cratea.rs:16         pub fn dispatch(self) {
cratea.rs:17         }
$ rustc -L crate=./ crateb.rs
error: linking with `cc` failed: exit code: 1
note: "cc" "-Wl,--as-needed" "-m64" "-L" "/usr/local/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-o" "crateb" "crateb.o" "-Wl,--whole-archive" "-lmorestack" "-Wl,--no-whole-archive" "-Wl,--gc-sections" "-pie" "-nodefaultlibs" "/tmp/tmp.8n2IVQ5qlk/libcratea.rlib" "/usr/local/lib/rustlib/x86_64-unknown-linux-gnu/lib/libstd-4e7c5e5c.rlib" "/usr/local/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcollections-4e7c5e5c.rlib" "/usr/local/lib/rustlib/x86_64-unknown-linux-gnu/lib/libunicode-4e7c5e5c.rlib" "/usr/local/lib/rustlib/x86_64-unknown-linux-gnu/lib/librand-4e7c5e5c.rlib" "/usr/local/lib/rustlib/x86_64-unknown-linux-gnu/lib/liballoc-4e7c5e5c.rlib" "/usr/local/lib/rustlib/x86_64-unknown-linux-gnu/lib/liblibc-4e7c5e5c.rlib" "/usr/local/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcore-4e7c5e5c.rlib" "-L" "./" "-L" "/usr/local/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-L" "/tmp/tmp.8n2IVQ5qlk/.rust/lib/x86_64-unknown-linux-gnu" "-L" "/tmp/tmp.8n2IVQ5qlk/lib/x86_64-unknown-linux-gnu" "-Wl,--whole-archive" "-Wl,-Bstatic" "-Wl,--no-whole-archive" "-Wl,-Bdynamic" "-ldl" "-lpthread" "-lrt" "-lgcc_s" "-lpthread" "-lc" "-lm" "-lcompiler-rt"
note: crateb.o: In function `main::h69a169139aab5413faa':
crateb.0.rs:(.text._ZN4main20h69a169139aab5413faaE+0x2c): undefined reference to `dispatch::Dispatch::dispatch::ha28d1bdf4c2d8d39uaa'
collect2: error: ld returned 1 exit status

error: aborting due to previous error

Happens in rustc 1.0.0-beta (9854143cb 2015-04-02) (built 2015-04-02) and rustc 1.0.0-nightly (083b8a404 2015-04-05) (built 2015-04-05).

I would expect this to fail when compiling cratea, but instead cratea compiles fine, but then any crate using it will fail compiling.

[alexcrichton]

I believe this is a duplicate of #16734, but thanks for the issue!

[daboross]

Ah, thank you for linking that!