Link failure due to exporting function with a non-exported return type

This code snippet causes a link failure. I am guessing it is because the return type of foo is not publicly exported from the crate it is causing a link failure in the test.

I tried this (reduced) code:

lib.rs

mod helper {
    pub struct Foo;
    impl Foo {
        pub fn baz(&self) { }
    }

    pub fn foo() -> Foo {
        return Foo;
    }
}

pub use helper::foo;

test.rs

extern crate lib;

#[test]
fn test() {
    lib::foo().baz();
}

I expected to see this happen: Definitely a clear error as opposed to a link failure. Probably an error stating that the return type of foo() is not visible outside the crate.

Instead, this happened: Linker error:

── env RUST_BACKTRACE=1 cargo test
   Compiling lib v0.1.0 (file:///Users/nwr/tmp/cargo-test/lib)
error: linking with `cc` failed: exit code: 1
note: "cc" "-m64" "-L" "/usr/local/lib/rustlib/x86_64-apple-darwin/lib" "/Users/nwr/tmp/cargo-test/lib/target/debug/foo-5f1f39478ede92a5.0.o" "-o" "/Users/nwr/tmp/cargo-test/lib/target/debug/foo-5f1f39478ede92a5" "-Wl,-force_load,/usr/local/lib/rustlib/x86_64-apple-darwin/lib/libmorestack.a" "-Wl,-dead_strip" "-nodefaultlibs" "/Users/nwr/tmp/cargo-test/lib/target/debug/liblib.rlib" "/usr/local/lib/rustlib/x86_64-apple-darwin/lib/libtest-74fa456f.rlib" "/usr/local/lib/rustlib/x86_64-apple-darwin/lib/libgetopts-74fa456f.rlib" "/usr/local/lib/rustlib/x86_64-apple-darwin/lib/libserialize-74fa456f.rlib" "/usr/local/lib/rustlib/x86_64-apple-darwin/lib/libterm-74fa456f.rlib" "/usr/local/lib/rustlib/x86_64-apple-darwin/lib/liblog-74fa456f.rlib" "/usr/local/lib/rustlib/x86_64-apple-darwin/lib/libstd-74fa456f.rlib" "/usr/local/lib/rustlib/x86_64-apple-darwin/lib/libcollections-74fa456f.rlib" "/usr/local/lib/rustlib/x86_64-apple-darwin/lib/librustc_unicode-74fa456f.rlib" "/usr/local/lib/rustlib/x86_64-apple-darwin/lib/librand-74fa456f.rlib" "/usr/local/lib/rustlib/x86_64-apple-darwin/lib/liballoc-74fa456f.rlib" "/usr/local/lib/rustlib/x86_64-apple-darwin/lib/liblibc-74fa456f.rlib" "/usr/local/lib/rustlib/x86_64-apple-darwin/lib/libcore-74fa456f.rlib" "-L" "/Users/nwr/tmp/cargo-test/lib/target/debug" "-L" "/Users/nwr/tmp/cargo-test/lib/target/debug/deps" "-L" "/usr/local/lib/rustlib/x86_64-apple-darwin/lib" "-L" "/Users/nwr/tmp/cargo-test/lib/.rust/lib/x86_64-apple-darwin" "-L" "/Users/nwr/tmp/cargo-test/lib/lib/x86_64-apple-darwin" "-l" "System" "-l" "pthread" "-l" "c" "-l" "m" "-l" "compiler-rt"
note: ld: warning: directory not found for option '-L/Users/nwr/tmp/cargo-test/lib/.rust/lib/x86_64-apple-darwin'
ld: warning: directory not found for option '-L/Users/nwr/tmp/cargo-test/lib/lib/x86_64-apple-darwin'
Undefined symbols for architecture x86_64:
  "helper::Foo::baz::heb3ebf21697cffffkaa", referenced from:
      test::h63ea6d9d3e0d725cfaa in foo-5f1f39478ede92a5.0.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

error: aborting due to previous error
Could not compile `lib`.

To learn more, run the command again with --verbose.

Meta

rustc --version --verbose (repos on 1.1.0 stable as well):

rustc 1.3.0-nightly (8ce69e856 2015-07-31)
binary: rustc
commit-hash: 8ce69e856a4def6ef39581823520c68944bd1c8e
commit-date: 2015-07-31
host: x86_64-apple-darwin
release: 1.3.0-nightly

Backtrace: None

[alexcrichton]

Closing as a duplicate of #16734.